Comparison of methods for calculating Franck–Condon factors beyond the harmonic approximation: how important are Duschinsky rotations?

Three different approaches for calculating Franck–Condon factors beyond the harmonic approximation are compared and discussed in detail. Duschinsky effects are accounted for either by a rotation of the initial or final wavefunctions – which are obtained from state-specific configuration-selective vibrational configuration interaction calculations – or by a rotation of the underlying multi-dimensional potential energy surfaces being determined from explicitly correlated coupled-cluster approaches. An analysis of the Duschinsky effects in dependence on the rotational angles and the anisotropy of the wavefunction is provided. Benchmark calculations for the photoelectron spectra of ClO₂, HS^?₂ and ZnOH^? are presented. An application of the favoured approach for calculating Franck–Condon factors to the oxidation of Zn(H₂O)⁺ and Zn₂(H₂O)⁺ demonstrates its applicability to systems with more than three atoms.     

Comparison of different experimental methods for the assessment of the room’s acoustics

The paper presents the acoustics analysis of three different enclosed spaces. These spaces (rooms) have different geometrical shapes and sizes and serve for different purposes. The early decay time, reverberation time, clarity and center time are evaluated with Dirac, WinMLS, Aurora and Caracad software using simple, low-cost equipment. The listed acoustic parameters were determined using linear sine sweep and impulsive sources. Comparisons between experimental measurements, simulations and analytic results were done. The room impulse response measurement proved to be the most reliable method to evaluate the properties of different rooms even if the measurements are perturbed by non-idealities of the low-cost equipment.     

Does the excitation of a plasmon resonance induce a strong chemical enhancement in SERS? On the relation between chemical interface damping and chemical enhancement in SERS

In this contribution, a fundamental new approach is made to explain high enhancement factors in surface-enhanced Raman spectroscopy (SERS) on the basis of chemical enhancement. Usually, high SERS enhancement factors are explained by electromagnetic enhancements due to the excitation of localized surface plasmon resonances and strong near field dipole–dipole coupling. However, very often the corresponding SERS spectra show clear signatures of a chemical enhancement. I propose that this contradiction is easily solved by taking chemical interface damping of the plasmon resonance into account. Chemical interface damping is caused by an electron transfer from the metallic structure into an adsorbate. However, this mechanism is also the basis for chemical enhancement in SERS, i.e., an electron transfers in the lowest unoccupied molecular orbital of the molecule and back to the metal. Hence, if a molecule causes a strong chemical interface damping, the excitation of plasmons is still the key factor for the SERS enhancement. But the reason for this enhancement might be not solely due to electromagnetic fields rather than by a chemical enhancement due to electron transfers from the metal to the molecules.     

Do the fundamental physical constants have the same values in different regions of space-time?

An analysis of quasar spectra yields highly reliable constraints on the possible variation of the fine-structure constant a and the proton-to-electron mass ratio μ during cosmological evolution from the epoch corresponding to a cosmological red shift z≈2.8 (i.e., ∼10¹⁰ years ago) to the current epoch and . Zh. Tekh. Fiz. 69, 1–5 (September 1999)     

Pure drug nanoparticles in tablets: what are the dissolution limitations?

There has been increasing interests for drug companies to incorporate drug nanoparticles into their existing formulations. However, technical knowledge in this area is still in its infancy and more study needs to be done to stimulate growth in this fledging field. There is a need to scrutinize the performance of pure drug nanoparticles in tablets, particularly relating formulation variables to their dissolution performance. Application of the pure form, synthesized without the use of surfactants or stabilizers, is often preferred to maximize drug loading and also to minimize toxicity. Cefuroxime axetil, a poorly water-soluble cephalosporin antibiotic, was used as the model drug in the formulation development. Drug release rate, tablet disintegration time, tensile strength and energy of failure were predominantly influenced by the amount of super-disintegrant, amount of surfactant, compression force and diluent species, respectively. The compression rate had minimal impact on the responses. The main hurdle confronting the effective use of pure drug nanoparticles in tablets is the difficulty in controlling aggregation in solution, which could potentially be aggravated by the tabletting process. Through the use of elevated levels of surfactants (8 w/w% sodium dodecyl sulphate), drug release from the nanoparticle preparation was enhanced from 58.0 ± 2.7% to 72.3 ± 0.7% in 10 min. Hence, it is recommended that physical formulations for pure drug nanoparticles be focused on the particle de-aggregation step in solution, if much higher rates are to be desired. In conclusion, even though pure drug nanoparticles could be easily synthesized, limitations from aggregation may need to be overcome, before successful application in tablets can be fully realized.     

What are the structural features of the active site that define binuclear copper proteins function?

The structural basis that define the physiological functions of binuclear copper enzymes is discussed in the frame of the data generated by a broad spectroscopic approach, spanning from paramagnetic NMR and pulsed EPR to x-ray absorption spectroscopies. The structural features discussed for the different oxidation and ligation states accessible to a binuclear copper sites are the coordination geometry for the first and second shell, the metal-metal distance and the role of the bridging exogenous ligand(s). A structural model will be presented to rationalize both the differentiation in function within the protein families and the reaction mechanism of those proteins that are enzymatically active.     

Nanotechnology between the lab and the shop floor: what are the effects on labor?

Nanotechnology’s effects on labor and employment have received little attention within research and debates on the social implications of nanotechnology. This article shows that, in spite of its incipient development, nanotechnology is unquestionably moving toward manufacturing, involving a still very small but increasing component of the labor force. Based on secondary data and the literature review, I compose a picture of the emerging jobs in nanotechnology and highlight four emerging trends in nanotechnology workers’ skills requirements. I show that, in addition to job creation, nanotechnology diffusion is likely to pose labor market changes that may be disruptive for some categories of workers.     

Pickering emulsion prepared by nano-silica particles – A comparative study for exploring the effect of various mechanical methods

Pickering emulsions are eco-friendly, stabilized by solid particles, and have an essential role in leading industries. Although Pickering emulations have found several applications, surprisingly few investigations have attempted to explore the effectiveness of various mechanical processes for its production. To fill these gaps, the present investigation comprehensively examined the application of various Pickering emulsion preparation processes such as rotor-stator homogenization emulsification (R-SH), ultrasonic emulsification, and their combined processes by using nano-silica particles. The influences of emulsification time and intensity on emulsion droplets' distribution were analyzed as indicative factors. The kerosene/water nano-silica Pickering emulsion was utilized for all assessments. The obtained results demonstrated that the main distribution peak of the emulsion prepared by R-SH occurred where the chord length was greater than 40 μm. Micro-scale nano-silica-aggregates generated large droplets, while the fine-emulsion fraction was significantly increased after ultrasonic treatment. The experimental results showed that the emulsion prepared only by ultrasound needed substantial power to form a Pickering emulsion since the oil phase was difficult to disperse in the water phase. Finally, it was concluded that preprocessing by R-SH could form a stable and uniform emulsion speedily, which is essential for ultrasound emulsion preparation.     

Electron heating in the measurement of electron temperature by Thomson scattering: are thermal plasmas thermal?

Thomson scattering measurements have yielded electron temperatures T(e) up to 7000 K greater than the ion temperature in 1 bar thermal plasmas. To account for laser heating of electrons, T(e) was measured as a function of laser pulse energy, and an unperturbed T(e) obtained by linear extrapolation to zero pulse energy. It is shown that the absorption of laser energy by the electrons, and the cooling of the electrons by collisions and radiative emission, depend strongly on T(e). Considering all these processes gives T(e) values that are in much closer agreement with the ion temperature.     

What are the instrumentation requirements for measuring the isotopic composition of net ecosystem exchange of CO2 using eddy covariance methods?

Better quantification of isotope ratios of atmosphere-ecosystem exchange of CO2 could substantially improve our ability to probe underlying physiological and ecological mechanisms controlling ecosystem carbon exchange, but the ability to make long-term continuous measurements of isotope ratios of exchange fluxes has been limited by measurement difficulties. In particular, direct eddy covariance methods have not yet been used for measuring the isotopic composition of ecosystem fluxes. In this article, we explore the feasibility of such measurements by (a) proposing a general criterion for judging whether a sensor's performance is sufficient for making such measurements (the criterion is met when the contribution of sensor error to the flux measurement error is comparable to or less than the contribution of meteorological noise inherently associated with turbulence flux measurements); (b) using data-based numerical simulations to quantify the level of sensor precision and stability required to meet this criterion for making direct eddy covariance measurements of the 13C/12C ratio of CO2 fluxes above a specific ecosystem (a mid-latitude temperate forest in central Massachusetts, USA); (c) testing whether the performance of a new sensor-a prototype pulsed quantum cascade laser (QCL) based isotope-ratio absorption spectrometer (and plausible improvements thereon)-is sufficient for meeting the criterion in this ecosystem. We found that the error contribution from a prototype sensor (approximately 0.2 per thousand, 1 SD of 10 s integrations) to total isoflux measurement error was comparable to (1.5 to 2x) the irreducible 'meteorological' noise inherently associated with turbulent flux measurements above this ecosystem (daytime measurement error SD of approximately 60% of flux versus meteorological noise of 30-40% for instantaneous half-hour fluxes). Our analysis also shows that plausible instrument improvements (increase of sensor precision to approximately 0.1 per thousand, 1 SD of 10 s integrations, and increased sensor stability during the half-hour needed to integrate eddy covariance measurements) should decrease the contribution of sensor error to the point where it is less than the contribution from meteorological noise. This suggests that new sensors using QCL-based isotope ratio absorption spectroscopy should make continuous long-term observations of the isotopic composition of CO2 fluxes via eddy covariance methods feasible.     

How are spin gap and pairing correlations of doped Mott insulators controlled by the geometry of the lattice structure?

Proposals to enhance the spin excitation gap and the pairing correlations in doped Mott insulators are reviewed. Design and tuning of flat dispersions near the Fermi level extend the critical region of the metal-to-Mott insulator transition thereby inducing stronger pairing instabilities. Several one- and two-dimensional decorated lattices are studied. We also discuss the tuning for stronger d-wave pairing instabilities in a microscopic model of high-T_c cuprates.     

Comparison of delayed myocardial enhancement in the early and late phase after contrast injection: is it possible to reduce the examination time for myocardial viability study?

OBJECTIVES: We studied whether we can obtain a myocardial viability study immediately after contrast injection to reduce the whole cardiac MR examination time. MATERIALS AND METHODS: We examined 36 patients with cardiovascular abnormality on comprehensive cardiac MRI. T1-weighted images with inversion recovery (IR) were obtained 5 min after stress perfusion with 0.05 mmol/kg of gadodiamide and 15 min after the resting perfusion with the same dose. (The latter images were obtained 25 min after the initial administration.) We evaluated the existence, the number of sectors, and the degree of enhancement at each time. The contrast ratio was also calculated. The number of the enhanced sectors and the contrast ratio were statistically compared using Student's t test. RESULTS: All 17 cases of delayed myocardial enhancement at 25 min after contrast injection showed some enhancement at 5 min after contrast injection. However, the number of enhanced sectors was larger at 25 min after the initial injection in 11 cases, and it was statistically significant (P=.017). The degree of enhancement was stronger at 25 min in 14 cases. However, the contrast ratio at 5 and 25 min after contrast injection was not significantly different (P=.245). CONCLUSION: Myocardial viability study immediately after contrast injection is too early to evaluate the extent of myocardial injury.     

Luminescence properties of the Mg co–doped Ce:SrHfO3 ceramics prepared by the Spark Plasma Sintering Method

1300 or 1400 °C pre–sintered Al/Ce/Mg:SrHfO₃ and Al/Ce:SrHfO₃ ceramics were prepared by the Spark Plasma Sintering (SPS) in order to search for a new scintillation material with a high–effective atomic number(Z_eff) and good light output. The SrHfO₃ has a high Z_eff of 60, and high gamma–ray detection efficiency is expected. Meanwhile it has a high melting point of over 2500 °C, and single crystal is hard to be grown. On the other hand, high melting materials can be prepared as ceramics, and the SPS method is a simple process to fabricate the ceramics within a few hours. Thus, we prepared the samples using the SPS method, and their optical and scintillation properties were investigated. We found that Al/Ce/Mg:SrHfO₃ and Al/Ce:SrHfO₃ ceramics had an emission wavelength at around 400 nm originating from 5d–4f transition of Ce³⁺. Moreover, Al/Ce/Mg:SrHfO₃ pre-sintered at a temperature of 1400 °C had a light output of approximately 5,000 ph/MeV. In this paper, the light output of Mg-co-doped samples was improved compared with the Mg-free ones. The light output also depends on the pre-sintering temperature.     

Survival at low temperatures in insects: what is the ecological significance of the supercooling point?

Many freezing-intolerant insects may die during long or even brief exposures to temperatures above their supercooling point (SCP). Consequently, the real ecological value of the SCP remains ambiguous, particularly for tropical species that never experienced cold exposures. The bimodal distribution of SCP is discussed in the light of sexual dimorphism. The importance of sex in insect cold hardiness has been regularly neglected and although we admit that in some species sex may be uneasy to determine, it should be taken into account in further studies. We suggest that supercooling ability may be, at least partially, a result of adaptations to other functions unrelated to cold, including the desiccation resistance. The potential causes of insect death at low temperatures during survival experiments have also been examined. Prolonged exposures at lethal low temperatures can produce deleterious effects (including death) even if the insect does not freeze; during long-term exposure to low temperatures the organisms may finally die from the exhaustion of energy reserves.     

Apertureless SNOM imaging of the surface phonon polariton waves: what do we measure?

The apertureless scanning near-field microscope (ASNOM) mapping of surface phonon polariton (SPP) waves being excited at the surface of the SiC polar crystal at a frequency corresponding to the lattice resonance was investigated. The wave with well-defined direction and source position, as well as a well-known propagation law, was used to calibrate the signal of an ASNOM. An experimental proof is presented showing that the signal collected by the ASNOM in such a case is proportional (as a complex number) to the local field amplitude above the surface, regardless of the tip response model. It is shown that the expression describing an ASNOM response, which is, in general case, rather complicated nonlinear function of a surface/tip dielectric constants, wavelength, tip vibration amplitude, tip shape etc., can be dramatically simplified in the case of the SPP waves mapping in a mid-IR range, due to a lucky combination of the tip and surface parameters for the case being considered. A tip vibration amplitude is much less than a running SPP wave field decay height in a normal direction. At the same time, the tip amplitude is larger than a characteristic distance at which a tip–surface electromagnetic near-field interaction plays a significant role.     

Optical properties of Zr5Ti7O24:Eu3+ prepared by the sol–gel technique

Thermal processes can lead to the creation of photoluminescence centers in sol–gel derived Zr₅Ti₇O₂₄:Eu³⁺ (ZT:Eu³⁺) systems. Photosensitivity starts with heat treatments at 700 ^°C in air. The photoluminescence excitation occurs in the 225–550 nm range. The emission spectra covers the 550–700 nm range and consist of several sharp lines associated with transitions between the stark components of the excited states of the 4f ⁶ configuration to the ⁷ F _j states of the Eu³⁺ ion. The crystalline structure of the compound was obtained by X-ray diffraction techniques and is associated with a space group Pbcn. The thermal treatments in the 700–960 ^°C range have corresponding effects on both, the crystalline parameters and the optical properties of the europium ions. Time-resolved experiments were performed and the results are presented and discussed in order to get a better understanding of the effects of the thermal treatments on the Eu³⁺ transition lifetimes.     

Characteristics of p-type ZnO:As thin films prepared by the ampoule-tube method and ZnO p–n homojunction

A p-type ZnO thin film was prepared using arsenic diffusion via the ampoule-tube method. This was followed by fabrication of a ZnO p–n homojunction using n-type ZnO and characterization of the device properties. The ZnO thin film exhibited p-type characteristics, with a resistivity of 2.19×10⁻³ Ω cm, a carrier concentration of 1.73×10²⁰/cm³, and a mobility of 26.7 cm²/V s. Secondary ion mass spectrometer analysis confirmed that in- and out-diffusion occurred simultaneously from the external As source and the GaAs substrate. The device exhibited the rectification characteristics of a typical p–n junction; the forward voltage at 20 mA was approximately 5.5 V. The reverse-bias leakage current was very low—0.1 mA for −10 V; the breakdown voltage was −11 V. The ampoule-tube method for fabricating p-type ZnO thin films may be useful in producing ultraviolet ZnO LEDs and other ZnO-based devices.     

Superconductivity of the Sr2Ca12Cu24O41 spin-ladder system: are the superconducting pairing and the spin-gap formation of the same origin?

Pressure-induced superconductivity in a spin-ladder cuprate Sr2Ca12Cu24O41 has not been studied on a microscopic level thus far although the superconductivity was already discovered in 1996. We have improved the high-pressure technique using a large high-quality crystal, and succeeded in studying the superconductivity using 63Cu nuclear magnetic resonance. We found that the anomalous metallic state reflecting the spin-ladder structure is realized and the superconductivity possesses an s-wave-like character in the meaning that a finite gap exists in the quasiparticle excitation: At a pressure of 3.5 GPa, we observed two excitation modes in the normal state from the relaxation rate T-11. One gives rise to an activation-type component in T-11, and the other T-linear component linking directly with the superconductivity. This gapless mode likely arises from free motion of holon-spinon bound states appearing by hole doping, and the pairing of them likely causes the superconductivity.