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The Gemini South telescope is now equipped with a new high-resolution spectrograph called GHOST (the Gemini High-resolution Optical SpecTrograph). This instrument provides high-efficiency, high-resolution spectra covering 347-1060 nm in a single exposure of either one or two targets simultaneously, along with precision radial velocity spectroscopy utilizing an internal calibration source. It can operate at a spectral element resolving power of either 76000 or 56000, and can reach a SNR$\sim$5 in a 1hr exposure on a V$\sim$20.8 mag target in median site seeing, and dark skies (per resolution element). GHOST was installed on-site in June 2022, and we report performance after full integration to queue operations in November 2023, in addition to scientific results enabled by the integration observing runs. These results demonstrate the ability to observe a wide variety of bright and faint targets with high efficiency and precision. With GHOST, new avenues to explore high-resolution spectroscopy have opened up to the astronomical community. These are described, along with the planned and potential upgrades to the instrument., Comment: Accepted in the Astronomical Journal; 26 pages, 24 figures and 4 tables

In this paper we deal with a stationary non-degenerate $p-$Kirchhoff type problem with critical non-linearity and a subcritical parametrized perturbation. We work on bounded domains of the Euclidean space, without any restriction on the dimension or on $p>0$. Variational methods will be utilized in combination with an analysis of the fibering functions of the energy functional, in order to obtain ground state solutions, as well as Mountain Pass solutions, depending on the values of the parameter. A local analysis of the energy functional will allow us to obtain non-trivial solutions even beyond the extremal parameter.

Angstrom confined solvents in two-dimensional laminates travel through interlayer spacings, gaps between adjacent sheets, and via in plane pores. Among these, experimental access to investigate the mass transport through in plane pores is lacking. Here, we create these nanopores in graphene oxide membranes via ion irradiation with precise control over functional groups, pore size and pore density. Low ion induced pore densities result in mild reduction and increased water permeation for the membranes. Higher pore densities lead to pronounced reduction and complete blockage of pure water however allows permeation of ethanol water mixture due to weakening of hydrogen network. We confirm with simulations, that the attraction of the solvents towards the pores with functional groups and disruption of the angstrom confined hydrogen network is crucial to allow in plane pore transport.

Dielectric breakdown strength is one of the critical performance metrics for gases and mixtures used in large, high pressure gas time projection chambers. In this paper we experimentally study dielectric breakdown strengths of several important time projection chamber working gases and gas-phase insulators over the pressure range 100 mbar to 10 bar, and gap sizes ranging from 0.1to 10 mm. Gases characterized include argon, xenon, CO2, CF4, and mixtures 90-10 argon-CH4,90-10 argon-CO2and 99-1 argon-CF4. We develop a theoretical model for high voltage breakdown based on microphysical simulations that use PyBoltz electron swarm Monte Carlo results as input to Townsend- and Meek-like discharge criteria. This model is shown to be highly predictive at high pressure, out-performing traditional Paschen-Townsend and Meek-Raether models significantly. At lower pressure-times-distance, the Townsend-like model is an excellent description for noble gases whereas the Meek-like model provides a highly accurate prediction for insulating gases., Comment: 19 pages, 6 figures, 2 tables

SW Sextantis systems are nova-like cataclysmic variables that have unusual spectroscopic properties, which are thought to be caused by an accretion geometry having part of the mass flux trajectory out of the orbital plane. Accretion onto a magnetic white dwarf is one of the proposed scenarios for these systems. To verify this possibility, we analysed photometric and polarimetric time-series data for a sample of six SW Sex stars. We report possible modulated circular polarization in BO Cet, SW Sex, and UU Aqr with periods of 11.1, 41.2 and 25.7 min, respectively, and less significant periodicities for V380 Oph at 22 min and V442 Oph at 19.4 min. We confirm previous results that LS Peg shows variable circular polarization. However, we determine a period of 18.8 min, which is different from the earlier reported value. We interpret these periods as the spin periods of the white dwarfs. Our polarimetric results indicate that 15% of the SW Sex systems have direct evidence of magnetic accretion. We also discuss SW Sex objects within the perspective of being magnetic systems, considering the latest findings about cataclysmic variables demography, formation and evolution., Comment: 29 pages, 17 figures

ZnO is a promising candidate as an environment friendly thermoelectric (TE) material. However, the poor TE figure of merit (zT) needs to be addressed to achieve significant TE efficiency for commercial applications. Here we demonstrate that selective enhancement in phonon scattering leads to increase in zT of RGO encapsulated Al-doped ZnO core shell nanohybrids, synthesized via a facile and scalable method. The incorporation of 1 at% Al with 1.5 wt% RGO into ZnO (AGZO) has been found to show significant enhancement in zT (=0.52 at 1100 K) which is an order of magnitude larger compared to that of bare undoped ZnO. Photoluminescence and X-ray photoelectron spectroscopy measurements confirm that RGO encapsulation significantly quenches surface oxygen vacancies in ZnO along with nucleation of new interstitial Zn donor states. Tunneling spectroscopy reveals that the band gap of ~ 3.4 eV for bare ZnO reduces effectively to ~ 0.5 eV upon RGO encapsulation, facilitating charge transport. The electrical conductivity enhancement also benefits from the more than 95% densification achieved, using the spark plasma sintering method, which aids reduction of GO into RGO. The same Al doping and RGO capping synergistically brings about drastic reduction of thermal conductivity, through enhanced phonon-phonon and point defect-phonon scatterings. These opposing effects on electrical and thermal conductivities enhances the power factors as well as the zT value. Overall, a practically viable route for synthesis of oxide - RGO TE material which could find its practical applications for the high-temperature TE power generation.

Germanene, a two-dimensional honeycomb germanium crystal, is grown at graphene/Ag(111) and hexagonal boron nitride (h-BN)/Ag(111) interfaces by segregating germanium atoms. A simple annealing process in N2 or H2/Ar at ambient pressure leads to the formation of germanene, indicating that an ultrahigh-vacuum condition is not necessary. The grown germanene is stable in air and uniform over the entire area covered with a van der Waals (vdW) material. As an important finding, it is necessary to use a vdW material as a cap layer for the present germanene growth method since the use of an Al2O3 cap layer resulted in no germanene formation. The present study also proved that Raman spectroscopy in air is a powerful tool for characterizing germanene at the interfaces, which is concluded by multiple analyses including first-principles density functional theory calculations. The direct growth of h-BN-capped germanene on Ag(111), which is demonstrated in the present study, is considered to be a promising technique for the fabrication of future germanene-based electronic devices., Comment: 34 Pages, 11 Figures

The present paper deals with a parametrized Kirchhoff type problem involving a critical nonlinearity in high dimension. Existence, non existence and multiplicity of solutions are obtained under the effect of a subcritical perturbation by combining variational properties with a careful analysis of the fiber maps of the energy functional associated to the problem. The particular case of a pure power perturbation is also addressed. Through the study of the Nehari manifolds we extend the general case to a wider range of the parameters.

Context: Polarimetry is a very powerful tool to uncover various properties of astronomical objects that remain otherwise hidden in standard imaging or spectroscopic observations. However, the reliable measurement of the low polarization signal from astronomical sources requires a good control of spurious instrumental polarization induced by the various components of the optical system and the detector. Aims: We perform a detailed multi-wavelength calibration study of the FORS2 instrument at the VLT operating in imaging polarimetric mode (IPOL) to characterize the spatial instrumental polarization that may affect the study of extended sources. Methods: We use imaging polarimetry of a) high signal-to-noise blank fields BVRI observations during full-moon, when the polarization is expected to be constant across the field-of-view and deviations originate from the instrument and b) a crowded star cluster in broad-band RI and narrow-band H{\alpha} filters, where individual polarization values of each star across the field can be measured. Results: We find an instrumental polarization pattern that increases radially outwards from the optical axis of the instrument reaching up to 1.4% at the edges, depending on the filter. Our results are well approximated by an elliptical paraboloid down to less than {\sim0.05\%} accuracy,and {\sim0.02\%} when using non-analytic fits. We present 2D maps to correct for this spurious instrumental polarization. We also give several tips and tricks to analyze polarimetric measurements of extended sources. Conclusions: FORS2 is a powerful instrument allowing to map the linear polarimetry of extended sources. We present and discuss a methodology to measure the polarization of such sources, and to correct for the spatial polarization induced in the optical system. This methodology could be applied to polarimetric measurements using other dual-beam polarimeters., Comment: 21 pages, 23 figures. Accepted in A&A

A methodology is presented to solve Arithmetic problems in Sinhala Language using a Neural Network. The system comprises of (a) keyword identification, (b) question identification, (c) mathematical operation identification and is combined using a neural network. Naive Bayes Classification is used in order to identify keywords and Conditional Random Field to identify the question and the operation which should be performed on the identified keywords to achieve the expected result. "One vs. all Classification" is done using a neural network for sentences. All functions are combined through the neural network which builds an equation to solve the problem. The paper compares each methodology in ARIS and Mahoshadha to the method presented in the paper. Mahoshadha2 learns to solve arithmetic problems with the accuracy of 76%., Comment: 34th National Information Technology Conference (NITC 2016)

It is established existence, uniqueness and multiplicity of solutions for a quasilinear elliptic problem problems driven by $\Phi$-Laplacian operator. Here we consider the reflexive and nonreflexive cases using an auxiliary problem. In order to prove our main results we employ variational methods, regularity results and truncation techniques.

The increasing number of synoptic surveys made by small robotic telescopes, such as the photometric Catalina Real-Time Transient Survey (CRTS), represents a unique opportunity for the discovery of variable sources and improves the statistical samples of such classes of objects. Our goal is the discovery of magnetic Cataclysmic Variables (mCVs). These are rare objects, which probe interesting accretion scenarios controlled by the white dwarf magnetic field. In particular, improved statistics of mCVs would help to address open questions on their formation and evolution. We performed an optical spectroscopy survey to search for signatures of magnetic accretion in 45 variable objects selected mostly from the CRTS. In this sample we found 32 CVs, 22 being mCV candidates from which 13 are previously unreported as such. If the proposed classifications are confirmed, it would represent an increase of 4% in the number of known polars and 12% in the number of known IPs. A fraction of our initial sample was classified as extragalactic sources or other types of variable stars by the inspection of the identification spectra. Despite the inherent complexity in identifying a source as a mCV, variability-based selection followed by spectroscopic snapshot observations has proved to be an efficient strategy for their discoveries, being a relatively inexpensive approach in terms of telescope time., Comment: 27 pages, 7 figures, published in the AJ, accepted version, replacement version with minor changes

In this paper we prove that the equation $ -( r^\alpha\phi(|u'(r)|)u'(r))' = \lambda r^\gamma f(u(r)), ~0 0$ is a real parameter and $f:{\bf{R}}\to{\bf{R}}$ is continuous, admits an infinite sequence of sign-changing solutions satisfying $u'(0) =u(R) =0$. The function $f$ is required to satisfy $tf(t)>0$ for $ t\neq 0$. Our technique explores fixed point arguments applied to suitable integral equations and shooting arguments. Our main result extends earlier ones in the case $\phi$ is in the form $\phi(t) = |t|^{\beta}$ for an appropriate constant $\gamma$.

This study confirms MLS110213:022733+130617 as a new eclipsing polar. We performed optical spectroscopic, polarimetric and photometric follow-up of this variable source identified by the Catalina Real Time Transient Survey. Using the mid-eclipse times, we estimated an orbital period of 3.787 h, which is above the orbital period gap of the cataclysmic variables. There are nine other known polars with longer orbital periods, and only four of them are eclipsing. We identified high and low-brightness states and high polarization modulated with the orbital period. The spectra are typical of polars, with strong high ionization emission lines and inverted Balmer decrement. The HeII4686 A line is as strong as Hbeta. We modelled the photometric and polarimetric bright-state light curves using the CYCLOPS code. Our modelling suggests an extended emitting region on the WD surface, with a mean temperature of 9 keV and B in the range 18 -- 33 MG, although the possibility that it could be a two-pole accretor cannot yet be ruled out. The WD mass estimated from the shock temperature is 0.67 Msol. The derived parameters are consistent with the eclipse profile. The distance was estimated as 406+- 54 pc using the Period-Luminosity-Colours method. MLS110213 populates a rare sub-group of polars, near the upper limit of the period distribution, important to understand the evolution of mCVs., Comment: 10 pages, 8 figures, accepted to be published in MNRAS on 05/12/2015

Due to their graphene-like properties after oxygen reduction, incorporation of graphene oxide (GO) sheets into correlated-electron materials offers a new pathway for tailoring their properties. Fabricating GO nanocomposites with polycrystalline MgB2 superconductors leads to an order of magnitude enhancement of the supercurrent at 5 K/8 T and 20 K/4 T. Herein, we introduce a novel experimental approach to overcome the formidable challenge of performing quantitative microscopy and microanalysis of such composites, so as to unveil how GO doping influences the structure and hence the material properties. Atom probe microscopy and electron microscopy were used to directly image the GO within the MgB2, and we combined these data with computational simulations to derive the property-enhancing mechanisms. Our results reveal synergetic effects of GO, namely, via localized atomic (carbon and oxygen) doping as well as texturing of the crystals, which provide both inter and intra granular flux pinning. This study opens up new insights into how low-dimensional nanostructures can be integrated into composites to modify the overall properties, using a methodology amenable to a wide range of applications.

In this work, we present the first results of a study of a new sample of 7 polar candidates from polarimetric data obtained at the Pico dos Dias / LNA observatory. From the four polars analysed so far, we confirm the presence of high and variable polarization in 3. The data will be analysed using the code CYCLOPS., Comment: Simp\'osio de F\'isica e Astronomia do Vale do Para\'iba

We present new data that confirm MLS110213:022733+130617 as a new eclipsing polar. Some system properties were estimated., Comment: Proceedings of the XIV Latin American Regional IAU Meeting - RevMexAA

In this study, Si and C were incorporated into polycrystalline MgB2 via in situ reaction of Mg and B with either SiC or with separate Si and C (Si+C). The electrical transport and magnetic properties of the two series of samples were compared. The corrected resistivity at 40K, Rho A(40K), is higher for the SiC reacted samples regardless of carbon (C) substitution level, indicating larger intragrain scattering because of the simultaneous reaction between Mg and SiC and carbon substitution during the formation of MgB2. In addition, because of the cleaner reaction route for the SiC reacted samples, the calculated active area that carries current, AF, is twice that of the (Si+C) samples. On the other hand, the upper critical field, Hc2, was similar for both sets of samples despite their different C substitution levels which proves the importance of defect scattering in addition to C substitution level. Hence, the form of the precursor reactants is critical for tuning the form of Hc2(T)., Comment: accepted for publication

In 2009 Loc and Schmitt established a result on sufficient conditions for multiplicity of solutions of a class of nonlinear eignvalue problems for the p-Laplace operator under Dirichlet boundary conditions, extending an earlier result of 1981 by Peter Hess for the Laplacian. Results on necessary conditions for existence were also established. In the present paper the authors extend the main results by Loc and Schmitt to the $\Phi$-Laplacian. To overcome the difficulties with this much more general operator it was necessary to employ regularity results by Lieberman, a strong maximum principle by Pucci and Serrin and a general result on lower and upper solutions by Le., Comment: 21 pages

The viewing geometry of the polar CP Tuc that better explains its optical and X-ray light curves is controversial. Previous modelling of white-light polarimetric data considered the partial self-eclipse of an extended inhomogeneous emitting region. Alternatively, phase-dependent absorption has been used to reproduce the X-ray data. This paper presents new optical polarimetric data of CP Tuc and a model that consistently explains its optical and X-ray data. The model was based on an extension of the CYCLOPS code that added X-ray bremsstrahlung emission and pre-shock region absorption to the original version, which only accounted for cyclotron emission. The new code creates the possibility of simultaneous optical and X-ray fitting. We show that self-eclipse and absorption data have distinct signatures on the X-ray spectra. Although we were able to reasonably fit the CP Tuc optical data to cases of absorption and self-eclipse, we were only able to reproduce the X-ray orbital modulation after considering the absorption in the pre-shock region. Specifically, we were unable to reproduce the X-ray observations in the self-eclipse case. We found that the primary emitting region in CP Tuc is located near the rotation pole that approximately points to the observer., Comment: 13 pages, 11 figures, accepted to be published in MNRAS

We present the basic concept of a new astronomical instrument: SPARC4 - Simultaneous Polarimeter and Rapid Camera in 4 bands. SPARC4 combines in one instrument: (i) photometric and polarimetric modes; (ii) sub-second time-resolution in photometric mode and excellent time-resolution in polarimetric mode; (iii) simultaneous imaging in four broad-bands for both modes. This combination will make SPARC4 a unique facility for ground-based optical observatories. Presently, the project is in its conceptual design phase., Comment: Poster presented at "Stellar Polarimetry: From birth to death". This article has been submitted to AIP Conference Proceedings. After it is published, it will be found at http://www.aip.org

We present time-resolved spectroscopy of the polar RBS0324(=1RXS J023052.9-684203) spanning more than one orbital cycle. The emission lines present complex and variable profiles. Radial velocities were determined for the HeII4686 and Hbeta emission lines. The curves are similar for both lines, with a semi-amplitude of about 250 km/s. The modulation of 1.5 mag of the continuum flux is compatible with those previously presented in the literature. All these characteristics are typical of polars., Comment: 5 pages, 3 figures http://www.konkoly.hu/cgi-bin/IBVS?5957

2MASS J09440940-5617117 was identified as a cataclysmic variable in 2007 by its spectrum. In this article we present optical differential photometry in the Rc band obtained using the 0.6-m telescope at Observatorio do Pico dos Dias/Brazil. The complete light curves confirm the presence of a deep eclipse. We derive an orbital period of 0.1879340(5) d. The eclipse has a width of 0.112 +- 0.003 orbital cycles., Comment: 4 pages, 5 figures, http://www.konkoly.hu/cgi-bin/IBVS?5971

From the optical to the X-ray frequencies, most of the continuum emission from AM Her systems originates in the post-shock region. Hence, using multi-spectral data can be useful to restrict the physical and geometrical properties of that region. In spite of that, distinct codes are used to model these frequency ranges. CYCLOPS is a code to model the optical cyclotron emission of polars. In this contribution, we present the first version of CYCLOPS-X, an improvement of CYCLOPS to fit simultaneously optical and X-ray data. The new code adds the bremsstrahlung as an emission process as well as the effects of X-ray absorption by the upper portion of the accretion column. As a first application of CYCLOPS-X, we present X-ray light curves using two sets of parameters provided by the optical modeling of CP Tuc. These two cases have very similar optical emission, but quite distinct light-curves in high energies. It illustrates the need of simultaneous modeling of the optical and X-ray emission to a proper description of the magnetic accretion in polars., Comment: 4 pages, poster presented at the conference on 'Physics of Accreting Compact Binaries', July 2010 in Kyoto, Japan; proceedings to be published by Universal Academy Press

CP Tuc (AX J2315-592) is a polar for which two accretion geometries have been put forward. They differ in the location of the accretion column on the white-dwarf surface. In this study, we present new multiband optical photometric and polarimetric data to study the post-shock position. These data are used as input for CYCLOPS, our new code for modeling the cyclotron emission from post-shock regions of polars. CYCLOPS has a full 3-D treatment of the radiative transfer and is a powerful tool to study the physical properties of the emitting region. We find reasonable fits for the optical data of CP Tuc in both scenarios. We suggest that it should be possible to constrain the location of the base of the accreting column by modeling the X-ray light curves., Comment: 6 pages; talk given at the conference on 'Physics of Accreting Compact Binaries', July 2010 in Kyoto, Japan; proceedings to be published by Universal Academy Press

A conceptual design was developed by Northrop/LTV for an advanced C-130 Center Wing Box (CWB) which could meet the severe mission requirements of the SOF C-130 aircraft. The goals for the advanced technology CWB relative to the current C-130H CWB were: (1) the same acquisition cost; (2) lower operating support costs; (3) equal or lower weight; (4) a 30,000 hour service life for the SOF mission; and (5) minimum impact on the current maintenance concept. Initially, the structural arrangement, weight, external and internal loads, fatigue spectrum, flutter envelope and design criteria for the SOF C-130 aircraft CWB were developed. An advanced materials assessment was then conducted to determine the suitability of advanced materials for a 1994 production availability and detailed trade studies were performed on candidate CWB conceptual designs. Finally, a life-cycle cost analysis was performed on the advanced CWB. The study results showed that a hybrid composite/metallic CWB could meet the severe SOF design requirements, reduce the CWB weight by 14 pct., and was cost effective relative to an all metal beefed up C-130H CWB.