Search results for "inho"

HEAT FLUX IN SUPERFLUID TRANSITION AND IN TURBULENT HELIUM COUNTERFLOW

First tests of the applicability of gamma-ray imaging for background discrimination in time-of-flight neutron capture measurements

2015

In this work we explore for the first time the applicability of using $\gamma$-ray imaging in neutron capture measurements to identify and suppress spatially localized background. For this aim, a pinhole gamma camera is assembled, tested and characterized in terms of energy and spatial performance. It consists of a monolithic CeBr$_3$ scintillating crystal coupled to a position-sensitive photomultiplier and readout through an integrated circuit AMIC2GR. The pinhole collimator is a massive carven block of lead. A series of dedicated measurements with calibrated sources and with a neutron beam incident on a $^{197}$Au sample have been carried out at n_TOF, achieving an enhancement of a factor…

Pedicularis sylvatica L. (K.R. Kupffer)

1923

Meža jāņeglītes pirmais atradums Latvijā. Atradne Kurzemē, Rucavā starp Visminu un Zirnāju Vizuļu mājām sausā vietā pļavas malā. Aprakstījis un K. R. Kupferam nodevis Nikolajs Malta. / Wald-Läusekraut erster Fund in Lettland. Gefunden in Kurland, Rutzau, Wiese zwichen Wismini und Zirnaju Visuli an trockenen Stelle am Rand den Wiese. Beschrieben und an K. R. Kupfer von Nikolai Malta übergeben. / Wood Lousewort's first find in Latvia. A deposit in Kurzeme, Rucava between Vismini and Zirnāji Vizuļi houses in a dry place at the edge of the meadow. Described and handed over to K. R. Kupfer by Nikolai Malta. [Attēls no LU Muzeja kolekcijas Herbarium Balticum (RIG I); (BOT2767)]

Common and separable behavioral and neural mechanisms underlie the generalization of fear and disgust

2021

Generalization represents the transfer of a conditioned responses to stimuli that resemble the conditioned stimulus (CS). Previous studies on generalization of defensive avoidance responses have primarily focused on fear and have neglected disgust generalization, which represents a key pathological mechanism in some anxiety disorders. In the present study we examined common and distinct mechanisms of fear and disgust generalization by means of a fear or disgust multi-CS conditioning and generalization paradigm with concomitant event-related potential (ERPs) acquisition in n = 62 subjects. We demonstrate that compared to fear, disgust-relevant generalized stimuli (GS) elicited larger expecta…

Isoelectronic series of oxygen deficient centers in silica: experimental estimation of homogeneous and inhomogeneous spectral widths

2008

We report nanosecond time-resolved photoluminescence measurements on the isoelectronic series of oxygen deficient centers in amorphous silica related to silicon, germanium and tin atoms, which are responsible of fluorescence activities at approximately 4 eV under excitation at approximately 5 eV. The dependence of the first moment of their emission band on time and that of the radiative decay lifetime on emission energy are analyzed within a theoretical model able to describe the effects introduced by disorder on the optical properties of the defects. We obtain separate estimates of the homogeneous and inhomogeneous contributions to the measured emission line width, and we derive homogeneou…

Photoluminescence spectral dispersion as a probe of structural inhomogeneity in silica

2011

We perform time-resolved photoluminescence measurements on point defects in amorphous silicon dioxide (silica). In particular, we report data on the decay kinetics of the emission signals of extrinsic oxygen deficient centres of the second type from singlet and directly excited triplet states, and we use them as a probe of structural inhomogeneity. Luminescence activity in sapphire (alpha-Al(2)O(3)) is studied as well and used as a model system to compare the optical properties of defects in silica with those of defects embedded in a crystalline matrix. Only for defects in silica did we observe a variation of the decay lifetimes with emission energy and a time dependence of the first moment…

Inhomogeneous Broadening of Photoluminescence Spectra and Kinetics of Nanometer-Thick (Phenethylammonium)2PbI4 Perovskite Thin Films: Implications fo…

2021

An outstanding potentiality of layered two-dimensional (2D) organic–inorganic hybrid perovskites (2DHPs) is in the development of solar cells, photodetectors, and light-emitting diodes. In 2DHPs, an exciton is localized in an atomically thin lead(II) halide inorganic layer of sub-nanometer thickness as in a quantum well sandwiched between organic layers as energetic and dielectric barriers. In previous years, versatile optical characterization of 2DHPs has been carried out mainly for thin flakes of single crystals and ultrathin (of the order of 20 nm) polycrystalline films, whereas there is a lack of optical characterization of thick (hundreds of nanometers) polycrystalline films, fundament…

Inhomogeneous width of oxygen-deficient centers induced by electron irradiation of silica

2009

We report a study of the luminescence activity of oxygen-deficient centers stabilized in as-grown synthetic silica, as compared with the same defects induced by $\ensuremath{\beta}$ irradiation at increasing doses, ranging from $1.2\ifmmode\times\else\texttimes\fi{}{10}^{3}$ to $5\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{kGy}$. We experimentally observe a progressive broadening of the luminescence band with increasing total electron dose released on samples. By analyzing our data within a theoretical model capable of separating homogeneous and inhomogeneous contribution to the total luminescence linewidth, we observe that the increasing of the width is entirely ascribable to t…

All-optical super resolved and extended depth of focus imaging with random pinhole array aperture

2008

In this paper, we present a novel approach which allows combining super resolved imaging with extended depth of focus while the result is obtained by all-optical means and no digital processing is required. The presented approach for the super resolved imaging includes attaching a random pinhole array plate to the aperture plane of the imaging system. The energetic efficiency of the system is high and it is much larger than an imaging through a single pinhole which also has extended depth of focus. The super resolving result is obtained by mechanic scanning of the aperture plane with the random plate.

Zur Frage der Charakterisierung stationärer Bewegungen in der Hydrodynamik

1958

Helmholtz andKorteweg propose that the steady motion of a viscous fluid under constant extraneous forces having a single-valued potential dissipates—for any given region and assuming that inertia terms in the dynamic equations can be neglected—less energy than any other motion with the same values of velocity at the boundary.—A generalization of this proposition is here given, and an application discussed. The application deals with the motion of a simple macromolecule model in an inhomogeneous field of flow—a motion caused only by the influence ofStokes' friction.