Experiences with an Inquiry-Based Ionic Liquid Module in an Undergraduate Physical Chemistry Laboratory.

The topic of ionic liquids is typically not taught at the undergraduate level. Many properties, such as conductivity, vapor pressure, and viscosity, of these so-called "green solvents" are unique compared to traditional molecular solvents. Using active learning techniques, we introduced an ionic liquid module in the physical chemistry laboratory where their structures and physical properties, namely, viscosity, conductivity, and vapor pressure, were explored in relation to molecular solvents. Summative and formative assessments show that a majority of the participants were able to grasp the key concepts of ionic liquids. We envision that our methods and strategies can be one of the building blocks of introducing ionic liquids into the undergraduate chemistry curriculum.

Fentanyl Assay Derived from Intermolecular Interaction-Enabled Small Molecule Recognition (iMSR) with Differential Impedance Analysis for Point-of-Care Testing.

Rapid and effective differentiation and quantification of a small molecule drug, such as fentanyl, in bodily fluids are major challenges for diagnosis and personal medication. However, the current toxicology methods used to measure drug concentration and metabolites require laboratory-based testing, which is not an efficient or cost-effective way to treat patients in a timely manner. Here, we show an assay for monitoring fentanyl levels by combining the intermolecular interaction-enabled small molecule recognition (iMSR) with differential impedance analysis of conjugated polymers. The differential interactions with the designed anchor interface were transduced through the perturbance of the electric status of the flexible conducting polymer. This assay showed excellent fentanyl selectivity against common interferences, as well as in variable body fluids through either testing strips or skin patches. Directly using the patient blood, the sensor provided 1%-5% of the average deviation compared to the "gold" standard method LC-MS results in the medically relevant fentanyl range of 20-90 nM. The superior sensing properties, in conjunction with mechanical flexibility and compatibility, enabled point-of-care detection and provided a promising avenue for applications beyond the scope of biomarker detection.

Using workers' compensation claims to investigate occupational injuries among residential day laborers and domestic workers.

BACKGROUND: While many states have legal provisions to extend workers' compensation eligibility to day laborers or domestic workers hired directly by homeowners or families, little is known about the nature or frequency of injury claims submitted on behalf of these "residential employees." METHODS: We examined California workers' compensation claims records for injuries that appear to have occurred in residential settings between 2008 and 2018 and where the employer of record was an individual or family. We examined the demographic, occupational, and injury characteristics of our sample and analyzed factors that contribute to the likelihood of a claim resulting in some sort of payment. RESULTS: We identified 5,463 workers' compensation claims that were likely submitted on behalf of residential employees. Claims most commonly reflected injuries to workers performing housekeeping tasks, followed by construction/maintenance and caregiving. Workers performing construction/maintenance or gardening/landscaping tasks were more likely to be injured on the same day of hire and were more likely to require hospitalization or emergency treatment for their injuries; however, these workers also had a smaller proportion of claims that resulted in payment. We found that employment tenure had the biggest impact on the likelihood of payment, with the odds increasing sharply after the first day of work. CONCLUSIONS: Although the claims in our data set likely represent only a small fraction of all injuries to residential day laborers and domestic workers during this period, we suggest that workers' compensation claims can provide valuable clues for better understanding occupational injuries among workers in this largely informal sector.

C-D Vibration at C2 Position of Imidazolium Cation as a Probe of the Ionic Liquid Microenvironment.

Unlike molecular solvents, imidazolium-based ionic liquids are entirely made of ions with spatial heterogeneity. There is a need for spectroscopic probes that can assess the microenvironment near the cations of these complex liquids. In this manuscript, we describe simple chemical procedures to label the C2 position of imidazolium cation with a C-D vibrational probe and show, through linear and nonlinear vibrational spectroscopies, that this C-D stretching mode can be a useful analytical tool to assess both the solvent microenvironment and solute-solvent interactions in imidazolium-based ionic liquids from the cation point of view. It is expected that this C-D vibration probe on the cation will lead to the development of innovative experimental strategies that can provide a better understanding of such ionic liquids.

Point-of-Care Determination of Acetaminophen Levels with Multi-Hydrogen Bond Manipulated Single-Molecule Recognition (eMuHSiR).

This work aims to face the challenge of monitoring small molecule drugs accurately and rapidly for point-of-care (POC) diagnosis in current clinical settings. Overdose of acetaminophen (AP), a commonly used over the counter (OTC) analgesic drug, has been determined to be a major cause of acute liver failure in the US and the UK. However, there is no rapid and accurate detection method available for this drug in the emergency room. The present study examined an AP sensing strategy that relies on a previously unexplored strong interaction between AP and the arginine (Arg) molecule. It was found that as many as 4 hydrogen bonds can be formed between one Arg molecule and one AP molecule. By taking advantages of this structural selectivity and high tenability of hydrogen bonds, Arg, immobilized on a graphene surface via electrostatic interactions, was utilized to structurally capture AP. Interestingly, bonded AP still remained the perfect electrochemical activities. The extent of Arg-AP bonds was quantified using a newly designed electrochemical (EC) sensor. To verify the feasibility of this novel assay, based on multihydrogen bond manipulated single-molecule recognition (eMuHSiR), both pharmaceutical and serum sample were examined. In commercial tablet measurement, no significant difference was seen between the results of eMuHSiR and other standard methods. For measuring AP concentration in the mice blood, the substances in serum, such as sugars and fats, would not bring any interference to the eMuHSiR in a wide concentration range. This eMuHSiR method opens the way for future development of small molecule detection for the POC testing.

Implications of Social and Legal Status on Immigrants' Health in Disaster Zones.

This commentary highlights how immigrants who are linguistically isolated, have limited social networks, and lack legal immigration status experience unique health risks in disaster zones. Research on immigrants and disasters tends to focus on immigrants with these characteristics who are residents of disaster-affected areas, disaster recovery workers, or both. We review the sparse research literature and provide examples of innovative but underresourced programs that reduce immigrants' exposure to disaster-related health hazards and economic exploitation in the recovery. We conclude with recommendations for advancing these initiatives while, simultaneously, addressing the anti-immigrant policies that contribute to these disaster-related inequities.

Strength, character, and directionality of halogen bonds involving cationic halogen bond donors.

Halogen bonds involving cationic halogen bond donors and anionic halogen bond acceptors have recently been recognized as being important in stabilizing the crystal structures of many salts. Theoretical characterization of these types of interactions, most importantly in terms of their directionality, has been limited. Here we generate high-quality symmetry adapted perturbation theory potential energy curves of a H3N-C[triple bond, length as m-dash]C-Br+Cl- model system in order to characterize halogen bonds involving charged species, in terms of contributions from electrostatics, exchange, induction, and dispersion, with special emphasis on analyzing contributions that are most responsible for the directionality of these interactions. It is found that, as in the case of neutral halogen bonds, exchange forces are important contributors to the directionality of charged halogen bonds, however, it is also found that induction effects, which contribute little to the stability and directionality of neutral halogen bonds, play a large role in the directionality of halogen bonds involving charged species. Potential energy curves based on the ωB97X-D/def2-TZVP/C-PCM method, which includes an implicit solvation model in order to mimic the effects of the crystal medium, are produced for both the H3N-C[triple bond, length as m-dash]C-Br+Cl- model system and for the 4-bromoaniliniumCl- dimer, which is based on the real 4-bromoanilinium chloride salt, whose crystal structure has been determined experimentally. It is found that, within a crystal-like medium, charged halogen bond are significantly weaker than in the gas phase, having optimum interaction energies up to approximately -20 kcal mol-1.

Ligands of Therapeutic Utility for the Liver X Receptors.

Liver X receptors (LXRs) have been increasingly recognized as a potential therapeutic target to treat pathological conditions ranging from vascular and metabolic diseases, neurological degeneration, to cancers that are driven by lipid metabolism. Amidst intensifying efforts to discover ligands that act through LXRs to achieve the sought-after pharmacological outcomes, several lead compounds are already being tested in clinical trials for a variety of disease interventions. While more potent and selective LXR ligands continue to emerge from screening of small molecule libraries, rational design, and empirical medicinal chemistry approaches, challenges remain in minimizing undesirable effects of LXR activation on lipid metabolism. This review provides a summary of known endogenous, naturally occurring, and synthetic ligands. The review also offers considerations from a molecular modeling perspective with which to design more specific LXRß ligands based on the interaction energies of ligands and the important amino acid residues in the LXRß ligand binding domain.

Exploring the (Very Flat) Potential Energy Landscape of R-Br⋠⋠⋠π Interactions with Accurate CCSD(T) and SAPT Techniques.

Halogen bonds involving an aromatic moiety as an acceptor, otherwise known as R-X⋅⋅⋅π interactions, have increasingly been recognized as being important in materials and in protein-ligand complexes. These types of interactions have been the subject of many recent investigations, but little is known about the ways in which the strengths of R-X⋅⋅⋅π interactions vary as a function of the relative geometries of the interacting pairs. Here we use the accurate CCSD(T) and SAPT2+3δMP2 methods to investigate the potential energy landscapes for systems of HBr, HCCBr, and NCBr complexed with benzene. It is found that only the separation between the complexed molecules have a strong effect on interaction strength while other geometric parameters, such as tilting and shifting R-Br⋅⋅⋅π donor relative to the benzene plane, affect these interactions only mildly. Importantly, it is found that the C6v (T-shaped) configuration is not the global minimum for any of the dimers investigated.

24-hour care: Work and sleep conditions of migrant Filipino live-in caregivers in Los Angeles.

INTRODUCTION: Live-in formal caregivers spend consecutive days in patients' homes, raising questions about their ability to secure adequate sleep while on duty. Few studies have examined sleeping conditions and outcomes for this growing workforce. METHODS: We collected weeklong sleep logs and interview data from 32 Filipino caregivers in Los Angeles who provide live-in services at least 3 consecutive days per week. RESULTS: Respondents recorded a total average of 6.4 sleep hours during workdays divided over 2.4 sleep periods. Caregivers rated sleep quality as lower while at work; over 40% indicated excessive daytime sleepiness. Female caregivers reported worse sleep outcomes than their male counterparts. Some variations in sleep outcomes were found by employment arrangements. CONCLUSION: Live-in caregivers experience frequent sleep interruptions at all hours of the day and night to attend to patients' needs. The resulting impacts on sleep quality pose risks for both work-related injury and errors in patient care. Am. J. Ind. Med. 59:1120-1129, 2016. © 2016 Wiley Periodicals, Inc.

Managers' perceptions of the value and impact of HAZWOPER worker health and safety training.

BACKGROUND: Worker training is a core component of the OSHA Hazardous Waste Operations and Emergency Response (HAZWOPER) standard, but few studies have considered what motivates managers to provide HAZWOPER training to employees or what they value in that training. METHODS: In 2012, four university-based programs conducted an exploratory survey of managers who sent employees to HAZWOPER courses. Results from 109 respondents were analyzed. RESULTS: Forty-two percent of respondents cited regulations as the most important reason to provide HAZWOPER training; many indicated they would provide less training if there were no standard in place. Three-quarters (74%) reported training had improved workplace conditions. Fewer than half said they were likely to involve trained employees in aspects of the organization's H&S program. DISCUSSION: Compliance with regulatory requirements is an important factor shaping managers' training delivery decisions. Managers recognize positive impacts of training. These impacts could be enhanced by further leveraging employee H&S knowledge and skills.

On the importance and origin of aromatic interactions in chemistry and biodisciplines.

Aromatic systems contain both σ- and π-electrons, which in turn constitute σ- and π-molecular orbitals (MOs). In discussing the properties of these systems, researchers typically refer to the highest occupied and lowest unoccupied MOs, which are π MOs. The characteristic properties of aromatic systems, such as their low ionization potentials and electron affinities, high polarizabilities and stabilities, and small band gaps (in spectroscopy called the N → V1 space), can easily be explained based on their electronic structure. These one-electron properties point to characteristic features of how aromatic systems interact with each other. Unlike hydrogen bonding systems, which primarily interact through electrostatic forces, complexes containing aromatic systems, especially aromatic stacked pairs, are predominantly stabilized by dispersion attraction. The stabilization energy in the benzene dimer is rather small (~2.5 kcal/mol) but strengthens with heteroatom substitution. The stacked interaction of aromatic nucleic acid bases is greater than 10 kcal/mol, and for the most stable stacked pair, guanine and cytosine, it reaches approximately 17 kcal/mol. Although these values do not equal the planar H-bonded interactions of these bases (~29 kcal/mol), stacking in DNA is more frequent than H-bonding and, unlike H-bonding, is not significantly weakened when passing from the gas phase to a water environment. Consequently, the stacking of aromatic systems represents the leading stabilization energy contribution in biomacromolecules and in related nanosystems. Therefore stacking (dispersion) interactions predominantly determine the double helical structure of DNA, which underlies its storage and transfer of genetic information. Similarly, dispersion is the dominant contributor to attractive interactions involving aromatic amino acids within the hydrophobic core of a protein, which is critical for folding. Therefore, understanding the nature of aromatic interactions, which depend greatly on quantum mechanical (QM) calculations, is of key importance in biomolecular science. This Account shows that accurate binding energies for aromatic complexes should be based on computations made at the (estimated) CCSD(T)/complete basis set limit (CBS) level of theory. This method is the least computationally intensive one that can give accurate stabilization energies for all common classes of noncovalent interactions (aromatic-aromatic, H-bonding, ionic, halogen bonding, charge-transfer, etc.). These results allow for direct comparison of binding energies between different interaction types. Conclusions based on lower-level QM calculations should be considered with care.

Do No Harm in Global Health Engagement.

This manuscript examines the principle of "Do No Harm" in DoD Global Health Engagement (GHE) efforts. It highlights the potential positive and negative consequences of health investments and explores how unintentional harm is addressed in a global health context. The manuscript also discusses the involvement of the U.S. military in global health and the concept of dual loyalty faced by military GHE practitioners. The goal is to understand the challenges of doing no harm and identify methods to mitigate or avoid unintended negative consequences in DoD GHE activities.

MP2.5 and MP2.X: approaching CCSD(T) quality description of noncovalent interaction at the cost of a single CCSD iteration.

The performance of the second-order Møller-Plesset perturbation theory MP2.5 and MP2.X methods, tested on the S22, S66, X40, and other benchmark datasets is briefly reviewed. It is found that both methods produce highly accurate binding energies for the complexes contained in these data sets. Both methods also provide reliable potential energy curves for the complexes in the S66 set. Among the routinely used wavefunction methods, the only other technique that consistently produces lower errors, both for stabilization energies and geometry scans, is the spin-component-scaled coupled-clusters method covering iterative single- and double-electron excitations, which is, however, substantially more computationally intensive. The structures originated from full geometrical gradient optimizations at the MP2.5 and MP2.X level of theory were confirmed to be the closest to the CCSD(T)/CBS (coupled clusters covering iterative single- and double-electron excitations and perturbative triple-electron excitations performed at the complete basis set limit) geometries among all the tested methods (e.g. MP3, SCS(MI)-MP2, MP2, M06-2X, and DFT-D method evaluated with the TPSS functional). The MP2.5 geometries for the tested complexes deviate from the references almost negligibly. Inclusion of the scaled third-order correlation energy results in a substantial improvement of the ability to accurately describe noncovalent interactions. The results shown here serve to support the notion that MP2.5 and MP2.X are reasonable alternative methods for benchmark calculations in cases where system size or (lack of) computational resources preclude the use of CCSD(T)/CBS computations. MP2.X allows for the use of smaller basis sets (i.e. 6-31G*) with results that are nearly identical to those of MP2.5 with larger basis sets, which dramatically decreases computation times and makes calculations on much larger systems possible.

The relative roles of electrostatics and dispersion in the stabilization of halogen bonds.

In this work we highlight recent work aimed at the characterization of halogen bonds. Here we discuss the origins of the σ-hole, the modulation of halogen bond strength by changing of neighboring chemical groups (i.e. halogen bond tuning), the performance of various computational methods in treating halogen bonds, and the strength and character of the halogen bond, the dihalogen bond, and two hydrogen bonds in bromomethanol dimers (which serve as model complexes) are compared. Symmetry adapted perturbation theory analysis of halogen bonding complexes indicates that halogen bonds strongly depend on both dispersion and electrostatics. The electrostatic interaction that occurs between the halogen σ-hole and the electronegative halogen bond donor is responsible for the high degree of directionality exhibited by halogen bonds. Because these noncovalent interactions have a strong dispersion component, it is important that the computational method used to treat a halogen bonding system be chosen very carefully, with correlated methods (such as CCSD(T)) being optimal. It is also noted here that most forcefield-based molecular mechanics methods do not describe the halogen σ-hole, and thus are not suitable for treating systems with halogen bonds. Recent attempts to improve the molecular mechanics description of halogen bonds are also discussed.

Hydrogen-Bonded Complexes in Binary Mixture of Imidazolium-Based Ionic Liquids with Organic Solvents.

Though local structures in ionic liquids are dominated by strong Coulomb forces, directional hydrogen bonds can also influence the physicochemical properties of imidazolium-based ionic liquids. In particular, the C-2 position of the imidazolium cation is acidic and can bind with suitable hydrogen bond acceptor sites of molecular solvents dissolved in imidazolium-based ionic liquids. In this report, we identify hydrogen-bonded microenvironments of the model ionic liquid, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate, and the changes that occur when molecular solvents are dissolved in it by using a C-D infrared reporter at the C-2 position of the cation. Our linear and nonlinear infrared experiments, along with computational studies, indicate that the molecular solvent dimethyl sulfoxide can form strong hydrogen-bonded dimers with the cation of the ionic liquid at the C-2 position. In contrast, acetone, which is also a hydrogen bond acceptor similar to dimethyl sulfoxide, does not show evidence of cation-solvent hydrogen-bonded conformers at the C-2 position. The outcome of our study on a broad scale strengthens the importance of cation-solute interactions in ionic liquids.

Evaluation of the performance of post-Hartree-Fock methods in terms of intermolecular distance in noncovalent complexes.

Dissociation curves calculated using multiple correlated QM methods for 66 noncovalent complexes (Rezác et al., J Chem Theory Comput 2011, 7, 2427) have allowed us to interpolate equilibrium intermolecular distances for each studied method. Comparison of these data with CCSD(T)/complete basis set reference geometries provides information on how these methods perform in geometry optimizations. The large set of systems considered here is necessary for reliable statistical evaluation of the results and assessment of the robustness of the studied methods. Our results show that advanced methods such as MP3 and CCSD provide significant improvement over MP2 only when empirical scaling is used. The best results can be achieved with spin component scaled CCSD optimized for noncovalent interactions, with a root mean square error of 0.4% of the equilibrium distance. Scaled MP3, the MP2.5 method, yields comparably good results (error 0.5%) while being substantially cheaper.