A Study of the Electrical Double Layer

The thesis is divided into four sections. A. The introduction traces the development of electrical double layer theory and outlines the essentials of the Helmholtz, Gouy-Chapman, and Stern concepts. The ideal polarised electrode is then considered, and the application of electrocapillarity techniques to the structural elucidation of the metal-solution interface is discussed. Modifications and extensions of the Stern theory described by Grahame are then introduced, and finally the principal experimental methods of double layer investigation are summarised. B. This is the main section of the work. It describes first an accurate alternating current bridge system designed to measure the differential capacity of the interface at a dropping mercury cathode in contact with a solution of some indifferent electrolyte. Thereafter the results obtained by this method are presented. Capacity data for aqueous N/10 potassium chloride are reported. The minimum value of 16.7 muF/cm2. is in good agreement with 16.1 muF/cm2. determined by Grahame. The effects on capacity of the addition of trace concentrations of a number of surface active substances, i.e., gelatin, eosin, methyl red, and pyridine were then investigated, and finally, pseudo capacities obtained in the presence of small concentrations of salts such as cadmium chloride, were used to determine the effects of the reagents already mentioned, on reversible reduction of the cation. The remaining part of this section is concerned with a systematic examination of capacity phenomena in some non aqueous solvents. Electrocapillarity measurements, using a capillary electrometer method were also made. Minimum capacities of 6.84 and 11.46 muF/cm2. were found for anhydrous acetic and formic acids respectively. The supporting electrolytes were 1 molal ammonium acetate and 1 molal ammonium formate. Although the high decomposition potential of sulphuric acid restricted capacity determinations, a value of 17.75 muF/cm2. for 98% (w/w ) acid is reported at -0.6 volt v. a mercury pool reference electrode. Surface charge densities have been derived both from electrocapillarity differentiation and capacity integration, and electrocapillarity curves have been determined by a further integration. Capacity and electrocapillarity data for water, anhydrous methanol, ethanol, n-propanol and pyridine with 1 molal lithium chloride as supporting electrolyte are presented. Some of the experimental work was carried out by the late Dr. J. C. James just prior to his death and so it was thought to be appropriate to complete the work and to extend it to other systems. Thus, surface charge densities and electrocapillarity curves for the non aqueous solvents above have been derived from capacity integration. The minimum capacity values for water, methanol, ethanol, n-propanol, and pyridine were found to be 16.25, 9.50, 8.00, 8.00, and 5.75 muF/cm2. The effects of cation variation for a given anion in methanol were determined by comparison of cathodic capacities for 1 molal lithium, sodium, potassium, and ammonium iodides. The same trends as in aqueous solution were found, but the effects were much more pronounced. C. A double layer capacity investigation of the system Cu/Cu++ was carried out by two different methods. The electrolyte was 0.5 M copper sulphate -1N sulphuric acid. An alternating current bridge system similar to that already mentioned was first used. The results were found to be frequency dependent, but a minimum capacity of 55 muF/cm2. at 10,000 cycles per second is reported. The second method employed an oscillographic technique designed to present cathodic double layer charging curves, the slope of which measures capacity. The oscillograms obtained were initially linear prior to electrolysis, but the slopes were highly susceptible to current density variations. The effects on the capacity of the copper system of trace concentrations of gelatin and thiourea were also investigated. D. The last section reports work of a different nature, viz. , the ion association which occurs between cations and dicarboxylate anions in aqueous solution. This was studied by potentiometric, conductometric, and spectrophotometric methods. Equilibrium constants are given, and the significance of these results is discussed

Weed Control in Lawns and Other Turf

Guide to weed control in lawns and other turf discusses methods of weed control, time of application, calibration of sprayers, dry spreaders, control of common weeds, and cleaning the sprayer

Antigenic mapping of an H9N2 avian influenza virus reveals two discrete antigenic sites and a novel mechanism of immune escape

H9N2 avian influenza virus is a major cause of poultry production loss across Asia leading to the wide use of vaccines. Efficacy of vaccines is often compromised due to the rapid emergence of antigenic variants. To improve the effectiveness of vaccines in the field, a better understanding of the antigenic epitopes of the major antigen, hemagglutinin, is required. To address this, a panel of nine monoclonal antibodies were generated against a contemporary Pakistani H9N2 isolate, which represents a major Asian H9N2 viral lineage. Antibodies were characterized in detail and used to select a total of 26 unique ‘escape’ mutants with substitutions across nine different amino acid residues in hemagglutinin including seven that have not been described as antigenic determinants for H9N2 viruses before. Competition assays and structural mapping revealed two novel, discrete antigenic sites “H9-A” and “H9-B”. Additionally, a second subset of escape mutants contained amino acid deletions within the hemagglutinin receptor binding site. This constitutes a novel method of escape for group 1 hemagglutinins and could represent an alternative means for H9N2 viruses to overcome vaccine induced immunity. These results will guide surveillance efforts for arising antigenic variants as well as evidence based vaccine seed selection and vaccine design

THE BALL ORIENTATIONS USED BY PLACE KICKERS AT THE 2019 RUGBY WORLD CUP AND THEIR ASSOCIATIONS WITH KICK SUCCESS

The outcomes of place kicks can have a large impact on Rugby Union match results. This study investigated the ball orientations used in place kicking and their potential implications for success. All 416 place kicks from the 2019 Rugby World Cup were grouped into one of three ball orientation categories, and predicted odds of success were calculated for each category using a binomial logistic regression which accounted for situational factors known to affect performance outcome. Kicks taken using a slanted orientation (n = 152) had the greatest odds of success (90.0%) when taken from the mean tournament distance (29.7 m), compared to a near vertical (n = 116) orientation (84.4%), and near horizontal (n = 148) orientation (86.8%). A further investigation into the impact characteristics associated with each ball orientation is required to better understand the relative merits of each

Relationship between premature ventricular complexes and depressive symptoms in non-ST-elevation acute coronary syndrome

Aims: Depression is a recognized risk marker for mortality among acute coronary syndrome (ACS) patients. We hypothesized that ventricular arrhythmia detected by inpatient telemetry monitoring is more frequent among ACS patients with elevated depressive symptoms compared to those without depressive symptoms. Methods and results: We analysed data from patients enrolled in a prospective observational study of depression in ACS. Telemetry recordings during the index admission (average recording 21.3±3.0 hours) were analysed for frequent premature ventricular complexes (PVCs), defined as ≥10 per hour. The self-report Beck Depression Inventory (BDI) was used to assess depressive symptoms. Among 200 ACS patients, frequent PVCs were observed in 29% of patients with moderate depressive symptoms (BDI ≥10), 27% of those with mild symptoms (BDI 5–9), and only 11% of those with no/minimal symptoms (p=0.02). Log-transformed PVCs per hour were associated with depressive symptom category (p=0.008). In a multivariable logistic regression model that included age, gender, left ventricular ejection fraction, cardiovascular risk score, heart rate, and QT interval, mild symptoms (OR 3.02, 95% 0.97–9.43, p=0.058) and moderate-severe symptoms (OR 3.94, 95% CI 1.27–12.22, p=0.018) were associated with frequent PVCs. Conclusions: In this sample of ACS patients, depressive symptoms were independently associated with frequent PVCs during inpatient telemetry monitoring

N-Terminal Pro–B-Type Natriuretic Peptide in the Emergency Department: The ICON-RELOADED Study

Background Contemporary reconsideration of diagnostic N-terminal pro–B-type natriuretic peptide (NT-proBNP) cutoffs for diagnosis of heart failure (HF) is needed. Objectives This study sought to evaluate the diagnostic performance of NT-proBNP for acute HF in patients with dyspnea in the emergency department (ED) setting. Methods Dyspneic patients presenting to 19 EDs in North America were enrolled and had blood drawn for subsequent NT-proBNP measurement. Primary endpoints were positive predictive values of age-stratified cutoffs (450, 900, and 1,800 pg/ml) for diagnosis of acute HF and negative predictive value of the rule-out cutoff to exclude acute HF. Secondary endpoints included sensitivity, specificity, and positive (+) and negative (−) likelihood ratios (LRs) for acute HF. Results Of 1,461 subjects, 277 (19%) were adjudicated as having acute HF. The area under the receiver-operating characteristic curve for diagnosis of acute HF was 0.91 (95% confidence interval [CI]: 0.90 to 0.93; p < 0.001). Sensitivity for age stratified cutoffs of 450, 900, and 1,800 pg/ml was 85.7%, 79.3%, and 75.9%, respectively; specificity was 93.9%, 84.0%, and 75.0%, respectively. Positive predictive values were 53.6%, 58.4%, and 62.0%, respectively. Overall LR+ across age-dependent cutoffs was 5.99 (95% CI: 5.05 to 6.93); individual LR+ for age-dependent cutoffs was 14.08, 4.95, and 3.03, respectively. The sensitivity and negative predictive value for the rule-out cutoff of 300 pg/ml were 93.9% and 98.0%, respectively; LR− was 0.09 (95% CI: 0.05 to 0.13). Conclusions In acutely dyspneic patients seen in the ED setting, age-stratified NT-proBNP cutpoints may aid in the diagnosis of acute HF. An NT-proBNP <300 pg/ml strongly excludes the presence of acute HF

The effect of Staphylococcus aureus carriage in late pregnancy on antibody levels to staphylococcal toxins in cord blood and breast milk.

We investigated the effect of carriage of Staphylococcus aureus in the later stages of pregnancy on levels of antibody specific to the S. aureus toxins, staphylococcal enterotoxin B (SEB), staphylococcal enterotoxin C (SEC) and toxic shock syndrome toxin-1 (TSST-1), in cord blood and breast milk and also explored the relationship between levels of antibody in antenatal serum and cord blood. Nasopharyngeal swabs and stool samples were collected on two occasions, from 96 women, during the last 6 weeks of pregnancy. Samples were cultured and S. aureus isolates were identified. Antenatal and cord blood samples from the same women and their infants were analysed for IgG antibody to SEB, SEC and TSST-1 by enzyme-linked immunosorbent assay. Breast milk samples were analysed for IgA antibody to the same toxins. We found that S. aureus carriage in pregnancy is common and exposure to a toxin-producing isolate boosts immunity. Over 89% of women and infants have some protective antibody to the toxins, and antitoxin IgG levels are higher in cord blood samples compared with antenatal samples. Levels of cord blood IgG and breast milk IgA specific for the staphylococcal toxins vary. Some infants lack protection and could be at risk of toxin-induced disease

Fitbit®: An accurate and reliable device for wireless physical activity tracking

Although physicians recognize the importance of physical activity in the prevention and maintenance of chronic diseases, few incorporate physical activity counseling into routine clinic visits. One major barrier has been the paucity of means to objectively assess patient's long-term physical activity patterns. We investigated if the Fitbit®, one of the most common wireless physical activity trackers in the consumer market, met reasonable validity and reliability standards such that they could be used by primary care physicians to monitor their patient's physical activity objectively between clinic visits. Keywords: Physical activity; Validation; Activity monitoring; Accelerometer; Walking; Fitbi