Bacterial Biofilm: Its Composition, Formation and Role in Human Infections

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Pseudomonas helmanticensis Ramírez et al. There are worse vices than McDonald's, but it's an easy target for the pious elite Tom Welsh. These mice were treated with cyclophosphamide to inhibit leukocytes. Journal of Bioscience and Bioengineering Revista da Sociedade Brasileira de Agronomia , , 12 ,

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Select materials that will not contribute TOC and particles to the system particularly in the primary and polishing sections. Minimize stainless steel material in the polishing loop and if used electropolishing is recommended. Maintain minimum scouring velocities in the piping and distribution network to ensure turbulent flow.

The recommended minimum is based on a Reynolds number of 3, Re or higher. This can range up to 10, Re depending on the comfort level of the designer. Supply UPW to manufacturing at constant flow and constant pressure to avoid system upsets such as particle bursts.

Utilize reverse return distribution loop design for hydraulic balance and to avoid backflow return to supply. Capacity plays an important role in the engineering decisions about UPW system configuration and sizing.

Larger fabs required larger size UPW systems. The figure below illustrates the increasing consumption driven by the larger size of wafer manufactured in newer fabs.

The industry responded to this issue and through extensive investigation, choice of higher purity materials, and optimized distribution design was able to reduce the design criteria for minimum flow, using Reynolds number criteria. The figure on the right illustrates an interesting coincidence that the largest diameter of the main supply line of UPW is equal to the size of the wafer in production this relation is known as Klaiber's law.

Growing size of the piping as well as the system overall requires new approaches to space management and process optimization. As a result, newer UPW systems look rather alike, which is in contrast with smaller UPW systems that could have less optimized design due to the lower impact of inefficiency on cost and space management. Another capacity consideration is related to operability of the system.

Small lab scale a few gallons-per-minute-capacities systems do not typically involve operators, while large scale systems usually operate 24x7 by well trained operators. As a result, smaller systems are designed with no use of chemicals and lower water and energy efficiency than larger systems.

Particles in UPW are critical contaminants, which result in numerous forms of defects on wafer surfaces. With the large volume of UPW, which comes into contact with each wafer, particle deposition on the wafer readily occurs. Once deposited, the particles are not easily removed from the wafer surfaces. With the increased use of dilute chemistries, particles in UPW are an issue not only with UPW rinse of the wafers, but also due to introduction of the particles during dilute wet cleans and etch, where UPW is a major constituent of the chemistry used.

While filters are used for the main loop, components of the UPW system can contribute additional particle contamination into the water, and at the point of use, additional filtration is recommended. Common materials include nylon , polyethylene , polysulfone , and fluoropolymers.

Filters will commonly be constructed of a combination of polymers, and for UPW use are thermally welded without using adhesives or other contaminating additives. The microporous structure of the filter is critical in providing particle control, and this structure can be isotropic or asymmetric. In the former case the pore distribution is uniform through the filter, while in the latter the finer surface provides the particle removal, with the coarser structure giving physical support as well reducing the overall differential pressure.

Filters can be cartridge formats where the UPW is flowed through the pleated structure with contaminants collected directly on the filter surface. In this configuration, the UPW is flowed across the hollow fiber, sweeping contaminants to a waste stream, known as the retentate stream. The retentate stream is only a small percentage of the total flow, and is sent to waste. The product water, or the permeate stream, is the UPW passing through the skin of the hollow fiber and exiting through the center of the hollow fiber.

The UF is a highly efficient filtration product for UPW, and the sweeping of the particles into the retentate stream yield extremely long life with only occasional cleaning needed. Use of the UF in UPW systems provides excellent particle control to single digit nanometer particle sizes. For wet etch and clean, most tools are single wafer processes, which require flow through the filter upon tool demand.

The resultant intermittent flow, which will range from full flow through the filter upon initiation of UPW flow through the spray nozzle, and then back to a trickle flow.

The trickle flow is typically maintained to prevent a dead leg in the tool. The filter must be robust to withstand the pressure and low cycling, and must continue to retain captured particles throughout the service life of the filter. This requires proper pleat design and geometry, as well as media designed to optimized particle capture and retention.

Certain tools may use a fixed filter housing with replaceable filters, whereas other tools may use disposable filter capsules for the POU UPW. For lithography applications, small filter capsules are used. Similar to the challenges for wet etch and clean POU UPW applications, for lithography UPW rinse, the flow through the filter is intermittent, though at a low flow and pressure, so the physical robustness is not as critical.

Point of use treatment is often applied in critical tool applications such as Immersion lithography and Mask preparation in order to maintain consistent ultrapure water quality. UPW systems located in the central utilities building provide the Fab with quality water but may not provide adequate water purification consistency for these processes.

In the case when urea, THM, isopropyl alcohol IPA or other difficult to remove low molecular weight neutral compounds TOC species may be present, additional treatment is required thru advanced oxidation process AOP using systems. This is particularly important when tight TOC specification below 1 ppb is required to be attained. These difficult to control organics have been proven to impact yield and device performance especially at the most demanding process steps.

One of the successful examples of the POU organics control down to 0. The semiconductor industry uses a large amount of ultrapure water to rinse contaminants from the surface of the silicon wafers that are later turned into computer chips used in devices we use every day. The ultrapure water is by definition extremely low in contamination, but once it makes contact with the wafer surface it carries residual chemicals or particles from the surface that then end up in the industrial waste treatment system of the manufacturing facility.

The contamination level of the rinse water can vary a great deal depending on the particular process step that is being rinsed at the time. Typical semiconductor plants have only two drain systems for all of these rinses which are also combined with acid waste and therefore the rinse water is not effectively reused due to risk of contamination causing manufacturing process defects. The following definitions are used by ITRS: Some semiconductor manufacturing plants have been using reclaimed water for non-process applications such as chemical aspirators where the discharge water is sent to industrial waste.

Water reclamation is also a typical application where spent rinse water from the manufacturing facility may be used in cooling tower supply, exhaust scrubber supply, or point of use abatement systems. UPW Recycling is not as typical and involves collecting the spent manufacturing rinse water, treating it and re-using it back in the wafer rinse process. Some additional water treatment may be required for any of these cases depending on the quality of the spent rinse water and the application of the reclaimed water.

These are fairly common practices in many semiconductor facilities worldwide, however there is a limitation to how much water can be reclaimed and recycled if not considering reuse in the manufacturing process. Recycling rinse water from the semiconductor manufacturing process has been discouraged by many manufacturing engineers for decades because of the risk that the contamination from the chemical residue and particles may end up back in the UPW feed water and result in product defects.

Modern Ultrapure Water systems are very effective at removing ionic contamination down to parts per trillion levels ppt whereas organic contamination of ultrapure water systems is still in the parts per billion levels ppb.

In any case recycling the process water rinses for UPW makeup has always been a great concern and until recently this was not a common practice. Increasing water and wastewater costs in parts of the US and Asia have pushed some semiconductor companies to investigate the recycling of manufacturing process rinse water in the UPW makeup system.

Some companies have incorporated an approach that uses complex large scale treatment designed for worst case conditions of the combined waste water discharge. More recently new approaches have been developed to incorporate a detailed water management plan to try to minimize the treatment system cost and complexity.

The key to maximizing water reclaim, recycle, and reuse is having a well thought out water management plan. A successful water management plan includes full understanding of how the rinse waters are used in the manufacturing process including chemicals used and their by products. With the development of this critical component, a drain collection system can be designed to segregate concentrated chemicals from moderately contaminated rinse waters, and lightly contaminated rinse waters.

Once segregated into separate collection systems the once considered chemical process waste streams can be repurposed or sold as a product stream, and the rinse waters can be reclaimed. A water management plan will also require a significant amount of sample data and analysis to determine proper drain segregation, application of online analytical measurement, diversions control, and final treatment technology.

Collecting these samples and performing laboratory analysis can help characterize the various waste streams and determine the potential of their respective re-use. In the case of UPW process rinse water the lab analysis data can then be used to profile typical and non-typical levels of contamination which then can be used to design the rinse water treatment system.

Stainless steel remains a piping material of choice for the pharmaceutical industry. From Wikipedia, the free encyclopedia. This article may be confusing or unclear to readers. Please help us clarify the article. There might be a discussion about this on the talk page. July Learn how and when to remove this template message. Traditionally the resistivity of water serves as an indication of the level of purity of UPW. Typical UPW quality is at the theoretical maximum of water resistivity Therefore the term has acquired measurable standards that further define both advancing needs and advancing technology in ultrapure water production.

Refer to the respective pharmacopoeia for details. International Technology Roadmap for Semiconductors. Archived from the original on September 21, Pharmaceutical Press and American Pharmacists Association. Electronic version, MedicinesComplete Browser version 3. Current version of the book. Archived from the original on Archived from the original on September 11, However, they also have the ability to introduce new organisms and, through imposition of different management practices, put selective pressures on the naturally present or introduced soil biota.

This provides the opportunity to manage soil organisms and their activities in order to enhance soil fertility and crop growth. Although probably enough is known in theory to manage these communities, considerable basic and applied research is required in order to achieve appropriate levels of biological husbandry and optimal management of these biological resources.

Effects of earthworms on plant production. Earthworm management in tropical agroecosystems, pp. Soil nutrient transformations in the rhizosphere via animal-microbial interactions. Guidelines and reference material on integrated soil and nutrient management and conservation for farmer field schools.

Interactions of bacteria, fungi and their nematode grazers: Strategies de reproduction chez les vers de terre. Dordrecht, Netherlands, Kluwer Academic Publishers. Food resources and diets of soil animals in a small area of Scots Pine litter. Les bases de la production vegetale. Tome 1, Le Sol. Collection sciences et techniques agricoles. Decomposition in terrestrial ecosystems.

The soil coleoptera community of a ropical grassland from Laguna Verde, Veracruz Mexico. The agricultural importance of termites in the tropics. Role of nematodes in decomposition. Nematodes in soil ecosystems, pp. Organic matter affects both the chemical and physical properties of the soil and its overall health.

Properties influenced by organic matter include: It also influences the effects of chemical amendments, fertilizers, pesticides and herbicides. Soil organic matter consists of a continuum of components ranging from labile compounds that mineralize rapidly during the first stage of decomposition to more recalcitrant residues difficult to degrade that accumulate as they are deposited during advanced stages of decomposition as microbial by-products Duxbury, Smith and Doran, Freshly added or partially decomposed plant residues and their non-humic decomposition products constitute the labile organic matter pool.

The more stable humic substances tend to be more resistant to further decomposition. The labile soil organic matter pool regulates the nutrient supplying power of the soil, particularly of nitrogen N , whereas both the labile and stable pools affect soil physical properties, such as aggregate formation and structural stability.

When crops are harvested or residues burned, organic matter is removed from the system. However, the loss can be minimized by retaining plant roots in the soil and leaving crop residues on the surface. Organic matter can also be restored to the soil through growing green manures, cuttings from agroforestry species and the addition of manures and compost. Soil organic matter is the key to soil life and the diverse functions provided by the range of soil organisms.

Soil micro-organisms are of great importance for plant nutrition as they interact directly in the biogeochemical cycles of the nutrients. Increased production of green manure or crop biomass aboveground and belowground increases the food source for the microbial population in the soil.

Agricultural production systems in which residues are left on the soil surface and roots left in the soil, e.

In one year experiment in Brazil, such practices resulted in a percent increase in microbial carbon biomass and a percent increase in microbial N biomass Figure A2. The roots of most plants are infected with mycorrhizae, fungi that form a network of mycelia or threads on the roots and extend the surface area of the roots.

In undisturbed soil ecosystems, e. Fine roots are the primary sites of mycorrhizal development as they are the most active site for nutrient uptake.

This partly explains the increase in mycorrhizal colonization under undisturbed situations as rooting conditions are far better than under conventional tillage.

Another consequence of increased organic matter content is an increase in the earthworm population. Earthworms rarely come to the soil surface because of their characteristics: Soil moisture is one of the most important factors that determine the presence of earthworms in the soil.

Through cover crops and crop residues, evaporation is reduced and organic matter in the soil is increased, which in turn can hold more water. Residues on the soil surface induce earthworms to come to the surface in order to incorporate the residues in the soil. The burrowing activity of earthworms creates channels for air and water; this has an important effect on oxygen diffusion in the rootzone, and the drainage of water from it.

Furthermore, nutrients and amendments can be distributed easily and the root system can develop, especially in acid subsoil in the existing casts.

The shallow-dwelling earthworms create numerous channels throughout the topsoil, which increases overall porosity, and thus bulk density Figures A2. The large vertical channels created by deep-burrowing earthworms increase water infiltration under very intense rainfall conditions. Many important chemical properties of soil organic matter result from the weak acid nature of humus. The ability of organic matter to retain cations for plant use while protecting them from leaching, i.

Many acid-forming reactions occur continually in soils. Some of these acids are produced as a result of organic matter decomposition by microorganisms, secretion by roots, or oxidation of inorganic substances. In particular, ammonium fertilizers, such as urea, and ammonium phosphates, such as monoammonium and diammonium phosphate, are converted rapidly into nitrate through a nitrification process, releasing acids in the process and thus increasing the acidity of the topsoil Figure A2.

When acids or bases are added to the soil, organic matter reduces or buffers the change in pH. This is why it takes tonnes of limestone to increase the pH of a soil significantly compared with what would be needed to simply neutralize the free H present in the soil solution. All of the free hydrogen ions in the water in a very strongly acid soil pH 4 could be neutralized with less than 6 kg of limestone per hectare.

However, from 5 to more than 24 tonnes of limestone per hectare would be needed to neutralize enough acidity in that soil to enable acidsensitive crops to grow. Almost all of the acid that must be neutralized to increase soil pH is in organic acids, or associated with aluminium Al where the pH is very low. However, with large values of soil organic matter, the pH will decrease less rapidly and the field will have to be limed less frequently. In comparing conventional and conservation tillage in Brazil, the highest values of soil CEC and exchangeable calcium Ca and magnesium Mg were found in legume-based rotation systems with the highest organic matter content Figure A2.

Organic matter releases many plant nutrients as it is broken down in the soil, including N, phosphorus P and sulphur S. Leguminous species are very important as part of a cereal crop rotation in view of their capacity to fix N from the atmosphere through symbiotic associations with rootdwelling bacteria.

After nine years, no tillage in combination with the intensive cropping system had resulted in a percent increase in soil N compared with conventional tillage. Although N uptake by plants was less in no-tillage systems, probably because of N immobilization and organic matter building, the maize yields under the different tillage systems did not differ.

As the no-tillage system was more efficient in storing soil N from legume cover crops in the topsoil, in the long term this system can increase soil N available for maize production Amado, Fernandez and Mielniczuk, Calegari and Alexander noted that the P content both inorganic P and total P of the surface layer cm was higher in the plots with cover crops after nine years.

Cover crops were shown to have an important P-recycling capacity, especially when the residues were left on the surface. This was especially clear in the fallow plots, where the conventional tillage plots had a P content 25 percent lower than the no-tillage plots.

Depending on the cover crop, the increase was between 2 and almost 30 percent. Even more important is the effect of land preparation on the increase of P availability in the soil Figure A2. Three to five years after initiating an intensified production system, both P and potassium K can be accumulated in the topsoil.

On the other hand, where direct seeding is practised and the crop residues are left on the surface, percent of the nutrients were concentrated in the top layer of the soil. Organic matter influences the physical conditions of a soil in several ways. Plant residues that cover the soil surface protect the soil from sealing and crusting by raindrop impact, thereby enhancing rainwater infiltration and reducing runoff.

Increased organic matter also contributes indirectly to soil porosity via increased soil faunal activity. Fresh organic matter stimulates the activity of macrofauna such as earthworms, which create burrows lined with the glue-like secretion from their bodies and intermittently filled with worm cast material. Surface infiltration depends on a number of factors including aggregation and stability, pore continuity and stability, the existence of cracks, and the soil surface condition.

Organic matter also contributes to the stability of soil aggregates and pores through the bonding or adhesion properties of organic materials, such as bacterial waste products, organic gels, fungal hyphae and worm secretions and casts. Moreover, organic matter intimately mixed with mineral soil materials has a considerable influence in increasing moisture holding capacity.

The quality of the crop residues, in particular its chemical composition, determines the effect on soil structure and aggregation. As noted above, the benefits of a soil that is rich in organic matter and hence rich in living organisms are many. Direct organic matter amendments include:. The effects of the management practices depend largely on the agroclimatic situation as temperature and moisture influence speed of decomposition and general cycling of organic matter and nutrients.

Improved yield and crop quality: Improved soil and crop health reduce impacts of disease-causing organisms pathogens and viruses and harmful bacteria. Soil organic matter is an important means of C sequestration, and organic matter management practices contribute to C storage up to 0. Soil organic matter consists of living parts of plants principally roots , dead forms of organic material principally dead plant parts , and soil organisms micro-organisms and soil animals in various stages of decomposition.

It has great impact upon the chemical, physical and biological properties of the soil. Organic matter in the soil gives the soil good structure, and enables the soil to absorb water and retain nutrients. It also facilitates the growth and life of the soil biota by providing energy from carbon compounds, N for protein formation, and other nutrients.

Some of the nutrients in the soil are held in the organic matter, comprising almost all the N, a large amount of P and some S. When organic matter decomposes, the nutrients are released into the soil for plant use. Therefore, the amount and type of organic matter in the soil determines the quantity and availability of these nutrients in the soil.

It also affects the colour of the soil. Dead matter constitutes about 85 percent of all organic matter in soils. Living roots make up about another 10 percent, and microbes and soil animals make up the remainder.

Organic matter that has fully undergone decomposition is called humus. The origins of the materials after formation of humus cannot be recognized. Humus is dark in colour and very rich in plant nutrients. It is usually found in the top layers of a soil profile. The dark colour of humus absorbs heat from the sun, thereby improving soil temperature for plant growth and microbial activity under cooler climatic conditions.

It increases soil fertility as it retains cations and conserves nutrients in organic forms and slowly releases required nutrients for plant uptake and growth. It binds soil particles together; the cementing and aggregation functions improving soil structure and aeration. It acts as a sponge in the soil, retaining soil moisture. Soils with high organic matter content can hold more water than those low in organic matter.

Decomposition is the general process whereby dead organic materials are transformed into simpler states with the concurrent release of energy and their contained biological nutrient and other elements in inorganic forms. Such forms are directly assimilable by micro-organisms and plants, and the remaining soil organic matter may be stabilized through physical and chemical processes or further decomposed Lavelle and Spain, These transformations of dead organic materials into assimilable forms involve the simultaneous and complementary processes of mineralization and humification:.

Mineralization is the process through which the elements contained in organic form within biological tissues are converted to inorganic forms such as nitrate, phosphate and sulphate ions. Humification is an anabolic process where organic molecules are condensed into degradation-resistant organic polymers, which may persist almost unaltered for decades or even centuries.

Decomposition is essentially a biological process. Nutrients taken up by plants are derived largely from the decomposition process. Micro-organisms are by far the major contributors to soil respiration and are responsible for percent of the total carbon dioxide CO 2 respired and, consequentl,y of the organic C respired Satchell, ; Lamotte, Therefore, decomposition is a process determined by the interactions of three factors: Omega 3 fish oils provide great general health benefits.

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