Cluster-Based Solidification and Growth Algorithm for Decagonal Quasicrystals.

A novel approach is used for the simulation of decagonal quasicrystal (DQC) solidification and growth. It is based on the observation that in well-ordered DQCs the atoms are largely arranged along quasiperiodically spaced planes parallel to the tenfold axis, running throughout the whole structure in five different directions. The structures themselves can be described as quasiperiodic arrangements of decagonal columnar clusters (cluster covering) that partially overlap in a systematic way. Based on these findings, we define a cluster interaction model within the mean field approximation, with effectively asymmetric interactions ranging beyond the nearest neighbors. In our Monte Carlo simulations, this leads to a long-range ordered quasiperiodic ground state. Indications of two finite-temperature unlocking phase transitions are observed, and are related to the two fundamental length scales that are characteristic for the system.

Toggling the Local Electric Field with an Embedded Adatom Switch.

By means of scanning probe microscopy we demonstrate that Au(+) on NaCl films adsorbs in an embedded, slightly off-centered Cl-Cl bridge position and can be switched between two equivalent mirror-symmetric configurations using the attractive force exerted by a scanning probe tip. Density functional theory calculations demonstrate that the displacement of the Au atom from the centered position of the bridge configuration is accompanied by a large lifting of the closest Cl atom leading to significant changes in the local electrostatic field. Our findings suggest that Au(+) can be used to toggle the local electrostatic field.

Manipulation of the charge state of single Au atoms on insulating multilayer films.

We show charge-state manipulation of single Au adatoms on 2-11 monolayer (ML) thick NaCl films on Cu surfaces by attaching or detaching single electrons via the tip of an atomic force microscope (AFM). Tristate charge control (neutral, negatively charged, and positively charged) is achieved. On Cu(100) and Cu(111) supports, charge tristability is achieved independently of the NaCl layer thickness. In contrast, on Cu(311), only Au anions are stable on the thinnest NaCl films, but neutral and positive charge states become sufficiently long lived on films thicker than 4 ML to allow AFM-based charge-state-manipulation experiments.

Discovery of a superconducting high-entropy alloy.

High-entropy alloys (HEAs) are multicomponent mixtures of elements in similar concentrations, where the high entropy of mixing can stabilize disordered solid-solution phases with simple structures like a body-centered cubic or a face-centered cubic, in competition with ordered crystalline intermetallic phases. We have synthesized an HEA with the composition Ta34Nb33Hf8Zr14Ti11 (in at. %), which possesses an average body-centered cubic structure of lattice parameter a=3.36 Å. The measurements of the electrical resistivity, the magnetization and magnetic susceptibility, and the specific heat revealed that the Ta34Nb33Hf8Zr14Ti11 HEA is a type II superconductor with a transition temperature Tc≈7.3 K, an upper critical field µ0H_c2≈8.2 T, a lower critical field µ0Hc1≈32 mT, and an energy gap in the electronic density of states (DOS) at the Fermi level of 2Δ≈2.2 meV. The investigated HEA is close to a BCS-type phonon-mediated superconductor in the weak electron-phonon coupling limit, classifying it as a "dirty" superconductor. We show that the lattice degrees of freedom obey Vegard's rule of mixtures, indicating completely random mixing of the elements on the HEA lattice, whereas the electronic degrees of freedom do not obey this rule even approximately so that the electronic properties of a HEA are not a "cocktail" of properties of the constituent elements. The formation of a superconducting gap contributes to the electronic stabilization of the HEA state at low temperatures, where the entropic stabilization is ineffective, but the electronic energy gain due to the superconducting transition is too small for the global stabilization of the disordered state, which remains metastable.

The two-dimensional cobalt oxide (9 × 2) phase on Pd(100).

The two-dimensional (2D) Co oxide monolayer phase with (9 × 2) structure on Pd(100) has been investigated experimentally by scanning tunneling microscopy (STM) and theoretically by density functional theory (DFT). The high-resolution STM images reveal a complex pattern which on the basis of DFT calculations is interpreted in terms of a coincidence lattice, consisting of a CoO(111)-type bilayer with significant symmetry relaxation and height modulations to reduce the polarity in the overlayer. The most stable structure displays an unusual zig-zag type of antiferromagnetic ordering. The (9 × 2) Co oxide monolayer is energetically almost degenerate with the c(4 × 2) monolayer phase, which is derived from a single CoO(100)-type layer with a Co(3)O(4) vacancy structure. Under specific preparation conditions, the (9 × 2) and c(4 × 2) structures can be observed in coexistence on the Pd(100) surface and the two phases are separated by a smooth interfacial boundary line, which has been analyzed at the atomic level by STM and DFT. The here described 2D Co oxide nanolayer systems are characterized by a delicate interplay of chemical, electronic, and interfacial strain interactions and the associated complexities in the theoretical description are emphasized and discussed.

Vibrational dynamics and surface structure of amorphous selenium.

In contrast to crystalline solids in which structural order governs dynamics and thermodynamics, the lack of long-range periodicity in amorphous materials is responsible for several anomalies. Although the relation between these anomalies and the 'bulk structure' is generally understood, the surface structure and the corresponding vibrational spectrum of amorphous solids is practically an unexplored theme. In this study, we resolve the differences in vibrational dynamics and atomic structure between bulk and surface (top 5 nm) atoms of amorphous selenium. We combine experimental (grazing incidence inelastic X-ray scattering) and computational (ab initio and semiempirical molecular orbital theoretical calculations) methods to scrutinize a variety of possible structural models. We find that a high concentration of particular types of 'coordination defects' in the surface layer is responsible for the observed differences. Resolving the structure of amorphous surfaces is, for example, important for understanding nanoparticles' properties where the surface-to-bulk ratio has a crucial role.

A reproducible porcine model of acute liver failure induced by intrajejunal acetaminophen administration.

BACKGROUND AND AIMS: Severe intoxication following acetaminophen overdose is the most common cause of acute liver failure (ALF) in many Western European and North American countries. A reproducible large animal model of acetaminophen intoxication has not been successfully evaluated previously. METHODS: Eight male pigs underwent acetaminophen intoxication receiving an initial enteric bolus of 250 mg/kg body weight acetaminophen followed by an acetaminophen plasma level (300-450 mg/l) adapted enteric maintenance dose of 1,000-3,000 mg/h to the onset of ALF (prothrombin time value <30%). Vital and ventilation parameters were continuously recorded until death. Saline, hydroxyethyl starch, fresh frozen plasma and erythrocyte units were used for volume substitution, and norepinephrine to prevent severe hypotension. RESULTS: All animals developed ALF after 25 ± 3 h, which was confirmed by laboratory values, the clinical course and histological examinations. All animals died due to ALF after a further 21 ± 5 h, precipitated by cerebral edema. CONCLUSIONS: Using an initial enteric acetaminophen bolus, followed by body weight-adapted acetaminophen plasma level intoxication, it was possible to establish a reproducible, clinically relevant porcine model which may be used for the investigation of novel therapeutic approaches in this life-threatening condition.

Portal vein stenting the first day after orthotopic liver transplantation for residual postthrombotic stenosis compromising portal flow.

BACKGROUND: Early portal vein impairment or thrombosis after liver transplantation is a significant risk factor for graft failure. CASE: Here, we describe a case of severe portal hypoperfusion after thrombectomy during liver transplantation that was treated with percutaneous stenting on the first postoperative day. Stenting was combined with embolization of varices and normalized portal inflow. RESULT: Liver function and portal flow were normal after 1 year of follow-up. CONCLUSION: This case demonstrates that percutaneous stenting is a safe and feasible therapeutic option even in the initial days after liver transplantation.

Liver transplantation for hilar cholangiocarcinoma: a German survey.

BACKGROUND: The present study reports a German survey addressing outcomes in nonselected historical series of liver transplantation (OLT) for hilar cholangiocarcinoma (HL). PATIENTS AND METHODS: We sent to all 25 German transplant centers performing OLT a survey that addressed (1) the number of OLTs for HL and the period during which they were performed; (2) the incidence of HL diagnosed prior to OLT/rate of incidental HL (for example, in primary sclerosing cholangitis); (3) tumor stages according to Union Internationale Centre le Cancer; (4) patient survival; and (5) tumor recurrence rate. RESULTS: Eighty percent of centers responded, reporting 47 patients who were transplanted for HL. Tumors were classified as pT2 (25%), pT3 (73%), or pT4 (2%). HL was diagnosed incidentally in 10% of cases. A primary diagnosis of PSC was observed in 16% of patients. Overall median survival was 35.5 months. When in-hospital mortality (n = 12) was excluded, the median survival was 45.4 months, corresponding to 3- and 5-year survival rates of 42% and 31%, versus 31% and 22% when in-hospital mortality was included. HL recurred in 34% of cases. Three- and 5-year survivals for the 15 patients transplanted since 1998 was 57% and 48%, respectively. Median survival ranged from 20 to 42 months based on the time period (P = .014). CONCLUSIONS: The acceptable overall survival, the improved results after careful patient selection since 1998, and the encouraging outcomes from recent studies all suggest that OLT may be a potential treatment for selected cases of HL. Prospective multicenter randomized studies with strict selection criteria and multimodal treatments seem necessary.

Anomalous phonon behavior: blueshift of the surface boson peak in silica glass with increasing temperature.

We present helium atom scattering measurements of the boson peak at the surface of vitreous silica between 127.0 and 368.5 K. The most probable energy shows a strong temperature dependence and increases linearly with temperature in the measured range. The observed blueshift of the surface boson peak (shift rate 0.008+/-0.002 meV/K) is a factor of 4 to 10 times stronger than shift rates measured in the bulk by inelastic neutron and Raman scattering. We suggest that the anomalous shift direction of the boson peak to higher energies with increasing temperature has the same origin as the unusual temperature dependence of the bulk modulus of silica glass.

Intestinal lipid absorption increases cold ischemia of the small bowel in rats.

UNLABELLED: The short cold ischemic tolerance of the gut is a major problem in small bowel transplantation. We have shown that intestinal lipid administration is beneficial during systemic inflammation like sepsis. METHODS: Rats were intestinally infused with either water or 1% olive oil for 12 hours. The small bowel was removed and stored in HTK solution on ice. At t = 0, t = 60, t = 120, t = 180, t = 240, t = 300, t = 360, t = 420, and t = 480 minutes, a tissue sample of the gut was fixed, stained, and analyzed by three independent observers. Damage score was calculated (0 = no damage, 1 = minor damage, 2 = major damage, 3 = loss of structure) for integrity of the mucosa, integrity of the basal membrane of the mucosa, and integrity of villy. The damage score was allocated when all three observers agreed on the same or a higher damage score. RESULTS: In all control animals minor damage for the integrity of the basal membrane occurred within 60 minutes, but in only 50% of the lipid-treated rats. In all control rats, major damage for both integrity of mucosa and villi occurred within 300 minutes or less, but only in 50% of the lipid-treated rats. In all control rats, the structure of the villi was completely lost within 480 minutes or less, whereas only 50% of the lipid treated animals reached maximal damage scores for either mucosa or villi. CONCLUSION: Intestinal lipid administration before cold storage clearly decreases histologic damage of the small bowel and might increase the tolerance for cold ischemia. Lipids or their metabolites stored in enterocytes may act as an antiinflammatory. Intestinal lipid administration in organ donors might be useful to increase cold ischemic tolerance of the small bowel.

Unexpected high stiffness of Ag and Au nanoparticles.

We studied the compressibility of silver (10 nm) and gold (30 nm) nanoparticles, n-Ag and n-Au, suspended in a methanol-ethanol mixture by x-ray diffraction (XRD) with synchrotron radiation at pressures up to 30 GPa. Unexpectedly for that size, the nanoparticles show a significantly higher stiffness than the corresponding bulk materials. The bulk modulus of n-Au, K(0)=290(8) GPa, shows an increase of ca. 60% and is in the order of W or Ir. The structural characterization of both kinds of nanoparticles by XRD and high-resolution electron microscopy identified polysynthetic domain twinning and lamellar defects as the main origin for the strong decrease in compressibility.

Immunosuppression in pancreas transplantation: the Euro SPK trials and beyond.

The Immunosuppression in Pancreas Transplantation was historically based on the fact that the pancreas is an extremely immunogenic organ. Quadruple drug therapy with polyclonal or monoclonal antibodies induction was the mainstay therapy since the introduction of Cyclosporine A. In the modern era of Immunosuppression, Mycophenolate Mofetil replaced Azathioprine while Tacrolimus-another potent calcineurin inhibitor-had-and still has-a difficult challenge to replaced Cyclosporine A, due to its potential diabetogenic effect. Thanks to the first two EuroSPK studies which prospectively tried to answer several questions in that field. But, the future challenge will be in understanding the impact of innate immunity and ischemic reperfusion injuries on the long-term graft function. Hopefully, new drugs will be available and tested to block unspecific deleterious reactions to attenuate the proinflammatory response. It will be the aim of the third Euro SPK Study.

A closed system for islet isolation and purification using the COBE2991 cell processor may reduce the need of clean room facilities.

During the isolation of human islets of Langerhans the digest has repeated direct contact with the ambient atmosphere. In order to fulfill GMP requirements in clinical applications, the entire cell preparation must be performed in clean room facilities. We hypothesized that the use of a closed system, which avoids the direct exposure of tissue to the atmosphere, would significantly ease the preparation procedure. To avoid the direct atmosphere exposure we tested a modification of the isolation and purification process by performing all islet preparation steps in a closed system. In this study we compared the isolation outcome of the traditional open preparation technique with the new closed system. Pancreata from 6-month-old hybrid pigs were procured in the local slaughterhouse. After digestion/filtration the digest was cooled, collected, and concentrated in centrifugation containers and purified thereafter in the COBE2991 by top loading (control). In the control group 502 +/- 253 IEQ per gram pancreas were purified. The total preparation time amounted to 12 h. In the closed system the digest was cooled and directly pumped into the COBE2991 for centrifugation followed by supernatant expelling. Bag filling, centrifugation, and expelling were repeated several times. Islets in pellet form were then purified by adding a gradient (bottom loading). Using this closed system 1098 +/- 489 IEQ per gram pancreas were purified with a total cell viability of 67 +/- 10% and a beta-cell viability of 41 +/- 13%. The total preparation time reduced to 6 h. After 24 h of cell culture the viability of beta-cells was still 56 +/- 10% and was only reduced after the addition of proapoptotic IL-1 and TNF-alpha to 40 +/- 4%, indicating that freshly isolated islets are not apoptotic. In conclusion, the closed system preparation is much faster, more effective, and less expensive than the traditional islet preparation. The closed system may be applicable for human islets preparations to restrict the need of clean room facilities for islet preparations to a minimum and may open the way for islet preparations without clean room demand.

Observation of the boson peak at the surface of vitreous silica.

The boson peak is an excess in the phonon density of states compared to the Debye model that appears in almost all glasses. It has been repeatedly measured in the bulk by a variety of methods, but its origin is still highly debated. Here we present first experimental evidence of the boson peak on the v-SiO2 surface. The measurements were obtained by helium atom scattering. The boson peak appears as a dispersionless mode of approximately 4 meV in the recorded time-of-flight spectra. It is clearly identified as an excess contribution to the low energy Debye-like region in the surface phonon spectral density which is extracted from the time-of-flight spectra using a straightforward theoretical model.

Increased translocator protein (TSPO) mRNA levels in colon but not in rectum carcinoma.

BACKGROUND: The peripheral-type benzodiazepine receptor or translocator protein (TSPO) is an 18-kDa protein involved in cell proliferation and apoptosis. TSPO was shown to be overexpressed in malignant tumors and cancer cell lines, correlating with enhanced malignant behavior. The present study analyzed the role of TSPO in patients with colorectal carcinomas. METHODS: Tumor tissues and corresponding normal mucosa from 55 patients who underwent resection for colorectal carcinomas were analyzed for TSPO expression in correlation to GAPDH expression(glyceraldehyde-3-phosphate dehydrogenase) using a multiplex RT-PCR assay. RESULTS: TSPO was overexpressed in 67% of the tumors in comparison to corresponding normal mucosa, and positivity as well as expression levels in colon carcinomas were significantly higher than in the rectum carcinomas. In contrast, TSPO expression was not different in intermediate versus high-grade tumors or in lymph node-positive versus -negative patients. CONCLUSION: The differences in TSPO expression between colon and rectum carcinoma may imply that these tumors are of different biological behavior.

[Liver transplantation]. / Lebertransplantation.

Liver transplantation has developed as standard therapy for end-stage liver disease and fulminant hepatic failure with excellent results. The application of new techniques including split liver and living donor liver transplantation (LDLT) has only marginally increased the total number of liver transplants. The experience in children however has proven that short and long-term survival can be achieved with LDLT. Currently, the widening gap between waiting lists and organ supply is the major limiting factor resulting in increasing waiting times and death on the waiting list affecting up to 20% of patients.

Infectious complications following 72 consecutive enteric-drained pancreas transplants.

New immunosuppressive protocols and advanced surgical technique resulted in an improved outcome of pancreatic transplantation (PTx) with infection remaining the most common complication. Seventy-two enteric-drained whole PTxs performed at the Innsbruck University Hospital between September 2002 and October 2004 were retrospectively analyzed. Prophylactic immunosuppression consisted of either the standard protocol consisting of single bolus antithymocyteglobulin (ATG) (Thymoglobulin, Sangstat or ATG Fresenius) induction (9 mg/kg), tacrolimus (TAC), mycophenylate mofetil (MMF) and steroids (38 patients) or a 4-day course of ATG (4 mg/kg) tacrolimus and steroids with MMF (n = 19), or Sirolimus (n = 15). Perioperative antimicrobial prophylaxis consisted of Piperacillin/Tazobactam (4.5 g q 8 h) in combination with ciprofloxacin (200 mg q 12 h) and fluconazole (400 mg daily). Ganciclovir was used for cytomegalovirus (CMV) prophylaxis if donor was positive and recipient-negative. Patient, pancreas, and kidney graft survival at 1 year were 97.2%, 88.8%, and 93%, respectively, with no difference between the groups. All retransplants (n = 8) and single transplants (n = 8) as well as all type II diabetics and nine of 11 patients older 55 years received standard immunosuppression (IS). The rejection rate was 14% and infection rate 46% with no difference in terms of incidence or type according to the three groups. Severe infectious complications included intra-abdominal infection (n = 12), wound infection (n = 7), sepsis (n = 13), respiratory tract infection (n = 4), urinary tract infection (n = 12), herpes simplex/human herpes virus 6 infection (n = 5), CMV infection/disease (n = 7), post-transplant lymphoproliferative disorder (PTLD, n = 3), invasive filamentous fungal infection (n = 4), Clostridial/Rotavirus colitis (n = 1), and endocarditis (n = 1). All four patients in this series died of infectious complications (invasive aspergillosis n = 2) (one with Candida glabrata superinfection), invasive zygomycosis (n = 1), PTLD (n = 1). Five grafts were lost (vascular thrombosis n = 3, pancreatitis n = 1, noncompliance n = 1). Infection represented the most frequent complication in this series and all four deaths were of infectious origin. Better prophylaxis and management of infections now should be the primary target to be addressed in the field of pancreas transplantation.

Simultaneous pancreas-kidney transplantation in a large multicenter study: surgical complications.

UNLABELLED: Simultaneous pancreas-kidney (SPK) transplantation has evolved as an effective treatment modality for patients with end-stage nephropathy owing to type 1 diabetes mellitus. This kidney-pancreas transplant procedure includes a number of risks, one of them being surgical complications, which were analyzed in this large prospective multicenter study. PATIENTS AND METHODS: The analysis included 205 patients randomly assigned to tacrolimus (n = 103) or cyclosporine ME (n = 102) in the Euro-SPK001 study. Surgical complications were defined as any intervention in the postoperative course related to the transplant procedure. RESULTS: The number of patients undergoing relaparotomy was significantly lower among the tacrolimus group (26.2%) as compared to the cyclosporine ME group (43.1%, P = .0109). Relaparotomy was performed earlier in the cyclosporine ME group (day 14 +/- 17) compared to patients in the tacrolimus group (day 26 +/- 26, P = .0506). Graft vessel thrombosis, intra-abdominal hemorrhage, and enteric or ureteral leakage within the first 3 months occurred significantly more frequently in cyclosporine ME-treated patients. Donor age above 45 years showed a negative impact on surgical complications. Relaparotomy had no impact on patient survival but significantly affected pancreas and kidney graft survival in both groups. CONCLUSION: This prospective, randomized, multicenter trial in patients undergoing primary SPK demonstrated a benefit of tacrolimus over cyclosporine ME with regard to the incidence of surgical complications and, consecutively, to kidney and pancreas graft survival.

Impact of steroid withdrawal on metabolic parameters in a series of 112 enteric/systemic-drained pancreatic transplants.

BACKGROUND: New immunosuppressive protocols and advanced surgical techniques have brought major improvements in pancreas transplantation outcomes. Steroid withdrawal might have a beneficial long-term effect on metabolic parameters. METHODS: We retrospectively analyzed 112 enteric-drained pancreas transplants (PTx) performed between March 1997 and October 2001. Prophylactic imunosuppression consisted of ATG induction, tacrolimus, MMF, and steroids. RESULTS: Actuarial patient, pancreas, and kidney graft survivals at 1 year were 96.4%, 86.7%, and 95.3%, respectively. The 5-year pancreatic graft survival was 77%. In addition to four patients who died with functioning grafts, eight grafts were lost due to intraabdominal infection; ten due to rejection; and the remaining three, due to other complications. One-year follow-up was available for 89 patients, Including 22 (25%) withdrawn from steroids. Significantly lower median serum cholesterol values were measured among patients off steroids (158 mg/dL [range 135 to 231 mg/dL] versus 188 mg/dL [range 91 to 278 mg/dl]; P = .005). In contrast, the difference in triglycerides did not reach statistical significance; that is, at last follow-up, at a median of 41.3 months posttransplant, 64 patients (70% of the available study population) were off steroids. Cessation of steroids resulted in significantly lower cholesterol (median 176 mg/dL [range 101 to 229 mg/dL] versus 196 mg/dL [range 107 to 339 mg/dL]; P = .047) and triglyceride values (median 74 mg/dL [range 34 to 299 mg/dL] versus 98 mg/dL [range 47 to 565 mg/dL]; P = .008), but had no impact on rejection rate, serum creatinine and urea, HbA(1c), or fasting blood glucose levels. CONCLUSIONS: Steroid withdrawal after pancreatic transplantation can be performed in the majority of cases without risking an immunologic complication, but it seems to be associated also with the benefit of improved lipid metabolism.