scholarly journals Physical Nature of The Density Maximum for Water at 4°C

2021 ◽  
Author(s):  
Vladimir Y. Gotsulsky ◽  
Salvatore Magazù ◽  
Nikolay P. Malomuzh
Keyword(s):  
Specific Volume ◽  
Physical Nature ◽  
Water Density ◽  
Main Attention ◽  
Density Maximum ◽  
New Approach ◽  
Thermal Expansion Coefficients ◽  
Triple Points ◽  
Expansion Coefficients

Abstract A new approach to the physical nature of the water density maximum at 4°C is proposed. The main attention is focused on the role of H-bonds in the formation of the specific volume and thermal expansion coefficients for ordinary and heavy water. It is shown that the minimum of the specific volume for water is connected with the amplification of H-bonds (D-bonds) role at approaching their triple points.

scholarly journals The Effect of Titanium Oxide Additions on the Phase Chemistry and Properties of Chromite-Magnesia Refractories

Ceramics ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 127-143 ◽  
Author(s):  
Johan PR De Villiers ◽  
Delphin Mulange ◽  
Andrie Mariana Garbers-Craig
Keyword(s):  
Thermal Expansion ◽  
Tetrahedral Site ◽  
Linear Thermal Expansion ◽  
Raw Material ◽  
Charge Balance ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Phase Chemistry ◽  
Nano Size

The microstructure of a direct-bonded chromite-magnesia refractory brick, typically used in copper and platinum converters, was modified by adding different amounts of nano-size TiO2 to the raw material mixture. Bricks with 0, 1, 3, 5, and 7 mass% TiO2 were produced and compared in terms of spinel formation; the role of the tetravalent cation Ti4+ in the bonding phase; as well as changes in density, porosity, thermal expansion, and internal stress. This was done through a comprehensive XRD and SEM-EDS study. It was found that Ti is accommodated in the secondary spinel that has formed, where Mg in excess of unity in the tetrahedral site combines with an equal amount of Ti in the octahedral sites to maintain charge balance. The 1 mass% TiO2 brick had the lowest bulk density (but not significantly different from the original chromite-magnesia brick), the smallest difference in unit cell volumes between the primary and secondary spinels, and the lowest stress arising from the smallest difference in linear thermal expansion coefficients of the phases present. The calculated porosities correspond well with experimentally determined apparent porosity values, whereas the linear thermal expansion coefficients calculated at 1392K are similar to the values measured from 293 to 1273 K.

Thermal Expansion and Viscoelasticity of Rubber in Relation to Crosslinking and Molecular Packing

1966 ◽  
Vol 39 (2) ◽  
pp. 408-417
Author(s):  
P. Mason
Keyword(s):  
Thermal Expansion ◽  
Free Volume ◽  
Specific Volume ◽  
Crosslink Density ◽  
Qualitative Change ◽  
Linear Increase ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Packing Effects

Abstract Effects of crosslinking on specific volume, thermal expansion coefficient, glass transition temperature (Tg) and viscoelasticity of rubber have been studied. Materials were prepared by heating purified natural rubber with varying amounts of cumyl peroxide. This procedure formed networks by intermolecular carbon-to-carbon bonding, and an approximately sixty-fold range of crosslink density was obtained. Crosslink density could be estimated with reasonable confidence up to about 1020/g. At this level the effects observed were, approximately, a one per cent decrease in specific volume; 23 per cent and 6 per cent decreases in the thermal expansion coefficients respectively below and above Tg; 5° C increase in Tg; and a displacement of the viscoelastic response by +5° C. These changes are accounted for in terms of the reduction in free volume consequent on crosslinking. There was also a qualitative change in behavior, the thermal expansion and viscoelastic transitional regions widening as crosslinking increased. The thermal expansion behavior is explained in terms of a linear increase in the variance of monomeric free volume with crosslinking up to 1020/g. At higher densities crosslinks are so close that their packing effects interact and the nature of the phenomenon changes.

Specific Volume and Ultrasonic Velocity Studies of the Liquid Crystal N-(p-n-hexyloxybenzylidene)-p-n-butylaniline (Hx BBA)

1983 ◽  
Vol 38 (7) ◽  
pp. 762-764 ◽  
Author(s):  
L. V. Choudary ◽  
J. V. Rao ◽  
P. N. Murty ◽  
C. R. K. Murty
Keyword(s):  
Thermal Expansion ◽  
Liquid Crystal ◽  
Ultrasonic Velocity ◽  
Specific Volume ◽  
Velocity Variation ◽  
Velocity Measurements ◽  
First Order ◽  
Smectic A ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

Abstract Specific volume and ultrasonic velocity measurements have been carried out on the liquid crystal N-(p-n-hexyloxybenzylidene)-p-n-butylaniline in the isotropic, nematic, smectic A, smectic B and smectic G phases. The variation of the specific volume with temperature shows that the corresponding transitions are of first order. Thermal expansion coefficients have been calculated for all the mesophases. The ultrasonic velocity variation with temperature confirms the transitions.

An extended criterion for estimation of glass-forming ability of metals

2007 ◽  
Vol 22 (5) ◽  
pp. 1378-1383 ◽  
Author(s):  
Dmitri V. Louzguine-Luzgin ◽  
Akihisa Inoue
Keyword(s):  
Thermal Expansion ◽  
Specific Volume ◽  
Intersection Point ◽  
Glass Forming Ability ◽  
Molten Metals ◽  
Metallic Liquid ◽  
Glass Forming ◽  
Thermal Expansion Coefficients ◽  
Pure Metals ◽  
Expansion Coefficients

If a metal contracts upon solidification, the specific volume of a metallic liquid phase must not be smaller than that of the corresponding crystal. As molten metals have higher thermal expansion coefficients compared with those of the corresponding crystals, the intersection point of two specific-volume–temperature plots of the liquid and the corresponding solid crystalline phase by analogy with Kauzmann’s paradox for entropy could be treated as an ideal glass-transition temperature. This paper describes this phenomenon observed for a number of pure metals and gives a semiempirical criterion for the achievement of a good glass-forming ability.

Defects in β-SiC thin films grown on α-SiC substrates

1988 ◽  
Vol 46 ◽  
pp. 568-569
Author(s):  
Karren L. More
Keyword(s):  
Thin Films ◽  
Semiconductor Device ◽  
Lattice Mismatch ◽  
Chemical Vapor ◽  
Substrate Material ◽  
Growth Interface ◽  
Si Substrates ◽  
Thermal Expansion Coefficients ◽  
Device Applications ◽  
Expansion Coefficients

Beta-SiC is an ideal candidate material for use in semiconductor device applications. Currently, monocrystalline β-SiC thin films are epitaxially grown on {100} Si substrates by chemical vapor deposition (CVD). These films, however, contain a high density of defects such as stacking faults, microtwins, and antiphase boundaries (APBs) as a result of the 20% lattice mismatch across the growth interface and an 8% difference in thermal expansion coefficients between Si and SiC. An ideal substrate material for the growth of β-SiC is α-SiC. Unfortunately, high purity, bulk α-SiC single crystals are very difficult to grow. The major source of SiC suitable for use as a substrate material is the random growth of {0001} 6H α-SiC crystals in an Acheson furnace used to make SiC grit for abrasive applications. To prepare clean, atomically smooth surfaces, the substrates are oxidized at 1473 K in flowing 02 for 1.5 h which removes ∽50 nm of the as-grown surface. The natural {0001} surface can terminate as either a Si (0001) layer or as a C (0001) layer.

METAMORPHOSES OF THE POSTMODERN DISCOURSEAND CURRENT CHALLENGES NEOMODERNISM

2019 ◽  
Author(s):  
Yu.V. IRKHIN
Keyword(s):  
World Politics ◽  
New Approach ◽  
Postmodern Theory ◽  
The World ◽  
Conservative Values

The article analyzes the problems, achievements and contradictions in the genesis of the contemporary postmodern discourse. The author has carried out complex research, systematized and showed the main features and differences of postmodernism and metamodernism, as well as the role of neoliberal values in their development. The author has considered a new approach to the study of society and politics: neomodernist discourse with the dominant conservative values, opposing postmodern theory, methodology and practice he has identified the features of neomodernism: historicism, patriotism and healthy nationalism, populism, transactionalismn and realism in the world politics.

Monitoring the marine environment for small round structured viruses (SRSVS): a new approach to combating the transmission of these viruses by molluscan shellfish

1998 ◽  
Vol 38 (12) ◽  
pp. 51-56 ◽  
Author(s):  
K. Henshilwood ◽  
J. Green ◽  
D. N. Lees
Keyword(s):  
Enteric Virus ◽  
Winter Period ◽  
Rt Pcr ◽  
Cloning And Sequencing ◽  
New Approach ◽  
Human Enteric Virus ◽  
Different Strains ◽  
The Uk ◽  
Public Health Protection

This study investigates human enteric virus contamination of a shellfish harvesting area. Samples were analysed over a 14-month period for Small Round Structured Viruses (SRSVs) using a previously developed nested RT-PCR. A clear seasonal difference was observed with the largest numbers of positive samples obtained during the winter period (October to March). This data concurs with the known winter association of gastroenteric illness due to oyster consumption in the UK and also with the majority of the outbreaks associated with shellfish harvested from this area during the study period. RT-PCR positive amplicons were further characterised by cloning and sequencing. Sequence analysis of the positive samples identified eleven SRSV strains, of both Genogroup I and Genogroup II, occurring throughout the study period. Many shellfish samples contained a mixture of strains with a few samples containing up to three different strains with both Genogroups represented. The observed common occurrence of strain mixtures may have implications for the role of shellfish as a vector for dissemination of SRSV strains. These results show that nested RT-PCR can identify SRSV contamination in shellfish harvesting areas. Virus monitoring of shellfish harvesting areas by specialist laboratories using RT-PCR is a possible approach to combating the transmission of SRSVs by molluscan shellfish and could potentially offer significantly enhanced levels of public health protection.

Lattice Thermal Conductivity Modelling of a Diatomic Nanoscale Material

2020 ◽  
Vol 10 (5) ◽  
pp. 602-609
Author(s):  
Adil H. Awad
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Correction Term ◽  
Nanoscale Material ◽  
New Approach ◽  
Two Samples ◽  
Conductivity Modelling ◽  
Callaway Model

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Methods: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

scholarly journals Neuroimmune Response Mediated by Cytokines in Natural Scrapie after Chronic Dexamethasone Treatment

Biomolecules ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 204
Author(s):  
Isabel M. Guijarro ◽  
Moisés Garcés ◽  
Pol Andrés-Benito ◽  
Belén Marín ◽  
Alicia Otero ◽  
...  
Keyword(s):  
Prion Diseases ◽  
Global Approach ◽  
Profile Data ◽  
Dexamethasone Treatment ◽  
New Approach ◽  
Complex Interactions ◽  
Natural Scrapie ◽  
Anti Inflammatory

The actual role of prion protein-induced glial activation and subsequent cytokine secretion during prion diseases is still incompletely understood. The overall aim of this study is to assess the effect of an anti-inflammatory treatment with dexamethasone on different cytokines released by neuroglial cells that are potentially related to neuroinflammation in natural scrapie. This study emphasizes the complex interactions existent among several pleiotropic neuromodulator peptides and provides a global approach to clarify neuroinflammatory processes in prion diseases. Additionally, an impairment of communication between microglial and astroglial populations mediated by cytokines, mainly IL-1, is suggested. The main novelty of this study is that it is the first one assessing in situ neuroinflammatory activity in relation to chronic anti-inflammatory therapy, gaining relevance because it is based on a natural model. The cytokine profile data would suggest the activation of some neurotoxicity-associated route. Consequently, targeting such a pathway might be a new approach to modify the damaging effects of neuroinflammation.

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