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Polycrystalline Pb3TeCo3V2O14, a structural analogue of the multiferroic Ba3NbFe3Si2O14, was synthesized and characterized using X-ray diffraction, magnetic susceptibility, specific heat, dielectric constant, and neutron diffraction. Magnetic susceptibility, specific heat capacity measurements, and bond valence analysis confirmed that the V5+ ion is nonmagnetic, while Co2+ is in its high spin state (S = 3/2). Two magnetic transitions were seen at TN1 = 8.6 K and TN2 = 6.0 K where the spins first adopt a magnetic structure with propagation vector k = (0.752,0,1/2) and reorder into a commensurate structure with propagation vector k = (5/6,5/6,1/2). Changes in the dielectric constant at both magnetic phase transitions suggest that magnetoelectric coupling exists in Pb3TeCo3V2O14.

The material and electrical properties of GaN-based light-emitting diodes (LEDs) grown on wet-etched stripe-patterned substrates were investigated. Footprint-like patterns, located directly above the inclined groove sidewalls, were found on the as-grown LED surface. Cross-sectional transmission electron microscopy (TEM) showed that ‘tumor’-like structures with poor crystal quality were initiated on the inclined sidewalls, seeding dislocation bundles in the subsequently grown crystal. The high dislocation density slowed down the growth above the inclined sidewall, resulting in the uneven morphology. The fabricated devices showed over 30% enhancement in light output power as a result of improvements in both internal and extraction efficiencies.

The genetic relationship of gestation length (GL) with birth and weaning weight (BW, WW) was investigated using data collected from the Hanwoo Experiment Station, National Institute of Animal Science, RDA, Republic of Korea. Analytical mixed models including birth year-season, sex of calf, linear and quadratic covariates of age of dam (days) and linear covariate of age at weaning (days) as fixed effects were used. Corresponding restricted maximum likelihood (REML) and Bayesian estimates of variance components and heritability were obtained with two models; Model 1 included only direct genetic effect and Model 2 included direct genetic, maternal genetic and permanent environmental effect. All the genetic parameter estimates from REML were corresponding to the Bayesian estimates. Direct heritability estimates for GL, BW, and WW were 0.48, 0.33 and 0.25 by Model 1. From Model 2, direct and maternal heritability estimates were 0.38 and 0.03 for GL, 0.14 and 0.05 for BW, and 0.08 and 0.05 for WW. Genetic correlation estimates between direct and maternal effects were 0.05 for GL, 0.59 for BW, and 0.52 for WW. Estimates of direct genetic correlation between GL and BW (WW) were 0.44 (0.21). Positive genetic correlation of GL with BW and WW imply that selection for greater BW or WW would lead to prolonged gestation length.

For the bias-assisted activation of p-GaN at low temperature in air, we deposited various metal contacts consisting of thin Ni/Au and Ni/Pt, and thick Ni layer structures. Annealing these metal contacts with an electrical bias enhances the diffusion of residual hydrogen in the p-GaN towards the interface. The hydrogen was enhanced accumulated at the interface between metal and p-GaN by bias applied. The extracted hydrogen can diffuse through the thin Ni/Au and Ni/Pt metal contacts and desorb from the surface under bias-assisted activation at 410 °C in air. The total resistance of the metal contact to p-GaN after bias-assisted activation decreases without thermal damage. In contrast, for a thick Ni contact on p-GaN, hydrogen accumulated at the interface, and diffusion of hydrogen into the air was obstructed. This condition results in a deteriorated contact resistance and decreases the transport current of the metal contact to p-GaN. The bias-assisted activation with thin Ni/Pt or Ni/Au contacts at 410 °C is practical to remove residual hydrogen from p-GaN and subsequently decreases the contact resistance. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We studied electrodeless photoelectrochemical (ELPEC) etching of GaN in a K2S2O8/KOH solution irradiated either continuously or periodically with ultraviolet (UV) light. The rate of recombination of electrons and holes at dislocation defects is greater than for crystalline GaN. The ELPEC etching with a continuous UV light resulted in a selective etching between dislocations and crystalline GaN and a rough etched surface. To reduce the recombination of the photo-generated carriers, the GaN was irradiated with periodical UV light modulated by a chopper during ELPEC etching. The shorter the interval of UV irradiation, the smoother is the etched GaN surface. A uniform and smooth etched surface was obtained with a root-mean-square (RMS) roughness 0.37 nm in solution (0.01 M KOH, 0.05 M K2S2O8) with a chopper frequency 2500 Hz. The p-GaN etching was also realized by ELPEC etching with a chopped UV source (ELPEC-CS etching) using an Au mask in K2S2O8/KOH solution. The etching rate of p-GaN was 2.8 nm/min at a chopper frequency of 3000 Hz and a power intensity of 63 mW/cm−2 in solution (0.5 M KOH, 0.05 M K2S2O8).

In this paper, formation of low resistance ohmic contact to p-type GaN using an alloy of Ni/Cu was reported. The Mg doped samples were deposited with Ni (20 nm)/Cu (20 nm) and then annealed in nitrogen ambient at different annealing temperatures ranging from 400 to 700 °C. A good ohmic contact with a specific contact resistance of 1.31×10 −4 Ω cm 2 was obtained when the sample was annealed at 600 °C for 30 s. The decrease of specific contact resistance is attributed to the increased contact area and local electric field, and extraction of hydrogen from the p-type GaN.

Photoelectrochemical (PEC) etching technique has been proven to be an effective method to etch GaN. Despite its success, investigations on etching-induced damage are still scare. In this work, the damage induced by PEC etching of GaN in KOH electrolyte was studied. Photoluminescence (PL) spectroscopy was used to explore the origin of etching-induced damaged layer. From the variable temperature PL measurements, the origin of etching-induced damage was attributed to be the defect complex of VGa-ON (gallium vacancy bonds to oxygeon on nitrogen antisite). With determination of the defect origin, the electronic transition in the etch damage-related yellow luminescence (YL) band was suggested to be deep donor-like state to shallow-acceptor transition. In addition, a post-treatment method with boiled KOH chemical etching was developed to remove the thin damaged layer. In this method, crystallographic etching characteristics of boiled KOH was observed to assist in the formation of smooth sidewall facets. As revealed by the reduction of yellow luminescence, we propose this novel technique as a near damage-free etching method.

Damage-free etching of GaN by Cl2, assisted by an ArF (193 nrm) excimer laser, is demonstrated. At low temperatures, photo-assisted etching can provide a better etch rate and largely improve the surface morphology and quality. AFM results show that the etched GaN surface is obtained with a root-mean-square roughness of 1.7 nm. As compared with the photoluminescence spectra of photoelectrochemical wet etched GaN, the photo-assisted cryogenic etching is proved to be a damage-free dry etching technique.

The intrinsic response of quantum dash lasers are measured using a pulse optical modulation technique. Our results show fast well-to-dash carrier capture and intra-dash carrier relaxation with K-factors independent on the pump wavelengths.

We demonstrate bandgap tuned InAs/InAlGaAs quantum-dash-in-well lasers grown on InP material using postgrowth quantum heterostructure intermixing. Compared to the control (non-intermixed) lasers, the light-current characteristics of lasers with emission wavelength tuned by over 100 nm shows insignificant changed suggesting that the quality of the intermixed material is well-preserved.

Three LOCOS-type isolations, viz. modified Scaled LOCOS (MSL), Sidewall Sealed MSL (SSMSL), and Recessed SSMSL (RSSMSL) are evaluated for the 0.6 /spl mu/m-pitch isolation of 256 Mbit DRAM. About 4000 /spl Aring/ field oxide grown in a 1100/spl deg/C wet ambient is found to be optimal for field oxide thinning and bird's beak "punch-through" effects. At a given pad oxide thickness of 100 /spl Aring/ the end-of-line encroachment is the largest for MSL isolation, which essentially rules out MSL as a possible candidate. Although both SSMSL and RSSMSL have similarly good isolation characteristics and diode leakages, only RSSMSL has the undesirable subthreshold double-hump effect and reduced gate oxide integrity, both of which are due to the sharp corners associated with the silicon recess etch of the RSSMSL structure. Therefore, for the three structure studied, only SSMSL is a viable candidate for the 0.6 /spl mu/m-pitch isolation of 256 Mbit DRAM.

Lymphoblastic lymphoma (LBL) frequently affects young adults and usually presents with a mediastinal mass as well as bone marrow involvement. Although the frequency of LBL in the Far East is higher than that of Western countries, no reports regarding treatment of this disease have as yet been reported. We herein report our treatment experience and verify the efficacy of the Stanford/Northern California Oncology Group (NCOG) protocol for this disease and recommend treatment strategies for LBL patients. We retrospectively reviewed the medical records of adult LBL patients treated in our hospital from 1986 to 1996. Twenty-seven patients were diagnosed to have LBL. These patients' ages ranged from 17 to 73 years old with a median of 23. Nineteen patients had an initial stage IV disease. Of the 23 cases in which immunological studies were performed, 20 proved to be of T cell lineage, 1 of B cell type, and the other 2 lacked both T and B markers. Three major chemotherapeutic regimens including prednisone, methotrexate, doxorubicin, cyclophosphamide, etoposide-mechlorethamine, vincristine, procarbazine, prednisone (ProMACE-MOPP), cyclophosphamide, hydroxydaunomycin, vincristine, prednisone (CHOP), and the Stanford/NCOG protocol were used to treat 3, 6, and 15 patients, respectively. Two other patients were treated with two different chemotherapeutic regimens, respectively. One patient was excluded for analysis because of initial treatment by surgery. The complete response (CR) rates with ProMACE-MOPP, CHOP, and the Stanford/NCOG regimens were 0%, 17%, 80% and median overall survival 9, 8.5, and 15 months, respectively. Five patients with stage II-III diseases achieved long-term disease-free survival of 11–36 months with the Stanford/NCOG protocol with a median follow-up of 24 months. Four patients in late stage or relapse received allogeneic bone marrow transplantation (BMT). Two of them obtained long-term disease-free survival. Two other patients in CR were treated with high-dose chemotherapy (HDCT) supported with autologous BMT and peripheral blood stem cell transplantation (PBSCT), respectively. The patient receiving HDCT with autologous PBSCT died of LBL relapse 6 months after transplantation. The other patient undergoing HDCT with autologous BMT died of fulminant hepatitis 5.5 months after transplantation. The median overall survival of all these 26 patients was 12 months. B symptoms and treatment without the Stanford/NCOG protocol were found to have significantly negative impacts on both patients' overall and progression-free survivals. Our results suggest that the Stanford/NCOG protocol may be an effective chemotherapy for adult LBL and may provide long-term remission for patients in an early stage of disease. For those patients with LBL in an advanced stage or in relapse, HDCT with allogeneic or autologous BMT is probably the treatment of choice.

To determine whether stromelysin gene can be introduced into and expressed in the cultured human trabecular cells as well as in the rat eye in vivo through means of a recombinant replication-deficient adenovirus.Stromelysin cDNA was obtained by reverse transcription-polymerase chain reaction with mRNA extracted from the cultured human trabecular cells after induction with interleukin 1alpha. Adenovirus vector that contains stromelysin cDNA was constructed by cotransfection of pJM17 and pDeltaA.CMV-str into the 293 cells. The expression of stromelysin in the cultured human trabecular cells was assayed by Western blot and zymography. The expression of stromelysin in the trabecular meshwork of the rat eyes was detected by in situ hybridization and immunohistochemistry.The constructed adenovirus vector contained stromelysin cDNA, but no E1 region. Western blot and zymogram revealed that the stromelysin could be expressed and that it possessed enzymatic activity in cultured human trabecular cells. In situ hybridization and immunostaining of the stromelysin showed that the complete form of stromelysin was expressed in the trabecular meshwork, the iris, and the uveoscleral outflow pathway of the rat eye.Stromelysin, a functional gene, can be transferred in vivo into rat eyes and in vitro into cultured human trabecular cells using a replication-deficient adenovirus vector. This shows the possibility of gene therapy in glaucoma.

A cDNA clone encoding a muscarinic acetylcholine receptor (mAChR) has been isolated from the nematode Caenorhabditis elegans. The nematode mAChR, consisted of 585 amino acids, displays a high degree of amino acid sequence homology to other invertebrate and vertebrate mAChRs. Excluding a highly variable middle portion of the third intracellular loop, the C. elegans mAChR shares about 51% amino acid sequence identity with a Drosophila mAChR and 42-44% identity with human m1-m5 mAChR subtypes. Comparison of the cDNA sequence with the corresponding genomic sequence reveals that the C. elegans mAChR gene contains ten introns, eight of them in the coding region. Pharmacological profiles of the C. elegans mAChR expressed in Chinese hamster ovary (CHO) cells were shown to be similar to those of mammalian counterparts, indicating that ligand binding domains of the receptor have been conserved during evolution. When this cloned receptor was expressed in Xenopus oocytes, acetylcholine evoked a transient Cl- current. Furthermore, activation of the receptor with oxotremorine, acetylcholine or carbachol resulted in the stimulation of phosphatidylinositol metabolism in CHO cells, suggesting that the receptor is coupled to phospholipase C activation.

Visual deprivation disrupting binocular development, such as that occurring with congenital cataract, is reported to cause asymmetric monocular optokinetic nystagmus (MOKN), as well as poor sensory and motorfusional outcome. We wanted to determine if symmetric MOKN could develop in cases of congenital cataract with good fusional outcome.We tested MOKN (with video and electro-oculographic recordings) and stereoacuity on 5 patients with good visual acuity and satisfactory ocular alignment after surgery for congenital cataract.Stereoacuity was better than 50 seconds of arc in 1 case of monocular cataract and 2 cases of bilateral cataract. These case patients had symmetric MOKN. In a monocular cataract case, symmetric MOKN was observed in spite of questionable stereoacuity (at least 500 arc/s). One patient showed asymmetric MOKN, despite good visual acuity, and stereoacuity of 200 arc/s.Patients with congenital cataract can have symmetric MOKN and good stereopsis. These cases suggest that MOKN symmetry develops along with good stereopsis, but the quality of stereopsis necessary for development of MOKN symmetry remains unclear.

Photoelectrochemical (PEC) etching technique has been proven to be an effective method to etch GaN. Despite its success, investigations on etching-induced damage are still scare. In this work, the damage induced by PEC etching of GaN in KOH electrolyte was studied. Photoluminescence (PL) spectroscopy was used to explore the origin of etching-induced damaged layer. From the variable temperature PL measurements, the origin of etching-induced damage was attributed to be the defect complex of VGa-ON (gallium vacancy bonds to oxygeon on nitrogen antisite). With determination of the defect origin, the electronic transition in the etch damage-related yellow luminescence (YL) band was suggested to be deep donor-like state to shallow-acceptor transition. In addition, a post-treatment method with boiled KOH chemical etching was developed to remove the thin damaged layer. In this method, crystallographic etching characteristics of boiled KOH was observed to assist in the formation of smooth sidewall facets. As revealed by the reduction of yellow luminescence, we propose this novel technique as a near damage-free etching method.

Ethambutol is a useful first line antituberculous drug, but can cause significant visual impairment. In order to determine the clinical manifestations of optic neuropathy associated with ethambutol, and the margin of drug safety in Koreans, we investigated ten men and four women, diagnosed between 1995 and 1997 at Seoul Municipal Boramae Hospital as suffering from ethambutol toxicity. After determining their history, including the period during which ethambutol had been administered, and its dose, a complete eye examination was performed, including measurement of best-corrected visual acuity, pupillary examination, color vision, fundus examination and a test of visual field. Ocular ethambutol toxicity was observed at a dose as low as 12.3 mg/kg. Abnormal ophthalmic findings include decreased visual acuity and abnormal visual field, especially in the central scotoma, and abnormal color perception. In conclusion, ethambutol at a low dose can cause optic neuropathy, and for the early detection of this, a color vision test is important.

Portions of the hemagglutinin neuraminidase (HN) gene of Newcastle disease virus (NDV) isolates from two recent outbreaks were sequenced to investigate epidemiology of this disease in Taiwan. These NDV isolates were all viscerotropic velogenic according to the clinical lesions produced in chickens. Sequence data were obtained from 14 NDV isolates (12 from 1995 and 2 from 1984). All isolates differed in their nucleotide sequences (from 0.3 to 15.3%), and represented potentially different strains of NDV. Phylogenetic analysis revealed that these isolates are closely related to viruses isolated from Japan and Malaysia. Some viruses isolated in 1995 appeared to evolve from viruses isolated in 1984. The results suggest that the 1995 outbreak of Newcastle disease (ND) in Taiwan may have been caused by multiple strains of velogenic NDV that have cocirculated in Taiwan for some time. Moreover, NDV isolates from racing pigeons were very similar to isolates from chickens in the same period, suggesting that both domestic and free-living birds were involved in the spread of ND in Taiwan.

The authors attempted to find a way to perform reliable delayed suture adjustment so that surgeons can investigate whether delayed adjustment actually gives more reliable and stable results. To prevent the formation of postoperative adhesions and delay the time of adjustment, the authors used polytetrafluoroethylene (PTFE) as a mechanical barrier.PTFE was placed between the free muscle end and the sclera as a physical barrier in 16 rabbits.PTFE could delay the adjustment for up to 4 weeks after surgery in 4 of 10 eyes in each group. After removal of PTFE, adjustment was possible up to 12 weeks because there was no adhesion between the muscle and the PTFE.Adjustment could be delayed up to 4 weeks in 40% of the experimental eyes using PTFE as a physical barrier.

A new cell culture modality had already been established in our laboratory. Using this model, living KB and GBM 8401 tumor cells grew and proliferated exponentially in semipermeable microcapsules, implanted in vivo. The culture method was designed as a modality for a predictive anticancer drug sensitivity test. Its advantages included providing a three-dimensional growth and in vivo supply of nutrients. Tumor cell sensitivity to drugs can be assessed in vivo. The assay is applicable to virtually all histological types of human tumor cells. Using this technique, anticancer drug sensitivity tests of KB and GBM 8401 cells were evaluated. The results showed that such encapsulated cells grew and proliferated rapidly. In addition, the proliferation of KB cells was more rapid than that of GBM 8401 cells under conventional monolayer and in vivo microcapsule culture states. They were very sensitive to adriamycin and fluorouracil, and relatively resistant to cyclophosphamide while cultured in vitro. The viability percentage of microencapsulated KB cells cultured in vivo for two weeks was around 80-90%, roughly similar to that of the same cells conventionally cultured in vitro. However, the proliferation rates of encapsulated KB and GBM 8401 cells in vivo were significantly inhibited by all the drugs tested, with KB cells inhibited more significantly than GBM 8401. These results also suggest that some anticancer drugs needing to be bioactivated in vivo had better test results by this technique, and thus false negative results could be excluded. Also, the good repair capacity of microcapsules implanted in vivo, for damaged tumor cells previously incubated with chemotherapeutic drugs, appears to provide a much better environment for cell growth because much essential nourishment can be supplied. The inhibition percentage of fluorouracil to encapsulated cancer cells from patients with adenocarcinoma of the colon was also tested; they were 69.8% in vivo and 76.5% in vitro. This fast, relatively inexpensive in vivo model can be used to screen various anticancer drugs and help clinical oncologists to select the most effective agents for individual patients.

A rapid colorimetric microtiter assay was used in this study to analysis drug cytotoxicity. Through the reduction of tetrazolium salt, MTT [3-(4, 5-dimethyl-thiazol-2-yl) 2,5-diphenyl tetrazolium bromide], by living cells to form a blue formazan product. The level of MTT cleavage by viable cells of various origins was found to be in direct proportion to the number of cells (between 500-10,000 cells/well). By MTT methods, the growth profile and chemosensitivity of 4 human tumor cell lines (KB, Hep-2, HA22T, and CoLo205) to 4 anticancer drugs (adriamycin, 5-fluorouracil, 6-mercaptopurine and cyclophosphamide) were assessed. Results from this assay were compared with data assimilated simultaneously by dye exclusion and clonogenic assay. In general, good correlation was observed among the clonogenic, dye exclusion and MTT assays for continuous drug exposures, yet the MTT assay was more rapid in testing in vitro chemosensitivity against human tumor cell lines. The dye exclusion assay was the most sensitive, followed by the clonogenic and then the MTT assays. The ID50 values obtained from the MTT assay were approximately 3 to 5 times lower than those from the other two methods. Based on these studies, MTT assay appears to be a rapid, convenient, economical and reasonable tool in the initial-stage screening of large number of the in vitro anticancer drugs.

4154 Background: Tolerance and outcomes of HIV+ anal cancer patients are questioned, especially since the emergence of High Active Anti-Retroviral Therapy (HAART) in the mid-1990s. Our experience in treating these patients before and during the HAART era is reported. Methods: From 1987–2003, 19 HIV+ invasive anal cancer patients were treated with: 30–60 Gy pelvic RT (2 Gy/d) + Mitomycin C (10 mg/m2 bolus on d1) + 5-FU (1000 mg/m2/d, continuous infusion d1–4 and 28–31). Results: Mean CD-4 count at cancer diagnosis was 311, with 9 on HAART. Mean CD-4 count for HAART was 383 and 247 for non-HAART. Stage distribution: 1 T1, 9 T2, 9 T3, 18 N0, 1 N3. Mean f/u was 40 months. 79% had complete response after chemoRT. 4 had locally persistent disease. There was 1 loco-regional recurrence and 2 distant metastases. 79% of the cohort is colostomy-free. Median OS has not been reached. OS at 2 and 3 years were: 88%and 79%, with 10 Alive and NED, 1 Alive with disease, 3 Dead of disease, 5 Dead from intercurrent disease (all secondary to AIDS). 1.5 year DFS was 74%. Break and CD-4 count < 200 had a statistically significant negative impact on DFS, but not OS. HAART did not affect either factor. 11 had RT break for median of 17 days. There was no Grade 4 skin toxicity. All completed the 2nd 5-FU cycle: 7 had delay (median 7 days) and 3 had dose decrease. There were 6 hospitalizations: 5 neutropenic fevers and 1 perineal abscess rupture. WBC Toxicity: 6-Grade 3 and 2-Grade 4. Platelet Toxicity: 2-Grade 3. Heme toxicity was not affected by HAART or CD4 count < 200. There were no treatment related deaths. Conclusion: HIV+ anal cancer patients have reasonable tolerance and outcomes with chemoRT. CD-4 count < 200 and break were negative prognostic factors for DFS. Our 79% colostomy free survival is similar to RTOG 9208, where suboptimal control was attributed to mandatory RT break. Factors influencing break include heme and skin toxicity. To improve the therapeutic ratio, substitution of Mitomycin-C with Cisplatin, IMRT, and Ethyol are being explored. No significant financial relationships to disclose.

5609 Background: Traditional tx for locally advanced squamous cell carcinoma [SCC] of oropharynx [OPX] has been oncologic resection + adjuvant RT. In recent years, organ preserving therapy with che...

5619 Background: Randomized trials have reported improved outcome by adding chemotherapy to radiation, but none have examined concurrent chemoradiation with and without adjuvant chemotherapy. This retrospective analysis seeks to review our experience. Methods: Records of 29 consecutively treated patients from 1997 to 2002 were reviewed; these included stage IIII(n=8) and stage IV(n=21) patients with a median age of 49years. All patients received concurrent chemoradiation with the majority (82.8%) receiving at least three courses of cisplatin(100mg/m2;days1,22,43). Seventeen patients received adjuvant chemotherapy with cisplatin(80mg/m2;day1) and fluorouracil(1000mg/m2/d;days1–4) every 4 weeks, with a majority(82.4%) receiving at least three courses. Twelve patients did not receive adjuvant chemotherapy. All patients received radiotherapy in 1.8–2.0 Gy/d fractions to 7020Gy median total dose. Results: After a median follow-up of 39.6 months, seven of 29 patients had recurrent(n=6)/persistent disease(n=1). ...

We report the introduction of deep energy levels into silicon following a hydrogen plasma anneal at 300 °C for 3 h. The wafers were heat treated prior to the hydrogen anneal to cause oxygen to precipitate using a three‐cycle high‐low‐high anneal. The deep level impurity concentrations generally exhibited a decreasing density into the wafer, indicative of damage originating from the surface. These findings are in contrast to other reported hydrogen plasma anneal results which generally show a reduction of deep level concentrations.

The design, fabrication, and characteristics of a 350-V, 100-A buried-gate static induction transistor (SIT) as a power switching device for applications in military and space environments because of its potential for radiation hardness, high-frequency operation, and the incorporation of on-chip smart power sensor and logic functions are described. The potential radiation hardness of this class of devices was evaluated by measurement of SIT characteristics after irradiation with 100-Mrad (2-MeV) electrons and up to 10/sup 16/ fission neutrons/cm/sup 2/. High-temperature operation and the possibility of radiation damage self-annealing are discussed. >

It is well known that recombination lifetimes are significantly degraded in oxygen‐precipitated silicon. The possible sources for lifetime degradation are expected to be oxygen precipitates (OP’s), dislocation loops, stacking faults, and point defects associated with self‐interstitials generated during the oxygen precipitation process. From the results of an extensive experimental study using IR absorption, TEM, DLTS, and SPV (surface photovoltage), we have found that OP’s are mainly responsible for the observed lifetime degradation and that recombination at OP’s takes place through Si/OP interface states. In addition we have observed that the lifetime degradation is more severe in p‐Si than in n‐Si even for identical densities and sizes of OP’s. A model for recombination at OP’s is presented in terms of the surface recombination velocity at the Si/OP interface and their average density and size. To explain the lifetime difference between n‐Si and p‐Si we propose a band bending around OP’s caused by positive fixed charges in the OP’s.

The measured short-circuit current density in bifacial dendritic web silicon solar cells has been found to decrease with decreasing base resistivity, particularly under back illumination. In addition, the ratio of short-circuit current under back illumination to short-circuit current under front illumination was observed to vary with light intensity. These observations reflect the fact that the minority-carrier lifetime in the base of these cells is a function of the base resistivity and the illumination level. The dopant was assumed to play only an indirect role in determining lifetime. This decrease in lifetime is shown to follow from a distribution of defect levels in the bandgap. These levels are a consequence of extended defects that have been observed in the web material, namely oxide precipitates and the dislocation cores that they decorate. The dopant, acts only in the indirect role of moving the Fermi level over an existing background distribution of defect levels that arise from the extended defects. Assuming a parabolic distribution of defect levels in the bandgap, the minority-carrier lifetime was calculated as a function of doping density and excess carrier concentration (illumination level) using the Shockley-Reed-Hall theory. The short-circuit current densities that were calculated using these lifetimes agreed reasonably well with measured values for bifacial dendritic web silicon solar cells. The measurements were made over a range of doping densities (6*10/sup 14/ to 3*10/sup 16/ cm/sup -3/) and illumination levels (0.001 to 1 sun) for both front and back illumination of the bifacial cells. >

In ionizing-radiation environments, oxide charge buildup in the buried oxide of SIMOX SOI material causes an increase in the back-channel leakage current, resulting in an instability in electronic circuits formed on SIMOX wafers. We report the measured distributions of radiation-induced oxide charge density in buried oxides formed by oxygen implantation. These are obtained by etch-back experiments including C-V measurements using a mercury probe and ellipsometer measurements. The results show a region of higher charge density about 1500A from the top interface with a lower density region within a few hundred angstroms of the top interface. The results also show that the oxide charge density decreases with annealing temperature. Some unusual optical properties of SIMOX oxide observed in ellipsometer measurements are discussed comparatively with thermal oxide.

A microencapsulation of living tumor cells by an improved membrane and droplet forming technique was established in our laboratory. This semipermeable microencapsulating membrane was impermeable to serum albumins (M.W. 66,000 or 45,000) and human hemoglobin (M.W. 64,000), but permitted passage of low molecular weight substances (alpha-Lactalbumin, or Trypsinogen; M.W. 14,200 or 24,000). The in vivo results showed that microencapsulated tumor cell lines (KB, human oral epidermoid cell; P-388 lymphocytic leukemia; GBM 8401/TSGH, glioma) and human colorectal carcinoma cells grew and proliferated exponentially within twenty days. The in vivo growth exhibited better than that in vitro. Histological and morphological findings of these four different kinds of tumor cells are similar to those of original tumor cells. Treatment of the microencapsulated tumor cells (MTC) with cytotoxic drugs (adriamycin, 5-fluorouracil and cyclophosphamide) in vitro showed no significant difference in percent inhibition (p greater than 0.05) between the encapsulated and non-encapsulated cells. The in vivo data indicated that different anti-cancer drugs had different inhibition effects. The results showed that the MTC model was useful for screening an appropriate cytotoxic drug and could be applied to clinical medicine in the near future.

Mouse salivary androgen-binding protein (ABP) is a major secretory product of the submaxillary glands. Although it is a common salivary protein among rodents generally, the function of ABP has yet to be determined. Here we report a comparison of the DNA coding sequences and putative amino acid sequences they determine for the three common alleles of the Alpha subunit gene (Abpa), alleles that appear to be diagnostic for the three subspecies of Mus musculus. Three other unique sequences were found in the species M. caroli, M. spretus, and M. spicilegus. Comparison of the six sequences shows that 8 of the 20 base substitution sites produce a high degree of variability in amino acids 32, 33, 36, and 39, a variability that creates unique sequence combinations in each species and subspecies. We compare the possibilities that selection or genetic drift caused this unusual microevolution and argue that selection is the more likely explanation. We speculate on the potential significance of this with respect to the proposal that ABP is involved in assortive mate kin selection.