Asymmetric synthesis of gonytolide A: strategic use of an aryl halide blocking group for oxidative coupling

The first synthesis of the chromanone lactone dimer gonytolide A has been achieved employing vanadium(V)-mediated oxidative coupling of the monomer gonytolide C. An o-bromine blocking group strategy was employed to favor para- para coupling and to enable kinetic resolution of (±)-gonytolide C. Asymmetric conjugate reduction enabled practical kinetic resolution of a chiral, racemic precursor and the asymmetric synthesis of (+)-gonytolide A and its atropisomer.We thank the National Institutes of Health (R35 GM-118173) for research support. Work at the BU-CMD is supported by NIH R24 Grant GM-111625. We thank Prof. Scott Miller and Dr. Anthony Metrano (Yale University) for helpful discussions and preliminary experiments. We thank the Uehara Memorial Foundation for a postdoctoral fellowship to T.I., the American Cancer Society for a postdoctoral fellowship to K.D.R. (PF-16-235-01-CDD), Dr. Jeffrey Bacon (Boston University) for X-ray crystal structure analyses, and Prof. Haruhisa Kikuchi (Tohoku University) for providing a natural sample of gonytolide A. NMR (CHE-0619339) and MS (CHE-0443618) facilities at Boston University are supported by the NSF. (R35 GM-118173 - National Institutes of Health; GM-111625 - NIH; Uehara Memorial Foundation; PF-16-235-01-CDD - American Cancer Society; CHE-0619339 - NSF; CHE-0443618 - NSF

Nonadiabatic generation of coherent phonons

The time-dependent density functional theory (TDDFT) is the leading computationally feasible theory to treat excitations by strong electromagnetic fields. Here the theory is applied to coherent optical phonon generation produced by intense laser pulses. We examine the process in the crystalline semimetal antimony (Sb), where nonadiabatic coupling is very important. This material is of particular interest because it exhibits strong phonon coupling and optical phonons of different symmetries can be observed. The TDDFT is able to account for a number of qualitative features of the observed coherent phonons, despite its unsatisfactory performance on reproducing the observed dielectric functions of Sb. A simple dielectric model for nonadiabatic coherent phonon generation is also examined and compared with the TDDFT calculations.Comment: 19 pages, 11 figures. This is prepared for a special issue of Journal of Chemical Physics on the topic of nonadiabatic processe

Suppression of Charge Equilibration leading to the Synthesis of Exotic Nuclei

Charge equilibration between two colliding nuclei can take place in the early stage of heavy-ion collisions. A basic mechanism of charge equilibration is presented in terms of the extension of single-particle motion from one nucleus to the other, from which the upper energy-limit of the bombarding energy is introduced for significant charge equilibration at the early stage of the collision. The formula for this limit is presented, and is compared to various experimental data. It is examined also by comparison to three-dimensional time-dependent density functional calculations. The suppression of charge equilibration, which appears in collisions at the energies beyond the upper energy-limit, gives rise to remarkable effects on the synthesis of exotic nuclei with extreme proton-neutron asymmetry.Comment: 4 pages, 4 figure

Global Thrombosis Test - a possible monitoring system for the effects and safety of dabigatran

© Otsui et al. 2015BACKGROUND: Dabigatran is an alternative to warfarin (WF) for the thromboprophylaxis of stroke in patients with non-valvular atrial fibrillation (NVAF). The advantage of dabigatran over WF is that monitoring is not required; however, a method to monitor the effect and the safety of dabigatran is not currently available. The Global Thrombosis Test (GTT) is a novel method to assess both clot formation and lysis activities under physiological conditions. OBJECTIVE: The aim of this study was to evaluate whether treatment with dabigatran might affect shear-induced thrombi (occlusion time [OT], sec) by the GTT, and to investigate the possibility that the GTT could be useful as a monitoring system for dabigatran. PATIENTS/METHODS: The study population consisted of 50 volunteers and 43 NVAF patients on WF therapy, who were subsequently switched to dabigatran. Using the GTT, the thrombotic status was assessed one day before and 1 month after switching anticoagulation from WF to dabigatran. RESULTS: The OT was 524.9 ± 17.0 sec in volunteers whereas that of NVAF patients on WF therapy was 581.7 ± 26.3 sec. The switch from WF to dabigatran significantly prolonged OT (784.5 ± 19.3 sec). One patient on WF therapy and 12 patients on dabigatran therapy were shown to have OT > 900 sec. CONCLUSION: The GTT could be used to assess the risk of dabigatran-related bleeding complications.Peer reviewe

A Gravitational Lens Model for the Lya Emitter, LAE 221724+001716 at z=3.1 in the SSA 22 Field

During the course of our Lyman continuum imaging survey, we found that the spectroscopically confirmed Lya emitter LAE 221724+001716 at z = 3.10 in the SSA 22 field shows strong Lyman continuum emission (lambda_rest ~ 900 A) that escapes from this galaxy. However, another recent spectroscopic survey revealed that the supposed Lyman continuum emission could arise from a foreground galaxy at z = 1.76 if the emission line newly detected from the galaxy at lambda_obs ~ 3360 A is Lya. If this is the case, as the angular separation between these two galaxies is very small (~ 0.6"), LAE 221724+001716 at z = 3.10 could be amplified by the gravitational lensing caused by this intervening galaxy. Here we present a possible gravitational lens model for the system of LAE 221724+001716. First, we estimate the stellar mass of the intervening galaxy as Mstar ~ 3.5x10^9 Msun from its UV luminosity and ~ 3.0x10^7--2.4x10^9 Msun through the SED fitting. Then, we find that the gravitational magnification factor ranges from 1.01 to 1.16 using the so-called singular isothermal sphere model for strong lensing. While LAE 221724+001716 is the first system of an LAE-LAE lensing reported so far, the estimated magnification factor is not so significant because the stellar mass of the intervening galaxy is small.Comment: 5 pages including 3 figures and 1 table, accepted for publication in ApJ on 13 Feb. 201

High-precision spectroscopy of ultracold molecules in an optical lattice

The study of ultracold molecules tightly trapped in an optical lattice can expand the frontier of precision measurement and spectroscopy, and provide a deeper insight into molecular and fundamental physics. Here we create, probe, and image microkelvin $^{88}$Sr$_2$ molecules in a lattice, and demonstrate precise measurements of molecular parameters as well as coherent control of molecular quantum states using optical fields. We discuss the sensitivity of the system to dimensional effects, a new bound-to-continuum spectroscopy technique for highly accurate binding energy measurements, and prospects for new physics with this rich experimental system.Comment: 12 pages, 4 figure

A New Measurement of the Stellar Mass Density at z~5: Implications for the Sources of Cosmic Reionization

We present a new measurement of the integrated stellar mass per comoving volume at redshift 5 determined via spectral energy fitting drawn from a sample of 214 photometrically-selected galaxies with z'<26.5 in the southern GOODS field. Following procedures introduced by Eyles et al. (2005), we estimate stellar masses for various sub-samples for which reliable and unconfused Spitzer IRAC detections are available. A spectroscopic sample of 14 of the most luminous sources with =4.92 provides a firm lower limit to the stellar mass density of 1e6 Msun/Mpc^3. Several galaxies in this sub-sample have masses of order 10^11 Msun implying significant earlier activity occurred in massive systems. We then consider a larger sample whose photometric redshifts in the publicly-available GOODS-MUSIC catalog lie in the range 4.4 <z 5.6. Before adopting the GOODS-MUSIC photometric redshifts, we check the accuracy of their photometry and explore the possibility of contamination by low-z galaxies and low-mass stars. After excising probable stellar contaminants and using the z'-J color to exclude any remaining foreground red galaxies, we conclude that 196 sources are likely to be at z~5. The implied mass density from the unconfused IRAC fraction of this sample, scaled to the total available, is 6e6 Msun/Mpc^3. We discuss the uncertainties as well as the likelihood that we have underestimated the true mass density. Including fainter and quiescent sources the total integrated density could be as high as 1e7 Msun/Mpc^3. Using the currently available (but highly uncertain) rate of decline in the star formationhistory over 5 <z< 10, a better fit is obtained for the assembled mass at z~5 if we admit significant dust extinction at early times or extend the luminosity function to very faint limits. [abridged]Comment: Accepted for Publication in ApJ, 39 page

K-Ras and β-catenin mutations cooperate with Fgfr3 mutations in mice to promote tumorigenesis in the skin and lung, but not in the bladder

The human fibroblast growth factor receptor 3 (FGFR3) gene is frequently mutated in superficial urothelial cell carcinoma (UCC). To test the functional significance of FGFR3 activating mutations as a ‘driver’ of UCC, we targeted the expression of mutated Fgfr3 to the murine urothelium using Cre-loxP recombination driven by the uroplakin II promoter. The introduction of the Fgfr3 mutations resulted in no obvious effect on tumorigenesis up to 18 months of age. Furthermore, even when the Fgfr3 mutations were introduced together with K-Ras or β-catenin (Ctnnb1) activating mutations, no urothelial dysplasia or UCC was observed. Interestingly, however, owing to a sporadic ectopic Cre recombinase expression in the skin and lung of these mice, Fgfr3 mutation caused papilloma and promoted lung tumorigenesis in cooperation with K-Ras and β-catenin activation, respectively. These results indicate that activation of FGFR3 can cooperate with other mutations to drive tumorigenesis in a context-dependent manner, and support the hypothesis that activation of FGFR3 signaling contributes to human cancer

Intense Source of Slow Positrons

We describe a novel design for an intense source of slow positrons based on pair production with a beam of electrons from a 10 MeV accelerator hitting a thin target at a low incidence angle. The positrons are collected with a set of coils adapted to the large production angle. The collection system is designed to inject the positrons in a Greaves-Surko trap [1]. Such a source could be the basis for a series of experiments in fundamental and applied research and would also be a prototype source for industrial applications which concern the field of defect characterization in the nanometer scale.Comment: submitted to N.I.M.