SYN -1,4-addition of carboxylate salts to cyclic allylic epoxides mediated by cuprous chloride

A mild method for the 1,4- opening of certain cyclic allylic epoxides has been found, using sodium carboxylates in the presence of cuprous chloride.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25416/1/0000865.pd

Long-term trends of midlatitude horizontal mesosphere/lower thermosphere winds over four decades

We analyse 43 years of mesosphere/lower thermosphere (MLT) horizontal winds obtained from a joint analysis of low frequency (LF) spaced receiver lower ionospheric drift measurements from late 1978 through 2008 and VHF meteor radar wind observations since summer 2004 at Collm (51.3∘ N, 13.0∘ E). Due to limitations of the earlier LF measurements, we restrict ourselves to the analysis of monthly mean winds near 90 km, which represents the meteor peak height as well as mean LF reflection heights in the MLT. We observe mainly positive trends of the zonal prevailing wind throughout the year, while the meridional winds tend to decrease in magnitude in both summer and winter. Furthermore, there is a change in long-term trends around the late 1990s, which is most clearly visible in summer MLT winds. We compare these measurements with long-term partial reflection radar observations of winds at 81–85 km over Juliusruh (54.6∘ N, 13.4∘ E) since 1990, and find general qualitative agreement of trends except for summer. The latter can be explained by the different altitudes considered, and by the latitude dependence of the summer mesospheric jet.</p

Tracking Turbulent Coherent Structures by Means of Neural Networks

[EN] The behaviours of individual flow structures have become a relevant matter of study in turbulent flows as the computational power to allow their study feasible has become available. Especially, high instantaneous Reynolds Stress events have been found to dominate the behaviour of the logarithmic layer. In this work, we present a viability study where two machine learning solutions are proposed to reduce the computational cost of tracking such structures in large domains. The first one is a Multi-Layer Perceptron. The second one uses Long Short-Term Memory (LSTM). Both of the methods are developed with the objective of taking the the structures' geometrical features as inputs from which to predict the structures' geometrical features in future time steps. Some of the tested Multi-Layer Perceptron architectures proved to perform better and achieve higher accuracy than the LSTM architectures tested, providing lower errors on the predictions and achieving higher accuracy in relating the structures in the consecutive time steps.This work was supported by RTI2018-102256-B-I00 of MINECO/FEDER. The computations of the new simulations were made possible by a generous grant of computing time from the Barcelona Supercomputing Centre, reference AECT-2020-2-0005.Aguilar-Fuertes, JJ.; Noguero-Rodríguez, F.; Jaen Ruiz, JC.; García-Raffi, LM.; Hoyas, S. (2021). Tracking Turbulent Coherent Structures by Means of Neural Networks. Energies. 14(4):1-15. https://doi.org/10.3390/en1404098411514

R+R2R + R^2 Gravity as R+R + Backreaction

Quadratic theory of gravity is a complicated constraint system. We investigate some consequences of treating quadratic terms perturbatively (higher derivative version of backreaction effects). This approach is shown to overcome some well known problems associated with higher derivative theories, i.e., the physical gravitational degree of freedom remains unchanged from those of Einstein gravity. Using such an interpretation of $R + \beta R^2$ gravity, we investigate a classical and Wheeler DeWitt evolution of $R + \beta R^2$ gravity for a particular sign of $\beta$, corresponding to non- tachyon case. Matter is described by a phenomenological $\rho \propto a(t)^{-n}$. It is concluded that both the Friedmann potential $U(a)$ (${\dot a}^2 + 2U(a) = 0$) and the Wheeler DeWitt potential $W(a)$ ($\left[-{\partial^2\over \partial a^2} + 2W(a)\right]\psi (a) =0$) develop repulsive barriers near $a\approx 0$ for $n>4$ (i.e., $p > {1\over 3}\rho$). The interpretations is clear. Repulsive barrier in $U(a)$ implies that a contracting FRW universe ($k>0, k=0, k<0$) will bounce to an expansion phase without a total gravitational collapse. Repulsive barrier in $W(a)$ means that $a \approx 0$ is a classically forbidden region. Therefore, probability of finding a universe with the big bang singularity ($a=0$ ) is exponentially suppressed.Comment: Accepted for publication in Phy. Rev. D.,18 pages, 6 figures, Latex fil

Hamiltonian formulation for the classical EM radiation-reaction problem: application to the kinetic theory for relativistic collisionless plasmas

A notorious difficulty in the covariant dynamics of classical charged particles subject to non-local electromagnetic (EM) interactions arising in the EM radiation-reaction (RR) phenomena is due to the definition of the related non-local Lagrangian and Hamiltonian systems. The lack of a standard Lagrangian/Hamiltonian formulation in the customary asymptotic approximation for the RR equation may inhibit the construction of consistent kinetic and fluid theories. In this paper the issue is investigated in the framework of Special Relativity. It is shown that, for finite-size spherically-symmetric classical charged particles, non-perturbative Lagrangian and Hamiltonian formulations in standard form can be obtained, which describe particle dynamics in the presence of the exact EM RR self-force. As a remarkable consequence, based on axiomatic formulation of classical statistical mechanics, the covariant kinetic theory for systems of charged particles subject to the EM RR self-force is formulated in Hamiltonian form. A fundamental feature is that the non-local effects enter the kinetic equation only through the retarded particle 4-position, which permits the construction of the related non-local fluid equations. In particular, the moment equations obtained in this way do not contain higher-order moments, allowing as a consequence the adoption of standard closure conditions. A remarkable aspect of the theory concerns the short delay-time asymptotic expansions. Here it is shown that two possible expansions are permitted. Both can be implemented for the single-particle dynamics as well as for the corresponding kinetic and fluid treatments. In the last case, they are performed a posteriori on the relevant moment equations obtained after integration of the kinetic equation over the velocity space. Comparisons with literature are pointed out

Quality indicators in radiation oncology: proposal of the Spanish Society of Radiation Oncology (SEOR) for a continuous improvement of the quality of care in oncology.

Purpose Current cancer treatment options include surgical intervention, radiotherapy, and chemotherapy. The quality of the provision of each of them and their effective coordination determines the results in terms of benefit/risk. Regarding the radiation oncology treatments, there are not stabilised quality indicators to be used to perform control and continuous improvement processes for healthcare services. Therefore, the Spanish Society of Radiation Oncology has undertaken a comprehensive project to establish quality indicators for use with the information systems available in most Spanish healthcare services. Methods A two-round Delphi study examines consensus of several possible quality indicators (n = 28) in daily practice. These indicators were defined after a bibliographic search and the assessment by radiation oncology specialists (n = 8). They included aspects regarding treatment equipment, patient preparation, treatment, and follow-up processes and were divided in structure, process, and outcome indicators. Results After the evaluation of the defined quality indicators (n = 28) by an expert panel (38 radiation oncologist), 26 indicators achieved consensus in terms of agreement with the statement. Two quality indicators did not achieve consensus. Conclusions There is a high degree of consensus in Spanish Radiation Oncology specialists on which indicators in routine clinical practice can best measure quality. These indicators can be used to classify services based on several parameters (patients, equipments, complexity of the techniques used, and scientific research). Furthermore, these indicators allow assess our current situation and set improvements’ objectives.pre-print241 K

Occupational exposure to nano-TiO2 in the life cycle steps of new depollutant mortars used in construction

The present work is focused on the measurement of workers exposure to nano-TiO2 in the life cycle steps of depollutant mortars. It has been done in the framework of the SCAFFOLD project, which aims at the management of potential risks arising from the use of manufactured nanomaterials in construction. Main findings can be summarized as follows: (1) The occupational exposure to nano- TiO2 is below 0.3 mg/m3 for all measured scenarios. The highest concentrations were measured during the cleaning task (in the nano- TiO2 manufacturing process) and during the application (spraying) of depollutant coatings on a wall. (2) It was found a high release of particles above the background in several tasks as expected due to the nature of the activities performed. The maximum concentration was measured during drilling and during adding powder materials (mean total particle concentration up to 5.591E+04 particles/cm3 and 5.69E+04 particles/cm3). However, considering data on total particle concentration released, no striking differences have been observed when tasks have been performed using conventional materials in the sector (control) and when using materials doped with nano-objects.European Commission's FP

On the energy of charged black holes in generalized dilaton-axion gravity

In this paper we calculate the energy distribution of some charged black holes in generalized dilaton-axion gravity. The solutions correspond to charged black holes arising in a Kalb-Ramond-dilaton background and some existing non-rotating black hole solutions are recovered in special cases. We focus our study to asymptotically flat and asymptotically non-flat types of solutions and resort for this purpose to the M{\o}ller prescription. Various aspects of energy are also analyzed.Comment: LaTe