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171.
We prove a 0‐1 law for the fragment of second order logic SO(∀∃*) over parametric classes of finite structures which allow only one unary atomic type. This completes the investigation of 0‐1 laws for fragments of second order logic defined in terms of first order quantifier prefixes over, e.g., simple graphs and tournaments. We also prove a low oscillation law, and establish the 0‐1 law for Σ14(∀∃*) without any restriction on the number of unary types. 相似文献
172.
Thomas R. Boussie Gary M. Diamond Christopher Goh Keith A. Hall Anne M. LaPointe Margarete K. Leclerc Vince Murphy James A. W. Shoemaker Howard Turner Robert K. Rosen James C. Stevens Francesca Alfano Vincenzo Busico Roberta Cipullo Giovanni Talarico 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2006,118(20):3356-3361
173.
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175.
Brad M. Rosen Gerard Lligadas Christian Hahn Virgil Percec 《Journal of polymer science. Part A, Polymer chemistry》2009,47(15):3931-3939
The development of a novel nucleophilic thio‐bromo “Click” reaction, specifically base‐mediated thioetherification of thioglycerol with α‐bromoesters, is reported. Combination of this thio‐bromo click reaction with subsequent acylation with 2‐bromopropionyl bromide provides an iterative two‐step divergent growth approach to the synthesis of a new class of poly(thioglycerol‐2‐propionate) (PTP) dendrimers. This approach is demonstrated in the rapid preparation of four generation (G1–G4) of PTP dendrimers with high‐structural fidelity. The isolated G1–G4 bromide‐terminated dendrimers can be used directly as dendritic macroinitiators for the synthesis of star‐polymers via SET‐LRP. Additionally, the intermediate hydroxy‐terminated dendrimers are analogs of other water‐soluble polyester and polyether dendrimers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3931–3939, 2009 相似文献
176.
Brad M. Rosen Virgil Percec 《Journal of polymer science. Part A, Polymer chemistry》2008,46(16):5663-5697
The heterolytic dissociation process associated with the activation of Single Electron‐Transfer Living Radical Polymerization is examined through the use of energy profile modeling. Monomer and initiator structure is correlated with the approximate activation barriers, energies of electrostatic ion‐radical pair formation, and stability of ion‐radical pair generated from the counteranion halide leaving group and the radical atom with partial positive charge density induced by its electron‐withdrawing substituent. Energy profiles permit access not just to one, but to all local minima, in the dissociation pathway and the identification of a global minimum. The location and energy of this global minimum allows for the placement of various initiators and dormant propagating macroradicals on the spectrum between stepwise and concerted dissociative electron‐transfer. The barrier for the activation step for alkyl‐halides derived from acrylates, vinyl halides, and styrenes, as well as from initiators bearing electron‐withdrawing groups is decreased in comparison to relatively more electron‐rich alkyl halides. This rate enhancement is explained through the sticky dissociative model wherein electron‐transfer is accelerated by the formation of strong ion‐radical pairs between radicals with partial positive charge density and their counteranion leaving group. Greater electron‐withdrawing capacity of the alkyl halide substituent increases the stability of the ion‐radical pair, reduces its equilibrium bond length, and accelerates electron‐transfer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5663–5697, 2008 相似文献
177.
Ryan C. Branski Katherine Verdolini Vlad Sandulache Clark A. Rosen Patricia A. Hebda 《Journal of voice》2006,20(3):432-442
SUMMARY: The basic science of wound healing is largely omitted from the curriculum of many voice clinicians. This fact is relatively disheartening as most therapeutic manipulation in the realm of laryngology and voice disorders deals with injured tissue. Therefore, the selection of therapeutic tasks for persons with vocal injury should ideally be informed by basic science in wound healing. Recently, several investigators have initiated lines of research to determine the course of vocal fold wound healing and the potential role of therapeutic agents, including behavioral agents. The current review seeks to provide a foundation of basic wound healing science and present the most current data regarding the wound healing process in the vocal folds. 相似文献
178.
T. Pavlin R. Wang R. McGorty M. S. Rosen D. G. Cory D. Candela R. W. Mair R. L. Walsworth 《Applied magnetic resonance》2007,32(1-2):93-112
We present a novel nuclear magnetic resonance (NMR) technique that provides a noninvasive, direct measurement of gas exchange
in a three-dimensional gas-fluidized bed of solid particles. The NMR spectrum of hyperpolarized 129Xe gas in an Al2O3 particle bed displays three resolved peaks corresponding to xenon in bubbles, the interstitial spaces (emulsion), and adsorbed
on particles. Modified NMR exchange and saturation recovery sequences, together with data analysis based on an exchange-coupled
set of Bloch equations, yield gas exchange rate constants between the emulsion and adsorbed phases, and between the bubble
and emulsion phases. The results are in approximate agreement with previously unverified predictions from well-known models
of fluidized bed behavior. Incorporation of NMR imaging methodologies would straightforwardly allow similar measurements on
a spatially resolved basis.
Authors' address: Ross W. Mair, Harvard Smithsonian Center for Astrophysics, MS 59, 60 Garden Street, Cambridge, MA 02138,
USA 相似文献
179.
Background
Freezing lesions to developing rat cortex induced between postnatal day (P) one and three (P1 – 3) lead to malformations similar to human microgyria, and further correspond to reductions in brain weight and cortical volume. In contrast, comparable lesions on P5 do not produce microgyric malformations, nor the changes in brain weight seen with microgyria. However, injury occurring at all three ages does lead to rapid auditory processing deficits as measured in the juvenile period. Interestingly, these deficits persist into adulthood only in the P1 lesion case [1]. Given prior evidence that early focal cortical lesions induce abnormalities in cortical morphology and connectivity [1–4], we hypothesized that the differential behavioral effects of focal cortical lesions on P1, P3 or P5 may be associated with underlying neuroanatomical changes that are sensitive to timing of injury. Clinical studies indicate that humans with perinatal brain injury often show regional reductions in corpus callosum size and abnormal symmetry, which frequently correspond to learning impairments [5–7]. Therefore, in the current study the brains of P1, 3 or 5 lesion rats, previously evaluated for brain weight, and cortical volume changes and auditory processing impairments (P21-90), were further analyzed for changes in corpus callosum volume. 相似文献180.
We present an experimental demonstration of the evolution of localization in frequency of light pulses that are repeatedly kicked by phase modulation and then propagated along equally spaced lengths of fiber with weak dispersion. The experiment was performed with a long fiber recirculating loop that allows us to follow the pulse's spectral changes after each cycle. 相似文献