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Low temperature optical absorption spectra are presented for a series of InAsxP1-x/InP strained layer multiple quantum well structures (0 < x = 0.35) grown by low pressure metal organic vapor phase epitaxy (LP-MOVPE) using trimethylindium (TMIn), tertiarybutylarsine (TBAs) and phosphine as precursors. The well widths and compositions in these structures are determined from high resolution x-ray diffraction and transmission electron microscopy. The absorption spectra are then analyzed by fitting the excitonic peak energy position with transition energies determined from a solution to the Schrödinger equation. We used the envelope function formalism with the Kane bands as the basis wavefunctions and included corrections for non parabolicity. From these fits and elasticity theory, both the bandgap of unstrained InAsxP1-x and the band offsets of these heterostructures are deduced self-consistently. The conduction band offsets are found between 72% and 75% of the total strained bandgap differences.

Five different parameters, time of incubation of the culture, type of culture medium, inoculum, strain of inbred mice, and age of mice, were tested using the LD50 technique to standardize a murine model for the evaluation of the virulence of Streptococcus suis capsular type 2 isolates. A model using 28 day-old mice belonging to CF1 strain appeared to give the best results. The inoculum size was the parameter most influencing the 50% lethal dose obtained with mice. Inoculation with 1-ml volume of a bacterial suspension instead of 0.1 or 0.5 ml decreased the LD50. The standardized model was used to evaluate the virulence of some isolates of known pathogenicity for pigs. The minimum lethal dose was used in the model and it appeared that the virulence of Streptococcus suis capsular type 2 isolates can be measured from highly virulent to totally avirulent.

Of a total of 561 isolates of Streptococcus suis recovered from various tissues of diseased pigs, 464 were from veterinary laboratories in Quebec and 97 were from western Canada, particularly Alberta (84). Almost 83% of all these isolates belonged to the 23 known S. suis capsular types. There was no marked difference between the two groups of isolates. Capsular type 2 was the most prevalent and represented 32% of all isolates. The other important capsular types were, in decreasing order, 3, 1/2, 8 and 4. Lungs, brain, and meninges were the source of the majority of isolates. More than 40% of all S. suis isolates were found in pure culture. The number of isolations of this microorganism was higher in piglets aged five to eight weeks than in any other age group.

The Fernelius extension to the Rosencwaig–Gersho theory for photothermal deflection spectroscopy (PDS) is modified to take into account multiple reflections and light trapping within a thin film-on-substrate system where both the thin film and the substrate can be absorbing. The extended model is used to simulate the PDS signal from bulk GaAs and GaNAs epilayers grown on GaAs substrates. While the PDS magnitude signal shows a strong dependence on the light trapping effects, the phase signal remains almost insensitive to this effect. However, the PDS relative phase is very sensitive to the sample thickness.

The presence of radial arterial lines may diminish distal digital perfusion. Using a pair of pulse oximeters on the index fingers of cannulated and noncannulated arms the saturation and oximeter pulse strength were assessed. Three hundred paired measurements in fifty consecutive Intensive Care patients were undertaken more than two hours after cannula insertion. The pulse strength was 19.7 (SD 6.1) and 19.7 (SD 5.7) on the cannulated and noncannulated sides while the saturation was 97.3 (SD 2.3) and 97.1 (SD 2.4) respectively. These differences are not clinically important and the study demonstrates that reliable pulse oximetry measurements may be made distal to a radial artery cannula. It is recommended that in each individual the placement of the sensor be such as to ensure the best signal and the most stable saturation readings.

Monoclonal antibodies (MAbs) and colloidal gold probes were used to localize circumsporozoite (CS) protein and two unrelated polypeptides in developing oocysts and salivary gland sporozoites of the 17X (NL) strain of Plasmodium yoelii. MAbs NYS1, NYS2, and NYS3 recognized different epitopes of the P. yoelii CS protein and produced similar patterns of immunolabelling on developing oocysts and sporozoites. A small percentage of oocysts contained developing sporoblasts and sporozoites that did not exhibit surface reactivity to MAbs NYS1, NYS2 or NYS3, although internal labelling was associated with endoplasmic reticulum (ER). These sporozoites were still capable of completing development and invading salivary glands where they could be found adjacent to sporozoites with densely labelled surface coats. If these sporozoites are infective, their presence may explain in part the failure of CS vaccines to completely protect immunized animals against challenge. The non-CS antigen recognized by MAbs NYS4 did not become abundant until late in sporogony. Some gold labelling was associated with the surface of budding and mature sporozoites, but the antigen was most abundant within the cytoplasm and micronemes. A second non-CS antigen identified by NYS5 first appeared in 7-day-old oocysts, although labelling was sparse. Small quantities of antigen appeared on the sporoblast membrane, cytoplasmic clefts and ER of oocysts and was associated with micronemes and the surface of budding and mature sporozoites. As the role played by non-CS antigens in the biology of the parasite is not yet known, further characterization of their function is needed before their potential as vaccine candidates can be determined.

A total of 349 isolates of Streptococcus suis retrieved from different tissues from diseased pigs were examined in this study. Only 48% of them could be categorized as one of serotypes 1 to 8 and 1/2. Among typable isolates, serotype 2 was the most prevalent (23%), followed by serotype 3 (10%). The majority of all isolates originated from lungs, meninges/brain, and multiple tissues. Forty-one percent of typable isolates and 33% of untypable isolates were retrieved in pure culture. Other isolates were found in conjunction with Pasteurella multocida, Escherichia coli, Actinobacillus pleuropneumoniae, Actinomyces pyogenes, and other streptococci. Typable S. suis isolates were more frequently isolated from pigs between five and ten weeks of age, while untypable isolates were mostly found in animals aged more than 24 weeks. No obvious monthly and/or seasonal variation of the prevalence of isolation of S. suis could be detected.

Spectroscopic ellipsometry (SE) was shown to be an accurate in situ method for determining the composition and thickness of III–V semiconductor layers during growth. In order to fully exploit the potential of SE for real-time in situ control, one needs to acquire a database of optical constants. In this article, we present the acquisition and parameterization (both composition and temperature) of a fully dynamic database and its use in the real-time composition control of InAlAs grown on InP. This is accomplished by acquiring SE data from growing films of different compositions, while the temperature is controlled using feedback from band-gap thermometry. The layer compositions are assessed by fitting high-resolution x-ray diffraction patterns with a simulation based on dynamical diffraction theory. In order to improve the stability during real-time control, the database was parameterized using a transfer function model. The parameterized database was then used, in real time, during growth to control the ...

GaPAsSb type-I quantum wells and symmetric InGaAs/GaPAsSb/InGaAs type-II quantum wells are proposed as long wavelength active layers for GaAs based optoelectronic devices. Room temperature photoluminescence from 1.2 to 1.5 μm is observed from the type-II quantum wells, while low temperature photoluminescence at 1.25 μm is observed from type-I quantum wells. A reflection high-energy electron diffraction peak that is extended parallel to the surface, while its width is perpendicular to the surface is narrow, suggests that spontaneous lateral composition modulation occurs in the GaPAsSb layers.

The first single-epitaxy top-emitting vertical-cavity surface-emitting laser emitting in the 1.55-1.61 /spl mu/m wavelength region is reported. CW operation is achieved up to 55/spl deg/C with an optical power of 0.45 mW obtained at 25/spl deg/C. Error free transmission by these lasers at 2.5 Gbit/s is obtained over 50 km of singlemode fibre without the need for optical amplification.

Spectroscopic ellipsometry (SE) and diffuse reflection spectroscopy (DRS) are used to control the Ga mole fraction and substrate temperature, respectively, during the growth of InGaAs lattice matched to InP. Ga mole fraction is controlled to within ±0.002 of its target value and substrate temperature is controlled to within ±2 °C of its target value. The same growth under constant thermocouple control would result in a 50 °C rise in real substrate temperature and a Ga composition 1% above its target value. In both cases, feedback control is achieved using a nested proportional-integral-derivative (PID) control loop, where, the inner loop consists of the conventional Eurotherm-thermocouple feedback loop and the outer loop updates the thermocouple setpoint using a PID control loop implemented in the control software. For composition control, the Ga cell thermocouple setpoint is increased (decreased) 0.2 °C for every 0.002 that the Ga mole fraction, given by the SE sensor, deviates below (above) the target value. During substrate temperature control, the thermocouple setpoint is updated based on the temperature difference between the DRS sensor and the user setpoint. Frequency loop shaping, based on a dynamical model of the system obtained from an identification experiment, is used to tune the outer PID loop.

Spectroscopic ellipsometry (SE) is an accurate in situ method for determining the composition and thickness of III–V semiconductor layers during growth. In order to achieve this control, an optical constant database is used to compare the modeled and experimental ellipsometric data. This procedure is very effective for controlling thickness and composition when the film has been growing for some time but is usually unreliable until several minutes into the growth (corresponding to ∼50 nm). To use SE for the control of thinner layers (1–20 nm), a different approach has to be used. A new strategy is proposed which consists in looking at the raw SE signal in a limited wavelength range where the signal varies almost linearly with the film thickness. For AlAs grown on GaAs, it is found the phase part of the SE signal for light between 2.5 and 2.8 eV varies nearly linearly with the AlAs thickness. A series of AlAs/GaAs multiquantum well structures are grown and analyzed. The thickness determined by this use of ...

InGaP/GaAs heterostructures and InGaP/In0.2Ga0.8As pseudomorphic high electron mobility structures were grown by solid source molecular beam epitaxy using valved arsenic and phosphorus sources. At 450 °C abrupt arsenic/phosphorus heterojunctions were obtained. Charge transfer was demonstrated at both normal and inverted InGaP/GaAs heterojunctions. From capacitance–voltage profiling measurements the InGaP/GaAs conduction band discontinuity was determined to be 0.15 eV with an interface charge density of 8×1010 cm−2. Consistent with a moderate conduction band discontinuity, single pulse doped In0.5Ga0.5P/In0.2Ga0.8As structures were grown with a channel sheet density of 1.5×1012 cm−2. Double pulse doped InGaP/AlGaAs/In0.2Ga0.8As/AlGaAs structures were also grown incorporating AlGaAs donor layers and an InGaP Schottky layer. Appropriate for power devices, high sheet densities (3.5×1012 cm−2 at 77 K) and high mobilities (6620 cm2/V s at 300 K; 16920 cm2/V s at 77 K) were obtained. The InGaAs quantum well phot...

The N-methyl-d-aspartate receptor channel-complex is widely distributed in the hippocampus, particularly in the CA1 region, in the terminal field of CA3 pyramidal axons and in the fascia dentata, in the terminal field of the perforant pathway. In the present study, we have examined, in the rat, the effect of specific lesions of various neuronal populations of the hippocampus on the distribution of several markers of the N-methyl-d-aspartate receptor-channel complex. Anoxic-ischemic treatment produced a destruction of CA1 pyramidal cells (postsynaptic element); this was associated with a 50% loss of N-methyl-d-aspartate, glycine and N-(1-phenylcyclohexyl)piperidine binding sites. In contrast, the destruction of CA3 pyramidal cells and their axons (presynaptic element) by kainate treatment did not induce significant changes in the density of binding sites. The present results therefore strongly support an exclusively postsynaptic localization of the N-methyl-d-aspartate receptor-channel complex in CA1; the possibility of a localization of the remaining binding sites on glial cells or interneurons is discussed. In the molecular layer of the fascia dentata, the anoxic-ischemic treatment produced a partial destruction of the median perforant pathway (presynaptic element) associated with a decrease in the density of N-methyl-d-aspartate, N-(1-[2-thienyl]cyclohexyl)piperidine and glycine binding sites; this suggests that, in contrast to CA1, in the molecular layer of the fascia dentata, N-methyl-d-aspartate receptor-binding sites are located both pre- and postsynaptically.

Freeze-fracturing has been used to study the formation of the triple layer pellicular complex of budding sporozoites of Plasmodium falciparum in the early oocyst. Sporozoites are formed from sporoblasts within the oocyst. The outer membrane of the sporozoites is derived from the single plasma membrane of the sporoblast while the inner 2 membranes are formed anew at the base of the differentiating sporozoites. A dense collar of intramembranous particles located on the P face of the outer membrane encircles the base of each budding sporozoite. The fact that this collar of intramembranous particles is located in the same region where the inner membranes of the sporozoites first make their appearance strongly suggests that the 2 are related, and that the collar may be related to either membrane synthesis or to membrane organization and assembly.

This paper describes the electrical properties of three n-type InP epilayers grown by MOVPE, in the same reactor, with three different bottles of trimethvlindium. Two typical samples show a reduced room temperature Hall mobility along with high temperature excitation to the conduction band. These features are in excellent agreement with a model accounting for a deep center or complex, with a binding energy dependent on the particular source material used for growth. Such a center is a strong scatterer when ionized, thus reducing high temperature mobility and becoming electrically inactive when neutral. The 77 K Hall mobility of the samples is not a measure of their purity and possible depletion effects did not appear to be significant.

The literature on benign recurrent cholestasis is reviewed, and three personal illustrative cases are briefly described. Benign recurrent cholestasis was familial in 31 % of the total of 39 known case

The interface between near stoichiometric hydrogenated amorphous silicon nitride (a‐SiNx :H) deposited on hydrogenated amorphous silicon (a‐Si:H) is studied using x‐ray photoelectron spectroscopy as a function of the electron escape angle. This method allows the study of a‐SiNx :H overlayers of about 40 A thickness which is typical of the thicknesses used for well and barrier layers in superlattices and quantum well structures. Within the instrument’s resolution, subnitride components constitute less than 1% of the interface bonds. It is therefore concluded that the interface is atomically abrupt.

The authors have analysed the predictive value of the basal and peak gastric acidity levels, measured preoperatively, in a series of 27 supraselective vagotomies. They recommend care in the choice of this operation for hypersecretors and they propose criteria for the preoperative selection of the candidates. They suggest determination of the preoperative basal gastric acidity level and a cimetidine suppression test to identify patients at high risk for recurrence of the ulcer.

In order to study the maternal-placental and foetal contamination, cytologic study and aerobic-anaerobic cultures were performed on 1 000 placentae of infants who were referred to the Intensive Care Unit. Bacteroides were isolated from 30 specimens, and on smears, Gram negative bacteria were found on 11 of these cases. Only in 2 infants Bacteroides were isolated from blood, gastric aspirate and meconium; 20 infants were said to be infected on clinical and biological bases; eight were normal. Bacteroides infection is usually benign; the symptoms are not specific; the diagnosis is often delayed and the treatment uneasy. Nowadays, Carbenicillin, Ticarcilin, Cefoxin or Metronidazole are advised, according to the sensibility of the organism.

During a four year period (1974--1977) 21 infants died as a result of severe necrotising enterocolitis (N.E.C.). In 9 cases, Clostridium perfringens was isolated. When this organism is recovered either from the placenta or from the first meconium and or when the signs of the disease appear within a few days of birth, materno-fetal transmission of the infection may be suspected. The infection occurs most frequently in neonates in whom the gastrointestinal tract was already colonized by Clostridium.