Field-induced anisotropy in the quasi-two-dimensional weakly anisotropic antiferromagnet [CuCl(pyz)2]BF4

We measured NMR and magnetic susceptibility for the quasi-two-dimensional, weakly XY-like, spin-1/2 square-lattice Heisenberg antiferromagnet [CuCl(pyz)(2)]BF4 (pyz = pyrazine = N2C4H4) near the critical temperature. The Neel temperature T-N and the order-parameter critical exponent beta were obtained from the NMR line broadening as a function of temperature. As the applied field strength (H parallel to c) was increased, T-N increased and beta decreased. This behavior indicates that the field effectively enhanced XY anisotropy. The susceptibility as a function of temperature did not show a clear feature for T_N, but showed field-dependent minima below T_N for both H parallel to c and H parallel to ab, where minimum features disappeared for μH_0 > 2T

Dust in Brown Dwarfs IV. Dust formation and driven turbulence on mesoscopic scales

Dust formation in brown dwarf atmospheres is studied by utilising a model for driven turbulence in the mesoscopic scale regime. We apply a pseudo-spectral method where waves are created and superimposed within a limited wavenumber interval. The turbulent kinetic energy distribution follows the Kolmogoroff spectrum which is assumed to be the most likely value. Such superimposed, stochastic waves may occur in a convectively active environment. They cause nucleation fronts and nucleation events and thereby initiate the dust formation process which continues until all condensible material is consumed. Small disturbances are found to have a large impact on the dust forming system. An initially dust-hostile region, which may originally be optically thin, becomes optically thick in a patchy way showing considerable variations in the dust properties during the formation process. The dust appears in lanes and curls as a result of the interaction with waves, i.e. turbulence, which form larger and larger structures with time. Aiming on a physical understanding of the variability of brown dwarfs, related to structure formation in substellar atmospheres, we work out first necessary criteria for small-scale closure models to be applied in macroscopic simulations of dust forming astrophysical systems.Comment: A&A accepted, 20 page

Passive and post-exercise cold-water immersion augments PGC-1alpha and VEGF expression in human skeletal muscle.

PurposeWe tested the hypothesis that both post-exercise and passive cold water immersion (CWI) increases PGC-1α and VEGF mRNA expression in human skeletal muscle.MethodStudy 1 Nine males completed an intermittent running protocol (8 × 3-min bouts at 90 % V̇O2max , interspersed with 3-min active recovery (1.5-min at 25 % and 1.5-min at 50 % V̇O2max ) before undergoing CWI (10 min at 8 °C) or seated rest (CONT) in a counterbalanced, randomised manner. Study 2 Ten males underwent an identical CWI protocol under passive conditions.ResultsStudy 1 PGC-1α mRNA increased in CONT (~3.4-fold; P < 0.001) and CWI (~5.9-fold; P < 0.001) at 3 h post-exercise with a greater increase observed in CWI (P < 0.001). VEGFtotal mRNA increased after CWI only (~2.4-fold) compared with CONT (~1.1-fold) at 3 h post-exercise (P < 0.01). Study 2 Following CWI, PGC-1α mRNA expression was significantly increased ~1.3-fold (P = 0.001) and 1.4-fold (P = 0.0004) at 3 and 6 h, respectively. Similarly, VEGF165 mRNA was significantly increased in CWI ~1.9-fold (P = 0.03) and 2.2-fold (P = 0.009) at 3 and 6 h post-immersion.ConclusionsData confirm post-exercise CWI augments the acute exercise-induced expression of PGC-1α mRNA in human skeletal muscle compared to exercise per se. Additionally CWI per se mediates the activation of PGC-1α and VEGF mRNA expression in human skeletal muscle. Cold water may therefore enhance the adaptive response to acute exercise

Observation of the Smectic C -- Smectic I Critical Point

We report the first observation of the smectic C--smectic I (C--I) critical point by Xray diffraction studies on a binary system. This is in confirmity with the theoretical idea of Nelson and Halperin that coupling to the molecular tilt should induce hexatic order even in the C phase and as such both C and I (a tilted hexatic phase) should have the same symmetry. The results provide evidence in support of the recent theory of Defontaines and Prost proposing a new universality class for critical points in layered systems.Comment: 9 pages Latex and 5 postscript figures available from [email protected] on request, Phys.Rev.Lett. (in press

Влияние степени повреждения листьев после обработки низкой температурой (охлаждения) на рост и репродуктивные параметры перца острого

Relevance. Pepper is sensitive to chilling temperatures in all growth stages and low temperatures are main factors affecting plant growth, fruit growth and development and productivity. Evaluation and identification low temperature (LT) tolerant pepper genotypes at different growth stages is actual in breeding program for developing new cultivars. In present study we investigated the effect of the leaf cold damage within 25% (LCD) after chilling treatment in seedling stage on vegetative and reproductive traits of pepper accessions with different cold tolerance.Material and methods. In this study two pepper accessions “PE-J-2” and “Neokgwang” selected as chilling tolerant and susceptible in juvenile stage (3-4 true leaf stage), were used respectively. The seedlings of the selected pepper accessions with 25% visual cold damages of leaf green part (become lightly yellowed-whited or desiccated-dried) and control non-treated (NT) were grown in a glasshouse condition (D/N 30-32/22-24°C) for 10 weeks to evaluate the effect of LCD on pepper accessions vegetative and reproductive parameters after chilling pre-treatment. In pepper plants the vegetative parameters such as plant height (PH), leaf length (LL) and width (LW), number of internodes (NI), length of main axis (LMA), plants fresh weight (PFW) and roots fresh weight (RFW), and reproductive the number of flowers (NFL) and fruits (NFR), fruit set ratio (FS), fruit length (FL) and diameter (FD), total yield per plant (TY) were measured. The experimental design of this study was completely randomized. Statistical analysis was performed using the SAS Enterprise Guide 7.1 (SAS Institute Inc., Cary, North Carolina, USA).Results. According to the research result several accessions were identified: the accessions screened in juvenile stage as cold tolerant cannot always manifest good some agronomical traits performance at growth stages and it may range depending on the genotype specific features. The seedlings with LCD within 25% may significantly affect the vegetative and reproductive parameters of pepper plants. The phenomenon was recorded more distinctive in the correlations between some vegetative and reproductive parameters among NT and LCD plants.Актуалность. Растения перца чувствительны к пониженным температурам на всех этапах роста, и низкие температуры являются основным фактором, влияющим на рост растений, рост и развитие плодов и продуктивность. Оценка и идентификация низкотемпературных (LT) устойчивых генотипов перца на разных стадиях роста актуальна в селекционной программе для создания новых сортов. В настоящем исследовании мы исследовали влияние повреждения листа в пределах 25% (LCD) после обработки низкой температурой в стадии проростков на рост, вегетативные и репродуктивные параметры образцов перца с различной холодоустойчивостью.Материал и методика. Использовали два образца перца «PE-J-2» и «Neokgwang», отобранные как устойчивый и чувствительный к низким температурам на ювенильной стадии развития (стадия 3-4 настоящих листьев), соответственно. Проростки выбранных образцов перца с 25% визуальными повреждениями зеленой части листа от низких температур (становятся слегка пожелтевшими-беловатыми или высушенными) и растения в контроле (NT) выращивали в условиях теплицы (день/ночь 30…32/22…24°C) в течение 10 недель, чтобы оценить влияние LCD на вегетативные и репродуктивные параметры образцов перца после предварительной обработки охлаждением. У растений перца были измерены вегетативные параметры, такие как высота растения (PH), длина листа (LL) и ширина (LW), количество междоузлий (NI), длина главной оси (LMA), свежая масса растений (PFW) и корней (RFW), а также репродуктивное признаки: количество цветков (NFL) и плодов (NFR), коэффициент завязывания плодов (FS), длина (FL) и диаметр (FD) плодов, общая продуктивность растения (TY). Эксперимент был полностью рандомизирован. Статистический анализ выполняли с использованием SAS Enterprise Guide 7.1 (SAS Institute Inc., Кэри, Северная Каролина, США).Результаты. В результате исследования было выявлено, что отобранные образцы острого перца, холодоустойчивые на стадии проростка, не всегда могут проявлять хорошие агрономические показатели на стадиях роста, и они могут колебаться в зависимости от особенностей генотипа. Проростки с повреждением листьев в пределах 25% могут существенно повлиять на рост вегетативных и репродуктивных параметров растений перца. Выявлены более четкие корреляции между некоторыми вегетативными и репродуктивными параметрами у NT и LCD растений

Dust in brown dwarfs and extra-solar planets IV. Assessing TiO2 and SiO nucleation for cloud formation modeling

Clouds form in atmospheres of brown dwarfs and planets. The cloud particle formation processes are similar to the dust formation process studied in circumstellar shells of AGB stars and in Supernovae. Cloud formation modelling in substellar objects requires gravitational settling and element replenishment in addition to element depletion. All processes depend on the local conditions, and a simultaneous treatment is required. We apply new material data in order to assess our cloud formation model results regarding the treatment of the formation of condensation seeds. We re-address the question of the primary nucleation species in view of new (TiO2)_N-cluster data and new SiO vapour pressure data. We apply the density functional theory using the computational chemistry package Gaussian 09 to derive updated thermodynamical data for (TiO2)_N-clusters as input for our TiO2 seed formation model. We test different nucleation treatments and their effect on the overall cloud structure by solving a system of dust moment equations and element conservation or a pre-scribed Drift-Phoenix atmosphere structure. Updated Gibbs free energies for the (TiO2)_N-clusters are presented, and a slightly temperature dependent surface tension for T=500 ... 2000K with an average value of sigma_infty = 480.6 erg 1/cm2. The TiO2-seed formation rate changes only slightly with the updated cluster data. A considerably larger effect on the rate of seed formation, and hence on grain size and dust number density, results from a switch to SiO-nucleation. Despite the higher abundance of SiO over TiO2 in the gas phase, TiO2 remains considerably more efficient in forming condensation seeds by homogeneous nucleation followed by heterogeneous grain growth. The paper discussed the effect on the cloud structure in more detail.Comment: accepted for publication in A&A (abstract abridged

Dopamine Regulation of Amygdala Inhibitory Circuits for Expression of Learned Fear.

GABAergic signaling in the amygdala controls learned fear, and its dysfunction potentially contributes to posttraumatic stress disorder (PTSD). We find that sub-threshold fear conditioning leads to dopamine receptor D4-dependent long-term depression (LTD) of glutamatergic excitatory synapses by increasing inhibitory inputs onto neurons of the dorsal intercalated cell mass (ITC) in the amygdala. Pharmacological, genetic, and optogenetic manipulations of the amygdala regions centered on the dorsal ITC reveal that this LTD limits less salient experiences from forming persistent memories. In further support of the idea that LTD has preventive and discriminative roles, we find that LTD at the dorsal ITC is impaired in mice exhibiting PTSD-like behaviors. These findings reveal a novel role of inhibitory circuits in the amygdala, which serves to dampen and restrict the level of fear expression. This mechanism is interfered with by stimuli that give rise to PTSD and may also be recruited for fear-related psychiatric diseases.1110Ysciescopu

Ferrimagnetic Heusler tunnel junctions with fast spin-transfer torque switching enabled by low magnetization

Magnetic random access memory that uses magnetic tunnel junction memory cells is a high performance, non-volatile memory technology that goes beyond traditional charge-based memories. Today its speed is limited by the high magnetization of the memory storage layer. Here we show that fast and highly reliable switching is possible using a very low magnetization ferrimagnetic Heusler alloy, Mn3Ge. Moreover, the tunneling magnetoresistance is the highest yet achieved for a ferrimagnetic material at ambient temperature. Furthermore, the devices were prepared on technologically relevant amorphous substrates using a novel combination of a nitride seed layer and a chemical templating layer. These results show a clear path to the lowering of switching currents using ferrimagnetic Heusler materials and, therefore, to the scaling of high performance magnetic random access memories beyond those nodes possible with ferromagnetic devices.Comment: main manuscript 14 pages, 4 main figures and supplementary information. Submitted to Nature naotechnolog

Coherent phonon control via electron-lattice interaction in ferromagnetic Co/Pt multilayers

The manipulation of coherent phonons in condensed systems has attracted fundamental interest, particularly for its applications to future devices. We demonstrate that a coherent phonon in Co/Pt nano-multilayer can be quantitatively controlled via electron-lattice coupling, specifically by changing the multilayer repeat number. To that end, systematic measurement of the time-resolved reflectivity and magneto-optical Kerr effect in Co/Pt multilayers was performed. The coherent phonon frequency was observed to be shifted with the change of the multilayer repeat number. This shift could be clearly explained based on the two-temperature model. Detailed analysis indicated that the lattice heat capacity and electron-lattice coupling strength are linearly dependent on the repeat number of the periodic multilayer structures. Accessing the control of coherent phonons using nanostructures opens a new avenue for advanced phonon-engineering applications.open1131sciescopu