bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of the colorectal surgical research across Europe, USA and Australasia
Authors: D’Souza R. , Srinivasa S. , Cribb B. , Hill L. , Hill A.
Published: October 2011

Aim  The annual scientific meetings of the Association of Coloproctology of Great Britain and Ireland (ACPGBI), the American Society of Colon and Rectal Surgeons (ASCRS), the European Society of Coloproctology (ESCP) and the Royal Australasian College of Surgeons (RACS) are the major fora for presentation of colorectal surgical research. Thus, their content could be a proxy of the content and quality of colorectal surgical research worldwide. We aimed to critically appraise the quantity, quality and topics of colorectal surgical research over the previous 5 years for the above meetings.

Method  All published abstracts from the ACPGBI, ASCRS, ESCP and the colorectal‐specific component of the RACS from 2006 to 2010 were appraised. Abstracts were coded by predefined categories pertaining to study type and topic.

Results  Level 1 evidence (systematic reviews/meta‐analyses) and level 2 evidence (randomized controlled trials) comprised 3% (95% CI 1–9%) and 5% (95% CI 2–11%), respectively, of research presented at the meetings. There was a predominance of level 4 evidence (retrospective studies) across all years (mean 54%, 95% CI 44–68%). Operative management was most commonly studied (mean 43%, 95% CI 36–49%). There was minimal research in perioperative care (mean 6%, 95% CI 2–13%) and basic surgical science (mean 6%, 95% CI 2–11%). Research related to perioperative care was significantly higher at the ACPGBI and RACS meetings than the ASCRS and ESCP meetings (P < 0.01).

Conclusion  The research at these meetings consists largely of retrospective reviews exploring operative management with minimal high quality scientific content. Active steps need to be taken to increase the quantity of high level evidence especially in topics other than operative management.
Evaluation of placental growth factor and soluble Fms‐like tyrosine kinase 1 as predictors of all‐cause and cardiovascular mortality in patients with Type 1 diabetes with and without diabetic nephropathy
Authors: Theilade S. , Lajer M. , Jorsal A. , Tarnow L. , Parving H.‐H. , Rossing P.
Published: October 2011

Diabet. Med. 29, 337–344 (2012)

Aims  Placental growth factor is a vascular endothelial growth factor involved in angiogenesis, vascular inflammation and plaque formation. Soluble Fms‐like tyrosine kinase 1 is a decoy receptor for placental growth factor, reducing its activity. The aim of this study is to evaluate the predictive value of placental growth factor and soluble Fms‐like tyrosine kinase 1 in relation to all‐cause and cardiovascular mortality and decline in kidney function in Type 1 diabetes.

Methods  This was a prospective, observational follow‐up study with 8 (0–13) years [median (range)] of follow‐up, including patients with Type 1 diabetes, of whom 458 had diabetic nephropathy [278 men; age 42 ± 11 years (mean ± sd), diabetes duration 28 ± 9 years, glomerular filtration rate 76 ± 33 ml min−1 1.73 m−2] and 442 had long‐standing normoalbuminuria (234 men; age 45 ± 12 years, diabetes duration 28 ± 10 years).

Results  Placental growth factor and soluble Fms‐like tyrosine kinase 1 levels measured at baseline were higher in patients with diabetic nephropathy compared with patients with long‐standing normoalbuminuria [median (range)] 15 (4–131) vs. 11 (7–64) ng/l, (P < 0.001) and 86 (42–3462) vs. 77 (43–1557) ng/l (P < 0.001), respectively. In patients with diabetic nephropathy, high levels of placental growth factor predicted all‐cause and cardiovascular mortality [hazard ratio 1.94 (1.16–3.24) and hazard ratio 2.91 (1.45–5.85)] after adjustment for sex, age, smoking, systolic blood pressure, HbA1c, cholesterol, glomerular filtration rate and previous cardiovascular disease. High levels of placental growth factor predicted increased risk of end‐stage renal disease [hazard ratio 2.77 (1.47–5.14)], but covariate adjustments attenuated the association [hazard ratio 1.89 (0.91–3.95)]. Among patients with long‐standing normoalbuminuria, placental growth factor levels predicted fatal and non‐fatal cardiovascular events [hazard ratio 1.97 (1.03–3.76)], but not all‐cause mortality. Baseline soluble Fms‐like tyrosine kinase 1 levels did not predict outcome in either group after adjustment.

Conclusion  Placental growth factor is elevated in patients with Type 1 diabetes and diabetic nephropathy and predicts all‐cause and cardiovascular mortality, but not deterioration of kidney function.
HIV/AIDS AND BANKING STABILITY IN DEVELOPING COUNTRIES
Authors: Leoni Patrick L.
Published: October 2011

We argue that the recent large increase in deposits’ turnover in many developing countries with high HIV/AIDS prevalence is associated with the spread of the disease. The point is that the need to pay for individual treatments force large‐scale withdrawals of households’ deposits, and that those large withdrawals put the banking industry at risk. In a standard demand‐deposit model where the HIV/AIDS prevalence among depositors is random, we show that (1) the probability of a large‐scale banking failure without a bank run increases as the odds of any prevalence level increases, and (2) it is always optimal to deposit, and thus to accept the risk of banking failure, to maintain long‐term investments in place.
A Contextual Mann‐Kendall Approach for the Assessment of Trend Significance in Image Time Series
Authors: Neeti Neeti , Eastman J. Ronald
Published: October 2011

One of the most common problems in estimating trends in image time series is the presence of contaminants such as clouds. There are many techniques for estimating robust trends but evaluating the significance of the trends can be difficult due to this increased variance. This article presents a novel approach called the Contextual Mann‐Kendall (CMK) test for assessing significant trends. This test uses the principle of spatial autocorrelation to characterize geographical phenomena, according to which a pixel would not be expected to exhibit a radically different trend from neighboring pixels. The procedure removes serial correlation through a prewhitening process. Then, similar to the logic of the Regionally Averaged Mann‐Kendall (RAMK) test, it combines the information from neighboring pixels while adjusting for cross‐correlation. CMK was compared with the Mann‐Kendall (MK) test in which contextual information was not involved for the mean annual NDVI over 22 years (1982–2003) in West Africa. With the MK test, ∼11% of the study area showed significant (p < 0.001) trends which increased to 16% when tested using the CMK test. Thus the CMK test produces a result that makes intuitive sense from a geographical perspective and enhances the ability to detect trends in relatively short time series.
Change point detection in copula ARMA–GARCH Models
Authors: Na Okyoung , Lee Jiyeon , Lee Sangyeol
Published: October 2011

In this article, we consider the problem of testing for a copula parameter change based on the cusum test. We first handle this issue in i.i.d. samples and extend it to semiparametric copula ARMA‐GARCH models. We construct the cusum test based on pseudo maximum likelihood estimation of the copula parameter and derive its limiting null distribution. Simulation results are reported for illustration.
Determination of inorganic elements in milk powder using wavelength dispersive X‐ray fluorescence spectrometer
Authors: HABIB‐UR‐REHMAN  , REHANA ISHRAT , YAWAR WASIM
Published: October 2011

The concentration of calcium, magnesium, phosphorus, potassium and trace elements, bromine, copper, iron, rubidium and zinc in different brands of milk powder and infant formulas have been determined using a wavelength dispersive X‐ray fluorescence spectrometer. Lithium fluoride (LiF200) and pentaerythritol (PET) crystals were used with flow proportional detector (FPC) for the measurement of intensity of characteristic X‐ray lines. Calibration curves were established using a set of synthetic standards in cornstarch matrix. The validation of the method was assessed by analysing an IAEA standard reference material of milk powder, IAEA‐153. The results were in good agreement with the certified values.
Developmental changes of TrkB signaling in response to exogenous brain‐derived neurotrophic factor in primary cortical neurons
Authors: Zhou Xianju , Xiao Hua , Wang Hongbing
Published: October 2011

J. Neurochem. (2011) 10.1111/j.1471‐4159.2011.07528.x

Neocortical circuits are most sensitive to sensory experience during a critical period of early development. Previous studies implicate that brain‐derived neurotrophic factor (BDNF) and GABAergic inhibition may control the timing of the critical period. By using an in vitro maturation model, we found that neurons at DIV (day in vitro) 7, around a period when functional synapses start to form and GABAergic inhibition emerges, displayed the most dynamic activation of extracellular signal‐regulated kinase 1/2 (ERK1/2) and CREB by exogenous BDNF. The BDNF‐stimulated transcriptional up‐regulation of CREB target genes was also the highest in DIV 7 neurons. The basal level of ERK1/2 and CREB activity, as well as the expression of CREB target genes, increased along with maturation, and neurons at DIV 13 and 22 displayed less dynamic responses to BDNF. Furthermore, we found that the developmentally regulated GABAergic inhibition correlated with the decline of BDNF‐mediated signaling during maturation. BDNF stimulation along with suppression of GABAergic inhibition enhanced the activation of ERK1/2‐CREB signaling and gene transcription in mature neurons. Conversely, BDNF stimulation along with enhancement of GABAergic inhibition reduced the overall induction of intracellular signaling in younger neurons. We propose that the less dynamic molecular changes may play a certain role in the loss of plasticity during maturation.
External environment
Authors: DREYER L. , ANDERSEN A. , PUKKALA E.
Published: October 2011

Air pollutants arising from traffic clustering and industrial production include a number of chemical compounds that at high doses are carcinogenic in animal models and in some instances also in humans. Direct epidemiological evidence for a carcinogenic effect of air pollution in humans is, however, weak, and most of the available studies are limited by lack of adequate control of confounding factors and other methodological drawbacks. Limited evidence exists for a link between urban air pollution and lung cancer, with reported relative risks of 1.0–1.5. About one‐third of the population of the Nordic countries, corresponding to 7.3 million people, lives in urban areas. If there is an excess risk associated with air pollution, the annual number of lung cancer cases around the year 2000 in the Nordic countries would range from 0 (no excess risk) to 1,800 (relative risk, 1.5). As the existence of a causal link between air pollution and cancer is not uncorroborated, measures for avoiding cancer from this source cannot be recommended.
Diet, obesity and low physical activity
Authors: WINTHER J. F. , DREYER L. , OVERVAD K. , TJØNNELAND A. , DE VERDIER M. GERHARDSSON
Published: October 2011

In the early 1980s, Doll and Peto estimated that about 35% of all deaths from cancer in the United States were attributable to dietary factors, with a margin of uncertainty ranging from 10 to 70%. Since then, several dietary factors, e.g. fat and meat, have been suggested to increase the risk for cancer, while other factors, e.g. fibre, fruit and vegetables, have been suggested to decrease the risk. The case‐control and cohort studies have, however, given ambiguous results, and the overall evidence is far from conclusive. The major findings on dietary factors that increase risk have been reported from case‐control studies, but have not been confirmed in large population‐based cohort studies. Although the research in this area indicates that diet is important in cancer prevention, current knowledge does not allow reliable estimates of the numbers and proportions of cancers that could be avoided through well‐described modifications of dietary habits. During the last 10 years, low physical activity has been pinpointed as a risk factor for cancers at various sites, especially the colon; however, the causal mechanism is still unknown. Obesity, defined as a body mass index of 30 or more, is consistently associated with endometrial and gall‐bladder cancers in women and renal‐cell cancer in both men and women. As the prevalence of obesity was between 5 and almost 20% in the Nordic populations in 1995, 625 cancer cases (310 endometrial cancers, 270 renal‐cell cancers in men and women and 45 gall‐bladder and bile‐duct cancers among women) can be predicted in the Nordic countries around the year 2000 to be caused by obesity. This implies that about 1% of all cancers in Nordic women and less than 1% of those in Nordic men could be avoided around the year 2000 if a healthy body weight could be maintained by all inhabitants.
Biological agents
Authors: WINTHER J. F. , MØLLER H. , TRYGGVADOTTIR L. , KJÆR S. K.
Published: October 2011

Although several biological agents have been linked convincingly with increased risks for cancer in humans, only infection of the lower female genital tract with human papillomavirus (HPV) and colonization of the gastrointestinal tract with Helicobacter pylori are of importance for cancer occurrence in the Nordic countries. HPV types 16 and 18, and probably types 31 and 33, are causally linked with cervical cancer and H. pylori, a Gram‐negative bacteria, with gastric cancer. The estimated prevalence of genital infections with oncogenic types of HPV among Nordic women and the associated risk estimates indicate that approximately 45% of all cervical cancers arising in the Nordic countries are caused by such infections. This will be equivalent to about 550 cases in these countries each year around 2000, or 1% of all cancers arising in these populations. Similarly, the 35% prevalence of persistent gastric infection with H. pylori in the adult Nordic population and the associated risk estimates indicate that some 58% of all gastric cancers in the Nordic countries are due to this bacteria. This will correspond to about 2,350 new cases annually around the year 2000, with 1,350 among men and 1,000 among women, or approximately 2% of all cancers arising in the Nordic population.
Interleukin (IL)‐17 versus IL‐27: opposite effects on tumor necrosis factor‐α‐mediated chemokine production in human keratinocytes
Authors: Fujiwara Susumu , Nagai Hiroshi , Oniki Shuntaro , Yoshimoto Takayuki , Nishigori Chikako
Published: October 2011

Abstract:  Tumor necrosis factor (TNF)‐α is known to play a pivotal role in the pathogenesis of psoriasis. TNF‐α has been shown to act directly on keratinocytes, thereby inducing the production of various kinds of chemokines, which contributes to the infiltration of leucocytes into the psoriatic lesions. Recent studies have shown that both interleukin (IL)‐17 and IL‐27 are increased in psoriatic lesional tissue. However, the interactions between TNF‐α, IL‐17 and IL‐27 in chemokine production by keratinocytes have not been fully elucidated. Here, we examined in human keratinocytes how TNF‐α, IL‐17 and IL‐27 affect production of chemokines that are involved in the pathogenesis of psoriasis. We found that IL‐17 and IL‐27 exert opposite effects on TNF‐α‐mediated chemokine production. This suggests that lesional balance of IL‐17 and IL‐27 is involved in the recruitment of T cells, natural killer cells, neutrophils, monocytes or dendritic cells, thereby affecting inflammation in skin diseases.
Prevalence and association of dental injuries with socioeconomic conditions and alcohol/drug use in adolescents between 15 and 19 years of age
Authors: Jorge Kelly O. , Oliveira Filho Paulo M. , Ferreira Efigênia F. , Oliveira Ana C. , Vale Miriam P. , Zarzar Patrícia M.
Published: October 2011

Abstract –  Background: The aim of the present study was to investigate the prevalence of dental trauma, etiological factors, predisposing factors, and associations with socioeconomic status and the risk of alcohol and illicit drug use among adolescents in the city of Belo Horizonte, Brazil. Methods: A cross‐sectional study was carried out that included clinical examinations and self‐administered questionnaires. The sample population was composed of 891 adolescents from public and private schools. The Social Vulnerability Index (SVI) was used for socioeconomic classification. Information on alcohol and illicit drug use was obtained using two questionnaires: the Alcohol Use Disorders Identification Test (AUDIT) and the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST). Results: The prevalence of traumatic dental injury (TDI) was 24.7%. Falls (17.7%) was the most frequently cited etiological factor in dental injury. Among the participants with TDI, 32.8% were students in the private school system (P = 0.006). A total of 56.8% of individuals with accentuated overjet had some type of TDI (P = 0.000). There was a high prevalence of adolescents who consumed alcoholic beverages (50.3%) and used illicit substances (15.2%). However, no statistically significant associations were found between these variables and the presence of TDI. The results of the analysis demonstrate that individuals in a private school system [prevalence ratio (PR) = 1.11; 95% confidence interval (CI): 1.03–1.20] and those with accentuated overjet (>3 mm) (PR = 1.17; 95% CI: 1.10–1.25) had a 1.11‐ and 1.17‐fold greater chance of belonging to the group of individuals diagnosed with some type of TDI. Conclusions: The prevalence of dental trauma in the study population was high. The same was true regarding alcohol and illicit drug use among the adolescents examined, although no statistically significant associations were found between these variables and a history of TDI. Private school system and accentuated overjet were significantly associated with dental trauma.
A self‐fulfilling prophecy: linking belief to behavior
Authors: Raman Varadaraja V.
Published: October 2011

The following contemplates the historical and evolving ideas of freewill and determinism in relation to the self. The role and utility of experiential freewill in the self‐fulfilling prophecy of the self is suggested.
Understanding, justifying, and finding oneself
Authors: Kamm Frances M.
Published: October 2011

This essay tries to explain some ways in which we can come to know about ourselves, in particular about what we think. It also tries to distinguish what we are and think from what we ought to be and think.
Functional defects of peripheral regulatory T lymphocytes in patients with progressive vitiligo
Authors: Ben Ahmed M. , Zaraa I. , Rekik R. , Elbeldi‐Ferchiou A. , Kourda N. , Belhadj Hmida N. , Abdeladhim M. , Karoui O. , Ben Osman A. , Mokni M. , Louzir H.
Published: October 2011

Auto‐reactive cytotoxic T lymphocytes play a key role in the progressive loss or destruction of melanocytes in vitiligo but the mechanism underlying the loss of self‐tolerance is unknown. A deregulation of regulatory T‐cell biology has recently been suggested. The analysis of the suppressive effects of peripheral T regulatory cells in vitiligo patients revealed a functional defect in seven of 15 cases. This defect was strongly correlated with disease activity. The evaluation of the percentage of peripheral regulatory T lymphocytes did not reveal any intrinsic quantitative defect. Yet, a decrease in the percentage of such cells was noted in patients with progressive forms, suggesting a recruitment of regulatory T cells from the peripheral blood to the site of injury. This was further corroborated by the significant increase of Forkhead box P3 expression in the vitiliginous skin of patients. Our data support the involvement of a functional defect of peripheral regulatory T cells in the pathogenesis of vitiligo and open new possibilities to advance therapeutic approaches.
The Asymmetry: A Solution
Authors: ROBERTS MELINDA A.
Published: October 2011

The Asymmetry consists of two claims. (A) That a possible person's life would be abjectly miserable –less than worth living – counts against bringing that person into existence. But (B) that a distinct possible person's life would be worth living or even well worth living does not count in favour of bringing that person into existence. In recent years, the view that the two halves of the Asymmetry are jointly untenable has become increasingly entrenched. If we say all persons matter morally whether they exist or not and on that basis try to explain the first half of the Asymmetry, we lose the second half of the Asymmetry. If we say that some persons do not matter morally and some do and on that basis try to explain the second half of the Asymmetry, we lose the first half of the Asymmetry – or else find ourselves with a principle that is either inconsistent or otherwise deeply troubled in some way that has nothing to do with the content of the Asymmetry itself. In this article, I propose an alternative approach to the Asymmetry which I will call Variabilism. By understanding each and every person, whether existing or not, to matter morally but variably– such that the moral significance of any loss incurred by any person is considered to depend, not on who incurs that loss and whether that person matters morally, but rather on where that loss is incurred in relation to the person who incurs it – we can both nicely ground the two halves of the Asymmetry and avoid the conceptual difficulties that have plagued competing approaches.
Insights into the development of face recognition mechanisms revealed by face aftereffects
Authors: Jeffery Linda , Rhodes Gillian
Published: October 2011

An important question in person perception is how we acquire the perceptual/cognitive mechanisms that characterize adult expertise. Children's performance on face recognition tests improves dramatically between age 4 and adolescence suggesting that our face recognition system may change during childhood. Yet, the source of this improvement is controversial. In this review, we consider whether changes in the way identity is represented/coded in face space could contribute to this age‐related improvement. Face aftereffects have been extensively applied to studying face coding in adults and more recently they have been applied to studying the mechanisms of face coding in children. Face aftereffects are temporary distortions of perception induced by exposure to faces and are thought to reflect the mechanisms underlying face perception. Face aftereffect techniques have revealed that children as young as 4 years of age show evidence of adult‐like face space organization, with opponent coding of face dimensions. These findings are consistent with an emerging picture that the key mechanisms of face perception are present early in childhood.
Detecting deception in second‐language speakers
Authors: Da Silva Cayla S. , Leach Amy‐May
Published: October 2011

Purpose. We examined whether language proficiency had an impact on lie detection.

Methods. We collected video footage of 30 targets who spoke English as their native or second language and who lied or told the truth about a transgression. Undergraduate students (N = 51) then judged the veracity of these 30 clips and indicated how confident they were in their ratings.

Results. Participants were more confident when judging native‐language truth‐tellers than second‐language truth‐tellers. In addition, participants were more likely to exhibit a truth‐bias when observing native‐language speakers, whereas they were more likely to exhibit a lie‐bias when viewing second‐language speakers.

Conclusions. Given the difficulties and biases associated with second‐language lie detection, further research is needed.
Do spinocerebellar neurones forward information on spinal actions of neurones in the feline red nucleus?
Authors: Jankowska E. , Nilsson E. , Hammar I.
Published: October 2011

Non‐technical summary  Limb movements are initiated and controlled by nerve cells in several brain regions. Of these, neurones in the red nucleus supplement actions of corticospinal neurones and may even substitute them after injuries of the motor cortex. We have investigated how commands sent from the red nucleus to spinal neurones, and via them to limb muscles, are monitored by a population of spinal neurones providing the cerebellum with feedback information on operation of spinal neuronal networks. The results show that actions expected to be evoked by neurones in the red nucleus on motoneurones may be monitored by the cerebellum, as actions of corticospinal neurones are, although they are monitored by spinal rather than reticulospinal neurones. These results may provide us with a better understanding of mechanisms contributing to the recovery of motor functions following brain injuries.
Thermal Instability in Fluid Layers in the Presence of Horizontal and Vertical Temperature Gradients
Authors: Unny T. E. , Niessen P.
Published: October 2011

In the horizontal crystal growth methods a horizontal temperature gradient is imposed upon a liquid material. Instances have been recorded when thermal convection has been found to occur in the liquid under these conditions. This report deals with a theoretical investigation on the occurrence of thermal instability in fluid layers subjected to both horizontal and vertical temperature gradients. The solutions obtained include the special case of thermal instability in fluid layers heated from below which has been well treated in the existing literature.
A Small-Strain Plasticity Theory for Planar Slip Materials
Authors: Wells C. H. , Paslay Paul R.
Published: October 2011

A plasticity theory is developed for a specific type of material characterized by coplanar motion of dislocation. Several results of the theory are given which make an experimental evaluation of the theory straightforward. The results of a limited experimental program for a particular nickel-base alloy are presented.
Behavior of Nonlinear Viscoelastic Material Under Simultaneous Stress Relaxation in Tension and Creep in Torsion
Authors: Lai J. S. Y. , Findley W. N.
Published: October 2011

An experimental and analytical investigation is presented for simultaneous stress relaxation in tension and creep in torsion of polyurethane in the nonlinear range of stresses. The method employed a multiple integral approach with an assumed product form of kernel function to describe creep behavior. The required constants were determined from pure creep experiments on polyurethane. The tension stress and shearing strain versus time for simultaneous stress relaxation and creep were computed from results of these pure creep tests alone, and the results were compared with experiments on the same polyurethane under simultaneous stress relaxation and creep. In the method of analysis, direct inversion of the equation for creep was used as a first approximation for relaxation. Means for obtaining successive approximations and for accounting for cross effects are described. The second approximation was found to be adequate to describe the observed behavior very satisfactorily.
Vibration and Dynamic Instability of a Beam-Plate in a Transverse Magnetic Field
Authors: Moon F. C. , Pao Yih-Hsing
Published: October 2011

Experiments show that the natural frequency of a beam-plate in a transverse static magnetic field decreases to near zero as the field attains a critical value which causes the same plate to buckle statically. Under an oscillating magnetic field the beam-plate is observed to become unstable and perform parametrically excited oscillations. A mathematical model based on a quasistatic solution for the magnetization in the deformed plate is proposed. The theoretical results agree very well with the experimental data. It is shown that the phenomena are analogous to those for a beam-column under static and dynamic axial forces.
Stability of Continuous Dynamic Systems With Parametric Excitation
Authors: Dickerson J. R. , Caughey T. K.
Published: October 2011

A Lyapunov-type approach is used to establish sufficient conditions guaranteeing the asymptotic stability of a class of partial differential equations with parametric excitation.
A Method for the Computation of Hollow Cylinder Explosions
Authors: Celmin¸sˇ Aivars
Published: October 2011

The collapse velocity of the liner in a hollow cylinder explosion is difficult to obtain experimentally and asymptotic formulas for the velocity are unavailable for such explosions. This paper presents a method for the computation of the collapse and fragment velocities by solving numerically the flow equations of an idealized flow of the explosive fumes. The results agree with available experimental data.
On Finite Symmetrical Deflections of Thin Shells of Revolution
Authors: Reissner Eric
Published: October 2011

Recent simplifications of linear shell theory through consideration of transverse shear deformations and stress moments with axes normal to the shell middle surface suggest analogous approaches to the corresponding problem of nonlinear theory. As a first step in this direction consideration is given here to the classical subject of finite symmetrical deformations of shells of revolution. The principal new results of the present analysis concern the form of strain-displacement and compatibility differential equations.
Experiments on the Flow Around a Sphere at High Reynolds Numbers
Authors: Maxworthy T.
Published: October 2011

Flow around a sphere for Reynolds numbers between 2 × 105 and 6 × 104 has been observed by measuring the pressure distribution around a circle of longitude under a variety of conditions. These include the effects of laminar and turbulent boundary layer separation, tunnel blockage, various boundary layer trip arrangements and inserting an object to disrupt the unsteady, recirculation region behind the sphere.
Increase of Bearing Loads Due to Large Normal Stress Differences in Viscoelastic Lubricants
Authors: Tanner R. I.
Published: October 2011

The calculation of increased bearing capacity due to large viscoelastic or normal stress effects is carried out exactly for plane slider bearings with a second-order fluid lubricant.
Moisture Stresses in a Long Hollow Wood Pole of Constant Outer and Inner Radius in a State of Plane Strain
Authors: Ghosh Basudev
Published: October 2011

Moisture stresses in a long hollow hygroscopic cylindrically aeolotropic circular cylinder in a state of plane strain are determined mathematically in infinite trigonometric series form. The analysis is then applied to find similar stresses in a long hollow wood pole made up of species walnut for a physically important moisture-content distribution. It is observed that the infinite sums representing the stresses converge and the stresses can be evaluated with the help of a digital computer up to any desired accuracy.
A Two-Region Model of the Turbulent Boundary Layer, With Emphasis on Interfacial Conditions
Authors: Gaddis J. L. , Lamb J. P.
Published: October 2011

Presented herein is a turbulent boundary-layer analysis which is based on a two-region characterization for eddy viscosity. The eddy viscosity for the inner region is described with the usual wall law whereas the outer region, which is characterized by large eddy scales, is treated through an application of Prandtl’s eddy viscosity model for free shear flows. A similarity solution for the outer region is obtained for a linearized motion equation and suitably joined to the inner solution by requiring continuity of shear stress and eddy viscosity. The present matching criteria for the two regions result in the preservation of the velocity profile shape in the defect plane while simultaneously yielding the correct longitudinal development of all layer parameters. It is shown that interfacial conditions are, collectively, the particular feature of incompressible flow which can serve as the point of reference for variable density transformations. A simple, parametric density scaling of the eddy viscosity is employed to demonstrate that the inner layer is much less sensitive to the density variation than the outer region. An improved compressibility transformation, based on ρε = ρ¯ε¯, is advanced.
Elastic Postbuckling Behavior of Stiffened and Barreled Cylindrical Shells
Authors: Hutchinson J. W. , Frauenthal J. C.
Published: October 2011

The initial postbuckling behavior of axially stiffened cylindrical shells is studied with a view to ascertaining the extent to which various effects such as stringer eccentricity, load eccentricity, and barreling influence the imperfection-sensitivity of these structures to buckling. In most cases, when these effects result in an increase in the buckling load of the perfect structure, they increase its imperfection-sensitivity as well. In some instances, however, barreling can significantly raise the buckling load of the shell while reducing its imperfection-sensitivity. The analysis, which is based on Koiter’s general theory of postbuckling behavior and is made within the context of Ka´rma´n-Donnell-type theory, takes into account nonlinear prebuckling deformations and different boundary conditions.
On the Linear Bending Theory of a Pressurized Torus
Authors: Kiusalaas Jaan , Dhanju K. S.
Published: October 2011

The intent of this note is to point out the role of initial displacements (due to manufacturing errors) in the analysis of toroidal shells by linear bending theory. It is shown that the stresses and displacement are very sensitive to small variations of the meridional curvature in the case of uniform pressure. On the other hand, the analysis is comparatively immune to these imperfections when the loading consists of forces or moments applied to the edges of the shell. These conclusions are drawn from the toroidal shell equations of Novozhilov and Zienova, which have been modified such as to include highest-order terms in initial displacements. No solution of the equations is attempted.
The Response of a Plate on an Elastic Foundation
Authors: Jones J. P.
Published: October 2011

There has been much recent interest in the possibility of hardening an underground structure by means of an elastic plate placed on the ground above the structure. To obtain a simple expression for the interaction pressure between the ground and the plate, the present analysis treats the problem of a plate on top of an acoustic medium subjected to a uniformly moving pressure pulse. It is found that an approximate equation suggested by S. B. Baldorf is quite valid in the superseismic range of load speed. The specific problem of a step function loading traveling with uniform velocity, superseismic to the foundation, is treated. The extension of this problem to an actual elastic foundation is straightforward and is not treated.
Principles of a General Quaternion-Operator Method of Spatial Kinematic Synthesis
Authors: Sandor George N.
Published: October 2011

The basic concepts of a general method of kinematic synthesis of space mechanisms are developed by means of vectors and quaternion operators applicable to path, function, and motion generation (body guidance) for finite and infinitesimal displacements (point, order, and combined point-order approximations). For writing the position equations, space mechanisms are represented by one or more loops of a general kinematic chain of ball-jointed bar-slideball members. Appropriate mathematical constraints on the relative freedom of these members render the general chain equivalent to the represented mechanism. The method leads to a system of equations of canonical simplicity, uniform for all tasks of finite spatial synthesis, often yielding closed-form linear solutions for small numbers of precision conditions. The same system of equations is then used to refine the solution for greater precision by numerical methods. Typical applications are indicated, some involving the use of a spatial finite circlepoint-center point theory, which includes classical planar Burmester theory as one of its special cases. An earlier general complex-number method of planar synthesis is shown to be a special case of the general spatial method introduced here.
Forces on a Sphere Moving Steadily Along a Circular Path in a Viscous Fluid
Authors: Odar Fuat
Published: October 2011

Forces on a sphere moving steadily along a circular path in a viscous fluid are measured and it is found that within the experimental range both the tangential and normal forces are dependent on the Reynolds number and not on the radius of the path; and it is found that the conventional drag coefficient can also be applied to a rotational motion.
Dynamic Behavior of a Foil in the Presence of a Lubricating Film
Authors: Eshel A. , Wildmann M.
Published: October 2011

Equations for the oscillations of a foil over a lubricating fluid film are derived and are simplified by a small parameter expansion. A few particular cases are discussed, and a linearized solution is obtained for the case of a massless, perfectly flexible foil moving at a speed U over an incompressible film. The solution reveals the interesting phenomenon that small disturbances in the film thickness, as well as symmetrical large disturbances, propagate at a speed U/2.
A Criterion for Ductile Fracture by the Growth of Holes
Authors: McClintock F. A.
Published: October 2011

From an available solution for the deformation of elliptical holes in a viscous material, a criterion is developed for fracture by the growth and coalescence of cylindrical holes under any prescribed history of applied principal components of stress and strain which do not rotate relative to the material. The criterion is extended to plastic materials by extrapolation from an analysis for the growth of circular holes under equiaxial transverse stress. Experiments on Plasticine substantiate the analysis and its extrapolation. For both plastic and viscous flow, most of the applied strain to fracture is found to occur while the holes are still small compared with their spacing. The most striking result is that in plastic materials there is a very strong inverse dependence of fracture strain on hydrostatic tension. The theory also indicates the effects of anisotropy, strain-hardening, and strain gradients on ductile fracture by the growth of holes.
Effect of Temperature Gradients on the Propagation of Elastoplastic
Waves
Authors: Francis P. H. , Lindholm U. S.
Published: October 2011

In this paper, the writers consider the problem of the propagation of an extensional elastoplastic wave through a long thin bar heated at the end to produce a continuously decreasing temperature profile. The temperature distribution is approximated as an exponential function, and the stress-strain curve is considered to be bilinear with temperature-dependent mechanical properties. The problem is formulated and solved numerically by the method of characteristics. Several graphical results are provided, and the effects of the temperature gradient and the mechanical properties are discussed in terms of plastic wave attenuation.
Boundary Effects in Wake Flow
Authors: Liu C. Y.
Published: October 2011

Analytical solutions are obtained for the problem of boundary effects on the fully developed wake (or cavity) behind an inclined flat plate at an arbitrary angle of attack. The investigation is based on the Helmholtz free-streamline theory. Results are applied to four cases: (a) Blockage in a fixed-wall tunnel, (b) planing on a stream of finite depth, (c) planing toward a waterfall, and (d) flow over a flat plate in a bounded jet. Comparisons with linearized theory and available experimental data are made.
Mechanical and Thermodynamic Considerations of an Assemblage of
Homogeneous Elastic-Plastic States
Authors: Rubin David
Published: October 2011

The mechanics and the thermodynamics of plastic deformation are considered in terms of a general assemblage or continuum of elastic, perfectly plastic elements or states. Such models not only match the external mechanical behavior of real materials structures and continua, but they also afford a simple thermodynamic definability. A consideration of the internal behavior shows that the stress-free state has the maximum elastic range. Hardening in the sense of an increasing macroscopic elastic range is accompanied by a release of stored strain energy; the stress-free state always is restorable. This behavior is appropriate for real structures and continua. However, it is precisely these continuum characteristics which make the assemblages inappropriate models of material behavior. Barriers to continuing plastic deformation are required which do exist on the microscale, but lie outside of the scope of the most complex of these thermodynamically well-defined assemblages.
Oscillating Rectilinear Fluid Flow Generator
Authors: Hoppmann W. H. , Kiss Edward
Published: October 2011

A Rectilinear Fluid Flow Generator of an oscillating type has been developed for the purpose of studying the rheological properties and flow characteristics of both Newtonian and non-Newtonian liquids [1]. It consists essentially of two long horizontal concentric cylinders, in which the annulus is filled with a liquid. The external tube is mounted on elastic supports, while the internal tube can be harmonically oscillated axially at a predetermined frequency and amplitude. The motion of the external tube and the resultant force (liquid drag) acting on it are readily measurable at any time. The principle of the apparatus depends on the fact that the outside tube motion is dynamically coupled to the inside tube motion by the liquid in the annulus which itself is caused to move by the controlled oscillations of the inside tube. It is assumed, at least in principle, that if the motion of the outside tube is known for a given motion of the inside tube, the constitutive equations for the liquid can be determined. Or conversely, if the constitutive equations are known, the motion of the outside tube can be calculated for a given motion of the inside driving cylinder. It has been shown that the solution of the Navier-Stokes equations can be obtained for the flow of a viscous liquid within the annulus between two infinitely long concentric tubes, for the case where the fluid motion is generated by a rectilinear harmonic motion of the inner tube while the outer tube is assumed to be supported by elastic springs and moving parallel to its longitudinal axis. The velocity and shear stress in the fluid have been obtained, and asymptotic solution for drag force, and tube motions, as well as a method for determining the liquid viscosity coefficient are discussed. It is shown that the theoretical solution is important for the study of the motions of the Rectilinear Fluid Flow Generator.
Transient Elastic Waves in Anisotropic Plates
Authors: Scott R. A. , Miklowitz Julius
Published: October 2011

The equations of motion of a linear elastic solid have been used to study the propagation of transient compressional disturbances in anisotropic plates, generated by several types of surface and edge loadings. A particular orientation of the axes of material symmetry was chosen, and several classes of anisotropic media have been considered. From the exact solutions obtained, a far-field analysis based on a low-frequency, large-wavelength approximation is given; and numerical results are presented for copper, ice, zinc, beechwood, and several isotropic media for comparison purposes.
Frequencies and Mode Shapes for Axisymmetric Vibration of Shells
Authors: Ross E. W. , Matthews W. T.
Published: October 2011

This paper treats the axisymmetric vibration of thin elastic shells. Estimates of natural frequencies and modes are obtained for a general class of domes by applying the approximations obtained in a previous paper by one of the authors. Numerical results are obtained for ellipsoidal shells, and one new theoretical result is found.
Stability of an Elastic Ring in a Rigid Cavity
Authors: Zagustin E. A. , Herrmann G.
Published: October 2011

A thin, elastic circular ring constrained in a rigid cavity is subjected to a uniformly distributed parallel loading per unit length of the ring in its plane. Stability of equilibrium in the large (snap-through) is investigated. This nonlinear problem is simplified by considering the region of separation of the ring at buckling to be small, an assumption supported by experiments. This restriction permits the construction of simple expressions for the dependence of the load on the deformation, for the load at buckling, and for other relevant quantities at and beyond buckling.
The Kinematics of Motion Through Finitely Separated Positions
Authors: Roth Bernard
Published: October 2011

A rigid body is studied in a series of finitely separated positions, in order to determine those points which lie on a special locus (a sphere, circle, plane, line, or cylinder). Equations governing these special points are derived and their numerical evaluation is discussed. Several numerical examples are presented. In a companion paper [21], these results are applied to the synthesis of spatial linkages, and special motions (e.g., planer and spherical) are incorporated into the general theory presented herein.
The Eigenvalue Problem for Two-Dimensional Regions With Irregular Boundaries
Authors: Roberts S. B.
Published: October 2011

A method for the construction of eigenfunctions for two-dimensional simply connected regions with irregular finite boundaries is presented. Solutions are obtained in the form of an eigenvalue power series which is shown to be uniformly convergent. The procedure is illustrated by application to the vibration problem of a class of thin membranes with epicycloidal boundary shapes.
Some Interaction Effects in a Problem of Plastic Beam Dynamics—Part 3: Experimental Study
Authors: Nonaka Taijiro
Published: October 2011

An experimental study is made of the permanent deformation of clamped beams with and without constraints against axial displacements at the ends. The beams carry a concentrated mass at the center and are subjected to blast loading at the central mass. Experimental results are compared with the theoretical predictions developed in earlier papers, Parts 1 and 2, and show general agreement.
Torsion of a Cylindrical Rod Welded to an Elastic Half Space
Authors: Freeman N. J. , Keer L. M.
Published: October 2011

A solution is given for the problem of the torsion of an elastic cylinder welded to an elastic half space. The problem was formulated so as to involve coupling between dual-integral equations and Dini series. These equations were reduced to a single integral equation. Numerical results are given and functions found that approximate the stress distribution.
On Stokes’ Problems for Linear Viscoelastic Fluids
Authors: Na T. Y. , Sidhom M. M.
Published: October 2011

The present Note considers the problems associated with the flow of linear viscoelastic fluids of the Maxwell type near an accelerating or oscillating plate (known as Stokes’ problems). Effect of the fluids’ relaxation time on their behavior is sought.
Viscous Flow in a Pipe With Absorbing Walls
Authors: Friedman M. , Gillis J.
Published: October 2011

A study is made of the steady-state axisymmetric flow of a homogeneous viscous liquid in a straight circular pipe with absorbing walls. The complete equations are solved numerically and the streamlines and other features of the flow are computed. Comparison is made with earlier results obtained by various approximate methods.
Parametric Instability of Circular Cylindrical Shells
Authors: Vijayaraghavan A. , Evan-Iwanowski R. M.
Published: October 2011

Parametric instability of thin, circular cylindrical shells subjected to in-plane longitudinal inertia loading arising from sinusoidal base excitation has been investigated analytically and experimentally. The shell under consideration was rigidly clamped at the base and free at the upper edge. In the applied excitation frequency range, the test specimens exhibited lateral vibrations, at half the driving frequency, with one half longitudinal wave and three full circumferential waves. The linear bending theory used in the analysis was adequate in predicting the incipience of instability, just as in the case of slender rods. Attention has been confined to investigating only the principal instability region, as observed during the experiments. Excellent agreement was obtained between the analytical and experimental results.