Anomalies of the electrical conductance of water near 4°C

The dependences of the electrical conductance of water (G) on temperature T upon quasi-static heating from 0 to 7°C with a rate of 0.1°C per 200?C250 s have been obtained by the capacitance method in the sound frequency ranges. Anomalies have been found in the dependences G(T) near 4°C for water containing charge carriers of different types and concentrations.     

Origin of the anomaly in the behavior of the viscosity of water near 0°C

The temperature dependence of the viscosity of water in the range of 240–340 K has been studied by the molecular dynamics method. The analysis of the data has revealed an anomaly in the behavior of the viscosity of water near 0°C. The appearance of this anomaly has been attributed to the formation of cluster structures at a decrease in the temperature.     

Anomaly of Microwave Absorption of Ice near –45°C under Plastic Deformation

Technical Physics - The microwave absorption of fresh ice subjected to plastic deformation when changing temperature from 0 to –60°C has been measured. A decrease in the losses of...     

On the role of a weak hydrogen bond OH…O in the formation of the anomalous dielectric response of crystals and polymers near 40°C

In some crystals, polymers, and gels that contain hydrogen bonds OH…O, NH…O of length 2.8–3 Å or water molecules, gigantic anomaly of dielectric permittivity (? ～ 10³–10⁶) is observed in certain circumstances at frequencies of 1–10⁶ Hz, which is accompanied by peculiarities in conductivity σ and dielectric losses tanδ. In crystals this effect appears after a sudden cooling to ?50°C and it is observed at slow heating in the range of 20–40°C. At the return temperature course from 40°C dependences ?(T), σ(T), and tanδ(T) have their usual values. Anomalies in objects that differ by their compositions are unified by their temperatures, which are all close to 40°C. Authors have made an attempt to explain the similarity of these phenomena by the features of hydrogen bonds that are present in the objects.     

Explicit analytical solutions of the anisotropic Brinkman model for the natural convection in porous media (Ⅱ)

Natural convective heat transfer phenomena in porous media are very common in the energy conversion and energy utilization field. Study on these phenomena is an impor- tant branch of heat and mass transfer at the moment[1,2]. For theoretical analysis in early time, the Darcy model proposed many years ago was often used. However, great im- provements have been made to the Darcy model in recent years in order to more accu- rately describe and more widely reflect the objective reality[3―7]. The…     

Interaction of binary cuprates with oxygen and water vapor at temperatures of 200–400°C

Interaction of binary cuprates with oxygen and water vapor at T = 200–400°C has been studied. It has been established that only compounds containing oxygen vacancy chains in their structure can absorb oxygen and moisture from annealing atmosphere. Absorption of oxygen brings about decrease in the lattice parameters while embedding of OH^? groups leads to their growth. In contrast to YBa₂Cu₃O _y , binary cuprates do not undergo phase transitions in interaction with the atmosphere. Saturation with water and formation of oxyhydroxides is followed by their hydrolytic decomposition involving formation of simpler oxides and hydroxides.     

60°C lead salt laser emission near 5-μm wavelength

A IV–VI double heterostructure laser made from molecular beam epitaxy grown PbSrSe/PbSe/PbSrSe has been operated in pulsed mode up to 333 K (60°C) at a wavelength of 4.78 μm. This is the highest mid-infrared diode laser operation temperature observed to date.     

High-resolution infrared spectrum of the fundamental band of LiCl at a temperature of 830°C

High-resolution Fourier transform spectra of ⁶LiCl and ⁷LiCl have been recorded at 830°C. A total of 2522 lines have been measured at 0.006 cm⁻¹ resolution in the 500- to 730-cm⁻¹ region. The data for all four isotopic species have been fit with a standard deviation of 0.00027 cm⁻¹ using 19 isotopically invariant rovibrational constants including five Δ_ij correction terms to the usual Dunham Y_ij terms. Comparison is made with the constants derived from a direct fit of the observed transitions to a Dunham potential function with only 13 coefficients including for Δ correction terms. The gas phase band center for the v = 1–0 transition of ⁷Li³⁵Cl is 634.0753(7) cm⁻¹.     

Analysis of the Liquid–Cluster State of Melts near the Melting Point

Technical Physics - We have analyzed the available data on the transition from equilibrium crystallization of melts of various substances to nonequilibrium explosive crystallization depending on...     

An experimental and kinetic modeling study of the auto-ignition of natural gas blends containing C1–C7 alkanes

Ignition delay time measurements for multi-component natural gas mixtures were carried out using a rapid compression machine at conditions relevant to gas turbine operation, at equivalence ratios of 0.5–2.0 in ‘air’ in the temperature range 650–1050 K, at pressures of 10–30 bar. Natural gas mixtures comprising C₁–C₇ n-alkanes with methane as the major component (volume fraction: 0.35–0.98) were considered. A design of experiments was employed to minimize the number of experiments needed to cover the wide range of pressures, temperatures and equivalence ratios. The new experimental data, together with available literature data, were used to develop and assess a comprehensive chemical kinetic model. Replacing 1.875% methane with 1.25% n-hexane and 0.625% n-heptane in a mixture containing C₁–C₅ components leads to a significant increase in a mixture's reactivity. The mixtures containing heavier hydrocarbons also tend to show a strong negative temperature coefficient and two-stage ignition behavior. Sensitivity analyses of the C₁–C₇ blends have been performed to highlight the key reactions controlling their ignition behavior.     

Dielectric study of natural inyoite in the frequency range from 10−1 to 107 Hz and the temperature range from −50 to 140°C

For the first time, the method of dielectric dispersion in the 10^?1–10⁷ frequency range is applied to study temperature the dependences of permittivity, conductivity, and dielectric modulus of natural inyoite in the temperature range from ?50 to 140°C. An anomalous increase in the parameters under consideration is observed at temperatures between 87 and 98°C. According to thermal gravimetrical measurements, this range is characterized by an anomaly resulting from a partial loss of crystallization water.     

Absorption spectrum of C2 molecules near 1.06 μm

An intracavity laser spectrometer has been used to study the laser-spark absorption spectrum of C₂ radicals near 1.06 μm. The spectra recorded have been assigned, and the rotational lines of the transitions 3-0, 4-1, and 5-2 b ³Σ _g ^? -a ³Π _u and 2-1 and 1-0 A ¹Π _u -X ¹Σ _g ⁺ have been identified. The vibrational and rotational temperatures have been determined.     

Results of measurements of the atmospheric muon flux in the zenith angle range of 85°–95°

The results of the study of the near-horizontal muon flux in the zenith angle range of 85–95 degrees are presented. In particular, the so-called albedo muons (atmospheric muons backscattered in the ground to the upper hemisphere are recorded in this range. The data of measurement series performed at the NEVOD-DECOR experimental complex are analyzed for 30 thousand of “live” time hours. Multiple Coulomb scattering of muons in the ground is simulated by theMonte-Carlo method using various models. The measured muon flux intensity is compared with the simulation results.     

Numerical investigation of natural convection heat transfer of nanofluids in a Γ shaped cavity

This paper analyzes the heat transfer and fluid flow of natural convection in a Γ shaped enclosure filled with Al₂O₃/Water nanofluid that operates under differentially heated walls. The Navier–Stokes and energy equations are solved numerically. Heat transfer and fluid flow are examined for parameters of non-uniform nanoparticle size, mean nanoparticle diameter, nanoparticle volume fraction, Grashof number and different geometry of enclosure. Finite volume method is used for discretizating positional expressions, and the forth order Rung-Kuta is used for discretizating time expressions. Also an artificial compressibility technique was applied to couple continuity to momentum equations. Results indicate that using nanofluid causes an increase in the heat transfer and the Nusselt number so that for R = 0.001 in Gr = 10³, the Nusselt number 25%, in Gr = 10⁴ 26%, and in Gr = 10⁵ 28% increases. Furthermore; by decreasing the mean diameters of nanoparticles, Nusselt number increases. By increasing R parameter (d_p,min/d_p,max) and nano particle volume fraction, Nusselt number increases.     

High sensitivity CW-CRDS of O enriched water near 1.6 μm

The absorption spectrum of ¹⁸O enriched water has been recorded by continuous wave cavity ring down spectroscopy between 5905.7 and 6725.7 cm⁻¹ using a series of fibred DFB lasers. The investigated spectral region corresponds to the important 1.55 μm transparency window of the atmosphere where water absorption is very weak. The typical CRDS sensitivity (noise equivalent absorption of 5×10⁻¹⁰ cm⁻¹) allowed for the detection of lines with intensity as low as 10⁻²⁸ cm/molecule while the minimum intensity value provided by HITRAN in the considered spectral region is 1.7×10⁻²⁴ cm/molecule. The line parameters were retrieved with the help of an interactive least squares multi-lines fitting program assuming a Voigt function as line profile. Overall, 4510 absorption lines belonging to the H₂¹⁸O, H₂¹⁶O, HD¹⁸O, HD¹⁶O and H₂¹⁷O water isotopologues were measured. Their intensities range between 3×10⁻²⁹ and 5×10⁻²³ cm/molecule at 296 K and the typical accuracy on the line positions is 1×10⁻³ cm⁻¹. 2074 of the observed lines attributed to H₂¹⁸O, HD¹⁸O and H₂¹⁷O are reported for the first time. The transitions were assigned on the basis of variational calculations resulting in 288, 135 and 38 newly determined rovibrational energy levels for the H₂¹⁸O, HD¹⁸O and H₂¹⁷O isotopologues, respectively. The new data set includes the band origin of the 4ν₂ bending overtone of H₂¹⁸O at 6110.4239 cm⁻¹ and rovibrational levels corresponding to J and K_a values up to 18 and 12, respectively, for the strongest bands of H₂¹⁸O: 4ν₂, ν₁+2ν₂, 2ν₂+ν₃, 2ν₁, ν₁+ν₃, and ν₂+ν₃. The obtained experimental results have been compared to the spectroscopic parameters provided by the HITRAN database and to the recent IUPAC critical review of the rovibrational spectrum of H₂¹⁸O and H₂¹⁷O as well as to variational calculations. Large discrepancies between the 4ν₂ variationally predicted and experimental intensities have been evidenced for the H₂¹⁸O and H₂¹⁶O molecules.     

Excitation of Alfvén vortices in the ionosphere by the magnetospheric convection

We analyze conditions for excitation of ULF waves in the ionospheric Alfvén resonator (IAR), taking into account the altitude-inhomogeneous profile of the magnetospheric convection velocity. This profile is formed as a result of interaction of the convective flow with the neutral atmosphere at altitudes 90–150 km. ULF waves comprise oblique Alfvén waves, trapped into the IAR, and ionospheric drift waves, which are in resonance with them. These waves together form strongly anisotropic, closed current loops, whose scale along the magnetic field greatly exceeds their transverse scale, i.e., l_z ≫ l_⊥, and can be considered Alfvén vortices. Within the framework of the proposed model of the ionosphere, we study the instability threshold and the amplitude growth rate of the Alfvén vortices as functions of different parameters (wave vector k_22A5, angle between the wave vector and the convection velocity, ratio of the Alfvén-wave and Pedersen conductivities, etc.). Some estimates are given in application to the observed small-scale field-aligned currents in the auroral ionosphere. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 5, pp. 376–390, May 2008.     

Anomalies of the static dielectric constant of Pb1−x Ge x Te

The static dielectric constant of Pb_1–x Ge _x Te (0x0.05) has been determined from differential capacitance measurements on Schottky-barriers in the temperature range of 4.2–300 K. A comparison with data deduced from the phonon frequencies via the Lyddane-Sachs-Teller relation shows substantial discrepancies which are attributed to lattice defects.Work supported by Jubiläumsfonds der Österreichischen Nationalbank