Surface-wave-enabled darkfield aperture for background suppression during weak signal detection

Sensitive optical signal detection can often be confounded by the presence of a significant background, and, as such, predetection background suppression is substantively important for weak signal detection. In this paper, we present a novel optical structure design, termed surface-wave-enabled darkfield aperture (SWEDA), which can be directly incorporated onto optical sensors to accomplish predetection background suppression. This SWEDA structure consists of a central hole and a set of groove pattern that channels incident light to the central hole via surface plasmon wave and surface-scattered wave coupling. We show that the surface wave component can mutually cancel the direct transmission component, resulting in near-zero net transmission under uniform normal incidence illumination. Here, we report the implementation of two SWEDA structures. The first structure, circular-groove-based SWEDA, is able to provide polarization-independent suppression of uniform illumination with a suppression factor of 1230. The second structure, linear-groove-based SWEDA, is able to provide a suppression factor of 5080 for transverse-magnetic wave and can serve as a highly compact (5.5 micrometer length) polarization sensor (the measured transmission ratio of two orthogonal polarizations is 6100). Because the exact destructive interference balance is highly delicate and can be easily disrupted by the nonuniformity of the localized light field or light field deviation from normal incidence, the SWEDA can therefore be used to suppress a bright background and allow for sensitive darkfield sensing and imaging (observed image contrast enhancement of 27 dB for the first SWEDA)

Influence of the anion potential on the charge ordering in quasi-one dimensional charge transfer salts

We examine the various instabilities of quarter-filled strongly correlated electronic chains in the presence of a coupling to the underlying lattice. To mimic the physics of the (TMTTF)$_2$X Bechgaard-Fabre salts we also include electrostatic effects of intercalated anions. We show that small displacements of the anion can stabilize new mixed Charged Density Wave-Bond Order Wave phases in which central symmetry centers are suppressed. This finding is discussed in the context of recent experiments. We suggest that the recently observed charge ordering is due to a cooperative effect between the Coulomb interaction and the coupling of the electronic stacks to the anions. On the other hand, the Spin-Peierls instability at lower temperature requires a Peierls-like lattice coupling.Comment: Latex, 4 pages, 4 postscript figure

Coexistence of charge density wave and spin-Peierls orders in quarter-filled quasi-one dimensional correlated electron systems

Charge and spin-Peierls instabilities in quarter-filled (n=1/2) compounds consisting of coupled ladders and/or zig-zag chains are investigated. Hubbard and t-J models including local Holstein and/or Peierls couplings to the lattice are studied by numerical techniques. Next nearest neighbor hopping and magnetic exchange, and short-range Coulomb interactions are also considered. We show that, generically, these systems undergo instabilities towards the formation of Charge Density Waves, Bond Order Waves and (generalized) spin-Peierls modulated structures. Moderate electron-electron and electron-lattice couplings can lead to a coexistence of these three types of orders. In the ladder, a zig-zag pattern is stabilized by the Holstein coupling and the nearest-neighbor Coulomb repulsion. In the case of an isolated chain, bond-centered and site-centered 2k_F and 4k_F modulations are induced by the local Holstein coupling. In addition, we show that, in contrast to the ladders, a small charge ordering in the chains, strongly enhances the spin-Peierls instability. Our results are applied to the NaV_2O_5 compound (trellis lattice) and various phases with coexisting charge disproportionation and spin-Peierls order are proposed and discussed in the context of recent experiments. The role of the long-range Coulomb potential is also outlined.Comment: 10 pages, Revtex, 10 encapsulated figure

Neuroprotective Effects against Glutamate-Induced HT-22 Hippocampal Cell Damage and Caenorhabditis elegans Lifespan/Healthspan Enhancing Activity of Auricularia polytricha Mushroom Extracts.

Oxidative stress is associated with several diseases, particularly neurodegenerative diseases, commonly found in the elderly. The attenuation of oxidative status is one of the alternatives for neuroprotection and anti-aging. Auricularia polytricha (AP), an edible mushroom, contains many therapeutic properties, including antioxidant properties. Herein, we report the effects of AP extracts on antioxidant, neuroprotective, and anti-aging activities. The neuroprotective effect of AP extracts against glutamate-induced HT-22 neuronal damage was determined by evaluating the cytotoxicity, intracellular reactive oxygen species (ROS) accumulation, and expression of antioxidant enzyme genes. Lifespan and healthspan assays were performed to examine the effects of AP extracts from Caenorhabditis elegans. We found that ethanolic extract (APE) attenuated glutamate-induced HT-22 cytotoxicity and increased the expression of antioxidant enzyme genes. Moreover, APE promoted in the longevity and health of the C. elegans. Chemical analysis of the extracts revealed that APE contains the highest quantity of flavonoids and a reasonable percentage of phenols. The lipophilic compounds in APE were identified by gas chromatography/mass spectrometry (GC/MS), revealing that APE mainly contains linoleic acid. Interestingly, linoleic acid suppressed neuronal toxicity and ROS accumulation from glutamate induction. These results indicate that AP could be an exciting natural source that may potentially serves as neuroprotective and anti-aging agents

Mushroom-derived bioactive compounds potentially serve as the inhibitors of SARS-CoV-2 main protease: An in silico approach

Background and aim Coronavirus Disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has now become the world pandemic. There is a race to develop suitable drugs and vaccines for the disease. The anti-HIV protease drugs are currently repurposed for the potential treatment of COVID-19. The drugs were primarily screened against the SARS-CoV-2 main protease. With an urgent need for safe and effective drugs to treat the virus, we have explored natural products isolated from edible and medicinal mushrooms that have been reported to possess anti-HIV protease. Experimental procedures We have examined 36 compounds for their potential to be SARS-CoV-2 main protease inhibitors using molecular docking study. Moreover, drug-likeness properties including absorption, distribution, metabolism, excretion and toxicity were evaluated by in silico ADMET analysis. Results Our AutoDock study showed that 25 of 36 candidate compounds have the potential to inhibit the main viral protease based on their binding affinity against the enzyme’s active site when compared to the standard drugs. Interestingly, ADMET analysis and toxicity prediction revealed that 6 out of 25 compounds are the best drug-like property candidates, including colossolactone VIII, colossolactone E, colossolactone G, ergosterol, heliantriol F and velutin. Conclusion Our study highlights the potential of existing mushroom-derived natural compounds for further investigation and possibly can be used to fight against SARS-CoV-2 infection. Taxonomy (classification by evise) Disease, Infectious Disease, Respiratory System Disease, Covid-19, Traditional Medicine, Traditional Herbal Medicine, Phamaceutical Analysis

Proton Stability in Six Dimensions

We show that Lorentz and gauge invariance explain the long proton lifetime within the standard model in six dimensions. The baryon-number violating operators have mass dimension 15 or higher. Upon TeV-scale compactification of the two universal extra dimensions on a square $T^2/Z_2$ orbifold, a discrete subgroup of the 6-dimensional Lorentz group continues to forbid dangerous operators.Comment: PRL accepted versio

Ferromagnetic effect and spin assignment for the 390 keV state in 62Cu

The 390 keV isomeric state of 62Cu is assigned as Jπ = 4+. The magnetic hyperfine interaction has been observed in the 60Ni(α, pnγ) 62Cu reaction and the deduced Larmor period is consistent with known values of g and the hyperfine field of Cu in Ni