444 research outputs found
Study of permeability characteristics of membranes Quarterly progress report, 9 Apr. - 9 Aug. 1968
Electrochemical cell constructed to measure membrane transport propertie
Study of permeability characteristics of membranes Quarterly reports, 9 Nov. 1967 - 9 Apr. 1968
Permeability characteristics and transport properties of membranes for salt water conversion, and experiment design
Matrix exponential via Clifford algebras
We use isomorphism between matrix algebras and simple orthogonal
Clifford algebras \cl(Q) to compute matrix exponential of a real,
complex, and quaternionic matrix A. The isomorphic image in
\cl(Q), where the quadratic form has a suitable signature is
exponentiated modulo a minimal polynomial of using Clifford exponential.
Elements of \cl(Q) are treated as symbolic multivariate polynomials in
Grassmann monomials. Computations in \cl(Q) are performed with a Maple
package `CLIFFORD'. Three examples of matrix exponentiation are given
Differential geometry with a projection: Application to double field theory
In recent development of double field theory, as for the description of the
massless sector of closed strings, the spacetime dimension is formally doubled,
i.e. from D to D+D, and the T-duality is realized manifestly as a global O(D,D)
rotation. In this paper, we conceive a differential geometry characterized by a
O(D,D) symmetric projection, as the underlying mathematical structure of double
field theory. We introduce a differential operator compatible with the
projection, which, contracted with the projection, can be covariantized and may
replace the ordinary derivatives in the generalized Lie derivative that
generates the gauge symmetry of double field theory. We construct various gauge
covariant tensors which include a scalar and a tensor carrying two O(D,D)
vector indices.Comment: 1+22 pages, No figure; a previous result on 4-index tensor removed,
presentation improve
Breathing silicon anodes for durable high-power operations
Silicon anode materials have been developed to achieve high capacity lithium ion batteries for operating smart phones and driving electric vehicles for longer time. Serious volume expansion induced by lithiation, which is the main drawback of silicon, has been challenged by multi-faceted approaches. Mechanically rigid and stiff polymers (e.g. alginate and carboxymethyl cellulose) were considered as the good choices of binders for silicon because they grab silicon particles in a tight and rigid way so that pulverization and then break-away of the active mass from electric pathways are suppressed. Contrary to the public wisdom, in this work, we demonstrate that electrochemical performances are secured better by letting silicon electrodes breathe in and out lithium ions with volume change rather than by fixing their dimensions. The breathing electrodes were achieved by using a polysaccharide (pullulan), the conformation of which is modulated from chair to boat during elongation. The conformational transition of pullulan was originated from its a glycosidic linkages while the conventional rigid polysaccharide binders have beta linkages.119201sciescopu
How a Diverse Research Ecosystem Has Generated New Rehabilitation Technologies: Review of NIDILRRās Rehabilitation Engineering Research Centers
Over 50 million United States citizens (1 in 6 people in the US) have a developmental, acquired, or degenerative disability. The average US citizen can expect to live 20% of his or her life with a disability. Rehabilitation technologies play a major role in improving the quality of life for people with a disability, yet widespread and highly challenging needs remain. Within the US, a major effort aimed at the creation and evaluation of rehabilitation technology has been the Rehabilitation Engineering Research Centers (RERCs) sponsored by the National Institute on Disability, Independent Living, and Rehabilitation Research. As envisioned at their conception by a panel of the National Academy of Science in 1970, these centers were intended to take a ātotal approach to rehabilitationā, combining medicine, engineering, and related science, to improve the quality of life of individuals with a disability. Here, we review the scope, achievements, and ongoing projects of an unbiased sample of 19 currently active or recently terminated RERCs. Specifically, for each center, we briefly explain the needs it targets, summarize key historical advances, identify emerging innovations, and consider future directions. Our assessment from this review is that the RERC program indeed involves a multidisciplinary approach, with 36 professional fields involved, although 70% of research and development staff are in engineering fields, 23% in clinical fields, and only 7% in basic science fields; significantly, 11% of the professional staff have a disability related to their research. We observe that the RERC program has substantially diversified the scope of its work since the 1970ās, addressing more types of disabilities using more technologies, and, in particular, often now focusing on information technologies. RERC work also now often views users as integrated into an interdependent society through technologies that both people with and without disabilities co-use (such as the internet, wireless communication, and architecture). In addition, RERC research has evolved to view users as able at improving outcomes through learning, exercise, and plasticity (rather than being static), which can be optimally timed. We provide examples of rehabilitation technology innovation produced by the RERCs that illustrate this increasingly diversifying scope and evolving perspective. We conclude by discussing growth opportunities and possible future directions of the RERC program
Observation of impurity accumulation and its compatibility with high plasma performance in W7-X
At the W7-X stellarator, the bolometer system has measured an intensive radiation zone in the inner plasma region (at a normalized radius Ļ ā¼ 0.3ā0.4) in the hydrogen plasma generated by electron cyclotron resonance heating; it differs from the normal plasma radiation distribution with an edge-localized emission zone. Spectroscopic diagnostics have recorded high-Z elements such as iron. This phenomenon happens in the plasma phases after gas supply turn-off, which results in all impurity relevant diagnostic signals increasing for several seconds. Despite the enhancement of the core radiation, the plasma energy confinement is improved. A transport analysis shows that this impurity radiation behavior is associated with a low diffusion coefficient (Dā¼ 0.02 m2 sā1) and a reversal of the convection around the radial position of the emission peak, which, under normal conditions, separates the zones of outward convection in the central (|V| ā¼ 0.1 m sā1) and inward convection in the outer region (|V| ā¼ 0.3 m sā1). An impurity accumulation around this radial position has been identified. The transport coefficients obtained are comparable with the theoretical predictions of collisional impurity transport. In the plasma phases studied, both impurity and energy confinement are enhanced. The mechanism responsible for the improvement is believed to be a reduction of micro-instabilities associated with the observed steepening of the density profile, initiated by a low edge plasma density (<1.0 Ć 1019 mā3) after switching off the gas fueling. The normalized temperature and density gradients fulfil the condition for the suppression of ITG turbulence
Quantum-Dot Light-Emitting Diodes with Nitrogen-Doped Carbon Nanodot Hole Transport and Electronic Energy Transfer Layer
Electroluminescence efficiency is crucial for the application of quantum-dot light-emitting diodes (QD-LEDs) in practical devices. We demonstrate that nitrogen-doped carbon nanodot (N-CD) interlayer improves electrical and luminescent properties of QD-LEDs. The N-CDs were prepared by solution-based bottom up synthesis and were inserted as a hole transport layer (HTL) between other multilayer HTL heterojunction and the red-QD layer. The QD-LEDs with N-CD interlayer represented superior electrical rectification and electroluminescent efficiency than those without the N-CD interlayer. The insertion of N-CD layer was found to provoke the Forster resonance energy transfer (FRET) from N-CD to QD layer, as confirmed by time-integrated and - resolved photoluminescence spectroscopy. Moreover, hole-only devices (HODs) with N-CD interlayer presented high hole transport capability, and ultraviolet photoelectron spectroscopy also revealed that the N-CD interlayer reduced the highest hole barrier height. Thus, more balanced carrier injection with sufficient hole carrier transport feasibly lead to the superior electrical and electroluminescent properties of the QD-LEDs with N-CD interlayer. We further studied effect of N-CD interlayer thickness on electrical and luminescent performances for high-brightness QD-LEDs. The ability of the N-CD interlayer to improve both the electrical and luminescent characteristics of the QD-LEDs would be readily exploited as an emerging photoactive material for high-efficiency optoelectronic devices.ope
The Arabidopsis ABA-Activated Kinase OST1 Phosphorylates the bZIP Transcription Factor ABF3 and Creates a 14-3-3 Binding Site Involved in Its Turnover
indicates that members of the Snf1-Related Kinases 2 family (SnRK2) are essential in mediating various stress-adaptive responses. Recent reports have indeed shown that one particular member, OPEN STOMATA (OST)1, whose kinase activity is stimulated by the stress hormone abscisic acid (ABA), is a direct target of negative regulation by the core ABA co-receptor complex composed of PYR/PYL/RCAR and clade A Protein Phosphatase 2C (PP2C) proteins. and that phospho-T451 is important for stabilization of ABF3. on T451 to create a 14-3-3 binding motif. In a wider physiological context, we propose that the long term responses to ABA that require sustained gene expression is, in part, mediated by the stabilization of ABFs driven by ABA-activated SnRK2s
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