Electronic structure of two interacting phosphorus δ-doped layers in silicon

Density functional theory is used to quantify the interaction of a pair of 1/4-monolayer phosphorus δ-doped layers in silicon. We investigate changes in the electronic structure as the distance between the two δ-doped layers is altered and identify the onset of interactions between the transverse and longitudinal bands. The calculations show that the valley splitting is insensitive to the separation distance, while the interlayer band splittings are insensitive to the representation used to describe the dopant disorder. These observations are exploited in a hybrid model which enables the calculation of accurate splittings of realistically disordered systems at tractable computational cost

Electronic structure models of phosphorus 0-doped silicon

We report a density-functional theory treatment of phosphorus 0-doped silicon. Using large asymmetric unit cells with up to 800 atoms, we obtain first-principles doping potentials, band energies, and donor-electron distributions. The explicit and nonempirical description of both valence and donor electrons improves upon previous models of this system. The effects of overlapping 0-doping potentials in smaller systems are adequately captured using a uniform band alignment shift

Population-based SEER trend analysis of overall and cancer-specific survival in 5138 patients with gastrointestinal stromal tumor

Background: The objective of the present population-based analysis was to assess survival patterns in patients with resected and metastatic GIST. Methods: Patients with histologically proven GIST were extracted from the Surveillance, Epidemiology and End Results (SEER) database from 1998 through 2011. Survival was determined applying Kaplan-Meier-estimates and multivariable Cox-regression analyses. The impact of size and mitotic count on survival was assessed with a generalized receiver-operating characteristic-analysis. Results: Overall, 5138 patients were included. Median age was 62 years (range: 18–101 years), 47.3% were female, 68.8% Caucasians. GIST location was in the stomach in 58.7% and small bowel in 31.2%. Lymph node and distant metastases were found in 5.1 and 18.0%, respectively. For non-metastatic GIST, three-year overall survival increased from 68.5% (95% CI: 58.8–79.8%) in 1998 to 88.6% (95% CI: 85.3–92.0%) in 2008, cancer-specific survival from 75.3% (95% CI: 66.1–85.9%) in 1998 to 92.2% (95% CI: 89.4–95.1%) in 2008. For metastatic GIST, three-year overall survival increased from 15.0% (95% CI: 5.3–42.6%) in 1998 to 54.7% (95% CI: 44.4–67.3%) in 2008, cancer-specific survival from 15.0% (95% CI: 5.3–42.6%) in 1998 to 61.9% (95% CI: 51.4–74.5%) in 2008 (all PTrend < 0.05). Conclusions: This is the first SEER trend analysis assessing outcomes in a large cohort of GIST patients over a 11-year time period. The analysis provides compelling evidence of a statistically significant and clinically relevant increase in overall and cancer-specific survival from 1998 to 2008, both for resected as well as metastatic GIST

Diagnostic accuracy of C-reactive protein and white blood cell counts in the early detection of inflammatory complications after open resection of colorectal cancer: a retrospective study of 1,187 patients

Purpose: Although widely used, there is a lack of evidence concerning the diagnostic accuracy of C-reactive protein (CRP) and white blood cell counts (WBCs) in the postoperative period. The aim of this study was to evaluate the diagnostic accuracy of CRP and WBCs in predicting postoperative inflammatory complications after open resection of colorectal cancer. Methods: In this retrospective study, clinical data and the CRP and WBCs, routinely measured until postoperative day5 (POD 5), were available for 1,187 patients who underwent colorectal cancer surgery between 1997 and 2009. Using the receiver-operating characteristic (ROC) methodology, the diagnostic accuracy was evaluated according to the area under the curve (AUC). Results: Three hundred forty-seven patients (29.2%; 95% CI, 26.7-31.9%) developed various inflammatory complications. Anastomotic leakage occurred in 8.0% (95% CI, 6.1-9.1%) of patients. The CRP level on POD 4 (AUC 0.76; 95% CI, 0.71-0.81) had the highest diagnostic accuracy for the early detection of inflammatory complications. With a cutoff of 123mg/l, the sensitivity was 0.66 (95% CI, 0.56-0.74), and the specificity was 0.77 (95% CI, 0.71-0.82). The diagnostic accuracy of the WBC was significantly lower compared to CRP. Conclusion: Measurement of CRP on POD 4 is recommended to screen for inflammatory complications. CRP values above 123mg/l on POD 4 should raise suspicion of inflammatory complications, although the discriminatory performance was insufficient to provide a single threshold that could be used to correctly predict inflammatory complications in clinical practice. WBC measurement contributes little to the early detection of inflammatory complications. Registered at www.clinicaltrials.gov (NCT01221324

Atomic-scale structure of the SrTiO3(001)-c(6x2) reconstruction: Experiments and first-principles calculations

The c(6x2) is a reconstruction of the SrTiO3(001) surface that is formed between 1050-1100oC in oxidizing annealing conditions. This work proposes a model for the atomic structure for the c(6x2) obtained through a combination of results from transmission electron diffraction, surface x-ray diffraction, direct methods analysis, computational combinational screening, and density functional theory. As it is formed at high temperatures, the surface is complex and can be described as a short-range ordered phase featuring microscopic domains composed of four main structural motifs. Additionally, non-periodic TiO2 units are present on the surface. Simulated scanning tunneling microscopy images based on the electronic structure calculations are consistent with experimental images

Risk Factors for Anastomotic Leakage after Rectal Cancer Resection and Reconstruction with Colorectostomy. A Retrospective Study with Bootstrap Analysis

Background: This study was designed to apply modern statistical methods to evaluate risk factors for anastomotic leakage after rectal cancer resection in a retrospective cohort of patients who received a colorectostomy. Whereas a diverting stoma and tumor height are considered proven risk factors for anastomotic leakage, a lack of evidence about additional risk factors persists. Methods: In a single-center study, 527 consecutive patients who received a colorectostomy after rectal cancer resection between 1991 and 2008 were retrospectively assessed. In addition to traditional uni- and multivariate regression, locally weighted scatterplot smoothing (LOWESS) regression and bootstrap analysis were applied to increase internal validity. Results: Anastomotic leakage occurred in 70 patients (13.3%; 95% confidence interval (CI), 10.5-16.5%) and mortality was 2.5% (95% CI, 1.4-4.2%). Diverting stoma (odds ratio (OR), 0.4; 95% CI, 0.17-0.61) and tumor height (OR, 0.88; 95% CI, 0.8-0.94) were proven to be protective. Neoadjuvant radiotherapy (OR, 2.15; 95% CI, 1.58-4.24) and intraoperative blood loss (OR, 1.05; 95% CI, 1.02-1.09) had a derogatory effect. Bootstrap analysis identified pre-existing vascular disease (95.5%), more advanced UICC stage III or IV tumors (95.7% or 91.5%, respectively), and intraoperative (96.1%) and postoperative (99.4%) blood substitution as harmful. Both intraoperative and postoperative blood substitution caused a dose-dependent increase in risk. Conclusions: Applying statistical resampling methods identified intraoperative blood loss, blood substitution, vascular disease, and advanced UICC stage as risk factors for anastomotic leakage. Greater distances between the tumor and the anal verge and performance of a diverting stoma were associated with a decreased risk of anastomotic leakag

Bismuth trichloride as a molecular precursor for silicon doping

Dopant impurity species can be incorporated into the silicon (001) surface via the adsorption and dissociation of simple precursor molecules. Examples include phosphine (PH3), arsine (AsH3), and diborane (B2H6) for the incorporation of phosphorus, arsenic, and boron, respectively. Through exploitation of precursor surface chemistry, the spatial locations of these incorporated dopants can be controlled at the atomic scale via the patterning of a hydrogen lithographic resist layer using scanning tunneling microscopy (STM). There is strong interest in the spatial control of bismuth atoms incorporated into silicon for quantum technological applications; however, there is currently no known precursor for the incorporation of bismuth that is compatible with this STM-based lithographic method. Here, we explore the precursor chemistry (adsorption, diffusion, and dissociation) of bismuth trichloride (BiCl3) on Si(001). We show atomic-resolution STM images of BiCl3 exposed Si(001) surfaces at low coverage and combine this with density functional theory calculations to produce a model of the surface processes and the observed features. Our results show that, at room temperature, BiCl3 completely dissociates to produce bismuth ad-atoms, ad-dimers, and surface-bound chlorine, and we explain how BiCl3 is a strong candidate for a bismuth precursor compound compatible with lithographic patterning at the sub-nanometer scale

Dissociation of CH₃–O as a Driving Force for Methoxyacetophenone Adsorption on Si(001)

The coverage-dependent behavior of p-methoxyacetophenone on the clean Si(001) surface was followed using X-ray photoelectron spectroscopy and supporting density functional theory calculations. Unlike other multifunctional organic molecules, this compound exhibits a high selectivity of adsorbate species formation by forming only two distinct adsorbate structures at low coverage, with a third configuration forming at high coverages. At low coverage, surface chemisorption is driven by methoxy group dissociation. However, at high coverage, the surface footprint required for this process is no longer available, leading to the formation of less thermodynamically stable adsorbates that are datively bonded to the surface with a smaller footprint. This coverage-dependent but well-defined behavior is promising in designing functional organic–inorganic interfaces on silicon

Diagnostic study and meta-analysis of C-reactive protein as a predictor of postoperative inflammatory complications after gastroesophageal cancer surgery

Purpose: This study assessed the diagnostic accuracy of C-reactive protein (CRP) after gastroesophageal cancer resection for postoperative inflammatory complications (PIC). Methods: The clinical data and CRP values of patients operated on for gastroesophageal cancer surgery between 1997 and 2009 were retrospectively analyzed. The results of this study were compared with published data using a meta-analytic approach for diagnostic outcomes. Results: Of 210 patients included in the study, 59 developed PIC (28.1%; 95% CI: 22.5-34.5%). On the postoperative day (POD) 4 and 7, CRP had the best diagnostic accuracy for PIC (AUC 0.77; 95% CI, 0.64-0.91, AUC 0.81; 95% CI, 0.71-0.91). Using a cut-off value of 141mg/L (95% CI, 131-278mg/L) for CRP on POD 4, the sensitivity was 0.78 (95% CI, 0.55-0.91), the specificity was 0.70 (95% CI, 0.53-0.83) and the NPV was 0.89 (95% CI, 0.77-0.95). The in-hospital mortality rate was 3.3% (95% CI, 1.5-6.9%). In a diagnostic meta-analysis that included two additional studies, CRP had a significant predictive value after POD 3. Conclusion: There is limited evidence for the diagnostic accuracy of CRP levels for PIC after gastroesophageal cancer surgery. CRP levels on POD 4 might be useful to rule out PIC, but its diagnostic accuracy is moderate at best. For clinical routine use CRP levels are clearly not sufficient to predict PIC and have to be interpreted in the context of the whole clinical pictur