bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of microscopy in authentication of traditional Tibetan medicinal plants of five Rhodiola (Crassulaceae) alpine species by comparative anatomy and micromorphology
Authors: Li Tao , Zhang Hao
Published: February 2008

A comparative analysis was undertaken to conduct an anatomical and micromorphological study of five species of Rhodiola—R. kirilowii, R. yunnanensis, R. crenulata, R. fastigata, and R. quadrifida—collected from the western Sichuan province plateau of China. Rhodiola plants are a popularly used ethnodrug from the Qinghai‐Tibetan plateau of China. Modern studies have shown that the plants of Rhodiola possess different pharmacological activities, chemical constituents, and efficiencies in clinical application. To distinguish five main species of Rhodiola and ensure their safety and efficacy, microscopic characteristics of roots, rhizomes, and stems, including transverse sections, stem and foliar epidermis, as well as the crude drug powder, were observed. The fixed, sectioned, and stained plant materials, as well as the crude powder, were studied using a light microscope according to the usual microscopic techniques. The results of the microscopic features were systematically and comparatively described and illustrated. The five species have distinct microscopic characteristic differences, thus allowing us to distinguish between the species. Also, semi‐quantitative and quantitative micrographic parameter tables were simultaneously presented. Further, a key to the five species and a comparative chart of the key authentication parameters based on these anatomic characteristics analyzed was drawn up and is presented for the Rhodiola species studied. The study indicated that light microscopy and related techniques provide a method that is convenient, feasible, and can be unambiguously applied to the authentication of species of Rhodiola. Microsc. Res. Tech., 2008. © 2008 Wiley‐Liss, Inc.
A method to isolate human limbal basal cells enriched for a subset of epithelial cells with a large nucleus/cytoplasm ratio expressing high levels of p63
Authors: Arpitha Parthasarathy , Prajna Namperumalsamy V. , Srinivasan Muthiah , Muthukkaruppan Veerappan
Published: February 2008

The objectives were to develop method of isolating viable human limbal basal cells in order to enrich a subset of small cells with a large Nucleus/Cytoplasm (N/C) ratio expressing high levels of p63, nuclear protein. Limbal tissues were treated with trypsin for 50 min at 37°C in an orbital shaker at 100 rpm with epithelial side down followed by additional 5 min with epithelial side up and then with Dispase II to obtain various epithelial fractions. Isolated cell fractions were assessed for colony forming efficiency and ΔNp63α, connexin (Cx43) mRNA levels. Cytospin smears were double‐immunostained for p63 and any one of the stem cell (SC) related markers and analyzed using a laser scanning confocal microscope and advanced image analysis software (Leica Confocal software, 2.61 build 1537 version) for quantification of fluorescence intensity. The isolated limbal basal cells were highly positive for ΔNp63α mRNA but expressing low Cx43 mRNA. They gave rise to higher number of large colonies with compact morphology in contrast to the limbal suprabasal/superficial (LS/S) colonies. Furthermore, a subset with a large N/C ratio expressing high levels of p63 was observed, as much as 25% among the limbal basal cell fraction, in contrast to only about 4% in the total limbal epithelial cells. Such cells were positive for K5 and negative for Ki67, Cx43, and 14‐3‐3s and were absent in the LS/S fraction. These results collectively substantiate our method of isolation of limbal basal layer cells containing an enriched population of cells with SC phenotype. Microsc. Res. Tech. 2008. © 2008 Wiley‐Liss, Inc.
Relative sea‐level change and postglacial isostatic adjustment along the coast of south Devon, United Kingdom
Authors: Massey Anthony C. , Gehrels W. Roland , Charman Dan J. , Milne Glenn A. , Peltier W. Richard , Lambeck Kurt , Selby Katherine A.
Published: February 2008

Previous sea‐level studies suggest that southwest Britain has the fastest subsiding coastline in the United Kingdom, but tide‐gauge data, GPS and gravity measurements and geophysical models show little evidence of anomalous subsidence in this region. In this paper we present 15 new sea‐level index points from four coastal barrier systems in south Devon. Eight are from compaction‐free basal sediments and others were corrected for autocompaction. Our data suggest that relative sea level along the south Devon coastline has risen by 21 ± 4 m during the past 9000 years. Sea‐level rise slowed during the middle and late Holocene and a rise of 8 ± 1 m has occurred since ca. 7000 cal. yr BP. Anomalous ages for many rejected points are attributed to sediment reworking during barrier transgression. The relative sea‐level history during the early and middle Holocene shows a good fit with geophysical model predictions, but the geological and modelled data diverge in the later Holocene. Unlike the geophysical models, sea‐level index points cannot differentiate between late Holocene relative sea‐level histories of south Devon and southwest Cornwall. It is suggested that this discrepancy can be resolved by obtaining additional high‐quality sea‐level index points covering the past 4000 years. Copyright © 2008 John Wiley & Sons, Ltd.
Effects of 1‐MCP applied postharvest on epicuticular wax of apples (Malus domestica Borkh.) during storage
Authors: Curry Eric
Published: February 2008

BACKGROUND: Certain apple cultivars develop a greasy feel when overripe. Treating fruits with the ripening inhibitor 1‐methylcyclopropene (1‐MCP, SmartFresh™) reduces fruit greasiness. This study examines the nature of this phenomenon. ‘Royal Gala’ apples were treated with 1‐MCP at 1.0 µl L−1 following harvest. Periodically, during storage at − 1 °C for up to 6 months, fruits were evaluated for internal ethylene concentration, fruit epicuticular wax morphology (using scanning electron microscopy) and non‐polar organic solvent‐extractable (NPOSE) wax constituents of the cuticle (using gas chromatography/mass spectrometry).

RESULTS: In 2004, 1‐MCP strongly inhibited internal ethylene production; however, total weight of NPOSE wax during storage was unaffected by treatment. In 2005, several wax constituents present in both ‘Autumn Gold’ and ‘Royal Gala’ showed differences during storage. In 2006, cuticular wax constituents comprising 80% of the total from ‘Royal Gala’ showed no treatment differences. Although several minor constituents did exhibit differences within treatment and sampling date, these did not appear sufficient to cause the subtle differences in surface wax morphology.

CONCLUSION: 1‐MCP strongly inhibited ethylene production and delayed development of certain wax constituents thought responsible for fruit greasiness during cold storage. Subtle differences in surface wax morphology appeared unrelated to wax production. Published in 2008 by John Wiley & Sons, Ltd.
Development and validation of a reversed‐phase HPLC method for quantitative determination of ginsenosides Rb1, Rd, F2, and compound K during the process of biotransformation of ginsenoside Rb1
Authors: Zhou Wei , Li Jiyang , Li Xinwei , Yan Qin , Zhou Pei
Published: February 2008

A simple and rapid gradient RP‐HPLC method for simultaneous separation and determination of related ginsenosides during the process of biotransformation of ginsenoside Rb1 has been developed. As many as four process ginsenosides have been separated and identified on an Eclipse XDB C18 column (4.6 mm×150 mm, 5 μm) with gradient elution using water and ACN as a mobile phase. The column was maintained at 30°C and the eluents were monitored with diode array detection at 203 nm. The method was validated in terms of linearity, sensitivity, precision, and accuracy. The correlation coefficients (r) for calibration curves of ginsenosides were in the range of 0.9996–1.0000. The proposed RP‐HPLC method was successfully applied to the analysis of fermentation broth and the recoveries of ginsenosides were in the range of 94.4–103.1% with RSD <2.87%. The method could be of use for rapid and routine evaluation of the quantity of ginsenosides during the biotransformation process of ginsenoside Rb1.
A model of wine tourist behaviour: a festival approach
Authors: Yuan Jingxue (Jessica) , Morrison Alastair M. , Cai Liping A. , Linton Sally
Published: February 2008

The study constructs a temporal model of wine tourist behaviour on the basis of the social psychologist' theory of consumer attitudes and related concepts with regard to past behaviour, satisfaction, perceived value and behavioural intentions. More importantly, this study added two dimensions to this model by proposing that satisfaction and perceived value had an impact on the attendees' intentions (i) to visit a local winery and (ii) to buy local wine products. Using a path analysis approach and data collected from the attendees at a regional wine festival, the study examined the above relationships. The results of this path analysis can be summarised as: (i) past behaviour influenced the intention to revisit and the level of perceived value, but had no effect on the level of satisfaction; (ii) perceived value strongly affected the level of satisfaction; (iii) satisfaction had a strong impact on future intentions to revisit and also an effect on intentions to visit local wineries and to buy local wine products; and (iv) perceived value affected the intentions to revisit the festival and to visit local wineries but did not influence the intentions to buy local wines. It is believed that the results of the present study will be useful to organisers of wine festivals and/or wine tourism developers. Copyright © 2008 John Wiley & Sons, Ltd.
1H and 13C NMR assignments of three nitrogen containing compounds from the mangrove endophytic fungus (ZZF08)
Authors: Tao Yiwen , Zeng Xianjian , Mou Chengbo , Li Jun , Cai Xiaoling , She Zhigang , Zhou Shining , Lin Yongcheng
Published: February 2008

A new natural product, named phomopsin A, 1‐(meta‐hydroxyphenyl)‐4‐hydroxy‐3‐isoquinolone (1), together with two known compounds cytochalasin H (2) and glucosylceramide (3), was isolated from the mangrove endophytic fungus Phomopsis sp. (ZZF08) obtained from the South China Sea coast. The structures were elucidated by 1D and 2D NMR experiments including COSY, HMQC, and HMBC. According to NMR and single‐crystal X‐ray diffraction, it was found that some assignments about 1H and 13C NMR data for cytochalasin H (2) were probably uncorrected in the previous reports. In our cytotoxicity assays, compound 1 showed moderate cytotoxicity toward KB cells with IC50 at 28.0 µg ml−1 and KBv200 cells with IC50 at 16.8 µg ml−1, and compound 2 exhibited strong cytotoxicity toward KB cells and KBv200 cells with IC50 less than 1.25 µg ml−1. Copyright © 2008 John Wiley & Sons, Ltd.
Micromechanical aspects of the shear strength of wet granular soils
Authors: El Shamy U. , Gröger T.
Published: February 2008

This paper presents a micromechanical model for the analysis of wet granular soils at low saturation (below 30%). The discrete element method is employed to model the solid particles. The capillary water is assumed to be in a pendular state and thus exists in the form of liquid bridges at the particle‐to‐particle contacts. The resulting inter‐particle adhesion is accounted for using the toroidal approximation of the bridge. Hydraulic hysteresis is accounted for based on the possible mechanism of the formation and breakage of the liquid bridges during wetting and drying phases. Shear test computational simulations were conducted at different water contents under relatively low net normal stresses. The results of these simulations suggest that capillary‐induced attractive forces and hydraulic hysteresis play an important role in affecting the shear strength of the soil. These attractive forces produce a tensile stress that contributes to the apparent cohesion of the soil and increases its stiffness. During a drying phase, capillary‐induced tensile stresses, and hence shear strength, tend to be larger than those during a wetting phase. The proposed model appears to capture the macroscopic response of wet granular materials and revealed a number of salient micromechanical mechanisms and response patterns consistent with theoretical considerations. Copyright © 2008 John Wiley & Sons, Ltd.
Reformulation and sampling to solve a stochastic network interdiction problem
Authors: Janjarassuk Udom , Linderoth Jeff
Published: February 2008

The network interdiction problem involves interrupting an adversary's ability to maximize flow through a capacitated network by destroying portions of the network. A budget constraint limits the amount of the network that can be destroyed. In this article, we study a stochastic version of the network interdiction problem in which the successful destruction of an arc of the network is a Bernoulli random variable, and the objective is to minimize the maximum expected flow of the adversary. Using duality and linearization techniques, an equivalent deterministic mixed integer program is formulated. The structure of the reformulation allows for the application of decomposition techniques for its solution. Using a parallel algorithm designed to run on a distributed computing platform known as a computational grid, we give computational results showing the efficacy of a sampling‐based approach to solve the problem. © 2008 Wiley Periodicals, Inc. NETWORKS, 2008
Competitive algorithms and lower bounds for online randomized call control in cellular networks
Authors: Caragiannis Ioannis , Kaklamanis Christos , Papaioannou Evi
Published: February 2008

We address an important communication issue arising in wireless cellular networks that utilize frequency division multiplexing (FDM) technology. In such networks, many users within the same geographical region (cell) can communicate simultaneously with other users of the network using distinct frequencies. The spectrum of the available frequencies is limited; thus, efficient solutions to the call control problem are essential. The objective of the call control problem is, given a spectrum of available frequencies and users that wish to communicate, to maximize the benefit, i.e., the number of users that communicate without signal interference. We consider cellular networks of reuse distance k ≥ 2 and we study the online version of the problem using competitive analysis. In cellular networks of reuse distance 2, the previously best known algorithm that beats the lower bound of 3 on the competitiveness of deterministic algorithms, works on networks with one frequency, achieves a competitive ratio against oblivious adversaries, which is between 2.469 and 2.651, and uses a number of random bits at least proportional to the size of the network. We significantly improve this result by presenting a series of simple randomized algorithms that have competitive ratios significantly smaller than 3, work on networks with arbitrarily many frequencies, and use only a constant number of random bits or a comparable weak random source. The best competitiveness upper bound we obtain is 16/7 using only four random bits. In cellular networks of reuse distance k> 2, we present simple randomized online call control algorithms with competitive ratios, which significantly beat the lower bounds on the competitiveness of deterministic ones and use only O(log k) random bits. Also, we show new lower bounds on the competitiveness of online call control algorithms in cellular networks of any reuse distance. In particular, we show that no online algorithm can achieve competitive ratio better than 2, 25/12, and 2.5, in cellular networks with reuse distance k ε {2, 3, 4}, k = 5, and k ≥ 6, respectively. © 2008 Wiley Periodicals, Inc. NETWORKS, 2008
Higher‐order beam analysis of box beams connected at angled joints subject to out‐of‐plane bending and torsion
Authors: Jang Gang‐Won , Kim Kyung Joo , Kim Yoon Young
Published: February 2008

The difficulty in the analysis of thin‐walled beams by a beam theory comes from slowly decaying end effects associated with warping and distortion. However, a beam theory without considering such effects yields inaccurate solutions especially near beam ends. Numerical analysis using a higher‐order beam theory capable of representing such effects is now available, but the analysis of a series of box beams connected by angled joints still remains an unsolved problem because of the lack of a matching condition at the joint. The objectives of this investigation are to develop a field‐variable‐matching technique at an angled joint through a higher‐order beam theory and to implement it in the finite element formulation. Thin‐walled box beams in consideration are assumed to be subject to out‐of‐plane bending and torsion. Thus, the minimization of three‐dimensional displacement mismatch is used to relate the field variables at a joint intersection. The minimization condition turns out to represent coupling effects of different deformation kinematics such as torsion, bending, distortion and warping. Point‐wise displacement matching is not possible with a higher‐order beam theory. The validity of the proposed technique was verified by a finite element analysis using two‐node higher‐order beam elements applied to some benchmark problems. Copyright © 2008 John Wiley & Sons, Ltd.
A new stabilized finite element method for reaction–diffusion problems: The source‐stabilized Petrov–Galerkin method
Authors: Ilinca F. , Hétu J.‐F.
Published: February 2008

This paper proposes a new stabilized finite element method to solve singular diffusion problems described by the modified Helmholtz operator. The Galerkin method is known to produce spurious oscillations for low diffusion and various alternatives were proposed to improve the accuracy of the solution. The mostly used methods are the well‐known Galerkin least squares and Galerkin gradient least squares (GGLS). The GGLS method yields the exact nodal solution in the one‐dimensional case and for a uniform mesh. However, the behavior of the method deteriorates slightly in the multi‐dimensional case and for non‐uniform meshes. In this work we propose a new stabilized finite element method that leads to improved accuracy for multi‐dimensional problems. For the one‐dimensional case, the new method leads to the same results as the GGLS method and hence provides exact nodal solutions to the problem on uniform meshes. The proposed method is a Galerkin discretization used to solve a modified equation that includes a term depending on the gradient of the original partial differential equation. Copyright © 2008 John Wiley & Sons, Ltd.
Reduced occurrence of childhood cancer in twins compared to singletons: Protection but by what mechanism?
Authors: Murphy M.F.G. , Bunch K.J. , Chen B. , Hemminki K.
Published: February 2008

Background

Several small studies combined have suggested that twins develop fewer childhood cancers than singletons. The national Swedish Family‐Cancer Database contains information on a large population of multiple births providing an unbiased dataset for the estimation of cancer risk in twins. Lifelong cancer incidence in these twins has already been reported as similar to that in singleton births. In contrast, the present paper presents robust estimates of a significantly reduced childhood cancer risk in twins to age 15.

Methods

Standardised incidence ratios (SIR) were used to measure cancer risk for twins, taking the corresponding rates for singletons as reference. Rates were adjusted for age, sex, period of birth, and residential area. Follow up data cover the period 1958–2002.

Results

Overall childhood cancer risk was significantly reduced in all twins (SIR 0.81 [95% CI: 0.69–0.94]) as was the risk for Wilms tumour (SIR 0.34 [95% CI: 0.09–0.88]). These significant reductions in risk were both driven by effects in same sex twins (overall cancer SIR 0.77 [95% CI: 0.64–0.93], Wilms tumour 0.12 [95% CI: 0.00–0.71]). Leukaemia risk was also significantly reduced for same sex twins (SIR 0.69 [95% CI: 0.47–0.97]).

Conclusions

Our study provides the evidence that twins experience less childhood cancer than singletons. The risk reduction is most marked for Wilms tumour but may, to a varying extent, be true for a number of childhood neoplasms. Pediatr Blood Cancer 2008;51:62–65. © 2008 Wiley‐Liss, Inc.
Improved survival for children with parameningeal rhabdomyosarcoma: Results from the AIEOP soft tissue sarcoma committee
Authors: Bisogno Gianni , De Rossi Costanza , Gamboa Yéssika , Sotti Guido , Ferrari Andrea , Dallorso Sandro , Donfrancesco Alberto , Cecchetto Giovanni , Calderone Milena , Gandola Lorenza , Rosolen Angelo , Carli Modesto
Published: February 2008

Background

Parameningeal rhabdomyosarcoma (PM‐RMS) is a rare, highly malignant pediatric tumor arising from locations adjacent to the meninges, from where it can spread intracranially.

Procedure

We reviewed 109 children with non‐metastatic PM‐RMS enrolled in the Italian RMS79, RMS88 and RMS96 protocols over a 24‐year period. All patients received intensive chemotherapy and standard or hyperfractionated and accelerated radiotherapy. Some had delayed surgery.

Results

Five‐year overall survival rose from 40% in the RMS79 to 72% in the RMS88 and RMS96 protocols (P = 0.01), where more intensive chemotherapy and hyperfractionated accelerated radiotherapy (HART) was used. Delayed surgery after initial treatment was statistically associated with a better prognosis. Unfavorable tumor characteristics for RMS arising in other sites, for example, histology, invasiveness or node involvement, did not predict outcome for PM‐RMS.

Conclusion

Outcome in PM‐RMS patients enrolled in three consecutive Italian protocols has progressively improved, as a result of intensive chemotherapy, delayed surgery and, possibly, HART, though improved imaging and radiotherapeutic tools may have had a role as well. Pediatr Blood Cancer 2008;50:1154–1158. © 2008 Wiley‐Liss, Inc.
Non‐anaplastic peripheral t‐cell lymphoma in childhood and adolescence: A Children's Oncology Group study
Authors: Hutchison Robert E. , Laver Joseph H. , Chang Myron , Muzzafar Tariq , Desai Sunil , Murphy Sharon , Schwenn Molly , Shuster Jonathan , Link Michael P.
Published: February 2008

Background

Peripheral T‐cell lymphomas (PTCL) other than anaplastic large cell lymphoma (ALCL) are rare in young patients. While a high proportion of adults with PTCL have poor risk disease, pediatric PTCL is not well characterized. This study examines the outcome of localized and advanced PTCL in pediatric patients treated in standardized fashion.

Procedure

We identified 20 pediatric patients diagnosed with PTCL whose tumor cells did not express CD30 and/or ALK, as determined by immunohistochemistry, between 1992 and 2000 on one of two treatment protocols for localized NHL (POG 9219) or advanced stage large cell lymphoma (POG 9315). All cases were centrally reviewed.

Results

The median age was 12.6 (range 0.7–16.9)—9 male and 11 female. Histological subtypes in the WHO Classification included PTCL, unspecified (12), extra‐nodal NK/T‐cell lymphoma of nasal type (4), subcutaneous panniculitis‐like T cell lymphoma (1) and enteropathy‐type T‐cell lymphoma (1). Two cases exhibited both T‐cell and histiocyte markers and were reclassified as histiocytic sarcoma per the WHO, although T‐lineage remains possible. Of 10 patients with localized disease, only two relapsed and 9 survive. Of 10 patients with advanced disease, six relapsed and five (50%) survive.

Conclusions

These results suggest that localized PTCL in children and adolescents is frequently cured with modern therapy, but that advanced stage cases may require novel therapy. Pediatr Blood Cancer 2008;51:29–33. © 2008 Wiley‐Liss, Inc.
Current awareness: Pharmacoepidemiology and drug safety
Authors:   John Wiley & Sons, Ltd.
Published: February 2008

In order to keep subscribers up‐to‐date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of pharmacoepidemiology and drug safety. Each bibliography is divided into 20 sections: 1 Reviews; 2 General; 3 Anti‐infective Agents; 4 Cardiovascular System Agents; 5 CNS Depressive Agents; 6 Non‐steroidal Anti‐inflammatory Agents; 7 CNS Agents; 8 Anti‐neoplastic Agents; 9 Haematological Agents; 10 Neuroregulator‐Blocking Agents; 11 Dermatological Agents; 12 Immunosuppressive Agents; 13 Autonomic Agents; 14 Respiratory System Agents; 15 Neuromuscular Agents; 16 Reproductive System Agents; 17 Gastrointestinal System Agents; 18 Anti‐inflammatory Agents ‐ Steroidal; 19 Teratogens/fetal exposure; 20 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted.
A comparative study of dispersing a polyamide 6 into a polypropylene melt in a Buss Kneader, continuous mixer, and modular intermeshing corotating and counter‐rotating twin screw extruders
Authors: Shon Keungjin , Bumm Sug Hun , White James L.
Published: February 2008

We have made a study of the development of phase morphology of an immiscible blend(75/25)(polypropylene–polyamide‐6) for different types of continuous mixers including (i) Buss Kneader, (ii and iii) modular intermeshing corotating and counter‐rotating twin screw extruders, and (iv) NEX‐T Kobelco Continuous Mixer. Comparisons are made using different screw configurations for each machine. Generally, in comparison of the different machines, the intermeshing counter‐rotating twin screw extruder produced the finest dispersed morphology. Using a droplet breakup kinetic model, we interpreted the blend dispersed phase droplet breakdown rate and coalescence rate. In comparison with our earlier study of the continuous mixing of agglomerates of CaCO3 particles the polymer droplet breakup rate was smaller than that of the particle agglomerates and the coalescence rates of droplets were many times greater than the particle reagglomerates rates. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Calculation and significance of the maximum polymer surface temperature T* in reciprocating cylinder‐on‐plate sliding
Authors: Samyn Pieter , Schoukens Gustaaf
Published: February 2008

Heat generation and surface temperature rise are the main parameters controlling friction and wear of polymers, while certain transitions in sliding behavior often are difficultly related to intrinsic polymer transition temperatures. The sliding temperature cannot be accurately measured through physical limitations in the contact interface, and different calculation methods are available. Some temperature models are reviewed and applied to the reciprocating sliding of polyimide (PI) and polyethylene terephthalate against a steel counterface. The bulk temperature and asperity flash temperature models cannot explain transitions in friction and wear for polymers under reciprocating sliding. The bulk temperature model provides too low temperatures, representing a long‐range temperature, while the asperity flash temperature model provides too high temperatures, not considering visco‐elastic deformation of the polymer surface. An experimental model for the maximum polymer surface temperature T* under reciprocating sliding is developed, considering the environmental temperature, gradual heating of the steel counterface, and additional heating of the polymer surface. The proposed temperature model is analytically validated by differential thermal analysis and thermogravimetric analysis. Transitions in tribological behavior are controlled by the maximum polymer surface temperature T*, coinciding with an endotherm reaction (PIs) or a glass transition and melting (polyethylene terephthalate). POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
In‐line measurements of the morphological parameters of PP/PA6 blends during extrusion in the transient mode
Authors: Pinheiro Luís A. , Hu Guo‐H. , Pessan Luiz A. , Canevarolo Sebastião V.
Published: February 2008

The real‐time measurement of the morphology of immiscible polymer blends based on polypropylene (PP) and polyamide 6 (PA6) was performed during melt blending in a twin‐screw extruder. The disperse phase particle size and concentration were obtained in‐line with an optical device placed at the die exit. To validate the response of the optical device, its detector was calibrated in advance in a bench using ceramic particles of well‐controlled size dispersed in water. The optical device was able to measure the changes in particle size and concentration and the data enabled the calculation of the particle extinction cross section. Melt blending experiments in the extruder were performed in a transient mode, where a small amount of the material was added as a pulse to the main melt flow. The pulses containing pellets of the PA6 and polypropylene grafted with acrylic acid (PP‐g‐AA) were added to the PP flow stream in different amounts. The detector's response increased with increasing concentrations in the PA6 and PP‐g‐AA. The disperse phase particle size decreased concomitantly because of the compatibilizing effect of the PP‐g‐AA on the PP/PA6 immiscible blend. That observation confirmed that the detector's response was directly related to the disperse phase particle size. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Das Rijke‐Rohr. Physikdidaktik
Authors: Bergeler Elmar
Published: February 2008

Das Rijke‐Rohr ist ein eindrucksvolles Freihandexperiment zur Veranschaulichung akustischer Resonatoren. Es besteht aus einem Glasrohr, in dessen unterer Hälfte ein Metallsieb angebracht ist. Wird dieses erhitzt und von der Flamme entfernt, so ertönt ein lautstarkes Orgelpfeifen. Ursache ist die Übertragung von thermischer Energie auf die sich in dem Rohr befindende Luft. Diese wird unter bestimmten Voraussetzungen zu akustisch wahrnehmbaren Schwingungen angeregt. Die Frequenzen der Schwingungen sind durch die Eigenfrequenzen der eingeschlossenen Luftsäule gegeben.
Quantenpunkte als Photonenquellen. Photonische Kristalle
Authors: Stumpf Wolfgang
Published: February 2008

Quantenpunkte in Nanoresonatoren sind Lichtquellen mit bestechenden Eigenschaften. Sie können als winzige Laser arbeiten, deren Laserschwelle extrem niedrig liegt. Nanoresonatoren und andere Licht leitende und steuernde Bauelemente lassen sich über photonische Kristalle realisieren. Quantenpunkte in Nanoresonatoren bieten der optischen Kommunikationstechnik eine interessante Zukunftsperspektive. Sie könnten eine extrem schnelle Schnittstelle zwischen optischer Datenübertragung und Elektronik bilden. Zudem könnten Nanoresonatoren hoher Güte, kombiniert mit Quantenpunkten, zukünftig als Quelle einzelner, ununterscheidbarer Photonen in der Quanteninformationsverarbeitung dienen.
Die Suche nach dem Absoluten. Zum 150. Geburtstag von Max Planck
Authors: Jacobi Manfred
Published: February 2008

In diesem Jahr jährt sich der Geburtstag von Max Planck zum 150. Mal. Als Schöpfer der Quantentheorie und als unermüdlicher Wissenschaftsorganisator verkörpert er eine einzigartige Persönlichkeit der Physikgeschichte. Als Physiker und als Mensch stand Planck an der Schwelle zum Übergang in ein neues Zeitalter.
Magnetismus mit Dreh. Spinspiralen an Oberflächen
Authors: von Bergmann Kirsten , Bode Matthias , Wiesendanger Roland
Published: February 2008

Nach der Theorie sind magnetische Spiralen auf atomarer Ebene möglich, die nur rechts‐ oder nur linksdrehend sind. Für den bevorzugten Drehsinn kann die sogenannte Dzyaloshinskii‐Moriya‐(DM)‐Wechselwirkung sorgen. Dazu muss sie stark genug sein, zudem darf das Gesamtsystem keine Inversionssymmetrie besitzen. Die DM‐Wechselwirkung beeinflusst den antiferromagnetischen Grundzustand so, dass die Spins sich nicht antiparallel ausrichten, sondern eine Spinspirale bilden. Eine solche Spirale wurde nun das erste Mal an einer Oberfläche nachgewiesen, die allein durch ihr Vorhandensein die Inversionssymmetrie bricht. Das Experiment wurde an einer atomar dünnen Manganschicht auf einem unmagnetischen Wolfram‐Substrat durchgeführt. Der Effekt könnte in der Spintronik Anwendung finden.
Ketchup – frisch gestrichen
Authors: Vilgis Thomas
Published: February 2008

Selbst die Currywurst an der Imbissbude inspiriert zu physikalisch orientierten Kreationen, vor allem das über die Wurst geschwappte Ketchup. Denn diese profane Tomatensauce ist ein willkommenes Studienobjekt für ganz besondere Fließeigenschaften. Entgegen ausgetretenen Pfaden bereiten wir heute grünes “Ketchup” aus Cornichons, die französische Variante der Essiggürkchen. Das Problem dabei ist, die Fließeigenschaften, fest in Ruhe, flüssig unter Scherkräften, genau einzustellen.
Monsterwellen aus Licht
Authors: Solli Daniel R. , Jalali Bahram , Ropers Claus
Published: February 2008

Seit Jahrhunderten berichten Seefahrer von gigantischen Wellen, die scheinbar aus dem Nichts und ohne Vorwarnung auftauchen. Erst Mitte der 1990er‐Jahre hat sich die Erkenntnis durchgesetzt, dass es sie wirklich gibt und sie für eine größere Zahl katastrophaler Schiffsunglücke verantwortlich waren. In Experimenten an der University of California in Los Angeles haben wir vor kurzem überraschenderweise in Lichtleitfasern Monsterwellen aus Licht nachgewiesen. Ursache hierfür ist eine Nichtlinearität der Faser.
Grüße vom Merkur
Authors: Bührke Thomas
Published: February 2008

Am 14. Januar flog die amerikanische Raumsonde Messenger am sonnennächsten Planeten Merkur vorbei. Dabei näherte sie sich bis auf 200 Kilometer der Oberfläche. Es ist der erste Besuch einer Sonde seit den Vorbeiflügen von Mariner 10 Mitte der 1970er Jahre. Sieben wissenschaftliche Instrumente sammelten bei diesem Vorbeiflug Messdaten, und eine Kamera funkte mehr als 12000 Aufnahmen zur Erde. Sie zeigen eine von Kratern zerklüftete Oberfläche, die auf den ersten Blick an die des Mondes erinnert. Doch in mancherlei Hinsicht unterscheidet sich Merkur von dem Erdtrabanten.
Die Welt hinter den Spiegeln
Authors: Schlichting H. Joachim
Published: February 2008

Real‐ und Spiegelwelt sind normalerweise gut auseinander zu halten. Doch manchmal kann ein ungewöhnlicher Kontext zu irritierenden Situationen führen.
Kann man die chinesische Mauer vom Mond aus sehen?
Authors: Müller Andreas
Published: February 2008

Der italienische Physiker Enrico Fermi war berühmt für seine Fähigkeit, eine komplexe Fragestellung auf das Wesentliche zu reduzieren und größenordnungsmäßig zu lösen. Bis heute sind Fermi‐Fragen und Fermi‐Lösungen eine beliebte Möglichkeit, um physikalische Vorgänge im Alltag oder auch fundamentale Fragestellungen zu klären. Mit der neuen Serie Fermis Corner wollen wir diese Kunst fortführen.
A template‐finding algorithm and a comprehensive benchmark for homology modeling of proteins
Authors: Vallat Brinda Kizhakke , Pillardy Jaroslaw , Elber Ron
Published: February 2008

The first step in homology modeling is to identify a template protein for the target sequence. The template structure is used in later phases of the calculation to construct an atomically detailed model for the target. We have built from the Protein Data Bank (PDB) a large‐scale learning set that includes tens of millions of pair matches that can be either a true template or a false one. Discriminatory learning (learning from positive and negative examples) is used to train a decision tree. Each branch of the tree is a mathematical programming model. The decision tree is tested on an independent set from PDB entries and on the sequences of CASP7. It provides significant enrichment of true templates (between 50 and 100%) when compared to PSI‐BLAST. The model is further verified by building atomically detailed structures for each of the tentative true templates with modeller. The probability that a true match does not yield an acceptable structural model (within 6 Å RMSD from the native structure) decays linearly as a function of the TM structural‐alignment score. Proteins 2008. © 2008 Wiley‐Liss, Inc.
An integrated approach to inferring gene–disease associations in humans
Authors: Radivojac Predrag , Peng Kang , Clark Wyatt T. , Peters Brandon J. , Mohan Amrita , Boyle Sean M. , Mooney Sean D.
Published: February 2008

One of the most important tasks of modern bioinformatics is the development of computational tools that can be used to understand and treat human disease. To date, a variety of methods have been explored and algorithms for candidate gene prioritization are gaining in their usefulness. Here, we propose an algorithm for detecting gene–disease associations based on the human protein–protein interaction network, known gene–disease associations, protein sequence, and protein functional information at the molecular level. Our method, PhenoPred, is supervised: first, we mapped each gene/protein onto the spaces of disease and functional terms based on distance to all annotated proteins in the protein interaction network. We also encoded sequence, function, physicochemical, and predicted structural properties, such as secondary structure and flexibility. We then trained support vector machines to detect gene–disease associations for a number of terms in Disease Ontology and provided evidence that, despite the noise/incompleteness of experimental data and unfinished ontology of diseases, identification of candidate genes can be successful even when a large number of candidate disease terms are predicted on simultaneously. Availability: www.phenopred.org. Proteins 2008. © 2008 Wiley‐Liss, Inc.
fRMSDPred: Predicting local RMSD between structural fragments using sequence information
Authors: Rangwala Huzefa , Karypis George
Published: February 2008

The effectiveness of comparative modeling approaches for protein structure prediction can be substantially improved by incorporating predicted structural information in the initial sequence‐structure alignment. Motivated by the approaches used to align protein structures, this article focuses on developing machine learning approaches for estimating the RMSD value of a pair of protein fragments. These estimated fragment‐level RMSD values can be used to construct the alignment, assess the quality of an alignment, and identify high‐quality alignment segments. We present algorithms to solve this fragment‐level RMSD prediction problem using a supervised learning framework based on support vector regression and classification that incorporates protein profiles, predicted secondary structure, effective information encoding schemes, and novel second‐order pairwise exponential kernel functions. Our comprehensive empirical study shows superior results compared with the profile‐to‐profile scoring schemes. We also show that for protein pairs with low sequence similarity (less than 12% sequence identity) these new local structural features alone or in conjunction with profile‐based information lead to alignments that are considerably accurate than those obtained by schemes that use only profile and/or predicted secondary structure information. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Thermal‐prehistory dependence of the phase stability in the structural phase transitions of Na2SO4 crystal
Authors: Choi Byoung‐Koo
Published: February 2008

After as‐grown Na2SO4 (V) crystal is transformed to high‐temperature phase (I), the transition sequence is I → II → III on cooling and III → I on reheating scan. The intermediate phase II occurs within a very narrow temperature range of 2–3 °C and the transition temperature of II → III has been known to be much reduced during subsequent cooling scans. Here, we found that all the transitions I → II → III as well as III → I depend greatly on the thermal prehistory. This is possibly related to an incompleteness of the transition from phase V to I near 240 °C. We also found that if the Na2SO4 (I), which is just transformed from the phase V, is heated above 600 °C, then all the peculiarities on transitions surprisingly disappear. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Atomistic force field and electronic properties of carbazole: from monomer to macrocycle
Authors: Vehoff Thorsten , Kirkpatrick James , Kremer Kurt , Andrienko Denis
Published: February 2008

An atomistic force‐field is developed for carbazole monomers, oligomers, and alkyne‐substituted polymers. This force‐field can be used to study the morphology of stacks of carbazole macrocycles. Charge transport of macrocycles in columnar arrangement is analyzed using non‐adiabatic high‐temperature Marcus theory. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton dephasing in quantum dots: Coupling to LO phonons via excited states
Authors: Muljarov E. A. , Zimmermann R.
Published: February 2008

We have found a novel mechanism of spectral broadening and dephasing in quantum dots (QDs) due to the coupling to longitudinal‐optical (LO) phonons. In theory, this mechanism comes into play only if the complete manifold of exciton levels (including those in the wetting‐layer continuum) is taken into account. We demonstrate this nontrivial dephasing in different types of QDs, using the exactly solvable quadratic coupling model, here generalized to an arbitrary number of excitonic states. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tyrosinase‐catalysed grafting of food‐grade gallates to chitosan: surface properties of novel functional coatings
Authors: Vartiainen Jari , Rättö Marjaana , Lantto Raija , Nättinen Kalle , Hurme Eero
Published: February 2008

Plasma‐activated biaxially oriented polypropylene (BOPP) films and paper substrate have been coated with functional chitosan solutions. Plasma treatment increased the amount of surface peroxide groups and carboxyl groups on the BOPP films. As a result of plasma activation, the surface energy increased from 30 to 50 dynes/cm. The enzyme tyrosinase catalysed the grafting of octyl gallate and dodecyl gallate to amino groups of chitosan polysaccharide. Resulting coatings exhibited strong antimicrobial activity against Gram‐positive Staphylococcus aureus and Gram‐negative Listeria innocua. After 24 h of incubation, a total reduction in both bacteria cell numbers varied between >4.9 and 1.4 logarithmic units. Grafted dodecyl gallate and octyl gallate at pH 6 were found to have the lowest reduction values of <3 logarithmic units for S. aureus, while 1.4 logarithmic reduction value was obtained for grafted dodecyl gallate at pH 6 against L. innocua. Chitosan coatings were also effective barrier layers against oxygen transmission although the transmission rates clearly increased in high‐humidity conditions. In dry conditions, however, the transmission rate of 2 cm3/(m2 · 24 h) was obtained with chitosan‐coated BOPP. Coatings did not have any effects on water vapour transmission. Both gallates were successfully grafted at pH 6. As increased flocculation and colour formation indicated, the tyrosinase‐catalysed grafting was more powerful with octyl gallate. Dodecyl gallate containing chitosan coatings was more hydrophobic as compared to octyl gallate. Total migration of substances into 95% ethanol was ≥5 mg/dm2, thus materials may be exploitable in packaging purposes in direct contact with certain foodstuffs. Copyright © 2008 John Wiley & Sons, Ltd.
Spatial distribution of cloud cover
Authors: Garcia Pedro , Benarroch Ana , Riera Jose Manuel
Published: February 2008

Satellite systems and high‐altitude platform systems working in Ka and V bands require the application of adaptive techniques in order to mitigate link degradations caused by atmospheric impairments such as those due to cloud cover. Among these techniques, resource sharing system techniques and site diversity need information on the spatial distribution of impairments caused by cloud cover, including the probability of simultaneous occurrence of adverse conditions in various regions.

A study has been performed in Spain, within the framework of COST Action 280, to investigate the large‐scale spatial distribution of cloud cover using synoptic meteorological data. Cloud cover distribution for individual sites and the spatial correlation properties for pairs of sites have been investigated. The geographical distributions of the values obtained from the statistical analysis have been represented in maps of contour lines using standard mapping procedures. Correlation parameters are expected to decrease with distance; however, the maps derived taking a given site as reference reveal a significant influence of climatic and geographic factors such as weather fronts, orography or the proximity to the sea. The statistics and maps obtained can be useful to optimize power sharing in multi‐beam satellite systems, as suggested in this paper. Copyright © 2008 John Wiley & Sons, Ltd.
Channel estimation and physical layer adaptation techniques for satellite networks exploiting adaptive coding and modulation
Authors: Cioni Stefano , De Gaudenzi Riccardo , Rinaldo Rita
Published: February 2008

The exploitation of adaptive coding and modulation techniques for broadband multi‐beam satellite communication networks operating at Ka‐band and above has been shown to theoretically provide large system capacity gains. In this paper, the problem of how to accurately estimate the time‐variant channel and how to adapt the physical layer taking into account the effects of estimator errors and (large) satellite propagation delays is analyzed, and practical solutions for both the forward and the reverse link are proposed. A novel pragmatic solution to the reverse link physical layer channel estimation in the presence of time‐variant bursty interference has been devised. Physical layer adaptation algorithms jointly with design rules for hysteresis thresholds have been analytically derived. The imperfect physical layer channel estimation impact on the overall system capacity has been finally derived by means of an original semi‐analytical approach. Through comprehensive system simulations for a realistic system study case, it is showed that the devised adaptation algorithms are able to successfully track critical Ka‐band fading time series with a limited impact on the system capacity while satisfying the link outage probability requirement. Copyright © 2008 John Wiley & Sons, Ltd.
Learning to read scientific text: Do elementary school commercial reading programs help?
Authors: Norris Stephen P. , Phillips Linda M. , Smith Martha L. , Guilbert Sandra M. , Stange Donita M. , Baker Jeff J. , Weber Andrea C.
Published: February 2008

This paper describes a comprehensive set of studies designed to assess the potential for commercial reading programs to teach reading in science. Specific questions focus on the proportion of selections in the programs that contain science and the amount of science that is in those selections, on the genres in which the science is portrayed, on the areas and topics of science covered, on the accuracy of the scientific content, on the text features used to communicate the science, and on the instructional strategies and assessment techniques recommended. The findings show that commercial reading programs have changed substantially from the days when they were dominated by literary texts and contained hardly any science. Now, there is a variety of genres and scientific content in about one fifth of the selections. The content is also generally accurate. So, there is considerable potential offered by these programs for teaching children to read science. Unfortunately, the findings also show that the recommended instructional strategies and assessment techniques do little to capitalize upon this potential. In particular, the findings demonstrate that, although most of the science is cast in the expository genre, most of the recommended instruction and assessment is more appropriate to the literary genres. © 2008 Wiley Periodicals, Inc.Sci Ed92:765–798, 2008