Search results for "BAND"

Valence bands of poly(methylmethacrylate) and photoion emission in vacuum ultraviolet region

1992

Photoion and photoelectron yields were measured for poly(methylmethacrylate) in the photon energy region of 8–40 eV using synchrotron radiation. Further, the valence‐band structure was investigated with ultraviolet photoelectron spectra and valence effective Hamiltonian calculations. A significant difference was observed between the photon energy dependencies of photoion and photoelectron yields. The threshold energy for photoion emission was found to be 10.5 eV, while that for photoelectron emission was 8.5 eV, indicating holes created near the valence‐band top do not contribute to the ion emission. At the higher‐energy region, the ion emission efficiency was found to be enhanced in the ph…

2018

In this article we explore the effects that new information and communication technologies (ICTs) have on family relations in Finland. The idea of ‘new connectivities’ works as a starting point for...

Flux and color variations of the quadruply imaged quasar HE 0435-1223

2011

aims: We present VRi photometric observations of the quadruply imaged quasar HE 0435-1223, carried out with the Danish 1.54m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as a function of time. methods: We monitored the object during two seasons (2008 and 2009) in the VRi spectral bands, and reduced the data with two independent techniques: difference imaging and PSF (Point Spread Function) fitting.results: Between these two seasons, our results show an evident decrease in flux by ~0.2-0.4 magnitudes of the four lensed components in the three filters. We also found a significant increase (~0.05-0.015) in their V-R …

Journalists’ Associations as Political Instruments in Central and Eastern Europe

2017

This editorial provides the overall context for the five cases—three national and two international—covered in this thematic issue. While the cases are from Central and Eastern Europe (CEE), they highlight fundamental questions of journalism everywhere, including contradictions between freedom and control, professionalism and politics, individual and collective. The associations of journalists serve as very useful platforms to study these questions, especially at historical turning points when the whole political system changed, as happened twice in CEE after World War II.

NOR regions of polychaete worms of the genus Ophryotrocha studied by chromosome banding techniques and FISH.

2000

This article reports the results of cytogenetic analyses carried out on 10 species of polychaete worms belonging to the genus Ophryotrocha (Dorvilleidae). Nucleolar organizer regions (NORs) were characterized by Ag staining, C-banding, CMA3 staining, and ribosomal fluorescent in situ hybridization (rDNA FISH). Extensive intraspecific variation in NOR number and distribution were observed in O. costlowi, O. sp. macrovifera, O. notoglandulata, O.l. labronica, O. l. pacifica (2n = 6), O. p. puerilis, O. diadema (2n = 8), O. hartmanni, O. gracilis (2n = 10). In O. sp. robusta (2n = 10), Ag-NORs were always located on a single chromosome pair. CMA3 staining suggests a possible trend toward a GC-…

Impact of secondary succession in abandoned fields on some properties of acidic sandy soils

2020

Abstract Abandonment of agricultural lands in recent decades is occurring mainly in Europe, North America and Oceania, and changing the fate of landscapes as the ecosystem recovers during fallow stage. The objective of this study was to find the impact of secondary succession in abandoned fields on some parameters of acidic sandy soils in the Borská nížina lowland (southwestern Slovakia). We investigated soil chemical (pH and soil organic carbon content), hydrophysical (water sorptivity, and hydraulic conductivity), and water repellency (water drop penetration time, water repellency cessation time, repellency index, and modified repellency index) parameters, as well as the ethanol sorptivit…

Production of nanometer-size GaAs nanocristals by nanosecond laser ablation in liquid.

2012

This paper reports the formation and characterization of spherical GaAs quantum dots obtained by nanosecond pulsed laser ablation in a liquid (ethanol or methanol). The produced bare GaAs nanoparticles demonstrate rather narrow size distribution which depends on the applied laser power density (from 4.25 to 13.9 J/cm 2 in our experiments) and is as low as 2.5 nm for the highest power used. The absolute value of the average diameter also decreases significantly, from 13.7 to 8.7 nm, as the laser power increases in this interval. Due to the narrow nanoparticle size dispersion achieved at the highest laser powers two absorption band edges are clearly distinguishable at about 1.72 and 3.15 eV w…

Failure analysis of normally-off GaN HEMTs under avalanche conditions

2020

Gallium nitride (GaN) high electron-mobility transistors (HEMTs) are promising devices in the power electronics field owing to their wide bandgap (WBG). However, all the potential advantages provided by their WBG require reliability improvement. In industrial applications, robustness is one of the main factors considered by circuit designers. This study focuses on the observation of the degradation behavior of the main waveforms of unclamped inductive-switching (UIS) test circuits of two different commercial GaN HEMT structures. The relevance of this study lies in the potential applications of these devices to high-voltage applications and automotive systems where they are subjected to many…

Optimal Design of an X-Band, Fully-Coaxial, Easily-Tunable Broadband Power Equalizer for a Microwave Power Module

2020

A microwave power module (MPM), which is a hybrid combination of a solid-state power amplifier (SSPA) as a driver and a traveling-wave tube amplifier (TWT) as the final high power stage, is a high-power device largely used for radar applications. A gain equalizer is often required to flatten the TWT output power gain owing to its big gain fluctuations over the operating frequency range. In this paper, the design of an X-band, fully-coaxial, easily-tunable broadband power equalizer for an MPM is presented. The structure is composed of a coaxial waveguide as the main transmission line and a coaxial cavity loaded with absorbing material as a resonant unit. Sensitivity analyses of the attenuati…

Occupational Safety and Health Risk Assessment in Engineered Nanoparticles Manufacturing Processes

2017

The engineered nanoparticles are more and more entering in Romanian working places, both in research laboratories and in manufacturing processes. Ever increasingly numerous evidence shows that this materials science revolution can generate significant health, safety and environmental hazards, in addition to the social, economic and ethical challenges involvedBased on the precautionary principle recommended be the European Union and a thorough literature review, this research is intended to introduce a framework for further development of an Occupational Health and Safety risk management foundation in this field of concern. Starting from a systematic approach in terms of occupational exposur…