Determination of energy levels of surface states in GaAs metal-semiconductor field-effect transistor using deep-level transient spectroscopy

The energy levels of surface states at the surface of GaAs were determined through capacitance deep-level transient spectroscopy of GaAs metal-semiconductor field-effect transistor with large gate periphery. Two types of hole-like traps are observed in the spectra. These originate from the surface states at the ungated regions between gate and source/drain electrodes. The activation energies of both surface states are determined to be 0.65 +/- 0.07 and 0.88 +/- 0.04 eV, which agree well with the energy levels of As-Ga(+) and As-Ga(++) within band gap of GaAs, responsible for the Fermi level pinning at the surface.open151

Determination of energy levels of surface states in GaAs metal-semiconductor field-effect transistor using deep-level transient spectroscopy

The energy levels of surface states at the surface of GaAs were determined through capacitance deep-level transient spectroscopy of GaAs metal-semiconductor field-effect transistor with large gate periphery. Two types of hole-like traps are observed in the spectra. These originate from the surface states at the ungated regions between gate and source/drain electrodes. The activation energies of both surface states are determined to be 0.65 +/- 0.07 and 0.88 +/- 0.04 eV, which agree well with the energy levels of As-Ga(+) and As-Ga(++) within band gap of GaAs, responsible for the Fermi level pinning at the surface.open151

Effects of deep levels on transconductance dispersion in AlGaAs/InGaAs pseudomorphic high electron mobility transistor

The effects of deep levels on the transconductance dispersion in an AlGaAs/InGaAs pseudomorphic high electron mobility transistor was interpreted using capacitance deep level transient spectroscopy (DLTS). Transconductance was decreased by 10% in the frequency range of 10 Hz-10 kHz at the negative gate bias, but it was increased at the positive one. In the DLTS spectra, two hole trap-like signals corresponding to surface states were only observed at the negative pulse bias, whereas the DX-center with the activation energy of 0.42 +/- 0.01 eV were observed at the positive one. The activation energy agrees well with that obtained from the temperature dependence of the positive transconductance dispersion, 0.39 +/- 0.03 eV. These provide evidence that the positive and negative transconductance dispersions are due to the DX center and surface states, respectively.open9

Measured and calculated seismic velocities and densities for granulites from xenolith occurrences and adjacent exposed lower crustal sections: A comparative study from the North China craton

Granulites from the Neogene xenolith-bearing Hannuoba alkaline basalt and from the Manjinggou-Wayaokou exposed lower crustal section in the Archean Huai'an terrain, which occurs within and surrounds the Hannuoba basalt, provide a unique opportunity for a comparative study on petrophysical properties and composition of the lower crust represented by these two types of samples. P and S wave velocities and densities of 12 Hannuoba lower crustal xenoliths and one associated spinel lherzolite xenolith as well as nine granulites and granulite-facies metasedimentary rocks from the Archean Huai'an terrain were measured in laboratory at pressures up to 600 MPa and temperatures up to 600°C. Calculations of P and S wave velocities were also made for the same suite of samples based on modal mineralogy and single-crystal velocities whose variations with composition are considered by using microprobe analyses and velocities of end members. The measured and calculated Vp at room temperature and 600 MPa, where the microcrack effect is considered to be almost eliminated, agree within 4% for rocks from the Manjinggou-Wayaokou section and the adjacent Wutai-Jining upper crustal to upper lower crustal section. In contrast, the xenoliths show systematically lower measured Vp by up to 15% relative to calculated velocities, even if decompression-induced products of kelyphite and glass are taken into account. The lower measured velocities for xenoliths are attributed to grain boundary alteration and residual porosity. This implies that although granulite xenoliths provide direct information about lower crustal constitution and chemical composition, they are not faithful samples for studying in situ seismic properties of the lower crust in terms of measured velocities due to alterations during their entrainment to the surface, which changes their physical properties significantly. In this respect, granulites from high-grade terrains are better samples because they are not subjected to significant changes during their slow transport to the surface and because physical properties depend primarily on mineralogy in addition to pressure and temperature. On the other hand, calculated velocities for granulite xenoliths are consistent with velocities for granulites from terrains, suggesting that they can be also used to infer lower crust composition by correlating with results from seismic refraction studies. Copyright 2000 by the American Geophysical Union.published_or_final_versio

Complex sequencing rules of birdsong can be explained by simple hidden Markov processes

Complex sequencing rules observed in birdsongs provide an opportunity to investigate the neural mechanism for generating complex sequential behaviors. To relate the findings from studying birdsongs to other sequential behaviors, it is crucial to characterize the statistical properties of the sequencing rules in birdsongs. However, the properties of the sequencing rules in birdsongs have not yet been fully addressed. In this study, we investigate the statistical propertiesof the complex birdsong of the Bengalese finch (Lonchura striata var. domestica). Based on manual-annotated syllable sequences, we first show that there are significant higher-order context dependencies in Bengalese finch songs, that is, which syllable appears next depends on more than one previous syllable. This property is shared with other complex sequential behaviors. We then analyze acoustic features of the song and show that higher-order context dependencies can be explained using first-order hidden state transition dynamics with redundant hidden states. This model corresponds to hidden Markov models (HMMs), well known statistical models with a large range of application for time series modeling. The song annotation with these models with first-order hidden state dynamics agreed well with manual annotation, the score was comparable to that of a second-order HMM, and surpassed the zeroth-order model (the Gaussian mixture model (GMM)), which does not use context information. Our results imply that the hierarchical representation with hidden state dynamics may underlie the neural implementation for generating complex sequences with higher-order dependencies

The ethics of CYP2D6 testing for patients considering tamoxifen

The CYP2D6 gene is responsible for the majority of tamoxifen metabolism. Recent compelling, yet limited data have determined that postmenopausal women who carry a functional polymorphism in the CYP2D6 gene have a worse clinical outcome than women who have a wild-type genotype. In this commentary we discuss the level of evidence needed to change clinical practice and whether CYP2D6 genotyping is appropriate for all women considering tamoxifen as part of their adjuvant therapy

L'evoluzione della nozione di "consumatore" fra tutela dei diritti della persona, economia collaborativa e futuro del mercato interno dell'Unione europea

Il saggio sescrive l'evoluzione della nozione di "consumatore" nel diritto dell'Unione europea. Il "consumatore" \ue8 stato definito giuridicamente in una prima fase del processo di integrazione economica dalla Corte di giustizia come soggetto mediamente informato e normalmente avveduto, onde superare gli ostacoli alla libera circolazione delle merci frapposti dagli Stati membri in ragione dell'esigenza imperativa di tutelare il "soggetto debole" nei rapporti commerciali di massa. In questa prima fase la nozione aveva quindi una funzione essenzialmente "dissuasiva" del protezionismo e non assumeva, quindi, connotati paternalistici. Con l'evoluzione dell'integrazione europea, l'accentuazione della sensibilit\ue0 giuridica dell'ordinamento UE per la "persona" ed i suoi diritti fondamentali, la nozione di "consumatore" ha iniziato a mutare, vedendosi affiancare quella di "soggetto vulnerabile" (direttiva 2005/29 CE) e, progressivamente, estendere caratteristiche di fragilit\ue0 individuale ed ingenuit\ue0 precedentemente sconosciute alla elaborazione giuridica della Corte. Il processo evolutivo in questione \ue8 ancora in corso, e rischia, soprattutto nei settori pi\uf9 sensibili (come, a titolo esemplificativo, quello alimentare) di creare ostacoli allo sviluppo economico, in totale controtendenza rispetto alle finalit\ue0 perseguite negli anni ottanta

Effects of cigarette smoke on endothelial function of pulmonary arteries in the guinea pig

<p>Abstract</p> <p>Background</p> <p>Cigarette smoking may contribute to pulmonary hypertension in chronic obstructive pulmonary disease by altering the structure and function of pulmonary vessels at early disease stages. The objectives of this study were to evaluate the effects of long-term exposure to cigarette smoke on endothelial function and smooth muscle-cell proliferation in pulmonary arteries of guinea pigs.</p> <p>Methods</p> <p>19 male Hartley guinea pigs were exposed to the smoke of 7 cigarettes/day, 5 days/week, for 3 and 6 months. 17 control guinea pigs were sham-exposed for the same periods. Endothelial function was evaluated in rings of pulmonary artery and aorta as the relaxation induced by ADP. The proliferation of smooth muscle cells and their phenotype in small pulmonary vessels were evaluated by immunohistochemical expression of α-actin and desmin. Vessel wall thickness, arteriolar muscularization and emphysema were assessed morphometrically. The expression of endothelial nitric oxide synthase (eNOS) was evaluated by Real Time-PCR.</p> <p>Results</p> <p>Exposure to cigarette smoke reduced endothelium-dependent vasodilatation in pulmonary arteries (ANOVA p < 0.05) but not in the aorta. Endothelial dysfunction was apparent at 3 months of exposure and did not increase further after 6 months of exposure. Smoke-exposed animals showed proliferation of poorly differentiated smooth muscle cells in small vessels (p < 0.05) after 3 months of exposure. Prolonged exposure resulted in full muscularization of small pulmonary vessels (p < 0.05), wall thickening (p < 0.01) and increased contractility of the main pulmonary artery (p < 0.05), and enlargement of the alveolar spaces. Lung expression of eNOS was decreased in animals exposed to cigarette smoke.</p> <p>Conclusion</p> <p>In the guinea pig, exposure to cigarette smoke induces selective endothelial dysfunction in pulmonary arteries, smooth muscle cell proliferation in small pulmonary vessels and reduced lung expression of eNOS. These changes appear after 3 months of exposure and precede the development of pulmonary emphysema.</p