Intimate Contact (intimate + contact)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Selected Abstracts

Toxicity assessment of reference and natural freshwater sediments with the LuminoTox assay

P. M. Dellamatrice
Abstract We examined the possibility of adapting the LuminoTox, a recently-commercialized bioanalytical testing procedure initially developed for aqueous samples, to assess the toxic potential of sediments. This portable fluorescent biosensor uses photosynthetic enzyme complexes (PECs) to rapidly measure photosynthetic efficiency. LuminoTox testing of 14 CRM (Certified Reference Material) sediments was first undertaken with (1) a "solid phase assay" (Lum-SPA) in which PECs are in intimate contact with sediment slurries for a 15 min exposure period and (2) an elutriate assay (Lum-ELU) in which PECs are exposed for 15 min to sediment water elutriates. CRM sediment toxicity data were then compared with those generated with the Microtox Solid Phase Assay (Mic-SPA). A significant correlation (P < 0.05) was shown to exist between Lum-SPA and Mic-SPA, indicating that both tests display a similar toxicity response pattern for CRM sediments having differing contaminant profiles. The sediment elutriate Lum-ELU assay displayed toxicity responses (i.e. measurable IC20s) for eight of the 14 CRM sediments, suggesting that it is capable of determining the presence of sediment contaminants that are readily soluble in an aqueous elutriate. Lum-SPA and Mic-SPA bioassays were further conducted on 12 natural freshwater sediments and their toxicity responses were more weakly, yet significantly, correlated. Finally, Lum-SPA testing undertaken with increasing mixtures of kaolin clay confirmed that its toxicity responses, in a manner similar to those reported for the Mic-SPA assay, are also subject to the influence of grain size. While further studies will be required to more fully understand the relationship between Lum-SPA assay responses and the physicochemical makeup of sediments (e.g., grain size, combined presence of natural and anthropogenic contaminants), these preliminary results suggest that LuminoTox testing could be a useful screen to assess the toxic potential of solid media. 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 395,402, 2006. [source]

A Simple and Innovative Route to Prepare a Novel Carbon Nanotube/Prussian Blue Electrode and its Utilization as a Highly Sensitive H2O2 Amperometric Sensor

Edson Nossol
Abstract The utilization of iron-based species (mainly metallic iron, hematite and magnetite) encapsulated into multi-walled carbon nanotubes (CNTs) as reactants in an electrochemical synthesis is reported for the first time in this work. Prussian blue (PB) is electrosynthesized in a heterogeneous reaction between ferricyanide ions in aqueous solution and the iron-species encapsulated into CNTs, resulting in novel CNT/PB paste electrodes. This innovative preparation route produces an intimate contact between the PB and the CNTs, which improves the stability and redox properties of PB. The PB formation and the chemical interaction between the PB and the CNTs are confirmed by Raman spectroscopy. The electrode is employed as a hydrogen peroxide amperometric sensor, resulting in a very low limit of detection (1.94,,10,8,mol L,1) and very high sensitivity (15.3,A cm,2M,1). [source]

Evaluation of an Inexpensive Small-Diameter Temperature Logger for Documenting Ground Water,River Interactions

Adam N. Johnson
Increasing numbers of studies are recording detailed temperature data for characterization of ground water,stream exchange. We examined laboratory and field operation of a small-diameter, stand-alone and inexpensive temperature logger capable of investigating stream,ground water exchange was examined. The Thermochron iButton is a 17.35-mm-diameter by 6-mm-thick instrument that costs <$10 when ordered in quantity. Testing of the loggers in a controlled temperature bath revealed a precision of 0.4C and an accuracy of 0.5C for a group of 201. More than 500 loggers have been installed in channels and in subchannel and floodplain ground water environments in two gravel-bedded rivers in the western United States. Loggers were placed as single devices and in vertical arrays in monitoring wells with diameters of 10.16, 5.08, 2.54, and 1.9 cm. We determined that the loggers have four principal advantages over more commonly used wired and currently available stand-alone logging devices: (1) the wireless nature does not require the instrument location to be associated with a control-recording system; (2) the small size allows for installation in small hand-driven or direct-push monitoring wells and thus intimate contact of the instruments with the hydrologic environment; (3) multiple loggers are easily suspended in a single fully perforated monitoring well, allowing for the collection of high-resolution temperature profile data; and (4) the low cost of the loggers allows for the deployment of large numbers, thus improving spatial resolution in shallow ground water floodplain scale studies. [source]

Self-Assembled Nanoparticles Based Fabrication of Gecko Foot-Hair-Inspired Polymer Nanofibers,

S. Kustandi
Abstract Wafer-scale polymer nanofabrillar structures have been fabricated using the combination of colloidal nanolithography, deep-silicon etching, and nanomolding to mimic the nanostructure of gecko foot-hairs. The artificial surface features densely packed polymeric nanofibrils with super-hydrophobic, water-repellent, and "easy-to-clean" characteristics. The lateral dimension of the nanofibrils is as small as 250,nm and an aspect-ratio as high as 10:1 has been achieved without lateral collapse between neighboring fibrils. The method allows both fabrication of synthetic structures over a large area and direct integration of a flexible membrane to assist the array of nanofibrils in making intimate contact with uneven surfaces. A single nanofibril exhibits a mean adhesive force ranging from (0.91,,0.34),nN to (1.35,,0.37),nN. In the macroscopic scale, the nanostructured surface can adhere firmly to a smooth glass substrate and inherits the in-use, self-cleaning property of the setal nanostructures found in gecko lamellae. [source]

Soft-Contact Optical Lithography Using Transparent Elastomeric Stamps and Application to Nanopatterned Organic Light-Emitting Devices

T.-W. Lee
Abstract Conventional photolithography uses rigid photomasks of fused quartz and high-purity silica glass plates covered with patterned microstructures of an opaque material. We introduce new, transparent, elastomeric molds (or stamps) of poly(dimethylsiloxane) (PDMS) that can be employed as photomasks to produce the same resist pattern as the pattern of the recessed (or non-contact) regions of the stamps, in contrast to other reports in the literature[1] of using PDMS masks to generate edge patterns. The exposure dose of the non-contact regions with the photoresist through the PDMS is lower than that of the contact regions. Therefore, we employ a difference in the effective exposure dose between the contact and the non-contact regions through the PDMS stamp to generate the same pattern as the PDMS photomask. The photomasking capability of the PDMS stamps, which is similar to rigid photomasks in conventional photolithography, widens the application boundaries of soft-contact optical lithography and makes the photolithography process and equipment very simple. This soft-contact optical lithography process can be widely used to perform photolithography on flexible substrates, avoiding metal or resist cracks, as it uses soft, conformable, intimate contact with the photoresist without any external pressure. To this end, we demonstrate soft-contact optical lithography on a gold-coated PDMS substrate and utilized the patterned Au/PDMS substrate with feature sizes into the nanometer regime as a top electrode in organic light-emitting diodes that are formed by soft-contact lamination. [source]

Artificial Stem Cell Niches,

ADVANCED MATERIALS, Issue 32-33 2009
Matthias P. Lutolf
Abstract Stem cells are characterized by their dual ability to reproduce themselves (self-renew) and specialize (differentiate), yielding a plethora of daughter cells that maintain and regenerate tissues. In contrast to their embryonic counterparts, adult stem cells retain their unique functions only if they are in intimate contact with an instructive microenvironment, termed stem cell niche. In these niches, stem cells integrate a complex array of molecular signals that, in concert with induced cell-intrinsic regulatory networks, control their function and balance their numbers in response to physiologic demands. This progress report provides a perspective on how advanced materials technologies could be used (i) to engineer and systematically analyze specific aspects of functional stem cells niches in a controlled fashion in vitro and (ii) to target stem cell niches in vivo. Such "artificial niches" constitute potent tools for elucidating stem cell regulatory mechanisms with the capacity to directly impact the development of novel therapeutic strategies for tissue regeneration. [source]

Intestinal dendritic cells: Their role in bacterial recognition, lymphocyte homing, and intestinal inflammation

S.C. Ng PhD
Abstract Dendritic cells (DCs) play a key role in discriminating between commensal microorganisms and potentially harmful pathogens and in maintaining the balance between tolerance and active immunity. The regulatory role of DC is of particular importance in the gut where the immune system lies in intimate contact with the highly antigenic external environment. Intestinal DC constantly survey the luminal microenvironment. They act as sentinels, acquiring antigens in peripheral tissues before migrating to secondary lymphoid organs to activate naive T cells. They are also sensors, responding to a spectrum of environmental cues by extensive differentiation or maturation. Recent studies have begun to elucidate mechanisms for functional specializations of DC in the intestine that may include the involvement of retinoic acid and transforming growth factor-,. Specialized CD103+ intestinal DC can promote the differentiation of Foxp3+ regulatory T cells via a retinoic acid-dependent process. Different DC outcomes are, in part, influenced by their exposure to microbial stimuli. Evidence is also emerging of the close interaction between bacteria, epithelial cells, and DC in the maintenance of intestinal immune homeostasis. Here we review recent advances of functionally specialized intestinal DC and their mechanisms of antigen uptake and recognition. We also discuss the interaction of DC with intestinal microbiota and their ability to orchestrate protective immunity and immune tolerance in the host. Lastly, we describe how DC functions are altered in intestinal inflammation and their emerging potential as a therapeutic target in inflammatory bowel disease. (Inflamm Bowel Dis 2010) [source]

Topical silver-impregnated dressings and the importance of the dressing technology

Keith Cutting
ABSTRACT A wide variety of silver-impregnated wound dressings has become available in recent years. This has given the practitioner choice but little evidence by which an appropriate dressing may be selected. In many instances, the ancillary function(s) of the dressing will become differentiating factors that influence choice. For example, the dressing capacity to manage exudate, maintain an optimum moist environment, reduce or avoid maceration, maintain an intimate contact with the wound bed, promote autolytic debridement, sequester bacteria and bind matrix metallo proteases (MMPs) are some of those functions that are of clinical significance and may dictate choice. In this article we present the evidence for these functions, thereby enabling practitioners to evaluate comparative dressing attributes, and so make an informed choice of which silver dressing best suits the needs of the wound under differing circumstances. [source]

Instinctive Incest Avoidance: A Paradigm Case for Evolutionary Psychology Evaporates

Westermarck proposed that humans have an incest avoidance instinct, triggered by frequent intimate contact with family members during the first several years of life. Westermarck reasons that (1) familial incest will tend to produce less fit offspring, (2) those humans without instinctive incest avoidance would hence have tended to die off and those with the avoidance instinct would have produced more viable offspring, and hence (3) familial incest would be, as indeed it is, universally and instinctively avoided (the desire simply does arise given early continuous intimate contact; the "potty principle" as some psychologists have succinctly termed it). Victorian Westermarck claimed this as a human adaptation. Evolutionary psychologists have generalized these claims to Pleistocene humans and their ancestors, to primates, and indeed to animals generally. Yet there is surprisingly little evidence for these claims of universal instinctive avoidance. Considerable inbreeding appears among large, territorial primates and may have been so with early humans and with their ancestors. While there is little reliable non-anecdotal evidence about incestuous behavior or the lack of it among humans, what little there is does not fit well with the Westermarck thesis. [source]

Structure and properties of phase change materials based on HDPE, soft Fischer-Tropsch paraffin wax, and wood flour

M. E. Mngomezulu
Abstract Phase-change materials based on high density polyethylene (HDPE), soft Fischer-Tropsch paraffin wax (M3), and alkali-treated wood flour (WF) were investigated. The blend and composite samples were prepared by melt mixing using a Brabender Plastograph, followed by melt pressing. They were characterized in terms of their morphology, as well as thermal, mechanical, thermo-mechanical, and water absorption properties. Although SEM micrographs showed some evidence of intimate contact between the WF particles and the HDPE matrix as a result of alkali treatment, poor filler dispersion, and interfacial adhesion were also observed. Partial immiscibility of the HDPE and the M3 wax was noticed, with the WF particles covered by wax. There was plasticization of the HDPE matrix by the wax, as well as partial cocrystallization, inhomogeneity and uneven wax dispersion in the polymer matrix. The HDPE/WF/M3 wax composites were more homogeneous than the blends. The presence of wax reduced the thermal stability of the blends and composites. Both the presence of M3 wax and WF influenced the viscoelastic behavior of HDPE. The HDPE/M3 wax blends showed an increase in the interfacial amorphous content as the wax content increases, which resulted in the appearance of a ,-relaxation peak. The presence of M3 wax in HDPE reduced the mechanical properties of the blends. For the composites these properties varied with WF content. An increase in wax content resulted to a decrease in water uptake by the composites, probably because the wax covered the WF particles and penetrated the pores in these particles. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Attitudes towards Sexuality, Sterilization and Parenting Rights of Persons with Intellectual Disabilities

M. Aunos
Background and Methods We review articles pertaining to attitudes towards sexuality, sterilization, procreation and parenting by people with intellectual disabilities. Most empirical studies were conducted after the appearance of the principles of normalization and role valorization in the 1970s. Results Across studies, special education teachers and university students appear to hold more positive attitudes towards sexuality and sexuality education programs than parents and service workers. People with intellectual disabilities have conservative attitudes towards sexual intercourse and homosexuality, but may be accepting intimate contact by familiar persons. Despite the ban on involuntary sterilization, it appears that many parents and teachers of persons with intellectual disabilities still support it as a form of contraception, especially for persons with severe intellectual disabilities. Likewise, attitudes towards parenting by persons with intellectual disabilities remain negative, and these attitudes may adversely affect the provision of competency-enhancing supports and services for parents with intellectual disabilities and their children. Conclusions It is recommended that new studies should be undertaken, comparing attitudes across different groups involved with persons with intellectual disabilities and examining the impact of prejudicial attitudes on sexual expression and parenting by persons with intellectual disabilities. [source]

Retinal pigment epithelial cells promote spatial reorganization and differentiation of retina photoreceptors

Olga L. German
Abstract Retina differentiation involves the acquisition of a precise layered arrangement, with RPE cells in the first layer in intimate contact with photoreceptors in the second layer. Here, we developed an in vitro coculture model, to test the hypothesis that RPE cells play a pivotal role in organizing the spatial structure of the retina. We cocultured rat retinal neurons with ARPE-19 epithelial cells under various experimental conditions. Strikingly, when seeded over RPE cells, photoreceptors attached to their apical surfaces and proceeded with their development, including the increased synthesis of rhodopsin. Conversely, when we seeded RPE cells over neurons, the RPE cells rapidly detached photoreceptors from their substrata and positioned themselves underneath, thus restoring the normal in vivo arrangement. Treatment with the metalloproteinase inhibitor TIMP-1 blocked this reorganization, suggesting the involvement of metalloproteinases in this process. Reorganization was highly selective for photoreceptors because 98% of photoreceptors but very few amacrine neurons were found to redistribute on top of RPE cells. Interestingly, RPE cells were much more efficient than other epithelial or nonepithelial cells in promoting this reorganization. RPE cells also promoted the growth of photoreceptor axons away from them. An additional factor that contributed to the distal arrangement of photoreceptor axons was the migration of photoreceptor cell bodies along their own neurites toward the RPE cells. Our results demonstrate that RPE and photoreceptor cells interact in vitro in very specific ways. They also show that in vitro studies may provide important insights into the process of pattern formation in the retina. 2008 Wiley-Liss, Inc. [source]

Racial Reconciliation in South Africa:Interracial Contact and Changes over Time

James L. Gibson
Relying upon,Gibson's (2004),theory equating lack of prejudice with interracial "reconciliation," we investigate racial attitudes based on a 2004 nationally representative survey of South Africans. We begin by documenting substantial group-based differences in intergroup prejudice, with Blacks being considerably less reconciled with Whites as compared to the three racial minorities' levels of reconciliation with Blacks. We also discover that the Black majority has become less reconciled with Whites over the period from Gibson's survey (in 2001) to the current survey (in 2004). Improvement in racial attitudes is observed among the other three groups. We next investigate intergroup contact as an explanation of differences in attitudes, finding some effects of mere contact and powerful effects of intimate contact. However, the consequences of contact differ across the various racial groups. [source]

Interlaminar contact development during thermoplastic fusion bonding

F. Yang
Fabrication of layered thermoplastics and thermoplastic-matrix composites using processes such as tow placement, tape laying, and resistance welding is fundamentally based on the principle of fusion bonding, which involves applying heat and pressure to contacting thermoplastic surfaces. One of the important processing steps,intimate contact development,is considered in this paper. Interlaminar intimate contact development has a strong dependency on the thermoplastic surface geometry. Profilometric measurements of common thermoplastic prepreg tows, such as AS4/PEEK and IM7/PIXA, show that surface roughness features appear at several length scales and that the surfaces have fractal asperity structures. In this paper, principles of fractal geometry are used to describe prepreg surfaces. Based on this description, a microscale fluid flow model is developed to relate a degree of intimate contact to the process parameters (pressure, temperature, and time) and the fractal parameters of the surface. The model development and comparisons with experimental data are presented and discussed. [source]

Characterization of electrochemical activity of a strain ISO2-3 phylogenetically related to Aeromonas sp. isolated from a glucose-fed microbial fuel cell

Kyungmi Chung
Abstract The microbial communities associated with electrodes in closed and open circuit microbial fuel cells (MFCs) fed with glucose were analyzed by 16S rRNA approach and compared. The comparison revealed that bacteria affiliated with the Aeromonas sp. within the Gammaproteobacteria constituted the major population in the closed circuit MFC (harvesting electricity) and considered to play important roles in current generation. We, therefore, attempted to isolate the dominant bacteria from the anode biofilm, successfully isolated a Fe (III)-reducing bacterium phylogenetically related to Aeromonas sp. and designated as strain ISO2-3. The isolated strain ISO2-3 could grow and concomitantly produce current (max. 0.24,A/m2) via oxidation of glucose or hydrogen with an electrode serving as the sole electron acceptor. The strain could ferment glucose, but generate less electrical current. Cyclic voltammetry supported the strain ISO2-3 was electrically active and likely to transfer electrons to the electrode though membrane-associated compounds (most likely c-type cytochrome). This mechanism requires intimate contact with the anode surface. Scanning electron microscopy revealed that the strain ISO2-3 developed multiplayer biofilms on the anode surface and also produced anchor-like filamentous appendages (most likely pili) that may promote long-range electron transport across the thick biofilm. Biotechnol. Bioeng. 2009; 104: 901,910. 2009 Wiley Periodicals, Inc. [source]

Nanoscale Structural and Electronic Properties of Ultrathin Blends of Two Polyaromatic Molecules: A Kelvin Probe Force Microscopy Investigation

CHEMPHYSCHEM, Issue 4 2006
Vincenzo Palermo Dr.
Abstract We describe a Kelvin Probe Force Microscopy (KPFM) study on the morphological and electronic properties of complex mono and bi-molecular ultrathin films self-assembled on mica. These architectures are made up from an electron-donor (D), a synthetic all-benzenoid polycyclic aromatic hydrocarbon, and an electron-acceptor (A), perylene-bis-dicarboximide. The former molecule self-assembles into fibers in single component films, while the latter molecule forms discontinuous layers. Taking advantage of the different solubility and self-organizing properties of the A and D molecules, multicomponent ultrathin films characterized by nanoscale phase segregated fibers of D embedded in a discontinuous layer of A are formed. The direct estimation of the surface potential, and consequently the local workfunction from KPFM images allow a comparison of the local electronic properties of the blend with those of the monocomponent films. A change in the average workfunction values of the A and D nanostructures in the blend occurs which is primarily caused by the intimate contact between the two components and the molecular order within the nanostructure self-assembled at the surface. Additional roles can be ascribed to the molecular packing density, to the presence of defects in the film, to the different conformation of the aliphatic peripheral chains that might cover the conjugated core and to the long-range nature of the electrostatic interactions employed to map the surface by KPFM limiting the spatial and potential resolution. The local workfunction studies of heterojunctions can be of help to tune the electronic properties of active multicomponent films, which is crucial for the fabrication of efficient organic electronic devices as solar cells. [source]

Evaluation of the sealed-tube low-temperature combustion method for the 13C/12C and 2H/1H ratio determinations of cellulose nitrate

Fa-Xiang Tao
Abstract Traditionally-suggested combustion time of 1 h at 550C) with the sealed-tube combustion method for determining the 13C/ 12C ratio of cellulose nitrate or other nitrogen-containing components could produce large negative deviation up to 1. Three types of cellulose are used to ascertain possible causes. The presence of nitrous oxide (N2O) formed during combustion is most likely responsible for this deviation. Prolongation of the combustion time (at least 5 h at 550C) and intimate contact between copper oxide and organic matter can greatly improve the analysis precision and effectively reduce this deviation to an acceptable level. Regardless of scattered carbon isotope data, hydrogen isotope data are all reproducible within 2 when this method is coupled with the high temperature uranium reduction method. Thus, care should be taken for determining carbon and nitrogen isotope compositions of nitrogen-containing substances using the low temperature sealed-tube combustion method. [source]

Evaluation of a novel biphasic calcium phosphate in standardized bone defects.

A histologic, histomorphometric study in the mandibles of minipigs
Abstract: Objective: A novel biphasic calcium phosphate (CaP) granulate consisting of hydroxyapatite (HA) and ,-tricalciumphosphate (TCP) was compared with pure HA and pure TCP and with autograft as positive control. Materials and methods: Four standardized bone defects were prepared in both mandibular angles of 16 minipigs and grafted with autogenous bone chips, HA, HA/TCP (60% : 40%), or TCP. Histologic and histomorphometric analysis of bone formation and graft degradation followed healing periods of 2, 4, 8, and 24 weeks. Results: 2 weeks: more bone formation in defects filled with autograft than with the three CaP materials (P<0.05). 4 weeks: bone formation differed significantly (P<0.05) between all four materials (autograft>TCP>HA/TCP>HA). 8 weeks: more bone formation in defects with autograft and TCP than with HA/TCP (P<0.05), and HA/TCP had more bone formation than HA (P<0.05). 24 weeks: no difference in bone formation between the groups. Autograft and TCP resorbed quickly and almost completely over 8 weeks, whereas HA/TCP and HA showed limited degradation over 24 weeks. Conclusion: All defects healed with mature lamellar bone and intimate contact between bone and the remaining graft material. The rate of bone formation corresponded to the content of TCP in the CaP materials. [source]