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Ex Situ (ex + situ)
Selected AbstractsSynthesis of single-walled carbon nanotubes with the laser vaporization method: Ex situ and in situ measurementsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 13 2006M. Cau Abstract In situ measurements were executed in the continuous wave CO2 -laser vaporization synthesis of single-walled carbon nanotubes (SWCNTs). The results were compared with the findings of the ex situ analysis of the product. Different catalysts (Co, Ni, Co/Ni, Ni/Y and Co/Y) were used and the temperature of the target surface (Ts) changed to compare the efficiency of the synthesis process. Our main results are related to the SWCNTs diameter which is depending on Ts and on the catalysts nature. The targets containing Y with Co or Ni atoms produce more and larger SWCNTs than Co/Ni targets. The SWCNTs' diameter is seen to increase with Ts. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Monitoring of Desulfitobacterium frappieri PCP-1 in pentachlorophenol-degrading anaerobic soil slurry reactorsENVIRONMENTAL MICROBIOLOGY, Issue 6 2000M. Lanthier Anaerobic biodegradation of pentachlorophenol (PCP) was studied in rotative bioreactors containing 200 g of PCP-contaminated soil and 250 ml of liquid medium. Reactors were bioaugmented with cells of Desulfitobacterium frappieri strain PCP-1, a bacterium able to dehalogenate PCP to 3-chlorophenol. Cells of strain PCP-1 were detected by quantitative PCR for at least 21 days in reactors containing 500 mg of PCP per kg of soil but disappeared after 21 days in reactors with 750 mg of PCP per kg of soil. Generally, PCP was completely removed in less than 9 days in soils contaminated with 189 mg of PCP per kg of soil. Sorption of PCP to soil organic matter reduced its toxicity and enhanced the survival of strain PCP-1. In some non-inoculated reactors, the indigenous microorganisms of some soils were also able to degrade PCP. These results suggest that anaerobic dechlorination of PCP in soils by indigenous PCP-degrading bacteria, or after augmentation with D. frappieri PCP-1, should be possible in situ and ex situ when the conditions are favourable for the survival of the degrading microorganisms. [source] Comparison of synthetic surfactants and biosurfactants in enhancing biodegradation of polycyclic aromatic hydrocarbonsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2003Randhir S. Makkar Abstract Polycyclic aromatic hydrocarbon (PAH) contamination of the environment represents a serious threat to the health of humans and ecosystems. Given the human health effects of PAHs, effective and cost-competitive remediation technologies are required. Bioremediation has shown promise as a potentially effective and low-cost treatment option, but concerns about the slow process rate and bioavailability limitations have hampered more widespread use of this technology. An option to enhance the bioavailability of PAHs is to add surfactants directly to soil in situ or ex situ in bioreactors. Surfactants increase the apparent solubility and desorption rate of the PAH to the aqueous phase. However, the results with some synthetic surfactants have shown that surfactant addition can actually inhibit PAH biodegradation via toxic interactions, stimulation of surfactant degraders, or sequestration of PAHs into surfactant micelles. Biosurfactants have been shown to have many of the positive effects of synthetic surfactants but without the drawbacks. They are biodegradable and nontoxic, and many biosurfactants do not produce true micelles, thus facilitating direct transfer of the surfactant-associated PAH to bacteria. The results with biosurfactants to date are promising, but further research to elucidate surfactant,PAH interactions in aqueous environments is needed to lead to predictive, mechanistic models of biosurfactant-enhanced PAH bioavailability and thus better bioremediation design. [source] How Elephants are Opening Doors: Developmental Neuroethology, Attachment and Social ContextETHOLOGY, Issue 5 2007G. A. Bradshaw Ethology's renewed interest in developmental context coincides with recent insights from neurobiology and psychology on early attachment. Attachment and social learning are understood as fundamental mechanisms in development that shape core processes responsible for informing behaviour throughout a lifetime. Each field uniquely contributes to the creation of an integrated model and encourages dialogue between Tinbergen's four analytical levels: ethology in its underscoring of social systems of behaviour and context, psychology in its emphasis on socio-affective attachment transactions, and neuroscience in its explication of the coupled development of brain and behaviour. We review the relationship between developmental context and behaviour outcome as a topic shared by the three disciplines, with a specific focus on underlying neuroethological mechanisms. This interdisciplinary convergence is illustrated through the example of abnormal behaviour in wild African elephants (Loxodonta africana) that has been systematically observed in human-caused altered social contexts. Such disruptions impair normative socially mediated neuroendocrinological development leading to psychobiological dysregulation that expresses as non-normative behaviour. Aberrant behaviour in wild elephants provides a critical field example of what has been established in ex situ and clinical studies but has been largely absent in wild populations: a concrete link between effects of human disturbance on social context, and short- and long-term neuroethology. By so doing, it brings attention to the significant change in theories of behaviour that has been occurring across disciplines , namely, the merging of psychobiological and ethological perspectives into common, cross-species, human inclusive models. [source] Microstructural Analysis of the Reinforced Al-Cu5mgti/Tib2 5,wt % Alloy for Investment Casting Applications,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Pedro Egizabal Abstract The paper describes the influence of 5,wt % titanium diboride (TiB2) particles on the microstructure of an Al-Cu alloy produced by plaster casting process. The elaboration route leads to a composite material with 1% of in situ TiB2 particles and 4% ex situ of TiB2 particles. The comparison of the reinforced alloy with the corresponding non-reinforced counterpart makes clear that the presence of TiB2 particles has a large influence in the observed microstructure. The presence of TiB2 particles decreases the grain sizes and the porosity level. It is also found that TiB2 particles play an important role in the precipitation events of Al2Cu precipitates that are formed during solidification at the TiB2/aluminum matrix interfaces. [source] Multifunctional FeCo/TiN Multilayer Thin Films with Combined Magnetic and Protective Properties,ADVANCED ENGINEERING MATERIALS, Issue 12 2009Christian Klever Abstract Coatings with thicknesses ranging from a few nanometer up to several micrometer produced by physical vapor deposition (PVD) processes have been established in engineering technologies since the early 1980s. In particular, magnetron sputtered wear resistance coatings are industrially established and capable to enhance tool lifetimes significantly. However, in cases where optical inspection of a coating in use is not possible, an intrinsic sensor function of the film would be beneficial. Therefore, the development of wear resistant coatings with an integrated sensor functionality based on the insertion of a magnetoelastic ferromagnetic phase is suggested. In combination with appropriate read-out electronics such a film system would be ready for online monitoring of the coatings' actual state (e.g., strain, temperature, volume loss). This paper focuses on the development of wear resistance coatings which simultaneously supply beneficial mechanical properties as well as ferromagnetic properties optimized for online non-contact read-out applications. Multilayer coatings obtained through alternate stacking of magnetron sputtered TiN and FeCo layers with a nominal total thickness of 1000,nm were produced as a model system meeting the above conditions. The bilayer period was varied down to 2.6,nm while the individual layer thickness ratio tTiN/tFeCo was determined by the deposition rates and maintained constant at a value of about 3/1. The films were vacuum annealed ex situ in a static magnetic field subsequent to the deposition. The constitution of the as-deposited and annealed coatings as well as their mechanical (nanohardness, Young's modulus) and magnetic properties (magnetization hysteresis, frequency-dependent permeability) are described. Finally, the suitability of the coatings for the use in remote-interrogable wear sensor applications is briefly discussed. [source] Late-glacial remains of woolly mammoth (Mammuthus primigenius) from Shropshire, UK: stratigraphy, sedimentology and geochronology of the Condover siteGEOLOGICAL JOURNAL, Issue 4 2009J. D. Scourse Abstract In 1986 remains of an adult woolly mammoth, Mammuthus primigenius (Blumenbach), were discovered at Norton Farm Pit, Condover, south of Shrewsbury, UK. Preliminary stratigraphical investigations indicated that this individual dated to the Devensian Late-glacial Interstadial, then the first evidence for survival of mammoth in Britain following the Last Glacial Maximum. Initial radiocarbon analysis confirmed this interpretation. Subsequent excavations in 1987/1988 recovered the remains of a further three juvenile mammoth individuals. All of these remains were found in the spoil heaps of overburden (ex situ) and their true stratigraphical context had to be reconstructed from the remnants surviving in the Pit. The 1987/1988 excavations enabled stratigraphical investigation of the site and submission of samples for radiocarbon (14C) dating, including the use of ultrafiltration pretreatment for bone samples, with the aims of reconstructing the geological and palaeoenvironmental evolution of the site and the sedimentary context of the unstratified mammoth remains. These results are presented here. This investigation indicates that the woolly mammoth remains at Condover derive from a dead-ice landscape dominated by eskers, kames and kettle-hole basins, and that the sedimentary sequence in which the mammoth remains were found forms the infilling of a kettle-hole basin. The sedimentary infilling and formation of the kettle-hole basin through ice block melt-induced subsidence were syngenetic. 14C determinations indicate that basin infill was initiated prior to Greenland Interstadial 1, and probably in Greenland Stadial 2 i.e. before 14.7,ka BP and that it continued until the early Holocene, around 8,ka BP. The sedimentological and 14C data indicate that the unstratified mammoth remains can be attributed to a dark grey clayey sandy silt (Unit C1), which accumulated during the earlier part of Greenland Interstadial 1 (14 to 14.5,ka BP) within an actively subsiding slow-flowing, beaded, fluvial network characterized by channels and pools/lakes, and with relatively shallow marginal slopes. The sedimentary architecture indicates survival of the buried ice block into Greenland Interstadial 1 and final melting only towards the end of the Interstadial at ca. 12.65,ka BP. Copyright © 2009 John Wiley & Sons, Ltd. [source] The role of the Species Survival Plan in Maned wolf Chrysocyon brachyurus conservationINTERNATIONAL ZOO YEARBOOK, Issue 1 2010N. SONGSASEN The Association of Zoos and Aquariums Maned Wolf Species Survival Plan (MWSSP) was established almost 25 years ago. The goals of the MWSSP are to (1) maintain a viable self-sustaining captive population in North America, (2) enhance health and well-being of individuals living in North American zoos and (3) promote conservation of this species through education and field-conservation initiatives. Since its inception, the MWSSP and member institutions have supported studies on nutrition, medical management, behaviour and reproductive biology, and published a husbandry manual, which serves as a guide for captive management of Maned wolves Chrysocyon brachyurus in North and South American zoos. Furthermore, the MWSSP has provided funding for field studies aimed at identifying potential threats to wild populations in range countries, including Brazil, Bolivia and Argentina, as well as for the first Population and Habitat Viability Assessment Workshop for this species. Finally, the MWSSP has played an active role in promoting education and outreach efforts in both the United States and range countries. In this paper, we review and discuss the roles of the MWSSP in ex situ and in situ conservation of the Near Threatened Maned wolf. [source] Role of the zoo veterinarian in the conservation of captive and free-ranging wildlifeINTERNATIONAL ZOO YEARBOOK, Issue 1 2007S. L. DEEM The challenges to execute wildlife conservation projects successfully have become more complex as anthropogenic changes continue to stress the planet, changing wild lands. As the wild becomes less so, more species are placed in captivity to improve their chances of long-term survival, while concurrently management (and medicine) for free-ranging wildlife has become increasingly important. A variety of disciplines, including veterinary medicine, is now recognized as key to wildlife conservation. Although veterinarians have been involved in conservation for decades, it is only recently that their role has become more appreciated in the larger conservation community. This realization of the contributions of veterinarians has occurred at a time when disease has been recognized as significantly impacting species' conservation both in situ and ex situ. Today, veterinarians work with captive and free-ranging animals to prevent and/or treat diseases that threaten species' survival. Most of these diseases are associated with the increasing human footprint. In this paper, I present wildlife health in today's world and the zoo veterinarian's role in wildlife conservation. [source] Bone Strength at Clinically Relevant Sites Displays Substantial Heterogeneity and Is Best Predicted From Site-Specific Bone DensitometryJOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2002Felix Eckstein Ph.D. Abstract In this study we test the hypotheses that mechanical bone strength in elderly individuals displays substantial heterogeneity among clinically relevant skeletal sites, that ex situ dual-energy X-ray absorptiometry (DXA) provides better estimates of bone strength than in situ DXA, but that a site-specific approach of bone densitometry is nevertheless superior for optimal prediction of bone failure under in situ conditions. DXA measurements were obtained of the lumbar spine, the left femur, the left radius, and the total body in 110 human cadavers (age, 80.6 ± 10.5 years; 72 female, 38 male), including the skin and soft tissues. The bones were then excised, spinal and femoral DXA being repeated ex situ. Mechanical failure tests were performed on thoracic vertebra 10 and lumbar vertebra 3 (compressive loading of a functional unit), the left and right femur (side impact and vertical loading configuration), and the left and right distal radius (fall configuration, axial compression, and 3-point-bending). The failure loads displayed only very moderate correlation among sites (r = 0.39 to 0.63). Ex situ DXA displayed slightly higher correlations with failure loads compared with those of in situ DXA, but the differences were not significant and relatively small. Under in situ conditions, DXA predicted 50-60% of the variability in bone failure loads at identical (or closely adjacent) sites, but only around 20-35% at distant sites, advocating a site-specific approach of densitometry. These data suggest that mechanical competence in the elderly is governed by strong regional variation, and that its loss in osteoporosis may not represent a strictly systemic process. [source] The Effects of Temperature on the Local Structure of Metakaolin-Based Geopolymer Binder: A Neutron Pair Distribution Function InvestigationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Claire E. White Neutron pair distribution function (PDF) analysis is utilized to advance the understanding of the local atomic structural characteristics of geopolymer binders derived from metakaolin, specifically the nature and amount of the water associated with these materials. Samples were heated in air to temperatures up to 1200°C, then analyzed ex situ by high momentum transfer neutron total scattering and PDF analysis. Water contained in large pores, along with water associated with hydration of potassium cations in the geopolymer framework structure, comprise the majority of water in this material. The remaining water is situated in small pores and as terminal hydroxyl groups attached to the Si,Al framework. The Si,Al framework structure undergoes only subtle rearrangement upon heating, but maintains a tetrahedral aluminosilicate framework environment. After crystallization with heating beyond 1000°C, the geopolymer gel is predominantly converted to leucite, with small amounts of amorphous mullite and glassy silica, which have never before been observed in heated geopolymers. This demonstrates the value of neutron PDF analysis to probe the local structure of these important geopolymeric materials. [source] SEDIMENT OXYGEN DEMAND IN THE ARROYO COLORADO RIVER,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2003Marty D. Matlock ABSTRACT: The lower reaches of the Arroyo Colorado have historically failed to meet their use under subsection 303(b) of the U.S. Clean Water Act due to fecal coliform bacteria and low dissolved oxygen (DO). Fish kills, especially at the tidal confluence at the Port of Harlingen, Texas, have been reported. Oxygen demand from sediment (SOD) for a river typically has two states-diffusion limited SOD (SOD) and potential SOD (pSOD), expressed when sediment is resuspended through increased flow or other disturbances. The objective of this research was to measure SOD in the Arroyo Colorado River in situ, estimate pSOD ex situ, and evaluate the relationship between SOD and the depositional environment. We measured SOD and pSOD in the Arroyo Colorado River at up to eight sites over three sampling events. We identified the sample sites based on a modified Rosgen geomorphic index for streambed stabilization. Sites with high sediment deposition potential had high SOD. The average values of SOD between sites were 0.62 g/m2/day (standard deviation 0.38 g/m2/day) and ranged from 0.13 to 1.2 g/m2/day. Potential SOD values ranged from as low as 19.2 to as high as 2,779 g/m3 sediment/ day. Potential SOD can serve as an indicator of the possible impact of SOD from resuspended sediment in stream systems. [source] Extended right liver grafts obtained by an ex situ split can be used safely for primary and secondary transplantation with acceptable biliary morbidityLIVER TRANSPLANTATION, Issue 7 2009Atsushi Takebe Split liver transplantation (SLT) is clearly beneficial for pediatric recipients. However, the increased risk of biliary complications in adult recipients of SLT in comparison with whole liver transplantation (WLT) remains controversial. The objective of this study was to investigate the incidence and clinical outcome of biliary complications in an SLT group using split extended right grafts (ERGs) after ex situ splitting in comparison with WLT in adults. The retrospectively collected data for 80 consecutive liver transplants using ERGs after ex situ splitting between 1998 and 2007 were compared with the data for 80 liver transplants using whole liver grafts in a matched-pair analysis paired by the donor age, recipient age, indications, Model for End-Stage Liver Disease score, and high-urgency status. The cold ischemic time was significantly longer in the SLT group (P = 0.006). As expected, bile leakage from the transected surface occurred only in the SLT group (15%) without any mortality or graft loss. The incidence of all other early or late biliary complications (eg, anastomotic leakage and stenosis) was not different between SLT and WLT. The 1- and 5-year patient and graft survival rates showed no statistical difference between SLT and WLT [83.2% and 82.0% versus 88.5% and 79.8% (P = 0.92) and 70.8% and 67.5% versus 83.6% and 70.0% (P = 0.16), respectively]. In conclusion, ERGs can be used safely without any increased mortality and with acceptable morbidity, and they should also be considered for retransplantation. The significantly longer cold ischemic time in the SLT group indicates the potential for improved results and should thus be considered in the design of allocation policies. Liver Transpl 15:730,737, 2009. © 2009 AASLD. [source] Ex situ cultivation of Aplysinaaerophoba close to in situ conditions: ecological, biochemical and histological aspectsMARINE ECOLOGY, Issue 2 2008Anne Klöppel Abstract Sponges provide the largest number of biologically active natural products known from the marine environment and continue to be a very well studied phylum of marine fauna. The Mediterranean sponge Aplysina aerophoba accumulates brominated isoxazoline alkaloids such as Aplysinamisin-1, Aerophobin-2, Isofistularin-3 and the biotransformation product Aeroplysinin-1, which possesses, for example, antibiotic and cytotoxic properties. Until now, it is still being discussed which organisms , the sponge itself or associated microorganisms , are responsible for metabolite production. For cultivating Aplysina individuals under ex situ conditions, we surveyed relevant ecological factors in situ and controlled them in our aquarium system. We maintained A. aerophoba for more than 9 months and analysed changes of metabolite content and composition, microbial association as well as morphology in situ and ex situ under different light exposure. Although sponges showed slight reduction during maintenance, ex situ cultivation similar to in situ conditions provides a promising method to keep sponges and obtain their bioactive metabolites. [source] Singlet oxygen inhibits nonradiative defects in porous siliconPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2009V. B. Pikulev Abstract Experimental evidences are presented for the first time that singlet oxygen generated ex situ acts as an inhibitor of nonradiative recombination in porous silicon (PSi). This effect is observed on a pristine PSi as well as on degraded porous layers quenched by ozone adsorption. A photoluminescence (PL) enhancement produced by singlet oxygen is accompanied with only slight oxidation of a PSi. We assume that the observed effect on PL efficiency is due to gentle selective oxidation of single defects on silicon nanocrystal surface. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Neandertal mandibles from the Sima de las Palomas del Cabezo Gordo, Murcia, southeastern SpainAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Michael J. Walker Abstract The Middle Paleolithic levels of the Sima de las Palomas have yielded eight partial mandibles (Palomas 1, 6, 7, 23, 49, 59, 80, and 88). Palomas 7, 49, 80, and 88 are immature, and Palomas 49, 59, 80, and 88 are among the latest Neandertals (,40,000 cal BP). Palomas 1 is geologically older (,50,000,60,000 cal BP), and the other three were found ex situ. The mandibles exhibit a suite of characteristics that align them with the Neandertals among later Pleistocene humans, including symphyseal morphology, symphyseal orientation, corpus robusticity, distal mental foramen position, retromolar space presence, wide immature dental arcade, and high-coronoid process with an asymmetrical mandibular notch. However, Palomas 6 lacks a retromolar space, Palomas 59 has a narrow lateral corpus, and Palomas 80 has a mesial mental foramen and open mandibular foramen. The Palomas mandibles therefore help to document that the late Middle Paleolithic of southern Iberia was the product of Neandertals. They also reinforce the presence of variability in both metric and discrete aspects of Neandertal mandibular morphology, both within and across samples, some of which may be temporal and/or geographic in nature. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] Nutritional chemistry of foods eaten by gorillas in Bwindi Impenetrable National Park, UgandaAMERICAN JOURNAL OF PRIMATOLOGY, Issue 7 2006Jessica M. Rothman Abstract Foods eaten by gorillas (Gorilla beringei) in Bwindi Impenetrable National Park (BINP), Uganda, were analyzed for their nutrient content. The goal of the study was to assess the amounts of fiber, protein, and sugars in the foods eaten by the Bwindi gorillas, and to determine whether condensed tannins and cyanide are present in these foods. A total of 127 food plant parts representing 84 plant species eaten by two groups of Bwindi gorillas were collected, processed, and analyzed for their chemical contents. The Bwindi gorilla ate foods that contain 2,28% crude protein (CP), 21,88% neutral detergent fiber (NDF), 14,60% acid detergent fiber (ADF), 2,42% acid detergent lignin (ADL), and ,1,50% water-soluble carbohydrates (WSC) on a dry matter (DM) basis. Moisture in these foods ranged from 7% to 96%. Approximately 35% of the foods analyzed contained condensed tannins, and two foods contained cyanogenic glycosides. This is the first detailed report regarding the nutritional chemistry of gorilla foods in Bwindi, many of which are also eaten by other primates. This unique data set adds to our knowledge about the nutritional composition of foods eaten by gorillas across habitats, is useful for understanding aspects of feeding behavior, and provides valuable comparative data for optimizing the diets of gorillas ex situ. Am. J. Primatol. 68:1,17, 2006. © 2005 Wiley-Liss, Inc. [source] Population structure of rice (Oryza sativa) landraces under farmer managementANNALS OF APPLIED BIOLOGY, Issue 1 2010S. Kumar Greater insight into the dynamics of genetic resources of crop plants is needed in order to pinpoint detrimental evolutionary patterns and draw up conservation priorities. The present study demonstrated farmer management of crop population structure and temporal evolution of rice genetic diversity in traditional production systems. The 16 STMS primers analysed for 11 rice landrace populations indicated enough polymorphism to fully differentiate the inter- and intrapopulation diversity. A total number of 98 alleles were recorded, of which 91 were common and seven were rare. The mean number of alleles per locus was 6.13 and for different groups of rice landrace populations, namely five populations of upland common landrace Jaulia, three populations of irrigated common landrace Thapachini and one population each of three distinct rare landraces were 4.37, 2.75 and 4.37, respectively. The study also compared genebank-conserved (ex situ) populations and on-farm-managed (in situ) landrace populations of same named landraces Jaulia and Thapachini, and revealed greater number of alleles per locus for on-farm-managed populations as compared to the populations under static management. A substantial number of alleles specific to populations under dynamic management could also be recorded. Further, the rare landrace populations included in the present study were more diverse than the common landrace populations. The rare landraces were distinct genetic entities largely representing locally common alleles. Investigating the population genetic structure is therefore helpful in monitoring change in diversity over time and space, and also for devising a rational plan for management of farmer landraces on-farm. [source] Atomic force microscopy applications in macromolecular crystallographyACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2001A. McPherson Atomic force microscopy (AFM) can be applied both in situ and ex situ to study the growth of crystals from solution. The method is particularly useful for investigating the crystallization of proteins, nucleic acids and viruses because it can be carried out in the mother liquor and in a non-perturbing fashion. Interactions and transformations between various growth mechanisms can be directly visualized as a function of supersaturation, as can the incorporation of diverse impurities and the formation and propagation of defects. Because the crystals can be observed over long periods, it is also possible to obtain precise quantitative measures of the kinetic parameters for nucleation and growth. Finally, AFM has allowed us to identify a number of previously unsuspected phenomena that influence nucleation, rate of growth and the ultimate perfection of macromolecular crystals. These are all features which are important in determining the ultimate resolution and quality of a crystal's diffraction pattern. [source] From Cloudy to Transparent: Chain Rearrangement in Hydrogen-Bonded Layer-by-Layer Assembled FilmsCHEMPHYSCHEM, Issue 3 2007Shuguang Yang Abstract The cloudiness of hydrogen-bonded LBL films assembled from polyvinylpyrrolidone (PVPON) and poly(acrylic acid) (PAA) is studied in detail by two approaches: spectroscopy (Fabry,Pérot fringes) and microscopy (AFM). Fabrication parameters such as temperature, molecular weight, pH value, and rinsing time, have notable influences on film cloudiness. The buildup of the PVPON/PAA film is a two-stage process of adsorption and chain rearrangement. Generally, adsorption is fast, while chain rearrangement is slow. The fast adsorption process traps defects, whereas the relatively slow chain-rearrangement process can not heal the defects in time; therefore, the number of defects continuously increases as LBL assembly proceeds, and a cloudy, heterogeneous film is produced. However, the as-prepared cloudy films become transparent and homogeneous on subsequent annealing in acidic water. UV/Vis spectroscopy and fluid AFM were applied to monitor this transition ex situ and in situ, respectively. It is found that increasing the annealing temperature accelerates the transition from cloudy to transparent, and the transition of the film made from higher molecular weight polymer is slower. [source] Recombinant bacteria for environmental release: what went wrong and what we have learnt from itCLINICAL MICROBIOLOGY AND INFECTION, Issue 2009V. De Lorenzo Abstract From a biotechnological point of view, bacteria can be seen as either pathogens to target with new drugs or as biocatalysts for large-scale processes in industry, agriculture or the environment. The last includes the exploitation of bacterial activities for bioremediation of toxic waste either in situ or ex situ. The onset of genetic engineering in the late 70s opened the possibility of tailoring recombinant bacteria for environmental release, aimed at biodegradation of otherwise recalcitrant chemicals. However, a few decades later the outcome of this prospect has been quite meager. The literature counts very few cases where the use of genetically engineered bacteria has been proven to be more efficient than natural microorganisms in elimination of recalcitrant compounds under natural (not laboratory) conditions. Fortunately, the emergence of Systems and Synthetic Biology in the last few years is helping to identify what were the caveats of the former approaches and how to correct them. In addition, robust design concepts imported from process engineering provides fresh approaches to the challenge of designing microorganisms á la carte for environmental applications. [source] | ||||||||||||||||||||||