Intracellular Calcium Decreases Upon Hyper Gravity-Treatment of <Emphasis Type="Italic">Arabidopsis Thaliana</Emphasis> Cell Cultures

Cell cultures of Arabidopsis thaliana (A.t.) respond to changes in the gravitational field strength with fluctuations of the amount of cytosolic calcium (Ca²⁺). In parabolic flight experiments, where hyper- and μg phases follow each other, μg clearly increased Ca²⁺, while hyper-g caused a slight reduction. Since the latter observation had not been reported before, we studied this effect in more detail. Using a special centrifuge for heavy items (ZARM, Bremen, Germany), we determined the hyper-g-dependent intracellular Ca²⁺ level with transgenic cell lines expressing the Ca²⁺ sensor, cameleon. This sensor exhibits a shift in fluorescence from 480 to 530 nm in response to Ca²⁺ binding. The data show a drop in the intracellular Ca²⁺ concentration with a threshold gravity of around 3 g. This is above hypergravity levels achieved during parabolic flights (1.8 g). The use of mutants with different sub-cellular targets of cameleon expression (nucleus, tonoplast, plasma membrane) gave the same results, i.e. Ca²⁺ is obviously exported from several intracellular compartments.     

Long-wavelength photodiodes based on <Emphasis Type="Italic">n</Emphasis>-GaSb/<Emphasis Type="Italic">n</Emphasis>-GaInAsSb/<Emphasis Type="Italic">p</Emphasis>-AlGaAsSb heterostructures

Photodiodes sensitive in the wavelength ranges 1–2.5 μm and 1–4.8 μm at room temperature have been created on the basis of n-GaSb/n-GaInAsSb/p-AlGaAsSb double-junction heterostructures of two types. The broadband photosensitivity of the diode structures of both types is indicative of the complete separation of photogenerated electron-hole pairs in the staggered n-p heterojunction (n-GaInAsSb/p-AlGaAsSb). The noise characteristics of photodetectors based on the proposed diode structures have been studied. Prospects of the use of these devices in thermophotovoltaic cells for low-temperature radiation sources are considered.     

Inference with progressively censored <Emphasis Type="Italic">k</Emphasis>-out-of-<Emphasis Type="Italic">n</Emphasis> system lifetime data

A system with n independent components which works if and only if a least k of its n components work is called a k-out-of-n system. For exponentially distributed component lifetimes, we obtain point and interval estimators for the scale parameter of the component lifetime distribution of a k-out-of-n system when the system failure time is observed only. In particular, we prove that the maximum likelihood estimator (MLE) of the scale parameter based on progressively Type-II censored system lifetimes is unique. Further, we propose a fixed-point iteration procedure to compute the MLE for k-out-of-n systems data. In addition, we illustrate that the Newton–Raphson method does not converge for any initial value. Finally, exact confidence intervals for the scale parameter are constructed based on progressively Type-II censored system lifetimes.     

Hypergravity of 10<Emphasis Type="Italic">g</Emphasis> Changes Plant Growth,Anatomy, Chloroplast Size,and Photosynthesis in the Moss <Emphasis Type="Italic">Physcomitrella patens</Emphasis>

The photosynthetic and anatomical responses of bryophytes to changes in gravity will provide crucial information for estimating how these plant traits evolved to adapt to changes in gravity in land plant history. We performed long-term hypergravity experiments at 10g for 4 and 8 weeks using the moss Physcomitrella patens with two centrifuges equipped with lighting systems that enable long-term plant growth under hypergravity with irradiance. The aims of this study are (1) to quantify changes in the anatomy and morphology of P. patens, and (2) to analyze the post-effects of hypergravity on photosynthesis by P. patens in relation to these changes. We measured photosynthesis by P. patens for a population of gametophores (e.g., canopy) in Petri dishes and plant culture boxes. Gametophore numbers increased by 9% for a canopy of P. patens, with 24–27% increases in chloroplast sizes (diameter and thickness) in leaf cells. In a canopy of P. patens, the area-based photosynthesis rate (A _canopy) was increased by 57% at 10g. The increase observed in A _canopy was associated with greater plant numbers and chloroplast sizes, both of which involved enhanced CO₂ diffusion from the atmosphere to chloroplasts in the canopies of P. patens. These results suggest that changes in gravity are important environmental stimuli to induce changes in plant growth and photosynthesis by P. patens, in which an alteration in chloroplast size is one of the key traits. We are now planning an ISS experiment to investigate the responses of P. patens to microgravity.     

The pH-induced thermosensitive poly (NIPAAm-<Emphasis Type="Italic">co</Emphasis>-AAc-<Emphasis Type="Italic">co</Emphasis>-HEMA)-<Emphasis Type="Italic">g</Emphasis>-PCL micelles used as a drug carrier

The macromonomer of 2-hydroxyethyl methyacrylate-caprolactone (HPCL) was synthesized by the ring-opening polymerization (ROP) of ε-caprolactone, which was initiated by 2-hydroxyethyl methyacrylate (HEMA). Then, the graft terpolymers of NIPAAm-co-AAc-co-HEMA-g-PCL (PHNA-CL) with varying mole ratios were subsequently synthesized by free radical polymerization of HEMA-PCL, N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc). PHNA-CL was further self-assembled in different types of solvent. All the as-prepared copolymers were characterized by ¹H NMR, FT-IR and GPC. Micellization behaviors of micelles were studied by TEM and DLS. The micelles exhibited a phase transition temperature which can be readily adjusted by changing pH value of the micellization system. Micelle loaded with doxorubicin (DOX) was used to evaluate the drug release behavior. The release of DOX from micelles could be controlled by changing pH value and temperature in buffer solutions. The micelles are potentially to be used as a new anticancer drug carrier for intracellular delivery.     

Mechanism of <Emphasis Type="Italic">p-n</Emphasis> junction breakdown at high reverse voltage ramps

It is shown that flat tunneling-assisted impact ionization fronts in p-n junctions operating at a high buildup rate (ramp) u of the reverse voltage can be obtained provided that the rate g_f of the tunneling generation of electron-hole pairs is much greater than the impact ionization rate g_i in the initial stage of breakdown. Usually (e.g., in silicon) g_f?g_i and, therefore, the multiplication of the first hundreds of electron-hole pairs due to the impact ionization leads to the avalanche-streamer transition much before the overlap of avalanches. In this case, the diode transition to the conducting state may be caused by the interelectrode gap shortage by a large number of streamers, the total resistance of which can be much smaller than the load resistance. A simple model of such a “multistreamer” breakdown is proposed according to which the switching time is virtually independent of the streamer parameters and is inversely proportional to u. The diode resistance in the conducting state significantly drops with increasing ramp u and grows with increasing velocity of streamers.     

Specific Heat Jump at T<Emphasis Type="Italic">c</Emphasis> of High T<Emphasis Type="Italic">c</Emphasis> Superconductors: Effect of Van Hove Singularity

In the BCS framework, exact expressions for the ratio between the jump in the specific heat at T _c and the normal phase specific heat are derived within the Van Hove singularity scenario. Analytical results are obtained for an isotropic s-wave and anisotropic d-wave pairing symmetries. Graphical solutions of the ratio as functions of ω _D /T _c and E _F /T _c , where ω _D is the cutoff energy and E _F is the Fermi energy, show significant deviations from the BCS value of 1.43.     

Impact-ionization-stimulated electroluminescence in isotype <Emphasis Type="Italic">n</Emphasis>-GaSb/<Emphasis Type="Italic">n</Emphasis>-AlGaAsSb/<Emphasis Type="Italic">n</Emphasis>-GaInAsSb heterostructures

We have studied electroluminescence in n-GaSb/n-AlGaAsSb/n-GaInAsSb heterostructures with isotype heterojunctions, in which the quantum efficiency of emission is increased due to the additional production of electron-hole pairs as a result of the impact ionization that takes place near the heterointerface. The impact ionization in such heterostructures is possible due to the presence of deep wells in the energy band structure.     

A comparative study of lignocellulosic ethanol productivities by <Emphasis Type="Italic">Kluyveromyces marxianus</Emphasis> and <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

The yeast Saccharomyces cerevisiae is commonly employed in industrial ethanol production, regardless of the capability of Kluyveromyces marxianus strains to produce ethanol at similar or higher levels and on inhibitory conditions. Therefore, in this work strains of S. cerevisiae (ethanol RED and AR5) and K. marxianus (SLP1 and OFF1) were compared for ethanol production from sugarcane bagasse (SCB) and wheat straw (WS) hydrolysates. As it is known, during the lignocellulosic hydrolysis not only free sugars were obtained (SCB, g L^?1: glucose 7.64, xylose 8.38, arabinose 2.43; and WS, g L^?1: glucose 6.07, xylose 6.36, arabinose 2.09) but also growth inhibitors of yeast such as hydroxymethylfurfural and furfural that could modify the fermentation capability. The volumetric ethanol productivity (Q _p) was evaluated, and it was observed that the K. marxianus SLP1 was the most efficient for ethanol production reaching a Q _p of 0.292 and 0.250 g L^?1 h^?1 on SCB and WS hydrolysates, respectively. In contrast, S. cerevisiae AR5 and ethanol RED exhibited a reduced Q _p on SCB, but similar values of Q _p to K. marxianus OFF1 on WS. The results obtained show that it is possible to select K. marxianus yeast strains for ethanol production using SCB and WS hydrolysates obtaining higher Q _p than S. cerevisiae yeast strains. Considering the efficiency of ethanol production and the tolerance to inhibitors, K. marxianus strain SLP1 possesses a great potential as an industrial yeast for lignocellulosic ethanol production.     

On the correspondence from Bayesian log-linear modelling to logistic regression modelling with <Emphasis Type="Italic">g</Emphasis>-priors

Consider a set of categorical variables where at least one of them is binary. The log-linear model that describes the counts in the resulting contingency table implies a specific logistic regression model, with the binary variable as the outcome. Within the Bayesian framework, the g-prior and mixtures of g-priors are commonly assigned to the parameters of a generalized linear model. We prove that assigning a g-prior (or a mixture of g-priors) to the parameters of a certain log-linear model designates a g-prior (or a mixture of g-priors) on the parameters of the corresponding logistic regression. By deriving an asymptotic result, and with numerical illustrations, we demonstrate that when a g-prior is adopted, this correspondence extends to the posterior distribution of the model parameters. Thus, it is valid to translate inferences from fitting a log-linear model to inferences within the logistic regression framework, with regard to the presence of main effects and interaction terms.     

Rate constant of <Emphasis Type="Italic">VT</Emphasis>/<Emphasis Type="Italic">VV</Emphasis> energy exchange in the collision of di- and polyatomic molecules within the SFO model

The numerical-analytical investigation of the shock forced oscillator (SFO) model is complete. Approaches for calculating the probabilities of quantum transitions from the initial to some final state with VV energy exchange of diatomic molecules and VV and VT energy exchange of polyatomic molecules are considered. Formulas for calculating the probabilities of the \({W_{{i_1},{i_2} \to {f_1},{f_2}}}\) transition for VV energy exchange in collision of molecules AB and CD within the harmonic approximation are represented (SFHO model). It is shown that the probabilities of a quantum transition in VV and VT energy exchange of polyatomic molecules can be calculated in terms of the quantum transition probability for VT energy exchange of diatomic molecules on the assumption of “frozen” quantum transitions of polyatomic molecules. The problem of determining the dissociation rate constant is considered by the example of a nitrogen molecule (N₂) in the N₂–N₂ system for the “improved” Lennard-Jones potential in VV energy exchange. The calculated dissociation rate constant is compared with the experimental data obtained for a shock tube.     

Spin Dynamics in the Bi-Directional Charge Density Wave State of High-<Emphasis Type="Italic">T</Emphasis><Subscript><Emphasis Type="Italic">c</Emphasis></Subscript> Superconductors

In this paper, we investigate the dynamical spin susceptibility in the bi-directional charge density wave (BCDW) state by adopting a random-phase approximation. In the BCDW state, we find that no spin resonance exists and only a broad commensurate peak appears for the frequency dependence of the dynamical spin susceptibility at Q = (π,π), though a low-energy spin gap feature can also be found as in the superconducting state. While the “hourglass” type of the dispersion for the BCDW state bears some similarities with that in the superconducting state, the momentum distribution of Im χ ^+?(Q,ω) is just the opposite with the incommensurate peaks lying along the diagonal direction for the energy below ω _c and along the axial direction above ω _c . In the coexistence of SC and BCDW, the frequency dependence of the dynamical spin susceptibility at Q = (π,π) generally shows the two-peak structure, reflecting two energy scales of the spin excitations. These unique features may serve as signatures to verify whether or not the BCDW state is responsible for the formation of the Fermi arcs.     

Effects of Short-Term Hypergravity Exposure are Reversible in <Emphasis Type="Italic">Triticum aestivum</Emphasis> L. Caryopses

Short-term hypergravity exposure is shown to retard seed germination, growth and photosynthesis in wheat caryopses. This study investigates the reversibility of effects of short-term hypergravity on imbibed wheat (Triticum aestivum var L.) caryopses. After hypergravity exposure (500 × g ? 2500 × g for 10 min) on a centrifuge, exposed caryopses were kept under normal gravity (1 × g) up to six days and then sown on agar. Results of the present study showed that percentage germination and growth were completely restored for DAY 6 compared to DAY 0. Restoration of germination and growth was accompanied by increased α-amylase activity. The specific activity of antioxidative enzyme viz. catalase and guaiacol peroxidase was lowered on DAY 6 compared to DAY 0 suggesting an alleviation of oxidative cellular damage against hypergravity stress. Chlorophyll pigment recovery along with chlorophyll fluorescence (PI and Fv/Fm) on DAY 6 indicates a transient rather than permanent damage of the photosynthetic apparatus. Thus, our findings demonstrate that short-term hypergravity effects are reversible in wheat caryopses. The metabolic cause of restoration of seed germination and growth upon transferring the caryopses to normal gravity is performed by a reactivation of carbohydrate- metabolizing enzymes, α-amylase and alleviation of oxidative stress damage with subsequent recovery of chlorophyll biosynthesis and photosynthetic activity.     

Analysis of Statoliths Displacement in <Emphasis Type="Italic">Chara</Emphasis> Rhizoids for Validating the Microgravity-Simulation Quality of Clinorotation Modes

In single-celled rhizoids of the green algae Chara, positively gravitropic growth is governed by statoliths kept in a dynamically stable position 10–25 μ m above the cell tip by a complex interaction of gravity and actomyosin forces. Any deviation of the tube-like cells from the tip-downward orientation causes statoliths to sediment onto the gravisensitive subapical cell flank which initiates a gravitropic curvature response. Microgravity experiments have shown that abolishing the net tip-directed gravity force results in an actomyosin-mediated axial displacement of statoliths away from the cell tip. The present study was performed to critically assess the quality of microgravity simulation provided by different operational modes of a Random Positioning Machine (RPM) running with one axis (2D mode) or two axes (3D mode) and different rotational speeds (2D), speed ranges and directions (3D). The effects of 2D and 3D rotation were compared with data from experiments in real microgravity conditions (MAXUS sounding rocket missions). Rotational speeds in the range of 60–85 rpm in 2D and 3D modes resulted in a similar kinetics of statolith displacement as compared to real microgravity data, while slower clinorotation (2–11 rpm) caused a reduced axial displacement and a more dispersed arrangement of statoliths closer to the cell tip. Increasing the complexity of rotation by adding a second rotation axis in case of 3D clinorotation did not increase the quality of microgravity simulation, however, increased side effects such as the level of vibrations resulting in a more dispersed arrangement of statoliths. In conclusion, fast 2D clinorotation provides the most appropriate microgravity simulation for investigating the graviperception mechanism in Chara rhizoids, whereas slower clinorotation speeds and rotating samples around two axes do not improve the quality of microgravity simulation.     

The Random <Emphasis Type="Italic">J</Emphasis>-Model with Biquadratic Interaction

The spin-1 model is studied on the Bethe lattice by including the bilinear J and biquadratic K exchange interactions into the Hamiltonian. The effects of J is randomized by using a bimodal random distribution with an adjustable parameter α which allows to study the cases of ±J-model and bond-dilution. The thermal variations of the order-parameters are studied to obtain the possible phase diagrams of the model. It is found that second-order phase transitions lines separate the ordered-phases, ferromagnetic, or antiferromagnetic, from the disordered one, i.e., the paramagnetic phase. The staggered quadrupolar phase lines are also found and only seen for higher negative K values for coordination number q=4 and 6, only. The reentrant behavior is also found for some of the phase transitions lines.     

Predicting scientific impact based on <Emphasis Type="Italic">h</Emphasis>-index

Predicting the future impact of a scientist/researcher is a critical task. The objective of this work is to evaluate different h-index prediction models for the field of Computer Science. Different combinations of parameters have been identified to build the model and applied on a large data set taken from Arnetminer comprised of almost 1.8 million authors and 2.1 million publications’ record of Computer Science. Machine learning prediction technique, regression, is used to find the best set of parameters suitable for h-index prediction for the scientists from all career ages, without enforcing any constraint on their current h-index values with R ² as a metric to measure the accuracy. Further, these parameters are evaluated for different career ages and different thresholds for h-index values. Prediction results for 1 year are really good, having R ² 0.93 but for 5 years R ² declines to 0.82 on average. Hence inferred that prediction of h-index is difficult for longer periods. Predictions for the researchers having 1 year experience are not precise, having R ² 0.60 for 1 year and 0.33 for 5 years. Considering scientists of different career ages, average R ² values for researchers having 20–36 years of experience were 0.99. For the researches having different h-index values, researchers having low h-index were difficult to predict. Parameters set comprising of current h-index, average citations per paper, number of coauthors, years since publishing first article, number of publications, number of impact factor publications, and number of publications in distinct journals performed better than all other combinations.     

Comprehensive Study of the Influence of Altered Gravity on the Oxidative Burst of Mussel (<Emphasis Type="Italic">Mytilus edulis</Emphasis>) Hemocytes

Microgravity induces alterations in the functioning of immune cell; however, the underlying mechanisms have not yet been identified. In this study, hemocytes (blood cells) of the blue mussel Mytilus edulis were investigated under altered gravity conditions. The study was conducted on the ground in preparation for the BIOLAB TripleLux-B experiment, which will be performed on the International Space Station (ISS). On-line kinetic measurements of reactive oxygen species (ROS) production during the oxidative burst and thus cellular activity of isolated hemocytes were performed in a photomultiplier (PMT)-clinostat (simulated microgravity) and in the 1g operation mode of the clinostat in hypergravity on the Short-Arm Human Centrifuge (SAHC) as well as during parabolic flights. In addition to studies with isolated hemocytes, the effect of altered gravity conditions on whole animals was investigated. For this purpose, whole mussels were exposed to hypergravity (1.8 g) on a multi-sample incubator centrifuge (MuSIC) or to simulated microgravity in a submersed clinostat. After exposure for 48 h, hemocytes were taken from the mussels and ROS production was measured under 1 g conditions. The results from the parabolic flights and clinostat studies indicate that mussel hemocytes respond to altered gravity in a fast and reversible manner. Hemocytes (after cryo-conservation) exposed to simulated microgravity (μ g), as well as fresh hemocytes from clinorotated animals, showed a decrease in ROS production. Measurements during a permanent exposure of hemocytes to hypergravity (SAHC) show a decrease in ROS production. Hemocytes of mussels measured after the centrifugation of whole mussels did not show an influence to the ROS response at all. Hypergravity during parabolic flights led to a decrease but also to an increase in ROS production in isolated hemocytes, whereas the centrifugation of whole mussels did not influence the ROS response at all. This study is a good example how ground-based facility experiments can be used to prepare for an upcoming ISS experiment, in this case the TRIPLE LUX B experiment.     

Triangular Ising Ferromagnet with Mixed Spins (<Emphasis Type="Italic">A</Emphasis> = 1/2, <Emphasis Type="Italic">B</Emphasis> = 1/2, <Emphasis Type="Italic">C</Emphasis> = 1): Dynamic Magnetic Properties and Hysteresis Curves

The dynamic properties of the triangular Ising ferromagnet consisting of the mixed spins A = 1/2, B = 1/2, and C = 1 is studied by using the mean-field theory (MFT) as well as Glauber-type stochastic dynamics (GSD). The coupling equations to investigate dynamic behaviors of the system are calculated, and phase transitions, phase diagrams, and hysteresis curves are obtained. From these studies, first- and second-order transition lines, the dynamic phase diagrams (DPDs) in the (T,h ₀) and (T,d) planes, and single hysteresis curves are presented. In the DPDs, dynamic tricritical point due to the first- and second-order phase transitions are observed. It is found that the dynamic hysteresis properties of the triangular system strongly depend on the temperature and crystal field.     

Structural,Elastic, Electronic,and Magnetic Properties of the Full-Heusler Compounds Ti<Subscript>2</Subscript>Ni<Emphasis Type="Italic">X</Emphasis> (<Emphasis Type="Italic">X</Emphasis>= Al,Ga, and In)

We present a quantum-mechanical first-principle calculation of the structural, elastic, electronic, and magnetic properties of the full-Heusler compounds Ti₂NiX (X= Al, Ga, and In). The calculation uses the full-potential linearized augmented plane waves plus local orbital method to describe Ti₂-based Heusler alloys. The results show that these compounds exhibit half metallic characteristics over a wide range of mesh parameters and obey the Slater–Pauling rule, which states that the total magnetic moment per unit cell M _t = Z _t? 18 for half-Heusler compounds XYZ and M _t = Z _t? 24 for full-Heusler X ₂ YZ compounds. For these new alloys Ti₂NiX (X= Al, Ga, and In), we initially considered the two possible L2₁ structures AlCu₂Mn and CuHg₂Ti. However, two subsequent structural studies showed that only the CuHg₂Ti-like structure is half metallic. Over a wide range of mesh parameters, the calculations give a total magnetic moment of 3.00 μ _B. These results suggest that Ti₂NiX (X= Al, Ga, and In) are promising materials for spintronic applications.