bluuebunny/crossref_metadata_2025 huggingface dataset:
Transition metal dihydrogen complexes: isotope effects on reactivity and structure
Authors: Heinekey D. Michael
Published: June 2007

Complexation of dihydrogen to transition metal centers was discovered by Kubas and coworkers in 1984. The notion that the simplest molecule in chemistry can act as a ligand to form relatively stable transition metal complexes has led to a paradigm shift in coordination chemistry. Crucial to the exploration of this intriguing new chemistry has been the use of isotope substitution. Several aspects of the coordination chemistry of dihydrogen have revealed fascinating isotope effects on reactivity, spectroscopy and in some cases structure. Complexation of HD has been used to diagnose bond distances from measurements of JHD and isotope effects for D2 versus H2 binding have been evaluated. Examples of quantum mechanical exchange coupling in H2 complexes have been described. These effects disappear when one of the H atoms is replaced by D. In molecules with bound hydrogen adjacent to a hydride ligand, non‐statistical occupancy of hydrogen versus hydride sites by deuterons has been observed. In some cases, isotope‐dependent structures have been established by the study of HD, HT and DT complexes using NMR spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd.
Ski areas, weather and climate: time series models for New England case studies
Authors: Hamilton Lawrence C. , Brown Cliff , Keim Barry D.
Published: June 2007

Wintertime warming trends experienced in recent decades, and predicted to increase in the future, present serious challenges for ski areas and whole regions that depend on winter tourism. Most research on this topic examines past or future climate‐change impacts at yearly to decadal resolution, to obtain a perspective on climate‐change impacts. We focus instead on local‐scale impacts of climate variability, using detailed daily data from two individual ski areas. Our analysis fits ARMAX (autoregressive moving average with exogenous variables) time series models that predict day‐to‐day variations in skier attendance from a combination of mountain and urban weather, snow cover and cyclical factors. They explain half to two‐thirds of the variation in these highly erratic series, with no residual autocorrelation. Substantively, model results confirm the “backyard hypothesis” that urban snow conditions significantly affect skier activity; quantify these effects alongside those of mountain snow and weather; show that previous‐day conditions provide a practical time window; find no monthly effects net of weather; and underline the importance of a handful of high‐attendance days in making or breaking the season. Viewed in the larger context of climate change, our findings suggest caution regarding the efficacy of artificial snowmaking as an adaptive strategy, and of smoothed yearly summaries to characterize the timing‐sensitive impacts of weather (and hence, high‐variance climate change) on skier activity. These results elaborate conclusions from our previous annual‐level analysis. More broadly, they illustrate the potential for using ARMAX models to conduct integrated, dynamic analysis across environmental and social domains. Copyright © 2007 Royal Meteorological Society
Seasonal forecasting of East Asian summer monsoon based on oceanic heat sources
Authors: Lee Eungul , Chase Thomas N. , Rajagopalan Balaji
Published: June 2007

We use the upper‐level divergence zone at 150 hPa to define the areas of study for the East Asian summer monsoon (EASM) and to show the advances and retreats of the EASM. We find that the EASM can be subdivided into a northern and southern component with distinctly different driving mechanisms. The northern EASM (NEASM) is affected by heat sources in the tropical oceans related to El Niño events while the southern EASM (SEASM) is affected by the subtropical oceans related to a North Pacific sea surface temperature (SST) dipole mode. A stronger NEASM is related to above‐normal western North Pacific (WNP) anticyclonic anomalies, while a stronger SEASM is related to below‐normal WNP anticyclonic anomalies. These WNP anticyclonic anomalies are connected to SST anomalies in the tropical and subtropical Pacific during the pre‐monsoon season (December∼May). We also find that NEASM precipitation can be predicted from regional oceanic heat sources, i.e. SST and ocean heat content, in the tropical Pacific and Indian Oceans during the pre‐monsoon season using a linear regression model. SEASM precipitation can be predicted from pre‐monsoon SST in the eastern North Pacific. The NEASM forecast model is more skillful than that for the SEASM. Copyright © 2007 Royal Meteorological Society
Development and validation of a stereoselective HPLC method for the determination of the in vitro transport of nateglinide enantiomers in rat intestine
Authors: Maddi Srinivas , Keshetty Srisailam , Mohan Ega Chandra , Rao Yamasani Madhusudan , Scriba Gerhard K. E.
Published: June 2007

A simple stereoselective high performance liquid chromatographic method was developed for the determination of the in vitro transport of the enantiomers of nateglinide (N‐(trans‐4‐isopropylcyclohexyl‐carbonyl)‐phenylalanine) in the rat intestine using a Chiralcel OJ‐RH column (150×4.0 mm, 5 μm). The effects of the mobile phase composition, pH, the flow rate, and the temperature on the chromatographic separation were investigated. The enantioseparation was achieved at 33°C using a mobile phase containing 100 mM potassium dihydrogen phosphate, pH 2.5, and ACN (32:68 v/v) delivered at a flow rate of 1 mL/min. The analytes were monitored at 210 nm and linearity (r >0.99) was obtained for a concentration range of 0.5–50 μg/mL. The LOD and LOQ were 0.2 and 0.5 μg/mL for the R‐enantiomer and 0.2 and 0.8 μg/mL for the S‐enantiomer, respectively. Both, the intra‐ and interday accuracy and precision of the calibration curves were determined. The method was successfully applied to estimate the in vitro passage of the enantiomers and the racemate of nateglinide in duodenum, jejunum, and ileum of rats. Generally, higher concentrations of nateglinide and the S‐enantiomer were observed when the racemate was administered compared to administration of the individual enantiomers of nateglinide.
Quantitative determination of L‐DOPA in tablets by high performance thin layer chromatography
Authors: Mennickent Sigrid , Nail Mario , Vega Mario , de Diego Marta
Published: June 2007

A densitometric high performance thin‐layer chromatographic (HPTLC) method was developed and validated for quantitative analysis of L‐DOPA in tablets. Chromatographic separation was achieved on precoated silica gel F 254 HPTLC plates using a mixture of acetone–chloroform–n‐butanol–acetic acid glacial–water (60:40:40:40:35 v/v/v/v/v) as mobile phase. Quantitative analysis was carried out at a wavelength of 497 nm. The method was linear between 100 and 500 ng/μL, with a correlation coefficient of 0.999. The intra‐assay variation was between 0.26 and 0.65% and the interassay was between 0.52 and 2.04%. The detection limit was 1.12 ng/μL, and the quantification limit was 3.29 ng/μL. The accuracy ranged from 100.40 to 101.09%, with a CV not higher than 1.40%. The method was successfully applied to quantify L‐DOPA in real pharmaceutical samples, including the comparison with HPLC measurements. The method was fast, specific, with a good precision, and accurate for the quantitative determination of L‐DOPA in tablets.
Fast gas chromatography‐full scan quadrupole mass spectrometry for the determination of allergens in fragrances
Authors: Mondello Luigi , Sciarrone Danilo , Casilli Alessandro , Tranchida Peter Quinto , Dugo Paola , Dugo Giovanni
Published: June 2007

The Scientific Committee for Cosmetics and NonFood Products in the 7th Amendment to the European Cosmetics Directive established 26 fragrance components, widely used in cosmetic products, as being responsible for a series of contact allergies (Directive 2003/15/EC, Official Journal of the European Union, L66/26, 11.3.2003). The regulation foresees that any allergen, present in excess of 100 mg/kg in rinse‐off and of 10 mg/kg in leave‐on formulations, must be reported on the label of the product. The present research reports a fast GC‐full scan quadrupole mass spectrometric method (under 5 min) for the qualitative/quantitative analysis of allergens in perfumes. Reliable peak identification was achieved through a twin‐filtered MS library matching procedure, considering a minimum degree of spectral similarity (90%) and retention data (a linear retention index window was applied). Peak quantification was carried out by using a specific extracted ion. In case a suspected allergen fell within its retention time window but presented a low degree of spectral purity (< 90%), analyte determination was achieved by using three extracted ions (one quantifier and two qualifiers). The fast GC‐MS method was validated in terms of intraday retention time and peak area precision, LODs and LOQs, and method linearity. Finally, peak skewing was also evaluated and was within more than acceptable limits.
Turning in Parkinson's disease patients and controls: The effect of auditory cues
Authors: Willems Anne‐Marie , Nieuwboer Alice , Chavret Fabienne , Desloovere Kaat , Dom René , Rochester Lynn , Kwakkel Gert , van Wegen Erwin , Jones Diana
Published: June 2007

Turning is an impaired activity in persons with Parkinson's disease (PwPD). The current study examines the turning characteristics in PwPD (9 freezers and 10 nonfreezers) and 9 controls, and explores the effect of rhythmic auditory cues while turning. Turning parameters were collected from a 180° left U‐turn during a noncued and a cued condition, using a 3D measuring system. Auditory cues were supplied with a metronome at a rhythm equaling the subject's comfortable step frequency during straight line walking. Results showed that in contrast to controls, PwPD used a wider turning‐arc and took smaller, narrower steps. In addition, they demonstrated a higher Coefficient of Variation (CV) of step duration (6.92%) compared to controls (4.88%, P < 0.05). The “wide‐arc” turning strategy of PwPD was more prominent in freezers than in nonfreezers. Auditory cues reduced the CV of step duration in PwPD (both freezers and nonfreezers) during turning (from 6.92 to 6.00%, P < 0.05). In summary: Cueing reduced the gait‐timing variability during turning, but PwPD maintained a wider arc to turn compared with controls. © 2007 Movement Disorder Society
Prognostic factors for the progression of Parkinson's disease: A systematic review
Authors: Post Bart , Merkus Maruschka P. , de Haan Rob J. , Speelman Johannes D. ,   CARPA Study Group
Published: June 2007

The purpose of this systematic review is to summarize studies that describe the course of Parkinson's disease (PD) and to identify factors that predict change in motor impairment, disability, and quality of life. A literature search was conducted in MEDLINE, EMBASE, CINAHL, and Web of Science limited to the English, French, German, Spanish, and Dutch language. Reports were selected if the study involved subjects with PD, the outcome measures described impairment, disability, or quality of life and follow‐up was at least 6 months. All included studies were scored for methodological quality. Data were extracted and summarized in a best evidence synthesis. We screened 1,535 titles and abstracts, of which 27 fulfilled our inclusion criteria. A meta‐analysis to quantitatively aggregate progression scores of motor impairment and disability was not possible because of the wide variety of outcome measures used and the heterogeneous study populations. Limited evidence is found for lower UPDRS‐ME at baseline, dementia and SE < 70% as prognostic factors for future motor impairment. There is strong evidence for higher age at onset and higher PIGD‐score; and limited evidence for higher bradykinesia‐score, non‐tremor dominant subtype, symmetrical disease at baseline, and depression as prognostic factors for progression of disability. Prognostic factors were identified for impairment and disability. The literature on prognosis in PD is not fulfilling the high methodological standards applied nowadays. There is a need for prospective cohorts of PD patients assembled at a common early point in the disease with long time follow‐up. © 2007 Movement Disorder Society
ATP1A3 mutation in the first asian case of rapid‐onset dystonia‐parkinsonism
Authors: Lee Jee‐Young , Gollamudi Seema , Ozelius Laurie J. , Kim Ji‐Young , Jeon Beom S.
Published: June 2007

We report a 38‐year‐old Korean man with sporadic rapid‐onset dystonia‐parkinsonism (RDP), who had a Thr 618 Met mutation in the Na+/K+‐ATPase α3 subunit gene (ATP1A3). At the age of 21, he acutely developed severe dystonia and parkinsonism, which rapidly deteriorated into a wheelchair‐bound state within 4 days. He is the first Asian RDP patient confirmed by genetic testing, ascertaining that RDP gene mutation is present in Asians. Pathophysiological considerations are briefly discussed. © 2007 Movement Disorder Society
Global weak solutions to a ferrofluid flow model
Authors: Amirat Youcef , Hamdache Kamel
Published: June 2007

We are concerned with the global solvability of the differential system introduced by Shliomis to describe the flow of a colloidal suspension of magnetized nanoparticles in a nonconducting liquid, under the action of an external magnetic field. The system is a combination of the Navier–Stokes equations, the magnetization equation, and the magnetostatic equations. We prove, by using a method of regularization, the existence of global‐in‐time weak solutions with finite energy to an initial boundary‐value problem and establish the long‐time behaviour of such solutions. The main difficulty is due to the singularity of the gradient magnetic force and the torque. Copyright © 2007 John Wiley & Sons, Ltd.
Fixed point strategies for elastostatic frictional contact problems
Authors: Laborde Patrick , Renard Yves
Published: June 2007

Several fixed point strategies and Uzawa algorithms (for classical and augmented Lagrangian formulations) are presented to solve the unilateral contact problem with Coulomb friction. These methods are analysed, without introducing any regularization, and a theoretical comparison is performed. Thanks to a formalism coming from convex analysis, some new fixed point strategies are presented and compared with known methods. The analysis is first performed on continuous Tresca problem and then on the finite dimensional Coulomb problem derived from an arbitrary finite element method. Copyright © 2007 John Wiley & Sons, Ltd.
Anti‐apoptotic activity of porcine cFLIP in ovarian granulosa cell lines
Authors: Matsuda‐Minehata Fuko , Goto Yasufumi , Inoue Naoko , Sakamaki Kazuhiro , Chedrese P. Jorge , Manabe Noboru
Published: June 2007

In mammalian ovaries, more than 99% of follicles undergo atresia during growth and development. Recently, we found that the expression of cellular FLICE‐like inhibitory protein long form (cFLIPL) decreased during follicular atresia in granulosa cells of porcine ovaries. In humans and other species, both the short (cFLIPS) and long (cFLIPL) forms of cFLIP are considered to function as cell survival factors that inhibit death ligand receptor‐mediated apoptosis. Since the anti‐apoptotic activity of porcine cFLIP (pcFLIP) in granulosa cells had not been determined, we examined the effect of pcFLIP on survival using granulosa‐derived cell lines. A human cervix adenocarcinoma cell line, HeLa, human ovarian granulosa tumor cell line, KGN, and porcine granulosa‐derived cell line, JC‐410, were used. By Western blotting, internal cFLIPL was detected in all cell lines, but only trace levels of cFLIPS were found in HeLa and KGN cells. To examine the anti‐apoptotic activity, pcFLIPS or pcFLIPL was overexpressed in HeLa and KGN cells. Transfected cells in which pcFLIPS or pcFLIPL was overexpressed, survived the induction of Fas‐mediated apoptosis, while almost all of the cells transfected with empty vector died. Then, we suppressed the expression of porcine cFLIPS and/or cFLIPL in JC‐410 cells using small interfering RNA (siRNA). When both cFLIPS and cFLIPL, or only cFLIPL was suppressed, cell viability declined significantly. From the results, we conclude that porcine cFLIPS and cFLIPL exhibit anti‐apoptotic activity in granulosa‐derived cells. It was strongly suggested that pcFLIP acts as a survival‐promoting factor in granulosa cells and determines whether porcine ovarian follicles survive or undergo atresia. Mol. Reprod. Dev. 74: 1165–1170, 2007. © 2007 Wiley‐Liss, Inc.
Most expressed transcripts in sexual organs and other tissues
Authors: Kouadjo Kouame E. , Yoshioka Mayumi , Nishida Yuichiro , St‐Amand Jonny
Published: June 2007

This study characterizes the most highly expressed transcripts of 15 intact tissues in mice by using the serial analysis of gene expression (SAGE) strategy which indicates the relative level of expression for each transcript matched to the tag. We show that the most abundant transcripts in the prostate, testis, and skeletal muscle characterize the main functions of these organs as an exocrine gland of male reproduction, spermatogenesis, and contraction, respectively. In addition, the top nine most abundant transcripts in the testis are tissue‐specific genes while the most abundant transcripts in the prostate are also abundantly expressed in the liver. Furthermore, the most abundant transcripts in the ovary, mammary gland, and vagina are related to steroidogenesis, adipocytes, and keratinization, respectively, whereas genes involved in the cell defence are abundantly expressed in the liver, lung, bone, mammary gland, and adipose tissue. These findings suggest that the top 10 transcripts are sufficient to characterize each tissue of the body. Mol. Reprod. Dev. 75: 230–242, 2008. © 2007 Wiley‐Liss, Inc.
Aberrant DNA methylation in porcine in vitro‐, parthenogenetic‐, and somatic cell nuclear transfer‐produced blastocysts
Authors: Bonk Aaron J. , Li Rongfeng , Lai Liangxue , Hao Yanhong , Liu Zhonghua , Samuel Melissa , Fergason Emily A. , Whitworth Kristin M. , Murphy Clifton N. , Antoniou Eric , Prather Randall S.
Published: June 2007

Early embryonic development in the pig requires DNA methylation remodeling of the maternal and paternal genomes. Aberrant remodeling, which can be exasperated by in vitro technologies, is detrimental to development and can result in physiological and anatomic abnormalities in the developing fetus and offspring. Here, we developed and validated a microarray based approach to characterize on a global scale the CpG methylation profiles of porcine gametes and blastocyst stage embryos. The relative methylation in the gamete and blastocyst samples showed that 18.5% (921/4,992) of the DNA clones were found to be significantly different (P < 0.01) in at least one of the samples. Furthermore, for the different blastocyst groups, the methylation profile of the in vitro‐produced blastocysts was less similar to the in vivo‐produced blastocysts as compared to the parthenogenetic‐ and somatic cell nuclear transfer (SCNT)‐produced blastocysts. The microarray results were validated by using bisulfite sequencing for 12 of the genomic regions in liver, sperm, and in vivo‐produced blastocysts. These results suggest that a generalized change in global methylation is not responsible for the low developmental potential of blastocysts produced by using in vitro techniques. Instead, the appropriate methylation of a relatively small number of genomic regions in the early embryo may enable early development to occur. Mol. Reprod. Dev. 75: 250–264, 2008. © 2007 Wiley‐Liss, Inc.
Does uroflow predict ISD?
Authors: Smith Phillip P. , Appell Rodney A.
Published: June 2007

Aim

The term superflow has been given to abnormally high flow rates in women, and has been thought to be indicative of intrinsic sphincteric deficiency (ISD), as ISD is associated with low urethral pressure. Pelvic organ prolapse (POP) damages the sphincteric mechanism extrinsic to the urethra. The aim of this study was to determine if ISD can be predicted from voiding flow rates in women with symptomatic POP.

Methods

The charts of 82 patients who had undergone surgery for repair of symptomatic vaginal prolapse were reviewed. Uroflow and urodynamic endpoints were compared between dry and stress incontinent patients, and correlations between abdominal leak point pressures (LPP) and pressure/flow data evaluated.

Results

Average maximum flow (Qmax) at uroflow was greater than at urodynamics with no significant difference in voided volumes. Twenty eight patients were found to have urodynamic stress incontinence (SUI), and an additional 19 to have “occult” stress incontinence. Patients with SUI had higher flow rates at urodynamics than continent patients. Voiding detrusor pressures and flow rates were not different when categorized by LPP cutoffs of 100 and 60 cm/w. Abdominal leak point pressure did not significantly correlate with any uroflow or urodynamic pressure/flow parameter.

Conclusions

Flow rates, whether determined by uroflow testing or at urodynamics, are not predictive of ISD as defined by a low abdominal leak point pressure, in patients with symptomatic POP. Either the effect of ISD on flow rates is a non‐linear complex relationship or LPP does not adequately define ISD. Neurourol. Urodyn. © 2007 Wiley‐Liss, Inc.
Zupfen am Lebensfaden: Experimente mit einzelnen DNS‐Molekülen
Authors: Fink Hans‐Werner , Escher Conrad
Published: June 2007

Das DNS‐Molekül ist nur zwei Nanometer dick und kann mehrere Millimeter lang sein. Herkömmliche Methoden zur Strukturanalyse erfordern die Herstellung von DNS‐Kristallen. Einzelne Moleküle lassen sich mit holographischen Methoden abbilden, wenn auch bislang nicht mit atomarer Auflösung. Die Hoffnung ruht auf Röntgenpulsen aus zukünftigen Freie‐Elektronen‐Lasern und auf kohärenten, langsamen Elektronen. Das Biopolymer bevorzugt in natürlicher wässriger Umgebung eine verknäulte Gestalt. Fluoreszenzmikroskope können zwar nicht die innere Struktur, aber die Bewegung einzelner DNS‐Moleküle in wässriger Lösung sichtbar machen. Auch die Messung der Energetik einzelner DNS‐Stränge in dieser natürlichen Umgebung gelingt schon.
Kinetische Farben. Spielwiese
Authors: Schlichting Hans‐Joachim , Suhr Wilfried
Published: June 2007

Mit verhältnismäßig einfachen Vorrichtungen lassen sich eindrucksvolle Farberscheinungen erzeugen. Diese Vorrichtungen mischen weißes Licht durch einen schnellen periodischen Wechsel farbiger Lichtpulse. In diesem Licht bewegte Objekte erscheinen daher in unterschiedlichen Farben. Neben den reinen Ausgangsfarben treten dabei auch Mischfarben aus unterschiedlich großen Anteilen dieser Ausgangsfarben sowie deren Komplementärfarben auf. Das Phänomen beeindruckt durch das unerwartete Hervorgehen von Farben aus weißem Licht.
Gebündeltes Röntgenlicht: Planare refraktive Röntgenlinsen
Authors: Last Arndt , Nazmov Vladimir , Reznikova Elena
Published: June 2007

Heute stehen Röntgenlinsen zur Verfügung, deren Einsatz viele neue Anwendungen ermöglicht. Zur Beleuchtung von Objekten mit Röntgenlicht eignen sich besonders Kapillaroptiken. Fresnel‐Zonenplatten und refraktive Röntgenlinsen werden eher zur vergrößernden Abbildung eingesetzt. Die Brechzahlen aller geeigneten Materialien unterscheiden sich im Röntgenlicht kaum von der Brechzahl der Luft. Deshalb bestehen refraktive Linsen aus einer Vielzahl von Einzellinsen. Sie eignen sich besonders für Photonenenergien oberhalb von 15 keV, wo die anderen Optiken bereits transparent werden. Die Einzellinsenelemente brauchen nicht mehr zueinander positioniert zu werden, wenn sie mit dem LIGA‐Verfahren oder durch anisotropes Tiefenätzen in Silizium gefertigt sind.
Moderne Zentauren: Physik des Fahrradfahrens
Authors: Schlichting Hans‐Joachim , Suhr Wilfried
Published: June 2007

Es gibt verschiedene Möglichkeiten, die Spitzen‐ und Dauergeschwindigkeiten beim Radfahren zu erhöhen, beispielsweise durch Gewichtsverminderung. Entscheidend ist jedoch der Luftwiderstand, da der Rollwiderstand so gut wie unabhängig von der Geschwindigkeit ist. Der Luftwiderstand nimmt jedoch quadratisch mit der Geschwindigkeit zu und erfordert folglich eine mit der dritten Potenz der Geschwindigkeit wachsende Antriebsleistung.
Di‐ and trivalent rare earth complexes stabilized by sterically demanding aminopyridinato ligands as initiators in ring‐opening polymerization reactions of ϵ‐caprolactone
Authors: Guillaume Sophie M. , Schappacher Michèle , Scott Natalie M. , Kempe Rhett
Published: June 2007

Salt elimination protocols using Ap*K {Ap*H = (2,6‐diisopropyl‐phenyl)‐[6‐(2,4,6‐triisopropyl‐phenyl)‐pyridin‐2‐yl]‐amine} lead to the rare earth aminopyridinato complex [Ap*LuCl2(thf)2], 4. Results of X‐ray crystal structure analyses of 4 and the corresponding single THF coordinated dimer are discussed. Ring‐opening polymerization of ε‐caprolactone initiated by complexes [Ap*LaBr2(thf)3], 2, [Ap*YbI(thf)2]2, 3 or 4 in the presence of NaBH4 allows the preparation, in a short reaction time, of α,ω‐dihydroxytelechelic polymers with high molar mass (
$ \bar{M}_{\rm n} $
up to 50,000) and moderate molar mass distributions (1.3 < $ \bar{M}_{\rm w} $/$ \bar{M}_{\rm n} $< 1.6). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3611–3619, 2007
The compatibilization effect of ethylene/styrene interpolymer on polystyrene/polyethylene blends
Authors: Tang Weihua , Tang Jian , Yuan Huilin , Jin Riguang
Published: June 2007

In this study, ethylene/styrene interpolymer (ESI) was used as compatibilizer for the blends of polystyrene (PS) and low‐density polyethylene (LDPE). The mechanical properties including impact, tensile properties, and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Impact measurements indicated that the impact strength of the blends increases slowly with LDPE content up to 40 wt %; thereafter, it increases sharply with increasing LDPE content. The impact energy of the LDPE‐rich blends exceeded that of pure LDPE, implying that the LDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI. Tensile tests showed that the yield strength of the PS/LDPE/ESI blends decreases considerably with increasing LDPE content. However, the elongation at break of the blends tended to increase significantly with increasing LDPE content. The compatibilization efficiency of ESI and polystyrene‐hydrogenated butadiene‐polystyrene triblock copolymers (SEBS) for PS/LDPE 50/50 was further compared. Mechanical properties show that ESI is more effective to achieve a combination of LDPE toughness and PS rigidity than SEBS. The correlation between the impact property and morphology of the ESI‐compatibilized PS/LDPE blends is discussed. The excellent tensile ductility of the LDPE‐rich blends resulted from shield yielding of the matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2136–2146, 2007
The Challenge of asthma in adolescence
Authors: de Benedictis Diletta , Bush Andrew
Published: June 2007

The adolescents with asthma are a distinct group of patients with different problems and needs compared to children and adults. Specific issues of asthma in adolescence are the variability of the clinical spectrum, the presence of particular risk factors for the persistence of symptoms, underdiagnosis and undertreatment of the disease. Refusal of the sick role, denial of symptoms, carelessness about dangerous inhalation exposure, erratic self‐medication, overexertion without taking precautions against exercise‐induced asthma, and a poor relationship between patients, their families, and often doctors are the main obstacles to successful management of asthma in this critical age. There are also major problems of compliance for these patients. The goal of optimal quality of life will be achieved only if the physician thoroughly understands the adolescent's needs and provides optimal care. Pediatr Pulmonol. 2007, 42:683–692. © 2007 Wiley‐Liss, Inc.
New method for the determination of the defect profile in thin layers grown over a substrate
Authors: Zubiaga A. , García J. A. , Plazaola F. , Tuomisto F. , Zúñiga J. , Muñoz‐Sanjosé V.
Published: June 2007

We present a new method to obtain information about the defect profile of films grown over high quality substrates. The method is valid, at least, for films where the positron mean‐diffusion length is small. We have used the method for the case of ZnO films grown over sapphire, but the method can be generalized very easily to other film/substrate systems. Applying the method to the ratio of W and S parameters obtained from Doppler broadening measurements, W/S plots, one can determine the thickness of the film and the defect profile trend in the film, when mainly one positron trap is contributing to positron trapping within the film. Indeed, the quality of such a characterization is very important for the potential technological applications of the film. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Many body effects seen in the positron annihilation experiment
Authors: Kontrym‐Sznajd G. , Sormann H.
Published: June 2007

The electron‐positron (e‐p) momentum density in p‐space for copper, magnesium, cadmium and yttrium, calculated by using various theoretical approaches, are compared with corresponding densities reconstructed from two‐dimensional angular correlation of annihilation radiation (2D ACAR) experimental spectra. We demonstrate that (at least for positrons in metals) strong electron‐electron (e‐e) correlations are clearly visible not only in the Compton scattering but also in positron annihilation experiments. Moreover, a proper description of e‐p correlations needs to include the lattice‐periodical crystal potential. In case of strong lattice effects, the increase of the e‐p enhancement with increasing momentum ‐ the so‐called Kahana‐like enhancement, is vanishing. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect studies of hydrogen loaded Nb: bulk metals and thin films
Authors: Čížek J. , Procházka I. , Daniš S. , Melikhova O. , Vlach M. , Žaludová N. , Brauer G. , Anwand W. , Mücklich A. , Gemma R. , Nikitin E. , Kirchheim R. , Pundt A.
Published: June 2007

Microstructure investigations of Nb loaded with H are presented in this work. The microstructure was examined by positron annihilation spectroscopy (PAS), combined with X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The behaviour of H‐loaded bulk samples and thin films was compared. First, the microstructure of the virgin (H‐free) specimens was characterized. Subsequently, the development of the microstructure during step‐by‐step electrochemical H charging was studied. The investigations were performed mainly in the low H concentration region (α‐phase), where the Nb‐H system represents a single phase interstitial solid solution. In bulk samples it was found that new vacancy‐like defects are introduced by H loading. Vacancies surrounded by H were detected also in the electron irradiated bulk samples. Nanocrystalline thin films were produced by sputtering at room temperature. They exhibit a significant volume fraction of grain boundaries with open volume defects which trap H. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
2D‐ACAR studies on microstructure characteristics of porous silicon
Authors: Sivaji K. , Sundar C. S. , Amarendara G. , Rajaraman R. , Padma G. , Sankar S.
Published: June 2007

Two dimensional electron momentum distributions (EMD) have been mapped by the two‐dimensional angular correlation of positron annihilation radiation (2D‐ACAR) to study the electronic structure and microstructural characteristics of porous silicon. The open volume defects associated with vacancies and their complexes present in the porous layer have been analysed using the EMD spectra. Also, the correlation between EMD and the pore formation mechanism was studied and the surface properties were analyzed along with the photoluminescence spectra. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reactions of free positrons in low temperature polyethylene: delayed Ps formation and positron localization
Authors: Hirade T. , Suzuki N. , Saito F. , Hyodo T.
Published: June 2007

Positronium (Ps) can be formed by a reaction of trapped electrons and free positrons at low temperatures in molecular solids. While Ps formation by Ore and spur process must be fast, Ps formation by trapped electrons and free positrons is possible even at later positron age. The evidence of this delayed Ps formation was obtained by age‐momentum correlation measurement of electron‐positron pair annihilation γ‐rays. In this work the S (t) parameter curves measured with trapped electrons and no trapped electrons in polyethylene are interpreted by introducing possible positron reactions. It is quite natural to believe that the delayed Ps formation competes with the positron localization. We have successfully obtained a good simultaneous fit to the observed time dependent S‐parameter curves, S (t), with and without the trapped electrons in the sample. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of the time resolution of a pulsed positron beam
Authors: Reurings Floris , Laakso Antti
Published: June 2007

We analyze the time resolution of the Helsinki pulsed positron beam. The multiple pulsing stages in the beam lead to a non‐trivial pulse shape, which must be taken into account in the subsequent analysis of the data. We study the performance of the pulsing stages and derive an expression for the resolution function, and find a good agreement with the measured spectrum. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Silicon and carbon vacancies in silicon carbide studied by coincidence Doppler broadening spectroscopy
Authors: Zhang J. D. , Cheng C. C. , Ling C. C. , Beling C. D. , Fung S.
Published: June 2007

Deconvoluted Coincidence Doppler Broadening Spectroscopy (CDBS) measurements have been made on 300 keV and 1.7 MeV electron irradiated SiC. The lower energy irradiation produces only carbon vacancies while the higher energy produces both carbon and silicon vacancies. This distinction is easily seen in the high (20‐35 mrad) momentum range where a clear atomic signal of Si is seen for the carbon vacancy. In addition to the higher momentum region the higher resolution of the deconvoluted CDBS spectra show structural information relating to the crystal lattice. The autocorrelation function obtained for positrons trapped at carbon vacancies is found to show a stronger lattice signal indicative of a more extended positron wave function and a less strongly bound state. Conversely that positron trapped at the silicon vacancy shows a more damped autocorrelation function characteristic of a more spatially confined positron state. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Subsurface zones in magnesium detected by variable energy positron beam
Authors: Dryzek J. , Schut H. , Dryzek E.
Published: June 2007

In the paper we present positron annihilation studies of the subsurface zones created below pure magnesium surface exposed to sliding. We used the conventional positron techniques i.e. positron lifetime spectroscopy and DSIP (Depth Scanning of the positron Implantation Profile) method, and variable positron energy beam technique. The obtained results suggest the creation of dislocations zone during dry sliding in the subsurface which weakly localize positrons. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of sonochemically synthesized Au‐Pd nanoparticles by using slow positron beam
Authors: Hori F. , Kojima T. , Tanaka S. , Akita T. , Iwai T. , Onitsuka T. , Taguchi N. , Iwase A.
Published: June 2007

Binary AuPd nanoparticles were prepared by sonochemical reduction of solutions containing Au3+, Pd2+ ions and surfactant (SDS: sodium dodecyl sulfate and PEG‐MS: polyethylene glycol monostearate). When using SDS as an additive, AuPd nanoparticles became a core‐shell structure of Au core and Pd shell. AuPd nanoparticle with core‐shell structure has catalytic activity superior to alloyed particle or Pd nanoparticles. In order to study the electronic states of AuPd nanoparticles, positron annihilation Doppler broadening measurements by using slow positron beam (energy range of 0.1 to 10 keV) have been performed for AuPd nanoparticles. The size and shape of the nanoparticles are also examined by using transmission electron microscope (TEM). The differences of Doppler broadening parameters between core‐shell, alloyed AuPd, pure Au and Pd particles were found. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of ceramic nanoparticles on grain growth in ultra fine grained copper prepared by high pressure torsion
Authors: Čížek J. , Procházka I. , Cieslar M. , Kužel R. , Matěj Z. , Cherkaska V. , Islamgaliev R. K. , Kulyasova O.
Published: June 2007

Bulk ultra‐fine grained (UFG) materials with no residual porosity can be produced by high pressure torsion (HPT). A number of UFG metals exhibit improved mechanical properties consisting in a favourable combination of very high strength and a reasonable ductility. Unfortunately, the thermal stability of UFG structure is rather low. Recrystallization takes place at elevated temperatures and the superior mechanical properties are lost. Thus, it is highly desirable to improve the thermal stability of UFG structure. In the present work we studied the thermal stability of UFG Cu containing Al2O3 nanoparticles. The aim of this work was to check whether the ceramic nanoparticles can inhibit grain growth and, thereby, to extend the thermal stability of UFG structure. We have found that the HPT deformed samples exhibit UFG structure with grain size around 150 nm and a high density of dislocations situated mainly in distorted layers along grain boundaries. The grain growth in the samples which contain 0.5 wt.% of the Al2O3 nanoparticles is shifted to a significantly higher temperatures compared to the pure UFG Cu. Thus, we can conclude that the addition of the Al2O3 nanoparticles (concentration at least 0.5 wt.%) leads to a significant improvement of the thermal stability of UFG structure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature dependence study of positronium formation in high density polyethylene by positron annihilation lifetime spectroscopy
Authors: Nahid F. , Beling C. D. , Fung S.
Published: June 2007

Positron annihilation lifetime spectroscopy has been used to study the formation of positronium in high density polyethylene as a function of temperature over the range 30 K‐350 K. It is observed that the thermal history of the sample, while having no influence on the positronium lifetime, has a strong effect on the formation of positronium. A hysteresis is seen in the positronium formation probability in cooling and heating cycles. This is explained on a two channel formation model, the first channel being through “blob” formation and the second through the pick‐up of shallow trapped electrons. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doppler broadening of positron annihilation radiation as a probe for the anisotropy of free‐volume‐holes in polymers
Authors: Palacio C. A. , Djourelov N. , Kuriplach J. , Dauwe C. , Laforest N. , Segers D.
Published: June 2007

Doppler broadening of annihilation radiation (DBAR) measurements have been performed in uniaxially hot‐drawn poly(methylmethacrylate) (PMMA) samples. The DBAR spectra were deconvoluted into three Gaussians. The full width at half‐maximum of the narrow component which is due to para‐Positronium (p‐Ps) self‐annihilation is under discussion. An anisotropy of the free volume holes (FVHs) has been detected by measuring the deformed samples at the stretching and transverse directions. The sample deformed at 280% was also measured as a function of the orientation angle (0°–90°) with respect to the stretching direction. The momentum distribution of p‐Ps, which is considered as a structureless particle confined in FVH of ellipsoidal or cuboid shape, was calculated as a function of the potential well size and depth and compared with experiment. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of cross‐linking on the free volume properties of natural rubber
Authors: Jobando V. O. , Quarles C. A.
Published: June 2007

We used Positron Annihilation Lifetime Spectroscopy (PALS) to investigate the effect of cross‐linking on the free volume properties of Natural Rubber (NR) composites. In order to form any meaningful product for industrial purposes, NR is mixed with different compounds, then cured in a process called vulcanization. One of the most important compounds used in the mixing process is sulfur. Sulfur forms cross‐links with NR restricting the mobility of the polymer chains. Addition of sulfur and vulcanization reduce the o‐Ps lifetime and intensity. By compating un‐vulcanized and vulcanized samples we show that sulfur inhibits Ps formation and that with cross‐link formation during vulcanization the o‐Ps lifetime and intensity both decrease with increasing sulfur concentration. Swelling measurements were also done using toluene absorption to measure cross–link density as a function of sulfur concentration. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron lifetime studies on the free volume changes during curing of rubber‐carbon black composites
Authors: Jobando V. O. , Quarles C. A.
Published: June 2007

The free volume behavior as a function of time during curing of natural rubber‐carbon black composites studied by positron annihilation lifetime spectroscopy (PALS) is reported. The lifetime and intensity of the ortho‐positronium (o‐Ps) pick‐off annihilation, which correlate with the average size and the number of holes respectively, were measured as a function of curing time. The samples were cured at 160 °C, while all PALS measurements were made at room temperature. Results for curing D706 (Duradene‐706), a synthetic rubber is also reported and compared with those found from natural rubber (NR). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron spectroscopy of high‐k dielectric films on SiC
Authors: Coleman P. G. , Burrows C. P. , Mahapatra R. , Wright N. G.
Published: June 2007

A correlation has been observed between the structural integrity and growth temperature of ∼80 nm‐thick TiO2 films grown on SiO2/4H‐SiC substrates as high‐k dielectric stacks for power device applications, using variable‐energy positron annihilation spectroscopy. The structural change, tentatively attributed to a decrease in oxygen vacancy concentration, was observed as the TiO2 growth temperature was increased in the range 700 to 1000 °C, whereas grain boundaries form in the polycrystalline material grown at the highest temperatures. It is proposed that the optimal electrical performance for films grown at 800 °C reflects a balance between decreasing vacancy concentration and increasing grain boundary formation. Because positrons are swept to the SiO2/SiC interface by a field in the substrate, VEPAS is strongly sensitive to interface states, which can have important consequences for channel mobility and thus the electrical performance of the devices. The use of a number of lineshape parameters (beyond the standard S and W) has been applied to these measurements, enabling clearer insights to be gained. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doppler broadening of annihilation radiation spectroscopy study using Richardson‐Lucy, Maximum Entropy and Huber methods
Authors: Yu D. P. , Zhang J. D. , Cheng V. , Beling C. D. , Fung S.
Published: June 2007

The Richardson‐Lucy, Maximum Entropy and Huber regularization methods are popularly used in solving ill‐posed inverse problems. This paper considers the use of these three methods in the deconvoluting DBARS (Doppler Broadening of Annihilation Radiation Spectroscopy) data. As DBARS data have a constant background on the high‐energy side and a long exponential tail on the low‐energy side, we check the different deconvolution schemes paying specific attention to the quality of the deconvolution at the peak and tail positions. Comparison of the three methods is made by testing on Monte‐Carlo simulated data both in terms of the deconvoluted quality and computational resources required. Finally, we apply these methods to experimental DBARS data taken on polycrystalline metal samples. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantitative precipitation forecasting in the Alps: The advances achieved by the Mesoscale Alpine Programme
Authors: Richard Evelyne , Buzzi Andrea , Zängl Günther
Published: June 2007

The improvement of Quantitative Precipitation Forecasting (QPF) in mountainous regions was a major supporting objective of the Mesoscale Alpine Programme (MAP) project P1 devoted to the study of orographic precipitation. This paper reviews the main MAP‐related achievements regarding QPF improvement and highlights the MAP impact on developing QPF research and planning future operational strategies. Recent results based on MAP case‐studies, on data analysis and assimilation, on quantification of model uncertainties, and on model intercomparison and verification substantiate the progress made in recent years in improving model performance in relation to short‐range, high‐resolution forecasting in complex topography regions, well represented by the European Alps. Copyright © 2007 Royal Meteorological Society
Gravity waves above a convective boundary layer: A comparison between wind‐profiler observations and numerical simulations
Authors: Böhme T. , Lane T. P. , Hall W. D. , Hauf T.
Published: June 2007

Wind‐profiler observations and three‐dimensional numerical modelling are used to investigate gravity waves generated over convectively active boundary layers on 12 and 13 May 2001 at Lindenberg, Germany. The results illustrate the importance of changes in the background wind and stability profile in influencing the vertical propagation of the gravity waves. The resultant changes in vertical propagation cause the dominance of relatively long‐wavelength, long‐period waves at high levels and the dominance of relatively short‐wavelength, short‐period waves near the top of the convective boundary layer. There are important differences between the two days in the wave‐propagation characteristics, due to subtle changes in the background flow conditions. Copyright © 2007 Royal Meteorological Society
Data assimilation in the FOAM operational short‐range ocean forecasting system: a description of the scheme and its impact
Authors: Martin M. J. , Hines A. , Bell M. J.
Published: June 2007

A detailed description of the data assimilation scheme used in the Forecasting Ocean Assimilation Model (FOAM) operational ocean forecasting system is presented. The theoretical basis for the scheme is an improved version of the analysis correction scheme, which includes information from previously assimilated data. The scheme requires the a priori specification of error covariance information for the background model field and the observations. The way in which these error covariances have been estimated is described and some examples are given. The FOAM system assimilates sea surface temperature, sea‐level anomaly, temperature profile, salinity profile and sea‐ice concentration data. Aspects of the scheme that are specific to each of these observation types are described.

Two sets of experiments demonstrating the impact of the data assimilation are presented. The first set are in an idealized identical‐twin setting, using the ${1}\over{9}$° ‐resolution North Atlantic FOAM configuration in which the state of the true ocean is assumed to be known. These experiments show that the analyses and forecasts are improved by assimilating the altimeter sea‐level‐anomaly data. The second set of experiments comprise data impact studies in a realistic hindcast setting. These experiments show a positive impact on the analyses from the Argo temperature‐ and salinity‐profile data. Copyright © 2007 Royal Meteorological Society