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PubMed1996

Observer reliability in histological grading of astrocytoma stereotactic biopsies.

This study provides an objective assessment of the reliability of histological grading of astrocytoma specimens obtained using stereotactic biopsy. Pathological diagnosis of brain tumors provides an index of disease severity and guides clinical practice in their treatment. It also functions as the gold standard in assessing the validity of diagnostic tests such as magnetic resonance imaging. Often diagnoses are made from biopsy material obtained using stereotactic technique. The current study was designed to evaluate this gold standard with regard to interobserver and intraobserver variability. Four certified neuropathologists from academic centers in the United States and Canada were asked to grade 30 brain biopsy specimens obtained stereotactically in patients with astrocytomas. Intraobserver agreement was analyzed in individual observers by comparing their first and second readings, separated by 5 to 14 weeks. Interobserver data were analyzed by comparing initial readings across all observers for individual diagnoses. Kappa analysis was used to measure agreement beyond chance. Intraobserver agreement was 74.73% for glioblastomas multiforme, 51.43% for anaplastic astrocytomas, and 65.22% for low-grade astrocytomas. The most common disagreements were between anaplastic astrocytomas and glioblastomas multiforme, followed by disagreements between anaplastic and low-grade astrocytomas. Interobserver agreement on initial readings was 62.41% (kappa 0.39) for glioblastomas, 36.04% (kappa 0.06) for anaplastic astrocytomas, and 57.14% (kappa 0.48) for low-grade astrocytomas. A significantly greater degree of reliability was seen in histopathological diagnoses of low- or high-grade astrocytomas than in those of intermediate-grade astrocytomas. Therefore, the highest variability occurs at the point of clinical decision making--namely, intermediate-grade tumors that may or may not be selected to receive adjuvant therapy. This considerable variability is an issue that needs to be recognized and further addressed by analysis of current and proposed astrocytoma grading schemes.

Astrocytoma↗
PubMed2006

Evaluation of regression models in metabolic physiology: predicting fluxes from isotopic data without knowledge of the pathway.

This study explores the ability of regression models, with no knowledge of the underlying physiology, to estimate physiological parameters relevant for metabolism and endocrinology. Four regression models were compared: multiple linear regression (MLR), principal component regression (PCR), partial least-squares regression (PLS) and regression using artificial neural networks (ANN). The pathway of mammalian gluconeogenesis was analyzed using [U-(13)C]glucose as tracer. A set of data was simulated by randomly selecting physiologically appropriate metabolic fluxes for the 9 steps of this pathway as independent variables. The isotope labeling patterns of key intermediates in the pathway were then calculated for each set of fluxes, yielding 29 dependent variables. Two thousand sets were created, allowing independent training and test data. Regression models were asked to predict the nine fluxes, given only the 29 isotopomers. For large training sets (>50) the artificial neural network model was superior, capturing 95% of the variability in the gluconeogenic flux, whereas the three linear models captured only 75%. This reflects the ability of neural networks to capture the inherent non-linearities of the metabolic system. The effect of error in the variables and the addition of random variables to the data set was considered. Model sensitivities were used to find the isotopomers that most influenced the predicted flux values. These studies provide the first test of multivariate regression models for the analysis of isotopomer flux data. They provide insight for metabolomics and the future of isotopic tracers in metabolic research where the underlying physiology is complex or unknown.

Journal Article↗
PubMed1991

Heterogeneity of rat liver cytosol casein kinase 2. Association between the alpha/alpha' -subunits of casein kinase 2 and the phosphorylatable protein pp49.

Casein kinase 2 activity could be resolved into three peaks by chromatography on DEAE-Sepharose. The peak eluted at high salt concentrations (casein kinase 2b) showed molecular and kinetic properties typical of the heterotetramer composed of alpha-(or alpha'-) and beta-subunits. In contrast, the peak that was eluted at low salt concentrations (casein kinase 2a) contained no beta-subunit but a phosphorylatable protein of 49 kDa (pp49), in addition to the alpha/alpha'-subunits. The presence of alpha/alpha'/alpha"-subunits in preparations of casein kinases 2a and 2b was confirmed by immunological assays. Casein kinase 2a had low specific activity and a very high apparent Km for beta-casein. The peak eluted at intermediate ionic strength contained the alpha/alpha'-subunits and variable amounts of beta-subunit and pp49, and had kinetic properties intermediate between those of casein kinases 2a and 2b. Experiments based on heat inactivation, inhibition by low concentrations of heparin and ability to use GTP as substrate suggested that phosphorylation of pp49 was catalysed by the alpha/alpha'-subunits of casein kinase 2. No similarities were observed in the phosphopeptide maps of pp49 and beta-subunit. These results show that the alpha/alpha'-subunits of rat liver cytosol casein kinase 2 can form complexes not only with the beta-subunit but also with pp49, and that the complexes containing pp49 have a reduced affinity for the exogenous protein substrate beta-casein.

Animals↗
PubMed1988

Immunocytochemical and ultrastructural characterization of coexistence of pancreatic polypeptide and glucagon-like immunoreactivity in the pancreatic endocrine cells of Sparus auratus L. (Teleostei).

Coexistence of pancreatic polypeptide (PP)- and glucagon-like immunoreactivity was demonstrated in the pancreatic endocrine cells of the teleost fish Sparus auratus. An immunofluorescence double-staining method revealed coexistence of glucagon- and PP-like immunoreactivity in endocrine cells of small and intermediate islets. In contrast to small islets, the intermediate ones also contained a variable number of glucagon-immunoreactive cells next to cells having both immunoreactivities. Coexistence of both immunoreactivities could not be observed in endocrine cells of the principal islet, whereas many cells containing glucagon and a few cells containing PP immunoreactivity were found. By an immunogold double-staining method the precise ultrastructural location of each immunoreactivity could be demonstrated. Again, cells containing glucagon- and/or PP-like immunoreactivity were found. Although, only two different types of granules were observed, four distinct cell types could be distinguished. Based on this granule morphology two cell types showing coexistence were found: one cell type, only present in the small islets, showing a different distribution of glucagon and PP immunoreactivity within the granules (predominantly in the center and periphery, respectively) and another cell type with larger granule cores, present in small as well as intermediate islets, having a mixed distribution of both immunoreactivities.

Animals↗
PubMed1997

Cosinor analysis of circadian peak expiratory flow variability in normal subjects, passive smokers, heavy smokers, patients with chronic obstructive pulmonary disease and patients with interstitial lung disease.

Peak expiratory flow (PEF) presents a circadian rhythm with a maximum in the afternoon, and a significant variability in its diurnal variations has been reported in normal subjects and in chronic obstructive pulmonary disease (COPD). In order to investigate whether passive smoking, active tobacco smoking, COPD and interstitial lung disease (ILD) are associated with changes in the circadian rhythm of PEF, five groups of adult male subjects, comparable for age, weight and height, were studied: group A: 30 clinically healthy subjects who never smoked, group B: 30 subjects passively exposed to tobacco smoking, group C 30 heavy smokers (> 20 cigarettes daily for at least 5 years), group D: 30 patients with nonasthmatic COPD (emphysema and/or chronic bronchitis), and group E: 15 patients with ILD (pneumoconiosis). Active tobacco smoking and exposure to passive smoking were assessed by the determination of the urinary cotinine concentration. A portable spirometer was used to measure PEF over a whole day, at 0.00, 6.00, 8.00, 10.00, 12.00, 14.00, 16.00, 18.00, 20.00, 22.00, and 24.00 h, all subjects leading a normal life. The 'mean cosinor' method was used for statistical analyses; the PEF variability was evaluated by the amplitude percent mesor (daily mean). All groups showed diurnal fluctuations in PEF values with significant (p < 0.05) circadian rhythms. The peaks of PEF rhythms occurred in the early afternoon, without significant (p > 0.05) differences between the groups. The cosinor mean was significantly (p < 0.05) lower in heavy smokers, in passive smokers, and in COPD patients than in controls. Controls, passive smokers, heavy smokers, COPD and ILD patients presented a PEF amplitude percent mesor (95% confidence limits) of 6.26% (range 4.57-7.95), 7.79% (range 5.07-10.51), 12.60% (range 7.61-17.59), 17.19% (range 10.18-23.50), and 3.98% (range 2.09-5.87), respectively, with significant differences (p < 0.05) between all groups, except between controls and passive smokers. These data suggest that tobacco smoke, both passive and active, does not modify the circadian peak of PEF, but modifies significantly its mesor and amplitude. In this respect, heavy smokers have the same pattern of COPD: lower mesor and greater amplitude; passive smokers present an intermediate situation. An increased diurnal variability in PEF could be considered as an early index of tobacco smoke damage and of developing COPD. When studying diurnal PEF variability, active and passive smoking habits should be considered.

Adult↗
PubMed2000

The relationship between the effect of lysine analogues and salt on the conformation of lipoprotein(a).

Lipoprotein(a) [Lp(a)] exhibits many of the same properties as plasminogen, owing to a similar structural makeup from a composite of multiple kringle domains. Shared behavior includes induction of an expanded conformation by lysine analogues, inhibition of this effect, and creation of a compact conformation by NaCl. Here, we examine in detail the independent and mutual effects of NaCl and 6-aminohexanoic acid (6-AHA) on the structure of Lp(a) and the relationship between the binding of the two ligands. We find that NaCl promotes the compact conformation while binding to Lp(a) homogeneously. In the absence of salt, 6-AHA leads to the complete unfolding of Lp(a), a process that is accompanied by cooperative binding. Reversal of conformation and weakening of binding occurred when one ligand was added to Lp(a) in the presence of the other, suggesting competitive binding. High concentrations of NaCl completely reversed the expansion of Lp(a) in 100 mM 6-AHA, and high concentrations of 6-AHA unfolded Lp(a) in the presence of 100 mM NaCl, but only by 30% in the case of the 15 kringle IV Lp(a) studied. Induction of the compact form of Lp(a) appears to be an effect in common with all salts examined and cannot be attributed solely to the anion, as in the case of plasminogen. The results were summarized in terms of a model of Lp(a) depicting the conformational alterations of apo(a) caused by the binding of the two ligands. In the compact conformation in NaCl, apo(a) is apposed to the particle surface. The fully expanded form in 6-AHA results from release of both the variable and constant kringle domains. In the intermediate form in water and in a solution containing both NaCl and 6-AHA, only the variable domain is released from the particle surface.

Aminocaproic Acid↗
PubMed1993

Predicting early and intermediate-term outcome of coronary angioplasty in the elderly.

BACKGROUND: Although the technical success rate of coronary angioplasty in the elderly in high, very old patients have increased risk of procedure-related death and late recurrence of severe angina. We proposed to determine baseline variables that predict early and intermediate-term failure of percutaneous transluminal coronary angioplasty (PTCA) in patients more than 65 so we could effectively stratify risk. METHODS AND RESULTS: We studied 982 patients at least 65 years old who had urgent or elective PTCA (1980 through 1990). Follow-up (mean, 25 months) was obtained for all patients. Multiple baseline variables were analyzed with univariate and multivariate logistic regression to select independent ones to fit predictive models for in-hospital death or myocardial infarction (overall rate, 6.3%), total in-hospital adverse outcome (overall rate, 18.7%), cumulative survival free of myocardial infarction (overall rate, 15% at 3 years), and cumulative survival free of late nonfatal myocardial infarction, bypass surgery, repeat PTCA, or recurrent severe angina (overall rate, 47% at 3 years). The most heavily weighted parameter in the probability regression equation for each end point was the number of diseased coronary artery segments with at least 70% stenosis. Advanced age was less important. The number of concomitant medical illnesses was predictive of late outcome but not early in-hospital events. Lowest risk quintile versus highest risk quintile event rate was 2.9% versus 14% for acute myocardial infarction or death and 17.2% versus 29% for cumulative in-hospital events. For posthospital events at 3 years' follow-up, lowest risk quintile death or myocardial infarction rate was 4% versus 33% for highest risk quintile. For cumulative late adverse events at 3 years, the event rate was 28% versus 63% for the highest risk quintile. CONCLUSIONS: These results stratify patients at high and low risk of early and intermediate-term success after PTCA and identify elderly patients in whom PTCA is most appropriate.

Age Factors↗
PubMed1999

Factors affecting adoptive transfer of resistance to Schistosoma mansoni in the snail intermediate host, Biomphalaria glabrata.

We examined potential variables affecting adoptive transfer of resistance to Schistosoma mansoni in Biomphalaria glabrata implanted with amebocyte-producing organs (APOs) from resistant snails. Transplants of 7 tissues other than the APO (heart, kidney, mantle, albumin gland, brain, digestive gland, and gonad) did not transfer resistance, suggesting a unique property of this structure. Only APOs from donors previously exposed to miracidia transferred resistance, although whether this is evidence for a priming effect or merely the elimination of susceptible donors is not known. Variability in the donor and in the implant itself apparently was unimportant, inasmuch as implants from small or large snails or from 2 separate donors all conferred similar levels of resistance. Recipients of APOs from 2 additional resistant strains of B. glabrata, 10-R2 and Salvador, also displayed resistance. However, no resistance was transferred by APOs from schistosome-refractory B. obstructa. Histological examination of implants removed from recipients that either did or did not show transferred resistance revealed no differences in mitotic activity. Furthermore, implanted APOs from B. obstructa displayed no mitotic activity. Finally, reexposure of snails with transferred resistance to a large dose of miracidia caused infection in 70%, suggesting that either transferred resistance is transitory or it can be overwhelmed.

Adoptive Transfer↗
PubMed2005

Self-fertilization and the escape from pollen limitation in variable pollination environments.

Seed production in many plants is pollen limited, likely because of unpredictable variation in the pollinator environment. One way for plants to escape the consequences of pollinator variability is to evolve mating systems, such as autonomous selfing, that assure reproduction without relying on pollinators. We explore this hypothesis through the construction and analysis of heuristic models of plant population dynamics in seed- or site-limited populations. Our analysis suggests several important points: the familiar rule that inbreeding depression greater than 0.5 maintains outcrossing significantly underestimates the threshold required under pollen limited conditions with prior selfing; variability in the pollination environment erodes the ability of inbreeding depression to maintain outcrossing; and variable pollination environments can result in stable intermediate rates of prior selfing. The results reflect the importance of geometric mean fitness (which in a variable environment is less than the arithmetic mean) in the face of temporal variation.

Genetics, Population↗
PubMed2006

Changes in galanin immunoreactivity in rat micturition reflex pathways after cyclophosphamide-induced cystitis.

Alterations in the expression of the neuropeptide, galanin, were examined in micturition reflex pathways of rat after cyclophosphamide (CYP)-induced cystitis of variable duration: acute (4 h), intermediate (48 h), or chronic (10 days). In control animals, galanin expression was present in specific regions of the gray matter in the rostral lumbar and caudal lumbosacral spinal cord, including: (1) the dorsal commissure (DCM); (2) superficial dorsal horn; (3) the regions of the intermediolateral cell column (L1-L2) and the sacral parasympathetic nucleus (SPN, L6-S1); and (4) the lateral collateral pathway (LCP) in lumbosacral spinal segments. Densitometry analysis demonstrated significant decreases (P< or =0.01) in galanin immunoreactivity (IR) in these regions of the L1-S1 spinal cord after acute or intermediate CYP-induced cystitis. In contrast, increases (P< or =0.01) in galanin-IR were observed in the DCM, SPN, or LCP regions in the L6-S1 spinal segments in rats with chronic cystitis. No changes in the number of galanin-immunoreactive cells were observed in the L1-S1 dorsal root ganglia (DRG) after CYP-induced cystitis of any duration. A small percentage of bladder afferent cells (Fast-blue-labeled) in the DRG expressed galanin-IR in control rats; this was not altered with cystitis. Galanin-IR was observed encircling DRG cells after chronic cystitis. These changes may contribute to urinary bladder dysfunction, altered sensation, and referred somatic hyperalgesia after cystitis.

Afferent Pathways↗
PubMed2002

Functional recovery of anterior semicircular canal afferents following hair cell regeneration in birds.

Streptomycin sulfate (1.2 g/kg i.m.) was administered for 5 consecutive days to 5-7-day-old white Leghorn chicks; this causes damage to semicircular canal hair cells that ultimately regenerate to reform the sensory epithelium. During the recovery period, electrophysiological recordings were taken sequentially from anterior semicircular canal primary afferents using an indentation stimulus of the canal that has been shown to mimic rotational stimulation. Chicks were assigned to an early (14-18 days; n = 8), intermediate (28-34 days; n = 5), and late (38-58 days; n = 4) period based on days after treatment. Seven untreated chicks, 15-67 days old, provided control data. An absence of background and indent-induced discharge was the prominent feature of afferents in the early period: only "silent" afferents were encountered in 5/8 experiments. In several of these chicks, fascicles of afferent fibers were seen extending up to the epithelium that was void of hair cells, and intra- and extracellular biocytin labeling revealed afferent processes penetrating into the supporting cell layer of the crista. In 3/8 chicks 74 afferents could be characterized, and they significantly differed from controls (n = 130) by having a lower discharge rate and a negligible response to canal stimulation. In the intermediate period there was considerable variability in discharge properties of 121 afferents, but as a whole the number of "silent" fibers in the canal nerve diminished, the background rate increased, and a response to canal stimulation detected. Individually biocytin-labeled afferents had normal-appearing terminal specializations in the sensory epithelium by 28 days poststreptomycin. In the late period, afferents (n = 58) remained significantly different from controls in background discharge properties and response gain. The evidence suggests that a considerable amount of variability exists between chicks in the return of vestibular afferent function following ototoxic injury and that the secretory function of regenerating hair cells might become functional before their transducer function.

Animals↗
PubMed2005

Coronary heart disease and polymorphisms in genes affecting lipid metabolism and inflammation.

Several biologic systems contribute to the pathophysiology of atherosclerosis and its complications, and within each of these systems many genes have been explored to establish the possible implication of their variability in coronary heart disease (CHD) risk. This report is focused on recent results pertaining to lipid and inflammatory genes, their variability, and their relationship with intermediate phenotypes and CHD. For both systems, there is no evidence at the present time that testing genetic polymorphisms might be of any benefit to the patient, for the diagnosis or prognosis of CHD, or for tailoring drug prescription. Understanding the genetics of complex traits like CHD will require a system approach that allows a modeling of the interaction among genes as well as between genetic and nongenetic sources of variation.

Coronary Disease↗
PubMed2005

Precision from drug stability studies. Investigation of reliable repeatability and intermediate precision of HPLC assay procedures.

A multi-company investigation is presented to obtain and compare precision results for LC assay procedures. Forty-four drug substances and drug products of various types subjected to 156 stability studies, with 2915 assay values in total, were included. This provides an excellent source of real long-term precision estimates, as the same analytical procedure was applied during the whole stability study, extending from 12 to 60 months. Intermediate precision was calculated either using the residual standard deviation of the regression line or applying an analysis of variances, depending on whether there was a significant degradation of the analyte or not. The results show impressively the large intervals where the individually calculated parameters scatter. Distribution ranges and averages for repeatability, intermediate precision, and the ratio between the two precision levels are mainly dependent on the type of drug product. Repeatabilities were found up to 0.8% for solutions, 1.6% for drug substances, 1.9% for tablets, 2.3% for creams, and 3.4% for a bath. For intermediate precision, which includes additional variability factors due to the reference standard, operator, equipment, reagents, etc., a similar dependency was obtained with a slightly changed order: up to 1.1% for drug substances, 2.2% for solutions, 2.3% for tablets, 3.1% for creams, and 3.2% for a bath. The ratio between the precision levels is up to 2.5 and similar for all investigated drug product types, apart from solutions with up to 5.3. These differences for the types of drug product may be explained by the influence of the sample and/or the sample preparation: the more complex, the higher the variability contribution. For the investigated examples, the impact of the analyte and of the concentration (dosage) seems to be of less importance. Therefore, a classification of drug product types for orientation on acceptable precision (ranges) for LC assay seems to be possible.

Algorithms↗
PubMed2002

Validation of a LC method for the analysis of oxaliplatin in a pharmaceutical formulation using an experimental design.

A rapid and sensitive RP-HPLC method with UV detection for routine control of oxaliplatin in a pharmaceutical formulation (Eloxatin) was developed. Quantitation was accomplished with the internal standard method. The procedure was validated by linearity (correlation coefficient=0.999948), accuracy, robustness and intermediate precision. Experimental design was used during validation to calculate method robustness and intermediate precision. For robustness test three factors were considered: percentage v/v of acetonitrile, flow rate and temperature; an increase in the flow rate results in a decrease of the drug found concentration, while the percentage of organic modifier and temperature have no important effect on the response. For intermediate precision measure the considered variables were: analyst, equipment and days. The RSD value (2.27%, n=24) indicated a good precision of the analytical method.

Antineoplastic Agents↗
PubMed1999

Comparing participants and nonparticipants in a smoking cessation trial: selection factors associated with general practitioner recruitment activity.

We studied the relationship between smokers' sociodemographic characteristics, their smoking habit, health status, and the probability of their having been approached for recruitment in the smoking cessation trial performed in Turin, Italy, with the aim of gathering information on the role of selection criteria adopted by general practitioners (GPs) in offering anti-smoking counseling. The 965 smokers who were offered participation in the trial were matched to a sample of eligible smokers (n = 277), selected from the rosters of the 42 GPs collaborating in the trial, who had not been invited to participate. The probability of being offered enrollment, estimated through a multiple conditional logistic regression model, assuming the GP as the matching variable, was significantly increased for intermediate (10-19 cigarettes per day: odds ratio [OR] = 4.13; 95% confidence interval [CI]: 2.63-6.47) and heavy (20 cigarettes per day or more: OR = 10.12; 95% CI: 6.51-15.75) smokers, for smokers diagnosed with chronic cardiovascular (OR = 2.06; 95% CI: 1.19-3.58), or respiratory (OR = 2.50; 95% CI: 1.40-4.48) diseases, and for smokers mentioning an intermediate number (2-4) of past quit attempts (OR = 3.70; 95% CI: 2.18-6.28). General Practitioners focused their recruitment activity on higer-risk smokers or smokers who had tried to quit, to offer more clues for intervention. Assessing the potential public health benefit of preventive interventions requires a more systematic evaluation of the generalizability of the reported findings.

Adult↗
PubMed1982

Subunit structure of insulin receptor of rat adipocytes as demonstrated by photoaffinity labeling.

Isolated rat adipocytes were incubated in the dark with either one or two radioiodinated photoreactive insulin derivatives, N epsilon B29-(azidobenzoyl) insulin (B29-MABI) and N alpha B1-(azidobenzoyl) insulin (B1-MABI), and were then exposed to light. Sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis and radioautography of the crude plasma membrane fraction after reduction showed that B29-MABI labeled specifically three proteins of Mr 130 000, 90 000, and 40 000 whereas B1-MABI labeled specifically two proteins of Mr 130 000 and 40 000. B1-MABI also variably labeled some bands of intermediate Mr between 130 000 and 90 000. In contrast, the labeling of the 40-kilodalton protein was not observed in our previous studies in which photolabeling was carried our on isolated plasma membrane preparations [Yip, C. C., Yeung, C. W. T. & Moule, M. L. (1980) Biochemistry 19, 70-76; Yeung, C. W. T., Moule, M. L., & Yip, C. C. (1980) Biochemistry 19, 2196-2203]. Without reduction, an Mr 300 000 band and a larger band which barely entered a 5-15% gradient gel were specifically labeled by both photoreactive insulins. Reduction of these two high molecular weight bands gave rise to the 130-, 90-, and 40-kilodalton bands. The labeling of these proteins was affected neither by the time or temperature of incubation nor by the addition of methylamine, chloroquine, bacitracin, phenylmethanesulfonyl fluoride, p-(chloromercuri) benzenesulfonic acid, Trasylol, N-ethylmaleimide, or benzamidine. The labeling of these proteins by the photoreactive insulin derivatives was inhibited by first incubating the adipocytes with a human autoimmune serum to insulin receptor. We therefore conclude that these proteins are subunits of the insulin receptor in intact adipocytes.

Adipose Tissue↗
PubMed2004

Scaling and management of fecal indicator bacteria in runoff from a coastal urban watershed in southern California.

This paper describes a series of field studies aimed at identifying the spatial distribution and flow forcing of fecal indicator bacteria in dry and wet weather runoff from the Talbert watershed, a highly urbanized coastal watershed in southern California. Runoff from this watershed drains through tidal channels to a popular public beach, Huntington State Beach, which has experienced chronic surf zone water quality problems over the past several years. During dry weather, concentrations of fecal indicator bacteria are highest in inland urban runoff, intermediate in tidal channels harboring variable mixtures of urban runoff and ocean water, and lowest in ocean water at the base of the watershed. This inland-to-coastal gradient is consistent with the hypothesis that urban runoff from the watershed contributes to coastal pollution. On a year round basis, the vast majority (>99%) of fecal indicator bacteria loading occurs during storm events when runoff diversions, the management approach of choice, are not operating. During storms, the load of fecal indicator bacteria in runoff follows a power law of the form L approximately Qn, where L is the loading rate (in units of fecal indicator bacteria per time), Q is the volumetric flow rate (in units of volume per time), and the exponent n ranges from 1 to 1.5. This power law and the observed range of exponent values are consistent with the predictions of a mathematical model that assumes fecal indicator bacteria in storm runoff originate from the erosion of contaminated sediments in drainage channels or storm sewers. The theoretical analysis, which is based on a conventional model for the shear-induced erosion of particles from land and channel-bed surfaces, predicts that the magnitude of the exponent n reflects the geometry of the stormwater conveyance system from which the pollution derives. This raises the possibility that the scaling properties of pollutants in stormwater runoff (i.e., the value of n) may harbor information about the origin of nonpoint source pollution.

Bacteria↗
PubMed2006

Synthesis and characterization of triazenide and triazene complexes of ruthenium and osmium.

Triazenide [M(eta2-1,3-ArNNNAr)P4]BPh4 [M = Ru, Os; Ar = Ph, p-tolyl; P = P(OMe)3, P(OEt)3, PPh(OEt)2] complexes were prepared by allowing triflate [M(kappa2-OTf)P4]OTf species to react first with 1,3-ArN=NN(H)Ar triazene and then with an excess of triethylamine. Alternatively, ruthenium triazenide [Ru(eta2-1,3-ArNNNAr)P4]BPh4 derivatives were obtained by reacting hydride [RuH(eta2-H2)P4]+ and RuH(kappa1-OTf)P4 compounds with 1,3-diaryltriazene. The complexes were characterized by spectroscopy and X-ray crystallography of the [Ru(eta2-1,3-PhNNNPh){P(OEt)3}4]BPh4 derivative. Hydride triazene [OsH(eta1-1,3-ArN=NN(H)Ar)P4]BPh4 [P = P(OEt)3, PPh(OEt)2; Ar = Ph, p-tolyl] and [RuH{eta1-1,3-p-tolyl-N=NN(H)-p-tolyl}{PPh(OEt)2}4]BPh4 derivatives were prepared by allowing kappa1-triflate MH(kappa1-OTf)P4 to react with 1,3-diaryltriazene. The [Os(kappa1-OTf){eta1-1,3-PhN=NN(H)Ph}{P(OEt)3}4]BPh4 intermediate was also obtained. Variable-temperature NMR studies were carried out using 15N-labeled triazene complexes prepared from the 1,3-Ph15N=N15N(H)Ph ligand. Osmium dihydrogen [OsH(eta2-H2)P4]BPh4 complexes [P = P(OEt)3, PPh(OEt)2] react with 1,3-ArN=NN(H)Ar triazene to give the hydride-diazene [OsH(ArN=NH)P4]BPh4 derivatives. The X-ray crystal structure determination of the [OsH(PhN=NH){PPh(OEt)2}4]BPh4 complex is reported. A reaction path to explain the formation of the diazene complexes is also reported.

Journal Article↗