Raman Investigation of the Low Temperature Phase Transitions in Monoclinic TlReO4

The Raman spectrum of monoclinic TlReO₄ is presented together with a factor group analysis and assignment of the bands. The phase transitions of monoclinic TlReO₄ is investigated below room temperature, and two phase transitions were identified between room temperature and 90 K. The room temperature monoclinic phase was converted to the orthorhombic phase at 170 K upon cooling, and to the tetragonal phase at 150 K. Upon heating back to room temperature the tetragonal phase persisted until the orthorhombic phase could be identified at 210 K and 220 K. From 230 K to room temperature the monoclinic phase could again be observed.     

Willgerodt-Kindler reaction at room temperature: Synthesis of thioamides from aromatic aldehydes and cyclic secondary amines

A simple method for the synthesis of thioamide derivatives in DMSO at room temperature and at 120 °C has been developed. Total 27 compounds were prepared under both conditions via a one-pot, three component reaction between substituted aromatic aldehydes, elemental sulfur powder, and cyclic secondary amines. By optimizing the mole ratio of sulfur powder and amines, we have successfully carried out Willgerodt-Kindler reaction of aromatic aldehydes at room temperature. At 120 °C, it is catalyst free reaction with lower reaction time whereas at room temperature, due to the additional amine molecule, Willgerodt-Kindler reaction of aromatic aldehydes is successfully carried out at room temperature. On gram-scale, the reaction is successfully attempted under both conditions with good yields.     

Change with temperature of the ESR spectra of peroxy radicals trapped in irradiated polytetrafluoroethylene

The ESR spectra of peroxy radicals in irradiated powders and oriented samples of polytetrafluoroethylene (PTEE) have been measured with a K-band spectrometer, and the principal values and directions of the g tensor were determined both at room temperature and at 77°K. In contrast to the spectra of the usual peroxy radicals, those trapped in γ-irradiated PTFE exhibited an ESR spectrum apparently having a larger principal value for g⊥ than for g∥ when measured at room temperature, although the normal principal values were observed at 77°K. As for the directions of the principal axes, g∥ was directed along the chain axis at room temperature and was perpendicular to the chain axis at 77°K. From the temperature change of the g tensor and the line shapes in the oriented samples, it is shown that the observed temperature change of the spectra is due to rapid rotation at room temperature around the chain axis rather than around the C? O bond axis. Assuming this, the apparent principal values of the g tensor at room temperature were calculated from the g tensor obtained at 77°K. for the rigid state, and the results are in good agreement with observations at room temperature. A structure for the peroxy radicals is also proposed. In addition, the spectral line shape function for the uniaxially oriented samples has been derived.     

Near and vacuum ultraviolet absorption spectra of polycrystalline and amorphous evaporated films of naphthacene,pentacene, perylene and coronene

The near- and vacuum-ultraviolet absorption spectra of polycrystalline and amorphous films of naphthacene, pentacene, perylene evaporated on substrate at room and low temperatures have been measured at room temperature. The changes in the spectra are explained in terms of the loss of molecular orientation and the change in Davydov splitting. The spectra for coronene evaporated at room temperature are also reported.     

金属铌表面氧化物的热稳定性研究

在早期人们认为金属铌只有在高温下才氧化,后来用表面分析方法对金属铌氧化作用的研究结果表明,它在室温下也能氧化。本文用X光电子能谱(XPS)研究了金属铌的氧化行为及其氧化物的热稳定性,发现金属铌的室温表面Nb_2O_5在真空中加热时能转变成金属Nb及其低价氧化物,而高温表面Nb_2O_5在同样条件下则不能转变成金属或其低价氧化物。     

Saponin Stabilization via Progressive Freeze Concentration and Sterilization Treatment

Saponin is a biopesticide used to suppress the growth of the golden apple snail population. This study aims to determine the stabilized conditions for saponin storage. The maceration process was used for saponin extraction, and for saponin concentration, progressive freeze concentration (PFC) was used. Afterwards, stability analysis was performed by storing the sample for 21 days in two conditions: Room temperature (26 °C) and cold room (10 °C). The samples kept in a cold room were sterilized samples that undergo thermal treatment by placing the sample in the water bath. The non-sterilized samples were kept in room temperature condition for 21 days. The results showed that saponin stored in the cold room (sterilized sample) has low degradation with higher concentration than those stored at room temperature in stability analysis with the highest saponin concentration (0.730 mg/mL) at a concentration temperature of −6 °C and concentration time of 15 min. The lowest saponin concentration obtained by saponin stored at room temperature (non-sterilized sample) is 0.025 mg/mL at a concentration temperature of −6 °C and concentration time of 10 min. Thus, the finding concluded that saponin is sensitive to temperature. Hence, the best storage condition to store saponin after thermal treatment is to keep it in a cold room at 10 °C.     

Living polymerization and block copolymerization of alpha-olefins by an amine bis(phenolate) titanium catalyst

An amine bis(phenolate) dibenzyl titanium complex having a methoxy donor on a side arm leads, upon activation with tris(pentafluorophenyl)borane, to unique living properties in alpha-olefin polymerization: exceptionally high molecular weight poly(1-hexene) is obtained in a living fashion at room temperature, living polymerization of 1-hexene is obtained above room temperature, and block copolymerization of 1-hexene and 1-octene at room temperature is described as well.     

Influence of base dynamics on the conformational properties of DNA: Observation of static conformational states in rigid duplexes at 77 K

Time-resolved fluorescence of 2-aminopurine-labeled DNA duplexes at 77 K reveals the relationship between base dynamics and the conformational heterogeneity that results in the well-known multiexponential fluorescence decay at room temperature. The conformation that exhibits rapid interbase charge transfer at room temperature is not populated in the frozen duplex at 77 K; this geometry is accessed by thermal motion of the bases, it is not a minimum energy structure of the duplex. Three photophysically distinct conformational states persist in the frozen duplex; these are minimum energy structures and do not interconvert at room temperature on the time scale of the 2-aminopurine excited-state lifetime.     

舰船用无溶剂环氧涂料常温释放物及高温热解物分析与评价

涂料作为舰船舱室及其部件的内部防护装饰材料已广泛地应用于舰船舱室,科技的发展使得涂料更新换代的步伐加快。舰船舱室经常处于全封闭状态,为减少舱室空气污染对船员的身心健康和战术技术发挥的不良影响,故对舰船舱室大气环境质量提出了更高更新的要求,因此舰船用涂料的筛选尤为重要。涂料作为常用的一种非金属材料其挥发物具有一定的毒性,尤其是对一些新的、毒性不明的涂料,必须先对其进行使用条件下的安全性评价,以便确定其可否应用于舰船舱室之中。本实验根据有关标准对舰船用低毒无溶剂环氧涂料常温释放物及高温热解物进行分析,并对其作卫生学评价,从而为舰船设计、建造部门在筛选艇用涂料方面提供可靠的科学依据。     

THE EFFECT OF IRRADIATION ON THE POLYETHERKETONE WITH CARDO GROUP

The effects of irradiation on the polyetherketone with cardo group (PEK-C) were studied. It was found that PEK-C can be crosslinked by irradiation under vacuum, while degradation reaction occurred in PEK-C at room temperature in the presence of air. Moreover. it was also found that Ts value of the crosslinked PEK-C at high temperature is higher than that at room temperature in the case of the same gel content, whose value is about 8℃higher than that of unirradiated PEK-C. The gelation dose of PEK-C at 300℃under vacuum is 1.5×10~4 Gy, which is about hundred times smaller than that at room temperature.     

Supramolecular gelation of alcohol and water by synthetic amphiphilic gallic acid derivatives

The supramolecular organogelation of alcohols was observed in relatively hydrophobic amphiphiles with a short oligo(ethylene glycol) unit and three long alkyl chains at room temperature, while the hydrogelation occurred in more hydrophilic gelators with a longer poly(ethylene glycol) unit and two long alkyl chains at various temperatures. When a hot aqueous solution of some of the synthetic hydrogelators was cooled down, the supramolecular hydrogel was formed at room temperature. In some other amphiphiles with less intermolecular interactivity in water at room temperature, a reverse phase transition of sol to gel was observed by elevating the temperature of their aqueous systems, especially below a physiological temperature, 37 °C. The supramolecular hydrogelation at a low or high temperature was dependent on a slight molecular modification of the synthetic amphiphiles.     

ESR investigation of a stable trapped hydrogen atom in X-ray-irradiated beta-tricalcium phosphate at room temperature

A stable trapped hydrogen atom in X-ray-irradiated beta-tricalcium phosphate (beta-Ca3(PO4)2, beta-TCP) was successfully detected at room temperature. This hydrogen atom is stable at ambient temperature for several months. Hyperfine structure of the hydrogen atom and superhyperfine structures of the two phosphorus atoms were observed by means of electron spin resonance (ESR) spectroscopy. Electron spin-echo (ESE) of the hydrogen atom was observed in X-ray-irradiated beta-TCP. At room temperature, relaxation times of the hydrogen atom in X-ray-irradiated beta-TCP were very long (phase memory time TM = 19.4 mus, spin-lattice relaxation time T1 = 75.8 mus) compared with those of usual paramagnetic species. The most important facts are the detections of ESE and electron spin-echo envelope modulation (ESEEM) at room temperature. At room temperature, the observations of ESE and ESEEM and the estimations for the relaxation times (TM, T1) of the hydrogen atom were carried out for the first time until now. TM was able to be measured from room temperature to 9 K. The short relaxation time TM below 20 K might be explained by the quantum tunneling effect of the hydrogen atom. Fourier transformation of the electron spin-echo envelope modulation (FT-ESEEM) at room temperature suggests the overlapping of the wave functions between the hydrogen atom and the two phosphorus atoms. The site of the hydrogen atom in the X-ray-irradiated beta-TCP was discussed on the basis of the continuous wave ESR (CW-ESR) and pulse-ESR analyses.     

Phosphorimetric Determination of Polycyclic Aromatic Hydrocarbons in Clinoptilolite-Filled Fibers at Room Temperature

The phosphorescence of polycyclic aromatic hydrocarbons (PAHs) adsorbed on natural zeolite (clinoptilolite) and clinoptilolite-filled acrylic fibers was studied at room temperature. The optimal conditions were selected for the phosphorescence of PAHs extracted from water and water–dioxane solutions at room temperature using clinoptilolite-filled fibers. The phosphorescence of PAHs in the clinoptilolite-filled fibers at room temperature is characterized by a high quantum yield and long lifetimes of PAH triplet states, as was the case at low temperatures (77 K). The results obtained indicate that the adsorbents used offer promise for the analytical chemistry of PAHs.     

An expeditious synthesis of isoxazoline using cetyltrimethylammonium cerium nitrate: A phase transferring oxidative 1, 3-diplor cycloaddition

An expeditious and effective method for synthesis of isoxazoline from aldoximes and activated alkenes using cetyltrimethylammonium cerium nitrate at room temperature is described. Reaction was completed within short time period in high yields at room temperature.     

Hierarchical Ni−Al hydrotalcite supported Pt catalyst for efficient catalytic oxidation of formaldehyde at room temperature

Catalytic oxidation at room temperature is recognized as the most promising method for formaldehyde (HCHO) removal. Pt-based catalysts are the optimal catalyst for HCHO decomposition at room temperature. Herein, flower-like hierarchical Pt/NiAl-LDHs catalysts with different [Ni²⁺]/[Al³⁺] molar ratios were synthesized via hydrothermal method followed by NaBH₄ reduction of Pt precursor at room temperature. The flower-like hierarchical Pt/NiAl-LDHs were composed of interlaced nanoplates and metallic Pt nanoparticles (NPs) approximately 3–4 nm in diameter were loaded on the surface of the Pt/NiAl-LDHs with high dispersion. The as-prepared Pt/NiAl21 nanocomposite was highly efficient in catalyzing oxidation of HCHO into CO₂ at room temperature. The high activity of the hierarchical Pt/NiAl21 nanocomposite was maintained after seven recycle tests, suggesting the high stability of the catalyst. Based on in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies, a reaction mechanism was put forward about HCHO decomposition at room temperature. This work provides new insights into designing and fabricating high-performance catalysts for efficient indoor air purification.     

Potassium Fluoride on Alumina: One-Pot Synthesis of N-Allyl Trichloroacetamides by Cascade Condensation-Sigmatropic Rearrangement

Allyl alcohols adsorbed on Al₂O₃-KF at room temperature reacted with trichloroacetonitrile and gave rearranged trichloroacetamides at room temperature, in one pot reaction.     

Benzhydryl as an efficient selective nitrogen protecting group for uracils

Regioselective N-substitution of the less active nitrogen within uracil analogues has been achieved following preliminary N-protection at the more active N-position with a benzhydryl protecting group. This protecting group is stable to concentrated HCl (aqueous) at reflux temperature, TFA at room temperature, and Pd-C-catalyzed normal pressure hydrogenation at room temperature; the benzhydryl group can be removed quantitatively and selectively with a 10% triflic acid solution in TFA at 0 degree C.     

Role of surface hydroxyl groups in promoting room temperature CO sensing by Pd-modified nanocrystalline SnO2

SnO₂/Pd nanocomposites were synthesized via sol-gel method followed by variable processing procedures. The materials are sensitive to CO gas in the concentration range 2-100 ppm at room operating temperature. It was shown that modification of nanocrystalline tin dioxide by Pd changes the temperature dependence of sensor response, decreasing the temperature of maximal signal. To understand the mechanism of room temperature CO sensitivity, a number of SnO₂/Pd materials were characterized by XRD, TEM, BET, XPS and TPR techniques. From the results of FTIR, impedance and sensing measurements under variable ambient conditions it was concluded that improvement in CO sensitivity for Pd-modified SnO₂ is due to alteration of CO oxidation pathway. The reaction of CO with surface OH-groups at room temperature was proposed, the latter being more reactive than oxygen species due to the possible chain character of the reactions. It was proposed that Pd additive may initiate chain processes at room temperature.     

Lewis acid-mediated Michaelis-Arbuzov reaction at room temperature: a facile preparation of arylmethyl/heteroarylmethyl phosphonates

A facile preparation of arylmethyl and heteroarylmethyl phosphonate esters was achieved involving a Lewis acid mediated Michaelis-Arbuzov reaction at room temperature. Interaction of arylmethyl halides/alcohols with triethyl phosphite in the presence of Lewis acid at room temperature afforded phosphonate esters in good yields.     

Molecular Iodine–Catalyzed Synthesis of 1,2,3,6-Tetrahydropyrimidines

A short and simple synthesis of tetrahydropyrimidine derivatives were accomplished in good to excellect yields at room temperature by the reaction of dimethylacetalynedicarboxylate, aniline, and formaldehyde in the presence of 5 mol% of molecular iodine at room temperature in ethanol for 5 min.