Formation of atom wires on vicinal silicon

The formation of atomic wires via pseudomorphic step-edge decoration on vicinal silicon surfaces has been analyzed for Ga on the Si(112) surface using Scanning Tunneling Microscopy and Density Functional Theory calculations. Based on a chemical potential analysis involving more than thirty candidate structures and considering various fabrication procedures, it is concluded that pseudomorphic growth on stepped Si(112), both under equilibrium and non-equilibrium conditions, must favor formation of Ga zig-zag chains rather than linear atom chains. The surface is non-metallic and presents quasi-one dimensional character in the lowest conduction band.Comment: submitte

Ga-induced atom wire formation and passivation of stepped Si(112)

We present an in-depth analysis of the atomic and electronic structure of the quasi one-dimensional (1D) surface reconstruction of Ga on Si(112) based on Scanning Tunneling Microscopy and Spectroscopy (STM and STS), Rutherford Backscattering Spectrometry (RBS) and Density Functional Theory (DFT) calculations. A new structural model of the Si(112)6 x 1-Ga surface is inferred. It consists of Ga zig-zag chains that are intersected by quasi-periodic vacancy lines or misfit dislocations. The experimentally observed meandering of the vacancy lines is caused by the co-existence of competing 6 x 1 and 5 x 1 unit cells and by the orientational disorder of symmetry breaking Si-Ga dimers inside the vacancy lines. The Ga atoms are fully coordinated, and the surface is chemically passivated. STS data reveal a semiconducting surface and show excellent agreement with calculated Local Density of States (LDOS) and STS curves. The energy gain obtained by fully passivating the surface calls the idea of step-edge decoration as a viable growth method toward 1D metallic structures into question.Comment: Submitted, 13 pages, accepted in Phys. Rev. B, notational change in Fig.

Mid-infrared diagnostics of starburst galaxies: clumpy, dense structures in star-forming regions in the Antennae (NGC 4038/4039)

Recently, mid-infrared instruments have become available on several large ground-based telescopes, resulting in data sets with unprecedented spatial resolution at these long wavelengths. In this paper we examine 'ground-based-only' diagnostics, which can be used in the study of star-forming regions in starburst galaxies. By combining output from the stellar population synthesis code Starburst 99 with the photoionization code Mappings, we model stellar clusters and their surrounding interstellar medium, focusing on the evolution of emission lines in the N- and Q-band atmospheric windows (8-13 and 16.5-24.5 micron respectively) and those in the near-infrared. We address the detailed sensitivity of various emission line diagnostics to stellar population age, metallicity, nebular density, and ionization parameter. Using our model results, we analyze observations of two stellar clusters in the overlap region of the Antennae galaxies obtained with VLT Imager and Spectrometer for mid Infrared (VISIR). We find evidence for clumpy, high density, ionized gas. The two clusters are young (younger than 2.5 and 3 Myr respectively), the surrounding interstellar matter is dense (10^4 cm^-3 or larger) and can be characterized by a high ionization parameter (logU > -1.53). Detailed analysis of the mid-infrared spectral features shows that a (near-)homogeneous medium cannot account for the observations, and that complex structure on scales below the resolution limit, containing several young stellar clusters embedded in clumpy gas, is more likely.Comment: 24 pages, 16 figures (3 in color), accepted for publication in Ap

Extended polarized semiclassical model for quantum-dot cavity QED and its application to single-photon sources

We present a simple extension of the semi-classical model for a two-level system in a cavity, in order to incorporate multiple polarized transitions, such as those appearing in neutral and charged quantum dots (QDs), and two nondegenerate linearly polarized cavity modes. We verify the model by exact quantum master equation calculations, and experimentally using a neutral QD in a polarization non-degenerate micro-cavity, in both cases we observe excellent agreement. Finally, the usefulness of this approach is demonstrated by optimizing a single-photon source based on polarization postselection, where we find an increase in the brightness for optimal polarization conditions as predicted by the model.Comment: 8 pages, for simple code see https://doi.org/10.5281/zenodo.347666

Predicting the likelihood of successful medical treatment of early pregnancy loss:development and internal validation of a clinical prediction model

STUDY QUESTION: What are clinical predictors for successful medical treatment in case of early pregnancy loss (EPL)? SUMMARY ANSWER: Use of mifepristone, BMI, number of previous uterine aspirations and the presence of minor clinical symptoms (slight vaginal bleeding or some abdominal cramps) at treatment start are predictors for successful medical treatment in case of EPL. WHAT IS KNOWN ALREADY: Success rates of medical treatment for EPL vary strongly, between but also within different treatment regimens. Up until now, although some predictors have been identified, no clinical prediction model has been developed yet. STUDY DESIGN, SIZE, DURATION: Secondary analysis of a multicentre randomized controlled trial in 17 Dutch hospitals, executed between 28 June 2018 and 8 January 2020. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women with a non-viable pregnancy between 6 and 14 weeks of gestational age, who opted for medical treatment after a minimum of 1 week of unsuccessful expectant management. Potential predictors for successful medical treatment of EPL were chosen based on literature and expert opinions. We internally validated the prediction model using bootstrapping techniques. MAIN RESULTS AND THE ROLE OF CHANCE: 237 out of 344 women had a successful medical EPL treatment (68.9%). The model includes the following variables: use of mifepristone, BMI, number of previous uterine aspirations and the presence of minor clinical symptoms (slight vaginal bleeding or some abdominal cramps) at treatment start. The model shows a moderate capacity to discriminate between success and failure of treatment, with an AUC of 67.6% (95% CI = 64.9-70.3%). The model had a good fit comparing predicted to observed probabilities of success but might underestimate treatment success in women with a predicted probability of success of ∼70%. LIMITATIONS, REASONS FOR CAUTION: The vast majority (90.4%) of women were Caucasian, potentially leading to less optimal model performance in a non-Caucasian population. Limitations of our model are that we have not yet been able to externally validate its performance and clinical impact, and the moderate accuracy of the prediction model of 0.67. WIDER IMPLICATIONS OF THE FINDINGS: We developed a prediction model, aimed to improve and personalize counselling for medical treatment of EPL by providing a woman with her individual chance of complete evacuation. STUDY FUNDING/COMPETING INTEREST(S): The Triple M Trial, upon which this secondary analysis was performed, was funded by the Healthcare Insurers Innovation Foundation (project number 3080 B15-191). TRIAL REGISTRATION NUMBER: Clinicaltrials.gov: NCT03212352

Analysis of MHC class I and II expression in relation to presence of HPV genotypes in premalignant and malignant cervical lesions.

Cervical intraepithelial neoplasia (CIN) grades I to III lesions (n = 94) and squamous cell carcinomas of the uterine cervix (n = 27) were analysed for MHC class I and II expression and presence of HPV genotypes. MHC class I and II expression was studied by immunohistochemistry and HPV typing was performed by general primer- and type-specific primer mediated PCR (GP/TS PCR). Both techniques were performed on paraffin embedded tissue sections. Results show disturbed MHC class I heavy chain expression in CIN I to CIN III, as well as in cervical carcinomas. Upregulated MHC class II expression on dysplastic epithelial cells was also found in the different CIN groups and carcinomas. Prevalence of HPV genotypes increased with the severity of the lesion, mainly due to the contribution of the HPV types 16 and 18. No correlation could be established between the presence of specific HPV genotypes and any MHC expression pattern in the different CIN groups or cervical carcinomas. In some cases these data were confirmed by RNA in situ hybridisation showing HPV 16 E7 transcripts in the same dysplastic/neoplastic cells from which MHC status was determined. The results indicate that local differences may exist in the type of cellular immune response to HPV induced lesions

Role of paan chewing and dietary habits in cervical carcinoma in Chennai, India

/=5 paan day(-1)=4.0; 95% CI 1.2-13.3). Among dietary habits, the highest vs lowest intake tertile for vegetables and fruit was associated with an OR of 0.5 (95% CI 0.2-1.0). Low education level and low body weight were also risk factors for ICC, but they did not account for the associations of paan chewing and low vegetable and fruit intake. In the analyses restricted to HPV-positive cases and controls, the inverse association with vegetable and fruit intake was confirmed. Conversely, the adverse influence of paan chewing on ICC risk seemed to be attributable to a higher prevalence of cervical HPV infection in women who chewed