bluuebunny/crossref_metadata_2025 huggingface dataset:
Stellenwert chemisch‐synthetischer Antitussiva und Expektorantien. Waisenkinder der pharmakologischen Forschung?
Authors: Kardos Peter
Published: October 2008

Obwohl Husten einer der häufigsten Beschwerden ist, verfügen wir nicht über effektive und nebenwirkungsarme Medikamente zur Therapie. Falls eine kausale Therapie (z.B. Operation des Bronchialkarzinoms) nicht möglich ist, oder die eingeleitete kausale Therapie nur langsam wirkt (z.B. die Tuberkulosetherapie) benötigen wir symptomatisch wirkende Medikamente zur Linderung. Es haben sich zwei therapeutische Ansätze eingebürgert: die antitussive Therapie für den nicht produktiven Reizhusten und die protussive Therapie mit Expektorantien zur Linderung des produktiven Hustens. Chemisch definierte Antitussiva werden aus Alkaloiden des Schlafmohns abgeleitet und haben mehr oder weniger ausgeprägt die Nebenwirkungen der Morphinderivate, die Addiktionsgefahr sollte keinesfalls unterschätzt werden. Ein objektiver Wirksamkeitsnachweis für die besonders in Deutschland beliebten Expektorantien fehlt, subjektiv werden sie jedoch häufig als hilfreich empfunden.
Stellenwert pflanzlicher Antitussiva und Expektorantien. Symptomatische Phytotherapie bei Husten
Authors: Kraft Karin
Published: October 2008

Die Inzidenz von Erkrankungen des Respirationstraktes steigt in Deutschland stark an, dies betrifft insbesondere die chronischen Erkrankungen wie die chronisch obstruktive Lungenerkrankung und das Asthma bronchiale. Der Stellenwert von pflanzlichen Drogen und ihren Zubereitungen ist bei diesen Erkrankungen bisher kaum zu beurteilen, da das Spektrum an verfügbaren Expektorantien und Antitussiva zwar relativ breit ist, diese jedoch ganz überwiegend bei akuten unkomplizierten Erkrankungen des Respirationstraktes eingesetzt werden und zwar immer mehr im Bereich der Selbstmedikation. Ein kompetenter Umgang mit Phytopharmaka ist jedoch bei allen Atemwegserkrankungen essenziell; die infolge der fehlenden Erstattungsfähigkeit mittlerweile überwiegende Selbstmedikation sollte arztgestützt erfolgen.
Inhalationstherapie bei Hustenerkrankungen: Methoden und Techniken. Wirkungsvolle Hustentherapie mit geeigneten Inhalationsgeräten
Authors: Berzel Hans Günter , Berzel Simon Gunter
Published: October 2008

In der Pneumologie spielt die Inhalationstherapie von Atemwegserkrankungen mit geeigneten Inhalationsgeräten und atemwegsgängigen Medikamenten eine bedeutungsvolle Rolle. Ein ausschließlich für alle Altersgruppen zu empfehlendes Inhalationsgerät gibt es nicht, vielmehr muss je nach Alter ein geeignetes Inhalationsinstrument ausgewählt werden. Es sollte leicht zu handhaben, gut pflegbar und transportabel sein und keine zu großen Anforderungen an Koordination und Compliance stellen. Gründliche Unterrichtungen über die Zielsetzung der Therapie, Applikationsform und Behandlungsdauer sind eminent wichtig. Frustrationen und Misserfolge durch ineffiziente Inhalationstherapien sind durch regelmäßige Schulungen und Kontrolldemonstrationen zu korrigieren.

Bei konsequenter praktischer Umsetzung ist eine wirkungsvolle Inhalationstherapie in allen Altersgruppen gut möglich. Dies beinhaltet nicht zuletzt auch den Einsatz topisch inhalierbarer Kortikosteroide über Dosieraerosole mit ventilgesteuerten Spacern selbst im Säuglings‐ und Kleinkindesalter. Kinder sollten ermutigt werden, Dosieraerosole mit einem vorgeschalteten Spacersystem über den Mund zu inhalieren, höhere Medikamentendepositionen werden hierdurch erreicht. Eine Gesichtsmaske für Säuglinge und Kleinkinder erleichtert die Behandlung auch unter dem Aspekt, dass Wirkverluste einzukalkulieren sind. Mit dem Einsatz effizienter Spacer‐ und Trockenpulver‐Inhaliersysteme hat sich die Notwendigkeit der Ausstattung mit Feuchtverneblern vermindert.

Druckluftgesteuerte Inhaliersysteme, verbesserte Pulverapplikatoren, fein‐ und langsam vernebelnde Lösungsaerosole sind neu eingeführt worden. Dosimetrisch gesteuerte und atemzugverstärkte Vernebler erhöhen bei kontrollierter Atmung nachhaltig die Wirksamkeit und Lungendeposition, so dass Patienten mit schweren chronischen Lungenkrankheiten auch mit dosiskritischen Medikamenten wirkungsvoll behandelt werden können. Sehr intensiv wird an neuen Methoden zur Erzeugung ultrafeiner Aerosole wie auch an Aerosolen selbst geforscht. Dies wird die Lebensperspektive chronisch atemwegskranker Patienten durch innovative Inhalationsmethoden auch in Zukunft erheblich verbessern.
Cocain‐Bindungsstelle am Dopamintransporter geklärt
Authors: Wenzel E. , Stark H.
Published: October 2008

Der Bindungsmechanismus des Cocains am Wiederaufnahmeprotein wurde als allosterische Bindungsstelle diskutiert. Umfangreiche Mutations‐ und Modellingstudien belegen ein mit Dopamin überlappendes Bindungsverhalten.
GDNF erhält catecholaminerge Neurone
Authors: Bakthiari N. , Stark H.
Published: October 2008

Ein Fehlen des neurotrophen Faktors GDNF führt zum Untergang von dopaminergen und insbesondere noradrenergen Neuronen in spezifischen Bereichen des zentralen Nervensystems.
Safer Sex auch unter antiretroviraler Therapie?
Authors: Winckler Thomas
Published: October 2008

Ein Ziel der modernen hoch‐aktiven, antiretroviralen Therapie (HAART) von HIV‐Infizierten ist die Senkung der Viruslast unter die Nachweisbarkeitsgrenze. Wie groß unter diesen Bedingungen das Risiko der Übertragung des HI‐Virus auf den Sexualpartner ist, wird von Fachleuten kontrovers diskutiert.
Non‐Hodgkin‐Lymphom: Personalisierte Therapie aus Pflanzen
Authors: Reichwein Simone , Warzecha Heribert
Published: October 2008

Die Therapie verschiedener Krebsformen durch die spezifische Stimulation des körpereigenen Immunsystems hat in den letzten Jahren großes Interesse geweckt. Besonders bei der Therapie von Lymphomen hat sich hier ein vielversprechender Therapieansatz entwickelt.
Trends in adherence to secondary prevention medications in elderly post‐myocardial infarction patients
Authors: Choudhry Niteesh K. , Setoguchi Soko , Levin Raisa , Winkelmayer Wolfgang C. , Shrank William H.
Published: October 2008

Background

Poor levels of medication adherence for patients with coronary heart disease (CHD) have been documented but it is unclear whether adherence has improved over time.

Methods

We assembled a retrospective cohort of lower‐income Medicare beneficiaries who were discharged from the hospital after their first acute myocardial infarction (MI) between 1 January 1995 and 31 December 2003. For patients prescribed a statin, ACEI/ARB, beta‐blocker, and all 3 of these medications after the hospital discharge, we evaluated medication adherence by determining the proportion of days covered (PDC) for each medication in the subsequent year.

Results

Our cohort consisted of a total of 33 646 patients. Adherence rates for statins and beta‐blockers, but not ACEI/ARB, increased significantly over time but remained suboptimal. For example, among those patients that received a statin after discharge, 38.6% were fully adherent with therapy in 1995 in contrast to 56.2% in 2003 (p value for trend <0.001). Of patients prescribed all 3 of statin, beta‐blocker, and ACEI/ARB, 29.1% and 46.4% were fully adherent in 1995 and 2003, respectively (p value for trend <0.001).

Conclusions

Our analysis demonstrates statistically significant but modest improvements in medication adherence for statins and beta‐blockers, but not ACEI/ARBs, among patients discharged from hospital after acute MI. Despite these improvements, rates of non‐adherence to these highly effective therapies remain extremely high. Given the health and economic consequences of non‐adherence, the development of cost‐effective strategies to improve medication adherence should be a clear priority. Copyright © 2008 John Wiley & Sons, Ltd.
A distributed research network model for post‐marketing safety studies: the Meningococcal Vaccine Study
Authors: Velentgas Priscilla , Bohn Rhonda L. , Brown Jeffrey S. , Chan K. Arnold , Gladowski Patricia , Holick Crystal N. , Kramer Judith M. , Nakasato Cynthia , Spettell Claire M. , Walker Alexander M. , Zhang Fang , Platt Richard
Published: October 2008

Purpose

We describe a multi‐center post‐marketing safety study that uses distributed data methods to minimize the need for covered entities to share protected health information (PHI). Implementation has addressed several issues relevant to creation of a large scale post‐marketing drug safety surveillance system envisioned by the FDA's Sentinel Initiative.

Methods

This retrospective cohort study of Guillain‐Barré syndrome (GBS) following meningococcal conjugate vaccination incorporates the data and analytic expertise of five research organizations closely affiliated with US health insurers. The study uses administrative claims data, plus review of full text medical records to adjudicate the status of individuals with a diagnosis code for GBS (ICD9 357.0). A distributed network approach is used to create the analysis files and to perform most aspects of the analysis, allowing nearly all of the data to remain behind institutional firewalls. Pooled analysis files transferred to a central site will contain one record per person for approximately 0.2% of the study population, and contain PHI limited to the month and year of GBS onset for cases or the index date for matched controls.

Results

The first planned data extraction identified over 9 million eligible adolescents in the target age range of 11–21 years. They contributed an average of 14 months of eligible time on study over 27 months of calendar time. MCV4 vaccination coverage levels exceeded 20% among 17–18‐year olds and 16% among 11–13 and 14–16‐year‐old age groups by the second quarter of 2007.

Conclusion

This study demonstrates the feasibility of using a distributed data network approach to perform large scale post‐marketing safety analyses and is scalable to include additional organizations and data sources. We believe these results can inform the development of a large national surveillance system. Copyright © 2008 John Wiley & Sons, Ltd.
Alkylating potential of N‐phenyl‐N‐nitrosourea
Authors: Manso J. A. , Pérez‐Prior M. T. , Gómez‐Bombarelli R. , González‐Pérez M. , Céspedes I. F. , García‐Santos M. P. , Calle E. , Casado J.
Published: October 2008

Alkylating agents are considered to be archetypical carcinogens. Since the decomposition of alkylnitrosoureas gives rise to alkyldiazonium ions without any need for metabolic activation, they offer an ideal series of compounds with which to examine the effect of variations in chemical structure on alkylating potential. Due to its instability N‐phenyl‐N‐nitrosourea is easily hydrolyzed to a benzenediazonium ion. Since N‐phenyl‐N‐nitrosourea shows a particular behavior when compared with other nitrosoureas, here its alkylating potential was studied. The nucleophile 4‐(p‐nitrobenzyl)pyridine (NBP), a trap for alkylating agents, was used as an alkylation substrate. Conclusions were drawn as follows: (i) the mechanism of the alkylation reaction of NBP by phenylnitrosourea is different from that caused by other nitrosoureas; (ii) the formation of the NBP–N‐phenyl‐N‐nitrosourea adduct occurs about 20,000‐fold slower than with N‐methyl‐N‐nitrosourea, one of the most effective carcinogenic nitrosoureas; and, (iii) a correlation was found between the alkylating potential of nitrosoureas and their tumorigenicity. Copyright © 2008 John Wiley & Sons, Ltd.
PMMA‐grafted dextran glycopolymers by atom transfer radical polymerization
Authors: Dupayage Ludovic , Save Maud , Dellacherie Edith , Nouvel Cecile , Six Jean‐Luc
Published: October 2008

The four‐step synthesis of amphiphilic glycopolymers associating dextran as backbone and poly(methyl methacrylate) (PMMA) as grafts is reported, using the “grafting from” strategy. In the first step, the dextran OH functions were partially acetylated. The second step consisted in linking initiator groups by reaction of 2‐bromoisobutyryl bromide (BiBB) with the unprotected OH functions. Third, the atom transfer radical polymerization (ATRP) of methyl methacrylate was carried out in DMSO from the resulting dextran derivative used as a macroinitiator. Finally, the cleavage of the acetate groups led to the expected glycopolymers. Careful attention was given both to the copolymer structure and the control of polymerization. PMMA grafts were analyzed by SEC‐MALLS after their deliberate cleavage from the backbone to evidence a controlled polymerization. Moreover, the mildness of the final deprotection conditions was proved to ensure acetate cleavage without either degrading dextran backbone and PMMA grafts or cleaving grafts from dextran backbone. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7606–7620, 2008
Synthesis of arborescent (Dendritic) polystyrenes via controlled inimer‐type reversible addition‐fragmentation chain transfer polymerization
Authors: Heidenreich Andrew J. , Puskas Judit E.
Published: October 2008

The reversible addition‐fragmentation chain transfer (RAFT) copolymerization of styrene and 4‐vinylbenzyl dithiobenzoate, a RAFT‐based inimer (initiator‐monomer), is described. Controlled polymerization was achieved in bulk conditions using thermal initiation at 110 °C to give arborescent polystyrene (arbPSt). The number‐average molecular weights of the polymers increased linearly with conversion and were much higher than theoretically calculated for a linear polymerization, reaching Mn = 364,000 g/mol with Mw/Mn = 2.65. Branching analysis by NMR showed an average of 3.5 branches per chain. SEC data, which were similar to those measured in arborescent polyisobutylene, supported the architectural analysis. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7621–7627, 2008
One‐pot synthesis of linear‐hyperbranched diblock copolymers via self‐condensing vinyl polymerization and ring opening polymerization
Authors: Zou Peng , Yang Li‐Ping , Pan Cai‐Yuan
Published: October 2008

The linear poly(ε–caprolacton)‐b‐hyperbrached poly(2‐((α‐bromobutyryl)oxy)ethyl acrylate) (LPCL‐b‐HPBBEA) has been successfully synthesized by simultaneous ring‐opening polymerization (ROP) of CL and self‐condensing vinyl polymerization (SCVP) of BBEA in one‐pot. The HPBBEA homopolymers were found to be formed in the polymerization because of the competitive reactions induced by initiation with bifunctional initiator, 2‐hydroxylethyl‐2′‐bromoisobutyrate (HEBiB), and inimer BBEA. The separation of LPCL‐b‐HPBBEA from the polymerization products was achieved by precipitation in methanol. With feed ratio increase of CL and BBEA to HEBiB, the molecular weights of PCL and HPBBEA blocks in the block copolymer enhanced; and the polymerization rate of CL started to decrease gradually after 12 h of polymerization, but the polymerization rate of BBEA was maintained until 24 h of polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7628–7636, 2008
Synthesis of poly(methyl acrylate) loops grafted onto silica nanoparticles via reversible addition‐fragmentation chain transfer polymerization
Authors: Rotzoll Robert , Vana Philipp
Published: October 2008

Reversible addition‐fragmentation chain transfer (RAFT) polymerization was used to produce poly(methyl acrylate) (pMA) loops grafted onto silica nanoparticles using doubly anchored bifunctional RAFT agents 1,4‐bis(3′‐trimethoxysilylpropyltrithiocarbonylmethyl)benzene (Z‐group approach) and 1,6‐bis(o,p‐2′‐trimethoxysilylethylbenzyltrithiocarbonyl)hexane (R‐group approach) as mediators. In both cases, molecular weights of the resulting surface‐confined polymer loops increased with monomer conversion, whereas the grafting density was significantly higher in the case of the R‐group supported RAFT polymerization due to mechanistic differences of the RAFT process at the surface. This result was evident from thermogravimetric analysis and supported by scanning electron microscopy. Polymer loops with molecular weights up to 53,000 g mol−1 were accessible with polydispersities of about 2.0 without and 1.5 with the addition of free RAFT agent. UV signals of the detached pMA loops measured via size exclusion chromatography were shifted to higher molecular weights compared with the corresponding RI signals, indicating branching reactions caused by the close proximity of growing radicals and polymer at the surface of the silica nanoparticles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7656–7666, 2008
Synthesis, characterization, and self‐assembly of ion‐bonded A2B rod‐coil copolymer with oligo(para‐phenyleneethynylene) as rod segment
Authors: Lu Dairen , Tao Kang , Wang Yun , Bai Ruke
Published: October 2008

Supramolecular A2B rod‐coil copolymer, composed of two polystyrene (PSt) arms and one oligo(para‐phenyleneethynylene) (OPE) arm linked via ionic bond, has been designed and successfully synthesized. First, a trifunctional initiator, methyl 1,3‐bis(bromomethyl)benzonate, was prepared and used to initiate the polymerization of styrene under atom transfer radical polymerization (ATRP) condition to provide polystyrene (PSt) carrying monoester group at the middle of polymer chain. Then, the ester group was transferred into tertiary amino group to give amino‐functionalized PSt, (PSt)2N(CH3)2. Subsequently, the ion‐bonded rod‐coil copolymer, (PSt)2OPE, was obtained by the reaction of (PSt)2N(CH3)2 with carboxy‐terminated OPE (OPECOOH). The resulting copolymer was characterized by nuclear magnetic resonance (NMR), Fourier transformer infrared (FTIR), and gel permeation chromatography (GPC) techniques. Vesicles and spherical micelles were generated from this supramolecular rod‐coil copolymer through the manipulation of the initial polymer concentration in toluene. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7667–7676, 2008
Mechanism and characterization of alkylene‐ and p‐ethylenebenzylene‐spaced polycarbosilanes ceramic precursor synthesized by electropolymerization
Authors: Cabasso Israel , Yuan Youxin , Wang Xinwei
Published: October 2008

An electropolymerization of haloalkylhalosilanes (ClRSiCH3Cl2) that possess two types of electroactive sites, that is, the CCl and SiCl bond is described. The one‐pot synthesis method is shown to yield branched polycarbosilanes having a regular carbon block‐spaced silicon backbone structure. A series of branched polycarbosilanes, [RSiCH3]n with R being CH2, C2H4, C3H6, and CH2C6H4C2H4, have been successfully electropolymerized with Mn up to 42,600 Dalton. Experimental and simulation cyclic voltammetry of these monomers and the computational examination of their LUMOs are applied to study the electropolymerization mechanism. The results suggest that polymerization proceeds by iterating steps involving (1) electroreduction of a CCl bond to a carbanion, which is catalyzed by silylanion radical [Cl
SiCl(CH3)RCl]
and/or Ni(0)/TDA‐1; and (2) nucleophilic attack of carbanions to SiCl bonds of a second monomer or oligomer to extend the polymer chain. The investigation reveals that the R spacer has a considerable impact on the polymerizability of the corresponding monomer. Such interfacial polymerization resembles a template polymerization, leading to unique microstructures that were preserved even after converted to silicon carbide ceramics at high temperatures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7677–7689, 2008
Synthesis of chiral amphiphilic diblock copolymers via consecutive RAFT polymerizations and their aggregation behavior in aqueous solution
Authors: Wang Jian , Xu Wenliang , Cheng Zhenping , Zhu Xiulin , Zhang Zhengbiao , Zhu Jian , Zhang Wei
Published: October 2008

Two chiral amphiphilic diblock copolymers with different relative lengths of the hydrophobic and hydrophilic blocks, poly(6‐O‐p‐vinylbenzyl‐1,2:3,4‐Di‐O‐isopropylidene‐D‐galactopyranose)‐b‐poly(N‐isopropylacrylamide) or poly(VBCPG)‐b‐poly(NIPAAM) and poly(20‐(hydroxymethyl)‐pregna‐1,4‐dien‐3‐one methacrylate)‐b‐poly(N‐isopropylacrylamide) or poly(MAC‐HPD)‐b‐poly(NIPAAM) were synthesized via consecutive reversible addition‐fragmentation chain‐transfer polymerizations of VBCPG or MAC‐HPD and NIPAAM. The chemical structures of these diblock copolymers were characterized by 1H nuclear magnetic resonance spectroscopy. These amphiphilic diblock copolymers could self‐assemble into micelles in aqueous solution, and the morphologies of micelles were investigated by transmission electron microscopy. By comparison with the lower critical solution temperatures (LCST) of poly(NIPAAM) homopolymer in deionized water (32 °C), a higher LCST of the chiral amphiphilic diblock copolymer (poly(VBCPG)‐b‐poly(NIPAAM)) was observed and the LCST increased with the relative length of the poly(VBCPG) block in the copolymer from 35 to 47 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7690–7701, 2008
Synthesis of terpyridine ligands and their complexation with Zn2+ and Ru2+ for optoelectronic applications
Authors: Vellis Panagiotis D. , Mikroyannidis John A. , Lo Chih‐Nan , Hsu Chain‐Shu
Published: October 2008

A series of soluble conjugated ligands TT, FT, PT, and NT that contained terpyridyl terminal units were synthesized by Heck coupling. These ligands absorbed at 341–434 nm and emitted blue–green light, with maximum at 440–522 nm and photoluminescence quantum yields of 0.15–0.71 in solution. The double‐layer electroluminescent devices with the configuration of ITO/PEDOT/ligand FT, PT, or NT/Ca/Al exhibited a brightness of 43–63 cd/m2. These ligands were further reacted with zinc(II) and ruthenium(II) ions and subsequent anion exchange to afford linear and supramolecular complexes. The photophysics of these complexes were investigated. A significant redshift of the emission maximum of the Zn complexes relative to the corresponding ligands was observed. The Ru complexes were used to fabricate photovoltaic devices with the structure ITO/PEDOT/Ru complex/P3HT:PCBM (1:1 wt/wt)/Ca/Al. The power conversion efficiency of these polymer–fullerene bulk heterojunction photovoltaic devices was up to 0.71%. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7702–7712, 2008
Polymer brushes containing sulfonated sugar repeat units: Synthesis, characterization, and in vitro testing of blood coagulation activation
Authors: Ayres N. , Holt D. J. , Jones C. F. , Corum L. E. , Grainger D. W.
Published: October 2008

A new polymer brush chemistry containing sulfonated carbohydrate repeat units has been synthesized from silicon substrates using ATRP methods and characterized both in bulk and using surface analysis. The polymer brush was designed to act as a mimic for the naturally occurring sulfonated glycosaminoglycan, heparin, commonly used for modifying blood‐contacting surfaces both in vitro and in vivo. Surface analysis showed conversion of brush saccharide precursor chemistry to the desired sulfonated polymer product. The sulfonated polymer brush surface was further analyzed using three conventional in vitro tests for blood compatibility—plasma recalcification times, complement activation, and thrombin generation. The sulfonated polymer brush films on silicon oxide wafers exhibited better assay performance in these blood component assays than the unsulfonated sugar functionalized polymer brush in all tests performed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7713–7724, 2008
Synthesis, photophysics, theoretical modeling, and electroluminescence of novel 2,7‐carbazole‐based conjugated polymers with sterically hindered structures
Authors: Tang Weihua , Lin Tingting , Ke Lin , Chen Zhi‐kuan
Published: October 2008

2,7‐dibromo‐N‐hexylcarbazole is successfully synthesized in three steps with an overall 37% yield. Novel 2,7‐carbazole‐based sterically hindered conjugated polymers are further synthesized. In the backbone structure of polymer P1, alkylated bithiophene moiety is β‐substituted with dodecyl chains on both thiophene rings, adopting the tail‐to‐tail configuration. While for polymers P2 and P3, partially planarized thieno[3,2‐b]thiophene moiety (P2) and β‐pentyl substituted thieno[3,2‐b]thiophene (P3) are incorporated. All polymers demonstrate efficient blue‐to‐green light emission, good thermal stability (Td ≥ 379 °C), and high glass transition temperatures (Tg = 118 °C). The optical and electronic properties of the resulted polymers are tuned by the incorporated alkyl chains. For instance, the incorporation of β‐pentyl group in thieno[3,2‐b]thiophene moiety endows P3 with blue‐shifted photophysical spectra, reduced fluorescence quantum yield and larger band gap in comparison with P2. The steric effect of incorporated alkyl chains is further illustrated by geometry optimization of three model oligomers (analogues to the repetition units of P1–P3) using density functional theory. Sterically hindered polymers P1 and P2 exhibit high charge transport ability and moderate electroluminescent properties in primarily tested single‐layer light‐emitting diodes (configuration: ITO/PEDOT:PSS/Polymer/Ca/Ag). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7725–7738, 2008
The synthesis and self‐assembly of ABA amphiphilic block copolymers containing styrene and oligo(ethylene glycol) methyl ether methacrylate in dilute aqueous solutions: Elevated cloud point temperatures for thermoresponsive micelles
Authors: Holder Simon J. , Durand Geraldine G. , Yeoh Chert‐Tsun , Illi Elodie , Hardy Nicholas J. , Richardson Tim H.
Published: October 2008

A series of ABA amphiphilic triblock copolymers possessing polystyrene (PS) central hydrophobic blocks, one group with “short” PS blocks (DP = 54–86) and one with “long” PS blocks (DP = 183–204) were synthesized by atom transfer radical polymerization. The outer hydrophilic blocks were various lengths of poly(oligoethylene glycol methyl ether) methacrylate, a comb‐like polymer. The critical aggregation concentrations were recorded for certain block copolymer samples and were found to be in the range circa 10−9mol L−1for short PS blocks and circa 10−12mol L−1for long PS blocks. Dilute aqueous solutions were analyzed by transmission electron microscopy (TEM) and demonstrated that the short PS block copolymers formed spherical micelles and the long PS block copolymers formed predominantly spherical micelles with smaller proportions of cylindrical and Y‐branched cylindrical micelles. Dynamic light scattering analysis results agreed with the TEM observations demonstrating variations in micelle size with PS and POEGMA chain length: the hydrodynamic diameters (DH) of the shorter PS block copolymer micelles increased with increasing POEGMA block lengths while maintaining similar PS micellar core diameters (DC); in contrast the values ofDHandDCfor the longer PS block copolymer micelles decreased. Surface‐pressure isotherms were recorded for two of the samples and these indicated close packing of a short PS block copolymer at the air–water interface. The aggregate solutions were demonstrated to be stable over a 38‐day period with no change in aggregate size or noticeable precipitation. The cloud point temperatures of certain block copolymer aggregate solutions were measured and found to be in the range 76–93 °C; significantly these were ∼11 °C higher in temperature than those of POEGMA homopolymer samples with similar chain lengths. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7739–7756, 2008
Synthesis of inverse star block copolymer by combination of ATRP, ring opening polymerization, and “click chemistry”
Authors: Yang Li‐Ping , Dong Xue‐Hui , Pan Cai‐Yuan
Published: October 2008

The inverse star block copolymer, (poly(ε‐caprolactone)‐b‐polystyrene)2‐core‐(poly(ε‐caprolactone)‐b‐polystyrene)2, [(PCL‐PS)2‐core‐(PCL‐PS)2] has been successfully prepared by combination of atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), and “Click Chemistry.” The synthesis includes the following five steps: (1) synthesis of a heterofunctional initiator with two ATRP initiating groups and two hydroxyl groups; (2) formation of (Br‐PS)2‐core‐(OH)2 via ATRP of styrene; (3) preparation of the (PCL‐PS)2‐core‐(OH)2 through “click” reaction of the α‐propargyl, ω‐acetyl terminated PCL with (N3‐PS)2‐core‐(OH)2 which was prepared by transformation of the terminal bromine groups in (Br‐PS)2‐core‐(OH)2 into azide groups; (4) the ROP of CL using (PCL‐PS)2‐core‐(OH)2 as macroinitiator to form (PCL‐PS)2‐core‐(PCL‐OH)2; and (5) preparation of the (PCL‐PS)2‐core‐(PCL‐PS)2 through the ATRP of styrene using (PCL‐PS)2‐core‐(PCL‐Br)2 as macroinitiator which was prepared by reaction of the terminal hydroxyl groups at the end of the PCL chains with 2‐bromoisobutyryl bromide. The characterization data support structures of the inverse star block copolymer and the intermediates. The differential scanning calorimeter results and polarized optical microscope observation showed that the intricate structure of the inverse star block copolymer greatly restricted the movement of the PS segments and PCL segments, resulted in the increase of the glass transition temperature of PS segments and the decrease of crystallization ability of PCL segments. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7757–7772, 2008
Production of Exploding Materials for Detonators: Control of Crystal Growth of Lead and Barium 2,4,6‐trinitroresorcinate
Authors: Orbovic Nikola , Codoceo Cristian Lorca
Published: October 2008

The production of lead and barium 2,4,6‐trinitroresorcinate in a suitable form for loading by gravity in detonator production has been investigated. During the work, we discovered that the synthesis of the mentioned salts in the presence of some crystal habit additives gives such characteristics of the products. A goal of our work was to investigate the role of some crystal growth additives in the nucleation, growth, size, and shape of lead 2,4,6‐trinitroresorcinate and barium 2,4,6‐trinitroresorcinate crystals. Among several crystal growth additives mentioned in the bibliography, we chose carboxymethylcellulose (sodium salt, viscosity 3–4 Pa⋅s), polyvinyl alcohol, as well as two new ones, cationic acrylamide copolymer salt, polyelectrolyte AS‐3605 and acrylic acid–acrylamide copolymer salt, Haicat (PraestrolR 835BS). As a synthesis pattern, we chose an aqueous procedure of synthesis, using solutions of lead(II) or barium salts and magnesium 2,4,6‐trinitroresorcinate. The crystal growth additives were added to one of the solutions, depending on their nature. During the research, most of the attention was focused on crystal size and shape, on safety handling and manipulation, as well as on the yield and process performing facility. The final products were qualified by chemical (Pb and NO2 group contents) and physical (crystal shape and size, bulk density, flowability, and impact and friction sensitivity) analyses.
Estimating Heats of Detonation and Detonation Velocities of Aromatic Energetic Compounds
Authors: Keshavarz Mohammad Hossein
Published: October 2008

A new method is introduced to predict reliable estimation of heats of detonation of aromatic energetic compounds. At first step, this procedure assumes that the heat of detonation of an explosive compound of composition CaHbNcOd can be approximated as the difference between the heat of formation of all H2OCO2 arbitrary (H2O, CO2, N2) detonation products and that of the explosive, divided by the formula weight of the explosive. Overestimated results based on (H2OCO2 arbitrary) can be corrected in the next step. Predicted heats of detonation of pure energetic compounds with the product H2O in the liquid state for 31 aromatic energetic compounds have a root mean square (rms) deviation of 2.08 and 0.34 kJ g−1 from experiment for (H2OCO2 arbitrary) and new method, respectively. The new method also gives good results as compared to the second sets of decomposition products, which consider H2, N2, H2O, CO, and CO2 as major gaseous products. It is shown here how the predicted heats of detonation by the new method can be used to obtain reliable estimation of detonation velocity over a wide range of loading densities.
Time‐resolved photoluminescence study of mesoporous ZnO nanostructures
Authors: Schwalm Michael , Horst Swantje , Chernikov Alexej , Rühle Wolfgang W. , Lautenschläger Stephan , Klar Peter J. , Meyer Bruno K. , Waitz Thomas , Tiemann Michael , Chatterjee Sangam
Published: October 2008

We report a systematic study of the photoluminescence properties of ZnO nanostructures. In particular, mesoporous ZnO powders of varying surface‐to‐mass ratio are investigated and compared to a bulk reference. At low temperatures the emission from higher‐energy states is very pronounced and even dominant for samples with high surface‐to‐mass ratio. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emission properties of ZnSe‐based pillar microcavities at elevated temperatures
Authors: Kalden Joachim , Lohmeyer Henning , Sebald Kathrin , Meeser Thomas , Gutowski Jürgen , Kruse Carsten , Gust Arne , Hommel Detlef , Wiersig Jan , Jahnke Frank
Published: October 2008

We present research achievements that advance the development of quantum dot based low threshold vertical cavity surface emitting lasers operating at elevated temperatures. We report on the optical properties of monolithic ZnSe‐based pillar microcavities. Measurements were performed on different microcavity structures containing either ZnCdSSe quantum wells or CdSe quantum dots, respectively, as their active region. For the quantum dot based structures, the implementation of additional MgS/ZnSSe barriers yield temperature stability of the quantum dot emission up to room temperature. Microphotoluminescence experiments show an enhanced collection efficiency for the quantum dot emission in spectral resonance with an optical microcavity mode.

High quality factors of up to Q = 7860 were achieved for quantum dot structures, while for quantum well devices Q = 3500 was reached as being analyzed by microphotoluminescence and micro‐reflectivity spectroscopy. For the quantum well structures, single mode stimulated emission at 510 nm is shown at 280 K under pulsed optical excitation. Threshold reduction with decreasing pillar diameter is observed in accordance to numerical calculations based on microscopic laser theory. The results are promising for the realization of efficient quantum dot based low threshold vertical cavity surface emitting laser devices operating at elevated temperatures in the near future. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mott transition of excitons in ZnSe studied by phase resolved reflection
Authors: Manzke Günter , Henneberger Klaus , Seemann Matthias , Stolz Heinrich
Published: October 2008

The Mott transition of excitons in a semiconductor with increasing carrier density is in principle well understood as a consequence of screening of the Coulomb interaction between carriers. While the position of the exciton stays widely unchanged the exciton peak disappears due to band gap shrinkage. However, a more quantitative check of applied theoretical models for the screening and of the role of quantum kinetic effects in this process is still open.We demonstrate that the phase‐resolved reflection in shallow‐confined ZnSSe heterostructures opens the possibility of a detailed study of the Mott transition due to the appearance of pronounced interferences effects of propagating polariton modes.

Our theoretical approach for the investigation of the influence of excited carriers on the dielectric susceptibility is based (i) on a quasi‐particle approximation for the carrier energies and damping, and (ii) on the semiconductor Bloch equations including dynamical screening and a quantum kinetic treatment of scattering. These manybody effects lead to drastic changes of both amplitude and phase of the reflected light: Jumps of the phase are steepened, show abrupt changes from +π to –π and are smoothed out, and interference peaks in the amplitude decrease and disappear completely with increasing excitation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ga(AsSb)/GaAs/(AlGa)As heterostructures: additional hole‐confinement due to quantum islands
Authors: Horst S. , Chatterjee S. , Hantke K. , Klar P. J. , Nemeth I. , Stolz W. , Volz K. , Bückers C. , Thränhardt A. , Koch S. W. , Rühle W. , Johnson S. R. , Wang J.‐B. , Zhang Y.‐H.
Published: October 2008

Formation of self‐organized Ga(AsSb) quantum‐islands during growth is shown to occur in a series of Ga(AsSb)/GaAs/(AlGa)As heterostructures, resulting in an in‐plane hole confinement of several hundred meV. The shape of the in‐plane confinement potential is nearly parabolic and thus yields almost equidistant hole energy levels. Transmission electronmicroscopy reveals that the quantum islands (QIs) are 100 nm in diameter and exhibit an inplane variation of the Sb concentration of more than 30%, which is the origin of the confinement. Up to seven bound hole states are observed in the photoluminescence spectra. Time‐resolved photoluminescence data are shown as function of excitation density. The influence of size and density of such structures as well as the mechanisms of growth are discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Performance changes of a vertical‐external‐cavity surfaceemitting laser by an intra‐cavity anti‐reflex‐coating
Authors: Horst S. , Chatterjee S. , Rühle W. , Brick P. , Diehl W. , Stolz W. , Kühn E. , Thränhardt A. , Koch S. W.
Published: October 2008

The influence of an intra‐cavity anti‐reflection coating on the switch‐on dynamics and the power input‐output characteristic of a vertical‐external‐cavity surface‐emitting laser (VECSEL) system are investigated. The experiments show a significantly higher threshold and slower switch‐on dynamics for anti‐reflection coated systems.

These differences originate in the changes in the mode strength at the active medium due to the more or less pronounced sub‐cavity. The presented simulations based on microscopic calculations are in good qualitatively agreement with the experiments. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interband vs. intersubband polaritons and the relevance of quantum confinement
Authors: Pereira Mauro F.
Published: October 2008

This paper presents a numerical study of the dependence of the coupling between light and intersubband transitions in quantum wells with respect to electronic quantum confinement. Different quantum wells are analysed and it is shown that intersubband polaritons and antipolaritons can be made more stable that interband polaritons by adjusting the intersubband population differences. This flexibility in control is no possible in the interband excitonic case and may be crucial for THz polaritonic‐based devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum condensation in electron–hole plasmas
Authors: Semkat D. , Kremp D. , Henneberger K.
Published: October 2008

Quantum condensation phenomena occur in Bose systems (Bose–Einstein condensation, BEC) as well as in strongly degenerate Fermi systems (BCS state). In Fermi systems with Bose‐like bound states both phenomena are possible.

A theoretical approach to describe quantum condensation in electron‐hole plasmas in the framework of realtime Green's functions is presented. The resulting phase boundary shows that there is a smooth crossover from BEC to BCS. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetooptical properties of quantum disks in the Faraday configuration
Authors: Schillak P. , Czajkowski G.
Published: October 2008

We show how to compute the optical functions (the complex magneto‐susceptibility, dielectric function, magneto‐reflection spectra) for semiconductor quantum disks exposed to a uniform magnetic field in the growth direction, including the excitonic effects. The optical response is calculated for an electromagnetic wave propagating in the growth direction, i.e. the wavevector is parallel to the static magnetic field, which corresponds to the so‐called Faraday configuration. The method uses the microscopic calculation of nanostructure excitonic wave functions and energy levels, and the macroscopic real density matrix approach to compute the electromagnetic fields and susceptibilities.

The electron‐hole screened Coulomb potential is adapted. The novelty of our approach is that the solution is obtained in terms of known one‐particle electron and hole eigenfunctions, since, in the considered nanostructure due to confinement effects accompanied by the e‐h Coulomb interaction, the separation of the relativeand center‐of‐mass motion is not possible. We obtain both the eigenvalues and the eigenfunctions. The convergence of the proposed method is examined. Numerical calculations have been performed for In0.55Al0.45As (disk)/ Al0.35Ga0.65As (barrier) disks. Good agreement with experiments has been obtained. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Motional enhancement of the exciton magnetic moment
Authors: Kochereshko V. P. , Platonov A. V. , Davies J. J. , Wolverson D. , Smith L. C. , Cox R. T. , Cibert J. , Mariette H.
Published: October 2008

In this paper we demonstrate that the magnetic moment of the exciton increases by an order of magnitude due to its motion along the magnetic field. The effect was observed for a set of quantum well structures with different well widths and based on various semiconductor compounds. The reason for this effect is mixing of the exciton's center of mass motion and the internal motion of electron and hole in the exciton. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Trion states in a dense 2DEG
Authors: Kochereshko V. P. , Klochikhin A. A. , Crooker S. A. , Karczewski G. , Kossut J.
Published: October 2008

Photoluminescence spectra taken from modulationdoped CdTe/(Cd0.7Mg0.3)Te quantum well structures with a two‐dimensional electron gas of moderate to high density (from ne ∼ 1010 up to ne ∼ 1012 cm–2) in magnetic fields from 0 T to 45 T were studied. The observed spectra were analyzed in terms of combined excitonelectron processes. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Semiconductor laser based THz generation and detection
Authors: Brenner Carsten , Hoffmann Stefan , Friedrich Claus‐Stefan , Schlauch Tobias , Klehr Andreas , Erbert Götz , Tränkle Günther , Jördens Christian , Salhi Mohammed , Koch Martin , Hofmann Martin R.
Published: October 2008

We present different concepts for compact and cost effective THz technology based on semiconductor diode lasers. First, we discuss THz sources starting with modelocked diode lasers for time domain THz sampling, and two‐colour diode lasers for continuous wave THz generation. Then we show how THz radiation can be generated directly out of two‐colour diode lasers and discuss possible schemes for an optimisation of this effect towards application relevant power levels. Finally, we demonstrate that diode lasers can also serve as detectors for THz radiation. We couple the emission of a THz gas laser into the active region of a diode laser and demonstrate that this leads to a variation of the voltage over the p‐n‐junction which is almost proportional to the THz power coupled into the device. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrafast dynamics and interlayer thermal coupling of hot carriers in epitaxial graphene
Authors: Sun Dong , Wu Zong‐Kwei , Divin Charles , Li Xuebin , Berger Claire , Heer Walt A. de , First Phillip N. , Norris Theodore B.
Published: October 2008

We report the first application of nondegenerate ultrafast pump‐probe spectroscopy to investigate the dynamics of hot Dirac Fermions in epitaxial graphene. The DT spectra can be understood in terms of the effect of hot thermal carrier distributions on interband transitions with no electron‐hole interaction. We also investigate the thermal coupling between carriers of doped and undoped layers. The coupling time is found to be below 500fs. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gain characteristics and lasing of Ga(NAsP) multi‐quantum well structures
Authors: Lange C. , Chatterjee S. , Kunert B. , Volz K. , Stolz W. , Rühle W. W. , Gerhardt N. C. , Hofmann M. R.
Published: October 2008

Lasing is demonstrated for a Ga(NAsP) multi quantumwell structure grown pseudomorphically on GaP using metal‐organic vapour‐phase epitaxy. For a series of temperatures ranging from 8 K to 290 K, the sample emission characteristics are determined. With increasing pump power, a spectral narrowing of the emitted light along with a blue‐shift is observed as the lasing threshold is approached.

Above the threshold, the emission splits up spectrally into a pattern of clearly distinguishable modes. In addition, the potential of this material concerning roomtemperature lasing is investigated by means of a variable stripe‐length experiment, where a modal gain of 10 cm–1 is observed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variance decomposition approach to the prediction of the seasonal mean circulation: Comparison with dynamical ensemble prediction using NCEP's CFS
Authors: Zheng X. , Straus D. M. , Frederiksen C. S.
Published: October 2008

Reanalysis data and a recently developed variance decomposition approach are applied to empirically predict seasonal mean 500 hPa geopotential height anomalies in both the Northern and Southern Hemisphere from the beginning of each season. The predictors are only several popular tropical SST indices and the annular mode indices at one month or one season lead. The statistical prediction is compared with the dynamical ensemble prediction of the National Centers for Environmental Prediction's coupled Climate Forecast System (CFS). It is found that their skills are quite comparable. The advantages and disadvantages of dynamical prediction and statistical prediction are discussed. A strategy for a new statistical–dynamical prediction which combines the advantages of both statistical and dynamical predictions is suggested. Copyright © 2008 Royal Meteorological Society
Ionisation in the absence of high voltage using supercritical fluid chromatography: a possible route to increased signal
Authors: Thite Mohini A. , Boughtflower Robert , Caldwell Jeff , Hitzel Laure , Holyoak Clare , Lane Stephen J. , Oakley Paul , Pullen Frank S. , Richardson Stefan , Langley G. John
Published: October 2008

Supercritical fluid chromatography (SFC) is fast becoming a technique of choice for the analysis of a wide range of compounds and has been found to be complementary to high‐performance liquid chromatography (HPLC). The combination of SFC and mass spectrometry (MS) affords a very useful tool in the separation and analysis of compounds. In this study the ionisation of samples in the absence of an applied electrospray voltage has been observed when using SFC/MS, with some compounds showing increased sensitivity when all ionisation source high voltage (HV) is removed. In an attempt to understand the mechanism of ionisation, a series of test compounds were analysed using standard electrospray ionisation (ESI) and atmospheric pressure chemical ionisation (APCI) source configurations and also different API source designs. In both cases, data were acquired with the applied high voltage on (normal conditions) or with the high voltage off, i.e. no voltage spray (novo‐spray). The standards were analysed with a range of pressure and modifier percentage conditions. To understand the nature of the ionisation process observed, this was compared with three established liquid‐to‐gas ionisation mechanisms. These were thermospray (TSP), charge residue model (CRM) of ESI and sonic spray ionisation (SSI). Experiments were undertaken in an attempt to explain this ionisation phenomenon and quantify any observed change in sensitivity. The most important point to note is that enhanced ionisation was observed under novo‐spray conditions in a SFC/MS configuration, which in certain cases provides a lowering in the overall limit of detection (LOD). Copyright © 2008 John Wiley & Sons, Ltd.