Minority electron transport anisotropy in p-type AlxGa1-xN/GaN superlattices

The minority electron diffusion length, L, in Mg-doped molecular beam epitaxy (MBE) grown p-type Al_xGa_1-xN/GaN superlattices with aluminum content x=0.1 and 0.2 was measured perpendicular and parallel to the superlattice planes by the electron beam induced current technique. A large anisotropy in the transport properties was observed with the effect varying from 1:3 to 1:6. We attribute an experimentally observed diffusion length anisotropy to minority electron scattering during transport across the potential barriers of the superlattice. Reference p-GaN samples were also investigated, and the diffusion length was observed to be isotropic in both MOCVD (L=0.5 μm) and MBE (L=0.27 μm) grown samples     

Cognitive MANET Design for Mission-Critical Networks

For mobile ad hoc networks used in network-centric operations, there is a growing need for a systematic methodology for analyzing/predicting the performance of the network over the mission duration. With the advance in cognitive networking as a possible means of exploiting unused spectrum, there is now a growing need to study how to design a cognitive network using an automated methodology. In this article we study the concepts and challenges for automatic design/ reconfiguration of cognitive MANETs. We describe the design objectives, imposed constraints, and involved parameters in MANETs. We describe how cognitive techniques can be employed to exploit the unused spectrum in military architectures. We then discuss the challenges facing the design/reconfiguration of a cognitive network and their implications at different network layers. We also describe possible implementation options for designing MANETs that employ cognitive features at all layers.     

Effects of dietary molybdenum on the metabolism of copper and molybdenum in young cattle

On separate occasions young cattle were injected intrarumenally with 99Mo or 64Cu or intravenously with 64Cu. The metabolism of the isotopes were compared to evaluate metabolic changes associated with molybdenum-induced copper deficiency. Molybdenum-99 metabolism was the same in both controls and experimental subjects. Marked differences in plasma kinetics were observed following intrarumenal 64Cu injection, with experimental animals displaying earlier plasma appearance and maintaining higher plasma levels than did controls. Similarly, higher plasma levels, more rapid plasma reappearance and greater fecal excretion were observed following intravenous injection of 64Cu in the experimental animals than in controls. A mechanism involving abnormal ceruloplasmin synthesis associated with the molybdenum-copper interaction is proposed.     

Pyloric stenosis: a 13-year experience in operative management

Infantile hypertrophic pyloric stenosis is best treated surgically, after an appropriate period of rehydration and resuscitation. Our experience with this entity has resulted in the performance of fewer contrast studies to establish the diagnosis as well as the use of an operative technique which can be safely applied to the teaching environment.     

Nitrogenase activity and respiration of cultures of Rhizobium spp. with special reference to concentrations of dissolved oxygen

Studies of nitrogenase in cultures of the cowpea rhizobia (Rhizobium spp.) strains 32H1 and CB756 are reported. Preliminary experiments established that, even when agar cultures were grown in air, suspensions of bacteria prepared anaerobically from them were most active at low concentrations of free dissolved O2. Consequently, assays for activity used low concentrations of O2, stabilized by adding the nodule pigment leghaemoglobin. In continuous, glutamine-limited cultures of 32H1, nitrogenase activity appeared only when the concentration of dissolved O2 in the cultures approached 1 muM. Lowering the glutamine concentration in the medium supplied to the culture from 2 to 1 mM halved the cell yield and nitrogenase activity was also diminished. Omitting succinate from the medium caused the concentration of dissolved O2 to rise and nitrogenase activity was lost. Upon restoration of the succinate supply, the O2 concentration immediately fell and nitrogenase was restored. The activity doubled in about 8 h, whereas the doubling time of this culture was 14 h. Sonic extracts of 32H1 cells from continuous cultures with active nitrogenase contained components reacting with antiserum against nitrogenase Mo-Fe protein from soybean bacteroids. Continuous cultures grown at higher O2 concentration, with only a trace of active nitrogenase, contained less of these antigens and they were not detected in highly aerobic cultures. Nitrogenase activity of a continuous culture was repressed by NH+4; the apparent half-life was about 90 min. Cells of 32H1 from a continuous culture growing at between 30 and 100 muM dissolved O2 possessed a protective mechanism which permitted respiration to increase following exposure to a rapid increase in O2 concentration from low levels (O2 shock). This effect disappeared as the O2 concentration for growth was reduced towards 1 muM.     

Haemorrhagic syndrome after massive transfusion of blood for traumatic liver rupture: disseminated intravascular coagulation? (Author''s transl)

The rate of control of thyrotoxicosis during the first 2 weeks of treatment was documented in 63 patients. Twenty-three patients received carbimazole 40 mg plus lithium carbonate 750 mg daily and a comparable group of 20 patients were given carbimazole 40 mg plus potassium iodide 120 mg daily. In the lithium treated patients the mean percentage fall of serum T4 after 2 weeks treatment was 49% and the fall in serum T3 57%. The results were similar in the iodide treated patients; the mean falls in serum T4 and T3 being 47% and 64%, respectively. Serum lithium values varied between 0.1-1.25 mEq./l; lithium side effects were minor. In a companion study 20 patients were treated with carbimazole alone. The responses in this group were less impressive; the mean falls in serum T4 and T3 at 2 weeks being 18% and 36%, respectively. It is concluded that lithium is a safe adjunct to conventional antithyroid drug therapy in the initial treatment of acute thyrotoxicosis.     

Consumer-professional collaboration for evaluation in neighborhood mental health programs

Neighborhood mental health programs are challenged with the scientific and fiscal necessity of evaluating their services. Since most such programs are joint endeavors of neighborhood residents (usually a consumer board) and nonneighborhood professionals, such evaluative efforts require the sanction and collaboration of both groups to be maximally effective. However, the authors point out that collaboration is often strained by lack of trust and conflicts of interest. Study design may fail to consider neighborhood values, with the result that the provision of services is impeded, consumers are frightened or coerced, the role of paraprofessionals is threatened, and the consumer board's responsibilities to the neighborhood are ignored. The authors discuss those four issues and suggest ways of resolving them.     

Left ventricular function by echocardiography in children with fixed aortic stenosis

Left ventricular function was evaluated echocardiographically within 24 hours of cardiac catheterization in 45 children with fixed aortic stenosis. Left ventricular systolic time intervals, mean velocity of circumferential fiber shortening, left ventricular end-diastolic volume and shortening fraction were evaluated. Some patients with severe aortic stenosis had a shortened preejection period, prolonged ejection time and increased mean velocity of circumferential fiber shortening in comparison with normal subjects, but these findings were not consistent within the group with severe aortic stenosis or apparent in patients with mild or moderate aortic stenosis. Left ventricular end-diastolic volume was smaller in children with severe obstruction than in normal children. Evaluation of the shortening fraction provided good separation of patients with significant obstruction from those with mild disease. Further, there was a linear correlation between the shortening fraction and the left ventricular-aortic gradient demonstrated at cardiac catheterization. This correlation was also of use in evaluating the response of patients to surgical relief of obstruction. Pre- and postoperative echocardiographic evaluation of the shortening fraction appears to provide a readily available noninvasive method of assessing the course and severity of obstruction in fixed aortic stenosis in children.     

Extratemporal facial nerve injury

Isolated traumatic facial nerve injury, frequently seen in wartime combat, may also be encountered among civilians. The clinical picture occurring as a result of such injury may be confusing because partial, or incomplete, damage to the peripheral nerve may mimic impairment of the central facial motor mechanism. In treating the patient with facial injury, life-threatening aspects of the injury must be assessed and stabilized first. Then, attention may be focused on the injured facial nerve, for which prompt surgical repair is the treatment of choice. Prior to surgery, the assessment of taste and hearing, as well as mastoid and skull x-ray films and electrodiagnostic tests are helpful in localizing the facial nerve injury.