New insight into the optical properties of amorphous Ge and Si

A short range disorder model, unlike present long range disorder theories, has been able to account well for both the density of states and the optical properties of amorphous Ge and Si. Our results indicate that the imaginary part of the dielectric function for amorphous Ge and Si has the same form as an averaged gradient matrix element as a function of energy. This conclusion should be valid for all tetrahedrally bonded amorphous solids.     

Aqueous electrolyte surfaces in strong electric fields: molecular insight into nanoscale jets and bridges

Exposing aqueous surfaces to a strong electric field gives rise to interesting phenomena, such as formation of a floating water bridge or an eruption of a jet in electrospinning. In an effort to account for the phenomena at the molecular level, we performed molecular dynamics simulations using several protocols on both pure water and aqueous solutions of sodium chloride subjected to an electrostatic field. All simulations consistently point to the same mechanisms which govern the rearrangement of the originally planar surface. The results show that the phenomena are primarily governed by an orientational reordering of the water molecules driven by the applied field. It is demonstrated that, for pure water, a sufficiently strong field yields a columnar structure parallel to the field with an anisotropic arrangement of the water molecules with their dipole moments aligned along the applied field not only in the surface layer but over the entire cross section of the column. Nonetheless, the number of hydrogen bonds per molecule does not seem to be affected by the field regardless of its strength and molecule’s orientation. In the electrolyte solutions, the ionic charge is able to overcome the effect of the external field tending to arrange the water molecules radially in the first coordination shell of an ion. The ion–water interaction interferes thus with the water–electric field interaction, and the competition between these two forces (i.e., strength of the field versus concentration) provides the key mechanism determining the stability of the observed structures.     

Structure and properties of the bronze laser alloyed with titanium

The paper describes the microstructure and properties (microhardness and wear resistance) of the bronze laser alloyed with titanium. The laser alloying was done using a pulsed Nd:YAG laser with a generated beam energy of 25-35 J. A very fine microstructure was formed under such rapid solidification conditions like laser treatment. The high chemical homogeneity and fine structure of the melted zone were attributed to high cooling rates due to the short interaction time with Nd:YAG pulsed laser radiation and relatively small volume of the melted material. The structure obtained in the surface layer after laser alloying permits to get a high level of hardness and an improved wear resistance.     

A theoretical insight into the solid-state optical properties of luminescent materials: the supermolecular approach

The way interchain interactions affect the absorption and luminescence properties of organic conjugated materials is addressed by means of correlated quantum-chemical calculations on molecular aggregates. Special emphasis is given to the influence of chain length and relative positions of the interacting units. The consideration of α -oligothiophenes in their crystalline structure allows us to shed light into the chain-length evolution of the optical splitting of the lowest optically-allowed excited state and to validate the theoretical approach by confronting the theoretical predictions to experimental results. Various strategies are proposed to prevent luminescence quenching when going from solutions to films or crystals.     

New insight into the parasitic bipolar amplification effect in single event transient production

In this paper, a new method is proposed to study the mechanism of charge collection in single event transient (SET) production in 90 nm bulk complementary metal oxide semiconductor (CMOS) technology. We find that different from the case in the pMOSFET, the parasitic bipolar amplification effect (bipolar effect) in the balanced inverter does not exist in the nMOSFET after the ion striking. The influence of the substrate process on the bipolar effect is also studied in the pMOSFET. We find that the bipolar effect can be effectively mitigated by a buried deep P⁺-well layer and can be removed by a buried SO₂ layer.     

New insight into the parasitic bipolar amplification effect in single event transient production

In this paper,a new method is proposed to study the mechanism of charge collection in single event transient (SET) production in 90 nm bulk complementary metal oxide semiconductor (CMOS) technology.We find that different from the case in the pMOSFET,the parasitic bipolar amplification effect (bipolar effect) in the balanced inverter does not exist in the nMOSFET after the ion striking.The influence of the substrate process on the bipolar effect is also studied in the pMOSFET.We find that the bipolar effect can be effectively mitigated by a buried deep P+-well layer and can be removed by a buried SO 2 layer.     

Some insight into the acoustics of the didjeridu

The Australian didjeridu is a unique and interesting instrument. Despite the fact that the bore shape is almost random in nature and varies considerably across different instruments, the didjeridu timbre is readily recognizable. This is also true despite the fact that the player can manipulate the timbre more than in most wind instruments, by changing the shape of his vocal tract. In this study we examine the didjeridu spectrum in detail, in order to determine the characteristics that are similar across different instruments, those that are constant for a given instrument, and those that are readily influenced by the player. To this end we recorded and analyzed the sounds of eight instruments of different quality, all of them played across a range of timbres. Examining the resultant spectra, along with the resonance frequencies of these instruments, leads to a number of interesting conclusions. One of these is that the random nature of the instrument bore is actually conducive to creating its typical timbre. We also give a preliminary explanation of the differences between good and poor instruments.     

New insights into the kinetics of formic acid decomposition on copper surfaces

We use both time-resolved and static high resolution electron energy loss spectroscopies (EELS) to follow the chemisorption and subsequent decompostion of formic acid (HCOOH) on a Cu(1100) surface. Two stable forms are identified: one, existent at elevated temperatures, is a symmetrically bonded formate species (HCOO) oriented normal to the surface whereas the second, a low temperature high coverage structure, is canted. We believe this latter species to be a mixed array of hydrogen bonded formate and formic acid molecules. The observed tilting is not reversible at constant coverage, but can be driven by dosing the sample with formic acid while cooling. The implications of our results with respect to the catalytic dehydrogenation of formic acid on copper at high surface coverage are discussed.     

Theoretical insight into the substituent effects on linear and nonlinear optical properties of azobenzene‐based chromophores

The linear and nonlinear optical properties of 4 kinds of experimental synthesized azobenzene‐based chromophores were investigated by different density functional theories (DFTs) upon the electronic structures. The structure‐property relationship was studied on each single molecule either in the gas phase or in diethylether and tetrahydrofuran (THF) solutions. The substituent effect on optical properties was revealed by checking the positions of substituent groups, and the influence of dynamic perturbation to the optical nonlinearity was investigated by simulating the experimental excitation. The results revealed that the substituent in the meta‐position of the azobenzene group affects the optical properties more significantly than that in the ortho‐position, which is in agreement with the experimental finding. The modulation of molecular hyperpolarizability of bridge‐substituted azobenzene derived by dynamic perturbation is not recommended because of the reduced dynamic hyperpolarizability relative to the static one. The different functions of the DFT method hardly affect the calculated results, while solvent effects of diethylether and THF solutions are significant on the optical properties, especially for optical nonlinearity. The information derived from the single chromophore may be helpful in the design and preparation of high‐performance nonlinear optical materials in further.     

Dielectric and electrical properties of a tungsten bronze tantalate ceramic

Using high temperature solid state reaction the polycrystalline sample of K₂Pb₂Dy₂W₂Ti₄Ta₄O₃₀ was prepared. Single-phase compound formation was confirmed by preliminary X-ray structural analysis. The surface morphology recorded by scanning electron microscope at room temperature exhibits a dense uniform grain distribution on the surface of the sample. Ferroelectricity in the material is confirmed by the variation of polarization with temperature. The temperature and frequency dependence of electrical parameters (impedance, modulus, conductivity, etc.) of the material exhibits a strong correlation with its microstructure (i.e., bulk, grain boundary, etc.) and electrical properties. A typical Arrhenius behavior was observed in the temperature dependence of dc conductivity. The nature of frequency dependence of ac conductivity obeys Jonscher's universal power law. The variation of current with temperature shows that the material has high pyroelectric coefficient and figure of merit, thus making it useful for pyroelectric sensors with working temperature upto 500 °C.     

The properties and the nature of ball lightning

The observed properties of ball lightning are given. A model of mean ball lightning taking average iarameters is based on observed data. By comparing the observed data with contemporary information on the processes occuring in activated air, different aspects of the ball lightning phenomenon are analysed. Among these are the ways of energy storage in ball lightning, the mechanisms of thermal processes, the form and structure of ball lightning, and the electrical phenomena and luminous processes in ball lightning. The separate problems are investigated on the basis of model experiments. Numerical analysis of various aspects of the phenomenon allows us to construct a phenomenological model of ball lightning. This model conforms well with the observed data and up-to-date information on the different physical processes. The experimental modelling of ball lightning is analysed. Analogues of ball lightning are considered. A general phenomenological scheme of ball lightning is given.     

New insight into the mechanism of DNA polymerase I revealed by single-molecule FRET studies of Klenow fragment

We use single-molecule FRET and newly-developed D-loop techniques to investigate strand displacement activity of Klenow fragment (exo-) of DNA polymerase I in DNA sequences rich in guanine and cytosine (GC) bases. We find that there exist in the FRET traces numerous ascending jumps, which are induced by the backsliding of Klenow fragment on DNA chains. Our measurements show that the probability of backsliding is closely related to the GC-richness and dNTP concentration: increasing the GC-richness leads to an increase in the backsliding probability, and increasing the dNTP concentration however leads to a decrease in the backsliding probability. These results provide a new insight into the mechanism of DNA polymerase I.     

Enhanced gelling properties of myofibrillar protein by ultrasound-assisted thermal-induced gelation process: Give an insight into the mechanism

Effects of the incorporation of ultrasound with varied intensities (0–800 W) into the thermal-induced gelation process on the gelling properties of myofibrillar protein (MP) were explored. In comparison with single heating, ultrasound-assisted heating (<600 W) led to significant increases in gel strength (up to 17.9%) and water holding capacity (up to 32.7%). Moreover, moderate ultrasound treatment was conducive to the fabrication of compact and homogenous gel networks with small pores, which could effectively impair the fluidity of water and allow redundant water to be entrapped within the gel network. Electrophoresis revealed that the incorporation of ultrasound into the gelation process facilitated more proteins to get involved in the development of gel network. With the intensified ultrasound power, α-helix in the gels lowered pronouncedly with a simultaneous increment of β-sheet, β-turn, and random coil. Furthermore, hydrophobic interactions and disulfide bonds were reinforced by the ultrasound treatment, which was in support of the construction of preeminent MP gels.     

Formation processes of CuCl and regenerated Cu crystals on bronze surfaces in neutral and acidic media

The paper is devoted to investigating the formation of CuCl and regenerated Cu crystals on bronze. Electrochemical behaviour of bronze in simulated anoxic edaphic media and occluded cell (O.C.) solutions was studied with cycle voltammetry (CV) and X-ray diffraction (XRD). Within potential range of −800 to +800 mV, oxidation occurred was largely a process in which Cu is oxidized to CuCl and the reduction process was a reverse of it. An atomic force microscopy (AFM) was used to observe the morphology of CuCl crystals, regenerated Cu crystals and corrosion interface at nm level. The deposition of regenerated Cu on simulated archaeological bronzes was simulated under experimental conditions for the first time. CuCl could be thoroughly reduced to pure Cu if reduction time interval were sufficiently prolonged. This provided a theoretical and experimental basis for getting rid of harmful CuCl patina from archaeological bronzes with electrochemical means.     

Insights into the physical properties and anisotropic nature of ErPdBi with an appearance of low minimum thermal conductivity

We theoretically study the structural, elastic and optical properties of Er Pd Bi together with its anisotropic behaviors using density functional theory. It is observed that Er Pd Bi satisfies the Born stability criteria nicely and possesses high quality of machinability. The anisotropic behavior of Er Pd Bi is reported with the help of theoretical anisotropy indices incorporating 3 D graphical presentation, which suggests that Er Pd Bi is highly anisotropic in nature. It is noticed that the minimum thermal conductivity is very low for Er Pd Bi compared to the several species. This low value of minimum thermal conductivity introduces the potentiality of Er Pd Bi in high-temperature applications such as thermal barrier coatings.In addition, deep optical insights of Er Pd Bi reveal that our material can be used in different optoelectronic and electronic device applications ranging from organic light-emitting diodes, solar panel efficiency, waveguides etc. to integration of integrated circuits. Therefore, we believe that our results will provide a new insight into high-temperature applications and will benefit for the development of promising optoelectric devices as well.     

Microscopic insight into the quasi-particle structure of odd-mass terbium isotopes

The present work has been focussed on the application of Projected Shell Model to study the negative parity rotational band structure up to the high spin states of the neutron-rich odd mass Terbium isotopes with neutron numbers ranging from 90 to 98. The structure evolution in these nuclei has been made on the basis of various nuclear structure properties like energy spectra, transition energies, wave functions and electromagnetic transition probabilities (B(E2) and B(M1)). Besides, the occurrence of back bending has also been reported in the present work.