6,874 research outputs found
Preparation, Testing and Characterization of Doped TiO2 Active in the Peroxidation of Biomolecules under Visible Light
Doped TiO2 samples using different preparative procedures were synthesized using either urea or thiourea leading to N- or S-doped TiO2. Photocatalytic peroxidation and oxidation (mineralization) of phosphatidylethanolamine (PE) lipid with doped TiO2 were carried out under light irradiation λ > 410 nm. The formation of conjugated double bonds in PE molecules was followed to detect the formation of peroxy radicals (peroxidation index) under light excitation (λ > 410 nm) when doped TiO2 was used. The kinetics of CO2 production was monitored during the mineralization of PE. Colored TiO2 powders were studied in detail by different and complementary physicochemical techniques. The band gap energies of colored TiO2 were determined by diffuse reflectance spectroscopy (DRS). The visible absorption shoulder of TiO2 was observed to follow Urbach\u27s law. The variation of the transient decay after 354 nm laser pulse excitation does not correlate with the different N− and S−TiO2 doping levels introduced by the addition of urea or thiourea. This suggests that the states (recombination centers or traps) introduced by the doping are not effective in varying the decay kinetics within the nanosecond and microsecond time scale. Elemental analysis shows comparable amounts of S- and N-doping of TiO2 when thiourea is used as dopant. X-ray diffraction reveals no rutile in S−TiO2 samples heated to 600 °C, suggesting that the addition of sulfur precludes rutilization during sample crystallization. X-ray photoelectron spectroscopy (XPS) of the S−TiO2 samples confirms the preferential localization of S on the 20 topmost layers of S−TiO2 upon calcination at 500 °C for 2 h
Acute pancreatitis and subdural haematoma in a patient with severe falciparum malaria: Case report and review of literature
Plasmodium falciparum infection is known to be associated with a spectrum of systemic complications ranging from mild and self-limiting to life-threatening. This case report illustrates a patient who had a protracted course in hospital due to several rare complications of falciparum malaria. A 21-year old man presented with a five-day history of high-grade fever, jaundice and abdominal pain and a two-day history of altered conscious state. A diagnosis of severe falciparum malaria was made based on the clinical presentation and a positive blood smear with parasitaemia of 45%. Despite adequate anti-malarial therapy with artesunate, the patient had persistent and worsening abdominal pain. Investigations suggested a diagnosis of acute pancreatitis, a rare association with falciparum malaria. However, in spite of supportive therapy for acute pancreatitis and a 10-day course of intravenous artesunate and oral doxycycline at recommended doses, he continued to be febrile with peripheral blood smear showing persistence of ring forms. Antimalarial therapy was, therefore, changed to quinine on the suspicion of possible artesunate resistance. On the 17th day of stay in hospital, the patient developed generalized tonic-clonic seizures. Computerized tomography of the brain showed bilateral fronto-parietal subdural haematomas that were surgically drained. His fever persisted beyond 30-days despite broad-spectrum antibiotics, quinine therapy and negative malarial smears. A possibility of drug fever was considered and all drugs were ceased. He subsequently became afebrile and was discharged on the 38th hospital admission day. Recognition of complications and appropriate management at each stage facilitated successful outcome. This report has been presented to highlight the occurrence of several rare complications of falciparum malaria in the same patient
Integral cross sections for electron-impact excitation of the 4 2P state in copper
We report integral cross sections for electron-impact excitation of the 4 2P state in copper for incident electrons with energies in the range from threshold to 100 eV. Measurements, based on an optical excitation function procedure, are compared with coupled-channel and coupled-channel-optical method calculations that we have also performed as a part of this study. Agreement between our measurements and theory was generally only modest. The present measurements are also found to be in quite good accord with the early near-threshold integral cross sections of Flynn et al. and the higher energy measurements from Ismail and Teubner. Where possible, comparison of our data is also made with earlier theory
Continuous wave-pumped wavelength conversion in low-loss silicon nitride waveguides
In this Letter we introduce a complementary metal-oxide semiconductor (CMOS)-compatible low-loss Si3N4 waveguide
platform for nonlinear integrated optics. The waveguide has a moderate nonlinear coefficient of 285 W∕km,
but the achieved propagation loss of only 0.06 dB∕cm and the ability to handle high optical power facilitate an
optimal waveguide length for wavelength conversion. We observe a constant quadratic dependence of the four-wave
mixing (FWM) process on the continuous-wave (CW) pump when operating in the C-band, which indicates that the
waveguide has negligible high-power constraints owing to nonlinear losses. We achieve a conversion efficiency of
−26.1 dB and idler power generation of −19.6 dBm. With these characteristics, we present for the first time, to the best of our knowledge, CW-pumped data conversion in a non-resonant Si3N4 waveguide
Wavelength Conversion in Low Loss Si3N4 Waveguides
We show wavelength conversion in a compact Si3N4 waveguide. Combining low loss, long length, relatively large nonlinear coefficient, high-power handling and absence of two-photon absorption, this platform is promising for integrated nonlinear optics applications
Automated Generation of User Guidance by Combining Computation and Deduction
Herewith, a fairly old concept is published for the first time and named
"Lucas Interpretation". This has been implemented in a prototype, which has
been proved useful in educational practice and has gained academic relevance
with an emerging generation of educational mathematics assistants (EMA) based
on Computer Theorem Proving (CTP).
Automated Theorem Proving (ATP), i.e. deduction, is the most reliable
technology used to check user input. However ATP is inherently weak in
automatically generating solutions for arbitrary problems in applied
mathematics. This weakness is crucial for EMAs: when ATP checks user input as
incorrect and the learner gets stuck then the system should be able to suggest
possible next steps.
The key idea of Lucas Interpretation is to compute the steps of a calculation
following a program written in a novel CTP-based programming language, i.e.
computation provides the next steps. User guidance is generated by combining
deduction and computation: the latter is performed by a specific language
interpreter, which works like a debugger and hands over control to the learner
at breakpoints, i.e. tactics generating the steps of calculation. The
interpreter also builds up logical contexts providing ATP with the data
required for checking user input, thus combining computation and deduction.
The paper describes the concepts underlying Lucas Interpretation so that open
questions can adequately be addressed, and prerequisites for further work are
provided.Comment: In Proceedings THedu'11, arXiv:1202.453
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