bluuebunny/crossref_metadata_2025 huggingface dataset:
Computation of the Pressure Distribution in Hydrodynamic Bearings Using Newton’s Method
Authors: Johansson and Lars , Wettergren Ha˚kan
Published: April 2004

In this paper an algorithm is developed where Reynolds’ equation, equilibrium equations and non-negativity of pressure are formulated as a system of equations, which are not differentiable in the usual sense. This system is then solved using Pang’s Newton method for B-differentiable equations.
Viscoelastic Lubrication With Phan-Thein-Tanner Fluid (PTT)
Authors: Akyildiz F. Talay , Bellout Hamid
Published: April 2004

We analyze the lubrication flow of a viscoelastic fluid to account for the time dependent nature of the lubricant. The material obeys the constitutive equation for Phan-Thein-Tanner fluid (PTT). An explicit expression of the velocity field is obtained. This expression shows the effect of the Deborah number (De=λU/L, λ is the relaxation time). Using this velocity field, we derive the generalized Reynolds equation for PTT fluids. This equation reduces to the Newtonian case as De→0. Finally, the effect of the Deborah number on the pressure field is explored numerically in detail and the results are documented graphically.
Thermoacoustic enrichment of the isotopes of neon
Authors: Geller D. A. , Swift G. W.
Published: April 2004

The enrichment of the neon isotopes in a thermoacoustic device is demonstrated. Because the thermal diffusion ratio of neon is small, an apparatus longer than a wavelength was necessary in order to easily observe the separation. The device was modular and extensible, so that arbitrarily large separations could in principle be obtained. The acoustic duct was a series of multiple, identical quarter-wavelength modules with side-branch drivers. In this way, waveforms close to that of a traveling wave were maintained in the duct, despite the high acoustic attenuation caused by the duct’s small diameter and large length. The concentrations of the isotopes were measured at one end of the duct using a quadrupole mass spectrometer. For the operating frequency of 227 Hz, the maximum separation gradient obtained was 0.43%/m, and mole fluxes at zero gradient as high as 3 nmol/s were observed. Effects of turbulence, though not observed, are also discussed, and the scaling properties of this method are compared with those of traditional mixture-separation methods.
An effective fluid model for landmine detection using acoustic to seismic coupling
Authors: Velea Doru , Waxler Roger , Sabatier James M.
Published: April 2004

A model is developed to describe the response of the ground to airborne sound in the presence of a buried landmine. The model describes both the near-field acoustic wave phenomena as well as the mechanical dynamics of the mine itself. Since buried landmines are typically close to the surface of the soil, the induced ground vibration is the result of near-field scattering so that classical asymptotic scattering theory cannot be used. Instead, the near-field problem is solved in a right circular waveguide with rigid walls. The waveguide contains air in the upper half, soil in the lower half, and a buried mine placed concentrically on the waveguide’s axis. The advantage of a waveguide model over infinite space models is that the resulting computer models are much more straightforward to code and run much more quickly. As the radius of the waveguide increases, the results of the waveguide model converge to those of the infinite space model. For low frequencies (a few hundred Hz) this convergence is quite rapid: it is found that a waveguide radius of 10 times the mine radius is more than sufficient. The results obtained are found to qualitatively explain the phenomena observed in the field.
A simple frequency-scaling rule for animal communication
Authors: Fletcher Neville H.
Published: April 2004

Different animals use widely different frequencies for sound communication, and it is reasonable to assume that evolution has adapted these frequencies to give greatest conspecific communication distance for a given vocal effort. Acoustic analysis shows that the optimal communication frequency is inversely proportional to about the 0.4 power of the animal’s body mass. Comparison with observational data indicates that this prediction is well supported in practice. For animals of a given class, for example mammals, the maximum communication distance varies about as the 0.6 power of the animal’s mass. There is, however, a wide spread of observed results because of the different emphasis placed upon vocal effort in the evolution of different animal species.
Comment on “An approximate transfer function for the dual-resonance nonlinear filter model of auditory frequency selectivity” [J. Acoust. Soc. Am. 114, 2112–2117] (L)
Authors: Duifhuis Hendrikus
Published: April 2004

This letter concerns the paper “An approximate transfer function for the dual-resonance nonlinear filter model of auditory frequency selectivity” [E. A. Lopez-Poveda, J. Acoust. Soc. Am. 114, 2112–2117 (2003)]. It proposes a correction of the historical framework in which the paper is presented. Additionally it mentions some general problems associated with filter-bank models, and it discusses the validity and usefulness of the “transfer function” concept for nonlinear filters.
High-frequency electromotile responses in the cochlea
Authors: Grosh Karl , Zheng Jiefu , Zou Yuan , de Boer Egbert , Nuttall Alfred L.
Published: April 2004

Mammalian outer hair cells (OHCs) convert electrical energy into mechanical energy. The significance of this electromotility rests in the ability of the OHCs to modulate the vibrations of the cochlear partition in vivo. While high-frequency electromotility of isolated OHCs has been demonstrated at frequencies up to 100 kHz, a similar measure of the effect of OHC electromotility on motion of the sensory epithelium has not been made in vivo. In this study, in vivo electrical stimulation of the guinea pig cochlea is found to induce a mechanical response of the basilar membrane for frequencies to at least 100 kHz, nearly twice the upper limit of hearing for the guinea pig. The perfusion of salicylate in the cochlea reversibly reduces the electromotile response, indicating that an OHC-mediated process is the key contributor.
Independent component analysis for automatic note extraction from musical trills
Authors: Brown Judith C. , Smaragdis Paris
Published: April 2004

The method of principal component analysis, which is based on second-order statistics (or linear independence), has long been used for redundancy reduction of audio data. The more recent technique of independent component analysis, enforcing much stricter statistical criteria based on higher-order statistical independence, is introduced and shown to be far superior in separating independent musical sources. This theory has been applied to piano trills and a database of trill rates was assembled from experiments with a computer-driven piano, recordings of a professional pianist, and commercially available compact disks. The method of independent component analysis has thus been shown to be an outstanding, effective means of automatically extracting interesting musical information from a sea of redundant data.
CONSTRAINTS IN QUANTUM GEOMETRODYNAMICS
Authors: GENTLE ADRIAN P. , GEORGE NATHAN D. , KHEYFETS ARKADY , MILLER WARNER A.
Published: April 2004

We compare different treatments of the constraints in canonical quantum gravity. The standard approach on the superspace of 3-geometries treats the constraints as the sole carriers of the dynamic content of the theory, thus rendering the traditional dynamical equations obsolete. Quantization of the constraints in both the Dirac and ADM square root Hamiltonian approaches leads to the well known problems of time evolution. These problems of time are of both an interpretational and technical nature. In contrast, the geometrodynamic quantization procedure on the superspace of the true dynamical variables separates the issues of quantization from the enforcement of the constraints. The resulting theory takes into account states that are off-shell with respect to the constraints, and thus avoids the problems of time. We develop, for the first time, the geometrodynamic quantization formalism in a general setting and show that it retains all essential features previously illustrated in the context of homogeneous cosmologies.
BORN–INFELD LAGRANGIAN USING CAYLEY–DICKSON ALGEBRAS
Authors: KUWATA S.
Published: April 2004

We rewrite the Born–Infeld Lagrangian, which is originally given by the determinant of a 4×4 matrix composed of the metric tensor g and the field strength tensor F, using the determinant of a (4·2n)×(4·2n) matrix H4·2n. If the elements of H4·2n are given by the linear combination of g and F, it is found, based on the representation matrix for the multiplication operator of the Cayley–Dickson algebras, that H4·2n is distinguished by a single parameter, where distinguished matrices are not similar matrices. We also give a reasonable condition to fix the parameter.
OPTIMIZED POST GAUSSIAN APPROXIMATION IN THE BACKGROUND FIELD METHOD
Authors: RAKHIMOV ABDULLA , YEE JAE HYUNG
Published: April 2004

We have extended the variational perturbative theory based on the background field method to include the optimized expansion of Okopinska and the post Gaussian effective potential of Stansu and Stevenson. This new method provides a much simpler way to compute the correction terms to the Gaussian effective action (or potential). We have also renormalized the effective potential in 3+1 dimensions by introducing appropriate counterterms in the Lagrangian.
HIGH PRECISION LATTICE QCD MEETS EXPERIMENT
Authors: LEPAGE P. , DAVIES C.
Published: April 2004

We review recent results in lattice QCD from numerical simulations that allow for a much more realistic QCD vacuum than has been possible before. Comparison with experiment for a variety of hadronic quantities gives agreement to within statistical and systematic errors of 3%. We discuss the implications of this for future calculations in lattice QCD, particularly those which will provide input for B-factory experiments.
SYNTHESIS AND STUDY OF SECOND HARMONIC GENERATION IN 4,4'-DINITROPHENYL 1,1'-ADIPAMIDE (DNPA)
Authors: TRIVEDI RASHMI , SEN PRATIMA , SEN PRANAY K.
Published: April 2004

We synthesized 4,4'-dinitrophenyl 1,1'-adipamide (DNPA) and studied optical second harmonic generation (SHG) in this organic material using the Kurtz method. The experimental analysis of SHG was made for a range of particle size of DNPA. It was observed that DNPA is nearly three times more SHG active than urea. It was also found that the compound is non-phasematchable and did not show any optical degradation for about an year when kept in ambient atmosphere.
THIRD-ORDER NONLINEARITIES AND OPTICAL LIMITING OF C60 POLYURETHANE–UREA FILMS
Authors: GUO SHENG-LI , GU BING , ZHANG TAO
Published: April 2004

We report on the measurement of the nonlinear optical absorption and refraction coefficients of C60-containing polyurethane–urea films on a nanosecond scale at a 532-nm wavelength, using the Z-scan technique. The optical limiting properties were also observed. The results show that the C60 polyurethane–urea is a kind of homogeneous material with a range of C60 content. With the difference in C60 content in polymers, the optical limiting properties are many and the required transmittance and transmitted energy can be altered depending on the C60 content in polymers. We suggest that the third-order nonlinearities and optical limiting behavior are consistent with excited-state absorption (reverse saturable absorption) as a mechanism.
Getting ready for reading: A follow‐up study of inner city second language learners at the end of Key Stage 1
Authors: Stuart Morag
Published: April 2004

Background: A previous study (Stuart, 1999) showed that early phoneme awareness and phonics teaching improved reading and spelling ability in inner‐city schoolchildren in Key Stage 1, most of whom were learning English as a second language.

Aims: The present study, a follow‐up of these children at the end of Key Stage 1, addresses four main questions: (1) Are these improvements maintained to the end of Key Stage 1? (2) Are different patterns of cognitive process evident in the word recognition skills of phonics trained versus untrained children? (3) Do the phonics trained children now also show a significant advantage in reading comprehension? (4) Are there differences in amount of reading, in self‐concept as readers and in oral vocabulary development between phonics trained and untrained children? Relationships between reading and spelling ages and Key Stage 1 SATs levels are also explored.

Sample: Data are reported from 101 seven‐year‐olds (85 of whom were second language learners) remaining from the original 112 children reported on previously.

Method: Children were tested on four standardized tests of reading, spelling and vocabulary, and on a further six experimental tests of phoneme segmentation, grapheme‐phoneme correspondence knowledge, regular, exception and nonword reading, author recognition and reading self‐concept.

Results: Lasting influences of early phoneme awareness and phonics teaching on phoneme awareness, grapheme‐phoneme correspondence knowledge, word reading and spelling were found. Part of the previously untrained group had now received structured phonics teaching, and were therefore treated as a third (late trained) group. Early and late‐trained groups showed similar levels of attainment and similar cognitive processing patterns, which were different from the untrained group. However, there were no influences of training on reading comprehension, self‐concept or oral vocabulary.

Conclusions: Early phoneme awareness and phonics training efficiently accelerates the word recognition and spelling skills of first and second language learners alike. However, this is not sufficient to bootstrap the development of language comprehension in the second language learners. Further research is needed into the kinds of language teaching that will best develop their oral and written language comprehension.
CAP Forum on Enron: What If Andersen Had Shredded in Toronto or Calgary? The Potential Criminal Liability of Canadian Public Accounting Firms*
Authors: GUNZ SALLY P. , SALTERIO STEVEN E.
Published: April 2004

Both Canadians and Americans often assume that the legal system, like many other aspects of society, works the same in both countries. Just as these assumptions often fail to stand up to detailed scrutiny, so too may the assumption that Arthur Andersen LLP could have been charged with and convicted of obstruction of justice in Canada. In this paper, we examine the hypothetical question of what would have happened if a public accounting firm had shredded documents, fearing a provincial securities regulatory investigation in Toronto or Calgary. We examine the key differences between both the law and the institutional environment in Canada and the United States to determine whether such a prosecution could occur in Canada. We find that the letter of the law would probably have resulted in a successful prosecution. However, because of differences in the institutional environments, a criminal prosecution of a Canadian public accounting firm would probably never have occurred. The implications of this conclusion are discussed.
End‐Capping as a Method for Improving Carrier Injection in Electrophosphorescent Light‐Emitting Diodes
Authors: Gong X. , Ma W. , Ostrowski J. C. , Bechgaard K. , Bazan G. C. , Heeger A. J. , Xiao S. , Moses D.
Published: April 2004

The electronic properties, carrier injection, and transport into poly(9,9‐dioctylfluorene) (PFO), PFO end‐capped with hole‐transporting moieties (HTM), PFO–HTM, and PFO end‐capped with electron‐transporting moieties (ETM), PFO–ETM, were investigated. The data demonstrate that charge injection and transport can be tuned by end‐capping with HTM and ETM, without significantly altering the electronic properties of the conjugated backbone. End‐capping with ETM resulted in more closely balanced charge injection and transport. Single‐layer electrophosphorescent light‐emitting diodes (LEDs), fabricated from PFO, PFO–HTM and PFO–ETM as hosts and tris[2,5‐bis‐2′‐(9′,9′‐dihexylfluorene)pyridine‐κ2NC3′]iridium(III), Ir(HFP)3 as the guest, emitted red light with brightnesses of 2040 cd m–2, 1940 cd m–2 and 2490 cd m–2 at 290 mA cm–2 (16 V) and with luminance efficiencies of 1.4 cd A–1, 1.4 cd A–1 and 1.8 cd A–1 at 4.5 mA cm–2 for PFO, PFO–HTM, and PFO–ETM, respectively.
Orientational Switching of Mesogens and Microdomains in Hydrogen‐Bonded Side‐Chain Liquid‐Crystalline Block Copolymers Using AC Electric Fields
Authors: Chao C.‐Y. , Li X. , Ober C. K. , Osuji C. , Thomas E. L.
Published: April 2004

In this report, we show that the microstructures of hydrogen‐bonded side‐chain liquid‐crystalline block copolymers can be rapidly aligned in an alternating current (AC) electric field at temperatures below the order–disorder transition but above the glass transition. The structures and their orientation were measured in real time with synchrotron X‐ray scattering. Incorporation of mesogenic groups with marked dipolar properties is a key element in this process. A mechanism related to the dissociation of hydrogen bonds is proposed to account for the fast orientation switching of the hydrogen‐bonded blends.
Colchicin‐Totalsynthesen im Vergleich: eine Reise durch 50 Jahre Organische Synthesechemie
Authors: Graening Timm , Schmalz Hans‐Günther
Published: April 2004

Colchicin, das Hauptalkaloid der Herbstzeitlose, ist einer der prominentesten Naturstoffe, der wie andere Tubulin‐bindende Wirkstoffe (z. B. Taxol und Epothilone) über ein großes pharmazeutisches Potenzial verfügt. Die ersten Synthesen von Colchicin in den späten 50er Jahren waren Meilensteine der Naturstoffsynthese. Aber auch heute noch stellt dieses strukturell vermeintlich einfache Molekül eine Herausforderung dar. So ist es erst in den letzten Jahren gelungen, Synthesen zu entwickeln, die effizient auch neue, strukturell modifizierte Colchicin‐Derivate totalsynthetisch zugänglich machen. Die vergleichende Betrachtung aller bekannten Colchicin‐Synthesen in diesem Aufsatz verdeutlicht nicht nur den Fortschritt der Organischen Synthese in den letzten Jahrzehnten. Es wird vielmehr gezeigt, dass die synthetischen Fragestellungen, die dieses Molekül aufwirft, nur mit einem hohen Maß an chemischer Kreativität beantwortet werden können. Nur wenige Zielverbindungen sind auf so facettenreiche Weise synthetisiert worden wie Colchicin.
Numerical analysis of rectangular microstrip patch over ground plane with rectangular aperture
Authors: Fortaki T. , Khedrouche D. , Bouttout F. , Benghalia A.
Published: April 2004

In this paper, a rigorous full‐wave analysis of rectangular microstrip patches over ground planes with rectangular apertures in substrates containing isotropic and anisotropic materials is presented. The dyadic Green's functions of the problem are efficiently determined in the vector Fourier transform domain. The integral equations for the unknown patch current and aperture field are solved numerically by applying the Galerkin method of moments. The TM set of modes issued from the magnetic wall cavity model are used to expand the unknown current on the patch. Also, the same basis functions are used for approximating the aperture field in accordance with the concept of complementary electromagnetic structures. The validity of the solution is tested by comparison of the computed results with experimental data. Numerical results show that changes in aperture length can drastically shift the resonant frequency. The aperture width, on the other hand, can be used for a fine adjustment of the operating frequency. Other results also indicate that dielectric anisotropy effect is especially significant when the size of the aperture is similar to that of the patch. Copyright © 2004 John Wiley & Sons, Ltd.
Buckling analysis of tapered lattice columns using a generalized finite element
Authors: Li Jin‐Jun , Li Guo‐Qiang
Published: April 2004

A generalized finite element for buckling analysis of tapered columns with various cross sections is established by using Chebyshev polynomial approach to the governing differential equation in this paper. The proposed formulation involves the effects of shear deformation and is therefore applicable to lattice columns. The change of the sectional properties along the length direction can be calculated exactly in the FE analysis. Buckling of a tapered lattice column, with respective lace bars and batten plates, is studied in the numerical example. The effects of shear deformation on the buckling loads of tapered lattice columns are specified. Copyright © 2004 John Wiley & Sons, Ltd.
Domain structures and etching morphologies of lithium niobate crystals with different Li contents grown by TSSG and double crucible Czochralski method
Authors: Zheng Y. , Shi E. , Wang S. , Lu Z. , Cui S. , Wang L. , Zhong W.
Published: April 2004

Stoichiometric lithium niobate single crystals with different Li contents have been grown both by the top‐seeded solution growth (TSSG) method from potassium containing flux and by the double crucible Czochralski (DC Cz) method. Spectroscopic properties (e.g. the UV absorption edge, Raman linewidth) and the Curie temperature measurement have been used for the characterization of the crystal composition. The double crucible Czochralski method is found to be suitable for mass production of stoichiometric LiNbO3 with Li content larger than 49.7 mol% and homogeneity of 0.03 mol%. The domain structures and etching morphologies on negative and positive c‐surface were also investigated by chemical etching method. A new domain structure of three‐fold symmetric sectors were observed in near‐stoichiometric LiNbO3 grown by TSSG method. The straight line arrangement hillocks on negative c‐surface and the net‐like arrangement etch lines were observed and explained by stress etching mechanism. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of Sr3TaGa3Si2O14 single crystal
Authors: Qi Haifeng , Wei Aijian , Wang Zengmei , Yuan Duorong
Published: April 2004

The specific rotation ρ of strontium tantalum gallium silicate Sr3TaGa3Si2O14 (STGS) piezoelectric single crystal was determined from 350 to 850 nm by measuring the optical transmission between parallel polarisers in Z direction. It is shown that Sr3TaGa3Si2O14 has quite large a value of ρ which is a little smaller than that of strontium niobium gallium silicate Sr3NbGa3Si2O14 (SNGS). The crystal with ordered structure which is isostructural to calcium gallium germanate Ca3Ga2Ge4O14 (CGG) was grown by Czochraiski technique. And its birefringence was also determined. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of conventional and ultrasound‐assisted extraction of carvone and limonene from caraway seeds
Authors: Chemat Smain , Lagha Ahcène , AitAmar Hamid , Bartels Paul V. , Chemat Farid
Published: April 2004

Extraction experiments with hexane were carried out at atmospheric pressure in Soxhlet, conventional and ultrasound extractions of ﬂaked caraway seeds, and detailed results are given for two major plant extract components, carvone and limonene. The results indicate that carvone yield and plant extract quality are better in ultrasound extraction compared to those given by conventional methodology. Extraction rates of carvone and limonene reported that ultrasound‐assisted extraction was 1.3–2 times more rapid, depending on temperature, than a conventional system, according to the rate constant obtained during the initial 10 minutes of extraction. Moreover, the SEM micrographs provided more evidence for the mechanical effects of ultrasound, mainly appearing on cell walls and shown by the destruction of cells, faulitating the release of their contents, in contrast to conventional maceration or extraction, which involve diffusion of plant extracts across glandular walls and causing cell rupture over longer time periods. Copyright © 2004 John Wiley & Sons, Ltd.
Aromatic plants of tropical central Africa. Part XLIX: chemical composition of essential oils of the leaf and rhizome of Aframomum giganteum K. Schum from Gabon
Authors: Agnaniet Huguette , Menut Chantal , Bessière Jean‐Marie
Published: April 2004

The chemical composition of the essential oils obtained by hydrodistillation of the leaves and rhizomes of Aframomum giganteum K. Schum grown in Gabon were investigated by GC–FID and GC–MS. The major compounds in the leaf oil were found to be cis‐pinocamphone (54%) and pinocarvone (10.1%), while the essential oil from the rhizomes is dominated by sesquiterpenes, namely β‐caryophyllene (10.5%) and their oxygenated derivatives (40%). The antioxidant and the antiradical activity of both samples were evaluated. Copyright © 2004 John Wiley & Sons, Ltd.
How to spot and use the “new” internal auditors
Authors: Pickett K. H. Spencer
Published: April 2004

Corporate boards, senior executives, and others are scrambling to respond to demanding Sarbanes‐Oxley requirements. CEOs need to look for new skills from their internal audit staff. But how can you spot these “new” internal auditors, and what's the best way to use them? The author has some answers. © 2004 Wiley Periodicals, Inc.
Using a “culture audit” to pick M&A winners
Authors: Schorg Chandra A. , Raiborn Cecily A. , Massoud Marc F.
Published: April 2004

It pays to look before you leap. By using a “culture audit,” the authors say you can save yourself from potential M&A disasters. Here's how to do it. © 2004 Wiley Periodicals, Inc.
Effect of pulsed shock waves on the activity of polyphenol oxidase, alkaline phosphatase and green fluorescent protein
Authors: Zuckerman H , Krasik YaE , Felsteiner J
Published: April 2004

Pulsed shock waves (PSW), generated using a benchtop system constructed in our laboratory, have potential for the preservation of foods, pharmaceuticals and cosmetics, since they can inactivate micro‐organisms as well as enzymes without heating. This paper presents the effect of PSW on polyphenol oxidase (PPO), which is related to food quality, and on alkaline phosphatase (AP), which is an indicator enzyme for milk pasteurisation. We also show the effect of PSW on green fluorescent protein (GFP). Results indicated that repeated applications of shock waves to enzymes and GFP at 4 °C were capable of reducing enzyme activity and the fluorescence of GFP. We showed that PSW decreased the activity of PPO and AP within a few microseconds at room temperature. The kinetics of enzyme activity reduction was affected by the number of applied shock wave pulses and followed an exponential relationship. Copyright © 2004 Society of Chemical Industry
Protein‐related changes during salting of milkfish (Chanos chanos)
Authors: Sannaveerappa Thippeswamy , Ammu Kunhithyil , Joseph Jose
Published: April 2004

Milkfish collected from brackish water culture ponds were wet and dry salted for 24 h and the dry‐salted fish were sun dried for 48 h. Biochemical changes, ie changes in α‐amino nitrogen, non‐protein nitrogen, salt‐soluble nitrogen, total free amino acids, essential amino acids and sulfhydryl groups, during salting and sun drying were studied. The reduction in these parameters was slightly higher in wet‐salted fish compared with dry‐salted fish. Further reduction in these parameters was noticed on sun drying of dry‐salted fish. Electrophoretic studies showed a decrease in the number of bands during wet and dry salting at a slow rate up to 9 h, after which high‐molecular‐weight proteins decreased faster than medium‐molecular‐weight proteins in both the 24 h wet‐ and dry‐salted samples. Further reduction in the number of bands and their intensity was observed on sun drying for 48 h. The medium‐molecular‐weight protein seems to be more stable. Copyright © 2004 Society of Chemical Industry
Plane of elastic non‐resisting tension material under foundation structures
Authors: Baratta A. , Corbi I.
Published: April 2004

In the frame of 2D‐static problems one approaches the problem of elastic‐NRT (not‐resisting tension) semi‐plane loaded on its limit line. This problem is intended to model the stress situation induced in the soil by a foundation structure. The solution, in terms of activated stress field, is searched for in the class of stress fields satisfying equilibrium and admissibility conditions, by applying an energy approach. Copyright © 2004 John Wiley & Sons, Ltd.
Free radicals mediated membrane damage by the saponins acaciaside A and acaciaside B
Authors: Nandi Bidyut , Roy Sakuntala , Bhattacharya Shelley , Sinha Babu Santi Prasad
Published: April 2004

Acaciaside A and B, two acylated triterpenoid bisglycoside saponins originally isolated from the funicles of Acacia auriculiformis, are known to have antihelmintic activity. In our previous investigation it was suggested that the conjugated unsaturated system of the saponins is involved in producing the damaging effect of saponins, probably by resulting free radicals that induce membrane damage through peroxidation. Here the interaction of saponins and the microsomal membrane was investigated in the presence and absence of superoxide dismutase, catalase and thiourea. Our results showed that superoxide dismutase signiﬁcantly blocked the effect of saponins‐induced membrane damage. Catalase had only a minor effect on saponins‐induced membrane damage and thiourea had no effect. The results suggest that in our model, saponins can generate superoxide anions and initiate lipid peroxidation. Copyright © 2004 John Wiley & Sons, Ltd.
The effect of Pycnogenol on fluoride induced rat kidney lysosomal damage in vitro
Authors: Arhima M. H. , Gulati O. P. , Sharma S. C.
Published: April 2004

Pycnogenol (PYC) is a procyanidin‐rich extract of the bark of French maritime pine (Pinus pinaster) with a potent ability to scavenge free radicals. Lysosome‐rich fractions from rat renal cortices were incubated with varying amounts of PYC and challenged with noxious doses of ﬂuoride. Controls were also included. The release of N‐acetyl‐β‐d‐glucosaminidase (NAG) isozymes in the supernatant was estimated by spectrophotometric methods. The protein content of the renal cortex was also determined. Our results show that ﬂuoride in unhealthy doses can cause a concentration dependent release of N‐acetyl‐β‐d‐glucosaminidase (NAG) isozymes from the renal lysosomes. This may be related to its known ability to initiate free radical formation or direct damaging effects on the lysosomal membrane. As a blend of bioﬂavonoids pycnogenol has a potent ability to scavenge free radicals. In our study PYC was effective in preventing ﬂuoride induced release of NAG isozymes from the renal lysosomes. Copyright © 2004 John Wiley & Sons, Ltd.
Incidentally Found Medullary Thyroid Cancer: Treatment Rationale for Small Tumors
Authors: Raffel Andreas , Cupisti Kenko , Krausch Markus , Wolf Achim , Schulte Klaus‐Martin , Röher Hans‐Dietrich
Published: April 2004

The object of this study was to assess the extent of surgery required for small sporadic medullary thyroid cancers (sMTCs). We retrospectively studied 261 patients with MTCs treated in our institution between 1986 and 2002 and identified 15 patients with small pT1 or pT2 sMTCs. The tumors were diagnosed incidentally, so surgical therapy was less than total thyroidectomy. Total thyroidectomy with or without neck dissection was applied to all other patients as standard surgical treatment of care. Patients were systematically followed up by postoperative ultrasonography, calcitonin, carcinoembryonic antigen levels, and pentagastrin stimulation tests. On long‐term follow‐up over a period of 4.6 years, the rate of biochemical cure in these patients who underwent less than total thyroidectomy for a sporadic incidentally diagnosed tumor was 100%. We concluded that completion thyroidectomy and neck dissection are not mandatory in patients in whom a solitary small sMTC is incidentally discovered by histologic diagnosis following operation so long as a genetic background is excluded. Nevertheless, such patients require systematic careful long‐term follow‐up.
Technique for incorporating the density functional Hessian into the geometry optimization of biomolecules, solvated molecules, and large floppy molecules
Authors: Chang R. , Barile P. A. , Maslen P. E.
Published: April 2004

Traditional geometry optimization methods require the gradient of the potential surface, together with a Hessian which is often approximated. Approximation of the Hessian causes difficulties for large, floppy molecules, increasing the number of steps required to reach the minimum. In this article, the costly evaluation of the exact Hessian is avoided by expanding the density functional to second order in both the nuclear and electronic variables, and then searching for the minimum of the quadratic functional. The quadratic search involves the simultaneous determination of both the geometry step and the associated change in the electron density matrix. Trial calculations on Taxol® indicate that the cost of the quadratic search is comparable to the cost of the density functional energy plus gradient. While this procedure circumvents the bottleneck coupled-perturbed step in the evaluation of the full Hessian, the second derivatives of the electron-repulsion integrals are still required for atomic-orbital-based calculations, and they are presently more expensive than the energy plus gradient. Hence, we anticipate that the quadratic optimizer will initially find application in fields in which existing optimizers breakdown or are inefficient, particularly biochemistry and solvation chemistry.
Hydrogen bonds in 1,4-dioxane/ammonia binary clusters
Authors: Shi Tujin , Ge Jianhong , Zhang Yunwu , Zhu Qihe
Published: April 2004

With synchrotron radiation, we have studied the photoionization and dissociation of 1,4-dioxane/ammonia clusters in a supersonic expansion. The observed major product ions are the 1,4-dioxane cation M+ and protonated cluster ions M(NH3)nH+ (where M=1,4-dioxane), and the intensities of the unprotonated cluster ions M(NH3)n+ are much lower. Fully optimized geometries and energies of the neutral cluster M(NH3)2 and related cluster ions have been obtained using the ab initio molecular orbital method and density functional theory. The potential energy surface of the excited state of M(NH3)2+ was also calculated. With these results, the mechanisms of different photoionization–dissociation channels have been suggested. The most probable channel is electron ejection from the highest occupied molecular orbital, followed by the dissociation into M+ and (NH3)2. For another main channel, after removing an electron from the second highest occupied molecular orbital, the intracluster proton transfer process takes place to form the stable unprotonated cluster ion M(NH3)H+–NH2, which usually leads to the dissociated protonated cluster ion M(NH3)H+ and a radical NH2.
Photodissociation spectroscopy and dynamics of the CH2CFO radical
Authors: Hoops Alexandra A. , Gascooke Jason R. , Kautzman Kathryn E. , Faulhaber Ann Elise , Neumark Daniel M.
Published: April 2004

The photodissociation spectroscopy and dynamics resulting from excitation of the B̃ 2A″←X̃ 2A″ transition of CH2CFO have been examined using fast beam photofragment translational spectroscopy. The photofragment yield spectrum reveals vibrationally resolved structure between 29 870 and 38 800 cm−1, extending ∼6000 cm−1 higher in energy than previously reported in a laser-induced fluorescence excitation spectrum. At all photon energies investigated, only the CH2F+CO and HCCO+HF fragment channels are observed. Both product channels yield photofragment translational energy distributions that are characteristic of a decay mechanism with a barrier to dissociation. Using the barrier impulsive model, it is shown that fragmentation to CH2F+CO products occurs on the ground state potential energy surface with the isomerization barrier between CH2CFO and CH2FCO governing the observed translational energy distributions.
Disentangling multidimensional femtosecond spectra of excitons by pulse shaping with coherent control
Authors: Abramavicius Darius , Mukamel Shaul
Published: April 2004

Sequences of carefully timed and shaped optical pulses provide femtosecond snapshots of molecular structure as well as electronic and vibrational dynamical processes, in analogy with multidimensional NMR. We apply a genetic learning algorithm towards the design of pulse sequences which simplify the multidimensional signals by controlling the relative intensities of various peaks. Numerical simulations demonstrate how poorly resolved weak features may be amplified and observed by using optimized optical pulses, specifically shaped to achieve a desired spectroscopic target.
Derivation of the electronic nonadiabatic coupling field in molecular systems: An algebraic-vectorial approach
Authors: Vértesi T. , Vibók Á. , Halász G. J. , Baer M.
Published: April 2004

In this Communication it is suggested that various elements of the nonadiabatic coupling matrix, τjk(s) are created by the singular nonadiabatic coupling terms of the system. Moreover, given the spatial distribution of these coupling terms in the close vicinity of their singularity points yields, according to this approach, the integrated intensity of the field at every point in the region of interest. To support these statements we consider the conical intersections of the three lower states of the H+H2 system: From an ab initio treatment we obtain the nonadiabatic coupling terms around each conical intersection separately (at its close vicinity) and having those, create the field at every desired point employing vector-algebra. This approach is also used to calculate the intensity of the Curl of those matrix elements that lack their own sources [τ13(s) in the present case]. The final results are compared with relevant ab initio calculations.
Independent particle theory with electron correlation
Authors: Beste Ariana , Bartlett Rodney J.
Published: April 2004

We formulate an effective independent particle model where the effective Hamiltonian is composed of the Fock operator and a correlation potential. Within the model the kinetic energy and the exchange energy can be expressed exactly leaving the correlation energy functional as the remaining unknown. Our efforts concentrate on finding a correlation potential such that exact ionization potentials and electron affinities can be reproduced as orbital energies. The equation-of-motion coupled-cluster approach enables us to define an effective Hamiltonian from which a correlation potential can be extracted. We also make the connection to electron propagator theory. The disadvantage of the latter is the inherit energy dependence of the potential resulting in a different Hamiltonian for each orbital. Alternatively, the Fock space coupled-cluster approach employs an effective Hamiltonian which is energy independent and universal for all orbitals. A correlation potential is extracted which yields the exact ionization potentials and electron affinities and a set of associated molecular orbitals. We also describe the close relationship to Brueckner theory.
Reaction of formaldehyde cation with molecular hydrogen: Effects of collision energy and H2CO+ vibrations
Authors: Liu Jianbo , Anderson Scott L.
Published: April 2004

The effects on the title reaction of collision energy (Ecol) and five H2CO+ vibrational modes have been studied over a center-of-mass Ecol range from 0.1 to 2.3 eV. Electronic structure and Rice–Ramsperger–Kassel–Marcus calculations were used to examine properties of various complexes and transition states that might be important. Only the hydrogen abstraction (HA) product channel is observed, and despite being exoergic, HA has an appearance energy of ∼0.4 eV, consistent with a transition state found in the electronic structure calculations. A precursor complex-mediated mechanism might possibly be involved at very low Ecol, but the dominant mechanism is direct over the entire Ecol range. The magnitude of the HA cross section is strongly, and mode specifically affected by H2CO+ vibrational excitation, however, vibrational energy has no effect on the appearance energy.
Hot-atom versus Eley–Rideal dynamics in hydrogen recombination on Ni(100). I. The single-adsorbate case
Authors: Martinazzo R. , Assoni S. , Marinoni G. , Tantardini G. F.
Published: April 2004

We compare the efficiency of the Eley–Rideal (ER) reaction with the formation of hot-atom (HA) species in the simplest case, i.e., the scattering of a projectile off a single adsorbate, considering the Hydrogen and Hydrogen-on-Ni(100) system. We use classical mechanics and the accurate embedded diatomics-in-molecules potential to study the collision system over a wide range of collision energies (0.10–1.50 eV), both with a rigid and a nonrigid Ni substrate and for impact on the occupied and neighboring empty cells. In the rigid model metastable and truly bound hot-atoms occur and we find that the cross section for the formation of bound hot-atoms is considerably higher than that for the ER reaction over the whole range of collision energies examined. Metastable hot-atoms form because of the inefficient energy transfer to the adsorbate and have lifetimes of the order 0.1–0.7 ps, depending on the collision energy. When considering the effects of lattice vibrations we find, on average, a consistent energy transfer to the substrate, say 0.1–0.2 eV, which forced us to devise a two-step dynamical model to get rid of the problems associated with the use of periodic boundary conditions. Results for long-lived HA formation due to scattering on the occupied cell at a surface temperature of 120 K agree well with those of the rigid model, suggesting that in the above process the substrate plays only a secondary role and further calculations at surface temperatures of 50 and 300 K are in line with these findings. However, considerably high cross sections for formation of long-lived hot-atoms result also from scattering off the neighboring cells where the energy transfer to the lattice cannot be neglected. Metastable hot-atoms are reduced in number and have usually lifetimes shorter than those of the rigid-model, say less than 0.3 ps. In addition, ER cross sections are only slightly affected by the lattice motion and show a little temperature dependence. Finally, we find also that absorption and reflection strongly depend on the correct consideration of lattice vibrations and the occurrence of trapping.
The adsorption and dissociation of Cl2 on the MgO (001) surface with vacancies: Embedded cluster model study
Authors: Xu Yi-Jun , Li Jun-Qian , Zhang Yong-Fan , Chen Wen-Kai
Published: April 2004

The adsorption of Cl2 at a low-coordinated oxygen site (edge or corner site) and vacancy site (terrace, edge, corner F, F+, or F2+ center) has been studied by the density functional method, in conjunction with the embedded cluster models. First, we have studied the adsorption of Cl2 at the edge and corner oxygen sites and the results show that Cl2, energetically, is inclined to adsorb at the corner oxygen site. Moreover, similar to the most advantageous adsorption mode for Cl2 on the MgO (001) perfect surface, the most favorable adsorption occurs when Cl2 approaches the corner oxygen site along the normal direction. A small amount of electrons are transferred from the substrate to the antibonding orbital of the adsorbate, leading to the Cl–Cl bond strength weakened a little. Regarding Cl2 adsorption at the oxygen vacancy site (F, F+, or F2+ center), both large adsorption energies and rather much elongation of the Cl–Cl bond length have been obtained, in particular at the corner oxygen vacancy site, with concurrently large amounts of electrons transferred from the substrate to the antibonding orbital of Cl2. It suggests, at the oxygen vacancy site, that Cl2 prefers to dissociate into Cl subspecies. And the potential energy surface indicates that the dissociation process of molecular Cl2 to atomic Cl is virtually barrierless.
Probing C–H⋯X hydrogen bonds in amide-functionalized imidazolium salts under high pressure
Authors: Lee Kwang Ming , Chang Hai-Chou , Jiang Jyh-Chiang , Lu Li-Chuan , Hsiao Chia-Jung , Lee Yi-Ting , Lin Sheng Hsien , Lin Ivan J. B.
Published: April 2004

We have probed under high pressure the C–H hydrogen bonds formed by N,N′-disubstituted imidazolium ions having PF6− and Br− counterions. High-pressure infrared spectral profiles, x-ray crystallographic analysis, and ab initio calculations allow us to make a vibrational assignment of these compounds. The appearance of a signal for the free-NH unit (or weakly bonded N–H⋯F unit) in the infrared spectrum of the PF6− salt indicates that conventional N–H⋯O and N–H⋯N hydrogen bonds do not fully dominate the packing. It is likely that the charge-enhanced C2–H⋯F interactions, combined with other weak hydrogen bonds, disturb the formation of N–H hydrogen bonds in the PF6− salt. This finding is consistent with the pressure-dependent results, which reveal that the C2–H⋯F interaction is enhanced upon increasing the pressure. In contrast to the PF6− salt, the imidazolium C–H bonds of the Br− salt have low sensitivity to high pressure. This finding suggests that the hydrogen bonding patterns are determined by the relative hydrogen bond acceptor strengths of the Br− and PF6− ions.
Response to “Comment on ‘Equations of state for fluids: The Dieterici approach revisited’ ” [J. Chem. Phys. 115, 1460 (2001)]
Authors: Sadus Richard J.
Published: April 2004

A re-evaluation is reported of earlier calculations for vapor–liquid equilibria [R. J. Sadus, J. Chem. Phys. 115, 1460(E) (2001); 116, 5913 (2202)] using the Dieterici–Carnahan–Starling (DCS) equation of state. The results for liquid-phase densities and properties near the critical point are generally consistent with the original work. However, the recalculated vapor-phase densities and coexistence pressures are shifted to substantially higher values. The implications for real fluids are that the DCS equation is likely to yield accurate predictions of both near-critical equilibria and the temperature-density behavior of the liquid phase at the expense of poor agreement with experiment for both vapor densities and pressures.
Polymorphism in simple liquids: A Gibbs ensemble Monte Carlo study
Authors: Pellicane Benedetto , Pellicane Giuseppe , Malescio Gianpietro
Published: April 2004

We perform Gibbs ensemble Monte Carlo (GEMC) simulations of a one-component system of hard spheres with a repulsive shoulder and an attractive well. We show the existence of two distinct liquid–gas and liquid–liquid phase equilibria. The GEMC estimate of the critical parameters, as following from an interpolation of the binodal points, is only slightly influenced by finite size effects. The liquid–gas critical temperature and pressure are lower than those of the liquid–liquid phase separation. A discussion of our findings in comparison with those of previous numerical studies is also presented.
General kinetic laws of monomolecular–bimolecular reaction A+B⇄C in solutions
Authors: Doktorov A. B. , Kadetov A. A. , Kipriyanov A. A.
Published: April 2004

Non-Markovian kinetic equations of the reversible monomolecular-bimolecular reactions of the type A+B⇄C (at arbitrary ratio between A and B concentrations) derived earlier are used in the calculation of kinetics on macroscopic space–time scales. It is found that the kinetics of the systems with different structure of reactants is universal, and it is the direct generalization of the kinetic law of mass action of formal chemical kinetics. The analysis of the kinetics allows one to establish the time range of the applicability of the law of mass action. It is shown that beyond these limits the usual kinetic law of mass action becomes invalid, and correct description of the kinetics even in the most rough approximation calls for the non-Markovian corrections to usual kinetic laws.