Pyroelectric study of polarization switching in Langmuir-Blodgett films of poly(vinylidene fluoride trifluoroethylene)

The ferroelectric switching in Langmuir-Blodgett films of poly (vinylidene fluoride trifluoroethylene) is studied. The films have a distribution of switching times several decades wide. Nearly a half of the film volume may be switched faster than 1 ms, though complete switching of a whole sample may require 100 s or more. The switching occurs through a domain nucleation and growth mechanism. The decay of polarization at zero bias is logarithmic in time, with a constant rate below 5% per decade at room temperatures. The coercive voltage may be as low as 5 V, which makes the films promising for use in nonvolatile random-access data storage

Generation of infrasonic signals during earthquakes under Lake Hovsgool (Northern Mongolia) on December 5, 2014

The paper discusses the results of the detection of seismic and infrasonic waves generated by a major earthquake and its aftershock (the moment magnitude MW=4.9 and MW=4.2 respectively), which occurred in northern Mongolia under Lake Hovsgool on December 5, 2014. The joint analysis of waveforms of seismic and infrasonic oscillations has shown that the signal recorded by the infrasound station of the Geophysical Observatory of the Institute of Solar-Terrestrial Physics SB RAS (ISTP SB RAS) is formed from sources of three generation types: local, secondary, and epicentral. This analysis enables us to propose a hypothesis of generation of epicentral infrasonic signal by flexural waves in an elastic ice membrane on the surface of Lake Hovsgool, which appear during the passage of seismic wave packets. This hypothesis explains the similarity between seismic and epicentral infrasonic signals, negative initial phase of epicentral infrasonic waves, and detection of a weak signal after a small-magnitude aftershock

Critical point in ferroelectric Langmuir-Blodgett polymer films

The ferroelectric critical point has been found in a ferroelectric polymer by exploring the influence of the electric field on the paraelectric-ferroelectric phase transition. Dielectric and pyroelectric measurements on 30-monolayer-thick films of the crystalline copolymer poly(vinylidene fluoride-trifluoroethylene) grown by Langmuir-Blodgett deposition show a single hysteresis loop below the zero-field phase transition temperature Tc0=80±10 °C, double hysteresis loops between Tc0 , and the critical temperature Tcr=145±5 °C, and no hysteresis above Tcr where the critical electric field is Ecr=0.93±0.1X109 V/m

ОПЫТ ХИРУРГИЧЕСКОЙ КОРРЕКЦИИ ВАЛЬГУСНОГО ОТКЛОНЕНИЯ ПЕРВОГО ПАЛЬЦА СТОПЫ У ПАЦИЕНТОВ С ПОПЕРЕЧНЫМ ПЛОСКОСТОПИЕМ И ДЕФОРМИРУЮЩИМ АРТРОЗОМ ПЕРВОГО ПЛЮСНЕФАЛАНГОВОГО СУСТАВА

Objective: to determine the opportunity of usage of Schede-Brandes procedure in the treatment of patients with hallux valgus. Material and methods. The results of Shede-Brandeis operation were studied in 119 patients (198 feet). The study included patients who were followed up long-term results of treatment for up to 10 years. The results of the surgical treatment were assessed by the AOFAS scale and total criteria proposed I.A. Pakhomov. According to these scales the following results were obtained: the good - in 59,59% of patients, satisfactory - in 22,73%, poor - in 17,68%. Conclusion. These results allow to recommend Schede-Brandes procedure for use in elderly patients with osteoporosis, concomitant vascular diseases of lower extremities and with rheumatoid arthritis.Цель исследования - определение перспективности дальнейшего использования артропластической резекции первого плюсне-фалангового сустава по Шеде-Брандесу при лечении hallux valgus. Материал и методы. Представлены результаты выполнения операции Шеде-Брандеса у 119 больных (198 стоп). В исследование включены пациенты, у которых удалось отследить отдаленные результаты лечения сроком до 10 лет. Для оценки результатов проведенного хирургического лечения использовалась шкала AOFAS, а также совокупные критерии, предложенные И.А. Пахомовым. Согласно этим шкалам получены следующие результаты: хорошие - у 59,59% пациентов, удовлетворительные - у 22,73% , неудовлетворительные - у 17,68% пациентов. Выводы. Полученные результаты позволяют рекомендовать данную методику для использования у пациентов пожилого возраста, с остеопорозом, сопутствующей патологией сосудов нижних конечностей, а также с ревматоидным полиартритом

Color mixing models for smart lighting systems based on RGBW and WW LEDs

Color mixing models to obtain white light with a predetermined values of correlated color temperature and brightness are presented. One model describes mathematical algorithm for combination of spectra for WW LEDs lighting systems, and other one for systems based on RGBW LEDs. Results of testing of created sample of LED light source for indoor lighting (“Amstrong” type) with implemention of presented color mixing models are shown

Degradation processes in LED modules

Electrical-heat-light degradation model of a light-emitting module has been developed in this work. The Monte-Carlo method was used to calculate the reliability time of LED modules with different halfwidth of LED chip series resistance. Separation of LED chips with different series resistance before assembling may increase the time of emission in a stable mode up to 10%

Europium coordination compounds based on carbacylamidophosphate ligands for metal-organic light-emitting diodes (MOLEDs)

In this work, the photo- and electroluminescence properties of new red phosphores based on europium complexes with carbacylamidophosphate (CAPh) ligands and additional aromatic ligands 1,10-phenantroline and 4,4'-bipyridine have been studied. Compounds Eu(L¹)₃(phen) (1), Eu(L²)₃(phen) (2), Eu2(L¹)₆(i-prOH)²(4,4'-bipy) (3) and Eu²(L²)₆(H2O)²(4,4'-bipy) (4), where HL – 2,2,2-trichloro-N-(dipiperidin-1-ylphosphoryl) acetamide, HL² – 2,2,2-trichloro-N-(dimorpholin-1-ylphosphoryl)acetamide, were synthesized. Technology of europium complexes coating from solutions with different concentrations in different solvents has been developed. Experimental samples of light-emitting planar heterostructures were fabricated using the device architecture comprising an anode (ITO), a hole transport layer of 1,4- Bis(diphenylamino)benzene (BDB), a layer of complex and a cathode (Al or Mg). Another heterostructure configuration with a hole-transport layer of poly(3,4- ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) has also been investigated. The different types of planar heterostructures were prepared, and their current-voltage characteristics have been discussed

Some aspects of thermal resistance measurement technique for IMPATT and light-emitting diodes

Some aspects of measuring the thermal resistance to a constant heat flow at a p-n junction–package region in IMPATT and light-emitting diodes are considered. We propose a method of studying the thermal resistance of high-power light-emitting diodes. This method makes it possible to increase accuracy of measuring the thermal resistance by determining the temperature at a linear section of the voltage−temperature curve. A possibility to measure the thermal resistance of IMPATT diodes by using the pulse I-V curves is shown. This enables one to simplify calculations and increase accuracy of measuring the thermal resistance

Technique and setup for diagnostics of p-n junction to case thermal resistance in high-power gallium nitride LEDs

We present a setup and procedure of studying p-n junction to case thermal resistance in high-power light-emitting diodes (LEDs) from their thermal relaxation. A set of LEDs mounted on a metal-core printed circuit board (MCPCB) were studied. The contributions to the total thermal resistance from a heavy heat sink, MCPCB, heat slug and LED chip are separated