bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of GnRH agonists in precocious puberty
Authors: Mul D , Hughes I A
Published: December 2008

In this review several aspects of gonadotrophin releasing hormone agonists (GnRHa) treatment in central precocious puberty (CPP) are highlighed. These include issues of the definition of precocity, assessment of CPP and thelarche variants. Indications for treatment with GnRH agonists are discussed, not only in CPP but also in children with other reasons to suppress central activation, e.g. adopted or developmental retardation. Finally, outcome data are summarized, both on growth and psychosocial parameters.
Briefing: Working platforms for tracked plant
Authors: Andrew Charles J. , Corke David , Skinner Hilary D.
Published: December 2008

If a piling rig overturns there can be a risk of casualties. Working platforms are critical for plant stability, and a good practice guide to the design, installation, maintenance and repair of ground-supported working platforms for tracked plant has been prepared. A simplified approach to the design calculations has been based on a punching shear failure mechanism. The platform design is an integrated package, from track loading through to geotechnical design.
A statistical guide for dynamic-penetration test interpretation
Authors: Navarro V. , Yustres A. , Sánchez J. , Candel M.
Published: December 2008

This paper presents a methodology, implemented into a computer code, to support the interpretation of dynamic penetration super-heavy (DPSH) soil tests. The program is based on the analysis of variance (Anova) to evaluate the equality of means of groups of number of blows. The aim was to assess the identification of the different layers constituting the soil profile on which the penetration test was performed. The paper includes three examples of the application of the methodology, which will highlight both its capabilities and its limitations.
Non-linear and linear models in design of retaining walls
Authors: Grammatikopoulou A. , St John H. D. , Potts D. M.
Published: December 2008

This paper compares non-linear and linear elasto-plastic models in the numerical analyses of a retaining wall in stiff clay. The paper aims to be applicable to routine design, where often a non-linear elasto-plastic model is not available and instead a linear elasto-plastic model is used. Current guidelines suggest deriving the appropriate linear elastic stiffness from the non-linear soil behaviour, on the basis of the expected straining in the ground. However, it is not always straightforward to choose a representative strain level. The paper presents profiles of linear elastic stiffness, back-calculated to match the maximum wall deflection of the non-linear analyses in the short term. On the basis of the non-linear soil stiffness–strain curve, the paper then derives a corresponding strain level for each linear elastic stiffness profile. Three different support systems are examined: a single-propped wall, a double-propped wall, and a top-down construction. A number of non-linear stiffness–strain curves are considered for the stiff clay and two K0 profiles are examined.
Briefing: Crossrail
Authors: Gannon M.
Published: December 2008

Crossrail, one of Europe’s largest infrastructure projects, received royal assent on 22nd July 2008. Construction of Crossrail is forecast to start in 2010 and become operational in 2017. This mega rail project is expected to provide a significant boost to the UK’s economy in terms of direct and indirect employment benefits. The scheme has taken nearly a decade to achieve this significant milestone having had its private bill rejected in the early 1990s. The UK’s central government has at long last provided ‘genuine’ political support and commitment to Crossrail, a critical factor during planning that is essential despite the scheme having a technically robust business case.
Briefing: Industrial disease: identifying the risks
Authors: Wynn D.
Published: December 2008

The paper presents a discussion of the potential employer liabilities of industrial diseases.
Briefing: Strategic Forum for Construction
Authors: Done R.
Published: December 2008

The paper details the role of the Strategic Forum for Construction (SFfC). It covers the membership of the forum and its priorities for the industry. Its priorities centre on the launch of the construction commitments and a series of targets for the industry up until 2012. The commitments and the targets focus on: integration and procurement; commitment to people; client leadership; sustainability; design quality; and health and safety.
MULTIPLE CONTROLS OF COMMUNITY STRUCTURE AND DYNAMICS IN A SUBLITTORAL MARINE ENVIRONMENT
Authors: Hereu Bernat , Zabala Mikel , Sala Enric
Published: December 2008

The structure and dynamics of ecological communities can be determined by both top‐down (e.g., predation) and bottom‐up (e.g., energy inputs) processes, which can act synergistically and across spatial and temporal scales. Here we aimed at understanding the role of multiple controls in a Mediterranean rocky sublittoral marine community that harbors a diverse algal community and strongly interacting herbivores, and which is subject to marked seasonality in energy inputs. We conducted an experiment by manipulating densities of the major consumers of benthic algae (fishes and sea urchins) in ∼100‐m2 enclosures in a marine reserve, and monitored algal assemblages over two and a half years. Most algae showed a marked annual cycle, with a biomass peak in late spring/summer and low biomass in winter, following seasonal fluctuations in resource availability, indicating the existence of bottom‐up processes. Sea urchins reduced the abundance of most algal species, indicating the existence of top‐down processes. The effect of fish grazing on algal abundances was significantly weaker. Sea urchin grazing was inhibited when predatory fish were present. Multivariate analysis showed that the interaction between seasonal resource inputs and herbivory induced the formation of algal assemblages characterized by different species abundances. The organization of algal assemblages was determined by the synergistic interaction between top‐down and bottom‐up processes: top‐down control regulated total algal abundance, while bottom‐up control determined seasonal fluctuations.
ENDOGENOUS AND EXOGENOUS CONTROL OF ECOSYSTEM FUNCTION: N CYCLING IN HEADWATER STREAMS
Authors: Valett H. M. , Thomas S. A. , Mulholland P. J. , Webster J. R. , Dahm C. N. , Fellows C. S. , Crenshaw C. L. , Peterson C. G.
Published: December 2008

Allochthonous inputs act as resource subsidies to many ecosystems, where they exert strong influences on metabolism and material cycling. At the same time, metabolic theory proposes endogenous thermal control independent of resource supply. To address the relative importance of exogenous and endogenous influences, we quantified spatial and temporal variation in ecosystem metabolism and nitrogen (N) uptake using seasonal releases of 15N as nitrate in six streams differing in riparian–stream interaction and metabolic character. Nitrate removal was quantified using a nutrient spiraling approach based on measurements of downstream decline in 15N flux. Respiration (R) and gross primary production (GPP) were measured with whole‐stream diel oxygen budgets. Uptake and metabolism metrics were addressed as z scores relative to site means to assess temporal variation. In open‐canopied streams, areal uptake (U; μg N·m−2·s−1) was closely related to GPP, metabolic rates increased with temperature, and R was accurately predicted by metabolic scaling relationships. In forested streams, N spiraling was not related to GPP; instead, uptake velocity (vf; mm/s) was closely related to R. In contrast to open‐canopied streams, N uptake and metabolic activity were negatively correlated to temperature and poorly described by scaling laws. We contend that streams differ along a gradient of exogenous and endogenous control that relates to the relative influences of resource subsidies and in‐stream energetics as determinants of seasonal patterns of metabolism and N cycling. Our research suggests that temporal variation in the propagation of ecological influence between adjacent systems generates phases when ecosystems are alternatively characterized as endogenously and exogenously controlled.
WHAT DO INTERACTION NETWORK METRICS TELL US ABOUT SPECIALIZATION AND BIOLOGICAL TRAITS
Authors: Blüthgen Nico , Fründ Jochen , Vázquez Diego P. , Menzel Florian
Published: December 2008

The structure of ecological interaction networks is often interpreted as a product of meaningful ecological and evolutionary mechanisms that shape the degree of specialization in community associations. However, here we show that both unweighted network metrics (connectance, nestedness, and degree distribution) and weighted network metrics (interaction evenness, interaction strength asymmetry) are strongly constrained and biased by the number of observations. Rarely observed species are inevitably regarded as “specialists,” irrespective of their actual associations, leading to biased estimates of specialization. Consequently, a skewed distribution of species observation records (such as the lognormal), combined with a relatively low sampling density typical for ecological data, already generates a “nested” and poorly “connected” network with “asymmetric interaction strengths” when interactions are neutral. This is confirmed by null model simulations of bipartite networks, assuming that partners associate randomly in the absence of any specialization and any variation in the correspondence of biological traits between associated species (trait matching). Variation in the skewness of the frequency distribution fundamentally changes the outcome of network metrics. Therefore, interpretation of network metrics in terms of fundamental specialization and trait matching requires an appropriate control for such severe constraints imposed by information deficits. When using an alternative approach that controls for these effects, most natural networks of mutualistic or antagonistic systems show a significantly higher degree of reciprocal specialization (exclusiveness) than expected under neutral conditions. A higher exclusiveness is coherent with a tighter coevolution and suggests a lower ecological redundancy than implied by nested networks.
ANIMAL MOVEMENTS IN HETEROGENEOUS LANDSCAPES: IDENTIFYING PROFITABLE PLACES AND HOMOGENEOUS MOVEMENT BOUTS
Authors: Barraquand Frédéric , Benhamou Simon
Published: December 2008

Because of the heterogeneity of natural landscapes, animals have to move through various types of areas that are more or less suitable with respect to their current needs. The locations of the profitable places actually used, which may be only a subset of the whole set of suitable areas available, are usually unknown, but can be inferred from movement analysis by assuming that these places correspond to the limited areas where the animals spend more time than elsewhere. Identifying these intensively used areas makes it possible, through subsequent analyses, to address both how they are distributed with respect to key habitat features, and the underlying behavioral mechanisms used to find these areas and capitalize on such habitats. We critically reviewed the few previously published methods to detect changes in movement behavior likely to occur when an animal enters a profitable place. As all of them appeared to be too narrowly tuned to specific situations, we designed a new, easy‐to‐use method based on the time spent in the vicinity of successive path locations. We used computer simulations to show that our method is both quite general and robust to noisy data.
How Entrepreneurs Use Symbolic Management to Acquire Resources
Authors: Zott Christoph , Huy Quy Nguyen
Published: December 2008

Results of a two-year inductive field study of British ventures show that entrepreneurs are more likely to acquire resources for new ventures if they perform symbolic actions—actions in which the actor displays or tries to draw other people's attention to the meaning of an object or action that goes beyond the object's or action's intrinsic content or functional use. We identify four symbolic action categories that facilitate resource acquisition: conveying the entrepreneur's personal credibility, professional organizing, organizational achievement, and the quality of stakeholder relationships. Our data show that entrepreneurs who perform a variety of symbolic actions from these categories skillfully and frequently obtain more resources than those who do not. Our data also suggest three factors—structural similarity, intrinsic quality, and uncertainty—that moderate the relationship between symbolic management and resource acquisition. We theorize how the various symbolic action categories shape different forms of legitimacy that help entrepreneurs acquire resources.
Auditor Litigation Risk and Corporate Disclosure of Quarterly Review Report
Authors: Krishnan Jagan , Zhang Yinqi
Published: December 2008

The U.S. Securities and Exchange Commission (SEC) recently made timely reviews of quarterly financial statements mandatory for all registrants. The objective is to improve corporate quarterly reporting. However, formal review reports are not required to be included in 10-Q filings, and may not even be issued by auditors. A priori, one would expect these reports to be useful to investors if they imply added auditor diligence or if they contain modifications to the standard report. We find that only 5.7 percent of the companies in our sample attached the auditor's review report in their 10-Q filings. Also the majority of these reports are “clean,” suggesting that clients may not be disclosing the reports when they are modified. After controlling for factors such as auditor type, agency costs, capital market transactions, and company size, we find a significant negative association between auditors' litigation risk and disclosure of the review report. In addition, we find that the disclosure of the review report is associated with auditor type and company size.
Impact of the SEC's Public Fee Disclosure Requirement on Subsequent Period Fees and Implications for Market Efficiency
Authors: Francis Jere R. , Wang Dechun
Published: December 2008

This study investigates the impact of the U.S. Securities and Exchange Commission's (SEC) mandated public disclosure of audit fees on subsequent period audit pricing. Our theoretical model predicts that the initial public disclosure of fees will lead to greater precision and reduced dispersion (less variance) in subsequent period fees. Using the new fee disclosures in the first two disclosure years (2000 and 2001), we find significantly smaller variances in audit fees as predicted for 2001 relative to 2000. In addition, we document that those clients that were “overcharged” (“undercharged”) in 2000 have significantly lower (higher) fees in 2001. However, there is greater downward fee adjustment than upward adjustment that suggests that clients have bargaining power over auditors. We also document that subsequent period fees appear to have completed the adjustment process by the second post-disclosure year (2002) with subsequent fees adjusting on average around 0.31 percent for each one percent of fee surprise in 2000. In sum, the evidence indicates that public disclosure has improved the precision of audit pricing (less variance) and this is a potentially more fundamental and lasting consequence of public disclosure, and transcends the SEC's original rationale, which was more narrowly premised on the conjectured adverse effect of nonaudit services on auditor independence.
Judgment and Decision Making Research in Auditing: A Task, Person, and Interpersonal Interaction Perspective
Authors: Nelson Mark , Tan Hun-Tong
Published: December 2008

This paper discusses judgment and decision making research in auditing—i.e., research that uses a psychological lens to understand, evaluate, and improve judgments, decisions, or choices in an auditing setting. Much of this work uses the laboratory experiment approach, but we also cover related studies that use survey and field study approaches. We classify extant auditing judgment and decision making (JDM) literature as covering three broad areas: (1) the audit task, (2) the auditor and his/her attributes, and (3) interaction between auditor and other stakeholders in task performance. We use this task, person, and interaction categorization to assess the cumulative knowledge generated in the past 25 years, as well as to identify knowledge gaps and opportunities for future research.
Distribution of Lindane in Water, Sediment, and Fish from the Warri River of the Niger Delta, Nigeria
Authors: Ezemonye Lawrence , Ikpesu Thomas , Tongo Isioma
Published: December 2008

Distribution of Lindane in Water, Sediment, and Fish from the Warri River of the Niger Delta, Nigeria

This paper is the first attempt to quantify the levels and the distribution pattern of lindane in the surface water, sediment and fish (Chrysichthys furcatus and Tilapia zilli). The samples were collected from three stations (Ovwian, Ekakpamre, and Ovu) of the Warri River in the western Niger Delta of Nigeria in 2006: during the dry (January-April) and wet seasons (May-August). The analysis included a total of 96 samples made up of 24 samples each for water, sediment, and fish. The pesticide levels were analysed using high performance liquid chromatography to elucidate its distribution in various environmental compartments. Residue levels in the matrices ranged from below the detection limit (BDL) to 1.37μg L-1 in water, BDL to 12.66 μg g-1 dry weight (dw) in sediment, BDL to 16.67 μg g-1dw in Chrysichthys furcatus, and BDL to 0.15 μg g-1dw in Tilapia zilli. The observed values were above the ecological benchmarks (0.01 μg L-1) recommended by the Nigerian Environmental Protection Agency and European Union. They were also relatively higher than in previous studies on the Nigerian environment, which calls for regular monitoring of the Niger Delta water bodies.
Atom as a “dressed” nucleus
Authors: Kalitvianski Vladimir
Published: December 2008

We show that the electrostatic potential of an atomic nucleus “seen” by a fast charged projectile at short distances is quantum mechanically smeared due to nucleus motion around the atomic center of inertia. For example, the size of the “positive charge cloud” in the Hydrogen ground state is much larger than the proper proton size. For target atoms in excited initial states, the effect is even larger. The elastic scattering at large angles is generally weaker than the Rutherford scattering since the effective potential at short distances is softer than the Colombian one due to a natural “cutoff”. In addition, the large-angle scattering leads to target atom excitations due to pushing the nucleus (⇒ inelastic processes). The Rutherford cross section is in fact inclusive rather than elastic. These results are analogous to those from QED. Non-relativistic atomic calculations are presented. The difference and the value of these calculations arise from nonperturbatively (exact) nucleus “dressing” that immediately leads to correct physical results and to significant technical simplifications. In these respects a nucleus bound in an atom is a simple but rather realistic model of a “dressed” charge in the QFT. This idea is briefly demonstrated on a real electron model (electronium) which is free from infinities.
The q-exponential family in statistical physics
Authors: Naudts Jan
Published: December 2008

The notion of a generalized exponential family is considered in the restricted context of non-extensive statistical physics. Examples are given of models belonging to this family. In particular, the q-Gaussians are discussed and it is shown that the configurational probability distributions of the micro-canonical ensemble belong to the q-exponential family.
Analytic expressions and approximations for the on-axis, aberration-free Rayleigh and Debye integral in the case of focusing fields on a circular aperture
Authors: Aarts R. M. , Braat J. J. M. , Dirksen P. , van Haver S. , van Heesch C. , Janssen A. J. E. M.
Published: December 2008

We present a derivation of the analytic result for on-axis field values of the Rayleigh diffraction integral, a result that was originally presented in a paper by Osterberg and Smith (1961). The method on which our derivation is based is then applied to other diffraction integrals used in acoustics and optics, e.g., the far-field Rayleigh integral, the Debye integral and the separate near-field part of the Rayleigh integral. Having available our on-axis analytic or semi-analytic solutions for these various cases, we compare the various integrals for wave numbers k pertaining to low-frequency acoustic applications all the way up to high-frequency optical applications. Our analytic results are compared to numerical results presented in the literature.
Preparation for Practice by Veterinary School: A Comparison of the Perceptions of Alumni from a Traditional and an Innovative Veterinary Curriculum
Authors: Jaarsma Debbie A.D.C , Dolmans Diana H.J.M , Scherpbier Albert J.J.A , Van Beukelen Peter
Published: December 2008

Alumni survey research can tap users’ perspectives on an educational product and thereby provide valuable information for outcomes assessment aimed at improving the quality of educational programs. The study documented here compared the perceptions of two groups of alumni from two curricula offered by the same veterinary school, where the traditional lecture-based curriculum had been gradually replaced by a reformed, more student-centered curriculum. Year 1 of the new curriculum started in 1995, while the old curriculum continued to be delivered to the entering class of 1994. The aim of our study was to determine whether the new program received more positive evaluations from the alumni and whether it was perceived as offering better preparation for veterinary practice. A questionnaire was sent to all alumni who had graduated in the period 2001–2003. Compared to alumni of the traditional program, alumni of the new curriculum reported higher perceived competence levels for clinical knowledge and skills (specific competencies) and for communication skills and academic skills (generic competencies). Alumni of both programs attributed difficulties in the transition from university to work to lack of experience with practical or technical skills and with primary-care cases. They suggested that more attention be paid to these aspects of practice and to practice/business management and communication with clients. The concrete changes in the curriculum appear to have had a noticeable positive effect, without the feared detrimental effect on knowledge acquisition. The results point to further program improvements, particularly for practice-oriented specific and generic skills.
Lansania Journal of arachnology and zoology – a rare and obscure Japanese natural history journal
Authors: TENNENT W. JOHN , YASUDA MASATOSHI , MORIMOTO KATSURA
Published: December 2008

Publication data relating to a rare and obscure Japanese journal Lansania Journal of arachnology and zoology (1929–1941) are examined. Available facts, together with a substantial body of circumstantial and anecdotal evidence suggest that many planned issues, including several cited by independent sources as having been published, were not published. Some biographical data relating to the editor, Kyukichi Kishida (1888–1968), are provided. Titles of all papers known to have been published in Lansania, with page numbers and claimed publication dates are presented, together with a list of 113 new zoological names proposed in the journal. Known library holdings of the journal worldwide are indicated. Details are provided of unpublished manuscripts in proof obtained from Kishida in the 1960s. The strong probability that some printed publication dates are inaccurate is discussed in detail.
Bird-keeping and the development of ornithological science
Authors: BIRKHEAD T. R. , van BALEN S.
Published: December 2008

We review the growth of knowledge in several areas of ornithology, and demonstrate the important, but largely unrecognized role of European bird-keeping in the development of several different areas of bird study. By ignoring the early bird-keeping literature, historians of ornithology have overlooked many significant observations. There are several reasons why the role of bird-keeping has been ignored, including the shifting boundaries of scientific ornithology and the varying relationship between bird-keeping and ornithology. We review the significance of observations of captive birds to ornithology and show that they have made important and previously unrecognized contributions to the following aspects of bird biology: song acquisition, function and anatomy; territory; breeding biology; external genitalia; migration; instinct and learning.
On the origin of khutū
Authors: LAVERS C. , KNAPP M.
Published: December 2008

Khutū was a material derived from an animal used by Medieval Asian peoples in the manufacture of knife handles and as an alexipharmic. Al-Bīrūnī (973–1048) made extensive enquiries into the origin of khutū but reached no definite conclusion. Literary scholars in the first half of the twentieth century identified the walrus and narwhal as probable sources, but in ignoring aspects of the literature on khutū’s appearance and provenance left a number of questions unanswered. We clarify and extend this research and identify further clues to the identity of khutū. We concur that walrus ivory was one source of khutū, suggest that the remains of “Ice Age” mammals may have influenced development of the medieval literature on khutū more than previous investigators realized, and offer a new hypothesis of khutū’s origin.
Copper Complexes of Nicotinic-Aromatic Carboxylic Acids as Superoxide Dismutase Mimetics
Authors: Suksrichavalit Thummaruk , Prachayasittikul Supaluk , Piacham Theeraphon , Isarankura-Na-Ayudhya Chartchalerm , Nantasenamat Chanin , Prachayasittikul Virapong
Published: December 2008

Nicotinic acid (also known as vitamin B3) is a dietary element essential for physiological and antihyperlipidemic functions. This study reports the synthesis of novel mixed ligand complexes of copper with nicotinic and other select carboxylic acids (phthalic, salicylic and anthranilic acids). The tested copper complexes exhibited superoxide dismutase (SOD) mimetic activity and antimicrobial activity against Bacillus subtilis ATCC 6633, with a minimum inhibition concentration of 256 μg/mL. Copper complex of nicotinic-phthalic acids (CuNA/Ph) was the most potent with a SOD mimetic activity of IC50 34.42 μM. The SOD activities were observed to correlate well with the theoretical parameters as calculated using density functional theory (DFT) at the B3LYP/LANL2DZ level of theory. Interestingly, the SOD activity of the copper complex CuNA/Ph was positively correlated with the electron affinity (EA) value. The two quantum chemical parameters, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), were shown to be appropriate for understanding the mechanism of the metal complexes as their calculated energies show good correlation with the SOD activity. Moreover, copper complex with the highest SOD activity were shown to possess the lowest HOMO energy. These findings demonstrate a great potential for the development of value-added metallovitamin-based therapeutics.
ON THE COMPLEXITIES OF MODELING HIV/AIDS IN SOUTHERN AFRICA
Authors: Nyabadza Farai
Published: December 2008

In this paper problems associated with the modeling of HIV/AIDS in Southern Africa are presented. A mathematical model is presented to highlight the three major challenges of modeling HIV/AIDS, i.e condom use, vertical transmission and treatment. The model analysis for the case, where the treatment parameter ñ = 0, is presented in terms of the model reproduction number R and threshold parameters RT and RA that show the contribution of vertical transmission. It is shown that if R, RT, RA < 1, then the disease free equilibrium point is both locally asymptotically and globally stable. Numerical simulations for the model are presented to determine the role of some key epidemiological parameters of the model.
The Current State of Musculoskeletal Clinical Skills Teaching for Preclerkship Medical Students
Authors: OSWALD ANNA E. , BELL MARY J. , SNELL LINDA , WISEMAN JEFFREY
Published: December 2008

Objective

Musculoskeletal (MSK) complaints have high prevalence in primary care practice (12%–20% of visits), yet many trainees and physicians identify themselves as weak in MSK physical examination (PE) skills. As recruitment to MSK specialties lags behind retirement rates, there is a short-age of physicians able to effectively teach this subject. We investigated current practices of Canadian undergraduate medical programs regarding the nature, amount, and source of preclerkship MSK PE clinical skills teaching; and documented the frequency and extent that Patient Partners® in Arthritis (PP®IA) are used in this educational setting.

Methods

A 2-page self-administered electronic questionnaire combining open- and close-ended questions was developed and piloted. It was distributed by e-mail to all Canadian undergraduate associate-deans and to 16/17 undergraduate MSK course organizers.

Results

Supervised practice in small groups and the PP®IA are the most prevalent teaching methods. Objective structured clinical examinations are the most prevalent evaluation methods. The average number of hours devoted to teaching these skills is very small compared to the prevalence of MSK complaints in the population. Canadian schools’ preclerkship MSK PE clinical skills teaching is heavily dependent on the contributions of non-MSK specialists.

Conclusion

The weak link in the Canadian MSK PE educational cycle appears to be the amount of time available for students’ deliberate practice with expert feedback. There is a need for methods to evaluate and further develop MSK PE teaching by non-MSK specialists. This and increased use of PP®IA at the preclerkship level may provide students more time for practice with feedback.
Electrocardiographic Findings in Psoriatic Arthritis: A Case-Controlled Study
Authors: FELD JOY , WEISS GIORA , ROSNER ITZHAK , ROZENBAUM MICHAEL , LAOR ARIE , RIMAR DORON , EDER LIHI , BITTERMAN HAIM , ZISMAN DEVY
Published: December 2008

Objective

We assessed cardiac conduction properties in patients with psoriatic arthritis (PsA).

Methods

Electrocardiogram (ECG) scans of 92 patients with PsA were compared to 92 age and sex matched nonpsoriatic, nonarthritic patients from general practice serving as controls.

Results

PR interval was found to be significantly longer in the PsA group compared to controls, 159.6 ± 21 ms versus 151.3 ± 26 ms, respectively (p = 0.021). No statistical difference was found with respect to the QRS interval or other atrial or ventricular conduction disturbances studied. No correlation was found between the PR interval and disease duration or PsA subtype. The use of non-steroidal antiinflammatory drugs did not affect the PR interval. Methotrexate was not found to influence the PR interval, compared to other disease modifying antirheumatic drugs. Two PsA patients (2.1%) had a PR interval > 0.2 ms. Their prolonged PR interval could not be explained by medication use. The abnormal prolongation of the PR interval was asymptomatic, requiring no additional intervention. No patient had complete heart block.

Conclusion

Our study may suggest subtle involvement of the atrioventricular node in patients with PsA.
Role of Polymorphisms in Adamantiades-Behçet’s Disease
Authors: KAKLAMANI VIRGINIA G. , SADIM MAUREEN , KOUMANTAKI YVONI , KAKLAMANIS PHEDON , PASCHE BORIS
Published: December 2008

Objective

We previously showed that Adamantiades-Behçet’s disease (A-BD) is associated with a lower incidence of malignancy compared with the general population. Transforming growth factor-β (TGF-β) has been shown to play a role in cartilage regeneration and is increased in patients with A-BD. We also found 2 functional polymorphisms of the TGF-β pathway, TGFBR1*6A and TGFB1*CC, that are associated with risk of malignancy. We tested whether incidence of these polymorphisms would differ in patients with A-BD compared with healthy controls of similar age and geographic location.

Methods

We performed a case-control study including 139 cases and 128 controls from Greece. Cases and controls were genotyped for TGFBR1*6A and TGFB1*CC.

Results

We found that cases had lower incidence of TGFBR1*6A compared with controls (11.3% vs 13.3%, respectively). Also, the incidence of TGFB1*CC was lower in cases than controls (24.6% vs 27.0%, respectively). These differences were not statistically significant.

Conclusion

Although there is a suggestion that the lower incidence of TGFBR1*6A in A-BD patients may play a protective role against development of malignancy, larger studies would be needed to fully evaluate the role of TGF-β and its polymorphisms in A-BD.
Ribonucleotide Reductase: Recent Advances
Authors: Stubbe JoAnne , Cotruvo Joseph A
Published: December 2008

Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides and play an essential role in nucleic acid metabolism in all organisms. RNRs have been divided into three classes. They share a structurally homologous subunit where the reduction occurs, with the chemistry being initiated by thiyl radical‐mediated abstraction of the nucleotide's 3′‐hydrogen atom. The classification of RNRs is based on the different strategies used to generate the transient thiyl radical. The class Ia and Ib RNRs use a diferric‐tyrosyl radical cofactor, the class II RNRs use adenosylcobalamin, and the class III RNRs use a glycyl radical generated by a [4Fe4S]1+cluster andS‐adenosylmethionine. This article focuses on the recent advances in our understanding of thein vitroandin vivomechanisms of formation of the metallocofactors in the class I RNRs inE. coliandS. cerevisiae. The discovery of a new class of RNR, class Ic, whose active cofactor is proposed to be an MnIVFeIIIcluster, and a summary of recent insights into the chemistry of the novel cofactor are also described. Finally, the current understanding of the unprecedented role of the metallocofactor in radical propagation over 35 Å in the class Ia—and presumably class Ib and Ic—RNRs is presented.
Acetylene Hydratase
Authors: Seiffert Grazyna B , Abt Dietmar , tenBrink Felix , Fischer David , Einsle Oliver , Kroneck Peter MH
Published: December 2008

The tungsten‐iron‐sulfur enzyme acetylene hydratase is a rather unique enzyme within the class of tungsten/molybdenum enzymes in the sense that it catalyzes a nonredox reaction, the addition of one molecule of water to the CC bond of acetylene to form acetaldehyde. Its crystal structure (1.26 Å) reveals a close to octahedral, or trigonalantiprismatic tungsten center, which binds a water molecule that gets activated by an adjacent aspartate residue such that it can attack an acetylene molecule bound in a distinct, hydrophobic pocket. This requires a strong shift of pKaof the aspartate, caused by a nearby low‐potential [4Fe–4S] cluster. To gain access to this novel W‐Asp‐active site, the protein evolved a new substrate channel distant from where it is found in other molybdenum and tungsten enzymes.
One‐Step Process for Creating Triple‐Shape Capability of AB Polymer Networks
Authors: Behl Marc , Bellin Ingo , Kelch Steffen , Wagermaier Wolfgang , Lendlein Andreas
Published: December 2008

Triple‐shape polymers can move from a first shape (A) to a second shape (B) and from there to a third shape (C), where both shape changes are induced by temperature increases. This triple‐shape capability is obtained for multiphase polymer networks after application of a complex thermomechanical programming process, which consists of two steps; these steps create shapes (B) and (A), while shape (C) is defined by the covalent crosslinks of the polymer network. Here, the creation of the triple‐shape capability for an AB polymer network system by a simple one‐step process similar to a conventional dual‐shape programming process is reported. The polymer networks are based on poly(ε‐caprolactone) (PCL) and poly(cyclohexyl methacrylate); favorable compositions for obtaining a triple shape effect have a PCL content between 35 and 60 wt%. This finding substantially facilitates handling of the triple‐shape technology and is an important step toward the realization of potential applications in which more than one shape change is required.
Strategy for spatial simulation of co‐rotating vortices
Authors: Deniau H. , Nybelen L.
Published: December 2008

The present numerical study is motivated by the challenge to simulate the three‐dimensional spatial dynamics of a co‐rotating vortex system, through the development of an elliptic instability (C. R. Phys. 2005; 6(4–5):431–450) using a high‐order solver of the compressible Navier–Stokes equations. This phenomenon was studied previously only by temporal simulations. The interest of spatial simulation is first to analyse the effect of the axial velocity on the merging process, which are neglected with the temporal approach, and to study interaction with jet flows. The numerical problem is the choice of boundary conditions (BCs): for the inflow and outflow conditions as well as for the lateral BCs to represent a fluid at rest. Special attention will be paid to the latter because the difficulties come from the non‐zero circulation of the vortex system considered. The classic BCs of Poinsot and Lele (J. Comput. Phys. 1992; 101: 104–129) based on the characteristics wave approach have been modified to be more adapted to the physics considered here. This new BC is based on the assumption of an irrotational flow close to the borders (in order to determine the magnitude of the waves), as the vorticity field is concentrated on the computational domain centre where the vortex system is initially placed. After a validation of these improved BCs and of all numerical tools used such as selective artificial dissipation, two spatial simulations of the vortex breakdown phenomenon have allowed validating our solver for a three‐dimensional case by comparison with the results of Ruith et al. (J. Fluid Mech. 2003; 486:331–378). Thus, the merging process of equal co‐rotating vortices through the development of elliptic instability with axial velocity were simulated. Three vortex flow configurations were considered with different vortex systems and velocity peaks ratio (azimuthal and axial velocities).

A numerical tool has been elaborated and validated for the simulation of spatial instability development in vortex flows. The first results show this ability, and the influence of the axial velocity on the dynamics of the instabilities. However, spatial simulations are limited by the computational resources (linked to the resolution and axial domain length to capture the merging process) and restricted to academic vortex flow configuration. Copyright © 2008 John Wiley & Sons, Ltd.
Thermodynamic consistent modelling of defects and microstructures in ferroelectrics
Authors: Müller Ralf , Schröder Jörg , Lupascu Doru C.
Published: December 2008

The paper describes the main phenomena associated with fatigue in ferroelectricmaterials due to defects and microstructural effects. An analysis the modelling on different length scales is presented. Starting from a thermodynamic analysis of the macroscopic material behavior other microscopic aspects are addressed. The introduction of an orientation distribution function allows for a computationally efficient extension of a single crystal model to realistic 3D structures. Additionally, the thermodynamic treatment of defects and domain wall motion is discussed to provide a better understanding of various micro‐mechanisms. It is explained by the concept of configurational/driving forces, how defects influence each other and how the mobility of domain walls is reduced in the presence of defects. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational modelling of microcracking effects in polycrystalline piezoelectric ceramics
Authors: Utzinger Johannes , Steinmann Paul , Menzel Andreas
Published: December 2008

Piezoelectric ceramics nowadays are widely commercialised in various fields of engineering technology and related constitutive modelling approaches constitute an active field of research. The physical performance of these materials is often limited by fatigue effects, possibly in combination with micro‐cracking phenomena. In this contribution, such micro‐crackbased fatigue effects in ferroelectric materials are computationally investigated by applying a cohesive‐type approach embedded into a finite element context. The geometry or rather discretisation of a representative specimen elaborated in this work refers to a natural grain structure on the meso‐level. Accordingly, the overall response of the underlying grains is approximated by means of coupled continuum elements, while the grain boundaries are discretised with interface elements. Interfacial constitutive relations are chosen to reflect highcycle‐fatigue, which finally is demonstrated by a fatigue‐motivated benchmark‐type boundary value problem. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constitutive Behaviour of Ferroelectric Piezoceramics: xperiments and Modeling
Authors: Kamlah Marc , Zhou Dayu , Laskewitz Bernd
Published: December 2008

Piezoceramics are presently being used increasingly as sensors and actuators in a wide variety of electromechanical applications, for instance, piezoelectric fuel injectors in common rail diesel and gasoline engines. We will introduce the basic mesoscopic domain mechanisms typical of these materials and their relation to macroscopic hysteresis phenomena and piezoelectric properties. In the attempt to improve the performance and especially the reliability of the components, considerable efforts have been made in the development of predictive constitutive models for the coupled and non‐linear electromechanical behaviour of piezoceramics. The success of such constitutive models depends strongly on the availability of suitable measurements. Supported by DFG, fruitful experimental work has been carried out for a commercial soft PZT polycrystalline material (PIC151, PI Ceramic) under co‐axial, coupled electromechanical loading at room temperature. Furthermore, we will discuss a micromechanical finite element simulation of a ferroelectric volume element, where each grain exhibits single crystal behaviour for the switching of its domains. Next, we will turn to macroscopic constitutive modeling. We will present a phenomenological as well as a micromechanically based model. We will present the application of these models to the analysis of poling processes of piezoceramic devices. The main purpose of this publication is to give a summary and to guide the reader to original papers for detailed reports. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomechanically coupled modelling of shape memory alloys in the framework of large strains
Authors: Christ Daniel , Reese Stefanie
Published: December 2008

In the present work we propose a new thermomechanically coupled material model for shape memory alloys (SMA) which includes the two main effects observed for these materials, pseudoelasticity and the shape memory effect. The constitutive equations are derived in the framework of large strains since the martensitic phase transformation involves inelastic deformations up to 10%, or even up to 20% if the plastic deformation after the phase transformation is taken into account. Therefore we apply a multiplicative split of the deformation gradient into elastic and inelastic parts, the latter concerning the martensitic phase transformation. An extended phase transformation function has been considered to include the tension‐compression asymmetry of textured SMA samples. In order to achieve a validation of the model by means of multiaxial experiments as well as to finally apply the concept in the simulation of complex structures, it is implemented into a finite element code. This implementation is based on an innovative integration scheme for the existing evolution equations and a monolithic solution algorithm for the coupled mechanical and thermal fields. The coupling effect is accurately investigated in several numerical examples including pseudoelasticity as well as the free and the suppressed shape memory effect. Finally, the model is used to simulate the pseudoelastic behaviour of an intracranial stent and the shape memory effect in a medical foot staple. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamic multifield modeling and simulation of electromagnetic, thermoelastic, viscoplastic solids
Authors: Unger Jaan , Stiemer Marcus , Svendsen Bob , Blum Heribert
Published: December 2008

The purpose of this work is the formulation and application of a continuum thermodynamic approach to the phenomenological modeling of a class of engineering materials which can be formed using strong magnetic fields. This is carried out in the framework of a thermodynamic, internal‐variable‐based formulation in which the deformation, temperature and magnetic fields are in general coupled. This coupling takes the form of the Lorentz force as an additional production of momentum, and the electromotive power as an additional production of energy, in the material. The constitutive formulation is based on the exploitation of the Müller‐Liu entropy principle. The resulting reduced relations are then adapted to the case of electromagnetic forming. In this context, dimensional analysis shows that, over the relevant length‐ and timescales of engineering interest, and for the materials of interest (e.g., aluminum alloys, steels) the evolution of the magnetic field is diffusive in nature, and thermal conduction is negligible. Finally, the model implementation is discussed and applied to the 3D simulation of electromagnetic sheet metal forming. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effective properties and size effects in filled polymers
Authors: Johlitz Michael , Steeb Holger , Jänicke Ralf , Diebels Stefan
Published: December 2008

Filled polymers are of special interest according to their superior mechanical properties. Special attention is given to nano‐filled polymers where not only the volume fraction but also the internal surface has a significant contribution to the effective properties. In the present contribution the increase in stiffness with decreasing size of the fillers at constant volume fraction of the fillers is modelled by a phenomenological, i.e. continuum‐based, approach taking into account large deformations. The proposed multiphase model allows for a systematic investigation of increasing surface‐to‐volume ratio which becomes important for micro‐ and nanosized fillers. The numerical treatment of the proposed model is based on a coupled Galerkin finite element formulation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)