A Two-Phase Mass Flow Rate Model for Nitrous Oxide Based on Void Fraction

In the field of space propulsion, self pressurized technology is an example of innovation capable of improving system performances through reduction of volumes and other optimizations. Potential applications are widespread and not limited to the propulsion panorama: from on-orbit maneuvering to in-orbit servicing, from refueling of satellites at the end of life to in situ resource exploitation for missions headed towards remote objects of the solar system. However, important drawbacks have been reported for these systems: modeling of fluids and thermal phenomena is complex, thus preventing accurate performance predictions. As a result, no comprehensive and accurate model capable of describing the dynamics of a self-pressurizing propellant tank has been developed so far. In this context, this paper proposes a two-phase mass flow rate model based on void fraction. N2O has been selected due to its use as a green and self-pressurized propellant for in-space propulsive applications. The aim of this paper is to describe the current mass flow rate models present in the literature for this fluid and compare the new model with the one proposed by Dyer. A model validation is also offered, and a test campaign is mentioned. Finally, preliminary results are shown and discussed: results are then compared with the ones obtained through the Dyer model, in order to retrieve a comprehensive comparison among the two simulation frameworks. Comments on the results are added, showing the improvements as well as the limitations of the proposed framework

Full coherent control of nuclear spins in an optically pumped single quantum dot

Highly polarized nuclear spins within a semiconductor quantum dot (QD) induce effective magnetic (Overhauser) fields of up to several Tesla acting on the electron spin or up to a few hundred mT for the hole spin. Recently this has been recognized as a resource for intrinsic control of QD-based spin quantum bits. However, only static long-lived Overhauser fields could be used. Here we demonstrate fast redirection on the microsecond time-scale of Overhauser fields of the order of 0.5 T experienced by a single electron spin in an optically pumped GaAs quantum dot. This has been achieved using full coherent control of an ensemble of 10^3-10^4 optically polarized nuclear spins by sequences of short radio-frequency (rf) pulses. These results open the way to a new class of experiments using rf techniques to achieve highly-correlated nuclear spins in quantum dots, such as adiabatic demagnetization in the rotating frame leading to sub-micro K nuclear spin temperatures, rapid adiabatic passage, and spin squeezing

Coherent, mechanical control of a single electronic spin

The ability to control and manipulate spins via electrical, magnetic and optical means has generated numerous applications in metrology and quantum information science in recent years. A promising alternative method for spin manipulation is the use of mechanical motion, where the oscillation of a mechanical resonator can be magnetically coupled to a spins magnetic dipole, which could enable scalable quantum information architectures9 and sensitive nanoscale magnetometry. To date, however, only population control of spins has been realized via classical motion of a mechanical resonator. Here, we demonstrate coherent mechanical control of an individual spin under ambient conditions using the driven motion of a mechanical resonator that is magnetically coupled to the electronic spin of a single nitrogen-vacancy (NV) color center in diamond. Coherent control of this hybrid mechanical/spin system is achieved by synchronizing pulsed spin-addressing protocols (involving optical and radiofrequency fields) to the motion of the driven oscillator, which allows coherent mechanical manipulation of both the population and phase of the spin via motion-induced Zeeman shifts of the NV spins energy. We demonstrate applications of this coherent mechanical spin-control technique to sensitive nanoscale scanning magnetometry.Comment: 6 pages, 4 figure

Traumatic-event headaches

BACKGROUND: Chronic headaches from head trauma and whiplash injury are well-known and common, but chronic headaches from other sorts of physical traumas are not recognized. METHODS: Specific information was obtained from the medical records of 15 consecutive patients with chronic headaches related to physically injurious traumatic events that did not include either head trauma or whiplash injury. The events and the physical injuries produced by them were noted. The headaches' development, characteristics, duration, frequency, and accompaniments were recorded, as were the patients' use of pain-alleviative drugs. From this latter information, the headaches were classified by the diagnostic criteria of the International Headache Society as though they were naturally-occurring headaches. The presence of other post-traumatic symptoms and litigation were also recorded. RESULTS: The intervals between the events and the onset of the headaches resembled those between head traumas or whiplash injuries and their subsequent headaches. The headaches themselves were, as a group, similar to those after head trauma and whiplash injury. Thirteen of the patients had chronic tension-type headache, two had migraine. The sustained bodily injuries were trivial or unidentifiable in nine patients. Fabrication of symptoms for financial remuneration was not evident in these patients of whom seven were not even seeking payments of any kind. CONCLUSIONS: This study suggests that these hitherto unrecognized post-traumatic headaches constitute a class of headaches characterized by a relation to traumatic events affecting the body but not including head or whiplash traumas. The bodily injuries per se can be discounted as the cause of the headaches. So can fabrication of symptoms for financial remuneration. Altered mental states, not systematically evaluated here, were a possible cause of the headaches. The overall resemblance of these headaches to the headaches after head or whiplash traumas implies that these latter two headache types may likewise not be products of structural injuries

Spin Relaxation in Ge/Si Core-Shell Nanowire Qubits

Controlling decoherence is the most challenging task in realizing quantum information hardware. Single electron spins in gallium arsenide are a leading candidate among solid- state implementations, however strong coupling to nuclear spins in the substrate hinders this approach. To realize spin qubits in a nuclear-spin-free system, intensive studies based on group-IV semiconductor are being pursued. In this case, the challenge is primarily control of materials and interfaces, and device nanofabrication. We report important steps toward implementing spin qubits in a predominantly nuclear-spin-free system by demonstrating state preparation, pulsed gate control, and charge-sensing spin readout of confined hole spins in a one-dimensional Ge/Si nanowire. With fast gating, we measure T1 spin relaxation times in coupled quantum dots approaching 1 ms, increasing with lower magnetic field, consistent with a spin-orbit mechanism that is usually masked by hyperfine contributions

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CT scan assessment in salivary gland lithiasis diagnosis

International audienceINTRODUCTION: The aim of the study was to assess computed tomography (CT) scan efficiency for the diagnosis of salivary lithiasis.METHODS: Patients who were included were all the patients who consulted in our department for main salivary gland (submandibular and parotid) obstruction symptoms between June 2014 and December 2016. A CT scan without injection was prescribed for all of them. The 163 patients were divided into two groups after the CT scan: patients with and without lithiasis. During surgery, we confirmed the presence or absence of the lithiasis previously diagnosed on the CT scan. The patients were divided in two groups: case and control groups. For statistical analysis, the sensitivity, specificity, and the negative and positive predictive values of the preoperative CT scan were calculated.RESULTS: A total of 163 patients with a salivary obstructive syndrome were included. On the CT scans, we found lithiases (hyperdense images) in 157 glands ("CT scan⊕" group), and we found no lithiasis in 6 glands ("CT scan" group). In the "CT scan⊕" group, 203 lithiases were present. During surgery, we found and removed lithiases in 155 patients (case group), and 8 patients had no lithiases (control group). The overall sensitivity, specificity, positive predictive value, and negative predictive values of the CT scan for the detection of lithiasis were 100%, 75%, 99%, and 100%, respectively. The specificity of CT scans for the lithiasis located in the anterior and middle third of the duct was 100%.DISCUSSION: According to our study, the CT scan is very efficient in diagnosing salivary main gland lithiases in patients with an obstructive syndrome.Copyright © 2017 Elsevier Masson SAS. All rights reserved

Double palatal flap for oro-nasal fistula closure

International audienceINTRODUCTION: The management of oral fistula to the nose depends on its etiology, its size and its location. Here, we describe a simple technique, inspired by the ones initially developed by Bardach for cleft palates repair. The surgical alternatives are discussed.TECHNICAL NOTE: The double palatal flap is a simple technique, allowing closure in a single session of a central or centro-lateral palate fistula. The key of this technique is the dissection between nasal and palate mucous layers, providing a sufficient amount of laxity to close the defect without tension.DISCUSSION: The double palatal flap can cover centro-lateral palate mucosal fistulae. It provides both aesthetic and functional results in a single stage. Reliability, simplicity and quickness are its main advantages. Outcomes are usually simple; Velar insufficiency may occur, that can be corrected by speech therapy.Copyright © 2017. Published by Elsevier Masson SAS