Methodological Issues in Multistage Genome-Wide Association Studies

Because of the high cost of commercial genotyping chip technologies, many investigations have used a two-stage design for genome-wide association studies, using part of the sample for an initial discovery of ``promising'' SNPs at a less stringent significance level and the remainder in a joint analysis of just these SNPs using custom genotyping. Typical cost savings of about 50% are possible with this design to obtain comparable levels of overall type I error and power by using about half the sample for stage I and carrying about 0.1% of SNPs forward to the second stage, the optimal design depending primarily upon the ratio of costs per genotype for stages I and II. However, with the rapidly declining costs of the commercial panels, the generally low observed ORs of current studies, and many studies aiming to test multiple hypotheses and multiple endpoints, many investigators are abandoning the two-stage design in favor of simply genotyping all available subjects using a standard high-density panel. Concern is sometimes raised about the absence of a ``replication'' panel in this approach, as required by some high-profile journals, but it must be appreciated that the two-stage design is not a discovery/replication design but simply a more efficient design for discovery using a joint analysis of the data from both stages. Once a subset of highly-significant associations has been discovered, a truly independent ``exact replication'' study is needed in a similar population of the same promising SNPs using similar methods.Comment: Published in at http://dx.doi.org/10.1214/09-STS288 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Parasites of Nile tilapia (Oreochromisniloticus) from selected fish farms and Lake Koftuin central Ethiopia

This study was conducted from October 2016 to January 2017 at Lake Koftu, Sebeta ponds and selected private fish farms in Wonchi area, Ethiopia. The main objective was to identify the major parasites of Oreochromis niloticus to the lowest possible Taxa, thereby determine the prevalence, mean intensities and mean abundances of parasites. A total of 302 O. niloticus (101 from Lake Koftu, 127 from Sebeta pond and 72 from selected small scale fish farms) were collected and examined for the presence of parasites.The overall prevalence of all parasites in Lake Koftu, Sebeta ponds and private fish farms were found to be 100%, 71.0% and 82.2% respectively. There was statistically significant difference (p<0.05) between the study sites in overall prevalence. Nine Taxa of parasites were identified in Lake Koftu, the Trematode Tylodelpyes spp. being the most prevalent parasite (93.1%). In Sebeta fish ponds, 11 Taxa of parasites were recovered from O. niloticus with the most prevalent parasite being Trichodina (37.5%) and four Taxa of parasites from small scale fish farms were identified and the highest prevalent parasite being with Trichodina spp (53.25%). The study showed that fingerlings from Lake Koftu had high prevalence of parasitic infestation and hence may be source of parasites for others when used for stocking small scale fish farms requiring intervention measures such as deworming before being stocked to other farms.Keywords: Ethiopia; Fish farms; Lake Koftu; Oreochromis niloticus; Parasites, Prevalenc

Session, Segmented Session, and Acute RPE and Affective Responses to Self-selected Treadmill Exercise

Please view abstract in the attached PDF file

Adenoma Characteristics at First Colonoscopy as Predictors of Adenoma Recurrence and Characteristics at Follow-Up

All patients with colorectal adenomas may not require identical follow-up. We aimed to determine if adenoma characteristics at initial colonoscopy could predict adenoma recurrence or characteristics at follow-up. The number of adenomas and the size, type, and degree of atypia in 479 patients in a polyp prevention trial were evaluated as predictors of the same characteristics at follow-up using odds ratios (ORs) with 95% confidence intervals (CIs). Multiple logistic regression analysis was performed to determine if several baseline characteristics were simultaneously associated with outcome

Probing the reaction pathway in (La_(0.8)Sr_(0.2))_(0.95)MnO_(3+δ) using libraries of thin film microelectrodes

Libraries of (La_(0.8)Sr_(0.2))_(0.95)MnO_(3+δ) (LSM) thin film microelectrodes with systematically varied thickness or growth temperature were prepared by pulsed laser deposition, and a novel robotic instrument was used to characterize these libraries in automated fashion by impedance spectroscopy. The measured impedance spectra are found to be described well by an electrochemical model based on a generalized transmission model for a mixed conducting oxide, and all trends are consistent with a reaction pathway involving oxygen reduction over the LSM surface followed by diffusion through the film and into the electrolyte substrate. The surface activity is found to be correlated with the number of exposed grain boundary sites, which decreases with either increasing film thickness (at constant growth temperature) or increasing film growth temperature (at constant thickness). These findings suggest that exposed grain boundaries in LSM films are more active than exposed grains towards the rate-limiting surface process, and that oxygen ion diffusion through polycrystalline LSM films is faster than many prior studies have concluded

Bulk Properties of the Oxygen Reduction Catalyst SrCo_(0.9)Nb_(0.1)O_(3-δ)

The perovskite SrCo_(0.9)Nb_(0.1)O_(3−δ) (SCN) has excellent electrochemical activity toward oxygen reduction, and it is also valuable as a possible model material for other state-of-the-art perovskite catalysts based on strontium and cobalt, such as Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ) (BSCF). Here we report thermogravimetric, conductivity, and diffraction measurements from SCN. We find that the thermodynamic stability limits of SCN are slightly more favorable than those reported for BSCF, although both materials exhibit a slow oxidative partial decomposition under likely operating conditions. In SCN, this decomposition is thermodynamically preferred when the average formal oxidation state of cobalt is greater than ∼3.0+, but due to sluggish kinetics, metastable SCN with higher cobalt valence can be observed. The oxygen stoichiometry 3−δ varies from 2.45 to 2.70 under the conditions studied, 500–1000 °C and 10^(–4)–1 bar O_2, which encompass both stable and metastable behavior. The electronic conductivity is p-type and thermally activated, with a value at 600 °C in air of 250 S cm^(–1), comparable to that of La_(0.8)Sr_(0.2)MnO_(3−δ). The polaron migration enthalpy decreases linearly from 0.30 to 0.05 eV as 3−δ increases from 2.52 to 2.64. Thermal and chemical expansivities are also reported

Measuring effect of the blooming of chemical curatives on the rate of cyclic fatigue crack growth in natural rubber filled with a silanized silica nanofiller

Two rubber compounds with different amounts of chemical curatives were prepared by mixing natural rubber with a high loading of a sulfur-bearing silanized precipitated amorphous white silica nanofiller. The chemical bonding between the filler and rubber was optimized via the tetrasulfane groups of the silane by adding a sulfenamide accelerator and zinc oxide. The rubber compounds were cured and stored at ambient temperature for 65 days before they were tested. One compound showed extensive blooming as a function of storage time. Thin tensile strips of the rubber vulcanizates containing an edge crack were repeatedly stressed at constant strain amplitude and test frequency at ambient temperature and crack length c was measured as a function of the number of cycles n. The cut growth per cycle, dc/dn, was calculated and plotted against the tearing energy, T. The blooming of the chemical curatives increased dc/dn by up to an order of magnitude at a constant T. This was due to the reagglomeration of the chemical curatives in the rubber and also within a thin layer approximately 15 to μm in size beneath the rubber surface. Under repeated stressing, cracks grew through the relatively weak agglomerated areas in the rubber and this caused the rate of crack growth to increase at a constant T

Meat intake, cooking-related mutagens and risk of colorectal adenoma in a sigmoidoscopy-based case-control study

Reported habits of red meat consumption, particularly red meat that has been cooked to the degree termed ‘well-done', is a positive risk factor for colorectal cancer. Under high, pyrolytic temperatures, heterocyclic amines (HCA) and benzo[a]pyrene (BP) molecules can form inside and on the surface of red meat, respectively. These compounds are precursors that are metabolically converted to compounds known to act as mutagens and carcinogens in animal models, yet their role in human colorectal carcinogenesis remains to be clarified. We investigated whether intake of these compounds is associated with risk of colorectal adenoma in the context of a polyp-screening study conducted in Southern California. Using a database of individual HCAs and BP in meats of various types and subjected to specified methods and degrees of cooking, we estimated nanogram consumption of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-3,4,8-trimethylimidazo[4,5-f] quinoxaline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and benzo[a]pyrene (BP). We observed a 6% increased risk of large (>1 cm) adenoma per 10 ng/day consumption of BP [OR = 1.06 (95% CI, 1.00-1.12), P (trend) = 0.04]. A major source of BP is red meat exposed to a naked flame, as occurs during the barbecuing process. Consistent with this finding an incremental increase of 10 g of barbecued red meat per day was associated with a 29% increased risk of large adenoma [OR = 1.29 (95% CI, 1.02-1.63), P (trend) = 0.04]. Individuals in the top quintile of barbecued red meat intake were at increased risk of large adenoma [OR = 1.90 (95% CI, 1.04-3.45)], compared with never consuming barbecued red meat. The consumption of oven-broiled red meat was inversely related to adenoma risk compared with non-consumers [OR = 0.49 (95% CI, 0.28-0.85)]. We did not identify any association with consumption of individual HCAs and colorectal adenoma risk. These results support the hypothesis that BP contributes to colorectal carcinogenesi