Approximating Nearest Neighbor Distances

Several researchers proposed using non-Euclidean metrics on point sets in Euclidean space for clustering noisy data. Almost always, a distance function is desired that recognizes the closeness of the points in the same cluster, even if the Euclidean cluster diameter is large. Therefore, it is preferred to assign smaller costs to the paths that stay close to the input points. In this paper, we consider the most natural metric with this property, which we call the nearest neighbor metric. Given a point set P and a path $\gamma$, our metric charges each point of $\gamma$ with its distance to P. The total charge along $\gamma$ determines its nearest neighbor length, which is formally defined as the integral of the distance to the input points along the curve. We describe a $(3+\varepsilon)$-approximation algorithm and a $(1+\varepsilon)$-approximation algorithm to compute the nearest neighbor metric. Both approximation algorithms work in near-linear time. The former uses shortest paths on a sparse graph using only the input points. The latter uses a sparse sample of the ambient space, to find good approximate geodesic paths.Comment: corrected author nam

Approximate Minimum Diameter

We study the minimum diameter problem for a set of inexact points. By inexact, we mean that the precise location of the points is not known. Instead, the location of each point is restricted to a contineus region (\impre model) or a finite set of points (\indec model). Given a set of inexact points in one of \impre or \indec models, we wish to provide a lower-bound on the diameter of the real points. In the first part of the paper, we focus on \indec model. We present an $O(2^{\frac{1}{\epsilon^d}} \cdot \epsilon^{-2d} \cdot n^3 )$ time approximation algorithm of factor $(1+\epsilon)$ for finding minimum diameter of a set of points in $d$ dimensions. This improves the previously proposed algorithms for this problem substantially. Next, we consider the problem in \impre model. In $d$-dimensional space, we propose a polynomial time $\sqrt{d}$-approximation algorithm. In addition, for $d=2$, we define the notion of $\alpha$-separability and use our algorithm for \indec model to obtain $(1+\epsilon)$-approximation algorithm for a set of $\alpha$-separable regions in time $O(2^{\frac{1}{\epsilon^2}}\allowbreak . \frac{n^3}{\epsilon^{10} .\sin(\alpha/2)^3} )$

Metabolism of profenofos to 4-bromo-2-chlorophenol, a specific and sensitive exposure biomarker.

Profenofos is a direct acting phosphorothioate organophosphorus (OP) pesticide capable of inhibiting β-esterases such as acetylcholinesterase, butyrylcholinesterase, and carboxylesterase. Profenofos is known to be detoxified to the biologically inactive metabolite, 4-bromo-2-chlorophenol (BCP); however, limited data are available regarding the use of urinary BCP as an exposure biomarker in humans. A pilot study conducted in Egyptian agriculture workers, demonstrated that urinary BCP levels prior to application (3.3-30.0 μg/g creatinine) were elevated to 34.5-3,566 μg/g creatinine during the time workers were applying profenofos to cotton fields. Subsequently, the in vitro enzymatic formation of BCP was examined using pooled human liver microsomes and recombinant human cytochrome P-450s (CYPs) incubated with profenofos. Of the nine human CYPs studied, only CYPs 3A4, 2B6, and 2C19 were able to metabolize profenofos to BCP. Kinetic studies indicated that CYP 2C19 has the lowest Km, 0.516 μM followed by 2B6 (Km=1.02 μM) and 3A4 (Km=18.9μM). The Vmax for BCP formation was 47.9, 25.1, and 19.2 nmol/min/nmol CYP for CYP2B6, 2C19, and 3A4, respectively. Intrinsic clearance (Vmax/Km) values of 48.8, 46.9, and 1.02 ml/min/nmol CYP 2C19, 2B6, and 3A4, respectively, indicate that CYP2C19 and CYP2B6 are primarily responsible for the detoxification of profenofos. These findings support the use of urinary BCP as a biomarker of exposure to profenofos in humans and suggest polymorphisms in CYP 2C19 and CYP 2B6 as potential biomarkers of susceptibility

Maximum gradient embeddings and monotone clustering

Let (X,d_X) be an n-point metric space. We show that there exists a distribution D over non-contractive embeddings into trees f:X-->T such that for every x in X, the expectation with respect to D of the maximum over y in X of the ratio d_T(f(x),f(y)) / d_X(x,y) is at most C (log n)^2, where C is a universal constant. Conversely we show that the above quadratic dependence on log n cannot be improved in general. Such embeddings, which we call maximum gradient embeddings, yield a framework for the design of approximation algorithms for a wide range of clustering problems with monotone costs, including fault-tolerant versions of k-median and facility location.Comment: 25 pages, 2 figures. Final version, minor revision of the previous one. To appear in "Combinatorica

A well-separated pairs decomposition algorithm for k-d trees implemented on multi-core architectures

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Variations of k-d trees represent a fundamental data structure used in Computational Geometry with numerous applications in science. For example particle track tting in the software of the LHC experiments, and in simulations of N-body systems in the study of dynamics of interacting galaxies, particle beam physics, and molecular dynamics in biochemistry. The many-body tree methods devised by Barnes and Hutt in the 1980s and the Fast Multipole Method introduced in 1987 by Greengard and Rokhlin use variants of k-d trees to reduce the computation time upper bounds to O(n log n) and even O(n) from O(n2). We present an algorithm that uses the principle of well-separated pairs decomposition to always produce compressed trees in O(n log n) work. We present and evaluate parallel implementations for the algorithm that can take advantage of multi-core architectures.The Science and Technology Facilities Council, UK

Peningkatan Kompentensi Guru IPA Biologi Sekolah Menengah Pertama melalui Pelatihan dan Pembekalan Materi di Laboratorium Kabupaten Pesisir Selatan

Tujuan pengabdian pada masayarakat ini untuk meningkatkan pemahaman guru Biologi tentang materi dan konsep IPA, dan meningkatkan kreatifitas serta menemukan cara-cara pendekatan pembelajaran yang kreatif dan inovatif sehingga materi mudah dimengerti oleh siswa, membantu guru mendiskusikan topik-topik yang kurang dipahami siswa sehingga guru bisa secara bersama-sama merencanakan pembelajaran yang lebih baik. Pendekatan yang dilakukan dengan memberikan pelatihan/penyuluhan berupa penguatan materi terutama di laboratorium, memberikan stimulasi kepada guru bagaimana mengembangkan ide dan pendekatan-pendekatan kreatif yang dapat membantu siswa memahami konsep yang diajarkan guru, membantu guru yang akan mengikuti ujian kompetensi guru agar lebih siap dan dan lebih memahami materi yang mungkin diujikan sebagai persiapan sertifikasi. Kegiatan PPM yang sudah dilakukan yaitu persiapan dengan mengadakan pertemuan dengan pihak Diknas Kabupaten Pesisir Selatan untuk memantapkan proses pelaksanaan dengan mendatangkan guru-guru IPA SMP sebanyak 20 Orang yang berasal dari berbagai kecamatan yang ada di Kabupaten Pesisir Selatan. Hasil analisis angket kompetensi guru-guru IPA didapat informasi pada aspek perencanaan memperoleh 68,74% dengan criteria cukup, hal yang sama terjadi pada evaluasi dengan nilai 65,65%. Sementara itu pada aspek pelaksanaan memperoleh 85,93% dengan criteria Baik sekali

Optimal Consensus set for nD Fixed Width Annulus Fitting

International audienceThis paper presents a method for fitting a nD fixed width spherical shell to a given set of nD points in an image in the presence of noise by maximizing the number of inliers, namely the consensus set. We present an algorithm, that provides the optimal solution(s) within a time complexity O(N n+1 log N) for dimension n, N being the number of points. Our algorithm guarantees optimal solution(s) and has lower complexity than previous known methods

Pengolahan Limbah Organik Dan Anorganik Sebagai Transmode Upaya Peningkatan Kreativitas Masyarakat Pantai Gondaria Pariaman

Upaya pelestarian dan pemeliharaan lingkungan agar terbebas dari limbah yaitu dengan cara pengolahan limbah dengan pola 3R. Konsep 3R mendorong masyarakat melakukan penanganan limbah dari sumbernya seperti pemilahan limbah dan pengemasan limbah dengan benar, mendorong penerapan konsep pemanfaatan sampah yang memiliki nilai ekonomi. Pengabdian Kepada Masyarakat dengan tema ”Berkarya Tanpa Batas” merupakan kegiatan pengolahan limbah organik dan limbah anorganik yang bertujuan untuk meningkatkan keterampilan dan kreatifitas masyarakat dalam penanganan limbah sehingga menambah wawasan masyarakat terhadap limbah yang dibuat dapat dijadikan kerajinan yang mempunyai nilai seni atau trash mode. Produk olahan sampah organik dan anorganik masyarakat terdiri dari tas dan bunga yang terbuat dari plastik. Sementara itu, kulit daun bawang putih diolah menjadi bunga. Pengolahan batok kelapa menjadi celengan, gelas, gantungan kunci, sendok, dan souvenir lainnya

Modes of Foreign Entry under Asymmetric Information about Potential Technology Spillovers

This paper studies the effect of technology spillovers on the entry decision of a multinational enterprise into a foreign market. Two alternative entry modes for a foreign direct investment are considered: Greenfield investment versus acquisition. We find that with quantity competition a spillover makes acquisitions less attractive, while with price competition acquisitions become more attractive. Asymmetric information about potential spillovers always reduces the number of acquisitions independently of whether the host country or the entrant has private information. Interestingly, we find that asymmetric information always hurts the entrant, while it sometimes is in favor of the host country