bluuebunny/crossref_metadata_2025_split huggingface dataset:
The computed force constants and vibrational spectra of toluene
Authors: Xie Yaoming , Boggs James E. 
Published: December 2004

AbstractThe complete harmonic force field and dipole moment derivatives have been computed for toluene at the Hartree‐Fock level using a 4‐21G basis set. The six scale factors optimized for benzene were used to scale the computed harmonic force constants of toluene. The vibrational frequencies of toluene computed from this scaled quantum mechanical force field are quite good. After a correction was made to two previously proposed spectral assignments, the mean deviation from the experimental frequencies is only 7.8 cm−1 except for the frequencies related to the methyl group. Five more scale factors for the vibrational modes of the methyl group were reoptimized. The final comparison showed an overall mean deviation of 7.5 cm−1 between the theoretical spectrum and the experimental spectrum. Computed intensities are qualitatively in agreement with experiments. They are highly useful in the investigation of questionable assignments.
Conformational study of the trinucleotide CpGpCp‐pentapeptide Gly5 complex: The important role of bridging water in the complex formation
Authors: Yoon Chang No , Jhon Mu Shik 
Published: December 2004

AbstractConformational changes in the RNA‐protein interaction were studied by calculating the intramolecular interaction energy of a model complex with the use of potential functions. The model complex has hydrogen‐bonded water molecules bridging polypeptide NH groups to 2'‐hydroxyl groups and sugar ring oxygen atoms. Since the sugar ring is constrained by the bridging water, preliminary calculations with the model compounds, the sugar ring, mononucleoside diphosphates, pCp and pGp, were carried out, and the flexibility and energetics of the sugar ring were compared with the previous results of DNA. The shift of the phase angle of the sugar ring occurred in the complex formation because of the hydrogen bond through the bridging water and the flexibility of the sugar ring. The free energy difference at 298 K is about −74.0 kcal/mol which was obtained from the intramolecular interaction energy difference of −67.5 kcal/mol by adding the conformational entropy change of 21.9 e.u., which in turn was calculated from the evaluation of the determinant of the matrix containing variances and covariances of the internal coordinates.
Matrix elements for anharmonic potentials: Application to I2 morse oscillator
Authors: Delgado‐barrio G. , Cortina A. M. , Varadé A. , Mareca P. , Villarreal P. , Miret‐artés S. 
Published: December 2004

AbstractMany authors have contributed expressions for obtaining analytical matrix elements for Morse oscillators. In this work, we discuss the advantages of using these expressions. At the same time, we propose a full numerical method to calculate these matrix elements and we compare, for the I2 system, the different results given by Gallas, Vasan, and Cross, and the variational method.
The second limit of hydrogen + carbon monoxide + oxygen mixtures
Authors: Baldwin R. R. , Jackson D. , Melvin A. , Rossiter B. N. 
Published: December 2004

AbstractPrevious studies by Buckler and Norrish of the second limit of CO and O2 mixtures containing small amounts (0.25–10%) of H2 have been used to obtain the velocity constant of the reaction

These estimates of k33 = 3.9 × 108 and 3.5 × 108 liter2 mole−2 sec−1 (M  H2) at 500° and 560°C, respectively, have been combined with other estimates over the range 300°–3500°K to give k33 = 3.0 × 108 exp (−3000/RT) for M  Ar; the considerable scatter in the available points does not encourage any great confidence in this expression and may be attributed at least partly to the different molecules used as M by different workers. For KCl‐coated and CsCl‐coated vessels at 540°C, studies of the second limit of H2 + O2 mixtures, to which CO has been added, have indicated that with both the surfaces, the effect of CO on the limit is masked by changes in the surface nature. In the case of CsCl, the results have enabled a lower limit of about 0.6 to be obtained for the efficiency of CO relative to H2 in the reaction

Use of a computer treatment to interpret the second limit of CO + H2 + O2 mixtures in aged boric‐acid‐coated vessels at 500°C gives a value of mCO = 0.74 ± 0.04 together with an estimate of k32 (H + CO + M″ = HCO + M″)/k4 = 0.022 ± 0.003, which leads to k32 = 2.3 × 108 liter2 mole−2 sec−1 (M  H2) at 500°C.
Vibrational excitation of deuterium fluoride and hydrogen fluoride by atomic and diatomic species
Authors: Blauer J. A. , Solomon W. C. , Owens T. W. 
Published: December 2004

AbstractThe vibrational excitation of HF and DF and the energy transfer efficiencies for various collision partners were investigated over the temperature and pressure ranges of 1400°K to 4100°K and 0.1 to 0.3 atm, respectively. The extent of excitation was determined as a function of time by continuously monitoring the infrared emission intensity at the center of the 1–0 vibration‐rotation band of the molecule. Collisional efficiencies of HF, N2, O2, F, Cl, and DF in relaxing HF and of DF, HF, and N2 in relaxing DF are reported. A comparison with relaxation data for pure HF taken at lower temperature suggests that long‐range attractive forces are mechanistically of major importance in the relaxation process. The relatively high efficiency of atomic chlorine in relaxing HF, i.e., (τP)HF–HF/(τP)HF–C1 ≥ 5 at 3000°K is discussed in terms of our previous result for atomic fluorine, i.e., (τP)HF–HF/(τP)HF–F = 18.
Reaction of H and D atoms with deuterated propylenes
Authors: Falconer W. E. , Sunder W. A. 
Published: December 2004

AbstractEffects of deuterium substitution in propylene on the relative rates of H(D) atom abstraction from and addition to the olefin, and on the orientation of H(D) atom addition, have been studied in the gas phase at room temperature. Effects of isotopic substitution of the olefinic hydrogen atoms on abstraction could not be observed, but abstraction is reduced five‐ to tenfold by deuteration of the methyl group. Deuteration of either olefinic position enhances the rate of addition to the substituted carbon atom. Disproportionation‐combination ratios for deuterium‐substituted propyl radicals are not greatly different from those for unsubstituted radicals, the largest effect being for C3D7 radicals, for which the overall kd/kc is reduced 10–15%.
A flash photolysis study of the rate of the reaction OH + CH4→ CH3+ H2O over an extended temperature range
Authors: Zellner Reinhard , Steinert Wolfram 
Published: December 2004

AbstractA flash photolysis system has been used to study the rate of reaction (1), OH + CH4→ CH3+ H2O, using time‐resolved resonance absorption to monitor OH. The temperature was varied between 300 and 900°K. It is found that the Arrhenius plot ofk1is strongly curved andk1(T) can best be represented by the expressionThe apparent Arrhenius activation energy changes from 15±1 kJ/mole at 300°K to 32±2 kJ/mole at 1000°K. On either side of our temperature range, both absolute rates and their temperature dependence are in good agreement with the results from most previous investigations.
Reactions of O 3PJ atoms with halogens: The rate constants for the elementary reactions O + BrCl, O + Br2, and O + Cl2
Authors: Clyne Michael A. A. , Monkhouse Penelope B. , Townsend Leslie W. 
Published: December 2004

AbstractDirect determinations of the rate constants (cm3/molec · sec) k1, k2, and k3 from 298 to 299°K are reported, using atomic resonance fluorescence in discharge flow systems:
equation image
One standard deviation.
The rate constant k1, which has not been determined previously, was found to possess an insignificant temperature coefficient (EA = (0 ± 700) J/mole) in the range of 299 to 619°K.The present result for k2 agrees well with reinterpreted values from the one previous determination. Measurements of O atom consumption rates and Br atom production rates in the O + Br2 reaction are interpreted to give an estimate of the rate constant k4, which has not been reported previously, at 298°K:

equation image
k3 has been measured at three temperatures between 299 and 602°K. The present and previous results for k3 were combined to give the following rate expression:
Predicting gas phase organic molecule reaction rates using linear free‐energy correlations. I. O(3P) and OH addition and abstraction reactions
Authors: Gaffney J. S. , Levine S. Z. 
Published: December 2004

AbstractLinear free‐energy (LFE) correlations for gas phase O(3P) and OH addition and abstraction reactions with a number of organic compounds have been established using existing room‐temperature rate constants evaluated from the literature. Addition reaction rate constant correlations with ionization potential and abstraction reaction rate constant correlations with bond dissociation energies are examined and compared to the LFE approach. Using multiple regression analysis, empirical linear equations are derived and used to predict rate constants for reactions of O(3P) and OH with a number of organic molecules. The use of LFE room‐temperature rate predictions permits chemical modeling efforts to be extended to compounds where experimental determinations of rate coefficients are lacking and also serves as a useful tool in evaluation of experimental rate measurements.
The ethylperoxy radical spectrum and rate constant for mutual interaction measured by flash photolysis and kinetic spectroscopy
Authors: Adachi Hiroyuki , Basco N. , James D. G. L. 
Published: December 2004

AbstractIntrinsic spectral and kinetic parameters have been measured for the ethylperoxy radical, which was formed in the gas phase by the flash photolysis of azoethane in the presence of an adequate excess of oxygen. Absolute values of the extinction coefficient ϵ(λ) were derived from complementary measurements of the yield of nitrogen and the absorbance of an equivalent concentration of ethylperoxy radicals. The absorption spectrum is broad, structureless and comparatively weak; ϵ(236) = 1.02 × 103 liter mole−1 cm−1 at the maximum, and the oscillator strength is 3.4 × 10−2. This spectrum resembles the spectrum of the methylperoxy radical closely in form, but it is less intense; the ratio of the values of oscillator strength is 0.5. The bimolecular reactions of mutual interaction of ethylperoxy radicals are not exclusively terminating, and ethoxy and hydroperoxy radicals are formed in kinetically significant quantities. A computer program was designed to simulate the rise and fall of the concentration of each radical species, and to perform the related kinetic analysis. This program predicted that a second‐order plot of the decline of the absorbance of the ethylperoxy radical during the dark period would not show a significant departure from linearity, a conclusion which was confirmed by experiment. Accordingly, the gradient of each such plot yielded a value of k'/ϵ(λ), where k' is the apparent value of the rate constant for the collective reactions of mutual interaction. This rate constant was evaluated from the product of corresponding values of k'/ϵ(λ) and ϵ(λ); individual values are independent of the wavelength of measurement, and the mean value is k' = (6.6 ± 0.5) × 107 liter mole−1 sec−1. Further kinetic analysis yielded the corresponding absolute value: k = (6.0 ± 0.6) × 107 liter mole−1 sec−1. This value fits the pattern of a relationship between rate constant and structure shown by the methylperoxy, isopropylperoxy, and tert‐butylperoxy radicals. Adequate sensitivity for the characterization of the spectrum of the ethylperoxy radical was achieved by the use of a pulsed xenon arc as the monitoring light source in conjunction with a dual beam detection system with twin cells and balanced photomultipliers, and the apparatus is described in detail.
A study of the reactions of fluorine with hydrogen and methane in the initiation phase using a miniature tubular reactor
Authors: Seeger C. , Rotzoll G. , Lübbert A. , Schügerl K. 
Published: December 2004

AbstractA small tubular reactor having an inner diameter of 1–2 mm andused as the source in a molecular beam apparatus is described in detail. This arrangement allows the study of fast reactions with reaction times smaller than 1 msec. The preexplosive reaction phase between F2 and H2 and CH4, respectively, is investigated to find out the initiation reactions. In the F2/H2 reaction, initiation is brought about by heterogeneous generation of F atoms or some other surface reaction. Evidence is also obtained for chain branching reactions. In the F2/CH4 case the dominant initiation reaction is the homogeneous reaction CH4 + F2 → CH3 + HF + F. The rate constant for the reaction between 300 and 400 K is 1012.3±0.3 exp[−47 ± 8 kJ/mol/RT] cm3/mol sec. The analysis of the experimental data also yields the rate constant for the propagation reaction CH3 + F2 → CH3 F + F, which is 1012.3±0.3 exp[−4.6 ±2.1 kJ/mol/RT] cm3/mol sec.
The reaction of atomic oxygen O(3P) with propane
Authors: Jewell Steven P. , Holbrook Kenneth A. , Oldershaw Geoffrey A. 
Published: December 2004

AbstractThe reaction of O(3P) atoms with propanehas been studied at temperatures near 300 K by using a discharge flow system. Oxygen atoms were generated in the absence of molecular oxygen by the reaction N + NO → N2 + O, nitrogen atoms having been generated in a microwave discharge. Rate constants for the reaction were measured in two ways, either by measurement of O‐atom decay in the presence of excess propane or by measuring the change in propane concentration after an appropriate time in the presence of an excess of oxygen atoms. The two methods were in good agreement, and the mean rate constant at 306 K is given by

A study of the products of the reaction under conditions corresponding to complete removal of oxygen atoms has shown that an important product of the reaction in the early stages is propene. This is difficult to explain interms of a mechanism involving alkoxy radicals similar to that which has been proposed for some other O(3P)–hydrocarbon reactions. An alternative mechanism is proposed in terms of successive hydrogen abstraction reactions.
Coupling rates and kinetics of arenediazonium cations with couplers utilized in the diazo reprographic process
Authors: Cox A. , Goodman P. D. , Kemp T. J. , de Moira P. Pinot 
Published: December 2004

AbstractStoichiometric and, in most cases, absolute rates of coupling of a series of m‐ and p‐substituted benzenediazonium ions with 2,3‐dihydroxynaphthalene‐6‐sulfonate ion (1) have been determined (i) at pH 5.6 (when one OH group is partly monoionized) and (ii) at pH 9.9 (when one OH group is completely ionized and the second slightly so). The rates at both pH values correlate with the σ+ parameter (except for the most reactive ArN at pH 9.9) and the contributions of the two reactive forms of the coupler evaluated. Detailed pH dependences of the coupling rate of the p‐chlorobenzenediazonium ion with (1) reveal a strong interaction between (1) and the borate ion, which strongly influences the coupling rate. Coupling rates have also been measured for both diazonium ions and couplers of importance in the diazo reprographic process.
Rate constants for the quenching of metastable O2(1Σ) molecules
Authors: Choo Kwang Yul , Leu Ming‐Taun 
Published: December 2004

AbstractSinglet molecular oxygen, O2(1Σ), is one of the important intermediate species in the atmospheres of Earth, Mars, and Venus. To elucidate the chemistry of this excited molecular oxygen, a series of kinetic measurements have been undertaken using the flow‐discharge/optical‐emission technique. By monitoring the characteristic emission (762 nm for 1Σ), the quenching rates for several important molecules have been obtained at room temperature. The following table summarizes measurements.

Quencher
Rate Constants (cm3/s)

CH2
(4.6 ± 0.5) × 10−13

H2
(7.0 ± 0.3) × 10−13

N2
(1.7 ± 0.1) × 10−15

Cl2
(4.5 ± 0.8) × 10−16

CO
(4.5 ± 0.5) × 10−15

O3
(2.2 ± 0.3) × 10−11

2,3 DBM‐2
(6.0 ± 0.1) × 10−13

The error limits represent one standard deviation. The systematic error is estimated to be about 15%. For CO2 and O3 molecules, the quenching rate constants were also measured in the temperature range of 245–362 K. In both reactions, negligible temperature dependences (with the activation energy less than 0.6 kcal/mole) were observed.
Pulse radiolysis study of the reaction of OH radicals with C2H4 over the temperature range 343–1173 K
Authors: Liu An‐Dong , Mulac William A. , Jonah Charles D. 
Published: December 2004

AbstractThe reaction of OH and OD radicals with ethylene in the presence of 1 atm argon and 6 Torr water vapor was studied in the temperature range 343–1173 K. The results reveal three kinetically separate temperature regions: (1) 343–563 K, where the disappearance of OH radical is dominated by the addition of OH to the double bond of ethylene; (2) 563–748 K, where concurrent reactions of addition, the reverse reaction of addition and H‐atom abstraction is dominant; and (3) 748–1173 K, where H‐atom abstraction is likely the main reaction. The rate for hydrogen abstraction is 2.4 × 10−11 exp[(−2104 ± 125)/T] cm3/molec‐s (for OD 2.1 × 10−11 exp[(−2130 ± 172)/T] cm3/molec‐s). There was no obvious pyrolysis of ethylene below 1073 K. The study of OD radical with ethylene shows a small isotope effect.
Das Korrosionsverhalten von Aluminiumbrozen
Authors: Franke Erich 
Published: December 2004

AbstractEs wird ein Überblick gegeben über Struktur, Schmelzen, Vergießen, mechanisch‐technologische Eigenschaften, Korrosionsverhalten und Einsatzmöglichkeiten von Aluminiumbronzen, die eine Gruppe von Legierungen umfassen, die sich hauptsächlich aus Kupfer und Aluminium zusammensetzen und denen im Laufe der Jahre zur Steigerung ihrer Güte und Erfüllung spezieller Anforderungen noch weitere Elemente, wie Zinn, Nickel und Mangan beigefügt worden sind. Als charakteristische Besonderheit dieser Bronzen ist ihre außerordentliche Fähigkeit anzusehen, durch Oxydation des in den Legierungen enthaltenen Aluminiums dünne, jedoch sehr dichte und festhaftende Filme auf ihren Oberflächen zu bilden, die die Bronzen gegen Korrosion und vor allem gegen Oxydation schnisch wichtigsten Kupferlegierungen gemacht, die ihre optimalen Eigenschaften bei mittleren Temperaturen zeigen, da in diesem Bereich auch ihre mechanischen Kennwerte besonders günstig sind.
Säurefeste Zemente
Authors: Waeser Bruno 
Published: December 2004

AbstractNach einigen geschichtlichen Ausführungen und notwendigen Begriffsbestimmungen werden zunächst die Silikatzemente besprochen, die aus Wasserglas und Füllstoffen aufgebaut werden, wobei recht erhebliche Festigkeiten erreicht werden können. Sie leiten über zu den Säuremörtel Hoechst, Keralith, Asplit, Kera Keranol, Kerasolitih oder dgl., Haveg, Prodorit und andere Kunstharz‐ bzw. Bitumenzemente sowie Asphaltmassen gehören, die im einzelnen behandelt werden. Den Abschluß für bilden die sonstigen Säurebaustoffe, für die sich die Bezeichnungen Phenolzemente, Schwefelzemente usw. eingeführt haben. Misch‐ bzw. Asbestzemente und säurefeste Bekleidungen auf Zement‐ bzw. Betongrundlage werden, soweit notwendig, gewürdigt. Den Prüfmethoden ist stärkste Beachtung zu schenken, um vor Schwierigkeiten geschützt zu sein.
Über die biologische Eisenkorrosion
Authors: Seelmeyer Günther 
Published: December 2004

AbstractDie Arbeit gibt eine Zusammenstellung unseres heutigen Wissens über die Korrosionsersheutigen, die durch Mikroorganismen auf Eisen hervorgebracht werden. Nach einem kurzen überblick über die Eigenschaften der hierfür in Frage kommenden Organismen werden die praktisch vorkommenden Erscheinungsformen und Begleiterscheinungen der biologischen Eisenkorrosion, sowie die Theorien, die bisher darüber aufgestellt wurden, besprochen. Die Arbeit endet mit einer Zusammenstellung der bis heute bekannten Verhütungsmöglichkeiten dieser Korrosionsart.
Die Rostschutzwirkung des Zements
Authors: Hebberling Hans 
Published: December 2004

AbstractUnter den Handelssorten des Zements und Betons sind mit Traß versetzter Portlandzement, Bimsbeton und Gipsschlackenzement besonders zur chemischen Rostumwandlung befähigt. Der Schutzwert dieser Baustroffe wird mehr von ihrem pH‐Wert als von der Dicke der Einbettung beeinflußt. Im Stahlbau verwendeter Beton muß in der Regel mindestens 300kg/m3 Zement enthateln. Der „ vorläufige”︁ Rostschutz durch Aufbringen dünner Zementschlämme hat sich in Fällen höherer Beanspruchung nicht durchweg bewährt. Es erscheint sodann eine einmalige Grundierung mit Bleimennige empfehlenswert, deren billigere Beisorte “V 40” das Eissen erwiesenermaßen auch ohne schützenden Deckanstrich 4½ Jahre und länger gegen Rostbildung zu schützen vermag. Alte Anstriche werden vor dem Einbetonieren am besten mit autogenen Flammstrahlern entfernt.
Mantelbeanspruchung von ausgekleideten Behältern am Beispiel des Zellstoffkochers
Authors: Kirschbaum Emil 
Published: December 2004

AbstractZellstoffkocher zerknallten häufig einige Stunden nach Dampfeinlaß, bei Inbetriebsetzung, nach Stillstand oder im Winter unter Einfluß kalter Zugluft. Auf Grund dieses Tatbestandes wurde die zusätzliche Beanspruchung des Eisenmantels durch die Wärmedehnung der Kocherauskleidung an einer technischen Anlage untersucht. Theoretische Ableitungen ergeben, daß die zusätzliche Beanspruchung unter sonst gleichen Bedingungen mit der Dicke der Ausmauerung zunimmt. Der Temperaturverlauf in der Wand eines Kochers wurde bei verschiedenen Ankochzeiten an 3 Stellen durch Einbau von je 10 Thermoelementen im Betrieb gemessen. Die Ergebnisse erhärten die theoretischen Betrachtungen und führen zu der Forderung, daß die Wärmeausdehnungszahl der säurefesten Auskleidung nicht größer als 0,92 × 10−5 m/m.° C sein darf. Dies ist insbesondere bei älteren Kochern zu beachten, deren Rundlaschenverbindungen nur auf die kleinere Beanspruchung in achsialer Richtung abgestimmt sind, wobei die zusätzliche Beanspruchung durch die warme Auskleidung nicht berücksichtigt ist. Weitere Ergebnisse der Untersuchung zeigen, daß aufgeheizte Kocher vor Abkühlung durch Zugluft besonders in der kalten Jahreszeit zu schüzen sind.
Über die Witterungsbeständigkeit von Graufarben durch Pinsel‐ und Spritzauftragverfahren
Authors: Buser Karl 
Published: December 2004

AbstractGegenstand der Untersuchung war die Klärung des Einflusses des Auftragsverfahrens auf die Witterungsbeständigkeit von Rostschutzfarben. In mehrjährigen Bewitterungsversuchen verhielten sich im Streichverfahren aufgebrachte Anstriche im allgemeinen besser als im Spritzverfahren aufgebrachte.
Säurebeständige Stähle in der Holzessigfabrikation
Authors: Wetternik L. , Zitter H. 
Published: December 2004

AbstractDie chemische Beanspruchung in der Holzessigindustrie ist größer als die in der Gärungsfabrikation, was durch Gehalte an homologen Säuren und empyrheumatischen Stoffen bedingt ist.Ein Stahl mit 18% Cr, 10% Ni und 2% Mo, der im allgemeinen für diese Essigsäure Verwendung findet, versagte an den Stellen stärkster Beanspruchung in Holzessigsäure. Es wurde daher versucht, durch Erhöhung des Cr‐ und Ni‐Gehaltes eine Verbesserung zu erzielen.Die besten Ergebnisse wurden mit einem bereits in der schwedischen Zellulosefabrikation verwendeten Stahl mit 27% Cr, 4,5% Ni und 1,5% Mo erreicht, der nach den Laboratoriumsversuchen im gesamten Konzentrations‐Temperaturbereich bis zum Siedepunkt voll beständig ist.Dieser Stahl besteht nur zum geringen Teil aus Austenit und weist daher eine größere Härte auf. Trotzdem ist er gut verarbeitbar und läßt sich auch befriedigend schweißen.