Separate Rankings Research Articles

Nonparametric methods for unbalanced multivariate data and many factor levels

We propose different nonparametric tests for multivariate data and derive their asymptotic distribution for unbalanced designs in which the number of factor levels tends to infinity (large a , small n i case). Quasi gratis, some new parametric multivariate tests suitable for the large a asymptotic case are also obtained. Finite sample performances are investigated and compared in a simulation study. The nonparametric tests are based on separate rankings for the different variables. In the presence of outliers, the proposed nonparametric methods have better power than their parametric counterparts. Application of the new tests is demonstrated using data from plant pathology.

Tensor product approximation with optimal rank in quantum chemistry

Tensor product decompositions with optimal separation rank provide an interesting alternative to traditional Gaussian-type basis functions in electronic structure calculations. We discuss various applications for a new compression algorithm, based on the Newton method, which provides for a given tensor the optimal tensor product or so-called best separable approximation for fixed Kronecker rank. In combination with a stable quadrature scheme for the Coulomb interaction, tensor product formats enable an efficient evaluation of Coulomb integrals. This is demonstrated by means of best separable approximations for the electron density and Hartree potential of small molecules, where individual components of the tensor product can be efficiently represented in a wavelet basis. We present a fairly detailed numerical analysis, which provides the basis for further improvements of this novel approach. Our results suggest a broad range of applications within density fitting schemes, which have been recently successfully applied in quantum chemistry.

WORLDWIDE ECONOMETRICS RANKINGS: 1989–2005

This paper updates Baltagi’s ~2003, Econometric Theory 19, 165–224! rankings of academic institutions by publication activity in econometrics over the period 1989–1999 to the period 1989–2005+ This ranking is based on 16 leading international journals that publish econometrics articles+ It is compared with the prior rankings by Hall ~1987, Econometric Theory 3, 171–194; 1990, Econometric Theory 6, 1–16! for the period 1980–1988+ In addition, a list of the top 150 individual producers of econometrics in these 16 journals over this 17-year period is provided+ This is done for theoretical econometrics and also for all contributions in econometrics+ Sensitivity analysis is provided using ~i! alternative weighting factors given to the 16 journals taking into account impact citations, excluding self-citations, size and age of the journal, ~ii! alternative time intervals, namely, 2000–2005, 1995–2005, and 1989–2005, ~iii! alternative ranking using the number of articles published in these journals, ~iv! separate rankings for both institutions and individuals by journal, ~v! rankings for institutions and individuals based on publications in three core econometrics journals+ What is certain is that econometrics now occupies a position in teaching programs that puts it on an equal footing with microeconomic and macroeconomic theory; and in research there seems to be no area of economics untouched by econometric method. To keep abreast of these changes, we intend to provide regular updates of the rankings of research activity presented in this issue of Econometric Theory+ —Peter C+B+ Phillips ~1987, Econometric Theory 3, 169!

MADNESS applied to density functional theory in chemistry and nuclear physics

We describe some recent mathematical results in constructing computational methods that lead to the development of fast and accurate multiresolution numerical methods for solving quantum chemistry and nuclear physics problems based on Density Functional Theory (DFT). Using low separation rank representations of functions and operators in conjunction with representations in multiwavelet bases, we developed a multiscale solution method for integral and differential equations and integral transforms. The Poisson equation, the Schrodinger equation, and the projector on the divergence free functions provide important examples with a wide range of applications in computational chemistry, nuclear physics, computational electromagnetic and fluid dynamics.We have implemented this approach along with adaptive representations of operators and functions in the multiwavelet basis and low separation rank (LSR) approximation of operators and functions. These methods have been realized and implemented in a software package called Multiresolution Adaptive Numerical Evaluation for Scientific Simulation (MADNESS).

Nonparametric methods in multivariate factorial designs for large number of factor levels

We propose different multivariate nonparametric tests for factorial designs and derive their asymptotic distribution for the situation where the number of replications is limited, whereas the number of treatments goes to infinity (large a, small n case). The tests are based on separate rankings for the different variables, and they are therefore invariant under separate monotone transformations of the individual variables. There are no restrictions on the covariance structure of the multivariate observations, and the methods also work for data that have ties or are measured on an ordinal scale. We compare the proposed tests to their parametric counterparts by simulating the power functions. In the presence of outliers, the new nonparametric tests show far superior power. The multivariate nonparametric tests can be used, e.g., in screening trials in agriculture or for survey data. We illustrate the application with a survey data set.

Multiresolution separated representations of singular and weakly singular operators

For a finite but arbitrary precision, we construct efficient low separation rank representations for the Poisson kernel and for the projector on the divergence free functions in the dimension d = 3 . Our construction requires computing only one-dimensional integrals. We use scaling functions of multiwavelet bases, thus making these representations available for a variety of multiresolution algorithms. Besides having many applications, these two operators serve as examples of weakly singular and singular operators for which our approach is applicable. Our approach provides a practical implementation of separated representations of a class of weakly singular and singular operators in dimensions d ⩾ 2 .

Fast Computation of Fourier Integral Operators

We introduce a general purpose algorithm for rapidly computing certain types of oscillatory integrals which frequently arise in problems connected to wave propagation, general hyperbolic equations, and curvilinear tomography. The problem is to numerically evaluate a so-called Fourier integral operator (FIO) of the form $\int e^{2\pi i \Phi(x,\xi)} a(x,\xi) \hat{f}(\xi) \d\xi$ at points given on a Cartesian grid. Here, $\xi$ is a frequency variable, $\hat f(\xi)$ is the Fourier transform of the input $f$, $a(x,\xi)$ is an amplitude, and $\Phi(x,\xi)$ is a phase function, which is typically as large as $|\xi|$; hence the integral is highly oscillatory. Because a FIO is a dense matrix, a naive matrix vector product with an input given on a Cartesian grid of size $N$ by $N$ would require $O(N^4)$ operations. This paper develops a new numerical algorithm which requires $O(N^{2.5} \log N)$ operations and as low as $O(\sqrt{N})$ in storage space (the constants in front of these estimates are small). It operates by localizing the integral over polar wedges with small angular aperture in the frequency plane. On each wedge, the algorithm factorizes the kernel $e^{2 \pi i \Phi(x,\xi)} a(x,\xi)$ into two components: (1) a diffeomorphism which is handled by means of a nonuniform FFT and (2) a residual factor which is handled by numerical separation of the spatial and frequency variables. The key to the complexity and accuracy estimates is the fact that the separation rank of the residual kernel is provably independent of the problem size. Several numerical examples demonstrate the numerical accuracy and low computational complexity of the proposed methodology. We also discuss the potential of our ideas for various applications such as reflection seismology.

Worldwide Econometrics Rankings: 1989-2005

This paper updates Baltagi’s (2003, Econometric Theory 19, 165-224) rankings of academic institutions by publication activity in econometrics from 1989-1999 to 1989-2005. This ranking is based on 16 leading international journals that publish econometrics articles. It is compared with the prior rankings by Hall (1980, 1987) for the period 1980-1988. In addition, a list of the top 150 individual producers of econometrics in these 16 journals over this 17-year period is provided. This is done for theoretical econometrics as well as all contributions in econometrics. Sensitivity analysis is provided using (i) alternative weighting factors given to the 16 journals taking into account impact citations, excluding self-citations, size and age of the journal, (ii) alternative time intervals, namely, (2000-2005), (1995-2005), and (1989-2005), (iii) alternative ranking using the number of articles published in these journals, (iii) separate rankings for both institutions and individuals by journal, (iv) rankings for institutions and individuals based on publications in three core econometrics journals.

A new genus from the continental slope off Brazil and the discovery of the first males in the Hirsutiidae (Crustacea: Peracarida: Bochusacea)

Montucaris distincta gen. nov. sp. nov., a new genus and species of hirsutiid, is described from the bathyal floor of the northern South Atlantic, off Brazil. It is easily distinguished from other members of the family by the reduced, one-segmented exopods of pereopods 5 and 6 and the array of stout triangular spines present on the anterior margin of the basis and proximal endopodal segments of the third pereopod. This discovery is notable as it includes the first record of males in the family, demonstrating that hirsutiids are gonochoristic. Developmental stages including mancas, preparatory females and juvenile males were recovered, in addition to numerous brooding females and two morphs of adult males. We infer that the new genus has a life cycle involving non-feeding terminal males with regressed mouthparts. These males display a bizarre cephalic configuration, with a clearly defined transverse dorsal suture on the dorsal cephalothoracic shield just behind the articulation of mandibles, a feature present also in syncarida and in some Thermosbaenacea and that we interpret as secondary. The peracaridan affinities of the Hirsutiidae are firmly established here after settling definitively the oostegitic nature of the setose plates present on the posteromedial margin of the pereopodal coxae of brooding females. The separate ordinal rank for hirsutiids – as the Bochusacea – with respect to the Mictacea, within which they had been previously classified, is favoured here. In addition, we highlight similarities between hirustiids and tanaidaceans that warrant further investigation. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society, 2006, 148, 169–208.

Nueva metodología para un ranking de universidades chilenas

This article questions the traditional methodology used for the preparation of university rankings, and suggests the development of leagues for Chilean universities based on the income of their graduates and verifying its statistical validit. Accordingly, the concept of "ranking” is limited to that of category, e.g. first, second and third class universities. The results show the following conclusions: first, there are important differences in the income of graduates from the different universities; second, the ranking and magnitude of the average income differentials depend on the profession considered, reaffirming the need to prepare separate rankings for each profession; and, third, it is observed that there is a reward for reputation between traditional versus derived, and between old private universities versus new private universities (for those established in the Metropolitan Region and the 5th Region).

Camilleacanthus nom. n., a new replacement name for Priacanthopsis Arambourg, 1967 (non Fowler, 1906) (Teleostei: Perciformes)

The new replacement name Camilleacanthus nom. n. is proposed for Priacanthopsis Arambourg, 1967 (non Fowler, 1906). The type and the only species C. crassispinus (Aramb.) deserves a separate generic rank, however, its relationships with the family Priacanthidae, in which it was originally placed, are obscure.

New Technique for Evaluating Adhesion Properties between Soft Materials

A new, simple apparatus for measuring the surface adhesion properties of soft materials was designed, where the adhesion force of a point contact between soft materials and the total energy required to separate the contact can be measured using the springs of phosphor–bronze thin plates with strain gauges. The adhesion between swollen hydrogels was studied here by this simple technique in air at room temperature. The gels used in the present preliminary experiments were poly(sodium acrylate) hydrogels physically cross-linked by aluminum ions. The adhesion force and the separation energy showed a power-law increase with separation velocity. The apparatus was applied to evaluate the adhesion properties of seven anti-inflammatory analgesic cataplasms on the market. It was found that the easiness to separate (rank of adhesion force and the separation energy) was consistent with the results of those obtained by organoleptic evaluations.

Tree structures associated to a family of functions

The research presented in this paper was motivated by our aim to study a problem due to J. Bourgain [3]. The problem in question concerns the uniform boundedness of the classical separation rank of the elements of a separable compact set of the first Baire class. In the sequel we shall refer to these sets (separable or non-separable) as Rosenthal compacta and we shall denote by ∝(f) the separation rank of a real-valued functionfinB1(X), withXa Polish space. Notice that in [3], Bourgain has provided a positive answer to this problem in the case ofKsatisfyingwithXa compact metric space. The key ingredient in Bourgain's approach is that whenever a sequence of continuous functions pointwise converges to a functionf, then the possible discontinuities of the limit function reflect a local ℓ1-structure to the sequence (fn)n. More precisely the complexity of this ℓ1-structure increases as the complexity of the discontinuities offdoes. This fruitful idea was extensively studied by several authors (c.f. [5], [7], [8]) and for an exposition of the related results we refer to [1]. It is worth mentioning that A.S. Kechris and A. Louveau have invented the rank rND(f) which permits the link between thec0-structure of a sequence (fn)nof uniformly bounded continuous functions and the discontinuities of its pointwise limit. Rosenthal'sc0-theorem [11] and thec0-index theorem [2] are consequences of this interaction.Passing to the case where either (fn)nare not continuous orXis a non-compact Polish space, this nice interaction is completely lost.

ROLE OF SLING INTEGRITY IN THE RESTORATION OF LEAK POINT PRESSURE IN THE RAT VAGINAL SLING MODEL

We tested the hypothesis that cutting the sling at its suburethral section does not cancel its anti-incontinence effect. We also examined the long-term effects of the sling on bladder function in a recently validated rat model of vaginal sling. Stress urinary incontinence was created in 60 female Sprague-Dawley rats by the previously established method of bilateral pudendal nerve transection. Under anesthesia 20 animals received a vaginal sling, 20 received a vaginal sling in which the suburethral portion of the sling was cut immediately after placement and 20 received a sham vaginal sling. Six weeks after the procedures leak point pressure was determined and a cystometrogram was done using anesthesia in each animal via a previously implanted suprapubic catheter. Kruskal-Wallis and pairwise separate rank multiple comparison tests were performed with a significance level of 0.05. The cut and intact slings increased leak point pressure similarly and these values were significantly higher than that of the sham sling (24.9 and 27.9 cm H2O, respectively, vs 20.7, p <0.0001). Peak micturition pressure was not significantly different among the 3 groups, indicating absent bladder outlet obstruction in the sling groups. Bladder compliance was significantly decreased 6 weeks after placement of a cut or intact sling compared with the sham sling (p = 0.007 and 0.05, respectively). An intact suburethral portion is not a requirement for sling effectiveness in the rat model of stress urinary incontinence. However, the sling procedure decreases bladder compliance. This may explain the observed voiding dysfunction associated with sling procedures.

MRA and low-separation rank approximation with applications to quantum electronics structures computations

We describe some recent mathematical results in constructing computational methods that lead to the development of fast and accurate multiresolution numerical methods for solving problems in computational chemistry (the so-called multiresolution quantum chemistry).Using low separation rank representations of functions and operators and representations in multiwavelet bases, we developed a multiscale solution method for integral and differential equations and integral transforms. The Poisson equation and the Schrodinger equation, the projector on the divergence free functions, provide important examples with a wide range of applications in computational chemistry, computational electromagnetic and fluid dynamics.We have implemented these ideas that include adaptive representations of operators and functions in the multiwavelet basis and low separation rank approximation of operators and functions. These methods have been implemented into a software package called Multiresolution Adaptive Numerical Evaluation for Scientific Simulation (MADNESS).

Ranking of pattern recognition parameters for premature ventricular contractions classification by neural networks

Detection and classification of ventricular complexes from a limited number of ECG leads is of considerable importance in critical care or operating room patient monitoring. Beat-to-beat detection allows the heart rhythm evolution to be followed and various types of arrhythmia to be recognized. A quantitative analysis is proposed of pattern recognition parameters for classification of normal QRS complexes and premature ventricular contractions (PVC). Twenty-six parameters have been defined: the width of the QRS complex, three vectorcardiogram parameters and 11 from two ECG leads. These parameters include: amplitudes of positive and negative peaks, area of positive and negative waves, various time-interval durations, amplitude and angle of the QRS vector, etc. They are measured for all QRS complexes annotated as ‘normals’ and ‘PVCs’ from the 48 ECG recordings of the MIT-BIH arrhythmia database. Neural networks (NN) are shown to be a useful instrument for the analysis of large quantities of parameters. Separate ranking of any parameter and homogeneous group ranking (amplitude, area, interval, slope and vector) were performed. From the two ECG leads, the first three ranked parameter groups for clustering of PVCs are amplitude, slope and interval, while for N clustering they are vector, amplitude and area. Considering the entire parameter set, we obtained N = 99.7% correct detection of normal QRS complexes and PVC = 98.5% of premature ventricular complexes. The study also shows that simultaneous analysis of two ECG channels yields better accuracy compared to using a single channel: the improvement is 0.1% in the classification of N beats and 4.5% for PVC beats.

Economic profiling of primary care physicians: consistency among risk-adjusted measures.

To investigate whether different risk-adjustment methodologies and economic profiling or "practice efficiency" metrics produce differences in practice efficiency rankings for a set of primary care physicians (PCPs). Twelve months of claims records (inpatient, outpatient, professional, and pharmacy) for an independent practice association HMO. Patient risk scores obtained with six profiling risk-adjustment methodologies were used in conjunction with claims cost tabulations to measure practice efficiency of all primary care physicians who managed 25 or more members of an HMO. For each of the risk-adjustment methodologies, two measures of "efficiency" were constructed: the standardized cost difference between total observed (standardized actual) and total expected costs for patients managed by each PCP, and the ratio of the PCP's total observed to total expected costs (O/E ratio). Primary care physicians were ranked from most to least efficient according to each risk-adjusted measure, and level of agreement among measures was tested using weighted kappa. Separate rankings were constructed for pediatricians and for other primary care physicians. Moderate to high levels of agreement were observed among the six risk-adjusted measures of practice efficiency. Agreement was greater among pediatrician rankings than among adult primary care physician rankings, and, with the standardized difference measure, greater for identifying the least efficient than the most efficient physicians. The O/E ratio was shown to be a biased measure of physician practice efficiency, disproportionately targeting smaller sized panels as outliers. Although we observed moderate consistency among different risk-adjusted PCP rankings, consistency of measures does not prove that practice efficiency rankings are valid, and health plans should be careful in how they use practice efficiency information. Indicators of practice efficiency should be based on the standardized cost difference, which controls for number of patients in a panel, instead of O/E ratio, which does not.

Concept-based ranking: a case study in the juridical domain

We explore the idea of automatically using the concepts of a thesaurus to improve search results. Our focus is on improving average precision figures, not recall. This is of interest because there is a tendency to accept the view that thesauri are recall-enhancing devices that are not good for improving precision figures.In our approach, the query terms are used to match concepts in the thesaurus. These concepts are then used to find other related concepts (narrow, broad, synonym), which are interpreted as independent sources of evidential knowledge. Each source of evidence is used to produce a separate concept-based ranking of the documents in the collection. These partial rankings are then combined into a final ranking. For this, we use a Bayesian belief network.To validate our ideas we do a case study in the juridical domain. Using a juridical thesaurus and a test collection containing more than 500 hundred thousand juridical documents, obtained from the legal court system in Brazil, we compare our concept-based ranking with the standard vectorial ranking. The results indicate improvements in average precision figures of roughly 30%.

Singular operators in multiwavelet bases

We review some recent results on multiwavelet methods for solving integral and partial differential equations and present an efficient representation of operators using discontinuous multiwavelet bases, including the case for singular integral operators. Numerical calculus using these representations produces fast O(N) methods for multiscale solution of integral equations when combined with low separation rank methods. Using this formulation, we compute the Hilbert transform and solve the Poisson and SchrA¶dinger equations. For a fixed order of multiwavelets and for arbitrary but finite- precision computations, the computational complexity is O(N). The computational structures are similar to fast multipole methods but are more generic in yielding fast O(N) algorithm development.

WORLDWIDE INSTITUTIONAL AND INDIVIDUAL RANKINGS IN ECONOMETRICS OVER THE PERIOD 1989–1999: AN UPDATE

This paper updates rankings of academic institutions by Hall (1990, Econometric Theory 6, 1–16) and Baltagi (1998, Econometric Theory 14, 1–43) by publication activity in econometrics over the period 1989–1999. This is based on 15 leading international journals that publish econometrics articles. In addition, a list of the top 150 individual producers of econometrics in these 15 journals over this period is provided. This is done for theoretical econometrics and also for all contributions in econometrics. Sensitivity analysis is provided using (i) alternative conversion factors given to the 15 journals based on citation impact factors, (ii) alternative ranking using the number of articles published in these journals, (iii) separate rankings for both institutions and individuals by journal, (iv) rankings for institutions and individuals based on publications in three core journals.I thank Peter C.B. Phillips for entrusting me with this study, three referees and the editor for their comments and suggestions, and P.M. Kisor for research assistance.