Marginally unstable Holmboe modes

Marginally unstable Holmboe modes for smooth density and velocity profiles are studied. For a large family of flows and stratification that exhibit Holmboe instability, we show that the modes with phase velocity equal to the maximum or the minimum velocity of the shear are marginally unstable. This allows us to determine the critical value of the control parameter R (expressing the ratio of the velocity variation length scale to the density variation length scale) that Holmboe instability appears R=2. We then examine systems for which the parameter R is very close to this critical value. For this case we derive an analytical expression for the dispersion relation of the complex phase speed c(k) in the unstable region. The growth rate and the width of the region of unstable wave numbers has a very strong (exponential) dependence on the deviation of R from the critical value. Two specific examples are examined and the implications of the results are discussed.Comment: Submitted to Physics of Fluid

Stratified shear flow instabilities at large Richardson numbers

Numerical simulations of stratified shear flow instabilities are performed in two dimensions in the Boussinesq limit. The density variation length scale is chosen to be four times smaller than the velocity variation length scale so that Holmboe or Kelvin-Helmholtz unstable modes are present depending on the choice of the global Richardson number Ri. Three different values of Ri were examined Ri =0.2, 2, 20. The flows for the three examined values are all unstable due to different modes namely: the Kelvin-Helmholtz mode for Ri=0.2, the first Holmboe mode for Ri=2, and the second Holmboe mode for Ri=20 that has been discovered recently and it is the first time that it is examined in the non-linear stage. It is found that the amplitude of the velocity perturbation of the second Holmboe mode at the non-linear stage is smaller but comparable to first Holmboe mode. The increase of the potential energy however due to the second Holmboe modes is greater than that of the first mode. The Kelvin-Helmholtz mode is larger by two orders of magnitude in kinetic energy than the Holmboe modes and about ten times larger in potential energy than the Holmboe modes. The results in this paper suggest that although mixing is suppressed at large Richardson numbers it is not negligible, and turbulent mixing processes in strongly stratified environments can not be excluded.Comment: Submitted to Physics of Fluid

Is It Time for a Universal Genetic Forensic Database?

The ethical objections to mandating forensic profiling of newborns and/or compelling every citizen or visitor to submit to a buccal swab or to spit in a cup when they have done nothing wrong are not trivial. But newborns are already subject to compulsory medical screening, and people coming from foreign countries to the United States already submit to fingerprinting. It is also worth noting that concerns about coercion or invasions of privacy did not give pause to legislatures (or, for that matter, even the European Court) when authorizing compelled DNA sampling from arrestees, who should not forfeit genetic privacy interests simply by virtue of being arrested

The Law of Genetic Privacy: Applications, Implications, and Limitations

Recent advances in technology have significantly improved the accuracy of genetic testing and analysis, and substantially reduced its cost, resulting in a dramatic increase in the amount of genetic information generated, analysed, shared, and stored by diverse individuals and entities. Given the diversity of actors and their interests, coupled with the wide variety of ways genetic data are held, it has been difficult to develop broadly applicable legal principles for genetic privacy. This article examines the current landscape of genetic privacy to identify the roles that the law does or should play, with a focus on federal statutes and regulations, including the Health Insurance Portability and Accountability Act (HIPAA) and the Genetic Information Nondiscrimination Act (GINA). After considering the many contexts in which issues of genetic privacy arise, the article concludes that few, if any, applicable legal doctrines or enactments provide adequate protection or meaningful control to individuals over disclosures that may affect them. The article describes why it may be time to shift attention from attempting to control access to genetic information to considering the more challenging question of how these data can be used and under what conditions, explicitly addressing trade-offs between individual and social goods in numerous applications

Reading sentences of words wtih rotated letters: An eye movement study

Participants’ eye movements were measured as they read sentences in which individual letters within words were rotated. Both the consistency of direction and the magnitude of rotation were manipulated (letters rotated all in the same direction, or alternately clockwise and anti-clockwise; by 30 or 60 degrees). Each sentence included a target word that was manipulated for frequency of occurrence. Our objectives were threefold: To quantify how change in the visual presentation of individual letters disrupted word identification, and whether disruption was consistent with systematic change in visual presentation; to determine whether inconsistent letter transformation caused more disruption than consistent letter transformation; to determine whether such effects were comparable for words that were high and low frequency to explore the extent to which they were visually or linguistically mediated. We found that disruption to reading was greater as the magnitude of letter rotation increased, although even small rotations impacted processing. The data also showed that alternating letter rotations were significantly more disruptive than consistent rotations; this result is consistent with models of lexical identification in which encoding occurs over units of more than one adjacent letter. These rotation manipulations also showed significant interactions with word frequency on the target word: gaze durations and total fixation duration times increased disproportionately for low frequency words when they were presented at more extreme rotations. These data provide a first step towards quantifying the relative contribution of the spatial relationships between individual letters to word recognition and eye movement control in reading

The trans influence in unsymmetrical pincer palladacycles: an experimental and computational study

A library of unsymmetrical SCN pincer palladacycles, [ClPd{2-pyr-6-(RSCH2)C6H3}], R = Et, Pr, Ph, p-MePh, and p-MeOPh, pyr = pyridine, has been synthesized via C–H bond activation, and used, along with PCN and N’CN unsymmetrical pincer palladacycles previously synthesized by the authors, to determine the extent to which the trans influence is exhibited in unsymmetrical pincer palladacycles. The trans influence is quantified by analysis of structural changes in the X-ray crystal and density functional theory (DFT) optimized structures and a topological analysis of the electron density using quantum theory of atoms in molecules (QTAIM) to determine the strength of the Pd-donor atom interaction. It is found that the trans influence is controlled by the nature of the donor atom and although the substituents on the donor-ligand affect the Pd-donor atom interaction through the varied electronic and steric constraints, they do not influence the bonding of the ligand trans to it. The data indicate that the strength of the trans influence is P > S > N. Furthermore, the synthetic route to the family of SCN pincer palladacycles presented demonstrates the potential of late stage derivitization for the effective synthesis of ligands towards unsymmetrical pincer palladacycles

Prenatal development is linked to bronchial reactivity: epidemiological and animal model evidence

Chronic cardiorespiratory disease is associated with low birthweight suggesting the importance of the developmental environment. Prenatal factors affecting fetal growth are believed important, but the underlying mechanisms are unknown. The influence of developmental programming on bronchial hyperreactivity is investigated in an animal model and evidence for comparable associations is sought in humans. Pregnant Wistar rats were fed either control or protein-restricted diets throughout pregnancy. Bronchoconstrictor responses were recorded from offspring bronchial segments. Morphometric analysis of paraffin-embedded lung sections was conducted. In a human mother-child cohort ultrasound measurements of fetal growth were related to bronchial hyperreactivity, measured at age six years using methacholine. Protein-restricted rats' offspring demonstrated greater bronchoconstriction than controls. Airway structure was not altered. Children with lesser abdominal circumference growth during 11-19 weeks' gestation had greater bronchial hyperreactivity than those with more rapid abdominal growth. Imbalanced maternal nutrition during pregnancy results in offspring bronchial hyperreactivity. Prenatal environmental influences might play a comparable role in humans

Nanoparticle metrology of silica colloids and super-resolution studies using the ADOTA fluorophore

We describe how a new fluorescent dye, methyl ADOTA (N-methyl-azadioxatriangulenium tetrafluoroborate), is an improvement on dyes reported previously for measuring silica nanoparticle size in sols using the decay of fluorescence anisotropy. Me(thyl)-ADOTA possesses the unusual combination of having a red emission and a long fluorescence lifetime of ~ 20 ns, leaving it better-placed to reveal particle sizes at the upper end of the 1-10 nm measurement range. For stable LUDOX colloids, Me-ADOTA is shown to offer higher measurement precision in ≤ 1/30th of the measurement time required for dyes previously used. In measurement times of only ~ 20 mins nanoparticle radii for LUDOX SM-AS, AM and AS-40 of 4.6 ± 0.3 nm, 5.9 ± 0.2 nm and 11.1 ± 1.1 nm, are in good agreement with two of the manufacturer’s values of 3.5 nm, 6 nm and 11 nm respectively. Unlike the Si-ADOTA (N-(4-(triethoxysilylethyl)urea-phenyl-) ADOTA tetrafluoroborate) derivative containing a reactive trimetoxysilane group, Me-ADOTA is shown to not induce aggregation of colloidal silica. Measurements on nanoparticles growing in an acidic silica hydrogel at pH 0.94, prior to the gel time of ~ 50 hr, reveals an average nanoparticle size up to ~ 6.3 nm, significantly larger than the 4.5 nm reported previously. The difference is most certainly due to the longer fluorescence lifetime of Me-ADOTA (~ 20 ns) revealing the presence of larger particles. Studies of growing silica clusters in an alcogel of tetraethyl orthosilicate (TEOS) were able to resolve a monotonically increasing average radius of 1.42 ± 0.10 nm to 1.81 ± 0.14 nm over a period of 48 hr. We have also assessed a carboxylic acid derivative of ADOTA (N-(3-carboxypropylene)-ADOTA tetrafluoroborate - Acid-ADOTA) using dSTORM super-resolution microscopy. Although demonstrating high photochemical stability and blinking, its lower brightness and relative propensity to aggregate limits Acid-ADOTA’s use for dSTORM

Antimüllerian hormone in relation to tobacco and marijuana use and sources of indoor heating/cooking

To evaluate exposure to tobacco, marijuana and indoor heating/cooking sources in relation to anti-Müllerian hormone (AMH) levels

Ammonia decomposition catalysis using lithium–calcium imide

Lithium–calcium imide is explored as a catalyst for the decomposition of ammonia. It shows the highest ammonia decomposition activity yet reported for a pure light metal amide or imide, comparable to lithium imide–amide at high temperature, with superior conversion observed at lower temperatures. Importantly, the post-reaction mass recovery of lithium–calcium imide is almost complete, indicating that it may be easier to contain than the other amide–imide catalysts reported to date. The basis of this improved recovery is that the catalyst is, at least partially, solid across the temperature range studied under ammonia flow. However, lithium–calcium imide itself is only stable at low and high temperatures under ammonia, with in situ powder diffraction showing the decomposition of the catalyst to lithium amide–imide and calcium imide at intermediate temperatures of 200–460 °C.</p