Origin of the Felkin-Anh(-Eisenstein) model: a quantitative rationalization of a seminal concept.

Quantum chemical calculations were carried out to quantitatively understand the origin of the Felkin-Anh(-Eisenstein) model, widely used to rationalize the π-facial stereoselectivity in the nucleophilic addition reaction to carbonyl groups directly attached to a stereogenic center. To this end, the possible approaches of cyanide to both ()-2-phenylpropanal and ()-3-phenylbutan-2-one have been explored in detail. With the help of the activation strain model of reactivity and the energy decomposition analysis method, it is found that the preference for the Felkin-Anh addition is mainly dictated by steric factors which manifest in a less destabilizing strain-energy rather than, as traditionally considered, in a lower Pauli repulsion.

What defines electrophilicity in carbonyl compounds.

The origin of the electrophilicity of a series of cyclohexanones and benzaldehydes is investigated using the activation strain model and quantitative Kohn-Sham molecular orbital (MO) theory. We find that this electrophilicity is mainly determined by the electrostatic attractions between the carbonyl compound and the nucleophile (cyanide) along the entire reaction coordinate. Donor-acceptor frontier molecular orbital interactions, on which the current rationale behind electrophilicity trends is based, appear to have little or no significant influence on the reactivity of these carbonyl compounds.

Evaluation of the Create@School Game-Based Learning-Teaching Approach.

The constructivist approach is interested in creating knowledge through active engagement and encourages students to build their knowledge from their experiences in the world. Learning through digital game making is a constructivist approach that allows students to learn by developing their own games, enhancing problem-solving skills and fostering creativity. In this context two tools, Create@School App and the Project Management Dashboard (PMD), were developed to enable students from different countries to be able to adapt their learning material by programming and designing games for their academic subjects, therefore integrating the game mechanics, dynamics, and aesthetics into the academic curriculum.

Empowering Citizens through Perceptual Sensing of Urban Environmental and Health Data Following a Participative Citizen Science Approach.

The growth of the urban population together with a high concentration of air pollution have important health impacts on citizens who are exposed to them, causing serious risks of the development and evolution of different chronic diseases. This paper presents the design and development of a novel participatory citizen science-based application and data ecosystem model. These developments are imperative and scientifically designed to gather and process perceptual sensing of urban, environmental, and health data.

Screening for retroviruses and hepatitis viruses using dried blood spots reveals a high prevalence of occult hepatitis B in Ghana.

Background: Recent advances in antiviral therapy show potential for a cure and/or control of most human infections caused by hepatitis viruses and retroviruses. However, medical success is largely dependent on the identification of the large number of people unaware of these infections, especially in developing countries. Dried blood spots (DBS) have been demonstrated to be a good tool for collecting, storing and transporting clinical specimens from rural areas and limited-resource settings to laboratory facilities, where viral infections can be more reliably diagnosed.

Exploring the Potential of Laser Ablation Carbon Isotope Analysis for Examining Ecology during the Ontogeny of Middle Pleistocene Hominins from Sima de los Huesos (Northern Spain).

Laser ablation of tooth enamel was used to analyze stable carbon isotope compositions of teeth of hominins, red deer, and bears from middle Pleistocene sites in the Sierra de Atapuerca in northern Spain, to investigate the possibility that this technique could be used as an additional tool to identify periods of physiological change that are not detectable as changes in tooth morphology. Most of the specimens were found to have minimal intra-tooth variation in carbon isotopes (< 2.3‰), suggesting isotopically uniform diets through time and revealing no obvious periods of physiological change.

[Bioethics is dead. Long live medical ethics!].

The purpose of this paper is to show a paradigmatic crisis in academic bioethics. Since an important part of bioethicists began to relativize the ethical prohibition of killing an innocent human being, one way or another they began to ally with the death industry: the business of abortion, and then that of euthanasia. The thesis of this paper is that by crossing that Rubicon bioethics has been corrupted and has lost its connection to the ethical, political and legal discourse.

Analysis of SnS2 hyperdoped with V proposed as efficient absorber material.

Intermediate-band materials can improve the photovoltaic efficiency of solar cells through the absorption of two subband-gap photons that allow extra electron-hole pair formations. Previous theoretical and experimental findings support the proposal that the layered SnS2 compound, with a band-gap of around 2 eV, is a candidate for an intermediate-band material when it is doped with a specific transition-metal. In this work we characterize vanadium doped SnS2 using density functional theory at the dilution level experimentally found and including a dispersion correction combined with the site-occupancy-disorder method.

Pulse shortening of gain switched single mode semiconductor lasers using a variable delay interferometer.

We propose a pulse shaping and shortening technique for pulses generated from gain switched single mode semiconductor lasers, based on a Mach Zehnder interferometer with variable delay. The spectral and temporal characteristics of the pulses obtained with the proposed technique are investigated with numerical simulations. Experiments are performed with a Distributed Feedback laser and a Vertical Cavity Surface Emitting Laser, emitting at 1.

Self-validating technique for the measurement of the linewidth enhancement factor in semiconductor lasers.

A new method for measuring the linewidth enhancement factor (α-parameter) of semiconductor lasers is proposed and discussed. The method itself provides an estimation of the measurement error, thus self-validating the entire procedure. The α-parameter is obtained from the temporal profile and the instantaneous frequency (chirp) of the pulses generated by gain switching.

[Outpatient use of topical antimicrobials in Spain associated with other drugs (2005-2007)].

Introduction: The consumption of antibiotics for systemic use has been well studied. However, data of topical use in our country are an anecdotal reference in the literature.

Objective: To evaluate the outpatient use of topical antimicrobials in Spain associated with other drugs during the period December 2005 and November 2007.

Two-dimensional electrophoresis and mass spectrometry for the identification of species-specific Trichinella antigens.

A proteomic approach was utilized for fine antigenic characterization of the closely related Trichinella genotypes Trichinella britovi T3 and Trichinella T8. Crude extract of muscle larvae L1 (LCE) from both isolates were analyzed by 2D-PAGE. Over 500 protein spots were reproducibly separated in both genotypes.

Size variation in Middle Pleistocene humans.

It has been suggested that European Middle Pleistocene humans, Neandertals, and prehistoric modern humans had a greater sexual dimorphism than modern humans. Analysis of body size variation and cranial capacity variation in the large sample from the Sima de los Huesos site in Spain showed instead that the sexual dimorphism is comparable in Middle Pleistocene and modern populations.