bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of clinical trial nurses: Transitioning from clinicians to clinical research coordinators
Authors: Park Hye‐Ja , Yu Soyoung
Published: April 2021

Aims

This study aimed to explore the role of clinical research coordinators (CRCs) and identify the importance and performance of the role as well as the factors that affect the professional recognition of their role.

Methods

A total of 102 CRCs from 10 hospitals were recruited for a survey. The Clinical Trial Nursing Questionnaire scale developed by Ehrenberger and Lillington was used to collect data for the importance–performance analysis. The importance and performance data were plotted on a two‐dimensional grid, and multiple stepwise linear regression analysis was used to determine the influencing factors on the CRC role.

Results

The influencing factors on the importance of the CRC role were frequency of protocol assessment, implementation and evaluation and professional nursing role performance. The influencing factors on performance were formal education and training in clinical research, institutional career ladder system for professional development and identification as a principal investigator in research studies. The influencing factor on the professional nursing role perception was the lower component of the ‘performance of professional nursing role’.

Conclusion

Formal educational preparation, identification as a principal investigator in research studies and clear career progression are supportive factors to the professional recognition of CRC as a specialized nursing role.
The experiences of therapists providing psychological treatment for adults with depression and intellectual disabilities as part of a randomised controlled trial
Authors: Smith Ian C. , Huws Jaci C. , Appleton Kim , Cooper Sally‐Ann , Dagnan Dave , Hastings Richard P. , Hatton Chris , Jones Robert S. P. , Melville Craig , Scott Katie , Williams Chris , Jahoda Andrew
Published: April 2021

Background

Health professionals were trained to deliver adapted psychological interventions for depression to people with learning disabilities and depression alongside a supporter. Exploring the delivery of psychological interventions can help increase access to therapy.

Method

Twenty‐seven participants took part in six focus groups, and the data were subject to a Framework Analysis.

Results

The structure and focus of the manualised therapies, and the use of specific techniques were perceived as key to service‐user engagement. Supporters' involvement was valued by therapists if they had a good relationship and regular contact with the individual they supported. Regular clinical supervision was regarded as vital in understanding their role, assessing progress and delivering the interventions.

Conclusions

The findings highlight that health professionals can embrace a focussed therapeutic role and increase access to psychological therapies for people with intellectual disabilities.
Diagnostic shifts in autism spectrum disorder can be linked to the fuzzy nature of the diagnostic boundary: a data‐driven approach
Authors: Tunç Birkan , Pandey Juhi , St. John Tanya , Meera Shoba S. , Maldarelli Jennifer E. , Zwaigenbaum Lonnie , Hazlett Heather C. , Dager Stephen R. , Botteron Kelly N. , Girault Jessica B. , McKinstry Robert C. , Verma Ragini , Elison Jed T. , Pruett John R. , Piven Joseph , Estes Annette M. , Schultz Robert T. ,   for the IBIS Network
Published: April 2021

Background

Diagnostic shifts at early ages may provide invaluable insights into the nature of separation between autism spectrum disorder (ASD) and typical development. Recent conceptualizations of ASD suggest the condition is only fuzzily separated from non‐ASD, with intermediate cases between the two. These intermediate cases may shift along a transition region over time, leading to apparent instability of diagnosis.

Methods

We used a cohort of children with high ASD risk, by virtue of having an older sibling with ASD, assessed at 24 months (N = 212) and 36 months (N = 191). We applied machine learning to empirically characterize the classification boundary between ASD and non‐ASD, using variables quantifying developmental and adaptive skills. We computed the distance of children to the classification boundary.

Results

Children who switched diagnostic labels from 24 to 36 months, in both directions, (dynamic group) had intermediate phenotypic profiles. They were closer to the classification boundary compared to children who had stable diagnoses, both at 24 months (Cohen’s d = .52) and at 36 months (d = .75). The magnitude of change in distance between the two time points was similar for the dynamic and stable groups (Cohen's d = .06), and diagnostic shifts were not associated with a large change. At the individual level, a few children in the dynamic group showed substantial change.

Conclusions

Our results suggested that a diagnostic shift was largely due to a slight movement within a transition region between ASD and non‐ASD. This fact highlights the need for more vigilant surveillance and intervention strategies. Young children with intermediate phenotypes may have an increased susceptibility to gain or lose their diagnosis at later ages, calling attention to the inherently dynamic nature of early ASD diagnoses.
Innovation in cannon puffing technology for the homogenization of bulk treatment: Half‐popped purple corn, a new healthy snack
Authors: Rajha Hiba N. , Debs Espérance , Abi Rached Rita , El Khoury Karl , Al‐Kazzi Mona , Mrad Rachelle , Louka Nicolas
Published: April 2021

A new innovative cannon puffing technology, called Vac‐Can‐Puff (VCP), consisting of a puffing gun connected to a vacuum pump, was conceived for the production of half‐popped purple corn snacks. This newly designed system was used to achieve a homogenized expansion of corn kernels in bulk. After selecting the soaking, puffing, and roasting methods, response surface methodology (RSM) was used to optimize the response variables: expansion ratio (ER) and general appreciation (GA) of kernels. It aimed at investigating the effects of puffing parameters: pressure of the steam injected (P), treatment time (T), and initial water content of the kernels (W). The central composite design resulted in an empirical model suggesting the following optima: P = 7.7 × 105 Pa, T = 14 s, and W = 32.8%, which are required to maximize desirability of the half‐popped kernels. The response parameters obtained under optimal conditions were 2.18 and 4.2 for ER and GA, respectively.

Practical Applications

Establishing an initial vacuum prior to steam injection in a puffing cannon, allowed to bring a solution to a long‐term issue related to the nonhomogeneous treatment in bulk. Whenever a thick layer of product is loaded in the cannon, a heterogeneous distribution of injected steam within the mass occurs, resulting in a dissimilarly expanded end product. Upon coupling the vacuum to the puffing cannon, the product then obtained is uniformly processed, with a well monitored expansion ratio. Half‐popped corn kernels resulting from treatment with Vac‐Can‐Puff (VCP) exhibited high organoleptic qualities in terms of taste, expansion ratio and desirability, without the use of any additives. Moreover, such products have the potential to be shaped as cakes, bars, or even associated with other products or flavors. Vac‐Can‐Puff is a manageable process since it does not require high technicality, and easy to implement in developing countries due to its low‐cost investment, operating and maintenance.
Is Medusa laughing again?
Authors: Rabinovich Irina
Published: April 2021

Caroline Lee Hentz's novella Fatal Cosmetic (1839) and Rebekah Hyneman's serial novella The Fatal Cosmetic (1853) are harbingers of American sensation fiction, though for more than a century and a half they were doomed to oblivion. Although different in style and characterization, both novelists aimed at propagating social and political agendas. This paper examines the development of this genre's key elements from earlier conformist ones to their later comprehensive materialization. Moreover, it examines the possible mythological and historical sources Hyneman's novella draws on.
Surgical ciliated cyst of the maxilla: Report of two cases
Authors: Vieira Gustavo de Souza , Gonçalves Sérgio Luiz Melo , de Oliveira Kenner Câmara , Cunha Karin Soares , Bezerra Adriana Raymundo , Maia Adriane Batista Pires , Reis Vanessa Paiva , Rodrigues Paulo da Costa , Conde Danielle Castex
Published: April 2021

Aims

Surgical ciliated cyst of the maxilla is a rare lesion that can develop as a delayed complication of surgical procedures involving the maxillary‐malar complex. We report two new cases of surgical ciliated cyst of the maxilla.

Material and Methods

This is a report of two cases of surgical ciliated cyst of maxilla that occurred 10 and 12 years after trauma and orthognathic surgeries, respectively, being the last a recurrent lesion. Both patients complained of a unilateral painful swelling in the face and had, on the computed tomography images, a well‐circumscribed unilocular hypodense lesion in the maxillary sinus. In the first case, there was a communication with the orbit floor and fenestration of the anterior wall of the maxilla.

Results

The histopathological examination of both lesions showed cysts lined by a ciliated cylindrical pseudostratified epithelium and stratified squamous epithelium. The first lesion also presented areas of cubic epithelium and some mucous cells. The fibrous wall of the cysts showed chronic inflammatory infiltrate and hyaline acellular areas. The cysts were enucleated and there is no evidence of recurrence after one year (first case) and three years (second case) of follow‐up.

Conclusion

Despite the low prevalence of the surgical ciliated cyst, surgeons, clinicians and pathologists must be aware of this lesion and it should be included in the differential diagnosis of maxillary cysts in patients with a previous local surgery.
3D‐Printed Screw‐Rod Auxiliary System for Unstable Atlas Fractures: A Retrospective Analysis
Authors: Wu Chao , Deng Jia‐yan , Li Tao , Zeng Bo‐fang , Hu Hai‐gang , Zhu Yuan‐fang , Wei Qin
Published: April 2021

Objective

To develop and validate the efficacy of a 3D‐printed screw‐rod auxiliary system for unstable atlas fractures.

Methods

This research is a retrospective analysis, and a total of 14 patients, including 11 males and three females, were enrolled in our hospital from January 2017 to March 2019 who underwent occipitocervical fusion assisted by the 3D‐printed screw‐rod auxiliary system were reviewed, and with an average age of 53.21 ± 14.81 years, an average body mass index (BMI) of 23.61 ± 1.93 kg/m2. The operation time, blood loss and radiation times during the operation were recorded. The maximum fracture displacement values of pre‐ and post‐operation were measured based on CT imaging. All screw grades were evaluated after surgery. The occipital‐cervical 2 (O‐C2) angle and occipitocervical inclination (OCI) angle of pre‐operation, post‐operation and the last following‐up were measured. The dysphagia scale 3 months after surgery and at the last follow‐up, the Neck Disability Index (NDI) 3 months after surgery and at the last follow‐up were assessed.

Results

All patients were completed the surgery successfully. There was no patient with severe dysphagia or aggravation of nerve injury. The follow‐up was from 12 to 14 months, and with an average of 12.5 months. The average surgery time, average blood loss and average radiation times for the 14 patients were 112.14 min, 171.43 mL and 5.07 times, respectively. There was a significant difference in maximum fracture displacement between pre‐ and post‐operation values (P < 0.05). A total of 56 screws were inserted in 14 patients, among them, three screws were classified as grade 1, and the other screws were classified as grade 0. There was a significant difference in the O‐C2 between pre‐operation and 3 days after operation (P = 0.002); There was a significant difference in OCI angles between pre‐operation and 3 days after operation (P < 0.05); there was no significant difference in the O‐C2 or OCI angle between 3 days after the operation and the last follow‐up (P = 0.079; P = 0.201). The dysphagia scales of two patients were assessed as mild at 3 months after surgery, and the others were assessed as normal at 3 months after surgery. All patients' dysphagia scores returned to normal at the last follow‐up. The average NDI and average neck Visual Analogue Scale (VAS) scores at the last follow‐up were 2.53 and 8.41, respectively.

Conclusion

It can objectively restore the OCI to normal with few post‐operative complications under the assistance of a screw‐rod auxiliary system to perform occipitocervical fusion for unstable atlas fractures and atlantooccipital joint instability.
Understanding the mechanistic basis of adaptation of perennial Sarcocornia quinqueflora species to soil salinity
Authors: Ahmed Hassan Ahmed Ibraheem , Shabala Lana , Shabala Sergey
Published: April 2021

Succulent halophytes can be used as convenient models for understanding the mechanistic basis of plant adaptation to salt stress. In this work, effects of salinity (0–1000 mM NaCl range) on growth, ion accumulation, and stomatal features were investigated in the succulent halophyte Sarcocornia quinqueflora. Elevated salinity levels up to 400 mM NaCl largely promoted dry matter yield, succulence, shoot surface area, and stomatal characteristics. Plant growth was optimal at 200 mM NaCl and reduced at concentrations exceeding 600 mM NaCl. Osmotic adjustment in a succulent shoot was achieved by a massive accumulation of inorganic ions, with Na+ and Cl− contributing approximately 85% of its osmolality, while organic compatible solutes and K+ were responsible for only approximately 15%. Shoot K+ was unchanged across the entire range of salinity treatments (200–1000 mM NaCl) and positively correlated with the transpiration rate (R = 0.98). Carbohydrates were not reduced at high salinity compared to plants at optimal conditions, implying that growth retardation at severe salt dosages was attributed to limitations in a vacuolar Na+ and Cl− sequestrations capacity rather than inadequate photosynthesis and/or substrate limitation. It is concluded that the superior salt tolerance of S. quinqueflora is achieved by the effective reliance on Na+ and Cl− accumulation for osmoregulation and turgor maintenance, and efficient K+ homeostasis for adequate stomatal functioning over the entire salinity range. The above findings could be instrumental in developing strategies to improve salinity stress tolerance in perennial horticultural crops and optimize their water‐use efficiency.
Plant aquaporins: A frontward to make crop plants drought resistant
Authors: Ahmed Sajad , Kouser Shaista , Asgher Mohd , Gandhi Sumit G.
Published: April 2021

Drought stress alters gene expression and causes cellular damage in crop plants. Drought inhibits photosynthesis by reducing the content and the activity of the photosynthetic carbon reduction cycle, ultimately decreasing the crop yield. The role of aquaporins (AQP) in improving the growth and adaptation of crop plants under drought stress is of importance. AQP form channels and control water transport in and out of the cells and are associated with drought tolerance mechanisms. The current review addresses: (1) the evolution of AQPs in plants, (2) the classification of plant AQPs, (3) the role of AQPs in drought alleviation in crop plants, and (4) the phytohormone crosstalk with AQPs in crops exposed to drought stress.
Veganism as a lifestyle movement
Authors: Gheihman Nina
Published: April 2021

In the last few years, the popularity of veganism has surged. Current literature on the cultural practice, which situates it within a social movements framework, cannot adequately explain this meteoric rise. A better approach is to view veganism as an emerging lifestyle movement based on individual consumption rather than political protest. After situating veganism within the literature on animal rights, this review then explains why a lifestyle movement perspective yields a more compelling account of its growing mainstream appeal. Drawing on both cultural and organizational sociology, this review provides insights into the cultural origins of veganism, its evolving relationship to other food movements, and highlights the key role played by cultural entrepreneurs, the key changemakers who are bringing veganism from the margins to the mainstream.
Utility of methicillin‐resistant Staphylococcus aureus (MRSA) nasal screening in patients with acute myeloid leukemia (AML)
Authors: Talagtag Millicynth , Patel Twisha S. , Scappaticci Gianni B. , Perissinotti Anthony J. , Schepers Allison J. , Petty Lindsay A. , Pettit Kristen M. , Burke Patrick W. , Bixby Dale L. , Marini Bernard L.
Published: April 2021

Background

Current literature has demonstrated the utility of the MRSA nasal screen as a de‐escalation tool to decrease unnecessary anti‐MRSA antibiotic therapy. However, data on the applicability of this test in patients with hematologic malignancy is lacking.

Methods

This is a single‐center, retrospective cohort study of patients with acute myeloid leukemia (AML) with or without a history of hematopoietic cell transplant (HCT), with pneumonia and MRSA nasal screening with respiratory cultures obtained. The primary outcome was to determine the negative predictive value (NPV) of the MRSA nasal screen for MRSA pneumonia. Secondary outcomes included sensitivity, specificity, positive predictive value (PPV) of the MRSA nasal screen and prevalence of MRSA pneumonia.

Results

Of 98 patients with AML and pneumonia, the prevalence of MRSA pneumonia was 4.1% with confirmed positive MRSA respiratory cultures observed in 4 patient cases. In patients with confirmed MRSA pneumonia, 3 had positive MRSA nasal screens while 1 had a false negative result, possibly due to a long lag time (21 days) between MRSA nasal screen and pneumonia diagnosis. Overall, the MRSA nasal screen demonstrated 75% sensitivity and 100% specificity, with a PPV of 100% and a NPV of 98.9%.

Conclusions

Given the low prevalence, empiric use of anti‐MRSA therapy in those AML and HCT patients with pneumonia may not be warranted in clinically stable patients. For patients in whom empiric anti‐MRSA antibiotics are initiated, nasal screening for MRSA may be utilized to de‐escalate anti‐MRSA antibiotics in patients with AML with or without HCT.
Enzymatic characterization of ancestral/group‐IV clade xyloglucan endotransglycosylase/hydrolase enzymes reveals broad substrate specificities
Authors: Seven Merve , Derman Ü. Cem , Harvey Andrew J.
Published: April 2021

Xyloglucan endotransglycosylase/hydrolase (XTH) enzymes play important roles in cell wall remodelling. Although previous studies have shown a pathway of evolution for XTH genes from bacterial licheninases, through plant endoglucanases (EG16), the order of development within the phylogenetic clades of true XTHs is yet to be elucidated. In addition, recent studies have revealed interesting and potentially useful patterns of transglycosylation beyond the standard xyloglucan–xyloglucan donor/acceptor substrate activities. To study evolutionary relationships and to search for enzymes with useful broad substrate specificities, genes from the ‘ancestral’ XTH clade of two monocots, Brachypodium distachyon and Triticum aestivum, and two eudicots, Arabidopsis thaliana and Populus tremula, were investigated. Specific activities of the heterologously produced enzymes showed remarkably broad substrate specificities. All the enzymes studied had high activity with the cellulose analogue HEC (hydroxyethyl cellulose) as well as with mixed‐link β‐glucan as donor substrates, when compared with the standard xyloglucan. Even more surprising was the wide range of acceptor substrates that these enzymes were able to catalyse reactions with, opening a broad range of possible roles for these enzymes, both within plants and in industrial, pharmaceutical and medical fields. Genome screening and expression analyses unexpectedly revealed that genes from this clade were found only in angiosperm genomes and were predominantly or solely expressed in reproductive tissues. We therefore posit that this phylogenetic group is significantly different and should be renamed as the group‐IV clade.
From Archive to GIS: Recovering Spatial Information for Tholos IV at the Palace of Nestor from the Notebooks of Lord William Taylour
Authors: Loy Michael , Stocker Sharon R. , Davis Jack L.
Published: April 2021

This article is a case study in doing new things with old data. In 1953 Lord William Taylour directed the excavation of a monumental vaulted tholos tomb known as 'Tholos IV' at the site of ancient Pylos, Messenia, Greece. The excavation was conducted over two months, during which detailed notes were recorded in three notebooks now kept in the Archives of the American School of Classical Studies at Athens. The formal publication of Tholos IV, however, contains only a basic narrative of the excavation, offering neither precise detail on stratigraphy, object find spots, nor even a complete inventory of small finds. The present study goes back to the original notebooks kept by Taylour and combines the data contained in them with a new digital survey of Tholos IV to produce a comprehensive and accurate 3D GIS model for the excavation. Furthermore, the GIS has been produced in such a way that its dataset is compatible with new excavation data currently generated in the ongoing Palace of Nestor Excavations (PONEX) project, bringing together two excavation campaigns conducted under very different circumstances, methodologies, and recording protocols. Discussion follows on how the production of this GIS deepens our understanding not just of the legacy excavation, but also of the site and its wider landscape.
An Iterative Numerical Method for Nonlinear Vibrations
Authors: Brock J. E.
Published: April 2021

A simple iterative procedure employing numerical integrations is presented for the analysis of free and forced vibrations of undamped systems having nonlinear elasticity. If the elasticity is symmetrical, it is always possible to make an excellent initial approximation, but the method may also be used in cases of unsymmetrical elasticity. Other applications, such as to systems having parameters which vary with time, are discussed.
Emissivity Calculations for Diatomic Gases
Authors: Penner S. S.
Published: April 2021

An approximate method for estimating radiant-heat transfer from gaseous emitters has been developed. An average absorption coefficient is used for an effective width of an entire vibration-rotation band. The procedure for determining an average absorption coefficient in terms of integrated absorption can be justified, approximately, for very large total pressures where the spectral half-width is no longer small compared with the rotational spacing. Because of this limitation, it is to be expected that the procedure proposed here will be particularly useful only in estimating gaseous emissivities for emitters in high-pressure combustion chambers. Nevertheless, it appears that the simplified procedure yields reasonable results even at relatively low total pressures. Thus a comparison of calculated and observed emissivities for CO at atmospheric pressure shows satisfactory agreement, especially at large optical densities. Representative emissivity calculations over a wide temperature range are described. Emissivity calculations on CO, NO, HF, HCl, HBr, and HI can be carried out very rapidly by the use of recently published data on these gases.
Evaluation of Stress Distribution in the Symmetrical Neck of Flat Tensile Bars
Authors: Aronofsky Julius
Published: April 2021

The local strains and the strain distribution in the necks of two flat tensile specimens have been measured. A strain-hardening function for the material was obtained from the results of tension tests on round bars. This strain-hardening function and the measured strains are used to determine the stress distribution in the neck. Good agreement between the calculated and the measured fracture load was obtained.
Solution to the Rolling Problem for a Strain-Hardening Material by the Method of Discontinuities
Authors: Winzer Alice
Published: April 2021

The problem of drawing and rolling of a thin plastic sheet between cylindrical guides was investigated recently by H. I. Ansoff, under the assumption that the material is in a state of plane plastic flow and obeys the Saint Venant-Mises yield condition (1, 2). He determined the stress distribution along the sheet by the method of characteristics and also by the method of discontinuity surfaces and found good agreement between these results as well as with experimental data. Since the computations required for the discontinuous solution are considerably less laborious than those necessary for the continuous solution, the same type of problem, but now under the assumption that the material displays strain-hardening, will be analyzed by the method of discontinuities. It seems reasonable to expect that the results so found constitute a close approximation to results based upon a continuous solution.
Pressure Distribution in the Calendering of Plastic Materials
Authors: Bergen J. T. , Scott G. W.
Published: April 2021

In the calendering, or rolling, of a plastic material in to sheet form by passing it between parallel rolls, hydrostatic pressure is exerted against the surface of the roll throughout the region of contact with the plastic mass. This pressure has been measured by means of a pressure-sensitive cylinder, inserted in the body of a 10-in-diam roll, together with high-speed oscillographic technique. The materials which were calendered consisted of a resin which exhibited flow properties characteristic of a viscous liquid, and several filled plastic compositions of commercial interest. Pressure maxima ranging up to 8000 psi were observed. Comparison of experimental results with theoretical expressions for pressure distribution, as given by several authors, indicates that the equation derived by Gaskell quite satisfactorily predicts the results for the case of the viscous liquid. The commercial plastics were found to exhibit pressure-distribution characteristics which were perceptibly different from those of the viscous liquid. Certain limitations of Gaskell’s treatment of nonviscous materials prevent its application to these experimental results.
Approximate Solutions of Compressible Flows Past Bodies of Revolution by Variational Method
Authors: Wang Chi-Teh , De Los Santos Socrates
Published: April 2021

Using the direct method of Rayleigh-Ritz in the calculus of variations, the problem of steady irrotational compressible flow past a body of revolution of arbitrary shape is formulated. In order to compare with the analytical solutions obtained by other investigators, two numerical examples have been carried out, namely, compressible flows past a sphere, and an ellipsoid of revolution. The results are found to be in excellent agreement with those computed by other approximate methods.
On Elastic Continua With Hereditary Characteristics
Authors: Volterra Enrico
Published: April 2021

In a previous paper (1) the free and forced vibrations of systems of one degree of freedom with hereditary damping characteristics were discussed. In the present paper the classical equations of motion for elastic media are extended on the basis of the general linear stress-strain law involving hereditary damping. These equations are applied to the case of free radial vibrations of a sphere. Furthermore, the free vibrations of strings, the free transverse vibrations of beams, and the free vibrations of rectangular and circular membranes are studied under the assumption of hereditary damping.
Vibrations of a Clamped Circular Plate Carrying Concentrated Mass
Authors: Roberson R. E.
Published: April 2021

The vibrations of a circular plate clamped at its edge and carrying a concentrated mass at its center are considered. The plate is excited by a motion of the framing, assumed rigid, to which it is clamped. The first four natural frequencies are displayed graphically as functions of mass ratio, and are calculated more precisely for μ = 0, μ = 0.05, and μ = 0.10. The motions of two subsystems with one degree of freedom are compared, one subsystem being driven by the framing and the other by the concentrated mass on the plate. The plate-mounted subsystem has a response in excess of the response of the framing-mounted subsystem if the framing is suddenly put into motion with constant velocity. Except in the neighborhood of their peaks, whose locations depend upon mass ratio, the subsystem resonance curves are depressed in height by increasing the mass ratio.
The Safety Factor of an Elastic-Plastic Body in Plane Strain
Authors: Drucker D. C. , Greenberg H. J. , Prager W.
Published: April 2021

Extremum principles are established for the safety factor of an elastic-plastic body made of a Prandtl-Reuss material and subjected to given surface tractions under conditions of plane strain. Since one of these principles establishes a maximum and the other a minimum property of the safety factor, it is possible to establish bounds for the safety factor by the joint use of these principles.
A New Method of Calculation of Reheat Factors for Turbines and Compressors
Authors: Kaye Joseph , Wadleigh K. R.
Published: April 2021

A simple method is presented for rapid accurate calculation of reheat factors for adiabatic turbines and compressors with an infinite number of stages. The method is limited to fluids for which the following equation of state is adequate pv = RT and for which the specific heat is a function of temperature only. The method is based on the concept of the step efficiency—the efficiency of an infinitesimal stage based on the reversible adiabatic work—and on the concept of the relative pressure function. The method is used to produce charts of reheat factors for turbines and compressors for several gases. A theoretical justification is given for empirical rules of thumb which have been widely used to predict reheat factors for turbines and compressors with a finite number of stages.
The Bending of Uniformly Loaded Sectorial Plates With Clamped Edges
Authors: Conway H. D. , Huang M. K.
Published: April 2021

This paper analyzes the bending of a sectorial plate, clamped on all edges and subjected to uniformly distributed load, by using two different methods of superposition on the elementary solution for a uniformly loaded circular plate with a clamped edge.
Linear Bending Theory of Isotropic Sandwich Plates by an Order-of-Magnitude Analysis
Authors: Gerard George
Published: April 2021

By use of an order-of-magnitude analysis, the equilibrium and stress-strain relations for the faces and core of a sandwich plate are examined in terms of the thickness of the plate. The analysis results in a set of simplified stress-strain relations for the sandwich plate, in addition to which the basic assumptions of previous sandwich-plate bending theories are obtained as the end result.
On the Axisymmetric Problem of the Theory of Elasticity for an Infinite Region Containing Two Spherical Cavities
Authors: Sternberg E. , Sadowsky M. A.
Published: April 2021

This paper contains a solution in series form for the stress distribution in an infinite elastic medium which possesses two spherical cavities of the same size. The loading consists of tractions applied to the cavities, as well as of a uniform field of tractions at infinity, and both are assumed to be symmetric with respect to the common axis of symmetry of the cavities and with respect to the plane of geometric symmetry perpendicular to this axis. The loading is otherwise unrestricted. The solution is based upon the Boussinesq stress-function approach and apparently constitutes the first application of spherical dipolar co-ordinates in the theory of elasticity. Numerical evaluations are given for the case in which the surfaces of the cavities are free from tractions and the stress field at infinity is hydrostatic. The results illustrate the interference of two sources of stress concentration in a three-dimensional problem. The approach used here may be extended to cope with the general equilibrium problem for a region bounded by two nonconcentric spheres.
The Effect of a Rigid Circular Inclusion on the Bending of a Thick Elastic Plate
Authors: Hirsch R. A.
Published: April 2021

The three-dimensional problem of the effect of a rigid circular inclusion on the bending of a thick elastic plate is solved approximately by the method of E. Reissner (1, 2). Comparison is made for the limiting cases of vanishing inclusion size, (plane strain), and vanishing thickness (Poisson-Kirchoff plate theory), with the work of J. N. Goodier (3) and M. Goland (4). Graphs showing the transition from the plane-strain solution to the Poisson-Kirchoff solution are given. Stress concentrations are calculated and plotted versus the inclusion diameter-plate thickness ratio. The stress concentrations are found to be less than predicted by the classical plate theory when the inclusion diameter approaches the same order of magnitude as the plate thickness.
Stresses and Deformations of Toroidal Shells of Elliptical Cross Section: With Applications to the Problems of Bending of Curved Tubes and of the Bourdon Gage
Authors: Clark R. A. , Gilroy T. I. , Reissner E.
Published: April 2021

This paper is concerned with the application of the theory of thin shells to several problems for toroidal shells with elliptical cross section. These problems are as follows: (a) Closed shell subjected to uniform normal wall pressure. (b) Open shell subjected to end bending moments. (c) Combination of the results for the first and second problems in such a way as to obtain results for the stresses and deformations in Bourdon tubes. In all three problems the distribution of stresses is axially symmetric but only in the first problem are the displacements axially symmetric.

The magnitude of stresses and deformations for given loads depends in all three problems on the magnitude of the two parameters bc/ah and b/c where b and c are the semiaxes of the elliptical section, a is the distance of the center of the section from the axis of revolution, and h is the thickness of the wall of the shell. For sufficiently small values of bc/ah trigonometric series solutions are obtained. For sufficiently large values of bc/ah asymptotic solutions are obtained. Numerical results are given for various quantities of practical interest as a function of bc/ah for the values 2, 1, 1/2, 1/4 of the semiaxes ratio b/c. It is suggested that the analysis be extended to still smaller values of b/c and to cross sections other than elliptical.
The Optimum Problem of the Sandwich Plate
Authors: Flügge W.
Published: April 2021

While numerous papers have been published on the stability of sandwich plates in compression, Fig. 1, so far, attention has almost exclusively been focused on the problem of finding the critical load under which the plate becomes unstable, assuming that the dimensions and the materials are given. Some 7 or 8 years ago the author realized that this is not enough for practical purposes. The engineer needs some advice as to how the dimensions of a plate should be chosen in order to obtain a favorable relation between its weight and the load carried. The method used in answering this question will be explained in this paper.
An Alternative Formulation of the Laws of Mechanics
Authors: Trent H. M.
Published: April 2021

The author proposes a set of laws of mechanics which are duals of those of Newton. These laws are based upon the concept of the continuity of transmitted forces around closed loops. They are particularly useful in those engineering problems where only knowledge of forces is of interest, since the laws lead directly to equations in which forces are the dependent variables.
A Variational Principle for the Mesh-Type Analysis of a Mechanical System
Authors: Toupin R. A.
Published: April 2021

The mesh-type equations for a dynamical system consisting of N-mass points are derived from the Newtonian form of the equations of motion. The appropriate Lagrangian for a variational principle is established for these equations.
Bending and Buckling of an Elastically Restrained Circular Plate
Authors: Reismann H.
Published: April 2021

This paper considers the effect of an elastic boundary restraint upon the deflection, moments, and critical (buckling) loads of a circular plate. The solutions given are based on the classical theory of plates and are exact within the assumptions underlying this theory. They include, as particular limiting cases, the known solutions for the simply supported and rigidly clamped edge. The physical significance of the results obtained is discussed in detail with particular emphasis upon the degree of restraint along the clamped edge.
Gas Cooling of a Porous Heat Source
Authors: Green Leon
Published: April 2021

A limiting case of solid-fluid heat transfer is examined, in which a gas passes through a porous wall of high specific surface with heat generation within the solid material. Dimensionless temperature profiles in the wall are presented in terms of the rate of heat generation, rate of flow, and thermal properties of the gas and solid. The pressure drop across the wall is approximated by using an average wall temperature and assuming isothermal conditions. Temperature profiles, pressure drops, and pumping-power/power-output ratios are calculated for the hypothetical case of a heated graphite wall cooled by helium. It is found that the thermal dependence of the gas viscosity produces a minimum in the pressure-drop versus flow-rate curve, and it appears that favorable pumping-power/power-output ratios can be obtained by the use of high pressures. The problem of temperature stability in a gas-cooled porous solid is pointed out and the need for experimental work emphasized. Use of the sweat-cooling technique for high-pressure, high-temperature ducts is suggested.
On the Stresses in a Rotating Disk of Variable Thickness
Authors: Lee Ti-Chiang
Published: April 2021

This paper presents an analytic solution of the stresses in a rotating disk of variable thickness. By introducing two parameters, the profile of the disk is assumed to vary exponentially with any power of the radial distance from the center of the disk. In some respects this solution may be considered as a generalization of Malkin’s solution, but it differs essentially from the latter in the method of solution. Here, the stresses are solved through a stress function instead of being solved directly. The required stress function is expressed in terms of confluent hypergeometric functions. Numerical examples are also shown for illustration.
Forced Lateral Vibration of Beam Carrying a Concentrated Mass
Authors: Hoppmann W. H.
Published: April 2021

In this paper a study is made of the problem of the lateral vibration of a simply supported beam with a concentrated mass attached at its mid-point. A force assumed to act at the mass in a direction normal to the length of the beam is represented by a sinusoidally time-varying function. The homogeneous form of the Bernoulli-Euler beam equation is solved considering the problem as one with time-dependent boundary conditions. To represent an important case of forced vibrations the solution is transformed to give the deflection and bending strain caused by a pulse type of load. Curves are plotted whereby the contributions to deflection and strain from the higher modes of vibration may be examined as functions of the ratio of attached mass to mass of beam. Results of computations for a specific beam and set of masses are presented, as well as experimental results for the same beam with similar pulse-type loads applied. Oscillograms show rather trenchantly the slow transition of the mass-beam system toward a one-degree-of-freedom system as the concentrated mass is increased.
Correlation of Creep Properties by a Diffusion Analogy
Authors: Green Leon
Published: April 2021

The necessity of atom movements for both creep and self-diffusion suggests a method of correlating the constant-stress creep properties of pure metals. The concept of steady-state creep is discarded, and two empirical approximations for the strain-time behavior of pure polycrystalline metals lead to a creep equation defining an activation energy as the only undetermined constant. For cases where the orientation of individual crystals is important, a second constant is required. Application of this equation to published creep data effects a correlation which indicates that the apparent activation energies observed for creep and self-diffusion show a similar temperature dependence. The effect of stress upon the activation energy for several metals is described approximately, but the need for further experiments encompassing lower values of stress is revealed. The qualitative effects of impurities, grain size, cold-working, and surface conditions upon creep as predicted by a diffusion analogy are found to be in agreement with experimental results, but it is noted that the analogy does not hold if creep deformation is obtained as a result of slip.
A Theory of Plastic Bending From a Statistical Aspect
Authors: Craemer Hermann
Published: April 2021

The apparent increase of the yield stress under bending with respect to that under pure tension is explained by the lesser probability that a weak element is situated close to an edge.
Minimum Weight of Tapered Round Thin-Walled Columns
Authors: Feigen Morris
Published: April 2021

It is shown that the optimum wall thickness of a cylindrical round tube column is a function of load only and is independent of diameter. The optimum wall thickness of a tapered round thin-walled column is found to be constant along its length. The optimum shape of a tapered round thin-walled column is derived, being that column whose bending stress in the buckled state is constant along its length. The weight ratio of the optimum tapered column to an equal-strength optimum cylindrical column is found to be 0.8924. It is shown that a double truncated cone whose diameter ratio is in the range 0.35 ⩽ D1/D2 ⩽ 0.50 closely approaches the optimum column. If it is specified that no portion of the double truncated cone shall yield, then the weight advantage of the cone over the cylindrical column is rapidly lost as the stress in the cylindrical column approaches the yield stress. In the inelastic range the weight advantage of the tapered column will be less than in the elastic range.
The Characteristics of Fuel Motion Which Affect Airplane Dynamics
Authors: Graham E. W. , Rodriguez A. M.
Published: April 2021

Problems in aircraft dynamics such as stability and response of the rigid airplane may be affected by fuel motion in the tanks. Such problems also might arise in connection with missiles. In this paper the response of the fuel to simple harmonic motions of a rectangular tank in translation, pitching, and yawing is studied. Using the force and moment expressions, simple mechanical systems equivalent to the fuel are constructed. These systems respond to motions of the tank walls in the same fashion as the fuel, producing identical forces and moments. The use of such mechanical analogies should simplify in many cases the analysis of the complete dynamic system.
The Frequency of Vibration of Rectangular Isotropic Plates
Authors: Hearmon R. F. S.
Published: April 2021

The object of the present paper is to collect the theoretical estimates available for calculating the frequency of vibration of rectangular isotropic plates subjected to various boundary conditions.
The Elastic Sphere Under Concentrated Loads
Authors: Sternberg E. , Rosenthal F.
Published: April 2021

This paper contains an exact solution for the stress distribution in an elastic sphere under two equal and opposite concentrated loads, applied at the end points of a diameter. The solution is based on the Boussinesq stress-function approach to axisymmetric problems and is represented as a sum of two solutions: A singular solution in closed form, and a series solution corresponding to surface tractions which are finite and continuous throughout the surface of the sphere. It is shown that the singularity at the points of application of the loads is not identical with that arising at a concentrated load acting normal to a plane boundary. The existence of pseudosolutions to the problem under consideration, as well as to concentrated-force problems in general, is illustrated, and the validity of the present solution is confirmed through a limit process applied to the case of tractions uniformly distributed over a portion of the boundary. The numerical results for the normal stress on the plane of symmetry perpendicular to the load axis, are compared with the corresponding stress values obtained in a recent three-dimensional photoelastic investigation of the same problem by Frocht and Guernsey (1).
Large Deflection Theory for Orthotropic Rectangular Plates Subjected to Edge Compression
Authors: Yusuff Syed
Published: April 2021

A theory is presented of the large deflections of orthotropic (orthogonally anisotropic) rectangular plates when the plate is initially slightly curved and its boundaries are subjected to the conditions prevailing in edgewise compression tests. Results are given of computations carried out for four different combinations of load and lamination in Fiberglas panels. These theoretical results duplicate the substantial variations in the load-strain and load-deflection diagrams obtained earlier in experiments at the Polytechnic Institute of Brooklyn.
Combined Tension-Torsion Tests for Aluminum Alloy 2S-O
Authors: Phillips Aris
Published: April 2021

In this paper ten combined tension-torsion tests with thin-walled circular tubes of aluminum alloy 2S-O are described. All specimens were loaded with variable stress ratios. It has been found that the theory of plastic flow represents the experimental results with much greater accuracy than does the theory of plastic deformations.
Calibration of Pressure Gages for Work in Ballistics
Authors: Raynor S.
Published: April 2021

For ballistics work where pressures of several thousand psi are encountered, it is essential that the gages used to measure transient pressures be checked against a “standard gage” of known behavior. Such a standard gage and the method of calibrating it are described in the paper.
Gravitational Stresses on Deep Tunnels
Authors: Yu Yi-Yuan
Published: April 2021

Gravitational stresses around a horizontal tunnel opening are determined by means of Muschelišvili’s complex variable method for solving two-dimensional elasticity problems. The tunnel is located at a large but finite depth underneath the horizontal ground surface. It has the shape of a general ovaloid, including the rounded-cornered square, the ellipse, and the circle as its special cases. The surrounding material is assumed to be elastic, isotropic, and homogeneous. Two problems are solved. In one problem an unlined tunnel is considered, which has a boundary free from external stresses. In the other the tunnel has a rigid lining, and a perfect bond is assumed to exist between the lining and the surrounding material so that the displacements at the boundary are zero.