The Suppression of Radiation Reaction and Laser Field Depletion in Laser-Electron beam interaction

The effects of radiation reaction (RR) have been studied extensively by using the ultraintense laser interacts with the counter-propagating relativistic electron. At the laser intensity at the order of $10^{23}$ W/cm$^2$, the effects of RR are significant in a few laser period for a relativistic electron. However, the laser at such intensity is tightly focused and the laser energy is usually assumed to be fixed. Then, the signal of RR and energy conservation cannot be guaranteed. To assess the effects of RR in a tightly focused laser pulse and the evolution of the laser energy, we simulate this interaction with a beam of $10^9$ electrons by means of Particle-in-Cell (PIC) method. We observed that the effects of RR are suppressed due to the ponderomotive force and accompanied by a non-negligible amount of laser field energy reduction. This is due to the ponderomotive force that prevents the electrons from approaching the center of the laser pulse and leads to the interaction at weaker field region. At the same time, the laser energy is absorbed through ponderomotive acceleration. Thus, the kinetic energy of the electron beam has to be carefully selected such that the effects of RR become obvious.Comment: 6 pages, 3 figure

Improvement of dielectric loss of doped Ba0.5Sr0.5TiO3 thin films for tunable microwave devices

Al2O3-Ba0.5Sr0.5TiO3 (Al2O3-BST) thin films, with different Al2O3 contents, were deposited on (100) LaAlO3 substrate by pulsed laser deposition (PLD) technique. The Al2O3-BST films was demosnstrated to be a suitable systems to fabricate ferroelectric thin films with low dielectric loss and higher figure of merit for tunable microwave devices. Pure BST thin films were also fabricated for comparison purpose. The films' structure and morphology were analyzed by X-ray diffractiopn and scanning electron microscopy, respectively; nad showed that the surface roughness for the Al2O3-BST films increased with the Al2O3 content. Apart from that, the broadening in the intensity peak in XRD result indicating the grain size of the Al2O3-BST films reduced with the increasing of Al2O3 dopant. We measured the dielctric properties of Al2O3-BST films with a home-made non-destructive dual resonator method at frequency ~ 7.7 GHZ. The effect of doped Al2O3 into BST thin films significantly reduced the dielectric constant, dielectric loss and tunability compare to pure BST thin film. Our result shows the figure of merit (K), used to compare the films with varied dielectric properties, increased with the Al2O3 content. Therefore Al2O3-BST films show the potential to be exploited in tunable microwave devices.Comment: 8 pages, 4 figures, 1 table. Accepted & tentatively for Feb 15 2004 issue, Journal of Applied Physic

Levetiracetam-induced psychosis in a Filipino female diagnosed with anti-N-methyl-D-aspartate receptor encephalitis: a case report

Levetiracetam (LEV), an SV2A inhibitor is a widely available anti-epileptic drug that is used to treat a range of partial and generalized seizure and juvenile myoclonic epilepsy. It is generally well tolerated and deemed safe due to the absence of drug-to-drug interaction. Despite its safety, there are adverse effects that can lead to the discontinuation of this anti-seizure medication. Some of the reported infrequent adverse effects are mood-related changes including agitation, depression, anxiety and suicidal ideations that can be observed after initiation or rapid up titration of the medication. The mechanism for this is still unknown but there are certain theories that attempted to determine the association. Risk factors reported were female sex, temporal lobe involvement and history of psychiatric disorder. In this case report, we present a 30-year-old female without history of psychiatric illness diagnosed with anti N-methyl-D-aspartate receptor (NMDAR) encephalitis who presented with seizure and was started on LEV for seizure control. She developed aggression and suicidal ideations secondary to initiation and up-titration of LEV. The symptoms resolved after discontinuation of the said medication.

Mobile radio interferometric geodetic systems

Operation of the Astronomical Radio Interferometric Earth Surveying (ARIES) in a proof of concept mode is discussed. Accuracy demonstrations over a short baseline, a 180 km baseline, and a 380 km baseline are documented. Use of ARIES in the Sea Slope Experiment of the National Geodetic Survey to study the apparent differences between oceanographic and geodetic leveling determinations of the sea surface along the Pacific Coast is described. Intergration of the NAVSTAR Global Positioning System and a concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) is briefly reviewed

Proteomic Analysis of Bacterial Expression Profiles Following Exposure to Organic Solvent Flower Extract of Melastoma candidum D Don (Melastomataceae)

Purpose: To identify potential antibacterial protein targets following exposure to Melastoma candidum extract.Methods: Plant extracts were prepared using sequential extraction method. Denaturing gel electrophoresis and MALDI TOF-TOF MS protein sequencing were used to identify differentialexpressed bacterial proteins. 96-well microplate method was used to determine the minimum inhibitory concentration (MIC) values. Thin layer chromatography (TLC) bio-autobiography and gaschromatography-mass spectrometry (GC-MS) were performed to determine the phytochemicals in the active fraction.Results: Five differentially expressed bacterial proteins (four from Escherichia coli and one from Staphylococcus aureus), were identified via proteomic approach. Among the bacterial proteins identified, glutamate decarboxylase, elongation factor-Tu and α-hemolysin are especially noteworthy, as they are implicated in critical bacterial pathways pertaining to survival in acidic environment, protein translation and virulence, respectively. Additionally, we tested and reported the minimum inhibition concentrations of different M. candidum fractions and gas chromatography-mass spectrometry GC-MS analysis of the active fraction.Conclusion: Glutamate decarboxylase, elongation factor-Tu and α-hemolysin represent potential antibacterial targets.Keywords: Escherichia coli, Staphylococcus aureus, Melastoma candidum, Glutamate decarboxylase, Elongation factor-Tu, α-Hemolysin, Protein expressio

Reactive Hall constant of Strongly Correlated Electrons

The zero-temperature Hall response within tight-binding models of correlated electrons is studied. Using the linear response theory and a linearization in the magnetic field B, a general relation for the reactive (zero frequency) Hall constant in the fast (transport) limit is derived, involving only matrix elements between the lowest excited states at B=0; for noninteracting fermions, the Boltzmann expression is reproduced. For a Fermi liquid with a well defined Fermi surface and linear gapless excitations an analogous expression is found more generally. In the specific case of quasi-one-dimensional correlated systems a relation of $R^0_H$ to the charge stiffness D is recovered. Similar analysis is performed and discussed for D and the compressibility.Comment: 8 pages, submitted to Phys.Rev.

Evaluation of Glucosidase Inhibitory and Cytotoxic Potential of Five Selected Edible and Medicinal Ferns

Purpose: To evaluate the glucosidase inhibitory and cytotoxic activities of five selected edible and medicinal ferns, namely, Blechnum orientale, Davallia denticulata, Diplazium esculentum, Nephrolepis biserrata, and Pteris vittata.Methods: The aqueous extracts of the five ferns were prepared by water extraction at 90 ºC for 1 h. Antiglucosidase assay was used to determine the effect of each extract on yeast alpha-glucosidase activity in vitro. Cytotoxicity was evaluated using methylthiazol tetrazolium assay on chronic myelogenous leukaemia cell line (K562). The phenolic, hydroxycinnamic acid, flavonoid and proanthocyanidin contents of the extracts were also determined.Results: The α-glucosidase inhibitory activity of D. esculentum (half maximal effective concentration, EC50 = 6.85 μg/ml) was considerably stronger than that of myricetin (EC50 = 53.21 μg/ml). B. orientale, D. esculentum, N. biserrata, and P. vittata were cytotoxic to K562 cells. P. vittata had the strongest cytotoxicity, although it was less potent than 5-fluorouracil. D. denticulata had the highest phenolic, hydroxycinnamic acid and flavonoid contents of all the extracts while B. orientale had the highest proanthocyanidin content.Conclusion: Among the five ferns evaluated, D. esculentum is a potential source of an antidiabetic agent and is recommended for further investigation in this regard. All the fern extracts, except D. denticulata, exhibited dose-dependent cytotoxicity against K562 cells.Keywords: Medicinal fern, α-Glucosidase inhibition, Cytotoxicity, Blechnum orientale, Davallia denticulata, Diplazium esculentum, Nephrolepis biserrata, Pteris vittat

Umklapp scattering from spin fluctuations in Copper-Oxides

The $\mathbf k$-dependent electronic momentum relaxation rate due to Umklapp scattering from antiferromagnetic spin fluctuations is studied within a renormalized mean-field approach to an extended $t-J$ model appropriate to YBa$_2$Cu$_3$O$_{7-x}$ and other cuprates. Transport coefficients are calculated in a relaxation time approximation. We compare these results with those obtained with the phenomenological assumption that all scattering processes dissipate momentum. We show that the latter, which violates momentum conservation, leads to quite different magnitudes and temperature dependences of resistivities and Hall coefficients.Comment: replaced by LaTeX file (due to problems with PostScript

Topological Dislocations and Mixed State of Charge Density Waves

We discuss the possibility of the ``mixed state'' in incommensurate charge density waves with three-dimensional order. It is shown that the mixed state can be created by applying an electric field perpendicular to the chains. This state consists of topological dislocations induced by the external field and is therefore similar to the mixed states of superfluids (type-II superconductor or liquid Helium II). However, the peculiar coupling of charge density waves with the electric field strongly modifies the nature of the mixed state compared to the conventional superfluids. The field and temperature dependence of the properties of the mixed state are studied, and some experimental aspects are discussed.Comment: 10 pages, Revtex format, no figures, to appear in Phys. Rev. Let