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Heterostructure low barrier diodes (HLBD) based on lattice-matched AlGaInAs triangular barrier have been designed, fabricated, and characterized for zero-bias millimeter-wave and submillimeter-wave detection. Detectors with different barrier height and various active areas have been measured in order to determine the best structure for low-level radiometric detection. Unmatched responsivity of 1500-2000 V/W have been measured around 100 GHz with a video resistance of 400 to 800 Ω. Thanks to these low-impedances high-matched responsivity of 6000 and 5200 V/W have been demonstrated around 90 and 180 GHz, respectively, with a bandwidth of 25 GHz. Avery low noise equivalent power of about 0.6 and 0.7 pW/,/Hz have been deduced at 90 and 180 GHz, respectively. We show also that the dynamic range of these detectors is more than six decades. This performance makes the HLBD an interesting device for low-level sub-THz detection applications.

OBJECTIVE: To assess the sensitivity and specificity of emergency physicians in detecting anxiety and depression in patients requiring admission to the emergency department (ED) observation care unit for complementary investigations/treatment. METHODS: 339 consecutive patients admitted to the emergency observation care unit of 14 EDs were interviewed with standardised questionnaires. The characteristics of the patients, EDs and attending ED physicians were collected. Patients' anxiety and depression were identified using the Hospital Anxiety and Depression Scale (HADS), a self-administered questionnaire. ED physicians were blind to the HADS score and were asked to declare whether they perceived anxiety and depression in each patient. The judgement of ED physicians and the HADS score were compared using sensitivity, specificity, positive and negative likelihood ratios. RESULTS: The HADS questionnaire was correctly completed by 310 patients who comprised the study population. HADS detected symptoms of anxiety in 148 patients (47%) and symptoms of depression in 70 patients (23%). ED physicians determined the presence or absence of anxiety with a sensitivity of 48% (95% CI 40% to 56%) and a specificity of 69% (95% CI 61% to 75%). Positive and negative likelihood ratios were 1.54 (95% CI 1.16 to 2.06) and 0.75 (95% CI 1.28 to 3.28) for anxiety. They detected the presence or absence of depression with a sensitivity of 39% (95% CI 28% to 51%) and a specificity of 78% (95% CI 72% to 83%). Positive and negative likelihood ratios were 1.75 (95% CI 1.20 to 2.56) and 0.78 (95% CI 1.26 to 3.87) for depression. CONCLUSION: Although patients presenting to the ED often experience anxiety and depression, these symptoms are poorly detected by ED physicians.

Critically ill patients often require emergency intubation. The use of etomidate as the sedative agent in this context has been challenged because it might cause a reversible adrenal insufficiency, potentially associated with increased in-hospital morbidity. We compared early and 28-day morbidity after a single dose of etomidate or ketamine used for emergency endotracheal intubation of critically ill patients.

Impaired oxygenation due to microcirculatory changes within the cerebral parenchyma may contribute to deterioration of intellectual function in vascular senile dementia (Hachinski score ≥ 7). The action of naftidrofuryl, used for treating elderly patients with senile dementia, was evaluated objectively in two groups of patients given naftidrofuryl either as a single intravenous dose or by chronic oral administration for three months. Their cerebral, microcirculatory flow rate was assessed before and after treatment by in vivo cineangioscintigraphy following an i.v. bolus of Tc-99m labelled erythrocytes. The deformability of erythrocytes from orally treated patients was also measured using an in vitro cellular transit time analyser (CTA) technique. A further experiment assessed the rheology of a rigid sub-population of erythrocytes in pathological samples when exposed to naftidrofuryl at concentrations appropriate to clinical use. Cerebral flow rates increased by about 20% and 30% after intravenous or chronic oral naftidrofuryl, respectively and these differences were statistically significant. In 10 orally treated patients, mean transit times by CTA decreased from 3.12 ms (day 0) to 2.70 ms (day 87 of treatment) (p<0.01). In the presence of naftidrofuryl, the proportion of the least deformable erythrocytes in pathological samples decreased by at least 50%. Clinical effects of naftidrofuryl on the cerebral microcirculation were not restricted to acute exposure. Naftidrofuryl may enhance the deformability of individual erythrocytes.

Tissue hypoxaemia can be evaluated by the noninvasive method of transcutaneous oxygen tension (tcpO2) measurement in patients with peripheral arterial occlusive disease (PAOD). The effects of naftidrofuryl (Praxilene®) on exercise-induced tissue ischaemia was objectively assessed by continuously measuring the tcpO2in 30 patients during three treadmill tests over a 3-month period in a randomized double-blind, placebo controlled, parallel group study. To be included in the study, the tcpO2and total walking distance had to be stable during the washout period (D-15-D0). The area under the tcpO2curves was scanned and automatically calculated after identification of baseline and the end of the treadmill test. The treadmill test on D30 and D90 was terminated at a similar walking distance to that obtained on D0. On D0 both groups were comparable (p = 0.22). The area under the curve (AUC) reduced significantly in the naftidrofuryl group between D0 and D30 (p, 0.001) and D0 and D90 (p, 0.001). However, no significant tcpO2AUC reduction was found in the placebo group (D0-D30, p = 0.58; D0-D90, p = 0.50). This was confirmed by calculation of the percentage of patients whose percentage change in the AUC on D90 was higher than the upper limit of the 90% confidence interval, calculated from the percentage change over the washout period. Of the 15 patients receiving naftidrofuryl, 66.6% exceeded this upper limit, compared with only 7% of patients receiving placebo (p = 0.0017). This study shows that naftidrofuryl has a protective effect on exercise-induced tissue ischaemia as measured by the tcpO2AUC in PAOD stage II patients.

The letter provides a study and an explanation of the starting phenomenon in an FET oscillator. It has been shown that the behaviour of the negative resistance with the amplitude of the RF signal leads to a lag effect in the response of the oscillator. This effect is due to the nonlinearity of the transconductance of the active device. Simulations have been made using accurate large signal models included in a time domain analysis software package.

In the letter experimental results are presented which show that distributed amplifiers can be used for power applications. These results are verified by comparing an analytic model predicted using SPICE 2 simulation with measurements between 0.3 and 12 GHz. It appears that a very broad band can be achieved and that the distributed amplifiers keep their self matching properties even under large-signal operation. Distributed-amplifier characteristics, under small-signal operations, are now well known.1−4 However, recent improvements in GaAs FET technology have created new prospects in large-signal and high-frequency conditions. To our knowledge, although some experimental results have been published3, no theoretical study has been carried out for large-signal conditions. The letter provides such a study.

Ultra-wideband monolithic HEMT amplifiers have been designed and fabricated using MOCVD heterostructures. It has been shown that by taking into account the multiple reflections at the gate load, a very flat gain can be achieved and the sensitivity of the amplifier to the load resistances can be considerably reduced. By suitable design, the frequency bandwidth of the amplifier can be increased above the cutoff frequency of the active devices. In particular, it is shown that the cascode configuration reduces the coupling between gate and drain lines and increases the gain-bandwidth product, but can generate oscillations. To verify our design approach, we present the results obtained on 2–42 GHz monolithic amplifiers using 0.5 μm HEMTs.

In the letter experimental results are presented which show that a continuous active gate travelling-wave transistor (TWT) can be used for medium power applications in a wide bandwidth. To reduce the gate resistance, a T-gate configuration has been chosen. This allows us to extend the frequency bandwidth of such a device. Simulations have been performed using small-and large-signal models taking in addition the parasitic capacitances into account A distributed Schottky diode has been used to adjust the phase synchronisation and therefore to achieve fllat gain.