bluuebunny/crossref_metadata_2025 huggingface dataset:
Interleukin‐6 polymorphism and bronchopulmonary dysplasia risk in very low‐birthweight infants
Authors: Usuda Touhei , Kobayashi Takehiro , Sakakibara Seiichi , Kobayashi Akira , Kaneko Takayuki , Wada Masaki , Onozuka Junya , Numata Osamu , Torigoe Katsumi , Yamazaki Hajime , Sato Takashi , Nagayama Yoshihisa , Uchiyama Makoto
Published: March 2012

Background:  The aim of the present study was to evaluate the role of interleukin (IL)‐6‐634 polymorphism in neonatal disorders such as bronchopulmonary dysplasia (BPD) and periventricular leukomalacia (PVL) in very low‐birthweight (VLBW) infants.

Methods:  This prospective cohort study included 202 infants (gestational age at birth, 23–34 weeks; birthweight, 500–1499 g). Genotypic analysis (polymerase chain reaction–restriction fragment length polymorphism) was performed with DNA extracted from whole‐blood samples.

Results:  Genotype distribution (66.8% CC, 28.2% CG, 5.0% GG) was similar to that in the adult Japanese population. BPD occurred in 85 infants (42.1%) among 202 VLBW infants. The duration of O2 therapy in infants with CG/GG genotypes was significantly longer than that in infants with the CC genotype (CG/GG vs CC: 40.3 ± 52.2 days vs 28.4 ± 32.6 days, P < 0.05), but the prevalence of BPD was not associated with the CG/GG genotype (CG/GG, 40.0%; CC, 46.3%, P= 0.24). Infants with CG/GG genotypes were more likely to have received postnatal corticosteroid therapy for BPD than those with the CC genotype (CG/GG vs CC: 20.9% vs 11.1%, P= 0.05). PVL occurred in six infants (3.0%). There was no significant difference in the prevalence of PVL among IL‐6‐634 polymorphisms (CG/GG, 3.0%; CC, 3.0%, P= 0.65).

Conclusions:  IL‐6‐634 polymorphism is associated with duration of oxygen therapy in VLBW infants. This suggests that the IL‐6‐634 polymorphism G allele is an aggravating factor of BPD. IL‐6‐634 polymorphism is not associated with PVL.
Incidence and risk factors of parenteral nutrition‐associated liver disease in newborn infants
Authors: Koseesirikul Photchanaphorn , Chotinaruemol Somporn , Ukarapol Nuthapong
Published: March 2012

Background:  The aim of the present study was to determine the incidence and risk factors of parenteral nutrition‐associated liver disease (PNALD) in neonates.

Methods:  A 1 year prospective cohort study was carried out at the neonatal intensive care unit and sick neonatal wards, Chiang Mai University Hospital. Newborns >1000 g, receiving >7 days of parenteral nutrition (PN), were enrolled. Liver function tests were done by the end of first, second, and fourth week, and then every 4 weeks until the PN was discontinued and the jaundice resolved. The diagnosis of PNALD relied on a history of PN, direct bilirubin >2 mg/dL, and exclusion of other causes of neonatal cholestasis. Selected patient factors and PN compositions were analyzed to determine the risks for development of PNALD.

Results:  A total of 24 infants with a mean gestational age and birthweight of 32.5 weeks and 1840 g were enrolled. Eight of the 24 developed PNALD. Compared to those without PNALD, gastrointestinal surgery, duration of enteral starvation, duration of PN, maximum PN caloric intake, and maximum carbohydrate intake were significantly associated with the development of liver disease. Despite the lack of statistical significance, there was a trend towards cholestasis in patients with sepsis. Elevation of direct bilirubin was the earliest biochemical change, observed in the first week after PN, followed by increased transaminases.

Conclusion:  Gastrointestinal surgery, duration of enteral starvation, duration of PN, maximum caloric and carbohydrate intake in PN were significant risks of PNALD in newborn infants.
Estimating the number of the people who inject drugs in Bali, 2010
Authors: SAWITRI ANAK AGUNG SAGUNG , BLOGG JAMES , ANGELA ROSY
Published: March 2012

Introduction and Aims. A population estimation study was performed in 2009–2010 to understand the apparent decrease in people who inject drugs (PWID) attending needle syringe programs (NSPs) and to calculate the number of PWID in Bali for service planning.

Design and Methods. The multiplier method was applied to the results of a survey of 125 PWID using data from 16 institutions to calculate benchmarks for five events. Respondents were also asked to nominate other PWID and the services they used and to name PWID who had died in the previous 3 years.

Results. There was consistency in the estimates calculated using the multipliers for police arrests, voluntary counselling and testing and NSP which produced estimates of 700, 723 and 769 PWID, respectively. The nominator method identified 529 PWID. The number of reported PWID deaths had decreased over the past 3 years and may reflect a shrinking in the population of PWID in Bali. Police data revealed a dramatic shift in arrests for drug possession in 2002–2003 compared with arrests during 2009. Heroin possession was recorded in 37.4% of 2002–2003 arrests but decreased to 3.1% in 2009, whereas amphetamine possession increased from 11% to 30.9% in the same period.

Discussion and Conclusions. Bali appears to have experienced a decrease in the number of PWID, which is likely to be related to death and to a pronounced shift to non‐injected drug use.[Sawitri AAS, Blogg J, Angela R. Estimating the number of the people who inject drugs in Bali, 2010. Drug Alcohol Rev 2012;31:813–817]
Age‐related patterns of drug use initiation among polydrug using regular psychostimulant users
Authors: DARKE SHANE , KAYE SHARLENE , TOROK MICHELLE
Published: March 2012

Introduction and Aims. To determine age‐related patterns of drug use initiation, drug sequencing and treatment entry among regular psychostimulant users.

Design and Methods. Cross‐sectional study of 269 regular psychostimulant users, administered a structured interview examining onset of use for major licit and illicit drugs.

Results. The mean age at first intoxication was not associated with age or gender. In contrast, younger age was associated with earlier ages of onset for all of the illicit drug classes. Each additional year of age was associated with a 4 month increase in onset age for methamphetamine, and 3 months for heroin. By the age of 17, those born prior to 1961 had, on average, used only tobacco and alcohol, whereas those born between 1986 and 1990 had used nine different drug classes. The period between initial use and the transition to regular use, however, was stable. Age was also negatively correlated with both age at initial injection and regular injecting. Onset sequences, however, remained stable. Consistent with the age‐related patterns of drug use, each additional year of age associated with a 0.47 year increase in the age at first treatment.

Discussion and Conclusions. While the age at first intoxication appeared stable, the trajectory through illicit drug use was substantially truncated. The data indicate that, at least among those who progress to regular illicit drug use, younger users are likely to be exposed to far broader polydrug use in their teens than has previously been the case.[Darke S, Kaye S, Torok M. Age‐related patterns of drug use initiation among polydrug using regular psychostimulant users. Drug Alcohol Rev 2012;31:784–789]
Evans on Bodily Awareness and Perceptual Self‐Location
Authors: Ávila Ignacio
Published: March 2012

In Chapter 7 of The Varieties of Reference Evans implicitly outlines a view to the effect that bodily awareness plays no role in perceptual self‐location or in the specification of our perceptual perspective of the world. In this paper I discuss this story and offer an alternative proposal. Then I explore some consequences of this account for our understanding of the elusiveness of the self in perceptual experience.
Friendly Relations: Situating Friendships Between Men and Women in the Early American Republic, 1780–1830
Authors: Good Cassandra A.
Published: March 2012

Men and women who became friends in the early American republic struggled with societal worries about the purity and chastity of their friendships. More so than other pairs of friends, heterosocial friends had to attend to how their friendships appeared to those around them. One of the most important ways of doing so was positioning a friendship in relation to spouses. In an era when marriage was the central structure for relations between men and women and fears of seduction and ruin were rampant, friends of the opposite sex needed to integrate their friendships within their marriages. This paper examines how men and women did so through the lens of their correspondence. Navigating a society without clear boundaries or rules for conducting a friendship between a man and a woman, individual pairs of friends improvised to create safe friendships in person and in letters. The careful intertwining of marriages and friendships they created demonstrates the way intimate social relationships were embedded in the social fabric of the early American republic.
An Army of Educators: Gender, Revolution and the Cuban Literacy Campaign of 1961
Authors: Herman Rebecca
Published: March 2012

The conventional scholarly narrative of gender in post‐revolutionary Cuba is that the revolutionary government prevented the emergence of an expressly feminist movement by addressing women's basic needs and simultaneously eliminating autonomous space for female organising. Recent scholarship has increasingly considered women's participation in revolutions in order to understand women's roles in post‐revolutionary societies. Looking beyond armed insurrection for instances of female participation in revolution, this article considers women's roles in the Cuban Literacy Campaign. An analysis of the testimonies of female former volunteer teachers and of the official rhetoric and content of the campaign suggests that the broader narrative of cooption, while certainly accurate overall, threatens to obscure instances in which women did challenge traditional gender norms in meaningful ways. This paper argues that the Cuban Literacy Campaign and the participation of women in that campaign significantly impacted Cuban patriarchal culture at a crucial moment of consolidation for the revolutionary regime. In other words, though the male‐led revolution did not give women the space to organise against patriarchy, by actively participating in the revolution, women did help change the nature of Cuban patriarchy.
Male Saints and Devotional Masculinity in Late Medieval England
Authors: Lewis Katherine J.
Published: March 2012

This article considers the ways in which the lives of male monastic saints circulating in late medieval England (and the cults of male saints more widely) were underpinned by certain ideas and ideals of masculinity and the functions which these performed. It argues for the significance of male saints serving as devotional models for the lay audience of these texts (both men and women). The two main sources are William Caxton's Golden Legend (published in 1483) and his Vitas Patrum (published after his death by Wynkyn de Worde in 1495). It therefore seeks to make a contribution to our understanding of the ways in which piety was used to assess masculinity, but also the extent to which piety as a social identity (both public and private in nature) was informed by notions of manliness.
Thrombolysis in Cervical Artery Dissection – Data from the Cervical Artery Dissection and Ischaemic Stroke Patients (CADISP) database
Authors: Engelter S. T. , Dallongeville J. , Kloss M. , Metso T. M. , Leys D. , Brandt T. , Samson Y. , Caso V. , Pezzini A. , Sessa M. , Beretta S. , Debette S. , Grond‐Ginsbach C. , Metso A. J. , Thijs V. , Lamy C. , Medeiros E. , Martin J. J. , Bersano A. , Tatlisumak T. , Touzé E. , Lyrer P. A. ,   for the Cervical Artery Dissection and Ischaemic Stroke Patients (CADISP)‐Study Group
Published: March 2012

Objective:  To examine whether thrombolysis for stroke attributable to cervical artery dissection (CeADStroke) affects outcome and major haemorrhage rates.

Methods:  We used a multicentre CeADStroke database to compare CeADStroke patients treated with and without thrombolysis. Main outcome measures were favourable 3‐month outcome (modified Rankin Scale 0–2) and ‘major haemorrhage’ [any intracranial haemorrhage (ICH) and major extracranial haemorrhage]. Adjusted odds ratios [OR (95% confidence intervals)] were calculated on the whole database and on propensity‐matched groups.

Results:  Among 616 CeADStroke patients, 68 (11.0%) received thrombolysis; which was used in 55 (81%) intravenously. Thrombolyzed patients had more severe strokes (median NIHSS score 16 vs. 3; P < 0.001) and more often occlusion of the dissected artery (66.2% vs. 39.4%; P < 0.001). After adjustment for stroke severity and vessel occlusion, the likelihood for favourable outcome did not differ between the treatment groups [ORadjusted 0.95 (95% CI 0.45–2.00)]. The propensity matching score model showed that the odds to recover favourably were virtually identical for 64 thrombolyzed and 64 non‐thrombolyzed‐matched CeADStroke patients [OR 1.00 (0.49–2.00)]. Haemorrhages occurred in 4 (5.9%) thrombolyzed patients, all being asymptomatic ICHs. In the non‐thrombolysis group, 3 (0.6%) patients had major haemorrhages [asymptomatic ICH (n = 2) and major extracranial haemorrhage (n = 1)].

Conclusion:  As thrombolysis was neither independently associated with unfavourable outcome nor with an excess of symptomatic bleedings, our findings suggest thrombolysis should not be withheld in CeADStroke patients. However, the lack of any trend towards a benefit of thrombolysis may indicate the legitimacy to search for more efficient treatment options including mechanical revascularization strategies.
Baroreflex mechanisms and response to exercise in patients with heart disease
Authors: Fukuma Nagaharu , Kato Kazuyo , Munakata Kazuo , Hayashi Hiroko , Kato Yuko , Aisu Noriko , Takahashi Hiroshi , Mabuchi Kousuke , Mizuno Kyoichi
Published: March 2012

Background

Past reports showed that the baroreflex continuously regulates hemodynamics during exercise. However, it is still clinically unclear. If baroreflex mechanism is able to influence actually exercise cardiovascular control, baroreflex sympathetic and/or parasympathetic function relates to response to exercise. Therefore, we examined the relationship of heat rate changes to both blood pressure increment and decrement with tolerance and chronotropic response to peak exercise in patients with heart disease.

Methods

In 25 male heart disease patients (60 ± 9 years) without decompensated heart failure, baroreceptor reflex sensitivity (BRS ms mmHg−1) was measured by reflex heart rate responses to changes in blood pressure after phenylephrine (P‐BRS) and nitroglycerin (N‐BRS) injection, respectively. Symptom‐limited treadmill exercise test was performed according to Bruce's protocol.

Results

(i) The absolute values of blood pressure change after the administrations were similar between the agents because the dosages of nitroglycerin and phenylephrine were set to equalize absolute changes in blood pressure. (ii) In this study population, the ratio of N‐BRS to P‐BRS was not significantly correlated with hypertension and diabetes mellitus. (iii) Exercise capacity (METs) (r = −0·626) and heart rate response to exercise per METs (r = 0·670) was significantly related to N‐BRS but not to P‐BRS.

Conclusion

We found that the abnormality of baroreflex function in the presence of blood pressure decrements can lead to insufficient capacity and easy sympathetic activation during exercise.
Lending in the Modern Era: Does Racial Composition of Neighborhoods Matter When Individuals Seek Home Financing? A Pilot Study in New England
Authors: Kuebler Meghan
Published: March 2012

This article explores the relationship between racial composition of neighborhoods and approval and origination of mortgages. It measures independent neighborhood effects, above and beyond applicant race effects preceding the recent housing market crisis for rental and owner–occupied homes. Mortgage applications are selected from the dozen most populated metropolitan areas in New England. Applications are linked to corresponding neighborhood data and generalized linear mixed modeling is applied. Data include prehousing market crash Housing Mortgage Disclosure Act data matched to American Community Survey 5–year data for over one million applications. Findings indicate, although controlling for income, gender, and race of the applicant, poverty and tenure, and additional socioeconomic variables, neighborhood racial composition has a statistically significant effect on whether mortgages are approved and originated. Minority presence is correlated with a negative effect on mortgage origination regardless of race of the individual loan applicant. More specifically, whites’ applications are also turned down in minority neighborhoods, especially black neighborhoods.
Going Regional: The Evolution of an Organizing Strategy in Detroit
Authors: Rusch Lara
Published: March 2012

In contexts of entrenched metropolitan inequality and limited local resources, organizers and community activists often feel a sense of urgency to target higher levels of government. This paper offers one such case from Detroit, of local organizing projects that “scaled up” in the mid–1990s to pursue a regional equity agenda. Drawing on participant observation, archival data, and interviews, the paper examines the process of unification and identifies key shifts in purpose, relational base, approach to leadership, and strategy for empowerment. While scaling up enabled members to engage in more sophisticated actions and influence higher levels of policy making, it also challenged the organization to maintain its member base. This research suggests that the process of scaling up poses tradeoffs for grassroots organizations, between responsiveness to existing members and building a regionally representative organization, capable of transcending divisions of the political environment.
Disability Risk Management and Postinjury Employment of Workers With Back Pain
Authors: Johnson William G. , Butler Richard J. , Baldwin Marjorie L. , Côté Pierre
Published: March 2012

Abstract

We analyze the outcomes of occupational back pain among four large employers that use one or more of the following disability management practices: aggressive return to work, claims management, medical management, or time‐limited job accommodations. Outcomes measured at 6 and 12 months postonset include: duration of initial work absence and the probability of returning to stable employment. Employment outcomes are better in firms with more proactive return‐to‐work policies than in firms with more restrictive policies. We devise a statistical test for attrition bias and conclude that sample attrition does not significantly alter our results.
Fuel Risk Management at American Electric Power
Authors: Buck Douglas , Elliott Dwayne , Niehaus Greg , Rives Bill , Thomas Laura
Published: March 2012

Abstract

The senior management team and board of directors at American Electric Power (AEP) have emphasized the importance of an Enterprise Risk Management approach for dealing with the wide array of risk exposures that the firm faces. Senior management has put in place a risk governance structure that facilitates the identification of major risk exposures, assesses their impact on the firm's overall risk profile, and interacts the risk management process with the strategic planning process. Central to this structure is the firm's Risk Executive Committee, which includes the senior leadership of the firm and the Enterprise Risk Oversight staff. Members of the AEP Enterprise Risk Oversight group have just returned from a meeting of the Risk Executive Committee. The discussion at the meeting focused on an event that recently came to the firm's attention—an unexpected disruption in the firm's coal supply over the coming year due to necessary repairs in railroad facilities near the coal source. By the end of the week, the Enterprise Risk Oversight group needs to communicate with the relevant teams within the organization as part of its effort to identify the potential repercussions of the event for the enterprise. In addition, the Risk Executive Committee would like the groups to identify other possible adverse events that could occur and steps that should be taken now in preparation.
Insurance Protection Funds in the European Union—Quo Vadis?
Authors: Monkiewicz Marek
Published: March 2012

Abstract

Contrary to the development in other major insurance markets in the world only 13 out of 27 EU member states have introduced until now some type of insurance protection funds (IPF). As a result around a third of the market is without any collective protection. There is also a continuous debate since 2001 among the member states on the need for such a system at the community level. The experiences of the latest financial crisis have raised new arguments for reorganizing the existing system to avoid regulatory arbitrage and to strengthen consumer security. Even the prospective implementation of provisions strengthening supervisory bodies, and the new solvency directive (so‐called Solvency II) are not fail‐safe solutions. This article is an attempt to review the current situation as regards IPF in the EU and to discuss possible development scenarios.
Intravenous Oxycodone for Pain Relief in the First Stage of Labour – Maternal Pharmacokinetics and Neonatal Exposure
Authors: Kokki Merja , Franco Maria Gonzalez , Raatikainen Kaisa , Välitalo Pyry , Sankilampi Ulla , Heinonen Seppo , Neuvonen Pertti J. , Kokki Hannu
Published: March 2012

Physiological changes during pregnancy may change pharmacokinetics of compounds. Oxycodone is an increasingly used opioid agonist in acute pain management but its pharmacokinetics in labouring women has not been established. We studied the maternal pharmacokinetics and neonatal exposure of intravenous oxycodone for pain relief in the first stage of labour. The study was prospective, open‐labelled and with a control group. After informed consent, 15 nulliparous parturients and newborns, and newborns in a control group were studied. In the study group, oxycodone boluses of 1 mg i.v., up to a cumulative dose of 5 mg, was administered when labour pain score was 5/10 or higher. As the control group, 30 other newborns after uncomplicated deliveries with no systemic opioids were assessed for the neonatal outcome. In the study group, maternal pharmacokinetics of oxycodone was measured from plasma concentrations during labour, and neonatal exposure was assessed from umbilical plasma samples using population pharmacokinetic methods. Maternal plasma oxycodone concentration decreased with a median half‐life of 2.6 hr (range, 1.8–2.8). Oxycodone concentrations in the umbilical plasma 2.7 μg/l (0.3–14.5) were similar as in maternal plasma 2.4 (0.1–14.8) μg/l at the time of birth. No severe or unexpected adverse effects were noted. To conclude, firstly, maternal elimination half‐life of i.v. oxycodone was significantly shorter than that reported in non‐pregnant women, and secondly, maternal plasma oxycodone at the birth correlated well with neonatal umbilical concentrations and may, thus, be used as an estimate of neonatal exposure.
Differentiation of Indian, East Timorese, Papuan and Floridian ‘CandidatusLiberibacter asiaticus’ isolates on the basis of simple sequence repeat and single nucleotide polymorphism profiles at 25 loci
Authors: Katoh H. , Davis R. , Smith M.W. , Weinert M. , Iwanami T.
Published: March 2012

Japanese isolates of ‘Candidatus Liberibacter asiaticus’ have been shown to be clearly differentiated by simple sequence repeat (SSR) profiles at four loci. In this study, 25 SSR loci, including these four loci, were selected from the whole‐genome sequence and were used to differentiate non‐Japanese samples of ‘Ca. Liberibacter asiaticus’ (13 Indian, 3 East Timorese, 1 Papuan and 8 Floridian samples). Out of the 25 SSR loci, 13 were polymorphic. Dendrogram analysis using SSR loci showed that the clusters were mostly consistent with the geographical origins of the isolates. When single nucleotide polymorphisms (SNPs) were searched around these 25 loci, only the upstream region of locus 091 exhibited polymorphism. Phylogenetic tree analysis of the SNPs in the upstream region of locus 091 showed that Floridian samples were clustered into one group as shown by dendrogram analysis using SSR loci. The differences in nucleotide sequences were not associated with differences in the citrus hosts (lime, mandarin, lemon and sour orange) from which the isolates were originally derived.
Contrasting the Predictions for Coulomb and Creep-Rate-Dependent Friction in the Modeling of Fiber-Draw Processes
Authors: Bechtel S. E. , Vohra S. , Jacob K. I.
Published: March 2012

One of the most important features in industrial fiber-drawing processes is the friction between filament tow and draw rollers, because it is what creates the tension in the fiber that performs the draw. To understand fiber draw, therefore, it would be valuable to examine the sensitivity of model predictions to the choice of the idealization of the friction incorporated in the model. This paper begins the comparative study by deriving and solving models for fiber draw, which for the first time study the friction between filament tow and draw rollers as something other than Coulomb friction, namely creep-rate-dependent friction. Sensitivity of the draw model to the choice of friction idealization is investigated by contrasting process simulations employing the usual Coulomb model for friction with simulations of the same processes employing the creep-rate-dependent friction model. It is demonstrated that the draw-model predictions of fiber behavior depend both qualitatively and quantitatively on the specific idealization of the friction between filament and rollers. For example, whereas the Coulomb friction model predicts adhesion zones on the rollers, in which the fibers and roller move together with no slip, there are strictly no adhesion zones with the creep-rate-dependent friction model, although with a choice of processing parameters the predicted relative velocity between fiber and roller can be made arbitrarily small. With the creep-rate-dependent friction model the fiber speed at the point of attachment to the draw roller must be greater than the roller surface speed for the equations of momentum to be satisfied. This small, but finite, abrupt change in speed profile can be interpreted as the formation of a neck in the fiber just upstream of the point of attachment to the roller.
The 2011 Koiter Lecture: The Simple Logic of Classical Nonlinear Thermodynamic Shell Theory
Authors: Simmonds J. G.
Published: March 2012

A classical nonlinear thermodynamic theory of elastic shells is derived by specializing the three-dimensional equations of motion and the second law of thermodynamics to a very general, shell-like body. No assumptions are made on how unknowns vary through the thickness. Extensional and bending strains are derived from the equations of motion via the principle of virtual power. The Coleman-Noll procedure plus the second law applied to an assumed form of the first law leads to constitutive relations plus reduced forms of the first and second laws. To avoid potential ill conditioning, a Legendre-Fenchel transformation is used to define a mixed-energy density, the logical place to impose the constitutive Kirchhoff hypothesis, if desired, because such an energy density rests, ultimately, on experiments. The Ladevèze-Pécastaings treatment of three-dimensional edge effects to obtain accurate two-dimensional solutions is discussed.
Static/Dynamic Edge Movability Effect on Non-Linear Aerothermoelastic Behavior of Geometrically Imperfect Curved Skin Panel: Flutter and Post-Flutter Analysis
Authors: Abbas Laith K. , Rui Xiaoting , Marzocca P. , Abdalla M. , De Breuker R.
Published: March 2012

This paper addresses the problem of the aerothermoelastic modeling behavior and analyses of skin curved panels with static and dynamic edge movability effect in high supersonic flow. Flutter and post-flutter behavior will be analyzed toward determining under which conditions such panels will exhibit a benign instability, that is a stable limit cycle oscillation, or a catastrophic instability, that is an unstable LCO. The aerothermoelastic governing equations are developed from the geometrically non-linear theory of infinitely long two dimensional curved panels. Von Kármán non-linear strain-displacement relation in conjunction with the Kirchhoff plate-hypothesis is adopted. A geometrically imperfect curved panel forced by a supersonic/hypersonic unsteady flow is numerically investigated using Galerkin approach. These equations are based on the third-order piston theory aerodynamic for modeling the flow-induced forces. Furthermore, the effects of thermal degradation and Kelvin’s model of structural damping independent of time and temperature are also considered in this model. Computational analysis and discussion of the finding along with pertinent conclusions are presented.
A Modified Storen-Rice Bifurcation Analysis of Sheet Metal Forming Limit Diagrams
Authors: Jaamialahmadi A. , Kadkhodayan M.
Published: March 2012

Bifurcation analysis is a theoretical prediction approach to measure the FLD when the localized neck causes development of vertex on subsequent yield surface as was adopted by Storen-Rice. Some analyses lead to solutions for special cases such as zero and minimum extension. They offer an equation which needs to be optimized with respect to the minimum limit strain versus neck orientation for the whole domain of FLD. Moreover, the previous reported results for the left-hand side of FLD are not quite satisfactory. In this paper, a re-investigation into bifurcation analysis adopted by S-R lead to modified equations which significantly improved FLD and could be respected as a more general approach to find FLD theoretically. The derivation and optimization procedure of equations are indicated and discussed in detail. The predicted limit strains are studied for different work hardening coefficients and compared with Storen-Rice, Zhu and some experimental data and the obtained results show more agreement. Furthermore, the present restrictions and the required conditions for validation of the Zhu approach are fully discussed.
Analysis of Sandwich Beams With a Compliant Core and With In-Plane Rigidity—Extended High-Order Sandwich Panel Theory Versus Elasticity
Authors: Phan Catherine N. , Frostig Yeoshua , Kardomateas George A.
Published: March 2012

A new one-dimensional high-order theory for orthotropic elastic sandwich beams is formulated. This new theory is an extension of the high-order sandwich panel theory (HSAPT) and includes the in-plane rigidity of the core. In this theory, in which the compressibility of the soft core in the transverse direction is also considered, the displacement field of the core has the same functional structure as in the high-order sandwich panel theory. Hence, the transverse displacement in the core is of second order in the transverse coordinate and the in-plane displacements are of third order in the transverse coordinate. The novelty of this theory is that it allows for three generalized coordinates in the core (the axial and transverse displacements at the centroid of the core and the rotation at the centroid of the core) instead of just one (midpoint transverse displacement) commonly adopted in other available theories. It is proven, by comparison to the elasticity solution, that this approach results in superior accuracy, especially for the cases of stiffer cores, for which cases the other available sandwich computational models cannot predict correctly the stress fields involved. Thus, this theory, referred to as the “extended high-order sandwich panel theory” (EHSAPT), can be used with any combinations of core and face sheets and not only the very “soft” cores that the other theories demand. The theory is derived so that all core/face sheet displacement continuity conditions are fulfilled. The governing equations as well as the boundary conditions are derived via a variational principle. The solution procedure is outlined and numerical results for the simply supported case of transverse distributed loading are produced for several typical sandwich configurations. These results are compared with the corresponding ones from the elasticity solution. Furthermore, the results using the classical sandwich model without shear, the first-order shear, and the earlier HSAPT are also presented for completeness. The comparison among these numerical results shows that the solution from the current theory is very close to that of the elasticity in terms of both the displacements and stress or strains, especially the shear stress distributions in the core for a wide range of cores. Finally, it should be noted that the theory is formulated for sandwich panels with a generally asymmetric geometric layout.
The Multimodal Dynamics of a Walnut Tree: Experiments and Models
Authors: Rodriguez M. , Ploquin S. , Moulia B. , de Langre E.
Published: March 2012

The dynamics of a walnut tree is investigated in order to better understand the mechanical interaction of trees with wind. Experimental data on the vibrational modes of the tree are obtained, using pull and release tests. These results are then used to validate a previous analytical approach that predicts the organization of modal frequencies as a function of two allometry parameters describing the branched tree geometry. In addition to these experimental results, vibration modes are also obtained from a finite element computation using a detailed digitization of the tree geometry. The comparison between experiments, computation, and the simple analytical approach confirm the specific organization of modes of such branched trees, with a high modal density and a spatial localization. Then the possible biological importance of this organization and the potential biomimetic applications are outlined.
Adhesion of a Compliant Cylindrical Shell Onto a Rigid Substrate
Authors: Shi Jiayi , Müftü Sinan , Wan Kai-tak
Published: March 2012

The mechanical deformation of an ideal thin-walled cylindrical shell is investigated in the presence of intersurface interactions with a planar rigid substrate. A Dugdale–Barenblatt–Maugis (DBM) cohesive zone approximation is introduced to simulate the convoluted surface force potential. Without loss of generality, the repulsive component of the surface forces is approximated by a linear soft-repulsion, and the attractive component is described by two essential variables, namely, surface force range and magnitude, which are allowed to vary. The nonlinear problem is solved numerically to generate the pressure distribution within the contact, the deformed membrane profiles, and the adhesion-delamination mechanics, which are distinctly different from the classical solid cylinder adhesion models. The model has wide applications in cell adhesion and nanostructures.
Transient Plane Wave Solutions to Homogeneous Equations of Orthotropic Thermoelasticity With Thermal Relaxation: Illustration
Authors: Brock L. M.
Published: March 2012

Complementary (homogeneous) transient solutions for orthotropic thermoelasticity with thermal relaxation admit plane waves that propagate in a principal plane without spatial attenuation, but with exponential decay in their wake. Three speeds that vary with decay coefficient and propagation direction exist, and each speed is associated with three reflections from a plane surface aligned with another principal plane. As examples, values from both speed sets are presented, as well as angles of reflection and decay coefficients for given incident waves. For a half-space surface that is traction-free but exhibits convection, surface temperature change is derived, and values also presented.
Simulation of Constrained Mechanical Systems—Part II: Explicit Numerical Integration
Authors: Braun David J. , Goldfarb Michael
Published: March 2012

This paper presents an explicit to integrate differential algebraic equations (DAEs) method for simulations of constrained mechanical systems modeled with holonomic and nonholonomic constraints. The proposed DAE integrator is based on the equation of constrained motion developed in Part I of this work, which is discretized here using explicit ordinary differential equation schemes and applied to solve two nontrivial examples. The obtained results show that this integrator allows one to precisely solve constrained mechanical systems through long time periods. Unlike many other implicit DAE solvers which utilize iterative constraint correction, the presented DAE integrator is explicit, and it does not use any iteration. As a direct consequence, the present formulation is simple to implement, and is also well suited for real-time applications.
Initial Elastic Properties of Unidirectional Ceramic Matrix Composite Fiber Tows
Authors: Blacklock M. , Hayhurst D. R.
Published: March 2012

The initial elastic properties of two unidirectional ceramic matrix composite tows, comprised of continuous, cylindrical fibers surrounded by one or more matrices, have been calculated using three different methods. The first uses finite element (FE) analysis of the tow to calculate values for elastic and shear moduli and Poisson’s ratios in the three principal directions, and in the absence of confirmatory experimental data is regarded as the most accurate for a wide range of fiber/matrix geometries and materials. The other two models are (i) rule of mixtures, ROM/volume averaging and (ii) the approximate equations of Halpin-Tsai and analytical relations based on slab representation for composite materials that rely on the elastic properties and volume fractions of the constituent materials. Initial elastic properties of the tows determined by the FE method are presented, and they are compared with predictions made by the other two techniques.
Strain Localization and Slip Instability in a Strain-Rate Hardening, Chemically Weakening Material
Authors: Brantut N. , Sulem J.
Published: March 2012

The stability of steady slip and homogeneous shear is studied for rate-hardening materials undergoing chemical reactions that produce weaker materials (reaction-weakening process), in drained conditions. In a spring- slider configuration, a linear perturbation analysis provides analytical expressions of the critical stiffness below which unstable slip occurs. In the framework of a frictional constitutive law, numerical tests are performed to study the effects of a nonlinear reaction kinetics on the evolution of the instability. Slip instabilities can be stopped at relatively small slip rates (only a few orders of magnitude higher than the forcing velocity) when the reactant is fully depleted. The stability analysis of homogeneous shear provides an independent estimate of the thickness of the shear localization zone due to the reaction weakening, which can be as low as 0.1 m in the case of lizardite dehydration. The potential effect of thermo-chemical pore fluid pressurization during dehydration is discussed, and shown to be negligible compared to the reaction-weakening effect. We finally argue that the slip instabilities originating from the reaction-weakening process could be a plausible candidate for intermediate depth earthquakes in subduction zones.
Length Scale for Transmission of Rotations in Dense Granular Materials
Authors: Padbidri Jagan M. , Hansen Carly M. , Mesarovic Sinisa Dj. , Muhunthan Balasingam
Published: March 2012

Deformation of granular materials is often characterized by strain localization in the form of shear bands, which exhibit a characteristic width of about 10–20 particle diameters. Much of the relative motion of particles within a shear band is accompanied by rolling, as opposed to sliding, since the latter requires more dissipative work. However, in a densely packed assembly, rolling cannot be accomplished without some sliding. This dissipative constraint implies a characteristic rotation transmission distance, i.e., the distance to which the information about rotation of a particle propagates. Here, we use the discrete element method to investigate this length and its directional dependence as function of the force chain network. We found that the rotation transmission distance correlates with the shear band width observed in experiments and previous numerical simulations. It is strongly dependent on the particle size distribution and the coefficient of interparticle friction, and weakly dependent on pressure. Moreover, the transmission of rotations is strongly directionally dependent following the pattern of force chains. To describe this dependence, we define a nonlocal tensorial description of force chain directionality.
A Micromechanics Based Constitutive Model for Brittle Failure at High Strain Rates
Authors: Bhat Harsha S. , Rosakis Ares J. , Sammis Charles G.
Published: March 2012

The micromechanical damage mechanics formulated by Ashby and Sammis, 1990, “The Damage Mechanics of Brittle Solids in Compression,” Pure Appl. Geophys., 133(3), pp. 489–521, and generalized by Deshpande and Evans 2008, “Inelastic Deformation and Energy Dissipation in Ceramics: A Mechanism-Based Constitutive Model,” J. Mech. Phys. Solids, 56(10), pp. 3077–3100. has been extended to allow for a more generalized stress state and to incorporate an experimentally motivated new crack growth (damage evolution) law that is valid over a wide range of loading rates. This law is sensitive to both the crack tip stress field and its time derivative. Incorporating this feature produces additional strain-rate sensitivity in the constitutive response. The model is also experimentally verified by predicting the failure strength of Dionysus-Pentelicon marble over strain rates ranging from ∼10− 6to 103s− 1. Model parameters determined from quasi-static experiments were used to predict the failure strength at higher loading rates. Agreement with experimental results was excellent.
Modified Stoney Equation for Patterned Thin Film Electrodes on Substrates in the Presence of Interfacial Sliding
Authors: Haftbaradaran Hamed , Soni Sumit K. , Sheldon Brian W. , Xiao Xingcheng , Gao Huajian
Published: March 2012

Mechanical stresses and failure are believed to be a major cause for the limited cycle life of lithium-ion batteries employing high capacity Si electrodes. Recent experiments have shown that patterned Si thin film electrodes on substrate exhibit improved cycling stability and substantial sliding at the film/substrate interface. To facilitate experimental studies of stress evolution in such systems, we have developed a modified Stoney equation which accounts for the effect of interfacial sliding on the relationship between curvature and stress in patterned thin films on substrate.
Rice’s Internal Variables Formalism and Its Implications for the Elastic and Conductive Properties of Cracked Materials, and for the Attempts to Relate Strength to Stiffness
Authors: Kachanov Mark , Sevostianov Igor
Published: March 2012

Rice’s internal variables formalism [1975, “Continuum Mechanics and Thermodynamics of Plasticity in Relation to Microscale Deformation Mechanisms,” in Constitutive Equations in Plasticity, edited by A. Argon, MIT Press, Cambridge, MA, pp. 23–75] is one of the basic tools in the micromechanics of materials. One of its implications is the possibility to relate the compliance/resistivity contributions of cracks—the key quantities in the problem of effective elastic/conductive properties—to the stress intensity factors (SIFs) and thus to utilize a large library of available solutions for SIFs. Examples include configurations that are common in materials science applications: branched and intersecting cracks, cracks with partial contact between crack faces, and cracks emanating from pores. The formalism also yields valuable physical insights of a qualitative character, such as the impossibility to correlate, in a quantitative way, the strength of microcracking materials and their stiffness reduction.
Some Remarks on the Effect of Interphases on the Mechanical Response and Stability of Fiber-Reinforced Elastomers
Authors: Bertoldi Katia , Lopez-Pamies Oscar
Published: March 2012

In filled elastomers, the mechanical behavior of the material surrounding the fillers -termed interphasial material-can be significantly different (softer or stiffer) from the bulk behavior of the elastomeric matrix. In this paper, motivated by recent experiments, we study the effect that such interphases can have on the mechanical response and stability of fiber-reinforced elastomers at large deformations. We work out in particular analytical solutions for the overall response and onset of microscopic and macroscopic instabilities in axially stretched 2D fiber-reinforced nonlinear elastic solids. These solutions generalize the classical results of Rosen (1965, “Mechanics of Composite Strengthening,” Fiber Composite Materials, American Society for Metals, Materials Park, OH, pp. 37–75), and Triantafyllidis and Maker (1985, “On the Comparison between Microscopic and Macroscopic Instability Mechanisms in a Class of Fiber-Reinforced Composites,” J. Appl. Mech., 52, pp. 794–800), for materials without interphases. It is found that while the presence of interphases does not significantly affect the overall axial response of fiber-reinforced materials, it can have a drastic effect on their stability.
On Electromechanical Coupling in Elastomers
Authors: Volokh K. Y.
Published: March 2012

Permittivity of electroactive elastomers alters during deformation. The influence of the permittivity alterations on the electrostriction of elastomers is studied in the present work. Particularly, acrylic elastomer VHB 4910 is considered. A polarization–electric field constitutive theory is introduced accounting for the influence of mechanical deformations. The theory is used to analyze a free electrostriction of a thin elastomer plate. The elastic stress in the plate is described by various constitutive models including neo-Hookean, Yeoh, Arruda-Boyce, and Ogden. Results show that the permittivity alterations during mechanical deformation practically do not affect the process of electrostriction.
Application of the Method of Reverberation Ray Matrix to the Early Short Time Transient Responses of Stiffened Laminated Composite Plates
Authors: Li Feng-Ming , Liu Chun-Chuan , Shen Sheng , Huang Wen-Hu
Published: March 2012

The method of reverberation ray matrix (MRRM) is extended to research the transient wave propagation and early short time transient responses of the stiffened laminated composite plates subjected to impact loads. The rib-stiffened laminated plates are modeled as the coupling systems in which the flexural motion for the laminated plate is considered, and the flexural and torsional motions are taken into account for the laminated stiffeners, which are modeled as the beams. The dynamic models of the laminated plates and beams in the Laplace phase space are established based on the first order shear deformation theory (FSDT). The reverberation ray matrix is determined by the continuous and boundary conditions of the stiffened laminated plate. The transient response corresponding to each ray group is calculated by the FFT algorithm. From the numerical results, it is seen that the early short time transient accelerations of the stiffened laminated plates are very large, while the early short time transient displacements are very small. Furthermore, the influences of the stiffeners and different impulse signals on the early short time transient responses of the stiffened laminated plates are also studied.
Peristaltic Flow of Pseudoplastic Fluid in an Asymmetric Channel
Authors: Noreen S. , Alsaedi A. , Hayat T.
Published: March 2012

This research is concerned with the peristaltic flow of pseudoplastic fluid. The problem formulation is made and then the solution analysis is presented, subject to a long wavelength and a low Reynolds number. The stream function and pressure gradient have been computed. Pumping and trapping phenomena are analyzed in detail.