Visible luminescence mechanism of ZnO nanoparticles synthesized by sol-gel method

We presented our investigations on the absorption and emission properties of the nanocrystalline ZnO particles of different particle sizes (2 nm-5 nm) by sol-gel method. In the room temperature PL spectra, three emission bands, ultraviolet (UV), blue and green were observed. With increasing the particle sizes, both the UV and the visible emission bands shifted to lower energies progressively. From the size-dependency, there was a linear relationship between the energetic maxima of the UV and the green emission bands with a slope of about 0.26, which indicated that the green luminescence of ZnO was produced by the transitions of electrons from deep level to the valence band (or shallow acceptor level). A linear dependence was also found between the energetic maxima of the UV and the blue emissions with a slope of 0.15, the origin this blue emission band is not clear at present. While in van Dijken et al.'s paper, however, they identified only two emission bands in the emission spectra, an UV and a broad visible emission band, and the linear fit between the energetic maxima of these two bands in particles of different sizes has a slope of 0.6, so they proposed that the visible emission in ZnO was originated from the recombination of a shallowly trapped electron with a deeply trapped hole. We attributed this divergence to the fact that the broad visible band is actually composed of two separate emission bands originated from two different recombination processes, and should not had been treated as one emission band.

Genome-wide association study identifies multiple novel loci associated with disease progression in subjects with mild cognitive impairment

Alzheimer's disease (AD) is the leading cause of dementia among the elderly population; however, knowledge about genetic risk factors involved in disease progression is limited. We conducted a genome-wide association study (GWAS) using clinical decline as measured by changes in the Clinical Dementia Rating-sum of boxes as a quantitative trait to test for single-nucleotide polymorphisms (SNPs) that were associated with the rate of progression in 822 Caucasian subjects of amnestic mild cognitive impairment (MCI). There was no significant association with disease progress for any of the recently identified disease susceptibility variants in CLU, CR1, PICALM, BIN1, EPHA1, MS4A6A, MS4A4E or CD33 following multiple testing correction. We did, however, identify multiple novel loci that reached genome-wide significance at the 0.01 level. These top variants (rs7840202 at chr8 in UBR5: P=4.27 × 10(-14); rs11637611 with a cluster of SNPs at chr15q23 close to the Tay-Sachs disease locus: P=1.07 × 10(-15); and rs12752888 at chr1: P=3.08 × 10(-11)) were also associated with a significant decline in cognition as well as the conversion of subjects with MCI to a diagnosis of AD. Taken together, these variants define approximately 16.6% of the MCI sub-population with a faster rate of decline independent of the other known disease risk factors. In addition to providing new insights into protein pathways that may be involved with the progress to AD in MCI subjects, these variants if further validated may enable the identification of a more homogeneous population of subjects at an earlier stage of disease for testing novel hypotheses and/or therapies in the clinical setting.

Excitons emissions and Raman scattering of ZnO nanoparticles embedded in BaF2 matrices by reactive magnetron sputtering

ZnO nanoparticles embedded in BaF2 matrix were fabricated by rf magnetic sputtering technology. The optical properties of high quality ZnO nanoparticles, thermally post treated in a N2 atmosphere, were investigated by temperature-dependence photoluminescence measurement. Free exciton and localized exciton were observed at the low temperature. Free exciton peak was at 3.374 eV and localized exciton peak was at 3.420 eV, dominating the PL spectrum at 77 K. Free exciton transition was observed at 3.310 eV at room temperature, whereas the localized exciton transition was at 3.378 eV. The multiple-phonon Raman scattering spectrum showed that ZnO nanoparticles embedded in BaF2 matrix had a large deformation energy originated from lattice mismatch between ZnO and BaF2 matrix. Analysis of the fitting results from the temperature dependence of FWHM of ZnO exciton illustrated that the large value of gamma(ph) was good qualitative agreement with the large deformation potential.

Natural occurrence of fumonisins b1 and b2 in corn from three main production provinces in China

A total of 255 corn samples collected in 2010 from three main corn production provinces of China (Liaoning, Shandong, and Henan) were analyzed for contamination with fumonisins (FB(1) and FB(2)). The incidence of contamination was significantly higher in samples from Liaoning than in samples from the other two provinces. Approximately 80.0% of the samples from Liaoning were contaminated with fumonisins, with a mean total fumonisin concentration of 3,990 ng/g. In contrast, the mean total fumonisin concentrations were 845 and 665 ng/g in samples from Shandong and Henan, respectively. The probable daily intake of fumonisins (0.3 μg/kg of body weight) is within the provisional maximum tolerable daily intake of 2.0 μg/kg of body weight set by the Joint Food and Agriculture Organization and World Health Organization Expert Committee on Food Additives.

Spin squeezing: transforming one-axis twisting into two-axis twisting

Squeezed spin states possess unique quantum correlation or entanglement and are significantly promising for advancing quantum information processing and quantum metrology. In recent back-to-back publications [C. Gross et al., Nature (London) 464, 1165 (2010) and Max F. Riedel et al., Nature (London) 464, 1170 (2010)], reduced spin fluctuations are observed leading to spin squeezing at -8.2 and -2.5 dB, respectively, in two-component atomic condensates exhibiting one-axis-twisting interactions. The noise reduction limit for the one-axis twisting scales as ∝1/N(2/3), which for a condensate with N∼10(3) atoms is about 100 times below the standard quantum limit. We present a scheme using repeated Rabi pulses capable of transforming the one-axis-twisting spin squeezing into the two-axis-twisting type, leading to Heisenberg limited noise reduction ∝1/N or an extra tenfold improvement for N∼10(3).

The mutL Mutation in Pseudomonas aeruginosa Isolates Reveals Multidrug-resistant Traits and Possible Evolutionary Trends

To evaluate the genetic differences and possible evolutionary trends of clinical multidrug-resistant (MDR) strains, Pseudomonas aeruginosa isolates were characterized by pulsed-field gel electrophoresis (PFGE) and evolutionary distances were estimated. A total of 85.7% of the P. aeruginosa isolates were MDR strains. Strains with the PFGE pattern A predominated; all were susceptible to amikacin and cefepime but resistant to levofloxacin and meropenem (except strain PA45 which was sensitive to meropenem). PFGE pattern H or P strains exhibited resistance to six to eight different antibiotics. PFGE pattern I or J strains were susceptible to all antibiotics tested. Two imperfect six base-pair tandem repeats, CTGGCG and CTGGCC, were found in the mutL gene. In conclusion, MDR characteristics and PFGE profiles were clearly correlated with the mutL phylogenetic tree. This indicates that mutations in mutL might contribute to genetic stability in adaptation by changing the MDR traits. Phylogenetic analysis of mutL revealed the MDR relatedness of P. aeruginosa strains.

The relationship between acid-suppressing drugs and phytobezoar formation: a retrospective analysis and discussion of phytobezoar formation

OBJECTIVES

Although phytobezoars are a rare cause of gastrointestinal obstruction, they are most commonly found in patients with previous gastric surgery. It is well known that predisposing factors of phytobezoar formation are ingestion of fruits containing soluble tannin, presence of dilute hydrochloric acid in the stomach, and gastric stasis or delayed emptying. We investigated whether intake of acid-suppressing drugs that neutralize gastric acidity or inhibit gastric acid secretion to constitute a hypo-acidic condition, increases the risk of phytobezoar formation.

MATERIALS AND METHODS

Between September 1992 and October 2008, 32 patients (24 male and 8 female) with gastrointestinal phytobezoars were diagnosed either surgically or endoscopically at the Tri-Service General Hospital, Taipei, Republic of China. The data were collected from hospital records and analyzed retrospectively.

RESULTS

Eighteen (56.25%) of all patients had previous gastric surgery and 6 (42.9%) of the 14 patients who had not undergone surgery had diabetes mellitus. The majority of admissions were during winter and spring (between October and March) (P < 0.01) and none of the patients had taken acid-suppressing drugs during the 6 months before detection of gastrointestinal phytobezoars.

CONCLUSIONS

In our study, intake of acid-suppressing drugs did not increase the risk of phytobezoar formation in patients with normal gastric motility. Moreover, we believe that the major factor in phytobezoar formation is gastric stasis or delayed emptying, which sufficiently prolongs the retention period of materials in the stomach, while dilute hydrochloric acid is a minor factor.

Faceted ice growth in hydrophilic and hydrophobic channels

This study is motivated by the cryo-preservation for tissues, which is related to the solidification of blood in a confined space. The morphological behavior of growing ice facet in 1.3 mm hydrophilic and hydrophobic channels is the focus of this study. Both DI water and KCl solution were solidified without seeds in the channels and the growing front facet was discussed in regards to contact angle, in-situ morphology, conductivity difference between two phases and solute segregation. For DI water, the formation of facets was observed during ice growth in both hydrophilic and hydrophobic channels and could be classified into two modes according to the local curvature of the interface. The facet was formed at different positions of the interface in hydrophilic and hydrophobic channels. Solutal segregation effect was taken into consideration to partially govern the interface morphology and the facet formation during solidification of the KCl solution. In addition, the growth rates of the ice growth with a facet were also compared and discussed.

Split of surface plasmon resonance of gold nanoparticles on silicon substrate: a study of dielectric functions

The split of surface plasmon resonance of self-assembled gold nanoparticles on Si substrate is observed from the dielectric functions of the nanoparticles. The split plasmon resonances are modeled with two Lorentz oscillators: one oscillator at ~1 eV models the polarization parallel to the substrate while the other at ~2 eV represents the polarization perpendicular to the substrate. Both parallel and perpendicular resonances are red-shifted when the nanoparticle size increases. The red shifts in both resonances are explained by the image charge effect of the Si substrate.

The synthesis and optical properties of ZnO nanocombs

The ZnO nanocombs were synthesized by chemical vapor deposition method, which the uniform and dense nanotips were along one side of the comb ribbon. The growth mechanism was described as free catalyst self-assembled and vapor-solid model. The optical properties related with the surface states were investigated by Raman and PL spectra. The large redshift of 1LO phonon peak was attributed to the surface and interface states. The normalized PL spectra showed that the deep-level emission decreased for the sample to be annealed in O2 ambient at 500 degrees C. On the contrary, the deep-level emission increased while for the annealed sample in O2 ambient at 600 degrees C. The deep-level emission was attributed to the transition from the shallow donor to the deep acceptor. The XPS analysis showed the existence of oxygen rich and Zn deficient in the ZnO nanocombs annealed at 600 degrees C. The abnormal temperature dependence of integrated PL intensity was attributed to the abundant surface states.

Characterization and optical transition in tb-doped 12CaO x 7Al2O3 powders

Tb-doped 12CaO x 7Al2O3 (C12A7:Tb3+) powders with strong green emission were prepared using the sol-gel method. X-ray diffraction, micro-Raman spectra, scanning electron microscopy and absorption spectra showed that C12A7:Tb3+ powders with grain size of 200-300 nm were synthesized. Porous powders could be formed as the concentration of Tb3+ was 5 at%. The absorption band around 209 nm was attributed to the host lattice absorption, and the bands around 255 nm and 274 nm were related to the 4f-5d transitions of Tb3+. The absorption intensity of the visible region was enhanced due to the presence of one 100 nm-diameter hole in every grain of C12A7:Tb3+ powders. The emission spectra showed noticeable influence of Tb-Tb cross relaxation, which favored the green photoluminescence (PL) over the blue PL. The study on the concentration quenching indicated that the energy transfers depopulating the 5D3 and 5D4 levels were assigned to the mechanisms of electric dipole-dipole and exchange interaction, respectively.

Probing the visible luminescence mechanism in ZnO nanoparticles by band edge modulation

The visible luminescence mechanism of ZnO is an important but controversial problem. In this paper, we report the structural and optical properties of Mg-doped ZnO nanoparticles (approximately 3-4 nm) synthesized via the sol-gel method. X-ray diffraction (XRD) analysis and absorption spectra observations revealed that Mg ions replace Zn ions in the lattice. In the room temperature photoluminescence (PL) spectra, three emission bands, ultraviolet (UV), blue, and green, were observed. With increasing concentration of Mg, the near band edge (NBE) emission band progressively shifted to the higher energy side. The green emission in the visible emission band, however, presented an inconspicuous shift. The reason is probably that the bottom of the conduction band in ZnO is determined by the Zn 4s state, and the top of the valence band is determined by the O 2p state. Mg ions in ZnO substitute for zinc ions and enter a slightly distorted tetrahedral site, which causes the bottom of the ZnO conduction band to be shifted to higher energy and leaves the top of the valence band unchanged. This combined with the fact that the deep level position is insensitive to the shift of the band edge led us to conclude that the green emission originates from electronic transition between the deep defect level and the top of the valence band (or very shallow acceptor level).

Lack of association between AKT1 variances versus clinical manifestations and social function in patients with schizophrenia

The elucidation of genotype-phenotype relationships in psychiatric research is at an early stage. V-akt murine thymoma viral oncogene homolog 1 (AKT1) is a serine/threonine kinase known as protein kinase B. Emerging studies have implicated the role of AKT1 in pathogenesis of schizophrenia; however, the findings have not been consistent. This study aims to examine the association of AKT1 polymorphisms with drug-free and post-treatment symptomatology and social function in patients with schizophrenia. One hundred and twenty newly hospitalised patients with acutely exacerbated schizophrenia who had never been treated by atypical antipsychotics were recruited. They received optimal treatment of risperidone for up to 42 days in the inpatient research unit. Clinical manifestations were monitored by Positive and Negative Syndrome Scale (PANSS) and social function by Nurses' Observation Scale for Inpatients Evaluation (NOSIE). Patients were genotyped for eight AKT1 Single Nucleotide Polymorphism (SNPs), which have been previously investigated for association with schizophrenia. At drug-free status and after best possible treatment of risperidone, genotypes of each SNP did not influence performances in NOSIE, PANSS-total, -positive, -negative and -general psychopathology profiles. These results suggest that AKT1 does not play a significant role in clinical and functional manifestations in patients with schizophrenia who receive risperidone treatment. Future research should also focus on the relationships between genotypes of other susceptibility genes and phenotypes or functional outcomes of schizophrenia.

Compact optical curvature sensor with a flexible microdisk laser on a polymer substrate

We demonstrate a chip-scale compact optical curvature sensor. It consists of a low threshold InGaAsP microdisk laser on a flexible polydimethylsiloxane polymer substrate. The curvature dependence of lasing wavelength was characterized by bending the cavity at different bending radii. The measurements showed that the lasing wavelength decreases monotonously with an increasing bending curvature. A good agreement between experiment and three-dimensional finite-difference time-domain simulation was also obtained. The sensitivity of the compact device to the bending curvature is -23.7 nm/mm from the experiment.

Flexible compact microdisk lasers on a polydimethylsiloxane (PDMS) substrate

Compact microdisk cavities were fabricated on a polydimethylsiloxane substrate. The lasing of the flexible compact cavity was achieved with a low threshold power. The whispering-gallery mode of the microdisk was also characterized with three-dimensional finite-difference time-domain simulation. The curvature dependence in output power and threshold was also demonstrated by bending the microdisk cavity.

Persistent dizziness and nausea in patients receiving postoperative epidural pain control after living donor liver transplantation: case reports

Dizziness and nausea are frequent problems among patients receiving patient-controlled epidural analgesia (PCEA) after major surgery. It is important to consider the various etiologies that might cause these adverse events, especially among patients who have undergone massive hepatic resection for living donor liver transplantation (LDLT). We have described 2 LDLT cases with persistent dizziness and nausea postoperatively despite several adjustments in PCEA management. Their symptoms were quickly relieved after suspension of PCEA medication. Our 2 cases of LDLT represented a unique setting for this type of complication.

Effects of silymarin on the resolution of liver fibrosis induced by carbon tetrachloride in rats

Silymarin, a standardized extract of the milk thistle (Silybum marianum), has a long tradition as a herbal remedy, and was introduced as a hepatoprotective agent a few years ago. However, the therapeutic effects of silymarin remain undefined. Carbon tetrachloride (CCl4) is a xenobiotic used extensively to induce oxidative stress and is one of the most widely used hepatic toxins for experimental induction of liver fibrosis in the laboratory. In this study, we investigated the restoration of the CCl4-induced hepatic fibrosis by high dose of silymarin in rats. After treatment with oil (as normal group; n = 6) or CCl4 [as model (n = 7) and therapeutic (n = 7) groups] by intragastric delivery for 8 weeks for the induction of liver fibrosis, the rats in the normal and model group were administered orally normal saline four times a week for 3 weeks whilst the therapeutic group received silymarin (200 mg/kg). The histopathological changes were observed with Masson staining. The results showed that the restoration of the CCl4-induced damage of liver fibrosis in the therapeutic group was significantly increased as compared to that in the model group. Moreover, silymarin significantly decreased the elevation of aspartate aminotransferase (AST), alanine aminotransferase, and alkaline phosphatase in serum, and also reversed the altered expressions of alpha-smooth muscle actin in liver tissue. Therefore, these findings indicated that silymarin may have the potential to increase the resolution of the CCl4-induced liver fibrosis in rats.

Preparation and visible emission of Er-doped 12CaO x 7Al2O3 powder

Er(3+)-doped 12CaO x 7Al2O3 (C12A7:Er3+) powders were prepared using the sol-gel method. X-ray diffraction, micro-Raman spectra and absorption spectra showed that C12A7:Er3+ powder had been obtained. Sharp and intense Er(3+)-related emission from C12A7:Er3+ powder with different Er3+ concentrations in the visible region at room temperature was investigated by analyzing the local structure of Ca atoms in C12A7, and it revealed that cation sites with low symmetry of the host were beneficial to the photoluminescence of Er3+ ions. The emission lines were attributed to two types of Er3+ centers, isolated Er3+ ions and complex centers formed by aggregation of Er3+ ions. The PL intensity might be affected by free oxygen species relative to Er3+ ions formed by charge compensation. The inverse temperature dependent luminescence from the upper level of 2H11/2 state and that from the lower level of 4S3/2 state implied that the thermalization or thermal equilibrium of electrons between the two closely emission states occurred.

Photoluminescence of ZnO nanocrystals embedded in BaF2 matrices by magnetron sputtering

This paper describes ZnO nanocrystals embedded in BaF2 matrices by the magnetron sputtering method in an attempt to use fluoride as a shell layer to embed ZnO nanocrystals core. BaF2 is a wide-band gap material, and can confine carriers in the ZnO films. As a result, the exciton emission intensity should be enhanced. The sample was annealed at 773 K, and X-ray diffraction (XRD) results showed that ZnO nanocrystals with wurtzite structure were embedded in BaF2 matrices. Raman-scattering spectra also confirmed the formation of ZnO nanoparticles. Abnormal longitudinal-optical (LO) phonon-dominant multiphonon Raman scattering was observed in the sample. Room-temperature photoluminescence (PL) spectra showed an ultraviolet emission peak at 374 nm. The origin of the ultraviolet emission is discussed here with the help of temperature-dependent PL spectra. The ultraviolet emission band was a mixture of free exciton and bound exciton recombination observed in the low temperature PL spectra (at 77 K). Abnormal temperature dependence of ultraviolet near-band-edge emission-integrated intensity of the sample was observed. The band tail state was observed in the absorption spectra, illustrating that the impurity-related defects were caused by the shell of the BaF2 grain layer. For comparison, ZnO films on BaF2 substrates were also fabricated by the magnetron sputtering method, and the same measurement methods were used.