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991.
Abazov VM Abbott B Abolins M Acharya BS Adams M Adams T Aguilo E Ahn SH Ahsan M Alexeev GD Alkhazov G Alton A Alverson G Alves GA Anastasoaie M Ancu LS Andeen T Anderson S Andrieu B Anzelc MS Arnoud Y Arov M Arthaud 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 S Banerjee P Barberis E Barfuss AF Bargassa P Baringer P Barreto J Bartlett JF Bassler U Bauer D Beale S Bean A Begalli M Begel M Belanger-Champagne C 《Physical review letters》2007,99(5):052001
We report the first direct observation of the strange b baryon Xi(b)- (Xi(b)+). We reconstruct the decay Xi(b)- -->J/psiXi-, with J/psi-->mu+mu-, and Xi--->Lambdapi--->ppi-pi- in pp collisions at square root of s =1.96 TeV. Using 1.3 fb(-1) of data collected by the D0 detector, we observe 15.2 +/- 4.4(stat)(-0.4)(+1.9)(syst) Xi(b)- candidates at a mass of 5.774 +/- 0.011(stat) +/- 0.015(syst) GeV. The significance of the observed signal is 5.5 sigma, equivalent to a probability of 3.3 x 10(-8) of it arising from a background fluctuation. Normalizing to the decay Lambda(b)-->J/psiLambda, we measure the relative rate sigma(Xi(b-) x B(Xi)b})- -->J/psiXi-)/sigma(Lambda(b)) x B(Lambda(b)-->J/psiLambda) = 0.28+/-0.09(stat)(-0.08)(+0.09)(syst). 相似文献
992.
Abazov VM Abbott B Abolins M Acharya BS Adams M Adams T Agelou M 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》2007,98(4):041801
We present the first experimental discrimination between the 2e/3 and 4e/3 top quark electric charge scenarios, using top quark pairs (tt) produced in pp collisions at (square root) s = 1.96 TeV by the Fermilab Tevatron Collider. We use 370 pb;{-1} of data collected by the D0 experiment and select events with at least one high transverse momentum electron or muon, high transverse energy imbalance, and four or more jets. We discriminate between b- and b-quark jets by using the charge and momenta of tracks within the jet cones. The data are consistent with the expected electric charge, |q|=2e/3. We exclude, at the 92% C.L., that the sample is solely due to the production of exotic quark pairs QQ with |q|=4e/3. We place an upper limit on the fraction of QQ pairs rho<0.80 at the 90% C.L. 相似文献
993.
Ricardo N. Marreto Elis E.C.V. Almeida Pricles B. Alves Edenilson S. Niculau Rogria S. Nunes Charlene R.S. Matos Adriano A.S. Araújo 《Thermochimica Acta》2008,475(1-2):53-58
Inclusion complexation with cyclodextrins is an effective way to improve stability and turn liquid materials into re-dispersible and easy-to-handle powders. In the present work, the complexation of L. gracilis essential oil, already recognized as a potent larvicide material, with hydroxylpropyl-β-cyclodextrin was performed using slurry and paste procedures and the complexes obtained were evaluated. The gas chromatography coupled to mass spectrometry (GC/MS) analysis showed a total volatile content of 99.24% in the L. gracilis oil. The characterization of the complex involved the analysis of the original essential oil, the surface, and the total extracted oils. The major components in L. gracilis essential oil were identified as carvacrol (23.52%), p-cymene (15.82%), γ-terpinene (14.17%), and thymol (7.27%). GC/MS results showed significant differences between the original oil, the slurry, and paste complexation. Thermal characterization indicates the occurrence of complexation, mainly in paste complexes, which presents a TG–DTA peak at 230–275 °C, probably related to oil loss. 相似文献
994.
The production of extracellular cellulase-free xylanase from Trichoderma inhamatum was evaluated in liquid Vogel medium with different carbon sources as natural substrates and agricultural or agro-industrial wastes. Optimal production of 244.02 U/mL was obtained with xylan as carbon source, pH 6.0 at 25 degrees C, 120 rpm, and 60-h time culture. Optimal conditions for enzyme activity were 50 degrees C and pH 5.5. Thermal stability of T. inhamatum xylanolytic complex expressed as T1/2 was 2.2 h at 40 degrees C and 2 min at 50 degrees C. The pH stability was high from 4.0 to 11.0. These results indicate possible employment of such enzymatic complex in some industrial processes which require activity in acid pH, wide-ranging pH stability, and cellulase activity absence. 相似文献
995.
In this study, gold nanoparticles (AuNP) were synthesized using a novel stabilizer based on dialdehyde starch polymer (DAS) and dimethyl sulfoxide (DMSO) and the nanomaterial was applied to develop a sensor for methyldopa detection. The nanoparticles were characterized by transmission electron microscopy and the proposed sensor was electrochemically characterized by electrochemical impedance spectroscopy, chronocoulometry and square-wave voltammetry. Under optimized conditions (0.1 mol L−1 McIlvaine buffer solution at pH 3.5 and 50 μL AuNP/DAS-DMSO), using square-wave voltammetry, the calibration curve presented a linear range of 0.99 to 19.60 μmol L−1, with a detection limit of 0.50 μmol L−1. The sensor showed good accuracy, with coefficients of variation of 7.8 % (inter-day; n=6) and 5.9 % (intra-day; n=3), and recovery values in the range of 95.3 to 105.2 %. The methyldopa content in a pharmaceutical sample was determined and the results show good correlation with the label value and the method recommended by the Pharmacopoeia, representing a fast and accurate alternative for detecting methyldopa in pharmaceutical products. 相似文献
996.
Ghosh M Alves C Tong Z Tettey K Konstantopoulos K Stebe KJ 《Langmuir : the ACS journal of surfaces and colloids》2008,24(15):8134-8142
In this paper we describe a method for creating multifunctional glass surfaces presenting discrete patches of different proteins on an inert PEG-functionalized background. Microcontact printing is used to stamp the substrate with octadecyltrichlorosilane to define the active regions. The substrate is then back-filled with PEG-silane {[[2-methoxypoly(ethyleneoxy)]propyl]trimethoxysilane} to define passive regions. A microfluidics device is subsequently affixed to the substrate to deliver proteins to the active regions, with as many channels as there are proteins to be patterned. Examples of trifunctional surfaces are given which present three terminating functional groups, i.e., protein 1, protein 2, and PEG. These surfaces should be broadly useful in biological studies, as patch size is well established to influence cell viability, growth, and differentiation. Three examples of cellular interactions with the surfaces are demonstrated, including the capture of cells from a single cell suspension, the selective sorting of cells from a mixed suspension, and the adhesion of cells to ligand micropatches at critical shear stresses. Within these examples, we demonstrate that the patterned immobilized proteins are active, as they retain their ability to interact with either antibodies in solution or receptors presented by cells. When appropriate (e.g., for E-selectin), proteins are patterned in their physiological orientations using a sandwich immobilization technique, which is readily accommodated within our method. The protein surface densities are highly reproducible in the patches, as supported by fluorescence intensity measurements. Potential applications include biosensors based on the interaction of cells or of marker proteins with protein patches, fundamental studies of cell adhesion as a function of patch size and shear stress, and studies of cell differentiation as a function of surface cues. 相似文献
997.
Leandro J. dos Santos Rosemeire B. Alves Rossimiriam P. de Freitas Jean-Franois Nierengarten Lucas E.F. Magalhes Klaus Krambrock Maurício V.B. Pinheiro 《Journal of photochemistry and photobiology. A, Chemistry》2008,200(2-3):277-281
The wide range of physical and chemical properties of modified fullerenes has drawn increasing attention in the past few years. As part of this research, this paper describes the preparation, characterization, and photophysical properties of a new fullerene derivative chemically modified with a tetrazole. The photophysical properties were studied by EPR radical spin-trapping technique and showed that reactive oxygen species (ROS) can be produced through UVA photosensitization. EPR spin-trapping experiments with singlet oxygen (1O2) and superoxide (O2−) inhibitors (β-carotene and superoxide dismutase, respectively) revealed also that: (i) the main ROS produced is 1O2 and (ii) 1O2 is being partially dismutated to O2−. The results suggest that this derivative can be used in biological applications, as for example, in topic photodynamic therapy (PDT) as a photosensitizer. 相似文献
998.
Claudianor?O.?Alves Marcos?T.?O.?PimentaEmail author 《Calculus of Variations and Partial Differential Equations》2017,56(5):143
In this work we use variational methods to prove results on existence and concentration of solutions to a problem in \(\mathbb {R}^N\) involving the 1-Laplacian operator. A thorough analysis on the energy functional defined in the space of functions of bounded variation \(BV(\mathbb {R}^N)\) is necessary, where the lack of compactness is overcome by using the Concentration of Compactness Principle due to Lions. 相似文献
999.
Elizabeth Stubbs Elizabeth Laskowski Phillip Conor Daniel Alves Heinze Dylan Karis 《高分子科学杂志,A辑:纯化学与应用化学》2017,54(4):228-235
A series of poly(ethylene glycol) monomethyl ether-block-poly(2-(dimethylamino)ethyl methacrylate) (mPEG-b-PDMAEMA) diblock copolymers were synthesized using atom transfer radical polymerization to achieve controlled polymer molecular weight and narrow molecular weight distribution. The thermoresponsive properties of the mPEG-b-PDMAEMA diblock copolymers in aqueous buffered solutions were determined using UV-Visible spectroscopy and dynamic light scattering. The cloud point, a soluble-to-insoluble transition, was observed for all mPEG-b-PDMAEMA diblock copolymer solutions. Increasing either the mPEG or PDMAEMA molecular weight resulted in a decrease in observed cloud points as a function of pH and polymer concentration. Changing the mPEG molecular weight determined whether a second, higher temperature, thermal transition was observed as a function of pH and polymer concentration. Controlling the thermoresponsive properties of mPEG-b-PDMAEMA diblock copolymers through polymer composition, concentration, and pH enables the tailoring of these copolymers for applications ranging from non-viral gene delivery to use as a strengthening agent in paper. 相似文献
1000.
Priscilla Mendes Arruda Antônio Canal Neto Mauro Cesar Martins Campos Henrique Raulino Coelho da Cruz Fábio Alves dos Santos 《International journal of quantum chemistry》2015,115(2):77-83
The Monte Carlo simulated annealing method is adapted to optimize correlated Gaussian‐type functions in nonrelativistic molecular environments. Starting from an atom‐centered atomic Gaussian basis set, the uncontracted functions are reoptimized in the molecular environments corresponding to the H2O, CN?, N2, CO, BF, NO+, CO2, and CS systems. These new molecular adapted basis sets are used to calculate total energies, harmonic vibrational frequencies, and equilibrium geometries at a correlated level of theory. The present methodology is a simple and effective way to improve molecular correlated wave functions, without the need to enlarge the molecular basis set. Additionally, this methodology can be used to generate hierarchical sequences of molecular basis sets with increasing size, which are relevant to establish complete basis set limits. © 2014 Wiley Periodicals, Inc. 相似文献