In vitro antimicrobial activity of Cymbopogon citratus (lemongrass) extracts against selected foodborne pathogens

Microbial contamination in food system poses risk towards public health. The usage of synthetic and chemical preservatives to prevent the contamination has become a growing concern due to the presence of deleterious and harmful substances that can cause environment and health problems in prolonged exposure. Thus, there are needs to overcome this problem by using natural products as food preservatives. In this study, the antimicrobial activities of methanolic Cymbopogon citratus (lemongrass) extracts were tested against five foodborne pathogens, namely Bacillus cereus, Escherichia coli O157:H7, Klebsiella pneumoniae, Staphylococcus aureus and Candida albicans. The susceptibility test, minimum inhibitory concentrations (MIC) and minimum bactericidal concentration (MBC) or minimum fungicidal concentration (MFC) were conducted using the broth microdilution techniques as described by Clinical and Laboratory Standard Institute (CLSI). C. citratus extract showed antimicrobial activity against all tested foodborne pathogens; B. cereus, E. coli O157:H7, K. pneumoniae, S. aureus and C. albicans with the inhibition zone of 12 mm, 7.5 mm, 11 mm, 10 mm and 9 mm, respectively. The MIC of C. citratus extract against B. cereus, E. coli O157:H7, K. pneumoniae, S. aureus and C. albicans was 0.08 mg/ml, 0.63 mg/ml, 0.04 mg/ml, 0.31 mg/ml, and 0.16 mg/ml, respectively, while the MBC or MFC was 1.25 mg/ml, 2.50 mg/ml, 2.50 mg/ml, 1.25 mg/ml and 1.25 mg/ml, respectively. Time-kill curves were determined to assess the correlation between MIC and bactericidal activity of C. citratus extract at concentrations ranging from 0× MIC to 4× MIC. The bactericidal endpoint for B. cereus, E. coli O157:H7, S. aureus and C. albicans was at 4× MIC after 2 h, 4× MIC after 2 h, 4× MIC after 30 min and 4× MIC after 4 h, respectively whereas K. pneumoniae was not completely killed after 4 hours of incubation at 4× MIC. The potent antimicrobial activity of C. citratus extract may support its usage as natural antimicrobial agent

Induced Ferromagnetism at BiFeO3/YBa2Cu3O7 Interfaces

Transition metal oxides (TMOs) exhibit many emergent phenomena ranging from high-temperature superconductivity and giant magnetoresistance to magnetism and ferroelectricity. In addition, when TMOs are interfaced with each other, new functionalities can arise, which are absent in individual components. Here, we report results from first-principles calculations on the magnetism at the BiFeO3/YBa2Cu3O7 interfaces. By comparing the total energy for various magnetic spin configurations inside BiFeO3, we are able to show that a metallic ferromagnetism is induced near the interface. We further develop an interface exchange-coupling model and place the extracted exchange coupling interaction strengths, from the first-principles calculations, into a resultant generic phase diagram. Our conclusion of interfacial ferromagnetism is confirmed by the presence of a hysteresis loop in field-dependent magnetization data. The emergence of interfacial ferromagnetism should have implications to electronic and transport properties.Comment: 13 pages, 4 figure

A high flux source of cold strontium atoms

We describe an experimental apparatus capable of achieving a high loading rate of strontium atoms in a magneto-optical trap operating in a high vacuum environment. A key innovation of this setup is a two dimensional magneto-optical trap deflector located after a Zeeman slower. We find a loading rate of 6x10^9/s whereas the lifetime of the magnetically trapped atoms in the 3P2 state is 54s.Comment: 12 pages, 16 figure

Optical Properties of Organometallic Perovskite: An ab initio Study using Relativistic GW Correction and Bethe-Salpeter Equation

In the development of highly efficient photovoltaic cells, solid perovskite systems have demonstrated unprecedented promise, with the figure of merit exceeding nineteen percent of efficiency. In this paper, we investigate the optical and vibrational properties of organometallic cubic perovskite CH3NH3PbI3 using first-principles calculations. For accurate theoretical description, we go beyond conventional density functional theory (DFT), and calculated optical conductivity using relativist quasi-particle (GW) correction. Incorporating these many-body effects, we further solve Bethe-Salpeter equations (BSE) for excitons, and found enhanced optical conductivity near the gap edge. Due to the presence of organic methylammonium cations near the center of the perovskite cell, the system is sensitive to low energy vibrational modes. We estimate the phonon modes of CH3NH3PbI3 using small displacement approach, and further calculate the infrared absorption (IR) spectra. Qualitatively, our calculations of low-energy phonon frequencies are in good agreement with our terahertz measurements. Therefore, for both energy scales (around 2 eV and 0-20 meV), our calculations reveal the importance of many-body effects and their contributions to the desirable optical properties in the cubic organometallic perovskites system.Comment: 5 pages, 4 figure

Ontology-Based Privacy Protection in Location Commerce

Location commerce extends e-commerce through the provision of location-related activities, but this gives rise to greater concerns about privacy invasion. To encourage the smooth growth of location commerce, it is suggested that control over the sharing of intimate information be given back to the consumer. This study proposes an ontology-based privacy protection (OPP) framework that allows consumers to specify their own privacy preferences and then uses these preferences to determine whether or not a message from a merchant can be delivered to a consumer. We use ontology to structure the knowledge to simplify the framework and allow for the possibility of automation. The system is believed to be context-aware, as the location, time, service type, information type, and other contextual data are taken into consideration. We develop a prototype system for demonstration and experiment, and show that the framework design is feasible and has a reasonable performance

Penetration depth study of LaOs4_4Sb12_{12}: Multiband s-wave superconductivity

We measured the magnetic penetration depth $\lambda(T)$ in single crystals of LaOs$_{4}$Sb$_{12}$ ($T_c$=0.74 K) down to 85 mK using a tunnel diode oscillator technique. The observed low-temperature exponential dependence indicates a s-wave gap. Fitting the low temperature data to BCS s-wave expression gives the zero temperature gap value $\Delta (0)= (1.34 \pm 0.07) k_B T_c$ which is significantly smaller than the BCS value of 1.76$k_B T_c$. In addition, the normalized superfluid density $\rho(T)$ shows an unusually long suppression near $T_c$, and are best fit by a two-band s-wave model.Comment: 5 pages, 2 figure

The Impact of Biculturalism on Language and Literacy Development: Teaching Chinese English Language Learners

According to the 2000 United States Census, Americans age five and older who speak a language other than English at home grew 47 percent over the preceding decade. This group accounts for slightly less than one in five Americans (17.9%). Among the minority languages spoken in the United States, Asian-language speakers, including Chinese and other Asian and Pacific Islander languages, have increased by more than 75 percent. Futher, the proportion of Asian language speakers having difficulty speaking English has almost doubled (Klein, Bugarin, Beitranena, & McArthur, 2004). Today, Chinese students are one of the largest groups of English Language Learners (ELLs) in the U.S. Children of Chinese immigrants to the U. S. face linguistic, cultural, and academic challenges. For teachers to be adequately prepared to design and implement instruction for Chinese ELLs, they must have an understanding of this population, the language differences between Chinese and English, and the most effective strategies for scaffolding language and literacy success. This article highlights two Chinese second-graders and their unique educational needs in order to provide insight and implications for instructing Chinese ELLs

Mutant glycyl-tRNA synthetase (Gars) ameliorates SOD1G93A motor neuron degeneration phenotype but has little affect on Loa dynein heavy chain mutant mice

Background: In humans, mutations in the enzyme glycyl-tRNA synthetase (GARS) cause motor and sensory axon loss in the peripheral nervous system, and clinical phenotypes ranging from Charcot-Marie-Tooth neuropathy to a severe infantile form of spinal muscular atrophy. GARS is ubiquitously expressed and may have functions in addition to its canonical role in protein synthesis through catalyzing the addition of glycine to cognate tRNAs. Methodology/Principal findings: We have recently described a new mouse model with a point mutation in the Gars gene resulting in a cysteine to arginine change at residue 201. Heterozygous Gars^{C201R/+} mice have locomotor and sensory deficits. In an investigation of genetic mutations that lead to death of motor and sensory neurons, we have crossed the Gars^{C201R/+} mice to two other mutants: the TgSOD1^{G93A} model of human amyotrophic lateral sclerosis and the Legs at odd angles mouse (Dync1h1^{Loa}) which has a defect in the heavy chain of the dynein complex. We found the Dync1h1^{Loa/+}; Gars^{C201R/+} double heterozygous mice are more impaired than either parent, and this is may be an additive effect of both mutations. Surprisingly, the Gars^{C201R} mutation significantly delayed disease onset in the SOD1^{G93A}; Gars^{C201R/+} double heterozygous mutant mice and increased lifespan by 29% on the genetic background investigated. Conclusions/Significance: These findings raise intriguing possibilities for the study of pathogenetic mechanisms in all three mouse mutant strains

Electrophysiological and Psychophysical Studies of Meridional Anisotropies in Children With and Without Astigmatism.

Purpose: We investigated the pattern of meridional anisotropies, if any, for pattern onset-offset visual evoked potential (POVEPs) responses and psychophysical grating acuity (GA) in children with normal letter visual acuity (20/20 or better). Methods: A total of 29 children (aged 3-9 years), nine of whom were astigmatic (AS), were recruited. Orientation-specific monocular POVEPs were recorded in response to sinewave grating stimuli oriented along the subjects' principal AS meridians. Horizontal and vertical gratings were designated Meridians 1 and 2, respectively, for nonastigmatic patients (Non-AS). Binocular POVEPs in response to the same stimuli, but oriented at 45°, 90°, 135°, and 180°, were recorded. Psychophysical GAs were assessed monocularly and binocularly along the same meridians using the same stimuli by a 2-alternative-forced-choice staircase technique. The C3 amplitudes and peak latencies of the POVEP and GAs were compared across meridians using linear mixed models (monocular) and ANOVA (binocular). Results: There were significant meridional anisotropies in monocular C3 amplitudes regardless of astigmatism status (P = 0.001): Meridian 2 (mean ± SE Non-AS, 30.13 ± 2.07 μV; AS, 26.53 ± 2.98 μV) was significantly higher than Meridian 1 (Non-AS, 26.14 ± 1.87 μV; AS, 21.68 ± 2.73 μV; P = 0.019), but no meridional anisotropies were found for GA or C3 latency. Binocular C3 amplitude in response to horizontally oriented stimuli (180°, 29.71 ± 3.06 μV) was significantly lower than the oblique (45°, 36.62 ± 3 .05 μV; P = 0.03 and 135°, 35.95 ± 2.92 μV; P = 0.04) and vertical (90°, 37.82 ± 3.65 μV; P = 0.02) meridians, and binocular C3 latency was significantly shorter in response to vertical than oblique gratings (P ≤ 0.001). Conclusions: Meridional anisotropy was observed in children with normal vision. The findings suggest that horizontal gratings result in a small, but significantly lower POVEP amplitude than for vertical and oblique gratings