Theoretical Interpretation Of Experimental Data Research Articles

The Brittle‐Ductile Transition Predicted by a Physics‐Based Friction Law

AbstractA theory of the brittle‐ductile transition (BDT) is shown to be a direct consequence of a recently developed physics‐based constitutive law for rock friction (Aharonov & Scholz, 2018, https://doi.org/10.1002/2016JB013829), which assumes exponential creep on contacts. The theory was previously tested against experimental data for sliding at low ambient temperature and stress. Here, theoretical interpretation of experimental data at high temperature and stress shows that at some point the real area of contact reaches a maximum value beyond which it becomes fixed. The constitutive law shows that this marks the onset of the BDT, beyond which sliding changes from frictional to an exponential flow law for low‐temperature plasticity. Application to the Earth's crust shows that beyond this point, strength fall linearly with depth until it intersects the power law for bulk flow of the country rock, which marks the lower boundary of the BDT. Modeling, constrained by experimental data for granite, predicts that the BDT starts at a temperature of about 300°C, at a depth of 11–13 km in the continental crust, depending on fault slip rate and temperature gradient. The completion of the BDT is similarly calculated to occur around 475°, at 16–18 km, in agreement with laboratory and field observations. The BDT is thus found to be a region spanning about 175°C with a width of several kilometers. Within the exponential flow region, the structural outcome would be a relatively narrow mylonitized fault zone, which widens into a broader region of shear at the base of the BDT.

Progress of Radar Observations of Meteors in Kazan (Russia) over the Last Sixty Years

AbstractThis paper presents a brief survey on the history of radar observations of meteors in Kazan from 1950s to present days. Such achievements of Kazan researchers as development and further improvement of original measuring equipment and antenna systems, of observational data processing methods, their contribution to the theory of physics of meteor phenomena and theoretical interpretation of experimental data are highlighted. A particular progress in meteor astronomy has been achieved with a new discrete quasi-tomoghraphic method for faint meteor showers identification that uses goniometer data of meteor radio reflections detected on radar as input data. The current state and new horizons of meteor studies in Kazan are stated.

Combined quantum-mechanical molecular mechanics calculations with NWChem and AMBER: Excited state properties of green fluorescent protein chromophore analogue in aqueous solution.

Combined quantum mechanical molecular mechanics (QM/MM) calculations have become a popular methodology for efficient and accurate description of large molecular systems. In this work we introduce our development of a QM/MM framework based on two well-known codes-NWChem and AMBER. As an initial application area we are focused on excited state properties of small molecules in an aqueous phase using an analogue of the green fluorescent protein (GFP) chromophore as a particular test case. Our approach incorporates high level coupled cluster theory for the analysis of excited states providing a reliable theoretical analysis of effects of an aqueous solvation environment on the photochemical properties of the GFP chromophore. Using a systematic approach, which involves comparison of gas phase and aqueous phase results for different protonation states and conformations, we resolve existing uncertainties regarding the theoretical interpretation of experimental data. We observe that the impact of aqueous environment on charged states generally results in blue shifts of the absorption spectra, but the magnitude of the effect is sensitive to both protonation state and conformation and can be rationalized based on charge movement into the area of higher/lower external electrostatic potentials. At neutral pH levels the experimentally observed absorption signal is most likely coming from the phenol protonated form. Our results also show that the high level electron correlated method is essential for a proper description of excited states of GFP. © 2017 Wiley Periodicals, Inc.

Negative capacitance peculiarities in a-Si:H/c-Si rectifier structure

Nontrivial negative capacitance (NC) effect, observed in a-Si:H/c-Si heterostructure devices, is discussed emphasizing the theoretical interpretation of experimental data. To explain NC effect, we have performed dark current voltage (I-V) and admittance measurements (C-V, G-V, C-f and G-f). The calculated values of series resistance (Rs) and barrier height (@FBo) have the values from 100 to [email protected] and 0.94 to 0.83eV, respectively. Also, below 50% helium dilution rate, diode ideality factor (n) becomes bigger than 2, because tunneling at junction interface plays a major role. The measured room temperature (294K) dark I-V result has been used during the fitting process for suggested capacitance model (Eq. (18)). The measured NC values exhibit strongly voltage depended behavior. This unexpected behavior is attributed to the presence of inductively coupled space charge region which might possibly be stemmed from the helium diluted a-Si:H material. It is seen that the measured NC values are well fitted with suggested capacitance model (Eq. (18)). Application of suggested correction formula on to experimental C-V data yields satisfactory results. It is shown that the calculated inductance values of the investigated device range from 10 to [email protected] and after correction, NC values are no longer observed in the Cd-V data.

Theoretical Analysis of Coagulation Kinetics in Brownian Disperse Systems

Analytical solution to the system of differential equations describing the coagulation kinetics in Brownian dilute disperse systems is obtained. The effect of the reversibility of aggregation in the secondary minimum on the coagulation kinetics in the primary minimum is analyzed. It is shown that experimental conditions can substantially affect the theoretical interpretation of experimental data.

Hadronic multiplicity at RHIC (and LHC)

We give a theoretical interpretation of experimental data on hadronic multiplicity, as a function of centrality and rapidity, in Au – Au and d – Au collisions at RHIC, in the framework of the Parton Saturation Model. We also present, in the same approach, our predictions for p – Pb and Pb – Pb collisions at LHC energies.

On boundary condition-induced states in low-dimensional semiconductor structures

We examine different solutions of multi-band k·p Hamiltonians. We refer mainly to the “intrinsic surface states”, with energies in the forbidden energy gap, that were proposed recently (Sercel et al. Phys. Rev. Lett. 83 (1999) 2394) for bare and capped nanocrystals. We review analytical and numerical results for different Hamiltonians and demonstrate that spurious solutions occur both for quantum dots and quantum wells. By showing peculiar characteristics of the proposed gap states, we argue that they are spurious solutions appearing in multi-band formulations due to infinite potential barrier imposed at the nanocrystal surface. We propose that these states are not physical and should be excluded from the theoretical interpretation of experimental data.

Acoustic signal attenuation, velocity, and filtering by beach sand, with different water content

The high-intensity acoustic pulses, transmitted by a piezoelectric transducer of center frequency 40 kHz, are sent through a beach sand medium and received, at up to 35-cm depth, by an identical receiver transducer. The received acoustic signals are then amplified and analyzed on computer. Experimental data are collected at different depth and water content of pore spaces between the grains. Experimental results show that sound arrival velocity decreases from 197 m/s for humid sand, to 120 m/s for partially water-saturated sand with air bubbles, which are always present. Acoustic signal attenuation increased by a factor of ten, from humid to partially water-saturated sand. The peak frequencies in FFT of the transmitted acoustic signal and its speed are dependent on compactness of the medium. The peak spectral amplitude is close to 9.7 kHz for humid sand and 7.5 kHz, for sand partially saturated with water. Experimental data on wave dispersion, phase velocity, and attenuation versus frequency, up to 24 kHz, are obtained. Latest results and tentative theoretical interpretation of experimental data, including porosity and grain size distribution, will be presented.

Negative capacitance effect in semiconductor devices

Nontrivial capacitance behavior, including a negative capacitance (NC) effect, observed in a variety of semiconductor devices, is discussed emphasizing the physical mechanism and the theoretical interpretation of experimental data. The correct interpretation of NC can be based on the analysis of the time-domain transient current in response to a small voltage step or impulse, involving a self-consistent treatment of all relevant physical effects (carrier transport, injection, recharging etc.). NC appears in the case of the non-monotonic or positive-valued behavior of the time-derivative of the transient current in response to a small voltage step. The time-domain transient current approach is illustrated by simulation results and experimental studies of quantum well infrared photodetectors (QWIPs). The NC effect in QWIPs has been predicted theoretically and confirmed experimentally. The huge NC phenomenon in QWIPs is due to the non-equilibrium transient injection from the emitter caused by the properties of the injection barrier and the inertia of the QW recharging.

Dielectric Spectroscopy and Emulsions. A Theoretical and Experimental Approach

ABSTRACT The theoretical interpretation of experimental data from the previous papers (1,2) are extended with the purpose to demonstrate the possibilities of a qualitative characterisation of flocculated emulsions by means of dielectric spectroscopy. Both low and high frequency limits of dielectric spectra are analysed, which is an extension of our previous paper (1) where only low frequency values were interpreted. Attention is paid to the emulsion stability with regard to flocculation in a dielectric spectrum. The influence of salt concentration inside the aqueous droplets in the dispersed phase is interpreted. The theoretical interpretation is based on a generalised model of the flocculated state, where floes are characterised not only by their shapes, but also by their volumes. The information of floe properties obtained by means of dielectric spectroscopy, and different hydrodynamic estimations characterising the flocculation process is compared and correlations are established.

Electrical transport and electronic properties of a amorphous carbon thin films

The present state of the experimental characterization of the electrical transport and electronic properties of amorphous carbon structures is briefly reviewed and our own reflections on this topic are classified. The theoretical interpretation of experimental data is based on a theory that derives the π electron energy spectra and the density of states. An estimate is given to test the applicability of the approximate electrical transport theories commonly used for different types of thin amorphous carbon films.

Theoretical interpretation of experimental data on 1,3-dipolar cycloadditions

Using the MINDO/3 method it has been shown that the two-steps mechanism, proposed in a previous paper 1 for the 1,3-dipolar cycladditions, is compatible with several existing experimental results. Firstly, the effects of the introduction of different substituents on the mechanism of the cycloadditions were studied. Secondly, the slight influence of the polarity of the solvent on the reaction rate has been interpreted by solvation calculations. Finally, the stereospecificity observed has been explained.

Diphosphoglycerate and inosine hexaphosphate control of oxygen binding by hemoglobin: a theoretical interpretation of experimental data.

A theoretical equation is presented for the control of cooperative adsorption on proteins and other linear macromolecules by hormones, drugs, ATP, and other "cardinal adsorbents." With reasonable accuracy, this equation describes quantitatively the control of oxygen binding to hemoglobin by 2,3-diphosphoglycerate and by inosine hexaphosphate.