100 kW DC biased, all semiconductor switch using Si P-I-N diodesand AlGaAs 2-D laser arrays

A two-dimensional laser array, delivering a peak power of 1 kW with an overall efficiency of 33%, was used to activate silicon p-i-n diodes. A single device, activated by a 1 kW laser, produced a holding voltage of 1000 V and conducted 56 A. When two similar p-i-n diodes were connected in parallel and activated by two 1 kW AlGaAs laser arrays, a holding voltage of 1000 V and conduction of 100 A were obtained     

Triggering GaAs lock-on switches with laser diode arrays

Progress toward the triggering of high-power photoconductive semiconductor switches (PCSSs) with laser diode arrays, is reported. An 850-W optical pulse from a laser diode array was used to trigger a 1.5-cm-long switch that delivered 8.5 MW to a 38.3-Ω load. Using 166-W arrays, it was possible to trigger a 2.5-mm-long switch delivering 1.2 MW with 600-ps rise-times at pulse repetition frequencies of 1 kHz. These 2.5-mm-long switches survived 10⁵ pulses at 1.0 MW levels. In single-pulse operation, up to 600 A was switched with laser diode arrays. The goal is to switch up to 5 kA in a single-shot mode and up to 100 MW repetitively at up to 10 kHz. At electric fields below 3 kV/cm GaAs switches are activated by creation of one electron-hole pair per photon. This linear mode demands high laser power and, after the light pulse, the carriers recombine in nanoseconds. At higher electric fields GaAs acts as a light-activated Zener diode. The laser light generates carriers as before, but the field induces gain such that the amount of light required to trigger the switch is reduced by a factor of up to 500. The gain continues until the field across the sample drops to a material-dependent lock-on field. The gain in the switch allows for the use of laser diodes     

An evaluation of introgression of Atlantic coast striped bass mitochondrial DNA in a Gulf of Mexico population using formalin-preserved museum collections

Striped bass Morone saxatilis populations in drainages along the Gulf of Mexico coast (Gulf) were depleted in the 1950s and 1960s, probably because of anthropogenic influences. It is believed that only the Apalachicola-Chattahoochee-Flint (A-C-F) river system continually supported a naturally reproducing population of Gulf lineage. Striped bass juveniles of Atlantic coast (Atlantic) ancestry were introduced to restore population abundances in the A-C-F from the late 1960s to the mid 1970s and in many other Gulf rivers from the 1960s to the present. We previously identified mtDNA polymorphisms that were unique to approximately 60% of striped bass from the A-C-F and which confirmed the continued successful natural reproduction of striped bass of Gulf maternal ancestry within the system. However, the genetic relatedness of the extant A-C-F population to 'pure' Gulf striped bass was not addressed. In this study, we determined the frequency of a diagnostic mtDNA XbaI polymorphism in samples of 'pure' Gulf striped bass that were collected from the A-C-F prior to the introduction of Atlantic fish, that were obtained from museum collections, and that were originally preserved in formalin. PCR primers were developed that allowed for amplification of a 191-bp mtDNA fragment that contained the diagnostic XbaI restriction site. Using RFLP and direct sequence analyses of the PCR amplicons, we found no significant differences in mtDNA XbaI genotype frequencies between the archived samples and extant A-C-F samples collected over a 15-year period. This indicates that significant maternally mediated introgression of Atlantic mtDNA genomes into the A-C-F gene pool has not occurred. Additionally, we found no evidence of the unique Gulf mtDNA genotype in striped bass from extant populations in Texas, Louisiana and the Mississippi River. These results highlight the importance of the A-C-F as a repository of striped bass to restore extirpated Gulf populations and the potential use of museum collections in retrospective population studies.     

Technical new feature

A continuous process for the commercial production of isopropenyl stearate (IPS) from triple pressed stearic acid and a stabilized form of propyne has been developed. Cost estimates, including capital costs, operating costs, and profitability, for commercial scale plant production which show the process to be economically feasible are presented. This potentially profitable process offers the advantages of reliable raw material sources, minimal external thermal requirements, and usable process waste streams. For a plant producing 5 million pounds of IPS per year, the selling price range is 80 to 107 cents/lb IPS, corresponding to a raw material cost range of 27 to 54 cents/lb of IPS. For a 20 million pound per year plant, the selling price range is 58 to 85 cents/lb IPS. The selling prices include a 20% annual return on fixed capital investment. Fixed capital requirement ranges from 2.7 to 10.9 million dollars (3rd quarter, 1975) for plants ranging in size from 5 to 50 million pounds of IPS per year, respectively.     

Parallel interval-based reasoning in medical knowledge-based system Clinaid

The paper continues a series of papers and a monograph [33], where we have described the conceptual structures as well as the basic architecture of a knowledge-based systemCunaid.     

Optically achieved p-i-n diode switch utilizing a two-dimensionallaser array at 808 nm as an optical source

The design, fabrication, and application of optically activated switches is described. A 0.25-mm-thick Si p-i-n diode, 3.0 mm in diameter, was tested using an 808-nm 2-D diode laser array (measuring about 2 mm×5 mm) as an optical source. Preliminary testing of a 0.25-mm-thick device has demonstrated a holding voltage of 1000 V and a conduction of 10 A upon activation with 200 W of optical power (the pulse width was 10 μs). The same device, while being pulse biased to 2.0 kV, has demonstrated 20-A pulses (100-ns pulse width) with less than 10-ns risetime. The laser peak power was 500 W     

Laser-activated p-i-n diode switch for RF application

Results obtained utilizing an optically activated RF switch in the 2-30-MHz range demonstrate the advantages in optically controlled high-power switches from HF to millimeter wave. Testing of a 0.25-mm-thick p-i-n device activated with 116-W peak optical power from a two-dimensional laser array in a 50-Ω system shows isolation between 20.8 and 49 dB, and an average insertion loss of 0.38 dB when measured between 2.5 and 30 MHz     

Treatment of acquired von Willebrand syndrome in patients with monoclonal gammopathy of uncertain significance: comparison of three different therapeutic approaches

Patients with monoclonal gammopathies of uncertain significance (MGUS) may develop an acquired bleeding disorder similar to congenital von Willebrand disease, called acquired von Willebrand syndrome (AvWS). In these patients, measures to improve hemostasis are required to prevent or treat bleeding episodes. We diagnosed 10 patients with MGUS and AvWS: 8 had IgGkappa (3) or lambda (5) MGUS and 2 IgM-kappa MGUS. Three therapeutic approaches were compared in them: (1) desmopressin (DDAVP), (2) factor VIII/von Willebrand factor (FVIII/vWF) concentrate, and (3) high-dose (1 g/kg/d for 2 days) intravenous Ig (IVIg). In patients with IgG-MGUS, DDAVP and FVIII/vWF concentrate increased factor VIII and von Willebrand factor in plasma, but only transiently. IVIg determined a more sustained improvement of the laboratory abnormalities and prevented bleeding during surgery (short-term therapy). In addition to the standard 2-day infusion protocol, a long-term IVIg therapy was performed in 2 patients with IgG-MGUS: repeated (every 21 days) single infusions of IVIg did improve laboratory abnormalities and stopped chronic gastrointestinal bleeding. On the other hand, IVIg failed to correct laboratories abnormalities in patients with IgM-MGUS. These comparative data obtained in a relative large and homogeneous group of patients with AvWS and MGUS confirm that DDAVP and FVIII/vWF concentrates improve the bleeding time (BT) and FVIII/vWF measurements only transiently, whereas IVIg provides a sustained treatment of AvWS associated with IgG-MGUS, but not with IgM-MGUS.     

A boundary element technique applied to the analysis of waveguideswith periodic surface corrugations

A boundary integral formulation is used to characterize Floquet-Bloch modes of two-dimensional multilayered periodic waveguides. A technique for matching fields inside the grating to those external to the grating region is described. Although a simple four-layer structure is used to illustrate the method, an extension to multilayer waveguide structures is straightforward. The mathematical formalism has been simplified, allowing for more efficient computations using fast Fourier transform algorithms     

Method of fabricating high-Q silicon varactor diodes

A new processing technique has been developed for the fabrication of high-Q and high-voltage varactor diodes. The process utilises ion implantation and laser annealing for heavily-doped p++ and n++ layers and epitaxial growth for low impurity concentrations. The technique provides good yield and repeatability, and it has allowed fabrication of varactor diodes which have breakdown voltages of 120 V and a Q as high as 600 at ?8 V bias and 50 MHz frequency.