Article

1998 ◽  
Vol 76 (2) ◽  
pp. 213-220
Author(s):  
Mitchell D Refvik ◽  
Adrian L Schwan
Keyword(s):  
Low Temperature ◽  
Key Words ◽  
Variable Temperature ◽  
Cyanide Ion ◽  
Structural Assignment ◽  
Vt Nmr ◽  
Silylation Reaction

Lithium (E)-1-hexenesulfenate (5a) was treated with a number of TMS-X (TMS = trimethylsilyl) reagents to afford N,N-bis(trimethylsilyl)-(E)-1-hexenesulfenamide (7a) and (or) di((E)-1 hexenyl) disulfide (8), usually in low yield. The cleanest reactions, those from use of TMS-Cl (to afford 7a) and TMS-CN (which yields 8) were analyzed by variable temperature NMR. It was found that the low-temperature silylation reaction using TMS-Cl affords 7a and thiosulfinate 12 as initial products. Warming the mixture coerces the decomposition of 12. Treatment of 5a with TMS-CN also yields thiosulfinate 12 which is reduced to disulfide 8 as the temperature warms, possibly by action of cyanide ion. Evidence is presented that allows a confident structural assignment of the transient thiosulfinate 12, and mechanisms are suggested for the formation of 12. The study also led to the NMR observation of (E)-1-hexenesulfenate (5a).Key words: sulfenate, thiosulfinate, variable temperature NMR (VT NMR), silylation.

Low-Temperature Liquid-Phase Synthesis and Electrochemical Activity of α-Nickel Hydroxide with Flower-Like Micro-/Nano-Structure

2011 ◽  
Vol 347-353 ◽  
pp. 3379-3383
Author(s):  
Zhi Wei Li ◽  
Xu Xiang ◽  
Zong Min Tian
Keyword(s):  
Liquid Phase ◽  
Low Temperature ◽  
Ethylene Glycol ◽  
Nickel Hydroxide ◽  
Variable Temperature ◽  
Mixed Solvents ◽  
Reaction Medium ◽  
Electrochemical Activity ◽  
Nano Structure ◽  
Pure Phase

The synthesis of α-nickel hydroxide has been achieved via a facile liquid-phase precipitation approach, using the mixed solvents of ethylene glycol and water as reaction medium at low temperature. The XRD characterization indicates that pure phase α-Ni(OH)2can be obtained under variable temperature and pH value. The products present a flower-like micro-/nano-structure assembled with curved nanosheets. The nanosheets have the width of 100~500 nm and the thickness of 20~70 nm. The cavities are formed in the structure due to the interconnection of curved nanosheets. The solvents play a key role in the formation of Ni(OH)2with different forms. Pure phase α-Ni(OH)2can only be synthesized in the mixed solvents of ethylene glycol and water. Cyclic voltammetry was applied to test the electrochemical activity of the as-synthesized α-Ni(OH)2. The findings suggest that the α-Ni(OH)2with a micro-/nano-structure exhibits excellent electrochemical activity, which may be considered as a promising candidate of electrode material.

scholarly journals Experimental study on the compression characteristics of soft soil based on low temperature effect

2021 ◽  
Vol 9 (4B) ◽  
Author(s):  
Jian Zhang ◽  
◽  
Chunpeng Han ◽  
Jiayi Tian ◽  
Qingjie Dong ◽  
...  
Keyword(s):  
Low Temperature ◽  
Phase Change ◽  
Compression Test ◽  
Variable Temperature ◽  
Soft Soil ◽  
Test Methods ◽  
Variable Load ◽  
Compression Tests ◽  
Different Temperatures ◽  
Freezing Condition

Based on the characteristics of long annual freezing time and short suitable construction period of soft soil in cold region, this paper discusses the feasibility of foundation treatment of soft soil in freezing-thawing layer under freezing condition. The deformation characteristics of soft soil in freezing-thawing layer in Hulunbuir area in China are studied by using two compression test methods, namely, constant temperature and variable load (CTVL) test, variable temperature and variable load (VTVL) test. The compressibility indexes under different temperatures and consolidation pressures are obtained. The research shows that the freezing-thawing soft soil has large compressibility, the maximum strain of CTVL test is 19.89%, and the maximum compression of VTVL test can reach 18.16%. The results of CTVL compression tests show that when the soil temperature is in the range of severe phase change (-1.5℃-0℃), the temperature change has the greatest influence on the compression coefficient of soil. The result of VTVL compression test shows that some additional deformation occurs under the action of low temperature. The additional deformation is further increased when the soil is under high consolidation pressure and in the severe phase change (-1.5℃-0℃).

CAD/CAM Zirconia for Dental Application

2013 ◽  
Vol 320 ◽  
pp. 505-511
Author(s):  
Ning Li ◽  
Zhi Kai Wu ◽  
Chao Jian ◽  
Wan Qian Zhao ◽  
Jia Zhen Yan
Keyword(s):  
Mechanical Properties ◽  
Low Temperature ◽  
Key Words ◽  
20Th Century ◽  
Dental Materials ◽  
Tetragonal Zirconia ◽  
Dental Application ◽  
Cad Cam ◽  
Low Temperature Aging ◽  
Temperature Aging

During the 20th century, both dental materials and dental technologies for the fabrication of dental prosthesis progressed remarkably. Owing to the increased demand of safety and aesthetics, 3 mol% yttria stabilized tetragonal zirconia polycrystalline has been recently introduced in prosthetic dentistry for the fabrication of crowns and fixed partial dentures, in combination with CAD/CAM technique. This greatly changed the conventional dental laboratory work which is labor-intensive and experience-dependent. This review mainly introduced the state of dental zirconia and the application of CAD/CAM technology in dentistry. Key words: Dental Zirconia; CAD/CAM Technique; Mechanical Properties; Transformation Toughing; Low Temperature Aging;

CRYOGENIC GREASE LUBRICANTS FOR ROCKET AND SPACE TECHNOLOGY

2021 ◽  
pp. 31-41
Author(s):  
Andrey D. PLOTNIKOV ◽  
Aleksandr V. VODOLAZHSKIY ◽  
Natalya S. YAKUPOVA
Keyword(s):  
Chemical Composition ◽  
Low Temperature ◽  
Key Words ◽  
Ir Spectrum ◽  
Practical Relevance ◽  
Space Technology ◽  
Potential Evaporation ◽  
Testing Methods ◽  
Solidification Temperature ◽  
Temperature Characteristics

The paper represents requirements for cryogenic grease lubricants used in the rocket and space technology. Data on lubricants based on perfluoropolyether liquid FEN is provided. New lubricant testing methods enabling to analyze their chemical composition and low-temperature characteristics are proposed. Quoted are investigation results for the equivalents of previously used cryogenic lubricants NIKA, NIRA and «Ametist». A practical relevance of the paper has been proven by introduction of low-temperature lubricants «Sever» currently being used in rocket and space items, as well аs successful application of the developed lubricant incoming inspection procedures at RSC Energia. Key words: low-temperature lubricant, perfluoropolyether liquid FEN, viscosity, solidification temperature, IR spectrum, potential evaporation.

scholarly journals Thermal denaturation of bovine longissimus thoracis aponeurosis, correlating contraction with optical changes

2006 ◽  
Vol 86 (2) ◽  
pp. 221-224 ◽  
Author(s):  
H. J. Swatland
Keyword(s):  
Low Temperature ◽  
Connective Tissue ◽  
Key Words ◽  
Thermal Denaturation ◽  
Water Bath

Beef rib roasts and steaks have a thick connective tissue aponeurosis which is often difficult to gelatinise by cooking. When heated in a water-bath, aponeurosis first increased in reflectance (maximum 0.026 ± 0.021 at 67.1 ± 5.5°C) before decreasing in reflectance as gelatinisation occurred. Contraction reached a maximum of 33.8 ± 15.8% of starting length at 69.2 ± 3.2°C and corresponded to the increase not the decrease in reflectance. Either contraction or increased reflectance might be used to select animals with low-temperature gelatinisation. Key words: Beef toughness, aponeurosis, cooking

Thermogravimetric, infrared and mass-spectroscopic analysis of the desorption of methanol, propan-1-ol, propan-2-ol and 2-methylpropan-2-ol from montmorillonite

Clay Minerals ◽  
1993 ◽  
Vol 28 (1) ◽  
pp. 123-137 ◽  
Author(s):  
C. Breen ◽  
J. J. Flynn ◽  
G. M. B. Parkes
Keyword(s):  
Thermogravimetric Analysis ◽  
Low Temperature ◽  
Ir Spectroscopy ◽  
Ir Spectra ◽  
Spectral Data ◽  
Spectroscopic Analysis ◽  
Variable Temperature ◽  
Trivalent Cation ◽  
Mass Spectral Data ◽  
Mass Spectral

AbstractThe desorption of methanol (MeOH), propan-1-ol (n-PrOH), propan-2-ol (i-PrOH) and 2-methylpropan-2-ol (t-BuOH) from Na+-, Ca2+-, Al3+-, Cr3+- and Fe3+-exchanged montmorillonite has been studied using variable temperature infrared (IR) spectroscopy and thermogravimetric analysis (TGA). Alcohol-saturated trivalent cation (M3+) exchanged samples exhibit maxima in the derivative thermograms at 20 and 110°C (MeOH), 30 and 160°C (n-PrOH), 20 and 110°C (i-PrOH) and 20, 55 and 80°C (t-BuOH). Alcohol-saturated Na+ and Ca2+-exchanged montmorillonite samples exhibit maxima at higher temperatures in the i-PrOH (20 and 140°C) and t-BuOH (30, 90 and 110°C) desorption profiles but at the same temperatures for MeOH and n-PrOH. Mass spectroscopic analysis of the vapours desorbed from the alcohol-treated samples show that the low-temperature maxima in the alcohol desorption from the M3+-exchanged clays are due to unchanged alcohol, whilst those occurring at 80°C (t-BuOH), 110°C (i-PrOH) and 160°C (n-PrOH) are due, in the main, to alkene produced from the intramolecular dehydration of the respective alcohol. Changes in the IR spectra of the adsorbed alcohols occur at temperatures which are in accord with the mass spectral data. No mass spectral evidence was found for the formation of dialkylethers via the competing intermolecular process but dimerisation and oligomerisation of t-BuOH were observed.

Evaluation of low temperature hardiness of strawberry plants under field and controlled conditions

1993 ◽  
Vol 73 (4) ◽  
pp. 1123-1125 ◽  
Author(s):  
J. M. Turner ◽  
K. K. Tanino ◽  
C. Stushnoff
Keyword(s):  
Low Temperature ◽  
Key Words ◽  
Scoring System ◽  
Growth Habit ◽  
Field Conditions ◽  
Mother Plant ◽  
Fragaria Ananassa ◽  
Plant Survival ◽  
Field Growth ◽  
Mother Plants

When acclimated strawberry plants (Fragaria × ananassa Duch. ’Redcoat’) from the field were placed in a programmable freezer, mother strawberry crowns were as hardy or hardier than daughter crowns when frozen to −11 °C. However, under field conditions, daughter plants expressed consistently greater hardiness than mother plants. Mulching had no effect on daughter plant survival, whereas enhanced mother plant survival was observed. Field-growth habit of mother crowns may be the important factor for consistent winter survival under prairie conditions. A simple scoring system was developed to predict survival of strawberry plants. Key words. Fragaria × ananassa Duch., strawberry, crowns, low temperature hardiness

scholarly journals Structural and Quantitative Analysis of Three C-Glycosylflavones by Variable Temperature Proton Quantitative Nuclear Magnetic Resonance

2017 ◽  
Vol 2017 ◽  
pp. 1-5 ◽  
Author(s):  
Jing Liu ◽  
Yang Liu ◽  
Zhong Dai ◽  
Lan He ◽  
Shuangcheng Ma
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Conformational Equilibrium ◽  
Variable Temperature ◽  
Drug Analysis ◽  
Limit Of Quantification ◽  
Quantitative Nuclear Magnetic Resonance ◽  
Vt Nmr ◽  
Mass Balance Approach ◽  
Nuclear Magnetic

Quantitative nuclear magnetic resonance is a powerful tool in drug analysis because of its speed, precision, and efficiency. In present study, the application of variable temperature proton quantitative nuclear magnetic resonance (VT-1H-qNMR) for the calibration of three C-glycosylflavones including orientin, isoorientin, and schaftoside as reference substances was reported. Since there was conformational equilibrium due to the restricted rotation around the C(sp3)-C(sp2) bond in C-glycosylflavones, the conformational behaviors were investigated by VT-NMR and verified by molecular mechanics (MM) calculation. The VT-1H-qNMR method was validated including the linearity, limit of quantification, precision, and stability. The results were consistent with those obtained from mass balance approach. VT-1H-qNMR can be deployed as an effective tool in analyzing C-glycosylflavones.

scholarly journals H2 Evolution from H2O via O–H Oxidative Addition Across a 9,10-Diboraanthracene

2020 ◽  
Author(s):  
Jordan W. Taylor ◽  
William Harman
Keyword(s):  
Low Temperature ◽  
Lewis Acids ◽  
31P Nmr ◽  
Variable Temperature ◽  
Oxidative Addition ◽  
H2 Evolution ◽  
Chloride Exchange ◽  
11B Nmr

The boron-centered water reactivity of the boroauride complex ([Au(B2P2)][K(18-c-6)]; (B2P2, 9,10-bis(2-(diisopropylphosphino)- phenyl)-9,10-dihydroboranthrene) and its corresponding twoelectron oxidized complex, Au(B2P2)Cl, are presented. The tolerance of Au(B2P2)Cl towards H2O was demonstrated and subsequent hydroxide/chloride exchange was acheived in the presence of H2O and triethylamine to afford Au(B2P2)OH. Au(B2P2)]Cl and [Au(B2P2)]OH are poor Lewis acids as judged by the Gutmann-Becket method, with [Au(B2P2)]OH displaying facile hydroxide exchange between B atoms of the DBA ring as evidenced by variable temperature 31P NMR and low temperature 1H and 11B NMR. The reaction of the reduced boroauride complex [Au(B2P2)]– with 1 equivalent of H2O produces a hydride/hydroxide product, [Au(B2P2)(H)(OH)]–, that, upon addition of a second equivalent of H2O, rapidly evolves H2 to yield the dihydroxide compound, [Au(B2P2)(OH)2]–. [Au(B2P2)]Cl can be regenerated from [Au(B2P2)(OH)2]– via HCl·Et2O, providing a synthetic cycle for H2 evolution from H2O enabled by O–H oxidative addition at a diboraanthracene unit.

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