bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation of the Pressure Distribution on a Right-Angled Wedge
Authors: Barnes F.H. , Grant I.
Published: July 2016

A comparison is made between three models of the two-dimensional flow of an inviscid fluid over a bluff body. The models are the Roshko free-streamline model, the Parkinson and Jandali wake-source model and the Bearman and Fackrell vortex-lattice model. The models are used to predict the surface pressure distribution on the front face of a right-angled wedge for the two symmetrical positions of the wedge, and a comparison is made with the experimental results of Slater. A further comparison is then made of Slater’s results for the surface pressure distributions on a wedge of finite thickness with the distributions predicted by the vortex-lattice model, for the wedge at a number of angular positions to the flow.
Unsteady Newton-Busemamn Flow Theory Part III. Frequency Dependence and Indicial Response
Authors: Hui W.H.
Published: July 2016

A complete unsteady Newton-Busemann flow theory, including centrifugal force corrections, was recently given by Hui and Tobak and successfully applied to study the dynamical stability of oscillating aerofoils (Part I) and bodies of revolution (Part II). The present paper extends these results, which are restricted to the first order in frequency, to general frequencies that may be applicable to flutter analysis as well. Furthermore, the new results are used to investigate the behaviour of the indicial response functions in unsteady flow at very high Mach numbers. In particular, it is found that for a family of body shapes in the Newtonian flow, including the cone, the wedge, the delta wing and slender aerofoils, the aerodynamic response to a step change in angle of attack or pitching velocity contains an impulse at the initial instant. This is followed by a rapid adjustment to the new steady-flow conditions, the adjustment time being equal to that required for a fluid particle to travel a distance of the body length. The impulse component appearing at the infinite Mach number limit (Newtonian flow) is in effect an apparent mass term, analogous to that which occurs initially in the aerodynamic indicial response at the zero Mach number limit (incompressible flow). In the latter case the initial impulse is followed by an asymptotic adjustment to the new steady-flow conditions, theoretically taking infinite time, in direct contrast to the rapid adjustment in Newtonian flow.
Concerning Dynamic Stall
Authors: Smith F.T.
Published: July 2016

The unsteady breakdown or stall of streamlined flow near the rounded leading edge of an aerofoil, as the small angle of attack is raised above its critical stall value, is studied theoretically for large Reynolds number motion. The unsteady developments take place first over a relatively slow time scale but then the corresponding solution breaks down with a singularity, forcing a switch to a faster and more nonlinear process. The latter involves a very pronounced local bulge appearing in the flow displacement, accompanied by reversed flow at the aerofoil surface, and comparisons with experimental observations of dynamic stall are noted.
Loads and Pressures Due to Underexpanded Jets Impinging on Wedges
Authors: Hunt B.L.
Published: July 2016

Loads have been measured on wedges placed symmetrically in supersonic jets of air. The jets were created by a nozzle with a radially divergent exit section having a lip Mach number of 2.2. The underexpansion ratio was varied from 1 to 2.2 and the distance between the nozzle exit section and the wedge apex was varied from 0 to 2 nozzle exit diameters. All wedges had a base width equal to the nozzle exit diameter: their total included apex angles covered the range 30° to 180°. Pressures were measured on the front faces and the bases for three of the wedges, hence enabling individual contributions to the overall force to be evaluated. Overall loads were measured by means of strain-gauged supports for all six wedges. It was found that the overall load coefficient is only weakly dependent on underexpansion ratio and wedge location but depends strongly on wedge angle. The maximum load coefficient recorded corresponded to 73% of the jet momentum. The base pressures contribute up to 59% of the overall load on a 45° wedge but rather less for larger wedge angles.
The Shape-Factor Relationship for Turbulent Boundary Layers
Authors: Telbany M.M.M. El , Niknejad J. , Reynolds A.J.
Published: July 2016

Consideration is given to the relationship H1 = f(H) linking the common shape factor H and the mass-flow shape parameter H1 which is used in entrainment models of boundary-layer development. A formula suggested by Green et al is found to be most nearly consistent with the measurements presented. However, a more exact prediction of H1 is obtained by introducing a factor involving the Reynolds number based on the local momentum thickness θ; thus H1 = f(H, Reθ). Predictions obtained by incorporating the appropriately modified entrainment equation into the well-known method of Green et al prove not to give an improved representation of the development of boundary layers studied experimentally by the authors and others. It is concluded that the modified formula for H1 is primarily useful in giving an improved specification of the overall boundary layer thickness δ = θ(H1 + H), and hence of other features of the developing profile.
The Synthesis of an Active Flutter Suppression Law Based on an Energy Criterion
Authors: Klein A.F.
Published: July 2016

Theory and results are presented which show that it is questionable to base a flutter suppression law, synthesised in terms of an energy dissipation criterion, entirely on aerodynamic data. It is shown that aileron mass balance and aileron/jack impedance can adversely affect regions of stability which have been predicted using aerodynamic terms alone. Comments are also made which attempt to unify various cost functions which are used when either an energy dissipation or an energy dissipation and storage criterion is used in the formulation of flutter suppression laws.
On an Approximate Method of Calculating Pressures on Non-lifting Head Shapes at Supersonic Speeds
Authors: Zienkiewicz H. K.
Published: July 2016

Slender-body theory is used to derive the ogive of curvature approximation for very slender, pointed, convex head shapes at supersonic speeds. Results of application of this approximation, together with the λ-method for circular arc ogives, to a variety of non-slender head shapes show very good agreement with the method of characteristics, van Dyke's second-order theory and experiment. Good agreement with the method of characteristics and with experiment is obtained even in cases when the stagnation pressure losses across the nose shock wave are not negligible.
On the Unsteady Motion of a Slender Body through a Compressible Fluid
Authors: Fraenkel L. E.
Published: July 2016

Ward's slender-body theory is extended to examine the unsteady motion of a slender body through a fluid at rest. The cross-sectional area and shape of the body, its forward velocity and its lateral motion are all arbitrary functions of time, but are subject to the restrictions of small disturbances. The length of the body is fixed. An approximate velocity potential is obtained by the joint use of two integral transforms, and the accuracy of this potential is discussed in some detail. General expressions for the aerodynamic forces acting on the body are derived in terms of a co-ordinate system which moves forward with the body in the mean direction of motion, but is fixed laterally. These expressions are then transformed, for the particular case of an oscillating rigid body moving forward with variable velocity, to expressions in terms of co-ordinates referred to the body axes. (The former co-ordinate system makes possible a fairly compact general treatment, whereas the latter is more convenient if the solution of a particular rigid-body problem is required.) Finally, arguments are advanced to justify the application of the slender-body theory to wings of slender plan form whose trailing edges are perpendicular to the direction of motion, and results are given for an oscillating wing moving forward with variable velocity.
Supersonic Flow Past Slender Bodies With Discontinuous Profile Slope
Authors: Fraenkel L. E. , Portnoy H.
Published: July 2016

Ward’s slender-body theory is extended to derive first approximations to the external forces on slender bodies of general cross section with discontinuous profile slope. Two classes of body are considered: bodies whose profile (typified by the local radius) is continuous between the nose and base, and certain bodies whose profile is discontinuous, such as bodies with annular or side air intakes and wing-bodies on which the wing has an unswept leading edge. (Where air intakes are concerned, it is assumed that they are sharp-edged and that there is no “ spillage ” of the internal flow).

The following conclusions apply to the former class of bodies. The variation of drag with Mach number is found to depend only on the discontinuities in the longitudinal rate of change of the cross-sectional area, and is thus independent of cross-sectional shape. The drag itself is unchanged if the direction of the flow is reversed. The expressions for lift and moment assume the same forms as for smooth pointed bodies, the lift depending only on conditions at the base of the body.

The general theory is applied to winged bodies of revolution with an unswept wing leading edge: the results bear a marked resemblance to those obtained by Ward. The results for wings alone are seen to be applicable, with one modification, to subsonic as well as to supersonic speeds.
The Lift of Twisted and Cambered Wings in Supersonic Flow
Authors: Lance G. N.
Published: July 2016

A generalised conical flow theory is used to deduce an integral equation relating the velocity potential on a delta wing (with subsonic leading edges) to the given downwash distribution over the wing. The complete solution of this integral equation is derived. This complete solution is composed of two parts, one being symmetric and the other anti-symmetric with respect to the span wise co-ordinate; each part represents a velocity potential. For example, if y is the spanwise co-ordinate and x is measured in the free stream direction, then a downwash of the form w= - α11 Ux|y| is symmetric and will give rise to a symmetric potential, whereas w= - α11 Ux|y| sgn y is anti-symmetric and gives rise to an anti-symmetric potential. The velocity potentials of such flows are given in the form of Tables for all downwashes up to and including homogenous cubics in the spanwise and streamwise co-ordinates. Table III gives similar formulae in the limiting case when the leading edges become transonic; these are compared with results given elsewhere and serve as a check on the results of Tables I and II.
Normal Loading on a Wedge-Shaped Plate
Authors: Godfrey D. E. R.
Published: July 2016

The equations of thin plate theory are expressed in polar co-ordinates and transformed using the Mellin transform. Problems involving discontinuous and isolated normal loadings may then be solved in the case of the built-in or freely supported wedge-shaped boundary.
The Effect of Sting Supports on the Base Pressure of a Blunt-Based Body in a Supersonic Stream
Authors: Donaldson I. S.
Published: July 2016

Experiments have been made to find the effect of the ratio of sting to base diameter on the base pressure of an axially symmetric body at zero incidence in a supersonic stream. The Mach number of the flow was 1·994 and the model boundary layer was turbulent. The model used was a one inch diameter circular cylinder without boat-tailing. It passed through and was supported upstream of the nozzle throat. This method of support allowed measurements to be made in the important (and hitherto unexplored) case of zero sting diameter.

As the sting to base diameter ratio was increased from 0 to 0·85, the base pressure decreased. The minimum value reached was approximately 0·8 of the value it would have at the base of a two-dimensional body with a similar ratio of boundary layer thickness to base height. The base pressure coefficient rose rapidly to zero as the ratio was further increased to unity.

Under the conditions of the experiments, with a sting to base diameter ratio of 0·4 the base pressure coefficient differed from that without a sting by approximately ten per cent. With the more modest ratio of 0·2, the difference was approximately three per cent.
Effect of Yielding on the Fatigue Properties of Test Pieces Containing Stress Concentrations
Authors: Gunn K.
Published: July 2016

A method of estimating the fatigue properties of notched test pieces when cyclic loads are applied in the presence of mean stresses is described. The method takes into account the local yielding which occurs near the base of the notch when the nominal stresses are sufficiently high. The general form of the predicted R/M diagrams closely resembles those obtained experimentally in previously published work.
Note on the Extension of Evvard’s Method to Wings with Subsonic Leading Edges Moving at Supersonic Speeds
Authors: Hancock G. J.
Published: July 2016

Evvard’s technique is applied to the problem of a thin finite wing moving at a supersonic speed when the leading edge is subsonic. It is developed in two methods:—

(i) in which the relationship between the pressure loading and the integrals of the downwash over the wing surface is extended as far as possible, and which has to be computed numerically;

(ii) in which approximations are made for the upwash velocities in the neighbourhood of the leading edge, resulting in a series of standard integrals for the estimation of the pressure loading.

Method (ii) is applied to the pressure loading on a flat plate triangular wing and cropped delta wing, and the application to more general shapes is discussed.
Approximation for the Effect of Twist on the Vibration of a Turbine Blade
Authors: Martin A. I.
Published: July 2016

Modern turbine blades are generally twisted about their axes, the shape resembling that of a helicoid. This makes the determination of their overtone frequencies much more difficult. The equations governing the flexural vibrations may be obtained from the Clebsch-Kirchhoff theory for rods which are naturally twisted. By using these equations, this paper considers a first-order approximation for the effect of uniform twist.
On the Stability of Accelerated Motion: Some Thoughts on Linear Differential Equations with Variable Coefficients
Authors: Collar A. R.
Published: July 2016

In studies of the stability of aeronautical systems, equations of motion are derived which have coefficients dependent on flight speed. Conventional practice treats the speed as constant, when a set of linear differential equations with constant coefficients results. Actually, since the speed varies during flight, it may be regarded as a prescribed function of time; the set of linear differential equations then has variable coefficients.

The treatment of the problem of stability then becomes much more complex in this case. A simple example is given to show that a system which is stable at any constant speed can become unstable during deceleration; the ordinary constant-speed criteria are, strictly, therefore inadequate. Some approaches to the discussion of stability during acceleration are suggested; a solution is given of the single second-order equation which enables the amplitude of oscillation of the solution to be studied. Inverse methods of approach are suggested, both for single and sets of equations, in which particular forms of acceleration corresponding to prescribed solutions are derived; and some tentative conclusions are drawn. As would be expected, the effects of acceleration depend on a dimensionless “acceleration number.”
A Random Distribution of Gusts Corresponding to a Measured Frequency of
Vertical Gusts
Authors: Fine M.
Published: July 2016

The paper describes a method of estimating the frequency of gust
components in the plane of a propeller from measurements of
vertical gust components, which are those
generally recorded. By this means additional flight recording is avoided and
the danger of under-estimating the frequency of gusts affecting the
propeller is reduced. Random distribution of gusts in space is assumed. It
is found that gust components in the plane of the propeller of 10 ft./sec.
or more occur 2·51 times as frequently as vertical components of 10 ft./sec.
or more. For speeds greater than 10 ft./sec., the ratio is higher.
The Lift on a Thin Aerofoil with a Jet-Augmented Flap
Authors: Spence D. A.
Published: July 2016

The method which was developed in an earlier paper for calculating the
lift on a thin jet-flapped aerofoil has been applied to the case in which
the jet enters the main stream tangentially from a deflected flap. The lift
derivative with respect to the (small) angle of deflection β is of the
form

where ,
E being the ratio of flap length to aerofoil
chord, and D0 a function
both of E and of the jet momentum coefficient
CJ. In the special
case CJ = 0,
Do vanishes and the
classical results for attached flow on flapped aerofoils without
super-circulation are obtained. More generally,
Do has been
evaluated over the range
0<CJ<5 for six
ratios E between 0·02 and 0·50, using an
electronic computer. The lift derivatives so found lie between those in the
limiting cases of “deflection” (E = 0) and “incidence” (E=1) which were
calculated in Reference 1. They show that the effectiveness of the jet-flap
scheme might be greatly increased by blowing over flaps of the order of 20
or 30 per cent of the chord, rather than over the small “shrouds” which have
hitherto been proposed.
The High Speed Flow of Gas Around Blunt Bodies
Authors: Serbin Hyman
Published: July 2016

A number of results derived by the author in earlier reports on the flow of air around blunt bodies moving at high speed are here collected in a unified analysis. The theory predicts in a satisfactory way the shock shape and detachment distance for two blunt bodies, a flat disc and a sphere. It is shown that the density ratio across a normal shock is a useful parameter, combining the effects of both the free stream Mach number and the ratio of specific heats.
Thermal Environment Tests of a High-Speed Aircraft Cockpit
Authors: Hughes T. L.
Published: July 2016

This paper describes rig tests made to evaluate the effectiveness of the cockpit insulation and cooling system of a high-speed aircraft.

The tests showed the dependence of cockpit internal temperature distribution and heat pick-up on the cooling air mass flow and inlet temperature. Analysis of the test data showed that there was considerable heat leakage into the cockpit; the heat leakage increased with cooling air flow and constituted two-thirds of the heat entering the cockpit when the air flow was moderately high (20 lb/min). Some of the leakage heat entered the cockpit through equipment mountings but it was evident that other leakage paths existed. One more obvious heat leakage path, at the canopy, is illustrated.

The tests also showed that the internal heat transfer coefficient increased with air flow, reaching a value of 2·5 C.H.U./hr ft2°C when the flow was 20 lb/min.
Compressible Radial Flow Between Parallel Discs
Authors: Moller P. S.
Published: July 2016

A combined experimental and theoretical study has been made of radial compressible flow without swirl between parallel discs when the fluid velocity is everywhere subsonic. It constitutes an extension of a previous analysis, wherein the flow was considered to be incompressible.

A similarity solution for the radial pressure distribution is shown to be possible only in special cases where certain terms in the equations of motion can be neglected. Approximate solutions are obtained for the laminar and the turbulent radial pressure distributions, using an integral momentum method. Both theories agree well with experiment. The critical Reynolds number for reverse transition is found to be approximately the same as that for incompressible flow in radial channels and circular pipes. The radial pressure level for compressible radial flow between parallel discs is found to be less than that for incompressible flow at the same mass-flow rate. The non-linear form, in pressure, of the compressible solution can be shown to account for this result.
Temporal changes in soil organic carbon and aggregate-associated organic carbon after reclamation of abandoned, salinized farmland
Authors: ZHANG F. H. , YANG H. C. , GALE W. J. , CHENG Z. B. , YAN J. H.
Published: July 2016

A field experiment was conducted to quantify changes in soil aggregation and aggregate-associated soil organic carbon (SOC) concentration 1, 3, 5 and 10 years after abandoned, salinized land in the Manasi River Basin was reclaimed for cotton (Gossypium hirsutumL.). Results showed that reclamation significantly increased SOC concentrations and SOC stocks. Specifically, 10 years of cotton production increased SOC concentrations by 45% in the 0–60 cm depth and SOC stocks by 35%. The SOC concentrations and stocks decreased as soil depth increased. Reclamation time, season and soil depth had significant interaction effects on SOC. The SOC concentrations were significantly and positively correlated with available soil nitrogen and available soil phosphorus. Compared with abandoned farmland, macro-aggregate-associated (>250µm) SOC concentrations in the 0–60 cm depth increased by 47% after 5 years of cotton production and by 53% after 10 years of cotton production. The contribution of macro-aggregate-associated SOC to total SOC in the 0–60 cm depth increased by 87% after 5 years of cotton production and by 69% after 10 years of cotton production. The findings indicate that soil aggregates were more stable after abandoned, salinized farmland was reclaimed for cotton production. Furthermore, cotton production can increase SOC concentrations and sequester C in this arid area.
New Evidence on the Forward Premium Puzzle
Authors: Boudoukh Jacob , Richardson Matthew , Whitelaw Robert F.
Published: July 2016

The forward premium anomaly (exchange rate changes are negatively related to interest rate differentials) is one of the most robust puzzles in financial economics. We recast the underlying parity relation in terms of lagged forward interest rate differentials, documenting a reversal of the anomalous sign on the coefficient in the traditional specification. We show that this novel evidence is consistent with recent empirical models of exchange rates that imply exchange rate changes depend on two key variables: the interest rate differential and the magnitude of the deviation of the current exchange rate from that implied by purchasing power parity.
A Rent-Protection Explanation for SEO Flotation-Method Choice
Authors: Wu Xueping , Wang Zheng , Yao Jun
Published: July 2016

We model how a rent-protection motive drives the choice of flotation method in new equity issuance between two polar cases: rights issues and cash offers. Unexpected new blockholders would emerge in control-diluting cash offers and share in jealously guarded control benefits. But rights issues help the incumbent controlling shareholders avoid control dilution and safeguard their private benefits. Under asymmetric information about private benefits, the choice of flotation method can convey information about hidden private benefits and hence firm value. Our model can explain even a negative announcement effect of rights issues, and it supports not just one but three important equilibriums.
Splitting a triangle
Authors: Gordon Russell A.
Published: July 2016

Let T be a triangle and let A be the area of T. Given a point p inside the triangle and a number r that satisfies 0 < r ≤ ½, we seek to count the number N (p, r) of straight lines that pass through p and cut T into two pieces so that one piece has area rA. As the point p and the ratio r vary, the value of N (p, r) ranges from 0 to 6. Given a ratio r, we want to determine the regions within T for which the function N (p, r) assumes various integer values. For example, a region inside T for which N (p, r) = 6 only exists for values of r between and ½, and we would like to quantify the area of this region (as a fraction of the total area of the triangle) as r varies.
Quadritangent spheres
Authors: Fox Michael
Published: July 2016

Every tetrahedron has a set of quadritangent spheres, that is, spheres that touch the four planes containing its faces. In this article I discuss three questions about them.

1. How many quadritangent spheres does a given tetrahedron have?

2. How can we find their sizes and positions with as little calculation as possible?

3. What relations exist between the vertices and points of contact that lie on anyone of the planes?
Holmes + Moriarty = Mathematics
Authors: Dence Thomas
Published: July 2016

In the autumn of 2011 the movie Sherlock Holmes: A Game of Shadows appeared (see [1]). It was a sequel to the Holmes movie from two years earlier. Unlike the first movie, A Game of Shadows Holmes' arch enemy Professor Moriarty featured more prominently than Holmes himself.

One scene, in particular, has Holmes sizing up his opponent by making a visit to Moriarty at his university office. But in the background sits Moriarty's blackboard, filled completely with mathematical equations, symbols, drawings, and formulas. One of these deserves our special attention.
Series involving ζ(n)
Authors: Jameson G.J.O.
Published: July 2016

Recall that for integers n ≥ 2, ζ (n) is defined by

Of course, ζ (1) is not defined, since is divergent. A well-known particular value is ζ (2) = π2/6: numerous alternative proofs of this fact have been presented in the Gazette, e.g. the recent notes [1], [2].
The Steiner-Lehmus angle-bisector theorem
Authors: Conway John , Ryba Alex
Published: July 2016

In 1840 C. L. Lehmus sent the following problem to Charles Sturm: ‘If two angle bisectors of a triangle have equal length, is the triangle necessarily isosceles?’ The answer is ‘yes’, and indeed we have the reverse-comparison theorem: Of two unequal angles, the larger has the shorter bisector (see [1, 2]).

Sturm passed the problem on to other mathematicians, in particular to the great Swiss geometer Jakob Steiner, who provided a proof. In this paper we give several proofs and discuss the old query: ‘Is there a direct proof?’ before suggesting that this is no longer the right question to ask.

We go on to discuss all cases when an angle bisector (internal orexternal) of some angle is equal to one of another.
Runs, strings and alphabets
Authors: Lewis Barry
Published: July 2016

In [1] Deshpande and Shiwalkar explore the number of double heads that may appear in sequences of coin tosses. They sought to answer questions such as,

‘If a (fair) coin is tossed r times, how many possible outcomes result in 0 double heads, how many result in 1 double head, …, how many result in (r – 1) double heads?’

Their answer involves Fibonacci expressions. Hirschhorn [2] extended these results using generating functions which on expansion led to some closed form expressions and the statistics of their distribution. Griffiths [3] continues this theme. Another article that touches on the basic idea – a run of particular outcomes – is [4] which is also the source of other references; [5] is also concerned with the same idea.
Two girls – the value of information
Authors: Parramore Keith , Stephens Joan
Published: July 2016

We came across the ‘two girls’ version of the children's gender problem nearly 35 years ago. How we came to it we cannot remember, but Martin Gardner had published a variant of it in the Scientific American in 1959. It re-emerged for us in the summer of 2010, following the publication of an article in Science News [1]. Subsequently Keith Devlin wrote about how this re-emergence impacted on him, and noting that ‘Probability Can Bite“ [2]. The mathematics herein reflects and extends that in Devlin's article.

In case the reader has not encountered the problem before, we first pose four problems.

1. A family has two children. One of them is a girl. What is the probability that they are both girls?

2. A family has two children. The younger is a girl. What is the probability that they are both girls?

3. A family has two children. One of them is a girl, and she was born on a Tuesday. What is the probability that they are both girls?

4. A family has two children. One of them is a girl, and she has green hair. What is the probability that they are both girls?
Conics and convexity
Authors: McLean K. Robin
Published: July 2016

In [1], W. D. Munn proved the following result.

Theorem 1: Infinitely many ellipses pass through the four vertices of a given convex quadrilateral.

Much of the geometry that I studied as an undergraduate in the 1950s concerned complex projective space, in which convexity plays no part. So I found Theorem 1 especially piquant and sought to understand it better. This article is the result. After examining the convexity of quadrilaterals in general, especially those inscribed in conics, I consider the following problem. Let P be a variable point in the plane, distinct from the vertices of a given convex quadrilateral ABCD. It is well known that there is a unique conic, S (P), through the five points A, B, C, D and P. How does the nature of this conic depend on the position of P? As a spin-off, we get a very short proof of Theorem 1. Finally I look at what happens when the quadrilateral ABCD is not convex. In this case, S (P) is always a hyperbola, but the distribution of A, B, C and D on its branches is still of interest.
Eigencircles and associated surfaces
Authors: Englefield M. J. , Farr G.E.
Published: July 2016

Linear algebra has many fruitful connections with geometry. This article develops one such connection: the relationship between a 2 × 2 matrix and an associated circle which we call theeigencircle.

This connection was first investigated in a previous paper of ours [1], but the present paper is self-contained, and in fact introduces eigencircles in a different way. Here we discuss some surfaces containing the eigencircle which also have a number of interesting properties and connections with the associated matrix.
Stop-sign theorems and binomial coefficients
Authors: Hilton Peter , Pedersen Jean
Published: July 2016

Dedicated to the memory of Russell Towle, a remarkable man who contributed so much to geometry and to other aspects of the quality of life.

We introduce an expanded notation where r + s = n, for the binomial coefficient , and then use this expanded notation to develop theorems involving 8 binomial coefficients, analogous to the Star of David Theorem, which. in its original form, involved the 6 neighbours of a given binomial coefficient in the Pascal Triangle (see Section 3), that appeared in [1,2,3,4,5,6,7,8,9].
An interesting strategic blunder
Authors: Smyth R.W.
Published: July 2016

I often recommend to my students that they follow their noses when solving mathematical problems. The role of intuition in creative mathematical work is difficult to explain. Still its value should never be underestimated and its development may be fostered by experience, including even unsuccessful trips down dead ends and meandering forays into thickets of apparently untameable complexity. In this article I invite you to corne with me and explore a simple calculus problem using any tools and ideas that seem to offer some promise of moving us along in the right direction. The scenic route embraces Taylor's formula, geometric series expansions, relations in Pascal's triangle, and matrix diagonalisation. Don't forget to bring along a pencil and some scrap paper… and a computer algebra system too, if you like.
Chris Ormell's article
Authors: Burn Bob
Published: July 2016

In [1], Chris Ormell raised a question about the uncountability of the real numbers. Ormell affirmed that only a countable collection of numbers may be defined by a finite number of words, a notion that stems from a letter of Richard (1905), reproduced in [2, p. 142]. This appears to conflict with Cantor's proof (1874) of the uncountability of the reals [3, p. 839]. Poincaré, whom Ormell claims as a witness in his defence, said ‘Now as is well known, Cantor proved that the continuum is not denumerable; this contradicts the proof of Richard. The question therefore arises which of the two proofs is correct. I maintain that they are both correct and that the contradiction is only apparent.’ [3, p. 1072] Poincaré then supplied a new proof that the points on an interval are not countable.
ADAPTIVE BAYESIAN ESTIMATION OF CONDITIONAL DENSITIES
Authors: Norets Andriy , Pati Debdeep
Published: July 2016

We consider a nonparametric Bayesian model for conditional densities. The model is a finite mixture of normal distributions with covariate dependent multinomial logit mixing probabilities. A prior for the number of mixture components is specified on positive integers. The marginal distribution of covariates is not modeled. We study asymptotic frequentist behavior of the posterior in this model. Specifically, we show that when the true conditional density has a certain smoothness level, then the posterior contraction rate around the truth is equal up to a log factor to the frequentist minimax rate of estimation. An extension to the case when the covariate space is unbounded is also established. As our result holds without a priori knowledge of the smoothness level of the true density, the established posterior contraction rates are adaptive. Moreover, we show that the rate is not affected by inclusion of irrelevant covariates in the model. In Monte Carlo simulations, a version of the model compares favorably to a cross-validated kernel conditional density estimator.
X-ray powder diffraction data for 5, 6-dihydro-3-(4-morpholinyl)-1-[4-(2-oxo-1-piperidinyl)phenyl]-2(1H)-pyridinone, C20H25N3O3
Authors: Wang Qing , Zeng Xia , Li Shan Shan , Li Ma Xiao , Li Hui
Published: July 2016

X-ray powder diffraction data for 5,6-dihydro-3-(4-morpholinyl)-1-[4-(2-oxo-1-piperidinyl)phenyl]-2(1H)-pyridinone, C20H25N3O3, are reported [a = 5.989(2), b = 6.669(3), c = 24.605(5)Å, α = 84.466(7)°, β = 89.859(6)°, γ = 69.074(4)°, unit-cell volume V = 913.11 Å3, Z = 2, and space group P−1]. No detectable impurities were observed.
Isolation and characterization of Antarctic psychrotrophStreptomycessp. strain INACH3013
Authors: Lavin Paris Leonardo , Yong Sheau Ting , Wong Clemente M.V.L. , De Stefano Mario
Published: July 2016

An actinobacterial strain with antimicrobial activity, INACH3013, was isolated from soil collected from Antarctica. The taxonomic status of the isolate was established using a polyphasic approach. The strain was identified as belonging to the genusStreptomycesbased on the scanning electron microscopic observation and partial 16S rRNA gene sequence analysis. The sequence analysis revealed that strain INACH3013 is closely related toStreptomyces fildesensis(99.8%),S. beijiangensis(98.1%) andS. purpureus(97.2%). A phylogenetic tree constructed using the partial 16S rRNA gene sequences of strain INACH3013 and closely related strains revealed that INACH3013 fell into the same subclade asS. fildesensisandS. purpureus. Strain INACH3013 was observed to be psychrotolerant, slightly halotolerant (up to 5% NaCl) and capable of inhibiting the growth of seven Gram-negative and eight Gram-positive foodborne pathogens. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of the strain is KJ624755.
Submarine landforms related to glacier retreat in a shallow Antarctic fjord
Authors: Wölfl Anne-Cathrin , Wittenberg Nina , Feldens Peter , Hass H. Christian , Betzler Christian , Kuhn Gerhard
Published: July 2016

Since the Last Glacial Maximum, ice has retreated through the fjords of the South Shetland Islands leaving a valuable record of submarine landforms behind. In this study, glacial landforms and sub-bottom characteristics have been mapped to investigate the late Holocene retreat behaviour of the Fourcade Glacier and to delineate past environmental processes in Potter Cove, King George Island. The comprehensive datasets include high-resolution swath bathymetry, shallow seismic profiling and one sediment core. Moraines, moraine incisions and glacial lineations were mapped on the sea floor in the inner part of the cove, whereas pockmarks, ice scour marks and channel structures were identified in the outer part. Sub-bottom characteristics have been assigned to different acoustic facies types indicating different depositional settings. The results reveal glacial recessions as well as stillstands and potential readvances during the late Holocene. Furthermore, the sediment record indicates that the Fourcade Glacier was situated inside the inner cove during the Little Ice Age (500–100 cal yr bp).
Filmic witness to the 1964 Kitty Genovese murder
Authors: RENTSCHLER CARRIE
Published: July 2016

This essay examines a body of films that represent and re-enact the infamous 1964 Catherine Genovese rape and murder, helping to define the crime as a problem of bystander non-intervention exacerbated by urban living conditions and the ‘high rise anxieties’ of apartment dwellers. The moving image culture around the Genovese case tells a story about male violence against women in the city through the perspective of urban apartment dwellers, who are portrayed as bystander witnesses to both the city and to the social relations of stranger sociability in the city. Films depict the killing of Kitty Genovese, sometimes through fictional analogues to her and the crime, as an outcome of failed witnessing, explicating those failures around changing ideas about urban social relations between strangers, and ways of surveilling the city street from apartment windows. By portraying urban bystanders as primarily non-interventionist spectators of the Genovese rape and murder, films locate the conditions of femicide and responsibility for it in detached modes of seeing and encountering strangers. By analysing film as forms of historic documentation and imagination, as artifacts of historically and contextually different ways of telling and revising the story of the Genovese murder as one of bystander non-intervention in gender violence in the city, the essay conceptualizes film and filmic re-enactments as a mode of paying witness to the past.
Three-Dimensional Face Recognition in Mild Cognitive Impairment: A Psychophysical and Structural MR Study
Authors: Lemos Raquel , Santana Isabel , Caetano Gina , Bernardino Inês , Morais Ricardo , Farivar Reza , Castelo-Branco Miguel
Published: July 2016

Objectives: Mild cognitive impairment (MCI) has been associated with a high risk of conversion to Alzheimer’s dementia. In addition to memory complaints, impairments in the visuospatial domain have been reported in this condition. We have previously shown that deficits in perceiving structure-from-motion (SFM) objects are reflected in functional reorganization of brain activity within the visual ventral stream. Here we aimed to identify structural correlates of psychophysical complex face and object recognition performance in amnestic MCI patients (n=30 vs. n=25 controls). This study was, therefore, motivated by evidence from recent studies showing that a combination of visual information across dorsal and ventral visual streams may be needed for the perception of three-dimensional (3D) SFM objects. Methods: In our experimental paradigm, participants had to discriminate 3D SFM shapes (faces and objects) from 3D SFM meaningless (scrambled) shapes. Results: Morphometric analysis established neuroanatomical evidence for impairment in MCI as demonstrated by smaller hippocampal volumes. We found association between cortical thickness and face recognition performance, comprising the occipital lobe and visual ventral stream fusiform regions (overlapping the known location of face fusiform area) in the right hemisphere, in MCI. Conclusions: We conclude that impairment of 3D visual integration exists at the MCI stage involving also the visual ventral stream and contributing to face recognition deficits. The specificity of such observed structure-function correlation for faces suggests a special role of this processing pathway in health and disease. (JINS, 2016, 22, 744–754)
Use of code-mixing by young hearing children of Deaf parents
Authors: KANTO LAURA , LAAKSO MARJA-LEENA , HUTTUNEN KERTTU
Published: July 2016

In this study we followed the characteristics and use of code-mixing by eight KODAs – hearing children of Deaf parents – from the age of 12 to 36 months. The children's interaction was video-recorded twice a year during three different play sessions: with their Deaf parent, with the Deaf parent and a hearing adult, and with the hearing adult alone. Additionally, data were collected on the children's overall language development in both sign language and spoken language. Our results showed that the children preferred to produce code-blends – simultaneous production of semantically congruent signs and words – in a way that was in accordance with the morphosyntactic structure of both languages being acquired. A Deaf parent as the interlocutor increased the number of and affected the type of code-blended utterances. These findings suggest that code-mixing in young bimodal bilingual KODA children can be highly systematic and synchronised in nature and can indicate pragmatic development.
Evaluating the healthiness of chain-restaurant menu items using crowdsourcing: a new method
Authors: Lesser Lenard I , Wu Leslie , Matthiessen Timothy B , Luft Harold S
Published: July 2016

Objective

To develop a technology-based method for evaluating the nutritional quality of chain-restaurant menus to increase the efficiency and lower the cost of large-scale data analysis of food items.

Design

Using a Modified Nutrient Profiling Index (MNPI), we assessed chain-restaurant items from the MenuStat database with a process involving three steps: (i) testing ‘extreme’ scores; (ii) crowdsourcing to analyse fruit, nut and vegetable (FNV) amounts; and (iii) analysis of the ambiguous items by a registered dietitian.

Results

In applying the approach to assess 22 422 foods, only 3566 could not be scored automatically based on MenuStat data and required further evaluation to determine healthiness. Items for which there was low agreement between trusted crowd workers, or where the FNV amount was estimated to be >40 %, were sent to a registered dietitian. Crowdsourcing was able to evaluate 3199, leaving only 367 to be reviewed by the registered dietitian. Overall, 7 % of items were categorized as healthy. The healthiest category was soups (26 % healthy), while desserts were the least healthy (2 % healthy).

Conclusions

An algorithm incorporating crowdsourcing and a dietitian can quickly and efficiently analyse restaurant menus, allowing public health researchers to analyse the healthiness of menu items.
Sweetened beverage consumption is a risk factor for depressive symptoms among adolescents living in Boston, Massachusetts, USA
Authors: Pabayo Roman , Dias Joice , Hemenway David , Molnar Beth E
Published: July 2016

Objective

To investigate the relationship between sweetened beverage consumption and depressive symptoms among adolescents.

Design

In a cross-sectional study, adolescents were asked how often they drank soda and fruit drinks in the past 7 d. Depressive symptoms were measured using a brief adapted version of the Modified Depression Scale. Summation scores were standardized using the Z-transformation. We used multilevel multiple linear regression models to estimate the association between soda and fruit drink consumption and depressive symptoms.

Setting

The 2008 Boston Youth Survey.

Subjects

Adolescents (n 1878), high-school students in grades 9–12 of Boston public schools, Massachusetts, USA.

Results

Compared with those who never drank soda in the past 7 d, those who consumed soda 2–6 times/week (β=0·18; 95 % CI 0·04, 0·32) or ≥1 times/d (β=0·29; 95 % CI 0·13, 0·45) had higher depressive symptoms. Similarly, those who consumed fruit drinks 2–6 times/week (β=0·14; 95 % CI 0·00, 0·28) and those who consumed ≥1 times/d (β=0·22; 95 % CI 0·04, 0·40) had higher depressive symptoms.

Conclusions

Frequent consumption of both soda and fruit drinks is associated with greater depressive symptoms among adolescents.
Manganese carbonates as possible biogenic relics in Archean settings
Authors: Rincón-Tomás Blanca , Khonsari Bahar , Mühlen Dominik , Wickbold Christian , Schäfer Nadine , Hause-Reitner Dorothea , Hoppert Michael , Reitner Joachim
Published: July 2016

Carbonate minerals such as dolomite, kutnahorite or rhodochrosite are frequently, but not exclusively generated by microbial processes. In recent anoxic sediments, Mn(II)carbonate minerals (e.g. rhodochrosite, kutnahorite) derive mainly from the reduction of Mn(IV) compounds by anaerobic respiration. The formation of huge manganese-rich (carbonate) deposits requires effective manganese redox cycling in an oxygenated atmosphere. However, putative anaerobic pathways such as microbial nitrate-dependent manganese oxidation, anoxygenic photosynthesis and oxidation in ultraviolet light may facilitate manganese cycling even in an early Archean environment, without the availability of oxygen. In addition, manganese carbonates precipitate by microbially induced processes without change of the oxidation state, e.g. by pH shift. Hence, there are several ways how these minerals could have been formed biogenically and deposited in Precambrian sediments. We will summarize microbially induced manganese carbonate deposition in the presence and absence of atmospheric oxygen and we will make some considerations about the biogenic deposition of manganese carbonates in early Archean settings.
W-ALGEBRAS FROM HEISENBERG CATEGORIES
Authors: Cautis Sabin , Lauda Aaron D. , Licata Anthony M. , Sussan Joshua
Published: July 2016

The trace (or zeroth Hochschild homology) of Khovanov’s Heisenberg category is identified with a quotient of the algebra$W_{1+\infty }$. This induces an action of$W_{1+\infty }$on the center of the categorified Fock space representation, which can be identified with the action of$W_{1+\infty }$on symmetric functions.
Examining hospice enrollment through a novel lens: Decision time
Authors: Wallace Cara L.
Published: July 2016

Objective:

No prior studies on hospice utilization have captured information about the amount of time between when one first learns of hospice as a potential option for care and when he/she actually enrolls. Little is in fact known about this decision-making process. The present study examines hospice enrollment by exploring relationships between hospice decision time and known barriers to care.

Method:

This was an exploratory cross-sectional study. Pearson's r was employed to identify bivariate relationships between barriers to care and decision time for hospice care. Independent-sample t tests and ANOVA were utilized to consider differences in decision time across key variables.

Results:

Some 90 hospice patients, or their primary decision maker, participated in the study from a not-for-profit hospice located in the southern United States. Decision time was correlated with referral source, use of disease-directed treatment, functional status (on the Palliative Performance Scale [PPS]), age, diagnosis, income, race, and spirituality—suggesting that decision time is a pertinent variable when examining hospice utilization. Differences in decision time were found across diagnosis, race, income, and referral source.

Significance of results:

This study provides implications for policy and practice, particularly for clinicians faced with initial conversations about hospice care. Differences in decision time highlight ongoing needs related to overcoming healthcare disparities, the important role of including families in initial conversations, and the potential need for varied approaches to talking about hospice care based upon diagnosis. Results also highlight the need for policies supportive of concurrent care, where hospice can be accessed alongside curative care.