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Understanding the internal structures of planets with a large H$_2$O component is important for the characterisation of sub-Neptune planets. The finding that the mini-Neptune K2-18b could host a liquid water ocean beneath a mostly hydrogen envelope motivates a detailed examination of the phase structures of water-rich planets. To this end, we present new internal structure models for super-Earths and mini-Neptunes that enable detailed characterisation of a planet's water component. We use our models to explore the possible phase structures of water worlds and find that a diverse range of interiors are possible, from oceans sandwiched between two layers of ice to supercritical interiors beneath steam atmospheres. We determine how the bulk properties and surface conditions of a water world affect its ocean depth, finding that oceans can be up to hundreds of times deeper than on Earth. For example, a planet with a 300 K surface can possess H$_2$O oceans with depths from 30-500 km, depending on its mass and composition. We also constrain the region of mass-radius space in which planets with H/He envelopes could host liquid H$_2$O, noting that the liquid phase can persist at temperatures up to 647 K at high pressures of $218$-$7\times10^4$ bar. Such H/He envelopes could contribute significantly to the planet radius while retaining liquid water at the surface, depending on the planet mass and temperature profile. Our findings highlight the exciting possibility that habitable conditions may be present on planets much larger than Earth., Comment: 19 pages, 15 figures. Accepted for publication in MNRAS

We report the discovery and characterization of two transiting planets around the bright M1 V star LP 961-53 (TOI-776, J = 8.5 mag, M = 0.54+-0.03 Msun) detected during Sector 10 observations of the Transiting Exoplanet Survey Satellite (TESS). Combining the TESS photometry with HARPS radial velocities, as well as ground-based follow-up transit observations from MEarth and LCOGT telescopes, we measured for the inner planet, TOI-776 b, a period of 8.25 d, a radius of 1.85+-0.13 Re, and a mass of 4.0+-0.9 Me; and for the outer planet, TOI-776 c, a period of 15.66 d, a radius of 2.02+-0.14 Re, and a mass of 5.3+-1.8 Me. The Doppler data shows one additional signal, with a period of 34 d, associated with the rotational period of the star. The analysis of fifteen years of ground-based photometric monitoring data and the inspection of different spectral line indicators confirm this assumption. The bulk densities of TOI-776 b and c allow for a wide range of possible interior and atmospheric compositions. However, both planets have retained a significant atmosphere, with slightly different envelope mass fractions. Thanks to their location near the radius gap for M dwarfs, we can start to explore the mechanism(s) responsible for the radius valley emergence around low-mass stars as compared to solar-like stars. While a larger sample of well-characterized planets in this parameter space is still needed to draw firm conclusions, we tentatively estimate that the stellar mass below which thermally-driven mass loss is no longer the main formation pathway for sculpting the radius valley is between 0.63 and 0.54 Msun. Due to the brightness of the star, the TOI-776 system is also an excellent target for the James Webb Space Telescope, providing a remarkable laboratory to break the degeneracy in planetary interior models and to test formation and evolution theories of small planets around low-mass stars., Comment: 26 pages, 15 figures, 8 tables. Accepted for publication in Astronomy & Astrophysics

We present an atmospheric transmission spectrum of the ultra-hot Jupiter WASP-76 b by analyzing archival data obtained with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). The dataset spans three transits, two with a wavelength coverage between 2900 and 5700 Armstrong, and the third one between 5250 and 10300 Armstrong. From the one-dimensional, time dependent spectra we constructed white and chromatic light curves, the latter with typical integration band widths of ~200 Armstrong. We computed the wavelength dependent planet-to-star radii ratios taking into consideration WASP-76's companion. The resulting transmission spectrum of WASP-76 b is dominated by a spectral slope of increasing opacity towards shorter wavelengths of amplitude of about three scale heights under the assumption of planetary equilibrium temperature. If the slope is caused by Rayleigh scattering, we derive a lower limit to the temperature of ~870 K. Following-up on previous detection of atomic sodium derived from high resolution spectra, we re-analyzed HST data using narrower bands centered around sodium. From an atmospheric retrieval of this transmission spectrum, we report evidence of sodium at 2.9-sigma significance. In this case, the retrieved temperature at the top of the atmosphere (10-5 bar) is 2300 +412-392 K. We also find marginal evidence for titanium hydride. However, additional high resolution ground-based data are required to confirm this discovery., Comment: 14 pages, 10 figures

The p53 tumour suppressor is a transcription activator that signals for cell cycle arrest and apoptosis. In its active form p53 is a tetramer, with each monomer organised in domains with different degrees of structural stability, ranging from the well folded DNA-binding domain (DBD) and tetramerization domain(TET), to the intrinsically disordered transactivation domain (TAD), and extreme C-terminal domain(CTD). Compared to all other domains, the structure/function relationship of the p53-CTD within the full-length p53 tetramer is still poorly understood due to its high degree of conformational disorder.Meanwhile, the structure of p53-CTD-like peptides has been well characterized when in complex with avariety of receptors, where, as other intrinsically disordered regions (IDR), it adopts specific, while diverse, conformations. Receptor-specific folding is likely to occur upon binding, either from a random coil, or as a result of an initial recognition of a pre-formed structural motif, known as molecular recognition feature (MoRF), selected by the receptor within the conformational ensemble of the IDP insolution. In this latter case, MoRFs act as nucleation sites, favouring the initiation of the folding process within the binding site. In this work we show the results of over 20ms of cumulative molecular dynamics(MD) simulations of a 22 residue peptide unbound in solution with sequence corresponding to thep53-CTD 367–388 section. Such extensive sampling allowed us to identify and characterize the structure of specific sets of minimal structural MoRFs within the p53-CTD peptide conformational ensemble at equilibrium. These motifs are short, involving only 3 to 4 residues, and specifically localized within the peptide sequence. Corresponding patterns of secondary structure propensity along the p53-CTDsequence are also predicted by disorder prediction calculations. Based on these findings we discuss how the structural complementarity of specific minimal structural MoRFs to the binding site of different receptors could regulate the p53-CTD binding promiscuity.

Gas hydrates are icelike compounds composed of water and methane gas in very compact form. There is substantial evidence from case histories that links gas hydrate dissociation to submarine slope failures and other geohazards. Theoretical analyses have also shown that upon dissociation gas hydrates will cause an increase in fluid pressure and a reduction in effective stress and thus result in loss of the soil strength. This paper presents a preliminary quantification of the effects of gas hydrate dissociation through development of a pore-pressure model that was incorporated into one- and two-dimensional slope stability analyses. The ensuing numerical study investigated submarine slope stability through parametric studies and application to two important case histories and found that dissociation of even small amounts of hydrate can have a significant destabilizing effect. Yet whether gas hydrate dissociation can alone cause large-scale slope failures has still to be demonstrated as there are often many destabilizing processes; however, this research highlights the importance of assessing the effects of gas hydrate dissociation on the behaviour of submarine slopes.Key words: gas hydrates, slope stability, marine, offshore, methane gas, instability.

The Freedom of Information Act became law in January 2005 and means that any information held by a public authority is eligible for release upon demand. It was designed to make government authorities more transparent and each authority is required to document what information it holds and how that information can be obtained.

The equations governing the three-dimensional motion of a two-body tethered satellite system are highly nonlinear, and their solutions are likely to exhibit interesting behavior typical to nonlinear systems. In this paper, these equations are analyzed using numerical tools such as phase portraits, spectral analysis, Poincare sections and Lyapunov exponents. Motion in the stationkeeping phase (when the tether length is constant) is studied, first considering the in-plane pitch motion only, and then considering the three-dimensional coupled pitch and roll motions. Regions of both regular (periodic or quasi-periodic) and chaotic motion are observed to exist in the planar system for only elliptic orbits, but in the case of coupled motion for both circular and elliptic orbits. The size of the chaotic region grows with eccentricity, and in the coupled motion circular orbit case with increasing values of the Hamiltonian.

All anaesthetic trainees must maintain a logbook. The recent extension of Specialist Registrar training from 4 to 5 years, granted by the Specialist Training Authority, is conditional upon a change to competency-based training. The Royal College of Anaesthetists defines competency as possession of the ‘trinity’ of knowledge, skills and attitudes. This raises the question of whether the present logbook is of value in recording training. I surveyed a national cohort of trainees to investigate the current logbook: how it is being used, its value and its shortcomings. All respondents kept logbooks, but 81% and 69% experienced problems recording subspecialty experience in Intensive Care and Pain, respectively. Less than 50% regularly analysed their logbooks and for 67% of Specialist Registrars, no (or minimal) attention was paid to the logbook at assessments. Overwhelmingly, 97% did not believe that the current logbook assessed competency. The value of Training Portfolios is discussed.

The paper describes the aeroelastic analysis of a tiltrotor configuration. The 1/5 scale wind tunnel semispan model of the V-22 tiltrotor aircraft is considered. The analysis is performed by means of a multi-body code, based on an original formulation. The differential equilibrium problem is stated in terms of first order differential equations. The equilibrium equations of every rigid body are written, together with the definitions of the momenta. The bodies are connected by kinematic constraint, applied in form of Lagrangian multipliers. Deformable components are mainly modeled by means of beam elements, based on an original finite volume formulation. Multidisciplinar problems can be solved by adding user-defined differential equations. In the presented analysis the equations related to the control of the swash-plate of the model are considered. Advantages of a multi-body aeroelastic code over existing comprehensive rotorcraft codes include the exact modelling of the kinematics of the hub, the detailed modelling of the flexibility of critical hub components, and the possibility to simulate steady flight conditions as well as wind-up and maneuvers. The simulations described in the paper include: 1) the analysis of the aeroelastic stability, with particular regard to the proprotor/pylon instability that is peculiar to tiltrotors, 2) the determination of the dynamic behavior of the system and of the loads due to typical maneuvers, with particular regard to the conversion from helicopter to airplane mode, and 3) the stress evaluation in ciriticl components, such as the pitch links and the conversion downstop spring.

Published studies suggest that mitogenic responses of lymphocytes can be reliably assessed by monitoring the expression of lymphocyte surface CD69 after 24 h of culture with the stimulant. We tested this hypothesis by determining the ability of lymphocyte CD69 expression to predict the outcome (normal or abnormal) of lymphocyte proliferative responses to anti-CD3 in a group of human immunodeficiency virus type 1 (HIV-1)-infected patients (n = 47). Cutoff values for defining normal and abnormal CD69 expression and proliferative ([3H]thymidine incorporation) responses were established with lymphocytes from healthy uninfected controls (n = 20). Lymphocytes from 29 HIV-infected patients exhibited an abnormal proliferative response, and those from 25 of the 29 also exhibited abnormal CD69 expression (sensitivity, 86.2%). Similarly, lymphocytes from 18 HIV-infected patients exhibited a normal proliferative response, and those from 16 of the 18 also exhibited normal CD69 expression (specificity, 88.9%). The predictive value of a normal CD69 result was 80%, and the predictive value of an abnormal CD69 result was 92.6%. These findings demonstrate that HIV-1-associated impairments in lymphocyte activation can be reliably detected by the rapid and nonradioactive CD69 expression assay.

A transdermal therapeutic system (TTS) has been developed for the continuous delivery of fentanyl citrate to provide ongoing analgesia in human patients with chronic pain. Several researchers believe that fentanyl transdermal patches have a place in postoperative pain control. The purpose of this study was to determine whether transdermal technology is an effective way of administering fentanyl to feline patients. Fentanyl patches were applied to the skin of six cats, and blood samples for fentanyl analysis were collected over 104 hours. This study establishes that the transdermal patch technology is an effective, long-lasting, cost-effective, noninvasive, and well-tolerated mode of deliverying fentanyl to cats.

Optimised multilayer structures and efficient coating designs have been found in several species of damselfly. We discuss these structures and the associated mechanisms responsible for the bright optical effects which they exhibit.

SUMMARY Photosynthetic area index (PAI), radiation interception (I) and dry matter partitioning between shoots and roots were measured for Miscanthus sinensis‘Giganteus' grown from micro-propagated transplants on a fertile peaty loam soil in eastern England. In the establishment year, Miscanthus plants produced 35 and 70 shoots plant-1 at densities of 4.0 and 1.8 plants m-2 respectively. At the higher density, there were 140 shoots m-2 with the largest reaching a height of 1.8 m; these canopies attained a maximum PAI of 5.45, intercepting 94% of incident radiation. Leaf lamina contributed c. 90% of total photosynthetic area with stems contributing the remainder. At the lower density, maximum PAI and I values were 2.88 and 86% respectively. PAI was related to I by calculating attenuation coefficients (k); these indicated that Miscanthus canopies were more effective at intercepting radiation per unit PAI at the lower density (k= -0.31) compared with the higher density (k= -0.20). Radiation interception was related to dry matter accumulated by calculating conversion efficiencies (e). At 4 plants m-2, × for shoot dry matter production was 1.17g MJ-1. Miscanthus partitioned a relatively large amount of total dry matter into below-ground biomass. By plant senescence, c. 30% of total dry matter had been partitioned into root and rhizome; rhizome biomass contributed 80% of below-ground dry matter, × increased to 1.62 g MJ-1 when calculated on a total dry matter basis (shoot + root + rhizome). Total dry matter production was increased 68% by a 2.2-fold increase in plant density.

Angiosarcoma is a rare malignant neoplasm of vascular or lymphatic endothelial origin that has a poor prognosis. The insidious symptoms, aggressive nature, and rare occurrence of this neoplasm leave a paucity of optimal treatment information. We describe the atypical presentation of an 88-year-old man who was diagnosed and treated for herpes zoster (HZ) in a local emergency department; consultation and biopsy obtained through our dermatology clinic later revealed a diagnosis of cutaneous angiosarcoma (CA).

Even though the tradition of osteopathic medicine is based in primary care, more osteopathic graduates than in the past are pursuing subspecialties within medicine. Some claim that medical specialties, such as dermatology, compromise osteopathic principles and philosophy. However, the authors contend that dermatology exemplifies the ideals expressed by Andrew Taylor Still, MD, DO, and explain how osteopathic manipulative treatment and the principles of osteopathic medicine can be applied to dermatologic disease and patient care.

Malignant melanoma is a relatively rare diagnosis in the adolescent population. A case report of a 15-year-old boy with metastatic malignant melanoma is presented followed by a brief review of the literature.

The complex response of glassy polymers to high strain‐rate dynamic loading necessitates accurate modeling of these events for comparison with experiments. The strain‐rate, temperature and the strain softening behavior are significant and must be considered for large deformations. Several constitutive relationships are discussed in terms of their applicability to modeling PMMA in gap‐tests.

This article presents an algorithmic approach to the evaluation of posterior mediastinal masses seen with computed tomography (CT). CT remains the study of choice, since it not only can be used to help confirm the presence of these masses, but it also helps define the (a) location and extent of the lesion, (b) adjacent organ involvement, or (c) vascular involvement. Causes of posterior mediastinal masses include esophageal lesions, congenital or acquired vascular lesions, foregut cysts, intrathoracic goiters, mediastinal pseudocysts, fat-containing tumors, adenopathy, neurogenic tumors, infectious spondylitis, and vertebral tumors. From the CT appearance of the lesion, one can often distinguish among the various masses and identify their origin and cause. This information enables patient triage and therapy to be expedited and, in most cases of posterior mediastinal masses, allows a correct diagnosis to be made solely on the basis of the CT examination.

Combined shock and shear loading of explosives has been shown to result in detonation of explosives at input pressures less than those required with a nearly planar shock. In this study, the effect of combined shock and shear loading on PBXN‐110 is investigated. The explosive sample is loaded by a TNT/Octol plane wave lens or a Pentolite pad in contact with a layer of PMMA followed by a cylindrical wave shaper that has one side angled at 45 degrees. The experiment is repeated for different thicknesses of the PMMA layer in order to vary the input pressure. In addition, the experiment is modeled using the Lagrangian finite element hydrocode EPIC, and the results of the experiments are compared with the numerical simulations.

The dorsal surfaces of the hindwings of the dragonflyRhyothemis resplendens(Odonata: Libellulidae) reflect a deep blue from the multilayer structure in its wing membrane. The layers within this structure are not flat, but distinctly ‘wrinkled’, with a thickness of several hundred nanometres and interwrinkle crest distances of 5 µm and greater. A comparison between the backscattered light fromR. resplendensand a similar, but un-‘wrinkled’ multilayer in the damselflyMatronoides cyaneipennis(Odonata: Calopterygidae) shows that the angle over which incident light is backscattered is increased by the wrinkling in theR. resplendensstructure. Whereas the reflection from the flat multilayer ofM. cyaneipennisis effectively specular, the reflection from the wrinkledR. resplendensmultilayer spans 1.47 steradians (equivalent to ±40° for all azimuthal angles). This property enhances the visibility of the static wing over a broader angle range than is normally associated with a smooth multilayer, thereby markedly increasing its conspicuousness.

Two otic products not containing miticidal active ingredients were compared for the treatment of otoacariasis in 20 cats. It was concluded that treatment of feline otoacariasis can be achieved using products with an oil/wax base in conjunction with routine ear cleaning and total body parasitacide treatment.

The hind wings of males of the damselfly Matronoides cyaneipennis exhibit iridescence that is blue dorsally and green ventrally. These structures are used semiotically in agonistic and courtship display. Transmission electron microscopy reveals these colours are due to two near-identical 5-layer distributed Bragg reflectors, one placed either side of the wing membrane. Interestingly the thicknesses of corresponding layers in each distributed Bragg reflector are very similar for all but the second layer from each outer surface. This one key difference creates the significant disparity between the reflected spectra from the distributed Bragg reflectors and the observed colours of either side of the wing. Modelling indicates that modifications to the thickness of this layer alone create a greater change in the peak reflected wavelength than is observed for similar modifications to the thickness of any other layer. This results in an optimised and highly effective pair of semiotic reflector systems, based on extremely comparable design parameters, with relatively low material and biomechanical costs.

In the mouse forced swimming test (FST) pretreatment with a subactive dose of lithium (1 mEq/kg), given IP 45 min before the test, facilitated the antidepressant activity of iprindole, fluoxetine, and moclobemide (given IP 30 min before the test). These antidepressants (ADS) were not active alone in the FST in this study. Moreover, when subactive lithium was combined with a wide range of ADS, each given at subactive doses, those ADS with serotoninergic properties (e.g. imipramine, citalopram, paroxetine, fluoxetine, trazodone, mianserin, and moclobemide) significantly reduced immobility times. ADS acting primarily on noradrenaline (NA) or dopamine (DA) systems (desipramine, maprotiline, viloxazine, and bupropion) did not significantly decrease immobility when given in combination with lithium. This was also the case for RO 16 6491 [a reversible, B specific monoamine oxidase inhibitor (MAOI)], nialamide, and pargyline (both irreversible, mixed MAOIs). The anti-immobility effect of iprindole in combination with lithium suggests either a direct or indirect action on the serotonin (5HT) system by this ADS whose mechanism of action remains obscure. These results, using an animal behavioral model of depression and combining our present knowledge of the acute action of various ADS, support the hypothesis that the potentiation by lithium of ADS is via direct 5HT mechanisms, indirectly via a NA/5HT link, and/or by second messenger systems. Lithium may also facilitate the expression of antidepressant activity of ADS not active by themselves in the FST.

Computers are becoming an invaluable part of the radiologist's environment whether they are used as a source of the patient's clinical or laboratory information, to store x-ray or pathologic reports or as a viewing station for films. The use of computers in the educational environment is but a natural extension of the increased computerization of the radiologic department. This article reviews the use of personal computers in a teaching environment via the construction of the computed tomography teaching program entitled "CT: The Game." The decisions that must be made in terms of hardware and software prior to program development as well as the actual development are discussed. The potential of computers in terms of continuing education as well as in residency training programs is discussed with the potential for the future addressed.

The decay properties of the levels at 3.941(3+), 5.476(4+) and 5.716 MeV (4+) in 26Mg have been investigated. Particle gamma-ray angular correlations were measured following the reactions 26Mg( alpha , alpha ' gamma )26Mg and 26Mg(p,p' gamma )26Mg enabling accurate branching ratios and E2/M1 mixing ratios to be determined. The lifetimes were obtained with the reaction 23Na( alpha ,p gamma )26Mg using the Doppler shift attenuation method. The transition from the 5.476(4+) to the 3.941 MeV (3+) state is shown to have an E2 strength of 12+9-4 Weisskopf units whilst the transitions from the 3.941 MeV state itself are essentially dipole. The data together with the revised branching ratios result in a new assignment of states to the Kpi =2+ and 3+ rotational bands.

A membrane filter technique using black membrane filters, MacConkey agar and fluorescence under ultraviolet (UV) light was investigated for the quantitative isolation of Pseudomonas aeruginosa from swimming pools. Three thousand four hundred forty-five samples were collected from public swimming pools and enumerated by this method over a 6-month period. Fluorescent cultures were isolated from 222 specimens. Seventy-seven of these fluorescent cultures were selected for biochemical screening, with 75 (97%) being verified as P. aeruginosa . To further assess the specificity and sensitivity of this UV screening technique, a comparative study was made of some morphological and biochemical characteristics of fluorescent pseudomonads obtained from different sources. The sensitivity of the method was unimpaired by either colony types or biochemical variations of P. aeruginosa . The failure of the other two fluorescent species, P. fluorescens and P. putida , to grow and/or fluoresce on MacConkey agar at 37 C illustrates the specificity of this technique. Further studies are needed to compare the viability of P. aeruginosa on MacConkey agar to that of efficacious nonselective media.

Negative parity states in 42Ca have been excited with the 39K( alpha ,p gamma )62Ca reaction at bombarding energies of 9.5 MeV and 11.5 MeV. The lifetimes of the known negative parity states at 3953(4-) keV. 4044(3-) keV and 4099(5-) keV were measured to be 4.7+or-0.3 ps, 240+or-70 fs and 580+or-145 fs respectively. Levels at 4353 keV and 4896 keV were shown to have Jpi of 4- and 5- with lifetimes of 760+or-100 fs and 80+or-30 fs respectively. Multipole mixing ratios were determined and several of the transitions were shown to have enhanced E2 strengths. The results are discussed in terms of the co-existence model of spherical and deformed states.

The structures of the nuclei 65,67Zn have been investigated by the techniques of gamma -ray spectroscopy in conjunction with the reactions 62,64Ni( alpha ,n)65,67Zn. Gamma-gamma coincidence measurements and yield curve measurements have been used to elucidate the decay schemes. Measurements of gamma -ray angular distributions and linear polarizations have been used to determine mixing ratios for the decays of several levels in both nuclei and to make spin assignments to the following levels in 65Zn: 1.958 (7/2+), 2.054 (13/2+), 2.135 (9/2+), 2.138 (11/2+) and in 67Zn: 0.979 (5/2+), 1.603 (7/2+), 1.640 (13/2+), 1.732 (11/2+), 1.782 (3/2,5/2)+, 1.807 (9/2+). Lifetime measurements have been made using the Doppler-shift attenuation method, and electromagnetic multipole transition strengths have been deduced. The data provide further evidence for the existence of particle-vibration coupling in this mass region.

The 4.350 MeV(3+) and 5.716 MeV(4+) states in 26Mg have been studied with particle gamma ray angular correlation measurements using the reactions 26Mg( alpha alpha ' gamma ) 26Mg with Ge(Li) detectors. Branching ratios and E2/M1 mixing ratios were deduced; in particular a new 815 keV transition (5.716 to 4.901 MeV) has been found. The E2 transition strengths of the cascading gamma rays with 1366 keV (4+ to 3+) and 1412 keV (3+ to 2+) of 3+or-1 and 9-3+4 Weisskopf units respectively support the assignment of the 4.350 and 5.716 MeV states to the Kpi =2+ rotational band based on the 2.938 MeV (2+) states. The results are compared with recent deformed shell model calculations. Nineteen further states between 6 and 9.1 MeV were excited; a decay scheme has been established and several branching ratios are reported. The possible assignment of high spins to some of the higher states is discussed.

Gravel of the Prudhoe Bay area of Alaska used in the construction of artificial islands has been examined in constant load creep experiments to determine the effects of temperature, stress, and salinity on its creep behavior in unconfined compression. Over the range of conditions studied, it is found that the creep behavior is strongly dependent on each of these variables. In addition, the ice content of the specimen, itself a strong function of temperature and salinity, is found to be an important strength-determining parameter.

For pt.I see ibid., vol.4, p.755 (1978). The techniques of gamma -ray spectroscopy have been employed to investigate the structure of levels below 2.0 MeV in excitation energy in 67Zn populated in the 64Ni( alpha ,n)67Zn reaction. Gamma-gamma coincidences have been recorded at several alpha -particle beam energies. Gamma-ray angular distributions and linear polarisations have been measured using an escape-suppressed spectrometer and a three-Ge(Li) Compton polarimeter respectively. The gamma -ray decay modes of the levels have been deduced. Spin and parity assignments have been made. Multipole mixing ratios have been obtained for many of the transitions. The lifetimes of 11 levels have been measured using the Doppler-shift attenuation method. The electromagnetic multipole transition strengths deduced show moderate E2 enhancements. The results have been compared with the particle-vibration coupling model, the Alaga model and the shell model with reasonable agreement in each case.

Stimulated emission data are presented on a large variety of strained‐layer quantum‐well heterostructures (QWH’s) and superlattices (SL’s) grown by metalorganic chemical vapor deposition (MOCVD). These structures consist of barrier‐well combinations of thickness LB,Lz ≲150 A made from GaAs‐InGaAs, GaAsP‐GaAs, and GaAsP‐InGaAs. Also employed are higher band‐gap confining layers of InxAlyGa1‐x‐yAs, AlyGa1−yAs1−xPx, and AlxGa1−xAs. All of the heterostructures are grown on a GaAs substrate with and, in some cases, without a graded layer. The strain range between 0.2 to 12.5×10−3 is examined. Photopumped, these heterostructures operate as continuous (cw) 300 K lasers, with thresholds of 1.6–7.5×103 W/cm2, for periods of time between 0.5 to >35 min. Under high‐level excitation, the equivalent of Jeq∼103 A/cm2, laser operation fails or is quenched by networks of dislocations (with 〈110〉 Burger’s vectors) that are generated within the strained‐layer region of the QWH’s or SL’s. These dislocation networks, which a...

The 62Ni( alpha ,n gamma )65Zn reaction has been studied at bombarding energies from 8.0 to 14.0 MeV. Angular distributions, linear polarisations and yield curves have been measured for transitions arising from odd-parity states with excitation energies up to about 2 MeV. Gamma-gamma coincidence measurements have been carried out. The Doppler-shift attenuation method has been applied to determine the lifetimes of the levels, and branching ratios, mixing ratios and transition rates have been deduced for the various gamma rays. Two transitions, not previously reported, have been found. Angular momenta and parities have been determined for all the states discussed. The predictions of the phonon-quasiparticle-coupling and shell models have been compared with the experimental results and found to be in reasonably good agreement.

Data are presented showing that it is possible to photopump and operate a quantum well heterostructure laser at equivalent current densities (Jeq) as low as 70 A/cm2. Continuous 300‐K laser operation of a single 60‐A GaAs (x=0) quantum well in the center of a ∼0.12‐μm‐thick x′∼0.30 Alx′Ga1−x′As waveguide (and carrier reservoir), which is confined by x″∼0.85 Alx″Ga1−x″As layers, is demonstrated at Ieq∼0.4 mA (168 W/cm2, Jeq∼70 A/cm2). These quantum well heterostructures are grown by organometallic vapor phase epitaxy.

Photoluminescence data are presented on a direct‐well GaAs1−xPx‐GaAs (x∼0.25) strained superlattice (SL) (barrier LB ∼75 A, quantum well Lz∼75 A) and on indirect‐well GaP‐GaAs1−xPx (x∼0.6) strained SL’s (LB, Lz∼120 A and LB, Lz∼60 A) grown by organometallic vapor phase epitaxy. Stimulated emission (at 300 and at 77 K) is observed in the former but only weak luminescence in the latter, thus establishing that a large density of defects at the heterointerfaces is not necessarily an issue in strained SL’s and that so far zone‐folding effects, and SL ‘‘indirect‐direct’’ conversion, have not been observed in indirect systems.

Continuous (cw) 300‐K laser operation of a 66‐period lower energy GaAs‐InxGa1−xAs (x∼0.2) strained superlattice (SL) and a higher energy 128‐period GaAs1−xPx‐GaAs (x∼0.25) strained SL is demonstrated. The strained SL’s are grown by organometallic vapor phase epitaxy (OMVPE) or metalorganic chemical vapor deposition (MOCVD) with higher gap quaternary confining layers and LB ∼75 A barriers and Lz ∼75 A quantum wells. These SL’s are unstable during high level excitation, failing in 2–20 min when operated cw at 300 K as photopumped lasers.

The Si impurity is diffused (850 °C, 10 h, x j ∼2.4 μm) into 2.4 μm of Al x Ga1−x As‐GaAs (x≳0.6) superlattice (barrier L B ≊320 A, quantum wellL z ≊280 A) and disorders it into bulk‐crystal Al x′Ga1‐x′As (x′≳0.32). The as‐grown infrared gap superlattice is converted selectively to red gap bulk crystal and, where undiffused and not disordered, is still capable of continuous 300‐K photopumped laser operation at a threshold of 4×103 W/cm2 (or J eq ∼1.7×103 A/cm2, 5145 A pump photon).