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Rolling Adjoints: Fast Greeks along Monte Carlo scenarios for early-exercise options
No full textIn this paper we extend the Stochastic Grid Bundling Method (SGBM), a regress-later Monte Carlo scheme for pricing early-exercise options, with an adjoint method to compute in a highly efficient manner the option sensitivities (the ``Greeks'') along the Monte Carlo paths, with reasonable accuracy. The path-wise SGBM Greeks computation is based on the conventional path-wise sensitivity analysis, however, for a regress-later technique. The resulting sensitivities at the end of the monitoring period are implicitly rolled over into the sensitivities of the regression coefficients of the previous monitoring date. For this reason, we name the method Rolling Adjoints, which facilitates Smoking Adjoints M. Giles, P. Glasserman, Smoking adjoints: fast Monte Carlo Greeks, Risk 19 (1) (2006) 88-92] to compute conditional sensitivities along the paths for options with early-exercise features
Probing defect states in few-layer MoS2 by conductance fluctuation spectroscopy
No full textDespite the concerted effort of several research groups, a detailed experimental account of defect dynamics in high-quality single-and few-layer transition-metal dichalcogenides remains elusive. In this paper we report an experimental study of the temperature dependence of conductance and conductance fluctuations on few-layer MoS2 exfoliated on hexagonal boron nitride and covered by a capping layer of high-kappa dielectric HfO2. The presence of the high-kappa dielectric made the device extremely stable against environmental degradation as well as resistant to changes in device characteristics upon repeated thermal cycling, enabling us to obtain reproducible data on the same device over a timescale of more than 1 year. Our device architecture helped bring down the conductance fluctuations of the MoS2 channel by orders of magnitude compared to previous reports. The extremely low noise levels in our devices made it possible to detect the generation-recombination noise arising from charge fluctuation between the sulfur-vacancy levels in the band gap and energy levels at the conductance band edge. Our work establishes conduction fluctuation spectroscopy as a viable route to quantitatively probe in-gap defect levels in low-dimensional semiconductors
Heterogeneity of ROS levels in antibiotic-exposed mycobacterial subpopulations confers differential susceptibility
No full textPhenotypically heterogeneous but genetically identical mycobacterial subpopulations exist in in vitro cultures, in vitro-infected macrophages, infected animal models and tuberculosis patients. In this regard, we recently reported the presence of two subpopulations of cells, which are phenotypically different in length and buoyant density, in mycobacterial cultures. These are the low-buoyant-density short-sized cells (SCs), which constitute similar to 10-20% of the population, and the high-buoyantdensity normal/long-sized cells (NCs), which form similar to 80-90% of the population. The SCs were found to be significantly more susceptible to rifampicin (RIF), isoniazid (INH), H2O2 and acidified nitrite than the NCs. Here we report that the RIF-/INH-/H2O2 -exposed SCs showed significantly higher levels of oxidative stress and therefore higher susceptibility than the equivalent number of exposed NCs. Significantly higher levels of hydroxyl radical and superoxide were found in the antibiotic-exposed SCs than in the equivalently exposed NCs. Different proportions of the subpopulation of SCs were found to have different levels of reactive oxygen species (ROS). The hydroxyl radical quencher, thiourea, and the superoxide dismutase mimic, TEMPOL, significantly reduced hydroxyl radical and superoxide levels, respectively, in the antibiotic-exposed SCs and NCs and thereby decreased their differential susceptibility to antibiotics. Thus, the present study shows that the heterogeneity of the reactive oxygen species (ROS) levels in these mycobacterial subpopulations confers differential susceptibility to antibiotics. We have discussed the possible mechanisms that can generate differential ROS levels in the antibiotic-exposed SCs and NCs. The present study advances our current understanding of the molecular mechanisms underlying antibiotic tolerance in mycobacteria
Two-dimensional magnetohydrodynamic turbulence with large and small energy-injection length scales
No full textTwo-dimensional magnetohydrodynamics, forced at (a) large length scales or (b) small length scales, display turbulent, but statistically steady, states with widely different statistical properties. We present a systematic, comparative study of these two cases (a) and (b) by using direct numerical simulations. We find that, in case (a), there is energy equipartition between the magnetic and velocity fields, whereas, in case (b), such equipartition does not exist. By computing various probability distribution functions, we show that case (a) displays extreme events that are much less common in case (b)
Cobalt(III)-Catalyzed Direct ortho-Alkenylation of Arylpyrazoles: A Comparative Study on Decarboxylation and Desilylation
No full textA comparative study on Co-III-catalyzed direct C-H bond alkenylation of 1-phenylpyrazole derivatives with alkynyl carboxylic acids and arylalkynylsilanes under redox-neutral conditions has been disclosed. These methods show excellent selectivity with good to excellent yields. Trimethylsilylacetylene has been utilized as a vinyl source to obtain the corresponding styrene derivatives. The major differences between these two reactions are the decarboxylation proceeds in the presence of a base additive whereas the desilylation takes place in the presence of an acid additive. The developed methodologies are compatible with a variety of functional groups
A COMBINATORIAL MODEL FOR COMPUTING VOLUMES OF FLOW POLYTOPES
No full textWe introduce new families of combinatorial objects whose enumeration computes volumes of flow polytopes. These objects provide an interpretation, based on parking functions, of Baldoni and Vergne's generalization of a volume formula originally due to Lidskii. We recover known flow polytope volume formulas and prove new volume formulas for flow polytopes. A highlight of our model is an elegant formula for the flow polytope of a graph we call the caracol graph. As by-products of our work, we uncover a new triangle of numbers that interpolates between Catalan numbers and the number of parking functions, we prove the log-concavity of rows of this triangle along with other sequences derived from volume computations, and we introduce a new Ehrhart-like polynomial for flow polytope volume and conjecture product formulas for the polytopes we consider
OH maser emission in the THOR survey of the northern Milky Way
No full textContext. OH masers trace diverse physical processes, from the expanding envelopes around evolved stars to star-forming regions or supernovae remnants. Providing a survey of the ground-state OH maser transitions in the northern hemisphere inner Milky Way facilitates the study of a broad range of scientific topics. Aims. We want to identify the ground-state OH masers at similar to 18 cm wavelength in the area covered by The HI/OH/Recombination line survey of the Milky Way (THOR). We will present a catalogue of all OH maser features and their possible associated environments. Methods. The THOR survey covers longitude and latitude ranges of 14 degrees.3 < l < 66 degrees.8 and b < +/- 1 degrees.25. All OH ground state lines (2)Pi(3/2) (J = 3/2) at 1612 (F = 1-2), 1665 (F = 1-1), 1667 (F = 2-2) and 1720 MHz (F = 2-1) have been observed, employing the Very Large Array (VLA) in its C configuration. The spatial resolution of the data varies between 12.5 `' and 19 `', the spectral resolution is 1.5 km s(-1), and the rms sensitivity of the data is similar to 10 mJy beam(-1) per channel. Results. We identify 1585 individual maser spots (corresponding to single spectral features) distributed over 807 maser sites (regions of size similar to 10(3)-10(4) AU). Based on different criteria from spectral profiles to literature comparison, we try to associate the maser sites with astrophysical source types. Approximately 51% of the sites exhibit the double-horned 1612 MHz spectra typically emitted from the expanding shells of evolved stars. The separations of the two main velocity features of the expanding shells typically vary between 22 and 38 km s(-1). In addition to this, at least 20% of the maser sites are associated with star-forming regions. While the largest fraction of 1720 MHz maser spots (21 out of 53) is associated with supernova remnants, a significant fraction of the 1720 MHz maser spots (17) are also associated with star-forming regions. We present comparisons to the thermal (CO)-C-13(1-0) emission as well as to other surveys of class II CH3OH and H2O maser emission. The catalogue attempts to present associations to astrophysical sources where available, and the full catalogue is available in electronic form. Conclusions. This OH maser catalogue presents a unique resource of stellar and interstellar masers in the northern hemisphere. It provides the basis for a diverse range of follow-up studies from envelopes around evolved stars to star-forming regions and Supernova remnants
Syntheses, structural variants and characterization of A(2)CdSn(2)S(6) (A = Cs, Rb and K) compounds
No full textFour new A(2)CdSn(2)S(6) (A= Cs(1), Rb(2), K(3-beta) and K(3-alpha)) compounds have been synthesized and characterized by X-ray diffraction and spectroscopic methods. The isostructural cesium(1) and rubidium(2) compounds have noncentrosymmetric three-dimensional tetrahedral CdSn2S6](2-) framework structure and show second-harmonic-generation response. The layered potassium compounds, 3-beta and 3-alpha, have centrosymmetric tetrahedral and octahedral CdSn2S6](2-) framework structures respectively and the compound 3-beta, on heating, transforms to compound 3-alpha. The compound 3-alpha undergoes facile potassium ion-exchange in aqueous medium with various mono-, di- and tri- valent cations at room temperature
MoS2-Modified Curcumin Nanostructures: The Novel Theranostic Hybrid Having Potent Antibacterial and Antibiofilm Activities against Multidrug-Resistant Hypervirulent Klebsiella pneumoniae
No full textThe recent emergence of hypervirulent clinical variants of Klebsiella pneumoniae (hvKP) causing community-acquired, invasive, metastatic, life-threatening infections of lungs, pleura, prostate, bones, joints, kidneys, spleen, muscles, soft-tissues, skin, eyes, central nervous system (CNS) including extrahepatic abscesses, and primary bacteremia even in healthy individuals has posed stern challenges before the existing treatment modalities. There is therefore an urgent need to look for specific and effective therapeutic alternatives against the said bacterial infection or recurrence. A new type of MoS2-modified curcumin nanostructure has been developed and evaluated as a potential alternative for the treatment of multidrug-resistant isolates. The curcumin quantum particles have been fabricated with MoS2 via a seed-mediated hydrothermal method, and the resulting MoS2-modified curcumin nanostructures (MQCs) have been subsequently tested for their antibacterial and antibiofilm properties against hypervirulent multidrug-resistant Klebsiella pneumoniae isolates. In the present study, we found MQCs inhibiting the bacterial growth at a minimal concentration of 0.0156 mu g/mL, while complete inhibition of bacterial growth was evinced at concentration 0.125 mu g/mL. Besides, we also investigated their biocompatibility both in vitro and in vivo. MQCs were found to be nontoxic to the SiHa cells at a dose as high as 1024 mu g/mL on the basis of the tested adhesion, spreading of the cells, and also on the various serological, biochemical, and histological investigations of the vital organs and blood of the Charles Foster Rat. These results suggest that MQCs have potent antimicrobial activities against hvKP and other drug resistant isolates and therefore may be used as broad spectrum antibacterial and antibiofilm agents
Generating a second-order topological insulator with multiple corner states by periodic driving
No full textWe study the effects of periodic driving on a variant of the Bernevig-Hughes-Zhang (BHZ) model defined on a square lattice. In the absence of driving, the model has both topological and nontopological phases depending on the different parameter values. We also study the anisotropic BHZ model and show that, unlike the isotropic model, it has a nontopological phase which has states localized on only two of the four edges of a finite-sized square. When an appropriate term is added, the edge states get gapped and gapless states appear at the four corners of a square; we have shown that these corner states can be labeled by the eigenvalues of a certain operator. When the system is driven periodically by a sequence of two pulses, multiple corner states may appear depending on the driving frequency and other parameters. We discuss to what extent the system can be characterized by topological invariants such as the Chern number and a diagonal winding number. We have shown that the locations of the jumps in these invariants can be understood in terms of the Floquet operator at both the time-reversal invariant momenta and other momenta which have no special symmetries