Ultra-broadband contactless imaging power meter.

Knowledge of the spatial and temporal distribution of heat flux is of great interest for the quantification of heat sources. In this work, we describe the development of a new ultra-broadband contactless imaging power meter based on electromagnetic to infrared technology. This new sensor and the mathematical processing of images enable the reconstruction of both spatial and amplitude distributions through a wide spectral range of sources. The full modeling of the thermoconverter based on 3D formalism of thermal quadrupoles is presented first before deriving a reduced model more suitable for quick and robust inverse processing. The inverse method makes it possible to simultaneously identify the heat losses and the spatial and temporal source distribution for the first time, to the best of our knowledge. Finally, measurements of multispectral sources are presented and discussed, with an emphasis on the spatial and temporal resolution, accuracy and capabilities of the power meter.

The Joule heating problem in silver nanowire transparent electrodes.

Silver nanowire transparent electrodes have shown considerable potential to replace conventional transparent conductive materials. However, in this report we show that Joule heating is a unique and serious problem with these electrodes. When conducting current densities encountered in organic solar cells, the average surface temperature of indium tin oxide (ITO) and silver nanowire electrodes, both with sheet resistances of 60 ohms/square, remains below 35 °C. However, in contrast to ITO, the temperature in the nanowire electrode is very non-uniform, with some localized points reaching temperatures above 250 °C. These hotspots accelerate nanowire degradation, leading to electrode failure after 5 days of continuous current flow. We show that graphene, a commonly used passivation layer for these electrodes, slows nanowire degradation and creates a more uniform surface temperature under current flow. However, the graphene does not prevent Joule heating in the nanowires and local points of high temperature ultimately shift the failure mechanism from nanowire degradation to melting of the underlying plastic substrate. In this paper, surface temperature mapping, lifetime testing under current flow, post-mortem analysis, and modelling illuminate the behaviour and failure mechanisms of nanowires under extended current flow and provide guidelines for managing Joule heating.

Pressure ulcers prevention efficacy of an alternating pressure air mattress in elderly patients: E²MAO a randomised study.

OBJECTIVE: Our aim was to compare Axtair One, an alternating pressure air mattress (APAM), with a viscoelastic foam mattress (VFM) in elderly patients at moderate to high risk of developing pressure ulcers (PUs). METHOD: A randomised, controlled, superiority, parallel-group, open-label, multicentre study, was conducted, between February 2012 and March 2015, in nine French, medium- and long-term stay facilities. Eligible patients were aged 70 and over, had no PUs on enrolment, were bedridden for at least 15 hours per day, had reduced mobility, an absent or minimal positioning capability, a Braden score <14, a nutritional status score >12 and a Karnofsky score <40%. The primary endpoint was the appearance of PUs over a 30-day monitoring period. The primary objective was to demonstrate a 50% reduction in instantaneous risk of PUs in the APAM versus the VFM group. Secondary objectives were to determine if preventive care was less frequent in the APAM group, the instantaneous relative risk of PUs (hazard ratio) was constant over time and the comfort experienced was higher in the APAM group and to verify the uniformity of the preventive benefit of an APAM, regardless of the level of exposure to major risk factors for PUs. RESULTS: We randomised 76 patients (39 in the APAM group and 37 in the VFM group). The groups were comparable on enrolment and throughout the study. The cumulative risk of PUs was estimated at 6.46% [95% confidence interval (CI): 1.64; 23.66] in the APAM group and at 38.91% [95% CI: 24.66; 57.59] in the VFM group, p=0.001 (log-rank test). The adjusted hazard ratio according to the Cox model with four prognostic factors for the appearance of PUs was 7.57 [95% CI: 1.67; 34.38, p=0.009]. Preventive care proved to be equivalent in both groups. The only risk factor significantly associated with an increased risk of PUs was the type of mattress (VFM). The comfort and tolerance perceived by the patients were both high and similar in the two groups. The constancy over time of the preventive benefit of an APAM could not be verified because of the lack of a sufficient number of events (appearance of PUs) in the APAM group. CONCLUSION: The APAM was superior to a VFM for preventing PUs in elderly patients, bedridden for more than 15 hours per day, severely dependent, at moderate-to high-risk of PUs, with an instantaneous risk for the appearance of PUs 7.57 times greater in the VFM group than in the APAM group. This study provides descriptive information and evidence for practice.

Infrared thermotransmittance-based temperature field measurements in semitransparent media.

Contactless temperature field measurements in or at the surfaces of semitransparent media are a scientific challenge as classical thermography techniques based on proper material emission cannot be used. In this work, an alternative method using infrared thermotransmittance for contactless temperature imaging is proposed. To overcome the weakness of the measured signal, a lock-in acquisition chain is developed and an imaging demodulation technique is used to retrieve the phase and amplitude of the thermotransmitted signal. These measurements, combined with an analytical model, enable the estimation of the thermal diffusivity and conductivity of an infrared semitransparent insulator (wafer of Borofloat 33 glass) and the monochromatic thermotransmittance coefficient at 3.3 µm. The obtained temperature fields are in good agreement with the model, and a detection limit of ±2 °C is estimated with this method. The results of this work open new opportunities in the development of advanced thermal metrology for semitransparent media.

From intermittent to nonintermittent behavior in two dimensional thermal convection in a soap bubble.

Turbulent thermal convection in half a soap bubble heated from below displays a new and surprising transition from intermittent to nonintermittent behavior for the temperature field. This transition is observed here by studying the high order moments of temperature increments. For high temperature gradients, these structure functions display Bolgiano-like scaling predicted some 60 years ago with no observable deviations. The probability distribution functions of these increments are Gaussian throughout the scaling range. These measurements are corroborated with additional velocity structure function measurements.

3D infrared thermospectroscopic imaging.

This work reports a multispectral tomography technique in transmission mode (called 3DITI for 3D Infrared Thermospectroscopic Imaging) based on a middle wavelength infrared (MWIR) focal plane array. This technique relies on an MWIR camera (1.5 to 5.5 µm) used in combination with a multispectral IR monochromator (400 nm to 20 µm), and a sample mounted on a rotary stage for the measurement of its transmittance at several angular positions. Based on the projections expressed in terms of a sinogram, spatial three-dimensional (3D) cubes (proper emission and absorptivity) are reconstructed using a back-projection method based on inverse Radon transform. As a validation case, IR absorptivity tomography of a reflective metallic screw is performed within a very short time, i.e., shorter than 1 min, to monitor 72 angular positions of the sample. Then, the absorptivity and proper emission tomographies of a butane-propane-air burner flame and microfluidic perfluoroalkoxy (PFA) tubing filled with water and ethanol are obtained. These unique data evidence that 3D thermo-chemical information in complex semi-transparent media can be obtained using the proposed 3DITI method. Moreover, this measurement technique presents new problems in the acquisition, storage and processing of big data. In fact, the quantity of reconstructed data can reach several TB (a tomographic sample cube of 1.5 × 1.5 × 3 cm3 is composed of more than 1 million pixels per wavelength).

[Study of methicillin-resistant Staphylococcus aureus colonization among intermediate-care facility patients]. / Etude de la colonisation par Staphylococcus aureus résistant à la méticilline dans des services de soins de suite.

PURPOSE: Prevalence of methicillin-resistant Staphylococcus aureus is high in the Poitiers teaching hospital, particularly in the intermediate care facilities. We performed a survey of methicillin-resistant Staphylococcus aureus colonization in the intermediate care facilities and 265 patients were included. METHODS: Nasal, cutaneous and wound swab cultures were done at the time of admission and at the time of the patients' departure. A decolonization procedure of methicillin-resistant Staphylococcus aureus carriers was performed using nasal application of fusidic acid and different soaps for the skin. At entry, 17.7% of patients were methicillin-resistant Staphylococcus aureus carriers (of at least one location). At departure, 30.4% were methicillin-resistant Staphylococcus aureus carriers. Among methicillin-resistant Staphylococcus aureus non-carriers at entry, 24.3% became methicillin-resistant Staphylococcus aureus carriers. RESULTS: The principal risk factor of carriage was the initial presence of a wound (RR = 3.6). The incidence rate of methicillin-resistant Staphylococcus aureus infection among the 265 patients included was 3%. CONCLUSION: The systematic screening of patients at the time of admission is expensive and isolation technically hard to manage in the intermediate care facilities. The risk factor we found in this study allow us to propose a 'light' screening limited to patients with wounds.

Thermoreflectance temperature measurement with millimeter wave.

GigaHertz (GHz) thermoreflectance technique is developed to measure the transient temperature of metal and semiconductor materials located behind an opaque surface. The principle is based on the synchronous detection, using a commercial THz pyrometer, of a modulated millimeter wave (at 110 GHz) reflected by the sample hidden behind a shield layer. Measurements were performed on aluminum, copper, and silicon bulks hidden by a 5 cm thick Teflon plate. We report the first measurement of the thermoreflectance coefficient which exhibits a value 100 times higher at 2.8 mm radiation than those measured at visible wavelengths for both metallic and semiconductor materials. This giant thermoreflectance coefficient κ, close to 10(-3) K(-1) versus 10(-5) K(-1) for the visible domain, is very promising for future thermoreflectance applications.

High speed heterodyne infrared thermography applied to thermal diffusivity identification.

We have combined InfraRed thermography and thermal wave techniques to perform microscale, ultrafast (microsecond) temperature field measurements. The method is based on an IR camera coupled to a microscope and synchronized to the heat source by means of phase locked function generators. The principle is based on electronic stroboscopic sampling where the low IR camera acquisition frequency f(acq) (25 Hz) undersamples a high frequency thermal wave. This technique permits the measurement of the emissive thermal response at a (microsecond) short time scale (microsecond) with the full frame mode of the IR camera with a spatial thermal resolution of 7 µm. Then it becomes possible to study 3D transient heat transfer in heterogeneous and high thermal conductive thin layers. Thus it is possible for the first time in our knowledge to achieve temperature field measurements in heterogeneous media within a wide range of time domains. The IR camera is now a suitable instrument for multiscale thermal analysis.