Mössbauer experiments on bismuth-antimony alloys

Alloys of bismuth and antimony, with compositions ranging from 5 to 100% Sb were investigated by Mössbauer spectrometry at 80°K using the 37.2keV γ-ray of ¹²¹Sb. The spectrum was a single line pattern for all compositions, the isomer shift being distinctly more negative for the semiconductor compositions (−3.27 ± 0.4 mm/sec, referred to InSb, for Bi₇₅ Sb₂₅) than for the semimetallic range. The linewidth was also a minimum for the Bi₇₅ Sb₂₅ composition, where the FWHM was 2.62±0.16 mm/sec. This linewidth was typically about 3 mm/sec for the semimetallic region.     

Clinical-scale investigation of stable isotopes in human blood: delta13C and delta15N from 406 patients at the Johns Hopkins Medical Institutions

Objective chemical biomarkers are needed in clinical studies of diet-related diseases to supplement subjective self-reporting methods. We report on several critical experiments for the development of clinically legitimate dietary stable isotope biomarkers within human blood. Our examination of human blood revealed the following: (1) Within blood clot and serum from anonymous individuals (201 males, 205 females) we observed: mean serum delta13C = -19.1 +/- 0.8 per thousand (standard deviation, SD); clot, -19.3 +/- 0.8 per thousand (SD); range = -15.8 per thousand to -23.4 per thousand. Highly statistically significant differences are observed between clot and serum, males and females for both clot and serum. For 15N (n = 206), mean serum = +8.8 +/- 0.5 per thousand (SD); clot +7.4 +/- 0.4 per thousand (SD); range = +6.3 per thousand to +10.5 per thousand. Blood serum is enriched in 15N relative to blood clot by +1.4 per thousand on average, which may reflect differing protein amino acid content. Serum nitrogen is statistically significantly different for males and females, however, clot shows no statistical difference. (2) Relative to clot, capillary blood is marginally different for 13C, but not 15N. Clot 13C is not significantly different from serum; however, it is depleted in 15N by 1.5 per thousand relative to serum. (3) We assessed the effect of blood additives (sodium fluoride and polymerized acrylamide resin) and laboratory process (autoclaving, freeze drying) commonly used to preserve or prepare venous blood. On average, no alteration in delta13C or delta15N is detected compared with unadulterated blood from the same individual. (4) Storage of blood with and without the additives described above for a period of up to 115 days exhibits statistically significant differences for 13C and 15N for sodium fluoride. However, storage for unadulterated blood and blood preserved with polymerized acrylamide resin does not change the delta13C or delta15N isotopic composition of the blood in a significant way. With these experiments, we gain a clinical context for future development of a stable isotope based dietary biomarker.     

Synthesizing Strained Azatriseptane Frameworks

Embedding seven-membered rings into polycyclic aromatic molecules is attractive as they can exert an influence on molecular conformation that ultimately changes the solubility and π-electronics. The considerations in designing and synthesizing a highly strained azatriseptane framework are discussed herein. We employ a twofold macrocyclization strategy to form the [7,7,7]-system and through scoping various strategies identify that the Friedel–Crafts approach is the key. In addition to the successes presented here, the synthetic limitations we have identified highlight the key challenges in forming triseptane frameworks and pave the way for second-generation analogues that may have various applications in optical and electronic organic materials.     

The pH dependent interaction between nicotine and simulated pulmonary surfactant monolayers with associated molecular modelling

Pulmonary surfactant is an endogenous material that lines and stabilises the alveolar air–liquid interface. Respiratory mechanics can be compromised by exposure to environmental toxins such as cigarette smoke, which contains nicotine. This study aims to determine the influence of nicotine on the activity of simulated lung surfactant at pH 7 and pH 9. In all cases, the addition of nicotine to the test zone caused deviation in surfactant film performance. Importantly, the maximum surface pressure was reduced for each system. Computational modelling was applied to assess key interactions between each species, with the Gaussian 09 software platform used to calculate electrostatic potential surfaces. Modelling data confirmed either nicotine penetration into the two‐dimensional structure or interfacial/electrostatic interactions across the underside. The results obtained from this study suggest that nicotine can impair the ability of pulmonary surfactant to reduce the surface tension term, which can increase the work of breathing. When extrapolated to gross lung function, alveolar collapse and respiratory disease (e.g. chronic airway obstruction) may result. The delivery of nicotine to the (deep) lung can cause a deterioration in lung function and lead to reduced quality of life. Copyright © 2017 John Wiley & Sons, Ltd.     

Gevrey regularity of the periodic gKdV equation

Using the multilinear estimates, which were derived for proving well-posedness of the generalized Korteweg-de Vries (gKdV) equation, it is shown that if the initial data belongs to Gevrey space Gσ, σ?1, in the space variable then the solution to the corresponding Cauchy problem for gKdV belongs also to Gσ in the space variable. Moreover, the solution is not necessarily Gσ in the time variable. However, it belongs to G3σ near 0. When σ=1 these are analytic regularity results for gKdV.     

The effect of iron and copper impurities on the wettability of sphalerite (110) surface

The effect of impurities in the zinc sulfide mineral sphalerite on surface wettability has been investigated theoretically to shed light on previously reported conflicting results on sphalerite flotation. The effect of iron and copper impurities on the sphalerite (110) surface energy and on the water adsorption energy was calculated with the semi-empirical method modified symmetrically orthogonalized intermediate neglect of differential overlap (MSINDO) using the cyclic cluster model. The effect of impurities or dopants on surface energies is small but significant. The surface energy increases with increasing surface iron concentration while the opposite effect is reported for increasing copper concentration. The effect on adsorption energies is much more pronounced with water clearly preferring to adsorb on an iron site followed by a zinc site, and copper site least favorable. The theoretical results indicate that a sphalerite (110) surface containing iron is more hydrophilic than the undoped zinc sulfide surface. In agreement with the literature, the surface containing copper (either naturally or by activation) is more hydrophobic than the undoped surface.     

A recyclable perfluoroalkylated PCP pincer palladium complex

A new fluorous PCP pincer ligand has been coordinated to Ni(II), Pd(II) and Pt(II). The air stable palladium complex, which promotes Heck reactions between methyl acrylate and either aryl bromides or iodides, can be recovered intact by fluorous solid-phase extraction and was reused four times in the Heck reaction between methyl acrylate and 4-bromoacetophenone without loss in catalytic activity.     

Phase range of the type-I clathrate Sr8Al(x)Si(46-x) and crystal structure of Sr8Al10Si36

Samples of the type-I clathrate Sr(8)Al(x)Si(46-x) have been prepared by direct reaction of the elements. The type-I clathrate structure (cubic space group Pm3n) which has an Al-Si framework with Sr(2+) guest atoms forms with a narrow composition range of 9.54(6) ≤ x ≤ 10.30(8). Single crystals with composition A(8)Al(10)Si(36) (A = Sr, Ba) have been synthesized. Differential scanning calorimetry (DSC) measurements provide evidence for a peritectic reaction and melting point at ～1268 and ～1421 K for Sr(8)Al(10)Si(36) and Ba(8)Al(10)Si(36), respectively. Comparison of the structures reveals a strong correlation between the 24k-24k framework sites distances and the size of the guest cation. Electronic structure calculation and bonding analysis were carried out for the ordered models with the compositions A(8)Al(6)Si(40) (6c site occupied completely by Al) and A(8)Al(16)Si(30) (16i site occupied completely with Al). Analysis of the distribution of the electron localizability indicator (ELI) confirms that the Si-Si bonds are covalent, the Al-Si bonds are polar covalent, and the guest and the framework bonds are ionic in nature. The Sr(8)Al(6)Si(40) phase has a very small band gap that is closed upon additional Al, as observed in Sr(8)Al(16)Si(30). An explanation for the absence of a semiconducting "Sr(8)Al(16)Si(30)" phase is suggested in light of these findings.