Interaction of reed and acoustic resonator in clarinetlike systems

Sound emergence in clarinetlike instruments is investigated in terms of instability of the static regime. Various models of reed-bore coupling are considered, from the pioneering work of Wilson and Beavers ["Operating modes of the clarinet", J. Acoust. Soc. Am. 56, 653--658 (1974)] to more recent modeling including viscothermal bore losses and vena contracta at the reed inlet. The pressure threshold above which these models may oscillate as well as the frequency of oscillation at threshold are calculated. In addition to Wilson and Beavers' previous conclusions concerning the role of the reed damping in the selection of the register the instrument will play on, the influence of the reed motion induced flow is also emphasized, particularly its effect on playing frequencies, contributing to reduce discrepancies between Wilson and Beavers' experimental results and theory, despite discrepancies still remain concerning the pressure threshold. Finally, analytical approximations of the oscillating solution based on Fourier series expansion are obtained in the vicinity of the threshold of oscillation. This allows to emphasize the conditions which determine the nature of the bifurcation (direct or inverse) through which the note may emerge, with therefore important consequences on the musical playing performances

News discourses on distant suffering: A critical discourse analysis of the 2003 SARS outbreak

News carries a unique signifying power, a power to represent events in particular ways (Fairclough, 1995). Applying Critical Discourse Analysis and Chouliaraki's theory on the mediation of suffering (2006), this article explores the news representation of the 2003 global SARS outbreak. Following a case-based methodology, we investigate how two Belgian television stations have covered the international outbreak of SARS. By looking into the mediation of four selected discursive moments, underlying discourses of power, hierarchy and compassion were unraveled. The analysis further identified the key role of proximity in international news reporting and supports the claim that Western news media mainly reproduce a Euro-American centered world order. This article argues that news coverage of international crises such as SARS constructs and maintains the socio-cultural difference between 'us' and 'them' as well as articulating global power hierarchies and a division of the world in zones of poverty and prosperity, danger and safety

Massive Spin Collective Mode in Quantum Hall Ferromagnet

It is shown that the collective spin rotation of a single Skyrmion in quantum Hall ferromagnet can be regarded as precession of the entire spin texture in the external magnetic field, with an effective moment of inertia which becomes infinite in the zero g-factor limit. This low-lying spin excitation may dramatically enhance the nuclear spin relaxation rate via the hyperfine interaction in the quantum well slightly away from filling factor equal one.Comment: 4 page

Characterization of Tryptophanase from Vibrio cholerae O1

AbstractTryptophanase (Trpase) encoded by the tnaA gene catalyzes the conversion of tryptophan to indole, which is an extracellular signaling molecule detected in various bacteria including Vibrio cholerae. Indole has been demonstrated to regulate biofilm formation, drug resistance, plasmid maintenance and spore formation of bacteria. In the present study, the tnaA gene from V. cholerae O1 (VcTrpase) was cloned and expressed in E. coli BL21(DE3) tn5:tnaA (a Trpase-deficient competent). VcTrpase was purified by Ni2+-NTA chromatography. The obtained VcTrpase had a molecular mass of approximately 49 kDa, a specific activity of 3 U/mg protein, and absorption peaks at 330 and 435nm. Using a site-directed mutagenesis technique, replacement of Arg419 by Val resulted in a VcTrpase completely devoid of activity. Thus, this site can be a target for drug design for controlling V. cholerae

Spectroscopic Evidence for the Localization of Skyrmions near Nu=1 as T->0

Optically pumped nuclear magnetic resonance measurements of Ga-71 spectra were carried out in an n-doped GaAs/Al0.1Ga0.9As multiple quantum well sample near the integer quantum Hall ground state Nu=1. As the temperature is lowered (down to T~0.3 K), a ``tilted plateau'' emerges in the Knight shift data, which is a novel experimental signature of quasiparticle localization. The dependence of the spectra on both T and Nu suggests that the localization is a collective process. The frozen limit spectra appear to rule out a 2D lattice of conventional skyrmions.Comment: 4 pages (REVTEX), 5 eps figures embedded in text, published versio

Study on Solar KANG Heating System for Cold Areas

AbstractThe current rural traditional heated kang cannot meet people's increasing requirements of comfort and environmental protection. This paper propose solar kang heating system in cold regions. System performance and heating effect were analyzed. We selected two typical rooms. One was set in traditional kang, and the other one was solar Kang type. Using temperature recording instrument and 64 roads inspection instrument and other instruments, we test the indoor temperature and the kang surface temperature of two rooms. Solar kang thermal resistance, heat storage, heat dissipation and heating effect were analyzed and compared. The results of the study show this system have the smaller fluctuation, more comfort while alleviating the kang surface overheat or super-cooling problem. It satisfied the requirements of indoor thermal comfort. The warming rate is 5.17°C/h, and the cooling rate is 3.01°C/h. These are slower than traditional Huokang speed. It improved the heat storage capacity of kang body with surface heat dissipation 1237W. Average temperature of the solar kang heating room was improved 3.28°C. It gets the smaller indoor temperature fluctuation. PMV values are concentrated about -0.5, and this basically meet the requirements of the user comfort

A non-catecholamine-producing sympathetic paraganglioma of the spermatic cord: the importance of performing candidate gene mutation analysis

textabstractBackground: Catecholamine-producing tumours are called pheochromocytomas when they are located in the adrenal gland and sympathetic paragangliomas when they are located elsewhere in the abdomen. Rarely these tumours do not produce catecholamines and even more rarely they arise in the spermatic cord. Over the past decade, systematic mutation analysis of apparently sporadic cases of pheochromocytomas and paragangliomas has elucidated the frequent presence of germ line mutations in one of five candidate genes, including RET, VHL, SDHB, SDHC, and SDHD. Clinical history and methods: We describe a 45-year-old man with a non catecholamine-producing paraganglioma of the spermatic cord. We performed SDHB immunohistochemistry and performed mutation analysis of the SDHB, SDHC, and SDHD genes. Results: There was no staining of tumour cells with SDHB immunohistochemistry, indicative of an SDH mutation. Mutation analysis demonstrated a germ line SDHD mutation (p.Val147Met). Conclusions: Systematic mutation analysis is required in paraganglioma patients for the detection of germ line mutations. This should be preceded by SDHB immunohistochemistry to limit the number of genes to be tested

Below the Belt? Territory and Development in China’s International Rise

China’s internationalization has been heralded by some as a new era of South–South cooperation. Yet such framings of development are pitched at an abstract space of the ‘global South’ which conceals more than it reveals. With some theory moving towards ontologies of ‘global development’, we need to capture both the connectedness and the local specificity of increasingly diffuse processes. This article sets out a more fine-grained understanding of how political territories and processes are imagined and produced by and through China’s internationalization, focusing on infrastructure as a ‘technology’ of territorialization. Much of the focus on China’s internationalization has been on state-to-state relations, but this obscures the ‘omni-channel politics’ that China practises. Using a critical literature review and illustrative case study, this article develops the idea of omni-channel politics to posit a view of ‘twisted’ territories in which political processes and development outcomes are more complex and contingent

Acquisition time and reproducibility of continuous arterial spin-labeling perfusion imaging at 3 T

SUMMARY: Arterial spin-labeling (ASL) is a relatively new and noninvasive MR imaging technique, used to measure cerebral blood flow (CBF). Scanning time and reproducibility remain important issues in the clinical applicability of ASL. We expected both to benefit from higher field strengths. We describe that when performing ASL at 3T, 20 averages suffice to obtain steady and reproducible CBF values. Scanning time can be as short as 3 minutes. A rterial spin labeling (ASL) is a noninvasive MR imaging technique, used for visualization and quantification of cerebral perfusion. Cerebral blood flow (CBF) values measured by ASL are comparable with CBF values measured by conventional techniques (eg, positron-emission tomography or susceptibility-weighted MR imaging). ASL is based on magnetic labeling of arterial blood water protons, which are used as an endogenous tracer of flow. Magnetic inversion takes place in a plane proximal to the brain. The decay rate of the labeled spins is sufficiently long to visualize perfusion of brain vasculature and microvasculature. Perfusion images are obtained by subtraction of successively acquired labeled and nonlabeled control images. In general, 40 to 60 paired acquisitions are averaged to improve perfusion signal intensity. ASL sequences differ in the way magnetic labeling is applied and are commonly classified as continuous or pulsed ASL (CASL or PASL, respectively). In CASL, continuous adiabatic inversion of spins is applied. In PASL, labeling is performed at once over a wide spatial range. Pseudocontinuous ASL (pCASL) has been introduced recently and uses a series of discrete labeling pulses. 1-8 Despite its advantages, scanning time and reproducibility remain important issues in the clinical applicability of ASL. The use of higher-field strengths could overcome these issues because of increased signal-to-noise ratio, prolonged T1-weighted relaxation time of labeled blood, and better spatial and temporal resolution. Also, we hypothesized that acquisition-related reproducibility of ASL will improve at higher-field strengths, whereas physiology-related reproducibility will not change. Previous CASL reproducibility studies were performed at 1.5T with test-retest timeframes of at least 1 hour. Technique After approval of the local ethics committee and written informed consent from all volunteers, we scanned 10 volunteers (5 men; age range, 25-33 years) without known cerebrovascular disease during 3 different sessions within 3 weeks. Each session protocol consisted of 2 CASL sequences preceded by MR angiography. All scans were performed on a 3T Intera MR scanner with a transmit-receive head coil from the manufacturer (Philips Medical Systems, Best, the Netherlands). The 3D time-of-flight MR angiography was obtained to allow for careful planning of the labeling plane perpendicular to the distal ascending portion of the internal carotid and basilar arteries, 10 -20 mm below the circle of Willis. For the ASL sequences, we implemented the amplitude-modulated CASL approach described by Alsop and Detre 5 , without compromising clinical specific absorption rate levels. We used spin-echo single-shot echo-planar imaging. The imaging volume was positioned parallel to the labeling plane with its center 60 mm above the labeling plane. ASL parameters were TR, 4500 ms; TE, 32ms; flip angle, 90°; FOV, 210 ϫ 210; section thickness, 7 mm with 1-mm gap; matrix size, 64 ϫ 45 (reconstructed to 64 ϫ 64); 50 averages; labeling duration, 2.0 s; radiofrequency pulse amplitude, 3.5 T; gradient strength, 2.5 mT/m; modulation frequency, 250 Hz; and postlabeling delay, 1.2 to 2.2 s. FSL (FMRIB-Software-Library, Functional Magnetic Resonance Imaging of the Brain Centre, Department of Clinical Neurology, University of Oxford, Oxford, UK) was used for off-line data processing. f ϭ ⌬MR 1a 2␣M con {e ϪwR1a Ϫ e Ϫ(ϩW)R1a } in which f is CBF (mL/g/s), ␣ is the labeling efficiency at 3T (0.68), 7 is the blood-brain partition coefficient (0.98 mL/g), ⌬M is the difference between labeled image and control image intensity, R 1a is the longitudinal relaxation time of blood (0.67 s Ϫ1 ), M con is the average control image intensity, ⌻ is the labeling duration (2 s), and w is the postlabeling delay (1.2-2.2 s)