Broadening of hot-spot response spectrum of superconducting NbN nanowire single-photon detector with reduced nitrogen content

The spectral detection efficiency and the dark count rate of superconducting nanowire single-photon detectors (SNSPD) has been studied systematically on detectors made from thin NbN films with different chemical compositions. Reduction of the nitrogen content in the 4 nm thick NbN films results in a more than two orders of magnitude decrease of the dark count rates and in a red shift of the cut-off wavelength of the hot-spot SNSPD response. The observed phenomena are explained by an improvement of uniformity of NbN films that has been confirmed by a decrease of resistivity and an increase of the ratio of the measured critical current to the depairing current. The latter factor is considered as the most crucial for both the cut-off wavelength and the dark count rates of SNSPD. Based on our results we propose a set of criteria for material properties to optimize SNSPD in the infrared spectral region.Comment: 15 pages, 6 figure

Probability of the resistive state formation caused by absorption of a single-photon in current-carrying superconducting nano-strips

We have studied supercurrent-assisted formation of the resistive state in nano-structured Nb and NbN superconducting films after absorption of a single photon. In amorphous narrow NbN strips the probability of the resistive state formation has a pronounced spectral cut-off. The corresponding threshold photon energy decreases with the bias current. Analysis of the experimental data in the framework of the generalized hot-spot model suggests that the quantum yield for near-infrared photons increases faster than the photon nergy. Relaxation of the resistive state depends on the photon energy making the phenomenon feasible for the development of energy resolving single-photon detectors.Comment: 9 pages, 9 figures, submitted to Eur. Phys. Journa

Geometry-induced reduction of the critical current in superconducting nanowires

Reduction of the critical current in narrow superconducting NbN lines with sharp and rounded bends with respect to the critical current in straight lines was studied at different temperatures. We compare our experimental results with the reduction expected in the framework of the London model and the Ginsburg-Landau model. We have experimentally found that the reduction is significantly less than either model predicts. We also show that in our NbN lines the bends mostly contribute to the reduction of the critical current at temperatures well below the superconducting transition temperature

The sorption-chromaticity determination of Fe(III) in the waters of the galvanic production

Developed out express Sorption-colorimetric methods for the determination of iron in water, based on the sorption concentration of detecting component of the solution impregnated in the polyurethane foam, the formation on the surface of a colored compound and then its definition in the sorbent matrix by measuring color intensity or chromaticity characteristics. The first method is based on determining the agitation of the sample solution with a tablet impregnated with PPU known mass, from which the air bubbles are removed, the second dynamic – by sampling by suction solution in the analytical cartridge impregnated with PPU. Discoloration polyurethane indicates the presence of iron (III) in water, and its content was determined by comparing the color intensity of foam tablets previously prepared color chart or chromaticity characteristics comparing analyte and standard solutions. The conditions of sorption-photometric analysis: the concentration of the photometric reagent impregnated in the foam, the degree of loading it impregnant, the phases of contact, the acidity of the environment. When using analytical cartridges lower limit of detection is 2 times higher, and the measurement error to 3.5% lower than with the tablets. The proposed test methods using polyurethane enable to carry out the analysis of wash water and the total flow of galvanizing plant before and after neutralization station “on the spot”, without the use of sophisticated instruments and highly skilled operator

Low-frequency dynamics of disordered XY spin chains and pinned density waves: from localized spin waves to soliton tunneling

A long-standing problem of the low-energy dynamics of a disordered XY spin chain is re-examined. The case of a rigid chain is studied where the quantum effects can be treated quasiclassically. It is shown that as the frequency decreases, the relevant excitations change from localized spin waves to two-level systems to soliton-antisoliton pairs. The linear-response correlation functions are calculated. The results apply to other periodic glassy systems such as pinned density waves, planar vortex lattices, stripes, and disordered Luttinger liquids.Comment: (v2) Major improvements in presentation style. One figure added (v3) Another minor chang

Адъювантная внутрипузырная химиотерапия с аквакомплексом глицеросольвата титана в сравнении с БЦЖ-терапией у больных немышечно-инвазивным раком мочевого пузыря высокого риска

Objective: to compare recurrence rate, progression rate and recurrence-free survival in patients with high-risk non-muscle-invasive bladder cancer (NMIBC) after adjuvant intravesical chemotherapy (IVCT) with titanium glycerosolvate aquacomplex (TGA) versus intravesical BCG therapy.Material and methods. In a retrospective multicenter clinical study initially were included 126 patients with NMIBC. Of all 126 patients, 94 patients with high-risk NMIBC were selected and divided into 2 groups using a pseudo randomization with propensity score matching to minimize systematic differences in the process of forming groups. The treatment group (n = 55) consisted of patients with high-risk NMIBC who received a 6-week course of adjuvant IVCT with TGA. In the control group (n = 39) patients received an induction 6-week course of adjuvant intravesical BCG therapy, 19 (49 %) of 39 patients received maintenance therapy. Both methods were compared according to recurrence rate, progression rate and recurrence-free survival. Significance of difference was set at p <0.05.Results. The compared groups of patients were well balanced in terms of clinical and morphological characteristics and the main risk factors for recurrence and progression of non-muscle-invasive bladder cancer, no significant differences were found between the groups (p >0.5). The recurrence rate in treatment and control groups was 33 % and 23 %, respectively (p = 0.31). The disease progression was observed in 1 (2 %) patient in the treatment group and in 4 (13 %) patients in the control group (p = 0.08). The median disease-free survival in both groups of patients was not reached at the time of analysis. Three- and five-year recurrence-free survival in the treatment group of patients were 71 % and 62 %, respectively; in the control group — 76 % and 72 %, respectively. There were no significant differences between recurrence-free-survival curves of the treatment and control groups (p = 0.58).Conclusion. Adjuvant IVCT with TGA has demonstrated a clinical effectiveness comparable to intravesical BCG therapy and it can be used as an alternative method of treatment in patients with high-risk NMIBC.Цель исследования — сравнить безрецидивную выживаемость, частоту рецидивов и прогрессирования заболевания у больных немышечно-инвазивным раком мочевого пузыря (НМИРМП) высокого риска после адъювантной внутрипузырной химиотерапии (ВПХТ) с аквакомплексом глицеросольвата титана (АГТ) в сравнении с внутрипузырной терапией бациллой Кальметта-Герена (БЦЖ).Материалы и методы. В ретроспективное мультицентровое сравнительное клиническое исследование исходно включены 126 пациентов с НМИРМП. Из них с использованием метода псевдорандомизации (propensity score matching) отобраны 94 пациента с НМИРМП высокого риска, которые были разделены на 2 группы: основную и контрольную. Основную группу (n = 55) составили больные, получившие 6-недельный курс адъювантной ВПХТ с АГТ. Пациенты контрольной группы (n = 39) получили индукционный 6-недельный курс адъювантной внутрипузырной БЦЖ-терапии в режиме 1 инстилляция в неделю, у 19 (49 %) из 39 больных проводилось поддерживающее лечение в срок от 2 до 16 мес. Сравнение эффективности различных методик адъювантной внутрипузырной терапии выполняли по показателям безрецидивной выживаемости, частоте рецидивов и прогрессирования заболевания. Достоверность различий устанавливали при уровне значимости p <0,05.Результаты. Сравниваемые группы больных были хорошо сбалансированы по клинико-морфологическим характеристикам и основным факторам риска рецидива и прогрессирования НМИРМП, достоверных различий между ними не выявлено (p >0,5). Частота рецидивов заболевания в основной и контрольной группах составила 33 и 23 % соответственно (р = 0,31). Прогрессирование заболевания установлено у 1 (2 %) больного в основной группе и у 4 (13 %) больных в контрольной группе (p = 0,08). Медиана безрецидивной выживаемости в обеих группах на момент проведения анализа не достигнута. Показатели 3- и 5-летней безрецидивной выживаемости в основной группе составили 71 и 62 %, в контрольной группе - 76 и 72 % соответственно. При сравнении кривых безрецидивной выживаемости основной и контрольной групп достоверных различий между ними не выявлено (p = 0,58).Заключение. Адъювантная ВПХТ с АГТ позволяет получить сопоставимые с внутрипузырной БЦЖ-терапией основные показатели эффективности и может применяться в качестве альтернативного метода лечения у больных НМИРМП высокого риска

Non-thermal response of YBCO thin films to picosecond THz pulses

The photoresponse of YBa2Cu3O7-d thin film microbridges with thicknesses between 15 and 50 nm was studied in the optical and terahertz frequency range. The voltage transients in response to short radiation pulses were recorded in real time with a resolution of a few tens of picoseconds. The bridges were excited by either femtosecond pulses at a wavelength of 0.8 \mu m or broadband (0.1 - 1.5 THz) picosecond pulses of coherent synchrotron radiation. The transients in response to optical radiation are qualitatively well explained in the framework of the two-temperature model with a fast component in the picosecond range and a bolometric nanosecond component whose decay time depends on the film thickness. The transients in the THz regime showed no bolometric component and had amplitudes up to three orders of magnitude larger than the two-temperature model predicts. Additionally THz-field dependent transients in the absence of DC bias were observed. We attribute the response in the THz regime to a rearrangement of vortices caused by high-frequency currents