Polymers used to influence cell fate in 3D geometry: New trends

The extracellular matrix (ECM) is a hydrogel-like structure comprised of several different biopolymers, encompassing a wide range of biological, chemical, and mechanical properties. The composition, organization, and assembly of the ECM play a critical role in cell function. Cellular behavior is guided by interactions that occur between cells and their local microenvironment, and this interrelationship plays a significant role in determining physiological functions. Bioengineering approaches have been developed to mimic native tissue microenvironments by fabricating novel bioactive hydrogel scaffolds. This review explores material designs and fabrication approaches that are guiding the design of hydrogels as tissue engineered scaffolds. As the fundamental biology of the cellular microenvironment is often the inspiration for material design, the review focuses on modifications to control bioactive cues such as adhesion molecules and growth factors, and summarizes the current applications of biomimetic scaffolds that have been used in vitro as well as in vivo.     

On the Mechanism of Lubrication by Tricresylphosphate (TCP)—The Coefficient of Friction as a Function of Temperature for TCP on M-50 Steel

A pin-on-disk tribometer was used to study the coefficient of friction as a function of temperature for tricresylphosphate (TCP) on CVM M-50 tool steel under the following conditions: TCP was present in a liquid reservoir (bulk lubrication), and TCP was applied as a liquid layer directly to the disk (limited lubrication). Under limited lubrication conditions, experiments were performed in dry (< 100 ppm H₂O) air, dry (< 20 ppm H₂O) nitrogen, dry nitrogen with the disks heated to 700°C, then cooled to room temperature before the TCP was applied and the measurements made (preheated disks), and moist nitrogen using preheated disks. The coefficient of friction decreased at a characteristic temperature, T_r T_r values observed were: 265°C for bulk lubrication conditions in dry air, 225°C for limited lubrication conditions in dry air, and 215°C for limited lubrication conditions in dry nitrogen. The use of preheated disks produced a sharp failure temperature at 218°C which was taken as the temperature about which the behavior of TCP should be judged. X-ray photoelectron spectroscopy confirmed the presence of phosphate on the surface of TCP-lubricated iron pins. Depth profile studies support the suggestion that a chemical reaction occurs between the TCP and the metal surface at T_r.     

The politics of ‘race’ and the transformation of the post-apartheid space economy

This paper provides an overview of the challenge of spatial reconfiguration facing South Africa. Set against a brief overview of the key aspects of the post apartheid urban policy milieu that, notwithstanding significant tensions within the ruling party, gave rise to a cabinet level policy commitment to a National Spatial Development Perspective (NSDP). The paper reflects on three key themes. The first issue outlined in the paper is the massive demographic shift that is taking place that underpins the development challenge. In particular trends in the process of population growth, labour market change and urbanization are summarized. Second, given the dominance of Africans in urban spaces, the paper outlines how efforts to achieve racial integration have erroneously focused on rural over urban development. A distinction is drawn between traditionalist pro-African views that give preferences to rural spending and modernist views that articulate an overly non-racial discourse that embraces a shift to urban development. Finally we argue that the failure of spatial planning as proposed by the NSDP was not inevitable, despite real flaws in the policy and its execution. The dithering on spatial policy that surrounded the NSDP must be understood as the outcome of political contestation within the ruling party and a misplaced conflation of the categories of rural and African.     

Microgravity materials and life sciences research applications of digital holography

We investigate the utility of digital holographic interferometry for analyzing gravity-dependent mass transport phenomena as applicable to materials and life science research topics. Digital holography is useful for measurement of parameters that introduce phase changes in light traversing the material of interest, such as temperature or concentration variations in an aqueous environment. We have constructed, tested, and verified a compact, portable digital holographic monitor (DHM) suitable for characterization of transparent samples. It has proved useful for the study of systems such as protein crystal growth solutions and has been proposed for further application into studies involving microbial metabolism. The DHM is also sufficiently rugged for field operation in challenging environments a s may be encountered in a spacecraft or industrial setting. We discuss some system capabilities and limitations.     

Attribute value reordering for efficient hybrid OLAP

The normalization of a data cube is the ordering of the attribute values. For large multidimensional arrays where dense and sparse chunks are stored differently, proper normalization can lead to improved storage efficiency. We show that it is NP-hard to compute an optimal normalization even for 1 × 3 chunks, although we find an exact algorithm for 1 × 2 chunks. When dimensions are nearly statistically independent, we show that dimension-wise attribute frequency sorting is an optimal normalization and takes time O(dn log(n)) for data cubes of size n^d. When dimensions are not independent, we propose and evaluate a several heuristics. The hybrid OLAP (HOLAP) storage mechanism is already 19-30% more efficient than ROLAP, but normalization can improve it further by 9-13% for a total gain of 29-44% over ROLAP.     

Transduction of normal and malignant oral epithelium by particle bombardment

Considerable basic research, mostly in the past 20 years, has elicited greatly increased knowledge concerning the structure and function of cell adhesion molecules. Scores of individual adhesion molecules have been identified and categorized as to major structural features, ligands recognized, and pattern of expression. Recent attention has been focused on the interaction of cell adhesion molecules with intracellular components, and the role of cell adhesion molecules in mediating cell signal transduction. Ongoing efforts to develop specific pharmacological agonists and antagonists for adhesion molecules holds great promise in clinical medicine. Abciximab (Reopro), a monoclonal antibody inhibitor of the platelet integrin alpha IIb beta 3, is currently approved and available to improve vessel patency in patients undergoing angioplasty. Similar approaches to develop adhesion-based therapies to block angiogenesis, tumor progression, and/or metastasis are under development and hold promise for patients with cancer.     

Surgical management of third nerve palsy

AIMS: A surgical technique has been developed in order to obtain ocular alignment in the primary position in patients with third nerve palsy. METHODS: A method for surgically correcting the vertical deviation and the pseudoptosis is described in three patients with longstanding third nerve palsy. By decreasing the ability of the non-involved eye to elevate, a fixation duress was created which eliminated the secondary deviation that characteristically occurs in such patients when the involved eye fixates. As a result of this technique, both eyes in all patients on attempted fixation were under similar duress, therefore requiring equal amounts of stimulation to move into the primary position. When the fixation duress was sufficient, elimination of the hypotropia and ptosis was achieved. Additionally, in order to correct the exotropia, generous recession and resection procedures in the involved eye and recession of the lateral rectus in the noninvolved eye were performed. RESULTS: Between 8 and 10 prism dioptres of esotropia were achieved and maintained in two patients. One patient had 20 prism dioptres of exotropia. Two patients had no residual ptosis and one required an additional anterior levator resection to achieve a satisfactory result. CONCLUSION: Patients with a third nerve palsy and a pseudoptosis may be candidates for this approach.     

Dose of hemodialysis and survival: differences by race and sex

CONTEXT: Although blacks receive lower doses of hemodialysis than whites, their survival when receiving dialysis treatment is better than that for whites. Previous studies of the relationship between the dose of dialysis and patient survival have not controlled for differences in patient characteristics. OBJECTIVE: To examine the association of mortality with the dose of hemodialysis for clusters of patients categorized by race and sex. DESIGN: Retrospective analysis of laboratory data and mortality outcomes from 1994, using a national database of hemodialysis patients. PATIENTS: A total of 18144 black and white patients receiving hemodialysis 3 times weekly who either lived the entire year receiving hemodialysis or died. MAIN OUTCOME MEASURES: The fractional reduction of urea in a single dialysis session as the measured hemodialysis dose (urea reduction ratio [URR]) after controlling for race, sex, age, and diabetes mellitus. Mortality was determined by strata of URRs and albumin and creatinine levels. RESULTS: Across all age categories, blacks had lower URRs than whites, and men had lower URRs than women. In an age-adjusted model for evaluating interactions among URRs, race, sex, and diabetes, the association of URR with mortality risk was weak among blacks, particularly black men. After adjustment for age and diabetes, death probability curves were most steep for white women with URR values less than 60%. The death probability curves were least steep for black men. There was no meaningful difference between death probability and albumin or creatinine concentration among the race by sex clusters. CONCLUSION: Using URR, the usual measure of hemodialysis dose, the assumption that the association between dialysis dose and survival is uniform across demographic groups appears incorrect. Comparisons of the quality of dialysis patient care should not rely on URR alone to predict patient survival.