957 resultados para free-space laser communication


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PURPOSE Despite different existing methods, monitoring of free muscle transfer is still challenging. In the current study we evaluated our clinical setting regarding monitoring of such tissues, using a recent microcirculation-imaging camera (EasyLDI) as an additional tool for detection of perfusion incompetency. PATIENTS AND METHODS This study was performed on seven patients with soft tissue defect, who underwent reconstruction with free gracilis muscle. Beside standard monitoring protocol (clinical assessment, temperature strips, and surface Doppler), hourly EasyLDI monitoring was performed for 48 hours. Thereby a baseline value (raised flap but connected to its vascular bundle) and an ischaemia perfusion value (completely resected flap) were measured at the same point. RESULTS The mean age of the patients, mean baseline value, ischaemia value perfusion were 48.00 ± 13.42 years, 49.31 ± 17.33 arbitrary perfusion units (APU), 9.87 ± 4.22 APU, respectively. The LDI measured values in six free muscle transfers were compatible with hourly standard monitoring protocol, and normalized LDI values significantly increased during time (P < 0.001, r = 0.412). One of the flaps required a return to theatre 17 hours after the operation, where an unsalvageable flap loss was detected. All normalized LDI values of this flap were under the ischaemia perfusion level and the trend was significantly descending during time (P < 0.001, r = -0.870). CONCLUSION Due to the capability of early detection of perfusion incompetency, LDI may be recommended as an additional post-operative monitoring device for free muscle flaps, for early detection of suspected failing flaps and for validation of other methods.

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El trabajo que aquí se presenta surge de la necesidad de conceptualizar y profundizar sobre el uso productivo del tiempo libre de las personas adultas mayores. Se llevará a cabo una aproximación teórica sobre las diferentes concepciones de tiempo libre y ocio como dimensiones interdisciplinarias que involucran elementos referidos al entorno en donde personas y comunidades buscan integrarse en un tiempo y espacio determinado

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El trabajo que aquí se presenta surge de la necesidad de conceptualizar y profundizar sobre el uso productivo del tiempo libre de las personas adultas mayores. Se llevará a cabo una aproximación teórica sobre las diferentes concepciones de tiempo libre y ocio como dimensiones interdisciplinarias que involucran elementos referidos al entorno en donde personas y comunidades buscan integrarse en un tiempo y espacio determinado

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El trabajo que aquí se presenta surge de la necesidad de conceptualizar y profundizar sobre el uso productivo del tiempo libre de las personas adultas mayores. Se llevará a cabo una aproximación teórica sobre las diferentes concepciones de tiempo libre y ocio como dimensiones interdisciplinarias que involucran elementos referidos al entorno en donde personas y comunidades buscan integrarse en un tiempo y espacio determinado

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This paper presents a simple gravity evaluation model for large reflector antennas and the experimental example for a case study of one uplink array of 4x35-m antennas at X and Ka band. This model can be used to evaluate the gain reduction as a function of the maximum gravity distortion, and also to specify this at system designer level. The case study consists of one array of 35-m antennas for deep space missions. Main issues due to the gravity effect have been explored with Monte Carlo based simulation analysis.

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The one-dimensional self-similar motion of an initially cold, half-space plasma of electron density 0,produced by the (anomalous) absorption of a laser pulse of irradiation = (j>0f/T(0< (< T) at the critical density nc(«c/«0=eoKe)213, where k, m, are Boltzmann's constant and the ion mass, and Ke X (electron temperature)5'2 = heat conductivity. If a >e- 4 ' 3 , a deflagration wave separates an isentropic compression with a shock bounding the undisturbed plasma, and an isentropic expansion flow to the vacuum. The structures of these three regions are completely determined; in particular, the Chapman-Jouguet condition is proved and the density behind the deflagration is found. The deflagration-compression thickness ratio is large (small) for a^e- 5 ' 3(a>e- 5 ' 3 ) . The compression to expansion ratio for both energy and thickness is 0(e"2). For Z,- large, a deflagration exists even if a~e~413. Condition a>e~4'3 may be applied to pulses that are not linear.

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The one-dimensional self-similar motion of an initially cold, half-space plasma of electron density n,produced by the (anomalous) absorption of a laser pulse of irradiation

€~4'3, a qualitative discussion of how plasma behavior changes with a, is given.

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The availability of suitable laser sources is one of the main challenges in future space missions for accurate measurement of atmospheric CO2. The main objective of the European project BRITESPACE is to demonstrate the feasibility of an all-semiconductor laser source to be used as a space-borne laser transmitter in an Integrated Path Differential Absorption (IPDA) lidar system. We present here the proposed transmitter and system architectures, the initial device design and the results of the simulations performed in order to estimate the source requirements in terms of power, beam quality, and spectral properties to achieve the required measurement accuracy. The laser transmitter is based on two InGaAsP/InP monolithic Master Oscillator Power Amplifiers (MOPAs), providing the ON and OFF wavelengths close to the selected absorption line around 1.57 µm. Each MOPA consists of a frequency stabilized Distributed Feedback (DFB) master oscillator, a modulator section, and a tapered semiconductor amplifier optimized to maximize the optical output power. The design of the space-compliant laser module includes the beam forming optics and the thermoelectric coolers.The proposed system replaces the conventional pulsed source with a modulated continuous wave source using the Random Modulation-Continuous Wave (RM-CW) approach, allowing the designed semiconductor MOPA to be applicable in such applications. The system requirements for obtaining a CO2 retrieval accuracy of 1 ppmv and a spatial resolution of less than 10 meters have been defined. Envelope estimated of the returns indicate that the average power needed is of a few watts and that the main noise source is the ambient noise.

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In this paper, we report on the progresses of the BRITESPACE Consortium in order to achieve space-borne LIDAR measurements of atmospheric carbon dioxide concentration based on an all semiconductor laser source at 1.57 ?m. The complete design of the proposed RM-CW IPDA LIDAR has been presented and described in detail. Complete descriptions of the laser module and the FSU have been presented. Two bended MOPAs, emitting at the sounding frequency of the on- and off- IPDA channels, have been proposed as the transmitter optical sources with the required high brightness. Experimental results on the bended MOPAs have been presented showing a high spectral purity and promising expectations on the high output power requirements. Finally, the RM-CW approach has been modelled and an estimation of the expected SNR for the entire system is presented. Preliminary results indicate that a CO2 retrieval precision of 1.5 ppm could be achieved with an average output power of 2 W for each channel.

Proposal for a Council Regulation (EC) on certain procedures for applying the Europe Agreement establishing an association between the European Communities and their Member States, of the one part, and the Czech Republic, of the other part; 94/0331 (ACC): Proposal for a Council Regulation (EC) on certain procedures for applying the Europe Agreement establishing an association between the European Communities and their Member States, of the one part, and the Slovak Republic, of the other part (presented by the Commission). Communication from the Commission: Request for Council assent and consultation of the ECSC committee, pursuant to Article 95 of the ECSC Treaty, concerning a draft; Commission Decision on certain procedures for applying the Europe Agreement establishing an association between the European Communities and their Member States, of the one part, and the Czech Republic, of the other part; Commission Decision on certain procedures for applying the Europe Agreement establishing an association between the European Communities and their Member States, of the one part, and the Slovak Republic, of the other part; Commission Decision on certain procedures for applying the Agreement on free trade and trade-related matters between the European Community, the European Atomic Energy Community and the European Coal and Steel Community of the one part, and the Republic of Estonia, of the other part, Commission Decision on certain procedures for applying the Agreement on free trade and trade-related matters between the European Community, the European Atomic Energy Community and the European Coal and Steel Community of the one part, and the Republic of Latvia, of the other part, Commission Decision on certain procedures for applying the Agreement on free trade and trade-related matters between the European Community, the European Atomic Energy Community and the European Coal and Steel Community of the one part, and the Republic of Lithuania, of the other part, Commission Decision on certain procedures for applying the Europe Agreement establishing an association between the European Communities and their Member States, of the one part, and the Republic of Bulgaria, of the other part; Commission Decision on certain procedures for applying the Europe Agreement establishing an association between the European Communities and their Member States, of the one part, and Romania, of the other part. COM (94) 680 final, 16 December 1994

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