Efectes de l’altura solar, la nuvolositat i la temperatura en les mesures dels piranòmetres de silici = Efectos de la altura solar, la nubosidad y la temperatura en las medidas de los piranometros de silicio

La mesura de la irradiància solar en superfície es fa mitjançant piranòmetres amb sensor termoelèctric o amb sensor de silici. Aquests darrers presenten una resposta espectral no uniforme i limitada a la banda de 400 a 1100 nm, i, a més, la seva sensibilitat depèn fortament de la temperatura. Els piranòmetres termoelèctrics, en canvi, presenten una resposta espectral uniforme en la banda solar, i un coeficient de temperatura reduït. L’objectiu de l’estudi que es presenta ha estat millorar l’acord entre les mesures d’irradiància global preses amb un piranòmetre termoelèctric CM11 de Kipp & Zonen, i diversos piranòmetres fotovoltaics o de silici Li200SA de Li-Cor. Com que la resposta angular dels sensors s’aparta en general de la resposta cosinus ideal, es proposen unes correccions a tal efecte. S’han analitzat les dades minutals corresponents a un cicle anual de mesures d’irradiància preses pels dos tipus de piranòmetres a l’estació radiomètrica de la Universitat de Girona. Les correccions proposades per la resposta angular dels instruments es basen en bibliografia prèvia, i també en simulacions realitzades amb un model espectral de transferència radiativa multicapa. La simulació ha permès obtenir correccions per compensar les diferents respostes angulars i espectrals dels dos tipus d’instruments. Per a cels serens, les correccions angulars i espectrals milloren notablement l’acord entre les mesures dels dos tipus de piranòmetres. També es proposa una correcció de l’efecte de la temperatura sobre la mesura dels piranòmetres de silici, obtinguda empíricament. Malgrat que les correccions s’han obtingut per a cels serens, han estat també aplicades a condicions de cel ennuvolat, caracteritzades objectivament mitjançant un algorisme basat en mesures d’irradiància global i difusa. Finalment s’ha comprovat que les correccions també milloren l’acord entre les mesures dels dos tipus de sensors independentment de l’extensió de la coberta de núvols

Empirical studies of cloud effects on UV radiation: A review

The interest in solar ultraviolet (UV) radiation from the scientific community and the general population has risen significantly in recent years because of the link between increased UV levels at the Earth's surface and depletion of ozone in the stratosphere. As a consequence of recent research, UV radiation climatologies have been developed, and effects of some atmospheric constituents (such as ozone or aerosols) have been studied broadly. Correspondingly, there are well-established relationships between, for example, total ozone column and UV radiation levels at the Earth's surface. Effects of clouds, however, are not so well described, given the intrinsic difficulties in properly describing cloud characteristics. Nevertheless, the effect of clouds cannot be neglected, and the variability that clouds induce on UV radiation is particularly significant when short timescales are involved. In this review we show, summarize, and compare several works that deal with the effect of clouds on UV radiation. Specifically, works reviewed here approach the issue from the empirical point of view: Some relationship between measured UV radiation in cloudy conditions and cloud-related information is given in each work. Basically, there are two groups of methods: techniques that are based on observations of cloudiness (either from human observers or by using devices such as sky cameras) and techniques that use measurements of broadband solar radiation as a surrogate for cloud observations. Some techniques combine both types of information. Comparison of results from different works is addressed through using the cloud modification factor (CMF) defined as the ratio between measured UV radiation in a cloudy sky and calculated radiation for a cloudless sky. Typical CMF values for overcast skies range from 0.3 to 0.7, depending both on cloud type and characteristics. Despite this large dispersion of values corresponding to the same cloud cover, it is clear that the cloud effect on UV radiation is 15–45% lower than the cloud effect on total solar radiation. The cloud effect is usually a reducing effect, but a significant number of works report an enhancement effect (that is increased UV radiation levels at the surface) due to the presence of clouds. The review concludes with some recommendations for future studies aimed to further analyze the cloud effects on UV radiation

Passive knee-extension test to measure hamstring tightness: influence of gravity correction

CONTEXT: A passive knee-extension test has been shown to be a reliable method of assessing hamstring tightness, but this method does not take into account the potential effect of gravity on the tested leg. OBJECTIVE: To compare an original passive knee-extension test with 2 adapted methods including gravity's effect on the lower leg. DESIGN: Repeated measures. SETTING: Laboratory. PARTICIPANTS: 20 young track and field athletes (16.6 ± 1.6 y, 177.6 ± 9.2 cm, 75.9 ± 24.8 kg). INTERVENTION: Each subject was tested in a randomized order with 3 different methods: In the original one (M1), passive knee angle was measured with a standard force of 68.7 N (7 kg) applied proximal to the lateral malleolus. The second (M2) and third (M3) methods took into account the relative lower-leg weight (measured respectively by handheld dynamometer and anthropometrical table) to individualize the force applied to assess passive knee angle. MAIN OUTCOME MEASURES: Passive knee angles measured with video-analysis software. RESULTS: No difference in mean individualized applied force was found between M2 and M3, so the authors assessed passive knee angle only with M2. The mean knee angle was different between M1 and M2 (68.8 ± 12.4 vs 73.1 ± 10.6, P < .001). Knee angles in M1 and M2 were correlated (r = .93, P < .001). CONCLUSIONS: Differences in knee angle were found between the original passive knee-extension test and a method with gravity correction. M2 is an improved version of the original method (M1) since it minimizes the effect of gravity. Therefore, we recommend using it rather than M1.

Aplicació de calculadora solar

El present treball fi de carrera consisteix en la realització de l'estudi, disseny i implementació d'una aplicació informàtica dins de la temàtica dels sistemes d'informació geogràfica (SIG) per realitzar el càlcul de la quantitat de llum solar rebuda pels diferents edificis d'una ciutat. L'aplicació s'ha desenvolupat sota l'entorn de GeoMedia, una plataforma comercial per tractar dades SIG, i ha estat programada en Visual Basic fent servir l'entorn Visual Studio 2012.

Aplicació de calculadora solar

Implantació d'una calculadora de radiació solar sobre els edificis d'una zona d'estudi.

Imagerie cardiaque non invasive: apport spécifique en clinique des nouvelles modalités (II). Evaluation fonctionnelle [Cardiac imaging: specific clinical role of newly developed non invasive techniques. Part II: functional evaluation].

The non-invasive evaluation of myocardial ischemia is a priority in cardiology. The preferred initial non-invasive test is exercise ECG, because of its high accessibility and its low cost. Stress radionuclide myocardial perfusion imaging or stress echocardiography are now routinely performed, and new non-invasive techniques such as perfusion-MRI, dobutamine stress-MRI or 82rubidium perfusion PET have recently gained acceptance in clinical practice. In the same time, an increasing attention has been accorded to the concept of myocardial viability in the decisional processes in case of ischemic heart failure. In this indication, MRI with late enhancement after intravenous injection of gadolinium and 18F-FDG PET showed an excellent diagnostic accuracy. This article will present these new imaging modalities and their accepted indications.

Improving QPF by blending techniques at the Meteorological Service of Catalonia

The current operational very short-term and short-term quantitative precipitation forecast (QPF) at the Meteorological Service of Catalonia (SMC) is made by three different methodologies: Advection of the radar reflectivity field (ADV), Identification, tracking and forecasting of convective structures (CST) and numerical weather prediction (NWP) models using observational data assimilation (radar, satellite, etc.). These precipitation forecasts have different characteristics, lead time and spatial resolutions. The objective of this study is to combine these methods in order to obtain a single and optimized QPF at each lead time. This combination (blending) of the radar forecast (ADV and CST) and precipitation forecast from NWP model is carried out by means of different methodologies according to the prediction horizon. Firstly, in order to take advantage of the rainfall location and intensity from radar observations, a phase correction technique is applied to the NWP output to derive an additional corrected forecast (MCO). To select the best precipitation estimation in the first and second hour (t+1 h and t+2 h), the information from radar advection (ADV) and the corrected outputs from the model (MCO) are mixed by using different weights, which vary dynamically, according to indexes that quantify the quality of these predictions. This procedure has the ability to integrate the skill of rainfall location and patterns that are given by the advection of radar reflectivity field with the capacity of generating new precipitation areas from the NWP models. From the third hour (t+3 h), as radar-based forecasting has generally low skills, only the quantitative precipitation forecast from model is used. This blending of different sources of prediction is verified for different types of episodes (convective, moderately convective and stratiform) to obtain a robust methodology for implementing it in an operational and dynamic way.

ON THE ROLE OF PERIOD-2 IN THE CIRCADIAN AND HOMEOSTATIC REGULATION OF SLEEP

Humans spend one third of their life sleeping, then we could raise the basic question: Why do we sleep? Despite the fact that we still don't fully understand its function, we made much progress in understanding at different levels how sleep is regulated. One model suggests that sleep is regulated by two processes: a homeostatic process that tracks the need for sleep and by a circadian rhythm that determines the preferred time-of-day sleep occurs. At the molecular level circadian rhythms are a property of interlocking transcriptional regula-tors referred to as clock genes. The heterodimeric transcription factors BMAL1::CLOCK/NPAS2 drive the transcription of many target genes including the clock genes Cryptochome1 (Cry1), Cry2, Period1 (Per1), and Per2. The encoded CRY/PER proteins are transcriptional inhibitors of BMAL1::CLOCK/NPAS2 thereby providing negative feedback to their own transcription. These genes seem, however, also involved in sleep homeostasis because the brain expression of clock genes, es-pecially that of Per2, increase as a function of time-spent-awake and because mice lacking clock genes display altered sleep homeostasis. The aim of first part of my doctoral work has been to advance our understanding the link that exists between sleep homeostasis and circadian rhythms investigating a possible mechanism by which sleep deprivation could alter clock gene expression by quantifying DNA-binding of the core-clock genes BMAL1, CLOCK and NPAS2 to their target chromatin loci including the E-box enhancers of the Per2 promoter. We made use of chromatin immunoprecipitation (ChIP) and quantitative poly-merase chain reaction (qPCR) to show that DNA-binding of CLOCK and BMAL1 to their target genes changes as a function of time-of-day in both liver and cerebral cortex. We then performed a 6h sleep deprivation (SD) and observed a significant decrease in DNA-binding of CLOCK and BMAL1 to Dbp. This is consistent with a decrease in Dbp mRNA levels after SD. The DNA-binding of NPAS2 and BMAL1 to Per2 was similarly decreased following SD. However, SD has been previously shown to in-crease Per2 expression in the cortex which seems paradoxical. Our results demonstrate that sleep-wake history can affect the molecular clock machinery directly at the level of the chromatin thereby altering the cortical expression of Dbp and Per2, and likely other targets. However, the precise dy-namic relationship between DNA-binding and mRNA expression, especially for Per2, remains elusive. The second aim of my doctoral work has been to perform an in depth characterization of cir-cadian rhythmicity, sleep architecture, analyze the response to SD in full null-Per2 knock-out (Per2-/-) mice, and Per1-/- mice, as well as their double knock-out offspring (Per1,2-/-) and littermate wildtype (Wt) mice. The techniques used include locomotor activity recording by passive infrared (PIR) sen-sors, EEG/EMG surgery, recording, and analysis, and cerebral cortex extraction and quantification of mRNA levels by qPCR. Under standard LD12:12 conditions, we found that wakefulness onset, as well as the time courses of clock gene expression in the brain and corticosterone plasma levels were ad-vanced by about 2h in Per2-/- mice compared to Wt mice. When released under constant dark condi-tions almost all Per2-/- mice (97%) became arrhythmic immediately. From these observations, we conclude that while Per2-/- mice seem to be able to anticipate dark onset, this does not result from a self-sustained circadian clock. Our results suggest instead that the earlier onset of activity results from a labile, not-self sustained 22h rhythm linked to light onset suggesting the existence of a light-driven rhythm. Analyses of sleep under LD12:12 conditions revealed that in both Per2-/- and Per1,2-/- mice the same sleep phenotypes are observed compared to Wt mice: increased NREM sleep frag-mentation and inability to adequately compensate the loss of NREM sleep. That suggests a possible role of PER2 in sleep consolidation and recovery.