Ceramic-metal composites for heat exchangers in concentrated solar power plants.

The efficiency of generating electricity from heat using concentrated solar power plants (which use mirrors or lenses to concentrate sunlight in order to drive heat engines, usually involving turbines) may be appreciably increased by operating with higher turbine inlet temperatures, but this would require improved heat exchanger materials. By operating turbines with inlet temperatures above 1,023 kelvin using closed-cycle high-pressure supercritical carbon dioxide (sCO2) recompression cycles, instead of using conventional (such as subcritical steam Rankine) cycles with inlet temperatures below 823 kelvin1-3, the relative heat-to-electricity conversion efficiency may be increased by more than 20 per cent. The resulting reduction in the cost of dispatchable electricity from concentrated solar power plants (coupled with thermal energy storage4-6) would be an important step towards direct competition with fossil-fuel-based plants and a large reduction in greenhouse gas emissions7. However, the inlet temperatures of closed-cycle high-pressure sCO2 turbine systems are limited8 by the thermomechanical performance of the compact, metal-alloy-based, printed-circuit-type heat exchangers used to transfer heat to sCO2. Here we present a robust composite of ceramic (zirconium carbide, ZrC) and the refractory metal tungsten (W) for use in printed-circuit-type heat exchangers at temperatures above 1,023 kelvin9. This composite has attractive high-temperature thermal, mechanical and chemical properties and can be processed in a cost-effective manner. We fabricated ZrC/W-based heat exchanger plates with tunable channel patterns by the shape-and-size-preserving chemical conversion of porous tungsten carbide plates. The dense ZrC/W-based composites exhibited failure strengths of over 350 megapascals at 1,073 kelvin, and thermal conductivity values two to three times greater than those of iron- or nickel-based alloys at this temperature. Corrosion resistance to sCO2 at 1,023 kelvin and 20 megapascals was achieved10 by bonding a copper layer to the composite surface and adding 50 parts per million carbon monoxide to sCO2. Techno-economic analyses indicate that ZrC/W-based heat exchangers can strongly outperform nickel-superalloy-based printed-circuit heat exchangers at lower cost.

Sirolimus conversion regimen versus continued calcineurin inhibitors in liver allograft recipients: a randomized trial.

A large prospective, open-label, randomized trial evaluated conversion from calcineurin inhibitor (CNI)- to sirolimus (SRL)-based immunosuppression for preservation of renal function in liver transplantation patients. Eligible patients received liver allografts 6-144 months previously and maintenance immunosuppression with CNI (cyclosporine or tacrolimus) since early posttransplantation. In total, 607 patients were randomized (2:1) to abrupt conversion (<24 h) from CNI to SRL (n = 393) or CNI continuation for up to 6 years (n = 214). Between-group changes in baseline-adjusted mean Cockcroft-Gault GFR at month 12 (primary efficacy end point) were not significant. The primary safety end point, noninferiority of cumulative rate of graft loss or death at 12 months, was not met (6.6% vs. 5.6% in the SRL and CNI groups, respectively). Rates of death at 12 months were not significantly different, and no true graft losses (e.g. liver transplantation) were observed during the 12-month period. At 52 weeks, SRL conversion was associated with higher rates of biopsy-confirmed acute rejection (p = 0.02) and discontinuations (p < 0.001), primarily for adverse events. Adverse events were consistent with known safety profiles. In conclusion, liver transplantation patients showed no demonstrable benefit 1 year after conversion from CNI- to SRL-based immunosuppression.

American Society of Transplant Surgeons' White Paper: impact of closed ICUs on transplant patients' care.

The following paper was produced by the collaborative effort of the Critical Care Task-Force of the American Society of Transplant Surgeons (ASTS) and was formally adopted by the ASTS Executive Council as the society's stand on the subject of 'closed' intensive care units.

Agro-industrial waste 'wheat bran' for the biosorptive remediation of selenium through continuous up-flow fixed-bed column.

Present study deals with the utilization of an agro-industrial waste wheat bran for the remediation of selenium species, Se(IV) and Se(VI) by continuous up-flow fixed-bed column system. Laboratory-scale column tests were performed to determine potentiality of wheat bran at various bed height, flow rates and initial metal ion concentration and it was found to be very potential biosorbent as it showed good sorption capacities of 72.54 microg/g and 62.51 microg/g for Se(IV) and Se(VI) respectively. Different models like Bed Depth Service Time (BDST), Thomas and Yoon-Nelson were applied to the experimental sorption data. The data showed very good fit to BDST model and sorption capacities (N(o)) computed using BDST model were 26,664 microg/L and 26,400 microg/L for Se(IV) and Se(VI) respectively. Also Yoon-Nelson model was found to show good agreement with the experimental kinetic results as compared to the Thomas model. Wheat bran was amenable to efficient regeneration with 10% NaOH. The biosorbent retained most of its original uptake capacity over three cycles of use. The excellent reusability of the biosorbent could lead to development of a viable metal remediation technology. Life factor calculation revealed that biosorbent bed will have sufficient capacity to avoid breakthrough at time t=0 up to 12.17 cycles for Se(IV) and 6.28 cycles for Se(VI) and bed would be completely exhausted after 56.89 cycles for Se(IV) and 18.73 cycles for Se(VI).

Biosorption of Cr(VI) from aqueous solution using A. hydrophila in up-flow column: optimization of process variables.

In the present study, continuous up-flow fixed-bed column study was carried out using immobilized dead biomass of Aeromonas hydrophila for the removal of Cr(VI) from aqueous solution. Different polymeric matrices were used to immobilized biomass and polysulfone-immobilized biomass has shown to give maximum removal. The sorption capacity of immobilized biomass for the removal of Cr(VI) evaluating the breakthrough curves obtained at different flow rate and bed height. A maximum of 78.58% Cr(VI) removal was obtained at bed height of 19 cm and flow rate of 2 mL/min. Bed depth service time model provides a good description of experimental results with high correlation coefficient (> 0.996). An attempt has been made to investigate the individual as well as cumulative effect of the process variables and to optimize the process conditions for the maximum removal of chromium from water by two-level two-factor full-factorial central composite design with the help of Minitab version 15 statistical software. The predicted results are having a good agreement (R (2) = 98.19%) with the result obtained. Sorption-desorption studies revealed that polysulfone-immobilized biomass could be reused up to 11 cycles and bed was completely exhausted after 28 cycles.

Cyclosporine promotes epstein-barr virus-infected human B-cell transformation assayed by three correlated assay methods.

We have reported that cyclosporine (CsA) has direct effect to promote Epstein-Barr virus (EBV) transformation of human peripheral blood B lymphocytes. In this article, we have reported that CsA promoted EBV-infected, human B-cell transformation as assayed by three methods of colony number counting, cell number counting, and (3)H-thymidine incorporation. At first, we sought to correlate the three methods in EBV-infected human B-cell transformation, observing that they are convenient correlate with each other, and only vary in the degree when transformed cells are compared to the controls. Based on these pilot experiments, the three assay methods were then applied to CsA-treated and nontreated, EBV-infected human B cells to investigate whether CsA treatment promoted EBV-infected human B-cell transformation. We observed that CsA treatment increased colony formation above the control value of 28 +/- 4.5/well to 49 +/- 4.3 (colonies/well; n = 5; P < .05). CsA treatment increased the cell number from the control of 33,025 +/- 1900 to 50,925 +/- 4194 (cells/well; n = 5; P < .05). CsA treatment increased (3)H-thymidine incorporation from the control result of 12,481 +/- 1341 to 26,514 +/- 5464 (CPM/well; n = 5; P < .05). In conclusion, CsA promoted EBV-B-cell transformation in three correlated assay methods in vitro using a model of posttransplant lymphoproliferative disorder.

Biosorption of arsenic from aqueous solution using agricultural residue 'rice polish'.

'Rice polish' (an agricultural residue) was utilized successfully for the removal of arsenic from aqueous solution. Various parameters viz. pH, biosorbent dosage, initial metal ion concentration and temperature were studied. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models were used and the system followed all three isotherms, showing sorption to be monolayer on the heterogeneous surface of the biosorbent. The maximum sorption capacity calculated using Langmuir model was 138.88 microg/g for As(III) at 20 degrees C and pH 7.0 and 147.05 microg/g at 20 degrees C and pH 4.0 for As(V). The mean sorption energy (E) calculated from D-R model indicated chemisorption nature of sorption. Study of thermodynamic parameters revealed the exothermic, spontaneous and feasible nature of sorption process in case of both As(III) and As(V). The pseudo-second-order rate equation described better the kinetics of arsenic sorption with good correlation coefficients than pseudo-first-order equation. Mass transfer, intraparticle diffusion, richenberg and elovich models were applied to the data and it was found that initially the sorption of arsenic was governed by film diffusion followed by intraparticle diffusion. Rice polish was found to be efficient in removing arsenic from aqueous solution as compared to other biosorbents already used for the removal of arsenic.

Biosorption of Cr(VI) from water using biomass of Aeromonas hydrophila: central composite design for optimization of process variables.

The potential use of biomass of Aeromonas hydrophila for biosorption of chromium from aqueous solution was investigated. The variables (pH, initial Cr(VI) concentration, biomass dose, and temperature) affecting process were optimized by performing minimum number of experimental runs with the help of central composite design. The results predicted by design were found to be in good agreement (R2 = 99.1%) with those obtained by performing experiments. Multiple regression analysis shows that uptake decreases with increase in pH and biomass dose, whereas it increases with increase in temperature and concentration. The maximum removal of Cr(VI) predicted by contour and optimization plots was 184.943 mg/g at pH 1.5, initial Cr(VI) concentration 311.97 mg/L, temperature 60 degrees C, and biomass dose 1.0 g. The removal of Cr(VI) was governed by adsorption of Cr(VI) as well as its reduction into Cr(III), which further gets adsorbed. The sorption capacity of biomass was calculated from experimental data using Langmuir sorption model and was found to be 151.50 mg/g at 40 degrees C and pH 1.5, which is comparable to other biosorbents. In addition to this, Dubinin-Radushkevich model was applied, and it was found that nature of sorption was chemisorption.

Successful management of eviscerated renal allograft with preservation of function.

Although most wound complications after renal transplantation are minor, the renal allograft, in its superficial and extraperitoneal location, is vulnerable to exposure if there is wound breakdown resulting in loss of overlying tissue. We describe a 66-year-old man who received a renal allograft from a deceased donor for end-stage renal disease (ESRD) secondary to polycystic kidney disease.His immediate posttransplant course was complicated by delayed graft function from acute tubular necrosis, reexploration for perigraft hematoma and subsequent wound dehiscence. After unsuccessful conservative wound care, the renal allograft became completely eviscerated due to fascial retraction of the dehisced wound. While the allograft was initially covered with a pedicled rectus femoris muscle flap, several local tissue rearrangements were required for definitive coverage. The allograft function was recovered after initial flap coverage and was subsequently maintained; follow-up more than 2 years after transplantation has demonstrated not only continued stable graft function but also complete healing of the dehiscent wound.

Two-dimensional confinement of nanorods in block copolymer domains.

Gold nanorods (NRs) self-orient during the self-assembly of a symmetric poly(styrene-b-methyl methacrylate) (PS-b-PMMA) film. The NRs are selectively sequestered and confined in lamellar PMMA domains, which are narrower than the NR length. This confinement orients 71% of NRs within +/- 5 degrees of the lamella plane. During solvent annealing, a gradient in the concentration of NRs is observed. This route to produce alternating layers containing conducting NRs separated by dielectric domains has the potential for fabricating self-assembled nanodevices.

Direct observation of nanoparticle embedding into the surface of a polymer melt.

Direct embedding of metal nanoparticles (NPs) into the surface of a polymer melt is observed by TEM and a new embedding mechanism proposed. Upon annealing above the glass transition temperature of polystyrene (PS), NPs (20 nm gold) are rapidly covered by a thin PS wetting layer, h* approximately 1.3-1.8 nm (i.e., about two or three monomers). Because it creates capillary pressure on a NP, this "universal" wetting layer is proposed to be responsible for NP embedding. The value of h* is independent of the molecular weight of PS and constant during the embedding process. The value of h* is found to be similar to the equilibrium wetting layer thickness of a polymer melt spreading on a metal substrate. Using a model that includes the spreading coefficient, long-range van der Waals interactions, and a chain-stretching penalty, h* is shown to be independent of the molecular weight of the polymer. Using this model and the measured value of h*, the interfacial energy between Au NP and PS is estimated to be 8.7 J/m2.

Financial analysis of potential donor management at a medicare-approved transplant hospital.

The purpose of this study was to perform a financial analysis of severe brain injured (SBI) patient management to determine potential reimbursement versus net losses in relation to organ donation and transplantation at a transplant center. We undertook a retrospective analysis of financial records of medically suitable referrals to the organ procurement organization (OPO) from our institution for fiscal years 2002-2003. This included (1) hospital cost and reimbursement, (2) OPO reimbursement for actual donors, (3) financial returns on local transplant activity solely supported by local donor activity and (4) Medicare incentives for local organ donation. There were 48 potential and 18 organ donors for this period. The consent rate reduced from 50% to 25% if family was offered withdrawal of care. After reimbursements from OPO, Medicare incentives and kidney transplant activity solely supported by local organ donation were figured in, the total returns were 244% of total cost of SBI patient management. Aggressive proactive management of severely brain injured patients remains a good medical practice. For Medicare-approved transplant centers, there are additional financial incentives to aggressively treat these patients and pursue organ donation. Prematurely offering withdrawal of care negatively impacts on the organ donation process and hurts institutions financially.

Vitamin E inhibits cyclosporin A and H2O2 promoted Epstein-Barr virus (EBV) transformation of human B cells as assayed by EBV oncogene LMP1 expression.

BACKGROUND: We have previously shown that oxidative stress induced by H2O2 or cyclosporin A (CsA) can promote Epstein-Barr virus (EBV) transformation of human B cells as analyzed by colony formation, cell number, and by 3H-thymidine incorporation. In this report, we used EBV oncogene LMP1 as a marker to analyze H2O2 or CsA promotion of EBV transformation of human B cells and to test whether antioxidant vitamin E could inhibit H2O2 or CsA promoted LMP1 expression in the EBV-infected cells. MATERIALS AND METHODS: Human splenocytes were prepared by centrifugation and plating technique to provide a greater than 80% pure preparation of B cells and were used for EBV infection. The EBV infected cells were treated with H2O2 (0.1 mM, 10 min), or with CsA (500 ng/ml) with or with out vitamin E (40 microM). The cells were cultured for up to 4 weeks. Samples were taken every week and were stained with phycoerythrin-conjugated mouse anti-LMP1 monoclonal antibody to assay LMP1 positive population by flow cytometry. RESULTS: In EBV-infected cells, the LMP1-positive cell population reached 14% after 4 weeks of culture. CsA or H2O2 treatment promoted LMP1 positive population to 43% and 41% after 4 weeks of culture. Vitamin E (40 microM) completely inhibited LMP1 expression in EBV-infected cells and in CsA- or H2O2-treated cells. CONCLUSION: In agreement with our previous observation, CsA or H2O2 can promote EBV transformation of human B cells. This oxidative stress induced promotion of EBV transformation can be blocked by antioxidant Vitamin E. This finding may have future therapeutic implications for post-transplant lymphoproliferative disorder.

Phi-LOG: a domain specific language for solving phylogenetic inference problems.

Domain experts think and reason at a high level of abstraction when they solve problems in their domain of expertise. We present the design and motivation behind a domain specific language called Phi-LOG to enable biologists (domain experts) to program solutions to phylogenetic inference problems at a very high level of abstraction. The implementation infrastructure (interpreter, compiler, debugger) for the DSL is automatically obtained through a software engineering framework based on Denotational Semantics and Logic Programming.

Cyclosporine directly causes oxidative stress and promotes Epstein-Barr virus transformation of human B cells.

BACKGROUND: We have previously shown that oxidative stress alone can promote transformation of human B cells infected with Epstein-Barr virus (EBV) in vitro, an accepted model mimicking posttransplant lymphoproliferative disorders (PTLDs). Our laboratory has investigated the direct effects of cyclosporine A (CyA) as an oxidant promoting B-cell transformation and we have proposed that CyA directly promotes B-cell transformation and that this effect can be blocked by antioxidants. METHODS: Human splenocytes were prepared by centrifugation and plating technique to provide a greater than 80% pure preparation of B cells that was used for the direct oxidative stress experiments. These cells were cocultured with CyA (500 ng/ml) and hydrogen peroxide (H(2)O(2), 0.15 mM) with or without antioxidant vitamin E (40 microM). Oxidative stress was evaluated by using a commercial lipid hydroperoxide (LPO) assay kit. In another set of three separate experiments, human B lymphocytes infected with EBV were cultured with CyA (500 ng/ml), H(2)O(2) (0.15 mM), and vitamin E (40 microM). B-Cell transformation by EBV was evaluated by counting colony number and [(3)H]-thymidine incorporation. RESULTS: At therapeutic concentrations, CyA (500 ng/mL) had an oxidative effect on human splenocytes in vitro, similar to the effect of H(2)O(2) (90 and 97% increases, respectively in LPO production over control P < 0.005), which was abrogated by the addition of vitamin E. Similarly, both CyA and H(2)O(2) promoted transformation of B cells infected with EBV(75 and 108% increases respectively in colony counts over control, P < 0.005). This effect was also blocked by vitamin E. CONCLUSIONS: Both CyA and H(2)O(2) have a direct oxidative effect on human B cells and cause promotion of EBV-induced transformation of B cells. These effects are blocked by the antioxidant vitamin E. These findings may have future therapeutic implications for PTLDs.

Genetic variation observed at three tetrameric short tandem repeat loci HumTHO1, TPOX, and CSF1PO--in five ethnic population groups of northeastern India.

This paper portrays the genetic variation observed at three tetrameric short tandem repeat (STR) loci HumTHO1, TPOX, and CSF1PO in five ethnic population groups from northeastern India. The study also specifies the suitability of use of these markers for forensic testing. The populations studied included three tribal groups (Kuki, Naga and Hmar), one Mongoloid caste group (Meitei), and a religious caste group (Manipuri Muslims). The loci were highly polymorphic in the populations, and all loci met Hardy-Weinberg expectations. No evidence for association of alleles among the loci was detected. The probability of match for the three loci of the most frequent genotype in the five population groups ranged between 2.6 x 10(-4) and 6.6 x 10(-5). The average heterozygosity among the population groups was approximately 70% with the overall extent of gene differentiation among the five groups being high (Gst = 0.046). Genetic affinity among the populations reveal very close association between the Kuki, Hmar, Naga, and Meitei. The Manipuri Muslims, despite being found in the same region, have had no admixture with these populations and maintain a substantial distance with the other groups. The genetic polymorphism data suggest that the studied systems can be used for human identity testing to estimate the frequency of a multiple locus STR DNA profile in population groups of northeastern India.

Using immersive VR as a tool for preoperative planning for minimally invasive donor nephrectomy.

For surgeons approaching minimally invasive donor nephrectomy it is important to identify variant anatomy preoperatively since this anatomy can vary significantly from patient to patient. The goal of this operation is to preserve the architecture and function of the organ so it can be transplanted and function successfully. The ability of the surgeon to navigate through an individual patient's anatomy in a virtual three-dimensional (3D) immersive environment augments understanding of anatomical relationships particular to that individual patient and facilitates conveying that information to other physicians and students. Utilizing automated 3D reconstruction of high contrast computed tomography (CT) scan files viewed in this way, surgeons reported a better preoperative understanding of the anatomical variations and encountered fewer surprises at the time of surgery.