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Search Results: 1 - 10 of 197840 matches for " N Charpak "
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Education and training in the implementation of kangaroo mother care
A-M Bergh, N Charpak, A Ezeonodo, RH Udani, E van Rooyen
South African Journal of Child Health , 2012,
Abstract: In the past three decades, kangaroo mother care (KMC) has been established as a safe and effective method of infant care, with the potential for improving the survival of low-birth-weight newborns, especially in low- and middle-income countries. Despite many implementation, education and training efforts, some countries are finding it difficult to increase their coverage of KMC, and individual institutions still struggle to get KMC institutionalised in a sustainable way. In the past decade a better understanding has emerged on the health system pathways followed in the implementation of KMC. The initiative reported in this paper started out with a review of education and training practices in the implementation of KMC across the world. This was discussed at an international workshop and further inputs were derived from individuals’ experience, unpublished literature provided by colleagues, and published material. This report gives an overview of some of the key implementation and training issues identified by the group and recommendations emanating from the collaborative process. A triangular change process that includes change agents and the choice of implementation and educational models is proposed. The different functions for change agents as drivers, trainers and implementers are discussed. The grassroots, policy and academic dimensions are presented as different pathways for initiating KMC. Educational models are developed locally and are determined by the context. Education and training in KMC should be underpinned by the same basic understanding of the concept and should be accompanied by the creation of awareness, committed ‘champions’, multidisciplinary teamwork and continuous support from senior management. It should be based on the evidence produced by research, conducted according to current best practice in education, and locally appropriate and applicable.
Determining the azimuthal properties of coronal mass ejections from multi-spacecraft remote-sensing observations with stereo secchi
N. Lugaz,J. N. Hernandez-Charpak,I. I. Roussev,C. J. Davis,A. Vourlidas,J. A. Davies
Physics , 2010, DOI: 10.1088/0004-637X/715/1/493
Abstract: We discuss how simultaneous observations by multiple heliospheric imagers can provide some important information about the azimuthal properties of Coronal Mass Ejections (CMEs) in the heliosphere. We propose two simple models of CME geometry that can be used to derive information about the azimuthal deflection and the azimuthal expansion of CMEs from SECCHI/HI observations. We apply these two models to four CMEs well-observed by both STEREO spacecraft during the year 2008. We find that in three cases, the joint STEREO-A and B observations are consistent with CMEs moving radially outward. In some cases, we are able to derive the azimuthal cross-section of the CME fronts, and we are able to measure the deviation from self-similar evolution. The results from this analysis show the importance of having multiple satellites dedicated to space weather forecasting, for example in orbits at the Lagrangian L4 and L5 points.
A new regime of nanoscale thermal transport: collective diffusion counteracts dissipation inefficiency
Kathleen M. Hoogeboom-Pot,Jorge N. Hernandez-Charpak,Erik H. Anderson,Xiaokun Gu,Ronggui Yang,Margaret M. Murnane,Henry C. Kapteyn,Damiano Nardi
Physics , 2014, DOI: 10.1073/pnas.1503449112
Abstract: Understanding thermal transport from nanoscale heat sources is important for a fundamental description of energy flow in materials, as well as for many technological applications including thermal management in nanoelectronics, thermoelectric devices, nano-enhanced photovoltaics and nanoparticle-mediated thermal therapies. Thermal transport at the nanoscale is fundamentally different from that at the macroscale and is determined by the distribution of carrier mean free paths in a material, the length scales of the heat sources, and the distance over which heat is transported. Past work has shown that Fourier's law for heat conduction dramatically over-predicts the rate of heat dissipation from heat sources with dimensions smaller than the mean free path of the dominant heat-carrying phonons. In this work, we uncover a new regime of nanoscale thermal transport that dominates when the separation between nanoscale heat sources is small compared with the dominant phonon mean free paths. Surprisingly, the interplay between neighboring heat sources can facilitate efficient, diffusive-like heat dissipation, even from the smallest nanoscale heat sources. This finding suggests that thermal management in nanoscale systems including integrated circuits might not be as challenging as projected. Finally, we demonstrate a unique and new capability to extract mean free path distributions of phonons in materials, allowing the first experimental validation of differential conductivity predictions from first-principles calculations.
Detector of alpha particles and x-rays operating in ambient air in pulse counting mode or/and with gas amplification
G. Charpak,P. Benaben,P. Breuil,V. Peskov
Physics , 2007, DOI: 10.1088/1748-0221/3/02/P02006
Abstract: Ionization chambers working in ambient air in current detection mode are widely used in several applications such as smoke detection, dosimetry, therapeutic beam monitoring and cetera. The aim of this work was to investigate if gaseous detectors can operate in ambient air in pulse counting mode as well as with gas amplification. . To investigate the feasibility of this method two types of open- end gaseous detectors were build and successfully tested. The first one was a single wire or multiwire cylindrical geometry detector operating in pulse mode at a gas gain of 1. The second type alpha detector was an innovative GEM-like detector with resistive electrodes operating in air in avalanche mode at high gas gains (up to 10E4). A detailed comparison between these two detectors is given as well as comparison with the commercially available alpha detectors. The main advantages of gaseous detectors operating in air in a pulse detection mode are their simplicity, low cost and high sensitivity. One of the possible applications of these new detectors is alpha particle background monitors which, due to their low cost can find wide application not only in houses, but in public areas: airports, railway station and so on.
Spectral Unmixing: Analysis of Performance in the Olfactory Bulb In Vivo
Mathieu Ducros, Laurent Moreaux, Jonathan Bradley, Pascale Tiret, Oliver Griesbeck, Serge Charpak
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0004418
Abstract: Background The generation of transgenic mice expressing combinations of fluorescent proteins has greatly aided the reporting of activity and identification of specific neuronal populations. Methods capable of separating multiple overlapping fluorescence emission spectra, deep in the living brain, with high sensitivity and temporal resolution are therefore required. Here, we investigate to what extent spectral unmixing addresses these issues. Methodology/Principal Findings Using fluorescence resonance energy transfer (FRET)-based reporters, and two-photon laser scanning microscopy with synchronous multichannel detection, we report that spectral unmixing consistently improved FRET signal amplitude, both in vitro and in vivo. Our approach allows us to detect odor-evoked FRET transients 180–250 μm deep in the brain, the first demonstration of in vivo spectral imaging and unmixing of FRET signals at depths greater than a few tens of micrometer. Furthermore, we determine the reporter efficiency threshold for which FRET detection is improved by spectral unmixing. Conclusions/Significance Our method allows the detection of small spectral variations in depth in the living brain, which is essential for imaging efficiently transgenic animals expressing combination of multiple fluorescent proteins.
Performance of wire-type Rn detectors operated with gas gain in ambient air in view of its possible application to early earthquake predictions
G. Charpak,P. Benaben,P. Breuil,E. Nappi,P. Martinengo,V. Peskov
Physics , 2010,
Abstract: We describe a detector of alpha particles based on wire type counters (single-wire and multiwire) operating in ambient air at high gas gains (100-1000). The main advantages of these detectors are: low cost, robustness and ability to operate in humid air. The minimum detectable activity achieved with the multiwire detector for an integration time of 1 min is 140 Bq per m3, which is comparable to that featured by commercial devices. Owing to such features the detector is suited for massive application, for example for continuous monitoring of Rn or Po contaminations or, as discussed in the paper, its use in a network of Rn counters in areas affected by earth-quakes in order to verify, on a solid statistical basis, the envisaged correlation between the sudden Rn appearance and a forthcoming earthquake.
Development of New Hole-Type Avalanche Detectors and the First Results of their Applications
G. Charpak,P. Benaben,P. Breuil,A. Di Mauro,P. Martinengo,V. Peskov
Physics , 2007, DOI: 10.1109/TNS.2008.924084
Abstract: We have developed a new detector of photons and charged particles- a hole-type structure with electrodes made of a double layered resistive material: a thin low resistive layer coated with a layer having a much higher resistivity. One of the unique features of this detector is its capability to operate at high gas gains (up to 10E4) in air or in gas mixtures with air. They can also operate in a cascaded mode or be combined with other detectors, for example with GEM. This opens new avenues in their applications. Several prototypes of these devices based on new detectors and oriented on practical applications were developed and successfully tested: a detector of soft X-rays and alpha particles, a flame sensor, a detector of dangerous gases. All of these detectors could operate stably even in humid air and/or in dusty conditions. The main advantages of these detectors are their simplicity, low cost and high sensitivity. For example, due to the avalanche multiplication, the detectors of flames and dangerous gases have a sensitivity of 10-100 times higher than commercial devices. We therefore believe that new detectors will have a great future.
Progress in the development of a S RETGEM-based detector for an early forest fire warning system
G. Charpak,P. Benaben,P. Breuil,P. Martinengo,E. Nappi,V. Peskov
Physics , 2009, DOI: 10.1088/1748-0221/4/12/P12007
Abstract: In this paper we present a prototype of a Strip Resistive Thick GEM photosensitive gaseous detector filled with Ne and ethylferrocene vapours at a total pressure of 1 atm for an early forest fire detection system. Tests show that it is one hundred times more sensitive than the best commercial ultraviolet flame detectors and therefore, it is able to reliably detect a flame of 1.5x1.5x1.5 m3 at a distance of about 1km. An additional and unique feature of this detector is its imaging capability, which in combination with other techniques, may significantly reduce false fire alarms when operating in an automatic mode. Preliminary results conducted with air filled photosensitive gaseous detectors are also presented. The approach main advantages include both the simplicity of manufacturing and affordability of construction materials such as plastics and glues specifically reducing detector production cost. The sensitivity of these air filled detectors at certain conditions may be as high as those filled with Ne and EF. Long term test results of such sealed detectors indicate a significant progress in this direction. We believe that our detectors utilized in addition to other flame and smoke sensors will exceptionally increase the sensitivity of forest fire detection systems. Our future efforts will be focused on attempts to commercialize such detectors utilizing our aforementioned findings.
Micromegas in a Bulk
I. Giomataris,R. De Oliveira,S. Andriamonje,S. Aune,G. Charpak,P. Colas,A. Giganon,Ph. Rebourgeard,P. Salin
Physics , 2005, DOI: 10.1016/j.nima.2005.12.222
Abstract: In this paper we present a novel way to manufacture the bulk Micromegas detector. A simple process based on the PCB (Printed Circuit Board) technology is employed to produce the entire sensitive detector. Such fabrication process could be extended to very large area detectors made by the industry. The low cost fabrication together with the robustness of the electrode materials will make it extremely attractive for several applications ranging from particle physics and astrophysics to medicine
Implementation of a Higher Quality dc Power Converter  [PDF]
N. N. Barsoum
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.22012
Abstract: Many single and three-phase converters are well developed, and covered up in most of electric markets. It is used in many applications in power systems and machine drives. However, an exact definite output signal from the dc side still not recognized. The waveforms of output voltage and current demonstrate an imperfect dc signal and constitute losses, harmonic distortion, low power factor, and observed some ripples. An approximately perfect rectifier bridge is the aim of this research. Perhaps it gives the ability to identify the parameters of the converter to obtain, as much as possible, a perfect dc signal with less ripple, high power factor and high efficiency. Design is implemented by simulation on Power Simulator PSIM, and practically, a series regulator LM723 is applied to provide regulating output voltage. Comparisons of both simulation and hardware results are made to observe differences and similarities.
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