bluuebunny/crossref_metadata_2025 huggingface dataset:
The Indispensable Metaphor of War:
Authors: Steinert Heinz
Published: August 2003

The hegemonic use of the war metaphor, especially in the field of `crime and punishment', is explained by its usefulness for the `populist structure' of politics. Warfare, punishment and policing are three different forms of the state monopoly of force with different logics and restrictions. The universalization of the experience of war is examined historically. Military basic training is a training in helplessness and authoritarianism. The `process of civilization' has led to war as mass destruction of population and infrastructure in the 20th century. In the populist appeal, value orientations such as `(patriarchal) family/community' and `warrior/masculinity' are mobilized. Populist politics connects these social values to `warfare' as well as to `crime and punishment'.
Imaging permeability structure within the highly permeable carbonate earth: Inverse theory and experiment
Authors: Yamamoto Tokuo
Published: August 2003

In most oil reservoir rocks, the squirt flow characteristic frequency (fsq) range of 10–100 kHz is much less than the Biot characteristic frequency (f0) range of 1 MHz–1 GHz. In contrast, carbonate aquifers have very high permeability (10–3000 d) and the two characteristic frequencies are reversed: f0from 10 Hz to 10 kHz and fsqfrom 1 MHz to 100 MHz. The principal objective of this paper is to develop a pilot inverse method for robust imaging of the high‐permeability structure within carbonate aquifers. An analytical approximate model called the super‐k model is developed. The super‐k model coincides numerically with the combined Biot and squirt‐flow mechanism model when permeability is higher than 100 md and the frequency is lower than 100 kHz (the super‐k regime). In the super‐k regime, the pore fluid is always relaxed so that the attenuation due to the Biot mechanism is roughly four times larger than that of the Biot model. Also, empirical equations are developed that relate the stiffness and rigidity of the skeletal frame and porosity of limestone to compression and shear wave velocities measured from ultrasonic data. The super‐k model is combined with the empirical elastic equations to derive a robust high permeability inverse model. Use of the super‐k inverse model is illustrated in an acoustic crosswell test section of a limestone aquifer between depths of 300 and 480 m over a horizontal width of 11 m. The acoustically imaged permeability, constructed from 4‐kHz velocity and attenuation tomograms, shows excellent agreement with the permeability data obtained hydraulically from pump tests and packer tests performed at four different depth intervals within the test section. The permeability image reveals that the high permeability channels run fairly randomly within the limestone aquifers.
An acoustic wave equation for orthorhombic anisotropy
Authors: Alkhalifah Tariq
Published: August 2003

Using a dispersion relation derived under the acoustic medium assumption, I obtain an acoustic wave equation for orthorhombic media. Although an acoustic wave equation does not strictly describe a wave in anisotropic media, it accurately describes the kinematics of P‐waves. The orthorhombic acoustic wave equation, unlike the transversely isotropic one, is a sixth‐order equation with three sets of complex conjugate solutions. Only one set of these solutions are perturbations of the familiar acoustic wavefield solution for isotropic media for incoming and outgoing P‐waves and, thus, are of interest here. The other two sets of solutions are simply the result of this artificially derived sixth‐order equation.
Incorporating mechanisms of fluid pressure relaxation into inclusion‐based models of elastic wave velocities
Authors: Taylor S. Richard , Knight Rosemary J.
Published: August 2003

Our new method incorporates fluid pressure communication into inclusion‐based models of elastic wave velocities in porous rocks by defining effective elastic moduli for fluid‐filled inclusions. We illustrate this approach with two models: (1) flow between nearest‐neighbor pairs of inclusions and (2) flow through a network of inclusions that communicates fluid pressure throughout a rock sample. In both models, we assume that pore pressure gradients induce laminar flow through narrow ducts, and we give expressions for the effective bulk moduli of inclusions. We compute P‐wave velocities and attenuation in a model sandstone and illustrate that the dependence on frequency and water‐saturation agrees qualitatively with laboratory data. We consider levels of water saturation from 0 to 100% and all wavelengths much larger than the scale of material heterogeneity, obtaining near‐exact agreement with Gassmann theory at low frequencies and exact agreement with inclusion‐based models at high frequencies.
New methods for shape and depth determinations from SP data
Authors: Abdelrahman El‐Sayed M. , El‐Araby Hesham M. , Hassaneen Abdel‐Rady G. , Hafez Mahfooz A.
Published: August 2003

We have extended our earlier derivative analysis method to higher derivatives to estimate the depth and shape (shape factor) of a buried structure from self‐potential (SP) data. We show that numerical second, third, and fourth horizontal‐derivative anomalies obtained from SP data using filters of successive window lengths can be used to simultaneously determine the depth and the shape of a buried structure. The depths and shapes obtained from the higher derivatives anomaly values can be used to determine simultaneously the actual depth and shape of the buried structure and the optimum order of the regional SP anomaly along the profile. The method is semi‐automatic and it can be applied to residuals as well as to observed SP data.

We have also developed a method (based on a least‐squares minimization approach) to determine, successively, the depth and the shape of a buried structure from the residual SP anomaly profile. By defining the zero anomaly distance and the anomaly value at the origin, the problem of depth determination has been transformed into the problem of finding a solution of a nonlinear equation of form f(z) = 0. Knowing the depth and applying the least‐squares method, the shape factor is determined using a simple linear equation.

Finally, we apply these methods to theoretical data with and without random noise and on a known field example from Germany. In all cases, the depth and shape solutions obtained are in good agreement with the actual ones.
Deconvolution and spatial resolution of airborne gamma‐ray surveys
Authors: Billings Stephen D. , Minty Brian R. , Newsam Garry N.
Published: August 2003

The first part of the paper presents a method for frequency domain deconvolution of airborne gamma‐ray surveys using a Wiener filter. A geometrical detector model is used to model gamma‐ray detection, with aircraft movement simply incorporated by a multiplicative term. The method requires estimation of the autocorrelation functions governing both signal and noise. The former is estimated through the radially averaged power spectrum of the survey data, whereas an error propagation analysis is used to estimate the latter, which is assumed white. Slight manual adjustments to the noise level are used to tune the reconstruction.

The technique is applied to a low‐altitude radiometric survey collected along closely spaced transects. Results are good for thorium, but are poor for both potassium and uranium. This can be attributed to the high noise levels in the potassium and uranium estimates, principally due to scattered gamma‐rays from high thorium concentration. Much better results are obtained when the method is applied to a survey with more typical radioelement concentrations. The reconstructions are improved significantly if an adaptive 2D Lee filter is applied prior to deconvolution.

The second part of the paper addresses how noise in the data and attenuation of signal due to the flying height limit the spatial resolution. The autocorrelation functions of signal and noise, along with the gamma‐ray model, can be used to determine how signal‐to‐noise ratio degrades with increasing height. The frequency where signal and noise are present in equal quantity can be used as an estimate of the spatial resolution. Predicted critical sampling rates range from 30 m at 20 m elevation to 60 m at 60 m elevation and 90 m at 120 m elevation.
Impact of flow‐simulation parameters on saturation scales and seismic velocity
Authors: Sengupta Madhumita , Mavko Gary
Published: August 2003

Scales of fluid saturation below seismic resolution introduce uncertainties in the interpretation of seismic velocity. A “coarse‐scale” or “patchy” distribution always has a higher effective seismic velocity than a “fine‐scale” or “uniform” distribution. We present a multidisciplinary study which links rock physics and seismic modeling with reservoir engineering, and provides strategies to reduce uncertainties in saturation scales. In our study, we performed fine‐scale flow simulations that helped us to understand which reservoir parameters control the subseismic‐resolution fluid distribution. Our studies show that when gas is injected into oil reservoirs, gravitational forces induce the formation of subresolution gas caps, which lead to patchy saturation at seismic scales. We also learned that the uniform saturation model is appropriate for most waterflooding into oil and for primary production scenarios where gas comes out of solution. Fluid density contrasts, mobility ratios, and residual oil saturations are some parameters that are crucial in constraining saturation scales.
Volume texture extraction for 3D seismic visualization and interpretation
Authors: Gao Dengliang
Published: August 2003

Visual inspection of poststack seismic image patterns is effective in recognizing large‐scale seismic features; however, it is not effective in extracting quantitative information to visualize, detect, and map seismic features in an automatic and objective manner. Although conventional seismic attributes have significantly enhanced interpreters' ability to quantify seismic visualization and interpretation, very few attributes are published to characterize both intratrace and intertrace relationships of amplitudes from a three‐dimensional (3D) perspective. These relationships are fundamental to the characterization and identification of certain geological features. Here, I present a volume texture extraction method to overcome these limitations. In a two‐dimensional (2D) image domain where data samples are visualized by pixels (picture elements), a texture has been typically characterized based on a planar texel (textural element) using a gray level co‐occurrence matrix. I extend the concepts to a 3D seismic domain, where reflection amplitudes are visualized by voxels (volume picture elements). By evaluating a voxel co‐occurrence matrix (VCM) based on a cubic texel at each of the voxel locations, the algorithm extracts a plurality of volume textural attributes that are difficult to obtain using conventional seismic attribute extraction algorithms. Case studies indicate that the VCM texture extraction method helps visualize and detect major structural and stratigraphic features that are fundamental to robust seismic interpretation and successful hydrocarbon exploration.
Robust inversion of seismic data using the Huber norm
Authors: Guitton Antoine , Symes William W.
Published: August 2003

The “Huber function” (or “Huber norm” ) is one of several robust error measures which interpolates between smooth (ℓ2) treatment of small residuals and robust (ℓ1) treatment of large residuals. Since the Huber function is differentiable, it may be minimized reliably with a standard gradient‐based optimizer. We propose to minimize the Huber function with a quasi‐Newton method that has the potential of being faster and more robust than conjugate‐gradient methods when solving nonlinear problems. Tests with a linear inverse problem for velocity analysis with both synthetic and field data suggest that the Huber function gives far more robust model estimates than does a least‐squares fit with or without damping.
3D ray+Born migration/inversion—Part 2: Application to the SEG/EAGE overthrust experiment
Authors: Operto Stéphane , Lambaré Gilles , Podvin Pascal , Thierry Philippe
Published: August 2003

The SEG/EAGE overthrust model is a synthetic onshore velocity model that was used to generate several large synthetic seismic data sets using acoustic finite‐difference modeling. From this database, several realistic subdata sets were extracted and made available for testing 3D processing methods. For example, classic onshore‐type data‐acquisition geometries are available such as a swath acquisition, which is characterized by a nonuniform distribution of long offsets with azimuth and midpoints.

In this paper, we present an application of 2.5D and 3D ray‐Born migration/inversion to several classical data sets from the SEG/EAGE overthrust experiment. The method is formulated as a linearized inversion of the scattered wavefield. The method allows quantitative estimates of short wavelength components of the velocity model.

First, we apply a 3D migration/inversion formula formerly developed for marine acquisitions to the swath data set. The migrated sections exhibit significant amplitude artifacts and acquisition footprints, also revealed by the shape of the local spatial resolution filters. From the analysis of these spatial resolution filters, we propose a new formula significantly improving the migrated dip section. We also present 3D migrated results for the strike section and a small 3D target containing a channel.

Finally, the applications demonstrate, that the ray+Born migration formula must be adapted to the acquisition geometry to obtain reliable estimates of the true amplitude of the model perturbations. This adaptation is relatively straightforward in the frame of the ray+Born formalism and can be guided by the analysis of the resolution operator.
Traveltime calculations from frequency‐domain downward‐continuation algorithms
Authors: Shin Changsoo , Ko Seungwon , Kim Wonsik , Min Dong‐Joo , Yang Dongwoo , Marfurt Kurt J. , Shin Sungryul , Yoon Kwangjin , Yoon Cheol Ho
Published: August 2003

We present a new, fast 3D traveltime calculation algorithm that employs existing frequency‐domain wave‐equation downward‐continuation software. By modifying such software to solve for a few complex (rather than real) frequencies, we are able to calculate not only the first arrival and the approximately most energetic traveltimes at each depth point but also their corresponding amplitudes. We compute traveltimes by either taking the logarithm of displacements obtained by the one‐way wave equation at a frequency or calculating derivatives of displacements numerically. Amplitudes are estimated from absolute value of the displacement at a frequency.

By using the one‐way downgoing wave equation, we also circumvent generating traveltimes corresponding to near‐surface upcoming head waves not often needed in migration. We compare the traveltimes computed by our algorithm with those obtained by picking the most energetic arrivals from finite‐difference solutions of the one‐way wave equation, and show that our traveltime calculation method yields traveltimes comparable to solutions of the one‐way wave equation. We illustrate the accuracy of our traveltime algorithm by migrating the 2D IFP Marmousi and the 3D SEG/EAGE salt models.
Feasibility of seismic characterization of multiple fracture sets
Authors: Grechka Vladimir , Tsvankin Ilya
Published: August 2003

Estimation of parameters of multiple fracture sets is often required for successful exploration and development of naturally fractured reservoirs. The goal of this paper is to determine the maximum number of fracture sets of a certain rheological type which, in principle, can be resolved from seismic data. The main underlying assumption is that an estimate of the complete effective stiffness tensor has been obtained, for example, from multiazimuth, multicomponent surface seismic and vertical seismic profiling (VSP) data. Although typically only a subset of the stiffness elements (or some of their combinations) may be available, this study helps to establish the limits of seismic fracture‐detection algorithms.

The number of uniquely resolvable fracture systems depends on the anisotropy of the host rock and the rheology and orientation of the fractures. Somewhat surprisingly, it is possible to characterize fewer vertical fracture sets than dipping ones, even though in the latter case the fracture dip has to be found from the data. For the simplest, rotationally invariant fractures embedded in either isotropic or transversely isotropic with a vertical symmetry axis (VTI) host rock, the stiffness tensor can be inverted for up to two vertical or four dipping fracture sets. In contrast, only one fracture set of the most general (microcorrugated) type, regardless of its orientation, is constrained by the effective stiffnesses. These results can be used to guide the development of seismic fracture‐characterization algorithms that should address important practical issues of data acquisition, processing, and inversion for particular fracture models.
Evolution of the cellular stress proteome: from monophyletic origin to ubiquitous function
Authors: Kültz Dietmar
Published: August 2003

Cells respond to acute environmental change by activating a stress response that is widely studied. However, knowledge of this stress response is fragmentary, and a unifying concept explaining its universality for many different species and types of stress is lacking. The need for a holistic view emphasizing the key aspects of the stress response is addressed by the following hypothesis. The cellular stress response is a reaction to any form of macromolecular damage that exceeds a set threshold, independent of the underlying cause. It is aimed at temporarily increasing tolerance limits towards macromolecular damage by utilizing a phylogenetically conserved set of genes and pathways that mediate global macromolecular stabilization and repair to promote cellular and organismal integrity under suboptimal conditions. This mechanism affords time for a separate set of stressor-specific adaptations,designed to re-establish cellular homeostasis, to take action. Supporting evidence, emerging conclusions, and ways to test this hypothesis are presented.
Regulation of a renal urea transporter with reduced salinity in a marine elasmobranch,Raja erinacea
Authors: Morgan Robyn L. , Ballantyne James S. , Wright Patricia A.
Published: August 2003

Marine elasmobranchs retain urea and other osmolytes, e.g. trimethylamine oxide (TMAO), to counterbalance the osmotic pressure of seawater. We investigated whether a renal urea transporter(s) would be regulated in response to dilution of the external environment. A 779 bp cDNA for a putative skate kidney urea transporter (SkUT) was cloned, sequenced and found to display relatively high identity with facilitated urea transporters from other vertebrates. Northern analysis using SkUT as a probe revealed three signals in the kidney at 3.1, 2.8 and 1.6 kb. Upon exposure to 50% seawater, the levels of all three SkUT transcripts were significantly diminished in the kidney (by 1.8- to 3.5-fold). In response to environmental dilution, renal tissue osmolality and urea concentration decreased, whereas water content increased. There were no significant differences in osmolyte and mRNA levels between the dorsal–lateral bundle and ventral sections of the kidney. Taken together, these findings provide evidence that the downregulation of SkUT may play a key role in lowering tissue urea levels in response to external osmolality.
Telepsychiatry in the Canary Islands: user acceptance and satisfaction
Authors: De Las Cuevas Carlos , Artiles Justo , De La Fuente Juan , Serrano Pedro
Published: August 2003

A telepsychiatry service, using ISDN videoconferencing, was established to provide psychiatric consultations for the population of El Hierro, the most westerly of the Canary Islands. During the first year of routine operation, a total of 40 patients had 40 initial and 126 follow-up teleconsultations. The main reason for the consultation identified in the general practitioner's referral form was to establish a diagnosis (60% of patients); the second most common reason was the management of a patient previously diagnosed (20% of patients). According to the results of a questionnaire survey, patients' acceptance of and satisfaction with the technology were high. In their first teleconsultation, about a third of them said that they experienced some initial inconvenience, but this disappeared after a few minutes. Ninety per cent of the patients considered that they received the follow-up care they required. Telepsychiatry was considered by physicians and patients as an adequate vehicle for mental health-care.
Alkoxy‐Substituted Hexastyrylbenzenes
Authors: Meier Herbert , Holst Hans Christof
Published: August 2003

Star‐shaped compounds 2a–e with a central benzene ring and six p‐substituted, (E)‐configured styryl groups have been prepared by a sequence of three‐fold Heck and three‐fold Wittig–Horner reactions. Alkoxy chains (OC3H7, OC6H13, OC10H21, OC12H25) on all six arms guarantee a good solubility of 2a–d, whereas the alternating hexyloxy and cyano substitution in 2e leads to an almost insoluble push‐pull system. Irradiation into the long‐wavelength absorption of 2a–d (with λmax values of 341–342 nm) results in a statistical photocross‐linking, which is characterized by the complete degradation of all stilbene chromophores.
Cover Picture: Chemistry and Biology of Roseophilin and the Prodigiosin Alkaloids: A Survey of the Last 2500 Years (Angew. Chem. Int. Ed. 31/2003)
Authors: Fürstner Alois
Published: August 2003

Raphael's “Mass of Bolsena” depicts the “miracle” that occurred in the small Italian village of Bolsena north of Rome in 1263. The cover picture shows part of the fresco, in which a “bleeding” host is the center of attention. Today we know that such phenomena, which could only be explained as a miracle in the Middle Ages, are caused by prodigiosin‐producing bacteria. With an emphasis on the total synthesis, A. Fürstner summarizes the chemistry and biology of these “prodigious” compounds in his Review on page 3582 ff.
Polymer‐supported palladium(II) complexes and their catalytic study
Authors: Antony R. , Tembe G. L. , Ravindranathan M. , Ram R. N.
Published: August 2003

Chloromethylated poly(styrene–divinylbenzene) copolymers with 8 and 14% crosslinking was functionalized to a Schiff‐base‐bearing polymer by the sequential oxidation of the chloromethyl group to an aldehydic group and subsequent condensation with a base. The anchoring of the metal ion to the liganded polymer beads was carried out by its reaction with an ethanolic solution of palladium(II) chloride. The physicochemical properties of the supported catalyst, including surface area, bulk density, and the swelling of the polymer in polar and nonpolar solvents, were studied. The catalysts were characterized by various techniques, including elemental analysis, DTA–thermogravimetric analysis, Fourier transform infrared spectroscopy, and diffuse reflectance spectroscopy. The surface morphology of the catalyst was studied by scanning electron microscopy. The catalytic hydrogenation of cis‐cyclooctene was investigated with the immobilized catalysts. The effects of various reaction parameters, including catalyst concentration, temperature, and hydrogen pressure on the reduction of olefin, were studied. The rate of the reaction was determined from hydrogen uptake measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 370–378, 2003
Small bubbles oxygenation membrane
Authors: Yasuda H. K. , Lin J. N.
Published: August 2003

Large bubbles emerge from porous membranes with small pores because the emerging bubbles spread on the membrane surface before they detache from the surface. If the sessile bubble contact angle (θ) is less than 45°, no spreading occurs, and the bubble size is determined by the size of hole. Even in this case, the equivalent diameter (of spherical bubble) is significantly larger than the pore diameter due to the bubble formation mechanism. If θ > 45°, the spreading of the emerging bubble on the surface occurs, and the bubble size is determined by the size of base of a sessile bubble, which depends on the value of θ, and is independent of the pore size. The equivalent diameter of a bubble could be greater in order of magnitude than the pore diameter. The same principle applies to the bubble formation from an inclined surface; however, the bubble formation is more complicated because of drifting of a developing bubble out of the orifice and the merging of sliding bubbles. In order to create small bubbles, it is necessary to create small orifices on a hydrophilic surface, of which θ < 45°, and two orifices should be separated beyond the maximum diameter of emerging bubble. A horizontal flat surface is the best for the creation of small‐sized bubbles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 387–398, 2003
Morphology of integral‐skin layers in hollow‐fiber gas‐separation membranes
Authors: Carruthers Seth B. , Ramos Gabriela L. , Koros William J.
Published: August 2003

The morphologies of polymeric integrally skinned asymmetric gas‐separation membranes are typically visualized as a thin gas‐selective skin region supported by a nonselective, low‐resistance porous structure. The validity of this visualization for defect‐free and defective membranes was investigated via scanning electron microscopy (SEM) in combination with traditional gas‐permeation measurements for previously reported ultrathin defect‐free hollow‐fiber membranes. Hollow‐fiber membranes were formed via a dry‐jet, wet‐quench process with a spinning solution composed of Matrimid® polyimide and components of varying volatility. For all the defect‐free membranes formed, SEM images revealed a prominent dense skin layer across the fibers' entire outer circumference. Skin‐thickness estimates from 36 SEM images and N2, O2, and He pure gas‐permeation measurements agreed to within 9, 7, and 24% for defect‐free membranes with 150‐, 300‐, and 600‐nm skin thicknesses, respectively. Defective membranes with O2/N2 gas selectivities of Knudsen values, nominally 50 and 80% of dense film values, exhibited a well‐developed nodular, partially developed nodular, and uniform dense layer (no nodules) skin morphologies, respectively. These results provide in‐depth experimental evidence for the existence of a distinct dense integral‐skin layer and suggest that the presence of nodules in the membrane's final skin morphology correlate to gas‐permeation defects. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 399–411, 2003
Measurement of thermal properties of polyaniline/metal from room temperature to 170°C
Authors: Joshi G. P. , Saxena N. S. , Sharma T. P. , Verma S. , Dixit V. , Mishra S. C. K.
Published: August 2003

The heat transfer through polyaniline (PANI) mixed with metals (manganese and iron) is studied by measuring its effective thermal conductivity (λe) and effective thermal diffusivity (χe) from room temperature to 170°C at normal pressure. Simultaneous measurements of the λe and χe values of samples A (100% Fe), B (50% Fe and 50% Mn), and C (100% Mn) of the PANI mixtures with different percentages of Fe and Mn are carried out using the transient plane source technique. It is observed that the λe and χe of the above samples are almost independent of the temperature in a range of temperatures. However, maximum values for the λe and χe are found for sample A at ∼140°C, sample B at ∼130°C, and sample C at ∼120°C. An empirical relationship deduced from a polynomial fit of the experimental data is established for the temperature dependence of the λe and χe values of these samples. Reasonably good agreement is obtained between the theoretically predicted results and the experimental data. This behavior is explained on the basis of bond formation between the metals (Fe and Mn) and nitrogen of the PANI matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 430–435, 2003
Thermotropic liquid‐crystalline copolyester (Rodrun LC3000)/thermoplastic elastomer (SEBS) in situ composites: II. Mechanical properties and morphology of monofilaments in comparison with extruded strands
Authors: Saikrasun S. , Bualek‐Limcharoen S. , Kohjiya S. , Urayama K.
Published: August 2003

Monofilaments of in situ composites were prepared from an immiscible blend of a thermotropic liquid‐crystalline polymer (TLCP), Rodrun LC3000, and a thermoplastic elastomer, styrene–(ethylene butylene)–styrene (SEBS), by a melt spinning process. Mechanical properties and the morphology of the composite monofilaments were investigated and compared with those of the extruded strands previously reported. The stresses at all tensile strains of the composite monofilaments were much higher than those of the extruded strands. The tensile strengths of both extruded strands and monofilaments were comparable, but the elongation at break of monofilaments dropped considerably. The tension sets of composite monofilaments were slightly higher than those of extruded strands. All composite monofilaments with TLCP content of ≤15 wt % exhibited good elastic recovery under the applied strain up to 200%. The dynamic mechanical storage modulus at 25°C of 10 wt % TLCP composite monofilament increased fourfold compared with that of the composite extruded strand and fivefold compared with that of the neat SEBS monofilament. The dramatic enhancement in the mechanical properties of in situ composite monofilaments is due to the formation of finer and longer TLCP fibrils (length‐to‐width ratio > 100) than those formed in the extruded strands. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 518–524, 2003
Effect of initiators and ethoxylation degree of non‐ionic emulsifiers on vinyl acetate and butyl acrylate emulsion copolymerization in the loop reactor
Authors: Sarac Ayfer , Yildirim Huseyin
Published: August 2003

Vinyl acetate and butyl acrylate copolymers were synthesized in the presence of ammonium persulfate and potassium persulfate initiators, mixture of non‐ionic and anionic emulsifiers, and polyvinyl alcohol as protective colloid in a loop reactor. The monomer ratio was chosen 85:15. The series of non‐ionic emulsifiers, which have 10–40 moles ethoxylated nonyl phenol, were combined with Nansa 66 (sodium dodecyl benzene sulfonate). The effects of the initiators on the physicochemical properties of copolymers were investigated by measuring conversion, viscosity, molecular weight, molecular weight distribution, and surface tension, respectively by using gravimetric method, Brookfield viscometer, gel permeation chromatograpy (GPC), and ring method. The effects of ethoxylation degrees of the non‐ionic emulsifiers to the same properties of copolymers were also investigated. It was determined that the copolymer viscosities showed different tendency for two initiators. They were increased by the increasing ethoxylation degree of the non‐ionic emulsifier for ammonium persulfate. In contrast, latex viscosity was decreased by increasing the ethoxylation degree in presence of potassium persulfate. Similar changes were also found in number average molecular weights of copolymers. On the other hand, weight average molecular weights of copolymers increased by increasing the ethoxylation degree of the non‐ionic emulsifier for both initiators. In the case of potassium persulfate, the surface tension values of copolymers increased by increasing the ethoxylation degree, but generally increasing the ethoxylation degree did not affect the surface tension of copolymer very seriously for two initiators. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 537–543, 2003
Anisotropic character and ultrasonic stiffness changes during the natural weathering of LDPE films
Authors: Chabira S. F. , Huchon R. , Sebaa M.
Published: August 2003

Blown extruded polyethylene films without stabilizers have been exposed outdoors under severe weathering conditions in the Sahara. The chemical aspect of aging has been followed by IR spectroscopy. The mechanical aspect of aging has been monitored by means of a nondestructive method. It consists of measuring velocities and attenuations of ultrasonic waves propagating in several directions in the film plane. Stiffness constants and energy dissipation terms have been calculated. From the results obtained it is shown that stiffening of the material leads to an increase of velocities and a decrease of wave attenuation. Moreover, the stiffness constants as well as the energy dissipation terms vary with aging and show a changing anisotropic character of the films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 559–564, 2003
High‐Pressure Selectivity Studies—A Simple Route to a Homochiral Wistarin Precursor
Authors: Knappwost‐Gieseke Costanze , Nerenz Frank , Wartchow Rudolf , Winterfeldt Ekkehard
Published: August 2003

The cycloaddition of spirobutenolide 3 to the homochiral cyclopentadiene 1 at 6.5 kbar leads exclusively to cycloadduct 5. Subsequent Diels–Alder or Michael additions again favour the cyclohexenone double bond; this perfect chemo‐ regio‐ and face selectivity was employed for a short and efficient approach to the wistarin framework.
A Density Functional Study To Choose the Best Fluorophore for Photon‐Induced Electron‐Transfer (PET) Sensors
Authors: Chatterjee Abhijit , Suzuki Toshishige M. , Takahashi Yukiko , Pacheco Tanaka David A.
Published: August 2003

Anthracenes bearing aliphatic or aromatic amino substituents, which behave as molecular sensors, have shown their potential to act as photon‐induced electron‐transfer (PET) systems. In this PET, the fluorophore moieties are responsible for electron release during protonation and deprotonation. The principle of hard and soft acids and bases (HSAB) deals with both intra‐ and intermolecular electron migration. It is possible to calculate the localized properties in terms of Fukui functions in the realm of density functional theory (DFT) and thus calculate and establish a numerical matchmaking procedure that will generate an a priori rule for choosing the fluorophore in terms of its activity. We calculated the localized properties for neutral, anionic, and cationic systems to trace the course of the efficiency. A qualitative scale is proposed in terms of the feasibility of intramolecular hydrogen bonding. To investigate the effect of the environment of the nitrogen atom on protonation going from mono‐ to diprotonated systems, we calculated the partial density of states and compared the activity sequence with reactivity indices. The results show that location of the nitrogen atom in an aromatic ring does not influence the PET, but for aliphatic chains it plays a role. Furthermore, the protonation/deprotonation scenario has been explained. The results show that the reactivity indices can be used as a suitable property for scaling the activity of fluorophore molecules for the PET process.
Why Does a Ga2 Dimer React Spontaneously with H2, but a Ga Atom Does Not?—A Detailed Quantum Chemical Investigation of the Differences in Reactivity Between Ga Atoms and Ga2 Dimers, in Combination with Experimental Results
Authors: Köhn Andreas , Himmel Hans‐Jörg , Gaertner Benjamin
Published: August 2003

The spontaneous and photoactivated reactions between Ga2 and H2 in a matrix of solid Ar at 12 K have been followed by using IR spectroscopy and have been shown to give access to several isomers of the subvalent hydride Ga2H2. We now present Raman spectra for this system, to complete its characterization on the basis of vibrational spectra. In addition, the differences between the reactivity of a Ga atom and a Ga2 dimer toward H2 are evaluated. The matrix isolation experiments have shown that Ga2 reacts spontaneously with H2, at 12 K, to give the cyclic subvalent hydride Ga(μ‐H)2Ga (D2h symmetry), which can be transformed into two other isomers of Ga2H2 by selective photoactivation. Interestingly, the spontaneous reaction is subject to a marked isotopic effect. In total, the experimental results provide detailed information about the reaction mechanism. In contrast to Ga2, Ga atoms do not react spontaneously with H2; on photoactivation they instead yield the radical species GaH2. The quantum chemical calculations presented herein start with an analysis of the structures and relative energies of the relevant species at the MP2 level, by using extended basis sets, and lead on to a discussion of the correlation diagrams for both reactions. Finally, CASSCF and MRCI methods, in combination with moderate‐sized basis sets, were employed to analyze in detail the mechanisms of the two reactions. It will be shown that the computational results, in concert with the experimental findings, provide a satisfying explanation of the contrasting reactivities of Ga and Ga2.
Synthesis of Hexasaccharide Fragments of Pectin
Authors: Clausen Mads H. , Madsen Robert
Published: August 2003

Short syntheses of partially methyl‐esterified hexagalacturonates 1–5 are described as part of the development of strategies for the preparation of larger pectic oligosaccharides. The methodology is based on the repeated coupling of galactose mono‐ and disaccharide donors onto a galactose acceptor until a hexagalactan is obtained. All glycosylations are carried out with n‐pentenyl glycosides to provide good yields of the desired α anomers. Pentenyl disaccharide donors are prepared by the coupling of two pentenyl galactosides controlled by either the armed–disarmed effect or by converting one pentenyl galactoside into the corresponding galactosyl bromide or fluoride. Two orthogonal protecting groups are employed at C6, which makes it possible to oxidize these positions to either the carboxylic acid or to the methyl ester. Each hexagalactan is therefore able to bifurcate into two different hexagalacturonates with a reverse methyl‐esterification pattern. The methyl ester distribution in the hexagalacturonates is confirmed by tandem mass spectrometry.
N⋅⋅⋅Br Halogen Bonding: One‐Dimensional Infinite Chains through the Self‐Assembly of Dibromotetrafluorobenzenes with Dipyridyl Derivatives
Authors: De Santis Alessandra , Forni Alessandra , Liantonio Rosalba , Metrangolo Pierangelo , Pilati Tullio , Resnati Giuseppe
Published: August 2003

The N⋅⋅⋅Br halogen bonding drives the self‐assembly of 1,4‐dibromotetrafluorobenzene (1 a) and its 1,3 or 1,2 analogues (1 b,c, respectively) with dipyridyl derivatives 2 a,b. The isomeric supramolecular architectures 3 a–f are obtained as cocrystals that are stable in the air at room temperature. The solid‐state features of these 1D infinite chains 3 have been fully characterized by single‐crystal X‐ray, Raman, and IR analyses. The occurrence of N⋅⋅⋅Br halogen bonding in solution has been detected with 19F NMR spectroscopy. The N⋅⋅⋅Br halogen bonding is highly selective and directional and the geometry of the single strands of noncovalent copolymers 3 is programmed by the geometry of halogen‐bonding donor and acceptor sites on the starting modules. The composition and topology of the instructed networks can be predicted with great accuracy. Experiments of competitive cocrystal formation established the strength of the N⋅⋅⋅Br interaction relative to other halogen bondings and the ability of different modules 1 to be involved in site‐selective supramolecular syntheses.
Copper–Metallomesogen Structures Obtained by Ionic Self‐Assembly (ISA): Molecular Electromechanical Switching Driven by Cooperativity
Authors: Camerel Franck , Strauch Peter , Antonietti Markus , Faul Charl F. J.
Published: August 2003

In a stepwise noncovalent multiple‐interaction strategy, copper(II) salts were complexed with the sodium salts of bathophenanthrolinedisulfonic acid (BPS) and bathocuproinedisulfonic acid (BCS), and organized into nanostructured materials by the addition of ammonium surfactants by means of the ionic self‐assembly (ISA) route. In the case of the methyl‐substituted BCS complexes, a slow color change from green to brick red was observed. UV and EPR investigations showed that the color change was due to a change in oxidation state, the resulting brick red color is typical for CuI species. It is concluded that steric interactions and mechanical packing into a supramolecular structure drive this electronic transition at the metal center. When complexation is performed with double‐tail ammonium surfactants, these metallomesogenic materials exhibit thermotropic liquid‐crystalline phase behavior, as investigated by polarized light microscopy, differential scanning calorimetry (DSC), and temperature‐dependent wide‐angle and small‐angle X‐ray analyses. The complexity of the observed phases increased with increasing tail length of the surfactants. Complexation with double‐tail C18 surfactants yielded highly organized materials for both the BPS and BCS ligands.
An Efficient One‐Pot Approach to Bridged Bicyclic Ring‐Systems through Consecutive Hetero‐Domino Transformations: A Mechanistic Rationale and Further Rearrangements
Authors: Finet Laure , Candela Lena José I. , Kaoudi Talbi , Birlirakis Nicolas , Arseniyadis Siméon
Published: August 2003

This article describes the design of olefin‐generated/reagent‐modulated consecutive hetero‐domino reactions of 1,2‐unsaturated bicyclic diols, which are potentially of great use, initiated by PhI(OAc)2, continued by [Pb(OAc)4], and completed by use of a mild base (K2CO3). Inversion of a quaternary center has been achieved through a three‐reaction sequence: a domino transformation followed by an m‐CPBA‐mediated Baeyer–Villiger oxidation and subsequent reductive lactone ring opening.
Cover Picture: Coordination Algorithms Control Molecular Architecture: [CuI4(L2)4]4+ Grid Complex Versus [MII2(L2)2X4]y+ Side‐By‐Side Complexes (M=Mn, Co, Ni, Zn; X=Solvent or Anion) and [FeII(L2)3][Cl3FeIIIOFeIIICl3] (Chem. Eur. J. 16/2003)
Authors: Lan Yanhua , Kennepohl Dietmar K. , Moubaraki Boujemaa , Murray Keith S. , Cashion John D. , Jameson Geoffrey B. , Brooker Sally
Published: August 2003

The cover picture shows how differing coordination algorithms control the molecular architecture of complexes of the pyridazine‐containing, two‐armed, acyclic Schiff base ligand L2 (left, prepared from one equivalent of 3,6‐diformylpyridazine and two equivalents of d‐anisidine). Two very different complexes of L2 self‐assemble from tetrahedral copper(I) versus octahedral zinc(II), nickel(II), and cobalt(II) controlled 1 : 1 reactions with L2. In both cases the metal ions are bridged by the pyridazine moieties in L2, but in the case of the tetrahedral copper(II) the result is a tetrametallic [2×2] grid complex ([CuI4(L2)4]4+: top right), whilst in the case of the octahedral metal(II) ions dimetallic side‐by‐side complexes, [MII2(L2)2(X)4]y+ (M = Mn, Co, Ni, Zn; X = solvent or anion), are formed (bottom right). The cover image was kindly generated by M. Crawford (University of Otago) with Strata Studio Pro (Strata). More details are given by S. Brooker and co‐workers on p. 3772 ff.
No‐Barrier Theory: Calculating Rates of Chemical Reactions from Equilibrium Constants and Distortion Energies
Authors: Guthrie J. Peter
Published: August 2003

No‐barrier theory is a new approach to the calculation of rate constants for reactions in solution, from the corresponding equilibrium constants. It requires relatively small molecular orbital theory calculations, and has been very successful. It is in the spirit of Marcus theory, but does not require an “intrinsic barrier”. The approach is explained, with an examination of the way in which the ideas on which it is based were “in the air”.
Fluorescence Spectroscopy of Single Molecules under Ambient Conditions: Methodology and Technology
Authors: Böhmer Martin , Enderlein Jörg
Published: August 2003

This review presents an overview of the fluorescence detection and spectroscopy of single molecules (SMS) in liquids and on surfaces under ambient conditions. The various techniques of SMS, such as confocal epifluorescence detection and wide‐field imaging are presented and discussed, together with the different methods of data analysis such as fluorescence correlation spectroscopy and burst‐by‐burst analysis. Selected applications of the various techniques in physics, chemistry, and biology are described.
Atomic Properties of Amino Acids: Computed Atom Types as a Guide for Future Force‐Field Design
Authors: Popelier Paul L. A. , Aicken Fiona M.
Published: August 2003

The quantum chemical topology (QCT) is able to propose atom types by direct computation rather than by chemical intuition. In previous work, molecular electron densities of 20 amino acids and smaller derived molecules were partitioned into a set of 760 topological atoms. Each atom was characterised by seven atomic properties and subjected to cluster analysis element by element, that is, C, H, O, N, and S. From the respective dendrograms, 21 carbon atom types were distinguished, 7 hydrogen, 2 nitrogen, 6 oxygen, and 6 sulfur atom types. Herein, we contrast the QCT atom types with those of the assisted model building with energy refinement (AMBER) force field. We conclude that in spite of fair agreement between QCT and AMBER atom types, the latter are sometimes underdifferentiated and sometimes overdifferentiated. In summary, we suggest that QCT is a useful guide in designing new force fields or improving existing ones. The computational origin of QCT atom types makes their determination unbiased compared to atom type determination by chemical intuition and a priori assumptions. We provide a list of specific recommendations.
PRICE: primitive centred schemes for hyperbolic systems
Authors: Toro E. F. , Siviglia A.
Published: August 2003

We present first‐ and higher‐order non‐oscillatory primitive (PRI) centred (CE) numerical schemes for solving systems of hyperbolic partial differential equations written in primitive (or non‐conservative) form. Non‐conservative systems arise in a variety of fields of application and they are adopted in that form for numerical convenience, or more importantly, because they do not posses a known conservative form; in the latter case there is no option but to apply non‐conservative methods. In addition we have chosen a centred, as distinct from upwind, philosophy. This is because the systems we are ultimately interested in (e.g. mud flows, multiphase flows) are exceedingly complicated and the eigenstructure is difficult, or very costly or simply impossible to obtain. We derive six new basic schemes and then we study two ways of extending the most successful of these to produce second‐order non‐oscillatory methods. We have used the MUSCL‐Hancock and the ADER approaches. In the ADER approach we have used two ways of dealing with linear reconstructions so as to avoid spurious oscillations: the ADER TVD scheme and ADER with ENO reconstruction. Extensive numerical experiments suggest that all the schemes are very satisfactory, with the ADER/ENO scheme being perhaps the most promising, first for dealing with source terms and secondly, because higher‐order extensions (greater than two) are possible. Work currently in progress includes the application of some of these ideas to solve the mud flow equations. The schemes presented are generic and can be applied to any hyperbolic system in non‐conservative form and for which solutions include smooth parts, contact discontinuities and weak shocks. The advantage of the schemes presented over upwind‐based methods is simplicity and efficiency, and will be fully realized for hyperbolic systems in which the provision of upwind information is very costly or is not available. Copyright © 2003 John Wiley & Sons, Ltd.