ALBERT

Description: Two classes of GRBs have been identified thus far without doubt and are prescribed to different physical scenarios—NS-NS or NS-BH mergers, and collapse of massive stars, for short and long GRBs, respectively. The existence of two distinct populations was inferred through a bimodal distribution of the observed durations \(T_{90}\) , and the commonly applied \(2~\mbox{s}\) limit between short and long GRBs was obtained by fitting a parabola between the two peaks in binned data from BATSE 1B. Herein, by means of a maximum likelihood (ML) method a mixture of two Gaussians is fitted to the datasets from BATSE, Swift , BeppoSAX , and Fermi in search for a local minimum that might serve as a new, more proper, limit for the two GRB classes. It is found that Swift and BeppoSAX distributions are unimodal, hence no local minimum is present, Fermi is consistent with the conventional limit, whereas BATSE gives the limit significantly longer (equal to \(3.38\pm 0.27~\mbox{s}\) ) than \(2~\mbox{s}\) . These new values change the fractions of short and long GRBs in the samples examined, and imply that the observed \(T_{90}\) durations are detector dependent, hence no universal limiting value may be applied to all satellites due to their different instrument specifications. Because of this, and due to the strong overlap of the two-Gaussian components, the straightforward association of short GRBs to mergers and long ones to collapsars is ambiguous.

Description: When luminosity of black hole accretion disks is greater than 0.06 Eddington luminosity ( \(L \geq0.06 L_{E} \) ), according to standard disk model, the inner region of these disks is radiation-pressure dominated (RPD) and unstable in thermal and viscous modes. Whereas this object conflicts with the observations, if \(0.01 L_{E}\leq L \leq0.5 L_{E}\) . Thus, the change of viscosity or considering relativistic corrections that are essential in realistic black hole accretion disks may solve this problem between theory and observation. An explanation by taking into account the effect of black hole spin with the presence of different viscosities on the secular and thermal instabilities in geometrically thin optically thick accretion disks is presented. In order to consider the effects of spin and general relativity, kerr space-time is used. A diffusive form of viscous stress tensor, a new form of fully relativistic shear stress tensor that is not used so far, power law, and parametric viscosity are considered. Investigations have been done in some parameters of viscosity and some values of spin. We conclude that the type of viscosity is effective in stabilization of the disk, whereas spin has no effect. Increasing stability or instability in the disk can be caused by spin, which this behavior is related to the type of viscous parameter. Thereby, spin can be effective on the temperature, accretion rate, and in the luminosity of the system.

Description: We describe a new type of NADH sensor based on a screen-printed electrode (SPE) modified with reduced graphene oxide (RGO) and poly(allylamine hydrochloride) (PAH). A mixture of graphene oxide (GO) and PAH was deposited on the surface of a carbon working electrode, and RGO was prepared in-situ by electrochemical reduction of GO. The oxidation peak of NADH was recorded at +450 mV (vs . silver pseudo-reference). Under optimized conditions, the electrode exhibits high electrocatalytic activity toward NADH oxidation, expressed by a high rate constant and a stable response up to 0.8 mM concentrations. The sensitivity is 108.6 μA·mM −1 ·cm −2 , the response time is 20 s (for 95 % of the steady state current), and the detection limit is 6.6 μM (at an S/N ratio of 3). A peak separation of about 300 mV was achieved in differential pulse voltammetric determination of NADH in the presence of ascorbic acid. This makes the new sensor a useful tool with potential analytical application in different dehydrogenase based systems. Graphical abstract ᅟ

Description: We describe an electrochemical immunosensor for the simultaneous determination of alpha-fetoprotein (AFP) and prostate specific antigen (PSA) via a modified glassy carbon electrode. Silica nanoparticles (200–300 nm i.d.) with good monodispersity and uniform shape were synthesized, and the following species were then consecutively immobilized on their surface: gold nanoparticles (AuNPs; 5–15 nm i.d.), secondary antibody (Ab 2 ) and the redox-probes Azure A or ferrocenecarboxy acid (Fc). In parallel, two types of primary antibodies (Ab 1 ) were co-immobilized on the surface of the dissolved reduced graphene oxide sheets (rGO) that were also decorated with AuNPs. In the presence of antigens (AFP or PSA), the Ab 2 /Si@AuNPs carrying Azure A and Fc are attached to the AuNP/rGO conjugate via a sandwich type immunoreaction. Differential pulse voltammetry (DPV) was employed to measure the resulting changes in the signal of Fc or Azure A. Two well-resolved oxidation peaks, one at −0.48 V (corresponding to Azure A) and other at + 0.12 V (corresponding to Fc; both vs. SCE) can be observed in the DPV curves. Under optimal conditions, AFP and PSA can be simultaneously determined in the range from 0.01 to 25 ng mL‾ 1 for AFP, and from 0.012 to 25 ng mL‾ 1 for PSA. The detection limits are 3.3 pg mL‾ 1 for AFP and 4.0 pg mL‾ 1 for PSA (at a signal-to-noise ratio of 3). The method was applied to (spiked) real sample analysis, and the recoveries are within 96.0 and 107.2 % for PSA, and within 100.9 and 105.8 % for AFP, indicating that this dual immunosensor matches the requirements of clinical analysis. Graphical abstract (A) Two types of signal labels preparation process. (B) The immunosensor preparation and detection process.

Description: A nanocomposite consisting of coral-like gold nanostructures on reduced graphene oxide (RGO) was synthesized with the assistance of dimethylbiguanide (DMBG). It was then fabricated on a glassy carbon electrode, coating with cysteamine in order to enable the immobilization of acetylcholinesterase (AChE) as a model enzyme whose activity of hydrolyzing the substrate of acetylthiocholine is inhibited by the pesticide triazophos. The biosensor has response to acetylthiocholine in the 0.3 ~ 300 μM concentration range at 0.65 V (vs. SCE). The inhibition of the enzyme by triazophos can be determined in concentrations of up to 210 ppb, with a detection limit of 0.35 ppb of triazophos ( S / N  = 3). The biosensor is highly reproducible and acceptably stable. Graphical Abstract Coral-like gold nanostructures supported on reduced graphene oxide were synthesized with the assistance of dimethylbiguanide to fabricate an acetylcholinesterase (AChE) biosensor, which exhibited high reproducibility and good stability, providing a good platform for the detection of organophosphorus pesticides.

Description: We consider the effect of a partial coverage of quasar broad-line regions (QSO BLRs) by intervening \(\mbox{H}_{2}\) -bearing clouds when a part of quasar (QSO) radiation passes by a cloud not taking part in absorption-line system formation of the QSO spectrum. That leads to modification of observable absorption line profiles and consequently to a bias in physical parameters derived from standard absorption line analysis. In application to the \(\mbox{H}_{2}\) absorption systems the effect has been revealed in the analysis of \(\mbox{H}_{2}\) absorption system in the spectrum of Q 1232+082 (see Ivanchik et al. in Mon. Not. R. Astron. Soc. 404:1583, 2010 , Balashev et al. in Mon. Not. R. Astron. Soc. 418:357, 2011 ). We estimate a probability of the effect to be detected in QSO spectra. To do this we derive distribution of BLR sizes of high-z QSOs from Sloan Digital Sky Survey (SDSS) Data Release 9 (DR9) catalogue and assume different distributions of cloud sizes. We conclude that the low limit of the probability is about 11 %. The latest researches shows that about a fifth of observed \(\mbox{H}_{2}\) absorption systems can be partially covered. Accounting of the effect may allow to revise significantly physical parameters of interstellar clouds obtained by the spectral analysis.

Description: The spatially homogeneous and anisotropic Bianchi type-V universe filled with interacting Dark matter and Holographic dark energy has been studied. The exact solutions of Einstein’s field equations are obtained by (i) applying the special law of variation of Hubble parameter that yields constant values of the deceleration parameter and (ii) using a special form of deceleration parameter. It has been observed that for suitable choice of interaction between dark matter and holographic dark energy there is no coincidence problem (unlike \(\varLambda\) CDM). Also, in all the resulting models the anisotropy of expansion dies out very quickly and attains isotropy after some finite time. The physical and geometrical aspects of the models are also discussed.

Description: The properties of nonlinear dust-acoustic rogue waves in an unmagnetized, collisionless, four-component dusty plasma system consisting of electrons, nonthermal ions, hot and cold dust species have been investigated. The basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of the rogue wave properties on the ion energetic population parameter is discussed. The results of the present investigation could be applicable in Saturn F-ring.

Description: In this paper, we study the reconstruction scenario of a dark energy model in the framework of modified Horava-Lifshitz \(F(R)\) gravity or \(F(\tilde{R})\) gravity. We assume generalized ghost pilgrim dark energy model in flat universe. We consider three well-known scale factors to analyze the behavior of reconstructed \(F(\tilde{R})\) model. These scale factors include bouncing and intermediate scale factors as well as scale factor representing the unification of matter and accelerated phases. The graphical representation is adopted to analyze the behavior of reconstructed model and equation of state parameter for different values of model parameter. The reconstructed model represents increasing and decreasing behavior with respect to time in all cases. The equation of state parameter represents phantom-like universe after transition for intermediate scale factor while quintessence behavior for bouncing and unified scale factors. We also found that the squared speed of sound exhibits the stability of all reconstructed models.

Description: We have performed a study on the performance of two microbial glucose sensors based on immobilized Gluconobacter oxydans ( G. oxydans ). The first one was prepared by modifying a glassy carbon paste electrode (GCPE) containing the microbial cells with graphene oxide (GO), the other one by modifying it with graphene-platinum hybrid nanoparticles (graphene-Pt NPs). The electrode was characterized by following the voltammetric signals of the oxidation of hexacyanoferrate(II) to hexacyanoferrate(III) via the oxidative enzymes contained in G. oxydans which convert glucose to gluconic acid. Optimizations were conducted with a conventional GCPE containing G. oxydans . After material optimization, the biosensors were applied to the determination of glucose. The linear and analytical ranges for GO based biosensor range from 1 to 75 μM (linear) and 1 to 100 μM (analytical), respectively, with a limit of detection (LOD) of (3 s/m) 1.06 μM (at an S/m of 3). On the other hand, the graphene-Pt hybrid nanoparticle based biosensor showed two linear ranges (from 0.3 to 1 µM and from 1 to 10 μM), a full analytical range from 1 to 50 μM, and an LOD of 0.015 μM. The graphene-Pt hybrid NP based sensors performs better and was applied to the determination of glucose in synthetically prepared plasma samples where it gave recoveries as 101.8 and 104.37 % for two different concentrations. Selectivity studies concerning fructose, galactose, L-ascorbic acid and dopamine were also conducted. Graphical Abstract The electrochemical performances of graphene oxide and graphene-platinum hybrid nanoparticle modified G. oxydans biosensors were compared.

Description: Copper nanoclusters (Cu-NCs) were fabricated by chemical reduction of Cu(II) ions using formaldehyde as the reductant and poly(vinyl pyrrolidone) as the protecting agent. The resulting Cu-NCs were characterized by TEM, FT-IR, UV–vis and XPS and fluorescence spectroscopy. The Cu-NCs display a luminescence quantum yield of about 13 %, and the emission peaks shift from 398 to 457 nm on increasing the excitation wavelength from 310 to 390 nm. The Cu-NCs possess a storage stability of at least 2 months and are stable in the presence of high concentrations of salt. Their fluorescence is strongly quenched by hypochlorite, while other common cations, anions and hydrogen peroxide have minor (or no) effects on fluorescence. On this basis, a fluorometric hypochlorite assay was developed that has a 0.1 μM detection limit and a linear range that extends from 1 to 30 μM. The method was successfully used to the determination of hypochlorite in local tap water samples, and the results agreed well with those obtained by a colorimetric method. Graphical Abstract Hypochlorite ion is found to quench the fluorescence copper nanoclusters synthesized by reduction of Cu(II) ion by formaldehyde in the presence of poly(vinyl pyrrolidone) serving as protecting agent. This finding resulted in a new fluorescence assay for hypochlorite.

Description: A nanoporous carbon derived from an aluminum-based metal-organic framework was deposited on stainless steel wires in a sol–gel matrix. The resulting fibers were applied to the solid-phase microextraction of the polycyclic aromatic hydrocarbons (PAHs) naphthalene, acenaphthene, fluorene, phenanthrene and anthracene from water and soil samples. The fiber was then directly inserted into the GC injector and the PAHs were quantified by GC-MS. The effects of salt addition, extraction temperature, extraction time, sample volume and desorption conditions on the extraction efficiency were optimized. A linear response to the analytes was observed in the 0.1 to 12 μg∙L −1 range for water samples, and in the 0.6 to 30 μg∙kg −1 for soil samples, with the correlation coefficients ranging from 0.9934 to 0.9985. The limits of detection ranged from 5.0 to 20 ng∙L −1 for water samples, and from 30 to 90 ng∙kg −1 for soil samples. The recoveries of spiked samples were between 72.4 and 108.0 %, and the precision, expressed as the relative standard deviations, is 〈12.8 %. Graphical Abstract A MOF derived nanoporous carbon coated fiber for use in solid-phase microextraction was prepared via sol–gel technology. The coated fiber has a porous, rough and wrinkled structure, and shows a high thermal stability, good extraction repeatability and long lifetime. The established HS-SPME-GC-MS method is suitable for the determination of the PAHs from water and soil samples.

Description: We describe uniform and high-temperature-stable mesoporous TiO 2 beads functionalized with gold nanoparticles (AuNPs-TiO 2 ) for use in conductometric sensing of gases and organic vapors. The size of the interconnected main mesopores of the TiO 2 beads ranges from 8 to 15 nm, and the AuNPs have diameters between 8 and 10 nm. The mesoporous TiO 2 beads are formed during calcination while the structure-directing template agent is removed. Monodispersed AuNPs are formed by reduction in-situ and are placed inside the mesoporous TiO 2 framework. This prevents aggregation of the AuNPs even at 500 °C. The materials were characterized by UV–vis spectroscopy, scanning and transmission electron microscopy, nitrogen adsorption-desorption, and X-ray diffraction. Comb-type gold electrodes were then fabricated on an alumina substrate and are shown to display excellent properties in terms of sensing ammonia, ethanol, methanol or acetone. The sensitivity (defined as the ratio of resistivities under vapor and air) of a typical AuNPs(0.5 %)-TiO 2 gas sensor for ethanol reached up to 5.65 at above 600 ppm at 75 °C. Response time and recovery times (t 90  ≤ 20 s) are faster than (or comparable to) other metal-doped TiO 2 sensors, and working temperatures are much lower. An interesting observation was made in that the changes in the conductivity of the sensor change with temperature. The sensor prepared with AuNPs(0.5 %)-TiO 2 is of the p-type (in its response to ammonia gas) at 45 °C, but becomes n-type at 20 °C. Obviously, rather slight changes in temperature lead to a complete change in the direction of the conductometric signal change. This may provide a new aspect in terms of selective and highly sensitive detection of ammonia at ambient and slightly elevated temperatures. Graphical abstract We describe uniform and high-temperature-stable mesoporous TiO 2 beads functionalized with gold nanoparticles (AuNPs-TiO 2 ) for use in conductometric sensing of gases and organic vapors. Interestingly, the changes in the conductivity of typical sensors were opposite with the increasing of temperature.

Description: Humidity and temperature sensors were fabricated from a nanocomposite consisting of CeO 2 -Co 3 O 4 hybrid nanoparticle-silicone adhesive and CeO 2 -Co 3 O 4 hybrid nanoparticle-polymer adhesive, respectively, to fix the material on a glass supported copper electrode. The impedance of the sensor decreases by a factor of 960 at a working frequency of 100 Hz, and by a factor of 800 at 1 kHz, on increasing relative humidity (RH) from 30 to 90 %. In parallel, the capacitances increase by factors of 567 and 355, respectively, under the same experimental conditions. The effect of temperature in the range from 25 to 70 °C on impedance (again at 100 Hz and 1 kHz) was also studied and found to decrease with increasing temperature. On going from 25 to 70 °C, the impedance measured at 100 Hz and 1 kHz decreases 2.22 and 1.58 times, respectively, in surface type sensors, while in sandwich type sensors this decrease is 3.0 and 2.08 times. The calculated average sensitivity to temperature is −1.02 and −0.8 % °C −1 for the surface type and −1.5 and −1.2 % °C −1 for the sandwich type sensors at frequencies of 100 Hz and 1 kHz, respectively. Graphical abstract A highly sensitive sensor with dual functionality for humidity and temperature has been fabricated by using CeO 2 -codoped Co 3 O 4 nanoparticles with silicone and polymer adhesive.

Description: Single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT) and graphene have been tested as carbon allotropes for the modification of carbon screen-printed electrodes (CSPEs) to simultaneously determine melatonin (MT) and serotonin (5-HT). Two groups of CSPEs, both 4 mm in diameter, were explored: The first includes commercial SWCNT, MWCNT and graphene, the second includes SWCNT, MWCNT, graphene oxide nanoribbons and reduced nanoribbons that were drop casted on the electrodes. The carbon nanomaterials enhanced the electroactive area in the following order: CSPE 〈MWCNTs 〈SWCNTs 〈graphene. This allowed the simultaneous determination of 5-HT and MT at the working potentials of +50 mV and +390 mV (vs. Ag), respectively. The use of carbon nanomaterials, in particular of graphene oxide nanoribbons on CSPEs, represents an excellent and disposable tool for sensing the two target molecules in even small sample volumes. Figures of merit for MT and 5-HT include (a) detection limit of 1.1 and 0.4 μM for MT and 5-HT, respectively; (b) an inter-electrode reproducibility with RSD ≤ 8 %; (c) 120 s response time, and (d) recoveries (in case of spiked samples) ranging from 94 to 103 % (with an RSD 〈 1 %). Graphical Abstract Carbon nanomaterials on screen-printed electrodes: smart electrochemistry for fast, simultaneous and reliable detection of serotonin the molecule of happiness and melatonin the molecule of darkness.

Description: We describe a sensitive photoelectrochemical (PEC) sensor for the determination of the herbicide clethodim. The PEC sensor was constructed by using amino-MIL-125/TiO 2 (MIL stands for Materials from Institute Lavoisier), an amino-functionalized metal-organic framework (MOF) modified with TiO 2 . The amino-MIL-125/TiO 2 was synthesized by a simple one-step solvothermal method and placed on a glassy carbon electrode where it displays photoelectrocatalytic activity. Scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and X-ray diffractometry (XRD) were used to characterize the amino-MIL-125/TiO 2 . In the sensing process, amino-MIL-125/TiO 2 is illuminated by visible light to produce electrons. These excited electrons are delivered to the glassy carbon electrode, leaving positively charged holes (h + ) on the surface of the amino-MIL-125/TiO 2 . The holes react with H 2 O to generate hydroxy radicals (•OH). Clethodim rapidly attacks the hydroxy radicals and improves the efficiency of charge separation, this leading to an enhanced photocurrent. Under the optimal experimental conditions, this photoelectrochemical method enables clethodim to be quantified in the concentration range from 0.2 to 25 μmol L −1 , with a detection limit (3 S/N) of 10 nmol L −1 . The assay was applied to the determination of clethodim in soil samples, and results were in acceptable agreement with data obtained by liquid chromatography/mass spectrometry. Graphical Abstract An amino-functionalized metal-organic framework (MOF) modified with titanium dioxide was synthesized and used as a new platform for photoelectrochemical sensing of the herbicide clethodim.

Description: In this paper, we investigate the role of electromagnetic field on the stability regions of charged self-gravitating compact objects by using the concept of cracking. For this purpose, we have applied local density perturbation scheme to the hydrostatic equilibrium equation as well as on physical parameters involved in the model. In particular, we have examined the cracking of charged compact objects like PSR J1614-2230, PSR J1903+327, Vela X-1, SMC X-1 and Cen X-3 with different values of charge. We conclude that these objects exhibit cracking and stability regions decreases with the increase of charge.

Description: In this paper we have studied the behavior of static spherically symmetric relativistic objects with locally anisotropic matter distribution considering the Tolman VII form for the gravitational potential \(g_{rr}\) in curvature coordinates together with the linear relation between the energy density and the radial pressure. The interior spacetime has been matched continuously to the exterior Schwarzschild geometry. We have investigated and analyzed different physical properties of the stellar model and presented graphically.

Description: We report on a new amplification strategy for use in an immunoassay for influenza virus subtype H7N9. Graphene sheets were first placed on a glassy carbon electrode (GCE), and gold nanoparticles were then electrodeposited as a support for a layer of alcohol dehydrogenase (ADH) in a sol–gel containing thiol groups. Protein A was used to properly orientate immobilized antibody against H7N9 on the sol–gel, and this is shown to result in strongly improved specificity of the antigen-antibody binding. Thus, a sensitive and specific immunosensor was obtained in which a quadruple signal amplification strategy is employed, viz. (a) via the use of graphene sheets, (b) via a hybridization chain reaction, (c) the use of hemin/G-quadruplex DNAzyme concatamers, and (d) the use of ADH. The hemin/G-quadruplex is a typical DNAzyme, which simultaneously acts as NADH oxidase and HRP-mimicking DNAzyme. The hybridization chain reaction-based DNAzyme concatamers assembled on multi-walled carbon nanotubes (MWCNTs) and the ADH represent a triple electrocatalytic enzyme cascade system. Sandwich immunoreactions occurred between the capture antibody on the electrode and the secondary antibody labeled with MWCNTs. Positively charged Methylene Blue (MB) was then used as an intercalator to detect the DNAzyme concatamer formed. The differential pulse voltammetric signals for MB are related to the concentration of H7N9 in the range from 8 to 60 pg · mL −1 , and the detection limit is 0.81 pg · mL −1 (at an S/N ratio of 3). This immunoassay is very sensitive, specific and robust. Graphical Abstract An electrochemical sandwich immunosensor has been developed for sensitive and specific detection of influenza virus subtype H7N9. Protein A was used to properly orientate antibody. The hybridization chain reaction based DNAzyme concatamers assembled on multi-walled carbon nanotubes (MWCNTs) and the ADH represent a triple electrocatalytic enzyme cascade system.

Description: This paper explores structure scalars of cylindrically symmetric spacetime in Brans-Dicke gravity. We construct twelve scalar factors using orthogonal splitting of the Reimann tensor and study their distinct dynamical interpretations. These structure scalars are used to derive a set of governing equations of the evolving system. It is concluded that cylindrical systems are necessarily inhomogeneous. Finally, we show that all possible static inhomogeneous cylindrical solutions can be obtained through structure scalars.

Description: In this Letter, based on Bianchi-I type cosmological model, we have studied the evolution of universe in terms of a vector field coupled to the scalar field. The symmetries of the system are calculated in the Noether approach, the scalar potential and the gauge kinetic function are also obtained following these symmetries. The dynamical equations are integrated numerically and the behaviors of cosmological evolution are presented certainly. Furthermore, the early-time and late-time scenarios are also reached asymptotically, that is, the universe is during the period of decelerating expansion in the early time while during the period of accelerating expansion in the late time. Moreover, we have also studied the expansion isotropization of the universe during evolution. There is no Kasner solution in the present case, while the universe would approach an isotropic Robertson-Walker one, concretely, a de Sitter type one in the late time.

Description: We describe a turn-off fluorescence-based strategy for the detection of ATP by making use of aptamer-triggered dsDNA concatamers. This sensitive and easily controlled method is based on consecutive hybridization induced by ATP aptamers and their sectional complementary DNAs to form dsDNA concatamers. The intercalator SYBR Green I (SGI) was employed as a fluorescent probe. In the absence of ATP, the probe produces a strong signal. However, on addition of ATP, the binding of aptamer and ATP cause the concatamers to collapse and to release SGI whose fluorescence then is quenched. The effect was exploited to design a selective ATP assay by relating the decrease in fluorescence to the ATP concentration. A lower detection limit of 6.1 μM and a linear response in the 0 to 5000 μM concentration range was accomplished. The strategy was applied to cellular ATP assays, and the results obtained by this strategy and by the gold standard method are in good agreement. The method is sensitive, simple and cost efficient, and hence is promising in terms of future applications to determine ATP in cellular and other systems. Graphical Abstract A turn-off fluorescence-based strategy for the selective detection of ATP by using aptamer-triggered dsDNA concatamers.

Description: In this paper, based on the BSBM theory, we investigate the dynamics of a homogeneous and anisotropic Bianchi type-V (BV) cosmological model subject to variation of the fine structure constant. By performing stability analysis, the anisotropic cosmic attractors are obtained and the anisotropic parameters are studied. The outcome confirms that universe underwent both anisotropy and variation of fine structure constant in the past for an accelerating expansion. However, the result also shows that both anisotropy and fundamental constant variation exist at the present epoch and even become greater in the future. This is in contradiction with the current observational data and therefore the model is not satisfactory.

Description: Our aim is to prove that long time series of solar observations measured with Metsähovi Radio Observatory’s 1.8-meter solar radio telescope, RT-1.8, at 11.2 GHz are reliable, and that the data can be used for solar cyclicity studies. We give a detailed description of RT-1.8 and its calibration. We compare 14 years of Metsähovi Radio Observatory’s solar data from solar cycles 23 and 24 to both Dominion Radio Astrophysical Observatory (DRAO 2015 ), Penticton, Canada 2.8 GHz and Nobeyama Solar Radio Observatory (NSRO 2015 ), Nobeyama, Japan 9.4 and 17.0 GHz data. Our results show high correlation between all data sets.

Description: A molecularly imprinted polymer (MIP) was prepared by self-polymerization of dopamine in the presence of bovine hemoglobin (BHb) and then deposited on the surface of an electrode modified with gold nanoparticles (AuNPs). Scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry were employed to characterize the modified electrode using the hexacyanoferrate redox system as an electroactive probe. The effects of BHb concentration, dopamine concentration, and polymerization time were optimized. Under optimized conditions, the modified electrode selectively recognizes BHb even in the presence of other proteins. The peak current for hexacyanoferrate, typically measured at + 0.17 V (vs. SCE), depends on the concentration of BHb in the 1.0 × 10 −11 to 1.0 × 10 −2  mg mL −1 range. Due to the ease of preparation and tight adherence of polydopamine to various support materials, the present strategy conceivably also provides a platform for the recognition and detection of other proteins. Graphical Abstract Gold nanoparticles and molecularly imprinted self-polymerization dopamine were modified on gold electrode surface to recognize and determine bovine hemoglobin. Under the optimized conditions, the modified electrode showed specific adsorption, selective recognition, and sensitive detection of bovine hemoglobin.

Description: We report on an electrochemical method for the determination of the activity of trypsin. A multi-functional substrate peptide (HHHAKSSATGGC-HS) is designed and immobilized on a gold electrode. The three His residues in the N-terminal are able to recruit thionine-loaded graphene oxide (GO/thionine), a nanocover adopted for signal amplification. Once the peptide is cleaved under enzymatic catalysis by trypsin (cleavage site: Lys residue), the His residues leave the electrode, and the GO/thionine cannot cover the peptide-modified electrode anymore. Thus, the changes of the electrochemical signal of thionine, typically acquired at a voltage of -0.35 V, can be used to determine the activity of trypsin. A detection range of 1 × 10 −4 to 1 U, with a detection limit of 3.3 × 10 −5  U, can be achieved, which is better than some currently available methods. In addition, the method is highly specific, facile, and has the potential for the detection of trypsin-like proteases. Graphical abstract Graphene oxide was adopted as a nanocover for the development of a sensitive electrochemical method to detect the activity of trypsin.

Description: We report on the microwave-assisted synthesis of ultrasmall Ce 3+ and Tb 3+ -doped SrF 2 nanocrystals (NCs) capped with glutathione (GSH). The NCs have an average size of about 5 nm and show bright green fluorescence upon photoexcitation at 290 nm. Fluorescence is strongly quenched by Hg(II) and Pb(II). This finding was applied to design a method for the fairly selective determination of these ions. The detection limits (for the 3σ/slope criterion) are 20 μM and 30 μM for Hg(II) and Pb(II) ions, respectively. The intensity of the luminescence can be restored by the addition of ethylenediaminetetraacetic acid (EDTA), and this suggests that these NCs can be used as reusable fluorescent probes. Graphical Abstract Scheme illustrating the metal induced change in the binding modality of GSH ligand upon addition of metal (M) ions and EDTA solution through metal-ligand interaction.

Description: We describe a novel magnetic nanosorbent that consists of nanowires consisting of a core of metallic iron and an iron (III) oxide shell. These nanowires were then deposited on graphene oxide to form a composite of the type Fe@Fe 2 O 3 /GO. Specifically, the magnetic composite is formed via electrostatic interaction between negatively charged GO nanosheets and positively charged Fe@Fe 2 O 3 nanowires in aqueous solution. The material was successfully applied to the extraction of the endocrine-disrupting phenols bisphenol A, triclosan and 2,4-dichlorophenol from water samples. Compared to neat graphene oxide, the composite material exhibits improved properties in terms of microextraction where both the hydrophilic graphene oxide and the Fe@Fe 2 O 3 nanowires participate in the adsorption of the hydrophilic analytes. The amount of adsorbent, pH of water sample, extraction time and desorption time, type and volume of desorption solution were optimized. Following extraction for the absorbent, the phenols were quantified by HPLC. The three phenols can be determined in 0.5 to 100 ng∙mL −1 concentration range, with limits of detection (at an S/N ratio of 3) ranging from 0.08 to 0.10 ng∙mL −1 . The repeatability was investigated by evaluating the intra- and inter-day precisions with relative standard deviations of lower than 7.5 % ( n  = 5). The recoveries from spiked real water samples were in the range from 84.8 to 92.0 %. The results indicate that the novel material can be successfully applied to the extraction and analysis of phenols from water samples. Graphical Abstract Scheme 1 procedure for the synthesis of Fe@Fe 2 0 3 /G0

Description: Immobilization of proteins on a solid support is critical with respect to the fabrication and performance of biosensors and biochips. Protein attachment with a preferable orientation can effectively avoid its denaturation and keeps its active sites fully exposed to solution, thus maximally preserving the bioaffinity or bioactivity. This review (with 140 refs.) summarises the recent advances in oriented immobilization of proteins with a particular focus on antibodies and enzymes. Following an introduction that describes reasons for oriented immobilization on (nano)surfaces, we summarize (a) methods for (bio)chemical affinity-mediated oriented immobilization (with sections on immunoglobulin G (IgG)-binding protein as the capture ligand, DNA-directed immobilization, aptamer- and peptide-mediated immobilization, affinity ligand and fusion tag-mediated immobilization, material-binding peptide-assisted immobilization); (b) methods for covalent oriented immobilization (with sections on immobilization via cysteine residues or cysteine tags, via carbohydrate moieties; via enzyme fusion or enzymatic catalysis, and via nucleotide binding sites of antibodies); (c) methods based on molecular imprinting techniques; (d) methods for characterization of oriented immobilized proteins; and then make conclusions and give perspectives. Graphical Abstract This review summarises recent advances in oriented immobilization of proteins based on strategies via bio−/chemical affinity, covalent bonding, and molecular imprinting techniques. Advantages and disadvantages of each approach are discussed.

Description: Magnetic oleate-coated Fe 3 O 4 nanoparticles were applied to the extraction of PCBs from fruit juices that were quantified by gas chromatography coupled to triple quadrupole mass spectrometry. Two methods were evaluated: The first method involves a two-step procedure that combines dispersive liquid-liquid microextraction with dispersive micro-solid phase extraction, and the second one involves magnetic solid-phase extraction (mSPE) carried out in a single step. The mSPE procedure is shown to be more sensitive, and therefore, it was optimized and applied to the analysis of PCBs in juices. The detection limits for all target PCBs are below 6 ng∙L −1 for apple juice, and 3 ng∙L −1 for grape juice. The enrichment factor is 125. Analysis of spiked fruit juice samples gave relative recoveries higher than 70 % for all PCBs except for PCB28 and PCB52. Graphical Abstract Diagram of the extractive methods using magnetic nanoparticles (MNPs): A ) two-step method combining dispersive liquid-liquid microextraction (DLLME) with dispersive micro solid-phase extraction (D-μ-SPE) and B ) one-step magnetic solid-phase extraction (mSPE) procedure

Description: Thin-layered molybdenum disulfide (MoS 2 ) was intercalated, via ultrasonic exfoliation, into self-doped polyaniline (SPAN). This material, when placed on a glassy carbon electrode (GCE), exhibits excellent electrical conductivity and synergistic catalytic activity with respect to the detection of bisphenol A (BPA). The electrochemical response of the modified GCE to BPA was investigated by cyclic voltammetry and differential pulse voltammetry. Under optimal conditions, the oxidation peak current (measured best at 446 mV vs. SCE) is related to the concentration of BPA in the range from 1.0 nM to 1.0 μM, and the detection limit is 0.6 nM. Graphical Abstract Thin-layered molybdenum disulfide (MoS 2 ) was intercalated into self-doped polyaniline (SPAN) via ultrasonic exfoliation. The special conjugated structure and functional groups of MoS 2 -SPAN composite help to adsorb BPA easily. MoS 2 -SPAN has a synergistic effect for catalyzing the oxidation of BPA. The BPA electrochemical sensor based on MoS 2 -SPAN has a high sensitivity and low detection limit.

Description: We have synthesized nitrogen-doped graphene nanoribbons (N-GrNRs) by unzipping multi-walled carbon nanotubes (CNTs) under strongly oxidizing conditions and subsequent doping with nitrogen by a low-temperature hydrothermal method. The N-GNRs were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy, and assembled on a disposable screen-printed carbon electrode to give a sensor for H 2 O 2 that was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, chronocoulometry and chronoamperometry. The nano-modified electrode displays enhanced electron transfer ability, and has a large active surface and a large number of catalytically active sites that originate from the presence of nitrogen atoms. This results in a catalytic activity towards H 2 O 2 reduction at near-neutral pH values that is distinctly improved compared to electrodes modified with CNTs or unzipped (non-doped) CNTs only. At a working potential of −0.4 V (vs. Ag/AgCl), the amperometric responses to H 2 O 2 cover the 5 to 2785 μM concentration range, with a limit of detection as low as 1.72 μM. This enzyme-free electrochemical sensor exhibits outstanding selectivity and long-term stability for H 2 O 2 detection. Graphical Abstract Nitrogen-doped graphene nanoribbons (N-GrNRs) were expediently synthesized for highly sensitive and selective detection of H 2 O 2 .

Description: We have investigated the possibility of sampling ammonium ion using the diffusive-gradients-in-thin-films technique (DGT) by introducing a novel binding agent that is based on micro-sized zeolite. The performance of zeolite-DGT was characterized by measurement of the following parameters: (1) the diffusion coefficient of ammonium ion in hydrogel; (2) the adsorption rate of ammonium ion by the zeolite binding gel; (3) the elution efficiency, and (4) the effects of pH, ionic strength and interfering ions on DGT. The method was validated by studying the uptake of ammonium ion from in freshwaters by zeolite gels which was found to be fast enough to meet the requirements of DGT. The concentrations determined via DGT agreed well with the concentrations determined in bulk solutions. Sampling of ammonium ion using zeolite-DGT was consistent over the pH 3 to 8 range and the 0.001 to 10 mM ionic strength range. The method also performs predictably in natural waters containing various metal ions. The technique is considered to be a viable passive tool for sampling ammonium from aqueous solutions. Graphical Abstract Schematic representation of the principle of DGT and the determination of mass accumulated on the binding gel.

Description: We report on a method for the determination of magnetic bead-labeled C-reactive protein (CRP), a biomarker of cardiovascular diseases and inflammations. It is using a flexible giant magnetoimpedance (GMI)-based platform. Micro-patterned GMI sensing elements were prepared from a cobalt-based commercial amorphous ribbon (Metglas® 2714A) using micro electro-mechanical system (MEMS) technology. A gold film was then deposited on the GMI sensing element to act as a support for the immuno platform. Sandwich assays are performed using antibody-antigen combinations and biotin-streptavidin interactions on the gold film substrate surface via self-assembled layers. The GMI ratios of the sensors with different concentrations of antigen against CRP were investigated. The results show that the presence of CRP antigens on the biosensor improves the GMI effect owing to the induced magnetic dipole of superparamagnetic beads, and that the GMI ratios show distinct changes at high frequency. This bioassay for CRP has a linear detection range between 1 to 10 ng·mL −1 . This new method in our perception provides a widely applicable basis for rapid diagnostic testing and will pave the way for future development of electrochemical point-of-care diagnostic devices for cardiac diseases. Graphical Abstract (a) Graphical illustration of CRP test setup. (b) Magnetic field arrangement of the beads under an applied magnetic field. (c) GMI changes in relation to the concentration of the CRP

Description: We describe the fairly easy preparation of thiol stabilized water soluble cadmium sulfide quantum dots and the modification of their surface with the human transferrin protein siderophiline. The particles are shown to enable targeted imaging of human breast adenocarcinoma cell (type MCF7). The fluorescence quantum yield of the modified QDs is ~0.74. The particles have an average diameter of 8.1 ± 0.1 nm as determined in solution by dynamic light scattering. The cancer cells were imaged by fluorescence microscopy of the QDs which display strong green fluorescenece under 350 nm excitation. A cytotoxicity assay showed 66 and 78 % cell viabilities, respectively, after 24 h of incubation with the QDs and modified QDs. Graphical Abstract Water-soluble cadmium sulfide QDs were modified with siderophiline (transferrin) and applied to fluorescent and targeted imaging of breast cancer cells. Left: control (human breast cancer cells (type MCF-7) were treated with QDs without siderophiline); right: human breast cancer cells (type MCF-7) treated with siderophiline modified QDs

Description: We describe the preparation of carbon dots (CDs) from glucose that possess high stability, a quantum yield of 0.32, and low toxicity (according to an MTT assay). They were used, in combination with the fluorogenic zinc(II) probe quercetin to establish a fluorescence resonance energy transfer (FRET) system for the determination of Zn(II). The CDs are acting as the donor, and the quercetin-Zn(II) complex as the acceptor. This is possible because of the strong overlap between the fluorescence spectrum of CDs and the absorption spectrum of the complex. The method enables Zn(II) to be determined in the 2 to 100 μM concentration range, with a 2 μM detection limit. The method was applied to image the distribution of Zn(II) ions in HeLa cells. Graphical Abstract Based on the fluorescence resonance energy transfer (FRET) between carbon dots and quercetin (QCT)-Zn 2+ , the fluorescence indicator was established, which displays high sensitivity and selectivity in the detection of Zn 2+ . The method was also applied to image the distribution of Zn(II) ions in HeLa cells.

Description: Sensitive detection of engineered nanoparticles (NPs) in air and in liquid samples is an important task and still a major challenge in analytical chemistry. Recent work demonstrated that it can be performed using surface plasmon microscopy (SPM) where binding of single NPs to a surface leads to the formation of characteristic patterns in differential SPM images. However, these patterns have to be discriminated from a noisy background. Computer-assisted recognition of nanoparticles offers a solution but requires the development of respective tools for data analysis. Hereby a numerical method for automated detection and characterization of images of single adsorbing NPs in SPM image sequences is presented. The detection accuracy of the method was validated using computer generated images and manual counting. The method was applied for detecting and imaging of gold and silver NPs adsorbing from aqueous dispersions and for soot and NaCl NPs adsorbing from aerosols. The determined adsorption rate was in range 0.1–40 NPs per (s mm 2 ) and linearly dependent on the concentration of nanoparticles. Depending on the type of NPs and signal to noise ratio, a probability of recognition of 90–95 % can be achieved. Graphical Abstract A computer-assisted method is presented for the detection and characterization of images of single adsorbing nanoparticles in surface plasmon microscopy images. The method was validated and can be applied to detecting and imaging of nanoparticles absorbed from aqueous dispersions and aerosols.

Description: This work investigates the theoretical and numerical studies on nonlinear propagation of ion acoustic solitary waves (IASWs) in an unmagnetized plasma consisting of nonextensive electrons, Boltzmann positrons and relativistic thermal ions. The Korteweg-de Vries (KdV) equation is derived by using the well known reductive perturbation method. This equation admits the soliton like solitary wave solution. The effects of phase velocity, amplitude of soliton, width of soliton and electrostatic nonlinear propagation of weakly relativistic ion-acoustic solitary waves have been discussed with graphical representation found in the variation of the plasma parameters. The obtained results can be helpful in understanding the features of small but finite amplitude localized relativistic ion-acoustic waves for an unmagnetized three component plasma system in astrophysical compact objects.

Description: This article describes a new procedure for multi-element preconcentration of heavy metal ions, specifically of Cr(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II) ions. The method is based on dispersive micro solid-phase extraction (DMSPE) of the metal complexes of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) by graphene oxide nanoparticles prior to energy dispersive X-ray fluorescence spectrometric (EDXRF) determination. The effects of pH, amount of graphene oxide, concentration of complexing reagent, sample volume and sorption time were optimized. The influence of commonly encountered other ions was also investigated. Under optimal conditions, the calibration plots cover the 2 to 150 ng mL −1 range for each element. The precision (at a 20 ng mL −1 level for n  = 10) is lower than 4.8 %, and the detection limits range is from 0.07 to 0.25 ng mL −1 . The DMSPE-EDXRF procedure was successfully applied to the determination of heavy metal ions in water and spiked water samples with recoveries between 94.4 and 103.5 %. Graphical Abstract Schematic of the dispersive solid-phase microextraction of metal complexes of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) using graphene oxide nanoparticles, followed by their energy dispersive X-ray fluorescence spectrometric determination.

Description: Systematic relationships of the subclass-averaged rise, decay times and durations of flare events as a function of the logarithmic peak flux ( \(\operatorname{ln}f\) ) are investigated, employing the soft X-ray flares observed by GOES during the period from September 1975 to October 2014. Different behaviors are found before and after 1997. Since 1997 they all vary linearly with \(\operatorname{ln}f\) , obeying the RV model. However, prior to 1997 they vary quadratically with \(\operatorname{ln}f\) , implying a different energy storage/release process of flaring. The discrepancy may be related to the variation in the turbulence in the corona caused by the weakening magnetic field strength in the recent two decades. This motivates us to propose a Stochastic-Diffusive model for explaining the above result, by assuming that the temporal rate of flare energy resulted by external forces is proportional to the total energy already stored in the flare system and inversely proportional to the size scale of diffusion.

Description: Intermediate inflation is considered in a non-canonical scalar field model, in which the kinetic term of scalar field is taken as a power-law function. The free parameters of the model are constrained by using the most recent observational data related to scalar spectra index, tensor-to-scalar ratio, and scalar perturbation amplitude. The results are used to depict the potential behavior of the model and estimate the initial and final time of inflation.

Description: In light of the recent interest in dynamical dark energy models based on a cosmology with varying gravitational and cosmological parameters \(G\) and \(\varLambda\) , we present here a model of inertia in a type of Friedmann universe with \(G = G_{0}(A/A_{0})^{\sigma}\) ; \(A\) being the dimensionless scale factor, that was recently studied by Singh et al. (Astrophys. Space Sci. 345:213, 2013 ). The proposed Machian model of inertia utilizes the curved space generalization of Sciama’s law of inertial induction, which is based on the analogy between the retarded far fields of electrodynamics and those of gravitation, and expresses the total inertial force \(F= -ma\) on an accelerating mass \(m\) in terms of contributions from all matter in the observable Universe. We show that for a varying Friedmann model with \(\sigma=-3/2\) , inertial induction alone can account for the total inertial force on the accelerating mass. We then compare this cosmological model with current observational constraints for the variation of \(G\) .

Description: Elemental abundance provides an effective vehicle to understand lunar petrologic characteristics and evolutional history. The APXS mounted on the Yutu rover provides a valuable opportunity to determine the major elemental abundances in lunar soil within a short distance. In this study, we processed the APXS spectra including energy calibration, dead time correction and nonlinear least-squares fitting, and determined the abundances of the lunar major elements using the fundamental parameter method. In the calculation of X-ray fluorescence yield, a finite element method (FEM) was employed to improve the accuracy. The major elemental abundances derived from Chang’E-3 (CE-3) APXS possess a good consistency with the result of LP-GRS (Lunar Prospector gamma-ray spectrometer) data in the landing region. Compared with the chemical composition of the returned lunar rock samples, we draw the conclusion that the lunar soils in CE-3 landing site are fragments of mare basalts. Our conclusion is supported by the geological map of Mare Imbrium.

Description: Mathematica program for various general observer quantities in the general theory of relativity has been developed which uses coordinate system, metric tensor and unit timelike velocity vector as input.

Description: We consider the cosmological system with two interacting fluids: dark energy and dark matter, in a homogeneous and isotropic universe with dissipation. The modified gravitational equation for dark matter is solved. The analytic representations for the Little Rip, the Pseudo Rip, and the bounce cosmology models with dissipation are obtained in terms of the thermodynamic parameters in the equation of state. We analyze the corrections in the energy density for dark matter, in view of the dissipative processes and the coupling with dark energy.

Description: In this paper, we have investigated Kantowski-Sachs space-time in the presence of anisotropic fluid with variable equation of state (EoS) parameter and constant deceleration parameter in the scale covariant theory of gravitation proposed by Canuto et al. (Phys. Rev. Lett. 39:429, 1977 ). We have found a determinate solution of the field equations of the theory using variation law for Hubble’s parameter given by Bermann (Nuvo Cimento 74:182, 1983 ). Our solution represents Kantowski-Sachs dark energy model in this theory. The physical and kinematical properties of the model are also discussed.

Description: Spatially homogeneous and anisotropic Kantowski-Sachs space-time is considered in the scale covariant theory of gravitation proposed by Canuto et al. (Phys. Rev. Lett. 39:429, 1977 ) in the presence of bulk viscous fluid containing one dimensional cosmic strings. A determinate solution of the field equations of this theory is presented using the special law of variation proposed by Bermann (Nuovo Cimento B74:183, 1983 ). We have also used the proportionality of shear scalar to the scalar expansion of the space time. The solution obtained represents a bulk viscous string cosmological model in this theory. Some physical and kinematical properties of the model are also discussed.

Description: We follow the development of nonaxisymmetric instabilities of self-gravitating disks from the linear regime to the nonlinear regime. Particular attention is paid to comparison of nonlinear simulation results with previous linear and quasi-linear modeling results to study the mass and angular momentum transport driven by nonaxisymmetric disk instabilities. Systems with star-to-disk mass ratios of \(M_{*}/M_{d} = 0.1\) and 5 and inner-to-outer disk radius ratios of \(r_{-}/r_{+} = 0.47\) to 0.66 are investigated. In disks where self-gravity is important, systems with small \(M_{*}/M_{d}\) and large \(r_{-}/r_{+}\) , Jeans-like J modes are dominant and the gravitational stress drives angular momentum transport. In disks where self-gravity is weak, systems with large \(M_{*}/M_{d}\) and large \(r_{-}/r_{+}\) , shear-driven P modes dominate and the Reynolds stress drives angular momentum transport. In disks where self-gravity is intermediate in strength between disks where P modes dominate and disks where J modes dominate, I modes control the evolution of the system and the Reynolds and gravitational stresses both play important roles in the angular momentum transport. In all cases, redistribution of angular momentum takes place on the characteristic disk timescale defined as the orbital period at the location of maximum density in the disk midplane. The disk susceptible to one-armed modes behaves differently than disks dominated by multi-armed spirals. Coupling between the star and the disk driven by one-armed modes leads to angular momentum transfer between the star and disk even when instability is in the linear regime. All modes drive spreading of the disk material and eventually accretion onto the star. The disks dominated by an I mode and one-armed mode do not lead to prompt fission or fragmentation. The J mode dominated disk fragments after instability develops.

Description: Amplitude modulation of a positron acoustic wave is considered in a four-component electron–positron plasma in the quantum magnetohydrodynamic regime. The important ingredients of this study are the inclusion of the particle exchange-correlation potential, quantum diffraction effects via the Bohm potential, and dissipative effect due to viscosity in the momentum balance equation of the charged carriers. A modified nonlinear Schrödinger equation is derived for the evolution of the slowly varying amplitude of the quantum positron acoustic wave by employing the standard reductive perturbation technique. Detailed analysis of the linear and nonlinear dispersions of the quantum positron acoustic wave is presented. For a typical parameter range, relevant to some dense astrophysical objects, it is found that the quantum positron acoustic wave is modulationally unstable above a certain critical wavenumber. Effects of the exchange-correlation potential and the Bohm potential in the wave dynamics are also studied. It is found that the quantum effect due to the particle exchange-correlation potential is significant in comparison to the effect due to the Bohm potential for smaller values of the carrier wavenumber. However, for comparatively larger values of the carrier wavenumber, the Bohm potential effect overtakes the effect of the exchange-correlation potential. It is found that the critical wavenumber for the modulation instability depends on the ratio of the equilibrium hot electron number density and the cold positron number density and on the ratio of the equilibrium hot positron number density and the cold positron number density. A numerical result on the growth rate of the modulation instability is also presented.

Description: We study a more complex case of Hohmann orbital transfer of a satellite by considering non-coplanar and elliptical orbits, instead of planar and circular orbits. We use as parameter the angle between the initial and transference planes that minimizes the energy, and therefore the fuel of a satellite, through the application of two non-tangential impulses for all possible cases. We found an analytical expression that minimizes the energy for each configuration. Some reasonable physical constraints are used: we apply impulses at perigee or apogee of the orbit, we consider the duration of the impulse to be short compared to the duration of the trip, we take the nodal line of three orbits to be coincident and the three semimajor axes to lie in the same plane. We study the only four possible cases but assuming non-coplanar elliptic orbits. In addition, we validate our method through a numerical solution obtained by using some of the actual orbital elements of Sputnik I and Vanguard I satellites. For these orbits, we found that the most fuel-efficient transfer is obtained by applying the initial impulse at apocenter and keeping the transfer orbit aligned with the initial orbit.

Description: In this paper, we have studied the Einstein-Rosen space time in \(f(R,T)\) gravity by considering the second model of Harko et al. (Phys. Rev. D 84:024020, 2011 ), \(f(R,T) = f_{1}(R)+f_{2}(T)\) , where \(f_{1}(R)=\lambda R\) ; \(f_{2}(T)=\lambda T\) and \(f_{1}(R)=\lambda R\) ; \(f_{2}(T)=\lambda T^{2}\) . The matter field is considered in the form of perfect fluid. It is observed that, the perfect fluid represent the Zel’dovich universe in both the forms.

Description: Ionospheric scintillation is a significant component of space-weather studies and serves as an estimate for the level of perturbation in the satellite radio wave signal caused due to small-scale ionospheric irregularities. B-spline functions are used on the GPS ground based data collected during the year 2007–2012 for modeling high- and mid-latitude ionospheric scintillation. Proposed model is for Hornsund, Svalbard and Warsaw, Poland. The input data used in this model were recorded by GSV 4004b receivers. For validation, results of this model are compared with the observation and other existing models. Physical behavior of the ionospheric scintillation during different seasons and geomagnetic conditions are discussed well. Model is found in good coherence with the ionospheric scintillation theory as well as to the accepted scintillation mechanism for high- and mid-latitude.

Description: Alloy nanoparticles of the type Pt x Fe (where x is 1, 2 or 3) were synthesized by coreduction with sodium borohydride in the presence of carbon acting as a chemical support. The resulting nanocomposites were characterized by scanning electron microscopy and X-ray diffraction. The nanocomposite was placed on a glassy carbon electrode, and electrochemical measurements indicated an excellent catalytic activity for the oxidation of glucose even a near-neutral pH values and at a working voltage as low as 50 mV (vs. SCE). Under optimized conditions, the sensor responds to glucose in the 10.0 μM to 18.9 mM concentration range and with a 3.0 μM detection limit (at an S/N ratio of 3). Interferences by ascorbic acid, uric acid, fructose, acetamidophenol and chloride ions are negligible. Graphical Abstract Nonenzymatic sensing of glucose is demonstrated at neutral pH values and low working potential using a glassy carbon electrode modified with platinum-iron alloy nanoparticles on a carbon support.

Description: In the Earth-Moon-spacecraft circular restricted three-body problem (CRTBP), the evaluation of the orbits near the Moon can distinctly reflect the complexity of the dynamical system. In this paper, the long-term behavior of the spatial orbit near the Moon is investigated in the CRTBP. The Poincare section, where the section points are defined as the lunar apsides, is an effective tool. The distribution of the long-term capture solutions and the orbital elements of the section points display the long-term behavior of the spatial lunar orbits from the qualitative and quantitative angles, respectively. As two kinds of important long-term lunar orbits, the quasi-periodic and periodic orbits are also investigated. Using the continuation scheme, we obtain the spatial lunar periodic orbit families. The characters of the periodic orbit families are discussed in detail. In addition, some applications of the spatial lunar periodic orbits are given. The method to investigate the long-term behavior of the spatial lunar orbits we present is simple and direct. We can easily locate the lunar quasi-periodic orbit and obtain the spatial periodic orbit family.

Description: Compact stars serve as a logical regimen for the implementation of theoretical models that are difficult to understand from an experimental setup. In our present work, we discuss the stability of self-gravitating compact objects by using the concept of cracking in the linear regime. We investigate the effect of density perturbation and local anisotropy on the stability regions of the following compact objects, neutron star PSR J1614-2230, the millisecond pulsar PSR J1903+327 and X-ray pulsars Vela X-1, SMC X-1, Cen X-3. We find that SMC X-1 is the stable compact object and all other exhibit cracking.

Description: In this paper, non-diagonal Bianchi type-IV space-time is investigated in Einstein general theory of relativity. The matter field is considered in the form of perfect dark energy fluid. It is interesting to observe that in this case, Bianchi type IV perfect dark energy fluid cosmological model does not exist. The space-time reduces to Minkowskian geometry.

Description: A single glass conical nanopore functionalized with 6-carboxymethyl-chitosan (CMC) was applied to study the binding of bovine serum albumin (BSA) because of both hydrophobic and hydrophilic interactions. The interactions between the CMC-modified nanopore and BSA within the confined space were studied via the ionic current passing the nanopore by measuring the current–voltage (I–V) curves in 10 mM KCl solution. The hydrophilicity of CMC was varied by adjusting the pH values. Significant changes in the ionic current were observed following attachment of BSA. The relative contributions of hydrophobic and hydrophilic interactions depend on whether solutions are acidic or basic. A linear relationship exists between the concentration of BSA (up to 500 nM) and the ionic current at pH 12. This suggests a potential application of the method for sensing proteins via sweep voltammetry on a nanoscale. The nanodevice described here can be made reversible by ultrasonication to remove the attached BSA molecules. Graphical Abstract A single glass conical nanopore functionalized with 6-carboxymethyl-chitosan (CMC) was used to study the hydrophobic/hydrophilic association with BSA molecules both in acid and basic conditions by using sweep voltammetry. A linear relationship between the concentration of additional BSA and the ionic current of the nanopore at pH 12 was achieved, which suggests a promising application in biosensing of proteins.

Description: We propose a new model of modified \(F(R)\) gravity theory with the function \(F(R) = (1/\beta) \arcsin(\beta R)\) . Constant curvature solutions corresponding to the flat and de Sitter spacetime are obtained. The Jordan and Einstein frames are considered; the potential and the mass of the scalar degree of freedom are found. We show that the flat spacetime is stable and the de Sitter spacetime is unstable. The slow-roll parameters \(\epsilon\) , \(\eta\) , and the \(e\) -fold number of the model are evaluated in the Einstein frame. The index of the scalar spectrum power-law \(n_{s}\) and the tensor-to-scalar ratio \(r\) are calculated. Critical points of autonomous equations for the de Sitter phase and the matter dominated epoch are found and studied. We obtain the approximate solution of equations of motion which is the deviation from the de Sitter phase in the Jordan frame. It is demonstrated that the model passes the matter stability test.

Description: Co@Pt core-shell nanoparticles (NPs) were synthetized by a two-step reductive method using carbon (Vulcan XC-72) as a solid support. The NPs were characterized by X-ray diffraction, field emission gun scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy. Their electrochemical performance was evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry, and these showed that the Co@Pt NPs display an electrocatalytic activity towards the oxidation of glucose that is much better than that of plain Pt NPs. Under optimized conditions and at pH 7.0, the oxidation current of glucose at a working potential of −50 mV (vs. SCE) is linearly related to its concentration in the 1.0 to 30 mM range, and the detection limit is 0.3 mM (S/N = 3). It therefore covers the clinical range. The sensor also exhibits excellent stability and repeatability. Graphical abstract Co@Pt core-shell nanoparticles (NPs) display an electrocatalytic activity towards the oxidation of glucose that is much better than that of plain Pt NPs. The oxidation current for glucose is linearly related to its concentration in the 1.0 to 30 mM range, and the detection limit is 0.3 mM (S/N =3).

Description: We report on a simple, sensitive and regenerable fluorescent nanoprobe for Zn(II) ion. It is based on the use of glutathione capped CdTe quantum dots (GSH-CdTe Q-dots). The bright fluorescence of these Q-dots is quenched on addition of diethylenetriaminepentaacetic acid (DTPA) due to the binding of DTPA to GSH. If, however, Zn(II) is added, it will bind DTPA and detach it from the surface of the Q-dots, this resulting in the fluorescence recovery. Under optimum conditions, the intensity of the restored fluorescence is proportional to the concentration of Zn(II) in the 0.48 to 90 μmol · L −1 range, with a limit of detection of 0.14 μmol · L −1 . The nanoprobe was applied to the determination of Zn(II) in spiked tap water and river water and gave satisfactory results. The findings were also applied to design a molecular logic gate where DTPA acts as the first input to the system by quenching the fluorescence of the GSH-CdTe Q-dots. Zn(II) acts as the second input and causes the detachment of DTPA from the Q-dots and a restoration of fluorescence. This system therefore represents a new IMP (IMPLICATION) logic gate. Graphical Abstract We describe a fluorescent nanoprobe for Zn(II) based on quantum dots, and its use in an IMP molecular logic gate. The nanoprobe was successfully applied to the determination of Zn(II) in spiked tap water and river water.

Description: We describe a nonenzymatic electrochemical sensor for uric acid. It is based on a carbon nanotube ionic-liquid paste electrode modified with poly(β-cyclodextrin) that was prepared in-situ by electropolymerization. The functionalized multi-walled carbon nanotubes and the surface morphology of the modified electrodes were characterized by transmission electronic microscopy and scanning electron microscopy. The electrochemical response of uric acid was studied by cyclic voltammetry and linear sweep voltammetry. The effects of scan rate, pH value, electropolymerization cycles and accumulation time were also studied. Under optimized experimental conditions and at a working voltage of 500 mV vs. Ag/AgCl (3 M KCl), response to uric acid is linear in the 0.6 to 400 μΜ and in the 0.4 to 1 mΜ concentration ranges, and the detection limit is 0.3 μΜ (at an S/N of 3). The electrode was successfully applied to the detection of uric acid in (spiked) human urine samples. Graphical Abstract SEM images of ( a ) carbon ionic liquid electrode (CILE) ( b ) MWNT-CILE ( c ) β-CD/CILE ( d ) β-CD/ MWNT-CILE. The surfaces of carbon ionic liquid electrode (CILE) ( a ) and MWNT-CILE ( b ) were homogenous and no separated carbon layers can be observed; After β- cyclodextrin (CD) was modified on CILE and MWNT-CILE, the surfaces of β-CD modified electrodes ( c and d ) exhibited loose and porous morphologies.

Description: The authors describe an electrochemical immunoassay for α-fetoprotein (α-FP) using a glassy carbon electrode (GCE) modified with a nanocomposite made from gold nanoparticles, graphene oxide and multi-walled carbon nanotubes (AuNPs/GO-MWCNTs) and acting as a signal amplification matrix. The nanocomposite was synthesized in a one-pot redox reaction between GO and HAuCl 4 without using an additional reductant. The stepwise assembly of the immunoelectrode was characterized by means of cyclic voltammetry and electrochemical impedance spectroscopy. The interaction of antigen and antibody on the surface of the electrode creates a barrier for electrons and causes retarded electron transfer, this resulting in decreased signals in differential pulse voltammetry of hexacyanoferrate which is added as an electrochemical probe. Using this strategy and by working at a potential of 0.2 V (vs. SCE), a wide analytical range (0.01 - 100 ng∙mL‾ 1 ) is covered. The correlation coefficient is 0.9929, and the limit of detection is as low as 3 pg∙mL‾ 1 at a signal-to-noise ratio of 3. This electrochemical immunoassay combines the specificity of an immunological detection scheme with the sensitivity of an electrode modified with AuNPs and GO-MWCNTs. Graphical Abstract Schematic illustration of the fabrication procedure of the immunosensor

Description: We describe the data processing pipeline developed to reduce the pointing observation data of Lunar-based Ultraviolet Telescope (LUT), which belongs to the Chang’e-3 mission of the Chinese Lunar Exploration Program. The pointing observation program of LUT is dedicated to monitor variable objects in a near-ultraviolet (245–345 nm) band. LUT works in lunar daytime for sufficient power supply, so some special data processing strategies have been developed for the pipeline. The procedures of the pipeline include stray light removing, astrometry, flat fielding employing superflat technique, source extraction and cosmic rays rejection, aperture and PSF photometry, aperture correction, and catalogues archiving, etc. It has been intensively tested and works smoothly with observation data. The photometric accuracy is typically ∼0.02 mag for LUT 10 mag stars (30 s exposure), with errors come from background noises, residuals of stray light removing, and flat fielding related errors. The accuracy degrades to be ∼0.2 mag for stars of 13.5 mag which is the \(5\sigma\) detection limit of LUT.

Description: In the Generalized Uncertainty Principle (GUP), there should be a minimal black hole whose size is comparable to the minimal length so that it cannot evaporate completely through the thermal radiation. Again, the black hole is not allowed to have a mass less than a scale of order Planck mass, which suggested a black hole remnant. We study the warped AdS 3 rotating black hole and calculate the entropy, heat capacity and critical mass with the help of GUP. We compute the area theorem with GUP correction.

Description: We describe an electrochemical sensor for nitric oxide that was obtained by modifying the surface of a nanofiber carbon paste microelectrode with a film composed of hexadecyl trimethylammonium bromide and nafion. The modified microelectrode displays excellent catalytic activity in the electrochemical oxidation of nitric oxide. The mechanism was studied by scanning electron microscopy and cyclic voltammetry. Under optimal conditions, the oxidation peak current at a working voltage of 0.75 V (vs. SCE) is related to the concentration of nitric oxide in the 2 nM to 0.2 mM range, and the detection limit is as low as 2 nM (at an S/N ratio of 3). The sensor was successfully applied to the determination of nitric oxide released from mouse hepatocytes. Graphical abstract NO electrochemical sensor based on CTAB-Nafion/CNFPME was fabricated through a simple method and applied to detect NO released from mouse hepatocytes successfully.

Description: The standard cosmological parallax–distance formula, as found in the literature, including text-books and reference books on cosmology, requires a correction. This correction stems from the fact that in the standard text-book derivation it has been ignored that any chosen baseline in a gravitationally bound system does not partake in the cosmological expansion. Though the correction is available in the literature for some time, the text-books still continue to use the older, incorrect formula, and its full implications are not yet fully realized. Apart from providing an alternate correct, closed-form expression that is more suitable and convenient for computations for certain limiting cases of FRW ( \(\varLambda=0\) ) world models, we also demonstrate how one can compute parallax distance for the currently favored flat-space accelerating-universe ( \(\varLambda〉0\) , \(k=0\) ) cosmologies. Further, we show that the correction in parallax distance at large redshifts could amount to a factor of three or even more. Moreover, even in an infinite universe the parallax distance does not increase indefinitely with redshift and that even the farthest possible observable point may have a finite parallax angle, a factor that needs to be carefully taken into account when using distant objects as the background field against which the parallax of a foreground object is to be measured. Some other complications that could arise in parallax measurements of a distant source, like that due to the deflection of incoming light by the gravitation field of the Sun and other planetary bodies in the solar system, are pointed out.

Description: Two-dimensional carbon nanomaterials ranging from single-layer graphene to defective structures such as chemically reduced graphene oxide were studied with respect to their use in electrodes and sensors. Their electrochemical properties and utility in terms of fabrication of sensing devices are compared. Specifically, the electrodes have been applied to reductive amperometric determination of hydrogen peroxide. Low-defect graphene (SG) was obtained through mechanical exfoliation of natural graphite, while higher-defect graphenes were produced by chemical vapor deposition (CVDG) and by chemical oxidation of graphite and subsequent reduction (rGO). The carbonaceous materials were mainly characterized by Raman microscopy. They were applied as electrode material and the electrochemical behavior was investigated by chronocoulometry, cyclic voltammetry, electrochemical impedance spectroscopy and amperometry and compared to a carbon disc electrode. It is shown that the quality of the graphene has an enormous impact on the amperometric performance. The use of carbon materials with many defects (like rGO) does not result in a significant improvement in signal compared to a plain carbon disc electrode. The sensitivity is 173 mA · M −1  · cm −2 in case of using CVDG which is about 50 times better than that of a plain carbon disc electrode and about 7 times better than that of rGO. The limit of detection for hydrogen peroxide is 15.1 μM (at a working potential of −0.3 V vs SCE) for CVDG. It is concluded that the application of two-dimensional carbon nanomaterials offers large perspectives in amperometric detection systems due to electrocatalytic effects that result in highly sensitive detection. Graphical abstract Graphene materials prepared by different techniques were studied as electrode material for the electrochemical detection of H 2 O 2 . Materials comprising a less defective structure showed a significantly higher sensitivity.

Description: A pH responsive nanogel composed of magnetite (Fe 3 O 4 ), silica and poly(4-vinylpyridine) was designed and utilized as an adsorbent for the simultaneous separation of ultra-trace amounts of cadmium, lead, copper and nickel ions. This solid phase extraction system was characterized by Fourier transform infrared spectrometry, transmission electron microscopy and X-ray diffraction analysis. The sorbent can be separated from the sample solution by applying an external magnetic field, and the analytes eluted with 1 M hydrochloric acid. The extracted ions were quantified by flame atomic absorption spectrophotometry. Effects of pH value, adsorption and desorption time, type, concentration and volume of the eluent, breakthrough volume, and effect of potentially interfering ions were studied. Under optimized conditions, the extraction efficiency is 〉98 %, the limits of detection are 0.03, 0.2, 0.6 and 0.9 ng mL −1 for Cd(II), Cu(II), Ni(II) and Pb(II), respectively, and the adsorption capacities for these ions are 52, 61, 75 and 65 mg g −1 . The sorbent has a high affinity for the above target ions. Eventually, the pH responsive system was used for rapid, efficient, fairly selective and highly sensitive extraction of these ions from various water samples. Graphical Abstract We describe a magnetite-silica-poly(4-vinylpyridine) nanogel that is pH-responsive and can act as a sorbent for the extraction of Cd(II), Cu(II), Ni(II) and Pb(II).

Description: We describe a facile method for the preparation of magnetic microparticles consisting of a metal-organic framework (MOF) of Cu(II)-BTC (BTC = 1,3,5-benzenetricarboxylate) for rapid magnetic solid-phase extraction (MSPE) of the dye Congo Red (CR) from aqueous solution. Magnetization of the MOF and solid-phase extraction of CR was simultaneously accomplished by mixing, under ultrasonication, the MOF and silica-coated magnetite microparticles in the solution to be extracted. Under optimized conditions, the magnetic MOF hybrid exhibits a fast adsorption rate and a high removal efficiency (〉97 %) toward CR even over 15-fold reuse, which also features high adsorption capacity of 97.7 and 92.5 % for cationinc Methylene Blue (MB) and Crystal Violet (CV), respectively. The desorption of CR from the magnetic MOF was realized by washing it with ethanol and water. The material is considered to be a promising new adsorbent for use in wastewater treatment and in analytical preconcentration. Graphical abstract We report on a method for magnetization of a Cu-BTC metal-organic framework for use in rapid magnetic solid phase extraction of Congo Red from aqueous solutions. The material maintains its high removal efficiency (of 〉97 %) over 15 recyclable experiments.

Description: We describe a nanostructured immunosensor for the cardiovascular biomarker netrin 1. A glassy carbon electrode was consecutively modified with multi-walled carbon nanotubes (MWCNTs), nafion (to retain the MWCNTs), thionine-coated gold nanoparticles (Thi@AuNPs), and monoclonal antibodies against netrin 1. The modified electrode was characterized by transmission electron microscopy, cyclic voltammetry, differential pulse voltammetry, UV-visible spectrophotometry and X-ray diffraction. The presence of Thi@AuNPs warrants direct and convenient immobilization of the antibody. This immunoelectrode enables netrin 1 to be determined, best at a voltage of −300 mV (vs. SCE), with a limit of detection of 30 fg mL −1 (at an S/N ratio of 3) after a 50 min incubation time. The detection range extends from 0.09 to 1800 pg∙mL −1 . The method is simple, sensitive, specific and reproducible. We presume this stable and reproducible biosensor to be useful for the early detection of cardiovascular diseases. Graphical Abstract A high sensitivity immunoassay was developed for the detection of netrin 1 based on multi-walled carbon nanotubes, thionine and gold nanoparticles. Its excellent performance is ascribed to the good conductivity of MWCNTs and the combination of materials.

Description: We describe a simple, highly sensitive, and selective colorimetric kinetic assay for the determination of potassium(I) by exploiting the specific recognition capability of an appropriate aptamer and catalytic signal amplification by gold nanoparticles (AuNPs). Amplification is based on the reduction of 4-nitrophenol by borohydride which is catalyzed by AuNPs. This leads to a color change of the solution from yellow to colorless, and the color change can be recognized with bare eyes or via photometry. The K(I)-selective aptamer is placed on the AuNPs and forms a tightly bound G-quadruplex with K(I) which partially masks the surface of the AuNPs and prevents 4-nitrophenol to be reduced at the catalytically active surface of the AuNPs. Hence, the rate of decoloration is retarded. The assay displays high selectivity for K(I) over other cations, has a linear response in the 0.1 nM to 10 μM concentration range, and a detection limit as low as 0.06 nM. In addition, these findings pave the way to novel analytical methods based on the use of gold nanoparticle-catalyzed chemical reactions. Graphical Abstract A simple, highly sensitive, and selective colorimetric kinetic assay for the determination of potassium(I) was represented.

Description: We describe a single-step solvothermal method for the preparation of nanocomposites consisting of graphene oxide and Fe 3 O 4 nanoparticles (GO/Fe 3 O 4 ). This material is shown to be useful as a magnetic sorbent for the extraction of flavonoids from green tea, red wine, and urine samples. The nanocomposite is taking advantage of the high surface area of GO and the magnetic phase separation feature of the magnetic sorbent. The nanocomposite is recyclable and was applied to the extraction of flavonoids prior to their determination by HPLC. The effects of amount of surfactant, pH value of the sample solution, extraction time, and desorption condition on the extraction efficiency, and the regeneration conditions were optimized. The limits of detection for luteolin, quercetin and kaempferol range from 0.2 to 0.5 ng∙ mL −1 in urine, from 3.0 to 6.0 ng∙mL −1 in green tea, and from 1.0 to 2.5 ng∙mL −1 in red wine. The recoveries are between 82.0 and 101.4 %, with relative standard deviations of 〈9.3 %. Graphical abstract The article describes a method for magnetic solid-phase extraction (MSPE) of trace amounts of natural substances in complex samples by using graphene oxide (GO)-Fe 3 O 4 nanoparticles as the sorbent.

Description: The propagation of non-linear electromagnetic waves is carefully analyzed on a curved spacetime created by static spherically symmetric mass and charge distribution. We compute how non-linear electrodynamics affects the geodesic deviation and the redshift of photons propagating near this massive charged object. In the first order approximation, the effects of electromagnetic self-interaction can be distinguished from the usual Reissner–Nordström terms. In the particular case of Euler–Heisenberg effective Lagrangian, we find that these self-interaction effects might be important near extremal compact charged objects.

Description: The behavior of short-term oscillations (≤one solar rotation) of the solar-wind parameters, galactic cosmic rays and geomagnetic indices are discussed during the last two solar minima between cycles \(22/23\) and cycles \(23/24\) . There are strong signatures of short-term oscillations of all the selected time series during the early phase of the minima, where the high speed streams are prominent structures in the heliosphere and these signatures almost die out at the end of the two minima. Result also suggests that the second and third harmonics of one solar rotation period of few parameters are prominent during the minimum between the cycles 22 and 23. Moreover, all the sub-harmonics/quasi-oscillations are more consistent and deviate less during the recent deep prolonged minimum. Through this work, we are reporting ∼7.1 days, ∼5.5 days, ∼4.4 days, ∼3.3 days oscillations, observed in few solar-wind parameters [interplanetary magnetic field \((B)\) , RMS standard deviation in the magnetic field ( \(\sigma_{B}\) ), southward component of magnetic field \((\mathit{Bz})\) and electric field \((\mathit{Ey})\) ] and geomagnetic ( \(D_{\mathit{sT}}\) and \(\mathit{AE}\) ) parameters during the solar minimum between cycles 23 and 24, in addition to ∼1.9 days oscillations which is observed in \(\mathit{Bz}\) , \(\mathit{Ey}\) and \(\mathit{AE}\) parameters.

Description: We consider the cosine Natural inflation model that is a good candidate to explain the initial accelerating phase of the universe. By computing the inflationary parameters in Einstein frame, we construct a consistency relation between the scalar spectral index, tensor-to-scalar ratio, as well as the running of the scalar spectral index and compare the results with recently released Planck 2015 observational data. Our results show that a Natural Inflation model in Einstein frame has a good agreement with the observational data.

Description: In this paper, we investigate \(f(T)\) cosmology and find an exact solution for \(f\) which gives a Little Rip cosmology. Also, considering accelerating cosmology with dark matter, the time-dependent solution is found. For these cases, by using solutions obtained from \(f(T)\) gravity we find expressions for \(\omega\) and \(\varLambda\) defined as time functions via equivalent description in terms of inhomogeneous fluid. This puts the question: which theoretical model describes the observational cosmology?

Description: A new class of solutions for Einstein’s field equations representing a static spherically symmetric anisotropic distribution of matter is obtained on the background of pseudo-spheroidal spacetime. We have prescribed the bounds of the model parameters \(k \) and \(p_{0} \) on the basis of the elementary criteria for physical acceptability, viz., regularity, stability and energy conditions. By taking the values of model parameters from the prescribed bounds, we have shown that our model is compatible with the observational data of a wide variety of compact stars like 4U 1820-30, PSR \(\mathrm{J}1903{+}327\) , 4U 1608-52, Vela X-1, PSR J1614-2230, SMC X-4 and Cen X-3.

Description: In this paper we perform the reconstruction scheme of the gravitational action within \(f(T,\mathcal{T})\) gravity, where \(T\) and \(\mathcal{T}\) denote the torsion scalar and the trace of the energy momentum tensor, respectively. We particularly focus our attention on the case where the algebraic function \(f(T,\mathcal{T})\) is decomposed as a sum of two functions \(f_{1}(T)\) and \(f_{2}(\mathcal{T})\) , i.e., \(f(T,\mathcal{T})=f_{1}(T)+f_{2}(\mathcal{T})\) . The description is essentially based on the scale factor and then, we consider two interesting and realistic expressions of this parameter and reconstruct the action corresponding to each phase of the universe. Our results show that some \(f(T,\mathcal{T})\) models are able to describe the evolution of the universe from the inflation phase to the late time dark energy dominated phase.

Description: Here 28 BL Lac objects, 18 FR I type radio galaxies, 4 FR I/II type radio galaxies and 10 FR II type radio galaxies are studied from FIR (far infrared) to optical region (180 μm to 0.44 μm) to understand the nature of infrared emission from these objects and the physical properties of dust in the emitting region. Using the flux densities from 2MASS, IRAS, ISO, SCUBA (40 % samples), WISE All-sky Data, AKARI (10 % samples) data and optical (B) observations, the spectral energy distributions are constructed. FIR and NIR spectral indices ( \(\alpha_{\mathrm{FIR}}\) and \(\alpha_{\mathrm{NIR}}\) ) are estimated. The dust temperatures and dust masses of all the samples are estimated from FIR flux densities. The SEDs of most of the samples (90 %) show steep slopes from FIR to optical region and about 10 % of the samples show flat continuous spectra from FIR to NIR region. The SEDs of 80 % FR I type radio galaxies and 1 out of 4 FR I/II type radio galaxies and two RBLs show a bump in the NIR to optical region. The SEDs of these sources are compared with Radiative transfer models. From FIR to MIR region, the SEDs of 90 % of the objects studied here can be fitted to the models with luminosities \(\mathrm{L}\sim 10^{9.5} \mathrm{L}_{0}\) , considering uncertainty from 10 % to 20 %. But the observable fluxes in the NIR region are higher and can be fitted to other models with higher \(\mathrm{L}\sim 10^{12.5} \mathrm{L}_{0}\) . Since there is a difference in emission in NIR region, mainly for FR I radio galaxies, so the variation of apparent K magnitudes with logarithm of redshift z is also studied. The WISE colours, ( \(\mathrm{W}_{1} - \mathrm{W}_{2}\) ) and ( \(\mathrm{W}_{2} - \mathrm{W}_{3}\) ) are compared with isodensity contours. Comparing with radiative transfer models it can be suggested that, in the FIR and MIR region the infrared emission is from the dust containing large grains, small graphites and PAHs at temperature ∼50 K–100 K. In the NIR region hot dust is mainly due to small grains at temperature ∼1200 K and the emission is mainly from synchrotron radiation produced in the inner part of the relativistic jets. The dust masses of RBLs are higher than those of XBLs and IBLs. FR II radio galaxies also have higher dust masses and that is mainly due to the clumpy dust which is very seldom in FR I radio galaxies. Dust clearly plays an important role in the evolution of these objects.

Description: We are interested in the periodic motion and bifurcations near the surface of an asteroid. The gravity field of an irregular asteroid and the equation of motion of a particle near the surface of an asteroid are studied. The periodic motions around the major body of triple asteroid 216 Kleopatra and the OSIRIS-REx mission target-asteroid 101955 Bennu are discussed. We find that motion near the surface of an irregular asteroid is quite different from the motion near the surface of a homoplastically spheroidal celestial body. The periodic motions around the asteroid 101955 Bennu and 216 Kleopatra indicate that the geometrical shapes of the orbits are probably very sophisticated. There exist both stable periodic motions and unstable periodic motions near the surface of the same irregular asteroid. This periodic motion which is unstable can be resonant or non-resonant. The period-doubling bifurcation and pseudo period-doubling bifurcation of periodic orbits coexist in the same gravity field of the primary of the triple asteroid 216 Kleopatra. It is found that both of the period-doubling bifurcations of periodic orbits and pseudo period-doubling bifurcation of periodic orbits have four different paths. The pseudo period-doubling bifurcation found in the potential field of primary of triple asteroid 216 Kleopatra shows that there exist stable periodic orbits near the primary’s equatorial plane, which gives an explanation for the motion stability of the triple asteroid 216 Kleopatra’s two moonlets, Alexhelios and Cleoselene.

Description: Properties of nonlinear ion-acoustic travelling waves propagating in a three-dimensional multicomponent magnetoplasma system composed of positive ions, negative ions and superthermal electrons are considered. Using the reductive perturbation technique (RPT), the Zkharov-Kuznetsov (ZK) equation is derived. The bifurcation theory of planar dynamical systems is applied to investigate the existence of the solitary wave solutions and the periodic travelling wave solutions of the resulting ZK equation. It is found that both compressive and rarefactive nonlinear ion-acoustic travelling waves strongly depend on the external magnetic field, the unperturbed positive-to-negative ions density ratio, the direction cosine of the wave propagation vector with the Cartesian coordinates, as well as the superthermal electron parameter. The present model may be useful for describing the formation of nonlinear ion-acoustic travelling wave in certain astrophysical scenarios, such as the D and F-regions of the Earth’s ionosphere.

Description: In this paper we show an application of the Minimum Spanning Tree (MST) clustering method to the high-energy \(\gamma\) -ray sky observed at energies higher than 10 GeV in 6.3 years by the Fermi -Large Area Telescope. We report the detection of 19 new high-energy \(\gamma\) -ray clusters with good selection parameters whose centroid coordinates were found matching the positions of known BL Lac objects in the 5th Edition of the Roma-BZCAT catalogue. A brief summary of the properties of these sources is presented.

Description: The surface of CdTe quantum dots (Q-dots) was modified with thioglycolic acid (TGA) and these Q-dots were then covalently conjugated to amino-functionalized silica-coated carbon dots (C-dot@SiO 2 ) via carbodiimide chemistry. The Q-dots form kind of “satellites” on the surface of the C-dot@SiO 2 nanoparticles. The nanoparticle conjugates display dual emission (with peaks at 441 nm and 605 nm) under UV excitation and were further characterized by transmission electron microscopy, UV–vis absorption and FTIR spectroscopy. The C-dot@SiO 2 @Q-dots hybrid spheres are shown to represent a ratiometric fluorescent probe for Cu 2+ in that the emission of the Q-dots is quenched by Cu 2+ , while the emission of the C-dots (which are coated with SiO 2 ) is not quenched. The ratio of the fluorescence intensities at 441 and 655 nm is related to the concentration of Cu 2+ in the range from 0.1 to 1.0 μM, with a 0.096 μM lower detection limit. The ratiometric probe was successfully applied to the determination of Cu 2+ in (spiked) vegetable and fruit samples by the standard addition method, and recoveries ranged from 96.7 to 100.8 %. Graphical Abstract Carbon dots were first coated with silica and then with CdTe quantum dots to give nanoparticles with an architecture of the type C-dot@SiO 2 @Q-dots. These are shown to be a viable ratiometric fluorescent probe for the detection of Cu(II).

Description: In this paper, capturing Near-Earth asteroids (NEAs) into bounded orbits around the Earth is investigated. Several different potential schemes related with gravity assists are proposed. A global optimization method, the particle Swarm Optimization (PSO), is employed to obtain the minimal velocity increments for each scheme. With the optimized results, the minimum required velocity increments as well as the mission time are obtained. Results of numerical simulations also indicate that using MGAs is an efficient approach in the capturing mission. The conclusion complies with the analytical result in this paper that a NEA whose velocity relative to the Earth less than 1.8 km/s can be captured by Earth by just one MGA. For other situations, the combination of MGAs and EGAs is better in sense of the required velocity-increments.

Description: We investigate the gauged Nambu-Jona-Lasinio model in curved space-time at the large \(N_{c}\) limit and in slow-roll approximation. The model can be described by the renormalization group corrected gauge-Higgs-Yukawa theory with the corresponding compositeness conditions. Evaluating the renormalization group (RG) improved effective action, we show that such model can produce CMB fluctuations and find inflationary parameters: spectral index, tensor-to-scalar-ratio and running of the spectral index. We demonstrate that the model can naturally satisfy the Planck 2015 data and maybe considered as an alternative candidate for Higgs inflation.

Description: Alumina (Al 2 O 3 ) with an average particle size of 63 μm was modified with the anionic surfactant sodium dodecyl sulfate (SDS) and then applied to (i) solid phase extraction and separation of both thallium(I) and thallium(III), and (ii) preconcentration of Tl(III) from waste water samples. Only Tl(III), in the form of its complex with diethylenetriaminepentaacetate (DTPA), was retained on the sorbent, from where it can be eluted with 40 % nitric acid. Thallium species were then quantified by ICP MS. The method was characterized by a LOD of 25 pg of Tl(I) and 160 pg of Tl(III) in 10 mL samples. A large excesses of Tl(I) over Tl(III) was tolerated, and relatively high levels of other metal ions, such as a 500-fold excess of Pb(II) and Cd(II), and a 2000-fold excess of Zn(II), respectively, do not interfere. The sorbent was easily prepared and possesses a high loading capacity, and these properties make it an attractive material for rapid and efficient extraction and speciation of Tl. Graphical abstract: Schematic of the SPE procedure for separation (with preconcentration) of Tl(III) from Tl(I) was developed and applied to direct speciation analysis of thallium in wastewater. Self-made columns packed with alumina coated with SDS were used. The method is resistant to interferences from Pb, Cd, Zn and tolerates a large excess of Tl(I) over Tl(III).

Description: Nonlinear ion acoustic shocks in homogenous multicomponent electron-positron-ion (e-p-i) dissipative magneto rotating plasmas are studied. Dissipation in the plasma system is included via kinematic viscosity of ions. The electrons and positrons are Lorentzian and following kappa distribution function. Reductive perturbation technique is applied to derive Korteweg de Vries Burgers (KdVB) equation. The effects of variation of positron density, positron spectral index, temperature ratio of kappa distributed electrons to kappa distributed positrons, ion kinematic viscosity and rotational frequency effects are discussed in the context of pulsar magnetosphere.