bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of microfeatures in selective laser sintered drug delivery devices
Authors: Cheah C M , Leong K F , Chua C K , Low K H , Quek H S
Published: January 2003

From initial applications in the fields of prosthesis, implants, surgery planning, anthropology, paleontology and forensics, the scope of rapid prototyping (RP) biomedical applications has expanded to include areas in tissue engineering (TE) and controlled drug delivery. In the current investigation, the feasibility of utilizing selective laser sintering (SLS) to fabricate polymeric drug delivery devices (DDDs) that are difficult to make using conventional production methods was studied. Two features, namely porous microstructure and dense wall formation, inherent in SLS fabricated parts were investigated for their potential roles in drug storage and controlling the release of drugs through the diffusion process. A study to determine the influence of key SLS process parameters on dense wall formation and porous microstructure of SLS fabricated parts was carried out. Composite-type DDDs incorporating dense wall and porous matrix features were designed and fabricated using SLS. The characteristics of the fabricated devices were investigated through micro-structural examination and in vitro release tests carried out using a drug model or dye in a simulated body environment.
A new capillary viscometer for small samples of whole blood
Authors: Marinakis G N , Barbenel J C , Tsangaris S G
Published: January 2003

A new capillary viscometer is described in which a column of blood is discharged under a constant pressure, producing a variety of shear stresses during a single test. Measurement of the viscosity of Newtonian sucrose solutions showed good agreement between the viscosity determined from the new system and the expected values. The viscosity of whole blood was measured in a cone-and-plate viscometer at a wide range of shear rates and characterized using a power law model; good agreement was obtained between the capillary and rotational results at low and medium shear rates. High shear rate results could also be obtained by increasing the driving pressure. The new viscometer proved to be simple to use, utilized a small test volume and produced reliable results.
The influence of shape and sliding distance of femoral head movement loci on the wear of acetabular cups in total hip arthroplasty
Authors: Bennett D , Orr J F , Beverland D E , Baker R
Published: January 2003

Wear of the polyethylene acetabular component is the most serious threat to the long-term success of total hip replacements (THRs). Greatly reduced wear rates have been reported for unidirectional, compared to multidirectional, articulation in vitro. This study considers the multidirectional motions experienced at the hip joint as described by movement loci of points on the femoral head for individual THR patients. A three-dimensional computer program determined the movement loci of selected points on the femoral head for THR patients and normal subjects using kinematic data obtained from gait analysis. The sizes and shapes of these loci were quantified by their sliding distances and aspect ratios with substantial differences exhibited between individual THR patients. The average sliding distances ranged from 10.0 to 18.1 mm and the average aspect ratios of the loci ranged from 2.5 to 9.2 for the THR patients. Positive correlations were found between wear rate and average sliding distance, the inverse of the average aspect ratio of the loci and the product of the average sliding distance and the inverse of the average aspect ratio of the loci. Patients with a normal hip joint range of motion produce multidirectional motion loci and tend to experience more wear than patients with more unidirectional motion loci. Differing patterns of multidirectional motion at the hip joint for individual THR patients may explain widely differing wear rates in vivo.
Effect of microseparation on contact mechanics in ceramic-on-ceramic hip joint replacements
Authors: Mak M M , Besong A A , Jin Z M , Fisher J
Published: January 2003

The contact mechanics in ceramic-on-ceramic hip implants are investigated in this study under the microseparation condition where the edge contact occurs between the superolateral rim of the acetabular cup and the femoral head. A three-dimensional finite element model is developed to examine the effect of the microseparation distance between the femoral head and the acetabular cup on the contact area and contact stresses between the bearing surfaces. It is shown that microseparation leads to edge contact and elevated contact stresses, and these are mainly dependent on the magnitude of separation, the radial clearance between the femoral head and the acetabular cup, and the cup inclination angle. For a small microseparation distance (less than the diametrical clearance), the contact occurs within the acetabular cup, and consequently an excellent agreement of the predicted contact pressure distribution is obtained between the present three-dimensional anatomical model and a simple two-dimensional axisymmetric model adopted in a previous study [5]. However, as microsegregation is increased further, edge contact between the superolateral rim and the femoral head occurs. Consequently, the predicted contact pressure is significantly increased. The corresponding contact area resembles closely the stripe wear pattern observed on both clinically retrieved and simulator-tested ceramic femoral heads [8, 9, 11]. Furthermore, introducing a fillet radius of 2.5 mm at the mouth of the acetabular cup is shown to reduce the contact stress due to edge contact, but only under relatively large microseparation distances.
Surface characterization and debris analysis of ceramic pairings after ten million cycles on a hip joint simulator
Authors: Affatato S , Ferrari G , Chevalier J , Ruggeri O , Toni A
Published: January 2003

This study was aimed at characterizing the ceramic wear particles produced during tests on a hip joint wear simulator of up to 10 million cycles. Alumina and alumina-zirconia composites were studied as commercial or potential hip joint products respectively. No ceramic particles could be observed, even after a careful isolation procedure. This confirms the low wear rate found for these materials in previous works (of the order of tenths of milligrams per million cycles). Surface characterization was conducted by means of scanning electron microscopy. It confirms the low wear regime of ceramic pairings and allows ceramic wear debris morphology to be defined. The effect of microstructure on surface wear is discussed.
A new combustion system of a heat-insulated natural gas engine with a pre-chamber having a throat valve
Authors: Sasaki H , Sekiyama S , Nakashima K
Published: January 2003

A ceramic heat-insulated natural gas engine has been developed which incorporates a pre-chamber and a throat valve to the main chamber. Low-pressure natural gas is supplied into the pre-chamber to form fuel-rich mixtures in the pre-chamber during the intake stroke while the throat valve is closed, while natural gas and exhaust gas recirculation (EGR) gas are charged in the intake port to form a homogeneous mixture in the main chamber. Experiments showed that spontaneous ignition took place near top dead centre (TDC) in the pre-chamber immediately after the throat valve was opened, followed by homogeneous charge compression ignition (HCCI) combustion in the main chamber, featuring very fast combustion and extremely low NOX emission. Effects of engine parameters including compression ratio, throat valve opening timing, the fuel fraction injected into the pre-chamber and the EGR ratio were investigated. It was found from the experiment that 85 per cent of the fuel supplied could be successfully burned in HCCI combustion in the main chamber being triggered by the spontaneous ignition in the pre-chamber, and the HCCI combustion could be controlled if the engine parameters mentioned above could be well optimized.
A study of the influence of exhaust gas recirculation and stoichiometry on the heat release in the end-gas prior to knock using rotational coherent anti-Stokes-Raman spectroscopy thermometry
Authors: Grandin B , Denbratt I , Bood J , Brackmann C , Bengtsson P-E
Published: January 2003

Heat release in the end-gas prior to autoignition was investigated using different experimental methods including transducers for heat flux and pressure as well as rotational coherent anti-Stokes-Raman spectroscopy, which is a laser-based method for non-intrusive instantaneous thermometry of the gas. The time history was examined in the cases of mixtures of various stoichio-metries, where some were diluted with exhaust gas recir-culation (EGR). The measured temperature history was compared with the isentropic temperature calculated from the cylinder pressure trace. This comparison revealed a difference in heat release from low-temperature reactions in the end-gas for the various mixtures tested at a constant indicated mean effective pressure and a fixed position of 50 per cent burnt charge. It is shown that lean mixtures tend to exhibit the highest knock intensity, mainly due to a decrease in specific heat, as compared to the richer mixtures, which result in an earlier knock onset and as a consequence higher knock intensity. Furthermore, the comparison of temperatures indicates that the rich mixtures have a high heat release from low-temperature chemistry, which to some extent negates the higher specific heat of the charge. As a consequence, a slight enrichment of the charge can lead to higher knock intensity in comparison with a stoichiometric mixture. In spite of the lower specific heat of the charge when a stoichiometric charge was diluted with cooled EGR, these mixtures showed a very low tendency to knock.
An experimental analysis of low-temperature and premixed combustion for simultaneous reduction of NOx and particulate emissions in direct injection diesel engines
Authors: Kimura S , Ogawa H , Matsui Y , Enomoto Y
Published: January 2003

A new combustion concept, named MK (modulated kinetics) combustion, has been developed, which reduces NOx and smoke simultaneously through high exhaust gas recirculation (EGR) and retarded injection timing. High-speed photography was employed to investigate the physical and chemical processes of MK combustion, and the results revealed that the combustion features premixed combustion and the low-temperature flames were accompanied by transparent appearances. Heat flux measurements and KIVA calculations were also made to investigate the effects of swirl, which serves to improve thermal efficiency in MK combustion. It was apparent that the swirl effectively governs the fuel distribution in the combustion chamber, suppressing HC formation and improving thermal efficiency by preventing the flames from contacting the cavity walls. Throughout these experiments, ignition delay and fuel injection duration were found to be the two key parameters that control MK combustion. Accordingly, ignition delay was prolonged by cooled EGR and fuel injection duration was shortened by high injection pressure to allow the MK combustion operation in a high load range.
Value Change in Oil and Gas Production: IV Unresolved Options with New Information Acquisition
Authors: Lerche I. , Noeth S.
Published: January 2003

This paper considers the situation after one has committed to acquiring new information but when the information acquired does not resolve completely an ambiguity in potential new reserves for a producing field. As a consequence, management must decide whether further studies are warranted at some cost and with only a finite probability such studies would lead to a successful venture, or whether it is more appropriate to abandon the investment. Because there are a large number of ways such an investigation can be handled, and because a large number of possible parameter values can influence the decision, in this paper we restrict the analysis to just two variables: either a fixed probability of success after further studies but with a variable cost for the studies, or where there is a fixed cost allowed for the studies but the success probability after the studies is variable. Other situations involving more complex but more realistic, groupings of variable and often unknown parameters will be considered in later papers in this series. The simple examples given here are provided to illustrate as sharply as possible extreme end-member situations when resolution is not achieved with acquisition of information alone.
“Assessing the Value of Information Management”
Authors: Kjensmo E. S.
Published: January 2003

The value of improving management of data and information as well as implementing processes to ensure knowledge sharing is often not considered when embarking on these investments. This note suggests a methodology that addresses how to estimate, measure and delineate the impact of information management (IM) technology and services relative to oil company business drivers, and quantify the business value an information management project can offer. In addition means to evaluate the risk and return on an information management investment will be provided.
Promoting Environmental Innovation in the Energy Sector: An Analytcial Framework for Dynamic Efficiency Assessments
Authors: Christiansen Atle Christer
Published: January 2003

It is increasingly being recognised that the development, adoption and diffusion of cleaner energy technologies are key determinants to success or failure in environmental policy, at least in the long term. However, it is still unclear what specific role there is for public policies and regulatory intervention in this field, and how to select an appropriate portfolio of policy action and instruments that does justice to all stages in the development cycle of technological change. The key objective of this paper is to provide an analytical framework for analysing and assessing the way in which public policy can promote environmentally benign technological change. The framework comprises a template that blends a mechanistic representation of causal variable-impact relationships with knowledge and insights from empirical research.

“It is widely agreed that technical innovation is the ultimate key to successful (meaning affordable as well as quantitatively adequate) global measures to stabilise the concentration of GHGs in the atmosphere” (Toman, 1998: 610)
Pines in the Himalayas: Past, Present and Future Scenario
Authors: Sinha Bhaskar
Published: January 2003

The Himalayas have a great environmental influence in the Indian subcontinent. But Himalayan ecosystems with their rich biodiversity are particularly fragile. In the recent past, India has been serially affected by several natural calamities like droughts, floods and even earthquakes. Scientists all over the world have warned of various contributing factors. But, the major cause has been attributed to one important matrix – the constant degeneration of the Himalayan ecology. Human activities have resulted in arrested succession, leading to exhaustion of the germplasm of larger shrubs and trees, and invasion of exotic weeds. Large-scale transformation of landscapes for chir-pine plantation in the Himalayas has resulted in changes in soil physicochemical and biological properties. In this article the author depicts the introduction of pines as well as the present and future consequences of pine culture in the Himalayas.
Superbeads: Immobilization in “Sweet” Chemistry
Authors: Nahalka Jozef , Liu Ziye , Chen Xi , Wang Peng George
Published: January 2003

Enzymatic oligosaccharide synthesis using recombinant glycosyltransferases is able to overcome the difficulties associated with chemical methods. Nonetheless, sugar nucleotide regeneration cycles are necessary for the glycosylation. The multistep enzyme reaction can be efficiently carried out on superbeads that are prepared by immobilizing multienzyme mixtures on bead support through fused binding domains.
Diastereoselective Hydroformylation of 2‐Substituted Allylic o‐DPPB‐Esters—On the Origin of 1,2‐Asymmetric Induction
Authors: Breit Bernhard , Heckmann Golo , Zahn Stephan K.
Published: January 2003

2‐Substituted secondary alcohol o‐DPPB esters (o‐DPPB=ortho‐diphenylphosphanylbenzoyl) have been prepared and their o‐DPPB‐directed diastereoselective hydroformylation examined. It was found that the diastereoselectivity increased as a function of the steric demand of the substituents both at the stereogenic center and in the alkene 2‐position. Hydrolytic cleavage of the o‐DPPB group afforded—via the lactols 29—the corresponding lactones 30, the relative configurations of the vicinal stereogenic centers of which were ascertainable by 2D‐NOESY spectroscopy. In addition, a crystal structure analysis of the hydroformylation product 2 d provided further confirmation of the relative configuration. Replacement of the ester carbonyl group of the o‐DPPB by a methylene unit resulted in significantly worse diastereoselectivity in the course of the hydroformylation (34→35), which indicates a decisive role for the ester carbonyl function. All the experimental observations were combined in a model of the origin of the 1,2‐asymmetric induction during the title reaction. The key feature is the consideration of diastereomeric trigonal‐bipyramidal rhodium‐hydrido‐olefin complexes I and II, capable on the basis of the Hammond postulate of acting as good models for the transition states of the selectivity‐determining hydrometalation step. Investigation of these complexes by force‐field methods indicated good correlation between theoretically predicted and experimentally determined diastereoselectivities.
Side‐On Bridging Coordination of N2: Spectroscopic Characterization of the Planar Zr2N2 Core and Theoretical Investigation of Its Butterfly Distortion
Authors: Studt Felix , Morello Lara , Lehnert Nicolai , Fryzuk Michael D. , Tuczek Felix
Published: January 2003

The vibrational and electronic structure of the side‐on N2‐bridged Zr complex [{(P2N2)Zr}2(μ‐η2:η2‐N2)] (P2N2=PhP(CH2SiMe2NSiMe2CH2)2PPh) were analyzed. The vibrational characterization of the planar Zr2N2 core was based on resonance Raman and infrared spectroscopy. In the Raman spectrum, the NN stretching band is found at 775 cm−1 with an isotope shift of 22 cm−1. Due to its appearance in many overtones and combination modes, the metal–metal stretch is assigned to the peak at 295 cm−1. The two ungerade modes of the Zr2N2 core were identified in the infrared spectrum. Based on these four vibrations of the Zr2N2 unit, a quantum chemical assisted normal coordinate analysis (QCA‐NCA) was performed. The force constants for the NN and ZrN bonds were calculated to be 1.53 and 2.58 mdyn Å−1, respectively. The butterfly distortion of the Zr2N2 unit obtained in DFT geometry optimizations of planar side‐on N2‐bridged Zr complexes was analyzed in more detail. It was found that on bending of the Zr2N2 core, the lone pairs of the axial amide ligands are rotated by 90°. The bent Zr2N2 unit is 11 kcal mol−1 lower in energy than the planar core due to a more uniform distribution of electron density between the metal atoms and N2 and delocalization of electron density from the amide ligands to the Zr2N2 unit. The spectroscopic implications of this distortion are analyzed.
Central projections of thoracic splanchnic and somatic nerves and the location of sympathetic preganglionic neurons in Xenopus laevis
Authors: Nakano Masato , Kishida Reiji , Funakoshi Kengo , Tsukagoshi Midori , Goris Richard C. , Kadota Tetsuo , Atobe Yoshitoshi , Hisajima Tatsuya
Published: January 2003

The central and peripheral organization of thoracic visceral and somatic nervous elements was studied by applying dextran amines to the proximal cut ends of the thoracic splanchnic and somatic nerves in Xenopus laevis. Many labeled dorsal root ganglion cells of visceral afferents, and all somatic afferents, were located in a single ganglion of one spinal segment, and the two types of cells were distributed topographically within the ganglion. The labeled sympathetic preganglionic neurons were located predominantly in the same area of the thoracic spinal gray as in other frogs and in mammals. The labeled visceral afferents projected to Lissauer's tract and the dorsal funiculus. The visceral fibers of the tract ascended to the level of the subcerebellar area, supplying collateral branches to the lateral one‐third of the dorsal horn and to the area of brainstem nuclei, including lateral cervical and descending trigeminal nucleus, and descended to the filum terminale. The visceral fibers of the dorsal funiculus were distributed to the dorsal column nucleus and the solitary tract. A similar longitudinal projection was also seen in the somatic afferents. The dual central pathway of thoracic primary afferents in the anuran spinal cord is a property held in common with mammals, but the widespread rostrocaudal projection through Lissauer's tract may be a characteristic of the anuran central nervous system. In frogs, the direct transmission of primary afferent information to an extremely wide area of the central nervous system may be important for prompt assessment of environmental factors and control of body functions. J. Comp. Neurol. 456:321–337, 2003. © 2003 Wiley‐Liss, Inc.
Comparison of antiangiogenic activities using paclitaxel (taxol) and docetaxel (taxotere)
Authors: Grant Derrick S. , Williams Torian L. , Zahaczewsky Michael , Dicker Adam P.
Published: January 2003

Tumor growth requires a competent vascular supply and angiogenesis has been considered as a potential target for the treatment of several cancers. The two clinically approved taxanes, paclitaxel and docetaxel, are novel antimitotic agents that are under extensive investigation in clinical trials. Both taxanes have demonstrated significant activity against many solid tumors, but little is known about the effect of paclitaxel and docetaxel on endothelial cell function and angiogenic processes. The purpose of our study was to examine and compare the effects of these drugs on angiogenic processes in vitro and in vivo. These processes include: proliferation, migration and differentiation of cultured human umbilical vein endothelial cells (HUVEC) (in vitro), capillary sprouting of rat aortic ring explants (ex vivo) and HT1080 tumor growth in vivo. Our results demonstrate that endothelial cells are 10–100‐fold more sensitive to these drugs than tumor cells. Additionally, comparison of the taxanes demonstrated that angiogenesis is blocked by both drugs primarily via inhibition of proliferation and differentiation (tube assay) and induction of cell death. Docetaxel, however, appears to be more potent at inhibiting angiogenesis, with an IC50 concentration 10× less than that of paclitaxel. We conclude that these important findings should be taken in account in clinical trials where tumor angiogenesis is being targeted. © 2002 Wiley‐Liss, Inc.
Development of resistance to vincristine and doxorubicin in neuroblastoma alters malignant properties and induces additional karyotype changes: A preclinical model
Authors: Kotchetkov Rouslan , Cinatl Jaroslav , Blaheta Roman , Vogel Jens‐Uwe , Karaskova Jana , Squire Jeremy , Hernáiz Driever Pablo , Klingebiel Thomas , Cinatl Jindrich
Published: January 2003

Cytotoxic drug treatment of neuroblastoma often leads to the development of drug resistance and may be associated with increased malignancy. To study the effects of long‐term cytotoxic treatment on malignant properties of tumor cells, we established 2 neuroblastoma cell sublines resistant to vincristine (VCR) and doxorubicin (DOX). Both established cell lines (UKF‐NB‐2rVCR20 and UKF‐NB‐2rDOX100) were highly resistant to VCR, DOX and vice‐versa but retained their sensitivity to cisplatin. UKF‐NB‐2rVCR20 and UKF‐NB‐2rDOX100 expressed significant amounts of P‐glycoprotein, while parental cells were P‐glycoprotein negative. GD2 expression was upregulated, whereas NCAM expression was decreased in both resistant cells. Spectral karyotype (SKY) analysis revealed complex aberrant karyotypes in all cell lines and additional acquired karyotype changes in both resistant cells. All cell lines harbored high levels of N‐myc amplification. Compared to parental cells, UKF‐NB‐2rVCR20 and UKF‐NB‐2rDOX100 exhibited more than 2‐fold increase in clonal growth in vitro, accelerated adhesion and transendothelial penetration and higher tumorigenicity in vivo. We conclude that development of drug resistance and acquisition of certain karyotypic alterations is associated with an increase of additional malignant properties that may contribute to the poor prognosis in advanced forms of NB. The 2 novel neuroblastoma cell sublines also provide useful models for the study of drug resistance in aggressive forms of neuroblastoma. © 2002 Wiley‐Liss, Inc.
Prospects for cannabinoids as anti‐inflammatory agents
Authors: Zurier Robert B.
Published: January 2003

The marijuana plant (Cannabis sativa) and preparations derived from it have been used for medicinal purposes for thousands of years. It is likely that the therapeutic benefits of smoked marijuana are due to some combination of its more than 60 cannabinoids and 200–250 non‐cannabinoid constituents. Several marijuana constituents, the carboxylic acid metabolites of tetrahydrocannabinol, and synthetic analogs are free of cannabimimetic central nervous system activity, do not produce behavioral changes in humans, and are effective antiinflammatory and analgesic agents. One cannabinoid acid in particular, ajulemic acid, has been studied extensively in in vitro systems and animal models of inflammation and immune responses. This commentary reviews a portion of the work done by investigators interested in separating the medicinal properties of marijuana from its psychoactive effects. Understanding the mechanisms of the therapeutic effects of nonpsychoactive cannabinoids should lead to development of safe effective treatment for several diseases, and may render moot the debate about “medical marijuana”. © 2002 Wiley‐Liss, Inc.
Effects of 1,25‐dihydroxyvitamin D3 on the distribution of androgen and vitamin D receptors in human prostate neonatal epithelial cells
Authors: Leman Eddy S. , Getzenberg Robert H.
Published: January 2003

Although many studies have examined the mechanisms of 1,25‐dihydroxyvitamin D3 (calcitriol or 1,25 D) action in different prostate cancer cell lines, little is known regarding the influence of this steroid on the normal prostate. The presence of both VDR and AR in normal prostatic tissues raises the distinct possibility of an important role for this hormone in the normal gland. In order to ascertain the possible role of 1,25 D on both AR and VDR in the normal prostate, the effects of calcitriol and dihydrotestosterone (DHT) on the normal human neonatal prostatic epithelial cell line, 267B‐1, were examined. These studies were approached by focusing on how 1,25 D in the presence or absence of DHT affects the distribution of AR and VDR in the cytoplasmic and nuclear compartments of the cells in terms of their protein levels and DNA binding activities. Immunoblot analyses show that 1,25 D increases the AR protein level in both the cytoplasmic and nuclear fractions but not the VDR protein level. On the other hand, the gel shift assays demonstrate that 1,25 D increases both the AR– and VDR–DNA binding activities in the nuclear fraction, whereas there is no increase in DNA binding activities in the cytoplasmic fraction. Addition of DHT along with 1,25 D does not affect the DNA binding activities of both AR and VDR. Overall, these studies suggest that 1,25 D actions on the normal prostate cells may be mediated independently through AR and VDR, respectively. © 2002 Wiley‐Liss, Inc.
A comparative simulation analysis of propane dehydrogenation in composite and microporous membrane reactors
Authors: Hou Kaihu , Hughes Ronald
Published: January 2003

Propane dehydrogenation has been simulated for a composite membrane reactor and a microporous membrane reactor using plug‐flow reactor models, in which both were packed with Pt/Al2O3 catalyst in the tube‐side. The reaction kinetics employed in the analysis were obtained from experimental data produced in an integral fixed bed reactor with the same catalyst. Comparative studies were carried out to analyse the performances of reactors containing the different membranes in terms of contact time, flow pattern and flow rate of sweep gas, and pressure. In general, the composite membrane reactors gave the better performance for all cases investigated.

© 2002 Society of Chemical Industry
Analysis of the elimination process of polymerisation inhibitors from styrene by means of adsorption
Authors: Rivero María J , Ibáñez Raquel , Ortiz M Inmaculada
Published: January 2003

This work is focused on the analysis, modelling and scale‐up of a process of styrene purification. The first step in synthetic rubber production is to eliminate 4‐tert‐butylcatechol (TBC) which is added to styrene to prevent homopolymerisation during transport and storage. This process is carried out on an industrial scale by means of adsorption onto activated alumina. Equilibrium experiments at 10 °C correlated to the Langmuir–Freundlich equation:

with a weighted standard deviation of 3.38%. Fixed bed column experiments were carried out on a laboratory scale to obtain breakthrough curves. A mathematical model that considers film and pore mass transfer resistances described satisfactorily the experimental results with a value of Dp = 3.96 × 10−9 m2 s−1 which was obtained from correlation of experimental data to simulated curves. Finally, a pilot plant was built and operated in order to verify the validity of the mathematical model and parameters obtained previously.

© 2002 Society of Chemical Industry
Asynchroneity of maximum glacier advances in the central Spanish Pyrenees
Authors: García‐Ruiz José M. , Valero‐Garcés Blas L. , Martí‐Bono Carlos , González‐Sampériz Penélope
Published: January 2003

The deglaciation history of the Escarra and Lana Mayor glaciers (Upper Gállego valley, central Spanish Pyrenees) had been reconstructed on the basis of detailed geomorphological studies of glacier deposits, sedimentological and palynological analyses of glacial lake sediments and an accelerator mass spectrometry (AMS) 14C chronology based on minimum ages from glacial lake deposits. The maximum extent of the Pyrenean glaciers during the last glaciation was before 30 000 yr BP and pre‐dated the maximum advances of the Scandinavian Ice Sheet and some Alpine glaciers. A later advance occurred during the coldest period (around 20 000 yr BP), synchronous with the maximum global ice extent, but in the Pyrenees it was less extensive than the previous one. Later, there were minor advances followed by a stage of debris‐covered glaciers and a phase of moraine formation near cirque backwalls. The deglaciation chronology of the Upper Gállego valley provides more examples of the general asynchroneity between mountain and continental glaciers. The asynchroneity of maximum advances may be explained by different regional responses to climatic forcing and by the southern latitude of the Pyrenees. Copyright © 2002 John Wiley & Sons, Ltd.
Computational complexity on computable metric spaces
Authors: Weirauch Klaus
Published: January 2003

We introduce a new Turing machine based concept of time complexity for functions on computable metric spaces. It generalizes the ordinary complexity of word functions and the complexity of real functions studied by Ko [19] et al. Although this definition of TIME as the maximum of a generally infinite family of numbers looks straightforward, at first glance, examples for which this maximum exists seem to be very rare. It is the main purpose of this paper to prove that, nevertheless, the definition has a large number of important applications. Using the framework of TTE [40], we introduce computable metric spaces and computability on the compact subsets. We prove that every computable metric space has a c‐proper c‐admissible representation. We prove that Turing machine time complexity of a function computable relative to c‐admissible c‐proper representations has a computable bound on every computable compact subset. We prove that computably compact computable metric spaces haveconcisec‐proper c‐admissible representations and show by examples that many canonical representations are of this kind. Finally, we compare our definition with a similar one by Labhalla et al. [22]. Several examples illustrate the concepts. By these results natural and realistic definitions of computational complexity are now available for a variety of numerical problems such as image processing, integration, continuous Fourier transform or wave propagation.
Adaptation of the postpartum support questionnaire for mothers with multiple sclerosis
Authors: Gulick Elsie E.
Published: January 2003

The purposes of this study were to determine the dimensionality of the Postpartum Support Questionnaire adapted for mothers with multiple sclerosis through factor‐analytic techniques and to provide construct validity for the factored dimensions. One hundred and seventy‐four mothers with multiple sclerosis comprised the sample. Using a priori criteria, a three‐factor structure, resulting from principal components analysis with an orthogonal rotation consisting of 24 of the 28 items, was found to best represent the dimensionality of the instrument. The three support factors—emotional, instrumental, and informational—showed acceptable coefficient alpha reliabilities at the 1‐, 3‐, and 6‐month administrations. Evidence of construct validity was shown in that, as hypothesized, (a) mothers with comparatively lower emotional distress reported higher levels of emotional and instrumental support, and (b) mothers with one child reported receiving more informational support during the 6‐month postpartum period than did mothers with more than one child. The results support the use of the 24‐item Postpartum Support Questionnaire in assessing the adequacy of these specific dimensions of social support needed by mothers with multiple sclerosis during the postpartum period. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:30–39, 2003
Applications of inward matrix products and matrix wave functions to Hückel MO theory, Slater extended wave functions, spin extended functions, and Hartree method
Authors: Carbó‐Dorca Ramon
Published: January 2003

The operation of inward matrix product and the concept of extended wave functions are jointly invoked to set up a general theoretical framework to obtain a new look at old quantum chemical procedures like Hückel method, Hartree theory, and some related questions. Among the discussion of several problems, the spin orbitals are presented as a matrix signature option, associated with an extended wave function in matrix form, common to both Hückel and Hartree theories, as well as in the fundaments of Slater determinants construction. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Allowed transitions in silicon isoelectronic ions
Authors: Saha B. , Mukherjee T. K. , Das A. K. , Mukherjee P. K.
Published: January 2003

Dipole‐allowed transitions have been studied for the first few members of the Si isoelectronic sequence. Transition energies, oscillator strengths, transition probabilities and quantum defect values have been estimated for the low‐ and high‐lying excited states of s and d symmetries up to the principal quantum number n=7 for these 3p open shell ions from P+ to Cr10+. Time‐dependent coupled Hartree–Fock (TDCHF) theory has been utilized to calculate such transition properties. Most of the results for transition energies, oscillator strengths, and transition probabilities for higher excited states are new. The transition energies for low‐lying excited states agree well with experimental data wherever available. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Pseudomonas stutzeri soluble nitrate reductase αβ‐subunit is a soluble enzyme with a similar electronic structure at the active site as the inner membrane‐bound αβγ holoenzyme
Authors: Hettmann Thomas , Anemüller Stefan , Borcherding Heike , Mathé Lutz , Steinrücke Peter , Diekmann Stephan
Published: January 2003

A two‐subunit (αβ) form of dissimilatory nitrate reductase from Pseudomonas stutzeri strain ZoBell was separated from the membrane‐residing γ‐subunit by a heat solubilization step. Here we present an optimized purification protocol leading to a soluble αβ form with high specific activity (70 U/mg). The soluble form has the stoichiometry α1β1 consisting of the 130 kDa α‐subunit and the 58 kDa β‐subunit. We did not observe any proteolytic cleavage in the course of the heat solubilization. The enzyme is competively inhibited by azide, but not by chlorate. It exhibits a K
M value of 3.2 mM for nitrate. We compare the enzymatic and electron paramagnetic resonance (EPR) spectroscopic properties of the αβ form with the αβγ holoenzyme which resides in the membrane and can be prepared by detergent extraction. The nearly identical EPR spectra for the Mo(V) signal of both enzyme preparations show that the active site is unaffected by the heat step. The factors influencing the binding of the α‐ and β‐subunit to the γ‐subunit are discussed.
Tautomeric state of α‐sarcin histidines. Nδ tautomers are a common feature in the active site of extracellular microbial ribonucleases
Authors: Pérez-Cañadilllas José Manuel , Garcı́a‐Mayoral Ma Flor , Laurents Douglas V , Martı́nez del Pozo Alvaro , Gavilanes José G , Rico Manuel , Bruix Marta
Published: January 2003

Extracellular fungal RNases, including ribotoxins such as α‐sarcin, constitute a family of structurally related proteins represented by RNase T1. The tautomeric preferences of the α‐sarcin imidazole side chains have been determined by nuclear magnetic resonance and electrostatic calculations. Histidine residues at the active site, H50 and H137, adopt the Nδ tautomer, which is less common in short peptides, as has been found for RNase T1. Comparison with tautomers predicted from crystal structures of other ribonucleases suggests that two active site histidine residues with the Nδ tautomer are a conserved feature of microbial ribonucleases and that this is related to their ribonucleolytic function.
Comparison of the effect of video glasses and nitrous oxide analgesia on the perceived intensity of pain and unpleasantness evoked by dental scaling
Authors: Bentsen Bo , Wenzel Ann , Svensson Peter
Published: January 2003

The aim of this study was to evaluate whether distraction induced by video glasses had an effect on the perceived intensity of pain and unpleasantness during dental scaling compared with the effect of nitrous oxide (N2O) analgesia. The pain stimulus was dental scaling (removal of dental calculus) with an ultrasonic scaler. As a standardised, non‐dental painful stimulus, Von Frey filaments were used. A total of 26 patients with superficial chronic periodontitis were enrolled in this randomised, controlled clinical study. The effect of video glasses was compared with N2O in one session and the effect of video glasses versus a control situation in another. The patients rated the intensity of pain and unpleasantness evoked by dental scaling and Von Frey filament stimulation on 100‐mm visual analogue scales (VAS). For dental scaling, there was no effect of video glasses on the perceived pain (p=0.85) or unpleasantness (p=0.73) nor of N2O (p=0.69 and p=0.51, respectively) compared with the control situation. Similarly, no significant difference was found between VAS scores in the video glasses and N2O session (p=0.48, p=0.58). A significant effect of video glasses and was found on the perceived pain intensity produced by Von Frey filament stimulation compared with the control situation, but no significant difference was seen between these methods (p=0.07). Post‐treatment interviews of the patients revealed that 81% of the patients in the video and 65% in the N2O session stated that the method had some beneficial effect on their overall experience of the treatment situation. In conclusion, administration of video glasses or N2O did not affect the perceived intensity of pain and unpleasantness evoked by dental scaling.
Implicit attitude towards pictures of back‐stressing activities in pain‐free subjects and patients with low back pain: an affective priming study
Authors: Goubert Liesbet , Crombez Geert , Hermans Dirk , Vanderstraeten Guy
Published: January 2003

In this paper, it is investigated whether an implicit evaluative‐negative attitude towards back‐stressing activities exists in pain‐free subjects and in chronic low back pain patients. Using an affective priming task, it was investigated whether pictures of threatening back‐stressing movements (primes) facilitate (respectively, slow down) the categorisation of subsequent evaluative‐negative (evaluative‐positive) words (targets). In study 1 using 20 pain‐free subjects, the affective priming effect indicated evidence for an implicit negative attitude towards pictures of back‐stressing activities. In study 2 using 30 low back pain patients, a reverse priming effect was found. In line with previous research, it is argued that this reverse priming effect is owing to the evaluative extremity of the primes: patients recognize the possibility that extreme primes will interfere with the categorisation of the targets and overcompensate for this possible effect. The implications for the prevention of negative attitudes towards back‐stressing activities in non‐clinical and clinical samples are discussed.
Methadone dose and post‐mortem blood concentration
Authors: CAPLEHORN JOHN R. M. , DRUMMER OLAF H.
Published: January 2003

The relationship of methadone dose with post‐mortem blood concentration was investigated using data collected from 1994 coronial cases in the Australian state of New South Wales. Data on 31 subjects were summarized using linear regression. The weight‐adjusted methadone dose, gender, methadone maintenance treatment status and its interaction with adjusted‐dose were all significant predictors of post‐mortem blood methadone concentration. Data on the death of a young man from the toxic effects of three daily doses of 30mg methadone are used to give an example of a pair of observed (0.74 mg/l) and predicted (0.48 mg/l) post‐mortem blood concentrations. The estimated post‐mortem blood concentration for male maintenance patients is at least twice the trough plasma levels estimated from previously published studies of living maintenance patients. The estimated post‐mortem blood concentration for female maintenance patients is at least three times the estimated trough level of living subjects. We conclude that post‐mortem methadone redistribution is probably the principal cause of the observed differences between males and females in post‐mortem blood concentrations and the differences between estimated concentrations for living and deceased subjects.
Photokeratitis and Other Phototoxic Effects on the Cornea and Conjunctiva
Authors: Cullen Anthony P.
Published: January 2003

Except when sleeping, the cornea and interpalpebral conjunctiva are exposed to the ambient environment, both natural and man-made. Levels of solar ultraviolet irradiance reaching the eye may exceed the damage threshold under a number of circumstances. The consequences of overexposure may be acute after a latent period, sequelae to an acute exposure, or long-term chronic effects. Previously derived action spectra for photokeratitis and photoconjunctivitis due to incoherent ultraviolet are presented. These reveal interspecies similarities for the levels of radiant energy reaching each tissue. The initial in vivo (clinical) signs of photokeratitis are due to lost or damaged epithelial cells with other signs produced by this primary response. The conjunctival signs include injection and chemosis. Chronic exposure to solar ultraviolet is a factor in climatic droplet keratopathy and pterygium. Phototoxic compounds or their by-products potentially can reach the cornea from the air, via the tears or aqueous humor, or from the limbal capillaries. However, the human cornea appears to be much less susceptible to the influence of phototoxic agents than the skin.
The quasilinearization method on an unbounded domain
Authors: Eloe Paul
Published: January 2003

We apply a method of quasilinearization to a boundary value problem for an ordinary differential equation on an unbounded domain. A uniquely determined Green’s function, which is integrable and of fixed sign, is employed. The hypotheses to apply the quasilinearization method imply uniqueness of solutions. The quasilinearization method generates a bilateral iteration scheme in which the iterates converge monotonically and quadratically to the unique solution.
Directional convexity of level lines for functions convex in a given direction
Authors: Prokhorov Dmitri , Szynal Jan
Published: January 2003

Let

K
(
φ
)

K(\varphi )

be the class of functions

f
(
z
)
=
z
+

a

2

z

2

+
…

f(z)=z+a_{2}z^{2}+\dots

which are holomorphic and convex in direction

e

i
φ

e^{i\varphi }

in the unit disk

D
D

, i.e. the domain

f
(
D
)

f(D)

is such that the intersection of

f
(
D
)

f(D)

and any straight line

{
w
:
w
=

w

0

+
t

e

i
φ

,
t
∈

R

}

\{w:w=w_{0}+te^{i\varphi },t\in \mathbb {R}\}

is a connected or empty set. In this note we determine the radius

r

ψ
,
φ

r_{\psi ,\varphi }

of the biggest disk

|

z

|

≤

r

ψ
,
φ

|z|\leq r_{\psi ,\varphi }

with the property that each function

f
∈
K
(
ψ
)

f\in K(\psi )

maps this disk onto the convex domain in the direction

e

i
φ

e^{i\varphi }

.
Obstructions to nonnegative curvature and rational homotopy theory
Authors: Belegradek Igor , Kapovitch Vitali
Published: January 2003

We establish a link between rational homotopy theory and the problem which vector bundles admit a complete Riemannian metric of nonnegative sectional curvature. As an application, we show for a large class of simply-connected nonnegatively curved manifolds that, if

C
C

lies in the class and

T
T

is a torus of positive dimension, then “most” vector bundles over

C
×
T

C\times T

admit no complete nonnegatively curved metrics.
Coactivation of Rac and Rho by Wnt/Frizzled signaling is required for vertebrate gastrulation
Authors: Habas Raymond , Dawid Igor B. , He Xi
Published: January 2003

Wnt/Frizzled (Fz) signaling controls cell polarity/movements during vertebrate gastrulation via incompletely defined mechanisms. We demonstrated previously that Wnt/Fz activation of Rho, a GTPase and regulator of cytoskeletal architecture, is essential for vertebrate gastrulation. Here we report that in mammalian cells andXenopusembryos, Wnt/Fz signaling coactivates Rho and Rac, another GTPase and distinct regulator of cytoskeletal architecture. Wnt/Fz activation of Rac is independent of Rho and mediates Wnt/Fz activation of Jun N-terminal kinase (JNK). Dishevelled (Dvl), a cytoplasmic protein downstream of Fz, forms a Wnt-induced complex with Rac independent of the Wnt-induced Dvl–Rho complex. Depletion or inhibition of Rac function perturbsXenopusgastrulation without affecting Wnt/Fz activation of the Rho or β-catenin pathway. We propose that parallel activation of Rac and Rho pathways by Wnt/Fz signaling is required for cell polarity and movements during vertebrate gastrulation.