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排序方式: 共有155条查询结果,搜索用时 15 毫秒
61.
Ron G Glister J Lee B Allada K Armstrong W Arrington J Beck A Benmokhtar F Berman BL Boeglin W Brash E Camsonne A Calarco J Chen JP Choi S Chudakov E Coman L Craver B Cusanno F Dumas J Dutta C Feuerbach R Freyberger A Frullani S Garibaldi F Gilman R Hansen O Higinbotham DW Holmstrom T Hyde CE Ibrahim H Ilieva Y de Jager CW Jiang X Jones MK Kang H Kelleher A Khrosinkova E Kuchina E Kumbartzki G LeRose JJ Lindgren R Markowitz P May-Tal Beck S McCullough E Meekins D Meziane M Meziani ZE Michaels R 《Physical review letters》2007,99(20):202002
High-precision measurements of the proton elastic form-factor ratio, mu pG p E/G p M, have been made at four-momentum transfer, Q2, values between 0.2 and 0.5 GeV2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q2 range the deviation from unity is primarily due to G p E being smaller than expected. 相似文献
62.
J. William Helton Igor Klep Scott McCullough 《Journal of Mathematical Analysis and Applications》2011,376(2):407-428
In this paper, we analyze problems involving matrix variables for which we use a noncommutative algebra setting. To be more specific, we use a class of functions (called NC analytic functions) defined by power series in noncommuting variables and evaluate these functions on sets of matrices of all dimensions; we call such situations dimension-free. These types of functions have recently been used in the study of dimension-free linear system engineering problems (Helton et al. (2009) [10], de Oliviera et al. (2009) [8]). In the earlier paper (Helton et al. (2009) [9]) we characterized NC analytic maps that send dimension-free matrix balls to dimension-free matrix balls and carry the boundary to the boundary; such maps we call “NC ball maps”. In this paper we turn to a more general dimension-free ball BL, called a “pencil ball”, associated with a homogeneous linear pencil
63.
Miller KM McCullough SM Lepekhina EA Thibau IJ Pike RD Li X Killarney JP Patterson HH 《Inorganic chemistry》2011,50(15):7239-7249
A series of metal-organic networks of CuSCN were prepared by direct reactions with substituted pyridine and aliphatic amine ligands, L. Thiocyanate bridging is seen in all but 1 of 11 new X-ray structures. Structures are reported for (CuSCN)L sheets (L = 3-chloro- and 3-bromopyridine, N-methylmorpholine), ladders (L = 2-ethylpyridine, N-methylpiperidine), and chains (L = 2,4,6-collidine). X-ray structures of (CuSCN)L(2) are chains (L = 4-ethyl- and 4-t-butylpyridine, piperidine, and morpholine). A unique N-thiocyanato monomer structure, (CuSCN)(3-ethylpyridine)(3), is also reported. In most cases, amine ligands are thermally released at temperatures <100 °C. Strong yellow-to-green luminescence at ambient temperature is observed for the substituted pyridine complexes. High solid state quantum efficiencies are seen for many of the CuSCN-L complexes. Microsecond phosphorescence lifetimes seen for CuSCN-L are in direct contrast to the nanosecond-lifetime emission of CuSCN. MLCT associated with pyridine π* orbitals is proposed as the excitation mechanism. 相似文献
64.
McCullough MP Huffaker R Marsh TL 《Nonlinear dynamics, psychology, and life sciences》2012,16(2):205-231
This paper applies the techniques of phase space reconstruction and recurrence quantification analysis to investigate U.S. livestock cycles in relation to recent literature on the business cycle. Results are presented for pork and cattle cycles, providing empirical evidence that the cycles themselves have slowly diminished. By comparing the evolution of production processes for the two livestock cycles we argue that the major cause for this moderation is largely endogenous. The analysis suggests that previous theoretical models relying solely on exogenous shocks to create cyclical patterns do not fully capture changes in system dynamics. Specifically, the biological constraint in livestock dynamics has become less significant while technology and information are relatively more significant. Concurrently, vertical integration of the supply chain may have improved inventory management, all resulting in a small, less deterministic, cyclical effect. 相似文献
65.
Let Ω be a region in the complex plane. In this paper we introduce a class of sesquianalytic reproducing kernels on Ω that we call B-kernels. When Ω is the open unit disk
and certain natural additional hypotheses are added we call such kernels k Bergman-type kernels. In this case the associated reproducing kernel Hilbert space
(k) shares certain properties with the classical Bergman space L2α of the unit disk. For example, the weighted Bergman kernels kβw(z)=(1−wz)−β, 1β2 are Bergman-type kernels. Furthermore, for any Bergman-type kernel k one has H2
(k)L2a, where the inclusion maps are contractive, and Mζ, the operator of multiplication with the identity function ζ, defines a contraction operator on
(k). Our main results about Bergman-type kernels k are the following two: First, once properly normalized, the reproducing kernel for any nontrivial zero based invariant subspace
of
(k) is a Bergman-type kernel as well. For the weighted Bergman kernels kβ this result even holds for all
ζ-invariant subspace
of index 1, i.e., whenever the dimension of
/ζ
is one. Second, if
is any multiplier invariant subspace of
(k), and if we set
*=
z
, then Mζ
is unitarily equivalent to Mζ acting on a space of
*-valued analytic functions with an operator-valued reproducing kernel of the type
where V is a contractive analytic function V :
→
(
,
*), for some auxiliary Hilbert space
. Parts of these theorems hold in more generality. Corollaries include contractive divisor, wandering subspace, and dilation theorems for all Bergman-type reproducing kernel Hilbert spaces. When restricted to index one invariant subspaces of
(kβ), 1β2, our approach yields new proofs of the contractive divisor property, the strong contractive divisor property, and the wandering subspace theorems and inner–outer factorization. Our proofs are based on the properties of reproducing kernels, and they do not involve the use of biharmonic Green functions as had some of the earlier proofs. 相似文献
Full-size image
66.
Simple Zeros of the Riemann Zeta-Function 总被引:1,自引:0,他引:1
Assuming the Riemann Hypothesis, Montgomery showed by meansof his pair correlation method that at least two-thirds of thezeros of Riemann's zeta-function are simple. Later he and Taylorimproved this to 67.25 percent and, more recently, Cheer andGoldston increased the percentage to 67.2753. Here we proveby a new method that if the Riemann and Generalized LindelöofHypotheses hold, then at least 70.3704 percent of the zerosare simple and at least 84.5679 percent are distinct. Our methoduses mean value estimates for various functions defined by Dirichletseries sampled at the zeros of the Riemann zeta-function. 1991Mathematics Subject Classification: 11M26. 相似文献
67.
Summary The synthesis of the new unsymmetrically substituted 16-membered macrocyclic complex, (3-acetyl-2,10,12-trimethyl-1, 5, 9,
13-tetraazacyclohexadeca-1, 3, 9, 11-tetraenato)-NiII, by template-controlled macrocyclization is reported. This complex has a single nucleophilic site available to react with
electrophilic reagents. The crystal structure of the acyclic precursor, (3-acetyl-10-methyl-5,9-diazatrideca-3, 8-diene-2,12-dionato)NiII shows that in the solid state it exists as a pair of enantiomers, arising from the presence of two possible skew boat conformations
adopted by the six-membered saturated metallochelate ring present in the molecule. 相似文献
68.
Cyclic voltammetry studies have shown that in the electro-oxidation of phenylindenes, the reaction pathway can be markedly dependent on the salt used as electrolyte, particularly when the substrate (indene) contains a relatively acidic hydrogen. 相似文献
69.
Li J Janout V McCullough DH Hsu JT Truong Q Wilusz E Regen SL 《Langmuir : the ACS journal of surfaces and colloids》2004,20(19):8214-8219
The monolayer properties of 5,11,17,23,29,35-hexakis[(N,N,N-trimethylamonium)-N-methyl-37,38,39,40,41,42-hexakis-n-hexadecyloxy-calix[6]arene hexachloride (1) have been characterized over aqueous solutions of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) as a function of pH. At high pH values (e.g., pH 10), such monolayers show relatively low surface viscosities. At low pH (e.g., pH 4.4), these monolayers exhibit relatively high surface viscosities. The barrier properties of single Langmuir-Blodgett bilayers of 1, which have been ionically cross-linked (i.e., "glued together") with PAA were found to correlate with changes in surface viscosity. Thus, bilayers that were fabricated under low pH conditions exhibited high permeation barriers and high permeation selectivity with respect to He and N(2). Given the extreme thinness of these glued bilayers (ca. 6 nm), the optimized He/N(2) selectivity of ca. 1000 is extraordinary. These results, taken together, demonstrate the feasibility of fine tuning the surface viscosity of monolayers of 1, and also the barrier properties of corresponding glued bilayers, by adjusting the pH of an aqueous subphase that contains a weak polyacid. 相似文献
70.
J L McCullough G D Weinstein J L Douglas M W Berns 《Photochemistry and photobiology》1987,46(1):77-82
Systemic injection of hematoporphyrin derivative (HpD) in contribution with visible light (red or blue-green) delivered by laser was used to treat a patient with psoriasis. The psoriatic lesions responded vigorously to laser treatments, forming eschars by 1 week post irradiation. In contrast, only minimal erythema was observed in the noninvolved, clinically normal appearing skin. Two approaches for localized HpD administration were investigated in the guinea-pig and minipig models as a means of achieving local photodynamic effects. Intracutaneous injection of HpD produced localized cutaneous photosensitization with either UVA or red light. Azone increased percutaneous penetration of HpD in human skin in vitro. Topical application of HpD and irradiation with UVA produced localized cutaneous photosensitivity and inhibition of epidermal DNA synthesis. 相似文献