bluuebunny/crossref_metadata_2025_split huggingface dataset:
Einführung in die Grundlagen der Bruchmechanik Teil 3:. Das Ermüdungsrißwachstum in bruchmechanischer Darstellung
Authors: Dander W. 
Published: May 2005

AbstractIm folgenden soll das Ermüdungsrißwachstum in der bruchmechanischen Darstellungsweise erläutert werden, wobei eine Beziehung zwischen der Wöhler‐Kurve (klassischer Ermüdungsversuch) und dem bruchmechanischen Ermüdungsversuch hergestellt wird, sowie einige für die Ingenieurpraxis interessante Aspekte erläutert werden.
Das Verhalten von galvanisch verzinktem unlegiertem Vergütungsstahl bei schwingender und stoßartiger Beanspruchung
Authors: Apel B. , Marrek K.‐H. , Prang W. 
Published: May 2005

AbstractDurch leicht reproduzierbare Untersuchungen wird nachgewiesen, daß der beim galvanischen Verzinken evtl. von der Probenoberfläche aufgenommene diffusible Wasserstoff ‐ hier absichtlich neben dem Zink kathodisch mit abgeschieden ‐ nur in einer begrenzten Zeitspanne vom Ende der Oberflächenbehandlung an gerechnet, das Bauteilverhalten bei dynamischer und stoßartiger Beanspruchung beeinflußt. Der normalgeglühte Gefügezustand wird in seinem Versprödungsverhalten mit einem schlecht vergüteten d. h. eigenspannungsbehafteten Material verglichen.
Untersuchungen zur Initiierung interkristalliner Schwingungsrisse in interstitiell freien (IF‐) Stählen
Authors: Kocik R. , Pries H. , Finke M. , Hagemann J. , Eisenberg S. 
Published: May 2005

AbstractBei Untersuchungen zur Ermüdungsfestigkeit interstitiell freier Stähle sind mit dem Auftreten interkristalliner Schwingungsrisse erstmals Schadensmechanismen aufgetreten, die den Einsatzbereich dieses für seine hervorragenden mechanischen Eigenschaften bekannten Werkstoffes erheblich begrenzen können. In metallographischen Untersuchungen konnten die für dieses Schadensbild bekannten Ursachen wie die Bildung von schalenförmigem Tertiärzementit oder die Schwächung der Korngrenzen durch Ausscheidungen ausgeschlossen werden. Im vorliegenden Beitrag werden Untersuchungsergebnisse mit hochauflösenden elektronenoptischen Analyseverfahren (TEN, AES) vorgestellt.
Untersuchungen zum Schweißen der aushärtbaren Aluminiumlegierungen AlMgSi 1 und AlCuMg 1 mit einem gepulsten Festkörperlaser
Authors: Beek I. , Weisheit A. , Mordike B. L. 
Published: May 2005

AbstractIn dieser Arbeit werden Ergebnisse zum Schweißen der aushärtbaren Aluminiumiumlegierungen AlMgSi 1 und AlCuMg 1 mittels eines gepulsten 1.2 kW Nd: YAG‐Lasers ohne Zusatzwerkstoff vorgestellt. Gefügt wurden 1 mm starke Bleche im I‐Stoß. Bei einer Spaltbreite von 50 μm sind Nähte mit nur geringem Durchhang realisierbar. Der geringe Strahldurchmesser (ca. 0.2mm im Fokus) führt zu sehr schmalen Nähten und Wärmeeinflußzonen. Der hohe Temperaturgradient im Schmelzbad führt zudem zu einer Kornfeinung im Schweißgut und nur zu geringfügigen Korngrenzanschmelzungen in der kritischen Übergangszone zwischen Schweißgut und Wärmeeinflußzone. Wird im ausgehärteten Zustand geschweißt, sinkt die Härte im Schweißgut auf das Niveau des lösungsgeglühten Zustandes ab. Da keine signifikante Verdampfung oder Oxidation von Legierungselementen auftritt, kann durch eine nachfolgende vollständige Aushärtungsbehandlung die max. Härte wieder erreicht werden. Die statischen Festigkeiten liegen über denen konventionell geschweißter Nähte. Gegenüber dem ungeschweißten Zustand ist allerdings auch bei diesen Nähten ein erheblicher Einbruch der Ermüdungsfestigkeit festzustellen.
High‐speed, thermally modulated SFE/GC for the analysis of volatile organic compounds in solid matrices
Authors: Liu Zaiyou , Farnsworth Paul B. , Lee Milton L. 
Published: May 2005

AbstractA coupled supercritical fluid extraction (SFE) and high‐speed gas chromatography (GC) system was developed which permits simultaneous sample extraction and analysis. A thermal desorption modulator at the head of a 50‐μm i.d. capillary column was used as an interface between the SFE and GC. The extraction fluid was first split between the modulator and a waste collection vessel. The substances introduced into the modulator were concentrated in the stationary phase and then released as a sharp injection pulse to the analytical column by electrical resistance heated thermal desorption. The modulator was operated at 10‐s time intervals, which generated consecutive concentration pulses to the column. These concentration pulses were separated into individual chromatograms by high‐speed GC. A set of chromatograms could be generated while the extraction proceeded. With this system, the extractant was sampled continuously so that the SFE process could be monitored in real time for selected components. Quantitative results could be extrapolated before extraction was complete from curves obtained by signal averaging of segmented chromatograms from the set.
High efficiency cross‐linked polyacrylamide coating for capillary electrophoresis of proteins
Authors: Huang Mingxian , Vorkink William P. , Lee Milton L. 
Published: May 2005

AbstractA highly efficient cross‐linked polyacrylamide capillary coating has been developed for capillary electrophoresis of proteins. The fused silica capillary tubing was pretreated with 7‐oct‐1‐enyltrimethoxysilane and then statically coated with the polymerization reagents. The copolymerization reaction was performed at 120°C when using a free‐radical initiator. Coated columns were evaluated for the separation of both basic and acidic proteins. Methylene bisacrylamide was added in the preparation of the cross‐linked polyacrylamide coating, and the cross‐linking effects on column performance were evaluated. Both linear and cross‐linked columns gave high separation efficiencies and good reproducibilities for proteins, and electroosmotic flow was eliminated. It was found that the cross‐linked polyacrylamide coatings produced nearly double the efficiencies and only one third the relative standard deviations in migration times for proteins when compared to linear polyacrylamide coatings. Highly efficient and reproducible separations of proteins in human serum samples were achieved using the cross‐linked column.
2‐Dimethoxyphosphoryl‐1,3‐dithiane: A comparison of NMR studies for 1H, 13C and 31P nuclei by one‐ and two‐dimensional NMR techniques
Authors: Engelhardt Michael , Hägele Gerhard , Mikolajczyk Marian , Balczewski Piotr , Wendisch Detlef 
Published: May 2005

Abstract2‐Dimethoxyphosphoryl‐1,3‐dithiane was obtained by the reaction of 2‐chloro‐1,3‐dithiane with trimethyl phosphite. Studies at 200, 360 and 400 MHz using 1H, 13C and 31P nuclei and 1D‐ and 2D NMR techniques are described. Long‐range coupling constants were extracted by iterative treatment of [AB]2CDMR6X spin systems. A rigid dithiane structure with axial phosphorus is consistent with the NMR results. Analogous dithianes and solid‐state structures are discussed.
Effect of lithium cation on the relaxation mechanisms of acids and alcohols
Authors: Lambert Joseph B. , Simpson Sharon Vlasak 
Published: May 2005

AbstractThe effect of lithium chloride on the relaxation mechanisms of simple acid and alcohols has been examined. Dipolar relaxation is predominant for acetic acid and ethanol. Lithium chloride (approximately 10%) significantly increases the rate of dipolar relaxation for all carbons and protons of acetic acid, probably through an increase in aggregate size or viscosity. Lithium chloride (approximately 1.5%) has a similar but smaller effect on the protons of ethanol. The methyl carbons and fluorines of trifluoroacetic acid and 2,2,2‐trifluoroethanol relax primarily by spin‐rotation. With about 10% lithium chloride, dipolar relaxation becomes more important for trifluoroacetic acid. With about 1.5% lithium chloride, trifluoroethanol possibly shows an enhancement of spin‐rotation relaxation for the CF3 nuclei.
Determination of the Karplus relationships for the C‐2, H‐1′ and C‐6, H‐1′ vicinal coupling paths of uridine derivatives
Authors: Davies David B. , Rajani Pramila , MacCoss Malcolm , Danyluk Steven S. 
Published: May 2005

AbstractA number of uracil cyclo‐nucleosides with known glycosidic bond conformations have been synthesized as model compounds for evaluating the Karplus parameters of vicinal carbon‐proton coupling across the glycosidic bond. The magnitudes of 3J(C‐2, H‐1′) and 3J(C‐6, H‐1′) were determined from proton‐coupled 13C NMR measurements, and both coupling constants showed an approximate Karplus dependence with dihedral angle. Careful analysis of the results on model compounds reveals that the C‐2, H‐1′ and C‐6, H‐1′ coupling paths are not equivalent, and so the magnitudes of Karplus parameters have been determined for each coupling path for the Karplus relationship in the form 3J=A cos2 θ + B cos θ + C, i.e. A6 = 6.2, B6 = −2.4 and C6 = 0.1 Hz and A2 = 5.0, B2 = 2.1 and C2 = 0.1 Hz. Comparison is made between proton‐carbon coupling magnitudes in nucleoside and peptide coupling paths.
The structural dependence of geminal and vicinal CC coupling constants
Authors: Cho Jung‐hyuck , Klessinger Martin , Tecklenborg Ute , Wilhelm Konrad 
Published: May 2005

AbstractCC coupling constants of ten bicyclic hydrocarbons and ten cyclic ethers or carbonyl compounds were determined from the satellites of broad band decoupled spectra or from INADEQUATE measurements. The influences of valence angles, dihedral angles, hybridization and heterosubstitution on geminal and vicinal CC coupling constants are discussed in terms of the algebraic additivity of the contributions from individual coupling paths within the framework of a multiple path mechanism.
119Sn and 1H NMR of the novel complexes [IrH(SnCl3)5]3‐ and [RhH(SnCl3)5]3‐
Authors: Yamakawa Tetsu , Shinoda Sumio , Saito Yasukazu , Moriyama Hiroshi , Pregosin Paul S. 
Published: May 2005

AbstractNew anionic complexes, [IrH(SnCl3)5]3‐ and [RhH(SnCl3)5]3‐, in which the hydride ligands are stabilized only by SnCl3− ligands, have been characterized by 119Sn and 1H NMR spectroscopy. These pentakis SnCl3− complexes are contained in catalyst solutions for the liquid‐phase dehydrogenation of propan‐2‐ol yielding acetone and dihydrogen.
NMR characterization of functional groups: 9‐isomer ratios of available chloromethylstyrene mixtures
Authors: Manatt Stanley L. , Khune G. D. , Khatri N. A. 
Published: May 2005

AbstractFrom the assignments of the 1H and 13C 11.7 tesla NMR spectra of available mixtures of m‐ and p‐chloromethylstyrene, the proportion of the meta and para compounds are easily determined. For these materials from two common commercial sources, proportions of 72 and 28% and 68 and 32% were found. These concentrations are substantially different from the often assumed 60 and 40% for the meta and para compounds, respectively. The influence of this difference on the desired properties of copolymers made from such mixtures is discussed. An alternative quantitative procedure for determining the chloromethyl group isomer ratios is also described which employs silver trifluoroacetate in acetone displacement of chloride and 19F NMR examination of the resulting ester mixture with a 2.3 tesla spectrometer.
Nuclear magnetic resonance III‐13C NMR spectral studies on substituted indoles
Authors: Biswas K. M. , Dhara R. N. , Mallik H. , Roy S. 
Published: May 2005

Abstract13C signal assignments of 3‐ethyl‐1‐methylindole (1), 1‐methyl‐3‐phenylindole (3), 1,3‐dimethyl‐2‐phenylindole (5), 1‐methyl‐2,3‐diphenylindole (10), 1,5‐dimethyl‐2,3‐diphenylindole (12), 7‐methoxy‐2,3‐diphenylindole (13), 7‐methoxy‐4‐methyl‐2,3‐diphenylindole (14) and 1‐(7‐methoxy‐4‐methyl‐2,3‐diphenyl‐6‐indolyl)‐1‐(7‐methoxy‐2,3‐diphenyl‐4‐indolyl)methane (15) are reported. Contrary to an earlier report on monophenylindoles, the para carbons of the phenyl groups of 3, 5, 10 and 12–15 resonate at lower frequencies than their ortho carbons. The methoxy carbon at position 7 in 15 absorbs at a higher frequency than other similar carbons in 13–15 owing to steric inhibition to resonance.
Motional anisotropy‐induced unequal deuterium NMR spin‐lattice relaxation of 3α‐deuteriocholesterol and 3β‐deuterioepi‐cholesterol in solution as a measure of sterol motion about the molecular axis
Authors: Murari Martha P. , Murari Ramaswamy , Baumann Wolfgang J. 
Published: May 2005

AbstractDeuterium spin‐lattice relaxation (T1) data for 3α‐deuteriocholesterol and 3β‐deuterioepicholesterol in solution were obtained at 12.21 MHz as a function of solvent viscosity (η). The correlation times (τc) for both 3‐deuteriosterols varied in a linear fashion over the range of viscosities studied. The data showed that although both 3α‐deuteriocholesterol and 3β‐deuterioepicholesterol undergo rapid reorientations (τc ≈︁ 10−11s) in solution, the relaxation of the deuterium in 3β‐deuterioeholesterol was approximately 2.5 times faster than in 3β‐deuterioepicholesterol. These unequal rates of relaxation are due to the difference in the angles between the CD bond and the molecular axis for the two sterol isomers. An equation containing an angular‐dependent term was derived to analyze the T1 data further. The effective correlation times (τeff), thus calculated, converged for identical viscosities. In the case of 3α‐deuteriocholesterol, it was determined that rotation about the molecular axis comprised up to 60% of the motions relaxing the deuteron. The results show that for molecules having an inherent anisotropy and undergoing isotropic motions, it is possible to separate the portion of motion due to rotation about the molecular axis from other motions which contribute to the relaxation processes at a specific center.
Carbon‐13 NMR Spin‐Lattice Relaxation and Molecular Motion in 2‐Phenyl‐1,3,2‐dioxarsolane and its 4‐Methyl and 4,5‐Dimethyl Derivatives
Authors: Aksnes D. W. , Ramstad K. 
Published: May 2005

Abstract13C NMR spin‐lattice relaxation times (T1) have been measured as a function of temperature for three 2‐phenyl‐1,3,2‐dioxarsolanes. The T1 data have been interpreted in terms of isotropic overall molecular reorientation, internal rotation about the AsPh bond and internal methyl rotation. Information on the relative order of magnitude of the overall and internal reorientations has been obtained. The internal rotation of the phenyl ring is thus 2—4 times faster than the overall molecular tumbling. Further, the internal rotation of the arsolane ring appears to be comparable to, or slightly faster than, the phenyl ring rotation. The association process which is believed to take place in the unsubstituted parent compound is reflected in its very high activation energy for overall reorientation (39 kJ mol−1 compared with 24‐25 kJ mol−1 for the methyl derivatives). The rotation of the methyl groups appears to be considerably more hindered in the cis isomer of 2‐phenyl‐4,5‐dimethyl‐1,3,2‐dioxarsolane than in the trans isomer and, in particular, the mono‐4‐methyl compound.
Carbon‐13 delta shifts and steric interactions in N‐aryl‐1‐isoindolinones and Isoindoline‐1,3‐diones
Authors: Khadim Mohammad A. , Colebrook L. D. 
Published: May 2005

AbstractConsistently deshielding 13C δ shifts resulting from the presence of aryl ortho substituents have been measured for the 3‐methylene carbon atoms of some N‐aryl‐1‐isoindolinones (0.12‐3.25 ppm) and for the carbonyl carbon atoms of these compounds and corresponding N‐arylisoindoline‐1,3‐diones (0.04‐1.47 ppm). Low‐temperature (−75 and −150 °C) 1H NMR studies indicate that steric barriers to internal rotation about the aryl CN bonds in the N‐aryl‐1‐isoindolinones are low. The compounds with the bulkiest aryl ortho substituents tend to show the largest δ shifts (particularly for the 3‐methylene carbons). No consistent correlation with the size of aryl ortho‐substituents or their expected electronic properties is evident.
Two‐dimensional INADEQUATE 13C NMR Study on Vitamin D3
Authors: Kruk C. , Jans A. W. H. , Lugtenburg J. 
Published: May 2005

AbstractTwo‐dimensional INADEQUATE 13C NMR spectroscopy has been used to find the carbon‐carbon connectivities of the carbon skeleton of vitamin D3. This information leads to the unambiguous assignment of the chemical shifts of all 27 carbon atoms of vitamin D3.
17O NMR spectroscopy of 4‐substituted pyridine N‐oxides: Substituent and solvent effects
Authors: Boykin D. W. , Baumstark A. L. , Balakrishnan P. 
Published: May 2005

AbstractThe 17O chemical shifts for 4‐substituted pyridine N‐oxides at natural abundance were measured in acetonitrile at 50°C. Electron withdrawing groups caused deshielding and electron donating groups caused shielding of the 17O resonance. The data are correlated with 17O chemical shifts of substituted anisoles by DSP treatment and with ionization potentials. The chemical shift range for the substituents (methoxy to nitro) is exceptionally large (102 ppm). The 17O signal of the pyridine N‐oxides is substantially shifted in aqueous solution; the differences in chemical shifts between acetonitrile and water for the nitro, parent and methoxy compounds are 85, 75 and 59 ppm, respectively.
Heavy metal spin‐ ½ nuclei. Platinum‐195 relaxation times in phosphorus‐platinum(o) compounds and their dependence on the geometry of the complex
Authors: Benn Reinhard , Michael Büch Holger , Reinhardt Rolf‐Dieter 
Published: May 2005

AbstractThe 195Pt NMR parameters of several phosphorus‐platinum(O) complexes [LnPt(O), L = phosphine or phospite, n = 2, 3, 4] have been investigated to illustrate the particular NMR properties of a spin‐1/2 heavy metal nucleus, and for elucidation of their dependence on the geometry of the complexes. In these compounds the T1 values vary as a function of the coordination number, n, over several orders of magnitude and, therefore, can be used as structure‐dependent parameters. In L2Pt complexes the relaxation rate varies with Bo2, and chemical shift anisotropy (CSA) is the dominant relaxation mechanism. In the L3Pt and L4Pt complexes spin‐rotation increasingly contributes to the relaxation. For the tirethylphosphine‐platinum complex (L3) the contribution of CSA is reduced by 45% at 7 T and 240 K, whereas the tetrahedral trimethylphosphine‐platinum (L4) and triethyl phosphite‐platinum (L4) complexes relax mainly by spin‐rotation even at 9.4 T.
Steric interaction between the peripheral substituents of 10(S)‐chlorophyll derivatives and its conformational consequences: A proton magnetic resonance study
Authors: Hynninen Paavo H. , Lötjönen Simo 
Published: May 2005

AbstractThe improved methods developed recently for the preparation of 10(S)‐chlorophyll derivatives have permitted a detailed comparison of their conformations with those of the corresponding 10(R) derivatives, utilizing 1H NMR spectroscopy. Starting from the highly purified 10(S) derivative and following its conversion to the corresponding 10(R) form by repeated 1H NMR spectral measurements in acetone‐d6, reliable values for the differences in the chemical shifts (Δδ) for each epimeric pair of compounds have been obtained. The relatively large Δδ values (0.1–0.2 ppm) observed for the P‐1‐CH2, P‐H‐2, P‐3a‐CH3 and 10b‐CH3 signals were interpreted as indicating the proximity of the C‐10 methoxycarbonyl group and the olefinic region of the phytyl group in the 10(S) derivatives. The proximity between these side‐chains was considered to be derived principally from the three closely spaced carbonyls in the 10(S) derivatives. To minimize repulsion among the carbonyls, the C‐7 and C‐10 side‐chains presumably assume conformations allowing maximal mutual distances for the carbonyls. As a compromise of various energetic factors, the phytyl group takes up a conformation where it bends to the right hand side of the macrocycle, or above rings V and III. This results in steric crowding between the olefinic region of the phytyl group and the C‐10 methoxycarbonyl group. In addition, the other chemical shift increments show that the steric crowding between the bulky side‐chains of the 10(S) derivatives increases the steric strain at the periphery of the macrocycle, relieved by pronounced conformational changes in rings IV and V and, to a lesser extent, also in the whole phorbin ring. The conformational differences were found to be larger for the magnesium‐free epimers than for the chlorophylls. In the former case, they were also manifested by relatively large Δδ values (0.1–0.5 ppm) for the pyrrole NH protons.
Concerted use of two‐dimensional NMR techniques in the ab initio assignment of complex spectra: Complete proton and carbon‐13 assignment of oligomycin A
Authors: Morris Gareth A. , Richards Michelle S. 
Published: May 2005

AbstractThe identification and complete 13C and 1H assignment of a sample of oligomycin A is described. 13C multiplicities were determined by the INEPT method; assignments were made by comparison of heteronuclear 13C‐1H chemical shift correlation, homonuclear COSY and homonuclear relayed coherence transfer two‐dimensional NMR spectra.
17O NMR spectroscopy of heterocycles. Steric effects for N‐oxides
Authors: Boykin D. W. , Balakrishnan P. , Baumstark A. L. 
Published: May 2005

AbstractThe 17O chemical shift data for a series of 2‐ and 4‐alkyi‐ and ‐aryl‐substituted pyridine N‐oxides, as well as those for quinoline N‐oxide (13), benzo[f]quinoline N‐oxide (14) and benzo [h]quinoline N‐oxide (15) at natural abundance were measured in acctonitrile at 75°C. 2‐Alkyl groups cause a deshielding effect on the N‐oxide chemical shifts compared with those of the 4‐alkyl isomers. The largest effects are noted for 2‐tert‐butylpyridine N‐oxide (8) and 2,6‐dimethylpyridine N‐oxide (12). Similarly, the 17 O chemical shift of 15 is deshielded by 18 ppm compared with that of 13 and 14. 17O chemical shift data were obtained for 2‐and 4‐tert‐butylanisoles and compared with those of 8 and 4‐tert‐butylpyridine N‐oxide (9). The sensitivity of the N‐oxide 17O chemical shifts was substantially greater than that for the anisoles, an effect that was also observed in an analysis of the 13CNMR data of the tert‐butyl groups of 8 and 9. Steric inhibition of resonance is noted for 3‐methyl‐4‐nitropyridine N‐oxide; the N‐oxide 17O signal was shielded and the NO2 17O signal was deshielded relative to those for 4‐nitropyridine N‐oxide.
Carbon‐13 and proton NMR spectra of 1(2H)‐isoquinolinone, 1(2H)‐phthalazinone, 4(3H)‐quinazolinone and their substituted derivatives
Authors: Spassov S. L. , Atanassova I. A. , Haimova M. A. 
Published: May 2005

AbstractThe 13C NMR chemical shifts, one‐bond and some long‐range 13C–1H coupling constants and the 1H NMR chemical shifts for isoquinolinone, phthalazinone, quinazolinone and their derivatives containing CH3, COOH, COOCH3 and CH2COOH substituents in the hetero‐ring are reported. The NMR data are in agreement with the lactam structure for all compounds studied; no evidence for the detectable presence of other tautomers was obtained.
14N nuclear quadrupole resonance in substituted isatin compounds
Authors: Bray P. J. , Mulkern R. V. , Greenbaum S. G. 
Published: May 2005

Abstract14N nuclear quadrupole resonances have been found for eight substituted isatin compounds. Variations in the electric field gradient (EFG) and asymmetry parameter, η, have been attributed to inductive rearrangement of the electron distribution at the nitrogen site. A correlation between the inductive Taft parameter, σ*, of the substituent and the charge density difference between the hybridized nitrogen bonding orbitals, σNHσNc, has been established. Implications of the results with respect to the available biological data on substituted isatins are discussed.
13C NMR and azomethine 1H NMR spectra of substituted N‐benzylideneanilines and hammett correlations
Authors: Echevarria Aurea , Miller Joseph , Nascimento M. Graça 
Published: May 2005

AbstractTwenty‐four N‐benzyliaeneanilines (four being new compounds) have been prepared, which are divided conveniently into three series: (I) with 4‐substituents, plus one compound with 3‐ and 4‐substituents; (II) with 4′‐substituents, plus one compound with 3′‐ and 4′‐substituents; and (III) with 4‐ and 4′‐substituents. Their 13C NMR spectra and the 1H NMR absorption of the hydrogen attached to the imidoyl carbon atom have been studied and their Hammett correlations were tested.