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Transmission electron microscopy (TEM), and low temperature reflectance and photoluminescence (PL) have been used to characterize heteroepitaxial CdTe(111) layers grown by molecular beam epitaxy directly onto nominally flat and misoriented Si(001) substrates. TEM observations confirmed that 1° offcut toward [110] in the Si(001) substrate suppressed formation of double domains, while increasing the azimuthal angle of the offcut relative to [110] suppressed twin formation. Under optimized growth conditions, residual twinning defects disappeared within about 2 μm from the substrate. Atomic-scale details of interfaces in this system were successfully recorded. Clear splitting of exciton states at the direct gap in optical reflectance and PL spectra demonstrated the existence of residual biaxial tensile strain of about 7 × 10−4in the CdTe layers, due to thermal expansion mismatch. A strain-shifted neutral acceptor-bound exciton peak dominated the 1.7 K photoluminescence spectrum, together with donor-to-acceptor and band-to-acceptor transitions involving a 49 meV shallow acceptor level. The sharpness of bound exciton peaks (about 0.6 meV full width at half maximum) supported the high layer quality.

Recent trials with selected patients have indicated that 99Tcm-tetrofosmin is a suitable agent for myocardial perfusion imaging. We performed 99Tcm-tetrofosmin perfusion imaging in an unselected group of 297 patients routinely referred to our department. Single photon emission tomographic (SPET) imaging was performed 45–60 min post-injection using a 2-day stress and rest protocol. Altogether, 192 patients were stressed on a treadmill and 105 using intravenous dobutamine. Comparison with angiography was possible in 86 patients, 65 of whom had atheromatous coronary artery disease and 21 of whom had normal coronary arteries (6 of whom fulfilled the criteria for syndrome X). The sensitivity for the detection of coronary artery disease was 94 (93 for exercise stress and 95 for dobutamine). The overall specificity was 85 (87 for exercise stress and 80 for dobutamine in the 15 normal patients and the segments supplied by disease-free coronary vessels in patients with disease elsewhere). We conclude that 99Tcm-tetrofosmin is a highly sensitive and specific agent for the detection of coronary artery disease, using both exercise and dobutamine stress, with few limitations.

Recent work has shown that rest 99Tcm-sestamibi uptake may underestimate the amount of perfused myocardium, suggesting infarct tissue in some instances when myocardium is hypoperfused but which will benefit from revascularization. Administration of nitrates before a resting 99Tcm-sestamibi injection has been shown to increase tracer uptake. We have used 99Tcm-tetrofosmin as a myocardial perfusion agent and imaged 30 patients at stress, rest and again at rest following administration of sublingual nitrates. All patients had angiographically demonstrated severe coronary artery disease and 27 patients had previous infarction. Twenty-one patients were stressed on a treadmill and nine using intravenous dobutamine. Images were analysed using both a visual and semi-quantitative analysis. Defects were observed in 39 coronary artery territories on stress 99Tcm-tetrofosmin imaging, 23 appearing fixed on standard rest imaging. Twelve (52) of these defects showed reversibility on rest with glyceryl trinitrate (GTN) imaging and increased reversibility was seen in 62 of defects reversible at rest. We conclude that, in patients with severe coronary artery disease and fixed rest defects, GTN given prior to the rest injection appears to improve the detection of ischaemic hypoperfused myocardium.

The interactions of lymphocytes with cultured synovial cells derived from rheumatoid arthritis patients were examined. A number of lymphoid cell lines bound to these cells. The adherence of several of these lines was inhibited by antibodies to fibronectin. The adherence of the T cell leukemia Jurkat was sensitive to inhibition by antibodies to the fibronectin receptors α4β1 and α5β1. The adherence of the β1 integrin negative B cell line RPMI 8866 was inhibited by antibodies to the vitronectin receptor, αvβ3. The interactions of several other cell lines with synovial cells appeared to be independent of this fibronectin-dependent pathway. These results indicate that multiple potential adhesion pathways for cellular interactions in the tissues may exist. The adherence to cell-associated fibronectin may play a contributory role in such processes for certain lymphocyte subsets.

CdTe layers have been grown by molecular beam epitaxy on 3 inch nominal Si(211) under various conditions to study the effect of growth parameters on the structural quality. The microstructure of several samples was investigated by high resolution transmission electron microscopy (HRTEM). The orientation of the CdTe layers was affected strongly by the ZnTe buffer deposition temperature. Both single domain CdTe(133)B and CdTe(211)B were obtained by selective growth of ZnTe buffer layers at different temperatures. We demonstrated that thin ZnTe buffer layers (<2 nm) are sufficient to maintain the (211) orientation. CdTe deposited at ∼300°C grows with its normal lattice parameter from the onset of growth, demonstrating the effective strain accommodation of the buffer layer. The low tilt angle (<1°) between CdTe[211] and Si[211] indicates that high miscut Si(211) substrates are unnecessary. From low temperature photoluminescence, it is shown that Cd-substituted Li is the main residual impurity in the CdTe layer. In addition, deep emission bands are attributed to the presence of AsTeand AgCdacceptors. There is no evidence that copper plays a role in the impurity contamination of the samples.

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ZnSe films were grown on GaAs substrates with various growth conditions by molecular beam epitaxy (MBE). The optical anisotropy of the films was determined by reflectivity difference spectroscopy (RDS) during and/or after growth. Comparison of the in situ RDS data with spectroscopic ellipsometry (SE) data suggests that RDS could be utilized to determine film thickness, alloy composition and temperature during growth. The RDS spectra were also compared with results from transmission electron microscopy (TEM), X-ray double-crystal rocking curve (DCRC) and Hall measurements. Comparison with the Hall effect showed that the magnitude of the optical anisotropy is generally larger for higher carrier concentrations. Comparison with TEM results and the full-width-at-half-maximum measurements by DCRC reveals that: (i) the E1structure arising from the bulk spatial distribution (BSD) is correlated with film quality; (ii) the amplitude of the interference below E0provides a measure of the ZnSeGaAsinterface quality; and (iii) the large anisotropy above the band gap is correlated with surface roughness.

The initial growth of thin ZnSe layers, grown on GaAs(0 0 1) using molecular beam epitaxy (MBE), has been studied using real-time reflection high-energy electron diffraction (RHEED), as well as X-ray double-crystal rocking curves (DCRC), reflectivity difference spectroscopy (RDS) and transmission electron microscopy (TEM). A noticeable difference in interface quality and growth was observed depending upon the initial precursor. Exposure to Se flux before growth led initially to three-dimensional growth, whereas exposure to Zn flux or no precursor led immediately to two-dimensional growth. X-ray DCRC and RDS confirmed that the overall sample quality was better with two-dimensional growth, and TEM observations were consistent with previous studies which have shown that initial three-dimensional growth is related to the formation of Ga2Se3at the interface, leading to high densities of stacking faults and edge dislocations.

The results of arsenic incorporation in HgCdTe layers grown by molecular beam epitaxy (MBE) are reported. The incorporation into MBE-HgCdTe was carried out by a method called planar doping. Arsenic was successfully incorporated during the MBE growth as acceptors. Result suggests that most of the arsenic incorporates as an active acceptor at the MBE growth temperature. These findings are very promising for MBE-HgCdTe technology. Some layers show enhanced p-type mobilities with no carrier freeze-out at low temperatures. These results are very promising for in situ fabrication of infrared devices using HgCdTe material.

Abstract: We have been fabricating x-ray photoconductor linear array detectors using molecular beam epitaxially (MBE) grown (lll)B undoped CdTe layers on (100) Si substrates. A novel technique was developed to remove the Si and to mount the fragile MBE grown CdTe layers onto insulating ceramic substrates. 256 channel linear photoconductor array devices were fabricated on the resulting CdTe layers. The resistivity of MBE (lll)B CdTe was high (>108 \cm) enough to utilize the material for low energy (8 ~ 25 keV) x-ray detectors. The stability of the detectors are satisfactory, and they were tested at room temperature routinely for over a year. The performance of the photoconductor was greatly improved when the detector was cooled to 230K. Due to its reduced dark current at low temperatures, the dynamic range of the detector response increased to nearly four decades at 230K.

Abstract: We have systematically studied the growth of CdTe (lll)B on Si(001)with different atomic step structures, defined uniquely by miscut tilt angle and direction. X-ray double crystal rocking curve (DCRC) analysis has been used to evaluate the crystalline quality and twin content of the films. High-resolution electron microscopy has been used to examine the CdTe(lll)B/Si(001) interface and to follow the microstructural evolution as a function of distance from the interface. Our results show that the formation of double domains and twins is very sensitive to the tilt parameters. When growth conditions are optimized, twins are not observed at distances greater than about 2.5 microns from the substrate surface. The best quality films exhibit a DCRC FWHM of 60 arc sec, for a film thickness of 17 m, the lowest value ever reported for heteroepitaxial growth of CdTe on Si or GaAs. In efforts to improve the nucleation process, precursors such as Te and As have been used, and we have shown that they improve the stability of the heterointerface.

Abstract: The growth of high quality (111)B oriented HgCdTe layers on CdZnTe/GaAs/Si and CdTe/Si substrates by Te-rich slider liquid phase epitaxy (LPE) is reported. Although the (111) orientation is susceptible to twinning, a reproducible process yielding twin-free layers with excellent surface morphology has been developed. The electrical properties and dislocation density in films grown on these substrates are comparable to those measured in HgCdTe layers grown on bulk CdTe substrates using the same LPE process. This is surprising in view of the large lattice mismatch that exists in these systems. We will report details of both the substrate and HgCdTe growth processes that are important to obtaining these results.

Abstract: We report the results of the transport properties and the recombination mechanisms of indium-doped HgCdTe(211)B (x ≈ 23.0% � 2.0%) layers grown by molecular beam epitaxy. We have investigated the origin(s) of the background doping limitation in these layers. Molecular beam epitaxially grown layers exhibit excellent Hall characteristics down to indium levels of 2 x 1015 cm−3. Electron mobilities ranging from (2-3) x 105 cm2/v-s at 23K were obtained. Measured lifetime data fits very well with the intrinsic band-to-band recombinations. However, below 2 x 1015 cm−3 doping levels, mobility vs temperature curves starts to reflect nonuniformity in carrier distribution. Also, when we reduced the Hg vacancy concentration down to 1012 cm−3 range, by annealing at 150�C, Hall characteristics shows an increase in the nonuniformity in the epilayers. It was found that after annealed at 150�C, the obtained SR defect level has a different origin than the previously obtain Hg-vacancy related defect level.

Abstract: X-ray photoelectron spectroscopy was used to measure the valence band discontinuity at the ZnSe/ZnSxSe1−x interface as a function of alloy composition. Due to the large lattice mismatch, the experimental values have to be corrected in order to account for strain in the ZnSe layers. We find the valence band discontinuity to vary between 0 and 0.76 eV as a function of S content x. This result is in excellent agreement with theoretical calculations. It also shows that the conduction band discontinuity is not negligibly small.

Abstract: We report the results of in situ arsenic doping by molecular beam epitaxy using an elemental arsenic source. Single Hg1−xCdxTe layers of x ∼0.3 were grown at a lower growth temperature of 175C to increase the arsenic incorporation into the layers. Layers grown at 175C have shown typical etch pit densities of 2E6 with achievable densities as low as 7E4cm−2. Void defect densities can routinely be achieved at levels below 1000 cm−2. Double crystal x-ray diffraction rocking curves exhibit typical full width at half-maximum values of 23 arcsec indicating high structural quality. Arsenic incorporation into the HgCdTe layers was confirmed using secondary ion mass spectrometry. Isothermal annealing of HgCdTe:As layers at temperatures of either 436 or 300C results in activation of the arsenic at concentrations ranging from 2E16 to 2E18 cm−3. Theoretical fits to variable temperature Hall measurements indicate that layers are not compensated, with near 100% activation after isothermal anneals at 436 or 300C. Arsenic activation energies and 77K minority carrier lifetime measurements are consistent with published literature values. SIMS analyses of annealed arsenic doping profiles confirm a low arsenic diffusion coefficient.

Abstract: Femtosecond pump-probe differential reflectivity spectroscopy is used to investigate the ultrafast cooling dynamics of hot photoexcited carriers in a high-quality ZnSe epilayer grown on GaAs. Comparison with a theoretical model based on a balance equation approach indicates that the observed reduction in the electron cooling rate with increasing carrier density (for carrier densities greater than ∼31017cm−3) is due to both screening of the Frhlich interaction and a non-equilibrium hot longitudinal optic-phonon population generated by the cooling electron distribution.

Abstract: The capability of growing state-of-the-art middle wavelength infrared (MWIR)-HgCdTe layers by molecular beam epitaxy (MBE) on large area silicon substrates has been demonstrated. We have obtained excellent compositional uniformity with standard deviation of 0.001 with mean composition of 0.321 across 1.5″ radii. R0A as high as 5 107 ω-cm2 with a mean value of 7 106 Θ-cm2 was measured for cut-off wavelength of 4.8 m at 77K. Devices exhibit diffusion limited performance for temperatures above 95K. Quantum efficiencies up to 63% were observed (with no anti-reflection coating) for cut-off wavelength (4.8–5.4) m @ 77K. Excellent performance of the fabricated photodiodes on MBE HgCdTe/CdTe/Si reflects on the overall quality of the grown material in the MWIR region.

Growth of CdTe(111)B on Si(100) by molecular beam epitaxy (MBE) was studied with photoelectron spectroscopy using synchrotron radiation. First, a monolayer of Te forms on top of the Si(100) substrate. We suggest that these Te atoms replace the Si dimer atoms and form dimer rows. The surface peak in the Si 2p spectra from clean Si(100) is replaced by four adatom-induced peaks. They are assigned to Si atoms bound to one, two, three and four Te atoms, respectively. Some Te seems to diffuse into the substrate. Finally, CdTe(111)B grows on such Te-terminated Si(100) surfaces, with little effect on the interface electronic structure.

The ultrafast relaxation dynamics of hot electrons, initially photoexcited with an excess energy of 300 meV, are monitored in a high-quality ZnSe epilayer grown on a GaAs substrate by using a time-resolved femtosecond differential reflection technique which exploits the intrinsic interferometric asymmetric Fabry-Perot sample structure. The results are consistent with the expected characteristic electronic LO-phonon emission time of 40 to 50 fs for carrier densities less than  3×10¹⁷ cm^—3. At higher carrier densities, comparison of the experimental data with a theoretical model indicates that the slowing of the electron cooling rate is due to both screening of the Fröhlich interaction and the “hot phonon effect”.

We have studied the minority-carrier lifetime on intentionally indium-doped (211)B molecular beam epitaxially grown Hg1-xCdxTe epilayers down to 80K with x ≈ 23.0% ± 2.0%. Measured lifetimes were explained by an Auger-limited band-to-band recombination process in this material even in the extrinsic temperature region. Layers show excellent electron mobilities as high as ≈2 x 105cm2v-1s-1at low temperatures. When the layers are compensated with Hg vacancies, results show that the Schockley-Read recombination process becomes important in addition to the band-to-band processes. From the values of τn0and τp0of one sample, the obtained defect level is acceptor-like and is somewhat related to the Hg vacancies.

Arsenic doped molecular beam epitaxy (MBE) (Hg,Cd)Te films were grown on (Cd,Zn)Te substrates. The concentration of arsenic was varied from 5 x 1018cm-3to 1 x 1020cm-3. After the growth, the epitaxial layers were annealed at various partial pressures of Hg within the existence region of (Hg,Cd)Te at temperatures ranging from 400 to 500°C. Hall effect and resistivity measurements were carried out subsequent to the anneals. 77K hole concentration measurements indicate that for concentrations of arsenic <1019cm−3, most of the arsenic is electrically active acting as acceptors interstitially and/or occupying Te lattice sites at the highest Hg pressures. At lower Hg pressures, particularly at annealing temperatures of 450°C and higher, compensation by arsenic centers acting as donors appears to set in and the hole concentration decreases with decrease in Hg pressure. These results indicate the amphoteric behavior of arsenic and its similarity to the behavior of phosphorus in (Hg,Cd)Te previously inferred by us. A qualitative model which requires the presence of arsenic occupying both interstitial and Te lattice sites along with formation of pairs of arsenic centers is conjectured.

1. In dogs anaesthetized with chloralose, small latex balloons were positioned at the left pulmonary vein‐atrial junctions so as to stretch this region. By recording action potentials from slips of the cervical vagi it was established that distension of these balloons stimulated receptor endings in the atrial endocardium which discharged into the myelinated branches of the vagi i.e. Paintal type A, type B and Intermediate type receptors. 2. In other dogs, cooling the cervical vagus in steps of 2 degrees C reduced this response in vagal myelinated fibres. With twelve receptors the response to distension was reduced by 30% when the vagus was cooled to 16 degrees C, by 70% when cooled to 12 degrees C and abolished at 8‐‐12 degrees C. 3. In a third group of dogs, distension of balloons at the pulmonary vein‐atrial junctions resulted in a reflex increase in heart rate. Cooling the cervical vagi in these dogs in stages to 8 degrees C reduced this increase in heart rate. In nine dogs the response was reduced by 20% when the vagi was cooled to 16 degrees C, by 70% when cooled to 12 degrees C and abolished between 12 and 8 degrees C. 4. In a fourth group of dogs, distension of balloons at the pulmonary vein‐atrial junctions was shown also to activate receptor endings in the atria which discharged into non‐myelinated branches of the Vagi. In twelve receptors, cooling the cervical vagus in steps of 2 degrees C reduced this evoked increase in activity in non‐myelinated fibres. These responses were abolished over a wide range of temperature unlike the responses observed above. 5. It is concluded that the increase in heart rate which follows distension of balloons at the pulmonary vein‐atrial junctions is mediated solely by the Paintal‐type receptors which discharge into the myelinated fibres in the vagi.

The symptomatic presentation of an unruptured sinus of Valsalva aneurysm is rare. A 48 year old man with a history of treated hypothyroidism, and a five year history of ileocolonic Crohn's disease of chronic low grade activity presented with a profound left hemiplegia. He was in sinus rhythm and normotensive. Cardiac auscultation was repeatedly normal. Computed tomography of the head performed early in the course of the illness was reported as normal. Duplex Doppler examination of the carotid arteries performed six months later revealed no significant atheroma. There was complete resolution of the neurological deficit over a period of months. A year later he presented with chest pain suggestive of myocardial ischaemia. Computed tomography, magnetic resonance imaging, transthoracic and transoesophageal echocardiography, and cardiac catheterisation pointed to a sinus of Valsalva aneurysm protruding into the left ventricular outflow tract. In view of the previous neurological event and ongoing chest pain suggestive of myocardial ischaemia, the lesion was resected. The patient made a good recovery and postoperative transoesophageal echocardiography showed normal aortic valve function with no residual regurgitation. This is the first reported case of pure left ventricular outflow tract extension of an unruptured left sinus aneurysm. The presentation with ischaemic cardiac pain does not seem to be explained by conventional mechanisms.

An isotope limb blood flow technique was used to assess the outcome of technically successful balloon angioplasty. Measurements were made on a total of 120 limbs, before angioplasty and at least once after angioplasty at 3 weeks, 3 months, 6 months, 12 months and 2–5 years. 67% of treated limbs showed a significant improvement in limb blood flow at 3 weeks. At 12 months following angioplasty 43% of limbs still showed an improvement in blood flow compared with the measurement made before angioplasty. However, a number of these limbs showed a significant fall in limb blood flow between 3 weeks and 12 months even though the 3 week and the 12 month flow figures were still greater than those before angioplasty. The degree of initial improvement in blood flow seen at 3 weeks persisted at 12 months after angioplasty without significant fall in only 30% of limbs. In 33% of limbs where the balloon angioplasty was technically successful there was no improvement in blood flow at 3 weeks. 80% of these limbs had further significant untreated disease angiographically, compared with 43% of limbs where there was an increase in limb blood flow.

A prospective study using contrast enhanced turbo-FLASH (Fast Low-Angle Shot) magnetic resonance (MR) angiography was performed to assess the arterial anatomy in patients who had advanced atherosclerotic aortoiliac disease. This new imaging sequence was employed in 17 patients and the results were compared with conventional abdominal aortography. MR angiography accurately detected all aortic occlusions (3/3), their sites and their extent. All nine iliac occlusions were correctly identified (sensitivity 100%, specificity of 90%). The sensitivity was 100% for stenosis of 50% or greater in the abdominal aorta, and the iliac and common femoral arteries. The degree of stenosis was overgraded in 20 of 51 lesions (39.2%). Mild stenosis was overgraded as moderate stenosis in 10 and as severe stenosis in three. Moderate stenosis was overgraded as severe stenosis in four. None of the mild or moderate stenoses resulted in areas of signal voids suggestive of occlusions. Three severe stenoses were seen as areas of signal voids (two iliac, one femoral). In the eight patients who had in total 10 aneurysmal dilatations of the aorta or the iliac arteries, MR angiography was superior in demonstrating the true extent of the aneurysms. We conclude that turbo-FLASH MR angiography has the potential to be a useful non-invasive imaging technique for patients with advanced aortoiliac disease.

Arsenic incorporation and doping in HgCdTe layers grown by molecular beam epitaxy (MBE) were examined in this paper. Arsenic incorporation into MBE-HgCdTe was carried out in two different ways: (1)ex-situarsenic ion-implantation on indium-doped n-type HgCdTe layers, and (2) through a new approach called arsenic planar doping. We report onex-situarsenic diffusion on indiumdoped MBE-HgCdTe layers at 450°C. In the investigated layers, arsenic redistribution occurs with a multi-component character. We obtained a diffusion coefficient of DAs= (1-3) × 10−13cm2/s at 450°C. Results of differential Hall and fabricated p-n junctions suggest that during high temperature annealing, arsenic preferentially substitutes into Te sublattices and acts as acceptor impurities. In the second case, arsenic has been successfully incorporated during the MBE growth as an acceptor in the planar doping approach. Withoutex-situannealing, as-grown layers show up to 50% activation of arsenic during the growth. These results are very promising forin-situfabrication of infrared devices using HgCdTe material.

Objective We aimed to describe the clinical characteristics of chronic pancreatitis (CP) and patient quality of life (QOL) in a resource-limited setting.Methods We performed a cross-sectional study including patients with clinical and radiological features of CP. We collected clinical data and assessed QOL using the European Organization for the Research and Treatment of Cancer Quality of Life Questionnaire.Results We included 103 patients (median age 44 years, 84 men). Median age at symptom onset was 36 (4–78) years. Around 70% of patients had diabetes mellitus and 62.1% had consumed alcohol; 36 (35%) were current smokers. The mean overall global QOL score was 68.7. Most patients (91.3%) sought treatment from multiple centers. Nineteen (18.5%) had pancreatic stone disease, 38 (36.9%) had persistent abdominal pain (median severity 7.8/10, 59 (57.3%) had steatorrhea, and 56 (54.4%) had jaundice. Poor QOL was significantly associated with weight loss, loss of appetite, and intractable pain. No correlation with age, sex, or alcohol consumption was noted.Conclusion A considerable proportion of patients with CP had troublesome symptoms. Intractable pain, loss of appetite, and weight loss were significantly associated with poor QOL. Further assessment is needed of patients’ psychosocial well-being and its association with QOL.

Abstract: Compositional changes induced in growing Hg1−xCdxTe layers as a function of the changes in temperature of the indium source in the MBE chamber have been analyzed in terms of the Hg-In alloy thermodynamics and changes in the activity of indium over the growing films as the Hg flux changes. Compositional changes induced by changes in the Te source temperature have been analyzed in terms of the changes in the activity of Cd over the growing layers. These analysis are helpful in understanding the compositional changes with variation of the growth parameters in the MBE chamber.

Aim:To identify markers of recurrence and survival in patients with locally advanced rectal cancer who received neoadjuvant chemoradiotherapy and surgery. Materials & methods:A total of 280 patients were identified in Manitoba between 2007 and 2012. Demographics and clinical data were collected. Cox regression models were used to identify outcome predictors. Results:A total of 53 patients achieved pathological complete response (pCR) and 160 patients received adjuvant chemotherapy (ACT). The median follow-up duration was 2.06 years. Recurrence and survival rates at 5 years were 33.2 and 77.0, respectively. pCR and lymphovascular invasion predicted recurrence. pCR and ACT predicted better survival. Conclusion:pCR is a significant predictor of recurrence and survival and may be considered as an oncological end point. The patients who achieve pCR may not derive additional survival benefit from ACT.

Multiple coronary artery fistulae are rare, complications can be life-threatening, and with large or symptomatic fistulae, intervention is mandatory. Both surgical and percutaneous interventions are well-described. We believe this is the first report of the embolization of an acquired fistula following initial surgical treatment of multiple congenital fistulae.

Valproate is a medication used in the treatment of seizures, bipolar disorder, migraines, and behavioral problems. Here we present a case of an 8-year-old boy who presented with hypertensive urgency after initiation of valproate. Primary treatment of his hypertension was ineffective. Blood pressure stabilization was achieved following discontinuation of valproate. Clinicians should be aware of the risk of developing hypertensive urgency with administration of valproate.

The spontaneous formation of so-called self-assembled quantum dots (SAQDs) during heteroepitaxial growth has attracted much recent interest because of potential device applications. Much attention has been directed towards the Ge/Si(001) system, in particular to characterize the island shape and size distributions as a function of growth conditions, i.e., Ge coverage and substrate temperature. Due to the lattice mismatch, a layer-to-island transition occurs at coverages greater than about 3 monolayers, and thereafter small, coherent hut clusters and larger coherent and incoherent dome clusters are observed. Interdiffusion of Si into the Ge islands as a strain-relief mechanism also occurs. Strategies for achieving better control of island size, shape, composition and separation continue to be sought. in this paper, we report a preliminary investigation of island growth in the alternative Ge/Si(l12) system.The Ge/Si(112) samples were grown by molecular beam epitaxy using a Riber 2300 system equipped with a Ge Knudsen effusion cell.

In recent years, GaN and its alloys have been the subject of an intense global research effort to develop its optoelectronic properties in the blue-green region of the spectrum. Of particular interest has been the fact that despite a high density of threading dislocations, on the order of 108to 1010per cm2, thin film devices retain their ability to emit light. The origin of this behavior remains unclear, and it has even been suggested that reducing the number of defects by employing different growth techniques does not necessarily increase the crystal's lasing abilities. As research is now aiming to grow GaN on silicon (silicon has a large lattice-mismatch to GaN) in order to develop an inexpensive LED technology, dislocations are likely to remain a major issue. It is therefore essential that we develop a fundamental understanding of the electronic structure of these defects, in order to determine their effect on the properties.

The epitaxial growth of CdTe on Si is currently being investigated as a means of generating an alternative substrate for the subsequent growth and processing of HgCdTe based infrared detecting devices. The most favorable orientation for the growth of high-quality HgCdTe is CdTe (111)B, which has been demonstrated to be grown on miscut Si (001) substrates with very high quality. However, twinning islands and multiple domains are present at the nucleation stage, which has a detrimental effect on the device properties.An alternative approach, which has the potential to overcome the multiple domain problems in the nucleation stage, is to grow CdTe (111) B on Si (111) substrates. However, previous reports have shown that the direct growth of CdTe onto Si (111) results in an A-polarity for the films. In an attempt to overcome this limitation, passivation of the substrate surface has been investigated.