A study of various oxide/silicon interfaces by Ar + backsurface bombardment

A low-energy (550 eV) argon beam is used to bombard the backsurfaces of 6 kinds of metal–oxide–semiconductor capacitors, and the resulting effects on their interface characteristics are then investigated. The gate oxide of these capacitors includes thermal oxide, trichloroethyene (TCE) oxide, NH3-nitrided oxide, reoxidized-nitrided oxide, rapid-thermal-nitrided oxide, and N2O-nitrided oxide. Measurements show that for bombardment times up to 45 min the interface-state density of all the devices, in general, decreases with increasing bombardment time/dose, and the midgap energy at the silicon surface tends to rise. Moreover, the bombardment is more effective in reducing acceptor-type than donor-type interface states. On the other hand, the change of fixed-charge density is more complex. For TCE, N2O-nitrided and reoxidized-nitrided oxides, fixed-charge density decreases initially with increasing bombardment time, but then increases, while the trend is reversed for the other gate oxides. A model with stress compensation and weak bond breaking is suggested to explain the results. ©1999 American Institute of Physics.published_or_final_versio

Effects of chemical composition on humidity sensitivity of Al/BaTiO3/Si structure

Argon-ion-beam sputtering technique has been applied to deposit barium titanate (BaTiO3) films on silicon wafers at room temperature under vacuum, and then Al/BaTiO3/Si structures were fabricated. Results show that the current and capacitance of these devices are sensitive to the change of relative humidity at room temperature, and saturation absorption (response) time as well as humidity sensitivity of the devices depend on the chemical composition of the BaTiO3 films. For higher annealing temperature and longer annealing time, the oxygen composition increases while fixed charge density decreases. These changes result in lower humidity sensitivity and longer response time.© 1995 American Institute of Physics.published_or_final_versio

Hypoglycemia and Death in Mice Following Experimental Exposure to an Extract of Trogia venenata Mushrooms

BACKGROUND: Clusters of sudden unexplained death (SUD) in Yunnan Province, China, have been linked to eating Trogia venenata mushrooms. We evaluated the toxic effect of this mushroom on mice. METHODS: We prepared extracts of fresh T. venenata and Laccaria vinaceoavellanea mushrooms collected from the environs of a village that had SUD. We randomly allocated mice into treatment groups and administered mushroom extracts at doses ranging from 500 to 3500 mg/kg and water (control) via a gavage needle. We observed mice for mortality for 7 days after a 3500 mg/kg dose and for 24 hours after doses from 500 to 3000 mg/kg. We determined biochemical markers from serum two hours after a 2000 mg/kg dose. RESULTS: Ten mice fed T. venenata extract (3500 mg/kg) died by five hours whereas all control mice (L. vinaceoavellanea extract and water) survived the seven-day observation period. All mice died by five hours after exposure to single doses of T. venenata extract ranging from 1500 to 3000 mg/kg, while the four mice exposed to a 500 mg/kg dose all survived. Mice fed 2000 mg/kg of T. venenata extract developed profound hypoglycemia (median= 0.66 mmol/L) two hours after exposure. DISCUSSION: Hypoglycemia and death within hours of exposure, a pattern unique among mushroom toxicity, characterize T. venenata poisoning

Localized primary renal aspergillosis in a diabetic patient following lithotripsy – a case report

<p>Abstract</p> <p>Background</p> <p>Primary renal aspergillosis is rare in diabetic patients. Diagnosis of localized primary renal <it>Aspergillus </it>infection in diabetic patients requires careful investigations due to its benign presentation and lack of associated systemic clinical features. There is also paucity of information on the role of conservative treatment of such localized infection with antifungal agents only. Here, we describe a case of localized renal aspergillosis in a type 2 diabetic patient with a brief review of literature.</p> <p>Case presentation</p> <p>We describe a case of unilateral renal aspergillosis following intracorporeal pneumatic lithotripsy (ICPL) in a type 2 diabetic man. The patient presented with mild pain in the left lumbar region and periodic expulsion of whitish soft masses per urethra, which yielded growth of <it>Aspergillus fumigatus</it>. He was treated initially with amphotericin B; however, it was stopped after 2 weeks, as he could not tolerate the drug. Subsequently, he was successfully treated with oral itraconazole.</p> <p>Conclusion</p> <p>Localized renal aspergillosis may be suspected in diabetic patients having history of urinary tract instrumentation, mild lumbar pain, passage of suspicious masses in urine and persistent pyuria. Examination of the suspicious substances expelled per urethra is essential for diagnosis as routine multiple urine analysis may yield negative results. Conservative treatment with oral itraconazole alone is effective in cases with incomplete obstruction.</p

Modeling Light Adaptation in Circadian Clock: Prediction of the Response That Stabilizes Entrainment

Periods of biological clocks are close to but often different from the rotation period of the earth. Thus, the clocks of organisms must be adjusted to synchronize with day-night cycles. The primary signal that adjusts the clocks is light. In Neurospora, light transiently up-regulates the expression of specific clock genes. This molecular response to light is called light adaptation. Does light adaptation occur in other organisms? Using published experimental data, we first estimated the time course of the up-regulation rate of gene expression by light. Intriguingly, the estimated up-regulation rate was transient during light period in mice as well as Neurospora. Next, we constructed a computational model to consider how light adaptation had an effect on the entrainment of circadian oscillation to 24-h light-dark cycles. We found that cellular oscillations are more likely to be destabilized without light adaption especially when light intensity is very high. From the present results, we predict that the instability of circadian oscillations under 24-h light-dark cycles can be experimentally observed if light adaptation is altered. We conclude that the functional consequence of light adaptation is to increase the adjustability to 24-h light-dark cycles and then adapt to fluctuating environments in nature

Structure and Photoluminescent Properties of ZnO Encapsulated in Mesoporous Silica SBA-15 Fabricated by Two-Solvent Strategy

The two-solvent method was employed to prepare ZnO encapsulated in mesoporous silica (ZnO/SBA-15). The prepared ZnO/SBA-15 samples have been studied by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherm, and photoluminescence spectroscopy. The ZnO/SBA-15 nanocomposite has the ordered hexagonal mesostructure of SBA-15. ZnO clusters of a high loading are distributed in the channels of SBA-15. Photoluminescence spectra show the UV emission band around 368 nm, the violet emission around 420 nm, and the blue emission around 457 nm. The UV emission is attributed to band-edge emission of ZnO. The violet emission results from the oxygen vacancies on the ZnO–SiO2interface traps. The blue emission is from the oxygen vacancies or interstitial zinc ions of ZnO. The UV emission and blue emission show a blue-shift phenomenon due to quantum-confinement-induced energy gap enhancement of ZnO clusters. The ZnO clusters encapsulated in SBA-15 can be used as light-emitting diodes and ultraviolet nanolasers

Screening Level of PAHs in Sediment Core from Lake Hongfeng, Southwest China

Using data from a 25-year retrospective of polycyclic aromatic hydrocarbons (PAHs) in sediment core from Lake Hongfeng, Southwest China, their possible sources and potential toxicologic significance were investigated. The total PAH concentrations (16 priority PAHs as proposed by the United States Environmental Protection Agency) in sediments ranged from 2936.1 to 5282.3 ng/g and gradually increased from the analyzed deeper sediments to surface sediments. PAHs were dominated by low molecular-weight components, especially phenanthrene (PHEN) and fluorene (FLU). However, a significantly increased number of high molecular-weight (HMW) PAHs was found in upper segments. The temporal trends of individual PAH species suggest that there may have been a change in energy use from low- to high-temperature combustion, especially after approximately 2001. PAH input to Lake Hongfeng originated mainly from domestic coal combustion and biomass burning, whereas fuel combustion characteristics have also been found in recent years. Sediment-quality assessment implied that potential adverse biologic impact could be a probability for most low-ring PAHs (including naphthalene, acenaphthylene, acenaphthylene, FLU, PHEN, and anthracene). Nevertheless, more concern should be paid to HMW PAHs in the future due to their rapidly increasing trends in upper sediments. Because only one core was analyzed in this study, more work is needed to confirm the sources and toxicity of PAHs in Lake Hongfeng

A survey of core and support activities of communicable disease surveillance systems at operating-level CDCs in China

<p>Abstract</p> <p>Background</p> <p>In recent years, problems like insufficient coordination, low efficiency, and heavy working load in national communicable disease surveillance systems in China have been pointed out by many researchers. To strengthen the national communicable disease surveillance systems becomes an immediate concern. Since the World Health Organization has recommended that a structured approach to strengthen national communicable disease surveillance must include an evaluation to existing systems which usually begins with a systematic description, we conducted the first survey for communicable disease surveillance systems in China, in order to understand the situation of core and support surveillance activities at province-level and county-level centers for disease control and prevention (CDCs).</p> <p>Methods</p> <p>A nationwide survey was conducted by mail between May and October 2006 to investigate the implementation of core and support activities of the Notifiable Disease Reporting System (NDRS) and disease-specific surveillance systems in all of the 31 province-level and selected 14 county-level CDCs in Mainland China The comments on the performance of communicable disease surveillance systems were also collected from the directors of CDCs in this survey.</p> <p>Results</p> <p>The core activities of NDRS such as confirmation, reporting and analysis and some support activities such as supervision and staff training were found sufficient in both province-level and county-level surveyed CDCs, but other support activities including information feedback, equipment and financial support need to be strengthened in most of the investigated CDCs. A total of 47 communicable diseases or syndromes were under surveillance at province level, and 20 diseases or syndromes at county level. The activities among different disease-specific surveillance systems varied widely. Acute flaccid paralysis (AFP), measles and tuberculosis (TB) surveillance systems got relatively high recognition both at province level and county level.</p> <p>Conclusions</p> <p>China has already established a national communicable disease surveillance framework that combines NDRS and disease-specific surveillance systems. The core and support activities of NDRS were found sufficient, while the implementation of those activities varied among different disease-specific surveillance systems.</p