Quasi van der Waals Epitaxy of Rhombohedral-Stacked Bilayer WSe2 on GaP(111) Heterostructure.

The growth of bilayers of two-dimensional (2D) materials on conventional 3D semiconductors results in 2D/3D hybrid heterostructures, which can provide additional advantages over more established 3D semiconductors while retaining some specificities of 2D materials. Understanding and exploiting these phenomena hinge on knowing the electronic properties and the hybridization of these structures. Here, we demonstrate that a rhombohedral-stacked bilayer (AB stacking) can be obtained by molecular beam epitaxy growth of tungsten diselenide (WSe2) on a gallium phosphide (GaP) substrate. We confirm the presence of 3R-stacking of the WSe2 bilayer structure using scanning transmission electron microscopy (STEM) and micro-Raman spectroscopy. Also, we report high-resolution angle-resolved photoemission spectroscopy (ARPES) on our rhombohedral-stacked WSe2 bilayer grown on a GaP(111)B substrate. Our ARPES measurements confirm the expected valence band structure of WSe2 with the band maximum located at the Γ point of the Brillouin zone. The epitaxial growth of WSe2/GaP(111)B helps to understand the fundamental properties of these 2D/3D heterostructures, toward their implementation in future devices.

Quantum Confinement and Electronic Structure at the Surface of van der Waals Ferroelectric α-In2Se3.

Two-dimensional (2D) ferroelectric (FE) materials are promising compounds for next-generation nonvolatile memories due to their low energy consumption and high endurance. Among them, α-In2Se3 has drawn particular attention due to its in- and out-of-plane ferroelectricity, whose robustness has been demonstrated down to the monolayer limit. This is a relatively uncommon behavior since most bulk FE materials lose their ferroelectric character at the 2D limit due to the depolarization field. Using angle resolved photoemission spectroscopy (ARPES), we unveil another unusual 2D phenomenon appearing in 2H α-In2Se3 single crystals, the occurrence of a highly metallic two-dimensional electron gas (2DEG) at the surface of vacuum-cleaved crystals. This 2DEG exhibits two confined states, which correspond to an electron density of approximately 1013 electrons/cm2, also confirmed by thermoelectric measurements. Combination of ARPES and density functional theory (DFT) calculations reveals a direct band gap of energy equal to 1.3 ± 0.1 eV, with the bottom of the conduction band localized at the center of the Brillouin zone, just below the Fermi level. Such strong n-type doping further supports the quantum confinement of electrons and the formation of the 2DEG.

Unidirectional Rashba spin splitting in single layer WS2(1-x)Se2xalloy.

Atomically thin two-dimensional (2D) layered semiconductors such as transition metal dichalcogenides have attracted considerable attention due to their tunable band gap, intriguing spin-valley physics, piezoelectric effects and potential device applications. Here we study the electronic properties of a single layer WS1.4Se0.6alloys. The electronic structure of this alloy, explored using angle resolved photoemission spectroscopy, shows a clear valence band structure anisotropy characterized by two paraboloids shifted in one direction of thek-space by a constant in-plane vector. This band splitting is a signature of a unidirectional Rashba spin splitting with a related giant Rashba parameter of 2.8 ± 0.7 eV Å. The combination of angle resolved photoemission spectroscopy with piezo force microscopy highlights the link between this giant unidirectional Rashba spin splitting and an in-plane polarization present in the alloy. These peculiar anisotropic properties of the WS1.4Se0.6alloy can be related to local atomic orders induced during the growth process due the different size and electronegativity between S and Se atoms. This distorted crystal structure combined to the observed macroscopic tensile strain, as evidenced by photoluminescence, displays electric dipoles with a strong in-plane component, as shown by piezoelectric microscopy. The interplay between semiconducting properties, in-plane spontaneous polarization and giant out-of-plane Rashba spin-splitting in this 2D material has potential for a wide range of applications in next-generation electronics, piezotronics and spintronics devices.

Hybridization and localized flat band in the WSe2/MoSe2heterobilayer.

Nearly localized moiré flat bands in momentum space, arising at particular twist angles, are the key to achieve correlated effects in transition-metal dichalcogenides. Here, we use angle-resolved photoemission spectroscopy (ARPES) to visualize the presence of a flat band near the Fermi level of van der Waals WSe2/MoSe2heterobilayer grown by molecular beam epitaxy. This flat band is localized near the Fermi level and has a width of several hundred meVs. By combining ARPES measurements with density functional theory calculations, we confirm the coexistence of different domains, namely the reference 2H stacking without layer misorientation and regions with arbitrary twist angles. For the 2H-stacked heterobilayer, our ARPES results show strong interlayer hybridization effects, further confirmed by complementary micro- Raman spectroscopy measurements. The spin-splitting of the valence band atKis determined to be 470 meV. The valence band maximum (VBM) position of the heterobilayer is located at the Γ point. The energy difference between the VBM at Γ and theKpoint is of -60 meV, which is a stark difference compared to individual single monolayer WSe2and monolayer WSe2, showing both a VBM atK.

Evidence for highly p-type doping and type II band alignment in large scale monolayer WSe2/Se-terminated GaAs heterojunction grown by molecular beam epitaxy.

Two-dimensional materials (2D) arranged in hybrid van der Waals (vdW) heterostructures provide a route toward the assembly of 2D and conventional III-V semiconductors. Here, we report the structural and electronic properties of single layer WSe2 grown by molecular beam epitaxy on Se-terminated GaAs(111)B. Reflection high-energy electron diffraction images exhibit sharp streaky features indicative of a high-quality WSe2 layer produced via vdW epitaxy. This is confirmed by in-plane X-ray diffraction. The single layer of WSe2 and the absence of interdiffusion at the interface are confirmed by high resolution X-ray photoemission spectroscopy and high-resolution transmission microscopy. Angle-resolved photoemission investigation revealed a well-defined WSe2 band dispersion and a high p-doping coming from the charge transfer between the WSe2 monolayer and the Se-terminated GaAs substrate. By comparing our results with local and hybrid functionals theoretical calculation, we find that the top of the valence band of the experimental heterostructure is close to the calculations for free standing single layer WSe2. Our experiments demonstrate that the proximity of the Se-terminated GaAs substrate can significantly tune the electronic properties of WSe2. The valence band maximum (VBM, located at the K point of the Brillouin zone) presents an upshift of about 0.56 eV toward the Fermi level with respect to the VBM of the WSe2 on graphene layer, which is indicative of high p-type doping and a key feature for applications in nanoelectronics and optoelectronics.

Strain and Spin-Orbit Coupling Engineering in Twisted WS2/Graphene Heterobilayer.

The strain in hybrid van der Waals heterostructures, made of two distinct two-dimensional van der Waals materials, offers an interesting handle on their corresponding electronic band structure. Such strain can be engineered by changing the relative crystallographic orientation between the constitutive monolayers, notably, the angular misorientation, also known as the "twist angle". By combining angle-resolved photoemission spectroscopy with density functional theory calculations, we investigate here the band structure of the WS2/graphene heterobilayer for various twist angles. Despite the relatively weak coupling between WS2 and graphene, we demonstrate that the resulting strain quantitatively affects many electronic features of the WS2 monolayers, including the spin-orbit coupling strength. In particular, we show that the WS2 spin-orbit splitting of the valence band maximum at K can be tuned from 430 to 460 meV. Our findings open perspectives in controlling the band dispersion of van der Waals materials.

Acute cholestasis as uncommon onset of Kawasaki disease: a case report.

BACKGROUND: Kawasaki disease (KD) or mucocutaneous lymph node syndrome is a vasculitis that mostly occurs in young children. Adult-onset KD (AKD) is rare and often misdiagnosed. Here we report a rare case of KD with cholestasis as principal symptom. CASE PRESENTATION: A 43-year-old caucasian man was admitted to our hospital for high fever, lack of appetite related to nausea and vomiting, headache and significant malaise. Physical examination highlighted fever, increasing jaundice, bilateral laterocervical lymph nodes, erythema of the palms, and strikingly red lips and conjunctiva. The clinical course was complicated by arterial hypotension, tachycardia, decreasing haemoglobin, increasing acute phase reactants tests, and multiorgan failure. Due to cardiovascular instability the patient was admitted to the local Intensive Care Unit. Chest X-ray, abdominal ultrasound, chest and abdominal CT and Colangio Magnetic Resonance were normal. Jaundice was investigated and infections, autoimmune diseases or drugs adverse reactions, were excluded. Also coronary artery computed tomography was carried out excluding coronary artery aneurysms. Broad-spectrum antibiotics were not effective. After exclusion other possible conditions, diagnosis of KD was set. He was treated with high doses of corticosteroids and acetylsalicylic acid and clinical conditions as well as laboratory exams improved. CONCLUSIONS: This report dealing with an adult onset of atypical KD may be of benefit to physicians of various specialties, including primary care doctors, hospital internists, intensivists and gastroenterologists due to its peculiarities. It demonstrates that a case of prolonged fever unresponsive to antibiotics and related to cholestatic jaundice, oedema or erythema of the extremity associated with desquamation of feet and hands, and red eyes, may suggest atypical form of KD.

High performance tunnel field effect transistors based on in-plane transition metal dichalcogenide heterojunctions.

In-plane heterojunction tunnel field effect transistors based on monolayer transition metal dichalcogenides are studied by means of self-consistent non-equilibrium Green's functions simulations and an atomistic tight-binding Hamiltonian. We start by comparing several heterojunctions before focusing on the most promising ones, i.e. WTe2-MoS2 and MoTe2-MoS2. The scalability of those devices as a function of channel length is studied, and the influence of backgate voltages on device performance is analyzed. Our results indicate that, by fine-tuning the design parameters, those devices can yield extremely low subthreshold swings (<5 mV/decade) and I ON/I OFF ratios higher than 108 at a supply voltage of 0.3 V, making them ideal for ultra-low power consumption.

On the origins of transport inefficiencies in mesoscopic networks.

A counter-intuitive behavior analogous to the Braess paradox is encountered in a two-terminal mesoscopic network patterned in a two-dimensional electron system (2DES). Decreasing locally the electron density of one channel of the network paradoxically leads to an increased network electrical conductance. Our low temperature scanning gate microscopy experiments reveal different occurrences of such puzzling conductance variations, thanks to tip-induced localized modifications of electron flow throughout the network's channels in the ballistic and coherent regime of transport. The robustness of the puzzling behavior is inspected by varying the global 2DES density, magnetic field and the tip-surface distance. Depending on the overall 2DES density, we show that either Coulomb Blockade resonances due to disorder-induced localized states or Fabry-Perot interferences tuned by the tip-induced electrostatic perturbation are at the origin of transport inefficiencies in the network, which are lifted when gradually closing one channel of the network with the tip.

Weekend Versus Weekday Admission and In-Hospital Mortality for Pulmonary Embolism: A 14-Year Retrospective Study on the National Hospital Database of Italy.

We assessed the association between weekday (WD) or weekend (WE) admission and mortality for patients hospitalized with acute pulmonary embolism (PE). Weekend included holidays. We analyzed hospital administrative data of all patients discharged with a diagnosis of PE extracted from the Italian Health Ministry database (January 2001 to December 2014). A total of 265 035 hospitalizations with a diagnosis of PE were retrieved, in which PE was the primary diagnosis in 198 565 (74.9%); 200 166 (75.5%) patients were admitted on WD and 64 869 (24.5%) on WE. Admissions for PE were more frequent on Mondays (41 917 admissions, 15.8% of all events) and less frequent on Saturdays (32 295 admissions, 12.2%) and Sundays (32 574 admissions, 12.3%). Patients admitted on WE were on average 1 year older, presented more frequently with respiratory failure, and had more common comorbidities. After adjustment for age, gender, comorbidities, and presence of respiratory failure, in-hospital mortality for patients admitted on WE was greater (odds ratio: 1.15, 95% confidence interval: 1.13-1.18; P < .001). This study supports that, in Italy, hospitalization for PE on WE is associated with a significantly higher mortality rate than on WD.

Circaseptan Periodicity of Cardiovascular Diseases.

The occurrence of cardiovascular events shows a different distribution during the week, with many studies reporting a Monday peak, possibly related to the role of stress associated with commencing weekly activities. Furthermore, a higher mortality has been observed among patients hospitalized for cardiovascular and other disorders on weekends, a phenomenon known as "weekend effect." Such effect may be explained by a higher level of disease severity among patients admitted over the weekend, and/or by a poorer quality of care associated with shortage of staff, lower experience of personnel, and limited availability of therapeutic and diagnostic procedures.

A modified Elixhauser score for predicting in-hospital mortality in internal medicine admissions.

BACKGROUND: In-hospital mortality (IHM) is an indicator of the quality of care provided. The two most widely used scores for predicting IHM by International Classification of Diseases (ICD) codes are the Elixhauser (EI) and the Charlson Comorbidity indexes. Our aim was to obtain new measures based on internal medicine ICD codes for the original EI, to detect risk for IHM. MATERIAL AND METHODS: This single-center retrospective study included hospital admissions for any cause in the department of internal medicine between January 1, 2000, and December 31, 2013, recorded in the hospital database. The EI was calculated for evaluation of comorbidity, then we added age, gender and diagnosis of ischemic heart disease. IHM was our outcome. Only predictors positively associated with IHM were taken into consideration and the Sullivan's method was applied in order to modify the parameter estimates of the regression model into an index. RESULTS: We analyzed 75,586 admissions (53.4% females) and mean age was 72.7±16.3years. IHM was 7.9% and mean score was 12.1±7.6. The points assigned to each condition ranged from 0 to 16, and the possible range of the score varied between 0 and 89. In our population the score ranged from 0 to 54, and it was higher in the deceased group. Receiver operating characteristic curve of the new score was 0.721 (95% CI 0.714-0.727, p<0.001). CONCLUSIONS: In order to make prognostic assessment, the use of a score could be of help in targeting interventions in older adults, identifying subjects at high risk for IHM.

The impact of dizziness on quality-of-life in the elderly.

Dizziness is a common medical condition that has been related to falls in the elderly, and it is, therefore, considered a severe social health problem. Particularly in the elderly, the impact of dizziness may be relevant, as it has been linked to several conditions, such as isolation, depression, reduced self autonomy, and self control. The social, functional, and psychological well-being of those affected can be hampered significantly, thus reducing the quality-of-life (QoL) perception. In addition, due to the aging of the population in the developed world, dizziness is becoming a growing public health problem; an optimal management of this condition includes, nowadays, the improvement of rehabilitative programs, as well as the evaluation of QoL status and its management. The aim of this paper is to evaluate the impact of dizziness on the QoL in the elderly, also analyzing the instruments available, nowadays, to evaluate QoL of dizzy patients.

Is female gender as harmful as bacteria? analysis of hospital admissions for urinary tract infections in elderly patients.

BACKGROUND: Urinary tract infections (UTIs) are common bacterial diseases. We related diagnosis of UTIs based on International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) and in-hospital mortality (IHM) in a cohort of hospitalized elderly subjects. METHODS: All patients admitted between 2000 and 2013 to the general hospital of Ferrara, in northeast Italy, with ICD-9-CM code of UTIs were included. IHM was the main outcome, and age, sex, type of microorganism, sepsis, and Charlson comorbidity index (CCI) based on ICD-9-CM, were also analyzed. RESULTS: The total sample included 2,266 patients (1,670 women, 73.7%) with UTIs and identification of a cultural organism. Mean age was 81.7±7.5 years (range, 65-103). One hundred and sixteen (5.1%, of whom 34.5% were male and 65.5% were female) cases developed sepsis, and 84 (3.7%, of whom 45.2% were male, 54.8% were female) had a fatal outcome. Nonsurvivors had lower prevalence of IVUs due to Escherichia coli (53.6 vs. 71.7%, p<0.001) and higher prevalence of UTIs due to Pseudomonas aeruginosa (19 vs 7.1%, p<0.001). Moreover, non-survivors developed more frequently sepsis (31% vs. 4.1%, p<0.001), and had higher CCI (2.81±2.43 vs. 2.21±2.04, p=0.011). IHM was independently associated, in decreasing order of odds ratios (ORs), with sepsis (OR 10.3; 95% confidence interval [95% CI] 6.113-17.460, p<0.001), P. aeruginosa infection (OR 2.541; 95% CI 1.422-4.543, p=0.002), female gender (OR 2.324; 95% CI 1.480-3.650, p<0.001), CCI (OR 1.103; 95% CI 1.005-1.210, p=0.038), age (OR 1.034; 95% CI 1.002-1.066, p=0.036), and E. coli infection (OR 0.5; 95% CI 0.320-0.780, p=0.002). CONCLUSIONS: In a large sample of elderly patients hospitalized for UTIs in a single center in northeastern Italy, apart the development of sepsis, IHM was much more dependent on pathogen and female gender than comorbidity index and age.

A possible relationship between renal impairment and complications development in type 2 diabetes mellitus: a prospective, observational study in Italy.

BACKGROUND: We investigated the relationship between complications development and estimated glomerular filtration rate (eGFR), in a cohort of type 2 diabetes mellitus (T2DM) outpatients. METHODS: This observational study considered 1284 T2DM outpatients, who had been followed-up for 4.5 ± 1.6 years. eGFR was estimated using Chronic Kidney Disease Epidemiology Collaboration equation. The independent relationship between development of complications and clinical data was evaluated, and hazard ratio (HR) by Cox regression analysis calculated. RESULTS: Mean age of the population was 66.8 ± 10.4 years; mean serum creatinine and eGFR were 1.05 ± 0.36 mg/dl and 71.6 ± 21.6 ml/min/1.73 m(2), respectively. Complications including death (14.2% of the whole population) were recorded in 504 subjects (39.3%). Patients with complications were older and more frequently male with history of hypertension, coronary heart disease, congestive heart disease, retinopathy, nephropathy and had higher levels of glycated hemoglobin. At Cox regression analysis, eGFR was the major risk factor for development of complications, and the HR increased according with lower eGFR (HR 1.53 and 1.86, for eGFR<45 and<30 ml/min/1.73 m(2), respectively). CONCLUSIONS: In our cohort of T2DM outpatients, a reduced eGFR was associated with an increased risk of complications development.

The crucial factor of hospital readmissions: a retrospective cohort study of patients evaluated in the emergency department and admitted to the department of medicine of a general hospital in Italy.

BACKGROUND: Early hospital readmissions, defined as rehospitalization within 30 days from a previous discharge, represent an economic and social burden for public health management. As data about early readmission in Italy are scarce, we aimed to relate the phenomenon of 30-day readmission to factors identified at the time of emergency department (ED) visits in subjects admitted to medical wards of a general hospital in Italy. METHODS: We performed a retrospective 30-month observational study, evaluating all patients admitted to the Department of Medicine of the Hospital of Ferrara, Italy. Our study compared early and late readmission: patients were evaluated on the basis of the ED admission diagnosis and classified differently on the basis of a concordant or discordant readmission diagnosis in respect to the diagnosis of a first hospitalization. RESULTS: Out of 13,237 patients admitted during the study period, 3,631 (27.4%) were readmitted; of those, 656 were 30-day rehospitalizations (5% of total admissions). Early rehospitalization occurred 12 days (median) later than previous discharge. The most frequent causes of rehospitalization were cardiovascular disease (CVD) in 29.3% and pulmonary disease (PD) in 29.7% of cases. Patients admitted with the same diagnosis were younger, had lower length of stay (LOS) and higher prevalence of CVD, PD and cancer. Age, CVD and PD were independently associated with 30-day readmission with concordant diagnosis and kidney disease with 30-day rehospitalization with a discordant diagnosis. CONCLUSIONS: Comorbid patients are at higher risk for 30-day readmission. Reduction of LOS, especially in elderly subjects, could increase early rehospitalization rates.

All-cause mortality and estimated renal function in type 2 diabetes mellitus outpatients: Is there a relationship with the equation used?

BACKGROUND: We investigated the relationship between serum creatinine (SCr) and estimated glomerular filtration rate (eGFR), evaluated by different formulae, and all-cause mortality (ACM) in type 2 diabetes mellitus (T2DM) outpatients. METHODS: This observational cohort study considered 1365 T2DM outpatients, who had been followed up for a period of up to 11 years. eGFR was estimated using several equations. RESULTS: Seventy subjects (5.1%) died after a follow-up of 9.8 ± 3 years. Univariate analysis showed that diagnosis of nephropathy (odds ratio (OR): 2.554, 95% confidence interval (CI): 1.616-4.038, p < 0.001) and microvascular complications (OR: 2.281, 95% CI: 1.449-3.593, p < 0.001) were associated with ACM. Receiving operating characteristic (ROC) curves showed that the areas under the curve for ACM were similar using the different eGFR equations. eGFR values were predictors of ACM, and the hazard ratios (HRs) of the different equations for eGFR estimation were similar. CONCLUSION: In our cohort of T2DM outpatients, different eGFR equations perform similarly in predicting ACM, whereas SCr did not.

Takotsubo cardiomyopathy and acute infectious diseases: a mini-review of case reports.

Takotsubo cardiomyopathy (TTC), also defined as "stress cardiomyopathy," is characterized by a systolic dysfunction localized in the apical and medial left ventricles. Takotsubo cardiomyopathy is more prevalent in females and it is usually related to an event triggered by physical or emotional stress. We systematically explored PubMed and Embase medical information source to identify case reports showing association between infection and TTC. For each kind of infection, we collected a set of data, including pathogen, site of infection, clinical outcome, patient age and sex, and author and year of publication. We found 26 articles dealing with 27 case reports (74% women). The mean age was 61.4 ± 13.7 years and bacterial infections were more frequent (n = 23, 85.2%). In 14 cases, there was a culture-based definition of the bacterial strain: gram+ in 8 cases (57.1%) and gram- in 6 cases (42.9%). Clinical outcome was always favorable.