THERMOPOWER AND ELECTRICAL RESISTIVITY OF LaxY1−xAl2 ALLOYS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 387-390
Author(s):  
A. T. BURKOV ◽  
E. BAUER ◽  
E. GRATZ ◽  
R. RESEL
Keyword(s):  
Electrical Resistivity ◽  
Fermi Level ◽  
Elevated Temperatures ◽  
Transport Theory ◽  
Minor Effect ◽  
Boltzmann Transport ◽  
Linear Temperature ◽  
Temperature Dependences ◽  
A Minor ◽  
D Model

The electronic transport theory predicts linear temperature dependences for the thermopower (S) and the electrical resistivity (ρ) at elevated temperatures. However, the experimental data for La x Y 1− x Al 2 alloys reveal nonlinear dependences for both, S(T) and ρ (T) . We relate this disagreement to the density of states (DOS) structure in the vicinity of the Fermi level. Based on the linearised Boltzmann transport equation, we obtain from the experimental temperature dependences of ρ and S an electron dependent function ϕ(ε), reflecting the energy dependence of DOS and that of scattering processes. In the scope of Mott's s-d model the 1/ϕ(ε) function is proportional to the DOS near the Fermi level. A comparison of the 1/ϕ(ε) function with available band structure calculations shows good agreement for YAl 2 and LaAl 2. In the case of alloys, the structure of DOS may cause a temperature dependence of the impurity contribution to the resistivity but has only a minor effect on S(T) at evelated temperatures.

scholarly journals Unusual metallic conductivity of high-Tc cuprates

2021 ◽  
Vol 5 (3) ◽  
pp. 183-191
Author(s):  
S. Dzhumanov ◽  
Sh.R. Malikov ◽  
Sh.S. Djumanov
Keyword(s):  
Transport Theory ◽  
Charge Carriers ◽  
Cooper Pairs ◽  
Linear Temperature Dependence ◽  
Linear Temperature ◽  
High Tc ◽  
Distinctive Features ◽  
Metallic Conductivity ◽  
Temperature Dependences ◽  
High Tc Cuprates

The intrinsic mechanisms of the unusual metallic transports of three types of relevant charge carriers (large polarons, excited (dissociated) polaronic components of bosonic Cooper pairs and bosonic Cooper pairs themselves) along the CuO2 layers of high-Tc cuprates are identified and the new features of metallic conductivity in the CuO2 layers (i.e. ab -planes) of underdoped and optimally doped cuprates are explained. The in-plane conductivity of high-Tc cuprates is associated with the metallic transports of such charge carriers at their scattering by lattice vibrations in thin CuO2 layers. The proposed charge transport theory in high-Tc cuprates allows to explain consistently the distinctive features of metallic conductivity and the puzzling experimental data on the temperature dependences of their in-plane resistivity pab. In underdoped and optimally doped cuprates the linear temperature dependence of pab(T) above the pseudogap formation temperature T∗ is associated with the scattering of polaronic carriers at acoustic and optical phonons, while the different (upward and downward) deviations from the linearity in pab(T) below T∗ are caused by the pseudogap effect on the conductivity of the excited Fermi components of bosonic Cooper pairs and by the dominating conductivity of bosonic Cooper pairs themselves in the normal state of these high-Tc materials.

Kinetics of the self-assembly of bold alpha -cyclodextrin [2]pseudorotaxanes with polymethylene threads bearing quaternary ammonium and phosphonium end groups

1998 ◽  
Vol 76 (6) ◽  
pp. 843-850
Author(s):  
Angela P Lyon ◽  
Nicola J Banton ◽  
Donal H Macartney
Keyword(s):  
Rate Constant ◽  
Self Assembly ◽  
Elevated Temperatures ◽  
Formation Rate ◽  
Minor Effect ◽  
Prolonged Heating ◽  
End Groups ◽  
A Minor ◽  
Kinetics Of

The kinetics and mechanism of the formation and dissociation of a series of [2]pseudorotaxanes, comprised of α -cyclodextrin (α -CD) as the cyclic component and the ([Me3N(CH2)nNMe3]2+ (n = 8-12), [Me2EtN(CH2)10NEtMe2]2+, and [Me3P(CH2)10PMe3]2+) dications as the threads, were determined by means of 1H and 31P NMR in aqueous solution. The length of the polymethylene chain (n) of the thread, which has a minor effect on the rate constant for pseudorotaxane formation, is important in the kinetics of the dissociation reactions, with the longer, more hydrophobic chains resulting in slower pseudorotaxane dissociation. The replacement of one methyl substitutent by an ethyl group in each of the end groups on the [Me3N(CH2)10NMe3]2+ thread results in a 30-fold decrease in the formation rate constant. Replacements, by ethyls, of two or all of the methyl substitutents prevent the formation of the pseudorotaxane, even after prolonged heating. The pseudorotaxane containing the {Me3P(CH2)10PMe3.; α-CD}2+ thread forms only at elevated temperatures by a slippage mechanism, and the rate constant for its self-assembly at 75°C (8 x 10-5 M-1 s-1) is more than 106 smaller than the rate constant at 75°C (200 M-1 s-1) extrapolated for the corresponding {Me3N(CH2)10NMe3 . α -CD}2+complex. The enthalpies and entropies of activation for the formation and dissociation of the [2]pseudorotaxanes decrease with an increase in the size and hydrophobicity of the end groups, suggesting a reduced role of desolvation of the quaternized atoms in the threading or dethreading processes.Key words: pseudorotaxane, α -cyclodextrin, kinetics, self-assembly, slippage, supramolecular.

scholarly journals Monovalent Copper and Silver Ions Block DNA Polymerase Chain Reaction

2021 ◽  
Author(s):  
Lea Moshkovich ◽  
Oshra Saphier ◽  
Stanislav Popov ◽  
Yoram Shotland ◽  
Eldad Silberstein ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Dna Polymerase ◽  
Elevated Temperatures ◽  
Copper Ions ◽  
Silver Ions ◽  
Antimicrobial Effect ◽  
Minor Effect ◽  
Chain Reaction ◽  
Polymerase Chain ◽  
A Minor

Abstract In the present study we present the dramatic effect that monovalent copper ions (Cu(I))have on the DNA polymerase chain reaction, and the moderate effect which monovalent silver ions (Ag(I)) have on it. Our research utilizes the commercial Polymerase Chain Reaction (PCR) system: in anaerobic conditions, in the presence of less than 0.1 mM of Cu(I) ions or in the presence of less than 10mM of Ag(I) ions, the PCR system was entirely shut down.Under the same conditions, 1 mM of divalent copper ions (Cu(II)) ions shows only a minor effect, while10mM of divalent Ni and Zn ions shows no effect at all.This finding can give some explanation for the strong antimicrobial activity of monovalent copper ions (Cu(I))as well as Ag(I). Although the mechanism of this effect is not yet fully understood, we recently published results showing that under the conditions of acidic pH, an unfavorable carbon source, low molecular oxygen concentration and elevated temperatures, the antibacterial action of Cu(I) ions is boosted, with a 106 bacterial population eliminated in less than 1 min by 0.4mM of Cu(I). Microscopy checking of E.coli morphology and light scattering testes showed mortality of bacteria with almost no lysis. These results suggest that rapid and lethal metabolic damage is the main mechanism of Cu(I)’s antimicrobial effect.

Improvement of monitoring of tertiary filtration with particle counting

2006 ◽  
Vol 6 (1) ◽  
pp. 1-9
Author(s):  
V. Miska ◽  
J.H.J.M. van der Graaf ◽  
J. de Koning
Keyword(s):  
Particle Surface ◽  
Minor Effect ◽  
Particle Size Distributions ◽  
Particle Volume ◽  
Mass Distributions ◽  
Particle Counting ◽  
Total Particle ◽  
Particle Counts ◽  
A Minor ◽  
Sample Dilution

Nowadays filtration processes are still monitored with conventional analyses like turbidity measurements and, in case of flocculation–filtration, with phosphorus analyses. Turbidity measurements have the disadvantage that breakthrough of small flocs cannot be displayed, because of the blindness regarding changes in the mass distributions. Additional particle volume distributions calculated from particle size distributions (PSDs) would provide a better assessment of filtration performance. Lab-scale experiments have been executed on a flocculation–filtration column fed with effluent from WWTP Beverwijk in The Netherlands. Besides particle counting at various sampling points, the effect of sample dilution on the accuracy of PSD measurements has been reflected. It was found that the dilution has a minor effect on PSD of low turbidity samples such as process filtrate. The correlation between total particle counts, total particle volume (TPV) and total particle surface is not high but is at least better for diluted measurements of particles in the range 2–10 μm. Furthermore, possible relations between floc-bound phosphorus and TPV removal had been investigated. A good correlation coefficient is found for TPV removal versus floc-bound phosphorus removal for the experiments with polyaluminiumchloride and the experiments with single denitrifying and blank filtration.

scholarly journals Linkage mapping identifies a non-synonymous mutation in FLOWERING LOCUS T (FT-B1) increasing spikelet number per spike

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jonathan Brassac ◽  
Quddoos H. Muqaddasi ◽  
Jörg Plieske ◽  
Martin W. Ganal ◽  
Marion S. Röder
Keyword(s):  
Flowering Time ◽  
Aspartic Acid ◽  
Synonymous Substitution ◽  
Minor Effect ◽  
Phenotypic Variance ◽  
Spikelet Number ◽  
Wheat Varieties ◽  
Trait Locus ◽  
A Minor ◽  
Spikelet Number Per Spike

AbstractTotal spikelet number per spike (TSN) is a major component of spike architecture in wheat (Triticumaestivum L.). A major and consistent quantitative trait locus (QTL) was discovered for TSN in a doubled haploid spring wheat population grown in the field over 4 years. The QTL on chromosome 7B explained up to 20.5% of phenotypic variance. In its physical interval (7B: 6.37–21.67 Mb), the gene FLOWERINGLOCUST (FT-B1) emerged as candidate for the observed effect. In one of the parental lines, FT-B1 carried a non-synonymous substitution on position 19 of the coding sequence. This mutation modifying an aspartic acid (D) into a histidine (H) occurred in a highly conserved position. The mutation was observed with a frequency of ca. 68% in a set of 135 hexaploid wheat varieties and landraces, while it was not found in other plant species. FT-B1 only showed a minor effect on heading and flowering time (FT) which were dominated by a major QTL on chromosome 5A caused by segregation of the vernalization gene VRN-A1. Individuals carrying the FT-B1 allele with amino acid histidine had, on average, a higher number of spikelets (15.1) than individuals with the aspartic acid allele (14.3) independent of their VRN-A1 allele. We show that the effect of TSN is not mainly related to flowering time; however, the duration of pre-anthesis phases may play a major role.

scholarly journals Band degeneracy enhanced thermoelectric performance in layered oxyselenides by first-principles calculations

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Ning Wang ◽  
Menglu Li ◽  
Haiyan Xiao ◽  
Zhibin Gao ◽  
Zijiang Liu ◽  
...  
Keyword(s):  
Density Functional ◽  
Transport Theory ◽  
Relaxation Times ◽  
Wide Band ◽  
Type Systems ◽  
Model Systems ◽  
Boltzmann Transport ◽  
Seebeck Coefficients ◽  
Boltzmann Transport Theory ◽  
P Type

AbstractBand degeneracy is effective in optimizing the power factors of thermoelectric (TE) materials by enhancing the Seebeck coefficients. In this study, we demonstrate this effect in model systems of layered oxyselenide family by the density functional theory (DFT) combined with semi-classical Boltzmann transport theory. TE transport performance of layered LaCuOSe and BiCuOSe are fully compared. The results show that due to the larger electrical conductivities caused by longer electron relaxation times, the n-type systems show better TE performance than p-type systems for both LaCuOSe and BiCuOSe. Besides, the conduction band degeneracy of LaCuOSe leads to a larger Seebeck coefficient and a higher optimal carrier concentration than n-type BiCuOSe, and thus a higher power factor. The optimal figure of merit (ZT) value of 1.46 for n-type LaCuOSe is 22% larger than that of 1.2 for n-type BiCuOSe. This study highlights the potential of wide band gap material LaCuOSe for highly efficient TE applications, and demonstrates that inducing band degeneracy by cations substitution is an effective way to enhance the TE performance of layered oxyselenides.

scholarly journals IL-6 Is Not Absolutely Essential for the Development of a TH17 Immune Response after an Aerosol Infection with Mycobacterium tuberculosis H37rv

Cells ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 9
Author(s):  
Kristina Ritter ◽  
Jan Christian Sodenkamp ◽  
Alexandra Hölscher ◽  
Jochen Behrends ◽  
Christoph Hölscher
Keyword(s):  
Immune Response ◽  
Inflammatory Diseases ◽  
Mycobacterial Infection ◽  
Minor Effect ◽  
Mycobacterium Tuberculosis H37rv ◽  
Th 17 ◽  
Anti Inflammatory ◽  
A Minor ◽  
Aerosol Infection ◽  
Deficient Mice

Anti-inflammatory treatment of chronic inflammatory diseases often increases susceptibility to infectious diseases such as tuberculosis (TB). Since numerous chronic inflammatory and autoimmune diseases are mediated by interleukin (IL)-6-induced T helper (TH) 17 cells, a TH17-directed anti-inflammatory therapy may be preferable to an IL-12-dependent TH1 inhibition in order to avoid reactivation of latent infections. To assess, however, the risk of inhibition of IL-6-dependent TH17-mediated inflammation, we examined the TH17 immune response and the course of experimental TB in IL-6- and T-cell-specific gp130-deficient mice. Our study revealed that the absence of IL-6 or gp130 on T cells has only a minor effect on the development of antigen-specific TH1 and TH17 cells. Importantly, these gene-deficient mice were as capable as wild type mice to control mycobacterial infection. Together, in contrast to its key function for TH17 development in other inflammatory diseases, IL-6 plays an inferior role for the generation of TH17 immune responses during experimental TB.

scholarly journals Sweet taste of heavy water

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Natalie Ben Abu ◽  
Philip E. Mason ◽  
Hadar Klein ◽  
Nitzan Dubovski ◽  
Yaron Ben Shoshan-Galeczki ◽  
...  
Keyword(s):  
Heavy Water ◽  
Calcium Release ◽  
Homology Modelling ◽  
Taste Receptor ◽  
Chemical Properties ◽  
Sweet Taste ◽  
Minor Effect ◽  
Dynamics Simulations ◽  
A Minor ◽  
Physical And Chemical

AbstractHydrogen to deuterium isotopic substitution has only a minor effect on physical and chemical properties of water and, as such, is not supposed to influence its neutral taste. Here we conclusively demonstrate that humans are, nevertheless, able to distinguish D2O from H2O by taste. Indeed, highly purified heavy water has a distinctly sweeter taste than same-purity normal water and can add to perceived sweetness of sweeteners. In contrast, mice do not prefer D2O over H2O, indicating that they are not likely to perceive heavy water as sweet. HEK 293T cells transfected with the TAS1R2/TAS1R3 heterodimer and chimeric G-proteins are activated by D2O but not by H2O. Lactisole, which is a known sweetness inhibitor acting via the TAS1R3 monomer of the TAS1R2/TAS1R3, suppresses the sweetness of D2O in human sensory tests, as well as the calcium release elicited by D2O in sweet taste receptor-expressing cells. The present multifaceted experimental study, complemented by homology modelling and molecular dynamics simulations, resolves a long-standing controversy about the taste of heavy water, shows that its sweet taste is mediated by the human TAS1R2/TAS1R3 taste receptor, and opens way to future studies of the detailed mechanism of action.

scholarly journals Effect of Different SiO2 Polymorphs on the Reaction Between SiO2 and SiC in Si Production

2021 ◽  
Vol 52 (2) ◽  
pp. 792-803
Author(s):  
Marit Buhaug Folstad ◽  
Eli Ringdalen ◽  
Halvard Tveit ◽  
Merete Tangstad
Keyword(s):  
Amorphous Silica ◽  
Reaction Rate ◽  
Reduction Reaction ◽  
Minor Effect ◽  
Target Temperature ◽  
Heating Rates ◽  
Significant Difference ◽  
Sio2 Polymorphs ◽  
A Minor ◽  
Final Composition

AbstractThis work investigates the phase transformations in silica (SiO2) during heating to a target temperature between 1700 °C and 1900 °C and the effect of SiO2 polymorphs on the reduction reaction 2SiO2 + SiC = 3SiO + CO in silicon production. Different heating rates up to target temperature have been used to achieve the different compositions of quartz, amorphous silica and cristobalite. The different heating rates had a minor effect on the final composition, and longer time at temperatures > 1400 °C were necessary to achieve greater variations in the final composition. Heating above the melting temperature gave more amorphous silica and less cristobalite, as amorphous silica also may form from β-cristobalite. Isothermal furnace experiments were conducted to study the extent of the reduction reaction. This study did not find any significant difference in the effects of quartz, amorphous silica or cristobalite. Increased temperature from 1700 °C to 1900 °C increased the reaction rate.

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