Graphics-processing-unit-based acceleration of electromagnetic transients simulation.

This paper presents a novel parallelization approach to speedup EMT simulation, using GPU-based computing. This paper extends earlier published works in the area, by exploiting additional parallelism to accelerate EMT simulation. A 2D-parallel matrix-vector multiplication is used that is faster than previous 1D-methods. Also this paper implements a simpler GPU-specific sparsity technique to further speed up the simulations as available CPU-based sparse techniques are not suitable for GPUs. Additionally, as an extension to previous works, this paper demonstrates modelling of a power electronic subsystem. A low granularity system, i.e. one with a large cluster of busses connected to others with a few transmission lines is considered, as is also a high granularity where a small cluster of busses is connected to other clusters thereby requiring more interconnecting transmission lines. Computation times for GPU-based computing are compared with the computation times for sequential implementations on the CPU. The paper shows two surprising differences of GPU simulation in comparison with CPU simulation. Firstly, the inclusion of sparsity only makes minor reductions in the GPU-based simulation time. Secondly excessive granularity, even though it appears to increase the number of parallel computable subsystems, significantly slows down the GPU-based simulation

Ubiquitination and proteasomal degradation of ATG12 regulates its proapoptotic activity

During macroautophagy, conjugation of ATG12 to ATG5 is essential for LC3 lipidation and autophagosome formation. Additionally, ATG12 has ATG5-independent functions in diverse processes including mitochondrial fusion and mitochondrial-dependent apoptosis. In this study, we investigated the regulation of free ATG12. In stark contrast to the stable ATG12–ATG5 conjugate, we find that free ATG12 is highly unstable and rapidly degraded in a proteasome-dependent manner. Surprisingly, ATG12, itself a ubiquitin-like protein, is directly ubiquitinated and this promotes its proteasomal degradation. As a functional consequence of its turnover, accumulation of free ATG12 contributes to proteasome inhibitor-mediated apoptosis, a finding that may be clinically important given the use of proteasome inhibitors as anticancer agents. Collectively, our results reveal a novel interconnection between autophagy, proteasome activity, and cell death mediated by the ubiquitin-like properties of ATG12

Atg12 Maintains Skeletal Integrity by Modulating Pro-Osteoclastogenic Signals and Chondrocyte Differentiation

Weightlessness and radiation, two unique elements of space, profoundly decreases bone mass. We aimed to elucidate the role of autophagy in maintaining structural integrity of the skeleton. We hypothesize that loss of autophagy in bone leads to an imbalance in pro-osteoclastogenic and pro-osteogenic signals, resulting in net bone loss. To test our hypothesis, we performed global postnatal deletion of Atg12 using tamoxifen-inducible Cre. Compared to Vehicle (Control) groups, Tamoxifen (Atg12 iKO) groups showed decreased LC3B-I to II conversion and increased p62 protein levels, consistent with loss of autophagy. qPCR revealed increased expression of pro-osteoclastogenic cytokines in bone and marrow respectively in male iKOs compared to controls. Microcomputed tomography revealed decreased cortical bone volume, cortical thickness and periosteal perimeter consistent with bone loss; and a longer primary spongiosa in male Atg12 iKOs display compared to male controls. Histology showed that compared to male controls, male iKOs had a profound increase in chondrocyte column length of the growth plate with hyper-expansion of both proliferating and hypertrophic zones. Taken together, these findings indicate that autophagy plays an important role in the maintenance of bone structural integrity by mediating the production of pro-osteoclastogenic signals and regulating chondrocyte proliferation and differentiation

Evolution of transonicity in an accretion disc

For inviscid, rotational accretion flows driven by a general pseudo-Newtonian potential on to a Schwarzschild black hole, the only possible fixed points are saddle points and centre-type points. For the specific choice of the Newtonian potential, the flow has only two critical points, of which the outer one is a saddle point while the inner one is a centre-type point. A restrictive upper bound is imposed on the admissible range of values of the angular momentum of sub-Keplerian flows through a saddle point. These flows are very unstable to any deviation from a necessarily precise boundary condition. The difficulties against the physical realisability of a solution passing through the saddle point have been addressed through a temporal evolution of the flow, which gives a non-perturbative mechanism for selecting a transonic solution passing through the saddle point. An equation of motion for a real-time perturbation about the stationary flows reveals a very close correspondence with the metric of an acoustic black hole, which is also an indication of the primacy of transonicity.Comment: 18 page

Buckwheat: Potential Stress-Tolerant Crop for Mid-Hills of Eastern Himalaya under Changing Climate

Under changing climate, identification and diversification of cropping systems having higher stress resilience and adaptability for fragile mountain ecosystems of Eastern Himalayan Region (EHR) are paramount. Lesser known and underutilized crop like buckwheat (BW) with year-round cultivation potential and having higher stress tolerance to prevailing stresses (low pH, low moisture) could be a crop of choice for abating malnutrition among hill inhabitants. Proper time of sowing of the crop is between mid-September and mid-December seemingly essential for better grain yield to the tune of 15.0–18.0 q ha−1, and the crop is found suitable to be grown all through the year for higher green biomass (12.6–38.4 q ha−1). Enhanced exudation of low-molecular-weight organic acids (LMWOA) like oxalic acid by buckwheat increased the solubilization of fixed forms of free phosphorus (P) to the extent of 35.0 to 50.0 micro gram per plant in ideal acid soil of the region (P) in acid soil. In addition, relatively increased resilience to moisture stress with improved stress physiological attributes adds more potentiality for enhancing cropping intensity of hill slopes of EHR. Few genotypes namely IC377275 (18.97q ha−1), IC26591 (17.1 qt ha−1), IC14890 (16.32q ha−1), and Himapriya (15.27q ha−1) are emerging as high-yielding types for productive cultivation in acid soils. Studies on the combined effects of acid soil and moisture stress would aid in novel crop improvement of buckwheat in EHR

PLIC proteins or ubiquilins regulate autophagy-dependent cell survival during nutrient starvation

Ubiquilins (UBQLNs) are adaptor proteins thought to deliver ubiquitinated substrates to proteasomes. Here, we show a role for UBQLN in autophagy: enforced expression of UBQLN protects cells from starvation-induced death, whereas depletion of UBQLN renders cells more susceptible. The UBQLN protective effect requires the autophagy-related genes ATG5 and ATG7, two essential components of autophagy. The ubiquitin-associated domain of UBQLN mediates both its association with autophagosomes and its protective effect against starvation. Depletion of UBQLN delays the delivery of autophagosomes to lysosomes. This study identifies a new role for UBQLN in regulating the maturation of autophagy, expanding the involvement of ubiquitin-related proteins in this process

Electrochemical Evaluation of Dopant Energetics and the Modulation of Ultrafast Carrier Dynamics in Cu-Doped CdSe Nanocrystals

Cyclic voltammetric and femtosecond transient absorption (TA) measurements on Cu⁺-doped CdSe nanocrystals (NCs) were utilized to reveal the energetics of the electroactive Cu⁺ dopant with respect to the band energies of CdSe NC host and the influence of Cu in tuning the carrier dynamics, respectively. Oxidation–reduction peaks due to an electroactive dopant within CdSe NC host have been traced to determine its energy level which was correlated to the dopant emission energy and Stokes shift. The low doping density of Cu does not significantly alter the band structure of CdSe as the shape of the TA spectra remains similar before and after doping. However, Cu⁺ acts as a hole localizing center decoupling the electronic wave function from the hole leading to slower Auger-assisted electron cooling in doped NCs. As hole localization to Cu⁺ is the primary step for dopant emission, in the presence of hole quenchers (aminophenols) the dopant emission gets drastically quenched. Interestingly, once hole is captured by Cu⁺ due to strong affinity for electron, external quenchers (nitrophenols) are unable to capture the electron as confirmed from steady state and time-resolved measurements establishing the role of Cu as an internal sensitizer for the charge carriers

Intraband Electron Cooling Mediated Unprecedented Photocurrent Conversion Efficiency of CdS_<i>x</i>Se_1–<i>x</i> Alloy QDs: Direct Correlation between Electron Cooling and Efficiency

Composition and size dependent band gap engineering with longer excited state charge carrier lifetime assist CdS_<i>x</i>Se_1–<i>x</i> alloy semiconductor quantum dots (QDs) as a promising candidate for quantum dot solar cell (QDSC). Colloidal CdS_<i>x</i>Se_1–<i>x</i> alloy QDs were synthesized using the hot injection method where a stoichiometric mixture of S-TOP and Se-TOP were injected at 270 °C in a mixture of Cd-oleate. The electron decoupled from hole in the alloyed structure due to delocalization of electron in electronically quasi type-II graded CdS_<i>x</i>Se_1–<i>x</i> alloyed structure. As a result, intraband electron cooling time increases from 100s of fs to sub 10 ps time scale in the alloyed graded structure. Extremely slow electron cooling time (∼8 ps) and less charge recombination (∼50% in >2 ns) as compared to both CdS and CdSe QDs are found to be beneficial for charge carrier extraction in QD solar cells. Using polysulfide electrolyte and Cu₂S-deposited ITO glass plates as photocathode, the efficiency of the QD solar cell was measured to be 1.1 (±0.07)% for CdS, 3.36 (±0.1)% for CdSe, and 3.95 (±0.12)% for CdS_0.7Se_0.3 QDs. An additional nonepitaxial CdS quasi-shell followed by ZnS passivation layer (TiO₂/ CdS_0.7Se_0.3 /quasi-CdS/ZnS) was deposited on top of the CdS_0.7Se_0.3 film which showed a photo current conversion efficiency (PCE) of 4.5 (±0.18) %. The overall 14% increase of PCE is due to the quasi CdS shell helps to separate more electrons through passivating the surface states of TiO₂