bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and conformational changes in solid‐phase chlorinated polyethylene
Authors: Stoeva S.
Published: July 2004

The structural and conformational changes in solid‐phase chlorinated polyethylene samples of different average molecular masses were studied with infrared spectroscopy. Characteristic absorption bands for both chlorinated polyethylene and chlorinated high‐molecular‐mass polyethylene, containing 1–56% Cl, were identified. The chlorine content in the macromolecular chains, ranging from 1 to 15%, was associated with the presence of single chloromethylene groups and short syndiotactic structural sequences of poly(vinyl chloride) derived from them. Higher degrees of chlorination, ranging from 20 to 56%, resulted in an increase in the relative part of the heterotactic structures with 1,2‐, 1,3‐, and 1,2,3‐modes of mutual location of the chlorine atoms within a fragment. Moreover, solid‐phase chlorinated polyethylenes with chlorine concentrations as high as 56% were polymers with a mixed amorphous–crystalline structure. On the basis of the intensity ratio of the absorption at 610 cm−1 to the absorption at 660 cm−1 for the corresponding characteristic absorption bands, the substitution of the hydrogen atoms for chlorine ones occurred predominantly in the trans‐methylene groups, which were located within the amorphous and intermediate phases of polyethylene with chlorine concentrations as high as 20%. Consequently, the relative part of the gauche chlorinated methylene groups increased. A trans‐to‐gauche conformational change was thought to have taken place during the solid‐phase chlorination of polyethylene under the influence of the bulky chlorine atoms. These changes were facilitated by the corresponding segmental mobility of the macromolecular chains. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 189–196, 2004
Preparation of microspheres with microballoons inside for floating drug‐delivery systems
Authors: Yang Zhenqiu , Song Baozhen , Li Qiaoxia , Fan Honglei , Ouyang Fan
Published: July 2004

The use of floating drug‐delivery systems is one method that is used to achieve prolonged gastric residence times. We developed a novel, multiple‐unit, floating drug‐delivery system of microspheres with microballoons inside from xanthan gum (XG) and gelatin (GA) by a water‐in‐oil method. With theophylline as the model drug, four formulations (FI–FIV) with different ratios of the two polymers were prepared. The size distribution, drug‐encapsulation efficiency, floating behavior, release characteristics, and morphological properties were investigated. The ratio of the two polymers influenced the size distribution, encapsulation efficiency, and drug release appreciably. With increasing amounts of GA, the percentage yield of the floating microspheres and the drug‐encapsulation efficiency decreased from 100 and 84.5% to 31 and 56.2%, respectively. The drug‐release rate also decreased with increasing GA content, which was attributed to an increase in the crosslinking extent. An initial burst was observed, and after that, the drug was released slowly by a near‐zero‐order pattern, which was attributed to the low solubility of theophylline and the possible complexes formed by XG and GA in the simulated gastric fluid (pH 1.2). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 197–202, 2004
Crosslinking of 1,9‐bis[glycidyloxypropyl]penta‐ (1′H,1′H,2′H,2′H‐perfluoroalkylmethylsiloxane)s with α,ω‐diaminoalkanes: The cure behavior and film properties
Authors: Grunlan Melissa A. , Lee Nam S. , Weber William P.
Published: July 2004

A series of nine films were prepared via phenol‐catalyzed thermal crosslinking reactions of 1,9‐bis‐ [glycidyloxypropyl]pentasiloxanes {1,9‐bis[glycidyloxypro‐ pyl]decamethylpentasiloxane (I), 1,9‐bis[glycidyloxypropyl]‐3,5,7‐tris(3′,3′,3′‐trifluoropropyl)heptamethylpentasiloxane (II), and 1,9‐bis[glycidyloxypropyl]‐3,5,7‐tris(1′H,1′H,2′H, 2′H‐perfluorooctyl)heptamethylpentasiloxane (III)} with α,ω‐diaminoalkanes [1,6‐diaminohexane (a), 1,8‐diaminooctane (b), and 1,12‐diaminododecane (c)]. The crosslink density was controlled by the choice of a–c. The cure behavior of I–III with a–c was studied with differential scanning calorimetry. The mechanical properties of the films were determined by dynamic mechanical thermal analysis. Their thermal stability was analyzed by thermogravimetric analysis. The surface properties of the films were evaluated with static contact‐angle measurements. These films represented a novel class of epoxies with an unusual combination of properties: high flexibility (low glass‐transition temperature), good thermal stability, and hydrophobic surfaces. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 203–210, 2004
Untersuchung verschiedener Bodenmodelle zur Berechnung von Fundamentplatten im Rahmen von FEM‐Lösungen
Authors: Barth Christian , Margraf Erik
Published: July 2004

#Die wirklichkeitsnahe Abbildung von Bauwerk‐Boden‐Wechselwirkungen in Finite‐Elemente‐Programmen ist ungeachtet des gegenwärtig hohen Entwicklungsstands der verfügbaren Software eine nicht zu unterschätzende Aufgabe. Einerseits erfordert die richtige Einbindung des Bodenmodells in die FE‐Berechnung viele Überlegungen und Kenntnisse, andererseits sind die in der Software implementierten Bodenmodelle aber für den Anwender nicht immer in ihrer gesamten Komplexität durchschaubar.

Anhand alltäglicher Aufgabenstellungen werden vier verschiedene häufig verwendete und in FEM‐Lösungen implementierte Bodenmodelle unterschiedlicher Softwarehersteller untersucht. Die erzielten Ergebnisse werden gegenübergestellt, und der Versuch einer Bewertung wird vorgenommen.
Der III. Lastfall für die statische Bemessung von verklebten Drucklinern – Biegezugbruch durch Haft‐ und Reibungsabtragung
Authors: Hu Yifeng , Hoch Albert
Published: July 2004

Es wird aufgrund der bisherigen Erfahrungen bei der Sanierung von Druckrohren mit verklebten Linern und theoretischen Überlegungen ein neues Versagensmodell (Biegezugbruch durch Haft‐ und Reibungsabtragung) abgeleitet. Dieses Bruchmodell wird als Lastfall III, zusätzlich zum Lastfall I und II für Liner (Cured‐in‐place pipe) gemäß ASTM F1216 – 98, untersucht. Basierend auf diesem mechanischen Modell wird ein neues Rechenmodell für die statische Bemessung mit Hilfe der Methode der Finiten Elemente entwickelt. Durch numerische Untersuchungen für ein Beispiel im Liner‐Altrohr‐Boden‐Verbundsystem mit diesem Rechenmodell wurden die wesentlichen Einflußfaktoren in diesem Lastfall ermittelt. Damit werden u.a. Vorschläge für weitere notwendige experimentelle Untersuchungen zu dem möglichen bemessungsmaßgebenden LastfallIII gemacht. Dadurch wird letztendlich auch für den LastfallIII eine wirtschaftliche Lösung zur Verfügung gestellt.
Traglastberechnung von schlanken Verpreßpfählen in weichen bindigen Böden
Authors: Wimmer Heinz , Ettinger Robert
Published: July 2004

Verpreßpfähle werden seit vielen Jahren als kostengünstiges Gründungselement eingesetzt. Sie erreichen dabei z. T. extreme Schlankheiten und sind daher knickgefährdet. Schadensfälle aus der jüngsten Vergangenheit lassen den Schluß zu, daß die zulässigen Pfahllasten überschätzt werden. In den Regelwerken werden keine detaillierten Angaben zur Berechnung realistischer Traglasten gegeben. Es wird ein Verfahren vorgestellt, das eine Abschätzung der Traglast mit den wesentlichen Eingangsparametern undränierte Kohäsion, Pfahlimperfektion sowie mit Berücksichtigung der elastoplastischen Eigenschaften von Pfahlwerkstoff und Boden mit verhältnismäßig geringem Aufwand erlaubt.
Über die Abnahme der Tragfähigkeit von Verpreßankern unter Angriff von kalklösender Kohlensäure
Authors: Hof Christiane , Triantafyllidis Theodor , Schmidt‐Döhl Frank
Published: July 2004

Die Anwesenheit kalklösender Kohlensäure in Böden bzw. Grundwasser führt zu einer zeitabhängigen Verminderung der Tragfähigkeit von Verpreßankern durch chemischen Angriff auf den Injektionsmörtel. Der Beitrag beschäftigt sich mit der experimentellen Simulation dieses lösenden Angriffs und dessen Einfluß auf die Ankertragfähigkeit. Es wurden zunächst reine Umströmungsversuche an Zementkörpern, gelagert sowohl in Wasser als auch in Böden, zur Bestimmung der Dicke der korrodierten Randzone in Abhängigkeit von der Konzentration an kalklösender Kohlensäure, der Zeit und der Durchlässigkeit des anstehenden Bodens durchgeführt. Dabei zeigt sich, daß der Korrosionsfortschritt z. T. diffusionsgesteuert abläuft. Anschließend wurden Kastenscher‐ und Ausziehversuche an korrodierten Zementkörpern durchgeführt, um die Abnahme der Scherfestigkeit und der Ausziehkraft in Abhängigkeit vom Korrosionsfortschritt zu bestimmen. Dabei zeigt sich, daß der Reibungswinkel und die Ausziehkraft trotz größer werdender Korrosionstiefe nur bis zum Erreichen eines Grenzwerts abnehmen. Dieser liegt bei den Ausziehversuchen höher als der durch den Anfangsspannungszustand gegebene Wert.
Die Mantelreibung – leistungsbestimmender Parameter bei verrohrten Großlochbohrungen im Lockergestein
Authors: Schumacher Lothar
Published: July 2004

Der vorliegende Aufsatz behandelt grundlegend die Problematik der Mantelreibung am Bohrrohr bei der Herstellung von verrohrten Drehbohrpfählen. Es wird ein praxistauglicher Prognosealgorithmus vorgestellt, der es ermöglicht, aus der zu bestimmenden mittleren Mantelreibung das notwendige Drehmoment zu errechnen, um somit eine leistungsgerechte und wirtschaftliche Bohrgeräteauswahl zu realisieren.
Verbesserte Näherungsberechnung von Bogenstaumauern nach der Schalentheorie
Authors: Herzog Max
Published: July 2004

Beim Vergleich der Beanspruchungen und Formänderungen von 15 Bogenstaumauern sehr unterschiedlicher Geometrien und Steifigkeitsverhältnisse gemäß einer vereinfachten Näherungsberechnung nach der Schalentheorie wird eine mindestens für die Vorbemessung und Kontrolle völlig ausreichende Übereinstimmung mit ausgewählten in‐situ‐Messungen festgestellt. Die erforderliche Handrechnung für die drei Hauptlastfälle Eigenlast, Wasserdruck und Temperaturänderung ist ohne Lösung eines Gleichungssystems in nur zwei Stunden zu bewältigen.
40 Jahre Wasserturm in Flensburg‐Mürwick
Authors: Starke Peter
Published: July 2004

Nachfolgend wird vom Werdegang eines nichtalltäglichen Hochbaus berichtet. Angefangen von Ausschreibung, Entwurf und Statik bis zur Ausführung mit Innenausbau dienen die seinerzeit gemachten Aufzeichnungen und Fotos als Unterlagen des hier vorgelegten Jubiläumsbeitrags. Es wird die Konstruktion unter Berücksichtigung ästhetischer Belange beschrieben, wie sie sich in der Zusammenarbeit mit einem namhaften Architekten ergab.

Die weitausladende, rotationssymmetrische Form von Außenhaut und Behälter war Anlaß, die erst ein knappes Jahrzehnt alte Spannbetontechnologie außer im Brückenbau auch im Hochbau anzuwenden.

Es werden Angaben über die Aufteilung in Fertigteile und Ortbeton gemacht, über den Kraftfluß vom Behälter bis ins Fundament, über Arbeitsvorbereitung und Herstellung des Bauwerks.
Ingenieuranalyse von Erdbebenschäden: Das Bingöl (Türkei)‐Erdbeben vom 1. Mai 2003
Authors: Schwarz Jochen , Abrahamczyk Lars , Lang Dominik H. , Maiwald Holger
Published: July 2004

Mit der Ingenieuranalyse der Erdbebenschäden des Magnitude6.6 Bingöl‐Erdbebens (Türkei) vom 1. Mai 2003 wird der Versuch unternommen, schadenbegünstigende Einflußfaktoren herauszuarbeiten. Die Schadensauswertungen, die instrumentellen Standortuntersuchungen und die Reinterpretation des Bauwerksverhaltens konzentrieren sich dabei auf die vor Ort aufgenommenen Stahlbetonkonstruktionen. Im Mittelpunkt stehen mehrgeschossige Schulgebäude, die trotz ihres Typenprojektcharakters deutliche Unterschiede im Schädigungsgrad (geringe Schädigung bis hin zum Kollaps) aufweisen. Es wird ein Schema zur Bewertung der Schadensursachen eingeführt, das die Intensität der Bodenbewegung, Resonanzeffekte zwischen Baugrund und Bauwerk, Richtungseffekte als auch Merkmale der konstruktiven Durchbildung einschließt.

Neben Phänomenen und typischen Schadensmustern, die bereits bei anderen Beben in der Region und auch weltweit festzustellen waren, werden Faktoren herausgearbeitet, die zu einer Verstärkung der Bodenbewegung beigetragen haben (können). Dies betrifft insbesondere die topographischen Besonderheiten, die auch durch die aktuelle Baunormung nicht ausreichend berücksichtigt erscheinen.

Ein für die Region typisches Stahlbetonrahmentragwerk wird der nichtlinearen statischen “pushover”‐Analyse unterzogen, um die Plausibilität zwischen den in Ortsnähe registrierten Bodenbeschleunigungen des Hauptbebens und dem beobachteten Bauwerksverhalten zu überprüfen. Dabei wird das methodische Vorgehen vorgestellt, um auf Grundlage der vor Ort aufgenommenen Materialkenngrößen und Bewehrungsdetails mittels steifigkeitsabhängiger Kapazitätskurven Aussagen über die Verletzbarkeit (u.a. bei stärkeren Beben) ableiten zu können.
Numerische Simulation des Knickverhaltens von Mauerwerk
Authors: Vassilev Todor , Jäger Wolfram
Published: July 2004

Im Aufsatz wird ein numerisches Vorgehen für die Simulation und Analyse des Knickverhaltens von Mauerwerkswänden vorgestellt. Der konzipierte Spannungs‐Dehnungs‐Ansatz gestattet es, das Biegedruckverhalten des Verbundwerkstoffs Mauerwerk realitätsnah zu modellieren. Der Einfluß der Verformungen auf die Tragfähigkeit wird durch die Formulierung des Gleichgewichts im verformten Zustand erfaßt. Das nichtlineare Materialverhalten, die Spannungsrestriktionen und die Systemmodifikation bei Rißbildung resultieren zu einer variablen Biegesteifigkeit und veränderlichen Koeffizienten der bestimmenden Differentialgleichung. Die Lösung gelingt im Rahmen einer iterativen numerischen Prozedur im Sinne des Übertragungsmatrizenverfahrens auf der Basis der Systemdiskretisierung und der abschnittsweisen Linearisierung der Systemparameter.
Ermittlung von Stabilisierungslasten im Holzbau
Authors: Möller Gunnar
Published: July 2004

Die Ermittlung von Stabilisierungslasten für Aussteifungsverbände erfolgt üblicherweise nach einem vereinfachten Verfahren der Holzbaunorm. Im vorliegenden Aufsatz werden zwei Verfahren für eine genaue Ermittlung der Stabilisierungskräfte vorgestellt. Das eine Verfahren beruht auf der Energiemethode und ist gültig für gabelgelagerte Einfeldträger mit kontinuierlicher seitlicher Stützung. Für Einfeldträger mit Belastung durch konstante Normalkräfte oder Biegemomente können hieraus Gleichungen für die Ermittlung der Seitenlast ermittelt werden. Eine weitere Nachweismöglichkeit ist die Ermittlung der Seitenlasten nach der Biegetorsionstheorie II.Ordnung für den räumlich belasteten und punktuell seitlich gestützten Stab für beliebige Lagerung und Belastung unter Verwendung des Übertragungsverfahrens. Die Ergebnisse beider Verfahren werden anhand von Beispielen verglichen.
3‐Methyl‐3‐sulfanylhexan‐1‐ol as a Major Descriptor for the Human Axilla‐Sweat Odour Profile
Authors: Troccaz Myriam , Starkenmann Christian , Niclass Yvan , van de Waal Matthijs , Clark Anthony J.
Published: July 2004

This study sets out to redress the lack of knowledge in the area of volatile sulfur compounds (VSCs) in axillary sweat malodour. Sterile odourless underarm sweat (500 ml) was collected from 30 male volunteers after excessive sweating. Five strains of bacteria, Corynebacterium tuberculostearicum, Corynebacterium minutissimum, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Bacillus licheniformis, were isolated and characterised for their ability to generate an authentic axillary odour from the sweat material collected. As expected, all of the five bacterial strains produced strong sweat odours. Surprisingly, after extensive olfactive evaluation, the strain of Staphylococcus haemolyticus produced the most sulfury sweat character. This strain was then chosen as the change agent for the 500 ml of odourless underarm sweat collected. After bacterial incubation, the 500‐ml sample was further processed for GC‐olfactometry (GC‐O), GC/MS analysis. GC‐O of an extract free of organic acids provided three zones of interest. The first was chicken‐sulfury, the second zone was onion‐like, and the third zone was sweat, clary sage‐like. From the third zone, a new impact molecule, (R)‐ or (S)‐3‐methyl‐3‐sulfanylhexan‐1‐ol, was isolated and identified by GC/MS, MD‐GC, and GC AED (atomic emission detector). (S)‐3‐methyl‐3‐sulfanylhexan‐1‐ol was sniff‐evaluated upon elution from a chiral GC column and was described as sweat and onion‐like; its opposite enantiomer, (R)‐3‐methyl‐3‐sulfanylhexan‐1‐ol, was described as fruity and grapefruit‐like. The (S)‐form was found to be the major enantiomer (75%).
Identification of Odoriferous Sulfanylalkanols in Human Axilla Secretions and Their Formation through Cleavage of Cysteine Precursors by a CS Lyase Isolated from Axilla bacteria
Authors: Natsch Andreas , Schmid Joachim , Flachsmann Felix
Published: July 2004

Human axillary odor is known to be formed upon the action ofCorynebacteriasp. onper seodorless axilla secretions. Besides the known odoriferous acids, we report the occurrence in human axilla secretions of four odoriferous sulfanylalkanols, namely 3‐sulfanylhexan‐1‐ol (3), 2‐methyl‐3‐sulfanylbutan‐1‐ol (4), 3‐sulfanylpentan‐1‐ol (5), and 3‐methyl‐3‐sulfanylhexan‐1‐ol (6). These compounds have a pungent sweat/kitchen odor, also reminiscent of onions with some fruity connotations, and perception thresholds in the pg/l range. It was postulated that the odorless precursors for these compounds are cysteine conjugates. Bacterial isolates obtained from the human axilla and belonging to theCorynebacteriawere, indeed, found to have the enzymatic capacity to release various thiols from cysteine conjugates. ThemetC gene, which is known to code for a cystathione‐β‐lyase, was cloned from the axilla isolateCorynebacterium striatumAx20 and heterologously expressed inE. coli.The pure recombinant enzyme cleaves various cysteine conjugates and has a similar substrate specificity as the cell homogenates of the wild‐type. The recombinant enzyme was finally incubated with odorless axilla secretions and shown to release odoriferous thiols.
Photo‐Induced Processes in Vitamin B6 Compounds
Authors: Vilanova Bartolomé , Adrover Miquel , Muñoz Francisco , Donoso Josefa
Published: July 2004

In this work, we applied multi‐wavelength stopped‐flow spectroscopy (MSFS) to study the chemical equilibria between tautomeric or hydrated forms of various vitamin B6 compounds and the Schiff base formed by ε‐aminocaproic acid (=6‐aminohexanoic acid) with pyridoxal 5′‐phosphate at 25° and variable pH. Since some of these compounds are photosensitive, we analyzed the possible occurrence of any secondary photo‐induced processes under the conditions of irradiation in the MSFS equipment (continuous irradiation with light from a 75‐W Xe lamp spanning the wavelength range of 200–700 nm). To determine the tautomeric composition of these compounds, the electronic absorption spectra were analyzed by means of log‐normal curves. Continuous irradiation of pyridoxamine and pyridoxal 5′‐phosphate over the wavelength range of 200–700 nm displaces the chemical equilibrium between the tautomeric or hydrated forms of these compounds. However, the Schiff base of ε‐aminocaproic acid with pyridoxal 5′‐phosphate is insensitive to the radiation used. The photo‐induced processes detected in pyridoxamine and pyridoxal 5′‐phosphate should be taken into account in examining vitamers by MSFS. In fact, these additional processes should be considered in studying the mechanism of action of vitamin B6‐dependent enzymes by the MSFS technique, whenever some free vitamer may be present in solution.
Thymosin β4 and Its N‐Terminal Tetrapeptide, AcSDKP, Inhibit Proliferation, and Induce Dysplastic, Non‐Apoptotic Nuclei and Degranulation of Mast Cells
Authors: Leeanansaksiri Wilairat , DeSimone Shirley K. , Huff Thomas , Hannappel Ewald , Huff Thomas F.
Published: July 2004

Thymosin β4 (Tβ4), a 5 kDa polypeptide, is a member of the β‐thymosin family. It acts as the principal intracellular G‐actin sequestering peptide and exhibits extracellular functions in angiogenesis and wound healing. The N‐terminus of Tβ4 contains a bioactive tetrapeptide, acSDKP, a negative regulator of hematopoietic stem‐cell proliferation. Here, we show that both peptides inhibit mast‐cell proliferation over the concentration range of 10−6 to 10−17 M with the maximum effect of both at 10−14 M. Both Tβ4 and acSDKP caused dysplastic mast‐cell nuclei that were confirmed by DAPI fluorescent staining. Flow‐cytometric analysis of ploidy revealed that the dysplastic nuclei were not multinucleated, but fragmented nuclei in G2 growth arrest. We could further demonstrate that 10−8 or 10−14 M Tβ4 or acSDKP induce mast‐cell degranulation. A concentration of 10−8 M Tβ4 or acSDKP caused 57 or 89% degranulation, respectively. A number of tryptic fragments of Tβ4 were assayed beside intact Tβ4 and the tetrapeptide, and found to be inactive.
Six New Constituents from the Roots of Erythrina variegata
Authors: Tanaka Hitoshi , Hirata Miyuki , Etoh Hideo , Sako Magoichi , Sato Masaru , Murata Jin , Murata Hiroko , Darnaedi Dedy , Fukai Toshio
Published: July 2004

Three new isoflavonoids, eryvarins M–O (1–3), two new 2‐arylbenzofurans, eryvarins P and Q (4 and 5), and a new 3‐aryl‐2,3‐dihydrobenzofuran, eryvarin R (6), together with three known compounds, were isolated from the roots of Erythrina variegata. The structures of these compounds were established by spectroscopic analysis. Eryvarin R (6) is an unusual 3‐aryl‐2,3‐dihydrobenzofuran derivative with a formyl (CHO) group. Eryvarin Q (5) showed potent antibacterial activity against methicillin‐resistant Staphylococcus aureus.
Base‐Pairing Systems Related to TNA Containing Phosphoramidate Linkages: Synthesis of Building Blocks and Pairing Properties
Authors: Ferencic Mathias , Reddy Goverdhan , Wu Xiaolin , Guntha Sreenivasulu , Nandy Jyoti , Krishnamurthy Ramanarayanan , Eschenmoser Albert
Published: July 2004

As part of a project that aims at screening TNA‐related oligonucleotide systems in which threose backbone units may have some or all of their oxygen functions replaced by nitrogen, two TNA analogs containing (2′NH)‐ and (3′NH)‐phosphoramidate groups, respectively, in place of phosphodiester groups were synthesized. They show base‐pairing properties that are very similar to those of TNA itself. We also synthesized 2′,3′‐diamino analogs of α‐L‐threofuranosyl mononucleosides, yet attempts to convert them to TNA analogs containing phosphodiamidate linker groups were not successful. Such 2′,3′‐diamino derivatives of threofuranosyl nucleosides may be of interest, however, as building blocks of TNA analogs that contain non‐phosphorous linker groups.
Reduction of carbon tetrachloride‐induced nephropathy by melatonin administration
Authors: Ogeturk Murat , Kus Ilter , Kavakli Ahmet , Oner Jale , Kukner Aysel , Sarsilmaz Mustafa
Published: July 2004

The aim of this study was to investigate possible protective effects of melatonin on carbon tetrachloride (CCl4)‐induced renal damage in rats. A total of 24 animals were divided into three equal groups: the control rats received pure olive oil subcutaneously, rats in the second group were injected with CCl4 (0.5 ml kg−1, s.c. in olive oil) and rats in the third group were injected with CCl4 (0.5 ml kg−1) plus melatonin (25 mg kg−1, s.c. in 10% ethanol) every other day for 1 month. At the end of the experimental period, the animals were sacrificed and blood samples were collected. The kidneys were removed and weighed. Urea and creatinine levels were determined in blood samples. Histopathological examination of the kidney was performed using light microscopic methods. Administration of CCl4 significantly increased relative kidney weight (g per 100 g body weight) and decreased serum urea levels compared to controls (p < 0.01). Melatonin treatment significantly (p < 0.01) reduced relative kidney weight, and it produced a statistically equal (p = 0.268) relative weight with the kidneys of control rats. CCl4 administration alone also caused histopathologically prominent damage in the kidney compared to the control group. Glomerular and tubular degeneration, interstitial mononuclear cell infiltration and fibrosis, vascular congestion around the tubules, and interstitial haemorrhage in perivascular areas were observed in the renal cortex and cortico‐medullary border. However, the affect of CCl4 on the medulla was limited. Melatonin provided protection against CCl4‐induced renal toxicity as was evident by histopathological evaluation. In view of the present findings, it is suggested that melatonin protects kidneys against CCl4 toxicity. Copyright © 2004 John Wiley & Sons, Ltd.
A perspective on good practice in community college assessment
Authors: Banta Trudy W. , Black Karen E. , Kahn Susan , Jackson Julia E.
Published: July 2004

Community colleges are increasingly pressed to develop assessment approaches of genuine value to students, faculty, and other stakeholders. Numerous institutional examples illustrate a set of principles for good practice in planning, implementing, and sustaining community college assessment.
Engaging faculty and students in classroom assessment of learning
Authors: Rouseff‐Baker Fay , Holm Andrew
Published: July 2004

Outcomes. Alternative assessment. Multiple measures. Analysis. Data. How does an institution move from academic discourse to authentic assessment of student learning? The answer is to engage the faculty and students in the process.
Assessment at the program level
Authors: Bers Trudy H.
Published: July 2004

Program‐level assessments at community colleges are particularly challenging because students often achieve their goals without completing a program, or they select an array of courses that suit their needs but do not fit within an officially recognized program of study.
Implications of state performance indicators for community college assessment
Authors: Burke Joseph C. , Minassians Henrik P.
Published: July 2004

The views of state legislators and agencies that govern higher education must be considered along with institutional perspectives on approaches to assessment of student learning outcomes. This chapter provides a review of performance indicators from twenty‐nine recent state reports and discusses their implications for the assessment of student learning outcomes at the campus level.
Assessment of online education: Policies, practices, and recommendations
Authors: Milam John , Voorhees Richard A. , Bedard‐Voorhees Alice
Published: July 2004

Online education has become deeply embedded in the offerings of most community colleges. This chapter discusses the challenges, models, and approaches to conducting assessment of student online learning and establishing outcomes for online education.
Learning outcomes for the twenty‐first century: Cultivating student success for college and the knowledge economy
Authors: Miles Cindy L. , Wilson Cynthia
Published: July 2004

This chapter provides an overview of the League for Innovation in the Community College's project on learning outcomes. The 21st Century Learning Outcomes Project was a three‐year project involving sixteen diverse community colleges that supported the development of practices for assessing and using student learning outcomes to improve student success.
Meeting the challenges of assessing student learning outcomes
Authors: Friedlander Jack , Serban Andreea M.
Published: July 2004

Although community colleges have made significant strides in assessing student learning outcomes, there are a number of significant challenges that need to be addressed in order to realize fully the anticipated benefits of these efforts. This chapter identifies these major challenges and provides specific suggestions that can be used by community colleges, state and accrediting agencies, and universities to facilitate the development, implementation, and continued support of student learning outcomes assessment initiatives that will increase student learning and achievement.
Molecular Structure of Proline
Authors: Allen Wesley D. , Czinki Eszter , Császár Attila G.
Published: July 2004

The molecular structures of the two lowest‐energy conformers of proline, Pro‐I and Pro‐II, have been characterized by ab initio electronic structure computations. An extensive MP2/6‐31G* quartic force field for Pro‐I, containing 62 835 unique elements in the internal coordinate space, was computed to account for anharmonic vibrational effects, including total zero‐point contributions to isotopomeric rotational constants. New re and improved r0 least‐squares structural refinements were performed to determine the heavy‐atom framework of Pro‐I, based on experimentally measured (A. Lesarri, S. Mata, E. J. Cocinero, S. Blanco, J. C. Lopez, J. L. Alonso, Angew. Chem. 2002, 114, 4867; Angew. Chem. Int. Ed. 2002, 41, 4673) rotational constant sets of nine isotopomers and our ab initio data for structural constraints and zero‐point vibrational (ZPV) shifts. Without the ab initio constraints, even the extensive set of empirical rotational constants cannot satisfactorily fix the molecular structure of the most stable conformer of proline, a 17‐atom molecule with no symmetry. After imposing the ab initio constraints, excellent agreement between theory and experiment is found for the heavy‐atom geometric framework, the root‐mean‐square (rms) residual of the empirical rotational constant fit being cut in half by adding ZPV corrections. The most significant disparity, about 0.07 Å, between the empirical and the best ab initio structures, concerns the r(N⋅⋅⋅H) distance of the intramolecular hydrogen bond. Some of the experimental quartic centrifugal distortion constants assigned to Pro‐II have been corrected based on data obtained from a theoretical force field.
Regio‐ and Stereospecific Cleavage of Silyl‐ and Disilylepoxides with Lithium Diphenylphosphide
Authors: Cuadrado Purificación , González‐Nogal Ana M. , Sarmentero M. Angeles
Published: July 2004

Unsubstituted or α‐ and β‐C‐substituted silylepoxides react stereospecifically with lithium diphenylphosphide, optionally followed by methylation, to give vinylphosphonium iodides or vinylphosphine oxides resulting from α‐opening and silyl enol ethers, vinylsilanes or α‐hydroxysilanes by β‐opening. On the other hand, α,β‐ or α,α‐disilylepoxides afforded β‐silyl vinylphosphine oxides or α‐silylated silyl enol ethers by α‐ and β‐cleavage, respectively. All compounds are interesting synthons in organic chemistry.
First Total Synthesis of Hormaomycin, a Naturally Occurring Depsipeptide with Interesting Biological Activities
Authors: Zlatopolskiy Boris D. , de Meijere Armin
Published: July 2004

Some unique features were disclosed during the structure elucidation of the cyclic depsipeptide hormaomycin (1), first isolated in 1989 from aStreptomyces griseoflavusstrain and found to have quite an interesting spectrum of biological activities. Besides one residue of the proteinogenic amino acid isoleucine [(S)‐Ile], it contains two units of 3‐methylphenylalanine [(βMe)Phe], one of (2R)‐allo‐threonine [a‐Thr] as well as two moieties of 3‐(trans‐2‐nitrocyclopropyl)alanine [(3‐Ncp)Ala] and one of 4‐(Z)‐propenylproline [(4‐PE)Pro]. The latter two have never been found in any natural product before. The side chain of1is terminated with the residue of 5‐chloro‐1‐hydroxypyrrole‐2‐carboxylic acid [Chpca]. This first synthetic access to hormaomycin1will make it possible to prepare structural analogues of this interesting natural depsipeptide in order to elucidate structure–activity relationships and the biologically active minimal unit.
Lead and Mercury Sensing by Calixarene‐Based Fluoroionophores Bearing Two or Four Dansyl Fluorophores
Authors: Métivier Rémi , Leray Isabelle , Valeur Bernard
Published: July 2004

A detailed study on the photophysical and complexing properties of calixarenes bearing two and four dansyl derivatives (Calix‐DANS2 and Calix‐DANS4) in a CH3CN/H2O mixture (60:40 v/v) is reported. Calix‐DANS2 shows a high selectivity towards Hg2+ over interfering cations (Na+, K+, Ca2+, Cu2+, Zn2+, Cd2+ and Pb2+) and a sensitivity in the 10−7 mol L−1 concentration range. The complexation of mercury ion induces a strong fluorescence quenching due to a well‐defined electron transfer process from the fluorophore to the metal center. Calix‐DANS4 exhibits an extremely high affinity for Pb2+ with a high selectivity over various competing ions. The unprecedented detection limit (4 μg L−1) is fully compatible with the level defined by the World Health Organisation. The affinity of Calix‐DANS4 for Pb2+ can be rationalized by the activation of the inert pair of electrons on Pb2+. The number of fluorophores involved in the complexation can be determined from a careful time‐resolved fluorescence characterization.
ULTRAMINE: A High‐Capacity Polyethylene–Imine‐Based Polymer and Its Application as a Scavenger Resin
Authors: Roice Michael , Christensen Søren F. , Meldal Morten
Published: July 2004

The synthesis of a novel high‐loading polyethylene–imine resin (ULTRAMINE) is described, and its application as a scavenger resin in various acylation reactions is demonstrated. The inverse suspension polymerization technique was used for the synthesis of well‐defined spherical polymer beads. Polymer beads with different cross‐linking densities were synthesized according to the degree of acryloylation of the polyethylene–imine polymer. The resin was characterized by various spectroscopic techniques. The size, shape, and morphological features of the resin were demonstrated by microscopy. The resin showed excellent swelling properties in both polar and nonpolar solvents. The chemical stability of the resin in various reagents and solvents was investigated and monitored by IR spectroscopy. The mechanical stability of the beads was determined by a single‐bead compressive experiment. The ULTRAMINE beads can be used as an excellent scavenger for excess acylating reagent, as demonstrated for a variety of reactions. ULTRAMINE‐red resin was derived from ULTRAMINE through exhaustive reduction of the amide carbonyl groups to yield an all‐amine resin.
Analysis of UV‐excited fluorochromes by flow cytometry using near‐ultraviolet laser diodes
Authors: Telford William G.
Published: July 2004

Introduction

Violet laser diodes have become common and reliable laser sources for benchtop flow cytometers. While these lasers are very useful for a variety of violet and some ultraviolet‐excited fluorochromes (e.g., DAPI), they do not efficiently excite most UV‐stimulated probes. In this study, the next generation of InGaN near‐UV laser diodes (NUVLDs) emitting in the 370–375‐nm range have been evaluated as laser sources for cuvette‐based flow cytometers.

Methods

Several NUVLDs, ranging in wavelength from 370 to 374 nm and in power level from 1.5 to 10 mW, were mounted on a BD Biosciences LSR II and evaluated for their ability to excite cells labeled with the UV DNA binding dye DAPI, several UV phenotyping fluorochromes (including Alexa Fluor 350, Marina Blue, and quantum dots), and the fluorescent calcium chelator indo‐1.

Results

NUVLDs at the 8–10‐mW power range gave detection sensitivity levels comparable to more powerful solid‐state and ion laser sources, using low‐fluorescence microsphere beads as measurement standards. NUVLDs at all tested power levels allowed extremely high‐resolution DAPI cell cycle analysis, and sources in the 8–10‐mW power range excited Alexa Fluor 350, Marina Blue, and a variety of quantum dots at virtually the same signal‐to‐noise ratios as more powerful UV sources.

Conclusions

These evaluations indicate that near‐UV laser diodes installed on a cuvette‐based flow cytometer performed nearly as well as more powerful solid‐state UV lasers on the same instrumentation, and comparably to more powerful ion lasers on a jet‐in‐air system, and. Despite their limited power, integration of these small and inexpensive lasers into benchtop flow cytometers should allow the use of flow cytometric applications requiring UV excitation on a wide variety of instruments. © 2004 Wiley‐Liss, Inc.
Effect of changing symbol rate on equalizer performance for band‐limited systems
Authors: Liu Hong‐Yu , Yen Rainfield Y.
Published: July 2004

In this work, the effect of changing symbol rate (or equivalently, symbol rate) on the equalizer performance for M‐ary PAM systems is investigated. We keep increasing the symbol rate (or equivalently, keep decreasing the symbol period) until a limit is reached. An effort is made to find this limit. In other words, we are investigating the possibility of increasing the symbol rate beyond the usual Nyquist rate. Since incessantly increasing the symbol rate will eventually produce channel spectrum null (almost null) which will render difficulties for equalization, decision‐feedback equalization combined with fractionally spaced sampling is used to overcome the difficulties. For a given channel bandwidth and a prescribed error probability, optimum symbol rates vs SNR are found so as to achieve maximum bit rates. Explanations are given for the resultant phenomena both analytically as well as by computer simulations. A theoretical channel model and a realistic twisted pair channel are used for demonstration. Important analytical expressions are given along with computer simulations to quantify performance results. Copyright © 2004 John Wiley & Sons, Ltd.
Effectiveness of progressive dose‐escalation of exenatide (exendin‐4) in reducing dose‐limiting side effects in subjects with type 2 diabetes
Authors: Fineman Mark S. , Shen Larry Z. , Taylor Kristin , Kim Dennis D. , Baron Alain D.
Published: July 2004

Background

Exenatide (exendin‐4) exhibits dose‐dependent glucoregulatory activity, but causes dose‐limiting nausea and vomiting. This study was designed to formally assess the possibility of inducing tolerance to the side effects of nausea and vomiting at therapeutic doses of exenatide, using a dose‐escalation methodology.

Methods

In this two‐arm, triple‐blind, multicenter study, 123 subjects with type 2 diabetes were enrolled and randomized; 99 (80.5%) of them completed the study. Subjects in the exenatide‐primed arm received subcutaneous exenatide, starting at 0.02 µg/kg three times a day (TID) and increasing in 0.02 µg/kg per dose increments every 3 days for 35 days. Subjects in the exenatide‐naive arm received placebo TID for 35 days. At the end of this 35‐day regimen, subjects in both arms received the same highest dose of exenatide (0.24 µg/kg TID) for 3 days. Thus, the exenatide‐naive arm received exenatide for the first time on Day 35.

Results

The exenatide‐primed arm had a lower proportion of subjects experiencing nausea and vomiting in response to exposure to the highest dose of exenatide (27 vs 56% in the exenatide‐naive arm; p = 0.0018). Kaplan–Meier estimates of cumulative incidence were 0.28 in the exenatide‐primed arm, compared with 0.68 in the exenatide‐naive arm (p ≤ 0.001). As predicted by the study design, fewer subjects in the exenatide‐primed arm reported severe nausea (29%) and vomiting (10%) than those in the exenatide‐naive arm (48 and 31%, respectively). In the exenatide‐primed arm, fasting serum glucose progressively declined over the first 35 days of dosing, but was unchanged in the exenatide‐naive arm (placebo phase) during the same interval.

Conclusion

Gradual dose‐escalation of exenatide successfully reduced the proportion of subjects experiencing dose‐limiting nausea and vomiting, with no loss of glucoregulatory activity, thus demonstrating the value of gradual dose‐escalation in mitigating the gastrointestinal side effects of exenatide. Copyright © 2004 John Wiley & Sons, Ltd.
Expression and function of integrin α4β1 and vascular cell adhesion molecule‐1 (VCAM‐1) during sympathetic innervation of the heart
Authors: Wingerd Kevin L. , Goodman Nichol L. , Leu Sergiu T. , Clegg Dennis O.
Published: July 2004

The interaction between the integrin α4β1 receptor on superior cervical ganglion (SCG) neurons and vascular cell adhesion molecule‐1 (VCAM‐1) in cardiac tissue has been implicated in proper development of the sympathetic innervation of the heart (Wingerd et al. [2002] J Neurosci 22:10772–10780). In this study, we examined the expression and function of α4β1 and VCAM‐1 in developing rat SCG and heart. In vitro, the α4β1‐dependent neurite outgrowth on VCAM‐1 decreased by approximately 50% from postnatal day 1 to 6. This down‐regulation was correlated with a shift in α4 isoform and a shift in α4 localization from neurites to cell bodies. This altered localization was also observed in vivo but on a different time scale. α4 was detected on most developing SCG neurons and on macrophages and blood vessels. In the heart, α4 was detected on sympathetic axons, but the percentage of α4‐positive fibers decreased with age. VCAM‐1 immunoreactivity was abundant in heart tissue throughout development, in close proximity to sympathetic axons. The regulation of α4β1 function, and localization of α4 and VCAM‐1, are consistent with a role for the α4β1–VCAM‐1 interaction in extension of sympathetic axons into the myocardium. Developmental Dynamics 231:359–369, 2004. © 2004 Wiley‐Liss, Inc.
Stat3 signaling is present and active during development of the central nervous system and eye of vertebrates
Authors: Yan Ye , Bian Wei , Xie Zhiqin , Cao Xinmin , Le Roux Isabelle , Guillemot Francois , Jing Naihe
Published: July 2004

Stat3, a member of the signal transducer and activator of transcription (STAT) family, plays a central role in mediating cell growth, differentiation, and survival signals. In this report, we show that Stat3 immunoreactivity was localized to specific regions in the developing mouse brain, neural tube, and eye from embryonic day 10.5 to postnatal day 0. The active form of Stat3 protein, which is phosphorylated on tyrosine 705 (pYStat3), was also found in the developing neural tube with more restricted distribution. An in ovo chick embryo electroporation assay showed that the endogenous chick Stat3 could drive consensus sis‐inducible element‐directed reporter gene expression. These results demonstrate that the active Stat3 protein is present and might play a role during the development of the central nervous system and eye. Developmental Dynamics 231:248–257, 2004. © 2004 Wiley‐Liss, Inc.
Role of cranial neural crest cells in visceral arch muscle positioning and morphogenesis in the Mexican axolotl, Ambystoma mexicanum
Authors: Ericsson Rolf , Cerny Robert , Falck Pierre , Olsson Lennart
Published: July 2004

The role of cranial neural crest cells in the formation of visceral arch musculature was investigated in the Mexican axolotl, Ambystoma mexicanum. DiI (1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethylindocarbocyanine, perchlorate) labeling and green fluorescent protein (GFP) mRNA injections combined with unilateral transplantations of neural folds showed that neural crest cells contribute to the connective tissues but not the myofibers of developing visceral arch muscles in the mandibular, hyoid, and branchial arches. Extirpations of individual cranial neural crest streams demonstrated that neural crest cells are necessary for correct morphogenesis of visceral arch muscles. These do, however, initially develop in their proper positions also in the absence of cranial neural crest. Visceral arch muscles forming in the absence of neural crest cells start to differentiate at their origins but fail to extend toward their insertions and may have a frayed appearance. Our data indicate that visceral arch muscle positioning is controlled by factors that do not have a neural crest origin. We suggest that the cranial neural crest‐derived connective tissues provide directional guidance important for the proper extension of the cranial muscles and the subsequent attachment to the insertion on the correct cartilage. In a comparative context, our data from the Mexican axolotl support the view that the cranial neural crest plays a fundamental role in the development of not only the skeleton of the vertebrate head but also in the morphogenesis of the cranial muscles and that this might be a primitive feature of cranial development in vertebrates. Developmental Dynamics 231:237–247, 2004 © 2004 Wiley‐Liss, Inc.
Pluripotent neural crest stem cells in the adult hair follicle
Authors: Sieber‐Blum M. , Grim M. , Hu Y.F. , Szeder V.
Published: July 2004

We report the presence of pluripotent neural crest stem cells in the adult mammalian hair follicle. Numerous neural crest cells reside in the outer root sheath from the bulge to the matrix at the base of the follicle. Bulge explants from adult mouse whisker follicles yield migratory neural crest cells, which in clonal culture form colonies consisting of over a thousand cells. Clones contain neurons, smooth muscle cells, rare Schwann cells and melanocytes, demonstrating pluripotency of the clone‐forming cell. Targeted differentiation into Schwann cells and chondrocytes was achieved with neuregulin‐1 and bone morphogenetic protein‐2, respectively. Serial cloning in vitro demonstrated self‐renewal capability. Together, the data show that the adult mouse whisker follicle contains pluripotent neural crest stem cells, termed epidermal neural crest cells (eNCSC). eNCSC are promising candidates for diverse cell therapy paradigms because of their high degree of inherent plasticity and due to their easy accessibility in the skin. Developmental Dynamics 231:258–269, 2004. © 2004 Wiley‐Liss, Inc.
Innervation‐dependent and fiber type‐specific transcriptional regulation of the slow myosin heavy chain 2 promoter in avian skeletal muscle fibers
Authors: Jiang Hongbin , Jordan Theresa , Li Jinyuan , Li Hui , DiMario Joseph X.
Published: July 2004

Skeletal muscle fiber type is regulated, in part, by innervation leading to transcriptional regulation of fiber type‐specific genes. Here, we report the initial characterization of the transcriptional regulation of the slow myosin heavy chain 2 (MyHC2) promoter in innervated and noninnervated slow medial adductor (MA) and fast pectoralis major (PM) muscle fibers in cell culture. The proximal 1358 bp of slow MyHC2 upstream DNA contains a functional E‐box and binding sites for myocyte enhancer factor 2 (MEF2) and nuclear factor of activated T cells (NFAT). Mutagenesis studies indicated that both MEF2 and NFAT binding sites are required for innervation‐induced slow MyHC2 promoter activity in MA muscle fibers. However, MEF2 transcription factor activity was unaffected by innervation and did not demonstrate fiber type‐specific interactions with the slow MyHC2 MEF2 binding site. NFAT transcription factor activity did increase in innervated MA muscle fibers and not in PM muscle fibers, indicating innervation and muscle fiber type‐specific regulation. However, transfection of constitutively active NFAT indicated that NFAT is insufficient to induce slow MyHC2 gene expression in either fast PM or slow MA muscle fibers without innervation. These results indicate the requirement for MEF2 and NFAT in innervation‐induced slow MyHC2 gene expression and suggest that additional innervation‐dependent and fiber type‐specific control of slow MyHC2 gene expression resides in MA and PM muscle fibers, respectively. Developmental Dynamics 231:292–302, 2004. © 2004 Wiley‐Liss, Inc.