Relation between the intensity of ir absorption bands of stretching vibrations of nitrogroups and their number in aromatic nitrocompounds

Yaroslavl' State University, 9 Matrosov Ave., Yaroslavl', 150023, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 6, pp. 30–37, November–December, 1995.     

Vibrational spectra and stereoisomerism of the hexopyranose cycle in epoxysaccharides

To whom correspondence should be addressd.     

The scattering of light on sound waves in the hypersonic range of frequencies the directional sensitivity of Brillouin light scattering

Brillouin spectroscopy of acoustic phonons in transparent crystals and nontransparent metallic Co/Cu superlattices is reviewed. The method presents a directional sensitivity of the experiment. This feature is useful in elastic constants measurements in crystals and analysis of in-plane anisotropies of hyper-sound and spin waves in superlattices. Results for the LiTaO₃, LiNbO₃, LiNbO₃:Cu, SLGO, SLAO crystals are provided. Spin wave results for the Co/Cu superlattices are presented.     

Temperature dependence of the indirect band gap, steepness parameter and related optical constants of [Kx(NH4)1−x]2ZnCl4 mixed crystals

Optical transmittance measurements near the absorption edge of [K_x(NH₄)_1−x]₂ZnCl₄ mixed crystals, where x=0.00, 0.232, 0.522, 0.644, 0.859 and 1.00, are reported over 276–350 K range. Analysis reveals that the type of transition is the indirect allowed one. The absorption edge shifted towards lower energy with increasing temperature. It is shown that [K_x(NH₄)_1−x]₂ZnCl₄ mixed crystals with x0.644 reveal a phase transition at 319 K, this phase disappeared at high concentrations of K⁺ ions. The steepness parameter is given, its value is used to estimate the temperature dependence of the indirect energy gap. In the region of the absorption edge, the absorption coefficient obeys Urbach's rule. Urbach parameters are investigated as a function of temperature.     

The new HMQC-based technique for the quantitative determination of heteronuclear coupling constants. Application for the measurement of 3J(H'(i),P(i+1)) in DNA oligomers

A new general J-HMQC-based technique is presented, which allows an accurate determination of heteronuclear coupling constants. The most important feature of this new approach includes acquisition of the two data sets with and without the additional pi(S)-pulse at the end of coupling evolution period. This enables preservation and separation of the two orthogonal terms of coupling evolution, which are manifested by in- and antiphase cross-peaks, respectively. The coupling magnitudes are evaluated by the nonlinear least-squares fitting of the ratios of integrated signal volumes for both kinds of signals. The effectiveness of the new sequence is demonstrated by determination of the 3J(H3'(i),P(i+1)) couplings in DNA octamer duplex d(GCGTACGC)(2) sample. Additionally, the ability of the new method for the measurement at the natural abundance level of 13C nuclei is presented for the beta-cyclodextrin.     

The Effect of Cricothyroid Muscle Action on the Relation Between Subglottal Pressure and Fundamental Frequency in an In Vivo Canine Model

The relation between subglottal pressure (P_s) and fundamental frequency (F₀) in phonation was investigated with an in vivo canine model. Direct muscle stimulation was used in addition to brain stimulation. This allowed the P_s-F₀ slope to be quantified in terms of cricothyroid muscle activity. Results showed that, for ranges of 0–2 mA constant current stimulation of the cricothyroid muscle, the P_s-F₀ slope ranged from 10 Hz/kPa to 60 Hz/kPa. These results were compared to similar slopes obtained in a previous study on excised larynges in which the vocal fold length was varied instead of cricothyroid activation. A physical interpretation of the P_s-F₀ slope is that the amplitude-to-length ratio of the vocal folds decreases with CT activity, resulting in a smaller time-varying stiffness. In other words, there is less dependence of F₀ on amplitude of vibration when the vocal folds are long instead of short.     

Shape-driving effect of the proton 1/2[541] band in 171Ta

High-spin states in ¹⁷¹Ta were populated through the heavy-ion fusion-evaporation reaction ¹⁵⁷Gd (¹⁹F, 5n)¹⁷¹Ta at 105MeV beam energy. Lifetimes of the levels of the πh_9/21/2[541] band have been measured by using the Doppler shift attenuation method. The transition quadrupole moments ( Q_t) and the quadrupole deformation (β₂) have been extracted. Both β₂ and Q_t values decrease slightly with increasing rotational frequency. The average β₂ value of 0.26 is 18% larger than that of the πh_11/2 9/2[514] band. Total Routhian Surface calculations have been performed with the non-axial deformed Woods-Saxon potential and the predicted values of the quadrupole deformation β₂ are in good agreement with that deduced from our lifetime measurement. The shape-driving effect is discussed.     

Theoretical investigations of the spin Hamiltonian parameters for the tetragonal [Rh(CN)4Cl2] complex in KCl

The spin Hamiltonian parameters (g factors, hyperfine structure constants and superhyperfine parameters) for the tetragonal [Rh(CN)₄Cl₂]⁴⁻ complex in KCl are theoretically investigated from the perturbation formulas of these parameters for a 4d⁷ ion in a tetragonally elongated octahedron. This center can be assigned to the substitutional Rh²⁺ on host K⁺ site reduced from Rh³⁺ by capturing one electron during the electron irradiation, associated with the two axial ligands CN⁻ replaced by two Cl⁻. The crystal-fields of the two axial Cl⁻ are weaker than those of the four planar CN⁻, yielding the tetragonal elongation distortion. This system belongs to the case of low spin (S = 1/2) under strong crystal-fields, different from that of high spin (S = 3/2) under weak and intermediate crystal-fields (e.g., 3d⁷ ions such as Fe⁺ and Co²⁺ in conventional chlorides). The calculated spin Hamiltonian parameters show good agreement with the experimental data. The above [Rh(CN)₄Cl₂]⁴⁻ complex due to the different axial and perpendicular ligands is unlike the tetragonally elongated [RhCl₆]⁴⁻ complex due to the Jahn–Teller effect in the similar NaCl:Rh²⁺ crystals.     

The Fate of [15N]Ammonium and [15N]Nitrate in the Soil of a 140-Year-Old Spruce Stand (Picea Abies) in the Fichtelgebirge (NE-Bavaria)

Abstract

A ¹⁵N tracer-experiment was carried out in a 140-year-old spruce stand (Picea abies (L.) Karst.) in the Fichtelgebirge (NE-Bavaria, Germany). Highly enriched (98 at%) [¹⁵N]ammonium and [¹⁵N]nitrate were applied as tracers by simulation of a deposition of 41.3 mol N ha^?1 with 11 water m^?2. To examine seasonal variations of uptake by spruce and understorey vegetation, different plots were labelled in spring, summer and autumn 1994.

One aim of the present study was to perfect a method of preparation of soil extracts for isotope ratio mass spectrometry (IRMS) measurements. Ammonium and nitrate from soil extracts were prepared for IRMS measurements by steam distillation and subsequent freeze drying. Additionally, tracer distribution and transformations in the soil nitrogen pools were examined. Ammonium, nitrate and total nitrogen were examined in the organic layer and the upper 10 cm of the mineral soil during 3 months after the first tracer application in spring 1994.

In July 1994, three months after tracer application, 40% of the [¹⁵N]ammonium label and 29% of the [¹⁵N]nitrate label, respectively, were recovered in the total N pool of the investigated soil horizons. In the organic layer the L/Of horizon retained most of the recovered tracers. Nitrification, immobilisation and mineralisation occurred even under the conditions of high soil acidity at the study site.     

The metabolic effect of resistant starch and yoghurt on the renal and faecal nitrogen and ammonia excretion in humans as measured by lactose-[15N2]ureide

Resistant starch (RS) and Lactobacillus acidophilus yoghurt (LC1) were supplemented simultaneously in healthy adults to evaluate the effect on the urinary and faecal nitrogen and ammonia excretion by means of lactose-[¹⁵N₂]ureide (¹⁵N-LU) degradation. Nineteen subjects received a regular daily diet either without or with supplementation of an RS-LC1-mixture composed of fibre of potatoes (RS type 1), wrinkle pea starch (RS type 2), and LC1 over a 20-day period in randomised order. Thereafter, ¹⁵N-LU was administered together with breakfast. Urine and faeces were collected over a period of 48 and 72 h, respectively. The ¹⁵N abundances were measured by isotope ratio mass spectrometry. The intake of the pre- and probiotic mixture composed of RS of type 1, type 2 and of LC1 significantly lowered the colonic generation and the renal excretion of toxic ¹⁵NH₃ and functioned as an ammonia shift from urinary to faecal ¹⁵N excretion when using ¹⁵N-LU as a xenobiotic marker.