Intramolecular and intermolecular contributions to the barriers for rotation of methyl groups in crystalline solids: Electronic structure calculations and solid state NMR relaxation measurements

The rotation barriers for 10 different methyl groups in five methyl-substituted phenanthrenes and three methyl-substituted naphthalenes were determined by ab initio electronic structure calculations, both for the isolated molecules and for the central molecules in clusters containing 8–13 molecules. These clusters were constructed computationally using the carbon positions obtained from the crystal structures of the eight compounds and the hydrogen positions obtained from electronic structure calculations. The calculated methyl rotation barriers in the clusters (Eclust) range from 0.6 to 3.4 kcal/mol. Solid-state 1H NMR spin–lattice relaxation rate measurements on the polycrystalline solids gave experimental activation energies (ENMR) for methyl rotation in the range from 0.4 to 3.2 kcal/mol. The energy differences Eclust – ENMR for each of the ten methyl groups range from −0.2 kcal/mol to +0.7 kcal/mol, with a mean value of +0.2 kcal/mol and a standard deviation of 0.3 kcal/mol. The differences between each of the computed barriers in the clusters (Eclust) and the corresponding computed barriers in the isolated molecules (Eisol) provide an estimate of the intermolecular contributions to the rotation barriers in the clusters. The values of Eclust – Eisol range from 0.0 to 1.0 kcal/mol

Intramolecular and intermolecular contributions to the barriers for rotation of methyl groups in crystalline solids: Electronic structure calculations and solid state NMR relaxation measurements

The rotation barriers for 10 different methyl groups in five methyl-substituted phenanthrenes and three methyl-substituted naphthalenes were determined by ab initio electronic structure calculations, both for the isolated molecules and for the central molecules in clusters containing 8–13 molecules. These clusters were constructed computationally using the carbon positions obtained from the crystal structures of the eight compounds and the hydrogen positions obtained from electronic structure calculations. The calculated methyl rotation barriers in the clusters (Eclust) range from 0.6 to 3.4 kcal/mol. Solid-state 1H NMR spin–lattice relaxation rate measurements on the polycrystalline solids gave experimental activation energies (ENMR) for methyl rotation in the range from 0.4 to 3.2 kcal/mol. The energy differences Eclust – ENMR for each of the ten methyl groups range from −0.2 kcal/mol to +0.7 kcal/mol, with a mean value of +0.2 kcal/mol and a standard deviation of 0.3 kcal/mol. The differences between each of the computed barriers in the clusters (Eclust) and the corresponding computed barriers in the isolated molecules (Eisol) provide an estimate of the intermolecular contributions to the rotation barriers in the clusters. The values of Eclust – Eisol range from 0.0 to 1.0 kcal/mol

Can deep sub-wavelength cavities induce Amperean superconductivity in a 2D material?

Amperean superconductivity is an exotic phenomenon stemming from attractive effective electron-electron interactions (EEEIs) mediated by a transverse gauge field. Originally introduced in the context of quantum spin liquids and high-Tc superconductors, Amperean superconductivity has been recently proposed to occur at temperatures on the order of 1-20 K in two-dimensional, parabolic-band, electron gases embedded inside deep sub-wavelength optical cavities. In this work, we first generalize the microscopic theory of cavity-induced Amperean superconductivity to the case of graphene and then argue that this superconducting state cannot be achieved in the deep sub-wavelength regime. In the latter regime, indeed, a cavity induces only EEEIs between density fluctuations rather than the current-current interactions which are responsible for Amperean pairing.Comment: 25 pages. Replaced with a greatly modified version, with the addition of an entirely new Section. This new Section presents a Green's function approach to EEEIs that highlights the profound difference between planar optical cavities and sub-wavelength cavitie

Exploring Genome-Wide – Dietary Heme Iron Intake Interactions and the Risk of Type 2 Diabetes

Aims/hypothesis: Genome-wide association studies have identified over 50 new genetic loci for type 2 diabetes (T2D). Several studies conclude that higher dietary heme iron intake increases the risk of T2D. Therefore we assessed whether the relation between genetic loci and T2D is modified by dietary heme iron intake. Methods: We used Affymetrix Genome-Wide Human 6.0 array data [681,770 single nucleotide polymorphisms (SNPs)] and dietary information collected in the Health Professionals Follow-up Study (n = 725 cases; n = 1,273 controls) and the Nurses’ Health Study (n = 1,081 cases; n = 1,692 controls). We assessed whether genome-wide SNPs or iron metabolism SNPs interacted with dietary heme iron intake in relation to T2D, testing for associations in each cohort separately and then meta-analyzing to pool the results. Finally, we created 1,000 synthetic pathways matched to an iron metabolism pathway on number of genes, and number of SNPs in each gene. We compared the iron metabolic pathway SNPs with these synthetic SNP assemblies in their relation to T2D to assess if the pathway as a whole interacts with dietary heme iron intake. Results: Using a genomic approach, we found no significant gene–environment interactions with dietary heme iron intake in relation to T2D at a Bonferroni corrected genome-wide significance level of $7.33 ×10^{-8}$ (top SNP in pooled analysis: intergenic rs10980508; $p = 1.03 × 10^{-6}$). Furthermore, no SNP in the iron metabolic pathway significantly interacted with dietary heme iron intake at a Bonferroni corrected significance level of $2.10 × 10^{-4}$ (top SNP in pooled analysis: rs1805313; $p = 1.14 × 10^{-3}$). Finally, neither the main genetic effects (pooled empirical p by SNP = 0.41), nor gene – dietary heme–iron interactions (pooled empirical p-value for the interactions = 0.72) were significant for the iron metabolic pathway as a whole. Conclusions: We found no significant interactions between dietary heme iron intake and common SNPs in relation to T2D

Taking Blockchain Seriously

In the present techno-political moment it is clear that ignoring or dismissing the hype surrounding blockchain is unwise, and certainly for regulatory authorities and governments who must keep a grip on the technology and those promoting it, in order to ensure democratic accountability and regulatory legitimacy within the blockchain ecosystem and beyond. Blockchain is telling (and showing) us something very important about the evolution of capital and neoliberal economic reason, and the likely impact in the near future on forms and patterns of work, social organization, and, crucially, on communities and individuals who lack influence over the technologies and data that increasingly shape and control their lives. In this short essay I introduce some of the problems in the regulation of blockchain and offer counter-narratives aimed at cutting through the hype fuelling the ascendency of this most contemporary of technologies

Metabolic evidence of viable myocardium in regions with reduced wall thickness and absent wall thickening in patients with chronic ischemic left ventricular dysfunction

AbstractReduced end-diastolic wall thickness with absent systolic wall thickening has been reported to represent nonviable myocardium in patients with chronic coronary artery disease. To assess whether reduced regional end-diastolic wall thickness and absent wall thickening accurately identify nonviable myocardium, 25 patients with ischemic left ventricular dysfunction (ejection fraction at rest 27 ± 10%) underwent positron emission tomography with oxygen-15-labeled water and 18fluorodeoxyglucose to assess metabolic activity and spin-echo gated nuclear magnetic resonance imaging to measure regional end-diastolic wall thickness and wall thickening. The presence of metabolic activity was defined as 18fluorodeoxyglucose uptake (corrected for partial volume) >50% of that in normal regions.Of 355 myocardial regions evaluated, 266 were hypokinetic or normokinetic at rest and 89 were akinetic (that is, absent wall thickening). 18Fluorodeoxglucose uptake was observed in 97% of the hypokinetic and normokinetic regions and in 74% of the akinetic regions. End-diastolic wall thickness was greater in akinetic regions with than in those without 18fluorodeoxyglucose uptake (11 ± 4 vs. 7 ± 3 nun, p < 0.01). The highest values for sensitivity and specificity of end-diastolic wall thickness in predicting the absence of metabolic activity in akinetic regions were 74% and 79%, respectively, and corresponded to an end-diastolic threshold of 8 mm. However, the positive predictive accuracy was only 55% and did not improve for other end-diastolic wall thickness values. In all myocardial regions, there was only a weak correlation between 18fluorodeoxyglucose activity and either end-diastolic wall thickness (r = 0.17) or wall thickening (r = 0.32).Thus, metabolic activity is present in many regions with reduced end-diastolic wall thickness and absent wall thickening. These data indicate that assessment of regional anatomy and function may be inaccurate in distinguishing asynergic but viable myocardium from nonviable myocardium

Cognition-Enhancing Drugs: Can We Say No?

Normative analysis of cognition-enhancing drugs frequently weighs the liberty interests of drug users against egalitarian commitments to a level playing field. Yet those who would refuse to engage in neuroenhancement may well find their liberty to do so limited in a society where such drugs are widespread. To the extent that unvarnished emotional responses are world-disclosive, neurocosmetic practices also threaten to provide a form of faulty data to their users. This essay examines underappreciated liberty-based and epistemic rationales for regulating cognition-enhancing drugs

GRB 060313: A New Paradigm for Short-Hard Bursts?

We report the simultaneous observations of the prompt emission in the gamma-ray and hard X-ray bands by the Swift-BAT and the KONUS-Wind instruments of the short-hard burst, GRB 060313. The observations reveal multiple peaks in both the gamma-ray and hard X-ray bands suggesting a highly variable outflow from the central explosion. We also describe the early-time observations of the X-ray and UV/Optical afterglows by the Swift XRT and UVOT instruments. The combination of the X-ray and UV/Optical observations provide the most comprehensive lightcurves to date of a short-hard burst at such an early epoch. The afterglows exhibit complex structure with different decay indices and flaring. This behavior can be explained by the combination of a structured jet, radiative loss of energy, and decreasing microphysics parameters occurring in a circum-burst medium with densities varying by a factor of approximately two on a length scale of 10^17 cm. These density variations are normally associated with the environment of a massive star and inhomogeneities in its windy medium. However, the mean density of the observed medium (n approximately 10^&#8722;4 cm^3) is much less than that expected for a massive star. Although the collapse of a massive star as the origin of GRB 060313 is unlikely, the merger of a compact binary also poses problems for explaining the behavior of this burst. Two possible suggestions for explaining this scenario are: some short bursts may arise from a mechanism that does not invoke the conventional compact binary model, or soft late-time central engine activity is producing UV/optical but no X-ray flaring.Comment: 28 pages, 6 figures. Accepted for publication in ApJ. Clarifications made and typos correcte

The central engine of GRB 130831A and the energy breakdown of a relativistic explosion

Gamma-ray bursts (GRBs) are the most luminous explosions in the universe, yet the nature and physical properties of their energy sources are far from understood. Very important clues, however, can be inferred by studying the afterglows of these events. We present optical and X-ray observations of GRB 130831A obtained by Swift, Chandra, Skynet, RATIR, Maidanak, ISON, NOT, LT and GTC. This burst shows a steep drop in the X-ray light-curve at $\simeq 10^5$ s after the trigger, with a power-law decay index of $\alpha \sim 6$. Such a rare behaviour cannot be explained by the standard forward shock (FS) model and indicates that the emission, up to the fast decay at $10^5$ s, must be of "internal origin", produced by a dissipation process within an ultrarelativistic outflow. We propose that the source of such an outflow, which must produce the X-ray flux for $\simeq 1$ day in the cosmological rest frame, is a newly born magnetar or black hole. After the drop, the faint X-ray afterglow continues with a much shallower decay. The optical emission, on the other hand, shows no break across the X-ray steep decrease, and the late-time decays of both the X-ray and optical are consistent. Using both the X-ray and optical data, we show that the emission after $\simeq 10^5$ s can be explained well by the FS model. We model our data to derive the kinetic energy of the ejecta and thus measure the efficiency of the central engine of a GRB with emission of internal origin visible for a long time. Furthermore, we break down the energy budget of this GRB into the prompt emission, the late internal dissipation, the kinetic energy of the relativistic ejecta, and compare it with the energy of the associated supernova, SN 2013fu.Comment: Accepted for publication by MNRAS. 21 pages, 3 figures, 8 tables. Extra table with magnitudes in the sourc