bluuebunny/crossref_metadata_2025 huggingface dataset:
Logistic Regression: A Brief Primer
Authors: Stoltzfus Jill C.
Published: October 2011

Academic Emergency Medicine 2011; 18:1099–1104 © 2011 by the Society for Academic Emergency Medicine

Regression techniques are versatile in their application to medical research because they can measure associations, predict outcomes, and control for confounding variable effects. As one such technique, logistic regression is an efficient and powerful way to analyze the effect of a group of independent variables on a binary outcome by quantifying each independent variable’s unique contribution. Using components of linear regression reflected in the logit scale, logistic regression iteratively identifies the strongest linear combination of variables with the greatest probability of detecting the observed outcome. Important considerations when conducting logistic regression include selecting independent variables, ensuring that relevant assumptions are met, and choosing an appropriate model building strategy. For independent variable selection, one should be guided by such factors as accepted theory, previous empirical investigations, clinical considerations, and univariate statistical analyses, with acknowledgement of potential confounding variables that should be accounted for. Basic assumptions that must be met for logistic regression include independence of errors, linearity in the logit for continuous variables, absence of multicollinearity, and lack of strongly influential outliers. Additionally, there should be an adequate number of events per independent variable to avoid an overfit model, with commonly recommended minimum “rules of thumb” ranging from 10 to 20 events per covariate. Regarding model building strategies, the three general types are direct/standard, sequential/hierarchical, and stepwise/statistical, with each having a different emphasis and purpose. Before reaching definitive conclusions from the results of any of these methods, one should formally quantify the model’s internal validity (i.e., replicability within the same data set) and external validity (i.e., generalizability beyond the current sample). The resulting logistic regression model’s overall fit to the sample data is assessed using various goodness‐of‐fit measures, with better fit characterized by a smaller difference between observed and model‐predicted values. Use of diagnostic statistics is also recommended to further assess the adequacy of the model. Finally, results for independent variables are typically reported as odds ratios (ORs) with 95% confidence intervals (CIs).
Critical Appraisal of Emergency Medicine Educational Research: The Best Publications of 2010
Authors: Shayne Philip , Coates Wendy C. , Farrell Susan E. , Kuhn DO Gloria J. , Lin Michelle , Maggio Lauren A. , Fisher Jonathan
Published: October 2011

ACADEMIC EMERGENCY MEDICINE 2011; 18:1081–1089 © 2011 by the Society for Academic Emergency Medicine

Objectives:  The objective was to critically appraise and highlight medical education research studies published in 2010 that were methodologically superior and whose outcomes were pertinent to teaching and education in emergency medicine (EM).

Methods:  A search of the English language literature in 2010 querying PubMed, Scopus, Education Resources Information Center (ERIC), and PsychInfo identified 41 EM studies that used hypothesis‐testing or observational investigations of educational interventions. Five reviewers independently ranked all publications based on 10 criteria, including four related to methodology, that were chosen a priori to standardize evaluation by reviewers. This method was used previously to appraise medical education published in 2008 and 2009.

Results:  Five medical education research studies met the a priori criteria for inclusion and are reviewed and summarized here. Comparing the literature of 2010 to 2008 and 2009, the number of published educational research papers increased from 30 to 36 and then to 41. The number of funded studies remained fairly stable over the past 3 years at 13 (2008), 16 (2009), and 9 (2010). As in past years, research involving the use of technology accounted for a significant number of publications (34%), including three of the five highlighted studies.

Conclusions:  Forty‐one EM educational studies published in 2010 were identified. This critical appraisal reviews and highlights five studies that met a priori quality indicators. Current trends and common methodologic pitfalls in the 2010 papers are noted.
Disorders linked to insufficient androgen action in male children
Authors: Sultan Charles , Paris Françoise , Terouanne Beatrice , Balaguer Patrick , Georget Virginie , Poujol Nicolas , Jeandel Claire , Lumbroso Serge , Nicolas Jean‐Claude
Published: October 2011

Virilization of the external genitalia in the male fetus requires testosterone and dihydrotestosterone (DHT), which is formed from testosterone by the action of the enzyme, 5α‐reductase type 2 (5αR‐2). Mediation of the effects of both testosterone and DHT requires a functional androgen receptor (AR) located in the cytoplasmic compartment of target cells. DHT (or testosterone) binding induces a conformational change which facilitates AR nuclear transport, phosphorylation and dimerization, ultimately regulating of the rate of transcription of androgen‐dependent genes. Any event which impaire DHT formation (mutation within the 5αR‐2 gene or 5αR‐2 inhibitors) or normal function of the AR (mutation in the AR gene, antiandrogens) may result in insufficient androgen action in the male fetus and in subsequent undervirilization in the newborn. Hypospadias may be due to a defect in androgen action due to mutation of the 5αR‐2 or of the AR gene. Mutation of unidentified genes is likely to underlie this displacement of the urethral meatus from the tip to the ventral side of the phallus. An aetiological role for environmental chemical products has been postulated, since ethnic as well as geographical differences in the incidence of hypospadias have been noted. Increasing evidence has been gathered indicating that widely used industrial and agricultural chemicals have deleterious effects on normal male sexual differentiation. Cryptorchidism and micropenis may represent an intersex phenotype, even if they are isolated. Aetiological factors include 5αR‐2 gene mutation, AR gene mutation or environmental hormonal disruptors. In conclusion, several phenotypes have been attributed to insufficient androgen action during fetal life. Whereas mutations in the 5αR‐2 gene and AR gene are natural, attention should be focused on environmental endocrine disruptors that are able to mimic steroid 5α‐reductase deficiency or partial androgen insensitivity syndrome.
Accidental gynecomastia in children
Authors: CHIUMELLO GIUSEPPE , GUARNERI MARIA PIA , RUSSO GIANNI , STROPPA LAURA , SGARAMELLA PAOLA
Published: October 2011

Any palpable breast tissue in men is abnormal except during: the neonatal period, adolescence and in elderly age. Gynecomastia in prepubertal children may be due to enhanced endogenous oestrogen production, drugs or unknown causes. After the onset of puberty gynecomastia may also be due to a deficiency of testosterone. Young men and boys are particularly sensitive to oestrogens and may develop gynecomastia from exposure to industrial oestrogen, to creams containing oestrogens, to antiandrogens or to unrecognized endocrine substances. Furthermore gynecomastia and others pubertal disorders in males and females may be due to ingestion of food containing oestrogens or oestrogenlike substances; many “epidemics” of gynecomastia among children have been described. Hormones ingested by meat can cause breast enlagement and other deleterious immediate or long term effects. In particular it is a common concern among paediatricians and endocrine specialists that environmental and dietary “contaminants” may interfere with the pubertal development. In the evaluation of all this data we can not ignore the toxic effects of contamination may be having both in the short term but, more particularly, in the long term in terms of morbidity, mortality and therefore social costs.
Effects of developmental exposure to diethylstilbestrol (DES) in rodents: clues for other environmental estrogens
Authors: NEWBOLD RETHA R.
Published: October 2011

The synthetic estrogen diethylstilbestrol (DES) is a potent perinatal endocrine disrupter. In humans and experimental animal models, exposure to DES during critical periods of differentiation permanently alters estrogen target tissues subsequently resulting in structural, functional, and long‐term abnormalities including neoplasia in reproductive tract tissues. Using the developmentally exposed rodent model, multiple mechanisms have been identified that play a role in DES‐induced toxic effects. Although DES is a potent estrogen, it can be used as a model compound to predict the effects of other environmental estrogens. It was, therefore, of particular interest that very low doses of DES were found to adversely affect fertility and increase tumor incidence. These effects were seen at environmentally relevant estrogen dose levels. Not surprising, new studies verify that DES effects are not unique; when other environmental chemicals with estrogenic activity were tested in the experimental rodent model, developmental exposure was shown to result in an increased incidence of neoplasia, including uterine adenocarcinoma, similar to that shown following DES exposure. Finally, a growing number of reports suggest that some adverse effects can be passed on to subsequent generations, although the mechanisms involved in these transgenerational events remain unknown. These data point out the possibility that environmental estrogens and other endocrine disrupting compounds are indeed valid suspects in the alarming rise in adverse reproductive health consequences in human and wildlife populations.
Possible health impact of animal oestrogens in food
Authors: Daxenberger Andreas , Ibarreta Dolores , Meyer Heinrich H.D.
Published: October 2011

Oestrogens govern reproductive functions in vertebrates, and are present in all animal tissues. The theoretical maximum daily intake (TMDI) of oestradiol‐17β by consumption of cattle meat is calculated to be 4.3 ng. Following the use of oestradiol‐containing growth‐promoting agents, TMDI is increased by a factor of 4.6 to 20 ng oestradiol‐17β, assuming that single dosage and ‘good animal husbandry’ are observed. Pork and poultry probably contain similar amounts of oestrogens as untreated cattle. The mean concentration of oestradiol‐17β in whole milk is estimated at 6.4 pg/ml. Scarce data available on eggs report up to 200 pg/g oestradiol‐17β. The risk evaluation of oestrogenic growth‐promoting agents is limited by analytical uncertainties. Residues of oestradiol‐17α and the importance of oestrogen conjugates are widely unknown. The performance of mass spectrometry still needs to be improved for confirmation of oestrogen concentrations in most food. At present, the potential relevance of oestradiol acyl esters, the actual daily production rate of oestradiol in prepubertal children, and the role of oestradiol metabolites in cancer are obscure. The presence of different cytoplasmic oestrogen receptor subtypes and potential oestradiol effects in non‐reproductive functions require further examination.
Genotoxicity of the steroidal oestrogens oestrone and oestradiol: possible mechanism of uterine and mammary cancer development
Authors: Liehr Joachim G.
Published: October 2011

Oestrogens, including the natural hormones oestrone and oestradiol, induce various tumours in laboratory animals and have been recognized to be carcinogens in humans, raising the risk for breast and uterine cancer. As part of the search for the mechanism of hormone‐induced carcinogenesis, various types of DNA damage have been detected which have been induced by oestrogens in cell‐free systems, in cells in culture, or in vivo. Nevertheless, oestrogens have been postulated to act only as promoters of mammary carcinogenesis by receptor‐mediated growth stimulation without consideration of their genotoxicity because these hormones failed to induce mutations in commonly used assays. More recently, oestradiol‐induced numerical chromosomal changes (aneuploidy) and structural chromosomal aberrations have been detected in cells in culture and in hamster kidney, a target of oestrogen‐induced cancer. In this animal model, oestradiol generates c‐myc gene amplification and microsatellite instability. Mutations of the hprt gene have been induced by oestradiol in V79 cells and by catecholoestrogen metabolites in Syrian hamster embryo cells. Sequencing of this gene isolated from V79 mutant clones revealed point mutations and deletions. It is concluded that oestradiol plays a dual role as mutagen/carcinogen and as growth‐stimulating hormone in the induction of tumours.
Regional differences in semen quality in Europe
Authors: Jorgensen Niels , Andersen Anne‐Grethe , Eustache Florence , Irvine D. Stewart , Suominen Jyrki , Petersen Jørgen Holm , Andersen Anders Nyboe , Auger Jacques , Cawood Elizabeth H.H. , Horte Antero , Jensen Tina Kold , Jouannet Pierre , Keiding Niels , Vierula Matti , Toppari Jorma , Skakkebßk Niels E.
Published: October 2011

Recent reports have indicated a decrease in semen quality of men in some countries, and suggested regional differences. A study was undertaken of semen samples from 1082 fertile men from four European cities (Copenhagen, Denmark; Paris, France; Edinburgh, Scotland; and Turku, Finland). Semen analysis was standardized, inter‐ laboratory differences in assessment of sperm concentration were evaluated, and morphology assessment centralized. Lowest sperm concentrations and total counts were detected for Danish men, followed by French and Scottish men. Finnish men had the highest sperm counts. Men from Edinburgh had the highest proportion of motile spermatozoa, followed by men from Turku, Copenhagen and Paris. Only the differences between Paris/Edinburgh and Paris/ Turku were statistically significant (P < 0.003 and P 0.002 respectively). No significant differences in morphology were detected. A general seasonal variation in sperm concentration (summer 70% of winter) and total sperm count (summer 72% of winter) was detected. Semen quality of a ‘standardized’ man (30 years old, fertile, ejaculation abstinence of 96 h) were estimated. Topically, sperm concentrations (x 106/ml) for winter/summer were: Turku 132/93; Edinburgh 119/84; Paris 103/73; and Copenhagen 98/69. These differences in semen quality may indicate different environmental exposures or lifestyle changes in the four populations. However, it remains to be seen whether such changes can account for these differences. These data may also serve as a reference point for future studies on time trends in semen quality in Europe.
Umm an‐Nar burial 401 at Bat, Oman: architecture and finds
Authors: Böhme Manfred , Al‐Sabri Biubwa Ali
Published: October 2011

The archaeological site at Bat has an important status with regard to research on the Umm an‐Nar culture. Investigations began there in 1972 and were revived in 2004, when the excavation of tomb 401 was begun. This paper presents the complete corpus of grave‐goods. Despite all the disturbances within the find layers, when comparing the two chambers it is possible to observe some indications of the different burial cycles and detect distinguishing characteristics. Taking into account the divergent earlier and later ceramic styles, burial use must be proposed between 2400 and 2200 BC. This date accords with observations of the architectural details of tomb 401 and with the sequence of tomb construction types in the Bat region.

This paper is dedicated to the memory of professor Gerd Weisgerber.
Erosion of a pollination mutualism along an environmental gradient in a south Andean treelet, Embothrium coccineum (Proteaceae)
Authors: Chalcoff Vanina R. , Aizen Marcelo A. , Ezcurra Cecilia
Published: October 2011

The limit of a species’ distribution can be determined biotically if an environmental gradient causes the loss of critical mutualists such as pollinators. We assessed this hypothesis for Embothrium coccineum, a self‐incompatible red‐flowered treelet growing along a strong west‐east precipitation gradient from rainforest to forest‐steppe ecotone in the rain shadow of the southern Andes in northwestern Patagonia. For 16 populations along this gradient, we quantified composition of the pollinator assemblage, pollination efficiency and limitation, and reproductive output. The treelet has a generalized pollination system, but the hummingbird Sephanoides sephaniodes was the most effective pollinator. The relative importance of this hummingbird as a flower visitor within populations influenced pollen transfer and fruit set more strongly than local precipitation. As hummingbirds and other pollinators, including passerine birds and nemestrinid flies, were replaced by bees towards the dry eastern range limit, pollen limitation increased and reproduction eventually failed. These results support the hypothesis that pollinators can act as important biotic filters influencing plant distribution, and warn against predictions of geographical range shifts based solely on climatic variables.
Gastroschisis with ceco‐appendicular agenesis: A novel presentation
Authors: Vaze Dhananjay , Hombalkar N. N. , Dhandore Priya
Published: October 2011

Gastroschisis is associated with intestinal atresia and malrotation. A few cases have been reported of appendicular agenesis associated with gastroschisis. No previous case has been reported of cecal agenesis with gastroschisis in the literature. As cecal agenesis is a very rare anomaly, its concomitant presentation with gastroschisis is extremely rare. We report a case of gastroschisis associated with ceco‐appendicular agenesis. The possible embryological explanation for the presentation is discussed.
Renal ischaemia/reperfusion injury: possible role of aquaporins
Authors: Hussein A.‐A. M. , El‐Dken Z. H. , Barakat N. , Abol‐Enein H.
Published: October 2011

Renal ischaemia/reperfusion (I/R) injury is a common problem that occurs when blood flow is interrupted to the kidney in case of kidney transplantation, aortic cross‐clamping and shock with subsequent resuscitation. Renal I/R injury is a complex conditions which includes the onset of an inflammatory process, which is associated with impairment of concentrating ability of the kidney and impairment of solute transport. Characteristically, renal I/R injury is associated with marked reduction in the protein expression of renal aquaporins (AQPs) mainly (AQP1, AQP2 and AQP3), and solute transporters were observed in this condition and could account for the impaired urinary concentration that observed in this condition. Recently, many agents were tested for a possible protective effect against this insult such as erythropoietin (EPO), α‐melanocyte‐stimulating hormone (α‐MSH) and α‐lipoic acid which were proved to prevent downregulation of AQPs and solute transporters. The aim of this short review is to outline the potential pathophysiological role of AQPs in renal I/R injury and to put a spotlight on the modulation of renal functions impairment in renal ischaemia by new drugs that prevent downregulation of AQPs.
Molecular biomass and MetaTaxogenomic assessment of soil microbial communities as influenced by soil DNA extraction procedure
Authors: Terrat Sébastien , Christen Richard , Dequiedt Samuel , Lelièvre Mélanie , Nowak Virginie , Regnier Tiffanie , Bachar Dipankar , Plassart Pierre , Wincker Patrick , Jolivet Claudy , Bispo Antonio , Lemanceau Philippe , Maron Pierre‐Alain , Mougel Christophe , Ranjard Lionel
Published: October 2011

Three soil DNA extraction procedures (homemade protocols and commercial kit) varying in their practicability were applied to contrasting soils to evaluate their efficiency in recovering: (i) soil DNA and (ii) bacterial diversity estimated by 16S rDNA pyrosequencing. Significant differences in DNA yield were systematically observed between tested procedures. For certain soils, 10 times more DNA was recovered with one protocol than with the others. About 15 000 sequences of 16S rDNA were obtained for each sample which were clustered to draw rarefaction curves. These curves, as well as the PCA ordination of community composition based on OTU clustering, did not reveal any significant difference between procedures. Nevertheless, significant differences between procedures were highlighted by the taxonomic identification of sequences obtained at the phylum to genus levels. Depending on the soil, differences in the number of genera detected ranged from 1% to 26% between the most and least efficient procedures, mainly due to a poorer capacity to recover populations belonging to Actinobacteria, Firmicutes or Crenarchaeota. This study enabled us to rank the relative efficiencies of protocols for their recovery of soil molecular microbial biomass and bacterial diversity and to help choosing an appropriate soil DNA extraction procedure adapted to novel sequencing technologies.
Successful resolution of juvenile paradental cysts after marsupialization in five consecutive patients
Authors: Lizio G , Corinaldesi G , Bianchi A , Marchetti C
Published: October 2011

Background:  Juvenile paradental cysts typically occur on the buccal aspect of mandibular first and second molars in children aged 6 to 11 years. The cysts may be treated by enucleation, with or without extraction of the involved teeth, or by marsupialization. This report demonstrates the success of a conservative surgical technique (marsupialization) and good outcomes in five juvenile paradental cyst cases.

Methods:  Five patients (two males, three females) with a mean age of 8.4 years, complaining of mandibular buccal swelling around the molars, underwent marsupialization of radiolucent lesions involving partially or fully erupted permanent first molars. Clinical, radiographic and histological characteristics led to diagnoses of juvenile paradental cysts.

Results:  The surgical procedures were simple to perform and resulted in complete remission of the lesions with no complications. The mean follow‐up time was 2.8 years. No recurrences were observed, the related teeth developed normally, and complete periodontal healing was achieved.

Conclusions:  The surgical marsupialization of juvenile paradental cysts achieved good outcomes without compromising the development of related teeth, and thus may be considered an appropriate treatment for paediatric patients.
Molecular Prevalence ofBartonella,Babesia, and HemotropicMycoplasmasp. in Dogs with Splenic Disease
Authors: Varanat M. , Maggi R.G. , Linder K.E. , Breitschwerdt E.B.
Published: October 2011

Background

Among diseases that cause splenomegaly in dogs, lymphoid nodular hyperplasia (LNH), splenic hemangiosarcoma (HSA), and fibrohistiocytic nodules (FHN) are common diagnoses. The spleen plays an important role in the immunologic control or elimination of vector‐transmitted, blood‐borne pathogens, includingBartonellasp.,Babesiasp., and hemotropicMycoplasmasp.

Objective

To compare the prevalence ofBartonellasp.,Babesiasp., and hemotropicMycoplasmasp.DNAin spleens from dogs withLNH, HSA, andFHN.

Materials and Methods

Paraffin‐embedded, surgically obtained biopsy tissues fromLNH(N = 50),HSA(N = 50), andFHN(N = 37) were collected from the anatomic pathology archives. Spleens from specific pathogen‐free (SPF) dogs (N = 8) were used as controls.Bartonellasp.,Babesiasp., andMycoplasmasp.DNAwas amplified byPCR, followed byDNAsequencing.

Results

Bartonellasp.DNAwas more prevalent inFHN(29.7%) andHSA(26%) as compared toLNH(10%) (P = .019, .0373, respectively) or control spleens (0.0%). The prevalence ofBabesiasp. and hemotropicMycoplasmasp.DNAwas significantly lower thanBartonellasp.DNAinHSA(P = .0005, .006, respectively) andFHN(P = .003, .0004, respectively). There was no statistically significant difference inDNAprevalence among the 3 genera in theLNHgroup.

Conclusions

The higher prevalence ofBartonellasp. inFHNandHSAwarrants future investigations to determine if this bacterium plays a role in the development of these splenic diseases.
Is Dunbar's number up?
Authors: Wellman Barry
Published: October 2011

This article is a commentary on ‘Relationships and the social brain: Integrating psychological and evolutionary perspectives’ (Sutcliffe, Dunbar, Binder, & Arrow, 2012).
Confidence inflation in eyewitnesses: Seeing is not believing
Authors: Douglass Amy Bradfield , Jones Eric E.
Published: October 2011

Purpose. Confidence inflation in eyewitnesses obscures a useful cue to identification accuracy and affects evaluations of eyewitnesses (e.g., Bradfield & McQuiston, 2004; Jones, Williams, & Brewer, 2008). We examine whether sensitivity to confidence inflation evidence is enhanced by seeing a videotape of the identification procedure.

Methods. Participants (N= 131) watched a videotaped trial in which the witness's original confidence statement was presented as part of a previously recorded videotaped identification procedure or read by the witness at trial. In addition, the witness's identification confidence was either consistently high or low at the time of the identification and high at the trial (i.e., it was inflated).

Results. Significant interactions demonstrated that confidence inflation evidence factored into judgments of the eyewitness and defendant guilt more strongly in the videotape condition compared with the read condition.

Conclusions. The present results support recommendations to collect immediate confidence reports and videotape identification procedures. Using videotape evidence may help innocent defendants convince jurors that the eyewitness's identification is not accurate.
On Stress-Strain Relations and Strain-Energy Expressions in the Theory of Thin Elastic Shells
Authors: Knowles J. K. , Reissner Eric
Published: October 2011

The stress-strain relations of Flu¨gge and Byrne for thin elastic shells are inverted to express strain quantities, and therewith the strain energy, in terms of stress resultants and couples. In this form, and upon omission of terms which are small of order h2/R2, the stress-strain relations and the strain-energy expression are shown to be simply related to corresponding results of Trefftz. The strain-energy formula of Trefftz is generalized to arbitrary orthogonal middle surface co-ordinates.
Earth Motion Beneath a Prescribed Boundary Displacement
Authors: Geldmacher R. C. , Dunkin J. W. , Anderson R. L.
Published: October 2011

Earth deflections beneath a prescribed boundary displacement were obtained theoretically and experimentally. The problem was stated in terms of a two-dimensional model and an attempt was made to design a corresponding experiment. Relative deflections between the surface of the earth and points of increasing depths within the earth were measured. The maximum depth was 42 ft 7 in, below the earth’s surface. Theoretical and experimental results were compared.
On the Elastic Bending of Columns Due to Dynamic Axial Forces Including Effects of Axial Inertia
Authors: Sevin Eugene
Published: October 2011

This study is concerned with the influence of axial inertia upon the elastic bending motion of initially slightly curved columns acted on by time-dependent axial forces. The equations of motion include both axial inertia and nonlinear strain terms. Numerical solutions were obtained for a similar problem previously studied by Hoff [1] but in which axial-inertia effects were neglected; i.e., the problem of a simply supported column initially bent in the shape of a half sine wave and loaded by displacing one end axially at a constant rate. The range of solutions pertains to conventional structural compression members (slenderness ratios less than 150), and to minimum rates of loading compatible with elastic response of common engineering materials. This study suggests that axial-inertia effects are of secondary importance in so far as the gross elastic response of conventional structural columns is concerned.
Subharmonic Oscillations of a Pendulum
Authors: Skalak Richard , Yarymovych M. I.
Published: October 2011

Large amplitude oscillations of a simple pendulum whose support moves with a prescribed vertical oscillation are studied by an approximate method. Subharmonics of order 1/2, 1/4, 1/6, and 1/8 are discussed and the theoretical results are compared with experiments. The stability of the theoretical steady states is investigated by the method of Andronow and Will.
Strain-Hardening Solutions to Axisymmetric Disks and Tubes
Authors: Perrone Nicholas
Published: October 2011

Solutions are obtained for annular disks and tubes made of a linearly strain-hardened material, loaded by a uniform tensile load on the outer boundary. The strain-hardening is assumed to follow a kinematic hardening flow law. In addition, a second solution for tubes which accounts for finite deformation is determined. Some numerical comparisons are made with existing isotropic hardening solutions.
Stresses in the Plastic Range Around a Normally Loaded Circular Hole in an Infinite Sheet
Authors: Mangasarian O. L.
Published: October 2011

The stresses in the plastic range around a normally loaded circular hole in an infinite sheet are found numerically on the basis of both J2 deformation and incremental theories. The results of deformation theory are quantitatively assessed in the light of a criterion, recently developed by Budiansky, for the acceptability of deformation theories. The criterion is completely satisfied. Moreover, the results obtained by using these two different theories of plasticity do not differ greatly despite the fact that the stress paths are far from being radial.
Heat Transfer for Laminar Flow in Ducts With Arbitrary Time Variations in Wall Temperature
Authors: Siegel Robert
Published: October 2011

An analysis is made for laminar forced-convection heat transfer in a circular tube or a parallel plate channel whose walls may undergo arbitrary time variations in temperature. The time-varying process can begin from an already established steady-state situation with heat transfer taking place, or the fluid and walls can be initially at the same uniform temperature. The fluid velocity distribution is fully developed and unchanging with time. At any instant during the transient the wall temperature is spatially uniform, that is, all portions of the wall simultaneously undergo the same temperature-time variation. The greater part of the analysis is concerned with the response to a step change in wall temperature, and the time required to reach steady state is given for this type of transient. Then the results are generalized to apply for arbitrary variations with time.
The Junction Problem of Solid-Slotted Cylindrical Shells
Authors: Cheng D. H. , Weil N. A.
Published: October 2011

This paper presents a solution for the problem of three cylindrical shells, one of which is slotted lengthwise. With slot length as one of the parameters, the solution includes the solid three-shell problem as a particular case. The results are applicable to the stress problem of a closed-end vessel supported either by a slotted or an ordinary skirt, or one that is mounted on top of another vessel. It is shown that slotting substantially reduces the critical stress at the junction.
On Three and Two-Dimensional Disturbances of Pipe Flow
Authors: Spielberg Kurt , Timan Hans
Published: October 2011

A system of ordinary, coupled differential equations is set up for three-dimensional disturbances of Poiseuille flow in a straight pipe of circular cross section. The commonly treated equations are shown to be special cases arising from particular assumptions. It is shown that in the nonviscous, and therefore also in the general case, there exists, in contrast to the analogous problem in Cartesian co-ordinates, no transformation reducing the given problem to a two-dimensional one. A fourth-order differential equation is derived for disturbances independent of the direction of the main flow. The solutions, which are obtained, show that those two-dimensional disturbances, termed cross disturbances, decay with time and do therefore not disturb the stability of the main flow. Explicit expressions for the cross disturbances are obtained and a discussion of their nature is given.
Stability of a Turbine-Generator Rotor Including the Effects of Certain Types of Steam and Bearing Excitations
Authors: Landzberg A. H.
Published: October 2011

The effects of certain steam forces and bearing oil-film forces on vibration stability of a turbine-generator rotor are considered. A matrix method for systematically calculating the characteristic equation of a real rotor is developed with the aid of complex notation. The matrices are 4 × 4 in size. Pedestal effects are not included. A simple example is worked out and the results are compared to those obtained by another author. Complete agreement is obtained in the determination of the characteristic equation.
Stresses in Curved Beams of Noncircular Center Line
Authors: Abbassi M. M.
Published: October 2011

The paper deals with the general case of a curved beam whose center line is a plane curve not necessarily circular. The body-stress equations and the compatibility equations for stresses in their general form are found for the chosen system of co-ordinates and put in their simplest form. Solutions for the equations with the aim of finding the stresses when the beam is subjected to a torque and to a bending out of its plane of initial curvature are obtained for both elliptic and circular cross sections of the beam. The case of a concentrated load at one end perpendicular to the plane of initial curvature is also considered.
Rupture Instability of Plane Membranes and Solids
Authors: Borg S. F.
Published: October 2011

A fundamentally new approach to the rupture-fracture problem is presented. Because of the particular type of dynamic phenomena being investigated, the formulation is given in terms of the conservation equations of continuum mechanics instead of in the usual elasticity-plasticity relations. The introduction of a similarity co-ordinate permits a complete closed-form solution to a particular problem of practical interest subject to certain compatibility conditions which depend upon the specific properties of the material under consideration.
Two-Dimensional Gas Jets
Authors: Cohen M. J.
Published: October 2011

A method is described for solving certain problems of subsonic aerodynamic design where flow boundaries in the physical plane are required to have specific dynamic characteristics. The method is tested on two type-problems with known exact solutions: the two-dimensional gas jet and the flow in the neighborhood of stagnation points. It has been found to give the solution with a degree of accuracy acceptable for practical design.
Experimental Comparative Study on Vortex-Induced Motion (VIM) of a Monocolumn Platform
Authors: Gonçalves Rodolfo T. , Rosetti Guilherme F. , Fujarra André L. C. , Nishimoto Kazuo
Published: October 2011

An analysis methodology is presented as well as a comparison of results obtained from vortex-induced motion (VIM) model tests of the MonoGoM platform, a monocolumn floating unit designed for the Gulf of Mexico. The choice of scale between the model and the platform in which the tests took place was a very important issue that took into account the basin dimensions and mooring design. The tests were performed in three different basins: the IPT Towing Tank in Brazil (Sept. 2005), the NMRI Model Ship Experimental Towing Tank in Japan (Mar. 2007), and the NMRI Experimental Tank in Japan (Jun. 2008). The purpose is to discuss the most relevant issues regarding the concept, execution, and procedures to comparatively analyze the results obtained from VIM model tests, such as characteristic motion amplitudes, motion periods, and forces. The results pointed out the importance of considering the 2DOF in the model tests, i.e., the coexistence of the motions in both in-line and transverse directions. The approach employed in the tests was designed to build a reliable data set for comparison with theoretical and numerical models for VIM prediction, especially that of monocolumn platforms.
Nonlinear Superposition Methods Applied to Continuous Ocean Wave Spectra
Authors: Johannessen Thomas B.
Published: October 2011

The present paper addresses the challenges associated with applying weakly nonlinear mode-coupled solutions for wave interaction problems to irregular waves with continuous spectra. Unlike the linear solution, the nonlinear solutions will be strongly dependent on cut-off frequency for problems such as the wave elevation itself or loads on a slender cylinder used together with typical ocean wave spectra. It is found that the divergence of the solutions with respect to the cut-off frequency is related to the nonlinear interaction between waves with very different frequencies. This is, in turn, linked to a long standing discussion about the ability of mode-coupled methods to describe the modulation of a short wave due to the presence of a long wave. In cases where nonlinear properties associated with a measured or assumed history of the surface elevation is sought, it is not necessary to calculate accurately the nonlinear evolution of the wave field in space and time. For such cases it is shown that results which are independent of frequency cut-off may be obtained by introducing a maximum bandwidth in frequency between waves which are allowed to interact. It is shown that a suitable bandwidth can be found by applying this method to the problem of back-calculating a linear wave profile from a measured wave profile. In order to verify that this choice of bandwidth is suitable for second and third order terms, nonlinear loads on a slender vertical cylinder are calculated using the FNV method of Faltinsen, Newman, and Vinje (1995, “Nonlinear Wave Loads on a Slender, Vertical Cylinder,” J. Fluid Mech., 289, pp. 179–198). The method is used to compare loads calculated based on measured surface elevations with measurements of loads on two cylinders with different diameters. This comparison indicates that the bandwidth formulation is suitable and that the FNV solution gives a reasonable estimate of loading on slender cylinders. There are, however, loading mechanisms that the FNV solution does not describe, notably the secondary loading cycle first observed by Grue et al. (1993, Higher Harmonic Wave Exciting Forces on a Vertical Cylinder, Institute of Mathematics, University of Oslo, Preprint No. 2). Finally, the method is employed to calculate the ringing response on a large concrete gravity base platform. The base moment response is calculated using the FNV loading on the shafts and linear loads from a standard diffraction code, together with a structural finite element beam model. Comparison with results from a recent model testing campaign shows a remarkable agreement between the present method and the measured response.
Wave number and damping characterization for sound and vibration mitigation in sandwich composite structures
Authors: Sargianis James J. , Suhr Jonghwan
Published: October 2011

With the rising demand for high performance composite materials, there is a great interest for multi-functional materials. Our research focuses on materials with high noise mitigation and passive structural damping with minimal sacrifice in bending stiffness. Specifically, we seek to understand the vibrational properties of carbon-fiber face sheet sandwich beams, with interest in wave number and damping characteristics. Both experimental and analytical methods were applied to characterize the wave number response of sandwich beams, from which coincidence frequencies were obtained. From the same frequency response function, structural damping ratios were calculated using the half-power bandwidth method. Results showed that for low frequency applications, decreasing bending stiffness has the greatest effect on increasing the coincidence frequency. However for higher frequency applications, an improvement in coincidence frequency can be seen if one reduces the core's shear modulus. Moreover it may be concluded that the high amplitudes seen in the wave number domain may be contributed to the lower structural damping values at low frequencies. With both wave number and damping properties being frequency dependent, one can optimize design parameters pertaining to a certain frequency range which will improve damping and acoustic properties while maintaining necessary flexural stiffness.
Acoustic scattering from unexploded ordnance in contact with a sand sediment: Mode identification using finite element models
Authors: España Aubrey L. , Williams Kevin L. , Kargl Steven G. , Zampolli Mario , Burnett David S. , Marston Philip L.
Published: October 2011

Previous work has illustrated the potential benefit of using low frequency sound as a means for detecting and classifying objects in contact with a sand sediment. In these situations, the wavelength of sound is on the order of the object dimensions, thus coupling to the objects resonant modes. This leads to an acoustic signature rich in physical phenomena unique to the object shape and elastic properties. Hybrid 2-D/3-D finite element models have been developed for unexploded ordnance in contact with a sand sediment. Previous work has demonstrated these models are in good agreement with data collected during experiments conducted in a test pond in 2010 [A. L. España et al., J. Acoust. Soc. Am. 129, 2685 (2011)]. In this paper, the finite element models are used as a means for mode identification and physical interpretation. These modes are visualized through plots of the pressure amplitudes and displacements along the UXO exterior and are explained using insights derived from physical acoustics. Finally, a full 3-D finite element model was developed to investigate the changes to the acoustic response in situations where the symmetry of the problem is broken and the hybrid 2-D/3-D method is no longer viable. [Research supported by ONR and SERDP.]
Acoustic imaging and structural acoustic analysis of scattering from buried targets at above-critical grazing angles
Authors: Waters Zachary J.
Published: October 2011

Laboratory experiments are conducted in order to examine above-critical angle source configurations for the detection and identification of objects fully buried in water-saturated sediments. A stationary broadband spherical source (3–40 kHz) insonifies realistic unexploded ordnance (UXO), as well as objects representing both natural and man-made clutter, at several aspects from above the critical angle. Bistatic returns, received on a two-dimensional synthetic array, are processed to generate volumetric acoustic images of the objects buried in a variety of orientations. Physical acoustics based interpretations are applied in order to identify features attributed to geometric and elastic scattering processes, as well as the interaction of scattered returns with the water-sediment interface. The symmetry of images attributed to cylindrically shaped UXO is suggested as a potential feature for the discrimination of these objects from clutter. The complementary role of volumetric imaging relative to feature-based identification from this same data set is discussed. [Work Supported by SERDP and ONR.]
Chromatical playing on diatonic harmonica: From physical modeling to sound synthesis
Authors: Millot Laurent
Published: October 2011

To understand chromatical playing on a diatonic harmonica one must consider both the instrument and the musician. For each of the harmonica holes, two reeds share a single reed chamber and, theoretically, there is one reed for each direction of airflow (blown or drawn note) while both reeds practically contribute to escaping airflow. The airflow model must take into account all 3D local airflow free jets passing between the plate and the local bent portion of the studied reed to give access to realistic numerical simulations. But to explain bends and overnotes, the vocal tract of the musician must be included and adapted. The vocal tract model must include at least a pressure excitation in the back cavity, the palatal constriction, the front cavity and a mix between lips channel and harmonica chamber. And, the physics involved in the whole model is acoustical nonlinear fluid mechanics rather than acoustical wave propagation. All relevant physical phenomena will be described and illustrated, sound synthesis given to listen. Moreover, a description of the time-variation of the vocal tract model will be proposed for ones thinking about real-time sound synthesis.
Alternative method to determine minimal load for reeds within an acoustical flow
Authors: Millot Laurent
Published: October 2011

To understand (free) reed(s) oscillations, a minimal acoustical load must be introduced between the excitation and the reed(s). Classically, the model for this load is either an acoustic admittance/impedance or a reflexion function. But with an existing acoustical flow as found within some experiments, the whole model should better use nonlinear acoustical flow descriptions. Considering electrofluid analogies to model local behavior of either incompressible or compressible elements, an iterative building of the acoustic load can be derived from which, for each studied load, a pure recursive linear filtering of the excitation can be found. With a time-independent excitation, the acoustic load can create instabilities or not according to the filter poles. Using this method one can find again the minimal load to explain oscillations of either single blown-closed or blown-open reed but also the minimal description of the vocal tract needed for chromatical playing on diatonic harmonica. It is also possible to easily derive the numerical approximation of the acoustic load and reed(s) equations using a single numerical scheme, if a highly sufficient sampling frequency is chosen (maybe greater than 44.1 or 48 kHz), to perform numerical simulations of the studied acoustical problem.
The diatonic harmonica, pipe resonators, and the siren
Authors: Brock Casey N. , Cottingham James P.
Published: October 2011

A number of measurements of reed motion and sound field have been made on a diatonic harmonica mounted on a fixed volume wind chamber. These include variation of sounding frequency with blowing pressure and the degree to which the sounding frequency and sound spectrum can be altered by attaching external pipe resonators. Differences were observed between the behavior of blow and draw reeds as well as the dependence of the results on whether the secondary reed in the reed chamber is allowed to vibrate. As noted by Helmholtz, at a simple level of analysis, the sound production of a free reed is similar to that of a siren, in both cases involving an air stream that is periodically interrupted. Our current results are compared with the results of measurements made in an earlier study of a siren in similar experimental configurations. [Work partially supported by National Science Foundation REU Grant PHY-1004860.]
Aperture extension for near-field acoustical holography applied to jet noise
Authors: Wall Alan T. , Gee Kent L. , Krueger David W. , Neilsen Tracianne B. , James Michael M.
Published: October 2011

Near-field acoustical holography (NAH) techniques are used to investigate noise source characteristics of high-power jets on military aircraft. Sound field reconstruction of large sources, measured with an aperture of limited size, may generally be performed with the use of patch NAH methods. Patch methods, such as statistically optimized near-field acoustical holography (SONAH), help to mitigate the effects of a truncated measurement aperture by avoiding the use of the spatial discrete Fourier transform operation. However, the lack of information outside the measurement aperture may lead to other errors, particularly when large propagation distances are required. Some missing data must be recovered to propagate beyond the immediate measurement region. Numerical aperture extension methods, in conjunction with SONAH, are employed to characterize high-power jet noise sound fields. These methods include complex interpolation and extension, analytic continuation, and in-plane holographic projection. [Work supported by Air Force SBIR.]