Ensemble GaAsSb/GaAs axial configured nanowire-based separate absorption, charge, and multiplication avalanche near-infrared photodetectors

In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate absorption, charge, and multiplication (SACM) region-based nanowire avalanche photodetector device on non-patterned Si substrate is presented. Our device exhibits a low breakdown voltage (V _BR) of ∼ -10 ± 2.5 V under dark, photocurrent gain (M) varying from 20 in linear mode to avalanche gain of 700 at V _BR at a 1.064 μm wavelength. Positive temperature dependence of breakdown voltage ∼ 12.6 mV K^-1 further affirms avalanche breakdown as the gain mechanism in our SACM NW APDs. Capacitance-voltage (C-V) and temperature-dependent noise characteristics also validated punch-through voltage ascertained from I-V measurements, and avalanche being the dominant gain mechanism in the APDs. The ensemble SACM NW APD device demonstrated a broad spectral room temperature response with a cut-off wavelength of ∼1.2 μm with a responsivity of ∼0.17-0.38 A W^-1 at -3 V. This work offers a potential pathway toward realizing tunable nanowire-based avalanche photodetectors compatible with traditional Si technology.

Identification of dispersal barriers for a colonising seagrass using seascape genetic analysis

Seagrasses are important habitats providing many ecological services. Most species have broad distributions with maximum dispersal distances of 100's of kms, however there is limited understanding of dispersal distances of colonising species like Halodule uninervis. It commonly grows in disturbed environments and could disperse to other meadows via clonal fragments. Effective conservation management requires greater understanding of genetic structure, dispersal barriers, and connectivity timescales to predict recovery following disturbance. Despite fragment viability of up to 28 days in a congenera, this theory remains untested in situ. Using 80 neutral single nucleotide polymorphisms, we investigated genetic diversity, gene flow patterns and structure among 15 populations of H. uninervis along 2000 km of Western Australian coastline. These data were combined with a multi-generational oceanographic dispersal model and a barrier dispersal analysis to identify dispersal barriers and determine which fragment dispersal duration (FDD) and timescale over which stepping-stone connectivity occurred, best matched the observed genetic structure. The 2-7 day FDD best matched the genetic structure with 4-12 clusters, with barriers to dispersal that persisted for up to 100 years. Modelling suggested greater fragmentation of metapopulations towards the southern edge of the species distribution, but genetic diversity did not decline. Several long-term boundaries were identified even with fragment viability of up to 28 days. This suggests H. uninervis dispersal is spatially limited by factors like oceanographic features and habitat continuity which may limit dispersal of this species. This study reiterates that potential dispersal does not equal realised dispersal, and management scales of 10's of kilometers are required to maintain existing meadows. Recruitment from distances further than this scale are unlikely to aid recovery after extreme disturbance events, particularly towards the range edge of H. uninervis distribution.

Ethnicity and seizure threshold

1. Seizure threshold is an important variable in modern ECT treatment planning. To date, age, gender, and electrode placement have been used to predict seizure threshold, but the potential impact of ethnicity has received little attention. 2. In a retrospective pilot study of patients who received ECT, 20 pairs of first admission, right unilateral-treated, age- and sex-matched black and white patients were compared. 3. Black patients had higher seizure thresholds and were more likely to require restimulation, despite the finding that they were more likely to have been receiving concomitant medications which lower seizure threshold. However, ethnicity was confounded with variations in ECT dose titration, which were the strongest predictor of seizure threshold. 4. There were no differences in seizure length. Further study is necessary to confirm the impact of ethnicity on seizure threshold.

Antipsychotics: Past and Future: National Institute of Mental Health Division of Services and Intervention Research Workshop, July 14, 1998

A workshop on "Antipsychotics: Past and Future" was convened by the National Institute of Mental Health (NIMH), Division of Services and Intervention Research (DSIR), on July 14, 1998, to review the results of recent antipsychotic drug research, discuss current standards of treatment, and identify areas needing further study. There has been a proliferation of new antipsychotic medications and a rapid increase in their clinical utilization. The new atypicals are beginning to supplant the older typical neuroleptic antipsychotics, and the scientific and ethical issues raised by this transition prompted the workshop. Given the apparent, albeit not fully defined, advantages of atypical drugs, particularly their safety profiles, the question is whether more comparisons with typical antipsychotics are warranted and whether clinical trial designs warrant (or would be justified in) the inclusion of typical drugs as standard active comparators. Workshop participants--including clinical researchers, patient advocates, bioethicists, and NIMH staff--discussed the conclusions drawn from current data, ethical issues for subjects in clinical trials, funding for ongoing studies using typical agents, and appropriate comparators for trials using atypical agents.

Psychoneuroendocrinology of depression. Prolactin

Prolactin provides us with a window to the brain in our quest for understanding the psychobiology of depression, since the regulation of its release involves some of the monamine neurotransmitter systems that have been implicated in the pathophysiology of depression. Investigation examining basal prolactin plasma concentrations in depressed patients, including assessments of the rhythm of prolactin release, have not provided clear, consistent findings. Further exploration of the precise mechanisms involved in serotonin-stimulated prolactin release should shed light on the pathophysiology of abnormal prolactin responsivity in depression, and by extension, the psychobiologic basis of depression.

ECT for the treatment of intractable mania in two prepubertal male children

We provide case reports of the successful use of electroconvulsive therapy (ECT) for intractable mania in two prepubertal male children. Both children responded well to ECT without significant complications. The report focuses in particular on the procedure and technique of doing ECT in this patient population.

Seizure activity causing loss of cardiac output after a Fontan operation

After a Fontan operation pulmonary blood flow is heavily dependent on respiration. Two patients with a Fontan and normal sinus rhythm developed episodes of collapse with loss of cardiac output secondary to the tonic phase of an epileptic fit. The forced expiratory effort during the tonic phase severely compromised systemic venous return and led to collapse due to loss of cardiac output.

Emergency percutaneous transluminal coronary angioplasty for intractable ventricular arrhythmias associated with acute anterior myocardial infarction

A previously fit marathon-running 54 year old man was admitted as an emergency having collapsed with chest pain caused by an acute transmural anterior myocardial infarction. He was initially resuscitated by his general practitioner then had recurrent episodes of ventricular flutter and fibrillation requiring continuing cardiopulmonary resuscitation and repeated defibrillation. During ambulance transfer and in the hospital emergency department he received appropriate intravenous antiarrhythmic drug treatment and a total of 63 transthoracic DC shocks, with good cardiac output between shocks. After his condition failed to stabilise in intensive care, an intra-aortic balloon pump was inserted and coronary angiography showed a proximal occlusion of the left anterior descending branch. Coronary angioplasty successfully re-opened the vessel with an excellent angiographic result. The intra-aortic balloon pump was withdrawn the following day and he was well enough to be discharged 7 days later. At 4 weeks he performed a satisfactory maximal exercise test and remains in New York Heart Association functional class I.

Doppler color flow mapping in the diagnosis of ventricular septal rupture and acute mitral regurgitation after myocardial infarction

Fifty consecutive patients with a newly acquired systolic murmur and severe cardiac decompensation following a recent myocardial infarction (27 with an anterior and 23 with an inferior infarct) were studied by a combination of two-dimensional echocardiography, spectral Doppler and Doppler color flow mapping. The initial ultrasound study defined a ventricular septal rupture in 43 patients and severe isolated mitral regurgitation in 7 patients (5 with papillary muscle rupture and 2 with severe papillary muscle dysfunction). All 50 patients had subsequent confirmation of the diagnosis by either cardiac catheterization or surgical inspection, or both. Two-dimensional echocardiography alone directly visualized a septal defect in only 17 (40%) of the 43 patients with ventricular septal rupture. In all 43 patients the mitral valve appeared normal on imaging. In six of the seven patients with isolated mitral regurgitation, two-dimensional echocardiography correctly demonstrated the structural abnormality of the mitral valve (five with flail anterior leaflet and one with posterior leaflet prolapse). The addition of Doppler color flow mapping greatly improved the diagnostic information in both patient groups. In all 43 patients with ventricular septal rupture, Doppler color flow mapping demonstrated both an area of turbulent transseptal flow and a diagnostic systolic flow disturbance within the right ventricle. In the seven patients with isolated papillary muscle rupture or dysfunction, Doppler color flow mapping not only demonstrated the presence of mitral regurgitation in all cases, but also identified the specific mitral leaflet abnormality by defining the direction of the regurgitant jet.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of ventricular septal rupture after myocardial infarction: value of colour flow mapping

Twenty patients with ventricular septal rupture after myocardial infarction were investigated by cross sectional echocardiography with integrated pulsed and continuous wave Doppler and colour flow mapping. Confirmatory cardiac catheterisation was performed in 12 patients. Eighteen patients had surgical repair with inspection of the defect. Six patients in whom recurrent ventricular septal rupture developed were also investigated by Doppler echocardiography and colour flow mapping. Cross sectional echocardiography correctly predicted the infarct territory in all cases but visualised the septal rupture in only seven (35%). Pulsed and continuous wave Doppler detected a disturbance of right ventricular systolic flow that was diagnostic of a ventricular septal rupture in 19 (95%), but this only accurately predicted the site in 14 (70%). Colour flow mapping studies showed a mosaic jet traversing the interventricular septum in all 20 cases, and this accurately predicted the site of rupture. In addition colour flow mapping defined three sites of ventricular septal rupture: apical, posterior, and anterior trabecular. Five of the six patients with recurrent rupture were correctly diagnosed by pulsed and continuous wave Doppler and all six were diagnosed by colour flow mapping. Cross sectional echocardiography with colour flow mapping is a highly sensitive and rapid technique for the assessment of postinfarction ventricular septal rupture before and after operation. It was more informative about the site of the rupture than pulsed and continuous wave Doppler echocardiography.

Balloon dilatation of the aortic valve: limited success and early restenosis

Balloon dilatation of the aortic valve was attempted 16 times in 15 patients with severe aortic stenosis. None died but one had a transient stroke after the procedure. At dilatation the gradient across the aortic valve was reduced by greater than 30% in 69% of patients and the Gorlin valve area (calculated in 7/15 patients) increased by 30% in half. But a comparison of Doppler gradients measured before and one to two days after dilatation in 11 patients showed a greater than 30% reduction in the simultaneously measured gradient in only four. Doppler gradient was the most accurate predictor of symptomatic benefit and a fall in Doppler gradient persisted mainly in patients whose peak to peak gradient fell by at least 40% at the time of the procedure. Balloon dilatation of the aortic valve is a relatively safe procedure but it is less successful than previous reports suggest, perhaps because of early restenosis. Some forms of aortic stenosis may be more amenable to this procedure than others.

Accurate detection of triple vessel disease in patients with exercise induced ST segment depression after infarction

The severity of coronary artery disease is an important determinant of prognosis after acute myocardial infarction. The ability of a symptom limited exercise test to predict the presence of triple vessel disease was assessed in 221 patients three weeks after infarction. Coronary angiography was performed in patients with exercise induced ST segment depression. The presence of ST segment depression alone was poorly indicative of triple vessel disease; however, some specific features of ST segment changes on exercise were of predictive value. Downsloping ST segment configuration alone or horizontal ST segment depression associated with an early onset and a late recovery time after exercise correctly identified 30 (90%) of 33 patients with triple vessel disease whereas it incorrectly identified only 6 (15%) of 39 patients with single and double vessel disease. An abnormal blood pressure response was also predictive. In patients with ST segment depression after infarction triple vessel disease can be detected accurately by a combination of the electrocardiographic and haemodynamic variables attained on exercise.

Usefulness of noninvasive Doppler measurement of ascending aortic blood velocity and acceleration in detecting impairment of the left ventricular functional response to exercise three weeks after acute myocardial infarction

Left ventricular (LV) function was assessed by Doppler ultrasound measurement of ascending aortic blood velocity and maximal acceleration in 165 patients 3 to 4 weeks after acute myocardial infarction (AMI); all were undergoing routine 12-lead electrocardiogram exercise stress testing. Patients were grouped according to electrocardiographic stress test response; a positive response was defined as at least 1 mm of ST-segment depression in any lead. The Doppler velocity signal yielded 3 variables of interest: peak velocity, maximal acceleration (an index of inotropic state) and the systolic velocity integral (an index of stroke volume). All 3 Doppler ejection variables were significantly lower at peak exercise in patients with a positive electrocardiographic stress test response than in those with negative response, with maximal acceleration showing the most significance (p less than or equal to 0.001). Coronary angiography was performed in 63 of the 67 patients with positive responses, and patients were separated into 2 groups according to extent of coronary artery disease (CAD): 1- and 2-vessel or 3-vessel CAD. Peak velocity and maximal acceleration were significantly lower in patients with 3-vessel CAD than in those with 1- and 2-vessel CAD (p less than or equal to 0.01 and p less than or equal to 0.01). Discriminant analysis showed maximal acceleration and peak velocity values at peak exercise to be 65% predictive of 3-vessel CAD, onset time to ST-segment depression was 74% predictive and the combination of Doppler and electrocardiographic variables increased 3-vessel CAD predictive value to 80%.(ABSTRACT TRUNCATED AT 250 WORDS)

Determinants of operative mortality for patients undergoing aortic valve replacement. Discriminant analysis of 1,479 operations

The influence of 35 preoperative and intraoperative characteristics on operative mortality risk after 1,479 isolated aortic valve replacement procedures (1967 to 1981) was investigated utilizing univariate and multivariate logistic regression analyses. Mean age at operation was 58 +/- 13 years; 72% of patients were men. Physiology was classified as aortic stenosis (58%), regurgitation (30%), or both (9%). The overall operative mortality rate was 7% +/- 1%, but there were substantial differences in operative mortality rates among physiological subgroups (aortic regurgitation, 10% +/- 2%; aortic stenosis, 6% +/- 1%; stenosis/regurgitation, 5% +/- 2%). Independent determinants of operative mortality rate in the entire group were advanced New York Heart Association functional class, renal dysfunction, physiological subgroup, atrial fibrillation, and older age. In the aortic regurgitation subgroup, functional class, atrial fibrillation, and operative year were independent predictors. In the aortic stenosis subgroup, the significant determinants were functional class, renal dysfunction, age, prosthetic valve dysfunction, and absence of angina. Concomitant coronary bypass grafting, previous operation, endocarditis, and ascending aortic replacement had no independent predictive effect on operative mortality rate. Thus, the early results of aortic valve replacement can be related to several specific variables describing the functional and physiological status of the patient. Operative mortality rate is not independently related to previous operation or concomitant operative procedures. Specific differences in risk factors exist among the various physiological subgroups, probably reflecting the pathophysiology of the different hemodynamic lesions. This information should provide for a more rational approach to aortic valve replacement, at least in terms of early risk/benefit deliberations.

Heart-lung transplantation for irreversible pulmonary hypertension

Combined heart and lung transplantation was carried out in 17 patients at Stanford University between March, 1981, and December, 1983. The recipients were between 22 and 45 years old. All patients had end-stage pulmonary hypertension; 10 had Eisenmenger's syndrome and the remaining 7, primary pulmonary hypertension. Five patients died within the first few postoperative weeks. The remainder are well between four weeks and 33 months from operation. The immunosuppressive protocol has consisted of cyclosporine with an initial course of rabbit antithymocyte globulin. Azathioprine also was given for the first two weeks and then was replaced with prednisone. Rejection, as diagnosed by cardiac biopsy, was treated with high doses of methylprednisolone. Modifications of technique that have developed include the removal of the recipient heart and lungs separately, and preservation of the lungs with a modified Collins' solution instead of a cardioplegic solution. Rejection occurred in 6 of the 12 survivors. Infections developed in 9 patients, but only one resulted in a fatal outcome (Legionella). Thus, the results of clinical heart-lung transplantation have been considerably superior to clinical efforts in lung transplantation. It is suggested that the combined operation is preferable for the following reasons: (1) all diseased tissue is removed, thus eliminating recurrent infection and ventilation/perfusion disparity; (2) transplantation of the entire heart-lung block preserves coronary-bronchial vascular anastomoses and makes airway dehiscence less likely; and (3) to date, diagnosis of rejection by cardiac biopsy has appeared to be a satisfactory method of diagnosing and treating pulmonary rejection.(ABSTRACT TRUNCATED AT 250 WORDS)

The results of surgery for active endocarditis of the native aortic valve

Between 1968 and 1981, 40 patients with active endocarditis of the native aortic valve were treated by aortic valve replacement (A.V.R.). There were 8 postoperative deaths (hospital mortality 20%). This included 5 patients who had developed cardiogenic shock prior to surgery. Antibiotic treatment for less than one week and positive cultures on the excised valve had poor prognostic implications but tended to be associated with irreversible haemodynamic failure. Twenty five patients underwent A.V.R. following the onset of severe pulmonary oedema. The hospital mortality in this group was 28% and the 5 year actuarial survival 56% (+/- 11%). Fifteen patients who had developed premature closure of the mitral valve (P.C.M.V.) on M-mode echocardiography but who had no overt signs of cardiac failure underwent A.V.R. with a single death (7% hospital mortality). The 5 year actuarial survival in this group was 87% (+/- 9%). P.C.M.V. is a useful prognostic sign identifying those patients with endocarditis on the native aortic valve likely to benefit from early surgery.

Heart and lung transplantation for pulmonary hypertension

Seventeen patients received combined heart and lung transplants at Stanford University between March 1981 and December 1983. All recipients were suffering from end-stage pulmonary hypertension. Five patients died within the first few postoperative weeks, but the remainder were well between 2 and 35 months after operation. Immunosuppression consisted of cyclosporine with an initial course of rabbit antithymocyte globulin, and azathioprine was given for the first 2 postoperative weeks. Maintenance immunosuppression was achieved with cyclosporine and prednisone. Rejection, as diagnosed by cardiac biopsy, was treated with intravenous methylprednisolone. The functional status of the survivors has been good, and upon discharge from the hospital, all returned to normal activity. Our preliminary experience indicates that cardiopulmonary transplantation represents a realistic therapeutic approach for patients with end-stage pulmonary disease.

Response of pulmonary circulation to oral pirbuterol in chronic airflow obstruction

The effects of the oral beta agonist pirbuterol on pulmonary haemodynamics and gas exchange were studied in nine patients with severe irreversible airflow obstruction and moderate arterial hypoxaemia. After administration of 15 mg pirbuterol pulmonary vascular resistance fell by 19% but cardiac output rose by 24%, so that pulmonary arterial pressure showed no significant change. Systemic arterial oxygen pressure fell by 7%, limiting the rise in oxygen delivery to 21%. All changes were significant at the 2% level. These results show that pirbuterol dilates the pulmonary bed at the cost of a slight worsening of gas exchange, which is compensated by an independent rise in blood flow.

Long term transvenous ventricular pacing in adults with congenital abnormalities of the heart and great arteries

Improved techniques of transvenous pacing have made it possible to use this approach in various congenital cardiac abnormalities. Transvenous active fixation pacing leads were implanted in seven patients aged 15 to 81 years with abnormal venous, atrioventricular, or ventriculoarterial connections with successful ventricular pacing.

Long-term survival following left ventricular aneurysmectomy

Ninety-four patients who underwent left ventricular aneurysmectomy between 1971 and 1980 are reviewed. In thirty-four cases this operation was combined with myocardial revascularisation. The overall hospital mortality was 6% with a five-year survival of 72% +/- 6%. Symptomatology dominated by dyspnoea, a raised left ventricular end diastolic pressure (L.V.E.D.P.) and ventricular dysrhythmias adversely affected survival. Combined myocardial revascularisation did not affect the hospital mortality but was associated with a trend toward improved long-term survival in two groups of patients viz those presenting with predominant angina and those with major stenoses of two or more coronary arteries. Fifteen patients agreed prospectively to post-operative cardiac catheterisation. Despite symptomatic relief no improvement in L.V.E.D.P. or ejection fraction was demonstrated in this group.

Open mitral valvotomy: fourteen years' experience

During the period 1968 to 1980, 222 patients with mitral valve disease in which stenosis was the dominant lesion were admitted under the care of the senior author. All patients presented with severe dyspnoea (NYHA grades 3 or 4). One hundred and fifty seven (71%) patients were treated by open mitral valvotomy. One patient died within 30 days of operation (0.6% hospital mortality) and one suffered a transient cerebrovascular accident. One hundred and twenty four (70%) patients were followed up for one to 14 years (mean 7.5 years). There were seven late deaths. Actuarial curves predict the 90.2% 10 year survival after open mitral valvotomy. Eight patients required mitral valve replacement for restenosis corresponding to 16% at 10 years. The remaining patients are in NYHA grades 1 and 2.

Effect of a timed interval between inhalation of beta-agonist and corticosteroid aerosols on the control of chronic asthma

A randomised double-blind crossover study was undertaken in 25 patients with variable airflow obstruction to assess the benefit of separating the inhalation of beta-agonist aerosols and corticosteroid aerosols by a timed interval of more than five minutes. Twenty-two patients (11 men and 11 women) completed 12 weeks of study; they inhaled 200 micrograms salbutamol followed either immediately or after a timed interval by 100 micrograms beclomethasone dipropionate two to four times daily. Morning and evening peak expiratory flow rates, symptom scores, additional beta-agonist inhaler usage, and subjective responses on a visual-analogue scale were recorded throughout. Results from the two last four-week periods, with and without the interval between drugs, were analysed. No differences were found. It is concluded that the theoretical benefit of delaying corticosteroid inhalation until optimum bronchodilatation has been achieved with a beta-agonist is not demonstrable in outpatient practice.