bluuebunny/crossref_metadata_2025 huggingface dataset:
A Note on the Classes of Non-Linear Semi-Special Permutations
Authors: Yacoub K. R.
Published: May 2009

In a recent paper [1], the author divided the semi-special permutations on [n] that are not linear into two classes. The first class consists of the semi-special permutations which, for all possible values of s, have s as a principal number and which induce modulo s the identity permutation. The second class consists of all the semi-special permutations, with principal number s, which induce modulo s linear permutations other than the identity, where again s takes all its possible values.
A Note on Some Inequalities
Authors: Flett T. M.
Published: May 2009

In the course of some recent work on Fourier series [5, 6] I had occasion to use a number of integral inequalities which were generalizations or limiting cases of known results. These inequalities may perhaps have other applications, and it seems worth while to collect them together in a separate note with one or two further results of a similar nature.

For any number k, used as an index (exponent), and such that K > 1, we write k' = k′(k–1), so that k and k′ are conjugate indices in the sense of Hölder's inequality.
The Packing of Spheres in the Space lp
Authors: Burlak Jane A. C. , Rankin R. A. , Robertson A. P.
Published: May 2009

A point x in the real or complex space lpis an infinite sequence,(x1, x2, x3,…) of real or complex numbers such that is convergent. Here p ≥ 1 and we write

The unit sphere S consists of all points x ε lp for which ¶ x ¶ ≤ 1. The sphere of radius a≥ ≤ 0 and centre y is denoted by Sa(y) and consists of all points x ε lp such that ¶ x - y ¶ ≤ a. The sphere Sa(y) is contained in S if and only if ¶ y ¶≤1 - a, and the two spheres Sa(y) and Sa(z) do not overlap if and only if

¶ y- z ¶≥ 2a

The statement that a finite or infinite number of spheres Sa (y) of fixed radius a can be packed in S means that each sphere Sa (y) is contained in S and that no two such spheres overlap.
Multiplication of Strongly Summable Series
Authors: Boyd A. V.
Published: May 2009

Given a series we define , by the relations

The series is said to be summable (C, k), where k > - 1, to the sum s if

to be summable (C, - 1) to s if it converges to s and nan = o(l); to be absolutely summable (C, k), or summable | C, k, to s if it is summable (C, k) to s and

and to be strongly Cesàro summable to s with order k > 0 and index p or summable [C; k, p] to s, if
Maximum Principles in matrix theory
Authors: Mirsky L.
Published: May 2009

Unless the contrary is stated, all matrices are understood to be complex and of type n × n. The transposed conjugate of A is denoted by A*. The non-negative square roots of the characteristic roots of A*A are called the singular values of A; they will be denoted by st(A), i = 1, …, n, where s1(A)≥…≥ sn(A). The symbol [A]k denotes the k × k submatrix standing in the upper left-hand corner of A. We shall write Ei(z1, …, zn) for the j-th elementary symmetric function of z1..., zn, and E1(A) for the j-th elementary symmetric function of the characteristic roots of A. It is understood that, throughout, 1≥j≥k≥n.
A generalization of Hurwitz's Theorem
Authors: Husemoller Dale H.
Published: May 2009

Hurwitz's theorem says that the limit of schlicht functions, in the topology of compact convergence, is again a schlicht function or a constant function. We generalize this to mappings between Riemann surfaces and get more precise information on the relation between the distribution of values of analytic functions and the topology of compact convergence on the space of all analytic maps.
A Class of Irreducible matrix representations of an Arbitrary Inverse Semigroup
Authors: Munn W. D.
Published: May 2009

By a ‘representation’ we shall mean throughout a representation by n × n matrices with entries from an arbitrary field. Elsewhere [9] the author has introduced the concept of a principal representation of a semigroup S (see § 3 below for the definition) and has shown that if S satisfies the minimal condition on principal ideals then every irreducible representation is of this type. Moreover, if S satisfies the minimal conditions on both principal left and right ideals, which together imply the minimal condition on principal two-sided ideals [6, Theorem 4], the irreducible representations of S can ultimately be expressed explicitly in terms of group representations.
Invariant Measures on Coset Spaces
Authors: Świerczkowski S.
Published: May 2009

In this note we consider measures on a left coset space G/H, where G is a locally compact group and H is a closed subgroup. We assume the natural topology in G/H and we denote the generic element of this space by xH (x∈G). Every element t∈G defines a homeomorphism of G/H given by t(xH) = (tx)H. A. Weil showed that a Baire measure on G/H invariant under all these homeomorphisms can exist only if

Δ(ξ) = δ(ξ) for each ξ ∈ H,

where Δ(x), δ(ξ) denote the modular functions in G, H [6, pp. 42–45]. We shall devote our investigations to inherited measures on G/H (cf. [3] and the definition below) invariant under homeomorphisms belonging to a normal and closed subgroup T ⊂ G.
On P. Hall's Generalisation of a Theorem of Frobenius
Authors: Sehgal S. K.
Published: May 2009

1. It is a well known theorem due to Frobenius that the number of solutions of the equation

Xn = 1

in a finite group G, is a multiple of the greatest common divisor (n, g) of n and the order g of G. Frobenius himself proved later that the number of solutions of the equation

Xn = a

where a is a fixed element of G, is a multiple of (n, ga), ga being the order of the centralizer Z(a) of ain G.
A Relation between Laplace and Hankel Transforms
Authors: Bhonsle B. R.
Published: May 2009

The Laplace transform of a function f(t) ∈ L(0, ∞) is defined by the equation

and its Hankel transform of order v is defined by the equation

The object of this note is to obtain a relation between the Laplace transform of tμf(t) and the Hankel transform of f(t), when ℛ(μ) > − 1. The result is stated in the form of a theorem which is then illustrated by an example.
Dual integral equations with trigonometrical kernels
Authors: Sneddon Ian N.
Published: May 2009

In the analysis of mixed boundary value problems in the plane, we encounter dual integral equations of the type

If we make the substitutions cos we obtain a pair of dual integral equations of the Titchmarsh type [1, p. 334] with α = − 1, v = − ½ (in Titchmarsh's notation). This is a particular case which is not covered by Busbridge's general solution [2], so that special methods have to be derived for the solution.
A characterization of inaccessible cardinals
Authors: Preston G. B.
Published: May 2009

A cardinal number which is too large to be reached by some process is generally said to be inaccessible by that process. Many kinds of inaccessible cardinals have been discussed and for a general survey the book of H. Bachmann [1, Chapter 7] may be consulted. We consider here two inaccessibility properties. We shall denote the cardinal of a set X by |X|. The first inaccessibility property will be called regularity: the cardinal| X| will be said to be regular if there does not exist a disjoint cover {X1: i ε I} of X such that

(i)|X1|<|X|, for each i in I, and

(ii)|I|<|X|.
An embedding theorem with amalgamation for cancellative semigroups
Authors: Howie J. M.
Published: May 2009

Let {Si; i ε I} be a finite or infinite family of cancellative semigroups. Let U be a cancellative semigroup, and suppose that there exists, for each i in I, a monomorphism φi: u→ Si. We are interested in finding a semigroup T with the following properties.

(a) For each i in I, there is a monomorphism λi: Si → T such that uφiλi = uøjλi for all u ɛ U and all i, j in I. That is to say, there exists a monomorphism λ: U → T which equals øiλi for all i in I.

Siλi∩Sjλj = Uλ (i, j ε I; i ≠ j).
A polynomial iteration for the spectral family of an operator
Authors: Bonsall F. F.
Published: May 2009

Let T be a bounded symmetric operator in a Hilbert space H. According to the spectral theorem, T can be expressed as an integral in terms of its spectral family {Eλ}, each Eλ being a certain projection which is known to be the strong limit of some sequence of polynomials in T. It is a natural question to ask for an explicit sequence of polynomials in T that converges strongly to Eλ. So far as the author knows, no complete solution of this problem has been given even when H has finite dimension, i.e. when T is a finite symmetric matrix. Since a knowledge of the spectral family {Eλ} of a finite symmetric matrix carries with it a knowledge of the eigenvalues and eigenvectors, a solution of the problem may have some practical value.
An arithmetic characterization of the parabolic points of G(2cos π/5)
Authors: Rosen David
Published: May 2009

By the group G(2 cos π/q) we mean the group of linear fractional transformations of the complex plane onto itself, generated by V(z)= — 1/z and U(z) = z+λq, where λq = 2 cos (π/q), qbeing a positive integer greater than 2. In this paper we shall be concerned only with the group given by q = 5, and we shall therefore omit the subscript 5 on the λ. We note that λ = λ5 satisfies the equation

x2–x–l=0;(1)

henceλ = (l + 5½)/2.
Theorems relating Hankel and Meijer's Bessel transforms
Authors: Sharma K. C.
Published: May 2009

In this note a theorem, giving a relation between the Hankel transform of f(x) and Meijer's Bessel function transform of f(x)g(x), is proved. Some corollaries, obtained by specializing the function g(x), are stated as theorems. These theorems are further illustrated by certain suitable examples in which certain integrals involving products of Bessel functions or of Gauss's hypergeometric function and Appell's hypergeometric function are evaluated. Throughout this note we use the following notations:
On the asymptotic expansion of Airy's Integral
Authors: Copson E. T.
Published: May 2009

The integral function

is known as Airy's Integral since, when z is real, it is equal to the integral

which first arose in Airy's researches on optics. It is readily seen that w= Ai(z) satisfies the differential equation d2w/dz2 = zw, an equation which also has solutions Ai(ωz), Ai(ω2z), where ω is the complex cube root of unity, exp 2/3πi. The three solutions are connected by the relation.
An improved method for dual trigonometrical series
Authors: Tranter C. J.
Published: May 2009

In a previous paper in this journal [1], I gave formulae for determining the coefficients in certain dual trigonometrical series. The derivation of these formulae involved rather sophisticated assumptions and some intricate manipulation of the hypergeometric function and relied heavily on the solution of Schlömilch's integral equation. I have now found a much simpler formal solution by using Mehler's integral representation of the Legendre polynomial and the final formulae for the coefficients can be given in a more attractive form. As the results of my previous work have had several recent applications to physical problems, it seems worth while to give some details of this improved solution.
Series involving products of two E-functions
Authors: Verma Arun
Published: May 2009

In 1958 Ragab [3] deduced the sums of certain infinite series involving a product of two E-functions in terms of E-functions. MacRobert [2] gave a very simple alternative method for proving the results of Ragab. Later, Ragab [4, 5] in 1962 used a method similar to the one given by MacRobert to deduce a number of summations involving products of E-functions. In this paper, some more general summations of E-functions, which contain Ragab's results as special cases, are given. It may be mentioned that all the series summed run from n = – ∞ to + ∞co instead of n = 0 to + ∞.
Perfect difference sets
Authors: Halberstam H. , Laxton R. R.
Published: May 2009

If the set K of r+1 distinct integers k0, k1 …, kr has the property that the (r+1)r differences ki–kj (0≦i, j≦r, i≠j) are distinct modulo r2+r+1, K is called a perfect difference set modr2+r+1. The existence of perfect difference sets seems intuitively improbable, at any rate for large r, but in 1938 J. Singer [1] proved that, whenever r is a prime power, say r = pn, a perfect difference set mod p2n+pn+1 exists. Since the appearance of Singer's paper several authors have succeeded in showing that for many kinds of number r perfect difference sets mod r2+r+1 do not exist; but it remains an open question whether perfect difference sets exist only when r is a prime power (for a comprehensive survey see [2]).
A lemma about the Epstein zeta-function
Authors: Ennola Veikko
Published: May 2009

Let h (m, n) = αm2 + 2δmn + βn2 be a positive definite quadratic form with determinant αβ–δ2 = 1. It may be put in the shape

with y > 0. We write (for s > 1)

The function Zn(s) may be analytically continued over the whole s-plane. Its only singularity is a simple pole with residue π at s = 1.
Generalizations of a well-known result in matrix theory
Authors: Thompson R. C.
Published: May 2009

Let A and C be m × m matrices and let B and D be n × n matrices, all with elements in a field F. Let AT denote the transpose of A. A well-known theorem states that, if every m × m matrix X for which AX = XA also satisfies CX = XC, then C = φ(A) for some polynomial φ(λ). In this note we establish the following simple generalizations.

Theorem 1. Let A and B have the same minimal polynomial m(λ). If each m × n matrix X over F for which AX = XB also satisfies CX = XD, then C = φ(A) and D = φ(B) for a polynomial φ(λ) over F.
An extension of a theorem of Gordon
Authors: Wright E. M.
Published: May 2009

In what follows all small Latin letters denote non-negative integers or functions whose values are non-negative integers. Let N = (n1, …, nj) be a j-dimensional vector and let q = q (k; N) = q(k; n1, …, nj) be the number of partitions of N into just k parts, each part being a vector whose components are non-negative integers. We write

for the generating function of q. We have

.
A Note on an asymmetric mixed boundary value problem for a half space with a cylindrical cavity
Authors: Narain Prem
Published: May 2009

In recent years interest in the mixed boundary value problems of mathematical physics has increased appreciably because of various applications. The mixed boundary value problems for simply-connected regions have been investigated widely and it can reasonably be hoped that within a short time the theory will reach a satisfactory stage. It appears, however, that very few problems for multiply-connected domains have been solved. Recently Srivastav [2] has considered the problem of rinding an axisymmetric potential function for a half space with a cylindrical cavity subject to mixed type boundary conditions. In a subsequent paper [1], Srivastav extends the analysis to the asymmetric problem and formulates the problem in terms of dual integral equations involving Bessel functions of the first and second kinds whose solution leads to the solution of the potential problem. The latter paper, however, involves heavy manipulations and complicated contour integrals.
A Note on the Hardy-Hille and Mehler formulas
Authors: Al-Salam W. A. , Carlitz L.
Published: May 2009

Let and Hn(x) be the nth Laguerre and Hermite polynomials, respectively. Two well-known bilinear generating formulas are the Hardy-Hille formula [1, p. 101]

and the mehler formula [1, p. 377]

This suggests the following problem. Consider the equation

where fa(x) is a polynomial in x of degree n with highest coefficient equal to 1,

A0 = B0 = 1. We shall also assume that ak = 1 and y0y1y2 … yk–1 ≠ 0. We seek all sets of polynomials {fn(x)} which satisfy (1.3), (1.4) and (1.5).
Affine semigroups over an arbitrary field
Authors: Clark W. Edwin
Published: May 2009

Let ℒ V denote the algebra of all linear transformations on an n-dimensional vector space V over a field Φ. A subsemigroup S of the multiplicative semigroup of ℒ V will be said to be an affine semigroup over Φ if S is a linear variety, i.e., a translate of a linear subspace of ℒ V.

This concept in a somewhat different form was introduced and studied by Haskell Cohen and H. S. Collins [1]. In an appendix we give their definition and outline a method of describing possibly infinite dimensional affine semigroups in terms of algebras and supplemented algebras.
Integrals involving E-functions
Authors: Ragab F. M. , Simary M. A.
Published: May 2009

In this paper two integrals involving E-functions are evaluated in terms of E-functions. The formulae to be established are:

where n is a positive integer,

and

where n is a positive integer,

and

the prime and the asterisk denoting that the factor sin {(s–s)π/2n} and the parameter βq+s–βq+s + 1 are omitted. The definitions and properties of MacRobert's E-function can be found in [1, pp. 348–352] and [3, pp. 203–206].
Congruences on a bisimple ω-semigroup
Authors: Munn W. D. , Reilly N. R.
Published: May 2009

In a semigroup S the set E of idempotents is partially ordered by the rule that e≦ƒ if and only if eƒ=e=ƒe. We say that S is an ω-semigroup if E={ei: i=0, 1, 2, …}, where

Bisimple ω-semigroups have been classified in [10]. From a group G and an endomorphism α of G a bisimple ω-semigroup S(G, α) can be constructed by a process described below in § 1: moreover, any bisimple ω-semigroup is isomorphic to one of this type.
A remark on the distributive law for an ideal in a commutative ring
Authors: Jensen C. U.
Published: May 2009

Let R be a commutative ring, with an identity element. It is the purpose of this note to establish conditions for an arbitrary but fixed ideal a of R to satisfy the distributive law

for all ideals b and c of R. In particular, in the Noetherian case, this will be related to the decomposition of a into prime ideals. We start with

Proposition 1. For a fixed ideal a in a commutative ring R with an identity element, the following conditions are equivalent.
On the Theory of Relaxation
Authors: Mitchell A. R. , Rutherford D. E.
Published: May 2009

§ 1. When a numerical method of obtaining an approximate solution of a linear differential equation is employed, the process involves two distinct types of approximation. The region of integration having been covered with a regular net, the differential equation and the appropriate boundary conditions are replaced by finite difference equations which are linear equations in the values of the dependent variable at the nodes of the net.
An Integral involving an E-function and an Associated Legendre Function of the First Kind
Authors: Macrobert T. M.
Published: May 2009

§ 1. Introductory. The formula to be proved is

where n is zero or a positive integer, R(m)>0, R(αs-l)>0, s = 1, 2, …, p, p≧q.
An Infinite Integral involving a Product of Two Modified Bessel Functions of the Second Kind
Authors: Macrobert T. M.
Published: May 2009

The formula to be established is

where l, m, n. are any numbers real or complex and R(b)>0. A similar result, involving Bessel Functions of the First Kind, was obtained by Hanumanta Rao [Mess, of Maths., XLVII. (1918), pp. 134–137].
Integrals of E-Functions expressed in Terms of E-Functions
Authors: Ragab F. M.
Published: May 2009

In § 2 the following two formulae will be established.

If, when p≧q + l, R(ar + k)>0, r = 1, 2,…, p and | ampz |<π,

If p≧q, the result holds if the integral is convergent.
Response of Jupiter's and Saturn's auroral activity to the solar wind
Authors: Clarke J. T. , Nichols J. , Gérard J.‐C. , Grodent D. , Hansen K. C. , Kurth W. , Gladstone G. R. , Duval J. , Wannawichian S. , Bunce E. , Cowley S. W. H. , Crary F. , Dougherty M. , Lamy L. , Mitchell D. , Pryor W. , Retherford K. , Stallard T. , Zieger B. , Zarka P. , Cecconi B.
Published: May 2009

While the terrestrial aurorae are known to be driven primarily by the interaction of the Earth's magnetosphere with the solar wind, there is considerable evidence that auroral emissions on Jupiter and Saturn are driven primarily by internal processes, with the main energy source being the planets' rapid rotation. Prior observations have suggested there might be some influence of the solar wind on Jupiter's aurorae and indicated that auroral storms on Saturn can occur at times of solar wind pressure increases. To investigate in detail the dependence of auroral processes on solar wind conditions, a large campaign of observations of these planets has been undertaken using the Hubble Space Telescope, in association with measurements from planetary spacecraft and solar wind conditions both propagated from 1 AU and measured near each planet. The data indicate a brightening of both the auroral emissions and Saturn kilometric radiation at Saturn close in time to the arrival of solar wind shocks and pressure increases, consistent with a direct physical relationship between Saturnian auroral processes and solar wind conditions. At Jupiter the correlation is less strong, with increases in total auroral power seen near the arrival of solar wind forward shocks but little increase observed near reverse shocks. In addition, auroral dawn storms have been observed when there was little change in solar wind conditions. The data are consistent with some solar wind influence on some Jovian auroral processes, while the auroral activity also varies independently of the solar wind. This extensive data set will serve to constrain theoretical models for the interaction of the solar wind with the magnetospheres of Jupiter and Saturn.
On the characteristics of Circumpolar Deep Water intrusions to the west Antarctic Peninsula Continental Shelf
Authors: Moffat C. , Owens B. , Beardsley R. C.
Published: May 2009

Hydrographic and current velocity observations collected from March 2001 to February 2003 on the west Antarctic Peninsula shelf as part of the Southern Ocean Global Ecosystems Dynamics program are used to characterize intrusions of Upper Circumpolar Deep Water (UCDW) and Lower Circumpolar Deep Water (LCDW) onto the shelf and Marguerite Bay. UCDW is found on the middle and outer shelf along Marguerite Trough, which connects the shelf break to Marguerite Bay, and at another location farther south. UCDW intrudes in the form of frequent (four per month) and small horizontal scales (≈4 km) warm eddy‐like structures with maximum vertical scales of a few hundred meters. However, no evidence of UCDW intrusions was found in Marguerite Bay. LCDW was found in several deep depressions connected to the shelf break, including Marguerite Trough, forming a tongue of relatively dense water 95 m thick (on average) that reaches into Marguerite Bay through Marguerite Trough. A steady advective‐diffusive balance for the LCDW intrusion is used to make an estimation of the average upwelling rate and diffusivity in the deep layer within Marguerite Trough, which suggest the LCDW layer is renewed approximately every six weeks.
On the spreading of South Atlantic Water into the Northern Hemisphere
Authors: Kirchner Kerstin , Rhein Monika , Hüttl‐Kabus Sabine , Böning Claus W.
Published: May 2009

The upper branch of the meridional overturning circulation in the North Atlantic is fed by cross‐equatorial transport of various water masses from the Southern Hemisphere. Here, we study the large‐scale spreading of South Atlantic Water (SAW) into the western tropical North Atlantic from the equator to 25°N. The fractions of SAW in the upper ocean water masses are quantified using a water mass analysis applied on a data set of conductivity‐temperature‐depth data from the Hydrobase project and the Argo float program. To fill gaps in the data coverage and to gain insight into the mechanisms involved, the observations are complemented with results from the high‐resolution Family of Linked Atlantic Model Experiments model (°), which has been shown to realistically simulate the inflow of SAW into the Caribbean. The analysis reveals the mean SAW propagation pathways in the North Atlantic and identifies the regions of largest variability. High SAW fractions in the thermocline and central water layers are limited to the region south of 10°N, where the water body consists of 80%–90% SAW. Thus, the zonal currents in the equatorial gyre are mainly formed of SAW. The weaker currents in the intermediate layer combined with a northward excursion of the North Equatorial Current allow the SAW in this layer to intrude farther north compared to the layers above. The transition into North Atlantic Water occurs gradually from 12°N to 20°N in the intermediate layer.
Measurement of soil carbon oxidation state and oxidative ratio by 13C nuclear magnetic resonance
Authors: Hockaday W. C. , Masiello C. A. , Randerson J. T. , Smernik R. J. , Baldock J. A. , Chadwick O. A. , Harden J. W.
Published: May 2009

The oxidative ratio (OR) of the net ecosystem carbon balance is the ratio of net O2 and CO2 fluxes resulting from photosynthesis, respiration, decomposition, and other lateral and vertical carbon flows. The OR of the terrestrial biosphere must be well characterized to accurately estimate the terrestrial CO2 sink using atmospheric measurements of changing O2 and CO2 levels. To estimate the OR of the terrestrial biosphere, measurements are needed of changes in the OR of aboveground and belowground carbon pools associated with decadal timescale disturbances (e.g., land use change and fire). The OR of aboveground pools can be measured using conventional approaches including elemental analysis. However, measuring the OR of soil carbon pools is technically challenging, and few soil OR data are available. In this paper we test three solid‐state nuclear magnetic resonance (NMR) techniques for measuring soil OR, all based on measurements of the closely related parameter, organic carbon oxidation state (Cox). Two of the three techniques make use of a molecular mixing model which converts NMR spectra into concentrations of a standard suite of biological molecules of known Cox. The third technique assigns Cox values to each peak in the NMR spectrum. We assess error associated with each technique using pure chemical compounds and plant biomass standards whose Cox and OR values can be directly measured by elemental analyses. The most accurate technique, direct polarization solid‐state 13C NMR with the molecular mixing model, agrees with elemental analyses to ±0.036 Cox units (±0.009 OR units). Using this technique, we show a large natural variability in soil Cox and OR values. Soil Cox values have a mean of −0.26 and a range from −0.45 to 0.30, corresponding to OR values of 1.08 ± 0.06 and a range from 0.96 to 1.22. We also estimate the OR of the carbon flux from a boreal forest fire. Analysis of soils from nearby intact soil profiles imply that soil carbon losses associated with the fire had an OR of 1.091 (±0.003). Fire appears to be a major factor driving the soil C pool to higher oxidation states and lower OR values. Episodic fluxes caused by disturbances like fire may have substantially different ORs from ecosystem respiration fluxes and therefore should be better quantified to reduce uncertainties associated with our understanding of the global atmospheric carbon budget.
Simulation of the interplay between resident and infiltrating water in partially saturated porous media
Authors: Gouet‐Kaplan Maxime , Tartakovsky Alexandre , Berkowitz Brian
Published: May 2009

The interplay between resident water already in the subsurface environment (“old water”) and infiltrating water (“new water”) is examined. A smoothed particle hydrodynamics technique is used to simulate the interplay between old water and new water in a porous medium over a cycle of drainage of old water and infiltration of new water. The effect of varying the average pore size is investigated via the Bond number. Four parameters (maximal mixing amount, minimal average size of old water pockets, mixing value for which the number of old water pockets decreases, and amount of old water remaining in the system for long times) are found to be independent of the average pore size. However, the rate of change is always higher for larger pores. In particular, some old water remains in the system within stable water pockets even after infiltrating new water reaches steady state.
Morphology, flow structure, and suspended bed sediment transport at two large braid‐bar confluences
Authors: Szupiany Ricardo N. , Amsler Mario L. , Parsons Daniel R. , Best James L.
Published: May 2009

Mid‐channel bars and their associated confluences are key morphodynamic nodes within braided rivers, with past studies having investigated the morphodynamics of small natural channels or laboratory models with relatively low width/depth (W/D) ratios, typically at <10. This paper investigates the morphology, suspended bed sediment distribution, and flow structure at two large braid bar confluences in the Río Paraná (Argentina), whereinW/Dratios are much higher (approaching 100) than in smaller channels. The results highlight the significant control of the cross‐sectional distribution of downstream flow velocity on confluence flow, suspended bed sediment concentration, and morphodynamics and indicate that this factor may become progressively more significant with increasing channel scale andW/Dratio, particularly when simple discharge (or momentum) ratios between the incoming flows are used to explain the flow dynamics. Additionally, secondary flow cells, often proposed to occupy a large part of the channel width in small river channel confluences, are only identified in relatively small portions of the channel width at these larger spatial scales. Such a restriction seems related to the generative mechanisms of secondary flows at these higherW/Dratios, which are likely to be dominated by turbulence generated along the mixing layer between the two flows and topographic influences that limit the spatial extent of these effects. This paper highlights the importance of these findings with respect to the flow and sediment dynamics of large channel confluences.
Towards a Kalman Filter based soil moisture analysis system for the operational ECMWF Integrated Forecast System
Authors: Drusch M. , Scipal K. , de Rosnay P. , Balsamo G. , Andersson E. , Bougeault P. , Viterbo P.
Published: May 2009

This paper presents the future European Centre for Medium‐Range Weather Forecasts soil moisture analysis system based on a point‐wise Extended Kalman Filter (EKF). The performance of the system is evaluated against the current operational Optimal Interpolation (OI) system. Both systems use proxy observations, i.e., 2 m air temperature and relative humidity. The spatial structure of the analysis increments obtained from both analyses are comparable. However, the EKF‐based increments are generally higher for the top soil layers then for the bottom layer. This gradient better reflects the underlying hydrological processes in that the strongest interaction between soil moisture and bare soil evaporation and transpiration through vegetation should occur in top layers where most of the roots are located. The impact on the forecast skill, e.g., air temperature at 2 m and 500 hPa height, is neutral. The new EKF surface analysis system offers a range of further development options for the exploitation of satellite observations for the initialization of the land surface in Numerical Weather Prediction.
Estimating the altitude of volcanic sulfur dioxide plumes from space borne hyper‐spectral UV measurements
Authors: Yang Kai , Liu Xiong , Krotkov Nickolay A. , Krueger Arlin J. , Carn Simon A.
Published: May 2009

The altitude of volcanic sulfur dioxide (SO2) plumes determines the transport and atmospheric residence time of derived sulfate aerosol, and hence their impacts on the environment and climate. Knowledge of the altitude of fresh eruption clouds is also very important in aviation safety to avoid flying through ash clouds and for forecasting of plume drift. In this paper, we demonstrate the altitude dependence of the spectral response in the backscattered ultraviolet (BUV) radiance when a SO2 absorption layer is added to an ozone‐laden atmosphere. The distinctive spectral response serves as the physical basis for simultaneous SO2 loading and altitude retrievals, which can improve the characterization of volcanic emissions. We accomplish this by extending the recently developed Iterative Spectral Fitting (ISF) algorithm to include effective plume altitude determination when performing simultaneous ozone and SO2 retrievals. The extended ISF algorithm is applied to hyper‐spectral Ozone Monitoring Instrument (OMI) measurements of two volcanic eruptions: Sierra Negra in October 2005 and Jebel al Tair in September 2007. The results show for the first time that a wide range of SO2 plume altitudes can be estimated directly from hyper‐spectral BUV radiance measurements.
Holidaying with the Family Pet: No Dogs Allowed!
Authors: Carr Neil , Cohen Scott
Published: May 2009

This paper assesses the extent to which dog owners located in Brisbane, Australia, wish to holiday with their pets, and whether there is a gap between this desire and reality. The paper also examines the extent to which this demand is being catered for by the tourism accommodation sector. The need for this study reflects the increasingly significant role dogs are playing in the lives of humans, and the scale of the dog-owning population. The results suggest that, although there is a strong desire among dog owners to take holidays with their pets, the actualisation of this desire is comparatively low. A significant obstacle to the realisation of this desire appears to be a dearth of pet-friendly accommodation. This has implications for the ability of the tourism industry to benefit from this potentially lucrative market, that is, the dog-owning population.
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absorption spectroscopy of shock-wave heating and compression in laser-driven planar foil
Authors: Sawada H. , Regan S. P. , Radha P. B. , Epstein R. , Li D. , Goncharov V. N. , Hu S. X. , Meyerhofer D. D. , Delettrez J. A. , Jaanimagi P. A. , Smalyuk V. A. , Boehly T. R. , Sangster T. C. , Yaakobi B. , Mancini R. C.
Published: May 2009

Time-resolved Al 1s-2p absorption spectroscopy is used to diagnose direct-drive, shock-wave heating and compression of planar targets having nearly Fermi-degenerate plasma conditions (Te∼10–40 eV, ρ∼3–11 g/cm3) on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. A planar plastic foil with a buried Al tracer layer was irradiated with peak intensities of 1014–1015 W/cm2 and probed with the pseudocontinuum M-band emission from a point-source Sm backlighter in the range of 1.4–1.7 keV. The laser ablation process launches 10–70 Mbar shock waves into the CH/Al/CH target. The Al 1s-2p absorption spectra were analyzed using the atomic physic code PRISMSPECT to infer Te and ρ in the Al layer, assuming uniform plasma conditions during shock-wave heating, and to determine when the heat front penetrated the Al layer. The drive foils were simulated with the one-dimensional hydrodynamics code LILAC using a flux-limited (f=0.06 and f=0.1) and nonlocal thermal-transport model [V. N. Goncharov et al., Phys. Plasmas 13, 012702 (2006)]. The predictions of simulated shock-wave heating and the timing of heat-front penetration are compared to the observations. The experimental results for a wide variety of laser-drive conditions and buried depths have shown that the LILAC predictions using f=0.06 and the nonlocal model accurately model the shock-wave heating and timing of the heat-front penetration while the shock is transiting the target. The observed discrepancy between the measured and simulated shock-wave heating at late times of the drive can be explained by the reduced radiative heating due to lateral heat flow in the corona.
Magnetic reconnection with pressure tensor in electron magnetohydrodynamics
Authors: Cai Huishan , Li Ding
Published: May 2009

The dissipation mechanisms of reconnection and the pressure gradient effects on tearing mode with guide magnetic field are analyzed systematically by including the electron pressure tensor in electron magnetohydrodynamics. It is found that which dissipation mechanism dominates, either pressure-based dissipation or inertia-based dissipation, has a great relation with the relative scaling orders between the electron thermal Larmor radius and electron inertia skin depth. The effects of pressure gradient also depend on the relative magnitude between parallel and perpendicular equilibrium pressure gradients. When the pressure-based dissipation is dominant, the condition that pressure drives or suppresses tearing mode instability also depends on the relative magnitude between parallel and perpendicular equilibrium pressure gradients.
Two-component relativistic density functional method for computing nonsingular complex linear response of molecules based on the zeroth order regular approximation
Authors: Devarajan Ajitha , Gaenko Alexander , Autschbach Jochen
Published: May 2009

We report the implementation of a frequency-dependent two-component relativistic density functional theory method based on the zeroth order regular approximation (ZORA) for computations of complex linear response of molecules including spin-orbit coupling. The implementation is based on Slater-type atomic orbital basis functions and makes extensive use of density fitting techniques. The complex response is obtained by applying damping in the computations. The method is validated by computations of the real and imaginary part of the static and dynamic polarizability of group 12 atoms, of a number of heavy-atom diatomic molecules, of a range of two- and three-dimensional gold clusters, and of group 8 oxides and metallocenes. Simulated spectra—a plot of extinction coefficient as a function of frequency—obtained from the isotropic imaginary polarizability are compared to broadened spectra obtained from two-component ZORA excitation energies and oscillator strengths.
Delta distributions supported on quadratic O(p,q)-invariant surfaces
Authors: Franssens Ghislain R.
Published: May 2009

An important subset of distributions encountered in physics is the set of multiplet delta distributions δcy(k), with support a quadratic O(p,q)-invariant surface cy≜{x∊Rn:P(x)=y}, n=p+q. The evaluation of these distributions for a general test function is not always sufficiently detailed in the classical literature, especially for those distributions that are defined as a regularization and/or when one needs their causal or anticausal version (for p=1 or q=1). This work intends to improve this situation by deriving explicit expressions for ⟨δcy(k),φ⟩, ∀p,q∊Z+, ∀k∊N, ∀y∊R, and ∀φ∊D(Rn), in a form suitable for practical applications. In addition, we also apply to these distributions a new approach to regularization. Distributions that need to be regularized are (equivalently) defined as extensions of a partial distribution. This extension process reveals in a natural way that regularized multiplet delta distributions are in general, uncountably multivalued. In the work of Gel’fand and Shilov [Generalized Functions (Academic, New York, 1964), Vol. 1] four types of multiplet delta distributions with support the null space c0 were introduced: δ1(k)(P), δ2(k)(P) and δ(k)(P+), δ(k)(P−). Our regularization method explains why this particular nonuniqueness was observed and further discloses the full extent of this nonuniqueness.
Mirror symmetry and vibrational structure in optical spectra of chlorophyll a
Authors: Rätsep Margus , Linnanto Juha , Freiberg Arvi
Published: May 2009

The absorption and fluorescence emission spectra of chlorophyll a in different organic solvents where the central Mg atom is either penta- or hexacoordinated have been studied using conventional and selective spectroscopy methods at ambient and cryogenic temperatures. A breakdown of the basic model mirror-symmetry rule in relation to the lowest-energy Qy transitions was observed due to Franck–Condon and Hertzberg–Teller interactions. Detailed vibrational structure in the ground electronic state, virtually independent of the Mg coordination state, was revealed by hole-burning fluorescence line-narrowing technique. The total Huang–Rhys factor associated with the linear vibronic coupling strength of the solvent collective vibrations and the local chlorophyll a intramolecular vibrations is equal to 0.53±0.07 in fluorescence and to 0.39±0.05 in absorption. The electron-phonon coupling part was also found to depend on the excitation wavelength within the inhomogeneously broadened absorption origin band, its average value being Sph≈0.38. All these numbers qualify for the weak vibronic coupling. A comparison of the conjugate Qy absorption and fluorescence emission spectra as well as the temperature dependence of the absorption spectra allowed unambiguous locating of the still controversial Qx absorption band position for penta- and hexacoordinated chlorophyll a species. The basic experimental findings have been qualitatively supported by semiempirical quantum chemical calculations.
A microfluidic mixing system for single-molecule measurements
Authors: Pfeil Shawn H. , Wickersham Charles E. , Hoffmann Armin , Lipman Everett A.
Published: May 2009

This article describes the design and fabrication of a microfluidic mixing system optimized for ultrasensitive optical measurements. Channels are replica-molded in polydimethylsiloxane elastomer and sealed with fused-silica coverglass. The resulting devices have broad chemical compatibility and extremely low fluorescence background, enabling measurements of individual molecules under well-characterized nonequilibrium conditions. Fluid delivery and pressure connections are made using an interface that allows for rapid assembly, rapid sample exchange, and modular device replacement while providing access for high numerical aperture optics.
Generation of room-temperature atmospheric H2/Ar microplasma jet driven with pulse-modulated ultrahigh frequency and its application to gold nanoparticle preparation
Authors: Shimizu Yoshiki , Kawaguchi Kenji , Sasaki Takeshi , Koshizaki Naoto
Published: May 2009

We developed a technique to prepare gold nanoparticles (AuNPs) by wire spraying employing a room-temperature atmospheric H2/Ar microplasma jet driven with pulsing ultrahigh frequency and to subsequently deposit the AuNPs on nonheat-resistant materials such as paper in ambient air without apparent damage. In this technique, the application of a pulse waveform with higher voltage but rather low duty cycle effectively lowered the time-averaged gas temperature and facilitated preparing AuNPs. The size, crystallinity, and optical absorption of the prepared AuNPs were characterized, and the derivation and size evolution mechanisms were simply discussed based on the characterizations.
Markovian milestoning with Voronoi tessellations
Authors: Vanden-Eijnden Eric , Venturoli Maddalena
Published: May 2009

A new milestoning procedure using Voronoi tessellations is proposed. In the new procedure, the edges of Voronoi cells are used as milestones, and the necessary kinetic information about the transitions between the milestones is calculated by running molecular dynamics (MD) simulations restricted to these cells. Like the traditional milestoning technique, the new procedure offers a reduced description of the original dynamics and permits to efficiently compute the various quantities necessary in this description. However, unlike traditional milestoning, the new procedure does not require to reinitialize trajectories from the milestones, and thereby it avoids the approximation made in traditional milestoning that the distribution for reinitialization is the equilibrium one. In this paper we concentrate on Markovian milestoning, which we show to be valid under suitable assumptions, and we explain how to estimate the rate matrix of transitions between the milestones from data collected from the MD trajectories in the Voronoi cells. The rate matrix can then be used to compute mean first passage times between milestones and reaction rates. The procedure is first illustrated on test-case examples in two dimensions and then applied to study the kinetics of protein insertion into a lipid bilayer by means of a coarse-grained model.
Ultrafast spin demagnetization by nonthermal electrons of TbFe alloy film
Authors: Kim Ji-Wan , Lee Kyeong-Dong , Jeong Jae-Woo , Shin Sung-Chul
Published: May 2009

An ultrafast spin demagnetization process of an amorphous Tb35Fe65 alloy film has been investigated by means of an all-optical pump-probe technique. Interestingly, steplike demagnetization on a subpicosecond time scale is observed before a much slower change on a time scale of tens of picoseconds. The steplike demagnetization at the subpicosecond scale is explained by the extended three-temperature model considering the interaction between a nonthermal electron and a spin system. The characteristic of subpicosecond demagnetization of TbFe alloy film is expected to be very useful in the manipulation of the spin state in ultrafast regime.
Global existence of classical solutions to the damped Vlasov–Klein–Gordon equations with small data
Authors: Ha Seung-Yeal , Lee Ho
Published: May 2009

We study the collective dynamics of an ensemble of relativistic charged particles interacting with a self-consistent damped Klein–Gordon field in spatial three dimensions. For this, we derive a priori pointwise decay estimates for a scalar Klein–Gordon field and its derivatives, when the initial data are small and compactly supported. These pointwise estimates yield the uniform boundedness of the velocity support, which establishes the global existence of classical solutions.
Covalent functionalization of ZnO surfaces: A density functional tight binding study
Authors: Moreira Ney H. , da Rosa Andreia L. , Frauenheim Thomas
Published: May 2009

We have demonstrated the covalent functionalization of 101̱0-ZnO surfaces with carboxylic acids by employing self-consistent charge density functional tight binding (SCC-DFTB) calculations. We have found two thermodynamically stable surface configurations: (i) a monolayer coverage with a bidentate chelating ligand and (ii) a half-monolayer coverage with a bidentate bridging ligand. In both cases, the electronic band structures show the presence of covalent surface/adsorbate interactions. Besides, a nonbonding carboxylate character is verified for the bidentate adsorbate. Our results are consistent with infrared spectroscopy experiments on functionalized ZnO nanostructures, and open possibilities for further investigations on functionalized ZnO-based materials for bio/chemical sensing.
The hydrogen abstraction reaction H+CH4. II. Theoretical investigation of the kinetics and dynamics
Authors: Espinosa-García J. , Nyman G. , Corchado J. C.
Published: May 2009

On a new potential energy surface (PES-2008) developed by our group (preceding paper), we performed an extensive kinetics study using variational transition-state theory with semiclassical transmission coefficients over a wide temperature range of 250–2000 K and a dynamics study using quasiclassical trajectory (QCT) and quantum-mechanical (QM) calculations at collision energies between 0.7 and 2.0 eV for the title reaction and isotopically substituted versions. Kinetically, the H+CH4 forward and reverse thermal rate constants reproduce the available experimental data, with a small curvature of the Arrhenius plot indicating the role of tunneling in this hydrogen abstraction reaction. Five sets of kinetic isotope effects are also calculated. In general, they reproduce the experimental information. Dynamically, we focused on the H+CD4 reaction because there are more experimental studies for comparison. Most of the available energy appears as product translational energy (55%–68%), with the HD product being vibrationally cold (v′=0,1) in agreement with experiment, although rotationally hotter than experiment. The reaction cross section is practically negligible at 0.7 eV and still small at 1.5 eV, reproducing the experimental evidence, although our values are smaller. The product angular distribution is analyzed using QCT and QM methods. While at low energies (0.7 eV) both the QCT and the QM calculations yield forward scattered CD3 product, i.e., a rebound mechanism, at high energy (1.2 eV) only the QM calculations reproduce the experiment. The agreement with this wide variety of kinetic and dynamic experimental data (always qualitative and in some cases quantitative) shows the capacity of the PES-2008 surface to describe the reaction system.