Showing posts with label Function. Show all posts
Showing posts with label Function. Show all posts

The Roles Function Organisation Of Imf Wto Wb Economics Essay

This essay aims to analyse and evaluate the impact of three international institutions namely, the International Monetary Fund (IMF), the World Bank and the World Trade Organisation (WTO) in securing global health and wellbeing. Their legitimacy and accountability have attracted a lot of debate and criticism. In the essay, the roles, functions and organisation of these institutions will be discussed followed by critique relating to presentation, influence and impact on global health/wellbeing and finally concluding with a critical evaluation and considerations of possible alternatives and improvements.

Ideas of Harry Dexter White of United States and the British economist John Maynard Keynes led to the establishment of the IMF which began its operations on the 1st of March 1947 in Washington D.C. Its purpose was to rebuild the international economy and prevent the economic crises such as the Great Depression. Membership to the IMF is voluntary and a country has to deposit a “quota subscription” which determines the voting power of that country and also how much that country could borrow from the fund in terms of financial crisis. The highest decision-making body in the fund is the Board of Governors who are not involved in the day to day running of the Fund and they meet once yearly. Currently with a membership of 187 countries the IMF provides systematic mechanisms for foreign exchange transactions in order to promote balanced global economic trade. The IMF advises and focuses on member countries’ macroeconomic policies to ensure its own wealth and that of its members are safeguarded.  It does surveillance of the member countries policies to ensure they do not have a negative effect on the exchange rates and trade markets. The IMF also does periodic consultations to check member countries overall economic positions and advises them on how to improve their economy. It also provides loans to countries that have problems with their balance of payments, (www.imf.org). The loans have conditions attached to them and the borrower countries must implement the economic reforms as determined by the IMF. These structural adjustment programmes (SAPs) are meant to help the countries to overcome the problems of their balance of payments (Driscoll, 1996).

The World Bank was established in 1944 to play a role in the reconstruction of post-war Europe.  It has a similar governance structure as the IMF, with a board of Governors with representatives from all member states as the highest decision-making body and the voting system is the same as that of the IMF. America holds the largest share of votes and the president is also by tradition a US citizen (Peet, 2003).  The World Bank group consists of five organizations but only two are usually referred to as the World Bank. For the purpose of this essay we will restrict our attention to these two. The International Bank for Reconstruction and Development (IBDR) provides long term loans and aid for economic development. It is financed from the sale of bonds on international finance markets and from interest gained from loan repayments. The International Development Association (IDA) focuses on giving credits and grants to poor countries. These interest free grants attract a 0.75 percent administrative charge per annum and are aimed to assist programmes of economic growth, reduce inequalities and improvement of living conditions.  IDA is funded from contributions from richer member countries and from income earned from IBDR financing. Like the IMF, the World Bank has conditions attached its loans (Global Health Watch, 2005-2006). The bank also provides technical assistance on development issues. It provides knowledge through education and analytical services. Since its establishment, the World Bank has become more engaged in issues of institutional and policy change in borrowing countries.  The bank defines what would be the best development approach on different projects at a particular time. Currently the Bank defines its mission as reducing global poverty by helping member countries through ensuring economic growth by “capacity building” and helping to create “infrastructure” (www.worldbank.org)

The WTO was established in 1995 as a successor to the previous General Agreement on Tariffs and Trade (GATT) which was established in 1947 after failed attempts to establish an International Trade Organisation (ITO) that would regulate trade. The idea of the ITO was discussed at the Bretton Woods Conference as necessary to complement the World Bank and the IMF. Due to the nature of the policies of the ITO, the US was not willing to commit itself to trade policies which would compromise its power thus efforts to establish the ITO failed (Peet 2003). The WTO’s function is to promote free and fair trade between member states with a view of promoting economic prosperity and contributing to international peace. This is achieved through the administration of trade agreements and acting as a forum for trade negotiations, helping to settle trade disputes, reviewing national trade policies, providing assistance to developing countries in trade policy issues through technical assistance and training programmes and cooperating with other international organisations such as the IMF and the World Bank, (www.wto.org). Unlike the IMF and the World Bank, the WTO is a more member-driven organisation where all major decisions are made by member states by reaching a consensus and the Secretariat has very limited powers. The WTO operates a one country one vote system. Members of the WTO agree to abide by the rules of the organisation.

Criticisms on IMF and the World Bank originate from their policies which many argue promote neoliberalism. Transparency on the functioning of the institutions has also been questioned. Governance of the two institutions is dominated by the industrialised countries mainly the G8. Due to their voting power, the industrialised countries act without much consultation with poor /developing countries who are underrepresented in the two institutions. As such, poor countries influence in policing change is limited, (www.brettonwoodsprojcet.org ). The Bank and the IMF have also been accused of promoting the top-down approach in development which has made them to be regarded as the experts in the field of financial regulation and economic development. Their prescriptive rules are viewed by many as able to undermine or eliminate alternative perceptions on development therefore are not always beneficiary to the recipients (Baum 2008).  

The IMF and the World Bank’s policies have had negative economic and social impact on many countries that have had financial assistance from them. They impose conditions on their loans based on what is termed the “Washington Consensus” which is criticised by many as a neoliberalist approach of trade liberalisation and development, investment and the financial sector, deregulation and the privatisation of nationalised industries and conditions that are not flexible to individual countries circumstances. The prescriptive recommendations by the World Bank and the IMF fail to address the economic problems within countries thereby promoting massive global economic inequalities (Darrow 2003:76). While it is argued that individual nations are responsible for their own social and economic policies, national policies are overridden by the conditions of the SAPs thereby leaving such countries indirectly losing their governance to the World Bank or the IMF (Peet, 2003). The introduction of the SAPs forced countries to enter the global market where they are struggling to survive due to its competiveness.

The emphasis on privatisation by the Bank led to a lot of job losses and states losing control of the provision of essential goods and services such as health care and education resulting in the collapse of such services. The market-driven approach to health services led to the commodification of the services leaving them unaccessible to many as they could not afford to pay for them (Darrow 2003).  Although the overall global life expectancy over the past century has increased, in developing countries that were affected by the SAPs, especially sub-Saharan Africa, the life expectancy decreased dramatically in some countries to as low as 36. This decline in life expectancy is attributed to the rise in poverty and the rise in infectious diseases such as the HIV/AIDS pandemic (WHO 1996). The rise in HIV/AIDS is also arguably linked to the SAPs in the sense that the  introduction of user fees on infectious diseases, people only accessed health services only when they showed symptoms and even still not all could access the services as they could not afford them (Rowden, 2009:148)

Baum, (2008) supported by Rowden (2009) argue that the influence of the World Bank in health issues as seen in its 1993 and 2004 reports, saw the WHO and UNICEF losing their positions as the International Public Health leaders, to the bank. They argue that the WHO’s primary care policies were overshadowed by the market-driven ideologies that led to the commodification of the health services and the increase in donor aid. The bank’s influence led to the promotion of a top-down approach which regards it as the expert in health issues at the expense of the indigenous knowledge. Such ideologies also promote the influence of imported culture which may not be appropriate for the communities, Farmer, (1999:35). The Bank has also been criticised for the types of projects it funds many of which are said to have social and environmental implications for the affected areas, (Nagel 2004).

The shortage of essential medical and drug supplies and personnel as state expenditure was reduced has led to the monopolising of the world’s trade in drugs, (Greenland, Labonte 2007).  SAPs also adversely affected food security as food subsidies were withdrawn, price supports for goods removed and prices rose, (www.fao.org). National laws such as those that protect health, safety, environment, industries and farming have also been affected by the interference of the global institutions in domestic policies of individual countries. Small industries and farmers are greatly affected as their products are undermined by cheaper imports. The free markets have also increased the monopoly of corporations at the expense of the indigenous knowledge and wealth of the poor causing uneven distribution of wealth therefore creating a wide gap between the rich and the poor countries, Global Health Watch, (2005-2006).

Although the WTO appears to be a more democratic organisation, debates on its transparency formulate from that it as a more closed organisation where many meetings are informal. These informal meetings are crucial before negotiations reach the more formal levels before a consensus can be reached between member countries. Although all member states are formally equal, in the fact that they all have the same opportunities regarding their voting power, the WTO is to a large extent controlled by the G8 while others have very limited influence and ability to keep up to date with all issues, (Global Health Watch, 2005-2006, Baum, 2008:101). The free trade agreements have negative effects on poor countries as they struggle to match the markets from developed countries. As the labour markets were deregulated, a lot of jobs were lost leading to massive increase in unemployment consequently leading to an increase in poverty. According to the WHO, over one fifth of the world’s population is living on less than two dollars a day. Furthermore the health expenditure in countries affected by SAPs declined to $13 per capita compared to the WHO’s recommended $32 per capita, (Rowden, 2009).

The three organisations have taken cognisance of some of the criticisms and debate over their legitimacy and accountability. They have demonstrated an increase in transparency through publication of policies and research which have contributed to effectiveness especially the Bank. It has improved on the way it is working with NGOs and also considered the environmental concerns of its project although some argue that there is still a lot be done in that area, (Peet, 2003). Pressure exerted on the Bank made it to reconsider its position against the universal ARV treatment. The IMF and the World Bank cancelled debts of some the poor countries. The three organisations have a lot of input in the road to achieve the Millennium Development Goals (MDGs). However, there are arguments that the MDGs alone do not address the issues of global political economic systems where rather than countries relying on donor aid; countries should be able to finance their own people’s needs using their national policies (Rowden, 2009).

Critics of the World Bank, IMF and the WTO are calling for a transformation of the global governance from neoliberalism towards governance that promotes policies that empower individual states to be responsible for their economic development. Ranges of ways on how this could be achieved have been suggested such as radical reform through collective action by different groups and organisations, decommissioning of the institutions, participation of representatives from different parts of the globe during global meetings. The representatives should be well-equipped with detailed knowledge and alternatives to policies. The NGOs have been praised and encouraged to continue with their contribution in the fight for fair global governance and some of their efforts have yielded results, (Peet, 2003; Rowden, 2009; Greenland, Labonte, 2007; Baum, 2008).  

Despite the criticisms on the World Bank, IMF and WTO, their role in securing the health and wellbeing of the world’s population is essential but there is need to address the way their policies have deviated from their original purpose to neoliberal market driven ideologies that promote the interests of a handful of countries at the expense of the lives of thousands of people who die everyday due to such policies. Similarly other international institutions responsible for health and development such as the WHO and the United Nations should also ensure that their primary aims are not being compromised by such policies.   



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Structure Organization And Function Of The Human Body Biology Essay

Biology » Structure Organization And Function Of The Human Body Biology Essay

Cell are the structural and functional units of all living organisms. Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular, or have many cells—an estimated 100,000,000,000,000 cells! Each cell is an amazing world unto itself: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Even more amazing is that each cell stores its own set of instructions for carrying out each of these activities.

Prokaryotic Cells - organisms that are lack of nuclear membrane, the membrane that surrounds the nucleus of a cell. Bacteria are the best known and most studied form of prokaryotic organisms, although the recent discovery of a second group of prokaryotes, called archaea, has provided evidence of a third cellular domain of life and new insights into the origin of life itself.

- prokaryotes are unicellular organisms that do not develop or differentiate into multicellular forms.

- are capable of inhabiting almost every place on the earth, from the deep ocean, to the edges of hot springs, to just about every surface of our bodies.

Prokaryotes are distinguished from eukaryotes on the basis of nuclear organization, specifically their lack of a nuclear membrane. Prokaryotes also lack any of the intracellular organelles and structures that are characteristic of eukaryotic cells. Most of the functions of organelles, such as mitochondria, chloroplasts, and the Golgi apparatus, are taken over by the prokaryotic plasma membrane. Prokaryotic cells have three architectural regions: appendages called flagella and pili—proteins attached to the cell surface; a cell envelope consisting of a capsule, a cell wall, and a plasma membrane; and a cytoplasmic region that contains the cell genome (DNA) and ribosomes and various sorts of inclusions.

Eukaryotes include fungi, animals, and plants as well as some unicellular organisms. Eukaryotic cells are about 10 times the size of a prokaryote and can be as much as 1000 times greater in volume. The major and extremely significant difference between prokaryotes and eukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place. Most important among these is the presence of a nucleus, a membrane-delineated compartment that houses the eukaryotic cell’s DNA. It is this nucleus that gives the eukaryote—literally, true nucleus—its name.

The outer lining of a eukaryotic cell is called the plasma membrane. This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of proteins and lipids, fat-like molecules. Embedded within this membrane are a variety of other molecules that act as channels and pumps, moving different molecules into and out of the cell. A form of plasma membrane is also found in prokaryotes, but in this organism it is usually referred to as the cell membrane.

The cytoskeleton is an important, complex, and dynamic cell component. It acts to organize and maintain the cell's shape; anchors organelles in place; helps during endocytosis, the uptake of external materials by a cell; and moves parts of the cell in processes of growth and motility. There are a great number of proteins associated with the cytoskeleton, each controlling a cell’s structure by directing, bundling, and aligning filaments.

Inside the cell there is a large fluid-filled space called the cytoplasm, sometimes called the cytosol. In prokaryotes, this space is relatively free of compartments. In eukaryotes, the cytosol is the "soup" within which all of the cell's organelles reside. It is also the home of the cytoskeleton. The cytosol contains dissolved nutrients, helps break down waste products, and moves material around the cell through a process called cytoplasmic streaming. The nucleus often flows with the cytoplasm changing its shape as it moves. The cytoplasm also contains many salts and is an excellent conductor of electricity, creating the perfect environment for the mechanics of the cell. The function of the cytoplasm, and the organelles which reside in it, are critical for a cell's survival.

Two different kinds of genetic material exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Most organisms are made of DNA, but a few viruses have RNA as their genetic material. The biological information contained in an organism is encoded in its DNA or RNA sequence.

Prokaryotic genetic material is organized in a simple circular structure that rests in the cytoplasm. Eukaryotic genetic material is more complex and is divided into discrete units called genes. Human genetic material is made up of two distinct components: the nuclear genome and the mitochondrial genome. The nuclear genome is divided into 24 linear DNA molecules, each contained in a different chromosome. The mitochondrial genome is a circular DNA molecule separate from the nuclear DNA. Although the mitochondrial genome is very small, it codes for some very important proteins.

The human body contains many different organs, such as the heart, lung, and kidney, with each organ performing a different function. Cells also have a set of "little organs", called organelles, that are adapted and/or specialized for carrying out one or more vital functions. Organelles are found only in eukaryotes and are always surrounded by a protective membrane. It is important to know some basic facts about the following organelles.

The nucleus is the most conspicuous organelle found in a eukaryotic cell. It houses the cell's chromosomes and is the place where almost all DNA replication and RNA synthesis occur. The nucleus is spheroid in shape and separated from the cytoplasm by a membrane called the nuclear envelope. The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure or interfere with its processing. During processing, DNA is transcribed, or synthesized, into a special RNA, called mRNA. This mRNA is then transported out of the nucleus, where it is translated into a specific protein molecule. In prokaryotes, DNA processing takes place in the cytoplasm.

Ribosomes are found in both prokaryotes and eukaryotes. The ribosome is a large complex composed of many molecules, including RNAs and proteins, and is responsible for processing the genetic instructions carried by an mRNA. The process of converting an mRNA's genetic code into the exact sequence of amino acids that make up a protein is called translation. Protein synthesis is extremely important to all cells, and therefore a large number of ribosomes—sometimes hundreds or even thousands—can be found throughout a cell.

Ribosomes float freely in the cytoplasm or sometimes bind to another organelle called the endoplasmic reticulum. Ribosomes are composed of one large and one small subunit, each having a different function during protein synthesis.

2. Describe and distinguish between the cell and tissue organizations and systems.

Tissues are the collection of similar cells that group together to perform a specialized function. The four primary tissue types in the human body: epithelial tissue, connective tissue, muscle tissue and nerve tissue.

Epithelial Tissue - The cells are pack tightly together and form continuous sheets that serve as linings in different parts of the body.  It serves as membranes lining organs and helping to keep the body's organs separate, in place and protected.  Some examples of epithelial tissue are the outer layer of the skin, the inside of the mouth and stomach, and the tissue surrounding the body's organs.

Connective Tissue - There are many types of connective tissue in the body.  It adds support and structure to the body.  Most types of connective tissue contain fibrous strands of the protein collagen that add strength to connective tissue.  Some examples of connective tissue include the inner layers of skin, tendons, ligaments, cartilage, bone and fat tissue.  In addition to these more recognizable forms of connective tissue, blood is also considered a form of connective tissue.

Muscle Tissue - Muscle tissue is a specialized tissue that can contract.  Muscle tissue contains the specialized proteins actin and myosin that slide past one another and allow movement.  Examples of muscle tissue are contained in the muscles throughout your body.

Nerve Tissue - Nerve tissue contains two types of cells: neurons and glial cells.  Nerve tissue has the ability to generate and conduct electrical signals in the body.  These electrical messages are managed by nerve tissue in the brain and transmitted down the spinal cord to the body.



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Structure Function Studies Of Helicobacter Pylori Urease Biology Essay

Biology » Structure Function Studies Of Helicobacter Pylori Urease Biology Essay

Urease catalyzes the hydrolysis of urea into ammonia and carbon dioxide. The release ammonia neutralizes the gastric acid, and allows the colonization of Helicobacter pylori in human stomach. The apo-urease undergoes a post-translation carbamylation of an active-site lysine residue, followed by insertion of two nickel ions essential for metal catalysis to the active site. In H. pylori, four urease accessory proteins, UreE, UreF, UreG, and UreH, are essential to the maturation process of urease. It is postulated that the apo-urease either bind a pre-formed UreG/UreF/UreH complex, or the individual urease accessory proteins sequentially to form a pre-activation complex. The Ni-binding protein UreE then interacts with the UreG of the complex, and triggers the GTP-dependent activation of urease.

How these urease accessory proteins interact with each other and with the urease to form the activation complex is poorly understood, partly because of the lack of high-resolution structures available for these urease accessory proteins. Until recently, the only urease accessory protein whose structure is available is UreE. We have recently determined the crystal structure of UreF, and have obtained a preliminary structure of the UreF/UreH complex. The novel structural information allows us to use the protein engineering approach to address the following questions: (1) Is the dimerization of H. pylori UreF/UreH complex essential to the maturation of urease? (2) Is the interaction between UreF and UreH essential to the maturation of urease? (3) Where is the interacting surface on the UreF/UreH complex that are responsible for binding UreG and the urease? As we have already obtained crystals of the UreG/UreF/UreH complex that diffract to good resolution, we propose to determine the crystal structure of this ternary complex. Through this work, the structures of all urease accessory proteins involved in urease maturation will be available, and together with the mutagenesis data, we will have a better understanding of how the urease accessory proteins associate with the urease to form the pre-activation complex for the maturation of urease.

Infection of Helicobacter pylori induces inflammation in the human stomach, and causes gastric or duodenal ulcers. High activity of urease is one of the factors that facilitate the colonization of H. pylori in the stomach. Urease catalyzes the hydrolysis of urea into ammonia, which neutralizes the gastric acid and allows the pathogen to survive in the human stomach.

In the active site of urease, there is a carbamylated lysine residue that are involved in binding two nickel ions essential to the metal catalysis of the enzyme. In H. pylori, the maturation of urease (i.e. the carbamylation of the active site lysine residue and the insertion of nickel ions) is assisted by four urease accessory proteins, namely, UreE, UreF, UreG, and UreH (UreH is the H. pylori ortholog of UreD found in other species). The current model for urease maturation suggests that the urease binds UreF, UreG and UreH to form a pre-activation complex, which then interacts with the Ni-binding protein UreE to trigger the GTP-dependent activation of urease.

How the urease accessory proteins interact with each other and with the urease for the maturation process is poorly understood. This proposal aims to address a number of important questions concerning the structure-function of urease accessory proteins UreF and UreH:

(1) Is the dimerization of H. pylori UreF/UreH complex essential to the maturation of urease?

We have determined the crystal structure of H. pylori UreF and UreF/UreH complex. Both of them exist as dimers in the crystal structure. Moreover, we showed that H. pylori UreF/UreH complex exists as a 2:2 dimer in solution. Based on the crystal structures, we will introduce mutations in the dimeric interface to break the dimerization of H. pylori UreF/UreH complex, and test if these mutations affect the in vivo maturation of urease.

(2) Is the interaction between UreF and UreH essential to the maturation of urease?

Our preliminary data showed that the truncation of the C-terminal residues of UreF breaks the UreF/UreH complex, and abolishes the activation of urease. To further investigate the functional importance of UreF/UreH interaction in urease maturation, we will introduce mutations in the interface of the UreF/UreH complex, and test if these mutations affect the formation of UreF/UreH complex, and in vivo maturation of urease.

(3) How does the UreF/UreH complex interact with UreG and the urease?

The UreF/UreH is also known to form bigger complexes with UreG, and with the urease. How UreF/UreH complex associates with UreG and the urease to form the activation complex for the maturation of urease is poorly understood. Based on the crystal structure of the UreF/UreH complex we solved, we propose to perform scanning mutagenesis to map the surface on UreF and UreH for interaction with UreG and with the urease. The mutants’ ability to form complex with UreG and the urease will be correlated with their ability to activate urease in vivo.

(4) What is the structure of UreG/UreF/UreH complex?

We have already obtained crystals of UreG/UreF/UreH complex. We propose to solve the high-resolution structure of the complex by X-ray crystallography. The structure will provide the first high-resolution structure of how these urease accessory proteins interact with each other.

Through this work, we will determine the crystal structure of UreF/UreH/UreG complex. Together with the mutagenesis data and the in vivo urease activation assay, our proposed work will contribute a significant step towards a better understanding on the structure-function relationship of these urease accessory proteins.

Objectives

To test whether the dimerization of the H. pylori UreF/UreH complex is essential to the maturation of urease

To investigate the functional interaction between UreF and UreH by mutagenesis.

To map the interaction surface on the UreF/UreH complex for binding UreG and the urease by scanning mutagenesis.

To determine the structure of UreG/UreF/UreH complex by X-ray crystallography

Activity of urease is one of the factors that facilitate colonization of Helicobacter pylori in the human stomach. Urease is a nickel-containing enzyme that hydrolyzes urea into ammonia and carbamic acid, which decomposes spontaneously into carbonic acid and ammonia [1].

NH2-CO-NH2 + H2O ? NH3 + NH2-COOH

NH2-COOH + H2O ? NH3 + H2CO3

The ammonia neutralizes the gastric acid, and allows the pathogen to survive in the human stomach.

The structure of urease from various species have been determined [2-5]. Urease is composed of ?, ? and ? subunits. In H. pylori, the ureA gene encodes the b and g subunits as a fusion protein, and the ureB gene encodes the a-subunit. In the active site of urease, a carbamylated lysine residue is involved in binding two nickel ions, which are essential to the catalysis of urea hydrolysis. The maturation of urease involves the carbamylation of the lysine residue and the insertion of nickel ions to the active site. In H. pylori, the urease accessory proteins that are involved in urease maturation are: UreE, UreF, UreG and UreH [1]. UreH is the H. pylori ortholog of UreD found in other species. In this proposal, we use the notation of ‘UreH(D)’ when we refer in general to the homologous UreH or UreD proteins, and use ‘UreH’ when we refer specifically to the protein UreH in H. pylori.

UreF and UreH(D) play pivotal roles in the formation of activation complex for the maturation of urease. UreF was reported to form complex with UreH(D) [6-9], and the two proteins interact with UreG to form the heterotrimeric complex UreG/UreF/UreH(D) [9, 10]. UreG is a SIMIBI class GTPase, which is homologous to the hydrogenase maturation factor HypB [11]. The apo-urease can form complex with UreG/UreF/UreH(D), or its components of UreH(D) and UreF/UreH(D) [9, 10, 12, 13]. It has been shown that apo-urease can be activated in vitro by just adding excess amount of carbon dioxide and nickel ion [14]. The in vitro activation of urease is increased when in complex with UreF/UreH(D) and UreG/UreF/UreH(D) [13, 15]. Chemical cross-linking experiments suggest that binding of UreF/UreH(D) may induce conformational changes of the urease [16], which may allow the diffusion of nickel ion and carbon dioxide into the active site to promote activation of urease [17].

The current model for in vivo urease maturation proposed by Hausinger’s group is illustrated in Fig. 1 [1]. The apo-urease interacts with UreG, UreF and UreH(D) to form a pre-activation complex. UreE, a dimeric nickel-binding protein, then interacts with UreG of the complex, and triggers the GTP-dependent activation of urease [15, 18, 19].

The formation of activation complex for the maturation of urease involves protein-protein interaction among the urease accessory proteins and the urease. However, structure-function studies of how these urease accessory proteins interact with each other was only poorly understood. One obstacle was that expression of UreH(D) alone in E. coli resulted in the formation of inclusion bodies. Recently, Hausinger’s group has successfully expressed soluble K. aerogenes UreD in fusion with the maltose binding protein (MBP-UreD), which allows for the first time in vitro characterization of UreH(D). They showed that UreH(D) can interact with UreF in ~ 1:1 binding ratio, but only weakly with UreG [9].

Until recently, the only urease accessory protein whose structure is available is UreE [18, 20-22]. The structure of UreF was recently determined by Chirgadze’s group [23], and in parallel, by our group [24]. The work proposed here will fill the much-needed gap of knowledge on the structure-function studies of urease accessory proteins.

1. We have determined the crystal structure of H. pylori UreF. Our group has determined the crystal structure of H. pylori UreF using the MAD method with Se-Met labeled protein [24]. The structure of the native UreF, refined to 1.85 Å resolution by us, is similar to the structure of Se-Met derivative reported independently by Lam et al. [23]. UreF is an all-alpha protein consisting of 10 helices. It forms dimers in the crystal structure (Fig. 2). The dimeric interface is formed by docking of helix-1 to the helix-8 and helix-9 of the opposite UreF molecule.

2. We have established an efficient protocol to express and purify UreF/UreH complex. As mentioned above, one obstacle for the structure-function studies of the UreF/UreH complex was that expression of UreH alone resulted in insoluble inclusion bodies (Fig. 3). We have successfully solved this problem by co-expressing UreH with GST-UreF in E. coli (Fig. 3). After affinity chromatography purification and removal of the GST-fusion tag, the UreF/UreH complex can be purified in large quantity (~10 mg per liter of bacterial culture).

3. We have established assays to correlate in vitro protein-protein interactions with in vivo maturation of urease. We showed that when co-expressed together, UreF and UreH form a soluble complex that can be pull-down by GST affinity column (Fig. 4A, lane 2). We noticed that the C-terminal residues of UreF were protected from degradation upon complex formation with UreH (Fig. 4A, lane 1 & 2). We showed that truncation of the C-terminal residues of UreF (UreF-DC20) disrupted the formation of a soluble UreF/UreH complex (Fig. 4A, lane 3). We have also established an assay to test the in vivo maturation of urease (Fig. 5), and showed that the mutation (UreF-DC20) that disrupted the interaction between UreF and UreH also abolished in vivo maturation of urease. By GST pull-down, we demonstrated that the UreF/UreH complex interacts with UreG (Fig. 4B, lane 4), and with the urease (Fig. 4B, lane 4). These preliminary data demonstrated that feasibility of the proposed structure-function studies.

4. We have obtained the preliminary crystal structure of H. pylori UreF/UreH complex. With the purified UreF/UreH complex, we were lucky to obtain crystals of the complex that diffract to high resolution (Fig. 6A). Diffraction data was collected to 2.5Å resolution. We phased the structure by molecular replacement using the structure of UreF as a search template. Our preliminary structure of UreF/UreH complex showed that the UreF/UreH complex forms a 2:2 dimer in the crystal structure (Fig. 6B). We anticipate that the refinement of the UreF/UreH complex structure will be finished very shortly, and the structure will provide a rational based for the mutagenesis studies proposed in this study.

5. We have showed that the UreF/UreH complex form dimers in solution. To test if the UreF and UreF/UreH form dimers in solution, we have loaded purified samples of UreF and UreF/UreH to an analytical size-exclusion-chromatography column coupled to a static light scattering detector (Fig. 7). The apparent M.W. for UreF was 43 kDa, which is in between the theoretical M.W. of a monomeric (28 kDa) and a dimeric (56 kDa) form of UreF. The results suggest that UreF alone does have a tendency to form dimers, and the dimeric form of UreF is in exchange with the monomeric form in solution. On the other hand, the formation of dimer is more-or-less complete in the UreF/UreH complex. The apparent M.W. measured for UreF/UreH complex was 116 kDa, which is consistent with the theoretical M.W. of 116 kDa for a 2:2 dimer of UreF/UreH complex.

6. We have established an efficient protocol to express and purify UreG/UreF/UreH complex, and obtained crystals of the complex. We have found that the most efficient way to obtain the H. pylori UreG/UreF/UreH complex is to co-express UreG, GST-UreF and UreH together in E. coli. The ternary complex can be easily purified by affinity chromatography followed by removal of GST-fusion tag by protease digestion. In our hand, the yield of UreG/UreF/UreH complex is ~5mg per liter of bacterial culture. More encouraging is that we have successfully obtained crystals of UreG/UreF/UreH that diffracted to a reasonable resolution of ~3Å (Fig. 8). These preliminary data strongly suggest that the proposed structure determination of the ternary complex of UreG/UreF/UreH by X-ray crystallography is highly feasible.

Track Record of PI

The PI has extensive experience on structure determination by both NMR and X-ray crystallography, and using protein engineering to probe the structure-function of proteins. In addition to the structure determination of UreF and UreF/UreH complex discussed above, he has solved the solution structure of barstar, an inhibitor of barnase, and studied its dynamics behavior by NMR spectroscopy [25, 26]. He also studied the effect of mutations on the stability and structural perturbation on the DNA-binding domain of the tumor suppressor p53 by NMR spectroscopy [27, 28]. He has used an approach that combines evidence from NMR experiments and molecular dynamics simulation to study the folding pathway and the denatured states of barnase and chymotrypsin inhibitor-2 [29-31]. Supported by previous GRF grants, he solved the solution [32] and crystal [33] structure of ribosomal protein L30e from Thermococcus celer, the crystal structures of a thermophilic acylphosphatase from Pyrococcus horikoshii to 1.5Å [34], and human acylphosphatase to 1.45Å [35], an orange fluorescent protein from Cnidaria tube anemone to 2.0Å [36], seabream antiquitin to 2.8Å [37], the crystal structure of trichosanthin in complex with the C-terminal residues of ribosomal stalk protein P2 to 2.2Å [38], and the solution structure of the N-terminal dimerization of P2 [39]. We believe that, with our strong background in structural biology and the solid preliminary data, we are in a leading position to determine the structure of the UreG/UreF/UreH ternary complex, and to study the how the urease accessory proteins interact with each other for the maturation of urease.

Our preliminary data suggest that the H. pylori UreF/UreH complex forms a 2:2 dimer in solution. Both the crystal structure of H. pylori UreF, and the preliminary structure of UreF/UreH complex suggest that the dimerization is likely to be mediated by UreF. It is presently not known whether the dimerization is a unique property of H. pylori UreF - for example H. pylori and K. aerogenes UreF only share 19% sequence identity. Interestingly, the quaternary structure of H. pylori urease is different from ureases from other bacterial species. Unlike the urease (UreABC) from K. aerogenes that forms a trimeric complex (UreABC)3, the H. pylori urease (UreAB) forms a tetramer of trimers ((UreAB)3)4. Nevertheless, that H. pylori UreF/UreH complex exists as a dimer in solution and in crystal structure raises an interesting question - is the dimerization of H. pylori UreF/UreH complex essential to the maturation of urease?

To address this question, we will introduce mutations that are designed to break the dimerization of UreF and UreF/UreH complex. As shown in Fig. 2, the dimeric interface is formed by docking of helix-1 to the helix-8 and helix-9 of the opposite UreF molecule. A closer look at the dimeric interface of the crystal structure of UreF reveals a number of interactions that may be importance to the dimerization of UreF (Fig. 9). For example, to break the hydrogen bonding network among Q37, Q205 and Q212, we will replace the Gln residue with either alanine or asparagine to create triple mutants of Q37A/Q205A/Q212A and Q37N/Q205N/Q212N. We anticipate that both truncation of and shortening of the amide chain should break the hydrogen bond network. To disrupt the hydrophobic interaction around F33, we will substitute the Phe residue with alanine (F33A) or with a polar residue (e.g. F33R). Substitution of polar residue like arginine at Phe-33 should highly disfavor dimerization because the high desolvation penalty will prevent the polar residue to be buried upon dimerization. If necessary, we will create quadruple mutants (e.g. Q37A/Q205A/Q212A/F33A) to ensure disruption of UreF dimerization.

3.1.1 GST pull-down assay for UreF/UreH interaction. First, we test if these mutants will affect the formation of soluble UreF/UreH complex by GST pull-down assay (Fig. 4A). UreH will be co-expressed with mutants of UreF fused with GST-tag, and the bacterial lysate will be loaded to a GSTrap column (GE Healthcare). After extensive washing with binding buffer (20 mM Tris pH7.5, 0.2M NaCl, 5mM DTT), the proteins will be eluted with 10mM glutathione.

As these mutations are located at the dimerization interface, which are far away from the UreF/UreH interface, we anticipate that they will not affect UreF/UreH interaction.

3.1.2 Size-exclusion-chromatography/static-light-scattering (SEC/LS). We will test if these mutants affect dimerization of UreF by SEC/LS. Purified samples of UreF mutants and its complex with UreH complex will be loaded to an analytical Superdex 200 column connected to an online miniDawn light scattering detector and an Optilab DSP refractometer (Wyatt Technologies). The light scattering data will be analyzed using the ASTRA software provided by the manufacturer to obtain the molecular weight of the protein samples.

If the mutations break the dimerization, we anticipate that the measured molecular weight will be 28 kDa for UreF, and 58 kDa for UreF/UreH complex.

3.1.3 In vivo maturation of urease. We will test if test if these mutants affect in vivo maturation of urease. We have established an assay for in vivo maturation of urease (Fig. 5). We have cloned the H. pylori urease operon, ureABIEFGH, into the pRSETA vector to create the pHpA2H vector. We will introduce the mutations into the ureF gene in the pHpA2H vector. E. coli will be transformed with wild-type and mutant pHpA2H vectors, or the negative control plasmids (pHpAB and the empty vectors). The bacterial cells will be grown in the presence of 0.5 mM nickel sulfate, and were induced overnight with 0.4 mM IPTG. After cell lysis by sonication, urease activity of the bacterial lysate will be assayed in 50 mM HEPES buffer at pH 7.5 with 50 mM urea substrate, and will be measured by the amount of ammonia released using the method described in ref. [40].

If the dimerization of UreF and UreF/UreH is essential to the maturation of urease, the mutations that break the dimerization will also abolish the maturation of urease. On the other hand, if the maturation of urease is not affected by these mutations, it is likely that the dimerization is not essential to the urease maturation.

Our preliminary data showed that removal of the C-terminal residues of UreF breaks the UreF/UreH complex, and abolishes the maturation of urease. The availability of a preliminary structure of UreF/UreH complex allows us to introduce site-directed mutations that are designed to break the UreF/UreH interaction, and to further investigate the functional importance of UreF/UreH interaction. Our structure showed that upon complex formation, the C-terminal residues of UreF become structured and form an extra helix (helix-11) that dock to a binding cavity of UreH. Three hydrophobic residues V235, I239, and M242 on helix-11 are buried to a hydrophobic pocket of UreH.

To further investigate the functional importance of UreF/UreH interaction in urease maturation, we will create alanine and hydrophobic-to-polar (e.g. V?N) substitutions at V235, I239 and M242, which are designed to break the UreF/UreH complex formation. We will test if these mutations affect the formation of the UreF/UreH complex by the GST pull-down assay described in 3.1.1, and if they affect maturation of urease as described in 3.1.3. If the interaction between UreF and UreH is essential to the maturation of urease, we anticipate the mutations that break the UreF/UreH interaction will also abolish the maturation of urease.

The UreF/UreH is also known to form bigger complexes with UreG, and with the urease (UreA/UreB). How UreF/UreH complex associates with UreG, and the urease to form the pre-activation complex (UreA/UreB-UreG/UreF/UreH) for the maturation of urease is poorly understood. It has been reported that UreG does not interact directly to the urease, suggesting the UreF/UreH complex serves as a bridge that recruits UreG to the activation complex.

Our group has recently collected 2.5Å diffraction data for the H. pylori UreF/UreH, and has obtained a preliminary structure of the complex, which allows us to identify surface residues of UreF and UreH. To map the interacting surface of UreF/UreH complex for binding of UreG and the urease (UreA/UreB), we propose to perform alanine-scanning mutagenesis of surface residues on UreF and UreH. We will first focus on relatively more conserved surface residues (For UreF: P44, I45, Y48, S51, E55, Y72, E119, R121, Y183, K195, Q201, Q205, H244, E245, R250, L251, S254. For UreH: D60, G61, T78, K84, P111, I115, F177, E140, R146, E151, R213). We will also introduce multiple substitutions at these residue positions, if they are close in space according to the preliminary structure of UreF/UreH complex. We will first test if these mutations affect UreF/UreH interaction as described in 3.1.1. If so, we will exclude those mutants from the library.

After we have created the mutant library of UreF/UreH complex, we will test the mutants' ability to form complex with UreG, and with the urease (UreA/UreB). In brief, mutants of the GST-UreF/UreH complex will be co-expressed in E. coli. Our preliminary data suggest that the GST fusion tag will not interfere with binding of UreG or UreA/UreB (Fig. 4B). The bacterial lysate of GST-UreF/UreH (or its mutants) will be mixed with bacterial lysate expressing UreG or UreA/UreB, and then loaded to a GSTrap column for the pull-down assay. For those mutations that break the interaction, we will also perform the reciprocal pull-down in which the GST-tag is fused to the UreH, UreG, UreA or UreB. This is to confirm that the breakage of interaction is due to the mutations, but not due to a nearby GST-tag.

To address the question if the interaction between UreF/UreH and UreF (or UreA/UreB) is essential to maturation of urease, we will test the ability of the UreF/UreH mutants to activation urease in vivo as described in 3.1.3. If the interaction is essential to urease maturation, we anticipate the mutations that break the interaction will also abolish the urease maturation.

3.4.1 Expression and purification of UreG/UreF/UreH complex - We have established an efficient expression purification protocols for the ternary UreG/UreF/UreH complex. His-GST-tagged UreF, UreG and UreH will be co-expressed together in E. coli BL21(DE3) strain using the expression plasmids pET-Duet-HisGST-UreF/UreG and pRSF-UreH. After affinity chromatography purification, the His-GST fusion tag will be removed by the PreScission Protease (GE Healthcare). The protein complex will be further purified by gel filtration. Typical yield of the UreG/UreF/UreH complex is ~ 5mg per liter of bacterial culture.

3.4.2 Optimization of crystallization conditions - Preliminary screening of crystallization conditions was performed. We have already obtained crystals of the UreG/UreF/UreH that diffract to ~3Å (Fig. 8). We will further optimize the crystallization condition by grid-searching the pH and precipitant concentrations, and addition of additives or detergents. Quality of the diffraction data will be used to guide optimization of the crystallization conditions. We will also optimize the cryo-protection procedures (e.g. the choice of cryo-protectants and their concentration) to improve the quality of diffraction data collected. When necessary, we have access to synchrontron beam line at Diamond Light Source, Oxford, through collaboration with Dr. Yu-Wai Chen (King's College London).

3.4.3 Phase determination - We will first attempt to phase the structure by molecular replacement. At the time of writing this proposal, we are refining the structure of H. pylori UreF/UreH complex. We will use the UreF/UreH complex structure as a search template to solve the phase of the UreG/UreF/UreH complex by molecular replacement. In parallel, we will also prepare selenium-methionine labeled sample of UreG/UreF/UreH for multi-wavelength anomalous diffraction (MAD) phasing by expressing the protein complex in minimal medium containing Se-Met as described in Doublie [41]. The H. pylori UreG, UreF, and UreH proteins contain 9, 10, and 8 methionine out of 199, 254, and 265 residues, which should provide enough phasing power for MAD phasing. The PI's group has previously established the expression protocols for Se-Met labeling for H. pylori UreF, and determined its structure by MAD phasing. We have access to synchrontron beam line at Diamond Light Source for collection of MAD data.

3.4.4 Model building and refinement - Models will be built interactively by the program COOT [42], and refined using PHENIX [43]. The progress of refinement will be monitored by Rfree- and R-factors. Quality of the crystal structure will be validated by the program MOLPROBITY [44].



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Secured Products To Function Engineering Essay

 


We need to look at the assembly because it is a key activity in manufacturing, as most products consist of several parts which must be collected together and secured for product to function.


Also it give us degree of movement freedom and mobility for various elements and enable material differentiation .therefore the various assembly methods can be classified into three elementary methods, manual assembly, mechanical assembly and robotic assembly


Assembly is very common, and perhaps regarded as necessary, but we should try to avoid it where ever we can, that way effects have been in over the years to find other methods to avoid assembly.


Due to high cost of labour, another method was considered, which is the automation and its main goals is to integrate various aspects of manufacturing operations to improve quality and minimize time cycle and labour cost.


Also it improves productivity, reduce human involvement, raise level of safety to personnel and reduce cost in raw material.


1.1 Flexibility is where the various individual manufacturing systems are incorporated into a single large scale system, in which the production of parts is controlled with the aid of a computer, and the advantages of this production system is a high flexibility for small effort and short time required to manufacture a new product.


1.2 Manual assembly: in manual assembly, the most significant factors are the sensors available in the form of vision, touch and sometimes hearing, also the ability of the assembler to make sensible judgment very quickly.


For parts with tolerances defects, the judgment becomes important when assembly, and the possibility that exist are: the part inserted can not reach its final location or the pert reaches the final location but does not give the require assembly.


Manual assembly is used in production situation where the work to be performed can be divided into small tasks, and the advantages in using manual assembly is using specialisation of labour by giving each one set of tasks to do repeat ably , this require high labour content therefore results in high cost.


It is a system where mechanical, electrical and computer-based system is used to operate and control production, this technology includes automatic machine tools, automatic assembly machines, industrial robot, storage automatic inspection system, feed back control and computer process control.


Types of automations : Fixed automation ,Flexible automation and programmable automation.


Reasons for Automating : some of these important reasons for automating are as follows :


Increase productivity, this mean grater out pit per hour of labour input , higher production rate achieved with automation than with manual operation.


High cost of labour: is enforcing business leaders to substitute machines for human labour.


Labour shortage.


Safety: by using automation the operation and transferring the operator from an active participation to a super visionary roll, work is made safer.


High cost of raw material: in manufacturing results in the need for greater efficiency is using this material, the reduction of scrap is one of these benefits.


Therefore when large production required quantity and high production rates, automation is used and examples of these products are:


Electric components.


Electronic components.


Bolting plants.


Tablet manufacturing plants etc.


1.4 The advantages of automated systems are:


Reduce labour cost and manufacturing lead time.


Increase labour productivity.


Improve product quality.


Increase production rate.


Reduce material handling cost and time.


Increase manufacturing control.


Improve workers safety.


Overcome limitation of manual labour,


Too expensive.


Some tasks are too difficult to automate.


Problems with physical access to work location.


Short product life cycle.


Usually one of a kind product is produced.


Reduce the risk of product failure.


1.5 The objective of the assignment is try to implement all the knowledge gained in the automation module on the chosen artefact “the electric switch”, and the intention is to disassemble the exercise, study it carefully and design a system to be assembled in large quantities and cost effectiveness by means of automation and manual processes.


Marketing history


The single electric switch is the most common type of switches, as it is found in


every house, office or factory, it is essential to the power source as its simple and


easy to use and economic due to low price.


There are more than one type on this off/on switch, single, double and they are


made of different type materials, plastic ,steel coated , chrome plated etc ,this


makes its prices varies


The main components of the lighting switch are:


Base: it is usually made of plastic material (pvc), and some manufacturer makes


them from chrome plated steel or any other safe long life material.


The switch button: it is the mechanical part of the switch ( acts as actuator), as its main function is to initiate the switch circuit operation (open and close), and is made of the same material as the base. For safety reasons the material should be a very good insulator.


2b- Spring: it is a small spring made of good steel, and is part of the mechanical


action, and assists in switching the power from on to off and vice versa


also due to its elasticity it last along time and prevents contact between solid parts.


Housing: this is the main part of the switch, as it contains all the electrical parts (terminals and their accessories), and is moulded plastic products ,which makes it good insulator to all the power terminals.


3a- Terminal (1) : consists of a block ,element, and a screw for tightening the


electrical wire, brass or copper is usually the martial that terminals are made of ,


and as known are good electricity conductors. (This is the common terminal)


3b- Terminals (2) & (3), made from the same material as terminal (1), the contacts


in all terminal are made of low resistance metal that makes or break the circuit


Each terminal consist of block (3b), element (3b1) and wire fasten screw (3b2).


Screw: fastens the housing assembly to the main base


1


2


2a


3


3a


3a1


3a2


3b


3b1


3b2


4


Base


Button


spring


Housing


Terminal 1(block)


Element


Screw


Terminal 2”block”(2 ea )


Element (2ea)


Screw (2ea)


Fastening screws


1


2


3


4


5


6


7


8


9


Load Assembly base into work carrier


Assembly subassembly Button


Assembly subassembly Terminal 1


Assembly subassembly Terminal 2


Assembly subassembly Terminal 3


Assembly subassembly housing to base


Check


Assembly screw


Remove compete switch


switch


Base


1


Button sub assy 2


Sub assembly housing


3


Screw


4


2


2a


3


Terminal 3a


3b (2 each)


3a


3a 1


3a 2


3b(2)


3b1(2)


3b2 (2)


b) Product structure


2


2b


4


1


3


3a


3a1


3a2


3b


3b1


3b2


c) Assembly structure based components


2


1


6


7


8


9


5


3


4


d) Assembly structure based on subassemblies


Product and Assembly Structure Charts


Component


description


Component number


Functional analysis


Manufacturing analysis


Feeding/loading analysis


Gripping Process


Work holding process


Inspection Process


Non Assembly Process


Sub assembly Total


Assembly Total


1.2


Base


1


A


1.3


2.2


1.5


Button


2


A


1.2


1


1


1


Spring


2a


A


2.1


1


1


Housing


3


A


1.3


2.2


1


Terminal 1


3a


A


1.5


1.5


1


Element


3a1


A


2.4


4


1


Screw


3a2


B


2.1


2.2


1


Terminal 2


3b


A


1.5


1.5


1


Element


3b1


A


2.4


4


1


Screw


3b2


B


2.1


2.2


1


1.5


Screw


4


B


2.1


2.2


1


Total


11


20


23


13.7


Design Efficiency = A component 8 x 100% = 72


Total Compts 11


Feeding Handling Ratio = Index Total ___20_____ = 1.8


A copmts 11


Fitting Ratio = Gripp-fit fix = __________________


A Compts


The design for assembly addresses product structure simplification; sense the total number of parts in a product is a key indicator of product assembly quality


A number on different DFA methods have bee development, and to be any interest to designers they need to be:


Complete i.e. have objectivity and creativity.


Systematic- which helps to ensure that all relevant issues are considered i.e. the organization of objective and creative parts of DFA methods.


Measurable and user-friendly


3.1 Lucas Method the method is based around an” assembly sequence flowchart”. The Lucas/Hull group has developed a knowledge based evaluation technique, it follows a procedure in which the important aspects of assemble and component manufacture are considered and rated. The system is to be integrated into a CAD system, where it should be possible to obtain the information required for the analysis work with the minimum of effort and time.


- Functional analysis


- Handling analysis, and this can be manual or feeding assembly


-Fitting analysis


Depending on this method the Artefact was disassembled and a view drawn shown all components (pieces), also a build up structure and an assembly structure were made (page 6).


3.2 Functional Analysis: is carried out according to the rule of value analysis and activities, degree of functional importance is then categorized.


Each activity is put to the system in turn, a description and name is given for parts.


The assembly parts for the artefact were carefully investigated and categorised into either “A” parts (demand by function) and “B” parts, and these by design only, from that the design for efficiency was:


NO of “A” components x100


Total NO of components


8 x 100 = 72%


11


As all components and subassemblies manufactured in different places and will be presented to same point for assembly so our analysis considered three areas:


Handling difficulties


The size of the component


The weight of the component


The transfer mechanism of a flow line must not only move partially completed work parts or assemblies between stations, it must also orient and locate the parts in the correct position for processing at each station, the general method for transporting can be classified to:


Continuous transfer


Synchronous transfer


Power and free transfer


The most suitable type of transport system for a given application depends on the following factors:


-The type of operation to be performed.


The number of stations on the line.


The work piece size and weight.


There are a various types of parts feeding devises and the most common are:


- Hopper, where components are loaded at the work station, they usually loaded into the hopper in bulk; this means they are randomly orientated in the hopper.


- Parts feeder: This mechanism removes the components from the hopper one at a time for delivery.


- Orientator: where proper orientation is established


- Feed back: used to transfer the components from the hopper and parts feeder to the location of the assembly work head.


The quality of gripping is the ability to hold a part in a way that allows the part to be inserted with the proviso that insertion is possible.


In manual assembly, the parts handling does not have gripping problems because of ability of people to perform insertion operation despite poor relationship between the mating parts.


The best grip must be a three point grip whose lines of action equally


spaced and act through a common point


Another common possibility is a three point grip, where positional errors perpendicular to the direction of grip are possible.


For flexible assembly it is advised to do the following for different tasks:


Use a universal gripper.


Use a turret of gripper.


Use gripper changing.


Use special multi-purpose gripper


The gripping is usually used for the parts witch are difficult to assemble in position due to its size or shape, and this case it is needed when assembly of the power wiring screws and the terminals in the housing.


In manual insertion, the basic insertion action is different to the automatic one. The part being inserted is deliberately misaligned so that contact is established between the mating parts, a combination of touch and sight then interact with the movement to do the operation.


There are three examples show this:


Even in blind situation, one a contact has been made the insertion operation is easy. Attempts by operator to achieve a relatively open tolerance insertion with out mating parts touching are usually unsuccessful.


People are not good at close tolerances.


In automated assembly no touch is needed if there is good alignment.


There are common design roles for assembly processes:


Insert from vertically.


Use chambers, tapers to assist in alignment.


Choose open tolerances as possible.


Do not have more than one insertion site.


Design so the can be released as soon as insertion has started


From the previous analysis tables there are two steps can be taken to redesign the “switch” or artefact:


- The terminal should come as a complete unit, this means the element is welded to the block and the screw in position, this will minimise the steps of the assembly and safe time and cost.


- The housing can be assembled to base by means of” snap fitting instead of the fastening screws.


The outcome of this redesign will result in:


A Reducing parts count


B Ensuring a visible assembly process at a minimum cost


C Reliable automatic assembly achieved


d- Standardisation of components


The FMS provides the efficiency of mass production for batch production, and its main advantages are:


- Increased productivity


- Shorten preparation time for new products


- Reduction of inventory parts


- Saving of labour cost


- Improved product quality


- Attracting skilled people


- Improved operators safety


4.1 Activity Flow Chart


Vibrator Bowel


5


Refuse tray


Poka Yoka


Stack magazine


Linear vibrator


1


4


2


3


Full Ballet


Pallet Magazine


6


ROBOT


Rotary Bowel Feeder


Feed the housing by means of a stack magazine, this magazine must be set up for each “switch” variant. (The housing should be held into the work carrier and secured).


Feed subassembly terminal 1 with the aid of a ballet magazine.


Feed subassembly terminals 2&3 with the aid of a ballet magazine.


Feed the base by the aid of a linear vibrator.


Feed button in base by the aid of vibrator bowel.


Feed the spring by the means of vibratory bowel feeder


Place the subassembly housing on base by means of snap.


Remove of acceptable completed assemblies with the aid of an index transfer system provided with ballets.


The sequences are handled with a Scara Robot with a gripper change system which are used to handle the terminals.


There are 3 work stations in this assembly, the assembly of the housing station, the assembly of the base station, and the third is the completed assembly station


The feed devises used are


Ballet magazine.


Stack magazine.


Linear vibrator.


Vibrator bowel


Poka Yoka : is used to test if the terminals are fitted in position or not.


The advantages of the proposal of re-designing the artefact could be summarized in the following:


Lower manpower cost.


Less automation or feeders) used.


Less time.


More productivity.


More safety


The cost after the re-design proposal should in general be cut down, and regarding the implementation stages there is no transfer from manual to semi-automation noted, but the main changes occurred are in the terminals, as they feed pre-assembled, so this will reduce time ,automated equipment and tooling.


Also the fasten screw is replaced by means of snap fitting, which will result in increase of the “A” numbers and therefore increase in the overhaul efficiency.



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