Suppression of parasitic lasing in high energy, high repetition rate Ti:sapphire laser amplifiers

Transverse parasitic lasing is well known for limiting the signal gain and the pulse energy that can be extracted from Ti:sapphire petawatt amplifiers. We have developed a technique for suppressing these parasitic lasing modes based on perfect refractive index-matching liquid doped with a broad-bandwidth absorber to suppress the transverse lasing while ensuring proper heat removal from the Ti:sapphire crystal. The 800 nm laser output with a bandwidth of 41 nm (FWHM) and peak energy of 22.7 J at a repetition rate of 1 Hz is demonstrated.     

An integrated chemical biology approach provides insight into cdk2 functional redundancy and inhibitor sensitivity

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Highlights? Demonstration that Cdk2 is rate-limiting for DNA replication due to insufficient Cdk1 activity ? A simple bioinformatic approach to design inhibitor resistant mutations in kinases ? Demonstration of distinct binding modes and selectivity of Cdk inhibitors ? Identification of kinetic and structural mechanisms of inhibitor resistance     

Spectral multipliers on a class of NA groups with rank two

We consider a family of real NA groups with rank two, and we prove that these groups have sub-Laplacians with differentiable Lp functional calculus for all p?1.     

From isocyanides to trichloropyruvamides: application to a new preparation of oxamide derivatives

Isocyanides react readily with trichloroacetic acid anhydride forming stable hydrates of trichloropyruvamides. These compounds are valuable intermediates for obtaining oxamides by reaction with TMSCl/NEt₃ followed by addition of an amine.     

Use of parallel synthesis to probe structure-activity relationships among 12-helical beta-peptides: evidence of a limit on antimicrobial activity

We report structure-activity trends among helix-forming beta-amino acid oligomers that are intended to mimic alpha-helical host-defense peptides. Parallel synthesis of two small, focused beta-peptide libraries allowed us to identify relatively short (11-residue) beta-peptides that display antimicrobial activity. These beta-peptides exhibit selectivity for bacteria relative to human red blood cells. A large hydrophobic helical surface is necessary for antimicrobial activity. Longer analogues (16 residues) of the most active library members were prepared and evaluated. Some of these longer beta-peptides showed very good antimicrobial activity, but none was more active than a previously reported beta-peptide [Porter, E. A.; Wang, X.; Lee, H.-S.; Weisblum, B.; Gellman, S. H. Nature 2000, 404, 565]. The extensive literature on alpha-helical host-defense peptides and related alpha-peptides indicates that such molecules are seldom active at concentrations below 1 microg/mL, and our results suggest that amphiphilic helical beta-peptides are subject to a comparable limit.     

Concise synthesis of pochonin A, an HSP90 inhibitor

[chemical reaction: see text]. An expedient synthesis of (-)-pochonin A is reported (seven steps). This natural product is closely related to radicicol and was shown to be a 90 nM inhibitor of HSP90.     

Electrospray mass spectrometry of lanthanide β-diketone complexes. II-Ligand-exchange processes involving acetate ions and Ln(tfc)3 complexes

Electrospray ionization on Ln(tfc)₃ complexes (Ln = Eu, Yb; tfc = D -3-trifluoroacetylcamphorate) was performed with samples dissolved in methanol–water containing acetic acid. The spectra were obtained with a four-sector mass spectrometer. The mass spectra exhibit ions containing tfc ligand in addition to ions with acetato ligand. Electro-spray and tandem mass spectra are presented.     

Rapid measurements of 235U fission product isotope ratios using an online,high-pressure ion chromatography inductively coupled plasma mass spectrometry protocol with comparison to isotopic depletion models

Journal of Radioanalytical and Nuclear Chemistry - An automated online separation–direct analysis method, RAPID (rapid analysis of post-irradiation debris), has been developed for the...     

New D-π-A-conjugated organic sensitizers based on α-pyranylidene donors for dye-sensitized solar cells

A series of new push-pull organic dyes incorporating a cyanoacrylic acid group as electron acceptor unit and α-chalcogenopyranylidene group (X = S; O) as electron donor unit has been synthesized, characterized and used as sensitizer for dye-sensitized solar cells (DSSCs). For the first time, α-pyranylidene and thiopyranylidene groups, have been evaluated in DSSC. To obtain the thermodynamic values of the solar cell, an investigation of their electrochemical (CV) and optical properties (UV–vis absorption spectroscopy) is also reported.