154 research outputs found
High resolution spectroscopy of methyltrioxorhenium: towards the observation of parity violation in chiral molecules
Originating from the weak interaction, parity violation in chiral molecules
has been considered as a possible origin of the biohomochirality. It was
predicted in 1974 but has never been observed so far. Parity violation should
lead to a very tiny frequency difference in the rovibrational spectra of the
enantiomers of a chiral molecule. We have proposed to observe this predicted
frequency difference using the two photon Ramsey fringes technique on a
supersonic beam. Promising candidates for this experiment are chiral oxorhenium
complexes, which present a large effect, can be synthesized in large quantity
and enantiopure form, and can be seeded in a molecular beam. As a first step
towards our objective, a detailed spectroscopic study of methyltrioxorhenium
(MTO) has been undertaken. It is an ideal test molecule as the achiral parent
molecule of chiral candidates for the parity violation experiment. For the
187Re MTO isotopologue, a combined analysis of Fourier transform microwave and
infrared spectra as well as ultra-high resolution CO2 laser absorption spectra
enabled the assignment of 28 rotational lines and 71 rovibrational lines, some
of them with a resolved hyperfine structure. A set of spectroscopic parameters
in the ground and first excited state, including hyperfine structure constants,
was obtained for the antisymmetric Re=O stretching mode of this molecule. This
result validates the experimental approach to be followed once a chiral
derivative of MTO will be synthesized, and shows the benefit of the combination
of several spectroscopic techniques in different spectral regions, with
different set-ups and resolutions. First high resolution spectra of jet-cooled
MTO, obtained on the set-up being developed for the observation of molecular
parity violation, are shown, which constitutes a major step towards the
targeted objective.Comment: 20 pages, 6 figure
Simultaneous Source Localization and Polarization Estimation via Non-Orthogonal Joint Diagonalization with Vector-Sensors
Joint estimation of direction-of-arrival (DOA) and polarization with electromagnetic vector-sensors (EMVS) is considered in the framework of complex-valued non-orthogonal joint diagonalization (CNJD). Two new CNJD algorithms are presented, which propose to tackle the high dimensional optimization problem in CNJD via a sequence of simple sub-optimization problems, by using LU or LQ decompositions of the target matrices as well as the Jacobi-type scheme. Furthermore, based on the above CNJD algorithms we present a novel strategy to exploit the multi-dimensional structure present in the second-order statistics of EMVS outputs for simultaneous DOA and polarization estimation. Simulations are provided to compare the proposed strategy with existing tensorial or joint diagonalization based methods
History, power, and electricity: American popular magazine accounts of electroconvulsive therapy, 1940–2005
Electroconvulsive therapy (ECT) is a psychiatric treatment that has been in use in the United States since the 1940s. During the whole of its existence, it has been extensively discussed and debated within American popular magazines. While initial reports of the treatment highlighted its benefits to patients, accounts by the 1970s and 1980s were increasingly polarized. This article analyzes the popular accounts over time, particularly the ways in which the debates over ECT have revolved around different interpretations of ECT's history and its power dynamics. © 2008Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57903/1/20283_ftp.pd
Progress toward a first observation of parity violation in chiral molecules by high-resolution laser spectroscopy
Parity violation (PV) effects in chiral molecules have so far never been
experimentally observed. To take this challenge up, a consortium of physicists,
chemists, theoreticians and spectroscopists has been established and aims at
measuring PV energy differences between two enantiomers by using
high-resolution laser spectroscopy. In this article, we present our common
strategy to reach this goal, the progress accomplished in the diverse areas,
and point out directions for future PV observations. The work of Andr\'e Collet
on bromochlorofluoromethane enantiomers, their synthesis and their chiral
recognition by cryptophanes made feasible the first generation of experiments
presented in this paper.Comment: 30 pages, 11 figure
A novel deletion at codon 441 of the APC gene associated with ophthalmic lesions (CHRPE) in a South African family
A novel mutation at codon 441 in exon 10 of the adenomatous polyposis coli (APC) gene was identified in a South African family of mixed ancestry, using a convenient, non-radioactive, heteroduplex-SSCP screening assay. This single thymidine deletion after nucleotide position 1322 creates a frameshift resulting in a downstream stop codon at amino acid residue 453 of the APC gene. Genotypes of nine family members were subsequently correlated with the presence or absence of congenital hypertrophy of the retinal pigment epithelium (CHRPE), since expression of this common extracolonic manifestation of FAP is largely determined by the length of the truncated protein. CHRPE was absent in the five unaffected family members analysed, while four mutation positive subjects showed these ophthalmic lesions. Correlation between the molecular analysis and ophthalmic examinations, performed without knowledge of clinical and genetic status respectively, provided additional evidence in favour of the view that the range of phenotypic expression in FAP may result from different allelic manifestations of APC mutations.Articl
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