Optical effects of spin currents in semiconductors

A spin current has novel linear and second-order nonlinear optical effects due to its symmetry properties. With the symmetry analysis and the eight-band microscopic calculation we have systematically investigated the interaction between a spin current and a polarized light beam (or the "photon spin current") in direct-gap semiconductors. This interaction is rooted in the intrinsic spin-orbit coupling in valence bands and does not rely on the Rashba or Dresselhaus effect. The light-spin current interaction results in an optical birefringence effect of the spin current. The symmetry analysis indicates that in a semiconductor with inversion symmetry, the linear birefringence effect vanishes and only the circular birefringence effect exists. The circular birefringence effect is similar to the Faraday rotation in magneto-optics but involves no net magnetization nor breaking the time-reversal symmetry. Moreover, a spin current can induce the second-order nonlinear optical processes due to the inversion-symmetry breaking. These findings form a basis of measuring a pure spin current where and when it flows with the standard optical spectroscopy, which may provide a toolbox to explore a wealth of physics connecting the spintronics and photonics.Comment: 16 pages, 7 fig

Field-Induced Magnetostructural Transitions in Antiferromagnetic Fe1+yTe1-xSx

The transport and structural properties of Fe1+yTe1-xSx (x=0, 0.05, and 0.10) crystals were studied in pulsed magnetic fields up to 65 T. The application of high magnetic fields results in positive magnetoresistance effect with prominent hystereses in the antiferromagnetic state. Polarizing microscope images obtained at high magnetic fields showed simultaneous occurrence of structural transitions. These results indicate that magnetoelastic coupling is the origin of the bicollinear magnetic order in iron chalcogenides.Comment: 5 pages, 5 figures, accepted for publication in Journal of the Physical Society of Japa

SNP identification in unamplified human genomic DNA with gold nanoparticle probes

Single nucleotide polymorphisms (SNPs) comprise the most abundant source of genetic variation in the human genome. SNPs may be linked to genetic predispositions, frank disorders or adverse drug responses, or they may serve as genetic markers in linkage disequilibrium analysis. Thus far, established SNP detection techniques have utilized enzymes to meet the sensitivity and specificity requirements needed to overcome the high complexity of the human genome. Herein, we present for the first time a microarray-based method that allows multiplex SNP genotyping in total human genomic DNA without the need for target amplification or complexity reduction. This direct SNP genotyping methodology requires no enzymes and relies on the high sensitivity of the gold nanoparticle probes. Specificity is derived from two sequential oligonucleotide hybridizations to the target by allele-specific surface-immobilized capture probes and gene-specific oligonucleotide-functionalized gold nanoparticle probes. Reproducible multiplex SNP detection is demonstrated with unamplified human genomic DNA samples representing all possible genotypes for three genes involved in thrombotic disorders. The assay format is simple, rapid and robust pointing to its suitability for multiplex SNP profiling at the ‘point of care’

Multiplexed, rapid detection of H5N1 using a PCR-free nanoparticle-based genomic microarray assay

<p>Abstract</p> <p>Background</p> <p>For more than a decade there has been increasing interest in the use of nanotechnology and microarray platforms for diagnostic applications. In this report, we describe a rapid and simple gold nanoparticle (NP)-based genomic microarray assay for specific identification of avian influenza virus H5N1 and its discrimination from other major influenza A virus strains (H1N1, H3N2).</p> <p>Results</p> <p>Capture and intermediate oligonucleotides were designed based on the consensus sequences of the matrix (M) gene of H1N1, H3N2 and H5N1 viruses, and sequences specific for the hemaglutinin (HA) and neuraminidase (NA) genes of the H5N1 virus. Viral RNA was detected within 2.5 hours using capture-target-intermediate oligonucleotide hybridization and gold NP-mediated silver staining in the absence of RNA fragmentation, target amplification, and enzymatic reactions. The lower limit of detection (LOD) of the assay was less than 100 fM for purified PCR fragments and 10³TCID₅₀units for H5N1 viral RNA.</p> <p>Conclusions</p> <p>The NP-based microarray assay was able to detect and distinguish H5N1 sequences from those of major influenza A viruses (H1N1, H3N2). The new method described here may be useful for simultaneous detection and subtyping of major influenza A viruses.</p

Thermal fission rate around super-normal phase transition

Using Langer's $Im F$ method, we discuss the temperature dependence of nuclear fission width in the presence of dissipative environments. We introduce a low cut-off frequency to the spectral density of the environmental oscillators in order to mimic the pairing gap. It is shown that the decay width rapidly decreases at the critical temperature, where the phase transition from super to normal fluids takes place. Relation to the recently observed threshold for the dissipative fission is discussed.Comment: 12 pages, Latex, Submitted to Physical Review C for publication, 3 Postscript figures are available by request from [email protected]

Biometric Risk Factors for Angle Closure Progression After Laser Peripheral Iridotomy

IMPORTANCE: Laser peripheral iridotomy (LPI) is the most common primary treatment for primary angle closure disease (PACD). However, there are sparse data guiding the longitudinal care of PAC suspect (PACS) eyes after LPI. OBJECTIVE: To elucidate the anatomic effects of LPI that are associated with a protective outcome against progression from PACS to PAC and acute angle closure (AAC) and to identify biometric factors that predict progression after LPI. DESIGN, SETTING, AND PARTICIPANTS: This was a retrospective analysis of data from the Zhongshan Angle Closure Prevention (ZAP) trial, a study of mainland Chinese people aged 50 to 70 years with bilateral PACS who received LPI in 1 randomly selected eye. Gonioscopy and anterior-segment optical coherence tomography (AS-OCT) imaging were performed 2 weeks after LPI. Progression was defined as the development of PAC or an acute angle closure (AAC) attack. Cohort A included a random mix of treated and untreated eyes, and cohort B included only eyes treated with LPI. Univariable and multivariable Cox regression models were developed to assess biometric risk factors for progression in cohorts A and B. Data were analyzed from January 4 to December 22, 2022. MAIN OUTCOME AND MEASURE: Six-year progression to PAC or AAC. RESULTS: Cohort A included 878 eyes from 878 participants (mean [SD] age, 58.9 [5.0] years; 726 female [82.7%]) of whom 44 experienced progressive disease. In a multivariable analysis, treatment (hazard ratio [HR], 0.67; 95% CI, 0.34-1.33; P = .25) was no longer associated with progression after adjusting for age and trabecular iris space area at 500 μm (TISA at 500 μm) at the 2-week visit. Cohort B included 869 treated eyes from 869 participants (mean [SD] age, 58.9 [5.0] years; 717 female [82.5%]) of whom 19 experienced progressive disease. In multivariable analysis, TISA at 500 μm (HR, 1.33 per 0.01 mm2 smaller; 95% CI, 1.12-1.56; P = .001) and cumulative gonioscopy score (HR, 1.25 per grade smaller; 95% CI, 1.03-1.52; P = .02) at the 2-week visit were associated with progression. Persistent angle narrowing on AS-OCT (TISA at 500 μm ≤0.05 mm2; HR, 9.41; 95% CI, 3.39-26.08; P <.001) or gonioscopy (cumulative score ≤6; HR, 2.80; 95% CI, 1.13-6.93; P =.04) conferred higher risk of progression. CONCLUSIONS AND RELEVANCE: Study results suggest that persistent angle narrowing detected by AS-OCT or cumulative gonioscopy score was predictive of disease progression in PACS eyes after LPI. These findings suggest that AS-OCT and gonioscopy may be performed to identify patients at high risk of developing angle closure who may benefit from closer monitoring despite patent LPI

Aquatic Global Passive Sampling (AQUA-GAPS) Revisited – First Steps towards a Network of Networks for Organic Contaminants in the Aquatic Environment

Organic contaminants, in particular persistent organic pollutants (POPs), adversely affect water quality and aquatic food webs across the globe. As of now, there is no globally consistent information available on concentrations of dissolved POPs in water bodies. The advance of passive sampling techniques has made it possible to establish a global monitoring program for these compounds in the waters of the world, which we call the Aquatic Global Passive Sampling (AQUA-GAPS) network. A recent expert meeting discussed the background, motivations, and strategic approaches of AQUA-GAPS, and its implementation as a network of networks for monitoring organic contaminants (e.g., POPs and others contaminants of concern). Initially, AQUA-GAPS will demonstrate its operating principle via two proof-of-concept studies focused on the detection of legacy and emerging POPs in freshwater and coastal marine sites using both polyethylene and silicone passive samplers. AQUA-GAPS is set-up as a decentralized network, which is open to other participants from around the world to participate in deployments and to initiate new studies. In particular, participants are sought to initiate deployments and studies investigating the presence of legacy and emerging POPs in Africa, Central and South America

Reducing Constraints in a Higher Dimensional Extension of the Randall and Sundrum Model

In order to investigate the phenomenological implications of warped spaces in more than five dimensions, we consider a $4+1+\delta$ dimensional extension to the Randall and Sundrum model in which the space is warped with respect to a single direction by the presence of an anisotropic bulk cosmological constant. The Einstein equations are solved, giving rise to a range of possible spaces in which the $\delta$ additional spaces are warped. Here we consider models in which the gauge fields are free to propagate into such spaces. After carrying out the Kaluza Klein (KK) decomposition of such fields it is found that the KK mass spectrum changes significantly depending on how the $\delta$ additional dimensions are warped. We proceed to compute the lower bound on the KK mass scale from electroweak observables for models with a bulk $SU(2)\times U(1)$ gauge symmetry and models with a bulk $SU(2)_R\times SU(2)_L\times U(1)$ gauge symmetry. It is found that in both cases the most favourable bounds are approximately $M_{KK}\gtrsim 2$ TeV, corresponding to a mass of the first gauge boson excitation of about 4-6 TeV. Hence additional warped dimensions offer a new way of reducing the constraints on the KK scale.Comment: 27 pages, 15 figures, v3: Additional comments in sections 1, 2 and 4. New appendix added. Five additional figures. References adde