Multiple exciton generation in nano-crystals revisited: Consistent calculation of the yield based on pump-probe spectroscopy

Multiple exciton generation (MEG) is a process in which more than one exciton is generated upon the absorption of a high energy photon, typically higher than two times the band gap, in semiconductor nanocrystals. It can be observed experimentally using time resolved spectroscopy such as the transient absorption measurements. Quantification of the MEG yield is usu- ally done by assuming that the bi-exciton signal is twice the signal from a single exciton. Herein we show that this assumption is not always justified and may lead to significant errors in the estimated MEG yields. We develop a methodology to determine proper scaling factors to the signals from the transient absorption experiments. Using the methodology we find modest MEG yields in lead chalcogenide nanocrystals including the nanorods

An Accurate and Compact High Power Monocycle Pulse Transmitter for Microwave Ultra-Wideband Radar Sensors with an enhanced SRD model: Applications for Distance Measurement for lossy Materiel

[EN] In This paper, a high power sub-nanosecond pulse transmitter for Ultra-wideband radar sensor is presented. The backbone of the generator is considered as a step recovery diode and unique pulse injected into the circuit, which gives rise to an ultra-wide band Gaussian pulse. The transistor driver and transmission line pulse forming the whole network are investigated in detail. The main purpose of this work is to transform a square waveform signal to a driving pulse with the timing and the amplitude parameters required by the SRD to form an output Gaussian pulse, and then into high monocycle pulses. In simulation aspect, an improved output response is required, in this way a new model of step recovery diode has been proposed as a sharpener circuit. This proposition was applied to increase the rise-time of the pulses. For a good range radar, a high amplitude pulse is indispensable, especially when it comes to penetrate thick lossy materiel. In order to overcome this challenge, a simple technique and useful solution is introduced to increase the output amplitude of the transmitter. This technique consists to connect the outputs of two identical pulse generators in parallel respecting the restrictions required. The pulse transmitter circuit is completely fabricated using micro-strip structure technology characteristics. Waveforms of the generated monocycle pulses over 10V in amplitude with 3.5 % in overshoot have been obtained. Good agreement has been achieved between measurement and simulation results.The author gratefully acknowledges the financial support provided by Pierre and Marie Curie University under the EMMAG Scholarship. This study was supported by DIMAS group, ITACA institute at City Polytechnic of innovation from university Polytechnic of Valencia.Ahajjam, Y.; Aghzout, O.; Catalá Civera, JM.; Penaranda-Foix, FL.; Driouach, A. (2019). An Accurate and Compact High Power Monocycle Pulse Transmitter for Microwave Ultra-Wideband Radar Sensors with an enhanced SRD model: Applications for Distance Measurement for lossy Materiel. Advanced Electromagnetics. 8(3):76-82. https://doi.org/10.7716/aem.v8i3.676S76828

La malnutrition des enfants de moins de cinq ans au Maroc dans les années 2000 : cause culturelle ou économique ?

Sur la base de l’Enquête Nationale sur la Consommation et les Dépenses des Ménages réalisée en 2001-2002 par le HCP, nous analysons les déterminants de la malnutrition des enfants de moins de cinq ans au Maroc. La malnutrition est appréhendée à l’aide de trois indicateurs anthropométriques : le retard de croissance, l’insuffisance pondérale et l’émaciation, mesurés respectivement par les indicateurs « taille pour âge », « poids pour âge » et « poids pour taille ». Les résultats montrent que le principal facteur de la malnutrition était économique : les enfants des ménages les plus pauvres et résidant en zone rurale étaient les plus concernés pas la malnutrition

Fractures De La diaphyse humérale Une étude rétrospective comparative de technique HACKETHAL Vs plaque vissée : A propos de 19 cas

Introduction: They represent 2% of all fractures. The main debate around recent fractures focuses on the therapeutic indications for all types of surgical stabilization have sometimes unconditional and strident defenders. Material and Methods: A series of 19 osteosynthesis was reviewed: 4 with other traumas, 1 case of skin incision and two initial radial nerve palsy. The osteosynthesis by plate was performed in 7 patients and by bundle pinning in 12 patients. The outcome evaluation was made with the listing for Stewart & Hundley amended. Results: For patients treated with plate: 2 postoperative radial nerve palsy. There were 1 non- union and no case of sepsis.71, 4% of patients had good and excellent results. For patients treated by bundle pinning: no radial nerve palsy, 1 case of non-union, and no cases of sepsis, under-acromial conflict, or of pin protrusion in the top. Good and very good results concerned 91, 7% of patients. Conclusion: The choice of therapeutic methods is difficult. There is no method that could lead to unanimous. The bundle pinning fixation could be this method, but the risk of stiffness of the shoulder is a feared complicationIntroduction Elles représentent 2% de l’ensemble des fractures ; Le débat principal autour des fractures de la diaphyse humérale se centre sur les indications thérapeutiques car tout type de stabilisation chirurgicale trouve des défenseurs parfois inconditionnels et véhéments. Matériels et Méthodes : Une série de 19 ostéosynthèses a été revue dont 4 polytraumatisés, 1 cas d’ouverture cutanée et deux paralysies radiales initiales. L'ostéosynthèse par plaque a été réalisée chez 7 patients et par embrochage fasciculé chez 12 malades. L’évaluation des résultats s'est faite avec la cotation de Stewart & Hundley modifiée. Résultats Pour les patients traités par plaque : Deux paralysies radiales post-opératoires, pas de pseudarthrose, pas de cas de sepsis. Les bons et très bons résultats concernent 71,4% des patients. Pour les patients traités par embrochage : pas de paralysie radiale ; 1 cas de pseudarthrose, pas de cas de sepsis, aucun cas de conflit sous acromiale ou de protrusion du clou en haut. Les bons et très bon résultats concernent 91,7% des patients. Conclusion Le choix entre les méthodes thérapeutiques est difficile. Il n'existe pas de méthode pouvant entraîner une adhésion unanime. L'embrochage fasciculé pourrait être cette méthode, mais le risque de raideur de l’épaule en fait une technique redoutée. L'ostéosynthèse par plaque aussi pourrait l’être mais son principal reproche est l’atteinte neurologique

Ambient-Dried, 3D-Printable and Electrically Conducting Cellulose Nanofiber Aerogels by Inclusion of Functional Polymers

This study presents a novel, green, and efficient way of preparing crosslinked aerogels from cellulose nanofibers (CNFs) and alginate using non-covalent chemistry. This new process can ultimately facilitate the fast, continuous, and large-scale production of porous, light-weight materials as it does not require freeze-drying, supercritical CO2 drying, or any environmentally harmful crosslinking chemistries. The reported preparation procedure relies solely on the successive freezing, solvent-exchange, and ambient drying of composite CNF-alginate gels. The presented findings suggest that a highly-porous structure can be preserved throughout the process by simply controlling the ionic strength of the gel. Aerogels with tunable densities (23–38 kg m−3) and compressive moduli (97–275 kPa) can be prepared by using different CNF concentrations. These low-density networks have a unique combination of formability (using molding or 3D-printing) and wet-stability (when ion exchanged to calcium ions). To demonstrate their use in advanced wet applications, the printed aerogels are functionalized with very high loadings of conducting poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:TOS) polymer by using a novel in situ polymerization approach. In-depth material characterization reveals that these aerogels have the potential to be used in not only energy storage applications (specific capacitance of 78 F g−1), but also as mechanical-strain and humidity sensors

Symplectic Fluctuations for Electromagnetic Excitations of Hall Droplets

We show that the integer quantum Hall effect systems in plane, sphere or disc, can be formulated in terms of an algebraic unified scheme. This can be achieved by making use of a generalized Weyl--Heisenberg algebra and investigating its basic features. We study the electromagnetic excitation and derive the Hamiltonian for droplets of fermions on a two-dimensional Bargmann space (phase space). This excitation is introduced through a deformation (perturbation) of the symplectic structure of the phase space. We show the major role of Moser's lemma in dressing procedure, which allows us to eliminate the fluctuations of the symplectic structure. We discuss the emergence of the Seiberg--Witten map and generation of an abelian noncommutative gauge field in the theory. As illustration of our model, we give the action describing the electromagnetic excitation of a quantum Hall droplet in two-dimensional manifold.Comment: 23 page

Bibliography, Background and Overview of UWB radar sensor

Due to the lack of studies in the literature that address the issue of UWB radar sensors, and also because of the great importance of this technology, which is gaining heavily in new application areas, such as the process industry and automotive engineering. A brief summary of the biography of UWB radar sensors have been treated and presented in this article, specifying the difference between pulsed radar sensors regarding CW radar sensor, and two subcategories SFCW FMCW, and highlight the benefits of each.Younes, A.; Catalá Civera, JM.; Penaranda-Foix, FL.; Driouech, A. (2014). Bibliography, Background and Overview of UWB radar sensor. International Journal of Engineering Research and Applications. 4(11):37-40. http://hdl.handle.net/10251/63314S374041

Time-Resolved IR Spectroscopy Reveals a Mechanism with TiO2 as a Reversible Electron Acceptor in a TiO2 - Re Catalyst CO2 Photoreduction System

Attaching the phosphonated molecular catalyst [Re$^{I}$Br(bpy)(CO)₃]⁰ to the wide-band gap semiconductor TiO₂ strongly enhances the rate of visible-light driven reduction of CO₂ to CO in dimethyl formamide (DMF) with triethanolamine (TEOA) as sacrificial electron donor. Herein, we show by transient mid-IR spectroscopy that the mechanism of catalyst photoreduction is initiated by ultrafast electron injection into TiO₂, followed by rapid (ps-ns) and sequential two-electron oxidation of TEOA that is coordinated to the Re center. The injected electrons can be stored in the conduction band (CB) of TiO₂ on a ms-s time scale, and we propose they lead to further reduction of the Re-catalyst and completion of the catalytic cycle. Thus, the excited Re catalyst gives away one electron and would eventually get three electrons back. The function of an electron reservoir would represent a role for TiO₂ in photo-catalytic CO₂ reduction that has previously not been considered. We propose that the increase in photocatalytic activity upon heterogenisation of the catalyst to TiO₂ is due to the slow charge recombination and the high oxidative power of the ReII species after electron injection, as compared to the excited MLCT state of the unbound Re catalyst or when immobilized on ZrO₂, which results in a more efficient reaction with TEOA.Knut and Alice Wallenberg Foundation, Swedish Energy Agency, Swedish Research Council, Austrian Christian Doppler Research Association, OMV Grou

An Advanced Electrical Properties Measurement Approach with a Designed Bi-Static Ultra-Wideband Impulse Radar Sensor

[EN] This paper reports on the development of a compact, low-cost, impulse bi-static UWB radar sensor for its use as non-destructive methods for electrical property measurement in industrial application. This UWB Radar sensor consists of an ultrashort-monocycle-pulse transmitter of 330 ps, an oscilloscope as a UWB sampling receiver with a high wide band of 6 GHz, and two UWB antennas ranging from 0.4 to 6 GHz. A new model of SRD has been introduced to decrease the rise time of the impulse. Performance of this UWB radar sensor was verified through two kinds of applications: range detection and electrical property measurements. All measurements have been carried out in an anechoic chamber with a distance variation between 80 and 300 cm. The full radar system provides good agreement between the experimental and theoretical results, which demonstrate its application in many fields, especially for electrical Property Measurements.The authors gratefully acknowledge the financial support provided by Pierre and Marie Curie University under the EMMAG Scholarship. This study was supported by DIMAS group, ITACA institute at City polytechnic of innovation from university polytechnic of Valencia.Ahajjam, Y.; Aghzout, O.; Catalá Civera, JM.; Penaranda-Foix, FL.; Driouach, A. (2018). An Advanced Electrical Properties Measurement Approach with a Designed Bi-Static Ultra-Wideband Impulse Radar Sensor. Progress in Electromagnetics Research-PIER. 75:167-178. https://doi.org/10.2528/PIERM18070305S1671787