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排序方式: 共有133条查询结果,搜索用时 15 毫秒
71.
Dr. Krishnamoorthy Sathiyan Dr. Ronen Bar-Ziv Dr. Vered Marks Prof. Dr. Dan Meyerstein Dr. Tomer Zidki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(64):15936-15943
Photocatalytic hydrogen production is proposed as a sustainable energy source. Simultaneous reduction and oxidation of water is a complex multistep reaction with high overpotential. Photocatalytic processes involving semiconductors transfer electrons from the valence band to the conduction band. Sacrificial substrates that react with the photochemically formed holes in the valence band are often used to study the mechanism of H2 production, as they scavenge the holes and hinder charge carrier recombination (electron-hole pairs). Here, we show that the desired sacrificial agent is one forming a radical that is a fairly strong reducing agent, and whose oxidized form is not a good electron acceptor that might suppress the hydrogen evolution reaction (HER). In an acidic medium, methanol was found to fulfill both these requirements better than ethanol and propan-2-ol in the TiO2-(M0-NPs) (M=Au or Pt) system, whereas in an alkaline medium, the alcohols exhibit a reverse order of activity. Moreover, we report that CH2(OH)2 is by far the most efficient sacrificial agent in a nontrivial mechanism in acidic media. Our study provides general guidelines for choosing an appropriate sacrificial substrate and helps to explain the variance in the performance of alcohol scavenger-based photocatalytic systems. 相似文献
72.
Ronen Peretz 《Applied Mathematics Letters》2011,24(6):850-853
In this paper we give a geometric proof for a version of the Pinchuk solution of the Strong Real Jacobian Conjecture. Moreover, we compute the location of the zero sets on the Pinchuk surface of the determinant of the Jacobians of the corresponding étale mappings. 相似文献
73.
Joshua Ray Windmiller Gabriela Valdés‐Ramírez Nandi Zhou Ming Zhou Philip R. Miller Chunming Jin Susan M. Brozik Ronen Polsky Evgeny Katz Roger Narayan Joseph Wang 《Electroanalysis》2011,23(10):2302-2309
This article describes the design of a new and attractive minimally‐invasive bicomponent microneedle sensing device for the electrochemical monitoring of the excitatory neurotransmitter glutamate and glucose. The new device architecture relies on the close integration of solid and hollow microneedles into a single biosensor array device containing multiple microcavities. Such microcavities facilitate the electropolymeric entrapment of the recognition enzyme within each microrecess. The resulting microneedle biosensor array can be employed as a minimally‐invasive on‐body transdermal patch, obviating the extraction/sampling of the biological fluid, thereby simplifying device requirements. The new concept is demonstrated for the electropolymeric entrapment of glutamate oxidase and glucose oxidase within a poly(o‐phenylenediamine) (PPD) thin film. The PPD‐based enzyme entrapment methodology enables the effective rejection of coexisting electroactive interferents without compromising the sensitivity or response time of the device. The resulting microneedle‐based glutamate and glucose biosensors thus exhibit high selectivity, sensitivity, speed, and stability in both buffer and undiluted human serum. High‐fidelity glutamate measurements down to the 10 µM level are obtained in serum. The attractive recess design also serves to protect the enzyme layer upon insertion into the skin. This simple, yet robust microneedle design is well‐suited for diverse biosensing applications in which real‐time metabolite monitoring is a core requirement. 相似文献
74.
Ronen Peretz 《Complex Analysis and Operator Theory》2013,7(5):1655-1674
The motivation for this paper comes from new ideas for solving the two-dimensional Jacobian Conjecture. The Jacobian Conjecture is one of the most famous open problems in algebraic geometry. This long-standing conjecture is no doubt one of the central problems in this well developed field of mathematics and hence the importance of investigating it. We can consider a semigroup of local diffeomorphisms on the affine space with a composition of mappings as its binary operation. We put a geometric fractal-like structure on this semigroup after equipping it with a natural metric (this is heavily dependent on the fact that our mappings are local diffeomorphisms). This structure is much more general than the structure of the ind-variety suggested by Kambayashi for étale polynomial mappings in the algebraic context. Hence, it applies to other semigroups such as the semigroup of all the entire functions in one complex variable with a nonvanishing first order derivative. This last semigroup is the theme of the current paper. We hope that the corresponding Hausdorff measure and Hausdorff dimension will enable us to relate the structure of the semigroup with arithmetic machinery such as certain Zeta functions. 相似文献
75.
Ronen Peretz 《Complex Analysis and Operator Theory》2013,7(1):183-191
We give applications of the discontinuity function of a discrete group for Fuchsian groups which act on the unit disk and which are finitely generated. We obtain two sets of theorems: One set corresponds to the Euclidean metric. The second set corresponds to the hyperbolic metric. These theorems state inequalities that involve combinatorial quantities (such as counting functions of the elements of the group with a given bounded length, or the order of growth of the group) and geometric quantities (such as distances of the images of a point under a fixed set of generators to the unit circle, or hyperbolic areas of certain disks). This paper is a sequel to the paper “The Discontinuity Function of Discrete Groups and Radius of Schlichtness” by the author, that recently appeared in this journal. 相似文献
76.
Xiao X Nogan J Beechem T Montaño GA Washburn CM Wang J Brozik SM Wheeler DR Burckel DB Polsky R 《Chemical communications (Cambridge, England)》2011,47(35):9858-9860
Interferometric lithographically fabricated porous carbon acts as active substrates for Surface Enhanced Raman Scattering (SERS) applications with enhancement factors ranging from 7 to 9 orders of magnitude. 相似文献
77.
Gottesman R Shukla S Perkas N Solovyov LA Nitzan Y Gedanken A 《Langmuir : the ACS journal of surfaces and colloids》2011,27(2):720-726
Colloidal silver has gained wide acceptance as an antimicrobial agent, and various substrates coated with nanosilver such as fabrics, plastics, and metal have been shown to develop antimicrobial properties. Here, a simple method to develop coating of colloidal silver on paper using ultrasonic radiation is presented, and the coatings are characterized using X-ray diffraction (XRD), high resolution scanning electron microscope (HRSEM), and thermogravimetry (TGA) measurements. Depending on the variables such as precursor concentrations and ultrasonication time, uniform coatings ranging from 90 to 150 nm in thickness have been achieved. Focused ion beam (FIB) cross section imaging measurements revealed that silver nanoparticles penetrated the paper surface to a depth of more than 1 μm, resulting in highly stable coatings. The coated paper demonstrated antibacterial activity against E. coli and S. aureus, suggesting its potential application as a food packing material for longer shelf life. 相似文献
78.
Golberg-Oster O Bar-Ziv R Yardeni G Zilbermann I Meyerstein D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(33):9226-9231
Methyl radicals react with TiO(2) nanoparticles (NPs) immersed in aqueous solutions to form transients in which the methyls are covalently bound to the particles. The rate constant for this reaction approaches the diffusion-controlled limit and increases somewhat with the number of methyls bound to the particle. The transients decompose to yield ethane. Thus, formally the particles "catalyse" the dimerization of the radicals, a reaction that is diffusion-controlled. Rutile powders behave similarly to the TiO(2) NPs whereas the mechanism for the decomposition of the transients formed in the analogous reaction of the radicals with anatase powders differs. These results are of importance as alkyl radicals are formed near the surface of TiO(2) in a variety of important photocatalytic processes. The results imply that the reactions of alkyl radicals with TiO(2) have to be considered in these processes. 相似文献
79.
The Nisan–Wigderson pseudo-random generator [19] was constructed to derandomize probabilistic algorithms under the assumption
that there exist explicit functions which are hard for small circuits. We give the first explicit construction of a pseudo-random
generator with asymptotically optimal seed length even when given a function which is hard for relatively small circuits.
Generators with optimal seed length were previously known only assuming hardness for exponential size circuits [13,26].
We also give the first explicit construction of an extractor which uses asymptotically optimal seed length for random sources
of arbitrary min-entropy. Our construction is the first to use the optimal seed length for sub-polynomial entropy levels.
It builds on the fundamental connection between extractors and pseudo-random generators discovered by Trevisan [29], combined
with the construction above.
The key is a new analysis of the NW-generator [19]. We show that it fails to be pseudorandom only if a much harder function
can be efficiently constructed from the given hard function. By repeatedly using this idea we get a new recursive generator,
which may be viewed as a reduction from the general case of arbitrary hardness to the solved case of exponential hardness.
* This paper is based on two conference papers [11,12] by the same authors.
† Research Supported by NSF Award CCR-9734911, NSF Award CCR-0098197, Sloan Research Fellowship BR-3311, grant #93025 of the
joint US-Czechoslovak Science and Technology Program, and USA-Israel BSF Grant 97-00188.
‡ Part of this work was done while at the Hebrew University and the Institute for advanced study.
§ This research was supported by grant number 69/96 of the Israel Science Foundation, founded by the Israel Academy for Sciences
and Humanities and USA-Israel BSF Grant 97-00188. 相似文献
80.
We investigate the structure of trapped Bose-Einstein condensates (BECs) with long-range anisotropic dipolar interactions. We find that a small perturbation in the trapping potential can lead to dramatic changes in the condensate's density profile for sufficiently large dipolar interaction strengths and trap aspect ratios. By employing perturbation theory, we relate these oscillations to a previously identified "rotonlike" mode in dipolar BECs. The same physics is responsible for radial density oscillations in vortex states of dipolar BECs that have been predicted previously. 相似文献