bluuebunny/crossref_metadata_2025 huggingface dataset:
Toward reliable calculations of heat and plastic flow during friction stir welding of Ti-6Al-4V alloy
Authors: Nandan R. , Lienert T. J. , DebRoy T.
Published: April 2008

Heat transfer and visco-plastic flow during friction stir welding of Ti-6Al-4V alloy have been modeled in three dimensions by numerically solving the equations of conservation of mass, momentum and energy using temperature dependent thermo-physical properties and temperature and strain-rate dependent viscosity values. The computed results showed that five important model parameters, i. e., the spatially variable friction coefficient, the spatially variable slip between the tool and the workpiece, the extent of viscous dissipation, the mechanical efficiency and the spatially variable heat transfer rate from the bottom surface of the workpiece significantly affected both the temperature fields and the computed torque on the tool. An important problem in the modeling of friction stir welding is that the values of these five parameters cannot be specified from fundamental principles and, and as a result, computed results are not always accurate. Here we show that by combining the heat transfer and plastic flow model with a genetic algorithm based optimization scheme, the values of the five uncertain parameters can be determined from a limited volume of experimental data so that the model predictions of peak temperatures and cooling rates match well with the experimental results. The computed results show that for the welding conditions reported in this paper, close to sticking condition prevailed at the tool – workpiece interface for all the experiments. The extent of viscous dissipation converted to heat was fairly low indicating lack of intimate atomic mixing in the stir zone. Computed three dimensional pressure distributions and streamlines were consistent with defect-free reliable welds for all conditions of welding studied.
Effect of lianas on tree regeneration in gaps and forest understorey in a tropical forest in Ghana
Authors: Toledo‐Aceves T. , Swaine M.D.
Published: April 2008

Questions:

Do lianas alter the relative success of tree species during regeneration? Are the effects of lianas on tree seedlings moderated by canopy openness? How are patterns of biomass allocation in tree seedlings affected by liana competition?

Location:

Tropical moist semi‐deciduous forest in Ghana.

Methods:

Seedlings of the treesNauclea diderrichii(pioneer),Khaya anthotheca(non‐pioneer light demander) andGarcinia kola(non‐pioneer shade bearer) were planted with the lianasAcacia kamerunensis(fast growing) andLoeseneriella rowlandii(slow growing) in large and small gaps (ca. 15% and 8% PAR respectively) and in the forest understorey (ca. 4% PAR). Seedling survival, growth and biomass allocation were measured.

Results:

Canopy openness moderated the interaction between liana and tree seedlings. The nature of the interaction was both liana and tree species specific and displayed temporal variation.Acaciacompetition effects were stronger in sites with greater canopy openness. In big gaps,Acaciareduced significantly the biomass ofNaucleaby 32% andKhayaby about 50%.Khayagrowth in leaf area was five times greater withoutAcacia, whileNaucleaandGarciniawere not affected.Acaciawas more plastic thanLoeseneriellain response to the environment and the tree species. Our results show that whileLoeseneriella, with lower rates of growth, did not affect seedling growth of the three species evaluated,Acaciacould alter the relative success of tree species during regeneration.

Conclusions:

There is evidence that competitive effects byAcaciaon tree regeneration through competition could modify tree species capacity to establish. Effects by lianas at the regeneration phase may have important implications for forest management.
Silver Nanoparticle Impregnated Polycarbonate Substrates for Surface Enhanced Raman Spectroscopy
Authors: Hasell T. , Lagonigro L. , Peacock A. C. , Yoda S. , Brown P. D. , Sazio P. J. A. , Howdle S. M.
Published: April 2008

The embedding of nanoscopic metal structures into polymeric matrices represents a convenient way to stabilise a controlled dispersion of protected nanoparticles whilst taking advantage of their physical characteristics. Supercritical carbon dioxide (scCO2) has been used to produce silver nanoparticles in optically transparent polycarbonate (PC) matrices allowing fine scale dispersions of particles to be produced within a prefabricated polymer component. Characterization of these nanocomposites has been performed using transmission electron microscopy (TEM) and UV‐vis spectroscopy. The substrates give excellent responses in surface‐enhanced Raman spectroscopy (SERS) for both 4‐aminothiophenol and rhodamine 6G target molecules. They offer significant benefits over more conventional SERS substrates in that they are cheap, flexible, mechanically robust and temporally stable. Post‐processing the films via simple etching techniques, provides an additional degree of design control and the potential to fabricate devices with unique excitation and detection geometries for a wide range of applications.
Controlling the Optical Properties of Inorganic Nanoparticles
Authors: Scholes Gregory D.
Published: April 2008

The sophistication with which we can now prepare and characterize inorganic nanoparticles has inspired new areas of research into the fundamental properties and applications of these fascinating nanoscale systems. In this article some of the recent ideas concerning control of their optical properties are examined and explained, focusing on semiconductor nanocrystals. It is known that the optical properties of nanocrystals can be size‐tunable, but it is less obvious how shape matters. To explain how size as well as shape matters, the electronic structure of nanocrystals is sketched in relatively simple terms, leading to an introduction to deeper concepts at the heart of spectroscopy such as the exciton fine structure. The exciton fine structure states, although obscured by inhomogeneous line broadening, dictate selection rules for optical excitation. These viewpoints are compared and contrasted to well‐established principles in molecular spectroscopy that provide inspiration as well as perspective. The control of optical poperties is founded on our ability to prepare good quality colloidal particles. Recent advances in nanocrystal shape control are described. The current status of heterostructures is examined, with an emphasis on charge separation in CdSe–CdTe nanorods.
Membrane‐Occluded Gold‐Palladium Nanoclusters as Heterogeneous Catalysts for the Selective Oxidation of Alcohols to Carbonyl Compounds
Authors: Mertens P. G. N. , Vandezande P. , Ye X. , Poelman H. , De Vos D. E. , Vankelecom I. F. J.
Published: April 2008

Pre‐formed polyvinylpyrrolidone‐stabilized gold‐palladium clusters, consisting of 80 mol% gold and with a mean size of 1.9 nm, were immobilized quantitatively in a porous polyimide membrane via the process of phase inversion, without loss of metal nanodispersion. The obtained gold‐palladium/polyimide membrane emerged as a highly active heterogeneous metal catalyst for the amide‐phase and solvent‐free oxidation of aliphatic, allylic and benzylic alcohols with full selectivity to the corresponding aldehydes and ketones, and could be recycled with excellently preserved catalytic activity and product selectivity. Occlusion of the optimized bimetallic clusters in the polyimide structure proved beneficial in view of their superior catalytic performance compared to the analogous colloidal gold‐palladium clusters.
Design of advanced PID controller for enhanced disturbance rejection of second‐order processes with time delay
Authors: Shamsuzzoha M. , Lee Moonyong
Published: April 2008

A design method for a proportional‐integral‐derivative (PID) cascaded with a lead‐lag compensator is proposed for enhanced disturbance rejection of the second‐order stable and unstable processes with time delay. A two‐degree‐of‐freedom control scheme is used to cope with both regulatory and servo problems. An ideal feedback controller equivalent to internal model control (IMC) is obtained through the IMC design principle, and is further simplified to the PID cascaded with a first‐order lead‐lag compensator. The simulation is conducted for a broad class of stable and unstable processes and the results are compared with those of recently published PID type controllers to illustrate the superiority of the proposed controller. For a reasonable comparison, the controllers in the simulation study are tuned to have the same degree of robustness by measuring the maximum sensitivity, Ms. The robustness of the controller is also investigated by simultaneously inserting a perturbation uncertainty in all parameters in order to obtain the worst‐case model mismatch. The proposed method illustrates greater robustness against process parameter uncertainty. © 2008 American Institute of Chemical Engineers AIChE J, 2008
Growth charts for patients affected with Morquio A disease
Authors: Montaño Adriana M. , Tomatsu Shunji , Brusius Ana , Smith Mary , Orii Tadao
Published: April 2008

Children with Morquio A disease grow poorly and become physically handicapped because of systemic bone disease. The purpose of this study was to describe observed growth patterns and their relationship with the physical condition of patients with Morquio A. In a one‐center study, questionnaire‐based longitudinal and cross sectional data were used to develop growth curves, to assess physical activity and to determine the incidence of surgical procedures in 354 patients with Morquio A. Mean birth lengths of boys and girls were 52.6 and 52.1 cm, respectively. The mean final heights for males and females at 18 years and older were 122.4 ± 21.5 and 113.1 ± 22.6 cm, respectively. These results corresponded to −7.4 SD for males and −7.7 SD for females compared to the normal healthy controls. Mean birth weights for boys and girls were 3.59 ± 0.58 and 3.5 ± 0.7 kg, respectively. The mean body mass index for males and females at over 18 years of age was 24.7 ± 6.1 and 25.6 ± 5.4 kg/m2, respectively. The growth pattern in Morquio A patients was characterized by impaired growth velocity after 1 year of age. This is the first report providing growth charts for patients with Morquio A, which can help with monitoring the disease and assessing the clinical efficacy of treatments. © 2008 Wiley‐Liss, Inc.
Absence of decussation of the superior cerebellar peduncles in patients with Joubert syndrome
Authors: Spampinato M. Vittoria , Kraas Jonathan , Maria Bernard L. , Walton Zeke J. , Rumboldt Zoran
Published: April 2008

Joubert syndrome (JS) is characterized by absence of decussation of both corticospinal tracts and superior cerebellar peduncles (SCP). Our hypothesis was that evidence for absence of SCP decussation may be found on routine brain MRI studies. Midsagittal T1‐weighted images from 20 JS patients and 30 age‐matched controls were retrospectively reviewed. An ill‐defined area of lower T1 signal in the inferior midbrain was considered the sign of SCP decussation, and its presence or absence was noted. Fractional anisotropy (FA) maps were obtained in three JS patients and four controls. The SCP decussation was not visualized in any subject under 30 months of age. In subjects above 30 months of age the sign of the SCP decussation was absent in all 6 JS patients and present in all 16 controls. FA maps confirmed the absence of the SCP decussation in the JS patients. The SCP decussation is well seen on routine brain MRI studies in controls older than 30 months of age and absent in all JS patients, confirming the proposed lack of commissural fibers in JS, and accounting in part for the molar tooth sign. © 2008 Wiley‐Liss, Inc.
What is the genetic relationship between anxiety and depression?
Authors: Hettema John M.
Published: April 2008

Anxiety and depression share a long, close history in psychiatric nosology and treatment. The anxiety disorders, individually and as a group, exhibit remarkably high rates of comorbidity with each other and with major depression. Analyses done in large‐scale epidemiologic surveys have identified major patterns of phenomenological overlap between these conditions. Researchers have tested hypotheses of shared genetic etiologies as a potential basis of this relationship. In general, available family studies have found mixed evidence for co‐aggregation of anxiety and depressive disorders, while twin studies more definitively indicate that shared genetic risk factors largely account for this comorbidity. Some of this appears to be accounted for by genetic variation in personality traits that broadly predispose to anxiety and depression. Molecular genetic studies of these conditions, though too early to draw firm conclusions, thus far provide tentative support for specific genetic loci that may generally influence susceptibility across the anxiety‐depressive spectrum. © 2008 Wiley‐Liss, Inc.
Identification of neurogenetic pathways of risk for psychopathology
Authors: Fisher Patrick M. , Muñoz Karen E. , Hariri Ahmad R.
Published: April 2008

Imaging genetics has been a highly effective and increasingly applied strategy for identifying the impact of genetic polymorphisms on individual differences in neural circuitry supporting complex behaviors. The application of imaging genetics towards further elucidating neural circuitry associated with the pathophysiology of psychiatric illness is of particular interest given its potential to guide the development and improvement of current therapeutic methods. The identification of genetic variants that contribute to or predict the disruption of specific neural pathways associated with psychopathology may also serve as useful markers of risk demarcating individuals with elevated susceptibility for psychiatric illness and affording early or even preemptive treatment strategies. In the continued development of this technique, recent multimodal neuroimaging strategies and studies examining the effects of multiple genes in concert within large subject populations have shown promise in the development of a more complete understanding of the interrelationships between genes, brain function, behavior and associated risk for psychopathology. © 2008 Wiley‐Liss, Inc.
Functional imaging: I. Relative predictive value of intracranial electroencephalography
Authors: Knowlton Robert C. , Elgavish Rotem A. , Limdi Nita , Bartolucci Al , Ojha Buddhiwardhan , Blount Jeffrey , Burneo Jorge G. , Ver Hoef Lawrence , Paige Lebron , Faught Edward , Kankirawatana Pongkiat , Riley Kristen , Kuzniecky Ruben
Published: April 2008

Objective

To gain information on the predictive and prognostic value of magnetic source imaging (MSI), 2‐[18F]fluoro‐2‐deoxy‐D‐glucose positron emission tomography (18FDG‐PET), and ictal single‐photon emission computed tomography (SPECT) as compared with intracranial electroencephalography (ICEEG) localization in epilepsy surgery.

Methods

This work was part of a cohort study of epilepsy surgery candidates not sufficiently localized with noninvasive studies. Of 160 patients enrolled over 4 years, 77 completed ICEEG seizure monitoring. Sensitivity, specificity, and predictive values relative to ICEEG were computed for each modality.

Results

Seizures were not captured in five patients. Of the 72 diagnostic ICEEG studies, seizure localization results were 74% localized, 10% multifocal, and 17% nonlocalized. Sixty‐one percent were localized to neocortical regions. Depending on patient subgroup pairs, sensitivity ranged from 58 to 64% (MSI), 22 to 40% (PET), and 39 to 48% (SPECT); specificity ranges were 79 to 88% (MSI), 53 to 63% (PET), and 44 to 50% (SPECT). Gains in diagnostic yield were seen only with the combination of MSI and PET or MSI and ictal SPECT. Localization concordance with ICEEG was greatest with MSI, but a significant difference was demonstrated only between MSI and PET. Moderate redundancy was seen between PET and ictal SPECT (κ = 0.452; p = 0.011).

Interpretation

Conclusively positive MSI has a high predictive value for seizures localized with ICEEG. Diagnostic gain may be achieved with addition of either PET or ictal SPECT to MSI. Diagnostic values for imaging tests are lower than “true values” because of the limitations of ICEEG as a gold standard. Ann Neurol 2008
Analysis of Lrrk2 R1628P as a risk factor for Parkinson's disease
Authors: Ross Owen A. , Wu Yih‐Ru , Lee Mei‐Ching , Funayama Manabu , Chen Meng‐Ling , Soto Alexandra I. , Mata Ignacio F. , Lee‐Chen Guey‐Jen , Chen Chiung Mei , Tang Michelle , Zhao Yi , Hattori Nobutaka , Farrer Matthew J. , Tan Eng‐King , Wu Ruey‐Meei
Published: April 2008

Common genetic variants that increase the risk for Parkinson's disease may differentiate patient subgroups and influence future individualized therapeutic strategies. Herein we show evidence for leucine‐rich repeat kinase 2 (LRRK2) c.4883G>C (R1628P) as a risk factor in ethnic Chinese populations. A study of 1,986 individuals from 3 independent centers in Taiwan and Singapore demonstrates that Lrrk2 R1628P increases risk for Parkinson's disease (odds ratio, 1.84; 95% confidence interval, 1.20–2.83; p = 0.006). Haplotype analysis suggests an ancestral founder for carriers approximately 2,500 years ago. These findings support the importance of LRRK2 variants in sporadic Parkinson's disease. Ann Neurol 2008
Amyloids: Not Only Pathological Agents but Also Ordered Nanomaterials
Authors: Cherny Izhack , Gazit Ehud
Published: April 2008

Amyloid fibers constitute one of the most abundant and important naturally occurring self‐associated assemblies. A variety of protein and peptide molecules with various amino acid sequences form these highly stable and well‐organized assemblies under diverse conditions. These assemblies display phase states ranging from liquid crystals to rigid nanotubes. The potential applications of these supramolecular assemblies exceed those of synthetic polymers since the building blocks may introduce biological function in addition to mechanical properties. Here we review the structural characteristics of amyloidal supramolecular assemblies, their potential use as either natural or de novo designed sequences, and the range of applications that have been demonstrated so far.
NMR studies of poly(2‐hydroxy ethyl methacrylate‐co‐2‐vinyl pyridine)
Authors: Hooda Sunita , Brar A. S. , Goyal Ashok Kumar
Published: April 2008

Copolymers of 2‐hydroxy ethyl methacrylate‐2‐vinyl pyridine (H/V) of different composition were synthesized by free radical bulk polymerization using azobisisobutyronitrile (AIBN) as an initiator under nitrogen atmosphere. The copolymer compositions were calculated from 1H NMR spectra. The reactivity ratios for H/V copolymers obtained from a linear Kelen‐Tudos method (KT) and nonlinear error‐in‐variables method (EVM) are rH = 0.50 ± 0.10, rV = 1.04 ± 0.08 and rH = 0.55, rV = 1.06 respectively. The complete spectral assignment of methine, methylene, methyl, carbonyl, and aromatic carbon regions in term of compositional and configurational sequences of H/V copolymers were done with the help of 13C{1H} NMR, distortionless enhancement by polarization transfer (DEPT), two‐dimensional heteronuclear single quantum coherence (HSQC) along with total correlated spectroscopy (TOCSY). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Making polyvinyl alcohol films iodinated at solution state before casting and its application
Authors: Shin Eun Joo , Lyoo Won Seok , Lee Yang Hun
Published: April 2008

This research focused on the manufacture a polarizing film with PVA iodinated at solution before casting (IBC) film, which was prepared by casting aqueous solutions of 10 wt % poly(vinyl alcohol) (PVA) containing boric acid with 0, 0.1, 0.5, and 1.0 mol/L of I2/KI aqueous solution, and I2/KI(1:2) with 0, 5, and 10 wt % of PVA. The lights of wavelengths between 450 and 700 nm were polarized in UV analysis. The degree of polarization and transmittance of the IBC polarizing film (10 wt % I2/KI and 0.5 mol/L boric acid) are 99.9% and 43.2%, respectively. The resistance of the heat and humidity of IBC polarizing films was higher than that of commercial polarizing films, which were elucidated by changing the transmittance of the films. This can be explained by the fact that the interaction between polyiodine molecules and PVA chains as the state of IBC is higher than that of the commercial state. The effect of boric acid may be strengthened for the resistance of heat and humidity. Crosslinking by boric acid improved thermal properties of the IBC polarizing films, resulting from the increases of degradation temperature in DSC and TG analysis. And the unit cell broadening occurred, which was caused by the intrusion of boric acid into PVA chains in X‐ray analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Properties of polypropylene/layered‐silicate nanocomposites and melt‐spun fibers
Authors: Lee Seung Hwan , Youn Jae Ryoun
Published: April 2008

Polypropylene (PP)/layered‐silicate organoclay nanocomposites and their fibers were prepared by melt compounding and melt spinning, respectively, in the presence or absence of compatibilizer (PP‐based maleic anhydride compatibilizer) to examine the effects of the organoclay dispersion and rheological behavior on the internal structure and tensile properties of the nanocomposite fibers. The compatibilized nanocomposites showed solidlike plateau behavior and strain hardening due to a three‐dimensional network structure in the shear and uniaxial elongational flows. The tensile properties of the nanocomposite fibers were reduced compared with those of the pure PP fibers because some of the layered silicates were present as partially aggregated forms and the molecular weight of the compatibilizer was lower than that of the pure PP matrix. It was also found that the tenacity of the nanocomposite fiber increased and then decreased as the compatibilizer content increased because the compatibilizer affected the internal structure of the nanocomposite fibers. The positive effect of the compatibilizer was to generate a more effective exfoliated structure of organoclay in the polymer matrix. The negative effect was that the melt‐spun nanocomposite fiber had a lower molecular weight than the pure PP fiber because the compatibilizer had a lower molecular weight. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Information ethics for and from Africa
Authors: Capurro Rafael
Published: April 2008

The first part of this article deals with some initiatives concerning the role of information ethics for Africa, such as the New Partnership for Africa's Development, United Nations Information Communications Technology (ICT), and the African Information Society Initiative particularly since the World Summit on the Information Society. Information Ethics from Africa is a young academic field, and not much has been published so far on the impact of ICT on African societies and cultures from a philosophical perspective. The second part of the article analyzes some recent research on this matter particularly with regard to the concept of ubuntu. Finally, the article addresses some issues of the African Conference on Information Ethics held February 3–5, 2007, in Pretoria, South Africa.1

The following essay is adapted from a keynote address delivered at the Africa Information Ethics Conference in Pretoria, South Africa, February 5–7, 2007. Under the patronage of UNESCO, sponsored by the South African government, and organized with assistance from the Department of Information Science at the University of Pretoria, the School of Information Studies at the University of Wisconsin‐Milwaukee, and the supporters and members of the International Center for Information Ethics (ICIE), the theme of the conference was “Ethical Challenges in the Information Age: The Joy of Sharing Knowledge.” The full version of the address as well as selected articles from the conference were published in Vol. 7 of ICIE's online journal, International Review of Information Ethics (for more information, visit http://icie.zkm.de)
The justification of intellectual property: Contemporary philosophical disputes
Authors: Himma Kenneth Einar
Published: April 2008

Once taken for granted as morally legitimate, legal protection of intellectual property rights have come under fire in the last 30 years as new technologies have evolved and severed the link between expression of ideas and such traditional material‐based media as books and magazines. These advances in digital technology have called attention to unique features of intellectual content that problematize intellectual property protection; any piece of intellectual content, for example, can be simultaneously appropriated by everyone in the world without thereby diminishing the supply of that content available to others. This essay provides an overview and assessment of the arguments and counterarguments on the issue of whether intellectual property should be legally protected.
The value of probabilistic prediction
Authors: Buizza Roberto
Published: April 2008

Probabilistic forecasts designed to estimate the probability density function of forecast states are potentially more valuable than single forecasts because (1) they can predict not only the most likely outcome but also the probability of occurrence of extreme and rare events and (2) probabilistic forecasts issued on consecutive days are usually more consistent than corresponding single forecasts. In this communication, the potential economic value of probabilistic and single forecasts are compared, and single and probabilistic forecasts of precipitation for a flooding event are analyzed to illustrate the potential value of consistency between successive forecasts. Copyright © 2008 Royal Meteorological Society
Night‐time NO3 and OH radical concentrations in the United Kingdom inferred from hydrocarbon measurements
Authors: Khan M. A. H. , Ashfold M. J. , Nickless G. , Martin D. , Watson L. A. , Hamer P. D. , Wayne R. P. , Canosa‐Mas C. E. , Shallcross D. E.
Published: April 2008

The hydrocarbon decay method (Rivett et al., 2003) has been used to analyse hydrocarbon data from four contrasting sites in the United Kingdom to estimate night‐time levels of NO3 and OH. Remarkably consistent results emerge using alkenes, revealing NO3 and OH levels in the range of 0.01–10 ppt and 1 × 104 − 1 × 106 molecule cm−3, respectively. Weak seasonal cycles are observed where NO3 levels peak in spring and OH in summer. Analysis using alkanes suggests that Cl atom levels of around 2 × 104 molecule cm−3 may be present. How Cl may be formed at night in such high quantities is unknown and may not be the answer to the disparity between the two methods. Copyright © 2008 Royal Meteorological Society
Schimmelpilzbildung im Bereich der Untersicht hölzerner Dachüberstände – Ursachen und Vermeidung
Authors: Göbelsmann Marc
Published: April 2008

An Außenflächen aus Holz oder Holzwerkstoffen sind insbesondere im Bereich der Untersicht von Dachüberständen vermehrt Schimmelpilzbildungen aufgetreten. Zur Vertiefung des Verständnisses der Ursachen dieses Problems wurden instationäre Berechnungen unter Berücksichtigung realitätsnaher klimatischer Randbedingungen vorgenommen.

Die Berechnungen ergaben insbesondere für klare Nächte infolge der Wärmeabgabe durch Strahlung eine Abkühlung der Konstruktion auf deutlich unter der Lufttemperatur liegende Temperaturwerte. Dies führt zu einem dem Dampfdruckgefälle folgenden Feuchtetransport in das Bauteil mit dem Resultat einer zeitweise auftretenden Zunahme der Holzfeuchte in der untersten Schicht der Holzschalung. Die Ergebnisse weisen darauf hin, dass bereits vor dem Erreichen der Taupunkttemperatur bzw. vor der Bildung von Oberflächentauwasser eine beträchtliche Zunahme der Holzfeuchte erfolgt! Mit der Zunahme der Holzfeuchte geht eine Zunahme des Risikos der Schimmelpilzbildung einher.

Es handelt sich bei der Schimmelpilzbildung im Bereich der Untersicht hölzerner Dachüberstände im Wesentlichen um ein bauphysikalisches Problem. Maßnahmen des Holzschutzes bekämpfen insofern lediglich die Symptome, jedoch nicht die Ursache der Schimmelpilzbildung! Eine Beseitigung der Ursache der Schimmelpilzbildung ist möglich, indem zwischen Dachschalung und Dachabdichtung eine dünne Wärmedämmung angeordnet wird. Maßnahmen des Holzschutzes sowie die Wahl geeigneter Hölzer bzw. Holzwerkstoffe werden flankierend als erforderlich angesehen.
Multiscale modeling of nucleic acids: Insights into DNA flexibility
Authors: Bomble Yannick J. , Case David A.
Published: April 2008

The elastic rod theory is used together with all‐atom normal mode analysis in implicit solvent to characterize the mechanical flexibility of duplex DNA. The bending, twisting, stretching rigidities extracted from all‐atom simulations (on linear duplexes from 60 to 150 base pairs in length and from 94‐bp minicircles) are in reasonable agreement with experimental results. We focus on salt concentration and sequence effects on the overall flexibility. Bending persistence lengths are about 20% higher than most experimental estimates, but the transition from low‐salt to high‐salt behavior is reproduced well, as is the dependence of the stretching modulus on salt (which is opposite to that of bending). CTG and CGG trinucleotide repeats, responsible for several degenerative disorders, are found to be more flexible than random DNA, in agreement with several recent studies, whereas poly(dA).poly(dT) is the stiffest sequence we have encountered. The results suggest that current all‐atom potentials, which were parameterized on small molecules and short oligonucleotides, also provide a useful description of duplex DNA at much longer length scales. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 722–731, 2008.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Conformational transitions of flanking purines in HIV‐1 RNA dimerization initiation site kissing complexes studied by CHARMM explicit solvent molecular dynamics
Authors: Sarzyńska Joanna , Réblová Kamila , Šponer Jiří , Kuliński Tadeusz
Published: April 2008

Dimerization of HIV‐1 genomic RNA is initiated by kissing loop interactions at the Dimerization Initiation Site (DIS). Dynamics of purines that flank the 5′ ends of the loop–loop helix in HIV‐1 DIS kissing complex were explored using explicit solvent molecular dynamics (MD) simulations with the CHARMM force field. Multiple MD simulations (200 ns in total) of X‐ray structures for HIV‐1 DIS Subtypes A, B, and F revealed conformational variability of flanking purines. In particular, the flanking purines, which in the starting X‐ray structures are bulged‐out and stack in pairs, formed a consecutive stack of four bulged‐out adenines at the beginning of several simulations. This conformation is seen in the crystal structure of DIS Subtype F with no interference from crystal packing, and was frequently reported in our preceding MD studies performed with the AMBER force field. However, as CHARMM simulations progressed, the four continuously stacked adenines showed conformational transitions from the bulged‐out into the bulged‐in geometries. Although such an arrangement has not been seen in any X‐ray structure, it has been suggested by a recent NMR investigation. In CHARMM simulations, in the longer time scale, the flanking purines display the tendency to move to bulged‐in conformations. This is in contrast with the AMBER simulations, which indicate a modest prevalence for bulged‐out flanking base positions in line with the X‐ray data. The simulations also suggest that the intermolecular stacking between purines from the opposite hairpins can additionally stabilize the kissing complex. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 732–746, 2008.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Improvements of enzyme activity and enantioselectivity via combined substrate engineering and covalent immobilization
Authors: Wang Pei‐Yun , Tsai Shau‐Wei , Chen Teh‐Liang
Published: April 2008

Esterases, lipases, and serine proteases have been applied as versatile biocatalysts for preparing a variety of chiral compounds in industry via the kinetic resolution of their racemates. In order to meet this requirement, three approaches of enzyme engineering, medium engineering, and substrate engineering are exploited to improve the enzyme activity and enantioselectivity. With the hydrolysis of (R,S)‐mandelates in biphasic media consisting of isooctane and pH 6 buffer at 55°C as the model system, the strategy of combined substrate engineering and covalent immobilization leads to an increase of enzyme activity and enantioselectivity from VS/(Et) = 1.62 mmol/h g and VS/VR = 43.6 of (R,S)‐ethyl mandelate (1) for a Klebsiella oxytoca esterase (named as SNSM‐87 from the producer) to 16.7 mmol/h g and 867 of (R,S)‐2‐methoxyethyl mandelate (4) for the enzyme immobilized on Eupergit C 250L. The analysis is then extended to other (R,S)‐2‐hydroxycarboxylic acid esters, giving improvements of the enzyme performance from VS/(Et) = 1.56 mmol/h g and VS/VR = 41.9 of (R,S)‐ethyl 3‐chloromandelate (9) for the free esterase to 39.4 mmol/h g and 401 of (R,S)‐2‐methoxyethyl 3‐chloromandelate (16) for the immobilized enzyme, VS/(Et) = 5.46 mmol/h g and VS/VR = 8.27 of (R,S)‐ethyl 4‐chloromandelate (10) for free SNSM‐87 to 33.5 mmol/h g and 123 of (R,S)‐methyl 4‐chloromandelate (14) for the immobilized enzyme, as well as VS/(Et) = 3.0 mmol/h g and VS/VR = 7.94 of (R,S)‐ethyl 3‐phenyllactate (11) for the free esterase to 40.7 mmol/h g and 158 of (R,S)‐2‐methoxyethyl 3‐phenyllactate (18) for the immobilized enzyme. The great enantioselectivty enhancement is rationalized from the alteration of ionization constants of imidazolium moiety of catalytic histidine for both enantiomers and conformation distortion of active site after the covalent immobilization, as well as the selection of leaving alcohol moiety via substrate engineering approach. Biotechnol. Bioeng. 2008;101: 460–469. © 2008 Wiley Periodicals, Inc.
Control of protein adsorption on functionalized electrospun fibers
Authors: Grafahrend Dirk , Calvet Julia Lleixa , Klinkhammer Kristina , Salber Jochen , Dalton Paul D. , Möller Martin , Klee Doris
Published: April 2008

Electrospun fibers that are protein resistant and functionalized with bioactive signals were produced by solution electrospinning amphiphilic block copolymers. Poly (ethylene glycol)‐block‐poly(D,L‐lactide) (PEG‐b‐PDLLA) was synthesized in two steps, with a PEG segment of 10 kDa, while the PDLLA block ranged from 20 to 60 kDa. Depending on the PEG and PDLLA segment ratio, as well as solvent selection, the hydrophilicity and protein adsorption could be altered on the electrospun mesh. Furthermore, an α‐acetal PEG‐b‐PDLLA was synthesized that allowed the conjugation of active molecules, resulting in surface functionalization of the electrospun fiber. Electrospun material with varying morphologies and diameter were electrospun from 10, 20, and 30 wt.% solutions. Sessile drop measurements showed a reduction in the contact angle from 120° for pure poly(D,L‐lactide) with increasing PEG/PDLLA ratio. All electrospun block PEG‐b‐PDLLA fibers had hydrophilic properties, with contact angles below 45°. The fibers were collected onto six‐arm star‐poly(ethylene glycol) (star‐PEG) coated silicon wafers and incubated with fluorescently labeled proteins. All PEG‐b‐PDLLA fibers showed no detectable adsorption of bovine serum albumin (BSA) independent of their composition while a dependence between hydrophobic block length was observed for streptavidin adsorption. Fibers of block copolymers with PDLLA blocks smaller than 39 kDa showed no adsorption of BSA or streptavidin, indicating good non‐fouling properties. Fibers were surface functionalized with Nε‐(+)‐biotinyl‐L‐lysine (biocytin) or RGD peptide by attaching the molecule to the PEG block during synthesis. Protein adsorption measurements, and the controlled interaction of biocytin with fluorescently labeled streptavidin, showed that the electrospun fibers were both resistant to protein adsorption and are functionalized. Fibroblast adhesion was contrasting between the unfunctionalized and RGD‐coupled electrospun fabrics, confirming that the surface of the fibers was functionalized. The PEG‐b‐PDLLA surface functionalized electrospun fibers are promising substrates for controlling cell–material interactions, particularly for tissue‐engineering applications. Biotechnol. Bioeng. 2008;101: 609–621. © 2008 Wiley Periodicals, Inc.
Anaerobic methanethiol degradation and methanogenic community analysis in an alkaline (pH 10) biological process for liquefied petroleum gas desulfurization
Authors: van Leerdam Robin C. , Bonilla‐Salinas Monica , de Bok Frank A.M. , Bruning H. , Lens Piet N.L. , Stams Alfons J.M. , Janssen Albert J.H.
Published: April 2008

Anaerobic methanethiol (MT) degradation by mesophilic (30°C) alkaliphilic (pH 10) communities was studied in a lab‐scale Upflow Anaerobic Sludge Bed (UASB) reactor inoculated with a mixture of sediments from the Wadden Sea (The Netherlands), Soap Lake (Central Washington), and Russian soda lakes. MT degradation started after 32 days of incubation. During the first 252 days, complete degradation was achieved till a volumetric loading rate of 7.5 mmol MT/L/day, and sulfide, methane, and carbon dioxide were the main reaction products. Temporary inhibition of MT degradation occurred after MT peak loads and in the presence of dimethyl disulfide (DMDS), which is the autooxidation product of MT. From day 252 onwards, methanol was dosed to the reactor as co‐substrate at a loading rate of 3–6 mmol/L/day to stimulate growth of methylotrophic methanogens. Methanol was completely degraded and also a complete MT degradation was achieved till a volumetric loading rate of 13 mmol MT/L/day (0.77 mmol MT/gVSS/day). However, from day 354 till the end of the experimental run (day 365), acetate was formed and MT was not completely degraded anymore, indicating that methanol‐degrading homoacetogenic bacteria had partially outcompeted the methanogenic MT‐degrading archea. The archeal community in the reactor sludge was analyzed by DGGE and sequencing of 16S rRNA genes. The methanogenic archea responsible for the degradation of MT in the reactor were related to Methanolobus oregonensis. A pure culture, named strain SODA, was obtained by serial dilutions in medium containing both trimethyl amine and dimethyl sulfide (DMS). Strain SODA degraded MT, DMS, trimethyl amine, and methanol. Flow sheet simulations revealed that for sufficient MT removal from liquefied petroleum gas, the extraction and biological degradation process should be operated above pH 9. Biotechnol. Bioeng. 2008;101: 691–701. © 2008 Wiley Periodicals, Inc.
Synthesis and Application of Fluorescein‐ and Biotin‐Labeled Molecular Probes for the Chemokine Receptor CXCR4
Authors: Oishi Shinya , Masuda Ryo , Evans Barry , Ueda Satoshi , Goto Yukiko , Ohno Hiroaki , Hirasawa Akira , Tsujimoto Gozoh , Wang Zixuan , Peiper Stephen C. , Naito Takeshi , Kodama Eiichi , Matsuoka Masao , Fujii Nobutaka
Published: April 2008

The design, synthesis, and bioevaluation of fluorescence‐ and biotin‐labeled CXCR4 antagonists are described. The modification of D‐Lys8 at an ε‐amino group in the peptide antagonist Ac‐TZ14011 derived from polyphemusin II had no significant influence on the potent binding of the peptide to the CXCR4 receptor. The application of the labeled peptides in flow cytometry and confocal microscopy studies demonstrated the selectivity of their binding to the CXCR4 receptor, but not to CXCR7, which was recently reported to be another receptor for stromal cell‐derived factor 1 (SDF‐1)/CXCL12.
Percutaneous transcatheter communication between the pulmonary artery and atrium following an extra‐cardiac Fontan
Authors: Mehta C. , Jones T. , De Giovanni J.V.
Published: April 2008

In a nonfenestrated modified Fontan, transcatheter creation of a fenestration presents technical difficulties, especially with the extra‐cardiac modification where a Gore‐Tex tube is placed between the inferior caval vein and the pulmonary arteries. The authors describe an alternative approach to perforating the Gore‐Tex tube to create a fenestration by making a communication between the pulmonary artery and the atrial chamber, thus bridging the two circulations through native tissue. © 2008 Wiley‐Liss, Inc.
Transcatheter occlusion of pulmonary arteriovenous malformations using the amplatzer vascular plug II
Authors: Tabori Nora E. , Love Barry A.
Published: April 2008

Pulmonary arteriovenous malformations (PAVMs) are a relatively uncommon but potentially life‐threatening condition manifested by cyanosis, paradoxical embolization, brain abscess, and rupture. A variety of transcatheter closure devices have been used to occlude PAVMs however risks of device embolization, incomplete closure, or large delivery systems have made each of these methods sub‐optimal. The Amplatzer Vascular Plug II (AVP II) is a new multisegmented, woven nitinol cylinder that can be deployed through a small delivery catheter. The AVP II differs from the original AVP in having a finer, more tightly woven nitinol frame and three, rather than one occlusive segment. The authors report the first use of the AVP II for occlusion of bilateral large arteriovenous malformations in a patient with hereditary hemorrhagic telangiectasia. © 2008 Wiley‐Liss, Inc.
The COURAGE trial in perspective
Authors: Prasad Abhiram , Rihal Charanjit , Holmes David R.
Published: April 2008

The indications for percutaneous coronary intervention (PCI) continue to evolve because of the steady improvement in technology, broadened patient and lesion selection criteria, and new evidence from clinical trials. Recently, the role of PCI in patients with chronic stable angina has received considerable scrutiny and has been the subject of great controversy. In these patients, the goals of therapy include the relief of symptom, treatment of ischemia, and reducing the need for subsequent interventions. Medical therapy is the cornerstone in the management of coronary artery disease and should be optimized in all patients. The COURAGE trial investigated the efficacy of combined PCI and optimal medical therapy (OMT) versus OMT alone in patients with stable disease. The trial confirmed several issues that have been already well delineated: (1) in low risk patients, the hard endpoints of death and MI are relatively infrequent and are not reduced by PCI – for prevention of these, OMT may be sufficient, (2) crossover from OMT to PCI is frequent, even in low risk patients, (3) PCI is very effective in reducing symptoms and myocardial ischemia, and (4) significant untreated ischemia is associated with greater likelihood of death and MI. © 2008 Wiley‐Liss, Inc.
Drug eluting stents for below the knee lesions in patients with critical limb ischemia
Authors: Rosales Oscar R. , Mathewkutty Shiny , Gnaim Charlie
Published: April 2008

Objectives: The purpose of this study was to assess the long‐term limb preservation and/or healing of ulcers in patients with critical limb ischemia (CLI) and severe infrapopliteal atherosclerotic disease treated with drug eluting stents (DES). Background: Percutaneous revascularization has become an effective treatment for CLI in patients with infrapopliteal atherosclerotic disease. Recent reports using DES in patients with CLI have documented excellent short‐term infrapopliteal vessel patency. Higher primary patency rates in infrapopliteal vessels treated with DES could translate into better long‐term clinical outcomes and improved limb salvage rates. Methods: Twenty‐four consecutive patients with CLI (defined as rest pain, nonhealing ulcers, or gangrene) because of severe infrapopliteal disease were treated with DES from August 2004 to June 2006. Results: Procedural success was achieved in 96% (27/28) of targeted lesions. There were no procedure‐related deaths, acute vessel thrombosis events, or need for urgent surgical intervention. There was one case of distal embolization. Clinical follow up, ranging 8–34 months, is available for 100% of patients of which 83% (20/24) achieved limb preservation and healing. Angiographic and/or sonographic follow up, ranging 6–34 months, is available in 79% (19/24) of patients of which 95% (18/19) had patent target vessels. Conclusions: DES is a safe and effective long‐term option for CLI due to severe infrapopliteal arterial disease. Long‐term vascular patency led to a high rate of limb preservation and low amputation rate. A multicenter trial should further elucidate the role of DES in the treatment of CLI. © 2008 Wiley‐Liss, Inc.
Self‐expanding and balloon expandable covered stents in the treatment of aortic coarctation with or without aneurysm formation
Authors: Kenny Damien , Margey Ronan , Turner Mark S. , Tometzki Andrew J. , Walsh Kevin P. , Martin Robin P.
Published: April 2008

Objectives: We describe our complete experience with covered stent implantation for aortic coarctation including short‐ to medium‐term outcomes. Background: Coarctation of the aorta is a heterogeneous disease process with multiple associated complications both with and without treatment. Covered stents have evolved to provide greater support to the aortic wall and a varied approach with choice of stent tailored to the anatomy of the patient is required. Methods: We retrospectively analyzed consecutive patient data from two congenital heart centers from March 2003 to October 2007. Results: We implanted 38 covered stents in 37 patients (20 female) of which three were self‐expanding stents. Median age was 29.6 years (9–65) with median weight of 71.5 kg (35–95). The indications for stent placement were native coarctation (n = 13); recurrent coarctation following surgical treatment (n = 11); aneurysm associated with previous coarctation surgery (n = 7); aorto‐bronchial fistula leading to acute hemoptysis (n = 2); stent fracture (n = 1); associated arterial duct (n = 2). One patient had a combination of acquired coarctation and false aneurysm. The median screening time was 10 min (3–22). The median systolic gradient of 26 mm Hg (10–60) was reduced to 4 mm Hg (0–20) postprocedure (P < 0.001). There were no deaths on median follow up of 11.5 months (1–56). One patient developed aortic rupture during the procedure and required emergency surgery. Conclusion: Covered stent implantation for treatment of aortic coarctation is safe and highly effective in selected patients. Self‐expanding stent grafts may be preferable to balloon expandable stents when there is aneurysm formation in the setting of aortopathy. © 2008 Wiley‐Liss, Inc.
Utilization of an aspiration thrombectomy catheter (Pronto) to treat acute atherothrombotic embolization during percutaneous revascularization of the lower extremity
Authors: Zafar Nayab , Prasad Anand , Mahmud Ehtisham
Published: April 2008

Acute limb ischemia is typically a surgical emergency and can occur secondary to distal embolization during catheter‐based percutaneous revascularization. We present a case of acute atherothrombotic embolization to the left lower extremity after stenting of the left proximal popliteal and anterior tibial arteries. This was successfully treated with the use of the coronary aspiration thrombectomy device Pronto (Vascular Solutions, Minneapolis, MN) resulting in flow restoration. © 2008 Wiley‐Liss, Inc.