119 research outputs found
Evidence from scanning tunneling microscopy in support of a structural model for the InSb(001)-c(8Ă—2) surface
In this letter we present evidence from scanning tunneling microscopy studies in support of a recently proposed structural model for the indium-terminated c(8×2) surface of InSb(001). This structural model, by Norris and co-workers, is based on a surface x-ray diffraction study [Surf. Sci. 409, 27 (1998)], and represents a significant departure from previously suggested models for the c(8×2) reconstruction on any (001) surface of the common III–V semiconductor materials. Although filled state images of the InSb(001)-c(8×2) surface have previously been published, empty states image of sufficient quality to extract any meaningful information have not previously been reported. The observations are in excellent agreement with the recently proposed model for this surface reconstruction
A new type of reconstruction on the InSb() surface determined by grazing incidence X-ray diffraction
The (3Ă—3) reconstruction of the InSb( ) surface has been investigated by grazing incidence X-ray diffraction and scanning tunneling microscopy. The structure is characterized by 6-atom rings on top of a slightly buckled InSb top double layer. Two types of rings have been found, an elliptic ring consisting of 4 In and 2 Sb atoms and a trigonal ring with 3 In and 3 Sb atoms. The bond angles and lengths are consistent with the concept of rehybridization and depolarization which explains the reconstructions of the (111) and (110) surfaces
Subtoxic Concentrations of Hepatotoxic Drugs Lead to Kupffer Cell Activation in a Human In Vitro Liver Model
Drug induced liver injury (DILI) is an idiosyncratic adverse drug reaction
leading to severe liver damage. Kupffer cells (KC) sense hepatic tissue
stress/damage and therefore could be a tool for the estimation of consequent
effects associated with DILI. Aim of the present study was to establish a
human in vitro liver model for the investigation of immune-mediated signaling
in the pathogenesis of DILI. Hepatocytes and KC were isolated from human liver
specimens. The isolated KC yield was cells/g liver tissue with a purity of
>80%. KC activation was investigated by the measurement of reactive oxygen
intermediates (ROI, DCF assay) and cell activity (XTT assay). The initial KC
activation levels showed broad donor variability. Additional activation of KC
using supernatants of hepatocytes treated with hepatotoxic drugs increased KC
activity and led to donor-dependent changes in the formation of ROI compared
to KC incubated with supernatants from untreated hepatocytes. Additionally, a
compound- and donor-dependent increase in proinflammatory cytokines or in
anti-inflammatory cytokines was detected. In conclusion, KC related immune
signaling in hepatotoxicity was successfully determined in a newly established
in vitro liver model. KC were able to detect hepatocyte stress/damage and to
transmit a donor- and compound-dependent immune response via cytokine
production
Mutual Zonated Interactions of Wnt and Hh Signaling Are Orchestrating the Metabolism of the Adult Liver in Mice and Human
The Hedgehog (Hh) and Wnt/β-Catenin (Wnt) cascades are morphogen pathways whose pronounced influence on adult liver metabolism has been identified in recent years. How both pathways communicate and control liver metabolic functions are largely unknown. Detecting core components of Wnt and Hh signaling and mathematical modeling showed that both pathways in healthy liver act largely complementary to each other in the pericentral (Wnt) and the periportal zone (Hh) and communicate mainly by mutual repression. The Wnt/Hh module inversely controls the spatiotemporal operation of various liver metabolic pathways, as revealed by transcriptome, proteome, and metabolome analyses. Shifting the balance to Wnt (activation) or Hh (inhibition) causes pericentralization and periportalization of liver functions, respectively. Thus, homeostasis of the Wnt/Hh module is essential for maintaining proper liver metabolism and to avoid the development of certain metabolic diseases. With caution due to minor species-specific differences, these conclusions may hold for human liver as well
Visualizing landscapes of the superconducting gap in heterogeneous superconductor thin films: geometric influences on proximity effects
The proximity effect is a central feature of superconducting junctions as it
underlies many important applications in devices and can be exploited in the
design of new systems with novel quantum functionality. Recently, exotic
proximity effects have been observed in various systems, such as
superconductor-metallic nanowires and graphene-superconductor structures.
However, it is still not clear how superconducting order propagates spatially
in a heterogeneous superconductor system. Here we report intriguing influences
of junction geometry on the proximity effect for a 2D heterogeneous
superconductor system comprised of 2D superconducting islands on top of a
surface metal. Depending on the local geometry, the superconducting gap induced
in the surface metal region can either be confined to the boundary of the
superconductor, in which the gap decays within a short distance (~ 15 nm), or
can be observed nearly uniformly over a distance of many coherence lengths due
to non-local proximity effects.Comment: 17 pages, 4 figure
A lattice gas model of II-VI(001) semiconductor surfaces
We introduce an anisotropic two-dimensional lattice gas model of metal
terminated II-IV(001) seminconductor surfaces. Important properties of this
class of materials are represented by effective NN and NNN interactions, which
result in the competition of two vacancy structures on the surface. We
demonstrate that the experimentally observed c(2x2)-(2x1) transition of the
CdTe(001) surface can be understood as a phase transition in thermal
equilbrium. The model is studied by means of transfer matrix and Monte Carlo
techniques. The analysis shows that the small energy difference of the
competing reconstructions determines to a large extent the nature of the
different phases. Possible implications for further experimental research are
discussed.Comment: 7 pages, 2 figure
Relationship between pp65 antigenemia levels and real-time quantitative DNA PCR for Human Cytomegalovirus (HCMV) management in immunocompromised patients
<p>Abstract</p> <p>Background</p> <p>Quantitative real-time PCR assays, which are more rapid and practical than pp65 antigenemia determination, are progressively becoming the preferred method for monitoring Human Cytomegalovirus (HCMV) reactivation. However, the relationship between HCMV DNA and antigenemia levels is still under investigation. The aim of this study was to analyse the relationship between HCMV DNA and pp65 antigenemia levels in order to identify clinically useful threshold values for the management of patients.</p> <p>Methods</p> <p>475 consecutive samples from 156 immunosuppressed patients were tested for HCMV by pp65 antigenemia and Real-time PCR assay.</p> <p>Results </p> <p>136 out of 475 consecutive samples derived from 48 patients showed evidence of HCMV infection. HCMV DNA was detected in 106 samples, pp65 antigen in 3, and both markers in 27. pp65 antigen detection was associated with higher HCMV DNA levels. The cut-off HCMV DNA level that best predicted pp65 antigenemia in this series of samples was 11,500 copies/ml, but different threshold levels could be observed for specific groups of patients. HCMV disease was observed in 5 out of 48 patients with active HCMV infection. The presence of clinical symptoms was associated with positive pp65 and with higher antigenemia levels. Higher HCMV DNA load at the onset of viral replication was correlated to the development of clinical symptoms.</p> <p>Conclusion</p> <p>Both pp65 antigenemia and HCMV DNA load can be useful for the prospective monitoring of immunocompromised subjects. Specific cut-off levels capable of triggering preemptive antiviral treatment should be determined in accordance to the type of test used and the characteristics of patients and prospectively validated.</p
Safety of liver resection and effect on quality of life in patients with benign hepatic disease: Single center experience
<p>Abstract</p> <p>Background</p> <p>Although liver resection has long been established for selected patients with benign hepatic disease, the success of surgical treatment of these patients cannot be evaluated exclusively through postoperative morbidity and mortality. Therefore, the aim of the study was to prove the safety of liver resection in the treatment of benign liver tumors and to evaluate the effect of surgical treatment on the patients' qauality of life.</p> <p>Methods</p> <p>A total of 146 patients who underwent liver resection because of benign liver tumors were included in this study. Postoperative outcome was assessed and patients evaluated their quality of life before surgery and at the present time using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core-30 (QLQ C-30).</p> <p>Results</p> <p>The rate of serious (> grade 2) complications was 4.1% with no postoperative death. The quality of life assessment revealed an overall improvement of general health status after resection (0.7 vs. 0.56, p < 0.001) and additionally a significant reduction of 6 out of 9 symptoms. Furthermore, compelling benefits in the patients' social and emotional coping could be detected after surgery.</p> <p>Conclusions</p> <p>Liver resection for benign liver disease is a safe procedure and leads to a significant improvement of quality of life in selected patients.</p
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