InGaN/GaN/AlGaN-Based Leds and Laser Diodes

InGaN quantum-well-structure blue LEDs were grown on epitaxially laterally overgrown GaN (ELOG) and sapphire substrates. The output power of both LEDs was as high as 6 mW at a current of 20 mA. The LED on sapphire had a considerable amount of leakage current in comparison with that on ELOG. These results indicate that In composition fluctuation is not caused by threading dislocations (TDs), free carriers are captured by radiative recombination centers before they are captured by nonradiative recombination centers in InGaN, and that the dislocations form the leakage current pathway in InGaN. Red LED with an emission peak wavelength of 650 nm was fabricated by increasing the In composition and thickness of InGaN well layer. When the laser diodes (LD) was formed on the GaN layer above the SiO2 mask region, the threshold current density was as low as 3 kAcm−2. When the LD was formed on the window region, the threshold current density was as high as 6 to 9 kAcm−2. There is a possibility that a leakage current due to a large number of TDs caused the high threshold current density on the window region. InGaN multi-quantum-well (MQW) structure LDs grown on the ELOG substrate showed an output power as high as 420 mW under RT-CW operation. The longest lifetime of 9,800 hours at a constant output power of 2 mW was achieved. The InGaN MQW LDs were fabricated on a GaN substrate. The fundamental transverse mode was observed up to an output power of 80 mW.

Postoperative Clostridium difficile infection with PCR ribotype 078 strain identified at necropsy in five Thoroughbred racehorses

Clostridium difficile is an important cause of acute enterocolitis in horses. We describe five cases of C difficile infection occurring postoperatively in Thoroughbred racehorses. Following diarrhoea or colic accompanied by a marked increase in packed cell volume (to ≥60 per cent) and leucopenia (≤4000 cells/μl) within two to four days after surgery in all five horses, four of them died or were euthanased because of colitis or severe diarrhoea. In these four horses, necrotising entero-typhlo-colitis was revealed by postmortem examination, and C difficile was recovered from the contents of the small and/or large intestine. The remaining horse was euthanased because of marked decline in general condition and the presence of a lung abscess, from which C difficile was isolated. The horse had had severe postoperative diarrhoea before the onset of respiratory disorder; laboratory tests for C difficile were not performed on the faeces. All C difficile isolates were toxin-A-positive, toxin-B-positive and actin-specific ADP-ribosyltransferase (CDT)-positive. The isolates were indistinguishable by pulsed field gel electrophoresis analysis, PCR ribotyping, and slpA sequence typing, and the slpA sequences and PCR ribotype patterns were identical to those of known PCR type 078. This case sequence might have been healthcare-associated infection, although there was about a four-month interval between each disease onset.

Molecular characterization of high-level-cholera-toxin-producing El Tor variant Vibrio cholerae strains in the Zanzibar Archipelago of Tanzania

Analysis of 1,180 diarrheal stool samples in Zanzibar detected 247 Vibrio cholerae O1, Ogawa strains in 2009. Phenotypic traits and PCR-based detection of rstR, rtxC, and tcpA alleles showed that they belonged to the El Tor biotype. Genetic analysis of ctxB of these strains revealed that they were classical type, and production of classical cholera toxin B (CTB) was confirmed by Western blotting. These strains produced more CT than the prototype El Tor and formed a separate cluster by pulsed-field gel electrophoresis (PFGE) analysis.

Early release of neutrophil chemotactic factor from isolated rat heart subjected to regional ischaemia followed by reperfusion

OBJECTIVE

The study was designed to demonstrate the time course of neutrophil chemotactic factor (NCF) release from blood-free isolated rat hearts and to clarify the characteristics of NCF in order to facilitate its identification.

METHODS

Coronary effluents were collected every minute from Langendorff perfused rat hearts during ligation of the left coronary artery for 40 min and reperfusion for 60 min. The neutrophil chemotactic activity in the effluents was assayed using modified Boyden's chambers with rat neutrophils isolated from peripheral blood as the indicator cells.

RESULTS

The NCF release started at 10 min of coronary artery occlusion. During the reperfusion period, NCF release peaked at 5 min (230% of preischaemic value). To clarify the characteristics of NCF, the changes in chemotactic activity were examined using various inhibitors and inactivators of possible NCF candidates (LTB4, PAF, 5-lipoxygenase, and thromboxane synthase). The heat stability of NCF was also examined to exclude heat labile molecules such as adenosine or complements appearing as NCF. Among the various substances examined, only PAF antagonists (CV-6209 and TCV-309 at concentrations of 10(-6) M and 10(-5) M respectively) abolished the chemotactic activity. However direct measurement of PAF in the effluents was unsuccessful.

CONCLUSION

NCF is released from the heart early after ischaemic insult, with the highest peak occurring at 5 min of reperfusion. PAF related substances might be the primary NCF in the effluent but this remains to be determined.

[Spike discharge detected by intra-arterial electroencephalography from intra-arterial guide wire in temporal lobe epilepsy]

The implantation of electrodes for intracranial electroencephalography (EEG) recording as presurgical evaluation of patients with intractable epilepsy is at present most important for planning epilepsy surgery. This method is most effective in temporal lobe epilepsy. We carried out intracranial EEG by means of insulated micro guide wire for endovascular surgery in two temporal lobe epilepsy cases, and spike discharges could be detected in lesional medial temporal lobe. Case 1 is a 29 year-old-male suffered from intractable complex partial seizure (CPS) for 18 years. He was diagnosed as left temporal lobe epilepsy and performed removal of amygdala, hippocampus, parahippocampal gyrus and fusiform gyrus. Case 2 is a 16 year-old-lady suffered from drug resistant CPS for 4 years. Under the diagnosis of right temporal lobe epilepsy, temporal lobectomy was performed. As the presurgical evaluation, under the implantation of subdural strip electrode in both cases, we carried intra-arterial EEG after angiography. Seeker Lite-10 guide wire was insulated with Tracker-10 unibody infusion catheter at sphenoidal portion of middle cerebral artery, and frequent interictal spike discharge was detected in lesional medial temporal lobes by two methods simultaneously.

[Multiple subpial transection after lesionectomy in an intractable epilepsy case]

A Sixty-one-year-old man was admitted to our hospital because of generalized convulsion. He had suffered from intractable epilepsy for 26 years. CT and MRI showed the right frontal cavernous angioma. On operation, intraoperative electrocorticography was performed after lesionectomy including surrounding glial scar and hemosiderin laden tissue. It showed epileptiform potentials in neighbor gyrus of the lesion. Because the removed sphere would be so broad, and we performed multiple subpial transection (MST). After MST, depression of background electrical activity and disappearance of spike discharge are seen. One and half year after operation, seizure was controlled by only phenobarbital administration.

[Surgical treatment and result of high aortic occlusion]

Twenty-one patients with high aortic occlusion treated at our institution from 1967 to 1986 were reviewed. There were seventeen men aged from 39 to 78 (mean age: 61.0) underwent surgical intervention. All patients presented clinical manifestations of vascular insufficiency of the lower limbs; rest pain in eleven patients, intermittent claudication in nine and the others. Sexual impotence was present in eight patients. Renal artery involvement was seen in one case, and renovascular hypertension was observed in this patient. Hypertension and ischemic heart disease were present in twelve cases, cerebrovascular insufficiency in one case, diabetes mellitus in three cases. The following surgical treatments were performed; end-to-end Y-shaped Dacron graft implantations from the infrarenal abdominal aorta to the common femoral arteries in six patients, onlay V-shaped Dacron graft implantations in three patients, axillofemoral extra-anatomic bypass in four patients, and amputation only in one. The hospital mortality was 18% (3/17). Twelve patients discharged from the hospital are followed up (average period was 118 months), but the follow up was lost in two patients. There were two late deaths, which course was not related to operations. The prognosis of high aortic occlusion after anatomic bypass is good, thus it was concluded that anatomic bypass with Y-shaped or V-shaped Dacron graft was recommended and extra-anatomic bypass might be performed only in a high risk patient.