775 research outputs found
Ab initio study of the giant ferroelectric distortion and pressure induced spin-state transition in BiCoO3
Using configuration-state-constrained electronic structure calculations based
on the generalized gradient approximation plus Hubbard U method, we sought the
origin of the giant tetragonal ferroelectric distortion in the ambient phase of
the potentially multiferroic material BiCoO3 and identified the nature of the
pressure induced spin-state transition. Our results show that a strong Bi-O
covalency drives the giant ferroelectric distortion, which is further
stabilized by an xy-type orbital ordering of the high-spin (HS) Co3+ ions. For
the orthorhombic phase under 5.8 GPa, we find that a mixed HS and low-spin (LS)
state is more stable than both LS and intermediate-spin (IS) states, and that
the former well accounts for the available experimental results. Thus, we
identify that the pressure induced spin-state transition is via a mixed HS+LS
state, and we predict that the HS-to-LS transition would be complete upon a
large volume decrease of about 20%.Comment: 6 pages, 6 figures, 2 table
Soil water distribution on different number of growing years of alfalfa pasture in the Loess Plateau of Northwest China
The alfalfa pastureland in the semiarid Loess Plateau region of Northwest China usually has dry soil layers. We studied the soil water variations on alfalfa (Medicago sativa L.) grassland with different number of growing years. Seven growing years of alfalfa grassland were chosen in this study: (1) 4-year-old, (2) 6-year-old, (3) 8-year-old, (4) 12-year-old, (5) 14-year-old, (6)18-year-old and (7) 26-year-old. The results showed that the highest soil water content, 12.0 -17.15%, with different number of growing years of alfalfa grassland occurred in 80 -100 cm soil layer, but gradually became stable below 300 cm soil layer. The soil water content with 4, 6 and 8 year alfalfa grassland was in the range of 13.66 - 14.76%, with 12 and 14 year ranged within 11.76 -1 1.87% and with 18 and 26 year within 10.5%. We also found that in 0 - 1000 cm soil layer, the soil water content with different number of growing years of alfalfa grassland had differences due to different soil water conditions and water-supplying capability. The soil water content with 4 and 6 year were 13.85 and 14.22%, respectively, with 8, 12 and 14 year were 12.98, 11.25 and 11.22%, respectively, and with 18 and 26 year were 10.27 and 10.76%, respectively. After alfalfa grew for >18 years, the annual recovery of its soil water at 0 - 200 cm soil depth was 1.49%, whereas the soil water with 18 and 26 year alfalfa pastureland at 200 - 1000 cm soil depth was only 10.10%, dry soil layers occurring in alfalfa pasture. The dry soil layer of alfalfa grassland appears at 160 - 600 cm soil depth in the Loess Plateau. We found that at 250 - 350 cm soil depth, the soil water content with 4 and 6 year alfalfa grassland was in the range of 10.23 - 10.48%, presenting slightly dry soil layer and for more than 8 year, alfalfa was in the range of 7.78 - 8.48%, presenting moderately dry soil layer. In summary, the soil water use of alfalfa would grow with the number of growing years and the depth of desiccated layers will become intensified and thicker.Keywords: Alfalfa grassland, different number of growing years, soil water content, dry soil layers, Loess Plateau of ChinaAfrican Journal of Biotechnology Vol. 9(35), pp. 5686-5693, 30 August, 201
Rare case of magnetic Ag ion: double perovskite CsKAgF
Normally or transition metals are in a low-spin state. Here using
first-principles calculations, we report on a rare case of a high-spin =1
magnetic state for the Ag ion in the double perovskite
CsKAgF. We also explored a possibility of a conventional low-spin
=0 ground state and find an associated tetragonal distortion to be 0.29
{\AA}. However, the lattice elastic energy cost and the Hund exchange loss
exceed the e crystal-field energy gain, thus making the low-spin
tetragonal structure less favorable than the high-spin cubic structure. We
conclude that the compact perovskite structure of CsKAgF is an
important factor in stabilizing the unusual high-spin ground state of
Ag.Comment: 6 pages, 6 figures, accepted for publication in PR
Multiobjective optimization of the production process for ground granulated blast furnace slags
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The production process of ground granulated blast furnace slag (GGBS) aims to produce products of the best grade and the highest yields. However, grade and yields are two competing objectives which can not be optimized at the same time by one single solution. Meanwhile, the production process is a multivariable strong coupling complicated nonlinear system. It is hard to establish the accurate mechanism model of this system. Considering above problems, we formulate the GGBS production process as an multiobjective optimization problem, introduce a least square support vector machine method based on particle swarm optimization to build the data-based system model and solve the corresponding multiobjective optimization problem by several multiobjective optimization evolutionary algorithms. Simulation example is presented to illustrate the performance of the presented multiobjective optimization scheme in GGBS production process
Use of the Nanobridge system for the Rapid Production of Pluipotent Stem Cells and Neural Progenitor Cells
The novel Nanobridge system allows the formation of cellular aggregates of pluripotent stem cells, which can then be grown in suspensions cultures allowing accurate control of the environment in which the cells are growing. The Nanobridge system utilizes a thermo-responsive poly N-isopropyl acrylamide (PNIPAM) polymer decorated with extracellular matrix (ECM) protein fragments (fibronectin or vitronectin) to bind to and bridge between adjacent cells and form cell aggregates at 370 C. A temperature shift from 370 C to 320 C causes the PNIPAM to become water soluble weakening the bonding between adjacent PNIPAM chains and allowing the aggregates to be broken down to smaller aggregates by increased shear forces. By returning the temperature to 370 C and increasing the culture volume with additional medium, the increased number of smaller aggregates are able to grow to a larger diameter. Repeating this cycle allows for the rapid expansion in cell numbers. In addition, the ability to vary the concentrations and ratios of the two components in the Nanobridge system, when coupled with the temperature shift procedure during passaging, allows for tight control over the aggregate diameters at all stages of the expansion process.
In this paper, two examples of using the Nanobridge system to culture stem cells will be described: firstly using the system for the rapid expansion of human embryonic stem cells whilst maintaining high viability and pluripotency, and secondly; using the system to develop a process to form neural cell aggregates and maintain and expand cells at a stem/progenitor (NPC) stage, obviating the need for the current cumbersome manual methods to produce larger numbers of NPCs.
In the first example, embryonic stem cells (hESC) WA09 were cultured in spinner flasks with the Nanobridge system. At the end of the growth phase, aggregates of 348 micron average diameter were reduced to an average diameter of 139microns after sub-passaging. When this cycle was repeated five times, there was a 500 fold increase in the number of cells produced, with a viability at the end of the process of 90% while maintaining key pluripotent markers NANOG, OCT3/4, SOX2, and DNMT3B. Characterization of the hESC aggregates was performed using the IN Cell Analyser 2200, which demonstrated that there was uniform cell viability and pluripotency marker distribution throughout the aggregates, ie there was no evidence of any diffusional limitations or necrotic regions within the aggregates. At the end of the expansion process it was shown that the cells were able to differentiate into all three germ layers, and that the cells could be converted, to cells types such as cardiomyocytes. The results demonstrate that the Nanobridge system is a simple and scalable method of producing large numbers of PSCs without the need for enzymes during passaging.
For the production of the neural progenitors (NPCs), hESC (WA09) cells were formed and cultured as Nanobridge aggregates with diameters of 200-300 mm. Differentiation was initiated by culturing the aggregates in mTESR medium with 5uM SB431542 and 100 nM LDN for 5 days. At day 5, the medium was changed to neural basal medium (NBM) supplemented with EGF and FGF2 for the next 5 days of culture. Cultures were maintained in NBM from day 10 onwards. Passaging was performed at day 5 and day 10 and thereafter on a weekly basis for 4 weeks. Temperature shift and mechanical shear were utilized to breakup aggregates and Nanobridge components and medium were replaced during passaging. Cells demonstrated upregulation and subsequent maintenance of neural-associated markers (PAX6, SOX1, and NCAM) in aggregate culture. Passaging resulted in an overall seven fold increase in the number of cells expressing the neural-associated markers. Furthermore, neural progenitor cell aggregates exhibited the capacity to differentiate towards a more mature phenotype as demonstrated by the outgrowth of neurites. This demonstrated that the Nanobridge system has the potential to facilitate the scale-up of NPC production in bioreactors for applications in regenerative medicine and pharmacological testing
SpotServe: Serving Generative Large Language Models on Preemptible Instances
The high computational and memory requirements of generative large language
models (LLMs) make it challenging to serve them cheaply. This paper aims to
reduce the monetary cost for serving LLMs by leveraging preemptible GPU
instances on modern clouds, which offer accesses to spare GPUs at a much
cheaper price than regular instances but may be preempted by the cloud at any
time. Serving LLMs on preemptible instances requires addressing challenges
induced by frequent instance preemptions and the necessity of migrating
instances to handle these preemptions.
This paper presents SpotServe, the first distributed LLM serving system on
preemptible instances. Several key techniques in SpotServe realize fast and
reliable serving of generative LLMs on cheap preemptible instances. First,
SpotServe dynamically adapts the LLM parallelization configuration for dynamic
instance availability and fluctuating workload, while balancing the trade-off
among the overall throughput, inference latency and monetary costs. Second, to
minimize the cost of migrating instances for dynamic reparallelization, the
task of migrating instances is formulated as a bipartite graph matching
problem, which uses the Kuhn-Munkres algorithm to identify an optimal migration
plan that minimizes communications. Finally, to take advantage of the grace
period offered by modern clouds, we introduce stateful inference recovery, a
new inference mechanism that commits inference progress at a much finer
granularity and allows SpotServe to cheaply resume inference upon preemption.
We evaluate on real spot instance preemption traces and various popular LLMs
and show that SpotServe can reduce the P99 tail latency by 2.4 - 9.1x compared
with the best existing LLM serving systems. We also show that SpotServe can
leverage the price advantage of preemptive instances, saving 54% monetary cost
compared with only using on-demand instances.Comment: ASPLOS 202
4-[(9-Ethyl-9H-carbazol-3-yl)iminoÂmethÂyl]phenol
In the title compound, C21H18N2O, the dihedral angle between the phenol ring and the carbazole system is 39.34 (2)°. InterÂmolecular O—H⋯N hydrogen bonds and C—H⋯π and π–π interÂactions [centroid–centroid distances = 3.426 (2) and 3.768 (2) Å] stabilize the crystal structure
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