Linear magnetoresistance in compensated graphene bilayer

We report a nonsaturating linear magnetoresistance in charge-compensated bilayer graphene in a temperature range from 1.5 to 150 K. The observed linear magnetoresistance disappears away from charge neutrality ruling out the traditional explanation of the effect in terms of the classical random resistor network model. We show that experimental results qualitatively agree with a phenomenological two-fluid model taking into account electron-hole recombination and finite-size sample geometry

Adsorption and two-body recombination of atomic hydrogen on 3^3He-4^4He mixture films

We present the first systematic measurement of the binding energy $E_a$ of hydrogen atoms to the surface of saturated $^3$He-$^4$He mixture films. $E_a$ is found to decrease almost linearly from 1.14(1) K down to 0.39(1) K, when the population of the ground surface state of $^3$He grows from zero to $6\times10^{14}$ cm$^{-2}$, yielding the value $1.2(1)\times 10^{-15}$ K cm$^2$ for the mean-field parameter of H-$^3$He interaction in 2D. The experiments were carried out with overall $^3$He concentrations ranging from 0.1 ppm to 5 % as well as with commercial and isotopically purified $^4$He at temperatures 70...400 mK. Measuring by ESR the rate constants $K_{aa}$ and $K_{ab}$ for second-order recombination of hydrogen atoms in hyperfine states $a$ and $b$ we find the ratio $K_{ab}/K_{aa}$ to be independent of the $^3$He content and to grow with temperature.Comment: 4 pages, 4 figures, all zipped in a sigle file. Submitted to Phys. Rev. Let

Analysis of the low density lipoprotein receptor gene (<i>LDLR</i>) mutation spectrum in Russian familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a very common human hereditary disease in Russia and in the whole world with most of mutations localized in the gene coding for the low density lipoprotein receptor (LDLR). The object of this review is to systematize the knowledge about LDLR mutations in Russia. With this aim we analyzed all available literature on the subject and tabulated the data. More than 1/3 (80 out of 203, i. e. 39.4 %) of all mutations reported from Russia were not described in other populations. To date, most LDLR gene mutations have been characterized in large cities: Moscow (130 entries), Saint Petersburg (50 entries), Novosibirsk (34 mutations) and Petrozavodsk (19 mutations). Other regions are poorly studied. The majority of pathogenic mutations (142 out of 203 reported here or 70 %) were revealed in single pedigrees; 61 variants of mutations were described in two or more genealogies; only 5 mutations were found in 10 or more families. As everywhere, missense mutations prevail among all types of nucleotide substitutions in LDLR, but the highest national specificity is imparted by frameshift mutations: out of 27 variants reported, 19 (or 70 %) are specific for Russia. The most abundant in mutations are exons 4 and 9 of the gene due to their largest size and higher occurrence of mutations in them. Poland, the Czech Republic, Italy and the Netherlands share the highest number of mutations with the Russian population. Target sequencing significantly accelerates the characterization of mutation spectra in FH, but due to the absence of systematic investigations in the regions, one may suggest that most of LDLR mutations in the Russian population have not been described yet

ТЕХНОЛОГИЯ VELOCITY VECTOR IMAGING И СТАНДАРТНОЕ ЭХОКАРДИОГРАФИЧЕСКОЕ ИССЛЕДОВАНИЕ В ОЦЕНКЕ МИОКАРДА ЛЕВОГО ЖЕЛУДОЧКА ПРИ ИНФАРКТЕ БЕЗ ПАТОЛОГИЧЕСКОГО ЗУБЦА Q

The purpose of the study was to assess the function of fibres of the left ventricle (LV) and its dynamics after revascularization in patients with non Q myocardial infarction using standard Echocardiography (EchoCG) and Velocity Vector Imaging (VVI). Materials and methods: 34 patients with MI were examined. Echocardiography studies were performed on the ultrasound scanner AcusonX 300 (Siemens), a 1–5 MHz transducer before and in early period after coronary artery bypass grafting (CABG). Results. Standard EchoCG showed systolic LV dysfunction before and after CABG, contractile dysfunction in 51 (8%) segment before the operation, with subsequent recovery of the function of the 28 (54%) of them. The effect of MI on LV function using VVI showed reducing strain (S) and normal strain rate (SR) of the longitudinal fibers, decrease S and SR of circular fibers and normal function of radial fibers. After GABG S and SR of longitudinal fibers has not changed, S and SR of the circular fibres are decreased. The function of radial fibers are normal. The study established a relationship between the level of LDH-1 and SR of the circular fibers of the LV prior to CABG. Increased level of LDH-1 in the early period after CABG can be a predictor of reduction of S and SR circular fibers. Conclusion: In patients with it is necessary to analyze not only the longitudinal and radial fibers, but also circular.Целью исследования была оценка функции волокон левого желудочка (ЛЖ) и ее динамики после реваскуляризации у пациентов с инфарктом миокарда (ИМ) без патологического зубца Q при использовании стандартной эхокардиографии (ЭхоКГ) и технологии Velocity Vector Imaging (VVI). Обследованы 34 пациента. ЭхоКГ-исследование выполняли на ультразвуковом сканере AcusonX 300 (Siemens) до и в ранние сроки после коронарного шунтирования (КШ). Стандартная ЭхоКГ показала отсутствие систолической дисфункции до и после КШ, наличие сократительной дисфункции в 51 (8%) сегменте до операции с последующим восстановлением 28 (54%) из них. Влияние ИМ на ЛЖ при использовании технологии VVI проявилось снижением деформации (S) продольных волокон при нормальном показателе скорости деформации (SR), снижением функции циркулярных и  нормальной функцией радиальных волокон. После КШ S продольных волокон не изменился, SR остался в норме, а S и SR циркулярных волокон снизились. Функция радиальных волокон не изменилась. Установлена связь между уровнем ЛДГ-1 и SR циркулярных волокон ЛЖ до КШ. Повышение уровня ЛДГ-1 после КШ позволяет подозревать ухудшение функции циркулярных волокон. Вывод: у  всех пациентов с  ИМ необходимо исследование не только продольных и радиальных, но и циркулярных волокон

Thermodynamics and Topology of Disordered Systems: Statistics of the Random Knot Diagrams on Finite Lattice

The statistical properties of random lattice knots, the topology of which is determined by the algebraic topological Jones-Kauffman invariants was studied by analytical and numerical methods. The Kauffman polynomial invariant of a random knot diagram was represented by a partition function of the Potts model with a random configuration of ferro- and antiferromagnetic bonds, which allowed the probability distribution of the random dense knots on a flat square lattice over topological classes to be studied. A topological class is characterized by the highest power of the Kauffman polynomial invariant and interpreted as the free energy of a q-component Potts spin system for q->infinity. It is shown that the highest power of the Kauffman invariant is correlated with the minimum energy of the corresponding Potts spin system. The probability of the lattice knot distribution over topological classes was studied by the method of transfer matrices, depending on the type of local junctions and the size of the flat knot diagram. The obtained results are compared to the probability distribution of the minimum energy of a Potts system with random ferro- and antiferromagnetic bonds.Comment: 37 pages, latex-revtex (new version: misprints removed, references added

Terahertz photoresponse of AlInSb/InSb/AlInSb quantum well structures

We have studied the photoresponse (transmission and photoconductivity of Corbino-shaped devices) of structures with InSb quantum wells (AlInSb barriers). To characterize the devices, the Shubnikov-de Haas (SdH) effect up to magnetic fields B of 7 T and current-voltage (I-V) characteristics at various magnetic fields were measured. Some of the samples showed clearly resolvable SdH oscillations. The I-V curves showed pronounced nonlinearities. The phototransmission and the photoconductivity at various terahertz (THz) frequencies were measured around 2.5 THz generated by a p-Ge laser. From the cyclotron resonance (transmission measurements) we deduced a cyclotron mass of 0.022m0. We also performed photoconductivity measurements on Corbino-shaped devices in the THz frequency range. Oscillations of the photoconductivity with maxima near the minima of the conductivity in the dark were observed. Thus, these devices are potentially suitable for the detection of THz radiation