The energetics of the isomeric anthrols

We report the results of geometry optimized MP2(FULL)/6-31G(d) quantum chemical calculations with zero-point vibrational energies and thermal corrections of the isomeric 1-, 2- and 9-anthrols and the tautomeric anthrone. We find that 1- and 2-anthrols have nearly the same enthalpy of formation and are some 6?kJ?mol^?1 more stable than their 9-isomer in accord with intuition based on steric hindrance. We find that anthrone is more stable than 9-anthrol by 13.7 ± 6.4?kJ?mol^?1, in satisfactory agreement with the value of 23 ± 8?kJ?mol^?1 suggested elsewhere by experiment and its associated analysis.     

Hepatic sarcoidosis: MR appearances in patients with chronic liver disease

Purpose

To describe the MR appearances of hepatic sarcoidosis in patients with chronic liver disease and correlate the results with clinical stage of disease as measured with the Mayo end-stage liver disease (MELD) score.

Materials and methods

Twenty patients with chronic liver disease and histopathological diagnosis of hepatic sarcoidosis who underwent MR imaging were included in this study. Two abdominal radiologists retrospectively reviewed all images for the presence of cirrhosis, imaging pattern of the liver, intrahepatic biliary dilatation, presence of areas of parenchymal atrophy, presence of splenic nodules and lymphadenopathy. Imaging findings were correlated with the MELD score.

Results

Of the patients, 14/20 had imaging findings of cirrhosis, 9/20 had a large macronodular pattern of liver cirrhosis and 5/20 had a diffuse pattern of liver cirrhosis. Peripheral wedge-shaped areas of parenchymal atrophy were observed in 10 patients. The combination of a central macronodular pattern and peripheral atrophy was observed in 9/20 patients. The pattern of cirrhosis had statistically significant correlation with the presence of wedge-shaped areas of parenchymal atrophy (p < 0.005). No statistically significant difference was revealed between the clinical score of patients who had imaging findings consistent with cirrhosis and those who did not.

Conclusion

MR imaging appearances of chronic sarcoid liver disease are diverse and do not appear to correlate with severity of clinical disease. Large central regenerative nodules and wedge-shaped areas of peripheral parenchymal atrophy are frequent findings and may help to suggest the diagnosis.     

Mimetic trust and intra‐organizational network dynamics

Dynamic network models based on the homophily principle are criticized for neglecting organizational context conditions and the impact of role structures on the evolution of intra‐organizational trust networks. Using a neo‐institutional framework it is argued that individuals in competitive environments will attempt to reduce uncertainty about the trustworthiness of potential trustees by imitating the sociometric choice behavior of persons in similar network positions. Three hypotheses are developed. The positional trust hypothesis predicts that individuals tend to trust other actors who occupy a similar network position as themselves. The mimetic trust hypothesis argues that individuals trust actors who are trusted by persons in their own network position. Finally, the advisory trust hypothesis claims that individuals prefer to maintain trust relations to persons occupying a position of third party intermediary than to persons in other positions. An exploratory empirical test of the hypotheses is carried out by reanalyzing a longitudinal network study of the relationships among 25 salesmen in the furniture department of a North American retail sales store during the 1950s. Blockmodelling procedures are used to identify structural positions in the networks, and log‐linear analysis is applied to determine stability of choices within and between structural positions. The results support the mimetic trust and the advisory trust hypothesis.     

Ornstein–Uhlenbeck processes time changed with additive subordinators and their applications in commodity derivative models

We characterize Ornstein–Uhlenbeck processes time changed with additive subordinators as time-inhomogeneous Markov semimartingales, based on which a new class of commodity derivative models is developed. Our models are tractable for pricing European, Bermudan and American futures options. Calibration examples show that they can be better alternatives than those developed in Li and Linetsky (2012)  [6]. Our method can be applied to many other processes popular in various areas besides finance to develop time-inhomogeneous Markov processes with desirable features and tractability.     

Heuristics and metaheuristics for the maximum diversity problem

This paper presents extensive computational experiments to compare 10 heuristics and 20 metaheuristics for the maximum diversity problem (MDP). This problem consists of selecting a subset of maximum diversity from a given set of elements. It arises in a wide range of real-world settings and we can find a large number of studies, in which heuristic and metaheuristic methods are proposed. However, probably due to the fact that this problem has been referenced under different names, we have only found limited comparisons with a few methods on some sets of instances. This paper reviews all the heuristics and metaheuristics for finding near-optimal solutions for the MDP. We present the new benchmark library MDPLIB, which includes most instances previously used for this problem, as well as new ones, giving a total of 315. We also present an exhaustive computational comparison of the 30 methods on the MDPLIB. Non-parametric statistical tests are reported in our study to draw significant conclusions.     

Patient-specific model of lung deformation using spatially dependent constitutive parameters

Breathing-induced spatially dependent lung deformation is predicted using patient-specific elastic properties with the contact–impact analysis model. The lung geometry is derived from 4D CT scan data of real patients. The spatially varying Young’s modulus for the patient is obtained from a previous study that used inverse deformation of the lung. The compact–impact analysis is implemented using the finite element method. The predicted lung deformation is compared with the results based on linear elasticity. The results are consistent with physiology, indicating large deformations near the diaphragm and smaller values at remote locations on the lobe. The effect of non-linearity of elastic property is most significant at the remote locations where the diaphragm-induced deformation is significantly attenuated.     

Oxidation of highly unstable <4 nm diameter gold nanoparticles 850 mV negative of the bulk oxidation potential

Here we describe the oxidation of <4 nm diameter Au nanoparticles (NPs) attached to indium tin oxide-coated glass electrodes in Br(-) and Cl(-) solution. Borohydride reduction of AuCl(4)(-) in the presence of hexanethiol or trisodium citrate (15 min) led to Au NPs <4 nm in diameter. After electrochemical and ozone removal of the hexanthiolate ligands from the thiol-coated Au NPs, Au oxidation peaks appeared in the range 0-400 mV vs Ag/AgCl (1 M KCl), which is 850-450 mV negative of the bulk Au oxidation peak near 850 mV. The oxidation potential of citrate-coated Au NPs is in the 300-500 mV range and those of 4 and 12 nm diameter Au NPs in the 660-780 mV range. The large negative shift in potential agrees with theory for NPs in the 1-2 nm diameter range. The oxidation potential of Au in Cl(-) solution is positive of that in Br(-) solution, but the difference decreases dramatically as the NP size decreases, showing less dependence on the halide for smaller NPs.     

Synthesis and functionalization of magnetite nanoparticles with different amino-functional alkoxysilanes

Superparamagnetic iron oxide (SPIO) nanoparticles show great promise for many biotechnological applications. This paper addresses the synthesis and characterization of SPIO nanoparticles grafted with three different alkoxysilanes: 3-aminopropyl-triethoxysilane (APTES), 3-aminopropyl-ethyl-diethoxysilane (APDES) and 3-aminopropyl-diethy-ethoxysilane (APES). SPIO nanoparticles with an average particle diameter of 10 nm were prepared by chemical sonoprecipitation. As confirmed by Fourier transform infrared (FTIR) spectroscopy, silylation of these nanoparticles occurs through a two-step process. Decreasing the number of alkoxide groups reduced the concentration of free amino groups on the SPIO surface ([SPIO-NH₂]—APTES>APDES>APES). This phenomenon results from steric contributions and the formation of H-bonded amines provided by the ethyl groups present in the APDES and APES molecules. A simulation of SPIO nanoparticles in a saline physiologic solution shows that the ethyl groups impart larger steric stability onto the ferrofluids, which reduces aggregation. The magnetization (M) versus magnetic field (H) curves show that the synthesized iron oxide nanoparticles display superparamagnetic behavior. The zero-field cooling (ZFC) and field cooling (FC) curves show that the changes in the blocking temperature depend on the alkoxysilane-functionalized particle surface.     

Envelopes of commutative rings

Given a significative class ℱ of commutative rings, we study the precise conditions under which a commutative ring R has an ℱ-envelope. A full answer is obtained when ℱ is the class of fields, semisimple commutative rings or integral domains. When ℱ is the class of Noetherian rings, we give a full answer when the Krull dimension of R is zero and when the envelope is required to be epimorphic. The general problem is reduced to identifying the class of non-Noetherian rings having a monomorphic Noetherian envelope, which we conjecture is the empty class.