MEMBRANE IMMOBILIZED REACTIVE Fe/Pd NANOPARTICLES: MODELING AND TCE DEGRADATION RESULTS

Detoxification of chlorinated organic compound is an important and urgent issue in water remediation nowadays. Trichloroethylene (TCE), as a model compound in this study, has been proved to be degraded effectively by bimetallic nanoparticles (NPs) in solution phase. In this study, Fe/Pd bimetallic NPs were synthesized in poly (acrylic acid) (PAA) functionalized polyvinylidene fluoride (PVDF) microfiltration membranes. TCE dechlorination with these bimetallic NPs was conducted under different pH values and different metal loadings to study the role of corrosion on reaction rates. One-dimensional mathematical model with pseudo first-order reaction kinetic was introduced to discuss the TCE dechlorination profile in membrane system. Reduction reaction in pores is affected by several parameters including NP loading and size, TCE diffusivity, void volume fraction and surface-area-based reaction rates. This model result indicated that modification is needed to correct the reaction rate obtained from bulk solution in order to represent the actual efficiency of NPs on reduction reaction. In addition, TCE dechlorination mainly occurred near NPs’ surface. Second part of model indicated that reduction mechanism with TCE adsorption-desorption behavior could be used to discuss dechlorination with a high TCE concentration

Enhanced Coupling Strength Gratings for Outcouplers in Optical Waveguides

Gratings used for silicon photonic waveguides were demonstrated with outcoupling efficiency greater than 60% in a short grating length of 13 µm at a wavelength of 1550 nm. Due to problems of generating light from silicon, light has to be generated by either growing III-V material, wafer bonding III-V material to silicon, or externally generated light has to be coupled into and out of silicon photonic waveguides. Gratings have been used in semiconductor lasers to obtain single frequency operation. Some applications such as telecommunications require a narrow and single spectral line. And such single frequency lasers are typically distributed Bragg reflector (DBR) lasers or distributed feedback (DFB) lasers. Gratings used for both DBR and DFB lasers in III-V materials are generally hundreds of micrometers long due to a low index contrast at the grating interface, a low grating confinement factor, or a low value of the electric field at the grating interface. If the short gratings demonstrated in silicon photonic waveguides could be obtained in III-V semiconductor waveguides, lasers could incorporate such short gratings to couple light into silicon photonic circuits. Addition of a thin, low-index liner layer over a surface grating combined with a high-index layer can result in short, efficient couplers for III-V waveguides with performance similar to grating couplers in silicon photonic waveguides. The same low-index liner and high index cover layer can also minimize reflections at transitions between sections of photonic integrated circuits or between a laser region and a DBR or grating coupler region. A detailed design of an enhanced coupling strength (ECS) grating integrated with a 9-QW and 5-QW laser structure emitting at a wavelength near 1550 nm has been presented. Both designs allow outcoupling of greater than 70% of the emitted light in a distance of about 20 µm in a single pass, which is a reduction of outcoupler grating length in such III-V waveguides by a factor of 50 or more compared to conventional grating outcouplers. Moreover, the ECS approach also allows designing a second-order grating that has near 100% reflection with insignificant outcoupling. Such a grating can provide equivalent performance at twice the grating period as a first order DBR grating, allowing the holographic fabrication of low-loss reflective gratings to laser wavelengths below 400 nm from the previous limit of about 800 nm

IceCube Non-detection of GRBs: Constraints on the Fireball Properties

The increasingly deep limit on the neutrino emission from gamma-ray bursts (GRBs) with IceCube observations has reached the level that could put useful constraints on the fireball properties. We first present a revised analytic calculation of the neutrino flux, which predicts a flux an order of magnitude lower than that obtained by the IceCube collaboration. For benchmark model parameters (e.g. the bulk Lorentz factor is \Gamma=10^{2.5}, the observed variability time for long GRBs is t_v=0.01 s and the ratio between the energy in accelerated protons and in radiation is \eta_p=10 for every burst) in the standard internal shock scenario, the predicted neutrino flux from 215 bursts during the period of the 40-string and 59-string configurations is found to be a factor of ~3 below the IceCube sensitivity. However, if we accept the recently found inherent relation between the bulk Lorentz factor and burst energy, the expected neutrino flux increases significantly and the spectral peak shifts to lower energy. In this case, the non-detection then implies that the baryon loading ratio should be \eta_p<10 if the variability time of long GRBs is fixed to t_v=0.01 s. Instead, if we relax the standard internal shock scenario but keep to assume \eta_p=10, the non-detection constrains the dissipation radius to be R>4x10^{12} cm assuming the same dissipation radius for every burst and benchmark parameters for fireballs. We also calculate the diffuse neutrino flux from GRBs for different luminosity functions existing in the literature. The expected flux exceeds the current IceCube limit for some luminosity functions, and thus the non-detection constrains \eta_p<10 in such cases when the variability time of long GRBs is fixed to t_v=0.01 s.Comment: Accepted by ApJ, 14 pages, 5 figures, typos corrected, scheduled for the June 10, 2012, v752 - 1 issu

Choked jet model for the neutrino emission associated with Tidal Disruption Events

Three tidal disruption event (TDE) candidates (AT2019dsg, AT2019fdr, AT2019aalc) have been found to be coincident with high energy astrophysical neutrinos in multi-messenger follow-ups. Recent studies suggest the presence of a quasi-spherical, optically thick envelope around the supermassive black holes in TDEs, resulted from stellar debris after the disruption. We study whether the neutrino signal can be explained by choked relativistic jets inside the envelope. While powerful jets, such as that in Swift J1644+57, can successfully break out the envelope, those with relatively weak power could be choked by the envelope. Choked jets can still accelerate cosmic rays through internal shocks or reverse shocks deep in the envelope, which further produce high-energy neutrinos via interaction with the thermal photons in the envelope. We explore the parameter space of the jets that can produce detectable neutrino flux while being choked. Under reasonable assumption about the envelope mass, we find that the cumulative neutrino numbers of three TDEs are consistent with the expected range imposed by observations. Compared with other proposed models, the relativistic bulk motion of the jets in our model can magnify the neutrino flux by Lorentz boosting. The neutrino time delay relative to the optical peak time of TDEs can be explained as the jet propagation time in the envelope before being choked. The discovery of TDE-associated neutrino events may suggest that jets might have been commonly formed in TDEs, as expected from super-Eddington accretion, but most of them are too weak to break out of the envelopes.Comment: 9 pages, 4 figures, submitted, comments are welcom

A Two-component Jet Model for the TeV and Multi-wavelength Afterglows of GRB 221009A

The TeV afterglow of BOAT GRB 221009A is interpreted as arising from a narrow jet while the radio to X-ray afterglows are interpreted as arising from a wide structured jet. However, there is no model explaining the TeV and lower-energy multi-wavelength afterglows simultaneously. We here investigate a two-component jet model, including an inner narrow core and an outer wide wing with an angular structure, to explain both the early TeV afterglow and multi-wavelength afterglows that last up to 100 days. We find that the radio afterglow and the TeV upper limit imposed by H.E.S.S. observations combine to constrain the circum-burst density to be low at larger radii. Thus, a decreasing density profile with radius is favored. Considering that the rising TeV light curve during the afterglow onset favors a constant-density medium, we invoke a stratified density profile, including a constant-density profile at small radii and a wind density profile at large radii. We find that the two-component jet model with such a stratified density profile can explain the TeV, X-ray and optical afterglows of GRB 221009A, although the radio fluxes exceed the observed ones by a factor of two at later epochs. The discrepancy in the radio afterglow could be resolved by invoking some non-standard assumption about the microphysics of afterglow shocks, such as a decreasing fraction of accelerated particles with time. The total kinetic energy of the two components in our model is $\lesssim 10^{52}{\rm erg}$, significantly smaller than that in the single structured jet models.Comment: 13 pages, 4 figure

Ethyl 6-(2-chloro­phen­yl)-4-methyl-1-(3-oxobut­yl)-2-thioxo-1,2,3,6-tetra­hydro­pyrimidine-5-carboxyl­ate

In the title mol­ecule, C18H21ClN2O3S, the pyrimidine ring exhibits a half-chair conformation. The ethyl group is disordered between two positions in a ratio 0.74:0.26. In the crystal structure, the mol­ecules are linked into chains along the a axis by N—H⋯O hydrogen bonds

Protein tyrosine phosphatases as potential therapeutic targets

Protein tyrosine phosphorylation is a key regulatory process in virtually all aspects of cellular functions. Dysregulation of protein tyrosine phosphorylation is a major cause of human diseases, such as cancers, diabetes, autoimmune disorders, and neurological diseases. Indeed, protein tyrosine phosphorylation-mediated signaling events offer ample therapeutic targets, and drug discovery efforts to date have brought over two dozen kinase inhibitors to the clinic. Accordingly, protein tyrosine phosphatases (PTPs) are considered next-generation drug targets. For instance, PTP1B is a well-known targets of type 2 diabetes and obesity, and recent studies indicate that it is also a promising target for breast cancer. SHP2 is a bona-fide oncoprotein, mutations of which cause juvenile myelomonocytic leukemia, acute myeloid leukemia, and solid tumors. In addition, LYP is strongly associated with type 1 diabetes and many other autoimmune diseases. This review summarizes recent findings on several highly recognized PTP family drug targets, including PTP1B, Src homology phosphotyrosyl phosphatase 2(SHP2), lymphoid-specific tyrosine phosphatase (LYP), CD45, Fas associated phosphatase-1 (FAP-1), striatal enriched tyrosine phosphatases (STEP), mitogen-activated protein kinase/dual-specificity phosphatase 1 (MKP-1), phosphatases of regenerating liver-1 (PRL), low molecular weight PTPs (LMWPTP), and CDC25. Given that there are over 100 family members, we hope this review will serve as a road map for innovative drug discovery targeting PTPs

Stable-isotopic and metagenomic analyses reveal metabolic and microbial link of aerobic methane oxidation coupled to denitrification at different O2 levels

Aerobic methane (CH4) oxidation coupled to denitrification (AME-D) can not only mitigate CH4 emission into the atmosphere, but also potentially alleviate nitrogen pollution in surface waters and engineered ecosystems, and it has attracted substantial research interest. O2 concentration plays a key role in AME-D, yet little is understood about how it impacts microbial interactions. Here, we applied isotopically labeled K15NO3 and 13CH4 and metagenomic analyses to investigate the metabolic and microbial link of AME-D at different O2 levels. Among the four experimental O2 levels of 21%,10%, 5% and 2.5% and a CH4 concentration of 8% (i.e., the O2/CH4 ratios of 2.62, 1.26, 0.63 and 0.31), the highest NO3--N removal occurred in the AME-D system incubated at the O2 concentration of 10%. Methanol and acetate may serve as the trophic linkage between aerobic methanotrophs and denitrifers in the AME-D systems. Methylotrophs including Methylophilus, Methylovorus, Methyloversatilis and Methylotenera were abundant under the O2-sufficient condition with the O2 concentration of 21%, while denitrifiers such as Azoarcus, Thauera and Thiobacillus dominated in the O2-limited environment with the O2 concentration of 10%. The competition of denitrifiers and methylotrophs in the AME-D system for CH4-derived carbon, such as methanol and acetate, might be influenced by chemotactic responses. More methane-derived carbon flowed into methylotrophs under the O2-sufficient condition, while more methane-derived carbon was used for denitrification in the O2-limited environment. These findings can aid in evaluating the distribution and contribution of AME-D and in developing strategies for mitigating CH4 emission and nitrogen pollution in natural and engineered ecosystems

Studying X-ray spectra from large-scale jets of FR II radio galaxies: application of shear particle acceleration

Shear particle acceleration is a promising candidate for the origin of extended high-energy emission in extra-galactic jets. In this paper, we explore the applicability of a shear model to 24 X-ray knots in the large-scale jets of FR II radio galaxies, and study the jet properties by modeling the multi-wavelength spectral energy distributions (SEDs) in a leptonic framework including synchrotron and inverse Compton - CMB processes. In order to improve spectral modelling, we analyze Fermi-LAT data for five sources and reanalyzed archival data of Chandra on 15 knots, exploring the radio to X-ray connection. We show that the X-ray SEDs of these knots can be satisfactorily modelled by synchrotron radiation from a second, shear-accelerated electron population reaching multi-TeV energies. The inferred flow speeds are compatible with large-scale jets being mildly relativistic. We explore two different shear flow profiles (i.e., linearly decreasing and power-law) and find that the required spine speeds differ only slightly, supporting the notion that for higher flow speeds the variations in particle spectral indices are less dependent on the presumed velocity profile. The derived magnetic field strengths are in the range of a few to ten microGauss, and the required power in non-thermal particles typically well below the Eddington constraint. Finally, the inferred parameters are used to constrain the potential of FR II jets as possible UHECR accelerators.Comment: 14 pages, 4 figures, 6 table, accepted for publication in MNRA

Slower and Less Variable Binocular Rivalry Rates in Patients With Bipolar Disorder, OCD, Major Depression, and Schizophrenia

When two different images are presented to the two eyes dichoptically, observers usually experience a perceptual alternation between the two images. This phenomenon, known as binocular rivalry, has been used as a powerful tool to investigate mechanisms of visual awareness. It was also found that the rates of perceptual alternation are slower in patients with bipolar disorder than in healthy controls (Pettigrew and Miller, 1998; Miller et al., 2003). To investigate the broader clinical relevance of binocular rivalry in psychiatric disorders, we measured the perceptual alternation rates during rivalry in healthy controls (n = 39) and in patients with different types of psychiatric disorders, including bipolar disorder type I (BD, n = 28), obsessive–compulsive disorder (OCD, n = 22), major depression (MD, n = 50), schizophrenia (SCZ, n = 44), and first-degree relatives (FDRs) of SCZ patients (n = 32). Participants viewed competing red–green images on a computer monitor through red–green anaglyph glasses and pressed buttons to record their perceptual alternations. The distributions of the rivalry rates were well described by a lognormal function in all groups. Critically, the median rate of perceptual alternation was 0.27 Hz for BD patients, 0.26 Hz for the OCD patients, 0.25 Hz for the MD patients, and 0.23 Hz and 0.27 Hz for the SCZ patients and their FDRs, respectively. All of which were significantly slower than the rate of 0.41 Hz obtained for the healthy controls, suggesting there may be shared genotypes between these different disorders. While rivalry alternations were generally slower in different types of psychiatric disorders compared to healthy controls, adding variance of rivalry rates in the analysis helped to partially separate among the different patient groups. Our results suggest that the slowing of binocular rivalry is likely due to certain common factors among the patient groups, but more subtle differences between different patient groups could be revealed when additional properties of rivalry dynamics are considered