Values Of NH Research Articles

Selective Hydration of a Carboxylate Group in Nitrobenzene

Abstract Eight different carboxylate ions were extracted with Crystal Violet into nitrobenzene. The Karl Fischer method was employed to determine the numbers of water molecules co-extracted with the carboxylate ions, i.e., their hydration numbers (nh) in nitrobenzene. The values of nh for the carboxylate ions were little dependent on their chemical structures, being 2.4 ± 0.2 as the average value.

Synthesis, biological activity, and solution structures of a cyclic dodecapeptide from the EGF-2 domain of blood coagulation factor VII.

The cyclic dodecapeptide, disulfide-cyclo-[H-Cys-Val-Asn-Glu-Asn-Gly-Gly-Cys(Acm)-Glu-Gln-Tyr-Cys-OH], which corresponds to the 91-102 sequence of the second epidermal growth factor domain of human blood coagulation factor VII, was synthesized using solid-phase procedures. It was shown to be an inhibitor at the key step in the induction of coagulation by the extrinsic pathway, i.e. the factor VII/tissue factor-catalyzed activation of coagulation factor X. The solution structure of this peptide was investigated by NMR spectroscopy and was computer-modeled via molecular mechanics. Structures were calculated based on 112 distance and nine dihedral angle constraints. The resulting backbone structures were classified into two structural subsets: one which exhibited a twisted '8'-shaped folding and another describing an open, circular 'O' outline. The local backbone structures of segments Asn3-Glu4-Asn5, Gly7-Cys8 and Gln10-Tyr11 were well preserved among the two subsets. Apart from the unrestrained N- and C-termini, Gly6 and Glu9 sites exhibited marked local disorder between the two subsets, suggesting localized flexible hinges likely to govern tertiary structure interconversion between the two subsets. Two transient hydrogen bonds were identified from pH chemical shift titrations by matching the pKa values of NH and carboxylate groups, which supported the occurrence of the '8' structure, and agreed with temperature coefficients of peptidyl NH resonances. Structure-function relationships of the peptide were discussed in terms of the likely physiological function of the disulfide-bonded loop in factor VII which the peptide represents.

Acute toxicity of ammonia on Litopenaeus vannamei Boone juveniles at different salinity levels.

Litopenaeus vannamei juveniles (total length 22+/-2.4 mm) were exposed to different concentrations of ammonia-N (un-ionized plus ionized ammonia as nitrogen), using the static renewal method at different salinity levels of 15 per thousand, 25 per thousand and 35 per thousand at pH 8.05 and 23 degrees C. The 24, 48, 72, 96 h LC50 values of ammonia-N on L. vannamei juveniles were 59.72, 40.58, 32.15, 24.39 mg l(-1) at 15 per thousand; 66.38, 48.83, 43.17, 35.4 mg l(-1) at 25 per thousand; 68.75, 53.84, 44.93, 39.54 mg l(-1) at 35 per thousand, respectively. The 24, 48, 72, 96 h LC50 values of NH(3)-N (un-ionized ammonia as nitrogen) were 2.95, 2.00, 1.59, 1.20 mg l(-1) at 15 per thousand; 2.93, 2.16, 1.91, 1.57 mg l(-1) at 25 per thousand; 2.78, 2.18, 1.82, 1.60 mg l(-1) at 35 per thousand, respectively. As the salinity decreased from 35 per thousand to 15 per thousand, susceptibility of ammonia-N increased by 115%, 132%, 140% and 162% after 24, 48, 72 and 96 h exposure, respectively. The "safety level" for rearing L. vannamei juveniles was estimated to be 2.44, 3.55, 3.95 mg l(-1) for ammonia-N and 0.12, 0.16, 0.16 mg l(-1) for NH(3)-N in 15 per thousand, 25 per thousand and 35 per thousand, respectively.

Dynamics of hydration of alcohols and diols in aqueous solutions

The 17 O NMR spin–lattice relaxation times, T 1 , of the solvent water in aqueous solutions of nine alcohols and five diols have been determined as a function of the concentration at 25°C. For the alcohol solutions, the concentration dependence of T 1 has been determined in the temperature range from 1 to 50°C. The value of n h [(τ c h / τ c 0 )-1] which has been obtained from the concentration dependence of T 1 has been defined as the dynamic hydration number (n DHN ). The values of the coordination numbers n h , have been estimated on the basis of the water-accessible surface areas (ASA) of the solute molecules. The rotational correlation times, τ c h , of water molecules around the solute molecules have been estimated and compared with that of pure water τ c 0 . The value of τ c h /τ c 0 =2.22 for Bu t OH at 25°C is the largest among the solutes investigated. The τ c h /τ c 0 values of the n-alcohols and diols increase with increasing ASA and become almost constant. The τ c h /τ c 0 values decrease with increasing temperature and approach constant value above 40°C. The temperature dependence of τ c h /τ c 0 for Bu t OH is the largest. The activation energy of τ c h for n-alcohols has the maximum value at ASA≈240 A 2 . These results are discussed by considering the molecular sizes. The τ c h /τ c 0 value for a diol was smaller than that of the corresponding n-alcohol. This result supports the concept that hydrophobic hydration is distributed by the OH groups of the solute molecules. The thermodynamic properties of hydration for n-alcohols, butanol isomers and diols are linearly dependent on their n DHN .

Electronic transport and specific heat of Ca-doped YBa2Cu3Ox-single crystals

Measurements of the anisotropic electrical resistivity, the Hall Effect, and the specific heat anomaly at Tc of Ca-doped YBa2Cu3Ox single crystals of various Ca and O contents are presented. The transport properties are discussed in terms of charge and spin separated quasiparticles and confirm that by doping Ca onto Y sites the hole concentration, nh, can be extended beyond the value achieved with O-doping alone at x=7.0. The jump in the specific heat at Tc which increases monotonously with x up to x=7.0 in Ca-free crystals displays a maximum in highly oxygenated Ca-doped crystals. This maximum, however, is displaced from the Tc(nh) maximum to higher values of nh, consistent with the model of induced superconductivity in the CuO chains.

Hall electron density and mobility in HgCdTe alloys with anomalous behavior of the Hall coefficient in weak magnetic field

It is difficult to extract unique values of the Hall electron density, nH, and Hall mobility, μH, in indium-doped Hg1−xCdxTe alloys usually in a region of weak magnetic fields where the Hall coefficient RH behaves anomalously. Since this is also the field region where the weak magnetic field condition of semiclassical transport equations is valid, derivatives of Hall resistivity ρxy(B) and the ratio (Hall angle) of ρxy(B) and transverse resistivity ρxx(B) with respect to the field are used to determine unique values of the weak magnetic field nH and μH. This analysis reduces to calculating the slopes of ρxy(B) and ρxy(B)/ρxx(B) in the region of weak magnetic fields where linearity is observed. The conductivity, σ0, determined from the ratio of the slopes is compared to the zero magnetic-field experimental value. The conductivities agree to within 10%, indicating that nH is constant in contrast to the RH result. The values of nH determined from the slopes are in very good agreement with the values of nH determined from a high magnetic field RH and from the period of Shubnikov–de Haas oscillations in heavily doped alloys.

Toxicities of ammonia and nitrite to Penaeus monodon adolescents

Penaeus monodon adolescents (91.0±8.0 mm) were exposed to various concentrations of ammonia (NH 3+NH 4 +) and nitrite in 20 ppt seawater at a pH of 7.57 and a water temperature of 24.5°C using the static renewal method. The LC50 values of ammonia-N (un-ionized plus ionized ammonia as nitrogen), NH 3-N (un-ionized ammonia-N) and nitrite-N decreased with longer exposures. The 24-, 48-, 96- and 144-h LC50 values were 97.9, 88.0, 53.4 and 42.6 mg/l of ammonia-N (1.76, 1.59, 0.96 and 0.77 mg/l of NH 3-N), respectively. The 24-, 48-, 96-, 144-, 192- and 240-h LC50 values of nitrite-N were 218, 193, 171, 140, 128 and 106 mg/l nitrite-N, respectively. The “thresholds” of ammonia and nitrite toxicity were found at 144 and 240 h, respectively, on a toxicity curve approaching an asymptote. Based on the incipient LC50 value and an application factor of 0.1, safe values for rearing adolescent P. monodon (20 ppt, 7.57 pH, 24.5°C) were calculated to be 4.26 mg/l ammonia-N, 0.08 mg/l NH 3-N and 10.60 mg/l nitrite-N.

The heating of the solar wind by the interstellar neutral gas

We use a time‐dependent, one‐dimensional, spherically symmetric, one‐fluid solar wind model to investigate the heating of the solar wind by an interaction with the interstellar neutral hydrogen. The interaction is modeled through particle, momentum, and energy source terms equivalent to those of T. E. Holzer (1972). The equations are solved using a flux‐corrected transport algorithm which incorporates stream‐stream heating directly into the model. We input solar wind data at 1 AU for the time between October 12, 1978, and February 25, 1980, and generate 52‐day averages of solar wind temperature as functions of radius out to 10 AU for values of the interstellar hydrogen density NH = 0.0, 0.03, and 0.1 cm−3. The radial dependence of temperature, averaged over the entire time period, yields power law exponents α = 0.714, 0.597, and 0.428 for the three densities, respectively. A more detailed comparison between the temperature measurements of Voyager 1 and Pioneer 11, and the model solar wind temperatures at the positions of these spacecraft indicates that the observations are consistent with solar wind heating by the interstellar neutral hydrogen, at least within the context of the model. We close with a suggestion for further data analysis to determine the radial gradient of proton temperature beyond 4 AU.

Pig thyroid AMP deaminase purification and some properties

AMP deaminase from pig thyroid gland was purified about 500-fold using phosphocellulose adsorption chromatography. The purified enzyme had a pH optimum of about 7.0. The kinetics of AMP deamination was sigmoid-shaped. The values of the cooperativity coefficient nH and the substrate concentrations required to reach half maximum valocity S0.5 calculated from the Hill equation were 1.65 and 5.63 mM respectively. The activity of the thyroid enzyme is regulated by adenine and guanine nucleotides, inorganic phosphate and potassium ions.

Ammonification and Nitrification of Urea in Different Egyptian Soils as Affected by its Application at Different Depths

In pot experiments, urea was applied to different Egyptian soils at a standard rate of 150 kg/fed. at different depths, namely at 0, 0.5, 1.0, and 2.0 inches below the surface of the soil. Moisture content was kept constant in all treatments so that the only variable factor was the depths of application. Representative soil samples were taken at intervals of 1, 3, 7, 14, and 28 days. They were periodically analysed for total microbial counts, urease activity, ammoniacal and nitrate nitrogen. Results can be summarized as follows: 1 The highest microbial densities were generally achieved when urea was mixed with the soil or laid at 2 inches depth. In calcareous soil, however, mixing urea with the soil gave the best result in this respect. Spreading urea on the surface of different soils gave the lowest microbial size during the experimental periods. 2. Urease activity was not appreciably affected with the depth of urea application. However, when urea was mixed with the soil, the highest urease activity was generally achieved. 3. NH 3 -N in loamy, saline, and alkaline soils showed no clear differences due to application of urea in different dephths. In sandy soil, however, mixing urea with the soil gave the highest values of NH3-N during the experimental period, followed by 2 inches depth application. In calcareous soil, either mixing or laying urea in 2 inches depth gave the highest values of NH 3 -N. In general, when applied on the surface, the lowest values of NH 3 -N were observed in all soils. 4. NO 3 -N in alkali and calcareous soils showed the highest values when urea was mixed with the soil. In the rest of the soils, application of urea either at 2 inches depth or mixed with the soil gave the highest values of NO 3 -N. Application of urea on the soil surface gave the lowest values in all the soils. This may be due to the high volatilization rate of ammonia in such treatment. In Gefäßversuchen wurde Harnstoff mit einer Menge von 150 kg/Feddan unterschiedlichen ägyptischen Böden in verschiedenen Tiefen verabreicht, und zwar 0,5, 1,0 und 2,0 Zoll unter der Oberfläche. Es wurden Proben am 1., 3., 7., 14. und 28. Tag entnommen. An ihnen wurde bestimmt: Gesamtkeimzahl, Ureaseaktivität, löslicher Ammon- und Nitratstickstoff. Höchste Gesamtkeimzahlen wurden ermittelt bei Einmischung von Harnstoff (Kontrolle) in den Boden oder Einbringung in 2 Zoll (5,08 cm) Tiefe. Die Ureaseaktivität war nicht von der Einbringungstiefe des Harnstoffs abhängig, doch war Einmischung in den Boden generell günstig. Vor allem im Sandboden ergab Einmischung in den Boden bzw. Einbringung in 2 Zoll Tiefe höhere NH 3 -N-Gehalte, am niedrigsten waren sie bei oberflächlicher Ausbringung. Gleiches gilt für die NO 3 -N-Gehalte.

The energy independence of proton-emulsion collisions

The density of shower particles in pseudorapidity space from proton-emulsion collisions at 200, 300 and 400 GeV/c is essentially energy independent but exhibits a linear growth with Nh (the number of heavy prongs), different in different parts of phase space. Deviations occur for the largest values of Nh and comparisons to the 67 GeV/c data show a rise in the density of particles in the central region between Serpukhov and FNAL energies. Special attention is given to the new 400 GeV/c data and some correlations between different parts of phase space are discussed.

Rotating Bending Fatigue Test of Large Press-Fitted Shaft under Two-Step Pulsating Load

In order to study rotating bending fatigue strengths and fatigue lives of press-fitted shafts under fluctuating load, fatigue tests were carried out under a two step pulsating load by using 29 specimens of 140 mm diameter. The test conditions are specified by the following notations : n0 : Reversal numbers in one loading cycle. nl : Reversal numbers under lower stress amplitude σl in one loading cycle. nh : Reversal numbers under higher stress amplitude σh in one loading cycle. nt : Transitional reversal numbers under the amplitude between σl and σh in one loading cycle. Six kinds of tests were made by varying the above factors, as n0, nh/n0, nt/n0 and σl. The fatigue lives were converted into cumulative values of nh by using the linear damage law. Through a logical analysis of these test results, it has been found that the fatigue lives decrease most remarkably comparing with those tested under constant stress amplitude if n0 becomes smaller and nt/n0 larger, and remarkably decrease when σl exceeds the crack initiating limit. On the contrary, it has been also presumed that the fatigue lives increase if n0 becomes larger, nt is negligible and σl does not exceed the crack initiating limit. Irrespective of the changing of the fatigue lives, the fatigue strengths at 10 million reversals under the higher stress amplitude were scarcely affected by the test conditions.

Chemical Exchange Reactions and H2 Formation in Dark Interstellar Clouds

Stecher and Williams1 have sought to explain the lack of 21 cm radiation in dark clouds on the basis of the formation of molecular H2. We wish to point out several serious deficiencies in their proposed production mechanism. Their chemical exchange process gives an H2 production rate1 This rate is extremely sensitive to the assumed values of nH and T. With their choice of values nH = 104 cm−3, T = 100.0° K, the timescale for complete recombination in the absence of dissociation is ∼ 108 yr—already considerably longer than the time for gravitational collapse at this density. A lower density nH < 103 cm−3 or a slightly lower gas temperature T ≲ 80° K (which, indeed, would be appropriate if cooling by H2 molecules is included) increases the recombination timescale to ≳ 1010 yr! These results are not at all surprising because Stecher and Williams adopt the highly dangerous procedure of using the extreme tail of an exponential distribution.

Dust and atomic hydrogen nearρ Ophiuchi

We discuss the distribution of dust and atomic hydrogen in and around a small dark cloud nearρ Ophiuchi. Although the obscuration reaches values as high as 8 magnitudes, the values ofNH derived inside the cloud do not differ markedly from those found at nearby, less obscured points. At low values of the obscuration, dust and hydrogen isophotes show satisfactory agreement, i.e.,NH increases withNG. However, we find thatNH starts decreasing for sufficiently large values ofNG. In the entire range of optical extinctions investigated our observations are satisfied by an expression of the typeNH=ANG exp (-BNG). Interpretation of this relationship suggests that an appreciable part of the hydrogen has been converted to molecular form inside the cloud. A tentative method for calculating the time elapsed since the conversion process began is proposed.

Studies on -NH 2 and -COOH groups in relation to ageing processes—effect of the alteration in the metabolism of thiolic substances

The investigations concerning the values of the free NH 2 and COOH functional groups of dried protein resulted from the blood serum of rats of various ages, point out that the number of free aminic and carboxylic groups diminishes in course of the ageing processes, and especially that of the NH 2 groups in significant ( P < 0·01). The old animals (rats) submitted to a Folcysteine-Oeriu treatment present an increase of free aminic and carboxylic groups of their dried protein, in comparison with the values found in the control old ones (untreated rats). The increase of the free aminic groups is especially noteworthy ( P < 0·01). We suggest that the metabolic alterations of -SH substances, characterized by an accumulation of disulphide groups (-S-S-) in course of the ageing processes, lead to protein modifications. Under the action of Folcysteine-Oeriu which sets free in the organism, by enzymatic route, the activated -SH groups, we find a tendency for the giant protein molecules to split into smaller ones, proper to younger organisms.

Estimation of the Energy of Hydrogen Bonds Formed in Crystals. III. Amides

Abstract The energies of hydrogen bonds formed in the crystalline state of thirteen amides and one amine have been estimated following the procedure proposed in a previous paper. The values of the energy of an NH···O bond can be estimated at about 4±1 kcal./mol. for the majority of compounds treated in this paper, except two lactams which show energy values as large as 6∼7 kcal./mol. A comparison was made between the energy values of NH···O and OH···O bonding using the data obtained by the author and other investigators.