This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO3 (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following ...slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350°C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO3. Room temperature dielectric constant (εr) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40K for both 1350°C and 1700°C sintered GMO. Present findings showed the possibility of application of GdMnO3 at room temperature as multifunctional materials.
• Preparation of single-phasic polycrystalline GdMnO3 sample by the solid state sintering route.• Observation of square type P–E hysteresis loop with higher saturation and remnant polarization.• Observation of antiferromagnetic behavior at 40K in polycrystalline GdMnO3.• Possibility of room temperature application of GdMnO3 as multifunctional material.
Cells constantly adapt to various environmental changes and stresses. The way in which nutrient and stress levels in a cell feed back to control metabolism and growth are, unsurprisingly, extremely ...complex, as responding with great sensitivity and speed to the 'feast or famine, slack or stress' status of its environment is a central goal for any organism. The highly conserved target of rapamycin complex 1 (TORC1) controls eukaryotic cell growth and response to a variety of signals, including nutrients, hormones and stresses, and plays the key role in the regulation of autophagy. A lot of attention has been paid recently to the factors in this pathway functioning upstream of TORC1. In this Commentary, we focus on a major, newly discovered upstream regulator of TORC1--the multiprotein SEA complex, also known as GATOR. We describe the structural and functional features of the yeast complex and its mammalian homolog, and their involvement in the regulation of the TORC1 pathway and TORC1-independent processes. We will also provide an overview of the consequences of GATOR deregulation in cancer and other diseases.
The survival of microorganisms within a cementitious geological disposal facility for radioactive wastes heavily depends on their ability to survive the calcium-dominated, hyperalkaline conditions ...resulting from the dissolution of the cementitious materials. The results from this study show that the formation of flocs, composed of a complex mixture of extracellular polymeric substances (EPS), provides protection against alkaline pH values up to 13.0. The flocs were dominated by
and
spp., producing a mannose-rich carbohydrate fraction incorporating extracellular DNA, resulting in Ca
sequestration. EPS provided a ∼10-μm thick layer around the cells within the center of the flocs, which were capable of growth at pH values of 11.0 and 11.5, maintaining internal pH values of 10.4 and 10.7, respectively. Microorganisms survived at a pH of 12.0, where an internal floc pH of 11.6 was observed, as was a reduced associated biomass. We observed limited floc survival (<2 weeks) at a pH of 13.0. This study demonstrates that flocs maintain lower internal pHs in response to the hyperalkaline conditions expected to occur within a cementitious geological disposal facility for radioactive wastes and indicates that floc communities within such a facility can survive at pHs up to 12.0.
The role of extracellular polymeric substances (EPS) in the survival of microorganisms in hyperalkaline conditions is poorly understood. Here, we present the taxonomy, morphology, and chemical characteristics of an EPS-based microbial floc, formed by a consortium isolated from an anthropogenic hyperalkaline site. Short-term (<2 weeks) survival of the flocs at a pH of 13 was observed, with indefinite survival observed at a pH of 12.0. Measurements from micro-pH electrodes (10-μm-diameter tip) demonstrated that flocs maintain lower internal pHs in response to hyperalkaline conditions (pH 11.0, 11.5, and 12.0), demonstrating that floc formation and EPS production are survival strategies under hyperalkaline conditions. The results indicate how microbial communities may survive and propagate within the hyperalkaline environment that is expected to prevail in a cementitious geological disposal facility for radioactive wastes; the results are also relevant to the wider extremophile community.
The prebiotic replication of information-coding molecules is a central problem concerning life's origins. Here, we report that amyloids composed of short peptides can direct the sequence-selective, ...regioselective and stereoselective condensation of amino acids. The addition of activated DL-arginine and DL-phenylalanine to the peptide RFRFR-NH
in the presence of the complementary template peptide Ac-FEFEFEFE-NH
yields the isotactic product FRFRFRFR-NH
, 1 of 64 possible triple addition products, under conditions in which the absence of template yields only single and double additions of mixed stereochemistry. The templating mechanism appears to be general in that a different amyloid formed by (Orn)V(Orn)V(Orn)V(Orn)V-NH
and Ac-VDVDVDVDV-NH
is regioselective and stereoselective for N-terminal, L-amino-acid addition while the ornithine-valine peptide alone yields predominantly sidechain condensation products with little stereoselectivity. Furthermore, the templating reaction is stable over a wide range of pH (5.6-8.6), salt concentration (0-4 M NaCl), and temperature (25-90 °C), making the amyloid an attractive model for a prebiotic peptide replicating system.
Although the nuclear pore complex (NPC) is best known for its primary function as the key regulator of molecular traffic between the cytoplasm and the nucleus, a growing body of experimental evidence ...suggests that this structure participates in a considerably broader range of cellular activities on both sides of the nuclear envelope. Indeed, the NPC is emerging as an important regulator of gene expression through its influence on the internal architectural organization of the nucleus and its apparently extensive involvement in coordinating the seamless delivery of genetic information to the cytoplasmic protein synthesis machinery.
Possible involvement of the antioxidative enzymes in salt tolerance was investigated in three submerged aquatic macrophytes, viz.
Hydrilla verticillata,
Najas indica and
Najas gramenia, which ...differed in their tolerance to salinity. NaCl in light resulted in significant decrease in the chlorophyll
a/
b ratio in
H. verticillata, which was significantly neutralized by the presence of DABCO (diazabicyclo2.2.2octane), sodium benzoate or mannitol along with the NaCl in the exposure medium indicating induction of oxidative stress upon salt treatment. All the three test species showed enhanced activity of superoxide dismutase (SOD; EC 1.15.1.1) and peroxidases (EC 1.11.1.7) upon exposure to either NaCl or SWS (seawater salinity); the increases in their activity in response to NaCl were positively correlated with the salt tolerance of the plants. Only
N. gramenia showed considerable increase in the activity of catalase (EC 1.11.1.6), while only
H. verticillata exhibited significant increase in the activity of ascorbate peroxidase (EC 1.11.1.11) in response to the salt treatment. A higher constitutive level of the antioxidative enzymes in the salt-tolerant
N. gramenia than in the salt-sensitive
H. verticillata coupled with significant increase in the activity of these enzymes, particularly of catalase and SOD, in the former upon salinity treatment suggested their active involvement in salt tolerance. The oxidative stress induced upon the salt treatment also indicated a possible involvement of the antioxidative enzymes in the process. The ion interaction study revealed significant modifying effect of Ca
2+, and also of Mg
2+ and K
+, on the changes induced by Na
+ in the activity of catalase and SOD suggesting that relative build-up of these ions inside cells could be of much importance in regulation of synthesis of antioxidative enzymes.
•The nanoscale connement remarkably lowers the Jahn-Teller distortion in NiCr2O4 nanochromite.•The dc magnetization results reveal a substantial enhancement in the spin collinearity in ...nanochromite.•The surface-core magnetic interaction leads to an anomalous hysteresis behavior in nanochromite.
We present the results of a detailed investigation of magnetism in spinel chromite NiCr2O4 magnetic nanoparticles (MNPs). Compared to the bulk NiCr2O4, the finite crystallite size of about 10 nm lowers the Jahn-Teller distortion and greatly enhances the collinearity of the spin structure in MNPs with considerably reduced “frustration index” = |θCW|/Tc. This leads to (longitudinal) ferrimagnetic ordering at much higher temperature, Tc≈100 K and suppression of (transverse) antiferromagnetic ordering in MNPs (cf. Tc ≃ 65 K and Ts ≃ 30 K in the bulk); a transition to the cluster spin glass state occurs at Tg = 19.0 K. Moreover, the M-H hysteresis loops show anomalous “hour-glass” behavior at fields near Hc in the vicinity of Tg; this non-monotonous Hc (T) variation can not be accounted from the celebrated Stoner-Wohlfarth model. The present study interprets the anomalous Hc (T) behavior in the framework of magnetically interacting core-shell structure with large surface anisotropy, and points out the importance of surface effects in nanochromites compared to their counterpart ferrites.
We report the discovery and analysis of a massive, compact, hierarchical triple system (TIC 470710327) initially identified by citizen scientists in data obtained by NASA’s Transiting Exoplanet ...Survey Satellite (TESS). Spectroscopic follow-up observations obtained with the HERMES spectrograph, combined with eclipse-timing variations (ETVs), confirm that the system is comprised of three OB stars, with a compact 1.10 d eclipsing binary and a non-eclipsing tertiary on a 52.04 d orbit. Dynamical modelling of the system (from radial velocity and ETVs) reveal a rare configuration wherein the tertiary star (O9.5-B0.5V; 14–17 Mꙩ) is more massive than the combined mass of the inner binary (10.9–13.2 Mꙩ). Given the high mass of the tertiary, we predict that this system will undergo multiple phases of mass transfer in the future, and likely end up as a double neutron star gravitational wave progenitor or an exotic Thorne–Żytkow object. Further observational characterization of this system promises constraints on both formation scenarios of massive stars as well as their exotic evolutionary end-products.
Eukaryotic cells possess a remarkably diverse range of organelles that provide compartmentalization for distinct cellular functions and are likely responsible for the remarkable success of these ...organisms. The origins and subsequent elaboration of these compartments represent a key aspect in the transition between prokaryotic and eukaryotic cellular forms. The protein machinery required to build, maintain, and define many membrane-bound compartments is encoded by several paralog families, including small GTPases, coiled-bundle proteins, and proteins with β-propeller and α-solenoid secondary structures. Together these proteins provide the membrane coats and control systems to structure and coordinate the endomembrane system. Mechanistically and evolutionarily, they unite not only secretory and endocytic organelles but also the flagellum and nucleus. The ancient origins for these families have been revealed by recent findings, providing new perspectives on the deep evolutionary processes and relationships that underlie eukaryotic cell structure.
Anthropogenic hyperalkaline sites provide an environment that is analogous to proposed cementitious geological disposal facilities (GDF) for radioactive waste. Under anoxic, alkaline conditions ...cellulosic wastes will hydrolyze to a range of cellulose degradation products (CDP) dominated by isosaccharinic acids (ISA). In order to investigate the potential for microbial activity in a cementitious GDF, cellulose samples were incubated in the alkaline (∼pH 12), anaerobic zone of a lime kiln waste site. Following retrieval, these samples had undergone partial alkaline hydrolysis and were colonized by a Clostridia-dominated biofilm community, where hydrogenotrophic, alkaliphilic methanogens were also present. When these samples were used to establish an alkaline CDP fed microcosm, the community shifted away from Clostridia, methanogens became undetectable and a flocculate community dominated by Alishewanella sp. established. These flocs were composed of bacteria embedded in polysaccharides and proteins stabilized by extracellular DNA. This community was able to degrade all forms of ISA with >60% of the carbon flow being channelled into extracellular polymeric substance (EPS) production. This study demonstrated that alkaliphilic microbial communities can degrade the CDP associated with some radioactive waste disposal concepts at pH 11. These communities divert significant amounts of degradable carbon to EPS formation, suggesting that EPS has a central role in the protection of these communities from hyperalkaline conditions.
A biofilm forming community able to degrade ISA was isolated from a hyperalkaline contaminated site.
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