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Crystallization kinetics of hyperquenched D2O liquid has been studied by Fourier transform infrared spectroscopy by determining the irreversible change in the spectra of stretching vibrations of the decoupled OH oscillator in ≊12 mol % HOD in D2O. The kinetics follows an almost exponential behavior with time. The exponent to the crystallization time, n, increases from its value of 1.0 at 152 K to 1.2 at 147 K and its value is slightly lower than that of H2O. The combined results of H2O and D2O indicate that temperature rather than the mass of the molecules determines n. Interpretation of n in terms of the morphology of grains formed seems inconsistent in view of the observed temperature effect. It is suggested that an alternative interpretation of n in terms of distribution of diffusion times, or time independent activation energy (barrier height to crystallization), is more appropriate. Calorimetric measurements for the crystallization of H2O yield results consistent with those from infrared spectroscopic study. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Metastable liquid water, obtained by heating its hyperquenched glassy state above its glass→liquid transition temperature, crystallizes to cubic ice. Kinetics of this crystallization has been studied by Fourier transform infrared spectroscopy by determining the change in the spectra of stretching vibrations of the decoupled OD oscillator in 3.6 mole % HOD in H2O. The crystallization kinetics follows the equation x=[1-exp(-ktn)] and is diffusion controlled. Annealing at a temperature below its glass→liquid transition temperature alters this kinetics as the grain–growth process begins to control the early stages of crystallization. [ABSTRACT FROM AUTHOR]

The dielectric permittivity and loss tangent of hyperquenched glassy water (HGW) have been measured for fixed frequencies of 1 and 10 kHz from 80 K to its crystallization temperature and corresponding measurements have been made of the crystallized forms. The effect of thermal cycling has been investigated. Except for a shoulder at T

Amorphous solid D2O from hexagonal and cubic ices and H2O from (HF, NH3, and NH4F) doped hexagonal ice have been prepared by Whalley’s method, and their thermal behavior has been investigated by differential scanning calorimetry from 103 to 250 K. For a heating rate of 30 K min-1 , the temperature of the onset of the reversible glass[larger_closed_square]liquid transition, Tg, is raised by about 4 K when H2O is substituted by D2O. Doping with NH3 and NH4F causes little change in Tg but with HF Tg becomes undetectable. The increase in heat capacity at Tg is reduced by about a factor of 3 on deuteration but marginal changes occur on doping with NH3 or NH4F. The increase in Tg on deuteration is ≊4 times of that observed for the amorphous forms made from the vapor and the liquid, and more than twice of that expected from isoviscous or isorelaxational states, assuming that the functional form of the molecular reorientation rates with temperature is unaffected by isotopic substitution. NH3 and NH4F as dopants, which generally increase the reorientation rate of water molecules in hexagonal and cubic ices, have no detectable effect on the calorimetric relaxation rate of the pressure-amorphized forms, thus indicating that the increase in the concentration of Bjerrum defects for these two dopants does not alter Tg. All these observations suggest that the structure of pressure-amorphized solids is topologically different from that of the amorphous forms made from the vapor and the liquid. [ABSTRACT FROM AUTHOR]

The dielectric permittivity and loss of vapor-deposited amorphous solid water (ASW) have been measured for fixed frequencies of 1 and 10 kHz from 80 K to its crystallization temperature. Similar measurements have also been made on the cubic ice formed after the crystallization of ASW and the hexagonal ice formed on heating the cubic ice. The loss tangent shows a broad sub-Tg relaxation peak centered at about 100 K and an approach towards a plateau value which appears as a shoulder. The peak is attributed to thermally activated rotation of H2O molecules with one or two dangling OH groups on the surface of the pores of the microporous sample, and the shoulder to localized motions within the network structure. Sintering of the samples on thermal cycling between 77 and ≊120 K in vacuo causes the broad peak to vanish. With increase in temperature, above Tg, the loss tangent shows the emergence of the expected α-relaxation peak of a liquid at T>Tg, whose completion is terminated by the onset of crystallization to cubic ice at about the same temperature for 1 kHz and for 10 kHz measurements. Thereafter, crystallization becomes slower, thus allowing further observation of the low-temperature part of the α-relaxation peak.The dielectric loss of amorphous solid water at 80 K is nearly 20 times that of the cubic ice formed on its crystallization after heating to 193 K, and nearly 3.5 times higher at Tg. The dielectric loss of the cubic ice formed on crystallization tends towards a plateau value prior to rapidly increasing with increase in temperature, an evidence for a low temperature relaxation which vanishes on conversion to hexagonal ice. This relaxation indicates a remnant topologically disordered structure of intergranular water and/or stacking faults in cubic ice. Samples sintered by thermal cycling in vacuo to ≊120 K crystallized in one step, whereas those without prior thermal cycling crystallized in two steps to cubic ice. Annealing of the... [ABSTRACT FROM AUTHOR]

The thermal behavior of hyperquenched glassy D2O was investigated by differential scanning calorimetry from 103 to 250 K, in order to investigate the isotope effect on the glass→liquid transition and on the liquid to cubic, and cubic to hexagonal ice. For a heating rate of 30 K min-1 the temperatures of the thermal effects are: 137 K for the onset of the reversible glass→liquid transition (Tg), 154 and 173 K for the beginning and the peak minimum of the crystallization exotherm, and ≊229 K for the peak minimum of the transformation cubic→hexagonal ice. Increase in heat capacity at Tg and the width of the glass transition are similar to those reported for glassy H2O. Tg of D2O is higher than that of H2O by an amount that is expected for isorelaxational and/or isoviscous states assuming that the functional form of the molecular reorientation rates with temperature is unaffected by the isotopic substitution. The increase in the temperature of crystallization of ‘‘fluid’’ D2O is ≊three times greater than the increase in the glass→liquid transition which causes Tg and devitrification to become more separated in D2O than in H2O. Implications of these results for both the inferred λ-type anomally at ≊228 K in H2O and at ≊233 K in D2O, and the presumed formation of a gel-like structure at these temperatures are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The Raman spectra of recovered hydrogen ordered H2O and D2O ice XIV were recorded and compared with the spectra of the corresponding hydrogen disordered phase (ice XII). On heating ice XIV, the transition to ice XII is observed. Subsequent cooling leads to the weak reappearance of ice XIV lattice vibrational peaks which demonstrates the reversibility of the hydrogen order ↔ disorder phase transition. However, cooling at ambient pressure produces a less ordered ice XIV than cooling under pressure which implies that pressure favours hydrogen ordering of ice XII. [Copyright &y& Elsevier]

Presents information on a study which described the preparation of different conjugatively spaced ferrocenyl- and octamethylferrocenyl-substituted terminal alkynes, and their metathesis polymerization. Use of the well-defined Schrock-type catalyst of general formula; Monomer synthesis; Polymer properties.

Investigates a low-temperature method for conformational substates of deoxyribonucleic acid. Results of the investigation; Discussion of the investigation.

Reports on a cryogenic technique for the isolation of carbonic acid. FTIR spectroscopy; Quenching of solutions of the two reactants, KHCO3 and HCl; Separation of the reaction product from the solvent.

Describes two distinct states of liquid water below 150 degrees Kelvin through calorimetric methods. Transformation of vapor-deposited amorphous solid and hyperquenched glassy water to a high-density amorphous solid; Effect of heating at atmospheric pressure; Occurrence of the two states which do not interconvert; Configurational relaxation of water and stress-induced amorphization.

Presents an erratum for an article on the kinetics of crystallizing water near 150K by Fourier transform infrared spectroscopy.

Two hydrogen ordered phases of ice were prepared by cooling the hydrogen disordered ices V and XII under pressure. Previous attempts to unlock the geometrical frustration in hydrogen-bonded structures have focused on doping with potassium hydroxide and have had success in partially increasing the hydrogen ordering in hexagonal ice I (ice Ih). By doping ices V and XII with hydrochloric acid, we have prepared ice XIII and ice XIV, and we analyzed their structures by powder neutron diffraction. The use of hydrogen chloride to release geometrical frustration opens up the possibility of completing the phase diagram of ice. [ABSTRACT FROM AUTHOR]

Presents research which studied the possibility of the presence of gaseous carbonic acid in outer space. Formation of solid carbonic acid in outer space; Results of experiments and thermodynamic analyses on crystalline carbonic acid; Free-energy considerations; Carbonic acid's traits in gas phase; Comparison with formic acid; Where gaseous carbonic acid could be present in outer space.

High-density amorphous ice was heated at constant pressures of between 0.52 to 1.9 GPa from 77 K up to 240 K. The formed phases were characterized by x-ray diffractograms of samples recovered under liquid N[sub 2] at 1 bar. The (meta)stability domain of ice XII thus revealed extends between ;≈158-212 K from ≈0.7 to ≈1.5 GPa. We further discuss whether ice XII has a low-temperamre region of stability within the ice VI domain. Our (meta)stability domain of ice XII is in a different region of water's phase diagram than that shown by Koza et al. [Phys. Rev. Lett. 84, 4112 (2000)]. [ABSTRACT FROM AUTHOR]

Sulfurous acid (H2SO3) has never been characterized or isolated on Earth. This is caused by the unfavorable conditions for H2SO3 within Earth''s atmosphere due to the high temperatures, the high water content and the oxidizing environment. Kinetic investigations by means of transition state theory showed that the half-life of H2SO3 at 300 K is 1 day but at 100 K it is increased to 2.7 billion years. Natural conditions to form H2SO3 presumably require cryogenic SO2 or SO2/H2O mixtures and high energy proton irradiation at temperatures around 100 K. Such conditions can be found on the Jupiter moons Io and Europa. Therefore, we calculated IR-spectra of H2SO3 which we compared with Galileo''s spectra of Io and Europa. From the available data we surmise that H2SO3 is present on Io and probably but to a smaller extent on Europa. [Copyright &y& Elsevier]

Using X-band ESR spectroscopy we have studied radicals produced by γ-irradiation at 77 K in hyperquenched glassy water (HGW) doped with thymine, 2′-deoxythymidyne, 2-deoxy-d-ribose, and the equimolar mixture of thymine and 2-deoxy-d-ribose. In HGW matrix the solute molecules are not freeze-concentrated, so the indirect radiation effects on biomolecules can be followed. The results are discussed in terms of the mechanism of radical formation and the role of sugar in radiation damage of nucleosides. [Copyright &y& Elsevier]

- A dispersive model of radical accumulation in irradiated solids is discussed by the example of hexagonal ice (Ih) and cubic ice (Ic) obtained by annealing of hyperquenched glassy water at 160 K. The model assumes that radical production upon γ-irradiation is accompanied by their second-order decay, which proceeds according to dispersive kinetics with the time-dependent specific reaction rate k(t) = Bt[sup α-1], where B = constant and α is the dispersion parameter equal to 0.40 for both the hexagonal and cubic ices. The radicals, OH in Ih, and OH plus HO[sub 2] in Ic are produced at the same rate upon γ-irradiation. The observed enhancement of radical accumulation in ice Ic in comparison with Ih is due to the marked decrease of radical recombination in ice Ic. This is rationalized by the hindrance of radical transport in the lattice of ice Ic containing substantial amounts of Bjerrum-type L-defects. [ABSTRACT FROM AUTHOR]

High-density amorphous ice (HDA), made by compression of hexagonal ice at 77 K, was heated at a constant pressure of 0.81 GPa up to 183 K and its phase transition followed by displacement-temperature curves. The crystalline phases, recovered at 77 K and 1 bar, were characterized by X-ray diffraction. Pure D[SUB2]O ice IV and nearly pure H[SUB2]O ice IV were formed on slow heating at a rate of 0.4 K min[SUP-1], whereas pure H[SUB2]O ice XII and D[SUB2]O ice XII were formed on fast heating at ≥15 K min[SUP-1]. On heating HDA at rates in between these two values a mixture of ice IV and ice XII was obtained, where their relative yields depended in a systematic manner on the heating rate. Conversion of HDA into either ice IV or ice XII is an example of a "parallel reaction" where the relative yields of ice IV and ice XII can be controlled by temperature, i.e., by the rate of heating, in our approach. It is conceivable that a similar behaviour occurs on crystallization of the related pressure-amorphized silica. [ABSTRACT FROM AUTHOR]

We investigated the PvuII endonuclease with its cognate DNA by means of molecular dynamics simulations. Comparing the complexed DNA with a reference simulation of free DNA, we saw structural changes at the scissile phosphodiester bond. At this GpC step, the enzyme induces the highest twist and axial rise, inclination is increased and the minor groove widened. The distance between the scissile phosphate group and the phosphate group of the following thymine base is shortened significantly, indicating a substrate-assisted catalysis. A feasible reason for this vicinity is the catalytically important amino acid residue lysine 70, which bridges the free oxygen atoms of the successive phosphate groups. Due to this geometry, a compact reaction pocket is formed where a water molecule can be held, thus bringing the reaction partners for hydrolysis into contact. The O1–P–O2 angle of the scissile nucleotide is decreased, probably due to a complexation of the negative oxygen atoms through protein and solvent contacts. [Copyright &y& Elsevier]

Polycrystalline hexagonal ice containing thymine was γ-irradiated at 77 K, and X-band electron paramagnetic resonance spectra of the resulting radicals were recorded at this temperature immediately after irradiation, and after thermal annealing of the samples at temperatures up to 250 K. The examined frozen samples were obtained from hyperquenched glassy aqueous solution containing 0.005 M of thymine, by using two different procedures: (i) crystallization of the glass by heating up to 250 K, and (ii) warming the glass up to room temperature to melt it, and subsequent cooling of the solution in liquid N2. Thymine-derived radicals were detectable only in the samples obtained by crystallization of the glass. We conclude that the extent of solute segregation is less for the frozen aqueous solution made by route (i) than by route (ii). Therefore, the solute is more hydrated in the frozen sample made by route (i) and the primary products of water radiolysis can react with the solute. The present results are compared with those reported for the thymine/hyperquenched glassy water system (Bednarek et al. , J. Phys. Chem. B 103 , 6824 (1999)). [ABSTRACT FROM AUTHOR]

Reports that the complex of B-DNA with polyamides freezes DNA backbone flexibility. Performance of three molecular dynamics simulations; How the beta-tail of the polyamide ligands contributes to binding.

Arising from: Y.-Z. Yue& C. A. Angell 427, 717-720 (2004); Yue& Angell reply.It has been unclear whether amorphous glassy water heated to around 140-150 K remains glassy until it crystallizes or whether instead it turns into a supercooled and very viscous liquid. Yue and Angell compare the behaviour of glassy water under these conditions to that of hyperquenched inorganic glasses, and claim that water stays glassy as it heats up to its crystallization point; they also find a‘hidden’glass-to-liquid transition at about 169 K. Here we use differential scanning calorimetry (DSC) heating to show that hyperquenched water deposited at 140 K behaves as an ultraviscous liquid, the limiting structure of which depends on the cooling rate-as predicted by theoretical analysis of the liquid-to-glass transition. Our findings are consistent with a glass-to-liquid transition-onset temperature (Tg) in the region of 136 K (refs 3,4), and they indicate that measurements of the liquid's properties may clarify the anomalous properties of supercooled water. [ABSTRACT FROM AUTHOR]