Charge-conjugation symmetry breaking and the absorption spectra of polyphenylenes

1995 ◽  
Vol 51 (8) ◽  
pp. 5546-5549 ◽  
Author(s):  
Yu. N. Gartstein ◽  
M. J. Rice ◽  
E. M. Conwell
Keyword(s):  
Symmetry Breaking ◽  
Absorption Spectra ◽  
Charge Conjugation

Two-photon absorption spectra of a near-infrared 2-azaazulene polymethine dye: solvation and ground-state symmetry breaking

2013 ◽  
Vol 15 (20) ◽  
pp. 7666 ◽  
Author(s):  
Honghua Hu ◽  
Olga V. Przhonska ◽  
Francesca Terenziani ◽  
Anna Painelli ◽  
Dmitry Fishman ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Absorption Spectra ◽  
Ground State ◽  
Near Infrared ◽  
Photon Absorption ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Polymethine Dye

Absorption spectroscopy of charged excitations in α-sexithiophene: evidence for charge conjugation symmetry breaking

1996 ◽  
Vol 210 (1-2) ◽  
pp. 229-234 ◽  
Author(s):  
P.A. Lane ◽  
X. Wei ◽  
Z.V. Vardeny ◽  
J. Poplawski ◽  
E. Ehrenfreund ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Absorption Spectroscopy ◽  
Charge Conjugation

Charge-conjugation symmetry breaking in poly (phenylenevinylene) derivatives

1996 ◽  
Vol 78 (3) ◽  
pp. 183-186 ◽  
Author(s):  
Yu.N. Gartstein ◽  
M.J. Rice ◽  
E.M. Conwell
Keyword(s):  
Symmetry Breaking ◽  
Charge Conjugation

Ultraviolet Absorption of Refractory Elements by a Dual Laser Plasma Method

1988 ◽  
Vol 102 ◽  
pp. 243-246
Author(s):  
J.T. Costello ◽  
W.G. Lynam ◽  
P.K. Carroll
Keyword(s):  
Absorption Spectra ◽  
Laser Plasma ◽  
Optical Pulse ◽  
Ionic Species ◽  
Neutral Species ◽  
Plasma Method ◽  
Plasma Technique ◽  
Refractory Elements ◽  
Delay Times ◽  
Dual Laser

AbstractThe dual laser-produced plasma technique for the study of ionic absorption spectra has been developed by the use of two Q-switched ruby lasers to enable independent generation of the absorbing and back-lighting plasmas. Optical pulse handling is used in the coupling cicuits to enable reproducible pulse delays from 250 nsec. to 10 msec, to be achieved. At delay times > 700 nsec. spectra of essentially pure neutral species are observed. The technique is valuable, not only for obtaining the neutral spectra of highly refractory and/or corrosive materials but also for studying behaviour of ionic species as a function of time. Typical spectra are shown in Fig. 1.

XUV Absorption Spectra of Carbon Ions

1988 ◽  
Vol 102 ◽  
pp. 71-73
Author(s):  
E. Jannitti ◽  
P. Nicolosi ◽  
G. Tondello
Keyword(s):  
Absorption Spectra ◽  
Cross Section ◽  
Theoretical Calculations ◽  
Photoionization Cross Section ◽  
Carbon Ions

AbstractThe photoabsorption spectra of the carbon ions have been obtained by using two laser-produced plasmas. The photoionization cross-section of the CV has been absolutely measured and the value at threshold, σ=(4.7±0.5) × 10−19cm2, as well as its behaviour at higher energies agrees quite well with the theoretical calculations.

Symmetry breaking in convergent-beam diffraction

1989 ◽  
Vol 47 ◽  
pp. 480-481
Author(s):  
D.J. Eaglesham
Keyword(s):  
Symmetry Breaking ◽  
Point Group ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
Space Groups ◽  
Atomic Displacements ◽  
Small Probe ◽  
Phase Sensitive ◽  
Convergent Beam

Convergent Beam Electron Diffraction is now almost routinely used in the determination of the point- and space-groups of crystalline samples. In addition to its small-probe capability, CBED is also postulated to be more sensitive than X-ray diffraction in determining crystal symmetries. Multiple diffraction is phase-sensitive, so that the distinction between centro- and non-centro-symmetric space groups should be trivial in CBED: in addition, the stronger scattering of electrons may give a general increase in sensitivity to small atomic displacements. However, the sensitivity of CBED symmetry to the crystal point group has rarely been quantified, and CBED is also subject to symmetry-breaking due to local strains and inhomogeneities. The purpose of this paper is to classify the various types of symmetry-breaking, present calculations of the sensitivity, and illustrate symmetry-breaking by surface strains.CBED symmetry determinations usually proceed by determining the diffraction group along various zone axes, and hence finding the point group. The diffraction group can be found using either the intensity distribution in the discs

Centrosome Aurora A gradient ensures single polarity axis in C. elegans embryos

2020 ◽  
Vol 48 (3) ◽  
pp. 1243-1253 ◽  
Author(s):  
Sukriti Kapoor ◽  
Sachin Kotak
Keyword(s):  
Symmetry Breaking ◽  
Cell Fate ◽  
Cell Cortex ◽  
Axis Formation ◽  
Aurora A Kinase ◽  
Aurora A ◽  
C Elegans ◽  
Cell Embryo ◽  
Polarity Establishment

Cellular asymmetries are vital for generating cell fate diversity during development and in stem cells. In the newly fertilized Caenorhabditis elegans embryo, centrosomes are responsible for polarity establishment, i.e. anterior–posterior body axis formation. The signal for polarity originates from the centrosomes and is transmitted to the cell cortex, where it disassembles the actomyosin network. This event leads to symmetry breaking and the establishment of distinct domains of evolutionarily conserved PAR proteins. However, the identity of an essential component that localizes to the centrosomes and promotes symmetry breaking was unknown. Recent work has uncovered that the loss of Aurora A kinase (AIR-1 in C. elegans and hereafter referred to as Aurora A) in the one-cell embryo disrupts stereotypical actomyosin-based cortical flows that occur at the time of polarity establishment. This misregulation of actomyosin flow dynamics results in the occurrence of two polarity axes. Notably, the role of Aurora A in ensuring a single polarity axis is independent of its well-established function in centrosome maturation. The mechanism by which Aurora A directs symmetry breaking is likely through direct regulation of Rho-dependent contractility. In this mini-review, we will discuss the unconventional role of Aurora A kinase in polarity establishment in C. elegans embryos and propose a refined model of centrosome-dependent symmetry breaking.

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