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.

X-ray Thomson scattering absolute intensity from the f-sum rule in the imaginary-time domain.

We present a formally exact and simulation-free approach for the normalization of X-ray Thomson scattering (XRTS) spectra based on the f-sum rule of the imaginary-time correlation function (ITCF). Our method works for any degree of collectivity, over a broad range of temperatures, and is applicable even in nonequilibrium situations. In addition to giving us model-free access to electronic correlations, this new approach opens up the intriguing possibility to extract a plethora of physical properties from the ITCF based on XRTS experiments.

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.

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.

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.

Gastric intramural pH as indicator of early allograft viability in orthotopic liver transplantation.

The determination of the viability of OLT grafts has relied upon metabolic tests of the liver, which take several hours to evaluate and therefore are only conclusive in most patients well into the postoperative period. Earlier diagnosis of graft failure or nonfunction would allow intraoperative reassessment of surgical technique and, in the case of graft failure, earlier planning for retransplantation. Since gastrointestinal mucosal ischemia is one of the earliest manifestations of impaired core tissue in the critically ill, a tonometric nasogastric tube (Tonomitor) was used in our patients to measure intramucosal gastric pH (pHi) during the preanhepatic (stage I), anhepatic (stage II), and neohepatic (stage III) phases of OLT in 35 patients as an indicator of graft liver function and viability. Based on the results of the pHi measurement 30 min after reperfusion during stage III, patients were divided into 2 groups using a pHi of 7.30 as the dividing point. Patients with a pHi equal or higher than 7.30 were assigned to group 1 (n = 24) and patients with a pHi lower than 7.30 were assigned to group 2 (n = 11). The pHi in group 1 patients averaged 7.37 +/- 0.5 30 min after reperfusion and throughout surgery. The pHi in group 2 patients was lower than that of the group 1 patients 30 min after reperfusion, 7.23 +/- 0.04 (P < 0.001). The pHi in 10 group 2 patients returned to normal within 3 hr after reperfusion and the pHi values for these patients were not significantly different from those of group 1 at 3 hr after reperfusion. The pHi in 1 group 2 patient remained lower than 7.30 and never returned to normal; this patient underwent retransplantation the following day. Utilizing the tonometric nasogastric tube to sample intramucosal pH allowed early detection of graft function and intermittent trending of pHi in patients with questionable graft function during the operative period. It also provided a means of assessing graft function independent of enzymatic criteria, which provide little information in the early phase of transplantation.

Evidence that antibodies to cytomegalovirus and the T cell receptor (TCR)/CD3 complex may have common ligands.

Immunoglobulins derived from sera containing anti-antiidiotypic antibodies (Ab2) generated in renal transplant recipients after OKT3 monoclonal antibody therapy, as reported in our previous study (1), have now been proved to bind to several bands of T cell membrane lysates (TCML) in immunoblotting analyses ranging in molecular weight from 40 to 55 KD. These sera also blocked the expression of the ligand binding to WT31 in flow cytometry. WT31 is a MAb that recognizes a common determinant on the T cell receptor (TCR). Immunoglobulins from these sera suppressed the activation of normal peripheral blood T lymphocytes (PBT) induced by OKT3. All patients (7/32) who developed this Ab2 had distinct culture-proved cytomegaloviral infections. In further immunoblotting studies, alpha F1, another MAb recognizing the framework of the TCR alpha chain, more deeply inserted in the T cell membrane, also showed binding to protein bands of cytomegalovirus pellet lysates derived from virus-infected embryonic fibroblasts. In addition, alpha F1 showed positive binding to several ligands in the membrane lysate of CMV-infected, but not noninfected MRC-5 cells. An anti-CMV MAb recognizing late nuclear antigen (LAb), also strongly bound to a approximately 50 KD band of TCML and several bands (approximately 34, approximately 40, and approximately 50 KD) of H33HJAJ1 (human T leukemia) cell lysate. Furthermore, alpha F1 immunoprecipitated a approximately 96 KD ligand of CMV-infected MRC5 lysate that had the same electrophoretic mobility as one of the proteins precipitable with LAb. Both LAb and alpha F1 also showed positive binding to paraformaldehyde-fixed and Triton X-100-permeabilized PBT in flow cytometry. Sera containing Ab2 blocked alpha F1 binding to acetone-fixed cytofuged PBT preparations on slides. Moreover, both alpha F1 and LAb inhibited mitogen-stimulated lymphocyte activation in vitro. These data support the notion that T cell functional abnormalities associated with CMV infection observed after treatment of transplant recipients with anti-T cell monoclonals might be caused by binding to T cell ligands by a variety of crossreacting human Igs operative in a regulatory network. Confirmatory evidence is the effect of MAbs generated against CMV virion epitopes crossreacting with T cell ligands, and vice versa.

Factors affecting the ten-year outcome of human renal allografts. The effect of viral infections.

Long-term (10-year) results of kidney transplantation have been analyzed from this center with respect to several variables. In this report the influence of viral disease was added in studying the effect of cadaver versus living-related donor, recipient race, and compliance. Over all, 10-year actuarial patient and graft survival were 68% and 48%, respectively. Cytomegalovirus, hepatitis B and C, and HIV-1 were studied for their effects, and survival curves analyzed statistically. Although cadaver and living-related donor, recipient race, and compliance were 3 main variables influencing graft survival, these 4 viruses were not selective in their effects on any of them. Hepatitis B surface antigen positivity and hepatitis C antibody positivity did not influence overall mortality or graft survival. Only cytomegalovirus seronegative status was important (as opposed to seropositive status, which was not). Of seronegative patients only those receiving a kidney from a seropositive donor were adversely affected. The presence of HIV-1 antibody had an adverse effect on graft survival, but the question remains as to whether overall mortality in HIV seropositive patients is any worse than those receiving dialysis therapy.

The effects of tissue-associated and MHC class II antigen presentation on in vitro lymphoproliferative responses against canine liver and kidney cell subpopulations.

Purified hepatocytes (LH), Kupffer cells (LKu), and intrahepatic biliary duct cells (LD) were isolated from canine livers, as well as tubular cells from canine kidneys, by enzymatic digestion, gradient centrifugation, and tissue culture techniques. Incubation of LH, LKu, and LD for 48 hr in a two-compartment diffusion chamber opposite two-way mixed lymphocyte cultures, or with canine gamma interferon purified and standardized in our laboratory, resulted in a significant increase in class II expression. This was detected in the cell analyzer with directly fluoresceinated B1F6, a monoclonal antibody (mab) generated in our laboratory vs. a canine class II monomorphic epitope. An amplification of the allogeneic mixed lymphocyte liver cell cultures (MLLC) of at least 2-fold was observed by preinduction of canine class II expression with IFN-gamma on LKu and LD cells, but an autologous reaction could not be elicited. However, an autologous as well as allogeneic lymphoproliferation against kidney tubular cells (MLKC) could be easily observed without IFN-gamma and amplified with IFN-gamma to stimulation indices of at least 3 times that of noninduced cultures. Dependence of the allogeneic MLLC and allogeneic and autologous MLKC on class II gene expression was also evidenced by blocking of 3H-thymidine uptake seen by incubation with 5 micrograms of B1F6. Another mab, I1F6, generated against tubular cells and inhibiting the autologous and allogeneic MLKC, had no blocking effect on lymphoproliferation with any of the liver cell preparations. No such tissue-specific mab (analogous to I1F6) has thus far been found in response to mouse immunization with LH, LKu, or LD. In the absence of accepted defined molecular probes in the dog as yet, we conclude that, in contrast to kidney tubular cells, cells of the normal canine liver do not readily stimulate a primary lymphoproliferative autoimmune reaction in vitro despite class II amplification. Thus autoreactivity (as opposed to alloreactivity) is much less prominent in immune recognition of purified cellular components of nondiseased liver tissue than of kidney tissue in which tissue-associated epitopes are more operative.

OKT3 induction via idiotypic networks of mirror-image immunosuppressive antiimmunoglobulins in renal transplant recipients.

Four of 21 renal transplant recipients treated with OKT3 for rejection episodes developed a second sustained (approximately 2 weeks) depression in CD3 peripheral blood lymphocyte cell-surface-marker expression. This occurred after OKT3 therapy had ceased, subsequent to a return toward baseline CD3 levels seen before OKT3 therapy was instituted. The second decrease in CD3 T cell counts was dissociated from CD2 marker T cell counts using flow cytometry and coincided with transient cytomegaloviral infections. Three phases of immunosuppression were defined in these 4 patients: phase I (during OKT3 treatment); phase II (after treatment when CD3 counts were reconstituted); and phase III (when CD3 counts again were depressed). During phase III, serum of the 4 affected patients could transfer a blocking effect on the expression of the CD3 marker of peripheral blood T cells of "normal" laboratory volunteers. Contained in these sera were human IgG antibodies that bound on Western blot analysis and by radioautography after immunoprecipitation to a protein band of a T cell membrane lysate with an m.w. of 23 kD. The reaction was identical to that seen with OKT3 (immunoprecipitation). Moreover, this Western blot binding could be virtually (but not completely) eliminated by multiple absorptions of the T cell membrane lysate with OKT3. By using an affinity-purified human anti-OKT3 IgG from one of the 4 patients, it was possible to immunoabsorb from phase III sera the CD3 blocking activity as well as the binding to the 23 KD protein band. A reverse immune absorption by the phase III sera with the anti-OKT3 IgG after ultracentrifugation prevented the anti-OKT3 IgG from binding to OKT3 coated plates in solid-phase radioimmunoassay. These data support the notion that autoimmune human anti-anti-id (Ab2) antibodies can occasionally be generated by treatment with OKT3, which are directed against CD3 complex epitopes similar to the ligand of OKT3.

A selective approach to preexisting portal vein thrombosis in patients undergoing liver transplantation.

Splanchnic venous inflow is considered mandatory to ensure graft survival after liver transplantation. Over a 68-month period, we performed 570 liver transplants in 495 patients. Portal vein thrombosis was present in 16 patients. At transplant, the extent of the occlusion included portal vein alone (n = 4), portal including confluence of the splenic and superior mesenteric veins (n = 8), portal, splenic, and distal superior mesenteric veins (n = 2), and the entire portal vein, splenic vein, and superior mesenteric vein (n = 2). The operative approach included thrombectomy alone (n = 5), anastomosis at the confluence of the splenic and superior mesenteric splenic veins (n = 8), and extra-anatomic venous reconstruction (n = 3). The mean operative blood loss was 22 +/- 22 units, and the mean operative time was 9.7 +/- 4.8 hours. The 1-year actuarial survival rate was 81%, with a mean follow-up of 12.5 months. In summary, with a selective approach and the use of innovative forms of splanchnic venous inflow, portal vein thrombosis is no longer a contraindication to liver transplantation.

The effect of curcumin on human B-cell immortalization by Epstein-Barr virus.

Cyclosporine is a commonly used immunosuppressant in solid-organ transplantation. It is, however, associated with an increased incidence of Epstein-Barr virus (EBV)induced post-transplant lymphoproliferative disorder (PTLD). In this study, human B lymphocytes isolated from healthy volunteers were immortalized in vitro with EBV. The effect of oxidative stress mediated by cyclosporine A or hydrogen peroxide on in vitro B cell immortalization was studied by coculturing immortalized B cells with cyclosporine A and hydrogen peroxide. Curcumin, a phenolic extract of the spice turmeric, was then used to observe its effect on this process. We found that in vitro B-cell immortalization with EBV was promoted by the oxidative stress induced by cyclosporine A and hydrogen peroxide, with the maximum effect seen at concentrations of 500 ng/ml and 100 microM, respectively. Curcumin blocked the B-cell immortalization in a dose-dependent fashion with nearly complete inhibition at 20 microM. We conclude that, because both hydrogen peroxide and cyclosporine A strongly promote in vitro B-cell immortalization with EBV (the putative process responsible for PTLD) and curcumin, an extract of a common spice is an effective inhibitor of this process; curcumin may be an effective adjunct in the prevention of PTLD in the patients undergoing therapy with cyclosporine A.

Transplantation of the liver combined with other organs.

Patients suffering from liver failure with other end-stage organ failures may benefit from combined organ transplant procedures. Liver transplantation has been combined with other transplants to treat otherwise-intractable diseases, such as advanced cystic fibrosis, primary hyperoxaluria, and cirrhosis. Multiple organ transplantation may be indicated following the resection of certain upper abdominal malignancies. Combining bone marrow and liver transplantation shows promise in improving the immunological tolerance of the liver graft.

Extending liver transplantation: reduced-size-, split-, and living-donor grafts.

The continued shortage of donor liver grafts has made it necessary to find new strategies for obtaining the best possible use of those available. Nowhere is the shortage more acute than in pediatric liver transplantation, where few liver grafts of appropriate size are available to infants and small children in need of transplantation. Initially, strategies were developed to fit larger grafts into smaller recipients. These techniques have been expanded upon, resulting in innovative procedures which increase the number of liver grafts such as living-donor liver transplantation and "split liver" techniques.

Liver transplantation for hepatocellular carcinoma.

Liver transplantation (LT) for hepatocellular carcinoma (HCC) has been controversial, however, with increasing experience the results of the procedure in these patients have improved. Earlier reports of poor result may have been secondary to advanced tumor and poor patient selection. Careful patient selection and preoperative assessment of tumor characteristic is essential before offering LT to these patients. Results of LT in carefully selected cases may be similar to patients receiving LT for other reasons. In cirrhotic patients LT may offer a better long-term survival than liver resection.

Middle cerebral artery transcranial Doppler velocity monitoring during orthotopic liver transplantation: changes at reperfusion--a report of six cases.

STUDY OBJECTIVE: To determine the effect of reperfusion of the grafted liver on transcranial Doppler blood flow velocity in the middle cerebral artery in humans during orthotopic liver transplantation. DESIGN: Clinical study. SETTING: University hospital. PATIENTS: 6 patients scheduled for orthotopic liver transplantation. INTERVENTIONS: Middle cerebral artery blood flow velocity (MCAVm) was monitored continuously using a transcranial Doppler (TCD) probe. The TCD measurements were noninvasive. MEASUREMENTS AND MAIN RESULTS: The EME TC2000S TCD probe (Nicolet, Inc., Memphis, TN) was secured to the head using a strap providing continuous measurement of MCAVm. All other data were recorded by a patient monitoring system and a respiratory gas analyzer. Averaged MCAVm increased significantly in 5 of 6 patients (p < 0.001) when pre-reperfusion and post-reperfusion values were compared. Maximum post-reperfusion values for MCAVm, pulsatility index (PI), and systolic Doppler velocity (Vs) were greater than the corresponding immediate pre-reperfusion values (p < 0.05, p < 0.05, and p < 0.001, respectively). The increases in MCAVm cannot be explained on the basis of hypercarbia alone and were observed in the presence of systemic arterial hypotension and abrupt increases in central venous pressure, particularly at the time of graft reperfusion. CONCLUSIONS: MCAVm increased with reperfusion of the grafted liver. These data suggest that multiple factors--including hypercarbia, lactic acidosis, or multiple vasoactive substances released by the grafted liver--may contribute to the observed increases in MCAVm, Vs, and PI.

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.

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).