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Using theory and experiments, we investigate granular surface avalanching due to material outflow from a narrow silo. The assumed silo geometry is a deep rectangular box, of moderate spanwise width and small gap thickness between smooth front and back walls. A small orifice deep below the free surface lets grains drain out at a constant rate. The resulting granular flows can therefore be assumed quasi-two-dimensional and quasi-steady over most of the surface descent history. To model these flows, we couple a kinematic model of deep granular flow with a dynamic model of shallow surface avalanching. We then compare the calculated flow fields with detailed particle tracking measurements, letting the silo ascend relative to the high-speed camera to increase spatial resolution. The results show that the avalanching surface shape and near-surface flow are controlled by the spanwise gradient in subsidence velocity, and how this gradient is in turn controlled by the height above orifice and the gap thickness. Whereas the deep flow pattern is rate independent, shallow avalanching is paced by the granular rheology.
Flowing over erodible beds, channelized granular avalanches can alter their volume by entraining or detraining basal grains. In detail, entrainment results from a gradual adjustment of stress and velocity profiles over depth, bringing bed material past yield (and vice versa for detrainment). To capture this process, we propose new depth-integrated equations that balance kinetic energy in addition to mass and momentum. The equations require a local granular rheology, assumed viscoplastic, but no extra erosion law. Entrainment rates are instead deduced from the depth-integrated layer dynamics. To check the approach, we obtain solutions for non-equilibrium heap flows, and compare them with experiments conducted in a seesaw channel.
Atom probe is a powerful technique for studying the composition of nano-precipitates, but their morphology within the reconstructed data is distorted due to the so-called local magnification effect. A new technique has been developed to mitigate this limitation by characterizing the distribution of the surrounding matrix atoms, rather than those contained within the nano-precipitates themselves. A comprehensive chemical analysis enables further information on size and chemistry to be obtained. The method enables new insight into the morphology and chemistry of niobium carbonitride nano-precipitates within ferrite for a series of Nb-microalloyed ultra-thin cast strip steels. The results are supported by complementary high-resolution transmission electron microscopy.
To investigate and compare the performance of head mirrors and headlights during otolaryngological examination.
The illuminance and illumination field of each device were measured and compared. Visual identification and visual acuity were also measured, in 13 medical students and 10 otolaryngology specialists.
The illuminance (mean ± standard deviation) of the LumiView, Kimscope 1 W and Kimscope 3 W headlights and a standard head mirror were 352.3 ± 9, 92.3 ± 4.5, 438 ± 15.7 and 68.3 ± 1.2 lux, respectively. The illumination field of the head mirror (mean ± standard deviation) was 348 ± 29.8 grids, significantly greater than that of the Kimscope 3 W headlight (183 ± 9.2 grids) (p = 0.0017). The student group showed no statistically significant difference between visual identification with the best headlight and the head mirror (score means ± standard deviations: 56.2 ± 9 and 53.3 ± 14.1, respectively; p = 0.3). The expert group scored significantly higher for visual identification with head mirrors versus headlights (59.7 ± 3.3 vs 55.2 ± 5.8, respectively; p = 0.0035), but showed no difference for visual acuity.
Despite the advantages of headlight illumination, head mirrors provided better, shadow-free illumination. Despite no differences amongst students, head mirrors performed better than headlights in experienced hands.
Nosocomial outbreaks of norovirus infection pose a great challenge to the infection control team.
Between November 1, 2009, and February 28, 2010, strategic infection control measures were implemented in a hospital network. In addition to timely staff education and promotion of directly observed hand hygiene, reverse-transcription polymerase chain reaction for norovirus was performed as an added test by the microbiology laboratory for all fecal specimens irrespective of the request for testing. Laboratory-confirmed cases were followed up by the infection control team for timely intervention. The incidence of hospital-acquired norovirus infection per 1,000 potentially infectious patient-days was compared with the corresponding period in the preceding 12 months, and the incidence in the other 6 hospital networks in Hong Kong was chosen as the concurrent control. Phylogenetic analysis of norovirus isolates was performed.
Of the 988 patients who were tested, 242 (25%) were positive for norovirus; 114 (47%) of those 242 patients had norovirus detected by our added test. Compared with the corresponding period in the preceding 12 months, the incidence of hospital-acquired norovirus infection decreased from 131 to 16 cases per 1,000 potentially infectious patient-days (P < .001 ), although the number of hospital-acquired infections was low in both the study period (n = 8) and the historical control periods (n = 11). The incidence of hospital-acquired norovirus infection in our hospital network (0.03 cases per 1,000 patient-days) was significantly lower than that of the concurrent control (0.06 cases per 1,000 patient-days) (P = .015). Forty-three (93%) of 46 norovirus isolates sequenced belonged to the genogroup II.4 variant.
Strategic infection control measures with an added test maybe useful in controlling nosocomial transmission of norovirus.
High-quality GaP, GaP@GaN and GaN@GaP nanowires were grown by a convenient vapor deposition technique. The wire-like and two-layers structures of GaP@GaN and GaN@GaP core-shell nanowires were clearly resolved using X-ray powder diffraction and high-resolution transmission electron microscopy (HRTEM) and their growth directions were identified. Photoluminescence intensity of GaP@GaN nanowires increased as temperature increased. The result was interpreted by the piezoelectric effect induced from lattice mismatch between two semiconductor layers. An unexpected peak at 386 cm-1 was found in the Raman spectra of GaN@GaP and assigned to a surface phonon mode due to the interface. Detailed synthetic conditions and possible growth mechanisms of those nanowires were proposed.
This work demonstrates the application of a Markov Chain Monte Carlo (MCMC) approach to modeling X-ray reflectometry (XRR) data taken from a sub 10 nm Hafnium oxide film. We present here a comparison of two structural models for a 6 nm HfxOy atomic layer deposition (ALD) film on Si. Using the MCMC method and two distinct structural models, we show evidence of a thin interface between the HfxOy and Si layers with a density much higher than native SiO2. Results from genetic algorithm XRR analysis and thickness measurements using cross-sectional transmission electron microscopy are included for comparison. We also demonstrate that our interpretation of HfxOy thickness differs between the two structural models (i.e., total film thicknesses may be partially additive within each model).
Noroviruses are an important aetiological agent of acute gastroenteritis. They are responsible for large outbreaks of disease in the community, hospitals and long-term-care facilities. The clinical manifestations of norovirus outbreaks in psychiatric units are rarely described. The disease burden and impact highlight the importance of timely notification and investigation of these outbreaks. We analysed the characteristics of four norovirus outbreaks which occurred during a 3-year period in an in-patient psychiatric care unit. A total of 184 patients were affected which included 172 hospitalized patients, seven healthcare workers (HCWs) and five psychiatric nursing-home residents. The mean incidence rate of norovirus gastroenteritis (NVG) in hospitalized patients during these outbreaks was 12·7%. These outbreaks were characterized by higher incidence in middle-aged male patients, predominant sickness of diarrhoea, short duration of illness, peaks in late winter and early spring, and higher susceptibility in acute psychiatric patients. HCWs had longer duration of illness than psychiatric patients. More than 10% of affected patients experienced ⩾2 infections. Infection control measures were instituted and a comprehensive, responsive standard operating procedure for NVG and outbreak management was developed. After implementation of these measures, no further outbreaks of NVG occurred during the study period.
The standard membrane filtration method of the UK has been modified in order to improve its specificity for enumerating Escherichia coli in the subtropical waters of Hong Kong. This involves incorporating into the membrane lauryl sulphate (mLS) method either an in situ urease test (the mLS-UA method), or an in situ β-glucuronidase test (the mLS-GUD method). The false-positive errors of the mLS-UA and mLS-GUD methods are low, ranging from 3–5%. A comparison between the membrane filtration (mLS-UA) method and the multiple tube technique in testing E. coli in subtropical beach-waters has demonstrated that the former can give much more precise counts, and is the method of choice for such a purpose. The mLS-GUD method, for which automated counting of E. coli colonies is possible, is a good alternative to mLS-UA in routine enumeration of this bacterial indicator in environmental waters.
The patch-clamp recording technique was used to examine the properties of the K+ channels in cultured equine sweat gland epithelial cells. With symmetric K+ solutions (140 mM), a single population of K+ channels was identified with a slope conductance of 187 pS and a reversal potential of around 0 mV. The channel was selective for K+ over Na+. Channel activity was increased by membrane depolarization. A 10-fold increase in [Ca2+]i produced an approximate 60 mV negative shift in the open state probability (Popen)-voltage curve. Externally applied tetraethylammonium ions (TEA+) caused a rapid and flickery block of the channel and reduced the unitary current amplitude. TEA+ bound to the blocking site with stoichiometry of 1:1 and with a dissociation constant (Kd) of 186 ± 27 µM at +40 mV. A weak voltage dependence of Kd was observed. Iberiotoxin (100 nM) reduced Popen but had no effect on single-channel conductance. Neither glibenclamide (10 µM) nor intracellular adenosine 5'-triphosphate (ATP, 1 mM) altered channel activity. In addition, ATP, when applied extracellularly, transiently activated the channel by increasing Popen. Channel activity was low around the resting membrane potential in the intact epithelia, indicating that these channels might not contribute to the resting K+ conductance. However, the channel could be activated in a regulated manner. The K+ channels may play a role in transepithelial fluid secretion in sweat gland.