Wave function engineering in quantum dot-ring nanostructures

Modern nanotechnology allows producing, depending on application, various quantum nanostructures with the desired properties. These properties are strongly influenced by the confinement potential which can be modified, e.g., by electrical gating. In this paper we analyze a nanostructure composed of a quantum dot surrounded by a quantum ring. We show that depending on the details of the confining potential the electron wave functions can be located in different parts of the structure. Since the properties of such a nanostructure strongly depend on the distribution of the wave functions, varying the applied gate voltage one can easily control them. In particular, we illustrate the high controllability of the nanostructure by demonstrating how its coherent, optical, and conducting properties can be drastically changed by a small modification of the confining potential.Comment: 8 pages, 10 figures, 2 tables, revte

Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

Two-dimensional materials offer new opportunities for both fundamental science and technological applications, by exploiting the electron spin. While graphene is very promising for spin communication due to its extraordinary electron mobility, the lack of a band gap restricts its prospects for semiconducting spin devices such as spin diodes and bipolar spin transistors. The recent emergence of 2D semiconductors could help overcome this basic challenge. In this letter we report the first important step towards making 2D semiconductor spin devices. We have fabricated a spin valve based on ultra-thin (5 nm) semiconducting black phosphorus (bP), and established fundamental spin properties of this spin channel material which supports all electrical spin injection, transport, precession and detection up to room temperature (RT). Inserting a few layers of boron nitride between the ferromagnetic electrodes and bP alleviates the notorious conductivity mismatch problem and allows efficient electrical spin injection into an n-type bP. In the non-local spin valve geometry we measure Hanle spin precession and observe spin relaxation times as high as 4 ns, with spin relaxation lengths exceeding 6 um. Our experimental results are in a very good agreement with first-principles calculations and demonstrate that Elliott-Yafet spin relaxation mechanism is dominant. We also demonstrate that spin transport in ultra-thin bP depends strongly on the charge carrier concentration, and can be manipulated by the electric field effect

The XMM-Newton serendipitous survey: VIII. the first XMM-Newton serendipitous source catalogue from overlapping observations

Context. XMM-Newton has observed the X-ray sky since early 2000. The XMM-Newton Survey Science Centre Consortium has published catalogues of X-ray and ultraviolet sources found serendipitously in the individual observations. This series is now augmented by a catalogue dedicated to X-ray sources detected in spatially overlapping XMM-Newton observations. Aims. The aim of this catalogue is to explore repeatedly observed sky regions. It thus makes use of the long(er) effective exposure time per sky area and offers the opportunity to investigate long-term flux variability directly through the source-detection process. Methods. A new standardised strategy for simultaneous source detection on multiple observations was introduced, including an adaptive-smoothing method to describe the image background. It was coded as a new task within the XMM-Newton Science Analysis System and used to compile a catalogue of sources from 434 stacks comprising 1789 overlapping XMM-Newton observations that entered the 3XMM-DR7 catalogue, have a low background and full-frame readout of all EPIC cameras. Results. The first stacked catalogue is called 3XMM-DR7s. It contains 71 951 unique sources with positions and parameters such as fluxes, hardness ratios, quality estimates, and information on inter-observation variability, directly derived from a simultaneous fit. Source parameters are calculated for the stack and for each contributing observation. About 15% of the sources are new with respect to 3XMM-DR7. Through stacked source detection, the parameters of repeatedly observed sources are determined with higher accuracy than in the individual observations. The method is more sensitive to faint sources and tends to produce fewer spurious detections. Conclusions. With this first stacked catalogue we demonstrate the feasibility and benefit of the approach. It supplements the large data base of XMM-Newton detections with additional, in particular faint, sources and adds variability information. In the future, the catalogue will be expanded to larger samples and continued within the series of serendipitous XMM-Newton source catalogues.FJC acknowledges financial support through grant AYA2015-64346-C2-1P (MINECO/FEDER) and MTC through grant ESP2016-76683-C3-1R (MINECO/FEDER

Cataclysmic Variables from Sloan Digital Sky Survey V -- the search for period bouncers continues

SDSS-V is carrying out a dedicated survey for white dwarfs, single and in binaries, and we report the analysis of the spectroscopy of cataclysmic variables (CVs) and CV candidates obtained during the final plug plate observations of SDSS. We identify eight new CVs, spectroscopically confirm 53 and refute eleven published CV candidates, and we report 21 new or improved orbital periods. Combined with previously published data, the orbital period distribution of the SDSS-V CVs does not clearly exhibit a period gap. This is consistent with previous findings that spectroscopically identified CVs have a larger proportion of short-period systems compared to samples identified from photometric variability. Remarkably, despite a systematic search, we find very few period bouncers. We estimate the space density of period bouncers to be $\simeq0.2\times10^{-6}\,\mathrm{pc}^{-3}$, i.e. they represent only a few per cent of the total CV population. This suggests that during their final phase of evolution, CVs either destroy the donor, e.g. via a merger, or that they become detached and cease mass transfer.Comment: Submitted to MNRA

Chinese and white Canadian satisfaction and compliance with physicians

BACKGROUND: Patient satisfaction has become an important indicator of primary care and healthcare system performance. Ethnic disparities in patient satisfaction and compliance with physician care have been studied in several countries. However, this issue has not received significant attention in Canada. The unique characteristics of the Canadian healthcare system and ethnic population make it worthwhile to examine this issue in this population. Therefore, we conducted a survey among Chinese and Whites in a Canadian city to determine their reported satisfaction, and perceptions of physicians. METHODS: The survey was conducted in English, Mandarin and Cantonese in 2005 among Chinese and White Canadians, 18 years of age or older, who had visited at least one physician in Canada. RESULTS: We analyzed 746 Chinese and 711 Whites in the general practitioner (GP) visit group and 485 Chinese and 637 Whites in the specialist visit group. A lower proportion of Chinese compared to Whites reported that they were very satisfied or satisfied with GP (73.7% vs. 92.8%) and specialist care (75.5% vs. 85.6%) and the differences between the two groups remained after adjustment for demographic variables and chronic conditions (risk adjusted OR: 0.70, 95%CI: 0.42–1.18 for the GP visit group and OR: 0.77, 95%CI: 0.48–1.23 for the specialist visit group). A similar proportion of Chinese and Whites reported that they always followed a physician's advice (59.4% vs. 59.6% for the GP visit group and 67.2% vs. 62.8% for the specialist visit group). Non-English speaking Chinese and recent arrivals in Canada were less likely to be satisfied with GPs than Chinese born in Canada [risk adjusted OR: 0.5, 95%CI: 0.3–0.9, 0.2 and 0.1–0.7, respectively]. CONCLUSION: Chinese Canadians reported lower satisfaction with physicians and perceived physicians slightly more negatively than White Canadians. Particularly, Chinese with limited English and short length of stay in Canada were less satisfied than Canadian born Chinese

Intermediate care in caring for dementia, the point of view of general practitioners: A key informant survey across Europe.

Background: Intermediate care is often defined as healthcare occurring somewhere between traditional primary (community) and secondary (hospital) care settings. High quality intermediate care is important in dementia, may prevent caregiver burnout and also lead to optimal care for people with dementia. However, very little is known about the point of intermediate care for persons with dementia in Europe. Research questions: What intermediate care services exist and how are they utilized in the care of people with dementia in Europe? Objective: This study aims at describing the point of view of General Practitioners on intermediate care services for people with dementia across Europe. Methods: Key informant survey was sent to GPs via a self-developed questionnaire with space for open ended comments. 16 European countries participated to this cross-sectional mixed method study. Given the volunteer nature of the study, no minimum sample size requirements were applied to participation. Convenience sampling technique was used to address variations due to regional variations and regulations within the same country. Descriptive analyses of all intermediate care facilities groups by countries were performed. Qualitative analyses approach was used for the optional-free text to exemplify and/or complete the reasons contained in the closed response categories. Results: The questionnaire was sent to 16 European countries. 583 questionnaires were analyzed. The responding physicians were 48 (± 11) years old on average and they had been in practice for an average of 18 (+ /11) years. The types of intermediate care considered were integrated at-home services, respite and relief services, day care centers and nursing homes. Their availability was considered very inhomogeneous by the majority of respondents. The main benefits of intermediate care cited were better medical care for the patient (78%), better quality of life for the caregiver (67%), prevention of the caregiver burden (73%) and a break for the caregiver (59%). The reported difficulties were: accessing these facilities due to limited financial support (76%) and cumbersome administrative procedures (67%). Many other facets of our findings were captured in the qualitative themes that emerged. Conclusion: Intermediate care in Europe is diverse and heterogeneous. Major concerns of GPs are about the cost issues and the cumbersome administrative procedures to access them

Burden of cardiovascular disease across 29 countries and GPs' decision to treat hypertension in oldest-old

OBJECTIVES: We previously found large variations in general practitioner (GP) hypertension treatment probability in oldest-old (>80 years) between countries. We wanted to explore whether differences in country-specific cardiovascular disease (CVD) burden and life expectancy could explain the differences. DESIGN: This is a survey study using case-vignettes of oldest-old patients with different comorbidities and blood pressure levels. An ecological multilevel model analysis was performed. SETTING: GP respondents from European General Practice Research Network (EGPRN) countries, Brazil and New Zeeland. SUBJECTS: This study included 2543 GPs from 29 countries. MAIN OUTCOME MEASURES: GP treatment probability to start or not start antihypertensive treatment based on responses to case-vignettes; either low (/=50% started treatment). CVD burden is defined as ratio of disability-adjusted life years (DALYs) lost due to ischemic heart disease and/or stroke and total DALYs lost per country; life expectancy at age 60 and prevalence of oldest-old per country. RESULTS: Of 1947 GPs (76%) responding to all vignettes, 787 (40%) scored high treatment probability and 1160 (60%) scored low. GPs in high CVD burden countries had higher odds of treatment probability (OR 3.70; 95% confidence interval (CI) 3.00-4.57); in countries with low life expectancy at 60, CVD was associated with high treatment probability (OR 2.18, 95% CI 1.12-4.25); but not in countries with high life expectancy (OR 1.06, 95% CI 0.56-1.98). CONCLUSIONS: GPs' choice to treat/not treat hypertension in oldest-old was explained by differences in country-specific health characteristics. GPs in countries with high CVD burden and low life expectancy at age 60 were most likely to treat hypertension in oldest-old. Key Points * General practitioners (GPs) are in a clinical dilemma when deciding whether (or not) to treat hypertension in the oldest-old (>80 years of age). * In this study including 1947 GPs from 29 countries, we found that a high country-specific cardiovascular disease (CVD) burden (i.e. myocardial infarction and/or stroke) was associated with a higher GP treatment probability in patients aged >80 years. * However, the association was modified by country-specific life expectancy at age 60. While there was a positive association for GPs in countries with a low life expectancy at age 60, there was no association in countries with a high life expectancy at age 60. * These findings help explaining some of the large variation seen in the decision as to whether or not to treat hypertension in the oldest-old

Variation in GP decisions on antihypertensive treatment in oldest-old and frail individuals across 29 countries

BACKGROUND: In oldest-old patients (>80), few trials showed efficacy of treating hypertension and they included mostly the healthiest elderly. The resulting lack of knowledge has led to inconsistent guidelines, mainly based on systolic blood pressure (SBP), cardiovascular disease (CVD) but not on frailty despite the high prevalence in oldest-old. This may lead to variation how General Practitioners (GPs) treat hypertension. Our aim was to investigate treatment variation of GPs in oldest-olds across countries and to identify the role of frailty in that decision. METHODS: Using a survey, we compared treatment decisions in cases of oldest-old varying in SBP, CVD, and frailty. GPs were asked if they would start antihypertensive treatment in each case. In 2016, we invited GPs in Europe, Brazil, Israel, and New Zealand. We compared the percentage of cases that would be treated per countries. A logistic mixed-effects model was used to derive odds ratio (OR) for frailty with 95% confidence intervals (CI), adjusted for SBP, CVD, and GP characteristics (sex, location and prevalence of oldest-old per GP office, and years of experience). The mixed-effects model was used to account for the multiple assessments per GP. RESULTS: The 29 countries yielded 2543 participating GPs: 52% were female, 51% located in a city, 71% reported a high prevalence of oldest-old in their offices, 38% and had >20 years of experience. Across countries, considerable variation was found in the decision to start antihypertensive treatment in the oldest-old ranging from 34 to 88%. In 24/29 (83%) countries, frailty was associated with GPs' decision not to start treatment even after adjustment for SBP, CVD, and GP characteristics (OR 0.53, 95%CI 0.48-0.59; ORs per country 0.11-1.78). CONCLUSIONS: Across countries, we found considerable variation in starting antihypertensive medication in oldest-old. The frail oldest-old had an odds ratio of 0.53 of receiving antihypertensive treatment. Future hypertension trials should also include frail patients to acquire evidence on the efficacy of antihypertensive treatment in oldest-old patients with frailty, with the aim to get evidence-based data for clinical decision-making

General practitioners' deprescribing decisions in older adults with polypharmacy: a case vignette study in 31 countries

BACKGROUND: General practitioners (GPs) should regularly review patients' medications and, if necessary, deprescribe, as inappropriate polypharmacy may harm patients' health. However, deprescribing can be challenging for physicians. This study investigates GPs' deprescribing decisions in 31 countries. METHODS: In this case vignette study, GPs were invited to participate in an online survey containing three clinical cases of oldest-old multimorbid patients with potentially inappropriate polypharmacy. Patients differed in terms of dependency in activities of daily living (ADL) and were presented with and without history of cardiovascular disease (CVD). For each case, we asked GPs if they would deprescribe in their usual practice. We calculated proportions of GPs who reported they would deprescribe and performed a multilevel logistic regression to examine the association between history of CVD and level of dependency on GPs' deprescribing decisions. RESULTS: Of 3,175 invited GPs, 54% responded (N = 1,706). The mean age was 50 years and 60% of respondents were female. Despite differences across GP characteristics, such as age (with older GPs being more likely to take deprescribing decisions), and across countries, overall more than 80% of GPs reported they would deprescribe the dosage of at least one medication in oldest-old patients (> 80 years) with polypharmacy irrespective of history of CVD. The odds of deprescribing was higher in patients with a higher level of dependency in ADL (OR =1.5, 95%CI 1.25 to 1.80) and absence of CVD (OR =3.04, 95%CI 2.58 to 3.57). INTERPRETATION: The majority of GPs in this study were willing to deprescribe one or more medications in oldest-old multimorbid patients with polypharmacy. Willingness was higher in patients with increased dependency in ADL and lower in patients with CVD