Metallic single-electron transistor without traditional tunnel barriers

We report on a new type of single-electron transistor (SET) comprising two highly resistive Cr thin-film strips (~ 1um long) connecting a 1 um-long Al island to two Al outer electrodes. These resistors replace small-area oxide tunnel junctions of traditional SETs. Our transistor with a total asymptotic resistance of 110 kOhm showed a very sharp Coulomb blockade and reproducible, deep and strictly e-periodic gate modulation in wide ranges of bias currents I and gate voltages V_g. In the Coulomb blockade region (|V| < 0.5 mV), we observed a strong suppression of the cotunneling current allowing appreciable modulation curves V-V_g to be measured at currents I as low as 100 fA. The noise figure of our SET was found to be similar to that of typical Al/AlOx/Al single-electron transistors.Comment: 5 pages incl. 4 fig

«Fragility» as a predictor of bleedings in elderly patients with atrial fibrillation taking direct oral anticoagulants

The purpose of the study is to assess the contribution of senile asthenia level to hemorrhagic complications quantity in elderly patients with atrial fibrillation (AF) taking direct oral anticoagulants (DOAC).Material and methods. Elderly patients &gt;75 y.o. with AF taking dabigatran, apixaban or rivaroxaban in full or reduced dosages and without special features of bleeding (such as double and triple antithrombotic therapy) were included in the study. If a patient was under anticoagulants before the study (but not earlier than one became 75 y.o.), this experience was also analyzed. All bleedings during the first 18 months of anticoagulating were taken in mind. Patients in different DOAC groups were comparable in age and concomitant pathology. The «fragility» index was evaluated at the stage of inclusion in the study; an adapted Rockwood scale was used.Results and discussion. 102 patients with AF &gt;75 y.o. taking dabigatran, apixaban or rivaroxaban in dosages corresponding to the instructions were included in the study. During the analyzed period, 19 small clinically significant hemorrhagic events that did not require hospitalization or cancellation of DOAC were recorded. Patients with and without bleeding in anamnesis were significantly differed only by «fragility» index score (р = 0,001). The differences between concomitant pathology level which are mentioned in scale, is also not statistically significant. The average age of patients with and without bleeding anamnesis was not also significantly different (p = 0.12). In the future, it is advisable to continue the study using several scales for assessing the severity of the «fragility» index. Thus, it is advisable to calculate the «fragility» index in patients &gt;75 years of age with AF taking DOAC

Josephson charge-phase qubit with radio frequency readout: coupling and decoherence

The charge-phase Josephson qubit based on a superconducting single charge transistor inserted in a low-inductance superconducting loop is considered. The loop is inductively coupled to a radio-frequency driven tank circuit enabling the readout of the qubit states by measuring the effective Josephson inductance of the transistor. The effect of qubit dephasing and relaxation due to electric and magnetic control lines as well as the measuring system is evaluated. Recommendations for operation of the qubit in magic points producing minimum decoherence are given.Comment: 11 pages incl. 6 fig

Postoperative cognitive dysfunction: etiology, clinical features, diagnosis

Introduction. The present study analyzed the possibility of using neuropsychological tests to assess postoperative cognitive dysfunction. New data were obtained: in the postoperative period, hippocampal memory impairments predominate in patients, which makes it expedient to use methods for diagnosing primary modal-nonspecific memory disorders in patients who are to undergo neurosurgical intervention on the spinal cord.The aim of the study to evaluate the influence of surgery with anesthesia on the cognitive functions of middle-age patients.Materials and methods. The study included 20 middle-aged patients. All patients had to undergo spinal surgery. Patients received total intravenous anesthesia with propofol induction (4–12 mg/kg/hr). Cognitive functions before and after the operation were made with the use of the MoCA, TMT A and B, FCSRT, state-trait anxiety inventory test (STAI).Results. The development of POCD was noted in 15% of cases. The patients showed a decrease in the FCSRT prompt index (1st day = 87 ± 9.0; 2nd day = 83 ± 15; p = 0,0005), while the overall severity of cognitive impairments (total score of MoCA) did not change significantly (standard deviation according to MoCA: 24.25 ± 2.86 on day 1 and 24 ± 3.24 on the second day, p = 0.61). The RT level decreased by day 2: 44.65 ± 7.4 versus 41.1 ± 8.2 (p = 0.001). Correlation analysis did not show the relationship between the age of patients, education level, comorbidity and development of POCD; however, the duration of anesthesia was associated with a decrease in MoCA scores (Pearson’s correlation coefficient r = –0.44; p = 0.050).Conclusion. Thus, our study shows that the study of hippocampal memory impairments is important in patients with POCD. These data differ from the data of researchers presented earlier, where the most important clinical manifestations of POCD are considered to be a decrease in attention and speed of mental processes. Of course, the small sample size dictates the need for additional research

Quantum state engineering with Josephson-junction devices

We review recent theoretical and experimental progress in quantum state engineering with Josephson junction devices. The concepts of quantum computing have stimulated an increased activity in the field. Either charges or phases (fluxes) of the Josephson systems can be used as quantum degrees of freedom, and their quantum state can be manipulated coherently by voltage and current pulses. They thus can serve as qubits, and quantum logic gates can be performed. Their phase coherence time, which is limited, e.g., by the electromagnetic fluctuations in the control circuit, is long enough to allow a series of these manipulations. The quantum measurement process performed by a single-electron transistor, a SQUID, or further nanoelectronic devices is analyzed in detail.Comment: An article prepared for Reviews of Modern Physics, 46 pages, 23 figure

Laboratory bleeding predictors in elderly patients with atrial fibrillation taking direct oral anticoagulants

Atrial fibrillation (AF) is one of the most common arrhythmias in patients ≥75 years of age. The increased risk of thrombosis due to age and the large number of concomitant diseases makes it evident that anticoagulant therapy is necessary. However, the same factors increase the risk of hemorrhagic complications, which are among the most dangerous side effects of anticoagulant therapy. That is why it is very important to identify patients with the highest probability of bleeding, whether large or small clinically significant and minor. The purpose of our study was to study the prognostic value of laboratory methods of examination with regard to the development of hemorrhagic events in elderly patients with AF taking direct oral anticoagulants (DOAC). The study enrolled 102 patients ≥75 years of age with AF of non-valve etiology taking dabigatran, apixaban, rivaroxaban at full or reduced doses. Anticoagulants were administered by outpatient and inpatient physicians. Both previous experience with DOAC prior to inclusion in the trial (if DOAC was previously prescribed) and prospective patient monitoring after inclusion in the trial were analyzed. The minimum analyzed period of DOAC intake was 18 months. Patients who underwent (n = 19) and did not undergo (n = 83) hemorrhagic events (all events were considered small by ISTH criteria) did not differ in any of the laboratory indicators potentially considered as predictors of hemorrhagic events

Periodic motions of coupled impact oscillators

International audienceWe study the existence and stability of time-periodic oscillations in a chain of coupled impact oscillators, for rigid impacts without energy dissipation. We formulate the search of periodic solutions as a boundary value problem incorporating unilateral constraints. This problem is solved analytically in the vicinity of the uncoupled limit and numerically for larger coupling constants. Different solution branches corresponding to nonlinear localized modes (breathers) and normal modes are computed

Physical mechanisms limiting the manufacturing yield of millimeter-wave power InP HEMTs

We have developed a methodology to diagnose the physical mechanisms limiting the manufacturing yield of millimeter-wave power InAlAs/InGaAs HEMTs on InP. A statistical analysis was carried out on DC figures of merit obtained from a large number of actual devices on an experimental wafer. Correlation studies and a Principal Component Analysis (PCA) of the results indicated that variations in Si delta-doping concentration introduced during MBE accounted for more than half of the manufacturing variance. Variations in the gate-source distance that is determined by the electron-beam alignment in the gate formation process were the second leading source of manufacturing variance

Biophysical basis for the geometry of conical stromatolites

Stromatolites may be Earth’s oldest macroscopic fossils; however, it remains controversial what, if any, biological processes are recorded in their morphology. Although the biological interpretation of many stromatolite morphologies is confounded by the influence of sedimentation, conical stromatolites form in the absence of sedimentation and are, therefore, considered to be the most robust records of biophysical processes. A qualitative similarity between conical stromatolites and some modern microbial mats suggests a photosynthetic origin for ancient stromatolites. To better understand and interpret ancient fossils, we seek a quantitative relationship between the geometry of conical stromatolites and the biophysical processes that control their growth. We note that all modern conical stromatolites and many that formed in the last 2.8 billion years display a characteristic centimeter-scale spacing between neighboring structures. To understand this prominent—but hitherto uninterpreted—organization, we consider the role of diffusion in mediating competition between stromatolites. Having confirmed this model through laboratory experiments and field observation, we find that organization of a field of stromatolites is set by a diffusive time scale over which individual structures compete for nutrients, thus linking form to physiology. The centimeter-scale spacing between modern and ancient stromatolites corresponds to a rhythmically fluctuating metabolism with a period of approximately 20 hr. The correspondence between the observed spacing and the day length provides quantitative support for the photosynthetic origin of conical stromatolites throughout geologic time