Psr1p interacts with SUN/sad1p and EB1/mal3p to establish the bipolar spindle

Regular Abstracts - Sunday Poster Presentations: no. 382During mitosis, interpolar microtubules from two spindle pole bodies (SPBs) interdigitate to create an antiparallel microtubule array for accommodating numerous regulatory proteins. Among these proteins, the kinesin-5 cut7p/Eg5 is the key player responsible for sliding apart antiparallel microtubules and thus helps in establishing the bipolar spindle. At the onset of mitosis, two SPBs are adjacent to one another with most microtubules running nearly parallel toward the nuclear envelope, creating an unfavorable microtubule configuration for the kinesin-5 kinesins. Therefore, how the cell organizes the antiparallel microtubule array in the first place at mitotic onset remains enigmatic. Here, we show that a novel protein psrp1p localizes to the SPB and plays a key role in organizing the antiparallel microtubule array. The absence of psr1+ leads to a transient monopolar spindle and massive chromosome loss. Further functional characterization demonstrates that psr1p is recruited to the SPB through interaction with the conserved SUN protein sad1p and that psr1p physically interacts with the conserved microtubule plus tip protein mal3p/EB1. These results suggest a model that psr1p serves as a linking protein between sad1p/SUN and mal3p/EB1 to allow microtubule plus ends to be coupled to the SPBs for organization of an antiparallel microtubule array. Thus, we conclude that psr1p is involved in organizing the antiparallel microtubule array in the first place at mitosis onset by interaction with SUN/sad1p and EB1/mal3p, thereby establishing the bipolar spindle.postprin

Removal of antagonistic spindle forces can rescue metaphase spindle length and reduce chromosome segregation defects

Regular Abstracts - Tuesday Poster Presentations: no. 1925Metaphase describes a phase of mitosis where chromosomes are attached and oriented on the bipolar spindle for subsequent segregation at anaphase. In diverse cell types, the metaphase spindle is maintained at a relatively constant length. Metaphase spindle length is proposed to be regulated by a balance of pushing and pulling forces generated by distinct sets of spindle microtubules and their interactions with motors and microtubule-associated proteins (MAPs). Spindle length appears important for chromosome segregation fidelity, as cells with shorter or longer than normal metaphase spindles, generated through deletion or inhibition of individual mitotic motors or MAPs, showed chromosome segregation defects. To test the force balance model of spindle length control and its effect on chromosome segregation, we applied fast microfluidic temperature-control with live-cell imaging to monitor the effect of switching off different combinations of antagonistic forces in the fission yeast metaphase spindle. We show that spindle midzone proteins kinesin-5 cut7p and microtubule bundler ase1p contribute to outward pushing forces, and spindle kinetochore proteins kinesin-8 klp5/6p and dam1p contribute to inward pulling forces. Removing these proteins individually led to aberrant metaphase spindle length and chromosome segregation defects. Removing these proteins in antagonistic combination rescued the defective spindle length and, in some combinations, also partially rescued chromosome segregation defects. Our results stress the importance of proper chromosome-to-microtubule attachment over spindle length regulation for proper chromosome segregation.postprin

Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems

The electrical power system is undergoing a revolution enabled by advances in telecommunications, computer hardware and software, measurement, metering systems, IoT, and power electronics. Furthermore, the increasing integration of intermittent renewable energy sources, energy storage devices, and electric vehicles and the drive for energy efficiency have pushed power systems to modernise and adopt new technologies. The resulting smart grid is characterised, in part, by a bi-directional flow of energy and information. The evolution of the power grid, as well as its interconnection with energy storage systems and renewable energy sources, has created new opportunities for optimising not only their techno-economic aspects at the planning stages but also their control and operation. However, new challenges emerge in the optimization of these systems due to their complexity and nonlinear dynamic behaviour as well as the uncertainties involved.This volume is a selection of 20 papers carefully made by the editors from the MDPI topic “Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems”, which was closed in April 2022. The selected papers address the above challenges and exemplify the significant benefits that optimisation and nonlinear control techniques can bring to modern power and energy systems

Bibliography of Lewis Research Center technical publications announced in 1984

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1984. All the publications were announced in the 1984 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Energy: A continuing bibliography with indexes

This bibliography lists 1920 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System from July 1, 1980 through September 30, 1980

Band Alignments and Interfaces in Kesterite Photovoltaics

The kesterite materials, Cu2ZnSn(S,Se)4, represent a promising class of absorber materials, for cheap, earth-abundant, non-toxic photovoltaic cells. However, the record efficiency of a device based on these materials is only 12.6 %, compared to 15 % required for the material to be commercially viable and 22.6 % for the related chalcopyrite material, CIGS. In this thesis, we consider the architecture of a typical kesterite solar cell, from the back contact to the window layer and identify possible causes of the open-circuit voltage deficit, and how this deficit can be reduced. We begin by investigating the necessity for photovoltaics as a result of climate change, caused by our use of fossil fuels, and how the technology of photovoltaics has developed. We also consider the physical principles of photovoltaics and then discuss kesterite materials and architecture and compare them to chalcopyrites. Thus, we begin by investigating the photoelectron spectroscopy of kesterite materials obtained from different synthetic routes, and determine, the band alignments of kesterite/buffer interfaces by the Anderson electron affinity rule and the more reliable Kraut method. Using the results, it is shown that the band offsets between CdS and the kesterite materials considered in this work are inappropriate for high-efficiency photovoltaics. In contrast, In2S3 shows advantageous band offsets in all cases. Simulations are then used to compare the CdS and In2S3 devices Another limit on the efficiency of kesterite photovoltaics is the formation of the n-type Mo(S,Se)2 at the back contact. The formation of this layer typically results in the formation of a reverse diode, opposed to the main photodiode, thus increasing the recombination rate of the photoholes. However, in CdTe devices, Mo is often used as a back contact, which can result in the formation of an analogous MoTe2 layer which does not seem to have this effect. By considering the effects of Ar+ ion induced defects upon single crystals or multilayers exfoliated from a single crystal, the possible reasons why MoTe2 does not have the same effect as the Mo(S,Se)2 layer are investigated. We will also consider the uppermost layer of the photovoltaic cell, the window layer, which usually consists of a transparent conducting oxide (TCO). However, most of the widely-used TCOs have considerable issues, such as scarcity, cost, and self-compensating defects. Hence the final experimental chapter will consider an alternative TCO: Ga2O3. This material has a considerably larger band gap than that of the other TCOs, making it of interest for a wide range of applications Despite this widespread interest, fundamental properties of the material are still poorly understood. Thus, in the final chapter we begin by investigating the fundamental surface properties of a β-Ga2O3 single crystal with a (2 ̅01) surface termination and show that contrary to previous reports, the material exhibits surface accumulation. We also investigate the properties of several of the other polymorphs of Ga2O3 later in the chapter. This thesis concludes by considering the impact of these findings upon the future of kesterite photovoltaics and describe the likely future development of the material and its prospects for commercial deployment