Mössbauer spectroscopic analysis of ancient Egyptian pottery

Ten pieces of Egyptian pottery ware and eleven silt samples collected at Hierakonopolis (Nile River, Egypt) were studied by Mössbauer spectroscopy. Three Nile silt samples and three pottery sherds were test fired and refired in an oxidized atmosphere up to 1100°C. Changes of the Mössbauer parameters depend upon the firing temperatures as well as the firing atmosphere. Three kinds of pottery were studied: Plum Red Ware, Straw Tempered Ware, and Orange Ware.     

Study of ancient pottery from Slovakia

Ancient pottery samples collected from south-west Slovakia were studied through subjective observation and by Mössbauer spectroscopy. This method is convenient for determining the provenance and the manufacture of pottery. Transformations, induced by firing the clay and characterized by Mössbauer spectroscopy, give valuable information regarding the manufacture as, for instance, the final temperature of firing in it. The relative abundance of Fe²⁺ and Fe³⁺ determines the atmosphere used to fire a pottery. It has been found that the determination of the firing atmosphere obtained through the subjective observation is in good agreement with that obtained using Mössbauer spectroscopy. An unfired and fired clay was also investigated.     

TotalK-vacancy production in Ne (10 MeV) traversing Al

Deexcitation of projectile inner shell vacancies created while traversing a solid foil may take place via competing processes: a) vacancy sharing with foil atoms in close impacts, b) radiative and non-radiative electron capture, and c) such X-ray and Auger electron transitions as are possible in the heavy ion projectile. The change inK-vacancy creation with foil thickness can be investigated by measuring either projectile or target X-rays where the vacancies are created by Coulomb excitation and processa. In the system Ne (10 MeV) on Al, detecting AlK X-rays, the NeK-vacancy production probability has been determined.     

Small angle critical scattering of neutrons by nickel

The critical magnetic scattering of neutrons by nickel was studied as a function of temperature and of the scattering vector κ in the range 0.008?0.04 Å^?1 for various specimens ranging from a single crystal to heavily deformed polycrystals. The shift of the temperature where the maximum of the scattered intensity is found as a function of scattering vector κ depends on the degree of crystalline imperfection. For the single crystal the observed shift is ΔT/T? 5 · 10^?3. On the basis of the Ornstein-Zernike theory the observed scattering by the single crystal yields the critical index \(\gamma = 2v = 1.32 \pm _{0.14}^{0.20} \) as predicted by most of the theories.     

The role of auger effect in thermostimulated phenomena in ionic crystals

Absorption and thermostimulated luminescence simultaneously with electric conductivity in KI crystals irradiated with X-rays at L.N.T. were measured. The kinetics of these and many other similar results obtained in other alkali halides are interpreted on the basis of Auger process occurring in consequence of the recombination of free holes with localized electrons inF-centers.     

Continuous-wave 2.52 Terahertz Gabor inline compressive holographic tomography

Continuous-wave (CW) 2.52 Terahertz (THz) 3D tomographic images were obtained by numerically reconstructing a single Gabor inline digital hologram based on modified compressive sensing reconstruction algorithm. Three metallic copper samples which are separately adhered to three Teflon plate were used as the targets. The actual axial resolution achieved was higher than 6 mm, and the lateral resolution was higher than 0.4 mm. Similarly, a paper clip and a handwritten character sample on a white paper were also imaged. Numerical simulation and experimental results verified the preferable reconstruction characteristics of the proposed modified algorithm. The feasibility of CW THz Gabor inline compressive holographic tomography is confirmed by adding barriers such as Teflon boards and thermal paper to block the samples.     

Prototype of a large neutron detector based on MWPC

A prototype of large-area position sensitive neutron detector was designed and constructed according to the requirements of the Small-Angle Scattering spectrometer of China Spallation Neutron Source(CSNS).The detector was based on the 3He neutron convertor and MWPC with an effective area of 650 mm×650 mm.A prototype was completed and tested with 55Fe X-ray.The high-pressure vessel was designed and constructed with high-strength aluminum alloy.A position resolution of about 4.6mm×2.3 mm(FWHM)and efficiency65%for neutrons with wavelength of 1.8?was determined after the operational gas filled.     

Conformal invariance in semi-infinite systems: Application to critical surface scattering

We show that conformal invariance constrains the form of correction terms in the cross-section for critical surface scattering of X-rays and neutrons. We also verify inO() the conformal symmetry of the two-point order parameter correlation function of semi-infinite systems at the ordinary and special phase transition.This work was supported by Bundesministerium für Forschung und Technologie     

Synthesis at the nanoscale of ZnO into poly(methyl methacrylate) and its characterization

In this paper, PMMA/ZnO nanocomposites have been prepared by a very simple, facile and versatile chemical approach. The prepared PMMA/ZnO nanocomposites possess no color, high transparency, good thermal stability, UV-shielding capability, luminescence and homogeneity. The chemical process involved solution mixing of ZnO nanoparticles dispersed in DMAc with the Polymethylmethacrylate (PMMA) matrix dissolved in the same solvent. The effect of ZnO content on the physical properties of the PMMA matrix is investigated by X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, UV–Vis absorption and photoluminescence spectroscopy. It was found that pure hexagonal ZnO nanoparticles with an average particle size of 4–8 nm were homogeneously dispersed in the PMMA matrix. A significant improvement in thermal properties was observed with the incorporation of 1.0 wt% ZnO nanoparticles. The prepared nanocomposite films are highly transparent and a clear excitonic peak is observed in their absorption spectra. Measurement of room temperature photoluminescence spectra shows intensive near-band edge emission peak at 3.28 eV without any structural defects for a nanocomposite film with a filler content of 1.0 wt%.     

Label Free Fluorometric Characterization of DNA Interaction with Cholate Capped Gold Nanoparticles Using Ethidium Bromide as a Fluorescent Probe

We demonstrated label free ethidium bromide assisted characterization of DNA interaction with cholate capped AuNPs. Interactions between ss/ds DNA and AuNPs with two different lengths (0.5 and 0.85 kb) were analyzed through fluorescence spectrophotometer and agrose gel electrophoresis analysis. Further results were confirmed by UV–globally visible spectrophotometer, DLS and TEM. As 0.5 and 0.85 kb of ssDNA effectively interacted with AuNPs through the van der Waals interaction which consequently led to the prevention of salt induced aggregation, EtBr intercalations as well as fluorescence shift with less binding constant 0.098 and 0.108 μM, respectively. On the contrary, the same length of dsDNA (0.5 and 0.85 kb) not interacted with AuNPs which led to the NPs aggregation, EtBr intercalation as well as fluorescence shift with increased binding constant 0.166 and 0.599 μM, respectively. This approach helped to understand the mode of interactions of DNA with cholate capped AuNPs without any modifications in a simple method and the results could be readout through the naked eye under the UV transilluminator. Figure

Fluorometric characterization of interaction of different lengths of ss/dsDNA with cholate capped AuNPs using EtBr as fluorescence probe     

Optimized AC conductivity correlated to structure,morphology and thermal properties of PVDF/PVA/Nafion composites

Polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA) composites were prepared by controlled loading of Nafion (5 to 15 wt%) by solution casting using water and dimethylformamide (DMF) as a solvent. The surface morphology of composite analyzed by atomic force microscopy (AFM) reveals the presence of Nafion ionomers. The increase in interlayer spacing of modified PVDF/PVA polymer system as a function of Nafion was detected by X-ray diffraction (XRD). The major change in Fourier transform infrared (FTIR) spectroscopy confirms the chemical bond C=O stretching around 1,700 cm^?1 due to Nafion. Differential scanning calorimetry (DSC) demonstrates the thermal stability of polymer composites and the decrease in melting temperature (T _m). The optimized AC conductivity (σ) of the prepared composite was evaluated by using an impedance analyzer as a function of temperature (40 to 150 °C) at constant 30-MHz frequency. The highest conductivity of 1.3?×?10^?2 S m^?1 was observed at 80 °C for 10 wt% of Nafion and correlated with structure, morphology and thermal properties of modified PVDF/PVA/Nafion composites. The experimental results may be useful for sensors, fuel cells and battery application domains.     

The ionic charge distribution of fission products and the influence of internal conversion on highly preionized heavy ions

At the mass spectrometer LOHENGRIN of the Institut Laue-Langevin the ionic charge state distributions of²³⁵U(n _th,f)-fission products separated according to their mass, nuclear charge and kinetic energy were determined. The mean values and the widths of the ionic charge state distributions are compared with semiempirical predictions. Deviations between the experimental data and the estimation of Nicolaev and Dmitriev are found. Furthermore, the influence of the internal conversion process on the ionic charge state distribution of highly ionized fission products was established. Internal conversion is observed mainly for odd-odd nuclei and nuclei with 59 neutrons. The Auger cascade following the internal conversion process shifts the ionic charge state distribution by about 3 charge units. The yield of conversion electrons per fragment was determined in the mass range 85≦A≦103.     

THz photomixer with milled nanoelectrodes on LT-GaAs

A terahertz (THz) photomixer: (i) a meander type antenna with integrated nanoelectrodes on (ii) a low temperature grown GaAs has been fabricated and characterized. It was designed for spectral range of 0.3–0.4 THz where molecular fingerprinting and sensing are performed. By combination of electron beam lithography with post-processing using focused ion beam (FIB), milling the THz emitter was successfully fabricated. Nanogaps as small as 40 nm width in the active area of photomixer were milled by FIB. Nanocontacts enhance electric fields of the illuminated and THz radiation and contribute to a better collection of photo-electrons. THz emission was obtained and spectrally characterized.     

Study of background processes with the formation of neutrons in nuclear reactions in the energy range of 26–32 kev

The nature of background processes accompanying astrophysical nuclear reactions induced by hydrogen, helium, and neon ions in deuterated targets with small cross sections has been studied in calculations and experiments. The experiments have been performed at a Hall pulsed plasma accelerator in the ion energy range of 26–32 keV. The yield of background neutrons and γ-quanta with energies below 4 MeV in the proton-induced D(p, γ)³He reaction is primarily due to the presence of a natural impurity of gaseous deuterium in gaseous hydrogen and the chain of D(D, ³He)n → (n, γ) or (n, n'γ) reactions. A small contribution comes from the chain of D(¹H, ¹H)D → D(D, ³He)n → (n, γ) or (n, n'γ) reactions. It has been shown that background neutrons and γ-quanta from the D(4He, γ)6Li reaction are entirely due to the chain of D(⁴He, ⁴He)D → D(D, ³He)n → (n, γ) or (n, n'γ) reactions. It has been shown that the yield of neutrons and γ-ray photons detected at the interaction of neon ions with deuterated targets is also entirely due to the chain of elastic- scattering reactions of neon ions on deuterons in the target and to subsequent inelastic processes of interaction of deuterons accelerated at elastic scattering with other deuterons of the target. The main contribution to the yields of background neutrons and γ-quanta comes from doubly charged neon ions. The main conclusion is that the explanation of the yield of neutrons and γ-quanta at the interaction of hydrogen, helium, and neon ions with deuterated targets does not require “exotic” theoretical models.     

Surface plasmon resonance and surface-enhanced Raman scattering activity of SiO2–Au core-cap nanostructure arrays

SiO₂–Au core-cap nanostructure arrays were prepared by dip-coating technique combined with wet chemical reduction method. The surface morphologies, structures, and optical properties of the obtained samples were characterized by scanning electron microscopy, X-ray diffraction, and ultraviolet–visible spectrophotometer, respectively. The surface-enhanced Raman scattering (SERS) activity of SiO₂–Au core-cap nanostructure arrays substrates was investigated using leucine as probe molecule. And the relationship between the SERS effect and the surface plasmon resonance (SPR) peaks was discussed. High-quality, stable, and reproducible SERS spectra of leucine were successfully obtained. When the maximum SPR peak matched with the excitation wavelength, the substrate gave rise to the highest SERS enhancement. Furthermore, six different fluorescent dyes were also chosen as probe molecules. It was found that the substrate showed good Raman enhancement and highly efficient fluorescence quenching characteristic on these fluorescent dyes.     

First production of ultracold neutrons with a solid deuterium source at the pulsed reactor TRIGA Mainz⋆

The production rates of ultracold neutrons (UCN) with a solid deuterium converter have been measured at the pulsed reactor TRIGA Mainz. Exposed to a thermal neutron fluence of n·cm^-2·pulse^-1, the number of detected very cold and ultracold neutrons ranges up to 200 000 at 7mol of solid deuterium (sD₂) in combination with a pre-moderator (mesitylene). About 50% of the measured neutrons can be assigned to UCN with energies E of where V _F(sD ₂) = 105 neV and V _F(guide) = 190 neV are the Fermi potentials of the sD₂ converter and our stainless steel neutron guides, respectively. Thermal cycling of solid deuterium, which was frozen out from the gas phase, considerably improved the UCN yield, in particular at higher amounts of sD₂.     

An in silico protocol for identifying mTOR inhibitors from natural products

The mammalian target of rapamycin (mTOR) is an anti-cancer target. In this study, we propose an in silico protocol for identifying mTOR inhibitors from the ZINC natural product database. First, a three-dimensional quantitative structure–activity relationship pharmacophore model was built based on known mTOR inhibitors. The model was validated with an external test set, Fischer’s randomization method, a decoy set and pharmacophore mapping conformation testing. The results showed that the model can predict the mTOR inhibition activity of the tested compounds. Virtual screening was performed based on the best pharmacophore model, and the results were then filtered using a molecular docking approach. In addition, molecular mechanics/generalized born surface area analysis was used to refine the selected candidates. The top 20 natural products were selected as potential mTOR inhibitors, and their structural scaffolds could serve as building blocks in designing drug-like molecules for mTOR inhibition.     

Plasmonic enhancement of optical absorption of UV radiation by Au nanoparticles dispersed on ZnO thin film

Ultraviolet photoconductivity in sol gel-derived ZnO thin film loaded with gold (Au) nanoparticle (NPs) is investigated. Au-NPs loaded ZnO thin film (Au-NPs/ZnO) is found to exhibit high photoconducting gain (K) of about 4.12 × 10³ as compared to the bare ZnO thin film-based photodetector (4.9 × 10¹). The enhanced photoconductive gain of Au-NPs/ZnO detector has been achieved due to simultaneous lowering of dark current which occurs due to Schottky barrier effect originated after dispersing the Au NPs on the surface of ZnO thin film. The enhancement in photocurrent upon UV illumination is due to trapping of UV radiation via plasmonic effect caused by Au-NPs and subsequently coupling of absorbed light with the optical modes of underlying semiconducting ZnO surface.     

Preparation and ionic conductivity of composite polymer electrolytes based on hyperbranched star polymer

Hyperbranched star polymer HBPS-(PPEGMA) _x was synthesized by atom transfer radical polymerization (ATRP) using hyperbranched polystyrene (HBPS) as macroinitiator and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as monomer. The structure of the prepared hyperbranched star polymer was characterized by ¹H NMR, ATR-FTIR, and GPC. Polymer electrolytes based on HBPS-(PPEGMA) _x , lithium salt, and/or nano-TiO₂ were prepared. The influences of lithium salt concentration and type, nano-TiO₂ content, and size on ionic conductivity of the obtained polymer electrolytes were investigated. The results showed that the low crystallinity of the prepared polymer electrolyte was caused by the interaction between lithium salt and polymer. The addition of TiO₂ into HBPS-(PPEGMA) _x /LiTFSI improved the ionic conductivity at low temperature. The prepared composite polymer electrolyte showed the highest ionic conductivity of 9?×?10^?5 S cm^?1 at 30 °C when the content of TiO₂ was 15 wt% and the size of TiO₂ was 20 nm.     

Laser generated Ag and Ag–Au composite nanoparticles for refractive index sensor

Localized surface plasmon resonance (LSPR) wavelength of metal nanoparticles (NPs) is highly sensitive to size, shape and the surrounding medium. Metal targets were laser ablated in liquid for preparation of spherical Ag and Ag@Au core–shell NP colloidal solution for refractive index sensing. The LSPR peak wavelength and broadening of the NPs were monitored in different refractive index liquid. Quasi-static Mie theory simulation results show that refractive index sensitivity of Ag, Ag–Au alloy and Ag@Au core–shell NPs increases nearly linearly with size and shell thickness. However, the increased broadening of the LSPR peak with size, alloy concentration and Au shell thickness restricts the sensing resolution of these NPs. Figure-of-merit (FOM) was calculated to optimize the size of Ag NPs, concentration of Ag–Au alloy NPs and Au shell thickness of Ag@Au core–shell NPs. The refractive index sensitivity (RIS) and FOM were optimum in the size range 20–40 nm for Ag NPs. Laser generated Ag@Au NPs of Au shell thickness in the range of 1–2 nm showed optimum FOM, where thin layer of Au coating can improve the stability of Ag NPs.