High spin states of Zr isotopes around A = 80 mass region — A study on cold and hot rotating nuclei

2019 ◽  
Vol 28 (11) ◽  
pp. 1950099
Author(s):  
Mamta Aggarwal ◽  
M. Kaushik ◽  
G. Saxena
Keyword(s):  
Low Temperature ◽  
High Temperatures ◽  
High Spin ◽  
Mass Region ◽  
Model Interaction ◽  
Hartree Fock ◽  
Prolate Shape ◽  
Good Accord ◽  
Increasing Temperature ◽  
Rotating Nuclei

High spin structure of Zr isotopes, in particular, around [Formula: see text] has been studied in yrast and nonyrast regions. Spin dependence of shapes for the yrast levels are investigated by employing Cranked Hartree–Fock–Bogoliubov (CHFB) theory using a [Formula: see text] model interaction and the calculations are in good accord with the experimental data. The nonyrast states are treated by incorporating temperature degree of freedom using the statistical theory (ST). Highly deformed prolate shapes dominate the nonrotating proton rich region at low temperatures (T) with coexisting oblate and prolate shapes in [Formula: see text]Zr. Hot rotating nuclei show highest deformation around [Formula: see text] among all the other Zr isotopes even at high temperatures. [Formula: see text]Zr exhibits interesting structural transitions, hence studied in detail in yrast and non yrast regions. Triaxiality predominates in both yrast and nearly yrast (low temperature) regions at low spins with transition to elongated shapes at mid spin values 30–38[Formula: see text] to highly deformed oblate shapes at higher spins. CHFB predicts a strong backbending effect at 32[Formula: see text] and 40[Formula: see text]. A shape coexistence between the rare shape phase of noncollective prolate and oblate is reported in [Formula: see text]Zr at low temperature and [Formula: see text]. Prolate shape phase disappears with increasing temperature and spin but the nucleus remains highly deformed (with [Formula: see text] at spin [Formula: see text]40[Formula: see text]) even at high temperatures of the order of 3–3.5[Formula: see text]MeV, hence a very promising candidate for GDR probes of nuclear shapes.

Tensile properties of finger-jointed lumber under high-temperature and oxygen-free conditions

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Kong Yue ◽  
Feng Wang ◽  
Weidong Lu ◽  
Zhongqiu Tang ◽  
Zhangjing Chen ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Tensile Properties ◽  
High Temperatures ◽  
Variable Temperature ◽  
Physical Property ◽  
Solid Wood ◽  
Nitrogen Atmosphere ◽  
Thermal Physical Property ◽  
Electron Microscopy Analysis ◽  
Increasing Temperature

Abstract A model for engineered wood was developed that considers the parallel-to-grain tensile strength of finger-jointed lumber at high temperatures relevant to fire conditions. The finger-jointed lumber was composed of Douglas fir, larch, and poplar wood with phenol-resorcinol-formaldehyde (PRF) as an adhesive. The tensile properties of the finger-jointed lumber were evaluated at high temperatures under oxygen-free conditions, i.e. in a nitrogen atmosphere. A combination of chemical and thermal-physical property analysis of the PRF adhesive and microscopic observations on the glueline was used to discuss the reduction of tensile strength of the parallel-to-grain finger-jointed lumber at variable temperature. The results show that the tensile strength of the finger-jointed lumber decreased linearly with increasing temperature. The parallel-to-grain tensile strength of the PRF finger-jointed samples at 20 and 280 °C were 84 and 5% of the tensile strength of the solid wood at 20 °C, respectively. The thermal-physical properties and scanning electron microscopy analysis revealed that the pyrolysis intensity of the PRF adhesive was lower than that of the wood at 220 °C or higher.

Infrared spectra of the ammonium ion in crystals. Part VIII. Spectroscopic criteria of highly-bent hydrogen bonds

1980 ◽  
Vol 58 (9) ◽  
pp. 867-874 ◽  
Author(s):  
Osvald Knop ◽  
Wolfgang J. Westerhaus ◽  
Michael Falk
Keyword(s):  
Low Temperature ◽  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Ammonium Ion ◽  
Temperature Transition ◽  
Increasing Temperature

Available evidence suggests that (1) the stretching frequencies of highly-bent hydrogen bonds decrease with increasing temperature, regardless of whether the bonds are static or dynamic in character, to a single acceptor or to several competing acceptors; and (2) departures from symmetric trifurcation (or bifurcation) toward asymmetric situations lower the stretching frequency. In further support of these criteria isotopic probe ion spectra between 10 K and room temperature have been obtained for taurine and for trigonal (NH4)2MF6 (M = Si, Ge, Sn, Ti). Evidence of a low-temperature transition at 100(10) K in trigonal (NH4)2SnF6 is presented, and existence of the previously reported transition at 38.6 K in trigonal (NH4)2SiF6 is confirmed. Symmetry changes associated with these transitions are discussed.

MO-Theoretical Studies on a Model Complex for Deoxymyoglobin

1998 ◽  
Vol 53 (9) ◽  
pp. 755-765
Author(s):  
Christian Kollma ◽  
Sighart F. Fischer ◽  
Michael C. Böhm
Keyword(s):  
High Spin ◽  
Ground State ◽  
High Spin State ◽  
Open Shell ◽  
Spin States ◽  
Hartree Fock ◽  
Intermediate Spin ◽  
Model Complex ◽  
Out Of Plane ◽  
Overlap Method

AbstractThe origin of the displacement of the Fe atom in deoxymyoglobin with respect to the porphyrin plane in the high-spin state is examined by a qualitative molecular orbital (MO) analysis on the extended Hückel level. We find that attachment of a fifth ligand (imidazole in our model complex) to Fe(II)porphyrin favors the out-of-plane shift due to a strengthening of the bonding interaction between Fe and the nitrogen of the imidazole ligand. This results in a high-spin (5 = 2) ground state with Fe shifted out-of-plane for the five-coordinate complex instead of an intermediate spin ground state (5 = 1) with Fe lying in the plane for four-coordinate Fe(II)porphyrin. The relative energies of the different spin states as a function of the distance between Fe and the porphyrin plane are evaluated using an ROHF (restricted open shell Hartree-Fock) version of an INDO (intermediate neglect of differential overlap) method. We observe a level crossing between high-spin and intermediate spin states whereas the low-spin (5 = 0) state remains always higher in energy.

scholarly journals Preventing thermoinhibition in a thermosensitive lettuce genotype by seed imbibition at low temperature

2003 ◽  
Vol 60 (3) ◽  
pp. 477-480 ◽  
Author(s):  
Warley Marcos Nascimento
Keyword(s):  
Seed Germination ◽  
Low Temperature ◽  
High Temperatures ◽  
Lactuca Sativa ◽  
Lettuce Seed ◽  
Temperature Dependent ◽  
Lettuce Seeds ◽  
Lactuca Sativa L ◽  
Lettuce Seed Germination ◽  
Dark Green

Lettuce (Lactuca sativa L.) seed germination is strongly temperature dependent and under high temperatures, germination of most of genotypes can be erratic or completely inhibited. Lettuce seeds of 'Dark Green Boston' (DGB) were incubated at temperatures ranging from 15° to 35°C at light and dark conditions. Other seeds were imbibed in dark at 20°; 25°; 30°; and 35°C for 8 and 16 hours and then transferred to 20 or 35°C, in dark. Seeds were also incubated at constant temperature of 20° and 35 °C, in the dark, as control. In another treatment, seeds were primed for 3 days at 15°C with constant light. DGB lettuce seeds required light to germinate adequately at temperatures above 25°C. Seeds incubated at 20°C had 97% germination, whereas seeds incubated at 35°C did not germinate. Seeds imbibed at 20°C for 8 and 16 hours had germination. At 35°C, seeds imbibed initially at 20°C for 8 and 16 hours, had 89 and 97% germination, respectively. Seeds imbibed at 25°C for 16 hours, germinated satisfactory at 35°C. High temperatures of imbibition led to no germination. Primed and non-primed seeds had 100% germination at 20°C. Primed seeds had 100% germination at 35°C, whereas non-primed seeds germinate only 4%. The first hours of imbibition are very critical for lettuce seed germination at high temperatures.

Large- Scale ab initio Simulations of Fe-doped SrTiO3 Perovskites

2002 ◽  
Vol 731 ◽  
Author(s):  
R.A. Evarestov ◽  
R.I. Eglitis ◽  
S. Piskunov ◽  
E. A. Kotomin ◽  
G. Borstel
Keyword(s):  
Energy Level ◽  
Ab Initio ◽  
High Spin ◽  
Spin State ◽  
Large Scale ◽  
Covalent Bonding ◽  
Hartree Fock ◽  
Ab Initio Simulations ◽  
Displacement Mode ◽  
Jahn Teller

AbstractUsing the Unrestricted Hartree-Fock method and supercells containing up to 160 atoms, we calculated the energy level positions in the gap and atomic geometry for the Fe4+ impurity substituting for a host Ti atom in SrTiO3. In agreement with experiment, the high spin (S=2) state is much lower in energy than the zero-spin state. The energy level positions strongly depend on the asymmetric displacement mode of the six nearest O ions which is a combination of the Jahn-Teller and breathing modes. A considerable covalent bonding between the Fe ion and four nearest O ions takes place.

scholarly journals Temperature and interlayer coupling induced thermal transport across graphene/2D-SiC van der Waals heterostructure

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Md. Sherajul Islam ◽  
Imon Mia ◽  
A. S. M. Jannatul Islam ◽  
Catherine Stampfl ◽  
Jeongwon Park
Keyword(s):  
High Temperatures ◽  
Thermal Transport ◽  
Van Der Waals ◽  
Thermal Conductance ◽  
Interlayer Coupling ◽  
Phonon Modes ◽  
Out Of Plane ◽  
System Temperature ◽  
Non Equilibrium Molecular Dynamics ◽  
Increasing Temperature

AbstractGraphene based two-dimensional (2D) van der Waals (vdW) materials have attracted enormous attention because of their extraordinary physical properties. In this study, we explore the temperature and interlayer coupling induced thermal transport across the graphene/2D-SiC vdW interface using non-equilibrium molecular dynamics and transient pump probe methods. We find that the in-plane thermal conductivity κ deviates slightly from the 1/T law at high temperatures. A tunable κ is found with the variation of the interlayer coupling strength χ. The interlayer thermal resistance R across graphene/2D-SiC interface reaches 2.71 $$\times$$ × 10–7$${\text{Km}}^{2} /{\text{W}}$$ Km 2 / W at room temperature and χ = 1, and it reduces steadily with the elevation of system temperature and χ, demonstrating around 41% and 56% reduction with increasing temperature to 700 K and a χ of 25, respectively. We also elucidate the heat transport mechanism by estimating the in-plane and out-of-plane phonon modes. Higher phonon propagation possibility and Umklapp scattering across the interface at high temperatures and increased χ lead to the significant reduction of R. This work unveils the mechanism of heat transfer and interface thermal conductance engineering across the graphene/2D-SiC vdW heterostructure.

scholarly journals Low-Temperature Esterification to Produce Oleic Acid-Based Wax Esters Catalyzed by 4-Dodecylbenzenesulfonic Acid

Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1471
Author(s):  
Zhenzhen Li ◽  
Wei Liu ◽  
Guolong Yang
Keyword(s):  
Oleic Acid ◽  
Low Temperature ◽  
Inhibitory Effect ◽  
Wax Esters ◽  
Molar Ratio ◽  
Efficient Catalyst ◽  
Dodecylbenzenesulfonic Acid ◽  
Effect Of Water ◽  
Solvent Free Conditions ◽  
Increasing Temperature

Synthesized oleic acid-based wax esters (e.g., cetyl oleate), which can replace spermaceti oil or jojoba oil, have been widely used in the cosmetic, pharmaceutical and other industries. In this work, 4-dodecylbenzenesulfonic acid (DBSA) has been successfully used as an efficient catalyst to synthesize oleic acid-based wax esters through esterification at 40 °C under solvent-free conditions. A 93.6% conversion rate of cetyl alcohol was obtained under optimal conditions: 10 mol% DBSA, a molar ratio of 1.3:1 oleic acid to alcohol, a reaction temperature 40 °C and a reaction time of 4 h. The effect of water content on esterification was investigated, and it was found that the inhibitory effect of water decreased significantly with increasing temperature. Moreover, DBSA-catalyzed esterification could be applied in the production of various oleic acid-based wax esters and excellent conversion (>90%) to esters was obtained under such mild conditions. DBSA-catalyzed low-temperature esterification is an efficient method for the production of liquid wax esters.

COLLECTIVE BANDS IN 68Se

2002 ◽  
Vol 11 (06) ◽  
pp. 531-538 ◽  
Author(s):  
K. C. TRIPATHY ◽  
R. SAHU
Keyword(s):  
Configuration Space ◽  
Single Particle ◽  
Fock States ◽  
Hartree Fock ◽  
Ground Band ◽  
Prolate Shape ◽  
Particle Orbits ◽  
Excited Band ◽  
Inert Core ◽  
Configuration Mixing

The collective bands of the N = Z nucleus 68 Se are studied within our deformed configuration mixing shell model based on Hartree–Fock states. The configuration space consists of the spherical single particle orbits 1p3/2, 0f5/2, 1p1/2 and 0g9/2 with 56 Ni as the inert core. A modified Kuo interaction for this basis space has been used in our calculation. The calculated ground band, K = 2+ excited band and the K = 5- excited band agree reasonably well with the experiment. Our calculation shows that the ground band is essentially of oblate shape and the excited K = 2+ band is of prolate shape. This is in agreement with the conclusions drawn from the recent experimental analysis.

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