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

HRM in the German business system: a review

Human resource management in Germany is deeply rooted in its institutional environment. Thus, US style HRM cannot be simply transferred to the German context. Nevertheless, the German business system is not hostile to HRM principles. Rather, these practices have to be adapted to the demands and constrains of the German socio-economic context. The key labour market institutions of collective bargaining, co-determination, and initial vocational training in particular require a pluralist style of human resource management. As our review suggests, these institutions support the implementation of some HRM principles while inhibiting others. Also, the concept of Strategic HRM in Germany may only be fully understood against the background of labour market institutions

Production and Reactivity of Ionized Clusters in the Gas Phase

A brief review of the experimental methods to obtain gas phase cluster ions is reported. Supersonic expansion and ionization, high pressure ion production and clusterization, ablation from solids are techniques used to study cluster chemistry. Studies of cluster ion formation from metal, metal oxides and metal carbides are illustrated together with considerations on their structure and stability

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

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

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