bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of clay concentration on the oxygen permeability and optical properties of a modified poly(vinyl alcohol)
Authors: Grunlan Jaime C. , Grigorian Ani , Hamilton Charles B. , Mehrabi Ali R.
Published: April 2004

The effect of clay concentration on the oxygen permeability and optical properties of a modified poly(vinyl alcohol) (PVOH) was studied. Sodium montmorrilonite (MMT‐Na+), at a concentration of 10 wt %, was found to decrease the oxygen permeability of the PVOH below 0.001 cc · mil/m2/day at 55% relative humidity. This low permeability is attributed to the strong interaction between PVOH and clay, as evidenced by an increase of more than 10°C in the glass transition temperature at this concentration. Transmission electron microscopy images show the high level of clay exfoliation that results from the strong affinity to PVOH. Haze and clarity were optical properties that changed significantly with increasing clay concentration. These values were 0.4 and 100%, respectively, in the absence of clay, but became 80 and 23% with 10 wt % MMT‐Na+. Transmission did not change as considerably, reaching a low of 73% with a clay concentration of 10 wt %. The ability to reduce the oxygen permeability of PVOH‐based systems at elevated humidity may prove advantageous for applications in food and flexible electronics packaging, where moisture sensitivity currently prevents them from being used. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1102–1109, 2004
Effect of bound rubber on characteristics of highly filled styrene–butadiene rubber compounds with different types of carbon black
Authors: Choi Sung‐Seen
Published: April 2004

Viscosity and cure time of a filled rubber compound having an accelerated sulfur cure system are affected by types and contents of the rubber and the filler as well as of the curatives. Bound rubber content is used as level of the reinforcement. Influence of bound rubber on viscosity and cure time of a rubber compound was studied using highly filled styrene–butadiene rubber compounds with carbon black having different structures. The bound rubber content increases with increase of the carbon black content and also increases as the carbon black structure is developed. The Mooney viscosity increases linearly with increase of the bound rubber content irrespective of the carbon black structure when the primary particle size of carbon black is nearly the same. The Mooney scorch time decreases linearly with increase of the bound rubber content irrespective of the carbon black structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1001–1006, 2004
Synthesis, characterization, and properties of intercalated poly(2‐ethyl hexylacrylate)/silicate nanocomposites: XRD, TEM, IR, TGA, superabsorbency, pressure‐sensitive adhesion, and biodegradation
Authors: Rana Pradeep Kumar , Swain Sarat Kumar , Sahoo Prafulla Kumar
Published: April 2004

Poly(2‐ethyl hexylacrylate) (PEHA)/silicate composites were synthesized by the emulsion polymerization of ethyl hexylacrylate (EHA) in the presence of sorbitol and the composites were analyzed to be of nano order. The nanocomposites so prepared were shown to be intercalated by X‐ray diffraction, transmission electron microscopy, and infrared spectroscopy. The thermal stability of the nanocomposites was found to be appreciably increased. These nanocomposites are potentially suitable for novel uses such as pressure‐sensitive adhesives and superabsorbents. The biodegradability and superabsorbency of these nanocomposites were evaluated for their commercial potential. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1007–1011, 2004
Multizone circulating reactor modeling for gas‐phase polymerization. II. Reactor operating with gas barrier in the downer section
Authors: Fernandes Fabiano A. N. , Lona Liliane M. F.
Published: April 2004

A new gas‐phase technology for polyolefin production is being developed to be commercially available for large‐scale production between 2004 and 2005. This new technology uses a multizone circulating reactor, which consists of two interrelated zones where two distinct and different fluodynamic regimes are realized, between which the polymer particles are kept in continuous circulation. In the first part, we presented a mathematical model for the reactor, and this second part of the article we present simulations when a gas barrier is introduced in the top of the downer section and its implications in the polymer characteristics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1053–1059, 2004
Multizone circulating reactor modeling for gas‐phase polymerization. I. Reactor modeling
Authors: Fernandes Fabiano A. N. , Lona Liliane M. F.
Published: April 2004

A new gas‐phase technology for polyolefin production is being developed to be commercially available for large‐scale production between 2004 and 2005. This new technology uses a multilane circulating reactor, which consists of two interrelated zones where two distinct and different fluodynamic regimes are realized, between which the polymer particles are kept in continuous circulation. This article presents a mathematical model for the multilane circulating reactor presenting the typical behavior of the reactor operation and a parameter sensibility analysis. Simulations were conducted for polyethylene production. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1042–1052, 2004
Fluorine in Medicinal Chemistry
Authors: Böhm Hans‐Joachim , Banner David , Bendels Stefanie , Kansy Manfred , Kuhn Bernd , Müller Klaus , Obst‐Sander Ulrike , Stahl Martin
Published: April 2004

Fluorinated compounds are synthesized in pharmaceutical research on a routine basis and many marketed compounds contain fluorine. The present review summarizes some of the most frequently employed strategies for using fluorine substituents in medicinal chemistry. Quite often, fluorine is introduced to improve the metabolic stability by blocking metabolically labile sites. However, fluorine can also be used to modulate the physicochemical properties, such as lipophilicity or basicity. It may exert a substantial effect on the conformation of a molecule. Increasingly, fluorine is used to enhance the binding affinity to the target protein. Recent 3D‐structure determinations of protein complexes with bound fluorinated ligands have led to an improved understanding of the nonbonding protein–ligand interactions that involve fluorine.
Zinc(II)‐Selective Ratiometric Fluorescent Sensors Based on Inhibition of Excited‐State Intramolecular Proton Transfer
Authors: Henary Maged M. , Wu Yonggang , Fahrni Christoph J.
Published: April 2004

To develop a zinc(II)‐selective emission ratiometric probe suitable for biological applications, we explored the cation‐induced inhibition of excited‐state intramolecular proton transfer (ESIPT) with a series of 2‐(2′‐benzenesulfonamidophenyl)benzimidazole derivatives. In the absence of ZnII at neutral pH, the fluorophores undergo ESIPT to yield a highly Stokes' shifted emission from the proton‐transfer tautomer. Coordination of ZnII inhibits the ESIPT process and yields a significant hypsochromic shift of the fluorescence emission maximum. Whereas the paramagnetic metal cations CuII, FeII, NiII, CoII, and MnII result in fluorescence quenching, the emission response is not altered by millimolar concentrations of CaII or MgII, rendering the sensors selective for ZnII among all biologically important metal cations. Due to the modular architecture of the fluorophore, the ZnII binding affinity can be readily tuned by implementing simple structural modifications. The synthesized probes are suitable to gauge free ZnII concentrations in the micromolar to picomolar range under physiological conditions.
Charge Density and Experimental Electrostatic Potentials of Two Penicillin Derivatives
Authors: Wagner Armin , Flaig Ralf , Dittrich Birger , Schmidt Horst , Koritsánszky Tibor , Luger Peter
Published: April 2004

Two penicillin derivatives, the active penamecillin and the inactive penamecillin‐1β‐sulfoxide, were used to study the relationship between their charge density and their activity. Single crystals of both compounds were measured at the synchrotron beamline F1 at the HASYLAB/DESY, at 100 K and up to resolutions of around 0.4 Å. Experimental charge densities were obtained by using the Hansen–Coppens multipole formalism. The cleavage of the amide bond in the β‐lactam ring is of paramount importance in the mechanism of action of penicillins. Topological analysis of this bond in terms of Bader's AIM theory showed that its strength is equal in both compounds; therefore a direct influence of bond strength on the activity can be ruled out. However, the two derivatives differ significantly in their experimental electrostatic potentials. These differences are discussed and provide further insight into the chemistry and activity of penicillins.
New Ligands for a General Palladium‐Catalyzed Amination of Aryl and Heteroaryl Chlorides
Authors: Rataboul Franck , Zapf Alexander , Jackstell Ralf , Harkal Surendra , Riermeier Thomas , Monsees Axel , Dingerdissen Uwe , Beller Matthias
Published: April 2004

The synthesis and application of monodentate N‐substituted heteroarylphosphines is described. In general, the ligands are conveniently prepared by selective metallation at the 2‐position of the respective N‐substituted heterocycle (pyrrole, indole) by using n‐butyllithium/tetramethylethylenediamine (TMEDA) followed by quenching with dialkyl‐ or diarylchlorophosphines. Of the different ligands prepared, the new dialkyl‐2‐(N‐arylindolyl)phosphines (cataCXium® P) perform excellently in the palladium‐catalyzed amination of aryl and heteroaryl chlorides. Coupling of both activated and deactivated chloroarenes proceeds under mild conditions (room temperature to 60 °C). By using optimized conditions remarkable catalyst productivity (total turnover number, TON, up to 8000) and activity (turnover frequency, TOF=14 000 h−1 at 75 % conversion) are observed.
Herstellung und Eigenschaften von Mikroreaktoren aus Glas
Authors: Dietrich T. R. , Freitag A. , Scholz R.
Published: April 2004

No abstracts.
Anwendung eines mikrostrukturierten Mehrkanalreaktors für kinetische Untersuchungen der oxidativen Dehydrierung von Propan
Authors: Steinfeldt N. , Linke D. , Jähnisch K. , Baerns M.
Published: April 2004

No abstracts.
IMPULSE – Ein neuartiger Ansatz für die Prozessentwicklung
Authors: Bayer T. , Matlosz M. , Jenck J.
Published: April 2004

No abstracts.
Chipreaktoren im Labor – Ein Beitrag zur nachhaltigen Umweltvorsorge
Authors: Köhler M.
Published: April 2004

No abstracts.
Organische Synthese mit mikrostrukturierten Reaktoren
Authors: Hessel V. , Löwe H.
Published: April 2004

Dieser Artikel beschreibt zunächst, welche Chancen mikrostrukturierte Reaktoren für den chemischen Anlagenbau haben. Die Eignung für die chemische Produktion wird als Schlüssel zum Markteintritt gesehen. Jahrhunderte langes Beharren auf konventioneller Rührtechnik und kapitalintensive Großanlagen verwehren einen schnellen Eintritt; langfristig können Neuanlagen aber mit mikrostrukturierten Reaktoren versehen werden. Erst Gesamtprozessbetrachtungen, die eine positive wirtschaftliche Bilanz ziehen, werden der chemischen Mikroprozesstechnik die Tür zum Anlagenbau öffnen. Wesentlich Argumente für mikrostrukturierte Reaktoren sind erhöhte Umsatz und Selektivität, erhöhte Raum‐Zeit‐Ausbeute, geringerer Abfall und erhöhte Sicherheit durch kleine Reaktorvolumina. Auf chipkartengroßen Reaktionssystemen lassen sich für das Screening Mehrstufensynthesen in einem Ablauf durchführen. Ebenso wird für das Screening von Einstufenreaktionen Information schneller und zuverlässiger zugänglich. Auch das sichere Arbeiten im Ex‐Bereich erweitert das klassische Prozessspektrum. Reaktionsführungen im Mikrostrukturreaktor beeinflussen auch nachfolgende Prozessschritte wie die Reinigung des Produkts und erniedrigen so z. B. die Energiekosten des Prozesses.
Mischen und organische Reaktionen in der chemischen Industrie
Authors: Bayer T. , Himmler K.
Published: April 2004

Mischvorgänge sind eine der wichtigsten Grundoperationen in der chemischen Industrie. Neben normalen Rührkesseln werden oft auch statische Mischer verwendet. Seit einigen Jahren erfreut sich aber auch die Mikrotechnik einer wachsenden Aufmerksamkeit in der Prozessentwicklung. Sie wird – insbesondere in der chemischen Verfahrenstechnik – zu einem wertvollen Werkzeug für Forschung und Entwicklung. Dabei wird die Mikroreaktionstechnik sowohl für die Entwicklung neuer Prozesse als auch bei der Optimierung existierender Verfahren angewandt. Mikrostrukturierte Mischer und Wärmeübertrager werden eingesetzt, um das Potenzial von chemischen Reaktionen – ohne Wärme‐ oder Stofftransportlimitierungen – zu untersuchen und zu optimieren. Auch erste Anwendungen über den Labormaßstab hinaus sind bekannt.
Carbon‐protonation of the pyrimidine ring: The story of a small molecule NMR problem
Authors: Demeter Ádám , Wéber Csaba
Published: April 2004

This article provides a case study of a small molecule structure determination problem from the perspective of the true experience of the authors. By starting from what was intended to be a routine acylation of an aminopyrimidine derivative, we arrive, via some intriguing detours, at an unexpected carbon‐protonated pyrimidine dimer. A didactic discussion is provided, which serves to highlight the way in which some puzzling questions cropped up during nuclear magnetic resonance (NMR) spectral interpretation, as well as the iterative process in which these problems were resolved gradually. Some of the crucial mental leaps that either slowed down or gave a thrust to the progress of structure elucidation are emphasized so as to be instructive in ways that go beyond the specifics of the problem. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 22A: 12–24, 2004.
Combination of endometrial thickness and time since menopause in predicting endometrial cancer in women with postmenopausal bleeding
Authors: Bruchim Ilan , Biron‐Shental Tal , Altaras Marco M. , Fishman Ami , Beyth Yoram , Tepper Ronnie , Aviram Rami
Published: April 2004

Purpose

This study was conducted to assess the combination of endometrial thickness, as measured by transvaginal sonography, and time since menopause, in predicting the presence of endometrial cancer in women with postmenopausal bleeding.

Methods

The study group consisted of 95 women with postmenopausal bleeding who underwent sonographic measurement of endometrial thickness followed by endometrial biopsy. No patient had ever received hormone replacement therapy.

Results

The mean endometrial thickness was significantly lower in the absence of endometrial carcinoma (6.9 ± 4.3 mm) than in its presence (13.5 ± 7.7 mm) (p < 0.005). The incidence of endometrial carcinoma increased with increases in endometrial thickness and the number of years since menopause. No patient had carcinoma when the endometrium was less than 5 mm thick, but 18.5% did when the thickness exceeded 9 mm. The incidence of cancer was 2.6% in women who had undergone menopause less than 5 years earlier but was 21.4% in women who had undergone menopause more than 15 years prior. Multiple logistic regression analysis showed that time since menopause and endometrial thickness were statistically significant predictors of endometrial carcinoma.

Conclusions

Time since menopause and endometrial thickness together define cutoff points for the diagnostic biopsy of tissue samples for endometrial carcinoma; that is, within a particular time interval, samspling should not be performed if the thickness is below a given value. When using cutoff points of 6 mm of endometrial thickness for women experiencing menopause 5–15 years prior and 5 mm in those going through menopause 15 or more years prior, approximately 60% of invasive procedures may be avoided. In addition, models derived by multiple logistic regression can be used to calculate a patient's risk of cancer based on her age and endometrial thickness. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:219–224, 2004; Published online in Wiley InterScience (www.interscience.wiley. com). DOI: 10.1002/jcu.20020
Placental thickness in the first half of pregnancy
Authors: Tongsong Theera , Boonyanurak Pongrak
Published: April 2004

Purpose

This study was conducted to establish normal values of placental thickness during the first half of pregnancy.

Methods

Normal pregnant women with singleton pregnancies between 8 and 20 weeks of gestation were recruited into the study. All the newborns were normal at birth. Placental thickness was measured perpendicularly through the thickest part of the placenta on transabdominal scans. The placental thickness data were analyzed for mean, standard deviation, 95% confidence interval, and 2.5th, 5th, 50th, 95th, and 97.5th percentile for each week of gestational age. The best‐fit mathematical model was derived by regression analysis.

Results

The total number of measurements was 333 and the number of measurements for each week of gestational age ranged from 9 to 37. Regression analysis yielded the following linear equation of the relationship: placental thickness (in mm) = gestational age (in weeks) × 1.4−5.6 (r = 0.82).

Conclusion

We have established a nomogram for placental thickness. This resource may be a useful aid in the early detection of placental abnormalities, such as hydropic placenta secondary to hemoglobin Bart's disease. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:231–234, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jcu.20023
Gene transfer into rabbit arteries with adeno‐associated virus and adenovirus vectors
Authors: Gruchała Marcin , Bhardwaj Shalini , Pajusola Katri , Roy Himadri , Rissanen Tuomas T. , Kokina Ilze , Kholová Ivana , Markkanen Johanna E. , Rutanen Juha , Heikura Tommi , Alitalo Kari , Büeler Hansruedi , Ylä‐Herttuala Seppo
Published: April 2004

Background

Gene transfer offers considerable potential for altering vessel wall physiology and intervention in vascular disease. Therefore, there is great interest in developing optimal strategies and vectors for efficient, targeted gene delivery into a vessel wall.

Methods

We studied adeno‐associated viruses (AAV; 9 × 108 to 4 × 109 TU/ml) for their usefulness to transduce rabbit arteries in vivo in comparison with adenoviruses (Adv; 1 × 109 to 1 × 1010 pfu/ml). 100 µl of viruses or placebo solution were injected intraluminally into transiently isolated carotid segments.

Results

In normal arteries AAV transduced mainly medial smooth muscle cells (SMC) while Adv transduced exclusively endothelial cells (EC). Mechanical injury to EC layer and internal elastic lamina enabled Adv to penetrate and transduce medial SMC. Transgene expression in EC after the AAV‐mediated gene transfer was very low. The use of the EC‐specific Tie‐1 promoter did not lead to specific transgene expression in EC. Transgene expression in SMC persisted for at least 100 days after the AAV treatment whereas the Adv‐mediated effect diminished in 14 days. AAV caused only a modest increase in EC VCAM‐1 expression and proliferation rate of vascular cells as compared with the mock‐treated arteries while Adv caused an extensive inflammatory cell infiltration, VCAM‐1 expression, vascular cell proliferation and morphological damages.

Conclusions

Significant differences were observed between the AAV and the Adv vectors in their patterns of arterial transduction and consequent inflammatory responses. These distinct properties may be utilized for different applications in vascular biology research and gene therapy for cardiovascular diseases. Copyright © 2004 John Wiley & Sons, Ltd.
Hydrodynamics‐based procedure involves transient hyperpermeability in the hepatic cellular membrane: implication of a nonspecific process in efficient intracellular gene delivery
Authors: Kobayashi Naoki , Nishikawa Makiya , Hirata Kazuhiro , Takakura Yoshinobu
Published: April 2004

Background

The mechanisms underlying the efficient gene transfer by a large‐volume and high‐speed intravenous injection of naked plasmid DNA (pDNA), a so‐called hydrodynamics‐based procedure, remain unclear and require further investigation. In this report, we have investigated possible mechanisms for the intracellular transport of naked pDNA by this procedure.

Methods

Propidium iodide (PI), a fluorescent indicator for cell membrane integrity, and luciferase‐ or green fluorescent protein (GFP)‐expressing pDNA were injected into mice by the hydrodynamics‐based procedure.

Results

PI was efficiently taken up by hepatocytes which appeared to be viable following the hydrodynamics‐based procedure. Pre‐expressed GFP in the cytosol was rapidly eliminated from the hepatocytes by a large‐volume injection of saline. The profiles of plasma ALT and AST showed a steady decline with the highest values observed immediately after the hydrodynamics‐based procedure. These results suggest that the hydrodynamics‐based procedure produces a transient increase in the permeability of the cell membrane. The cellular uptake process appeared nonspecific, since simultaneous injection of an excess of empty vector did not affect the transgene expression. Sequential injections of a large volume of pDNA‐free saline followed by naked pDNA in a normal volume revealed that the increase in membrane permeability was transient, with a return to normal conditions within 30 min. Transgene expression was observed in hepatocyte cultures isolated 10 min after pDNA delivery and in the liver as early as 10 min after luciferase‐expressing RNA delivery, indicating that pDNA delivered immediately by the hydrodynamics‐based procedure has the potential to produce successful transgene expression.

Conclusions

These findings suggest that the mechanism for the hydrodynamics‐based gene transfer would involve in part the direct cytosolic delivery of pDNA through the cell membrane due to transiently increased permeability. Copyright © 2004 John Wiley & Sons, Ltd.
Spanningk‐arc‐strong subdigraphs with few arcs ink‐arc‐strong tournaments
Authors: Bang‐Jensen Jørgen , Huang Jing , Yeo Anders
Published: April 2004

Given ak‐arc‐strong tournamentT, we estimate the minimum number of arcs possible in ak‐arc‐strong spanning subdigraph ofT. We give a construction which shows that for eachk≥ 2, there are tournamentsTonnvertices such that everyk‐arc‐strong spanning subdigraph ofTcontains at least$nk + {k(k-1)\over 2}$arcs. In fact, the tournaments in our construction have the property that every spanning subdigraph with minimum in‐ and out‐degree at leastkhas$nk + {k(k-1)\over 2}$arcs. This is best possible since it can be shown that everyk‐arc‐strong tournament contains a spanning subdigraph with minimum in‐ and out‐degree at leastkand no more than$nk + {k(k-1)\over 2}$arcs. As our main result we prove that everyk‐arc‐strong tournament contains a spanningk‐arc‐strong subdigraph with no more than$nk + 136k^2$arcs. We conjecture that for everyk‐arc‐strong tournamentT, the minimum number of arcs in ak‐arc‐strong spanning subdigraph ofTis equal to the minimum number of arcs in a spanning subdigraph ofTwith the property that every vertex has in‐ and out‐degree at leastk. We also discuss the implications of our results on related problems and conjectures. © 2004 Wiley Periodicals, Inc. J Graph Theory 46: 265–284, 2004
T‐complete functions for thin and thick plates on elastic foundation
Authors: Wróblewski Adam
Published: April 2004

This article deals with Trefftz functional systems for thin and thick plates on one‐ and two‐parameter Winkler foundation. The T‐complete set is derived by solving the homogeneous equations of the problem. This can be done with the method of separation of variables. For each separation parameter we deal with ordinary, linear differential equations (4th order for the Kirchhoff plate and set of fourth‐ and second‐order equations for the Reissner‐Mindlin plate) so the demanded number of fundamental solutions (linearly independent) is equal to the order of equation. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005
Improvement of the interfacial compatibility between sugar cane bagasse fibers and polystyrene for composites
Authors: García‐Hernández Edgar , Licea‐Claveríe Angel , Zizumbo Arturo , Alvarez‐Castillo Alberto , Herrera‐Franco Pedro J.
Published: April 2004

Sugar cane bagasse fibers were modified by surface treatments using either physical or chemical methods in order to improve their adhesion to polystyrene matrices. The surface treatment methods used were alkaline treatment, treatment with silane coupling agents, physical coating with polystyrene and grafting of polystyrene with and without crosslinker. Fiber modifications were monitored by Fourier Transform Infrared Spectroscopy (FTIR), Differential Thermal Analysis coupled with Thermogravimetric Analysis (DTA‐TGA) and Scanning Electron Microscopy (SEM). On the other hand, the improvement of the adhesion between sugar cane modified fibers and polystyrene was assessed by micromechanical pull‐out and by macromechanical Iosipescu tests. It was found, from Interfacial Shear Strength values (IFSS), that substantial improvements in fiber‐matrix compatibility were achieved. According to micro‐ and macromechanical test results, the IFSS increased for all treated fibers as compared to non‐treated fibers. Particularly, both the coating the fibers or grafting with polystyrene using crosslinker resulted in substantial adhesion improvement to the polystyrene matrix in comparison with the non‐treated fibers and fibers treated by alkaline and silane methods only. Polym. Compos. 25:134–145, 2004. © 2004 Society of Plastics Engineers.
Quality of life of patients with cancer in India: Challenges and hurdles in putting theory into practice
Authors: Pandey Manoj
Published: April 2004

Although well establish in west, quality of life is a relatively new concept in India. The success of treatment is still measured in term of number of years and not as number of quality years. We carried out a systematic review of the reports published from India on quality of life in cancer patients. Majority of the studies originated from the southern part of India, this was not surprising as this part has literacy rates and health indices at par with developed countries. The studies mainly dealt with translation of existing tools in local vernacular, development of new tools, cross‐sectional studies, and studies on palliative care. This article reviews these studies and presents the results of what has been done so far and goes on to stipulate what more needs to be done. Copyright © 2004 John Wiley & Sons, Ltd.
Approximate Method for Predicting Chapman‐Jouguet State for Condensed Explosives
Authors: Nagayama Kunihito , Kubota Shiro
Published: April 2004

The dependence of the detonation velocity on the initial density is available for several condensed high explosives. It gives a collection of Rayleigh lines on a pressure‐volume plane starting from different initial volume points. It is shown that a collection of the Chapman‐Jouguet (C‐J) states on each Rayleigh line can be described by an envelope function of Rayleigh lines. Based on the analytical expression of the envelope function, formulae for other C‐J parameters are derived.
Probing flexibility and “induced‐fit” phenomena in aldose reductase by comparative crystal structure analysis and molecular dynamics simulations
Authors: Sotriffer Christoph A. , Krämer Oliver , Klebe Gerhard
Published: April 2004

Aldose reductase is a promising target for the treatment of diabetic complications, and as such, has become the focus of various drug design projects. As revealed by a survey of available crystal structures, the protein shows pronounced induced‐fit effects upon ligand binding. Although helping to explain the enzyme's substrate promiscuity, phenomena of this kind are still responsible for significant complications in structure‐based design efforts directed to aldose reductase. Accordingly, a deeper understanding of the principles governing conformational alterations in this enzyme would be of utmost practical importance. As a first step in addressing this issue, molecular dynamics (MD) simulations have been carried out. The ultrahigh resolution crystal structure of aldose reductase complexed with inhibitor IDD594 served as ideal starting point for a set of different simulations of nanosecond time scale: the native complexed state with bound inhibitor, the uncomplexed state (after removal of the inhibitor) at standard temperature, and the uncomplexed state at elevated temperature. The reference simulation of the complex exhibits extraordinary stability of the overall fold, whereas two distinct conformational substates are found for the binding‐site region. In contrast, already at standard temperature pronounced changes are observed in the binding region during the simulation of the uncomplexed state. Leu300, for example, closes the access to the pocket opened by IDD594. On the other hand, conformations around the catalytic site are highly conserved, with the His110–Tyr48–NADP+ orientation being stabilized by a water molecule. Detailed analysis of the trajectories allows to reveal a set of distinct conformational substates that may prove useful as alternative structural templates in virtual screening for new aldose reductase inhibitors. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Structural and sequence comparisons arising from the solution structure of the transcription elongation factor NusG from Thermus thermophilus
Authors: Reay Paul , Yamasaki Kazuhiko , Terada Takaho , Kuramitsu Seiki , Shirouzu Mikako , Yokoyama Shigeyuki
Published: April 2004

NusG is an essential bacterial protein modulator of transcriptional elongation and termination events, and interacts directly with RNA polymerase and Rho protein. Found also in Archaea, NusG shows stretches of sequence similarity to the eukaryotic transcription elongation factor Spt5. Herein, the three‐dimensional solution structure of the bacterial NusG from Thermus thermophilus, which shows 43% amino acid sequence similarity to the Escherichia coli NusG, is described, and a survey of NusG and Spt5 amino acid sequences is presented. Although there is a clear evolutionary and functional relationship between these proteins, it is evident from the structural, sequence, and biochemical data that their binding specificities to both nucleic acids and other proteins differ. Proteins 2004. © 2004 Wiley‐Liss, Inc.
A detailed comparison of current docking and scoring methods on systems of pharmaceutical relevance
Authors: Perola Emanuele , Walters W. Patrick , Charifson Paul S.
Published: April 2004

A thorough evaluation of some of the most advanced docking and scoring methods currently available is described, and guidelines for the choice of an appropriate protocol for docking and virtual screening are defined. The generation of a large and highly curated test set of pharmaceutically relevant protein–ligand complexes with known binding affinities is described, and three highly regarded docking programs (Glide, GOLD, and ICM) are evaluated on the same set with respect to their ability to reproduce crystallographic binding orientations. Glide correctly identified the crystallographic pose within 2.0 Å in 61% of the cases, versus 48% for GOLD and 45% for ICM. In general Glide appears to perform most consistently with respect to diversity of binding sites and ligand flexibility, while the performance of ICM and GOLD is more binding site–dependent and it is significantly poorer when binding is predominantly driven by hydrophobic interactions. The results also show that energy minimization and reranking of the top N poses can be an effective means to overcome some of the limitations of a given docking function. The same docking programs are evaluated in conjunction with three different scoring functions for their ability to discriminate actives from inactives in virtual screening. The evaluation, performed on three different systems (HIV‐1 protease, IMPDH, and p38 MAP kinase), confirms that the relative performance of different docking and scoring methods is to some extent binding site–dependent. GlideScore appears to be an effective scoring function for database screening, with consistent performance across several types of binding sites, while ChemScore appears to be most useful in sterically demanding sites since it is more forgiving of repulsive interactions. Energy minimization of docked poses can significantly improve the enrichments in systems with sterically demanding binding sites. Overall Glide appears to be a safe general choice for docking, while the choice of the best scoring tool remains to a larger extent system‐dependent and should be evaluated on a case‐by‐case basis. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Determination of carnitine and acylcarnitines in plasma by high‐performance liquid chromatography/electrospray ionization ion trap tandem mass spectrometry
Authors: Vernez Laurence , Wenk Markus , Krähenbühl Stephan
Published: April 2004

A high‐performance liquid chromatography/mass spectrometry method was developed for the determination of carnitine, its biosynthetic precursor butyrobetaine, and eight acylcarnitines in plasma. The procedure includes a solid‐phase extraction for carnitine and short‐ and medium‐chain acylcarnitines, and a liquid‐liquid extraction for protein‐bound long‐chain acylcarnitines, followed by separation on a reversed‐phase column in the presence of a volatile ion‐pairing reagent. Detection was achieved using an ion‐trap mass spectrometer run in the tandem mass spectrometry (MS/MS) mode. The choice of the matrix for calibrators, used for quantification of these endogenous compounds, was also investigated. Validation was performed for standard quality controls diluted with 4% bovine serum albumin solution and for spiked plasma quality control samples at concentrations between 0.5 and 80 μmol/L, depending on the compound. Intra‐ and inter‐day precisions for the determination of carnitine were below 3.4% and accuracies were between 95.2 and 109.0%. Application of the method to the diagnosis of pathological acylcarnitine profiles of metabolic disorders in a patient suffering from methylmalonic aciduria is presented. The method allows quantification of carnitine, butyrobetaine, acetylcarnitine and propionylcarnitine, and semiquantitative analysis of medium‐ and long‐chain acylcarnitines. In contrast with other methods, no derivatization step is needed. Copyright © 2004 John Wiley & Sons, Ltd.
Stable carbon isotope analysis of different tissues of beef animals in relation to their diet
Authors: De Smet Stefaan , Balcaen An , Claeys Erik , Boeckx Pascal , Van Cleemput Oswald
Published: April 2004

As part of a larger experiment, 31 young bulls, divided into three groups, were given different diets containing either C3 plants or a combination of C3 and C4 plant‐based feeds in three feeding periods before slaughter. Variation in the proportion of C4 plant material in the diets was made by including or not maize or maize‐derived ingredients, whereas the other dietary constituents were from C3 plants. Analysis of stable carbon isotope ratios (δ13C value) was performed on different tissues taken at slaughter: blood, plasma, liver, kidney fat, hair, muscle and ruminal contents. Blood and plasma samples were also taken at the beginning of each period. A highly significant difference was found in the δ13C values of blood and plasma samples taken from animals that had received a diet of only C3 plants or with 59% C4 material for 70 days. The δ13C values of all different samples taken at slaughter were highly significantly different between the three feeding groups that had received diets with 0, 13.5 or 35% C4 material for on average 137, 139 and 83 days, respectively. For the three groups, samples of hair, muscle, plasma, whole blood and liver were significantly enriched in 13C compared with the diet (except for liver in one group), whereas kidney fat was significantly depleted. The proportion of C4 plant material could be accurately estimated from the δ13C values of different tissue samples. Stable carbon analysis of different tissues from beef animals can be used to trace back diets containing variable proportions of C3 and C4 plant material. Copyright © 2004 John Wiley & Sons, Ltd.
“You can exercise your way out of HIV” and other stories: The role of biological knowledge in adolescents' evaluation of myths
Authors: Keselman Alla , Kaufman David R. , Patel Vimla L.
Published: April 2004

A primary objective for science education is to impart robust knowledge that has applicability to real‐world problems. This article presents research investigating the relationship between adolescents' conceptual understanding of the biological basis of HIV and critical reasoning. Middle and high school students were interviewed about their understanding of HIV and were subsequently asked to evaluate scenarios that contained myths about HIV. On the basis of their responses to the interview questions, students' understanding of HIV was categorized into three models, naïve, intermediate, and advanced. The results indicate that knowledge mediated students' responses in specific ways. Students at different levels of HIV knowledge reasoned in qualitatively different ways about the myths. A significant relationship was found between students' understanding of HIV biology and the level of biological reasoning. We found that students who employed cellular‐level biological reasoning were more likely to reject the myths than students who employed just system‐level reasoning or nonspecific biological reasoning. The findings emphasize the importance of conceptual understanding in the critical evaluation of information that may serve as a basis for making decisions about HIV. We conclude with discussing the implications of the findings for science and health education. © 2004 Wiley Periodicals, Inc. Sci Ed 88:548–573, 2004
Sexual experience alters D1 receptor–mediated cyclic AMP production in the nucleus accumbens of female Syrian hamsters
Authors: Bradley Katherine C. , Mullins Amanda J. , Meisel Robert L. , Watts Val J.
Published: April 2004

Drugs of abuse produce long‐term changes in dopamine neurotransmission and receptor‐effected intracellular signaling. Similar changes in neuronal activity are mediated by motivated behaviors. To explore cellular mechanisms underlying these neuroadaptations following sexual experience, cyclic AMP accumulation following stimulation of D1 dopamine receptors, G‐proteins, and adenylate cyclase was compared in the nucleus accumbens and caudate nucleus of sexually naive and experienced female hamsters following sexual behavior. Direct stimulation of adenylate cyclase with forskolin or indirectly by activation of G‐proteins with Gpp(NH)p produced dose‐dependent increases in the formation of cyclic AMP in the nucleus accumbens and caudate nucleus, with no effects of sexual experience on these measures. Specific D1 receptor stimulation increased Gpp(NH)p‐induced adenylate cyclase activity in the nucleus accumbens and caudate nucleus of all animals. Interestingly, this stimulation was further enhanced only in membranes from the nucleus accumbens, but not from the caudate nucleus, of sexually experienced hamsters compared to the response of naive females. These results demonstrate that sexual behavior experience can sensitize mesolimbic dopamine pathways and that this sensitization occurs through an increase in D1 receptor–mediated signaling. Synapse 53:20–27, 2004. © 2004 Wiley‐Liss, Inc.
Use of Imiquimod Cream 5% in the Treatment of Localized Morphea
Authors: Man Jeremy , Dytoc Marlene T.
Published: April 2004

Fibrosis is characterized by the increased deposition of collagen and other matrix components by fibroblasts. This process occurs as a reaction to inflammation and is mediated by numerous cytokines including transforming growth factor β (TGF-β). Localized cutaneous scleroderma or morphea is characterized by fibrosis. Current treatment for morphea includes topical, intralesional, or systemic corticosteroids, vitamin D analog (calcitriol and calcipotriol), photochemotherapy, laser therapy, antimalarials, phenytoin, D-penicillamine, and colchicine, all with varying degrees of success. In this case report, imiquimod cream 5% (Aldaraå), which induces interferon and in turn inhibits TGF-β, was employed to treat morphea.
Staphylococcus aureus peptidoglycan stimulates granulocyte macrophage colony‐stimulating factor production from human epidermal keratinocytes via mitogen‐activated protein kinases
Authors: Matsubara Masahiro , Harada Daisuke , Manabe Haruhiko , Hasegawa Kazuhide
Published: April 2004

Epidermal keratinocytes with atopic dermatitis (AD) overproduce mediators such as granulocyte macrophage colony‐stimulating factor (GM‐CSF), which are associated with pathology of AD. We found that peptidoglycan (PGN) of Staphylococcus aureus, which is frequently observed in lesion with AD, induced the production of numerous mediators such as GM‐CSF and regulated on activation, normal T‐cell expressed and secreted. Moreover, PGN phosphorylated extracellular‐signal‐regulated kinases and p38 mitogen‐activated protein kinase, which were involved in the induction of GM‐CSF expression. These results suggested that PGN of S. aureus directly exacerbates inflammation of inflammatory skin disease.
Streptococcal antigen I/II binds to extracellular proteins through intermolecular β‐sheets
Authors: Kelemen Lóránd , Rizk Samer , Debreczeny Mónika , Ogier Joelle , Szalontai Balázs
Published: April 2004

One of the functions associated with the oral streptococcal surface protein I/II is to bind to human extracellular matrix molecules or blood components, which could act as opportunistic ligands in pathological circumstances. In order to understand the relative specificity of the binding repertoire of this bacterial adhesin, we examined by infrared measurements the mode of binding of the protein I/II from Streptococcus mutans OMZ175 (I/IIf) to fibronectin and fibrinogen. This approach revealed the β‐structure forming capacity of I/IIf upon interaction with both proteins. The forming of intermolecular β‐structures may provide a non‐selective way of interaction between I/IIf and its possible targets.
Variability of the Intertropical Convergence Zone recorded in coral isotopic records from the central indian Ocean (Chagos Archipelago)
Authors: Pfeiffer Miriam , Dullo Wolf-Christian , Eisenhauer Anton
Published: April 2004

We have analyzed the stable oxygen isotopic composition of twoPoritescorals from the Chagos Archipelago, which is situated in the geographical center of the Indian Ocean. Coral δ18O at this site reliably records temporal variations in precipitation associated with the Intertropical Convergence Zone (ITCZ). Precipitation maxima occur in boreal winter, when the ITCZ forms a narrow band across the Indian Ocean. The Chagos then lies within the center of the ITCZ, and rainfall is strongly depleted in δ18O. A 120-yr coral isotopic record indicates an alternation of wet and dry intervals lasting 15 to 20 yr. The most recent 2 decades are dominated by interannual variability, which is tightly coupled to the El Niño–Southern Oscillation (ENSO). This is unprecedented in the 120 yr of coral record. As the ITCZ is governed by atmospheric dynamics, this provides evidence of a major change in the coupled ENSO–monsoon system.
Collembola help lichens in competition with algae
Authors: Aptroot André , Berg Matty P.
Published: April 2004

Collembola are terrestrial arthropods that prefer humid environments, probably because their relatively thin chitinous carapace is vulnerable to dehydration. They feed primarily on algae, but certain Collembola may feed on lichens (Leinaas & Somme 1984). They are often found in lichen samples, but the lichens involved do not generally appear to be damaged. Microclimatic conditions within lichens may favour occupation by Collembola as the humidity in the interior of foliose lichen thalli may be relatively high compared to that of the surroundings (Prinzig & Wirtz 1997).
The lichen Leptogium subaridum, a new Mediterranean-NW American disjunction
Authors: Aragón G. , Martínez I. , Otálora M. A. G.
Published: April 2004

Several epiphytic specimens of the genus Leptogium (Ach.) Gray with a foliose thallus and numerous marginal and laminal isidia collected in central and southern Spain, and previously identified as Leptogium magnussonii Degel. & P. M. Jørg., varied considerably. Two morphological forms have been differentiated: one with clusters of granulose or coralloid, aggregated isidia, identified as typical L. magnussonii and the other with clavate to dactyliform isidia as in L. subaridum P. M. Jørg. & Goward. Meanwhile, when studying the lichen L. lichenoides from some European herbaria, three epiphytic specimens belonging to L. subaridum, one from Morocco, one from Italy and the other from Greece, were identified. These new records of the latter species extend its distribution from NW America to S Europe and N Africa. In addition, mature apothecia are reported for the first time. We briefly characterize the species based on material from the new localities using the morphological and anatomical terminology proposed in Jørgensen (1994).
NEW TAXA IN PAPHIA AND DIMORPHANTHERA (ERICACEAE) IN PAPUASIA AND THE PROBLEM OF GENERIC LIMITS IN VACCINIEAE
Authors: STEVENS P. F.
Published: April 2004

New species of Ericaceae recently collected in Papua New Guinea necessitate a re-evaluation of the status of Agapetes subgenus Paphia section Paphia. The combination of molecular and morphological data confirms that Agapetes, currently a genus of about 100 species from Fiji, New Caledonia and Queensland to mainland SE Asia, and most diverse in the latter area, cannot be maintained in its current circumscription. Various taxonomic solutions that do justice to our current knowledge of the morphology and relationships of the two main parts of the genus are discussed. The reinstatement of Paphia does least violence nomenclaturally. All 23 taxa recognized in Paphia are listed, 14 new combinations of Agapetes from the New Guinea–SW Pacific area are made in Paphia, three new species are described (P. megaphylla, P. vulcanicola and P. woodsii), and an incompletely known taxon is characterized. A key to all taxa is presented. In Dimorphanthera, five new species are described (D. angiliensis, D. anomala, D. antennifera, D. cratericola and D. inopinata), three reduced to synonymy, one reduced to a variety and one variety recognized as a species (D. continua). A key to the 87 taxa currently recognized in the genus is presented.
A NEW SPECIES OF STREPTOCARPUS (GESNERIACEAE) FROM THE PONDOLAND COAST, SOUTH AFRICA
Authors: BELLSTEDT D. U. , EDWARDS T. J.
Published: April 2004

The new species Streptocarpus lilliputana (Gesneriaceae), collected on the Pondoland coast, South Africa, is described. Although its alliances are not obvious in terms of corolla morphology and rosulate habit, it approaches S. gardenii and its allies. The pollen and stigma of S. lilliputana differ markedly from the stenopalynous grains and bilobed stigmas of the other South African rosulate species. Streptocarpus lilliputana is exceedingly rare and is a further endemic from the Pondoland centre.
Variability in Sun photometer–derived total ozone over a tropical urban station
Authors: Raj P. Ernest , Devara P. C. S. , Pandithurai G. , Maheskumar R. S. , Dani K. K. , Saha S. K. , Sonbawne S. M.
Published: April 2004

A portable, handheld, multichannel Sun photometer (ozonometer) has been used to measure total column ozone over Pune (18°32′N, 73°51′E, 559 m above mean sea level), India, a tropical urban station. Data collected on about 575 mostly clear‐sky days during the 5 year period from May 1998 to May 2003 have been used in this study to examine diurnal and seasonal variations. The overall daily mean total ozone at this station is 254 Dobson units (DU), with a variability of about 7%, while the most frequently occurring value is in the range 241–250 DU. The diurnal (daytime) patterns are observed to be different in the winter (December–February), premonsoon (March–May), and postmonsoon (October–November) seasons. There exists a predominant seasonal oscillation in total ozone, with higher values (265 DU) during premonsoon months and lower values (246 DU) during winter months. Ground‐based Sun photometer–derived total ozone variations compare very well with those obtained by Earth Probe‐Total Ozone Mapping Spectrometer.