To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
We comprehensively studied InGaN/GaN heterostructures grown by molecular beam epitaxy (MBE) using a variety of methods of optical spectroscopy, such as cathodoluminescence microscopy (CL), time-integrated and time-resolved photoluminescence. To correlate the fluctuations in emission wavelength with values for the optical amplification we performed gain measurements in edge-stripe geometry. The lateral homogeneity can be drastically improved using a template of GaN grown on the sapphire substrate by metal-organic vapor phase epitaxy (MOVPE). Gain values up to 62 cm−1 were found in samples with low indium fluctuations, which is comparable to values for high-quality InGaN/GaN heterostructures grown by MOVPE.
We comprehensively studied InGaN/GaN heterostructures grown by molecular beam epitaxy (MBE) using a variety of methods of optical spectroscopy, such as cathodoluminescence microscopy (CL), time-integrated and time-resolved photoluminescence. To correlate the fluctuations in emission wavelength with values for the optical amplification we performed gain measurements in edge-stripe geometry. The lateral homogeneity can be drastically improved using a template of GaN grown on the sapphire substrate by metal-organic vapor phase epitaxy (MOVPE). Gain values up to 62 cm-1 were found in samples with low indium fluctuations, which is comparable to values for high-quality InGaN/GaN heterostructures grown by MOVPE.
We used high-pressure grown GaN single crystal substrates to fabricate dislocation free optoelectronic devices like light emitting diodes and laser diodes structures. The latter ones demonstrated laser action under optical pumping condition with the threshold of about 200 kW/cm2 at room temperature. In the present paper we would focus on the specific aspects of the homoepitaxial growth by MOVPE method including epi-ready substrate preparation and surface polarity choice. We believe that our results demonstrate clearly the feasibility of device fabrication based on high-pressure grown GaN bulk crystals.
Free and bound exciton luminescences as well as donor-acceptor pair recombination of GaN epitaxial layers on 6H-SiC and sapphire substrates were investigated using time integrated and time resolved photoluminescence measurements at low temperatures. Lifetimes are determined for the donor bound exciton at 3.4722eV and for two acceptor bound excitons with energies of 3.4672eV and 3.459eV. Luminescences between 3.29eV and 3.37eV are identified as due to excitons deeply bound to centers located near the substrate-epilayer interface.
Sodium butyrate (SB) provided orally favours body growth and maturation of the gastrointestinal tract (GIT) in milk-fed pigs. In weaned pigs, conflicting results have been obtained. Therefore, we hypothesised that the effects of SB (3 g/kg DM intake) depend on the period (before v. after weaning) of its oral administration. From the age of 5 d, thirty-two pigs, blocked in quadruplicates within litters, were assigned to one of four treatments: no SB (control), SB before (for 24 d), or after (for 11–12 d) weaning and SB before and after weaning (for 35–36 d). Growth performance, feed intake and various end-point indices of GIT anatomy and physiology were investigated at slaughter. The pigs supplemented with SB before weaning grew faster after weaning than the controls (P < 0·05). The feed intake was higher in pigs supplemented with SB before or after weaning (P < 0·05). SB provided before weaning improved post-weaning faecal digestibility (P < 0·05) while SB after weaning decreased ileal and faecal digestibilities (P < 0·05). Gastric digesta retention was higher when SB was provided before weaning (P < 0·05). Post-weaning administration of SB decreased the activity of three pancreatic enzymes and five intestinal enzymes (P < 0·05). IL-18 gene expression tended to be lower in the mid-jejunum in SB-supplemented pigs. The small-intestinal mucosa was thinner and jejunal villous height lower in all SB groups (P < 0·05). In conclusion, the pre-weaning SB supplementation was the most efficient to stimulate body growth and feed intake after weaning, by reducing gastric emptying and intestinal mucosa weight and by increasing feed digestibility.
We study the classical problem of planar shock refraction at an oblique density discontinuity, separating two gases at rest. When the shock impinges on the density discontinuity, it refracts, and in the hydrodynamical case three signals arise. Regular refraction means that these signals meet at a single point, called the triple point. After reflection from the top wall, the contact discontinuity becomes unstable due to local Kelvin–Helmholtz instability, causing the contact surface to roll up and develop the Richtmyer–Meshkov instability (RMI). We present an exact Riemann-solver-based solution strategy to describe the initial self-similar refraction phase, by which we can quantify the vorticity deposited on the contact interface. We investigate the effect of a perpendicular magnetic field and quantify how its addition increases the deposition of vorticity on the contact interface slightly under constant Atwood number. We predict wave-pattern transitions, in agreement with experiments, von Neumann shock refraction theory and numerical simulations performed with the grid-adaptive code AMRVAC. These simulations also describe the later phase of the RMI.
Background and objective: Previous studies mainly conducted on elective patients recommend doses of 0.9–1.2 mg kg−1 rocuronium to obtain comparable intubation conditions with succinylcholine 1.0 mg kg−1 after 60 s during a rapid-sequence induction. We decided to compare the overall intubating conditions of standard doses of rocuronium 0.6 mg kg−1 and succinylcholine 1.0 mg kg−1 during a strict rapid-sequence induction regimen including propofol and alfentanil. Methods: Male and female patients (ASA I–III) older than 17 yr scheduled for emergency abdominal or gynaecological surgery and with increased risk of pulmonary aspiration of gastric content were randomized to a rapid-sequence induction with succinylcholine 1.0 mg kg−1 or rocuronium 0.6 mg kg−1. Patients with a predicted difficult airway were excluded. A senior anaesthesiologist ‘blinded’ for the randomization performed the intubation 60 s after injection of the neuromuscular blocker. Intubating conditions were evaluated according to an established guideline. Tracheal intubation not completed within 30 s was recorded as failed. Results: 222 patients were randomized. Three patients had their operation cancelled and 10 did not fulfil the inclusion criteria. Clinically acceptable intubation conditions were present in 93.5% and 96.1% of patients in the succinylcholine group (n = 107) and the rocuronium group (n = 102), respectively (P = 0.59). Conclusions: During a rapid-sequence induction with alfentanil and propofol, both rocuronium 0.6 mg kg−1 and succinylcholine 1.0 mg kg−1 provide clinically acceptable intubation conditions in 60 s in patients scheduled for emergency surgery. Under the conditions of this rapid-sequence induction regimen rocuronium may be a substitute for succinylcholine.
Recombinant glucagon-like peptide-1 (7–36)amide (rGLP-1) was recently shown to cause significant weight loss in type 2 diabetics when administered for 6 weeks as a continuous subcutaneous infusion. The mechanisms responsible for the weight loss are not clarified. In the present study, rGLP-1 was given for 5d by prandial subcutaneous injections (PSI) (76nmol 30min before meals, four times daily; a total of 302·4nmol/24h) or by continuous subcutaneous infusion (CSI) (12·7nmol/h; a total of 304·8nmol/24h). This was performed in nineteen healthy obese subjects (mean age 44·2 (sem 2·5) years; BMI 39·0 (sem 1·2)kg/m2) in a prospective randomised, double-blind, placebo-controlled, cross-over study. Compared with the placebo, rGLP-1 administered as PSI and by CSI generated a 15% reduction in mean food intake per meal (P=0·02) after 5d treatment. A weight loss of 0·55 (sem 0·2) kg (P<0·05) was registered after 5d with PSI of rGLP-1. Gastric emptying rate was reduced during both PSI (P<0·001) and CSI (P<0·05) treatment, but more rapidly and to a greater extent with PSI of rGLP-1. To conclude, a 5d treatment of rGLP-1 at high doses by PSI, but not CSI, promptly slowed gastric emptying as a probable mechanism of action of increased satiety, decreased hunger and, hence, reduced food intake with an ensuing weight loss.
The ideal magnetohydrodynamic spectrum of gravitating plane plasmas with equilibrium
flow is investigated. Flow makes the spectral problem non-self-adjoint, so
that the spectrum can become overstable. The criteria for cluster spectra to appear
are derived analytically and both stable and unstable sides of the spectrum are examined
numerically. Above certain critical values of the shear flow at the resonant
surface, the gravitating interchange modes disappear. However, the local extrema
of the continua can then take over the cluster spectrum.
The preweaning growth and carcass characteristics offour lamb genotypes were analysed for variation attributable to the intrauterine cohabitant (IUC) phenomenon, where within-sex variation is attributed to the sex of a twin's womb-mate. The four genotypes resulted from the following matings: Poll Dorset rams × Merino ewes, Poll Dorset rams × (Border Leicester × Merino) ewes, Texel rams × Merino ewes and Texel rams × (Border Leicester × Merino) ewes. Four hundred and twenty twin lambs participated in the preweaning study and of these, 209 were slaughtered to generate carcass data. Some of these genotypes displayed within-sex variation in weaning weight and fat score, preweaning average daily gain, skin-fold thickness, carcass fatness and eye muscle dimensions attributable to the IUC phenomenon. Genotypic differences in the responses of lambs to the IUC phenomenon were also observed. The IUC phenomenon appears to involve prenatal programming, an hypothesis that attributes postnatal characteristics to events during differentiation. The IUC phenomenon is analogous to the intrauterine position phenomenon in fecund mammals, where variations in prenatal steroid concentrations programme for permanent alterations in postnatal reproductive characteristics. The growth responses reported in this paper provide evidence of variation due to prenatal programming. While the magnitude of the responses to the IUC phenomenon were not large, the data presented indicate that under field conditions, the magnitude of growth responses to the IUC phenomenon may be as great as those observed between breeds. If so, further examination of the role that an animal's IUC may have on its subsequent performance could aid the development of more sensitive indices for breed evaluation and progeny selection.
Bounds on the rate of convergence measured by the variation distance are obtained for the number of large spacings and for two occupancy problems connected with multinomial and Pólya sampling. The bounds are derived by imbedding techniques together with the elementary coupling inequality.
Email your librarian or administrator to recommend adding this to your organisation's collection.