In-plane optical response of Bi2Sr2CuO6

We report on infrared reflectivity measurements of the $ab$-plane response of superconducting Bi$_2$Sr$_2$CuO$_6$ single crystals. The frequency dependent conductivity has a maximum near 700 cm$^{-1}$ at room temperature, which shifts to lower frequency and merges with a Drude-peak below 100 K. We attribute the unusual behaviour of the mid-infrared conductivity to low frequency transitions between electronic bands of mainly BiO character near the $\overline{M}$ point. The linear temperature dependence of the low-frequency resistivity can be followed down to approximately 40 K where it saturates.Comment: Revtex, 4 pages, 4 postscript figures, Phys. Rev. B, in pres

Features of the water regime and photosynthesis in hybrid forms of cherry plum under the dry wind season conditions

Background. The results of a study on the drought resistance of cherry plum hybrid forms are presented. Water retention capacity of leaves and chlorophyll fluorescence were measured under the simulated conditions close to the dry wind season.Materials and methods. The water regime parameters were studied for five cherry plum genotypes in 2021 and 2022. Leaves of four hybrid forms developed at the Nikita Botanical Gardens and the reference cherry plum hybrid cultivar ‘Rumyanaya Zorka’ (Prunus rossica Erem.) were taken into the experiments. Using the guidelines by G. N. Eremeev and A. I. Lishchuk, a series of experiments on controlled leaf wilt at the air temperature of +27°C and relative humidity of 30% were conducted on cherry plum to assess the functional state of the photosynthetic apparatus during the development of water stress under dry wind conditions. The experiments were carried out in a Binder climate chamber. Chlorophyll fluorescence was measured using a portable Floratest fluorometer. The measurements were based on the parameters of the chlorophyll fluorescence induction curve (CFI) obtained on native leaves. The leaves of cv. ‘Rumyanaya Zorka’ in the state of complete watering served as the reference.Results and discussion. Dependence was identified between chlorophyll fluorescence and moisture content in the leaves of the studied samples. The hybrids were found to respond to drought in different ways. A relatively increased ability to retain moisture during dehydration was observed in form 12/26 whose leaves gave off moisture more slowly and restored their turgor better. It is promising for cultivation in areas with insufficient water supply. Form 99/36 had the lowest potential drought resistance. Forms 99/14 and 9/28 occupied an intermediate position

Systematics of c-axis Phonons in the Thallium and Bismuth Based Cuprate Superconductors

We present grazing incidence reflectivity measurements in the far infrared region at temperatures above and below Tc for a series of thallium (Tl2Ba2CuO6, Tl2Ba2CaCu2O8) and bismuth (Bi2Sr2CuO6, Bi2Sr2CaCu2O8, and Bi(2-x)Pb(x)Sr2CaCu2O8) based cuprate superconductors. From the spectra, which are dominated by the c-axis phonons, longitudinal frequencies (LO) are directly obtained. The reflectivity curves are well fitted by a series of Lorentz oscillators. In this way the transverse (TO) phonon frequencies were accurately determined. On the basis of the comparative study of the Bi and Tl based cuprates with different number of CuO2 layers per unit cell, we suggest modifications of the assignment of the main oxygen modes. We compare the LO frequencies in Bi2Sr2CaCu2O8 and Tl2Ba2Ca2Cu3O10 obtained from intrinsic Josephson junction characteristics with our measurements, and explain the discrepancy in LO frequencies obtained by the two different methods.Comment: 8 pages Revtex, 6 eps figures, 3 tables, to appear in Phys. Rev.

Влияние активации на удельную поверхность и пористую структуру углеродных волокон на основе вискозы и ПАН-волокна (УКН-5000)

The results of a research on the influence of activation of carbon fibers in CO2 current on the change in their specific adsorptive surface and porous structure are presented. The fibers under study were produced from viscose and polyacrylonitrile. It is shown that as a result of activation the specific surface of carbon fibers can be increased from 0.3 to 1900 m2 /g, and the volume of porous space, from 0.1 to 400 cm3 /g. It is established that the nature of the initial fiber has an essential influence on the extent of change in specific surface and porous structure. After activation fibers based on viscose have significantly greater values of specific surface and a bigger fraction of micropores in their structure than fibers based on polyacrylonitrile.П оказано, что при активации адсорбционная поверхность углеродных волокон может быть увеличена от 0.3 до 1900 м2/г. Существенное влияние на степень изменения адсорбционной поверхности и пористой структуры волокна оказывает его природа

Аберрантный ангиогенез в ткани головного мозга при экспериментальной болезни Альцгеймера

The aim was to study the molecular mechanisms of the violation of the structural and functional integrity ofthe blood-brain barrier in chronic neurodegeneration of the Alzheimer’s type associated with the development of cerebral angiopathy.Materials and methods. The transgenic model of Alzheimer’s disease is the B6SLJ-Tg line mice (APPSwFlLon,PSEN1 * M146L * L286V) 6799Vas group which includes 9 months aged males. The control group included C57BL / 6 x SJL mice, males aged 9 months.Results. The total length of the vessels in the area of the dentate gyrus is 2.5 times greater in transgenic animal models of Alzheimer’s disease than in animals of the control group (p < 0.01). The average diameter of blood vessels in all areas of the hippocampus is smaller compared with the control (p < 0.05). Transgenic modeling of neurodegeneration in the CA2 zone of the hippocampus increases the relative area of tissue with increased permeability of blood-brain barrier (BBB) (17.80 [9.15; 36.75]) compared to control (1.38 [0.04; 7.60]) at p < 0.05. A similar difference (p < 0.05) is also observed in the hippocampal area CA1. A tendency (p > 0.05) to decrease the number of CD31+ endothelial cells in the dentate gyrus of the hippocampus (21.52 [17.56; 24.50]) in animals of the experimental group compared with the control group (23.08[21.18; 29.84]) was detected. A similar situation is observed in the CA2 and CA3 areas of the hippocampus.Conclusion. Neurodegenerative changes in the hippocampus of animals with a transgenic AD model are associated with impaired microcirculation in the brain tissue as a result of a reduction in the diameter and branching of blood vessels, and damage and increased permeability of BBB.Цель – изучение молекулярных механизмов нарушения структурно-функциональной целостности гематоэнцефалического барьера (ГЭБ) при хронической нейродегенерации  альцгеймеровского типа, ассоциированной с развитием церебральной ангипопатии. Материалы и методы. Опытная группа – генетическая модель болезни Альцгеймера (БА) – мыши линии B6SLJ -Tg(APPSwFlLon,PSEN1*M146L*L286V)6799Vas, самцы в возрасте 9 мес. Контрольная группа – мыши линии C57BL/6 x SJL, самцы в возрасте 9 мес.Результаты. У животных с генетической моделью БА в зубчатой извилине гиппокампа  общая длина сосудов в 2,5 раза больше, чем у контрольной группы (p < 0,01), при этом  средний диаметр сосудов во всех областях гиппокампа меньше по сравнению с контролем (p < 0,05). Выявлено, что при генетическом моделировании  нейродегенерации в СА2 зоне гиппокампа наблюдается увеличение относительной  площади ткани с повышенной проницаемостью ГЭБ (17,80 [9,15;36,75]) по сравнению с контролем (1,38 [0,04;7,60]) при p < 0,05. Подобное различие (p < 0,05) наблюдается и в зоне СА1 гиппокампа. У животных опытной группы выявлена тенденция (p > 0,05) к снижению количества CD31+ эндотелиальных клеток в зубчатой извилине гиппокампа (21,52 [17,56; 24,50]) по сравнению с контролем (23,08 [21,18; 29,84]). Аналогичная ситуация наблюдается в зонах СА2 и СА3 гиппокампа.Заключение. Нейродегенеративные изменения в гиппокампе животных с генетической  моделью БА ассоциированы с нарушением микроциркуляции в ткани головного мозга в  результате сокращения диаметра и разветвленности сосудов, повреждения и повышения проницаемости ГЭБ

Scanning tunneling spectroscopy of high-temperature superconductors

Tunneling spectroscopy played a central role in the experimental verification of the microscopic theory of superconductivity in the classical superconductors. Initial attempts to apply the same approach to high-temperature superconductors were hampered by various problems related to the complexity of these materials. The use of scanning tunneling microscopy/spectroscopy (STM/STS) on these compounds allowed to overcome the main difficulties. This success motivated a rapidly growing scientific community to apply this technique to high-temperature superconductors. This paper reviews the experimental highlights obtained over the last decade. We first recall the crucial efforts to gain control over the technique and to obtain reproducible results. We then discuss how the STM/STS technique has contributed to the study of some of the most unusual and remarkable properties of high-temperature superconductors: the unusual large gap values and the absence of scaling with the critical temperature; the pseudogap and its relation to superconductivity; the unprecedented small size of the vortex cores and its influence on vortex matter; the unexpected electronic properties of the vortex cores; the combination of atomic resolution and spectroscopy leading to the observation of periodic local density of states modulations in the superconducting and pseudogap states, and in the vortex cores.Comment: To appear in RMP; 65 pages, 62 figure

H2S- and NO-Signaling Pathways in Alzheimer's Amyloid Vasculopathy: Synergism or Antagonism?

Alzheimer's type of neurodegeneration dramatically affects H2S and NO synthesis and interactions in the brain, which results in dysregulated vasomotor function, brain tissue hypoperfusion and hypoxia, development of perivascular inflammation, promotion of Aβ deposition, and impairment of neurogenesis/angiogenesis. H2S- and NO-signaling pathways have been described to offer protection against Alzheimer's amyloid vasculopathy and neurodegeneration. This review describes recent developments of the increasing relevance of H2S and NO in Alzheimer's disease (AD). More studies are however needed to fully determine their potential use as therapeutic targets in Alzheimer's and other forms of vascular dementia

Влияние инсулинорезистентности на нарушение метаболизма глюкозы в миндалине головного мозга при экспериментальной болезни Альцгеймера

Purpose. Glucose metabolism is tightly regulated in the brain. Aberrant glucose metabolism is an important feature of neurodegenerative diseases, as inAlzheimer’s disease. The transport of glucose to the cell membrane is realized through the activity of insulin-regulated aminopeptidase (IRAP) which controls transfer of glucose transporter to the plasma membrane. IRAP is considered as one of the key markers of insulin resistance in Alzheimer’s disease. However, the question of the mechanism of the action of the IRAP remains open. The aim of the study was to study the effect of IRAP expression on cells of the neuronal and glial lineage, glucose transporter (GLUT4) expression in the brain amygdala on emotional memory in animals with experimental Alzheimer’s disease.Materials and methods. The study was performed with two experimental models of Alzheimer’s disease in mice. The experimental group was mice of the CD1 line, males aged 4 months (Alzheimer’s disease model with the intra-hippocampal administration of beta-amyloid 1-42 (1 µl) bilaterally in the CA1 area). The control group was mice of the CD1 line, males aged 4 months (sham-operated animals with the intrahippocampal administration of Phosphate buffered salin (1 µl) bilaterally in the CA1). The genetic model of Alzheimer’s disease is the B6SLJ-Tg line mice (APPSwFlLon, PSEN1*M146L*L286V) 6799Vas, males aged 4 months. The control group consisted of C57BL/6xSJL mice, males aged 4 months. Evaluation of emotional memory was carried out using “Fear conditioning” protocol. Expression of molecule-markers of insulin-resistance in the amygdala was studied by immunohistochemistry followed by confocal microscopy.Results. Aberrant associative learning and emotional memory was revealed in animals with an experimental model of Alzheimer’s disease. A decrease (p ≤ 0,05) of IRAP expression on cells of neuronal and glial nature, associated with GLUT4 down-regulation was detected in amygdala of brain in animals with experimental Alzheimer’s disease.Conclusion. Decreased number of IRAP-immunopositive neuronal and astroglial cells, as well as IRAP+/ GLUT4+ in cells of amygdala in animals with an experimental model of Alzheimer’s disease, indicates the development of insulin resistance in amygdala of brain, which was in correlation with the hippocampus in performing cognitive functions and memorizing associated with emotionally colored events. Цель. В головном мозге метаболизм глюкозы четко регулируется, поэтому его нарушение является важной особенностью нейродегенеративных заболеваний, в частности болезни Альцгеймера. Транспорт глюкозы в мембрану клетки реализуется за счет активности инсулин-регулируемой аминопептидазы (IRAP), которая влияет на память и обучение, и рассматривается как один из ключевых маркеров инсулинорезистентности при болезни Альцгеймера. Однако вопрос о механизме действия IRAP остается открытым. Цель исследования – изучение влияния экспрессии IRAP на клетках нейрональной и глиальной природы, а также совместно с инсулинзависимым глюкозным транспортером (GLUT4) в миндалине головного мозга на эмоциональную память у животных с экспериментальной болезнью Альцгеймера.Материал и методы. Исследование проводили на животных с использованием двух экспериментальных моделей болезни Альцгеймера – инъекционной и генетической. Опытная группа – мыши линии CD1, самцы в возрасте 4 мес, которым билатерально вводили бета-амилоид 1-42 в зону гиппокампа CA1 (сornu аmmonis)по 1 мкл. Контрольная группа – мыши линии CD1, самцы в возрасте 4 мес, которым билатерально вводили растворитель для бета-амилоида – фосфатно-солевой буфер в зону CA1 по 1 мкл.Генетическая модель болезни Альцгеймера – мыши линии B6SLJ –Tg(APPSwFlLon,PSEN1*M146L*L286 V)6799Vas, самцы в возрасте 4 мес. Контрольная группа – мыши линии C57BL/6xSJL, самцы в возрасте 4 мес. Оценку эмоциональной памяти проводили с использованием нейроповеденческого тестирования Fear conditioning. Экспрессию молекул-маркеров инсулинорезистентности в миндалине изучали методом иммуногистохимии с последующей конфокальной микроскопией.Результаты. У животных с экспериментальной моделью болезни Альцгеймера выявлено нарушение ассоциативного обучения и эмоциональной памяти. Выявлено снижение (р ≤ 0,05) экспрессии IRAP на клетках нейрональной и глиальной природы, а также (совместно с GLUT4) в миндалине головного мозга у животных с экспериментальной болезнью Альцгеймера.Заключение. Уменьшение числа IRAP-иммунопозитивных нейрональных и астроглиальных клеток, а также экспрессии IRAP/GLUT4 в клетках миндалины у животных с экспериментальной моделью болезни Альцгеймера указывает на развитие инсулинорезистентности в миндалине головного мозга, находящейся во взаимосвязи с гиппокампом при осуществлении когнитивных функций и запоминания, сопряженных с эмоционально окрашенными событиями.

The irreversibility line of overdoped Bi_{2+x}Sr_{2-(x+y)}Cu_{1+y}O_{6 +- delta} at ultra-low temperatures and high magnetic fields

The irreversible magnetization of the layered high-T_{c} superconductor Bi_{2+x}Sr_{2-(x+y)}Cu_{1+y}O_{6 +- delta} (Bi-2201) has been measured by means of a capacitive torquemeter up to B=28 T and down to T=60 mK. No magnetization jumps, peak effects or crossovers between different pinning mechanisms appear to be present. The deduced irreversibility field B_{irr} can not be described by the law B_{irr}(T)=B_{irr}(0)(1-T/T_{c})^n based on flux creep, but an excellent agreement is found with the analytical form of the melting line of the flux lattice as calculated from the Lindemann criterion. The behavior of B_{irr}(T) obtained here is very similar to the resistive critical field of a Bi-2201 thin film, suggesting that magnetoresistive experiments are likely to be strongly influenced by flux lattice melting.Comment: 4 pages, 4 eps figure

Novel role for the innate immune receptor toll-like receptor 4 (TLR4) in the regulation of the wnt signaling pathway and photoreceptor apoptosis

Recent evidence has implicated innate immunity in regulating neuronal survival in the brain during stroke and other neurodegenerations. Photoreceptors are specialized light-detecting neurons in the retina that are essential for vision. In this study, we investigated the role of the innate immunity receptor TLR4 in photoreceptors. TLR4 activation by lipopolysaccharide (LPS) significantly reduced the survival of cultured mouse photoreceptors exposed to oxidative stress. With respect to mechanism, TLR4 suppressed Wnt signaling, decreased phosphorylation and activation of the Wnt receptor LRP6, and blocked the protective effect of the Wnt3a ligand. Paradoxically, TLR4 activation prior to oxidative injury protected photoreceptors, in a phenomenon known as preconditioning. Expression of TNFα and its receptors TNFR1 and TNFR2 decreased during preconditioning, and preconditioning was mimicked by TNFα antagonists, but was independent of Wnt signaling. Therefore, TLR4 is a novel regulator of photoreceptor survival that acts through the Wnt and TNFα pathways. © 2012 Yi et al