Design Rules for Obtaining Narrow Luminescence from Semiconductors Made in Solution.

Solution-processed semiconductors are in demand for present and next-generation optoelectronic technologies ranging from displays to quantum light sources because of their scalability and ease of integration into devices with diverse form factors. One of the central requirements for semiconductors used in these applications is a narrow photoluminescence (PL) line width. Narrow emission line widths are needed to ensure both color and single-photon purity, raising the question of what design rules are needed to obtain narrow emission from semiconductors made in solution. In this review, we first examine the requirements for colloidal emitters for a variety of applications including light-emitting diodes, photodetectors, lasers, and quantum information science. Next, we will delve into the sources of spectral broadening, including "homogeneous" broadening from dynamical broadening mechanisms in single-particle spectra, heterogeneous broadening from static structural differences in ensemble spectra, and spectral diffusion. Then, we compare the current state of the art in terms of emission line width for a variety of colloidal materials including II-VI quantum dots (QDs) and nanoplatelets, III-V QDs, alloyed QDs, metal-halide perovskites including nanocrystals and 2D structures, doped nanocrystals, and, finally, as a point of comparison, organic molecules. We end with some conclusions and connections, including an outline of promising paths forward.

Reductively Stable Hydrogen-Bonding Ligands Featuring Appended CF2-H Units.

We present the development of ligands featuring the unconventional hydrogen bond donor, -CF2H, within a metal's secondary coordination sphere. When metalated with palladium, o-CF2H-functionalized 1,10-phenanthroline provides highly directed H-bonding interactions with Pd-coordinated substrates. Spectroscopic and computational analyses with a series of X-type ligand acceptors (-F, -Cl, -Br, -OR) establish the H-bonding interaction strength for the -CF2H group (∼3 kcal/mol). The synthesis of Pd0/Ni0 complexes and subsequent coupling (Ni) highlight the unique reductive and base compatibility of the -CF2H hydrogen bond donor group.

Defluorinative Functionalization of Pd(II) Fluoroalkyl Complexes.

When subjected to arylboranes, anionic trifluoromethyl and difluorobenzyl palladium(II) complexes undergo fluoride abstraction followed by 1,1-migratory insertion. The resulting intermediate fluoroalkyl species can be induced to undergo a subsequent transmetalation and reductive elimination from either an in situ formed fluoroboronate (FB(Ar3)-) or an exogenous boronic acid/ester (ArB(OR)2) and nucleophilic activator, representing a net defluorinative arylation reaction. The latter method enabled a structurally diverse substrate scope to be prepared from either an isolated palladium-CF3 complex, or from Pd(PPh3)4 and other commercially available reagents.

Hydrogen Bonding to a Dinitrogen Complex at Room Temperature: Impacts on N2 Activation.

We report an experimental and computational analysis of the effects of hydrogen bonding to a metal dinitrogen complex. A series of H-bond donors over a wide p Ka range (Δ 20) interact with the nitrogen unit of a ReI-(N2) complex at room temperature. Analysis by 15N NMR, IR spectroscopy, association equilibria, and DFT studies indicates that the H-bonding interaction polarizes and weakens the N-N bond. These results provide insight into the role of the secondary sphere residues in nitrogenase enzymes.

The Semireduced Mechanism for Nitric Oxide Reduction by Non-Heme Diiron Complexes: Modeling Flavodiiron Nitric Oxide Reductases.

Flavodiiron nitric oxide reductases (FNORs) are a subclass of flavodiiron proteins (FDPs) capable of preferential binding and subsequent reduction of NO to N2O. FNORs are found in certain pathogenic bacteria, equipping them with resistance to nitrosative stress, generated as a part of the immune defense in humans, and allowing them to proliferate. Here, we report the spectroscopic characterization and detailed reactivity studies of the diiron dinitrosyl model complex [Fe2(BPMP)(OPr)(NO)2](OTf)2 for the FNOR active site that is capable of reducing NO to N2O [Zheng et al., J. Am. Chem. Soc. 2013, 135, 4902-4905]. Using UV-vis spectroscopy, cyclic voltammetry, and spectro-electrochemistry, we show that one reductive equivalent is in fact sufficient for the quantitative generation of N2O, following a semireduced reaction mechanism. This reaction is very efficient and produces N2O with a first-order rate constant k > 102 s-1. Further isotope labeling studies confirm an intramolecular N-N coupling mechanism, consistent with the rapid time scale of the reduction and a very low barrier for N-N bond formation. Accordingly, the reaction proceeds at -80 °C, allowing for the direct observation of the mixed-valent product of the reaction. At higher temperatures, the initial reaction product is unstable and decays, ultimately generating the diferrous complex [Fe2(BPMP)(OPr)2](OTf) and an unidentified ferric product. These results combined offer deep insight into the mechanism of NO reduction by the relevant model complex [Fe2(BPMP)(OPr)(NO)2]2+ and provide direct evidence that the semireduced mechanism would constitute a highly efficient pathway to accomplish NO reduction to N2O in FNORs and in synthetic catalysts.

Testing the Push-Pull Hypothesis: Lewis Acid Augmented N2 Activation at Iron.

We present a systematic investigation of the structural and electronic changes that occur in an Fe(0)-N2 unit (Fe(depe)2(N2); depe = 1,2-bis(diethylphosphino)ethane) upon the addition of exogenous Lewis acids. Addition of neutral boranes, alkali metal cations, and an Fe2+ complex increases the N-N bond activation (Δ νNN up to 172 cm-1), decreases the Fe(0)-N2 redox potential, polarizes the N-N bond, and enables -N protonation at uncommonly anodic potentials. These effects were rationalized using combined experimental and theoretical studies.

Bis{(R)-N-[(R)-2-benz-yloxy-1-(4-tert-butyl-phen-yl)eth-yl]-2-methyl-propane-2-sulfinamide} monohydrate.

The asymmetric unit of the title compound, 2C23H33NO2S·H2O, contains one organic mol-ecule in a general position and one co-crystallized water mol-ecule on a crystallographic twofold axis. Each water mol-ecule serves as a hydrogen-bond donor to a pair of S=O acceptors on symmetry-related mol-ecules. Thus, each trio of mol-ecules forms one title formula unit. These groupings are further connected along [010] via weak non-classical C-H⋯O hydrogen bonds.

Pharmacological Characterization of SDX-7320/Evexomostat: A Novel Methionine Aminopeptidase Type 2 Inhibitor with Anti-tumor and Anti-metastatic Activity.

Methionine aminopeptidase type 2 (METAP2) is a ubiquitous, evolutionarily conserved metalloprotease fundamental to protein biosynthesis which catalyzes removal of the N-terminal methionine residue from nascent polypeptides. METAP2 is an attractive target for cancer therapeutics based upon its over-expression in multiple human cancers, the importance of METAP2-specific substrates whose biological activity may be altered following METAP2 inhibition, and additionally, that METAP2 was identified as the target for the anti-angiogenic natural product, fumagillin. Irreversible inhibition of METAP2 using fumagillin analogues has established the anti-angiogenic and anti-tumor characteristics of these derivatives; however, their full clinical potential has not been realized due to a combination of poor drug-like properties and dose-limiting central nervous system (CNS) toxicity. This report describes the physicochemical and pharmacological characterization of SDX-7320 (evexomostat), a polymer-drug conjugate of the novel METAP2 inhibitor (METAP2i) SDX-7539. In vitro binding, enzyme, and cell-based assays demonstrated that SDX-7539 is a potent and selective METAP2 inhibitor. In utilizing a high molecular weight, water-soluble polymer to conjugate the novel fumagillol-derived, cathepsin-released, METAP2i SDX-7539, limitations observed with prior generation, small molecule fumagillol derivatives were ameliorated including reduced CNS exposure of the METAP2i, and prolonged half-life enabling convenient administration. Multiple xenograft and syngeneic cancer models were utilized to demonstrate the anti-tumor and anti-metastatic profile of SDX-7320. Unlike polymer-drug conjugates in general, reductions in small molecule-equivalent efficacious doses following polymer conjugation were observed. SDX-7320 has completed a phase I clinical safety study in patients with late-stage cancer and is currently being evaluated in multiple phase Ib/II clinical studies in patients with advanced solid tumors.

Exposure to social bots amplifies perceptual biases and regulation propensity.

Automated accounts on social media that impersonate real users, often called "social bots," have received a great deal of attention from academia and the public. Here we present experiments designed to investigate public perceptions and policy preferences about social bots, in particular how they are affected by exposure to bots. We find that before exposure, participants have some biases: they tend to overestimate the prevalence of bots and see others as more vulnerable to bot influence than themselves. These biases are amplified after bot exposure. Furthermore, exposure tends to impair judgment of bot-recognition self-efficacy and increase propensity toward stricter bot-regulation policies among participants. Decreased self-efficacy and increased perceptions of bot influence on others are significantly associated with these policy preference changes. We discuss the relationship between perceptions about social bots and growing dissatisfaction with the polluted social media environment.

Tuning ligand field strength with pendent Lewis acids: access to high spin iron hydrides.

Geometrically flexible 9-borabicyclo[3.3.1]nonyl units within the secondary coordination sphere enable isolation of high-spin Fe(ii)-dihydrides stabilized by boron-hydride interactions and a rare example of an isolable S = 3/2 reduction product. The borane-capped Fe(ii)-dihydride: (1) rapidly deprotonates E-H (E = N, O, P, S) bonds to afford borane-stabilized Fe adducts and (2) releases H2 upon exposure to π-acids. The Lewis acids provide an avenue for redox-leveling in analogy to the near constant operating potential for N2 reduction in nitrogenase.

Inexperienced examiners and the Foot Posture Index: A reliability study.

The Foot Posture Index (FPI-6) is a reliable (experienced examiners) assessment tool used in clinical practice to classify foot posture. No work has been completed to determine the reliability of the FPI-6 between novice examiners. Therefore, the aim was to determine the inter-examiner reliability of the FPI-6 using two novice examiners (graduate level osteopathy students). The FPI-6 was used to classify the feet of 83 students recruited as part of a larger study. Data were collected simultaneously by both examiners, but there was no communication between them. The scoring system provided by the FPI-6 manual was used to assess all feet. Collated data were assessed between examiners for reliability based on raw, transformed and foot type scores. The inter-examiner reliability was high for both left (intra-class correlation coefficient ICC2,1 = 0.86) and right (ICC2,1 = 0.85) feet for the novice examiners. When data were assessed based on foot type classification the examiners agreed on 76% of the left feet and 82% of the right feet with Kappa values of 0.73 and 0.72 respectively. The FPI-6 is a robust clinical tool that can be reliably utilised by inexperienced clinicians.

Analyzing media coverage of the global fund diseases compared with lower funded diseases (childhood pneumonia, diarrhea and measles).

BACKGROUND: Pneumonia, diarrhea and measles are the leading causes of death in children worldwide, but have a disproportionately low share of international funding and media attention. In comparison, AIDS, tuberculosis and malaria--diseases that also significantly affect children--receive considerably more funding and have relatively high media coverage. This study investigates the potential relationship between media agenda setting and funding levels in the context of the actual burden of disease. METHODS: The news databases Lexis Nexis, Factiva, and Google News Archive were searched for the diseases AIDS, TB and Malaria and for lower funded pediatric diseases: childhood pneumonia, diarrhea, and measles. A sample of news articles across geographic regions was also analyzed using a qualitative narrative frame analysis of how the media stories were told. RESULTS: There were significantly more articles addressing the Global Fund diseases compared to the lower funded pediatric diseases between 1981 and 2008 (1,344,150 versus 291,865 articles). There were also notable differences in the framing of media narratives: 1) There was a high proportion of articles with the primary purpose of raising awareness for AIDS, TB and malaria (46.2%) compared with only 17.9% of the pediatric disease articles. 2) Nearly two-thirds (61.5%) of the AIDS, tuberculosis and malaria articles used a human rights, legal or social justice frame, compared with 46.2% for the lower funded pediatric disease articles, which primarily used an ethical or moral frame. CONCLUSION: This study demonstrates that lower funded pediatric diseases are presented differently in the media, both quantitatively and qualitatively, than higher funded, higher profile diseases.

Stigmatizing smokers: public sentiment toward cigarette smoking and its relationship to smoking behaviors.

Public sentiment in the United States has been evolving against cigarette smoking. Providing support for stronger tobacco control legislation, unfavorable public sentiment has contributed to the decrease in the size of the smoking population in this country. The present study hypothesizes that the unfavorable public sentiment may also discourage cigarette smoking by creating an unfavorable "smoking climate" in which smoking is socially rejected as a deviant behavior. Analyses of several secondary data-sets provided evidence that smoking rates are lower in the states where the public holds relatively unfavorable sentiment toward cigarette smoking. The relationship between public sentiment and smoking rates was significant even after controlling for the effects of state-level tobacco control measures, such as cigarette taxes and smoking restrictions in private workplaces and restaurants. We also found that smokers who have experienced unfavorable public sentiment are more willing to quit smoking than those who have not, supporting the hypothesized effects of antismoking public sentiment on smoking behaviors.