5. Changing the state of matter

Author(s):  
Peter Atkins

‘Changing the state of matter’ considers the transformations states of matter undergo from one form to another during the processes of freezing, boiling, dissolving, and mixing. All such transformations and the corresponding equilibria that are reached in state transitions can be expressed in terms of the chemical potential and the pushing power it represents. Changes in temperature and pressure can lower or raise boiling and freezing points. Josiah Gibbs' phase rule is concerned with the equilibria between various forms of matter. Phase diagrams help chemists draw conclusions about the compositions of mixtures, minerals, and alloys. Transitions in solutions, including osmosis, and solid-to-solid phase transitions are also discussed.

Author(s):  
Wolfgang Dreyer ◽  
Frank Duderstadt

The necessary heat treatment of single-crystal semi-insulating gallium arsenide (GaAs), which is deployed in micro- and optoelectronic devices, generates undesirable liquid precipitates in the solid phase. The appearance of precipitates is influenced by surface tension at the liquid–solid interface and deviatoric stresses in the solid. The central quantity for the description of the various aspects of phase transitions is the chemical potential, which can be additively decomposed into a chemical and a mechanical part. In particular, the calculation of the mechanical part of the chemical potential is of crucial importance. We determine the chemical potential in the framework of the St. Venant–Kirchhoff law, which gives an appropriate stress–strain relation for many solids in the small-strain regime. We establish criteria that allow the correct replacement of the St. Venant–Kirchhoff law by the simpler Hooke law. The main objectives of this study are the following: (i) we develop a thermo-mechanical model that describes diffusion and interface motions, which are both strongly influenced by surface tension effects and deviatoric stresses, (ii) we give an overview and outlook on problems that can be posed and solved within the framework of the model, and (iii) we calculate non-standard phase diagrams for GaAs above 1059 K, i.e. those that take into account surface tension and deviatoric stresses, and we compare the results with classical phase diagrams without these phenomena.


Biomolecules ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1014
Author(s):  
Macy L. Sprunger ◽  
Meredith E. Jackrel

Aberrant protein folding underpins many neurodegenerative diseases as well as certain myopathies and cancers. Protein misfolding can be driven by the presence of distinctive prion and prion-like regions within certain proteins. These prion and prion-like regions have also been found to drive liquid-liquid phase separation. Liquid-liquid phase separation is thought to be an important physiological process, but one that is prone to malfunction. Thus, aberrant liquid-to-solid phase transitions may drive protein aggregation and fibrillization, which could give rise to pathological inclusions. Here, we review prions and prion-like proteins, their roles in phase separation and disease, as well as potential therapeutic approaches to counter aberrant phase transitions.


1993 ◽  
Vol 30 (02) ◽  
pp. 365-372 ◽  
Author(s):  
Søren Asmussen ◽  
Ger Koole

A Markovian arrival stream is a marked point process generated by the state transitions of a given Markovian environmental process and Poisson arrival rates depending on the environment. It is shown that to a given marked point process there is a sequence of such Markovian arrival streams with the property that as m →∞. Various related corollaries (involving stationarity, convergence of moments and ergodicity) and counterexamples are discussed as well.


1994 ◽  
Vol 127 (1) ◽  
pp. 41-99 ◽  
Author(s):  
Paolo Cermelli ◽  
Morton E. Gurtin

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
НИНА МАЛАХОВА ◽  
Fatima Dzgoeva

Abstract Background and Aims Clinical studies in recent years have revealed a close relationship between hormonal disorders in women with CKD and the duration and quality of life, bone mineral and related disorders of the cardiovascular system. In individual studies, there is a tendency to improve the indicators of mineral and bone metabolism and the state of the cardiovascular system in hormonal or other drug-induced correction of hormonal dysfunctions in women. - Aims to study the effect of estrogen deficiency on bone and mineral metabolism in a population of women suffering from CKD stages III-V Method The study included 52 women who met the clinical criteria for the possible appointment of hormone therapy (both replacement and combined oral contraceptives) for the purpose of a detailed examination of the state of their cardiovascular system and bone-mineral metabolism in dynamics (with an interval of 10-12 months) in order to assess the degree of influence of estrogen-deficient conditions on the course of such common complications of CKD as cardiovascular diseases and pathology of the bone system. The age of the patients ranged from 26 to 61 years (mean age-50.65±9.17 years). The duration of CPN averaged 77.02 months.. The stages of CKD were determined according to the K/DOQI (2012) criteria, and the glomerular filtration rate was calculated using the CKD-EPI formula. The following parameters were evaluated: the concentration of sclerostin, osteoprotegerin, fibroblast growth factor 23 (FGF-23), parathyroid hormone, total calcium, phosphorus, alkaline phosphatase, creatinine, and urea. Follicle-stimulating hormone( FSH), luteinizing hormone(LH) and estradiol were determined by solid-phase chemiluminescent enzyme immunoassay (commercial sets of Alkor-Bio, St. Petersburg). Serum concentrations of sclerostin, sRANKL (soluble RANKL), and osteoprotegerin were determined by the enzyme-linked immunoassay using Biomedica gruppe test systems. Results The examined patients showed hormonal dysfunctions (82%), accompanied by changes in the content of sex hormones: the concentration of estradiol was below normal: 123.4±72.5 pmol/l and 150.0-450.0 pmol/l, respectively, in patients and in normal (p<0.01), which confirms the presence of estrogen deficiency in the examined patients . Concentrations of FSH and LH exceeded the norm in the group of patients as a whole: 91.6±46.1 IU/l and 3.0-8.0 IU/l FSH content in patients and normal; 51.8±32.1 IU/l and 3.0-10.0 IU/l LH in patients and normal. In the group of patients as a whole, an increase in the level of sclerostin to 28.5 ± 9.2 pmol/l was detected ( norm 12±33.45 pmol/l), an increase in the level of osteoprotegerin to 6.9±0.4 pmol/l (norm 2.7 pmol/l). Positive and negative correlations were found between the levels of morphogenetic proteins, sex hormones, and characteristic parameters of hormonal dysfunctions Conclusion Pre-and postmenopausal women with CKD have hormonal dysfunctions, including disorders of sexual and reproductive function, menstrual cycle, decreased fertility, increased risks of miscarriage at its onset, the basis of hormonal dysfunctions is the absence of LH peaks and changes in the concentration of estradiol depending on the phase of the cycle, hypoestrogenemia. It is assumed that there is a pathogenetic link between hormonal dysfunctions and disorders in the system of bone metabolism regulatory proteins in patients with CKD.


2018 ◽  
Author(s):  
P. Bowlan ◽  
L. Smilowitz ◽  
B. F. Henson ◽  
N. Suvorova ◽  
D. Oschwald

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