Persistence of transition state structure in chemical reactions driven by fields oscillating in time

Chemical reactions subjected to time-varying external forces cannot generally be described through a fixed bottleneck near the transition state barrier or dividing surface. A naive dividing surface attached to the instantaneous, but moving, barrier top also fails to be recrossing-free. We construct a moving dividing surface in phase space over a transition state trajectory. This surface is recrossing-free for both Hamiltonian and dissipative dynamics. This is confirmed even for strongly anharmonic barriers using simulation. The power of transition state theory is thereby applicable to chemical reactions and other activated processes even when the bottlenecks are time-dependent and move across space

Chemical reactions induced by oscillating external fields in weak thermal environments

Chemical reaction rates must increasingly be determined in systems that evolve under the control of external stimuli. In these systems, when a reactant population is induced to cross an energy barrier through forcing from a temporally varying external field, the transition state that the reaction must pass through during the transformation from reactant to product is no longer a fixed geometric structure, but is instead time-dependent. For a periodically forced model reaction, we develop a recrossing-free dividing surface that is attached to a transition state trajectory [T. Bartsch, R. Hernandez, and T. Uzer, Phys. Rev. Lett. 95, 058301 (2005)]. We have previously shown that for single-mode sinusoidal driving, the stability of the time-varying transition state directly determines the reaction rate [G. T. Craven, T. Bartsch, and R. Hernandez, J. Chem. Phys. 141, 041106 (2014)]. Here, we extend our previous work to the case of multi-mode driving waveforms. Excellent agreement is observed between the rates predicted by stability analysis and rates obtained through numerical calculation of the reactive flux. We also show that the optimal dividing surface and the resulting reaction rate for a reactive system driven by weak thermal noise can be approximated well using the transition state geometry of the underlying deterministic system. This agreement persists as long as the thermal driving strength is less than the order of that of the periodic driving. The power of this result is its simplicity. The surprising accuracy of the time-dependent noise-free geometry for obtaining transition state theory rates in chemical reactions driven by periodic fields reveals the dynamics without requiring the cost of brute-force calculations

The effects of nitroxyl (HNO) on soluble guanylate cyclase activity: interactions at ferrous heme and cysteine thiols

It has been previously proposed that nitric oxide (NO) is the only biologically relevant nitrogen oxide capable of activating the enzyme soluble guanylate cyclase (sGC). However, recent reports implicate HNO as another possible activator of sGC. Herein, we examine the affect of HNO donors on the activity of purified bovine lung sGC and find that, indeed, HNO is capable of activating this enzyme. Like NO, HNO activation appears to occur via interaction with the regulatory ferrous heme on sGC. Somewhat unexpectedly, HNO does not activate the ferric form of the enzyme. Finally, HNO-mediated cysteine thiol modification appears to also affect enzyme activity leading to inhibition. Thus, sGC activity can be regulated by HNO via interactions at both the regulatory heme and cysteine thiols

Biomimetic Sniffing Improves the Detection Performance of a 3D Printed Nose of a Dog and a Commercial Trace Vapor Detector

Unlike current chemical trace detection technology, dogs actively sniff to acquire an odor sample. Flow visualization experiments with an anatomically-similar 3D printed dog’s nose revealed the external aerodynamics during canine sniffing, where ventral-laterally expired air jets entrain odorant-laden air toward the nose, thereby extending the “aerodynamic reach” for inspiration of otherwise inaccessible odors. Chemical sampling and detection experiments quantified two modes of operation with the artificial nose-active sniffing and continuous inspiration-and demonstrated an increase in odorant detection by a factor of up to 18 for active sniffing. A 16-fold improvement in detection was demonstrated with a commercially-available explosives detector by applying this bio-inspired design principle and making the device “sniff” like a dog. These lessons learned from the dog may benefit the next-generation of vapor samplers for explosives, narcotics, pathogens, or even cancer, and could inform future bio-inspired designs for optimized sampling of odor plumes.United States. Department of Homeland Security. Advanced Research Projects Agency (Interagency Agreement HSHQPM-13-X-00107)United States. Air Force (Contract FA8721-05-C-0002)United States. Air Force (Contract FA8702-15-D-0001

“We wanted a forever family”: Altruistic, individualistic, and motivated reasoning motivations for adoption among LGBTQ individuals

The purpose of this study was to explore motivations for adoption among a diverse sample of LGBTQ adoptive parents and prospective adopters (n = 366), who were recruited through a U.K. network of LGBTQ adoptive and foster families to complete an online survey. Quantitative analysis showed that the majority did not think that being LGBTQ would negatively influence their experience of adopting, although they were evenly split regarding the expectation of whether they would be matched with a harder-to-place child. To explore LGBTQ parents’ motivations for adoption, a thematic analysis of the qualitative data was conducted. One overarching theme was identified Seeking permanency, together with three often closely related subthemes: Altruistic/Moral motivation, Individualistic/Intrinsic motivation, and Motivated reasoning. The findings reflect important changes in U.K. law since the Adoption and Children Act in 2002 permitted same-gender couples to adopt. We suggest ways to inform the recruitment of potential LGBTQ adoptive parents

Reframing Kurtz’s Painting: Colonial Legacies and Minority Rights in Ethnically Divided Societies

Minority rights constitute some of the most normatively and economically important human rights. Although the political science and legal literatures have proffered a number of constitutional and institutional design solutions to address the protection of minority rights, these solutions are characterized by a noticeable neglect of, and lack of sensitivity to, historical processes. This Article addresses that gap in the literature by developing a causal argument that explains diverging practices of minority rights protections as functions of colonial governments’ variegated institutional practices with respect to particular ethnic groups. Specifically, this Article argues that in instances where colonial governments politicize and institutionalize ethnic hegemony in the pre-independence period, an institutional legacy is created that leads to lower levels of minority rights protections. Conversely, a uniform treatment and depoliticization of ethnicity prior to independence ultimately minimizes ethnic cleavages post-independence and consequently causes higher levels of minority rights protections. Through a highly structured comparative historical analysis of Botswana and Ghana, this Article builds on a new and exciting research agenda that focuses on the role of long-term historio-structural and institutional influences on human rights performance and makes important empirical contributions by eschewing traditional methodologies that focus on single case studies that are largely descriptive in their analyses. Ultimately, this Article highlights both the strength of a historical approach to understanding current variations in minority rights protections and the varied institutional responses within a specific colonial government

Resting and Exercise Cardiovascular Magnetic Resonance Imaging for the Assessment of Mitral Regurgitation

Background Mitral regurgitation (MR) is a heterogeneous disease requiring accurate investigations to guide optimal management. Cardiovascular magnetic resonance (CMR) provides reference standard biventricular assessment and highly reproducible MR quantification. Exercise-CMR (Ex-CMR) combines CMR with physiological stress; further development may allow comprehensive MR assessment. Therefore CMR is ideal to assist clinical decision making and assess research outcomes. Aims The thesis aims were to: 1) Develop and validate an Ex-CMR protocol assessing biventricular volumes and great vessel flow in healthy volunteers, 2) Evaluate the validated Ex-CMR protocol in primary MR patients, 3) Compare cardiac reverse remodelling and residual MR post mitral valve repair (MVr) vs replacement (MVR) in primary MR patients 4) Assess cardiac reverse remodelling after percutaneous mitral valve intervention for primary MR. Methods 1) Free-breathing, respiratory navigated Compressed-SENSE short-axis cines and aortic/pulmonary phase contrast magnetic resonance sequences were validated against clinical sequences at rest and used during Ex-CMR in 12 healthy volunteers, 2) 10 primary MR patients underwent the validated Ex-CMR protocol, 3) Of 83 moderate-severe primary MR patients, 72 (30 MVr, 22 MVR, 20 controls) completed CMR imaging at baseline and 6 months after mitral surgery or observation (control group). 4) Of 11 primary MR patients, 10 completed CMR imaging at baseline and 6-months after percutaneous intervention. Findings 1) Biventricular volumes and great vessel flow assessment during continuous supine Ex-CMR is feasible in healthy volunteers using the Compressed-SENSE Ex-CMR protocol, demonstrating good/excellent intra/inter-observer reproducibility, 2) The validated Ex-CMR protocol is feasible in asymptomatic primary MR patients demonstrating effective forward left ventricular ejection fraction is augmented by decreases in MR, 3) MVR results in comparable cardiac reverse remodelling to MVr with lower residual quantitated MR and better right ventricular ejection fraction (compared with controls) 4) In primary MR, percutaneous valve intervention results in MR reduction and positive left-ventricular reverse remodelling