Search results for "Polar"
showing 10 items of 3817 documents
Longitudinal contribution to the alignment polarization of quarks produced in e + e - -annihilation: an O (α s ) effect
1996
We calculate the longitudinal contribution to the alignment polarization Pl of quarks produced in e+e− annihilation. In the Standard Model, the longitudinal alignment polarization vanishes at the Born term level and thus receives its first non-zero contribution from the O(αs) tree graph process. We provide analytical and numerical results for the longitudinal alignment polarization of massless and massive quarks, in particular for the recently discovered top quark.
Polar angle dependence of the longitudinal polarization of quarks produced in e + e - -annihilation
1997
We calculate one-loop radiative QCD corrections to the three polarized and unpolarized structure functions that determine the beam-quark polar angle dependence of the longitudinal polarization of light and heavy quarks produced in e+e−-annihilations. We present analytical and numerical results for the longitudinal polarization and its polar angle dependence. We discuss in some detail the zero-mass limit of our results and the role of the anomalous spin-flip contributions to the polarization observables in the zero-mass limit. Our discussion includes transverse and longitudinal beam polarization effects.
Beam-Recoil Polarization Measurement of π0 Electroproduction on the Proton in the Region of the Roper Resonance
2017
The helicity-dependent recoil proton polarizations P_{x}^{'} and P_{z}^{'} as well as the helicity-independent component P_{y} have been measured in the p(e[over →],e^{'}p[over →])π^{0} reaction at four-momentum transfer Q^{2}≃0.1 GeV^{2}, center-of-mass proton emission angle θ_{p}^{*}≃90°, and invariant mass W≃1440 MeV. This first precise measurement of double-polarization observables in the energy domain of the Roper resonance P_{11}(1440) by exploiting recoil polarimetry has allowed for the extraction of its scalar electroexcitation amplitude at an unprecedentedly low value of Q^{2}, establishing a powerful instrument for probing the interplay of quark and meson degrees of freedom in t…
Quantum light depolarization: the phase-space perspective
2008
Quantum light depolarization is handled through a master equation obtained by coupling dispersively the field to a randomly distributed atomic reservoir. This master equation is solved by transforming it into a quasiprobability distribution in phase space and the quasiclassical limit is investigated.
Molecular quenching and relaxation in a plasmonic tunable system
2008
Molecular fluorescence decay is significantly modified when the emitting molecule is located near a plasmonic structure. When the lateral sizes of such structures are reduced to nanometer-scale cross sections, they can be used to accurately control and amplify the emission rate. In this Rapid Communication, we extend Green's dyadic method to quantitatively investigate both radiative and nonradiative decay channels experienced by a single fluorescent molecule confined in an adjustable dielectric-metal nanogap. The technique produces data in excellent agreement with current experimental work.
ACTION POTENTIAL, MEMBRANE CURRENTS AND FORCE OF CONTRACTION IN MAMMALIAN HEART MUSCLE FIBRES TREATED WITH QUINIDINE
1978
The effects of quinidine on electrical and mechanical activity were investigated in atrial and/or ventricular heart muscle preparations from guinea pigs and cats. Quinidine (1--100 micrometer) exerted negative inotropic effects in papillary muscles from guinea pigs and cats. In guinea-pig left atria, a positive inotropic effect was superimposed on the negative inotropic effect in response to quinidine. Quinidine (100 micrometer) prolonged the duration of the action potential in guinea-pig atria but shortened it in guinea-pig ventricular muscle. In cat papillary muscles, the late repolarization was markedly prolonged by quinidine, but virtually no change of the plateau phase was observed. Th…
Supramolecular hierarchy among halogen and hydrogen bond donors in light-induced surface patterning
2015
Halogen bonding, a noncovalent interaction possessing several unique features compared to the more familiar hydrogen bonding, is emerging as a powerful tool in functional materials design. Herein, we unambiguously show that one of these characteristic features, namely high directionality, renders halogen bonding the interaction of choice when developing azobenzene-containing supramolecular polymers for light-induced surface patterning. The study is conducted by using an extensive library of azobenzene molecules that differ only in terms of the bond-donor unit. We introduce a new tetrafluorophenol-containing azobenzene photoswitch capable of forming strong hydrogen bonds, and show that an io…
Nonsense polarity, RNA processing and decay in phage f1.
2011
Nonsense polarity in most cases depends on activation of cryptic transcription terminators. We found that the strong polar effect observed in the nonsense polar mutant R4 of phage f1, mapping in the 5’ proximal region of gene III, instead depends on enhanced instability of mutant mRNAs, whose pattern can be restored by reduction of RNase E activity. rne -(ts) E. coli strains allowed to explore the mechanisms underlying f1 mRNA processing and degradation. The major gene III species, a 1.8 Kb long molecule, appeared to be a secondary transcript, whose decay is modulated by a REP, located at its 3' end. The RNA pool of a mutagenized phage unable to form that structure, lacks completely that tr…
Mollwo–Ivey relations for optical absorption bands of the atomic and F′ centres in alkali halides
2001
Evidence indicates that two classes of the transient IR-absorption bands: (a) with maxima at 0.27-0.36 eV in NaCI, KCI, KBr, KI and RbCl and due to shallow electron traps or bound polarons according to Jacobs (Phys. Stat. Sol. B 129 (1985) 755) and Korovkin and Lebedkina (Fiz. Tverd. Tela (Russian) 35 (1993) 642), and (b) with maxima at 0.15-0.36 eV in NaI, NaBr, NaCl : I, KCl : I I, RbCl: I and RbBr : I, due to on-centre STE localised at iodine-dimer according to Hirota et al. (J. Phys. Soc. Japan 63 (1994) 2774, Phys. Rev. B 52 (1995) 7779) and Edamatsu and Hirai (Mater. Sci. Forum 239-241 (1997) 525), are caused by the same defect. We propose that the defect is an atomic alkali impurity …
Recent progress in photoemission microscopy with emphasis on chemical and magnetic sensitivity
1997
Abstract With the improved access to synchrotron radiation sources photoemission electron microscopy is developing into a versatile analytical tool in surface and materials science. The broad spectral range and the well-defined polarization characteristics of synchrotron light permit a unique combination of topographic, chemical, and even magnetic investigations down to a mesoscopic scale. The potentiality of photoemission electron microscopy is demonstrated by several experiments on surfaces and microstructured thin film systems, which have been carried out with a newly designed instrument. We discuss its different modes of operation with respect to both microscopy and spectroscopy. A comb…