Photometric compliance of tablet screens and retro-illuminated acuity charts as visual acuity measurement devices

Mobile technology is increasingly used to measure visual acuity. Standards for chart-based acuity tests specify photometric requirements for luminance, optotype contrast and luminance uniformity. Manufacturers provide some photometric data but little is known about tablet performance for visual acuity testing. This study photometrically characterised seven tablet computers (iPad, Apple inc.) and three ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts with room lights on and off, and compared findings with visual acuity measurement standards. Tablet screen luminance and contrast were measured using nine points across a black and white checkerboard test screen at five arbitrary brightness levels. ETDRS optotypes and adjacent white background luminance and contrast were measured. All seven tablets (room lights off) exceeded the most stringent requirement for mean luminance (≥ 120 cd/m2) providing the nominal brightness setting was above 50%. All exceeded contrast requirement (Weber ≥ 90%) regardless of brightness setting, and five were marginally below the required luminance uniformity threshold (Lmin/Lmax ≥ 80%). Re-assessing three tablets with room lights on made little difference to mean luminance or contrast, and improved luminance uniformity to exceed the threshold. The three EDTRS charts (room lights off) had adequate mean luminance (≥ 120 cd/m2) and Weber contrast (≥ 90%), but all three charts failed to meet the luminance uniformity standard (Lmin/Lmax ≥ 80%). Two charts were operating beyond manufacturer’s recommended lamp replacement schedule. With room lights on, chart mean luminance and Weber contrast increased, but two charts still had inadequate luminance uniformity. Tablet computers showed less inter-device variability, higher contrast, and better luminance uniformity than charts in both lights-on and lights-off environments, providing brightness setting was >50%. Overall, iPad tablets matched or marginally out-performed ETDRS charts in terms of photometric compliance with high contrast acuity standards

SWARM Optimization of Force Model Parameters in Micromilling

Because of the improvement of machine-tool and tool performances in micro cutting field, the interest on these processes is increasing. Therefore, researchers involved in micro manufacturing processes focused their attention on these types of processes with the aim of improving the knowledge on the phenomena occurring during micro cutting operations. The objective of this work is to develop a modelling procedure for forecasting cutting forces in micromilling considering the tool run-out and the cutting tool geometry. The designed modelling procedure combines information coming from a force model, an optimization strategy and some experimental tests. The implemented force model is based on specific cutting pressure and actual instantaneous chip section. The tool run-out and the cutting tool geometry were considered in the analytical model. The adopted optimization strategy was based on the Particles Swarm strategy due to its suitability in solving analytical non-linear models. The experimental tests consisted in realizing micro slots on a sample made of Ti6Al4V. The comparison between experimental and analytical data demonstrates the good ability of the proposed procedure in correctly defining the model parameters

Near-infrared spectroscopy study of tourniquet-induced forearm ischaemia in patients with coronary artery disease

Near-Infrared Spectroscopy (NIR) can be employed to monitor local changes in haemodynamics and oxygenation of human tissues. A preliminary study has been performed in order to evaluate the NIRS transmittance response to induced forearm ischaemia in patients with coronary artery disease (CAD). The population consists in 40 patients with cardiovascular risk factors and angiographically documented CAD, compared to a group of 13 normal subjects. By inflating and subsequently deflating a cuff placed around the patient arm, an ischaemia has been induced and released, and the patients have been observed until recovery of the basal conditions. A custom LAIRS spectrometer (IRIS) has been used to collect the backscattered light intensities from the patient forearm throughout the ischaemic and the recovery phase. The time dependence of the near-infrared transmittance on the control group is consistent with the available literature. On the contrary, the magnitude and dynamics of the NIRS signal on the CAD patients show deviations from the documented normal behavior, which can be tentatively attributed to abnormal vessel stiffness. These preliminary results, while validating the performance of the IRIS spectrometer, are strongly conducive towards the applicability of the NIRS technique to ischaemia analysis and to endothelial dysfunction characterization in CAD patients with cardiovascular risk factors.Publisher PD

Educación ambiental, vida en la naturaleza y ciencia escolar : Estado de situación y posibles estrategias de integración

La construcción de relaciones entre Vida en la Naturaleza, Educación Ambiental y Ciencia Escolar da lugar a un campo de trabajo educativo sobre el cual es posible trazar diversas configuraciones didácticas. Desde esta perspectiva, en el presente estudio se analiza el estado de situación de este campo relacional a partir de los resultados obtenidos de encuestas realizadas a estudiantes de Institutos Superiores de Formación Docente en Educación Física, para luego proponer posibles estrategias de intersección didáctica, siempre desde el marco referencial que brinda la tríada conceptual: motricidad, ambiente próximo y planetariedad. Las propuestas están dirigidas a enriquecer la formación inicial de futuros educadores así como también a contribuir en la formación permanente de docentes de diversos profesorados, pudiendo ser extendidas a facilitadores del ámbito educativo no forma

An electrooptical muscle contraction sensor

An electrooptical sensor for the detection of muscle contraction is described. Infrared light is injected into the muscle, the backscattering is observed, and the contraction is detected by measuring the change, that occurs during muscle contraction, between the light scattered in the direction parallel and perpendicular to the muscle cells. With respect to electromyography and to optical absorption-based sensors, our device has the advantage of lower invasiveness, of lower sensitivity to electromagnetic noise and to movement artifacts, and of being able to distinguish between isometric and isotonic contractions

Palaeoseismicity studies on end-Pleistocene and Holocene lake deposits around Basle, Switzerland

Palaeoseismological investigations in the lakes of Seewen and Bergsee in the Basle region, Switzerland and southern Germany, revealed characteristic event horizons in an otherwise uniform background sedimentary record. Dated and correlated based on radiocarbon ages, palynostratigraphy and sedimentation rates, some of these event horizons show soft-sediment deformation features and fractures that can be interpretated as being the result of earthquake shaking. Two of the event horizons with clear indications for earthquake deformation were detected in both lakes, showing approximately the same age as indicated by radiocarbon dating. A third event horizon with fractures of apparent seismogenic origin, was detected at several drill sites in only one lake (Bergsee). Three further event horizons, two in the Bergsee and one in Lake Seewen, are of uncertain origin, though they show some characteristics that could well be caused by earthquakes. Based on the observations in both lakes, five events were detected of which three are most probably related to earthquakes which occurred between 180 BC-1160 BC, 8260 BC-9040 BC and 10 720 BC-11 200 BC, respectively. The Basle region is well known for the strongest historical earthquake north of the Alps, the AD 1356 Basle earthquake. Based on combined historical and palaeoseismological data, it has been inferred that earthquakes with size comparable to the AD 1356 Basle earthquake have occurred several times within the last 12 000 yr and that the recurrence time for such strong earthquakes are in the range of 1500-3000 y

Rupture Reactivation during the 2011 M_w 9.0 Tohoku Earthquake: Dynamic Rupture and Ground-Motion Simulations

Near‐source ground‐motion observations and kinematic source inversions suggest that the rupture process of the 2011 M_w 9.0 Tohoku earthquake involved rupture reactivation, that is, repeated rupture nucleation in the same hypocentral area. This unusual phenomenon may have provided a second breath to the rupture that enhanced its final size. Here, we propose that rupture reactivation may have been governed by a slip‐weakening friction model with two sequential strength drops, the second one being activated at large slip. Such frictional behavior has been previously observed in laboratory experiments and attributed to pressurization of fault‐zone fluids by mineral decomposition reactions activated by shear heating, such as dehydration and decarbonation. Further evidence of this double‐slip‐weakening friction model is obtained here from the dynamic stress changes in the hypocentral region derived from a finite source inversion model. We incorporate this friction model in a dynamic rupture simulation comprising two main asperities constrained by source inversion models and several deep small asperities constrained by backprojection source imaging studies. Our simulation produces ground‐motion patterns along the Japanese coast consistent with observations and rupture patterns consistent with a kinematic source model featuring rupture reactivation. The deep small asperities serve as a bridge to connect the two main asperities, and the rupture reactivation mechanism is needed to reproduce the observed ground‐motion pattern. Therefore, we argue that rupture reactivation during the 2011 Tohoku earthquake is consistent with a second strength drop, possibly caused by activation of thermochemical weakening processes at large slip

Enantioselective HF loss promoted by resonant two photon ionization of supersonically expanded (R)-1-phenyl-2,2,2-trifluoroethanol clusters.

(R)-1-Phenyl-2,2,2-trifluoroethanol and its hydrogen bonded adducts with achiral (water, tetrahydrofuran) and chiral solvent mols. ((R)- and (S)-butan-2-ol, (R)- and (S)-3-hydroxy-tetrahydrofuran) have been ionized by resonant two-photon absorption. The presence of photofragments, attributable to the occurrence of a hydrogen fluoride loss reaction, has been interpreted with the aid of theor. predictions at the DFT level of theory with the inclusion of dispersive terms. The HF elimination process takes place by a mechanism involving the preliminary C.alpha.-H hydrogen transfer to an hydroxyl oxygen assisted by the solvent mol. which is followed by extrusion of the HF mol. The calcd. energy barriers depend on the type of solvent as well as on its configuration and are consistent with the obsd. fragmentation ratios

Molecular and supramolecular chirality: R2PI spectroscopy as a tool for the gas-phase recognition of chiral systems of biological interest.

A review. In life sciences, diastereomeric chiral mol./chiral receptor complexes are held together by a different combination of intermol. forces and are therefore endowed with different stability and reactivity. Detn. of these forces, which are normally affected in the condensed phase by solvent and supramol. interactions, can be accomplished through the generation of diastereomeric complexes in the isolated state and their spectroscopic investigation. This review presents a detailed discussion of the mass resolved Resonant Two Photon Ionization (R2PI-TOF) technique in supersonic beams and introduces an overview of various other technologies currently available for the spectroscopic study of gas phase chiral mols. and supramol. systems. It reports case studies primarily from the authors' recent work using R2PI-TOF methodol. for chiral recognition in clusters contg. mols. of biol. interest. The measurement of absorption spectra, ionization and fragmentation thresholds of diastereomeric clusters by this technique allow the detn. of the nature of the intrinsic interactions, which control their formation and which affect their stability and reactivity

Evaluating the effect of network density and geometric distribution on kinematic source inversion models

The effect of network density and geometric distribution on kinematic non-linear source inversion is investigated by inverting synthetic ground motions from a buried strike-slip fault (Mw 6.5), that have been generated by dynamic spontaneous rupture modelling. For the inversion, we use a physics-based regularized Yoffe function as slip velocity function. We test three different cases of station network geometry: (i) single station, varying azimuth and epicentral distance; (ii) multistation circular configurations, that is stations at similar distances from the fault, and regularly spaced around the fault; (iii) irregular multistation configurations using different numbers of stations. Our results show: (1) single station tests suggest that it may be possible to obtain a relatively good source model even using a single station. The best source model using a single station is obtained with stations at which amplitude ratios between three components are not large. We infer that both azimuthal angle and source-to-station distance play an important role in the design of optimal seismic network for source inversion. (2) Multistation tests show that the quality of the inverted source systematically correlates neither with the number of stations, nor with waveform misfit. (3) Waveform misfit has a direct correlation with the number of stations, resulting in overfitting the observed data without any systematic improvement of the source. It suggests that the best source model is not necessarily derived from the model with minimum waveform misfit. (4) A seismic network with a small number of well-spaced stations around the fault may be sufficient to obtain acceptable source inversio