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A microwave photoconductivity decay (MPCD) technique, which probes conductivity change in wafers in response to either an above-band-gap or below-band-gap laser pulse, has been used to characterize recombination lifetime in high-purity 4H-SiC substrates produced with three different anneal processes. The above-band-gap (266 nm) decay times vary from ∼10 ns to tens of microseconds in the 4H-SiC substrates depending on the wafer growth parameters. Wafers produced using the three processes A (as-grown), B (annealed at 2000 °C), and C (annealed at 2600 °C) have decay times of 10–20 ns, 50–500 ns, and tens of microseconds, respectively. The differences in decay times are attributed to low, medium, and high densities of recombination centers in process C, B, and A wafers, respectively. The MPCD results correlate with other characterization results such as deep level transient spectroscopy, which also showed that the 2600 °C anneal process significantly reduces defect densities, resulting in the enhanced recombination lifetimes. Modeling and one-dimensional simulations indicate a trapping center closer to the conduction band results in a longer MPCD decay transient, but such a trapping based model for the enhanced lifetimes is not compatible with the wide range of experimental characterization results described in this work, which indicate an annealing out of recombination centers at 2600 °C. [ABSTRACT FROM AUTHOR]

We present results of a thermal anneal process that increases the minority carrier lifetime in SiC substrates to in excess of 3 μs, compared to the starting as-grown substrates with lifetimes typically in the <10 ns range. Measurement of lifetimes was conducted using microwave-photoconductive decay. Electron beam induced current measurements exhibited minority carrier diffusion lengths of up to 65 μm, confirming the enhanced carrier lifetime of the annealed substrate material. Additionally, positron annihilation spectroscopy and deep level transient spectroscopic (DLTS) analysis of samples subjected to this anneal process indicated that a significant reduction of deep level defects, particularly Z1/Z2, may account for the significantly enhanced lifetimes. The enhanced lifetime is coincident with a transformation of the original as-grown crystal into a strained or disordered lattice configuration as a result of the high temperature anneal process. The operational performance of p-i-n diodes employing drift layers fabricated from the annealed high-lifetime substrates confirmed conductivity modulation in the diodes consistent with ambipolar carrier lifetimes in the microsecond range. [ABSTRACT FROM AUTHOR]

A radio-frequency photoreflectance technique, which senses changes in sample conductivity as carriers recombine following excitation by a laser pulse, has been used to measure the recombination parameters in 0.55-eV InGaAsSb lattice matched to GaSb. Doubly capped lifetime structures with variable active layer thicknesses are used to extract the surface recombination velocity, while an analysis of the samples with different doping concentrations is used to obtain Auger (C) and radiative (B) recombination parameters. Parameter extraction for the samples evaluated gives C=(1±0.4)×10-28 cm6/s and B=(3±1.5)×10-11 cm3/s for 0.55-eV InGaAsSb lattice matched to GaSb. The Auger and radiative recombination coefficients obtained from high-level injection decay times in low doping concentration samples show very good agreement with the values obtained from low-level injection conditions. [ABSTRACT FROM AUTHOR]

The key material and device parameters governing the electrical performance of high voltage 4H-SiCPiN diodes have been investigated using experimental results and numerical simulations. Reverse recovery characteristics show an increase in both carrier lifetime and anode injection efficiency at elevated temperature. Open circuit voltage decay measurements are used to estimate carrier lifetimes (τ≈0.6μs at T=25°C increasing to τ≈2μs at T=225°C) that are comparable to values measured on starting material prior to fabrication using micro-wave photoconductivity decay techniques. [ABSTRACT FROM AUTHOR]

Splenosis, the autotransplantation of splenic tissue, is most commonly seen after traumatic splenic rupture and splenectomy. It also can occur during embryonic development. Intraperitoneal, intrathoracic, and retroperitoneal sites have been reported. Although the presence of the splenic tissue often is asymptomatic and an incidental finding, it may present with pain or be confused with various pathologies including neoplasia. Because most pediatric splenectomies are performed for hemolytic disorders, parenchymal disruption must be contained to avoid recurrent disease. We present a case in which the devascularized spleen was contained in a bag and fragmented in situ. Splenosis developed in the retrieval port site after laparoscopic splenectomy and cholecystectomy. Port-site splenosis needs to be considered in the differential diagnosis of port-site pain and a palpable nodule postsplenectomy. [ABSTRACT FROM AUTHOR]

Objective: This is a retrospective study of the role of postoperative epidural analgesia in major spinal surgical procedures. With the number and complexity of the procedures performed on the spine ever-increasing, this method of analgesia is becoming more important., Methods: Results of 74 consecutive cases of major spinal surgeries between January 2000 and January 2001 at the Spine Division, Amritha Institute of Medical Sciences and Research Centre, Kochi, India, were studied. 32 cases were posterior procedures and the other 42 were anterior procedures of the thoracic and lumbar regions. The use of various combinations of local anaesthetic and opioid to control postoperative pain after spinal surgery were analysed., Results: 36 (49%) of 74 patients did not require any parenteral supplements. Of the remaining 38 patients who required supplementary parenteral analgesia in the first 48 hours, 25 (34%) received a single dose and 13 (18%) required more than one dose. The number of patients requiring parenteral analgesia immediately after operation were 11; between 2 and 6 hours were 12; and between 6 and 24 hours were 11. Of the 74 patients, 67 had a sound sleep after epidural administration. There were 2 cases of respiratory depression and 2 of transient hypotension., Conclusion: Most epidural analgesic regimens significantly reduced postoperative pain, and the requirement for supplementary parenteral analgesics was minimal. Adverse effects were rare, yet we recommend that patients treated with this protocol be managed in high-dependency units.

Background: Various agents have been implicated in causing tissue necrosis after intravenous infusions have extravasated. These include solutions of calcium, potassium, bicarbonate, hypertonic dextrose, cytotoxic drugs and antibiotics. Views on management of these injuries differ, and range from a non-operative conservative approach to early debridement and grafting., Methods: A retrospective review was undertaken of the hospital files of patients with extravasation injuries seen in three Australian hospitals. Nine patients were identified, and their management and long-term follow up are reported., Results: Age ranged from 17 days to 60 years. Two patients received their injuries from solutions containing isotonic dextrose/saline. The other seven patients received injuries from a variety of solutions including calcium gluconate (n = 1), parenteral nutrition (n = 1), sodium bicarbonate (n = 1), immunoglobulin (n = 1), gentamicin and penicillin (n = 1), flucloxacillin (n = 1), and the chemotherapeutic agents epirubicin and cyclophosphamide (n = 1). The sites involved included the dorsum of the right foot (n = 3), the dorsum of the left foot (n = 3), the right groin (n = 1), the right hand (n = 1) and the left hand (n = 1). Four patients were managed by delayed debridement and split skin grafting, while five were treated non-operatively. Prolonged scar management was necessary in seven of the nine patients. Final results were satisfactory in all patients who received skin grafting and in all patients who were managed conservatively., Conclusions: Management of extravasation injuries should be conservative if possible. Delayed debridement and split skin grafting is required if the area of skin loss is extensive. Scar management remains a problem. Prevention of these injuries with the education of both medical and nursing staff remains the ultimate aim.