Quantum fluctuations of D5dD_{5d} polarons on C60C_{60} molecules

The dynamic Jahn-Teller splitting of the six equivalent $D_{5d}$ polarons due to quantum fluctuations is studied in the framework of the Bogoliubov-de Gennes formalism. The tunneling induced level splittings are determined to be $^2 T_{1u} \bigoplus ^2 T_{2u}$ and $^1 A_g \bigoplus ^1 H_g$ for $C_{60}^{1-}$ and $C_{60}^{2-}$, respectively, which should give rise to observable effects in experiments.Comment: REVTEX 3.0, 13 pages, to be published in Phys. Rev.

Unusual cause of mechanical ileus: abdominal cocoon syndrome

A 38-year-old black male patient was admitted with diarrhea and nausea over two days and aggravating pain in the meso- and epigastium that resolved after urination. He had no surgical history and only an episode of pulmonary tuberculosis five years earlier, for which he was properly treated. Physical examination revealed a tender and distended abdomen with clangorous sounds. His temperature was 36.1°C. Routine laboratory blood analyses were normal. An abdominal ultrasound revealed diffuse distention of the small intestine. A computed tomography (CT) scan showed a conglomerate of dilated small bowel loops in the meso- and hypogastrium, suggestive for a supravesical mechanical small bowel obstruction. Peritoneal thickening was seen in the right epigastrium (Figure A, white arrow). An explorative laparoscopy revealed a whitish, thickened membrane encapsulating the small bowels as a ‘cocoon’ (Figure B). Extensive adhesiolysis released an intestinal kinking in the lower abdomen, just above the bladder. No resection was needed. Histopathology of the membrane showed fibrocollagenous tissue with mixed inflammatory infiltrate

EVAPORATION: a new vapour pressure estimation methodfor organic molecules including non-additivity and intramolecular interactions

We present EVAPORATION (Estimation of VApour Pressure of ORganics, Accounting for Temperature, Intramolecular, and Non-additivity effects), a method to predict (subcooled) liquid pure compound vapour pressure <i>p</i><sup>0</sup> of organic molecules that requires only molecular structure as input. The method is applicable to zero-, mono- and polyfunctional molecules. A simple formula to describe log<sub>10</sub><i>p</i><sup>0</sup>(<i>T</i>) is employed, that takes into account both a wide temperature dependence and the non-additivity of functional groups. In order to match the recent data on functionalised diacids an empirical modification to the method was introduced. Contributions due to carbon skeleton, functional groups, and intramolecular interaction between groups are included. Molecules typically originating from oxidation of biogenic molecules are within the scope of this method: aldehydes, ketones, alcohols, ethers, esters, nitrates, acids, peroxides, hydroperoxides, peroxy acyl nitrates and peracids. Therefore the method is especially suited to describe compounds forming secondary organic aerosol (SOA)

Lung donation after circulatory death

PURPOSE OF REVIEW The current review presents a concise update on published literature on donation after circulatory death (DCD) and lung transplantation (LTx). Worldwide an increasing need for lungs is evident, however the utilization rate of DCD lung donors is still considerably low. In this summary article, we reviewed both the experimental background and international clinical experience. RECENT FINDINGS Our analysis confirmed satisfactory results for LTx from DCD donors, which equals the results from donation after brain death. Although most studies reported on short-term results, some confirmed these results on the long-term and development of chronic lung allograft dysfunction. Our review summarizes the different DCD categories and underlines the potential of the DCD V category. We analyze the barriers to implement a DCD program, discuss the more recent advances like ex-vivo lung perfusion and describe the future challenges. SUMMARY Based on the current short-term and long-term clinical results, we believe that barriers for DCD utilization should be overcome, resulting in a safe implementation of more DCD LTx programs worldwide. VIDEO ABSTRACT

Radiative transfer as a Bayesian linear regression problem

Electromagnetic radiation plays a crucial role in various physical and chemical processes. Hence, almost all astrophysical simulations require some form of radiative transfer model. Despite many innovations in radiative transfer algorithms and their implementation, realistic radiative transfer models remain very computationally expensive, such that one often has to resort to approximate descriptions. The complexity of these models makes it difficult to assess the validity of any approximation and to quantify uncertainties on the model results. This impedes scientific rigour, in particular, when comparing models to observations, or when using their results as input for other models. We present a probabilistic numerical approach to address these issues by treating radiative transfer as a Bayesian linear regression problem. This allows us to model uncertainties on the input and output of the model with the variances of the associated probability distributions. Furthermore, this approach naturally allows us to create reduced-order radiative transfer models with a quantifiable accuracy. These are approximate solutions to exact radiative transfer models, in contrast to the exact solutions to approximate models that are often used. As a first demonstration, we derive a probabilistic version of the method of characteristics, a commonly-used technique to solve radiative transfer problems

Theory of Spontaneous Polarization of Endohedral Fullerenes

A pseudo-Jahn-Teller model describing central atom distortions is proposed for endohedral fullerenes of the form A@C$_{60}$ where A is either a rare gas or a metal atom. A critical (dimensionless) coupling $g_c$ is found, below which the symmetric configuration is stable and above which inversion symmetry is broken. Vibronic parameters are given for selected endohedral fullerenes.Comment: 4 pages, REVTEX, 1 Postscript figure. [Phys. Rev. Lett. (in press)

Jahn–Teller instability in cationic boron and carbon buckyballs B₈₀⁺ and C₆₀⁺: a comparative study

This paper investigates the Jahn–Teller effect in the icosahedral cation B80+ and compares the descent in symmetry with that in C60+. For both cations the icosahedral ground state is a 2Hu state, which exhibits a H [multiply sign in circle] (g ⊕ 2h) Jahn–Teller instability. A detailed construction of the potential energy surface of B80+ using different DFT methods including B3LYP/6-31G(d), VWN/6-31G(d), PBE/TZP and PBE/6-31G(d) shows that, contrary to C60+, which prefers D5d symmetry, the ground state of B80+ adopts S6 point group symmetry. A D3d structure is identified as a saddle point among the S6 minima of B80+. The distortion of D3d to S6 in B80+ is attributed to a superposition of Jahn–Teller and pseudo-Jahn–Teller effects. Imaginary modes, transforming as the gg representation, which are present in neutral icosahedral B80, form the dominant symmetry breaking active modes. The pronounced difference between the JT effects in the boron and carbon buckyball cations is due to the plasticity of the boron caps. The calculated Jahn–Teller stabilization of B80+ is nearly 1549 cm−1 (PBE/TZP), which exceeds the stabilization of 596 cm−1 computed for C60+ at the same level

Drivers of vegetation change in grasslands of the Sheffield region, northern England, between 1965 and 2012/13

Questions: How has vegetation species diversity and species composition changed between 1965 and 2012/13 in acidic and calcareous grasslands? What has driven this change in vegetation? Location: A 2400-km2 area around Sheffield, northern England. Methods: In 1965 a survey was conducted to describe grassland vegetation of the Sheffield region. We repeated this survey in 2012/13, revisiting acidic and calcareous grassland sites (455 quadrats). Climate, N and sulphur deposition, cattle and sheep stocking rates, soil pH, altitude, aspect and slope were considered to be potential drivers of variation in vegetation. We analysed temporal changes in vegetation and examined relationships with spatial and temporal variation in driver variables. Results: Both acidic and calcareous grasslands showed clear changes in species composition between the two time periods. In acidic grasslands there was no significant change in richness but there were declines in diversity. There were significant increases in Ellenberg N. Nitrogen deposition and grazing were identified as potential drivers of spatial and temporal patterns but it was not possible to discriminate the respective impacts of potential drivers. In calcareous grasslands there were declines in species richness, diversity and appropriate diversity indices. Climate and soil pH were identified as potential drivers of spatial and temporal patterns. Conclusions: Despite only small site losses compared to other surveys in the UK, especially within the national park, both calcareous and acidic grasslands showed very clear changes in species composition. In acidic grasslands, high abundance of Pteridium aquilinum was a particular problem and had increased considerably between the two survey periods. Atmospheric N deposition and grazing were identified as drivers of species diversity. A number of calcareous grasslands showed signs of reduced management intensity leading to scrub invasion

Dynamical Jahn-Teller Effect and Berry Phase in Positively Charged Fullerene I. Basic Considerations

We study the Jahn-Teller effect of positive fullerene ions $^2$C$_{60}^{+}$ and $^1$C$_{60}^{2+}$. The aim is to discover if this case, in analogy with the negative ion, possesses a Berry phase or not, and what are the consequences on dynamical Jahn-Teller quantization. Working in the linear and spherical approximation, we find no Berry phase in $^1$C$_{60}^{2+}$, and presence/absence of Berry phase for coupling of one $L=2$ hole to an $L=4$/$L=2$ vibration. We study in particular the special equal-coupling case ($g_2=g_4$), which is reduced to the motion of a particle on a 5-dimensional sphere. In the icosahedral molecule, the final outcome assesses the presence/absence of a Berry phase of $\pi$ for the $h_u$ hole coupled to $G_g$/$H_h$ vibrations. Some qualitative consequences on ground-state symmetry, low-lying excitations, and electron emission from C$_{60}$ are spelled out.Comment: 31 pages (RevTeX), 3 Postscript figures (uuencoded

Estimating fusion properties for functionalised acids

Multicomponent organic aerosol (OA) is likely to be liquid, or partially liquid. Hence, to describe the partitioning of these components, their liquid vapour pressure is desired. Functionalised acids (e.g. diacids) can be a significant part of OA. But often measurements are available only for solid state vapour pressure, which can differ by orders of magnitude from their liquid counterparts. To convert such a sublimation pressure to a subcooled liquid vapour pressure, fusion properties (two out of these three quantities: fusion enthalpy, fusion entropy, fusion temperature) are required. Unfortunately, experimental knowledge of fusion properties is sometimes missing in part or completely, hence an estimation method is required. Several fusion data estimation methods are tested here against experimental data of functionalised acids, and a simple estimation method is developed, specifically for this family of compounds, with a significantly smaller estimation error than the literature methods