Crystalline orientation effects on conical structure formation in femtosecond laser irradiation of silicon and germanium

Irradiation of Si(1 0 0), Si(1 1 1), Si(1 1 0), Ge(1 0 0), and Ge(1 1 1) is compared for 150 fs, 800 nm wavelength pulses in a rough vacuum atmosphere. The surface crystalline orientation of the material is found to affect the final morphology, with (1 1 1)- and (1 1 0)-surface orientations exhibiting a much higher tendency for conical structure formation under multiple-pulse irradiation. Using cross-sectional transmission electron microscopy, the structures on Si(1 1 1) are found to have primarily crystalline cores with the same crystalline orientation as the substrate. The results show that the crystalline orientation of the target should be considered in laser machining applications.     

A rapid and sensitive bioanalytical LC–MS/MS method for the quantitation of a novel CDK5 inhibitor 20–223 (CP668863) in plasma: Application to in vitro metabolism and plasma protein-binding studies

A rapid, selective, and sensitive liquid chromatography coupled with tandem mass spectrometry (MS/MS) method was developed and validated for the quantitation of the novel CDK5 inhibitor ‘20–223' in mouse plasma. Separation of analytes was achieved by a reverse-phase ACE Excel C₁₈ column (1.7 μm, 100 × 2.1 mm) with gradient elution using 0.1% formic acid (FA) in methanol and 0.1% FA as the mobile phase. Analytes were monitored by MS/MS with an electrospray ionization source in the positive multiple reaction monitoring mode. The MS/MS response was linear over the concentration range 0.2–500 ng/mL for 20–223. The within- and between-batch precision were within the acceptable limits as per Food and Drug Administration guidelines. The validated method was successfully applied to plasma protein binding and in vitro metabolism studies. Compound 20–223 was highly bound to mouse plasma proteins (>98% bound). Utilizing mouse S9 fractions, in vitro intrinsic clearance (CL_int) was 24.68 ± 0.99 μL/min/mg protein. A total of 12 phase I and II metabolites were identified with hydroxylation found to be the major metabolic pathway. The validate method required a low sample volume, was linear from 0.2 to 500 ng/mL, and had acceptable accuracy and precision.     

Further studies on the application of vinylogous amides and β-halovinylaldehydes to the regiospecific synthesis of unsymmetrical,polyfunctionalized 2,3,4- and 1,2,3,4- substituted pyrroles

Highly functionalized pyrroles with appropriate regiochemical functionality represent an important class of marine natural products and potential drug candidates. We describe herein a detailed study of the reaction of α-aminoacid esters with vinylogous amides and also β-halovinylaldehydes for the regiospecific synthesis of 2,3,4-trisubstituted and 1,2,3,4-tetrasubstituted pyrroles. Since the vinylogous amides and β-halovinylaldehydes are readily available precursors, rapid access to a wide variety of unsymmetrically substituted pyrroles is accomplished via this methodology.     

Modifications in the simultaneous determination of carbon,hydrogen, and nitrogen

Summary Improved analytical procedures are presented for the simultaneous determination of carbon, hydrogen, and nitrogen in solid organic materials by the gas volumetric method. The accuracy is improved, and the method is less dependent upon the analyst's technique.

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Zusammenfassung Verbesserte Verfahren für die gleichzeitige gasvolumetrische Bestimmung von Kohlenstoff, Wasserstoff und Stickstoff in festen organischen Verbindungen werden beschrieben. Die Genauigkeit wurde verbessert, und die Ergebnisse sind weniger von der Arbeitstechnik des Analytikers abhängig.

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Résumé On présente une amélioration des procédés analytiques pour le dosage simultané du carbone, de l'hydrogène et de l'azote dans les matériaux solides organiques par la méthode volumétrique gazeuse. La précision est meilleure et la méthode dépend moins de la technique de l'analyste.

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Work was performed under the auspices of the U. S. Atomic Energy Commission.     

Group VI metal aminoborylene complex-catalyzed demercuration reactions of bis(alkynyl)mercurials

The first catalytic application of the Group VI metal borylene complexes [(CO)(5)M[double bond]BN(SiMe(3))(2)] involves the demercuration reaction of bis(alkynyl)mercurials, [Hg(C[triple bond]CR)(2)], with formation of a series of buta-1,3-diynes.     

Radiochemical measurement of <Superscript>237</Superscript>Np in a solution of mixed radionuclides: Experiences in chemical separation and alpha-spectrometry

A radiochemical procedure is described for the measurement of 0.1 Bq ²³⁷Np in a solution containing similar activity concentrations of Th, U, Pu and Am as well as activity concentrations of ⁶⁰Co, ⁹⁰Sr and ¹³⁷Cs one hundred times higher. A tracer of ²³⁹Np (milked from ²⁴³Am) was used as an isotopic spike for chemical yield determination. The relationship between gamma-counting geometries for ampoule (liquid) and NdF₃ (solid) ²³⁹Np sources was established so that Np chemical yields could be measured by a comparative method. Efficiencies of alpha-spectrometers for ²³⁷Np in NdF₃ sources were measured by a bootstrap technique. Two sets of experiments were designed and used to test out the procedure.     

电感耦合等离子体-发射光谱法（ICP-AES）快速测定饮用水中8种微量元素

用电感耦合等离子体-发射光谱法（ICP-AES）同时快速测定饮用水中微量的铜、铅、锌、铁、锰、镉、铬、砷,具有快速、简便、灵敏度高等优点,精密度为1．2％～8．2％（RSD,n=5）．回收率为90％～110％．     

Comparison of time-dependent density-functional theory and coupled cluster theory for the calculation of the optical rotations of chiral molecules

A comparison of the abilities of time-dependent density-functional theory (TDDFT) and coupled cluster (CC) theory to reproduce experimental sodium D-line specific rotations for 13 conformationally rigid organic molecules is reported. The test set includes alkanes, alkenes, and ketones with known absolute configurations. TDDFT calculations make use of gauge-including atomic orbitals and give origin-independent specific rotations. CC rotations are computed using both the origin-independent dipole-velocity and origin-dependent dipole-length representations. The mean absolute deviations of calculated and experimental rotations are of comparable magnitudes for all three methods. The origin-independent DFT and CC methods give the same sign of [alpha]D for every molecule except norbornanone. For every large-rotation ketone and alkene for which DFT and CC yield the incorrect sign as compared to liquid-phase experimental data, the corresponding optical rotatory dispersion (ORD) curve is bisignate, suggesting that the two models cannot reliably reproduce the relative excitation energies and antagonistic rotational strengths of multiple competing electronic states that contribute to the total long-wavelength rotation. Several potential sources of error in the theoretical treatments are considered, including basis set incompleteness, vibrational and temperature effects, electron correlation, and solvent effects.     

The energetics of tetrahydrocarbazole aromatization over Pd(111): a computational analysis

The carbazole moiety is a component of many important pharmaceuticals including anticancer and anti-HIV agents and is commonly utilized in the production of modern polymeric materials with novel photophysical and electronic properties. Simple carbazoles are generally produced via the aromatization of the respective tetrahydrocarbazole (THCZ). In this work, density functional theory calculations are used to model the reaction pathway of tetrahydrocarbazole aromatization over Pd(111). The geometry of each of the intermediate surface species has been determined and how each structure interacts with the metal surface addressed. The reaction energies and barriers of each of the elementary surface reactions have also been calculated, and a detailed analysis of the energetic trends performed. Our calculations have shown that the surface intermediates remain fixed to the surface via the aromatic ring in a manner similar to that of THCZ. Moreover, the aliphatic ring becomes progressively more planer with the dissociation of each subsequent hydrogen atom. Analysis of the reaction energy profile has revealed that the trend in reaction barriers is determined by the two factors: (i) the strength of the dissociating ring-H bond and (ii) the subsequent gain in energy due to the geometric relaxation of the aliphatic ring.     

Emptiness Formation Probability

We consider products of random matrices that are small, independent identically distributed perturbations of a fixed matrix \({\mathcal{T}_0}\). Focusing on the eigenvalues of \({\mathcal{T}_0}\) of a particular size we obtain a limit to a SDE in a critical scaling. Previous results required \({\mathcal{T}_0}\) to be a (conjugated) unitary matrix so it could not have eigenvalues of different modulus. From the result we can also obtain a limit SDE for the Markov process given by the action of the random products on the flag manifold. Applying the result to random Schrödinger operators we can improve some results by Valko and Virag showing GOE statistics for the rescaled eigenvalue process of a sequence of Anderson models on long boxes. In particular, we solve a problem posed in their work.