Intuitive approach to the unified theory of spin relaxation

Spin relaxation is conventionally discussed using two different approaches for materials with and without inversion symmetry. The former is known as the Elliott-Yafet (EY) theory and for the latter the D'yakonov-Perel' (DP) theory applies. We discuss herein a simple and intuitive approach to demonstrate that the two seemingly disparate mechanisms are closely related. A compelling analogy between the respective Hamiltonians is presented, and that the usual derivation of spin-relaxation times, in the respective frameworks of the two theories, can be performed. The result also allows us to obtain less canonical spin-relaxation regimes, i.e. the generalization of the EY when the material has a large quasiparticle broadening, and the DP mechanism in ultrapure semiconductors. The method also allows a practical and intuitive numerical implementation of the spin-relaxation calculation, which is demonstrated for MgB2, which has anomalous spin-relaxation properties

Abstracts from the 20th International Symposium on Signal Transduction at the Blood-Brain Barriers

https://deepblue.lib.umich.edu/bitstream/2027.42/138963/1/12987_2017_Article_71.pd

Dynamics of Tissue Patterning in Hydra

In this work we explored regeneration and homeostatic body patterning of the simple cnidarian Hydra. Thanks to its evolutionary position, this animal is well suited to identify cellular and molecular mechanisms of tissue organization conserved among metazoans. In the first part, we used regenerating Hydra tissue spheroids as a model for understanding how mechanical signals affect cellular self-organization and tissue patterning. In this system, the specification of missing body parts is accompanied by tissue stretching generated through periodic osmotically driven inflation and deflation cycles. However, their role in regeneration was not known. We found that these oscillations are not only accompanying but required for successful symmetry breaking and regeneration. The data also indicated that the cellular readout is continuous rather than cyclic as the spheroids did not seem to have a mechanism for counting the oscillations. We identified this readout to be the transcription of a key organizer-defining factor Wnt3, which is quantitatively related to the overall amount of tissue stretching experienced by the spheroid. Moreover, when supplied externally, Wnt3 enables successful regeneration without mechanical stimulation. Beyond elucidating the role of mechanical oscillations for Hydra regeneration, the work points out a potentially conserved mechanism for translating mechanical stretching into chemical signals. Since tissue stretching also triggers the expression of Wnt ligands in various developmental contexts in vertebrates, it can represent a conserved feature of this signaling pathway. The second part used unbiased approaches to identify factors downstream of the Wnt organizer, regulating the differentiated cell identities. This led to the discovery of a conserved zinc-finger transcription factor Zic4 to be a crucial cell fate regulator in Hydra. Upon its knockdown, tentacle battery cells transdifferentiate to the basal disk cells, likely in a cell-cycle dependent manner. These findings suggested a possible general framework for the connection of fate specification and axial position of epithelial cells in the Hydra body. We also explored new strategies to find new small molecules, such as metabolites, involved in patterning and discuss one putative example

Fractured Exhaled Nitric Oxide and Biologic Therapies for Paediatric Asthma

Bronchial asthma is the most frequently diagnosed chronic respiratory disease in children. Treatment approaches should aim to achieve the disease control, reduce limiting symptoms, and improve the quality of life. Routine treatment of patients with asthma relies on assessment of symptoms and spirometry results. These diagnostic and therapeutic strategies do not consider the level of inflammation in the airways as a fundamental pathognomonic feature of the disease. The use of biomarkers is increasing in the context of efforts to better understand individual asthma pathways (asthma endotyping), with the potential for personalized treatment with innovative biologics. Elevated levels of exhaled nitric oxide (FENO) represent an indirect marker of T2 inflammation in airways. FENO is one of the few biomarkers that have been applied in routine clinical practice. High levels predict a good therapeutic response to treatment with corticosteroids and selected biologics (Omalizumab, Dupilumab, Mepolizumab, Tezepelumab), or an increased risk of asthma exacerbation. The aim of this review is to evaluate the advantages, disadvantages, and potential applications of this test in relation to new treatment options using biologics for asthma

Effect of nitrogen fertilization on metabolisms of essential and non-essential amino acids in field-grown grain maize (Zea mays L.)

Ve dvouletých polních experimentech byl aplikován dusík ve formě močoviny (0, 120 and 240 kg N/ha) k zrnové kukuřici(Zea mays L.) hybridu KWS 2376. Dvouletý průměrný obsah celkového dusíku v zrně při sklizni byl 1,54 %. Největší dávka N redukovala většinu ze 17 stanovenýc aminokyselin (AA)v zrně ve srovnání s ostatními variantami. Pravděpodobnou příčinou tohoto jevu mohl být negativní vliv na cyklus trikarboxylových kyselin nebo deficience uhlíkatých skeletů pro asimilaci NH4+ do amidů a aminokyselin. Obsah limitující aminokyseliny lysinu nebyl ovlivněn N-hnojením, přičemž dvouletý průměrný obsah byl 2.02 mg/g sušiny. Z hlediska rozdílů ve hnojení byl zřetelný vliv ročníku s maximální akumulací aminokyselin serinu, prolinu, methioninu, threoninu, argininu a lysinu. Zvyšující se dávky dusíku redukovaly akumulaci asparaginu a glycinu a naopak zvyšovaly akumulaci tyrosinu. Dávky dusíku mají signifikantní efekt na maximální akumulaci valinu, isoleucinu, leucinu, phenylalaninu, histidinu, cysteinu a alaninu již při první zvýšené dávce dusíku(120 kg N/ha).In two-year field experiments, nitrogen (N) in the form of urea (0, 120 and 240 kg N/ha) was applied to grain maize (Zea mays L.) hybrid KWS 2376. The two-year mean content of total grain N at harvest was 1.54%. The highest N dose reduced most of the 17 amino acids (AA) analysed in the grain compared with the other treatments. Possible reasons for this could be an adverse effect on the tricarboxylic acid cycle or deficiency of carbon skeletons for the assimilation of NH4+ into amides and amino acids. The content of the limiting amino acid lysine was not influenced by N fertilisation, with a mean two-year content of 2.02 mg/g DM. Taking into account the differences in fertilisation the effect of the year was seen in the maximal accumulation of amino acids serine, proline, methionine, threonine, arginine and lysine. Increasing rates of nitrogen reduced the accumulation of asparagine and glycine, and, on the contrary, increased the accumulation of tyrosine. Nitrogen rates have a significant effect on the maximal accumulation of valine, isoleucine, leucine, phenylalanine, histidine, cysteine and alanine and appeared as early as after the first increased rate of nitrogen (120 kg N/ha)

Mineralogy, alteration patterns, geochemistry, and fluid properties of the Ag-Au epithermal deposit Nová Baňa, Slovakia

In this contribution, we report new data on mineralogy, alteration patterns, geochemistry, fluid properties and source of fluids for the deposit Nová Baňa, one of the smaller epithermal deposits in the Middle Miocene Štiavnica andesite stratovolcano (Western Carpathians, Slovakia). Ore veins and the associated rocks were studied in samples from outcrops and old mines, grab samples, and bore holes from the central part of the deposit (ore structures Althandel, Jozef, Jakub, Vavrinec), northern part (Freischurf), SE part (Gupňa) and SW part (Šibeničný vrch). Pervasive hydrothermal alteration transformed the rock-forming minerals into a mixture of adularia and fine-grained quartz, with lesser amount of pyrite, Ti oxides and Fe oxides. This assemblage was further altered to omnipresent interstratified illite/smectite that was used in this study as a geothermometer, corroborating the results from the fluid inclusion work. Ore minerals comprise predominantly pyrite, sphalerite, galena but all sulfides are relatively sparse in the samples studied. Minerals of precious metals are electrum, Ag-tetrahedrite, acanthite, members of the polybasite-pearceite and pyrargyrite-proustite solid solution, and rare miargyrite, Hg-Ag tetrahedrite, and diaphorite. In the central part, we have found also some stibnite. In the SE part of the deposit, acanthite, uytenbogaardtite, and petrovskaite occur and seem to be related to supergene enrichment of the ores. In bulk ore samples, Zn usually dominates over Pb and Cu. The average Ag:Au ratio for the entire deposit is 64:1. The concentrations of precious metals in the grab samples reach maxima of 50 ppm Au and 570 ppm Ag in the SE part and 116 ppm Au and 1110 ppm Ag in the central part of the deposit. Fluid inclusions show signs of trapping of a heterogeneous fluid. In the central, northern and SE parts of the deposit, homogenization temperatures of 190–260 °C and consistently low salinities of <5 wt% NaCl eq were recorded. In the SW part, primary fluid inclusions gave homogenization temperatures of 160–180 °C and similar low salinities. The secondary inclusions, however, show salinities up to 24 wt% NaCl eq., interpreted as fluid boiling almost to dryness. Isotopic composition of quartz and clay minerals is recalculated to fluid composition of −5.6 to −0.6 ‰ δ18Ofluid and −80 to −36 ‰ δDfluid, indicating mixed character of hydrothermal fluids falling between the compositions of magmatic and meteoric waters, with predominance of meteoric waters. Assuming hydrostatic pressure in the fluids, the measured data suggest paleodepths of ore formation of 50–170 m in the SW part of the ore deposit, 130–420 m in the SE and N parts, and a range of 120–470 m for the central part. These observations, comparison with other epithermal deposits in the Central Slovak volcanic field, and additional data from published literature show that Nová Baňa is a low- to intermediate sulfidation epithermal deposit, genetically associated to late rhyolitic volcanic activity in this area

The transcription factor Zic4 promotes tentacle formation and prevents epithelial transdifferentiation in Hydra

The molecular mechanisms that maintain cellular identities and prevent dedifferentiation or transdifferentiation remain mysterious. However, both processes are transiently used during animal regeneration. Therefore, organisms that regenerate their organs, appendages, or even their whole body offer a fruitful paradigm to investigate the regulation of cell fate stability. Here, we used Hydra as a model system and show that Zic4, whose expression is controlled by Wnt3/β-catenin signaling and the Sp5 transcription factor, plays a key role in tentacle formation and tentacle maintenance. Reducing Zic4 expression suffices to induce transdifferentiation of tentacle epithelial cells into foot epithelial cells. This switch requires the reentry of tentacle battery cells into the cell cycle without cell division and is accompanied by degeneration of nematocytes embedded in these cells. These results indicate that maintenance of cell fate by a Wnt-controlled mechanism is a key process both during homeostasis and during regeneration. </p