Sealed Glass Tube Research Articles

Development of a certified reference material for D-phenylalanine with evaluation of enantiomeric purity.

D-Phenylalanine (D-Phe) is a small chiral organic molecule that is both an important pharmaceutical intermediate and used as a calibrator for quantifying amino acids in liquid chromatography-circular dichroism. We have developed a process for a national certified reference material (CRM) for D-Phe following ISO 17034:2016. The identity of D-Phe was confirmed using mass spectrometry (MS) and nuclear magnetic resonance (NMR), infrared, and ultraviolet (UV) spectroscopy. The absolute optical conformation was also determined using circular dichroism (CD) spectroscopy and optical rotation measurements. Impurities were identified via liquid chromatography (LC) with a UV-Vis detector and a charged aerosol detector (CAD) and LC-MS. Both mass balance and quantitative NMR were employed for value assessment, and the associated uncertainty was evaluated. The certified purity was determined to be 0.995 ± 0.003g/g, a validation that was confirmed by CD using L-Phe CRM as a calibrator. Twenty milligrams of raw material was packed in sealed brown glass tubes for storage, and no inhomogeneity was observed. Stability tests revealed that the D-Phe CRM remained stable at -20°C for at least 26months, at 4°C for at least 14days, and at 25°C and 60°C for at least 7days. The D-Phe CRM can be used to ensure the accuracy and reliability of D-Phe quantitation in the pharmaceutical field and also as a calibrator to ensure traceability to the International System of Units (SI) for L-Phe quantitation and protein purity analysis using LC-CD methods. The approach outlined in this paper also has potential for use in the development of other chiral CRMs.

The effect of Xylocaine spray on suture material degradation.

To compare the tensile strength of fast absorbable Polyglactin 910 suture material when impregnated with various agents for local anesthesia and to investigate whether the presence of ethanol in Xylocaine spray could explain a potential reduction in tensile strength after use of Xylocaine spray. In all, 120 suture samples of Polyglactin 910 were divided into four groups of 30. These four groups were randomly impregnated with isotonic sodium chloride, isotonic sodium chloride plus Xylocaine spray, isotonic sodium chloride plus Xylocaine gel, or isotonic sodium chloride plus ethanol. After impregnation, the sutures were stored in sealed glass tubes in a heating cabinet at 37°C for 72 h. Thereafter, the tensile strength of these 120 samples was assessed by a universal tensile testing machine. The maximal force needed to break the suture material was recorded in newtons (N). Fast absorbable Polyglactin 910 suture material impregnated with Xylocaine spray or ethanol showed weakened tensile strength (mean values 11.40 and 11.86 N, respectively), whereas the specimens impregnated with Xylocaine gel or sodium chloride retained their tensile strength better (mean values 13.81 and 13.28 N, respectively; mean difference between Xylocaine gel and Xylocaine spray -2.41 N, P < 0.001). In this invitro experiment, ethanol and Xylocaine spray weakened the tensile strength of fast absorbable Polyglactin 910 sutures. Use of Xylocaine spray, which contains ethanol, for local anesthesia might lead to early breakdown of the suture material and wound rupture. The authors suggest caution when using Xylocaine spray in combination with fast absorbable Polyglactin 910 suture.

Chemical stability investigation of haloolefin refrigerants and their blends with lubricants

This paper examines the findings of highly accelerated life tests (HALT), conducted according to ASHRAE Standard 97 sealed glass tube methodology for R-123 like, R-134a like and R-410A/R-404A like lower global warming potential (GWP) alternatives. Additionally, possible chemical breakdown pathways are reviewed for the new haloolefin refrigerants. Note, compositions for the following blends are shown as percent by weight. For R-123 like refrigerants, R-1336mzz(Z), R-1336mzz(E), R-514A (74.7% R-1336mzz(Z)/25.3% R-1130(E)), R-1233zd(E), and R-1224yd(Z) were examined with and without lubricants. R-1233zd(E) and R-1224yd(Z) were evaluated with mineral oil and the rest were evaluated with polyalkylene glycol (PAG), polyolester (POE) and polyvinyl ether (PVE) lubricants. For R-134a like refrigerants, R-1234ze(E), R-450A (42% R-134a/58% R-1234ze(E)), R-515B (91.1% R-1234ze(E)/8.9% R-227ea), R-1234yf, R-513A (56% R-1234yf/44% R-134a), and R-516A (77.5% R-1234yf/8.5% R-134a/14.0% R-152a) were examined with and without PAG, POE, and PVE lubricants. For R-410A/R-404A like, R-454B (68.9% R-32/31.1% R-1234yf), R-454C (21.5% R-32/78.5% R-1234yf), R-455A (3.0% R-744/21.5% R-32/75.5% R-1234yf), and R-468A (3.5% R-1132a/21.5% R-32/75.0% R-1234yf) were also examined with PAG, POE and PVE lubricants. R-466A (49% R-32/11.5% R-125/39.5% CF3I) was part of this study but will not be covered since it does not contain a haloolefin component.

Charles Cagniard de Latour

Charles Cagniard de la Tour (1777-1859) was a French physicist and chemist that carried a detailed study of the phase transformation of a saturated liquid under the influence of pressure and temperature and proved that inside a sealed glass tube the fluid would become first a saturated vapor, and then turn continuously into superheated vapor, no matter what the pressure. He discovered the existence of a critical point, without using this concept. Cagniard de la Tour used a microscope to investigate the phenomenon of fermentation, particularly by beer yeast, its causes and effects, and proved that it was caused by a living organism and was not a pure chemical reaction. He also studied the pyrolysis of woody matter in a sealed atmosphere and showed that it resulted in the formation of tarry and sticky carbonaceous material, accompanied by a gas atmosphere.@font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-536870145 1107305727 0 0 415 0;}@font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-536859905 -1073732485 9 0 511 0;}p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Calibri",sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Calibri; mso-fareast-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;}.MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-family:"Calibri",sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Calibri; mso-fareast-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi;}div.WordSection1 {page:WordSection1;}

Heating temperature and water activity of alfalfa seeds affect thermal inactivation of Salmonella and maintaining seed viability

Sprouts have been involved in many outbreaks of salmonellosis where seeds were identified as the likely source of contamination. This study aimed to develop an effective heat treatment that could achieve a >5-log reduction of Salmonella inoculated on alfalfa seeds while maintaining seed viability and vigor. Effects of seeds' water activity (aw) and heat treatment temperature on Salmonella inactivation and seed viability were determined. Alfalfa seeds were dip-inoculated with a four-strain Salmonella cocktail and dried to aw of 0.05–0.20. The inoculated seeds were then placed in sealed glass tubes and heated at 65.9, 71.0, and 76.6 °C for up to 180 h. Increasing aw of seeds greatly improved thermal inactivation of Salmonella. For example, to achieve a >5-log reduction of Salmonella on seeds, treatment times of 140 and 60 h at 71.0 °C were required for aw of 0.1 and 0.2, respectively. Treatment temperature also greatly affected inactivation of Salmonella on alfalfa seeds. For example, to achieve a >5-log reduction of Salmonella on seeds with aw of 0.2, treatment times of 180 and 60 h were required for temperatures of 65.9 and 71.0 °C, respectively. Seeds' aw was critical for preserving seed viability. When seeds were treated at 71.0 °C for 60 h, increasing aw from 0.1 to 0.2 decreased the sprout yield ratio from 103.9 % to 73.7 %. Treatment of seeds with aw of 0.1 at 71.0 °C was found to be optimum for achieving a desirable Salmonella inactivation level while maintaining seed viability, resulting in 4.2 and 6.0 log reductions of Salmonella and yield ratios of 100.7 % and 96.1 % after 100- and 140-h treatments, respectively. This optimum heat treatment was compared with the traditional 20,000-ppm chlorine wash in terms of Salmonella inactivation and preservation of seed viability and found to be a far superior disinfection method. The chlorine treatment achieved 1.8 and 2.0 log reductions of Salmonella and yield ratios of 70.9 % and 65.1 % after 15- and 20-min treatments, respectively.

Growth of Pentacene Crystals by Naphthalene Flux Method.

We report the crystal growth of pentacene from a solution of naphthalene. The solubility of pentacene in naphthalene was evaluated by optical absorption at elevated temperature. The crystal growth was performed in an H-shaped sealed glass tube or metal vessels sealed with ultrahigh-vacuum compatible flanges placed in heated two-zone aluminum blocks. The obtained crystals had a single-crystal-like appearance and flat surface. They were made of aligned microtwins of the “bulk type” (interlayer spacing 14.5 Å) polymorph.

Cold Plasma Discharge Tube Enhances Antitumoral Efficacy of Temozolomide.

Glioblastoma (GBM) is a fatal human brain tumor with a low survival rate. Temozolomide (TMZ) has been widely used in GBM therapy with noticeable side effects. Cold plasma is an ionized gas that is generated near room temperature. Here, we demonstrated the enhancement therapeutic efficacy of TMZ via using a cold plasma source based on nonequilibrium plasma in a sealed glass tube, named a radial cold plasma discharge tube (PDT). The PDT affected glioblastoma cells' function just by its electromagnetic (EM) emission rather than any chemical factors in the plasma. The PDT selectively increased the cytotoxicity of TMZ on two typical glioblastoma cell lines, U87MG and A172, compared with normal astrocyte cell line hTERT/E6/E7 to some extent. Furthermore, on the basis of a patient-derived xenograft model, our preliminary in vivo studies demonstrated the drastically improved mean survival days of the tumor-barrier mice by more than 100% compared to control. The PDT is not only independent of continuous helium supply but is also capable of resisting the interference of environmental changes. Thus, the PDT was a stable and low-cost cold atmospheric plasma source. In short, this study is the first to demonstrate the promising application of PDTs in GBM therapy as a noninvasive and portable modality.

Effect of Al2O3 scales from pre-oxidation on the microstructural evolution and phase transition of NiAlHf coatings at 1200 °C

The pre-oxidation treatment was conducted for NiAlHf coatings in a sealed glass tube with low oxygen atmosphere at 900 °C. The microstructure evolution and oxidation resistance of the NiAlHf coatings with and without pre-oxidation treatment were systematically investigated via isothermal oxidation at 1200 °C for up to 200 h in laboratory air. The results revealed that a dense Al2O3 scale was formed on the NiAlHf coating surface after pre-oxidation treatment, which could effectively reduce oxygen pressure and Al consumption on the NiAlHf coating surface. Furthermore, the NiAlHf coating microstructure evolution was effectively delayed from β-NiAl to the γ′-Ni3Al phase due to Al2O3 scale formation by pre-oxidation treatment. Oxidation resistance of the NiAlHf coating with pre-oxidation treatment was improved after 200 h of oxidation, of which the oxidation rate constant was enhanced by 40% compared to the NiAlHf coating without pre-oxidation treatment. The mechanism of oxygen diffusion inhibition by pre-oxidation was also discussed. This research was beneficial to understand the effect of pre-treatment on the NiAHf coating microstructure evolution and could further guide the improvement of the oxidation resistance of NiAlHf coatings for long-term oxidation.

Direct Proof of Volatile and Adsorbed Hydrocarbons on Solid Catalysts by Complementary NMR Methods

AbstractIn this paper, both volatile and strongly adsorbed products of heavy hydrocarbon conversion on a zeolite were investigated by gas‐phase and solid‐state NMR. For this purpose, the reactions were carried out in sealed glass tubes under vacuum to collect the volatile reaction products. This procedure is demonstrated for pure 2‐ethylphenol conversion on ultra‐stabilized zeolite Y leading to both the formation of light alkanes and deoxygenation products. The above‐mentioned method is useful to improve the understanding of heavy hydrocarbon conversion under batch conditions.

Structural Characterization of Amorphous VS4 and Its Amorphous Phase Transformation during Li Insertion

Vanadium sulfide (VS4) is one of the promising positive electrode materials for high capacity lithium ion secondary batteries. In this study, we prepared an amorphous VS4 (a-VS4) by mechanical treatment of the crystalline VS4 (c-VS4) and characterize its local structure. Furthermore, its lithium insertion/extraction behavior was investigated using solid-state nuclear magnetic resonance (NMR), X-ray pair distribution function (PDF), and Raman spectroscopy analyses.Crystalline VS4 was synthesized from V2S3 (99%, Kojundo Chemical Lab.) and S (99.9%, Wako).1 The mixture was heated in a sealed glass tube under vacuum at 400 °C for 12 h. Then, the amorphous VS4 was prepared from the crystalline sample by mechanical milling for 40 h at 270 rpm. A working electrode was prepared from a mixture of the active material (a-VS4), conductive carbon, and Teflon binder in a weight ratio of 59:29:12. Coin-type or laminate-type cells were assembled in an Ar-filled glove box. The cells were cycled between 1.5 and 2.6 V at a constant current density of 59.8 mA g–1 using a TOSCAT-3100 battery-testing system (Toyo System). They were then carefully disassembled at selected discharge/charge states in the glove box and rinsed with dimethyl carbonate (DMC) to remove the residual electrolyte solution.Local structures of c-VS4 and a-VS4 were characterized and the structural changes of the electrode samples were examined by NMR spectroscopy, X-ray PDF analyses, and Raman spectroscopy. Operando 7Li NMR measurements were performed to study the Li insertion/extraction process under electrochemical operation.2 It is known that c-VS4 has a unique structure, in which the Peierls-distorted one-dimensional chains of V-V bonds along the c axis are loosely connected to each other through van der Waals interactions. We confirmed that a-VS4 shows a chain structure similar to that of c-VS4. The chain structure is found to change drastically during the Li insertion process to form amorphous Li3VS4, where the V ions become tetrahedrally coordinated by S ions. The valence states of V and S ions simultaneously change from V4+ and S– (a-VS4) to V5+ and S2– (a-Li3VS4), respectively. When the Li insertion proceeds further (i.e., a-Li3+d VS4), the valence state of V ion is reduced, and a broad 7Li NMR peak shifts to higher frequencies (Fig. 1). After the 1st cycle, the amorphous VS4 recovers the chain-like structure although it is highly disordered. It is also found that the conversion reaction to metallic V and Li2S are observed when the cell is discharged to 0.2 V.This study indicates that the Li insertion/extraction process of the amorphous sulfur-rich transition metal (TM) sulfides such as a-VS4 and a-TiS4 3 involves the amorphous-amorphous phase transformation, which is related to the changes in the bonding nature of sulfide species and the coordination number of TM ions. The amorphous host structure can accommodate these modifications, which is clearly different from the Li insertion/extraction mechanism in crystalline electrode materials.This work is based on results obtained from a project, “Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 (RISING2)”, JPNP16001, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References Koganei et al., Solid State Ionics, 323, 32-36 (2018).Shimoda et al., RSC adv. 9, 23979-23985 (2019).Sakuda et al., J. Am. Chem. Soc., 139, 8796-8799 (2017). Figure 1

Variations of TSNA Levels in Tobaccos Upon Heating at Moderate Temperatures

Summary Tobacco-specific nitrosamines (TSNAs) including nitrosoanabasine (NAB), nitrosoanatabine (NAT), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and nitrosonornicotine (NNN) are naturally present at trace levels in tobacco. During tobacco processing, preparation of expanded tobacco, and when tobacco is used in heat-not-burn type cigarettes, the tobacco is exposed to different degrees of heat. Heating of tobacco has been reported in the literature to increase the level of TSNAs. Since the increase of TSNAs in heated tobacco is still not well understood, the present study evaluated TSNA levels in six types of tobacco as a function of moderate heat exposure. These tobaccos included: flue-cured lower stalk, flue-cured upper stalk (US), Burley lower stalk, Burley upper stalk (US), and two Oriental blends (Turkey, Greece, Bulgaria, Northern Republic Macedonia). Heating was performed in sealed glass tubes at oven temperatures of 100 °C, 150 °C, 200 °C, and 250 °C for time intervals of 2 min and 5 min. The temperatures inside the glass tubes were lower than the targets and were monitored separately as a function of glass tube heating. The study showed no meaningful differences within tobacco type (by stalk position) but showed considerable differences in the levels of TSNAs between different tobaccos, with the Burley tobaccos having the highest levels, and the Orientals the lowest. For all tobacco types, TSNAs increase to some extent when temperature increases. For 2-min heating, the increase in TSNAs is relatively small up to about 200 °C, but the levels almost double when the oven temperature increases to 250 °C. For 5-min heating, the increase in TSNAs starts at about 150 °C with a maximum at 200 °C which can reach more than double the initial TSNA level. Longer heating at 250 °C (5 min) starts to cause TSNAs decomposition and the levels are reduced.

Structural Characterization of Amorphous VS4 and Its Amorphous Phase Transformation during Liinsertion

Vanadium sulfide (VS4) is one of the promising positive electrode materials for high capacity lithium ion secondary batteries. In this study, we prepared an amorphous VS4 (a-VS4) by mechanical treatment of the crystalline VS4 (c-VS4) and characterize its local structure. Furthermore, its lithium insertion/extraction behavior was investigated using solid-state nuclear magnetic resonance (NMR), X-ray pair distribution function (PDF), and Raman spectroscopy analyses.Crystalline VS4 was synthesized from V2S3 (99%, Kojundo Chemical Lab.) and S (99.9%, Wako).1 The mixture was heated in a sealed glass tube under vacuum at 400 °C for 12 h. Then, the amorphous VS4 was prepared from the crystalline sample by mechanical milling for 40 h at 270 rpm. A working electrode was prepared from a mixture of the active material (a-VS4), conductive carbon, and Teflon binder in a weight ratio of 59:29:12. Coin-type or laminate-type cells were assembled in an Ar-filled glove box. The cells were cycled between 1.5 and 2.6 V at a constant current density of 59.8 mA g–1 using a TOSCAT-3100 battery-testing system (Toyo System). They were then carefully disassembled at selected discharge/charge states in the glove box and rinsed with dimethyl carbonate (DMC) to remove the residual electrolyte solution.Local structures of c-VS4 and a-VS4 were characterized and the structural changes of the electrode samples were examined by NMR spectroscopy, X-ray PDF analyses, and Raman spectroscopy. Operando 7Li NMR measurements were performed to study the Li insertion/extraction process under electrochemical operation.2 It is known that c-VS4 has a unique structure, in which the Peierls-distorted one-dimensional chains of V-V bonds along the c-axis are loosely connected to each other through van der Waals interactions. We confirmed that a-VS4 shows a chain structure similar to that of c-VS4. The chain structure is found to change drastically during the Li insertion process to form amorphous Li3VS4, where the V ions become tetrahedrally coordinated by S ions. The valence states of V and S ions simultaneously change from V4+ and S– (a-VS4) to V5+ and S2– (a-Li3VS4), respectively. When the Li insertion proceeds further (i.e., a-Li3+d VS4), the valence state of V ion is reduced, and a broad 7Li NMR peak shifts to higher frequencies (Fig. 1). After the 1st cycle, the amorphous VS4 recovers the chain-like structure although it is highly disordered. It is also found that the conversion reaction to metallic V and Li2S are observed when the cell is discharged to 0.2 V.This study indicates that the Li insertion/extraction process of the amorphous sulfur-rich transition metal (TM) sulfides such as a-VS4 and a-TiS4 3 involves the amorphous-amorphous phase transformation, which is related to the changes in the bonding nature of sulfide species and the coordination number of TM ions. The amorphous host structure can accommodate these modifications, which is clearly different from the Li insertion/extraction mechanism in crystalline electrode materials.

Émile Meyerson and mass conservation in chemical reactions: a priori expectations versus experimental tests

In his celebrated historic-epistemological work Identite et realite, Emile Meyerson claimed that the scientific conservation principles were first suggested and accepted for philosophical reasons, and only afterwards were submitted to experimental tests. One of the instances he discussed in his book is the principle of mass conservation in chemical reactions. Meyerson pointed out that several authors, from Antiquity to Kant, accepted the idea of quantitative conservation of matter; and Lavoisier himself was strongly influenced by a priori ideas, using this principle instead of attempting to test it. This paper will review Meyerson’s claim and historic evidence, focusing especially the late nineteenth and early twentieth century, when the principle of mass conservation was tested in highly accurate experiments. Instead of confirming the principle, some of those experiments led to the detection of anomalies. Hans Landolt, for instance, noticed that there were some small violations of the principle. He observed mass variations of about 10−6 in chemical reactions produced in hermetically sealed glass tubes. Since Landolt was a famous chemist, his results produced a strong response. Several researchers repeated his experiments, with different results. Landolt himself improved his experiments, with a balance that could detect mass changes of 10−7. After changes of the experimental procedure, the chemical reactions did not show significant mass changes. There was not, however, any “crucial experiment” “proving” that mass was conserved. The observed anomalies were set aside mainly by theoretical reasons, after the discovery of radioactivity and the development of the theory of relativity.

H/D Exchange Using Hot Heavy Water.

Metal-catalyzed H/D exchange in hydrothermal deuterium oxide, performed in an autoclave using external heating or in a sealed glass tube under microwave irradiation, was shown to be an efficient method for preparing various deuterium-labeled compounds. Phosphonium salts for the Wittig reaction were deuterated at the α-position in the presence of MS 4A under microwave irradiation; primary alcohols and primary/secondary amines were deuterated at the α-position in the presence of ruthenium catalyst under microwave irradiation; metal-catalyzed direct C-H functionalizations on sp³ and sp² carbon gave the corresponding fully deuterated products under hydrothermal conditions. These methods gave various deuterium-labelled compounds efficiently using D₂O as a D-atom source.

Cosublimation: A Rapid Route Toward Otherwise Inaccessible Halogen-Bonded Architectures

Several synthetic techniques are available for the preparation of halogen-bonded adducts, including traditional solvent-evaporation methods and mechanochemistry. With the intention of reducing solvent usage and experimental times, we establish cosublimation as a synthetic technique for preparing halogen-bonded cocrystals, focusing on the C–I···N motif involving nitrogen-containing heterocycles. We selected four common halogen-bond donors (I2, 1,4-diiodobenzene, 1,4-diiodotetrafluorobenzene, 1,3,5-trifluoro-2,4,6-triiodobenzene) and four halogen-bond acceptors (2,3,5,6-tetramethylpyrazine, 1,4-diazabicyclo[2.2.2]octane, 2,2′-bipyridyl, 1-adamantanecarbonitrile), by virtue of their range in volatility, and explored all 16 combinations via the following methods: solvent evaporation, overnight cosublimation in a sealed glass tube using a two-zone furnace, and expedited cosublimation in a vacuum sublimation apparatus. We show that the raw crystals obtained from overnight cosublimation are of suitable quality f...

Preliminary assessment of stable nitrogen and oxygen isotopic composition of USGS51 and USGS52 nitrous oxide reference gases and perspectives on calibration needs.

Despite a long history and growing interest in isotopic analyses of N2 O, there is a lack of isotopically characterized N2 O isotopic reference materials (standards) to enable normalization and reporting of isotope-delta values. Here we report the isotopic characterization of two pure N2 O gas reference materials, USGS51 and USGS52, which are now available for laboratory calibration (https://isotopes.usgs.gov/lab/referencematerials.html). A total of 400 sealed borosilicate glass tubes of each N2 O reference gas were prepared from a single gas filling of a high vacuum line. We demonstrated isotopic homogeneity via dual-inlet isotope-ratio mass spectrometry. Isotopic analyses of these reference materials were obtained from eight laboratories to evaluate interlaboratory variation and provide preliminary isotopic characterization of their δ15 N, δ18 O, δ15 Nα , δ15 Nβ and site preference (SP ) values. The isotopic homogeneity of both USGS51 and USGS52 was demonstrated by one-sigma standard deviations associated with the determinations of their δ15 N, δ18 O, δ15 Nα , δ15 Nβ and SP values of 0.12 mUr or better. The one-sigma standard deviations of SP measurements of USGS51 and USGS52 reported by eight laboratories participating in the interlaboratory comparison were 1.27 and 1.78 mUr, respectively. The agreement of isotope-delta values obtained in the interlaboratory comparison was not sufficient to provide reliable accurate isotope measurement values for USGS51 and USGS52. We propose that provisional values for the isotopic composition of USGS51 and USGS52 determined at the Tokyo Institute of Technology can be adopted for normalizing and reporting sample data until further refinements are achieved through additional calibration efforts.

Structural characterizations, thermal behavior, and electrical measurements of the amidosulfonic acid catalyzed thermal ring‐opening polymerization of substituted cyclotriphosphazene in 1,2,4‐trichlorobenzene solution

AbstractIn this study, we aimed to design and synthesize poly[3,3,5,5‐tetrachloro‐1,1‐bis{spiro(2′,2″‐dioxy‐1′‐1″‐biphenylyl)}phosphazene] (3) in order to obtain a polymer which is resistant to moisture and hydrolysis and also contains chlorine atoms within its structure. For this reason, the polymerization experiments of polymer 3 were performed using ring‐opening polymerization (ROP) of 3,3,5,5‐tetrachloro‐1,1‐bis[spiro(2′,2″‐dioxy‐1′,1″‐biphenylyl)]cyclotriphosphazene (2) at different time and temperature. In particular, ROP of 2 was successful in 1,2,4‐trichlorobenzene solution in the presence amidosulfonic acid and promoter (CaSO4.2H2O) in sealed glass tubes under vacuum for 60, 72, and 96 hr at 220°C. The changes in molecular weight and molecular weight distribution of the polymer 3 were noted as a function of polymerization reaction time. The structure of polymer 3 was approved by gel permeation chromatography (GPC), FT‐IR, NMR spectroscopy (31P, 1H, 13C), and elemental analysis. The glass transition temperature (Tg) and thermal stability of polymer 3 were determined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Dielectric properties of 3 were determined as a function of frequency at five different temperatures by an impedance analyzer. The activation energy of polymer 3 was calculated using Flynn–Wall–Ozawa (F–W–O) integral method.

Reversible Ligand Protonation of a Mn(I) PCP Pincer Complex To Afford a Complex with an η2-Caryl–H Agostic Bond

The first manganese PCP pincer complex, [Mn(PCPNEt-iPr)(CO)3], was obtained by treating [Mn2(CO)10] and 2-chloro-N1,N3-bis(diisopropylphosphanyl)-N1,N3-diethylbenzene-1,3-diamine (P(C-Cl)PNEt-iPr) in CH3CN under solvothermal conditions in a sealed microwave glass tube for 8 h at 140 °C. Protonation of this complex with HBF4·Et2O leads to the formation of the cationic Mn(I) complex [Mn(κ3P,CH,P-P(CH)PNEt-iPr)(CO)3]BF4, which features an η2-Caryl–H agostic bond. There was no evidence for the formation of a Mn(III) hydride species. The agostic C–H bond is comparatively acidic, and even relatively weak bases, such as NEt3, deprotonate this bond to re-form the starting material [Mn(PCPNEt-iPr)(CO)3]; protonation is fully reversible. Substitution of one CO ligand was achieved upon treatment with NO+, affording the cationic complex [Mn(PCPNEt-iPr)(CO)2(NO)]+, where the two CO ligands are trans to one another.

Vapor-Phase Growth and Structural Characterization of Single Crystals of Magnesium Doped Two-Dimensional Fullerene Polymer Mg2C60

Single crystals of magnesium doped fullerene polymer Mg2C60 can be directly grown via a binary vapor-phase mixture of Mg and C60, in sealed glass tubes at elevated temperatures. This is the first single crystal, in metal-doped two-dimensional fullerene polymers, which enables precise X-ray structural refinement. The Mg2C60 crystallizes in a monoclinic space group, I2/m, with lattice parameters of a = 9.324(2) A, b = 9.041(2) A, c = 14.817(3) A, and β = 91.699(10)°. A Mg atom is located at each tetrahedral fullerene ball interstice, where the shortest Mg–C distance is 2.341(2) A, suggesting that the Mg cation is in van der Waals contact with carbon p orbitals. The precise structure of the two-dimensional fullerene polymer network is characterized by comparison with structural data reported previously on powder samples.

Investigation into degradation properties of low-viscosity silicone liquid/paper insulation systems for diagnosis in liquid-immersed transformers

Thermal and electrical degradation properties in low-viscosity (20 mm2/s, (20 cSt) at 25 °C) silicone liquid and insulation paper were investigated to improve reliability and to enable preventive maintenance technology in transformers. Heat-accelerated degradation in samples of 20 cSt silicone liquid and insulation paper in sealed glass tubes with copper, silicon steel, and pressboard was examined to replicate the environment of the transformer tank. After the examinations, the tensile strength of the paper was measured, and the quantity of decomposition compounds was also measured. It was concluded that diagnosing faults by analyzing decomposition compounds with silicone liquid should be possible in the same way that it is with conventional mineral oil.