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911.
A series of SERS-active nanostructures were produced by exposing a freshly deposited silver film (fabricated to be as free from roughness as practicable) to a solution containing a mixture of 1-decanethiol (m) and 1,9-nonanedithiol (d) of varying concentrations of m to d, then allowing colloidal silver nanoparticles to interact with the surface. Silver nanoparticles were found to bind exclusively to films which were prepared from solutions with a nonzero concentration of the dithiol implying that the nanoparticles were tethered to the silver surface by the dithiol with one of the thiolate groups bound to the nanoparticle and the other to the silver film. Intense SERS spectra were observed even from samples in which the m/d concentration ratio was so large that the adsorbed molecules in the vicinity of only approximately 8 +/- 3 nanoparticles were illuminated by the diffraction-limited focused laser beam. At such high dilution, the molecules (numbering at most approximately 330) residing in the SERS "hot spots" associated with the approximately 8 nanoparticles consisted primarily of m (although, of course, for each nanoparticle, at least one molecule in the hot spot had to be d to serve as the linker). This was corroborated by the SERS spectra. An analysis is presented, which accounts for the fact that as the concentration ratio of m/d increases, the SERS intensity associated with bands belonging to m first increases to a maximum then decreases. The nanoparticle-metal film system presented here is a simple embodiment of a more general range of SERS-active sensing platforms in which a molecular tether is used to create a SERS hot spot that (although nanosized) is large enough to accommodate analyte molecules that cannot themselves function as linkers, which are subsequently detected by SERS at the few-molecule level. 相似文献
912.
Abelev BI Aggarwal MM Ahammed Z Anderson BD Anderson M Arkhipkin D Averichev GS Bai Y Balewski J Barannikova O Barnby LS Baudot J Bekele S Belaga VV Bellingeri-Laurikainen A Bellwied R Benedosso F Bhardwaj S Bhasin A Bhati AK Bichsel H Bielcik J Bielcikova J Bland LC Blyth SL Bonner BE Botje M Bouchet J Brandin AV Bravar A Burton TP Bystersky M Cadman RV Cai XZ Caines H Calderón de la Barca Sánchez M Castillo J Catu O Cebra D Chajecki Z Chaloupka P Chattopadhyay S Chen HF Chen JH Cheng J 《Physical review letters》2006,97(15):152301
Transverse momentum spectra of pi+/-, p, and p up to 12 GeV/c at midrapidity in centrality selected Au + Au collisions at square root sNN=200 GeV are presented. In central Au + Au collisions, both pi +/- and p(p) show significant suppression with respect to binary scaling at pT approximately >4 GeV/c. Protons and antiprotons are less suppressed than pi+/-, in the range 1.5 approximately < pT approximately < 6 GeV/c. The pi-/pi+ and p/p ratios show at most a weak pT dependence and no significant centrality dependence. The p/pi ratios in central Au + Au collisions approach the values in p + p and d + Au collisions at pT approximately >5 GeV/c. The results at high pT indicate that the partonic sources of pi+/-, p, and p have similar energy loss when traversing the nuclear medium. 相似文献
913.
Adams J Aggarwal MM Ahammed Z Amonett J Anderson BD Arkhipkin D Averichev GS Badyal SK Bai Y Balewski J Barannikova O Barnby LS Baudot J Bekele S Belaga VV Bellingeri-Laurikainen A Bellwied R Berger J Bezverkhny BI Bharadwaj S Bhasin A Bhati AK Bhatia VS Bichsel H Bielcik J Bielcikova J Billmeier A Bland LC Blyth CO Blyth SL Bonner BE Botje M Boucham A Bouchet J Brandin AV Bravar A Bystersky M Cadman RV Cai XZ Caines H Sánchez MC Catu O Cebra D Chajecki Z Chaloupka P Chattopadhyay S Chen HF 《Physical review letters》2006,97(15):152302
Measurements of the production of forward pi0 mesons from p + p and d + Au collisions at square root sNN=200 GeV are reported. The p + p yield generally agrees with next-to-leading order perturbative QCD calculations. The d + Au yield per binary collision is suppressed as eta increases, decreasing to approximately 30% of the p + p yield at eta =4.00, well below shadowing expectations. Exploratory measurements of azimuthal correlations of the forward pi0 with charged hadrons at eta approximately 0 show a recoil peak in p + p that is suppressed in d + Au at low pion energy. These observations are qualitatively consistent with a saturation picture of the low-x gluon structure of heavy nuclei. 相似文献
914.
Adams J Aggarwal MM Ahammed Z Amonett J Anderson BD Anderson M Arkhipkin D Averichev GS Bai Y Balewski J Barannikova O Barnby LS Baudot J Bekele S Belaga VV Bellingeri-Laurikainen A Bellwied R Bezverkhny BI Bhardwaj S Bhasin A Bhati AK Bichsel H Bielcik J Bielcikova J Bland LC Blyth CO Blyth SL Bonner BE Botje M Bouchet J Brandin AV Bravar A Bystersky M Cadman RV Cai XZ Caines H Calderón de la Barca Sánchez M Castillo J Catu O Cebra D Chajecki Z Chaloupka P Chattopadhyay S Chen HF Chen JH 《Physical review letters》2006,97(16):162301
The STAR Collaboration at the Relativistic Heavy Ion Collider reports measurements of azimuthal correlations of high transverse momentum (pT) charged hadrons in Au+Au collisions at higher pT than reported previously. As (pT) is increased, a narrow, back-to-back peak emerges above the decreasing background, providing a clear dijet signal for all collision centralities studied. Using these correlations, we perform a systematic study of dijet production and suppression in nuclear collisions, providing new constraints on the mechanisms underlying partonic energy loss in dense matter. 相似文献
915.
Abazov VM Abbott B Abolins M Acharya BS Adams M Adams T Agelou M Agram JL Ahn SH Ahsan M Alexeev GD Alkhazov G Alton A Alverson G Alves GA Anastasoaie M Andeen T Anderson S Andrieu B Anzelc MS Arnoud Y Arov M Askew A Asman B Assis Jesus AC Atramentov O Autermann C Avila C Ay C Badaud F Baden A Bagby L Baldin B Bandurin DV Banerjee P Banerjee S Barberis E Bargassa P Baringer P Barnes C Barreto J Bartlett JF Bassler U Bauer D Bean A Begalli M Begel M Belanger-Champagne C Bellantoni L Bellavance A 《Physical review letters》2006,97(15):151804
We present a search for associated Higgs boson production in the process pp-->WH-->WWW*-->l;+/-nul'+/-nu'+X in final states containing two like-sign isolated electrons or muons (e+/-e;+/-, e+/-micro+/-, or micro+/-micro+/-). The search is based on D0 run II data samples corresponding to integrated luminosities of 360-380 pb-1. No excess is observed over the predicted standard model background. We set 95% C.L. upper limits on sigma(pp-->WH)xBr(H-->WW*) between 3.2 and 2.8 pb for Higgs boson masses from 115 to 175 GeV. 相似文献
916.
Ian Anderson 《Discrete Mathematics》2010,310(2):312-324
Write a≡3⋅2−1 and where p is an odd prime. Let c be a value that is congruent (modp) to either a or b. For any x from Zp?{0}, evaluate each of x and within the interval (0,p). Then consider the quantity where the differences are evaluated in the interval (0,p−1), and the quantity where the differences are evaluated (modp+1) in the interval (0,p+1). As x varies over Zp?{0}, the values of each of and give exactly two occurrences of nearly every member of 1,2,…,(p−1)/2. This fact enables a and b to be used in constructing some terraces for Zp−1 and Zp+1 from segments of elements that are themselves initially evaluated in Zp. 相似文献
917.
Regular semisimple Hessenberg varieties are a family of subvarieties of the flag variety that arise in number theory, numerical analysis, representation theory, algebraic geometry, and combinatorics. We give a “Giambelli formula” expressing the classes of regular semisimple Hessenberg varieties in terms of Chern classes. In fact, we show that the cohomology class of each regular semisimple Hessenberg variety is the specialization of a certain double Schubert polynomial, giving a natural geometric interpretation to such specializations. We also decompose such classes in terms of the Schubert basis for the cohomology ring of the flag variety. The coefficients obtained are nonnegative, and we give closed combinatorial formulas for the coefficients in many cases. We introduce a closely related family of schemes called regular nilpotent Hessenberg schemes, and use our results to determine when such schemes are reduced. 相似文献
918.
G. D. Anderson T. Sugawa M. K. Vamanamurthy M. Vuorinen 《Mathematische Zeitschrift》2010,266(1):181-191
We describe, in terms of generalized elliptic integrals, the hyperbolic metric of the twice-punctured sphere with one conical
singularity of prescribed order. We also give several monotonicity properties of the metric and a couple of applications. 相似文献
919.
Given a graph , a set is a dominating set of if every vertex of is either in or adjacent to a vertex in . The domination number of , denoted , is the minimum cardinality of a dominating set of . Vizing’s conjecture states that for any graphs and where denotes the Cartesian product of and . In this paper, we continue the work by Anderson et al. (2016) by studying the domination number of the hierarchical product. Specifically, we show that partitioning the vertex set of a graph in a particular way shows a trend in the lower bound of the domination number of the product, providing further evidence that the conjecture is true. 相似文献
920.
Ricardo Elgul Samad Lilia Coronato Courrol Ademar Benévolo Lugão Anderson Zanardi de Freitas Nilson Dias Vieira 《Radiation Physics and Chemistry》2010,79(3):355-357
We report here the creation of color centers in commercial, transparent PMMA samples by ultrashort pulses from a Ti:Sapphire laser emitting at 800 nm, with spatial control. Although the 800 nm photon energy is not sufficient to ionize the polymer, the centers are created following a multiphotonic absorption that causes the ionization. We propose that the free electrons quivering motion on the pulse electric field displaces atoms from its equilibrium positions, creating free radicals and double bonds that coalesce into color centers. The absorption and emission spectra of the centers were measured, but a dose-like curve could not be built due to the presence of damages created along with the centers that scatter the excitation and emission lights due to the commercial sample's poor optical quality. 相似文献