Superradiant emission in a high-mobility two-dimensional electron gas.

We use terahertz time-domain spectroscopy to study gallium arsenide two-dimensional electron gas samples in external magnetic field. We measure cyclotron decay as a function of temperature from 0.4 to10Kand a quantum confinement dependence of the cyclotron decay time belowT0=1.2K. In the wider quantum well, we observe a dramatic enhancement in the decay time due to the reduction in dephasing and the concomitant enhancement of superradiant decay in these systems. We show that the dephasing time in 2DEG's depends on both the scatteringrateand also on the distribution of scattering angles.

Circuit techniques for wireless brain interfaces.

Efficient, miniaturized wireless recording is critical for both existing and emerging health-monitoring applications. One important example of this is in the brain interface community, where new technologies allow improved observation and understanding of brain functions. This, in turn, drives the need for ever smaller, lower power, and higher performance circuitry for chronic recording. This paper describes circuit and system techniques for low power wireless brain interfaces. Active and passive architectures are described and compared, and measured in-vivo data from both are presented.

Synthesis and biological evaluation of bupropion analogues as potential pharmacotherapies for cocaine addiction.

A series of bupropion (1a) analogues (1b-1ff) were synthesized, and their in vitro and in vivo pharmacological properties evaluated with the goal of developing a 1a analogue that had better properties for treating addictions. Their in vitro pharmacological properties were examined by [(3)H]dopamine ([(3)H]DA), [(3)H]serotonin ([(3)H]5HT), and [(3)H]norepinephrine ([(3)H]NE) uptake inhibition studies, and by binding studies at the dopamine, serotonin, and norepinephrine transporters using [(125)I]RTI-55 in cloned transporters. Several analogues showed increased [(3)H]DA uptake inhibition with reduced or little change in [(3)H]5HT and [(3)H]NE uptake inhibition relative to bupropion. Thirty-five analogues were evaluated in a 1 h locomotor activity observation test and 32 in an 8 h locomotor activity observation test and compared to the locomotor activity of cocaine. Twenty-four analogues were evaluated for generalization to cocaine drug discrimination after i.p. administration, and twelve analogues were tested in a time course cocaine discrimination study using oral administration. 2-(N-Cyclopropylamino)-3-chloropropiophenone (1x) had the most favorable in vitro efficacy and in vivo pharmacological profile for an indirect dopamine agonist pharmacotherapy for treating cocaine, methamphetamine, nicotine, and other drugs of abuse addiction.

NeuralWISP: A Wirelessly Powered Neural Interface With 1-m Range.

We present the NeuralWISP, a wireless neural interface operating from far-field radio-frequency RF energy. The NeuralWISP is compatible with commercial RF identification readers and operates at a range up to 1 m. It includes a custom low-noise, low-power amplifier integrated circuit for processing the neural signal and an analog spike detection circuit for reducing digital computational requirements and communications bandwidth. Our system monitors the neural signal and periodically transmits the spike density in a user-programmable time window. The entire system draws an average 20 muA from the harvested 1.8-V supply.

Replication molds having nanometer-scale shape control fabricated by means of oxidation and etching.

A means of accurate control of the curvature radius of molds that are used in nanostructure replication techniques is presented. The local non-uniform growth of SiO2 at regions with high curvature is used to fabricate molds with a curvature radius ranging anywhere between 10 and 250 nm. The mold radius is predicted by numerical simulation as a function of oxidation temperature and time and confirmed by a series of oxidation and etching experiments. The silicon, silicon dioxide, and polymer nanostructures are analyzed by scanning electron microscopy and compared with the theory. Replication into photo-plastic polymer from various sharp and round molds is performed, and their properties are discussed. Our results are useful for designing nanostructures in the area of soft lithography and nanoprobe engineering.

Projection of the magnocellular red nucleus to the region of the accessory abducens nucleus in the rabbit.

The projection of the magnocellular red nucleus (RNm) to the region of the accessory abducens nucleus (AABD) was traced in rabbit using the bidirectional tracer wheat germ agglutinin-horseradish peroxidase (WGA-HRP). In one set of animals, recordings of antidromic responses from RNm neurons elicited by electrical stimulation of the rubrospinal tract were used to localize injections of WGA-HRP for orthograde labeling of RNm terminals. In a different set of animals, horseradish peroxidase was injected into the retractor bulbi muscle to retrogradely label motoneurons of the AABD. The positions of RNm fibers and terminals were examined and compared to the locations and distribution of AABD cell bodies and labeled dendrites. Analyses revealed that along the entire rostrocaudal extent of the AABD, RNm efferents terminate primarily lateral to, or in the lateral aspects of, labeled motoneurons. For the rostral AABD, RNm efferents terminate only lateral to the nucleus. Although the terminals are not positioned to contact cell bodies of the AABD, they could overlap with dendrites that extend in the lateral direction. RNm efferents terminate more extensively within the posterior AABD, overlapping within both dendritic and cell body regions of the nucleus. Even in this posterior region, however, RNm efferents were distributed primarily over the lateral half of the nucleus. These data show that RNm can monosynaptically influence the AABD, through primarily its lateral and posterior aspects. Our findings also show that a major target of RNm efferents is the reticular cell population located lateral to the AABD, suggesting that the RNm also may affect AABD motoneuronal output indirectly through its projection to reticular cells.

Pneumatic compression or aspirin prophylaxis against thromboembolism in total hip arthroplasty.

We prospectively studied the use of either aspirin or intermittent pneumatic compression (IPC) as prophylaxis against thromboembolism after 330 consecutive total hip arthroplasties. Duplex ultrasonography of the veins of both lower extremities and ventilation-perfusion lung scans were done preoperatively and 7 to 14 days postoperatively. Eight patients in the IPC group (5%) had asymptomatic deep vein thrombosis; there were no symptomatic thrombi. In the aspirin group, 10 patients (7%) had asymptomatic deep vein thrombosis and two patients (1%) had symptomatic deep vein thrombosis. This difference was not statistically significant. There were no fatal pulmonary emboli in either group. In the IPC group, only one patient had symptomatic pulmonary embolism and 20 patients (22 hips [12%]) had asymptomatic pulmonary embolism. In the aspirin group, two patients (1%) had symptomatic pulmonary embolism and 26 patients (18%) had asymptomatic pulmonary embolism. This difference in asymptomatic pulmonary embolism between the two groups was statistically significant. Both groups had a low incidence of deep vein thrombosis, as shown by Duplex ultrasonography, but IPC was more effective than aspirin in preventing asymptomatic pulmonary embolism after total hip arthroplasty.

Tibial artery injuries.

Twenty-eight consecutive patients with tibial or peroneal artery injury are reported. Of these, eight underwent direct arterial repair, eight received vein graft reconstruction, and the involved artery was ligated in the remainder, with amputation required for various reasons in four. Tibial or peroneal artery injury is a relatively common problem. Successful management requires an aggressive approach to early diagnosis, which in turn requires a high index of suspicion and arteriography. Early appropriate management will prevent the serious complications of ischemia, false aneurysm, arteriovenous fistula, and fascial compartment compression. The reconstruction of injured arteries of the lower leg is usually possible and should be accorded more attention than it has received in the past.

Injury to the popliteal artery.

Popliteal artery injury is a common clinical problem which has been associated with a relatively high rate of limb loss. Proper management of popliteal artery injury, which includes attention to minimizing delay, repair of venous injury, careful technique and appropriate fasciotomy can result in substantial improvement in the rate of limb salvage following popliteal artery injury.

Arterial surgery for arm ischemia. A survey of 136 patients.

A series of 136 patients with upper extremity ischemia requiring operative correction is presented. Causes of the ischemia included trauma, atherosclerosis, embolism, iatrogenic causes, radiation injury, and cervical rib syndrome. Operations included primary repair, various bypass grafts and embolectomy. Illustrative case reports are used to emphasize important points. The subclavian, axillary and brachial arteries have been considered separately. In general, ischemia of the arm caused by a discrete lesion is amenable to surgical correction with an excellent change of success.

Comparative properties of the inclusion body proteins of the nucleopolyhedrosis viruses of Neodiprion sertifer and Lymantria dispar.

A comparison was made on the properties of the inclusion body proteins of two insect viruses: the nucleopolyhedrosis viruses of the European pine sawfly, Neodiprion sertifer, Geoffroy, and the gypsy moth, Lymantria dispar, Linnaeus. The inclusion body proteins were characterized by the following parameters: amino acid composition, polyacrylamide gel electrophoresis in the absence and presence of sodium dodecyl sulfate--mercaptoethanol, isoelectric focusing, and alkaline protease activity. The properties of the inclusion body proteins of the two viruses were similar in many respects, but clear differences were observed. A principal difference was the absence of alkaline protease activity associated with the inclusion body proteins of N. sertifer nucleopolyhedrosis virus.

Early detection of pregnancy-associated serum protein using antiserum to placental antigens.

Antisera against human placental proteins were developed in goats and rabbits, using immunoadjuvants and a prolonged injection schedule. The antisera were absorbed with normal serum proteins and then tested in immunodiffusion against normal and pregnancy sera. Two bands of precipitation due to pregnancy antigens were observed in pregnancy sera as early as 18 days after conception. Detection of these antigens has possibilities for application as an early pregnancy test.