The Foundations of Linear Stochastic Electrodynamics

An analysis is briefly presented of the possible causes of the failure of stochastic electrodynamics (SED) when applied to systems with nonlinear forces, on the basis that the main principles of the theory are correct. In light of this analysis, an alternative approach to the theory is discussed, whose postulates allow to establish contact with quantum mechanics in a natural way. The ensuing theory, linear SED, confirms the essential role of the vacuum–particle interaction as the source of quantum phenomena.     

A possible evidence for a violation of Heisenberg's position-momentum uncertainty relation

In the light of recent works by Fitchard and Mackinnon, experimental evidence by Nuttall and Gallon is interpreted as an indication of a violation of Heisenberg's uncertainty relation. Possible loopholes and their avoidance in future experiments are discussed.     

Structural characterization studies on the natural mineral pyrophyllite

A light-yellow-colored pyrophyllite (Al₂O₃·SiO₂) mineral obtained from Vempalli, Cuddapah district, Andhra Pradesh, India, is investigated in the present work. Chemical analysis carried out using energy-dispersive spectroscopy (EDX) shows that Fe₂O₃ is present by about 1.56?wt%. Structural characterization was performed using X-ray diffraction (XRD). XRD results suggest that the unit cell is monoclinic with a = 5.16, b = 8.798, c = 9.347 Å and β = 100.46°. The ligands around the metal ion present in the structure are investigated using FTIR spectroscopy. EDX analysis indicates that iron and titanium are only two transition metals present in it. Morphology studied using scanning electron microscopy suggests that the unit cell consists of a dioctahedral layered structure. Fe³⁺ is present in the location of Al³⁺ in the unit cell of pyrophyllite. Electron paramagnetic resonance results indicate that the unit cell of the crystal contains Fe(III), and its g values are found to be 4.10 and 2.0. Infrared properties are due to the presence of silicate and hydroxyl anions as ligands. Nonlinear optical measurements carried out using Z-scan reveal the occurrence of strong nonlinear optical limiting in the material, indicating potential applications in laser safety devices.     

Vibrational spectra and harmonic force fields of pyrrolidine derivatives: comparison between HF, MP2 and DFT force fields

Infrared and Raman spectra are reported for the isotopic species of pyrrolidine-d₀ (PY) and -d₁ and for N-methylpyrrolidine-d₀ (NMP), -d₂, -d₃ and -d₈. A complete assignment of the experimentally observed bands to normal modes is presented and discussed in particular in the CH/CD stretching region. The molecular structures and harmonic force fields were calculated ab initio at the Hartree–Fock (HF), the second order Møller–Plesset (MP2) and the density functional theory (DFT) level with the 6-31G* basis set. The force fields were fitted by use of 7 (PY) and 4 (NMP) independent scale factors. The spectra calculated with the DFT force fields are in better agreement with the experiment than those calculated by the MP2 and HF force fields. Though some scaled fundamental frequencies show larger deviations from the experimental ones, the mean percentage deviations of calculated frequencies from experimental fundamentals are less than 2.6% for all isotopic species of PY and NMP under study. The results indicate that density functional theory is a reliable tool to get a deeper insight in the assignment of vibrational spectra and the nature of normal modes of pyrrolidine derivatives.     

Heisenberg's uncertainty relation of position and momentum in experiments without mutual disturbance

Arranging target atoms in a plane monolayer, one may produce by atomic or nuclear reaction an ensemble of particles with small initial position spread without disturbing their momentum spread. This would either allow a violation of Heisenberg's uncertainty relation, by creating a situation not described by quantum mechanics hence rendering quantum mechanics incomplete, or, if the uncertainty relation should hold also in this non-disturbative situation, it would mean a permanent violation of energy conservation. Thus an uncertainty relation for position and momentum and energy conservation appear to be mutually exclusive.1. Recently also Croca [5] proposed another way of determining a x without interfering with p_X.2. To forbid even speaking of an initial position spread smaller than that indicated by the wave function [6] would amount to circular reasoning and the denial of a falsification of quantum mechanics.     

Non-Linear Interactions and Exchange Rate Prediction: Empirical Evidence Using Support Vector Regression

This paper analysed the prediction of the spot exchange rate of 10 currency pairs using support vector regression (SVR) based on a fundamentalist model composed of 13 explanatory variables. Different structures of non-linear dependence introduced by nine different Kernel functions were tested and the predictions were compared to the Random Walk benchmark. We checked the explanatory power gain of SVR models over the Random Walk by applying White’s Reality Check Test. The results showed that the majority of SVR models achieved better out-of-sample performance than the Random Walk, but in overall they failed to achieve statistical significance of predictive superiority. Furthermore, we observed that non-mainstream Kernel functions performed better than the ones commonly used in the machine-learning literature, a finding that can provide new insights regarding machine-learning methods applications and the predictability of exchange rates using non-linear interactions between the predictors.     

A reevaluation of the assignment of the vibrational fundamentals and the rotational analysis of bands in the high-resolution infrared spectra of trans- and cis-1,3,5-hexatriene

Assignments of the vibrational fundamentals of cis- and trans-1,3,5-hexatriene are reevaluated with new infrared and Raman spectra and with quantum chemical predictions of intensities and anharmonic frequencies. The rotational structure is analyzed in the high-resolution (0.0013-0.0018 cm⁻¹) infrared spectra of three C-type bands of the trans isomer and two C-type bands of the cis isomer. The bands for the trans isomer are at 1010.96 cm⁻¹ (ν₁₄), 900.908 cm⁻¹ (ν₁₆), and 683.46 cm⁻¹ (ν₁₇). Ground state (GS) rotational constants have been fitted to the combined ground state combination differences (GSCDs) for the three bands of the trans isomer. The bands for the cis isomer are at 907.70 cm⁻¹ (ν₃₃) and 587.89 cm⁻¹ (ν₃₅). GS rotational constants have been fitted to the combined GSCDs for the two bands of the cis isomer and compared with those obtained from microwave spectroscopy. Small inertial defects in the GSs confirm that both molecules are planar. Upper state rotational constants were fitted for all five bands.     

Analysis of rotational structure in the high-resolution infrared spectrum and assignment of vibrational fundamentals of butadiene-2,3-C2

The 2,3-¹³C₂ isotopomer of butadiene was synthesized, and its fundamental vibrational fundamentals were assigned from a study of its infrared and Raman spectra aided with quantum chemical predictions of frequencies, intensities, and Raman depolarization ratios. For two C-type bands in the high-resolution (0.002 cm⁻¹) infrared spectrum, the rotational structure was analyzed. These bands are for ν₁₁ (a_u) at 907.17 cm⁻¹ and for ν₁₂ (a_u) at 523.37 cm⁻¹. Ground state and upper state rotational constants were fitted to Watson-type Hamiltonians with a full quartic set of centrifugal distortion constants and two sextic ones. For the ground state, A₀ = 1.3545088(7) cm⁻¹, B₀ = 0.1469404(1) cm⁻¹, and C₀ = 0.1325838(2)  cm⁻¹. The small inertial defects of butadiene and two ¹³C₂ isotopomers, as well as for five deuterium isotopomers as previously reported, confirm the planarity of the s-trans rotamer of butadiene.     

Designing State-of-the-Art Gas Sensors: From Fundamentals to Applications

Gas sensors are crucial in environmental monitoring, industrial safety, and medical diagnostics. Due to the rising demand for precise and reliable gas detection, there is a rising demand for cutting-edge gas sensors that possess exceptional sensitivity, selectivity, and stability. Due to their tunable electrical properties, high-density surface-active sites, and significant surface-to-volume ratio, nanomaterials have been extensively investigated in this regard. The traditional gas sensors utilize homogeneous material for sensing where the adsorbed surface oxygen species play a vital role in their sensing activity. However, their performance for selective gas sensing is still unsatisfactory because the employed high temperature leads to the poor stability. The heterostructures nanomaterials can easily tune sensing performance and their different energy band structures, work functions, charge carrier concentration and polarity, and interfacial band alignments can be precisely designed for high-performance selective gas sensing at low temperature. In this review article, we discuss in detail the fundamentals of semiconductor gas sensing along with their mechanisms. Further, we highlight the existed challenges in semiconductor gas sensing. In addition, we review the recent advancements in semiconductor gas sensor design for applications from different perspective. Finally, the conclusion and future perspectives for improvement of the gas sensing performance are discussed.     

Rotational analysis of bands in the high-resolution infrared spectra of the three species of butadiene-1,4-d2; refinement of the assignments of the vibrational fundamentals

Samples of trans,trans and cis,cis forms of butadiene-1,4-d₂ have been synthesized and found to contain useful amounts of the cis,trans species as a contaminant. Assignments of fundamental frequencies for the three isotopomers of butadiene-1,4-d₂ have been extended and improved from investigations of their Raman spectra as well as their infrared (IR) spectra. High-resolution IR spectra have been recorded for the three isotopomers, and a rotational analysis has been completed for strong bands of each species. Ground state and some upper state rotational constants have been fit. Corresponding ground state moments of inertia compare favorably with equilibrium moments of inertia obtained from B3LYP/6-311++G** theory. Two ¹³C isotopomers are being prepared, and an improved structural analysis of butadiene will soon be available to assess how π-electron delocalization affects its structure.