Evaluation of the microstructural, electronic and optoelectronic properties of ƴ-CuCl thin films and their fabrication on Si substrates

Cuprous chloride is a direct wide bandgap (Eg = ~ 3.4 eV) semiconductor with a large excitonic binding energy (~ 190 meV). In this study, CuCl has been deposited by the vacuum evaporation method on a variety of substrates (amorphous silica glass, indium tin oxide (ITO) coated on glass and Silicon (100)) substrates, encapsulated and characterized as a potential material for optoelectronic applications. Some of the samples were also oxygen plasma treated for durations of 1, 2 and 3 minutes, respectively. Room temperature x-ray diffraction (XRD) measurements show that CuCl grows preferentially in a (111) orientation irrespective of the underlying substrate. Microstructural properties of the films gave nearly the same values for untreated CuCl films deposited on glass, ITO and Si substrates (particle size, L = 9.6 nm ± 1 nm). On the other hand, the microstructural properties of the plasma treated films vary as a function of plasma treatment duration. At 10 K, the photoluminescence (PL) spectrum of the untreated CuCl/Si films using 244 nm excitation reveals four peaks: the Z₃ free exciton occurring at 3.203 ± 0.003 eV, the I₁ impurity bound exciton located at 3.181 ± 0.003 eV, the M free biexciton occurring at 3.160 ± 0.003 eV and N₁ impurity bound to bi-exciton located at 3.135 ± 0.003 eV. However, the 20 K PL spectra of the untreated CuCl films deposited on all three substrates (using a 325 nm excitation) revealed only the Z₃ free exciton, the I₁ impurity bound exciton and the N₁ impurity bound biexciton at 3.204 eV, 3.18 eV and 3.152 eV, respectively, irrespective of the underlying substrate. The room temperature PL spectra of the films were dominated by the Z₃ free exciton. The measured band gap increased as the temperature increases, which is opposite to most conventional semiconductors. This anomalous effect is believed to be related to electron-phonon renormalization or coupling of the electronic structure of CuCl. On the other hand the PL spectra of the O₂ plasma immersed film were all mainly dominated by the free Z₃ free exciton only. In addition, at low temperatures a broad band ascribed to an oxygen related emission process is observed at ~ 3 eV in all the plasma treated samples. The band gap of the O₂ plasma immersed films follow the anomalous temperature dependency in a similar manner to the untreated films; however the plasma treated films were less sensitive to temperature. Both steady state DC and AC impedance spectroscopy experiments suggested that the untreated CuCl is a mixed ionic-electronic semiconductor material. Room temperature steady state DC measurements using reversible electrodes (Cu) gave an Ohmic response while using irreversible electrodes (Au) gave an exponential I–V behaviour, both in conformance with Wagner’s defect chemistry analysis of a mixed ionicelectronic material. An electronic conductivity of the order of 2.3 × 10-7 S/cm was deduced to be in coexistence with Cu⁺ ionic conductivity using irreversible electrodes (Au), while a total conductivity of the order of 6.5 × 10-7 S/cm was obtained using reversible electrodes (Cu) at room temperature. The Arrhenius plot of the electrical characteristics of the untreated films reveal two distinct regimes corresponding to electronic conduction below ~ 270 K and a Cu⁺ extrinsic ionic conduction mechanism ix above that temperature. Due to the fact that at low temperatures, the thermal energy is inadequate for maintaining considerable ionic motion, it follows that the mode of conduction at lower temperatures is ascribed to electronic processes. On the other hand, the Arrhenius plot of the plasma treated films showed a single regime throughout most of the temperature range. This is interpreted to be an electronically dominant conduction mechanism. The large increase in the conductivity of the treated CuCl films (over 100 fold) is ascribed to effect of oxygen introducing an acceptor state in CuCl films. This is due to the fact that oxygen dissolves in cuprous halides on substitutional anionic sites. Cathodic deposition of Cu metal via electrolytic decomposition was observed when a steady state voltage greater than 5 V was applied to both the untreated and the plasma treated films. This poses a great challenge in utilizing this material to fabricate optoelectronic devices under the influence of steady state source. The untreated films were successfully encapsulated using organic polysilsesquioxane (PSSQ) and cyclo olefin copolymer (COC) dielectrics. However, both encapsulants failed to prevent the O2 plasma immersed films from oxidising, and this will also represent a future challenge for this technology

Human papillomavirus vaccination coverage in Luxembourg : implications of lowering and restricting target age groups

Background: In Luxembourg, a national Human Papillomavirus (HPV) vaccination programme was introduced in 2008, targeting 12-17 year old girls offering a choice of bivalent or quadrivalent vaccine free of charge. In 2015, the programme was changed offering the bivalent vaccine only to 11-13 year old girls. The aim of this study was to evaluate the HPV vaccination coverage, to assess the impact of age target changes and compare vaccination coverage to other European countries. Methods: Anonymous HPV vaccination records consisting of individual vaccine doses obtained free of charge in pharmacies between 2008 and 2016 were extracted from the Luxembourgish Social Security database. Additional aggregate tables by nationality and municipality were analysed. Results: Of the target cohort of 39,610 girls born between 1991 and 2003 residing in Luxembourg, 24,550 (62.0%) subjects obtained at least one dose, 22,082 (55.7%) obtained at least two doses, and 17,197 (43.4%) obtained three doses of HPV vaccine. The mean age at first dose was 13.7 years during 200814 and 12.7 years in 2016 after the age target change. Coverage varied significantly by nationality (p < 0.0001): Portuguese (80%), former Yugoslays (74%), Luxembourgish (54%), Belgian (52%), German (47%), French (39%) and other, nationalities (51%). Coverage varied also by geographical region, with lower rates (<50%) noted in some Northern and Central areas of Luxembourg (range: 38% to 78%). Conclusion: Overall HPV vaccination coverage in Luxembourg is moderate and varied by nationality and region. The policy changes in 2015 did not have a substantial impact except lowering age at initiating vaccination. Options to improve coverage deserve further investigation

Use of cumulative incidence of novel influenza A/H1N1 in foreign travelers to estimate lower bounds on cumulative incidence in Mexico

Background: An accurate estimate of the total number of cases and severity of illness of an emerging infectious disease is required both to define the burden of the epidemic and to determine the severity of disease. When a novel pathogen first appears, affected individuals with severe symptoms are more likely to be diagnosed. Accordingly, the total number of cases will be underestimated and disease severity overestimated. This problem is manifest in the current epidemic of novel influenza A/H1N1. Methods and Results: We used a simple approach to leverage measures of incident influenza A/H1N1 among a relatively small and well observed group of US, UK, Spanish and Canadian travelers who had visited Mexico to estimate the incidence among a much larger and less well surveyed population of Mexican residents. We estimate that a minimum of 113,000 to 375,000 cases of novel influenza A/H1N1 have occurred in Mexicans during the month of April, 2009. Such an estimate serves as a lower bound because it does not account for underreporting of cases in travelers or for nonrandom mixing between Mexican residents and visitors, which together could increase the estimates by more than an order of magnitude. Conclusions: We find that the number of cases in Mexican residents may exceed the number of confirmed cases by two to three orders of magnitude. While the extent of disease spread is greater than previously appreciated, our estimate suggests that severe disease is uncommon since the total number of cases is likely to be much larger than those of confirmed cases

Searching in Unstructured Overlays Using Local Knowledge and Gossip

This paper analyzes a class of dissemination algorithms for the discovery of distributed contents in Peer-to-Peer unstructured overlay networks. The algorithms are a mix of protocols employing local knowledge of peers' neighborhood and gossip. By tuning the gossip probability and the depth k of the k-neighborhood of which nodes have information, we obtain different dissemination protocols employed in literature over unstructured P2P overlays. The provided analysis and simulation results confirm that, when properly configured, these schemes represent a viable approach to build effective P2P resource discovery in large-scale, dynamic distributed systems.Comment: A revised version of the paper appears in Proc. of the 5th International Workshop on Complex Networks (CompleNet 2014) - Studies in Computational Intelligence Series, Springer-Verlag, Bologna (Italy), March 201

Comparison of Compliance with Cervical Cancer Screening among Women aged 18 and above in Arkansas and the United States

Introduction: Cervical cancer preys on women without access to preventative screening. Any woman who has developed an invasive case of cervical cancer should be regarded as a failure of screening. Disparities in access to screening, triage, and treatment fuel an uneven distribution in the burden of cervical cancer within the United States; weighing unusually heavy on the Southern States like Arkansas. The purpose of this study was to evaluate demographic and behavioral risk factors for cervical cancer and identify potential barriers which may influence the likelihood of complying with current Pap test recommendations on a state level, in Arkansas, and also a national scale, in the United States. Materials and Methods: National data from the 2014 Behavioral Risk Factor Survey System (BRFSS) was used to collect demographic characteristics and behavioral risk factors among females aged 18 and above in Arkansas and the United States. BFRSS data included a total of 1,587 women in Arkansas and 162,222 in the United States who were aged 18 and above and eligible to receive Pap tests. Women with a medical history of hysterectomy that included the removal of the cervix were excluded from analysis because they are not considered to be medically eligible to receive Pap tests. Results: Socioeconomic status, age, race, and health insurance were significantly associated with likelihood to comply with current screening recommendations among women in both Arkansas and the United States. Arkansan women who had less than a 12-year education (Odds Ratio (OR) = 1.41, 95% Confidence Interval (CI) = 1.04, 1.64) and were without health insurance (OR = 3.56, 95% CI = 1.66, 7.66) were more likely to be non-compliant with Pap testing, which is similar to the finding on the national level. The prevalence of Pap test compliance was significantly lower among women in Arkansas when compared to US average in every sociodemographic sector. Discussion: According to US Census data collected in 2013, Arkansas had the highest cervical cancer incidence of 10.6 per 100,000 person-years, while the national average was 7.7 per 100,000 person-years. Therefore, future population-based cervical cancer interventions in Arkansas should target the promotion of Pap test compliance among the most vulnerable subpopulations (i.e., low socioeconomic status, minority, medically under or uninsured). Organized screening interventions might include offering free or reduced cost Pap testing in both urban and rural locations

On inversely θ-semi-open and inversely θ-semi-closed functions

In this paper, we introducethe concepts of inversely 6-semi-openandinversely 6-semi-closed functions andobtain their charactcrizationsif it is possible in terms of 6-closure and6-intcrior by using sets determined by thefibres of the function. Finally, we obtainits relationships withthe strongly @-continuous