9,537 research outputs found
Organocatalytic synthesis of axially chiral atropisomers
This review summarises the recent progress made in the organocatalytic synthesis of atropisomeric compounds. Methodologies based on dynamic kinetic resolution and direct access to BINOL-like biaryls are described. A particular emphasis is given to reaction mechanisms and to the development of strategies to obtain stable products by increasing the barrier to atropisomer interconversion during the reaction
Recommended from our members
Medical Expertise, Bodies, and the Law in Early Modern Courts
Commissioned 3000-word essay for the section Focus of ISIS, the leading journal in the history of science internationally. This section aims to present innovative historiographical approaches, in this case in relation to the theme 'Science and Law'. While discussing recent studies in the history of early modern legal medicine, the article outlines the future research agenda in the area, with a special focus on epistemological issues, including the specific nature of medico-legal evidence, and the role of medical semiotics in its makin
Corporate governance, enterprise risk management, and inter-temporal risk transfer
This work is an initial attempt to describe the interconnections among corporate governance, enterprise risk management, and the phenomena of inter-firm risk transfer that occurs in combination with firms’ income smoothing. Corporate governance is conceived as a set of rules according to which a firm is managed and governed by its top managers. Extant literature on corporate governance has pointed out the benefits of the adoption, at a firm level, of a comprehensive enterprise risk management process. We note that, although such an adoption favors the smoothing of a firm’s income, in smoothing the income a firm, it also gives rise to an inter-temporal transfer of risk from the firm itself to its stakeholders, specifically to suppliers and employees. Such transfer of risk depends on the strength of a firm contractual power and on the structural relationships established by a firm with its stakeholders. We therefore argue that larger-sized organizations affiliated with a business group are likely to smooth income to a greater extent than smaller-sized organizations unaffiliated with a business group. The paper also offers some discussions of the findings and points out some important issues to be addressed in future studies
Relations for a periodic array of flap-type wave energy converters
This paper investigates the interaction of plane incident waves with a wave
farm in the open ocean. The farm consists of a periodic array of large
flap-type wave energy converters. A linear inviscid potential-flow model,
already developed by the authors for a single flap in a channel, is considered.
Asymptotic analysis of the wave field allows to obtain new expressions of the
reflection, transmission and radiation coefficients of the system. It is shown
that, unlike a line of heaving buoys, an array of flap-type converters is able
to exploit resonance of the system transverse modes in order to attain high
capture factor levels. Relations between the hydrodynamic coefficients are
derived and applied for optimising the power output of the wave farm.Comment: Accepted for publication on Applied Ocean Research, 26 Sept 201
Electrical permittivity and resistivity time lapses of multiphase DNAPLs in a lab test
Dense Non-Aqueous Phase Liquids (DNAPLs) induce variation in electromagnetic characteristics of the ground e.g. electric permittivity and resistivity. The most used indirect methods in the mapping of these physical characteristics are electrical resistivity and ground penetrating radar. To better understand the effect of DNAPL release on electrical permittivity and resistivity in a water saturated medium, we carried out a controlled laboratory experiment where the host material was simulated by glass beads and the DNAPL by HFE-7100 (hydrofluoroether). The experiment measured the electric resistivity and permittivity of each fluid, the multi-phase fluid system, and the host material, along with time-lapse electrical resistivity and GPR measurements in a controlled cell. We found that the different phases of DNAPL within a saturated medium (free, dissolved and gaseous phase) affect the physical characteristics differently. The reflection pull-up behind contaminated sediments, which is normally detected by GPR, was mainly inferred from the HFE free phase. The dissolved phase causes small variations in electric permittivity not usually readily detected by GPR measurements. Both the dissolved and free HFE phases induce variation in resistivity.
The study showed that GPR and electrical resistivity differ in sensitivity to the different HFE phases, and can be complementary in the characterization of DNAPL contaminated sites
Hydrodynamics of the Oscillating Wave Surge Converter in the open ocean
A potential flow model is derived for a large flap-type oscillating wave
energy converter in the open ocean. Application of the Green's integral theorem
in the fluid domain yields a hypersingular integral equation for the jump in
potential across the flap. Solution is found via a series expansion in terms of
the Chebyshev polynomials of the second kind and even order. Several
relationships are then derived between the hydrodynamic parameters of the
system. Comparison is made between the behaviour of the converter in the open
ocean and in a channel. The degree of accuracy of wave tank experiments aiming
at reproducing the performance of the device in the open ocean is quantified.
Parametric analysis of the system is then undertaken. It is shown that
increasing the flap width has the beneficial effect of broadening the bandwidth
of the capture factor curve. This phenomenon can be exploited in random seas to
achieve high levels of efficiency.Comment: Submitted to: EJMB/Fluids, 16/07/201
A numerical method to calculate the muon relaxation function in the presence of diffusion
We present an accurate and efficient method to calculate the effect of random
fluctuations of the local field at the muon, for instance in the case muon
diffusion, within the framework of the strong collision approximation. The
method is based on a reformulation of the Markovian process over a discretized
time base, leading to a summation equation for the muon polarization function
which is solved by discrete Fourier transform. The latter is formally
analogous, though not identical, to the integral equation of the original
continuous-time model, solved by Laplace transform. With real-case parameter
values, the solution of the discrete-time strong collision model is found to
approximate the continuous-time solution with excellent accuracy even with a
coarse-grained time sampling. Its calculation by the fast Fourier transform
algorithm is very efficient and suitable for real time fitting of experimental
data even on a slow computer.Comment: 7 pages, 3 figures. Submitted to Journal of Physics: Condensed Matte
A new tool for the evaluation of the rehabilitation outcomes in older persons. a machine learning model to predict functional status 1 year ahead
Purpose To date, the assessment of disability in older people is obtained utilizing a Comprehensive Geriatric Assessment (CGA). However, it is often difficult to understand which areas of CGA are most predictive of the disability. The aim of this study is to evaluate the possibility to early predict—1year ahead—the disability level of a patient using machine leaning models.
Methods Community-dwelling older people were enrolled in this study. CGA was made at baseline and at 1year follow-up. After collecting input/independent variables (i.e., age, gender, schooling followed, body mass index, information on smoking, polypharmacy, functional status, cognitive performance, depression, nutritional status), we performed two distinct Support Vector Machine models (SVMs) able to predict functional status 1year ahead. To validate the choice of the model, the results achieved with the SVMs were compared with the output produced by simple linear regression models.
Results 218 patients (mean age = 78.01; SD = 7.85; male = 39%) were recruited. The combination of the two SVMs is able to achieve a higher prediction accuracy (exceeding 80% instances correctly classified vs 67% instances correctly classified by the combination of the two linear regression models). Furthermore, SVMs are able to classify both the three categories,
self sufficiently, disability risk and disability, while linear regression model separates the population only in two groups (self-sufficiency and disability) without identifying the intermediate category (disability risk) which turns out to be the most critical one.
Conclusions The development of such a model can contribute to the early detection of patients at risk of self-sufficiency loss
Over-reassurance and undersupport after a 'false alarm': a systematic review of the impact on subsequent cancer symptom attribution and help seeking
This literature review examined research into the impact of a previous 'all-clear' or non-cancer diagnosis following symptomatic presentation ('false alarm') on symptom attribution and delays in help seeking for subsequent possible cancer symptoms
- …