Tidal effects and the proximity decay of nuclei

We examine the decay of the 3.03 MeV state of (8)Be evaporated from an excited projectilelike fragment following a peripheral heavy-ion collision. The relative energy of the daughter alpha particles exhibits a dependence on the decay angle of the (8)Be(*), indicative of a tidal effect. A comparison of the measured tidal effect with a model suggests a measurable nuclear proximity interaction.     

Measurement of branching fractions and mass spectra of B-->Kpipigamma

We present a measurement of the partial branching fractions and mass spectra of the exclusive radiative penguin processes B-->Kpipigamma in the range m(Kpipi)<1.8 GeV/c(2). We reconstruct four final states: K(+)pi(-)pi(+)gamma, K(+)pi(-)pi(0)gamma, K(S)(0)pi(-)pi(+)gamma, and K(S)(0)pi(+)pi(0)gamma, where K(S)(0)-->pi(+)pi(-). Using 232 x 10(6) e(+)e(-)-->BB events recorded by the BABAR experiment at the SLAC PEP-II asymmetric-energy storage ring, we measure the branching fractions B(B(+)-->K(+)pi(-)pi(+)gamma)=[2.95+/-0.13(stat)+/-0.20(syst)] x 10(-5), B(B(0)-->K(+)pi(-)pi(0)gamma)=[4.07+/-0.22(stat)+/-0.31(syst)] x 10(-5), B(B(0)-->K(0)pi(+)pi(-)gamma)=[1.85+/-0.21(stat)+/-0.12(syst)] x 10(-5), and B(B(+)-->K(0)pi(+)pi(0)gamma)=[4.56+/-0.42(stat)+/-0.31(syst)] x 10(-5).     

Observation of B Meson decays to b1pi and b1K

We present the results of searches for decays of B mesons to final states with a b1 meson and a charged pion or kaon. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 382x10(6) BB[over ] pairs produced in e+e- annihilation. The results for the branching fractions are, in units of 10(-6), B(B+-->b1(0)pi+)=6.7+/-1.7+/-1.0, B(B+-->b1(0)K+)=9.1+/-1.7+/-1.0, B(B0-->b1(-/+)pi(+/-))=10.9+/-1.2+/-0.9, and B(B0-->b1(-)K+)=7.4+/-1.0+/-1.0, with the assumption that B(b1-->omega pi)=1. We also measure charge and flavor asymmetries A(ch)(B+-->b1(0)pi+)=0.05+/-0.16+/-0.02, Ach(B+-->b1(0)K+)=-0.46+/-0.20+/-0.02, A(ch)(B0-->b1(-/+)pi(+/-))=-0.05+/-0.10+/-0.02, C(B0-->b1(-/+)pi(+/-))=-0.22+/-0.23+/-0.05, DeltaC(B0-->b1(-/+)pi(+/-))=-1.04+/-0.23+/-0.08, and A(ch)(B0-->b1(-)K+)=-0.07+/-0.12+/-0.02. The first error quoted is statistical, and the second systematic.     

Amplitude analysis of the B+/--->phiK*(892)+/- decay

We perform an amplitude analysis of B+/--->phi(1020)K*(892)+/- decay with a sample of about 384 x 10(6) BB[over ] pairs recorded with the BABAR detector. Overall, twelve parameters are measured, including the fractions of longitudinal fL and parity-odd transverse f perpendicular amplitudes, branching fraction, strong phases, and six parameters sensitive to CP violation. We use the dependence on the Kpi invariant mass of the interference between the JP=1(-) and 0+ Kpi components to resolve the discrete ambiguity in the determination of the strong and weak phases. Our measurements of fL=0.49+/-0.05+/-0.03, f perpendicular=0.21+/-0.05+/-0.02, and the strong phases point to the presence of a substantial helicity-plus amplitude from a presently unknown source.     

碱金属钾对Ni基催化剂纤维素水蒸气气化活性的影响

采用两段式催化气化方式研究了生物质热解气化过程中碱金属的挥发对Ni基催化剂活性的影响。实验结果表明,负载K盐的纤维素水蒸气催化气化过程中,K挥发后会在催化剂表面沉积,而少量K的存在和表面沉积不但能够提高镍基催化剂的抗积炭能力,而且有助于提高其催化活性,产生更多的氢气。然而纤维素中K的浓度过大,将会抑制Ni基催化剂的效果;K在催化剂上的沉积随催化剂循环次数的增加而增加,K的含量愈高,对催化剂的抑制效果愈明显,从而缩短了催化剂的使用寿命。     

Incorporating high-pressure electroosmotic pump and a nano-flow gradient generator into a miniaturized liquid chromatographic system for peptide analysis

We integrate a high-pressure electroosmotic pump (EOP), a nanoflow gradient generator, and a capillary column into a miniaturized liquid chromatographic system that can be directly coupled with a mass spectrometer for proteomic analysis. We have recently developed a low-cost high-pressure EOP capable of generating pressure of tens of thousands psi, ideal for uses in miniaturized HPLC. The pump worked smoothly when it was used for isocratic elutions. When it was used for gradient elutions, generating reproducible gradient profiles was challenging; because the pump rate fluctuated when the pump was used to pump high-content organic solvents. This presents an issue for separating proteins/peptides since high-content organic solvents are often utilized. In this work, we solve this problem by incorporating our high-pressure EOP with a nano-flow gradient generator so that the EOP needs only to pump an aqueous solution. With this combination, we develop a capillary-based nano-HPLC system capable of performing nano-flow gradient elution; the pump rate is stable, and the gradient profiles are reproducible and can be conveniently tuned. To demonstrate its utility, we couple it with either a UV absorbance detector or a mass spectrometer for peptide separations.     

Parameterization of Org27569: An allosteric modulator of the cannabinoid CB1 G protein‐coupled receptor

The cannabinoid CB₁ receptor is a class A G protein‐coupled receptor (GPCR) that is the most widely expressed GPCR in the brain. Many GPCRs contain allosteric binding sites for endogenous and/or synthetic ligands, which are topographically distinct from the agonist‐binding site that is known as the orthosteric site. While both endogenous and synthetic ligands that act at the CB₁ orthosteric site have been known for some time, compounds that act at a CB₁ allosteric site have only recently been discovered. The most studied of these is 5‐chloro‐3‐ethyl‐1H‐indole‐2‐carboxylic acid [2‐(4‐piperidin‐1‐ylphenyl)ethyl]amide (Org27569). Because allosteric ligands are thought to act through conformational changes in the receptor that are transmitted from the allosteric to the orthosteric site, computational studies of the structural and dynamic interactions of Org27569 with the CB₁ receptor are crucial to achieve a molecular level understanding of the basis of action of this important new class of compounds. To date, such computational studies have not been possible due to the lack of a complete set of molecular mechanics force field parameters for Org27569. Here, we present the development of missing CHARMM force field parameters for Org27569 using previously published methods and the validation and application of these new parameters using normal mode analysis and molecular dynamics simulations combined with experimental infrared measurements. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

Gas-bubble effects on the formation of colloidal iron oxide nanocrystals

This paper reports that gas bubbles can be used to tailor the kinetics of the nucleation and growth of inorganic-nanocrystals in a colloidal synthesis. We conducted a mechanistic study of the synthesis of colloidal iron oxide nanocrystals using gas bubbles generated by boiling solvents or artificial Ar bubbling. We identified that bubbling effects take place through absorbing local latent heat released from the exothermic reactions involved in the nucleation and growth of iron oxide nanocrystals. Our results show that gas bubbles display a stronger effect on the nucleation of iron oxide nanocrystals than on their growth. These results indicate that the nucleation and growth of iron oxide nanocrystals may rely on different types of chemical reactions between the iron-oleate decomposition products: the nucleation relies on the strongly exothermic, multiple-bond formation reactions, whereas the growth of iron oxide nanocrystals may primarily depend upon single-bond formation reactions. The identification of exothermic reactions is further consistent with our results in the synthesis of iron oxide nanocrystals with boiling solvents at reaction temperatures ranging from 290 to 365 °C, by which we determined the reaction enthalpy in the nucleation of iron oxide nanocrystals to be -142 ± 12 kJ/mol. Moreover, our results suggest that a prerequisite for effectively suppressing secondary nucleation in a colloidal synthesis is that the primary nucleation must produce a critical amount of nuclei, and this finding is important for a priori design of colloidal synthesis of monodispersed nanocrystals in general.     

Probing the photoinduced metal-nitrosyl linkage isomerism of sodium nitroprusside in solution using transient infrared spectroscopy

We study photoinduced metal-nitrosyl linkage isomerism in sodium nitroprusside (Na(2)[Fe(II)(CN)(5)NO]·2H(2)O, SNP) dissolved in methanol using picosecond transient infrared (IR) spectroscopy. The high sensitivity of this technique allows the simultaneous observation of two known metastable (MS) iron-nitrosyl linkage isomers of SNP, [Fe(II)(CN)(5)(η(1)-ON)](2-) (MS1) and [Fe(II)(CN)(5)(η(2)-NO)](2-) (MS2), at room temperature. The transient population of free nitrosyl radicals (NO·) is also measured in the sample solution. These three transient species are detected using their distinct nitrosyl stretching frequencies at 1794 cm(-1) (MS1), 1652 cm(-1) (MS2), and 1851 cm(-1) (NO·). The metastable isomers and NO· are formed on a subpicosecond time scale and have lifetimes greater than 100 ns. A UV (400 nm)-pump power dependence study reveals that MS1 can be formed with one photon, while MS2 requires two photons to be populated at room temperature in solution. Other photodissociation products including cyanide ion, Prussian blue, and [Fe(III)(CN)(5)(CH(3)OH)](2-) are observed. We develop a photochemical kinetic scheme to model our data, and the analysis reveals that photoisomerization and photodissociation of the metal-NO moiety are competing photochemical pathways in SNP dissolved in methanol at room temperature. Based on the analysis, the solvent-associated Fe(III) species and Prussian blue form on a 130 and 320 ps time scale, respectively. The simultaneous detection and characterization of photoinduced linkage isomerism (MS1 and MS2) and photodissociation of the metal-NO bond in SNP highlights the importance of understanding the role played by metastable metal-nitrosyl linkage isomers in the photochemistry of metal-nitrosyl compounds in chemistry and biology.