Interface effects in d-wave superconductor-ferromagnet junctions

Measurements of the differential conductance spectra of YBa2Cu3O7-SrRuO3 and YBa2Cu3O7-La0.67Ca_0.33MnO3 ramp-type junctions along the node and anti-node directions are reported. The results are consistent with a crossed Andreev reflection effect only in YBa2Cu3O7-SrRuO3 junctions where the domain wall width of SrRuO3 is comparable with the coherence length of YBa2Cu3O7. No such effect was observed in the YBa2Cu3O7-La0.67Ca0.33MnO3 junctions, which is in line with the much larger (x10) domain wall width of La0.67Ca0.33MnO3. We also show that crossed Andreev exists only in the anti-node direction. Furthermore, we find evidence that crossed Andreev in YBa2Cu3O7 junctions is not sensitive to nm-scale interface defects, suggesting that the length scale of the crossed Andreev effect is larger than the coherence length, but still smaller than the La0.67Ca0.33MnO3's domain wall width.Comment: 5 pages, 6 figure

Transport and spectroscopic properties of superconductor - ferromagnet - superconductor junctions of La1.9Sr0.1CuO4La_{1.9}Sr_{0.1}CuO_4 - La0.67Ca0.33MnO3La_{0.67}Ca_{0.33}MnO_3 - La1.9Sr0.1CuO4La_{1.9}Sr_{0.1}CuO_4

Transport and Conductance spectra measurements of ramp-type junctions made of cuprate superconducting $La_{1.9}Sr_{0.1}CuO_4$ electrodes and a manganite ferromagnetic $La_{0.67}Ca_{0.33}MnO_3$ barrier are reported. At low temperatures below $T_c$, the conductance spectra show Andreev-like broad peaks superposed on a tunneling-like background, and sometimes also sub-gap Andreev resonances. The energy gap values $\Delta$ found from fits of the data ranged mostly between 7-10 mV. As usual, the gap features were suppressed under magnetic fields but revealed the tunneling-like conductance background. After field cycling to 5 or 6 T and back to 0 T, the conductance spectra were always higher than under zero field cooling, reflecting the negative magnetoresistance of the manganite barrier. A signature of superparamagnetism was found in the conductance spectra of junctions with a 12 nm thick LCMO barrier. Observed critical currents with barrier thickness of 12 nm or more, were shown to be an artifact due to incomplete milling of one of the superconducting electrodes.Comment: 10 figure

Proximity induced superconductivity by Bi in topological Bi2Te2SeBi_2Te_2Se and Bi2Se3Bi_2Se_3 films: Evidence for a robust zero energy bound state possibly due to Majorana Fermions

Point contact conductance measurements on topological $Bi_2Te_2Se$ and $Bi_2Se_3$ films reveal a signature of superconductivity below 2-3 K. In particular, critical current dips and a robust zero bias conductance peak are observed. The latter suggests the presence of zero energy bound states which could be assigned to Majorana Fermions in an unconventional topological superconductor. We attribute these novel observations to proximity induced local superconductivity in the films by small amounts of superconducting Bi inclusions or segregation to the surface, and provide supportive evidence for these effects.Comment: Accepted for publication in Physical Review B (Dec. 20, 2011), 15 figures. Version V1: arXiv:1111.3445v1 [cond-mat.supr-con] 15 Nov 201

Magnetic field dependence of the proximity-induced triplet superconductivity at ferromagnet/superconductor interfaces

Long-ranged superconductor proximity effects recently found in superconductor-ferromagnetic (S-F) systems are generally attributed to the formation of triplet-pairing correlations due to various forms of magnetic inhomogeneities at the S-F interface. In order to investigate this conjecture within a single F layer coupled to a superconductor, we performed scanning tunneling spectroscopy on bilayers of La2/3Ca1/3MnO3 (LCMO) ferromagnetic thin-films grown on high temperature superconducting films of YBa2Cu3O7- (YBCO) or Pr1.85Ca0.15CuO4 (PCCO) under various magnetic fields. We find a strong correlation between the magnitude of superconductor-related spectral features measured on the LCMO layer and the degree of magnetic inhomogeneity controlled by the external magnetic field. This corroborates theoretical predictions regarding the role played by magnetic inhomogeneities in inducing triplet-pairing at S-F interfaces.This research was supported in parts by the joint German-Israeli DIP Project (G.K. and O.M.), the United States-Israel Binational Science Foundation (O.M.), the Harry de Jur Chair in Applied Science (O.M.), the Karl Stoll Chair in advanced materials at the Technion (G.K.), the Leverhulme Trust through an International Network Grant (J.W.A.R., M.G.B. and O.M.) and the Royal Society (J.W.A.R.).This is the accepted manuscript version. The final published version is available from the publishers at http://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.180506. © 2014 AP

Organizational Heterogeneity of Vertebrate Genomes

Genomes of higher eukaryotes are mosaics of segments with various structural, functional, and evolutionary properties. The availability of whole-genome sequences allows the investigation of their structure as “texts” using different statistical and computational methods. One such method, referred to as Compositional Spectra (CS) analysis, is based on scoring the occurrences of fixed-length oligonucleotides (k-mers) in the target DNA sequence. CS analysis allows generating species- or region-specific characteristics of the genome, regardless of their length and the presence of coding DNA. In this study, we consider the heterogeneity of vertebrate genomes as a joint effect of regional variation in sequence organization superimposed on the differences in nucleotide composition. We estimated compositional and organizational heterogeneity of genome and chromosome sequences separately and found that both heterogeneity types vary widely among genomes as well as among chromosomes in all investigated taxonomic groups. The high correspondence of heterogeneity scores obtained on three genome fractions, coding, repetitive, and the remaining part of the noncoding DNA (the genome dark matter - GDM) allows the assumption that CS-heterogeneity may have functional relevance to genome regulation. Of special interest for such interpretation is the fact that natural GDM sequences display the highest deviation from the corresponding reshuffled sequences

Mate choice for genetic quality when environments vary: suggestions for empirical progress

Mate choice for good-genes remains one of the most controversial evolutionary processes ever proposed. This is partly because strong directional choice should theoretically deplete the genetic variation that explains the evolution of this type of female mating preferences (the so-called lek paradox). Moreover, good-genes benefits are generally assumed to be too small to outweigh opposing direct selection on females. Here, we review recent progress in the study of mate choice for genetic quality, focussing particularly on the potential for genotype by environment interactions (GEIs) to rescue additive genetic variation for quality, and thereby resolve the lek paradox. We raise five questions that we think will stimulate empirical progress in this field, and suggest directions for research in each area: 1) How is condition-dependence affected by environmental variation? 2) How important are GEIs for maintaining additive genetic variance in condition? 3) How much do GEIs reduce the signalling value of male condition? 4) How does GEI affect the multivariate version of the lek paradox? 5) Have mating biases for high-condition males evolved because of indirect benefits

ПОРІВНЯЛЬНА ХАРАКТЕРИСТИКА ІМУННОГО СТАТУСУ ПРИ РІЗНИХ ТИПАХ ПЕРЕБІГУ У ХВОРИХ ІЗ СПОРАДИЧНОЮ ТА СІМЕЙНОЮ ФОРМАМИ РОЗСІЯНОГО СКЛЕРОЗУ

In recent decades, the leading role of immunopathological disorders in the pathogenesis of multiple sclerosis (MS) has been conclusively proven. However, the complex and ambiguous nature of clinical and immunological relationships in different types of MS, given the hereditary burden of this disease, need further study. Material and Methods. An analysis of 197 immunograms was performed in patients with different types of MS course with sporadic and familial forms: 110 – in patients with sporadic and 27 – with familial forms in a relapsing course (RC); 41 – with sporadic and 19 – with familial forms with progressive types of course (PC) of MS. To determine the cellular and humoral immunity links in blood serum, 16 indicators were studied within the normative values, above and below the norm. Results. The analysis showed that in two forms with RT, a pronounced deficiency of the regulatory cell link (CD4 and CD8) and an increased content of lymphocytotoxic autoantibodies (p<0.05) were found. In the family form of RT, the number of studies with an increase in IgM and complement significantly combined with leukopenia and B-lymphocytosis (p<0.05). With PC RS for the sporadic form, complement, immune complexes and lymphocytotoxic autoantibodies were significantly increased. With help of mathematical (permutation method) and statistical (contingency tables) analyzes, were obtained the following: reliable numerical differences between the forms; the average number of deviations from the norm for all immunological indicators; connections between pairs of characters according to the chi-square criterion with enumeration of all possible pairs of 16 immunological indicators. As a result of researches, significant differences were obtained in the structural organization of the immune imbalance for sporadic and familial forms of MS, that selectively affected both the cellular and humoral components of immunity, as well as the integral indicators obtained using mathematical methods.В последние десятилетия убедительно доказана ведущая роль иммунопатологических нарушений в патогенезе рассеянного склероза (РС). Однако, сложный и неоднозначный характер клинико-иммунологических взаимоотношений при разных типах течения РС, с учетом наследственной отягощенности этого заболевания, требуют дальнейшего изучения. Материал и методы. Проведен анализ 197 иммунограмм у больных с разными типами течения рассеянного склероза (РС) при спорадической и семейной формах: 110 – у больных со спорадической и 27 – с семейной формами при рецидивирующем течении (РТ); 41 – со спорадической и 19 – с семейной формами при прогредиентных типах течения (ПТ) РС. Для определения клеточного и гуморального звеньев иммунитета в сыворотке крови исследовались 16 показателей в пределах нормативных значений, выше и ниже нормы. Результаты. Проведенный анализ показал, что при двух формах с РТ был обнаружен выраженный дефицит регуляторного клеточного звена (СD4 и СD8) и повышенное содержание лимфоцитотоксических аутоантител (р<0,05). При семейной форме РТ достоверно преобладало число исследований с повышением IgМ и комплемента, которые сочетаются с лейкопенией и В-лимфоцитозом (р<0,05). При ПТ РС для спорадической формы были достоверно повышены комплемент, иммунные комплексы и лимфоцитотоксические аутоантитела. С помощью математического (метод пермутации) и статистического (таблицы сопряженности) анализов получены: достоверные числовые различия между формами; среднее количество отклонений от нормы по всем иммунологическим показателям; связи между парами признаков по критерию хи-квадрат с перебором всех возможных пар из 16 иммунологических показателей. Выводы. В результате проведенных исследований были получены существенные различия в структурной организации иммунного дисбаланса для спорадической и семейной форм РС, которые дифференцировано затрагивали как клеточное и гуморальное звенья иммунитета, так и интегральные показатели, полученные с помощью математических методов.В останні десятиліття переконливо доведена провідна роль імунопатологічних порушень у патогенезі розсіяного склерозу (РС). Однак, складний і неоднозначний характер клініко-імунологічних взаємовідносин при різних типах перебігу РС, з урахуванням спадкової обтяженості цього захворювання, потребують подальшого вивчення. Матеріал і методи. Проведено аналіз 197 імунограм у хворих з різними типами перебігу РС при спорадичній і сімейній формах: 110 – у хворих з спорадичною і 27 – з сімейною формами при рецидивному перебігу (РП); 41 – з спорадичною і 19 – з сімейною формами при прогредієнтних типах перебігу (ПП) РС. Для визначення клітинної і гуморальної ланок імунітету в сироватці крові досліджували 16 показників у межах нормативних значень, вище і нижче норми. Результати. Проведений аналіз показав, що при двох формах з РП був виявлений виражений дефіцит регуляторної клітинної ланки (СD4 та СD8) і підвищений вміст лімфоцитотоксичних аутоантитіл (р<0,05). При сімейній формі з РП достовірно переважало число досліджень з підвищенням IgМ і комплементу в поєднанні з лейкопенією і В-лімфоцитозом (р<0,05). При ПП РС для спорадичної форми були достовірно підвищені комплемент, імунні комплекси і лімфоцитотоксичні аутоантитіла. За допомогою математичного (метод пермутації) і статистичного (таблиці спряженості) аналізів отримані: достовірні числові відмінності між формами; середня кількість відхилень від норми за всіма імунологічними показниками; зв’язки між парами ознак за критерієм хі-квадрат з перебором всіх можливих пар з 16 імунологічних показників. У результаті проведених досліджень були отримані істотні відмінності в структурній організації імунного дисбалансу для спорадичної і сімейної форм РС, які диференційовано зачіпали як клітинну і гуморальну ланки імунітету, так і інтегральні показники, отримані за допомогою математичних методів