Identifying Outliers in Correlated Water Quality Data

Evaluating water quality data for outliers is a good quality control/quality assessment procedure whether the data are used for monitoring or for modeling. Often water quality data are correlated, e.g., carbonaceous biochemical oxygen demand (CBOD) has some correlation with NH3. Univariate methods for identifying outliers do not consider the correlation between variables and may identify too many data points as outliers or miss observations which have extreme ratios between variables, e.g., a raw wastewater sample with relatively low CBOD but high NH3. Testing for outliers using multivariate methods such as the Mahalanobis distance, Jackknife distance, p-values, or Hadi’s automatically incorporates the correlation or covariance between variables and is fundamentally more correct. Such multivariate methods can better identify potential outliers and avoid eliminating valid data.     

The Serotonergic Agonists Quipazine, CGS-12066A, and α-Methylserotonin Alter Motor Activity and Induce Hindlimb Stepping in the Intact and Spinal Rat Fetus.

The effects of serotonergic agonists were examined in intact and spinal fetuses, using an in vivo fetal rat preparation. On Gestational Day 20, fetuses were prepared with a midthoracic or sham spinal transection. Dose-response curves were obtained for quipazine (nonselective 5-hydroxytryptamine [5-HT] agonist; 1.0-10.0 mg/kg), CGS-12066A (5-HT1B agonist; 1.0-30.0 mg/kg), and α-methylserotonin (α-Me-5-HT; 5-HT? agonist; 0.2-15.0 mg/kg). During a 10-min test, each of the agonists (delivered via intraperitoneal injection) influenced fetal behavior: They increased the occurrence of head movements, mouthing, and hindlimb stepping. Quipazine and α-Me-5-HT also promoted hindlimb activity in spinal fetuses. Thus, stimulation of the fetal 5-HT system modulates motor activity at multiple levels of the developing central nervous system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Computer user verification using login string keystroke dynamics

The keystroke dynamics of a computer user's login string provide a characteristic pattern that can be used for identity verification. Timing vectors for several hundred login attempts were collected for ten “valid” users and ten “forgers”, and classification analysis was applied to discriminate between them. Three different classifiers were applied, and in each case the key hold times were more effective features for discrimination than the interkey times. Best performance was achieved by an inductive learning classifier using both interkey and hold times. A high rate of typographical errors during login entry is reported. In practice, these are usually corrected errors-that is, they are strings which include backspaces to correct earlier errors-but their presence confounds the use of typing-style analysis as a practical means of securing access to computer systems     

The effect of hydrogen, tritium and decay helium on the fracture toughness of a stainless steel superalloy

The effect of tritium and helium-3 on tensile properties, fracture toughness properties and fracture mechanisms was studied in a modified A-286 alloy, and compared to the effects of hydrogen. The yield strength and work hardening rate showed no sensitivity to helium-3 in the concentration range studied, but the tensile ductility decreased with increased helium concentration. Fracture toughness with tritium plus helium decreased below that obtained with hydrogen alone. Helium-3 caused a decrease in tensile ductility and fracture toughness because it precipitates on and induces failure at grain boundaries.     

Production of anti-erythrocyte antibodies by leukemic and nonleukemic B cells in chronic lymphocytic leukemia patients

We have assessed the specificity of antibodies from the leukemic B cells of five patients with both chronic lymphocytic leukemia and autoimmune hemolytic anemia (CLL-AHA). Leukemic cells from one patient displayed surface immunoglobulin with heavy and light chain isotypes identical to that of the patient's anti-red blood cell (RBC) antibodies, and the leukemic cells secreted antibodies in vitro with anti-RBC activity. However, in the remaining patients, the leukemic cells displayed surface immunoglobulin with light chain isotypes different from that of the patient's anti-RBC antibodies and secreted antibodies in vitro with no detectable anti-RBC activity. Thus, there are two distinct classes of CLL-AHA patients, differentiated by the presence or absence of an anti-RBC antibody-producing leukemic B cell clone. The apparent heterogeneity in the source of pathogenic anti-RBC antibodies may impact the treatment response of the two classes of CLL-AHA patients.     

Effect of postmolding heat treatment on in vitro properties of a polyanhydride implant containing gentamicin sulfate

A polyanhydride implant containing gentamicin sulfate was fabricated using a laboratory-scale injection-molding machine. After injection molding, the implants were subject to heat treatment at 60°C for various time periods with or without nitrogen protection. The impact of this heat treatment on the in vitro properties of the implants including copolymer molecular weights, mechanical properties, and in vitro drug-release profiles was investigated. This heat treatment caused a drastic drop in the molecular weight of the copolymer. Heating without nitrogen protection resulted in the hardening of the implant, but heating in the presence of nitrogen rendered the implant less rigid. It was also found that a faster in vitro drug release profile was shown by implants heated without nitrogen protection and a pronounced slowing down in drug release was exhibited by implants heated with nitrogen protection.     

Data-dependent sampling of two-dimensional signals

Samples taken at scattered points of a finite-support two-dimensional signal can be interpolated to recover an approximation of the original signal. Given a bound on the number of samples, where should they be placed to enable the most accurate reconstruction? Or, given an error bound for the reconstruction, what is the minimum number of samples required, and where should they be placed? In this paper we introduce search schemes that provide good candidate solutions to these problems, for digital signals. Natural Neighbour Interpolation is used in iterative sample removal and movement processes to obtain sparse sample patterns. For pictures and Digital Elevation Models, fewer samples are required if the interpolant is onlyC ⁰ continuous at the data sites, than if it isC ¹. Retained samples lie on the ridges and valleys of the laplacian.     

Detection and monitoring of algal blooms using SeaWiFS imagery

Abstract

The study presented here is a part of an attempt to improve the operational algorithm used at the Centre de Météorologie Spatiale (CMS) to calculate Sea Surface Temperature (SST) from Advanced Very High Resolution Radiometer (AVHRR) data. The errors produced by SST retrieval algorithms are analysed through two experiments: an examination of the errors calculated on a validation file and an analysis of the temperatures of oceanic cloud-free areas seen under two distinct satellite zenith angles (θ) for consecutive night-time orbits. This Letter presents the part of the study dedicated to the effect of large viewing angles on the retrieval of SST. Correction terms are proposed and compared, on the same set of data, to split window algorithms using θ dependent coefficients