Experimental fitting to the bipolaronic model of the normal-state resistance of Bi_2Sr_2CaCu_2O_8 single crystals

Normal-state resistance data from Bi_2Sr_2CaCu_2O_8 single crystals were fitted to the (bi)polaronic conduction model, $R=R_0 (T+\sigma_b T^2)/(1+bT)$, with satisfactory agreement over a wide temperature range. The fluctuating conduction region is found to be much narrower than that in the usual sense, as is the case for a charged Bose-gas. We estimate the effective (bi)polaron mass to be ~ 4m_e.Comment: 2 pages + 2 postscript figures. Submitted to M2S-HTSC-VI(Houston) Conferenc

On the effects of using CO2 and F2 lasers to modify the wettability of a polymeric biomaterial.

Enhancement of the surface properties of a material by means of laser radiation has been amply demonstrated previously. In this work a comparative study for the surface modification of nylon 6,6 has been conducted in order to vary the wettability characteristics using CO2 and excimer lasers. This was done by producing 50 μm spaced (with depths between 1 and 10 μm) trench-like patterns using various laser parameters such as varying the laser power for the CO2 laser and number of pulses for the excimer laser. Topographical changes were analysed using optical microscopy and white light interferometry which indicated that both laser systems can be implemented for modifying the topography of nylon 6,6. Variations in the surface chemistry were evaluated using energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy analysis and showed that the O2 increased by up to 1.5% At. and decreased by up to 1.6% At. for the CO2 and F2 laser patterned samples, respectively. Modification of the wettability characteristics was quantified by measuring the advancing contact angle, which was found to increase in all instances for both laser systems. Emery paper roughened samples were also analysed in the same manner to determine that the topographical pattern played a major role in the wettability characteristics of nylon 6,6. From this, it is proposed that the increase in contact angle for the laser processed samples is due to a mixed intermediate state wetting regime owed to the periodic surface roughness brought about by the laser induced trench-like topographical patterns

On the use of CO2 laser induced surface patterns to modify the wettability of Poly(methyl methacrylate) (PMMA)

CO2 lasers can be seen to lend themselves to materials processing applications and have been used extensively in both research and industry. This work investigated the surface modification of PMMA with a CO2 laser in order to vary the wettability characteristics. The wettability characteristics of the PMMA were modified by generating a number of patterns of various topography on the surface using the CO2 laser. These induced patterns were trench and hatch with scan dimensions of 50 and 100 μm. Through white light interferometry it was found that for all laser patterned samples the surface roughness had significantly increased by up to 3.1 μm. The chemical composition of selected samples were explored using X-ray photoelectron spectroscopy and found that the surface oxygen content had risen by approximately 4% At. By using a sessile drop device it was found that, in comparison to the as-received sample, 50 μm dimensions gave rise to a more hydrophilic surface; whereas 100 μm dimensions gave rise to either no change in contact angle or an increase making the PMMA hydrophobic. This can be explained by combinations of surface roughness and γp contributing to the observed contact angle, in addition to the possibility of different wetting regimes taking place owed to the variation of topographies over the as-received and laser patterned samples

Interaction of CO2 laser-modified nylon with osteoblast cells in relation to wettability

It has been amply demonstrated previously that CO2 lasers hold the ability to surface modify various polymers. In addition, it has been observed that these surface enhancements can augment the biomimetic nature of the laser irradiated materials. This research has employed a CO2 laser marker to produce trench and hatch topographical patterns with peak heights of around 1 μm on the surface of nylon 6,6. The patterns generated have been analysed using white light interferometery, optical microscopy and X-ray photoelectron spectroscopy was employed to determine the surface oxygen content. Contact angle measurements were used to characterize each sample in terms of wettability. Generally, it was seen that as a result of laser processing the contact angle, surface roughness and surface oxygen content increased whilst the apparent polar and total surface energies decreased. The increase in contact angle and reduction in surface energy components was found to be on account of a mixed intermediate state wetting regime owing to the change in roughness due to the induced topographical patterns. To determine the biomimetic nature of the modified and as-received control samples each one was seeded with 2×104 cells/ml normal human osteoblast cells and observed after periods of 24 hours and 4 days using optical microscopy and SEM to determine mean cell cover densities and variations in cell morphology. In addition a haeymocytometer was used to show that the cell count for the laser patterned samples had increased by up to a factor of 1.5 compared to the as-received control sample after 4 days of incubation. Significantly, it was determined that all laser-induced patterns gave rise to better cell response in comparison to the as-received control sample studied due to increased preferential cell growth on those surfaces with increased surface roughness

Evaluation of sedimentation rate methodology reveals an unusual pediatric subpopulation with lupus or lupus-like syndrome and hemolytic anemia

Purpose Sedimentaion rate is often used to manage pediatric patients with rheumatologic disease. Most management decisions are dependent on studies which have used Wintrobe or Westergren sedimentation rate methodologies. However, these methods suffer from the need for relatively large amounts of blood and long turn-around times. Determination of sedimentation rate using laser kinetic rate determination has allowed calibration to Westergren methods, low volume of blood needed for testing and very rapid results. We sought to compare the Wintrobe method to the ESR Stat method (kinetic method; HemaTechnologies, Lebanon NJ) to determine suitability of the ESR Stat method for patient testing. Go to: Methods We performed a prospective comparison between the traditional Wintrobe and ESR Stat sedimentation rates in consecutive pediatric patients at a tertiary care pediatric hospital. Wintrobe and ESR Stat sedimentation data was fitted using a logarithmic model. Outliers were defined as those samples with ESR Stat sedimentation rates greater than 80 mm/hr and Wintrobe sedimentation rates less than 30 mm/hr (normal or mildly elevated sedimentation rate). Retrospective chart review was performed on all patients undergoing testing. Go to: Results A total of 131 pediatric patients (with one patient undergoing repeat testing because of sedimentation rate discrepancy) were tested. Age range was 18 months to 34 years with 29% being male. A logarithmic model appeared to best fit the data (R2 = 0.7768) and is seen below. Of interest was the identification of four patients who had apparently normal or mildly elevated sedimentation rates by the Wintrobe method versus an extremely high (greater than 120 mm/hr) by the ESR Stat method. These patients were noted to have lupus or lupus-like syndrome and a history of hemolytic anemia. Non-outlier samples were from patients who did not this combination of disease morbidities. Figure 1 Go to: Conclusion Discrepancies in Wintrobe and ESR Stat sedimentation rates may identify a subgroup of with lupus (or lupus-like syndrome) and a history of hemolytic anemia. Careful consideration of methodology is needed when sedimentation rate testing is performed on pediatric lupus patients

Ex Vivo Expansion of Human Mesenchymal Stem Cells in Defined Serum-Free Media

Human mesenchymal stem cells (hMSCs) are presently being evaluated for their therapeutic potential in clinical studies to treat various diseases, disorders, and injuries. To date, early-phase studies have indicated that the use of both autologous and allogeneic hMSCs appear to be safe; however, efficacy has not been demonstrated in recent late-stage clinical trials. Optimized cell bioprocessing protocols may enhance the efficacy as well as safety of hMSC therapeutics. Classical media used for generating hMSCs are typically supplemented with ill-defined supplements such as fetal bovine serum (FBS) or human-sourced alternatives. Ideally, culture media are desired to have well-defined serum-free formulations that support the efficient production of hMSCs while maintaining their therapeutic and differentiation capacity. Towards this objective, we review here current cell culture media for hMSCs and discuss medium development strategies

Quick Git Setup

Version control is widely adopted in industry because it enables software development in groups, yet few students gain sufficient experience through their undergraduate courses. Even though version control is ideal for work submission, faculty may avoid it in favor of course management systems used only in academia. This tutorial introduces software to automate setting up version control with cloud project hosting services, and gives experience with version control as a side-effect of work submission and collection. This tutorial assumes no prior experience