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781.
Stephen M. Buckley 《Journal d'Analyse Mathématique》1999,79(1):215-240
The concept of an H-chain set in a doubling spaceX, which generalizes that of a Hölder domain in Euclidean space, is defined and investigated. We show that every H-chain set is mean porous and that its outer layer has measure bounded by a power of its thickness. As a consequence, we show that a John-Nirenberg type inequality holds on an open subset Ω ofX if, and often only if, Ω is an H-chain set. 相似文献
782.
Andy B. Anderson 《The Journal of mathematical sociology》2013,37(1):69-83
Individuals simultaneously choose and are affected by their web of connections. This paper explores this co‐evolution of individual and network in the context of longitudinal attitudinal and sociometric data collected from a government agency, the Office of Information and Regulatory Affairs. Analysis of these data suggests that networks vary in their elasticity ‐ where the internal network of the agency was rigid, but the extra‐organizational network quite fluid. Further, the data suggest that, consistent with theories of socialization, individuals differ in plasticity ‐ how they are affected by the network ‐ where the cross‐sectional analysis of the data suggest that individuals were molded by the organization, but that the attitudes of individuals who left were unaffected by the change in milieu. 相似文献
783.
The cosmological natural selection (CNS) hypothesis holds that the fundamental constants of nature have been fine‐tuned by an evolutionary process in which universes produce daughter universes via the formation of black holes. Here, we formulate the CNS hypothesis using standard mathematical tools of evolutionary biology. Specifically, we capture the dynamics of CNS using Price's equation, and we capture the adaptive purpose of the universe using an optimization program. We establish mathematical correspondences between the dynamics and optimization formalisms, confirming that CNS acts according to a formal design objective, with successive generations of universes appearing designed to produce black holes. © 2013 Wiley Periodicals, Inc. Complexity 18: 48–56, 2013 相似文献
784.
We demonstrate, for the first time to our knowledge, an optical parametric amplifier directly pumped by a femtosecond oscillator. Wavelength-tunable pulses in the ranges 0.65-0.85 microm (signal) and 1.4-2.5 microm (idler) are generated at a repetition frequency of 1 MHz. For pumping the beta-barium borate crystal we use a microjoule Yb:KY(WO4)2 femtosecond oscillator with cavity dumping. Pulses with 30 nJ of energy and a duration of 16 fs are achieved from a supercontinuum seed generated in a sapphire plate. 相似文献
785.
In this paper, the fabrication and characterization of a high-index low loss polyethylene terephatate (PET) optical waveguide is presented. Dip-coating technique has been used to fabricate the optical waveguide using PET. Various waveguide properties, such as mode effective refractive index, optical loss, dispersion and waveguide thickness as a function of temperature of waveguides and substrates have been reported. Optical losses of as low as 0.7 dB cm–1 waveguides can be obtained if the formation temperature can be controlled between 30 and 35°C. In addition, we suggested that it is a suitable material for optoelectronic waveguide devices. 相似文献
786.
On the Design of Optimization Strategies Based on Global Response Surface Approximation Models 总被引:1,自引:0,他引:1
András?SóbesterEmail author Stephen?J.?Leary Andy?J.?Keane 《Journal of Global Optimization》2005,33(1):31-59
Striking the correct balance between global exploration of search spaces and local exploitation of promising basins of attraction
is one of the principal concerns in the design of global optimization algorithms. This is true in the case of techniques based
on global response surface approximation models as well. After constructing such a model using some initial database of designs
it is far from obvious how to select further points to examine so that the appropriate mix of exploration and exploitation
is achieved. In this paper we propose a selection criterion based on the expected improvement measure, which allows relatively
precise control of the scope of the search. We investigate its behavior through a set of artificial test functions and two
structural optimization problems. We also look at another aspect of setting up search heuristics of this type: the choice
of the size of the database that the initial approximation is built upon. 相似文献
787.
Andy Wijaya Katherine A. Brown Joshua D. Alper Kimberly Hamad-Schifferli 《Journal of magnetism and magnetic materials》2007
Fe-doped Au nanoparticles are ideal for biological applications over magnetic oxides due to their conjugation chemistry, optical properties, and surface chemistry. We present an AC magnetic field heating study of 8 nm Fe-doped Au nanoparticles which exhibit magnetic behavior. Magnetic heating experiments were performed on stable aqueous solutions of the nanoparticles at room temperature. The nanoparticles exhibit magnetic field heating, with a specific absorption rate (SAR) of 1.84 W/g at 40 MHz and H=100 A/m. The frequency dependence of the heating follows general trends predicted by power loss equations and is similar to traditional materials. 相似文献
788.
Microcapillary liquid chromatography/tandem mass spectrometry using alkaline pH mobile phases and positive ion detection 总被引:1,自引:0,他引:1
Extending the dynamic range of microcapillary liquid chromatography/tandem mass spectrometry (LC/MS/MS) peptide sequencing methods is essential for extracting new discoveries from proteomic studies. The complexity of global protein digests and in vivo processed peptide repertoires (as isolated from immunologically important HLA complexes) have led to the development of novel separation methods to increase the number of peptides identified by a single analysis. Separation of complex mixtures by multidimensional high-performance liquid chromatography (HPLC) decreases the number of isolated peptides contained in each fraction and increases the likelihood of detecting low abundant peptides in a background of dominant signals. In this study, we have evaluated the use of two dimensions of reversed-phase chromatography for resolving and sequencing naturally processed HLA-A2 presented peptide repertoires. The first dimension of separation was reversed-phase chromatography using the strong ion pairing reagent trifluoroacetic acid (TFA) to ensure the highest efficiency of peptide fractionation. The second dimension of reversed-phase chromatography was online with an electrospray ionization (ESI) ion trap mass spectrometer. Mobile phases used for the second dimension of chromatography were modified with volatile reagents including a contemporary acetate-modified acidic solvent, which was compared with mobile phases prepared with ammonium hydroxide at an alkaline pH. As expected, we demonstrate improved separation of the HLA-A2 presented fractions using the alkaline pH conditions. However, less obvious was the improved peptide signal-to-noise detected for peptide signals by positive ion ESI ion trap mass spectrometric detection, which was attributed to a reduced chemical background when using the alkaline pH mobile phases that allowed the ion trap to fill with the peptide ions until the automatic gain control detected a full trap. The term 'wrong-way-round ionization' has been used to describe intense [M+H](+) ions generated during ESI under strongly basic solutions. Ultimately, a larger number of the HLA-A2 peptide repertoire was sequenced by coupling TFA-modified reversed-phase fractionation with alkaline-modified microcapillary LC/MS/MS analysis of each fraction. In the present report, we compare the two second-dimension approaches and demonstrate the quality of data that was acquired using alkaline pH reversed-phase conditions. 相似文献
789.
Dr. Heather Au Dr. Noelia Rubio Dr. David J. Buckley Dr. Cecilia Mattevi Prof. Milo S. P. Shaffer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6545-6553
Graphite intercalation compounds (GICs) are often used to produce exfoliated or functionalised graphene related materials (GRMs) in a specific solvent. This study explores the formation of the Na-tetrahydrofuran (THF)-GIC and a new ternary system based on dimethylacetamide (DMAc). Detailed comparisons of in situ temperature dependent XRD with TGA-MS and Raman measurements reveal a series of dynamic transformations during heating. Surprisingly, the bulk of the intercalation compound is stable under ambient conditions, trapped between the graphene sheets. The heating process drives a reorganisation of the solvent and Na molecules, then an evaporation of the solvent; however, the solvent loss is arrested by restacking of the graphene layers, leading to trapped solvent bubbles. Eventually, the bubbles rupture, releasing the remaining solvent and creating expanded graphite. These trapped dopants may provide useful property enhancements, but also potentially confound measurements of grafting efficiency in liquid-phase covalent functionalization experiments on 2D materials. 相似文献
790.