Study of the influence of different forest species on the microbial activity in soils

Microcalorimetry was used to study the seasonal evolution over one year of the microbial activity in a humic-eutrophic Cambisol soil as a function of its forest cover. The study was carried out on three soils with identical origin but covered with different forest species: pine, eucalyptus, and a typical Atlantic-humid riverside forest. Some other physical, chemical and biological properties and environmental parameters, mainly humidity and environmental temperature, were considered to analyze their influence on soil microbial activity. The study was performed using a microcalorimeter Thermal Analysis Monitor 2277 in which the experiments were carried out with 1 g soil samples treated with 1.25 mg glucose g^–1 soil. From the measured results it follows that pine forest soil is the least productive of the three, as it generates an average heat of 2.7 vs. 5.9 J g^–1 generated by the eucalyptus forest soil and 3.1 J g^–1 generated by the riverside forest soil. These results are dependent on the remaining physical, chemical and biological features analysed and because of this, pine forest soil, with a pH value 3.3 in spring, shows a small capacity to maintain a stable microbial population which is the lowest of the three (0.079·10⁸ to 0.46·10⁸ microorganisms g^–1 soil) while riverside soil microbial population is in the range from 7.9·10⁸ to 17·10⁸ microorganisms g^–1 soil.     

南极冰雪样品中超痕量重金属的分析测定进展

本文全面阐述了南极冰雪样品中重金属分析测定的发展概况和极地样品分析中出现的困难，评述了各种分析方法（包括富集技术、超灵敏的分析技术）的优缺点，并指出其发展方向。引用文献４７篇。     

Gas hydrate fast nucleation from melting ice and quiescent growth along vertical heat transfer tube

Gas hydrates, or clathrate hydrates, are ice-likecrystal, composed of host lattice (cavities) formed byhydrogen-bonded water molecules, and other guestmolecules called guest molecules. The guest mole-cules act with host lattice in weak van der Waals force…     

Frozen state transitions in relation to freeze drying

Freeze-drying is used as a gentle dehydration method for heat sensitive materials especially in food and pharmaceutical industries. Most materials, including dissolved sugars in water, do not crystallise during freezing prior to freeze-drying. Supersaturated, freeze-concentrated solutions are amorphous materials and they solidify into a glassy state when their temperature is depressed to below the glass transition temperature,T _g. Differential scanning calorimetry has been used to show that maximally freeze-concentrated sugar solutions, when properly frozen, show during heating a glass transition,T _g , which is followed by ice melting endotherm with onset atT _m . Low molecular weight materials are difficult to freeze-dry as they have lowT _g , andT _m slightly above T _g . High molecular weight materials, such as carbohydrate polymers, exhibit improved dehydration characteristics and they have _g and _m at about the same temperature close to the melting point of pure water. The amorphous, glassy structure typical of freeze-dried materials is formed during prefreezing and retained after removal of ice and the unfrozen water from the freeze-concentrated material. Dehydration temperatures belowT _g allow removal of ice within the solid, glassy solutes, but temperatures aboveT _m result in collapse. The frozen state transitions and properties of freeze-dried materials can be shown in state diagrams which are used to derive proper freeze-drying conditions and storage requirements for various materials.     

The role of the ice rules in the thermal properties of potassium dihydrogen phosphate

Calorimetric properties of potassium dihydrogen phosphate are examined by analysis of the heat capacity data taken from the literature and from a recent measurement. The analysis is based on an extensive use of harmonic heat capacity functions to separate the effect of the phase transition from the vibrational contribution. The transition enthalpy and entropy derived are 421 J mol^–1 and 3.79 J K^–1 mol^–1, respectively. Characteristic temperatures of the lattice vibrations including the Debye temperature (254±18) K were determined. The transition entropy, exceeding the value compatible with the ice-rules, is consistent with the temperature dependence of the heat capacity. The implication of the result is discussed by comparison with the hydrogen bond networks in copper formate tetrahydrate and thallium dihydrogen phosphate.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayContribution No. 113 from Microcalorimetry Research Center.     

An FT-IR demonstration of the occurrence of satellite bands in the spectra of hydrogen bonds in crystals

OH stretching fundamentals in the spectra of hydrogen-bonded crystals are accompanied by satellite bands due to sum and difference transitions involving one quantum of the OH stretching vibration and one or more quanta of the low-frequency vibration of the hydrogen bond. Such satellites were detected in the FT-IR spectra of two hydrogen-bonded crystals, ice and methanol.NRCC No. 29006     

Algebraic surfaces of general type withK 2=2p g−1,p g≥5

This paper mainly deals with minimal algebraic surfaces of general type withK ²=2p _g–1. We prove that forp _g7 all these surfaces are birational to a double cover of some rational surfaces, and all but a finite classes of them have a unique fibration of genus 2; then we study their structures by determining their branch loci and singular fibres. We study similarly for surfaces withp _g=5, 6. Lastly we show that whenp _g13 all these surfaces are simply-connected.     

On the Computational Complexity of the Minimum Committee Problem

Two special cases of the Minimum Committee Problem are studied, the Minimum Committee Problem of Finite Sets (MCFS) and the Minimum Committee Problem of a System of Linear Inequalities(MCLE). It is known that the first of these problems is NP-hard (see (Mazurov et al., Proc. Steklov Inst. Math., 1:67–101, 2002)). In this paper we show the NP-hardness of two integer optimization problems connected with it. In addition, we analyze the hardness of approximation to the MCFS problem. In particular, we show that, unless NP⊂TIME(n ^O(loglogn )), for every ε>0 there are no approximation algorithms for this problem with approximation ratio (1–ε)ln (m–1), where m is the number of inclusions in the MCFS problem. To prove this bound we use the SET COVER problem, for which a similar result is known (Feige, J. ACM, 45:634–652, 1998). We also show that the Minimum Committee of Linear Inequalities System (MCLE) problem is NP-hard as well and consider an approximation algorithm for this problem.