bluuebunny/crossref_metadata_2025 huggingface dataset:
Ribosomal binding and antibacterial activity of ethylene glycol‐bridged apidaecin Api137 and oncocin Onc112 conjugates
Authors: Goldbach Tina , Knappe Daniel , Reinsdorf Christoph , Berg Thorsten , Hoffmann Ralf
Published: July 2016

Recent surveillance data on antimicrobial resistance predict the beginning of the post‐antibiotic era with pan‐resistant bacteria even overcoming polymyxin as the last available treatment option. Thus, new substances using novel modes of antimicrobial action are urgently needed to reduce this health threat. Antimicrobial peptides are part of the innate immune system of most vertebrates and invertebrates and accepted as valid substances for antibiotic drug development efforts. Especially, short proline‐rich antimicrobial peptides (PrAMP) of insect origin have been optimized for activity against Gram‐negative strains. They inhibit protein expression in bacteria by blocking the 70S ribosome exit tunnel (oncocin‐type) or the assembly of the 50S subunit (apidaecin‐type binding). Thus, apidaecin analog Api137 and oncocin analog Onc112 supposedly bind to different nearby or possibly partially overlapping binding sites. Here, we synthesized Api137/Onc112‐conjugates bridged by ethylene glycol spacers of different length to probe synergistic activities and binding modes. Indeed, the antimicrobial activities against Escherichia coli and Pseudomonas aeruginosa improved for some constructs, although the conjugates did not bind better to the 70S ribosome of E. coli than Api137 and Onc112 using 5(6)‐carboxyfluorescein‐labelled Api137 and Onc112 in a competitive fluorescence polarization assay.

In conclusion, Api137/Onc112‐conjugates showed increased antimicrobial activities against P. aeruginosa and PrAMP‐susceptible and ‐resistant E. coli most likely because of improved membrane interactions, whereas the interaction to the 70S ribosome was most likely not improved relying still on the independent apidaecin‐ and oncocin‐type binding modes. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.
Implications of non‐coding RNAs in viral infections
Authors: Sharma Nikhil , Singh Sunit K.
Published: July 2016

The advances in RNA sequencing have unveiled various non‐coding RNAs (ncRNAs), which modulate the gene expression. ncRNAs do not get translated into proteins. These include transfer RNAs, ribosomal RNAs, microRNA (miRNA), short interfering RNA, long non‐coding RNA, piwi‐interacting RNA and small nuclear RNA. ncRNAs regulate gene expression at various levels and control cellular machinery. miRNAs have been reported in plants, animals, several invertebrates and viruses. The miRNAs regulate the gene expression post‐transcriptionally. Viral infection strongly influences the abundance and the distribution of miRNAs and other ncRNAs within the host cells. Viruses may encode their own miRNA, which help in the viral life cycle and other aspects of pathogenesis. Viruses are known to successfully modulate the expression pattern of ncRNAs. The ncRNA‐based strategies adopted by viruses for their survival present a complex picture of host–virus interactions. Copyright © 2016 John Wiley & Sons, Ltd.
ZrCl4 Catalysed Diastereoselective Synthesis of Spirocarbocyclic Oxindoles via [4+2] Cycloaddition
Authors: Kumar Kapil , Siddique Julekha , Gangar Mukesh , Goyal Sandeep , Rawal Ravindra K. , Nair Vipin A.
Published: July 2016

Spirocarbocyclic‐oxindole is priviledged scaffold in heterocyclic chemistry, which paved the attention of synthetic chemist due to generation of a new stereocenter. Numerous methodologies have been developed for spirooxindoles but very few methods are available for carbocyclic oxindoles. Most of the reported cycloaddition reactions are five membered rings instead of six membered rings, tethered with oxindole scaffold. Lewis acid catalysed Diels Alder reaction is a comparatively better approach to functionalize this unique scaffold. An efficient diastereoselective synthesis of spirocarbocyclic‐oxindoles with six membered cabocyclic backbone was achieved via ZrCl4 catalyzed [4+2] cycloaddition of α‐ylideneoxindoles with dienes in good to excellent yields within a short span of time.
Regioselectivity in Acetylation of Cellulose in Ionic Liquids
Authors: Abe Mitsuru , Sugimura Kazuki , Nishio Yoshiyuki
Published: July 2016

Distribution of substituents on the anhydroglucose unit of cellulose (at C2, C3 and C6 positions) is one of the important topics in the derivatization chemistry, but the regioselectivity control is generally difficult. In this report, we exemplified that cellulose acetates having a similar total degree of substitution (∼2.3) were obtained in the relevant derivatization but regioselectivity (C6 > C3 > C2, C2 > C6 > C3, C6 > C2 > C3, or C6 > C3=C2) by a simple one‐pot reaction (25 °C; 3 h) with acetyl chloride or acetic anhydride in various ionic liquids (ILs). The order of the regional degree of substitution associated with the C2 and C3 positions was successfully correlated with the variation of anion species incident to the acetylating reagent‐IL combination. In the use of acetyl chloride, the observed difference in the substituent distribution was attributable to whether a pre‐reaction between the in‐fed reagent and the anion moiety of the solvent IL was possible or not.
Concise Review: Perspectives and Clinical Implications of Bone Marrow and Circulating Stem Cell Defects in Diabetes
Authors: Fadini Gian Paolo , Ciciliot Stefano , Albiero Mattia
Published: July 2016

Diabetes mellitus is a complex systemic disease characterized by severe morbidity and excess mortality. The burden of its multiorgan complications relies on an imbalance between hyperglycemic cell damage and defective endogenous reparative mechanisms. Inflammation and abnormalities in several hematopoietic components are typically found in diabetes. The discovery that diabetes reduces circulating stem/progenitor cells and impairs their function has opened an entire new field of study where diabetology comes into contact with hematology and regenerative medicine. It is being progressively recognized that such rare circulating cell populations mirror finely regulated processes involved in hematopoiesis, immunosurveillance, and peripheral tissue homeostasis. From a clinical perspective, pauperization of circulating stem cells predicts adverse outcomes and death. Furthermore, studies in murine models and humans have identified the bone marrow (BM) as a previously neglected site of diabetic end-organ damage, characterized by microangiopathy, neuropathy, fat deposition, and inflammation. As a result, diabetes impairs the mobilization of BM stem/progenitor cells, a defect known as mobilopathy or myelokathexis, with negative consequences for physiologic hematopoiesis, immune regulation, and tissue regeneration. A better understanding of the molecular and cellular processes that govern the BM stem cell niche, cell mobilization, and kinetics in peripheral tissues may uncover new therapeutic strategies for patients with diabetes. This concise review summarizes the current knowledge on the interplay between the BM, circulating stem cells, and diabetes, and sets the stages for future developments in the field.

Abstract Video Link: https://youtu.be/n57R4BIYYcs
Plasma clusterin levels and risk of dementia, Alzheimer's disease, and stroke
Authors: Weinstein Galit , Beiser Alexa S. , Preis Sarah R. , Courchesne Paul , Chouraki Vincent , Levy Daniel , Seshadri Sudha
Published: July 2016

Introduction

Genetic variation in the clusterin gene has been associated with Alzheimer Disease (AD), and the clusterin protein is thought to play a mechanistic role. We explored the associations of clusterin plasma levels with incident dementia, AD, and stroke.

Methods

Plasma clusterin was assessed in 1532 nondemented participants from the Framingham Study Offspring cohort between 1998 and 2001 (mean age, 69 ± 6; 53% women). We related clusterin levels to risk of incident dementia, AD, and stroke using Cox‐proportional hazards models and examined potential interactions.

Results

A significant interaction of plasma clusterin levels with age was observed. Clusterin was significantly associated with increased risk of dementia among elderly persons (>80 years; hazard ratio [HR], 95% confidence interval = 6.25, 1.64–23.89; P = .007) and with decreased risk of dementia (HR = 0.53, 0.32–0.88; P = .013) and stroke (HR = 0.78, 0.63–0.97; P = .029) among younger participants.

Discussion

The association between plasma clusterin levels and risk of dementia and stroke may be modified by age or an age‐related factor.
Supporting hurricane inventory management decisions with consumer demand estimates
Authors: Morrice Douglas J. , Cronin Paul , Tanrisever Fehmi , Butler John C.
Published: July 2016

Matching supply and demand can be very challenging for anyone attempting to provide goods or services during the threat of a natural disaster. In this paper, we consider inventory allocation issues faced by a retailer during a hurricane event and provide insights that can be applied to humanitarian operations during slow‐onset events. We start with an empirical analysis using regression that triangulates three sources of information: a large point‐of‐sales data set from a Texas Gulf Coast retailer, the retailer's operational and logistical constraints, and hurricane forecast data from the National Hurricane Center (NHC). We establish a strong association between the timing of the hurricane weather forecast, the forecasted landfall position of the storm, and hurricane sales. Storm intensity is found to have a weaker association on overall inventory decisions. Using the results of the empirical analysis and the NHC forecast data, we construct a state‐space model of demand during the threat of a hurricane and develop an inventory management model to satisfy consumer demand prior to a hurricane making landfall. Based on the structure of the problem, we model this situation as a two‐stage, two‐location inventory allocation model from a centralized distribution center that balances transportation, shortage and holding costs. The model is used to explore the role of recourse, i.e., deferring part of the inventory allocation until observing the state of the hurricane as it moves towards landfall. Our approach provides valuable insights into the circumstances under which recourse may or may not be worthwhile in any setting where an anticipated extreme event drives consumer demand.
Evaluating information diffusion speed and its determinants in social media networks during humanitarian crises
Authors: Yoo Eunae , Rand William , Eftekhar Mahyar , Rabinovich Elliot
Published: July 2016

The rapid diffusion of information is critical to combat the extreme levels of uncertainty and complexity that surround disaster relief operations. As a means of gathering and sharing information, humanitarian organizations are becoming increasingly reliant on social media platforms based on the Internet. In this paper, we present a field study that examines how effectively information diffuses through social media networks embedded in these platforms. Using a large dataset from Twitter during Hurricane Sandy, we first applied Information Diffusion Theory to characterize diffusion rates. Then, we empirically examined the impact of key elements on information propagation rates on social media. Our results revealed that internal diffusion through social media networks advances at a significantly higher speed than information in these networks coming from external sources. This finding is important because it suggests that social media networks are effective at passing information along during humanitarian crises that require urgent information diffusion. Our results also indicate that dissemination rates depend on the influence of those who originate the information. Moreover, they suggest that information posted earlier during a disaster exhibits a significantly higher speed of diffusion than information that is introduced later during more eventful stages in the disaster. This is because, over time, participation in the diffusion of information declines as more and more communications compete for attention among users.
Comparing the Course of Mental Health Over the First Year After Stroke With Healthy Controls in Colombia, South America
Authors: Sutter Megan , Olabarrieta Landa Laiene , Calderón Chagualá Amilkar , Chacón Peralta Helmer , Vergara Torres Gina , Perrin Paul B. , Arango‐Lasprilla Juan Carlos
Published: July 2016

Background

Stroke is a primary cause of death and disability in upper‐middle–income countries such as Colombia. Given the lack of comprehensive rehabilitation for stroke patients in Colombia, there is a need to assess longitudinal mental health problems poststroke in this region.

Objective

To compare the course of mental health in stroke patients to healthy controls over the first year poststroke in Ibague, Colombia.

Design

Cross‐sectional study.

Setting

The Psychological Attention Center of Antonio Nariño University in Ibague, Colombia.

Participants

Stroke patients (n = 50) and age‐ and gender‐matched healthy controls (n = 50).

Methods

Patients and controls completed self‐report Spanish versions of demographic information, injury‐related characteristics, and mental health questionnaires

Main Outcome Measurements

Outcomes assessed included mental health (depression, anxiety, and stress) at 3, 6, and 12 months poststroke.

Results

Hierarchical linear models suggested that stroke patients had worse depression and anxiety over time than controls (P < .001). Among patients, depression and anxiety decreased over time (P < .001), whereas stress increased over time (P < .01). The findings suggest that although anxiety and depression improved over time in stroke patients, their mental health remained significantly lower than that of controls.

Conclusions

This is the first study to examine the course of mental health over the first year poststroke in Latin America, specifically in Ibague, Colombia. Despite the improvements in anxiety and depression over the first year poststroke, patient anxiety and depression were still worse in comparison to those in healthy controls. The current findings indicate a need for rehabilitation services in Colombia, especially targeting mental health issues.

Level of Evidence

I
Impact of Cognition on Burn Inpatient Rehabilitation Outcomes
Authors: Bajorek Alexander J. , Slocum Chloe , Goldstein Richard , Mix Jacqueline , Niewczyk Paulette , Ryan Colleen M. , Hendricks Carla Tierney , Zafonte Ross , Schneider Jeffrey C.
Published: July 2016

Background

A significant proportion of burn injury patients are admitted to inpatient rehabilitation facilities (IRFs). There is increasing interest in the use of functional variables, such as cognition, in predicting IRF outcomes. Cognitive impairment is an important cause of disability in the burn injury population, yet its relationship to IRF outcomes has not been studied.

Objective

To assess how cognitive function affects rehabilitation outcomes in the burn injury population.

Design

Retrospective study.

Setting

Inpatient rehabilitation facilities in the United States.

Participants

A total of 5347 adults admitted to an IRF with burn injury between 2002 and 2011.

Methods or Interventions

Multivariable regression was used to model rehabilitation outcome measures, using the cognitive domain of the Functional Independence Measure (FIM) instrument as the independent variable and controlling for demographic, medical, and facility covariates.

Main Outcome Measurements

FIM total gain, readmission to an acute care setting at any time during inpatient rehabilitation, readmission to an acute care setting in the first 3 days of IRF admission, rate of discharge to the community setting, and length of stay efficiency.

Results

Cognitive FIM total at admission was a significant predictor of FIM total gain, length of stay efficiency, and acute readmission at 3 days (P < .05). Cognitive FIM total scores did not have an impact on acute care readmission rate or discharge to the community setting.

Conclusions

Cognitive status may be an important predictor of rehabilitation outcomes in the burn injury population. Future work is needed to further examine the impact of specific cognitive interventions on rehabilitation outcomes in this population.

Level of Evidence

II
Preferencias de carrera en médicos que eligen rotaciones rurales de mayor duración
Authors: Hays Richard
Published: July 2016

Introducción: En Australia, los estudiantes de medicina rotan en especialidades clínicas durante 6-8 semanas en hospitales urbanos. Para aumentar el interés por las carreras rurales, los estudiantes de algunas escuelas pueden elegir  rotaciones de mayor duración (hasta un año) en clínicas rurales. Las rotaciones longitudinales integradas (LIC, por sus siglas en inglés) ocurren en lugares de atención primaria, como clínicas rurales y escuelas de medicina rural.
Objetivo: Evaluar el efecto de las rotaciones rurales más extensas sobre la decisión final en la carrera de medicina en Australia.
Método: Se estudiaron 3 grupos de estudiantes graduados en 2011: 276 con al menos 700 h de prácticas rurales (casi la mitad del año académico), 772 de las mismas escuelas con menos de 700 h de prácticas rurales y 5,326 de 16 escuelas que, o bien no ofrecieron rotaciones rurales, o muy pocos las realizaron. Se compararon los datos de los 3 grupos con la prueba de 2.
Resultados: Un total de 3,483 estudiantes fueron de lugares otorgados por la Commonwealth (CSP); 1,375 de lugares asegurados con rotaciones rurales (MRBS) o médicas (BMP); 414 con pago completo en lugares domésticos (DFF), y 926 en zonas con pago completo internacional (IFF). Es más probable que los estudiantes CSP elijan una LIC en comparación con los IFF ( 256.4; p < 0.05). Los que eligieron una LIC tuvieron más rotaciones rurales (2 124.5, p < 0.05) y elección por las carreras fuera de las áreas metropolitanas y en comunidades más pequeñas ( 2 182.2, p < 0.05). Aquellos que realizaron LIC tuvieron preferencias similares a las de otros estudiantes en las carreras futuras, con excepción de medicina de urgencias y medicina rural, aunque no para medicina familiar (2 53.4; p < 0.05).
Discusión y conclusiones: Los médicos con rotaciones rurales parecen tener mayor preferencia por carreras en el área rural una vez graduados, lo que parece ser una estrategia que podría aumentar el número de médicos en áreas rurales. Se necesita más investigación para determinar los desenlaces de todos los modelos de las rotaciones rurales, con la inclusión de modelos de hospitales más pequeños de medicina general y modelos de atención primaria. La relevancia para otros sistemas de educación y el contexto en Australia también deben ser estudiados.
Testing the “tropical storm” hypothesis of Yucatan Peninsula climate variability during the Maya Terminal Classic Period
Authors: Medina-Elizalde Martín , Polanco-Martínez Josué Moises , Lases-Hernández Fernanda , Bradley Raymond , Burns Stephen
Published: July 2016

We examine the “tropical storm” hypothesis that precipitation variability in the Yucatan Peninsula (YP) was linked to the frequency of tropical cyclones during the demise of the Classic Maya civilization, in the Terminal Classic Period (TCP, AD 750—950). Evidence that supports the hypothesis includes: (1) a positive relationship between tropical storm frequency and precipitation amount over the YP today (proof of feasibility), (2) a statistically significant correlation between a stalagmite (Chaac) quantitative precipitation record from the YP and the number of named tropical cyclones affecting this region today (1852—2004) (calibrationsensu lato), and, (3) correlations between the stalagmite Chaac precipitation record and an Atlantic basin tropical cyclone count record and two proxy records of shifts in macroscale climate and ocean states that influence Atlantic tropical cyclongenesis. At face value, regional paleotempestology proxy records suggest that tropical storm activity in the YP was either similar or significantly lower than today during the TCP. The “tropical storm” hypothesis has implications for our understanding of the role the hydrological cycle played in the collapse of Classic Maya polities and the role of tropical storms in possibly ameliorating future drought in the YP and other tropical regions.
Sustainable development goals, universal health coverage and equity in health systems: the Orang Asli commons approach
Authors: Wong Y. S. , Allotey P. , Reidpath D. D.
Published: July 2016

Universal health coverage is a key health target in the Sustainable Development Goals (SDGs) that has the means to link equitable social and economic development. As a concept firmly based on equity, it is widely accepted at international and national levels as important for populations to attain ‘health for all’ especially for marginalised groups. However, implementing universal coverage has been fraught with challenges and the increasing privatisation of health care provision adds to the challenge because it is being implemented in a health system that rests on a property regime that promotes inequality. This paper asks the question, ‘What does an equitable health system look like?’ rather than the usual ‘How do you make the existing health system more equitable?’ Using an ethnographic approach, the authors explored via interviews, focus group discussions and participant observation a health system that uses the commons approach such as which exists with indigenous peoples and found features that helped make the system intrinsically equitable. Based on these features, the paper proposes an alternative basis to organise universal health coverage that will better ensure equity in health systems and ultimately contribute to meeting the SDGs.
Three-dimensional instabilities and inertial waves in a rapidly rotating split-cylinder flow
Authors: Lopez Juan M. , Gutierrez-Castillo Paloma
Published: July 2016

The nonlinear dynamics of the flow in a differentially rotating split cylinder is investigated numerically. The differential rotation, with the top half of the cylinder rotating faster than the bottom half, establishes a basic state consisting of a bulk flow that is essentially in solid-body rotation at the mean rotation rate of the cylinder and boundary layers where the bulk flow adjusts to the differential rotation of the cylinder halves, which drives a strong meridional flow. There are Ekman-like layers on the top and bottom end walls, and a Stewartson-like side wall layer with a strong downward axial flow component. The complicated bottom corner region, where the downward flow in the side wall layer decelerates and negotiates the corner, is the epicentre of a variety of instabilities associated with the local shear and curvature of the flow, both of which are very non-uniform. Families of both high and low azimuthal wavenumber rotating waves bifurcate from the basic state in Eckhaus bands, but the most prominent states found near onset are quasiperiodic states corresponding to mixed modes of the high and low azimuthal wavenumber rotating waves. The frequencies associated with most of these unsteady three-dimensional states are such that spiral inertial wave beams are emitted from the bottom corner region into the bulk, along cones at angles that are well predicted by the inertial wave dispersion relation, driving the bulk flow away from solid-body rotation.
Estimation of the Effect of a Parameter Change on the Roots of Stability Equations
Authors: Mitchell K.
Published: July 2016

A method is given for calculating approximately the changes in the roots of a stability secular equation caused by a change in any of the parameters involved. General formulas are given applicable to any quartic equation, and special formulae are also given applicable to the stability of an aeroplane: lateral stability in the text, and longitudinal stability in an appendix.

The method of using the formulae is illustrated by applying them to a particular calculation of the lateral stability of an aeroplane, and a check of the results is made by comparing the predicted approximate changes with those calculated by solution of the modified period equations. It is shown that the formulae are reliable, for this typical case, for any reasonable changes in any parameter other than nv.

If the changes in the derivatives are made equal to the probable error with which they can be measured, the formulae enable us to evaluate the probable errors of the roots. These are found to be considerable, and to arise mainly from uncertainties in yv, nv and nr: if these could be reduced to 0.03 in yv and 0.006 in the others, the uncertainties in the roots would be reduced to some ten per cent, of their values, except for a larger uncertainty in the root corresponding to the slow spiral motion.
Theory of an oscillating supersonic aerofoil
Authors: Sewell Geoffrey L.
Published: July 2016

In the previous linearised theories of steady supersonic flow past a slender oscillating aerofoil, the shock line at the nose has been assumed to be a straight, stationary one, so that no vorticity is produced on passing through it. In the present treatment, the possibility that the shock may be both curved and moving is taken into account, but the result is exactly the same as that obtained by the previous treatments (e.g. Temple and Jahn).
Note on the dependence of flap hinge moment derivatives on hinge
position
Authors: Duncan W.J.
Published: July 2016

It is shown to be a consequence of kinematics and statics that the
aerodynamic derivative expressing the rate of change of hinge moment of a
plain flap with the angular setting of the flap varies parabolically with
the chordwise position of the hinge. The derivative expressing the rate of
change of hinge moment with incidence of the main surface varies linearly
with the hinge position. Similar conclusions hold for the derivatives of the
hinge moment with respect to the corresponding angular velocities.
The Profile Drag of Yawed Wings of Infinite Span
Authors: Young A.D. , Booth T.B.
Published: July 2016

A method is developed for calculating the profile drag of a yawed wing of infinite span, based on the assumption that the form of the spanwise distribution of velocity in the boundary layer, whether laminar or turbulent, is insensitive to the chordwise pressure distribution. The form is assumed to be the same as that accepted for the boundary layer on an unyawed plate with zero external pressure gradient. Experimental evidence indicates that these assumptions are reasonable in this context. The method is applied to a flat plate and the N.A.C.A. 64-012 section at zero incidence for a range of Reynolds numbers between 106 and 108, angles of yaw up to 45°, and a range of transition point positions. It is shown that the drag coefficients of a flat plate varies with yaw as cos½ Λ (where Λ is the angle of yaw) if the boundary layer is completely laminar, and it varies as if the boundary layer is completely turbulent. The drag coefficient of the N.A.C.A. 64-012 section, however, varies closely as cos½ Λ for transition point positions between 0 and 0.5 c. Further calculations on wing sections of other shapes and thicknesses and more detailed experimental checks of the basic assumptions at higher Reynolds numbers are desirable.
Longitudinal Waves in Beams
Authors: Bishop R. E. D.
Published: July 2016

The elementary engineering theory of longitudinal waves in beams allows for no dispersion, whereas Love's corrected version of it predicts that very short waves are not propagated. A new correction is added which overcomes these defects. To do this, a simple theorem is proved concerning certain types of closed region. A method of improving Love's formula and the present one is illustrated.
Aerofoil Theory for Swallow Tail Wings of Small Aspect Ratio
Authors: Robinson A.
Published: July 2016

A method is developed for the calculation of the aerodynamic forces acting on a “swallow tail” wing (Figs. l(a) and l(b)) of small aspect ratio. For a given incidence, lift and induced drag coefficient are, within the limits of the theory, proportional to aspect ratio and independent of Mach number. The exact solution is derived for the limiting case of small sweepback of the trailing edge. A numerical method is indicated for the more general case.
The Arithmetic of Field Equations
Authors: Thom A.
Published: July 2016

The paper describes in detail an older method than Relaxation of approximating to the solution of equations of the Laplace and Poisson type. The corresponding fourth order equations are discussed briefly, and a method of dealing with certain non-linear equations is indicated. A description is also given of the propagation of errors in the fields due to various causes.
The Distribution of Lift over the Surface of Swept Wings
Authors: Küchemann D.
Published: July 2016

A simple method is given for calculating, in incompressible flow, the spanwise and chordwise loadings on thin swept wings with symmetrical aerofoil sections and of moderate and large aspect ratios. The present note is based on, and continues, the investigation described in an earlier paper. The design of swept wings with given spanwise and chordwise load distributions, obtained by modifying the plan form of the wing or by adding camber and twist, is briefly considered, as well as the design of swept wings which give minimum induced drag.
Impulsive and Indicial Admittances of Simple Dynamical Chains
Authors: Duncan W. J.
Published: July 2016

The responses of systems, whose equations of motion are linear, to arbitrary applied forces are conveniently calculable by the use of impulsive or indicial admittances. Expressions for these admittances are here given explicity for some simple dynamical chains and the procedure for their calculation in chains with more degrees of freedom is outlined. Some general characteristics of the dynamical chains are also examined.
The Application of a Block Diagram Representation to Aircraft Stability Analysis
Authors: Summerlin F. A. , Sullivan N.
Published: July 2016

The block diagram representing an aircraft in either its lateral or longitudinal motion is given and is used to explain the aircraft response in the antisymmetric stick-fixed case. A generalised autopilot is added to the aircraft diagram and the method of analysing the combination by conventional servo techniques is indicated. It is shown how an estimate can be made of the effects on stability of non-linearities in the output member of the control system.
Trends in the Development of Liquid Propellant Rocket Engines
Authors: Andrews E. G. D. , Mottram A. W. T.
Published: July 2016

The authors predict that rocket engines will fall into two categories. In both, combustion pressures will approach 200 atmospheres to attain optimum vehicle performance, balancing increased pumping losses and engine mass against increased expansion efficiency and reduced dissociation. For general purposes, engines will be intrinsically convenient: storable propellants will give specific impulses around 270 lb. sec./lb., and engine specific weights will be between 0·02 and 0·03. For exacting applications, the greatest overall convenience may necessitate using unpleasant propellants so as to obtain the highest performance. Immediate research into the use and handling of these is essential if future engine development is not to be hampered.
The Influence of Biaxial Mean Stresses on the Failure of Tubes by Fatigue
Authors: Cox H. L. , Owen N. B.
Published: July 2016

Thin-walled tubes, in. in diameter, of three hard aluminium alloys and of mild steel have been tested in fatigue under three systems of alternating stresses while subjected to biaxial mean tensions imposed by means of internal pressure. In fatigue under direct or bending stresses the hoop tension in the walls of the aluminium alloy tubes did not seriously reduce the fatigue endurance, but it did markedly affect the mode and rate of crack propagation; cracks initially transverse to the tube axis tended to develop very rapidly in the axial direction. This tendency was present under both fluid and gas pressure, and under gas pressure the cracks propagated so fast that the test piece was often blown to pieces before the gas pressure fell by leakage through the cracks. The gradual taper in wall thickness along the fillets joining the test section to the enlarged ends offered no barrier to propagation of the axial cracks and the whole test piece, including its enlarged ends, was often shattered. Propagation of the axial cracks was preventible by sufficiently reducing the fillet radius, or by a ring glued on. Under alternating torsion, both endurance and mode of failure were affected by internal gas pressure. The initial fatigue crack, either circumferential or axial, often extended over a length comparable with the diameter of the tube, except under low ranges of shear stress when the crack length was sometimes very short. At each end the cracks forked in a characteristic manner and under moderate gas pressure the portions of tHe wall between the prongs of the fork were blown outwards. Under high pressure explosive failure and fragmentation often occurred. Mild steel under alternating torsion with internal gas pressure exhibited the same modes of failure, and two or more fatigue cracks were often formed simultaneously. Under high hoop tension, cracks propagated rapidly and one test piece, after two million cycles endurance, failed by exploding. However, no mild steel test piece was fragmented. A tentative explanation is offered of the reason why, in tubes of small diameter, rather short fatigue cracks may be expected to lead to fast fracture under the static loading. Attention is drawn to the inference that the initial fatigue crack itself must develop very quickly to considerable length.
The Theory of Melting Ablation, with Vaporisation, Gas-Phase Chemical Reaction, Surface Pyrolysis, and Transient Effects
Authors: Spalding D. B.
Published: July 2016

Standard techniques of mass-transfer theory are used for the prediction of ablation rates; the thermodynamic and chemical-kinetic material properties are introduced by way of enthalpy-composition diagrams; the interface condition is given as the root of a single non-linear equation involving material properties. The paper treats both steady ablation and unsteady ablation, the latter by means of a quasi-steady assumption which confines transient effects to the solid phase.

Detailed comparisons are made with the methods of Sutton, Bethe and Adams, and Lees. The formulations of the paper are shown to be equivalent to, but more general than, those of the earlier authors; it is suggested that they are simpler as well. Some improvements over previous practice are recommended in connection with the calculation of the shear stress at the interface.
The Elastic Instability of a Complete Spherical Shell
Authors: Thompson J.M.T.
Published: July 2016

The elastic instability of a complete spherical shell under uniform external pressure is studied experimentally and theoretically. The premature snapping of a thin elastic shell, made of polyvinyl chloride, is seen to be classical in nature. The experimental maximum pressure and pre-snapping bending deformation are correlated with the theoretical behaviour of an initially imperfect shell. The large deflection behaviour of a perfect shell is assessed experimentally, and the stable post-buckling states are observed to be rotationally symmetric. A fairly precise theoretical analysis of these states is performed, the use of a high-speed digital computer allowing a considerable advance over previous treatments. The experimental and theoretical post-buckling curves are in good agreement, yielding the first detailed correlation of post-snapping equilibrium states in the field of shell instability.
The Stacking of Compressor Stage Characteristics to Give an Overall Compressor Performance Map
Authors: Doyle M. D. C. , Dixon S. L.
Published: July 2016

A method of calculation is developed to compute the overall performance of a multi-stage axial compressor, from a knowledge of the individual stage characteristics, by a “stacking” technique. Compressor models are designed and their overall performance calculated. These results are compared to show, qualitatively, the effect of alterations in design and stage performance on overall performance and to find how compressors should be designed for optimum performance.
The Static Aeroelasticity of Slender Configurations
Authors: Hancock G. J.
Published: July 2016

The validity and applicability of the static margin (stick fixed) Kn,

where

as defined by Gates and Lyon is shown to be restricted to the conventional flexible aircraft. Alternative suggestions for the definition of static margin are put forward which can be equally applied to the conventional flexible aircraft of the past and the integrated flexible aircraft of the future. Calculations have been carried out on simple slender plate models with both linear and non-linear aerodynamic forces to assess their static stability characteristics.
Effect of Linear Damping on Flutter Speed Part I: Binary Systems
Authors: Nissim E.
Published: July 2016

A study of the effect of linear damping on flutter speed is described. The energy exchange at flutter is considered in each degree of freedom of a general n-degrees-of-freedom system and an energy compatibility equation is formed. An analytical discussion of binary systems, based on the energy compatibility equation, is then presented.
Practical Bypass Mixing Systems for Fan Jet Aero Engines
Authors: Frost T. H.
Published: July 2016

Mixing systems have many applications in gas turbines and aircraft jet propulsion, e.g. mixing zones in combustion chambers, ejectors for jet lift thrust augmentors and supersonic propulsion systems. A further application similar to that of combustion chamber mixing is that of mixing the cold and hot exhausts of a bypass jet engine. These are both characterised by mixing at constant static pressure and approximately constant total pressure as opposed to the more general case of unequal pressures in ejector systems (Fig. 1).

The exhaust mixing process as used in Rolls-Royce bypass jet engines, e.g. Spey and Conway, enables the potential of the bypass principle, in terms of minimum weight and fuel consumption, to be exploited by a simple practical device.

This is achieved by mixing the two streams in a common duct of fairly short dimensions with a corrugated metal interface on the inlet side. The consideration of these practical systems forms the main topic of this paper.
Shear Buckling of Orthogonally Stiffened, Infinitely Long Simply-Supported Plates–Stiffeners having Torsional and Flexural Rigidities
Authors: Rockey K. C. , Cook I. T.
Published: July 2016

The paper presents a solution to the buckling under shear stress of infinitely long plates orthogonally reinforced by stiffeners having both flexural and torsional rigidity. Each family of stiffeners is assumed to consist of equally spaced identical stiffeners. Numerical results are given for the case of a plate with transverse stiffeners and a central longitudinal stiffener for the following three cases:

(i)

Transverse and longitudinal stiffeners of closed tubular cross-section.

(ii)

Transverse stiffeners of closed tubular cross-section, longitudinal stiffeners possessing only flexural rigidity.

(iii)

Transverse stiffeners possessing only flexural rigidity, the longitudinal stiffeners being of closed tubular cross-section.

Relationships between the buckling stress parameter K and the flexural rigidity parameter γ of the stiffeners are presented for each of the three cases when the identical transverse stiffeners are placed at spacings of d, 0·8d and 0·5d, where d is the depth of the webplate.

Case (i) has provided values of the buckling coefficient K for finite rectangular plates clamped on three edges and simply-supported on the remaining edge.
A Comparison of Two Integral Equation Methods for High Subsonic Lifting Flows
Authors: Nixon D
Published: July 2016

A comparison is made of two recently published integral equation methods for calculating the high subsonic flow around lifting and non-lifting aerofoils. It is shown that one method leads to a non-unique solution.
A Numerical Method for Calculating Viscous Flow Round Multiple-Section Aerofoils
Authors: Seebohm T , Newman B G
Published: July 2016

A numerical method is described for predicting incompressible, attached flow round multiple-section aerofoils at high Reynolds number. Interaction between wakes and boundary layers is not accounted for, but the method is nevertheless suitable for optimisation of design in the take-off condition. The solution is obtained in three steps:

(i)

The calculation of the outer, potential flow using a conventional Kutta condition for each aerofoil section.

(ii)

The calculation of viscous boundary layers and wakes.

(iii)

The combination of the inviscid and viscous solutions to effect proper matching at the edges of the boundary layers and wakes and a more accurate specification of the circulation in the inviscid flow.
Surface Heat Exchangers
Authors: Claire R Le
Published: July 2016

Among the many problems which face airframe manufacturers, cooling is certainly one of the most important, particularly as a special watch must be kept on the type of solution to be adopted, since the lowest fuel penalty must be incurred in flight.
Periodic Wake Behind a Circular Cylinder at Low Reynolds Numbers
Authors: Hussain A K M F , Ramjee V
Published: July 2016

The effects of free-stream turbulence and of sinusoidal free-stream pulsations of controlled frequencies and amplitudes on the periodic wake of a circular cylinder are investigated experimentally by employing hot-wire and smoke visualisation techniques. In addition, the effects of cylinder yaw and mild favourable and adverse pressure gradients on the vortex shedding mechanism have been explored.

The data relating frequency to mean velocity follow Berger’s relation; this relation is uninfluenced by free-stream turbulence intensities up to 8 per cent. As the longitudinal turbulence intensity increases from 0.3 to 8 per cent, the downstream distance Lp behind the cylinder over which the hot-wire signal is periodic decreases progressively, indicating that the otherwise steady periodic wake interacts non-linearly with the three-dimensional free-stream turbulence and undergoes either transition or rapid diffusion by turbulence, depending on both the Reynolds number and the turbulence intensity. For a given turbulence intensity, Lp decreases also with increasing Reynolds number.

The shedding frequency behind a yawed cylinder does not vary as the cosine of the yaw angle ϕ for ϕ < 50°; the signal switches intermittently between periodic and irregular form as the yaw is increased from 0 to 70°. Mild pressure gradients (favourable as well as adverse) do not affect the shedding frequency; this is confirmed by smoke visualisation, which also shows that the pressure gradient changes the longitudinal vortex spacing downstream; the measured frequency is that determined by the local Reynolds number corresponding to the Berger relation.

Sinusoidal streamwise pulsations of controlled frequencies, and of amplitudes up to 10 per cent of free-stream velocity, have no effect on the natural shedding frequency; this is confirmed by smoke visualisation of the cylinder wake. However, the wake signal is amplitude-modulated at a frequency equal to the difference between the pulsation frequency and the natural shedding frequency corresponding to the free-stream mean velocity. The vortices are diffused faster in the presence of pulsation. When the pulsation amplitude is increased beyond 20 per cent, the hot-wire signal frequency in the wake equals the driving frequency; the frequency in the wake centre is also that of the pulsation. The effect of free-stream pulsation on the periodic wake is different from that due to longitudinal or transverse cylinder vibration, when lock-in has been observed.

It appears that free-stream disturbances – random or periodic – cannot account for the “Tritton jump”.
A Simulation of a Supersonic Intake on a Hybrid Computer
Authors: Colbourne D.E.
Published: July 2016

A simulation of the steady-state and dynamic performance of a supersonic powerplant intake is described. A lumped-parameter form of the equations of motion for a compressible fluid is developed. The resulting equations, together with steady-state characteristics, are used to model the performance of a two-dimensional supersonic intake. The model is implemented on the NGTE hybrid computer. The performance, both steady-state and transient, of the resulting real-time simulation has been investigated. Step and frequency responses at two high Mach number flight conditions have been examined and compared with test data. The favourable comparisons obtained demonstrate the validity of the chosen technique.
The Development of Intermittent Turbulence on a Swept Attachment Line Including the Effects of Compressibility
Authors: Poll D.I.A.
Published: July 2016

A model of the boundary layer transition process at an infinite swept attachment line under incompressible flow conditions and in the presence of a gross upstream disturbance is developed. The approach adopted is based upon the spot concepts of Emmons which are well established for transition on a flat plate. An extension to compressible flow situations is made by means of a simple transformation which reduces the process to an equivalent incompressible form. A new criterion for predicting the onset of attachment-line transition is proposed.
On the Application of Linearized Theory to Multi-Element Aerofoils Part I: Tandem Flat Plate Aerofoils
Authors: Watt G.D. , Parkinson G.V.
Published: July 2016

A linearized two-dimensional incompressible potential flow theory for two-element uncambered tandem aerofoil sections is developed. It leads to formulas for lift and moment which can be calculated rapidly on a programmable hand calculator, and which reduce, when the two aerofoil elements come together, to the familiar thin-aerofoil formulas for an aerofoil with a simple flap. The theory is shown to give lift and moment predictions which are in good agreement with predictions of numerical potential flow theory.
The Measurement of High Speed Air Velocity and Temperature using Sound Wave Photography
Authors: Elliott D. E.
Published: July 2016

A transient sound wave is generated by discharging a spark in an air stream, the velocity and temperature of which are required. After a time interval of about 25 microseconds a shadowgraph photograph of the sound wave is taken; a second photograph is obtained after a further known time interval of the same order. The two exposures, both on the same negative, show the propagation of the sound wave in the air stream and from this the Mach number, the true velocity, the local velocity of sound, and hence the temperature, can be calculated.

Using this method, measurements of Mach numbers of the order of 0·5 gave values between 98 per cent, and 100 per cent, of those calculated from pressure measurements. Typical examples of the sound wave photographs are shown. With further development along the lines indicated in the paper greater accuracy should be possible. The local speed of sound was measured to an estimated accuracy of ±1·5 per cent.

Since only a very short time interval is needed to obtain the photographs, the method appears promising for investigating explosions of brief duration, or dealing with flows of pulsating character.
Note on a Null Method for the Direct Measurement of Pressure Coefficients
Authors: Tanner L. H.
Published: July 2016

Values of the pressure coefficient Cp between +1 and -1 can be measured directly in incompressible flow by comparison with the known pressures on a circular cylinder placed in the tunnel working section. The development of the method and the apparatus required are described. The method gives more consistent and accurate readings than can easily be obtained with normal manometer measurements, particularly when the pressure differences are small and the tunnel speed not very steady. Since the coefficients depend on Reynolds number only, less precise measurement and control of tunnel speed are required, unless, the coefficients to be measured are subject to critical scale effects. Possible ways of extending the range of coefficients which can be measured are suggested.