Electric field gradients in s-, p- and d-metal diborides and the effect of pressure on the band structure and Tc_c in MgB2_2

Results of FLMTO-GGA (full-potential linear muffin-tin orbital -- generalized gradient approximation) calculations of the band structure and boron electric field gradients (EFG) for the new medium-T$_c$ superconductor (MTSC), MgB$_2$, and related diborides MB$_2$, M=Be, Al, Sc, Ti, V, Cr, Mo and Ta are reported. The boron EFG variations are found to be related to specific features of their band structure and particularly to the M-B hybridization. The strong charge anisotropy at the B site in MgB$_2$ is completely defined by the valence electrons - a property which sets MgB$_2$ apart from other diborides. The boron EFG in MgB$_2$ is weakly dependent of applied pressure: the B p electron anisotropy increases with pressure, but it is partly compensated by the increase of core charge assymetry. The concentration of holes in bonding $\sigma$ bands is found to decrease slightly from 0.067 to 0.062 holes/B under a pressure of 10 GPa. Despite a small decrease of N(E$_F$), the Hopfield parameter increases with pressure and we believe that the main reason for the reduction under pressure of the superconducting transition temperature, T$_c$, is the strong pressure dependence of phonon frequencies, which is sufficient to compensate the electronic effects.Comment: 12 pages, 3 figure

Tuning the properties of complex transparent conducting oxides: role of crystal symmetry, chemical composition and carrier generation

The electronic properties of single- and multi-cation transparent conducting oxides (TCOs) are investigated using first-principles density functional approach. A detailed comparison of the electronic band structure of stoichiometric and oxygen deficient In$_2$O$_3$, $\alpha$- and $\beta$-Ga$_2$O$_3$, rock salt and wurtzite ZnO, and layered InGaZnO$_4$ reveals the role of the following factors which govern the transport and optical properties of these TCO materials: (i) the crystal symmetry of the oxides, including both the oxygen coordination and the long-range structural anisotropy; (ii) the electronic configuration of the cation(s), specifically, the type of orbital(s) -- $s$, $p$ or $d$ -- which form the conduction band; and (iii) the strength of the hybridization between the cation's states and the p-states of the neighboring oxygen atoms. The results not only explain the experimentally observed trends in the electrical conductivity in the single-cation TCO, but also demonstrate that multicomponent oxides may offer a way to overcome the electron localization bottleneck which limits the charge transport in wide-bandgap main-group metal oxides. Further, the advantages of aliovalent substitutional doping -- an alternative route to generate carriers in a TCO host -- are outlined based on the electronic band structure calculations of Sn, Ga, Ti and Zr-doped InGaZnO$_4$. We show that the transition metal dopants offer a possibility to improve conductivity without compromising the optical transmittance

Outpatient management of patients with peripheral artery disease by cardiologists or surgeons: influence on the prognosis and prevalence of surgical interventions

Highlights. The study shows for the first time that during the three-year follow-up of patients with diseases of the arteries of the lower extremities in the observation groups of a general surgeon and a cardiologist, adverse events (myocardial infarction, stroke, amputation, disability) and deaths occurred more often in a surgeon than a cardiologist. The study proves the correctness and real benefit of such an approach with the involvement of a cardiologist to the outpatient stage of management of a complex cohort of patients with atherosclerosis of the vessels of the lower extremities.Aim. To study the effect the outpatient observation of patients with peripheral arteries disease (PAD) by cardiologists and surgeons has on timing and prevalence of reconstructive surgery and the prognosis of patients. Methods We analyzed the data on 585 PAD patients who underwent outpatient observation from 2010 to 2017, dividing them into 2 groups. The first group (131 patients) managed by an surgeon; the second (454 patients) managed by a cardiologist. Since the groups were not comparable in terms of the initial parameters, the comparability of patients in the groups (observation by a surgeon or by a cardiologist) was achieved using pseudorandomization. The follow-up period was three years; we assessed the incidence of deaths, adverse events, and the prevalence of reconstructive operations.Results. During a three-year follow-up the 1st group, compared with the 2nd, had more deaths in general (p<0.001), death from cardiac causes (p = 0.045), from stroke (p><0.001), as well as the total number of adverse events (p><0.001) and disability (p = 0.065). Indications for reconstructive surgery on the lower extremities arteries (LEA), and operations frequency were comparatible in groups. Amputation history, taking diuretics, presence of rhythm disturbances, and management by a surgeon increased the risk of adverse outcomes. Management by a cardiologist, reconstructive LEA surgeries, female sex improved the prognosis of patients. Conclusion Observation of PAD patients by a cardiologist contributes to a higher frequency of optimal drug therapy by patients and can reduce the number of adverse events in patients and improve their survival without affecting the timing and frequency of reconstructive LEA surgeries. Keywords Peripheral atherosclerosis • Outpatient follow-up • Optimal drug therapy • Reconstructive surgery>˂ 0.001), death from cardiac causes (p = 0.045), from stroke (p˂ 0.001), as well as the total number of adverse events (p˂ 0.001) and disability (p = 0.065). Indications for reconstructive surgery on the lower extremities arteries (LEA), and operations frequency were comparatible in groups. Amputation history, taking diuretics, presence of rhythm disturbances, and management by a surgeon increased the risk of adverse outcomes. Management by a cardiologist, reconstructive LEA surgeries, female sex improved the prognosis of patients.Conclusion. Observation of PAD patients by a cardiologist contributes to a higher frequency of optimal drug therapy by patients and can reduce the number of adverse events in patients and improve their survival without affecting the timing and frequency of reconstructive LEA surgeries.Highlights. The study shows for the first time that during the three-year follow-up of patients with diseases of the arteries of the lower extremities in the observation groups of a general surgeon and a cardiologist, adverse events (myocardial infarction, stroke, amputation, disability) and deaths occurred more often in a surgeon than a cardiologist. The study proves the correctness and real benefit of such an approach with the involvement of a cardiologist to the outpatient stage of management of a complex cohort of patients with atherosclerosis of the vessels of the lower extremities.Aim. To study the effect the outpatient observation of patients with peripheral arteries disease (PAD) by cardiologists and surgeons has on timing and prevalence of reconstructive surgery and the prognosis of patients. Methods We analyzed the data on 585 PAD patients who underwent outpatient observation from 2010 to 2017, dividing them into 2 groups. The first group (131 patients) managed by an surgeon; the second (454 patients) managed by a cardiologist. Since the groups were not comparable in terms of the initial parameters, the comparability of patients in the groups (observation by a surgeon or by a cardiologist) was achieved using pseudorandomization. The follow-up period was three years; we assessed the incidence of deaths, adverse events, and the prevalence of reconstructive operations.Results. During a three-year follow-up the 1st group, compared with the 2nd, had more deaths in general (p<0.001), death from cardiac causes (p = 0.045), from stroke (p><0.001), as well as the total number of adverse events (p><0.001) and disability (p = 0.065). Indications for reconstructive surgery on the lower extremities arteries (LEA), and operations frequency were comparatible in groups. Amputation history, taking diuretics, presence of rhythm disturbances, and management by a surgeon increased the risk of adverse outcomes. Management by a cardiologist, reconstructive LEA surgeries, female sex improved the prognosis of patients. Conclusion Observation of PAD patients by a cardiologist contributes to a higher frequency of optimal drug therapy by patients and can reduce the number of adverse events in patients and improve their survival without affecting the timing and frequency of reconstructive LEA surgeries. Keywords Peripheral atherosclerosis • Outpatient follow-up • Optimal drug therapy • Reconstructive surgery>˂ 0.001), death from cardiac causes (p = 0.045), from stroke (p˂ 0.001), as well as the total number of adverse events (p˂ 0.001) and disability (p = 0.065). Indications for reconstructive surgery on the lower extremities arteries (LEA), and operations frequency were comparatible in groups. Amputation history, taking diuretics, presence of rhythm disturbances, and management by a surgeon increased the risk of adverse outcomes. Management by a cardiologist, reconstructive LEA surgeries, female sex improved the prognosis of patients.Conclusion. Observation of PAD patients by a cardiologist contributes to a higher frequency of optimal drug therapy by patients and can reduce the number of adverse events in patients and improve their survival without affecting the timing and frequency of reconstructive LEA surgeries

The use of {99m}Tc-Al[2]O[3] for detection of sentinel lymph nodes in cervical cancer patients

The purpose of the study was to evaluate the feasibility of using {99m}Tc-Al[2]O[3]- based radiopharmaceutical, a novel molecular imaging agent for sentinel lymph node detection in patients with invasive cervical cancer. The study included 23 cervical cancer patients (TlaNxMx- T[2]bNxMx) treated at the Tomsk Cancer Research Institute. At 18 hours before surgery, 80 MBq of the {99m}Tc-Al[2]O[3] were injected peritumorally, followed by single-photon emission computed tomography (SPECT) of the pelvis and intraoperative SLN identification. Twenty-seven SLNs were detected by SPECT, and 34 SLNs were identified by intraoperative gamma probe. The total number of identified SLNs per patient ranged from 1 to 3(the mean number of SLNs was 1.4 per patient). The most common site for SLN detection was the external iliac region (57.2%), followed by the internal iliac, obturator, presacral and retrosacral regions (they amounted to 14%, respectively),and the parametrial region (1%). Sensitivity in detecting SLNs was 100% for intraoperative SLN identification and 79% for SPECT image

Cyclotron enhancement of tunneling

A state of an electron in a quantum wire or a thin film becomes metastable, when a static electric field is applied perpendicular to the wire direction or the film surface. The state decays via tunneling through the created potential barrier. An additionally applied magnetic field, perpendicular to the electric field, can increase the tunneling decay rate for many orders of magnitude. This happens, when the state in the wire or the film has a velocity perpendicular to the magnetic field. According to the cyclotron effect, the velocity rotates under the barrier and becomes more aligned with the direction of tunneling. This mechanism can be called cyclotron enhancement of tunneling