Negative normal stress in semiflexible biopolymer gels

When subject to stress or external loads, most materials resist deformation. Any stable material, for instance, resists compression-even liquids. Solids also resist simple shear deformations that conserve volume. Under shear, however, most materials also have a tendency to expand in the direction perpendicular to the applied shear stress, a response that is known as positive normal stress. For example, wet sand tends to dilate when sheared, and therefore dries around our feet when we walk on the beach. In the case of simple solids, elastic rods or wires tend to elongate when subject to torsion. Here, we show that networks of semiflexible biopolymers such as those that make up both the cytoskeleton of cells and the extracellular matrix exhibit the opposite tendency: when sheared between two plates, they tend to pull the plates together. We show that these negative normal stresses can be as large as the shear stress and that this property is directly related to the nonlinear strain-stiffening behaviour of biopolymer gels.     

Nonfunctionalized nanocrystals can exploit a cell's active transport machinery delivering them to specific nuclear and cytoplasmic compartments

We use high content cell analysis, live cell fluorescent imaging, and transmission electron microscopy approaches combined with inhibitors of cellular transport and nuclear import to conduct a systematic study of the mechanism of interaction of nonfunctionalized quantum dots (QDs) with live human blood monocyte-derived primary macrophages and cell lines of phagocytic, epithelial, and endothelial nature. Live human macrophages are shown to be able to rapidly uptake and accumulate QDs in distinct cellular compartment specifically to QDs size and charge. We show that the smallest QDs specifically target histones in cell nuclei and nucleoli by a multistep process involving endocytosis, active cytoplasmic transport, and entering the nucleus via nuclear pore complexes. Treatment of the cells with an anti-microtubule agent nocodazole precludes QDs cytoplasmic transport whereas a nuclear import inhibitor thapsigargin blocks QD import into the nucleus. These results demonstrate that the nonfunctionalized QDs exploit the cell's active transport machineries for delivery to specific intranuclear destinations.     

Multifunctional chondroitin sulphate for cartilage tissue-biomaterial integration

A biologically active, high-strength tissue adhesive is needed for numerous medical applications in tissue engineering and regenerative medicine. Integration of biomaterials or implants with surrounding native tissue is crucial for both immediate functionality and long-term performance of the tissue. Here, we use the biopolymer chondroitin sulphate (CS), one of the major components of cartilage extracellular matrix, to develop a novel bioadhesive that is readily applied and acts quickly. CS was chemically functionalized with methacrylate and aldehyde groups on the polysaccharide backbone to chemically bridge biomaterials and tissue proteins via a twofold covalent link. Three-dimensional hydrogels (with and without cells) bonded to articular cartilage defects. In in vitro and in vivo functional studies this approach led to mechanical stability of the hydrogel and tissue repair in cartilage defects.     

Duplex scanning alone is not sufficient imaging before secondary procedures after lower extremity reversed vein bypass graft

PURPOSE: Duplex surveillance of lower extremity reversed vein bypass grafts (LERVG) is a means of identifying patients at risk for occlusion. The perceived accuracy of duplex scan as a means of identifying stenoses has led many surgeons to perform graft revision on the basis of duplex scan alone. This may result in missing additional lesions that are threatening patency. To assess the role of duplex scan as the sole imaging method before revision of LERVGs, we reviewed consecutive patients undergoing revisions who underwent preoperative arteriography after identification of duplex scan abnormalities. METHODS: Duplex scan results, operative reports, and preoperative arteriograms for patients undergoing LERVG revision from January 1990 to December 1997 were reviewed. A standard duplex scan surveillance protocol was followed, and attempts were made to survey the entire graft, including inflow and outflow. Duplex scan results were compared with the results of preoperative arteriograms and the operation performed to determine if all significant lesions were identified by means of duplex scan alone. RESULTS: Two hundred five LERVG revisions were performed. The 5-year assisted primary patency rate was 91%. In 119 cases (58%), arteriography did not contribute significantly to duplex scan findings. Arteriography significantly contributed to operative planning in 86 cases (42%). In 38 cases (19%), only a low-flow state was identified by means of duplex scan, and a correctable stenosis was identified by means of arteriography. In 48 cases (23%), additional significant lesions corrected at operation were identified by means of arteriography. These included 26 inflow, 16 graft, and 8 outflow lesions. Arteriography was most useful as a means of determining the revision procedure performed when there were inflow lesions (P <.05) or when the proximal anastomosis was to the profunda or superficial femoral arteries (P <.05). All frequently performed bypass graft configurations had some discrepancy between arteriographic and duplex scan findings. CONCLUSION: Available data do not permit prediction of which LERVG are immune from missed lesions in a duplex scan surveillance protocol. This suggests to us that arteriography is mandatory before LERVG revisions.     

MPEG-4 Video and Image Coding on Digital Signal Processors

The emerging MPEG-4 standard encompasses a wide variety of applications, many of which are suitable for implementation on a Digital Signal Processor (DSP). In particular, consumer products with embedded multimedia capability, such as set-top boxes and wireless communicators, are suitable for DSP-based implementation. With a programmable approach, various algorithmic tradeoffs can be made, based on processing capability. For best performance, careful attention must be paid to memory allocation, data transfer, and ordering of instructions to best match the DSP architecture. We discuss implementing simple profile MPEG-4 video on the low-power TMS320C54x, core profile on the TMS320C6x, and scalable texture profile, which could be implemented on either processor family.     

Phospholipid composition of the granular amebocyte from the horseshoe crab, Limulus polyphemus

The phospholipid composition was determined for the amebocyte of the primitive arthropod Limulus polyphemus. The total fatty acid composition of the cells' lipids was analyzed by gas chromatography/mass spectrometry (GC/MS) of fatty acid methyl esters (FAME). The FAME analysis revealed high levels of 20-carbon polyunsaturated fatty acids (PUFA), especially arachidonic (20∶4n-6) and eicosapentaenoic (20∶5n-3) acids. Almost 20% of the total lipid profile was comprised of dimethyl acetals of 16- to 20-carbon chain lengths, indicative of plasmalogens in the phospholipid pool. Phospholipids, analyzed by high-pressure liquid chromatography, included phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI), sphingomyelin (SPH), and cardiolipin (CL). PE and PC levels predominated at 42.2 and 36.3%, respectively. Smaller amounts of PS (9.0%) and PI (6.2%) were present, as well as low levels of SPH (4.6%), CL (1.6%), and trace amounts of lysophosphatidylcholine. The major phospholipid species, PE, PC, PS and PI, were collected and their molecular species were examined by electrospray-ionization mass spectrometry. The molecular species within the phospholipid classes reflected the high levels of PUFA seen in the total lipid profile. PI was mainly composed of 18∶0a/20∶4. Over half of the PS consisted of 18∶0a/18∶1 and 18∶0a/20∶4. The major PE species were 20∶1p/20∶5, 20∶1p/20∶4, 18∶0p/20∶5, and 18∶0p/20∶4. PC had the largest distribution of molecular species, and its most abundant species were 16∶0e/20∶5, 16∶0e/20∶4, and 16∶0p/20∶4. The presence of 16∶0e/20∶4 is the first documentation of a specific precursor to platelet-activating factor in an invertebrate hemocyte. Note: at the sn-1 position: [a=1=O-acyl, e=1-O-alkylether, and p=1-O-alk-1′-enyl (plasmalogen)].     

Changes in fertilizer and manurial practices during 1960–1990: implications for N and P inputs to the Ythan catchment, N.E. Scotland

A suggested increase in the growth of macrophytic algae within the Ythan estuary (N.E. Scotland) over recent years has been linked to the increased amounts of nitrogen in the form of NO₃–N entering the estuary from the river. The increased NO₃ concentration in the river has been associated with recent changes in farming practices in this predominantly agricultural catchment. Terrestrially derived phosphorus is also considered to contribute increasingly to eutrophication of fresh waters. Historical agricultural census data together with appropriate surveys of fertilizer practice were used to calculate the total quantities of fertilizer and manure derived N and P applied annually over the wholeYthan catchment during the period 1960 – 1990. While the total agricultural land area has remained similar, significant changes in cropping practice have occurred. In particular, a greater proportion of land is given to autumn sown crops while the area of grassland has declined. These changes in farming practice are associated with differences in both the total amounts and timing of fertilizer applied. The use of inorganic N in the catchment has trebled since 1960 and is currently approximately 6400 tonnes (104 kg N/ha). The use of P has decreased by more than a quarter to 1274 tonnes (21 kg P/ha) over a similar time period. There has been no obvious change in total quantity of N and P derived from animal manures, estimated to be 44 and 11 kg per ha, respectively, when averaged over the area of agricultural land. Cattle and sheep numbers have remained relatively constant and together account for approximately 80% of the manure N and 70% of the manure P produced annually. However, poultry have declined by 70% since 1960 while pig numbers have increased six-fold. The average annual application rate of manure derived N over the whole catchment (44 kg/ha) is considerably below that proposed at the farm scale in the EC Nitrate Directive (210–170 kg/ha). However, on a local scale difficulties may arise for large manure producing concerns such as dairy or pig units.     

The influence of in-store music on wine selections.

This field study investigated the extent to which stereotypically French and German music could influence supermarket customers' selections of French and German wines. Music with strong national associations should activate related knowledge and be linked with customers buying wine from the respective country. Over a 2-week period, French and German music was played on alternate days from an in-store display of French and German wines. French music led to French wines outselling German ones, whereas German music led to the opposite effect on sales of French wine. Responses to a questionnaire suggested that customers were unaware of these effects of music on their product choices. The results are discussed in terms of their theoretical implications for research on music and consumer behavior and their ethical implications for the use of in-store music. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feeling controlled in marriage: A phenomenon specific to physically aggressive couples?

Spouses in maritally happy nonaggressive (H; n?=?21), distressed nonaggressive (DNA; n?=?16), and distressed aggressive (DA; n?=?20) marriages were interviewed about their perceptions of their spouse as controlling. Four areas of spousal control were assessed: involvement in decision making, relationships with family and friends, freedom to plan activities independently, and sense of competence and self-respect. Overall, as expected, spouses in happy marriages reported feeling less controlled than spouses in the 2 distressed groups. Few gender differences were obtained, with the exception that wives in aggressive marriages were more likely to report that their husbands controlled their sense of competence and self-respect. Differences between the DA and DNA groups depended on the specific area of control. Wives in the aggressive couples were significantly more likely than their husbands to state that their spouse's aggression was an attempt to control them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Theory and research on small groups.

Review of book: R. Scott Tindale et. al (Eds.) Theory and Research on Small Groups. New York: Plenum Press. 1998, 277 pp. Reviewed by Mark F. Stasson, Michael J. Markus, and Jason W. Hart. (PsycINFO Database Record (c) 2010 APA, all rights reserved)