Multiple photon Hamiltonian in linear quantum optical networks

We give an alternative derivation for the explicit formula of the effective Hamiltonian describing the evolution of the quantum state of any number of photons entering a linear optics multiport. The description is based on the effective Hamiltonian of the optical system for a single photon and comes from relating the evolution in the Lie group that describes the unitary evolution matrices in the Hilbert space of the photon states to the evolution in the Lie algebra of the Hamiltonians for one and multiple photons. We give a few examples of how a group theory approach can shed light on some properties of devices with two input ports.Comment: 6 pages. Comments welcom

Energy Spectrum of a constrained Quantum Particle and the Willmore Energy of the constraining Surface

Geometric and topological bounds are obtained for the first energy level gap of a particle constrained to move on a compact surface in 3-space. Moreover, geometric properties are found which allows for stationary and uniformly distributed wave functions to exist on the surface

Parabolicity of invariant Surfaces

We present a clear and practical way to characterize the parabolicity of a complete immersed surface that is invariant with respect to a Killing vector field of the ambient space.Comment: 12 pages, 2 figure

Malalties de transmissió sexual

Treballs d'Educació Farmacètica als ciutadans. Unitat Docent d'Estades en Pràctiques Tutelades. Facultat de Farmàcia, Universitat de Barcelona. Curs: 2014, Tutor: Antoni Miró. Coordinadora: Marian March Pujol

Osteotomía proximal de tibia con estabilización mediante grapa compresora

Se revisan 60 pacientes con 78 osteotomías proximales de tibia —70 valguizantes y 8 varizantes— estabilizadas con una grapa de nuevo diseño con propiedades compresoras, debido a la elasticidad de su material. El seguimiento de los pacientes osciló entre los 3 y 10 años. De acuerdo con los criterios tradicionales de Coventry (1973), hemos obtenido buenos resultados en 61 osteotomías (78%), regulares en 11 (14%) y malos en 6 (8%). No se detectaron pérdidas de corrección, ni migraciones de la grapa. Las complicaciones fueron: una paresia del extensor largo del primer dedo del pie, 2 infecciones superficiales de partes blandas y 2 edemas postoperatorios persistentes de extremidad inferior. La consolidación se obtuvo en una media de 49 días (rango 30-67). La nueva grapa compresora permite reducir al mínimo o eliminar la inmovilización con yeso, facilita una precoz movilización postoperatoria de la rodilla, y disminuye los riesgos de pérdida de corrección.A total of 78 high tibial osteotomies —70 for valguization and 8 for varization— in 60 patients were reviewed. I all cases, the osteotomy was stabilized by a new staple designed with compressive effect, due to the elasticity of the material used. The follow-up of the patients ranged from 3 to 10 years. According to Coventry's criteria (1973), good results were obtained in 61 osteotomies (78%), fair in 11 (14%) and poor in 6 (8%). Neither loss of correction nor migration of the staple were detected. Complications were found as paresia of the extensor longus of the first toe in one case, infection of the soft tissues in 2 cases and persisting postoperative edema of the lower extremity in other 2 patients. Healing of the osteotomy was achieved in 49 days average (range, 30-67). The new compressive staple permit to reduce or eliminate postoperative plaster inmovilization, facilitate an early knee rehabilitation, and diminish the risk for loss of correccion

Peer assessment of individual contribution in group work: a student perspective

With group work increasing in popularity at universities, students no longer feel it is acceptable to be awarded the same group mark. This presents a significant challenge in awarding an individual mark which reflects unequivocally the time and effort a student has invested in a group project. To address this challenge, a tool to evaluate individual peer assessed contribution (IPAC) has been developed at University College London (UCL). The aim of this paper is to report on the perceptions of students regarding their experience of peer assessment in group work, since these perceptions are key to ensuring that a tool, such as IPAC, is accepted and used effectively by staff and students alike. The views of 133 students were acquired through anonymous surveys and focus groups ranging from first year undergraduate to doctoral students across 12 different departments. Results showed that 92% of students are in favour of peer assessment with a positive trend to using the IPAC tool. Receiving constructive feedback was considered imperative amongst respondents, which in turn should identify clearly the points of error; highlight explicitly the areas for improvement; and thus reflect accurately the mark being awarded. The attributes that students valued to be important when assessing their teammates were, in decreasing order of priority, attendance at meetings, listening and communication, actual contribution to the project deliverables, quality of the work produced, personal circumstances, and finally time management and organization skills. The detailed analysis and conclusions drawn from this study are the focus of this paper

Parametrical study of the dispersion of an alternative fire suppression agent through a real-size extinguisher system nozzle under realistic aircraft cargo cabin conditions

[EN] Nearly all active fire extinguishing systems consist of injecting an agent into the space set on fire. For aircraft cargo cabins, the agent widely used up to date is Halon 1301. The FAA provides a level of safety for this fire suppression agent that needs to be used in a volumetric concentration of 6% and needs to be acting for a duration of 0.5 s. On the other hand, Halon 1301 is known to contribute to the retrenchment of Earth's atmospheric ozone layer, therefore it is going to be prohibited in the incoming years. The FAA has defined an equivalent level of safety in terms of the performance of the alternative agents. In this research, two different alternative fire suppression agents and two nozzles were tested at two vessel back-pressure conditions using a new design in purpose facility and an injection system able to control the injection pressure and the injection duration (the agent injected mass) in order to satisfy the FAA performance conditions. The discharge volume is a rectangular constant volume constant pressure vessel of approximately 0.85 m(3) and 1.5 m of length that is provided with two transparent windows of 0.75 m x 1.5 m to ensure an optical access to study the whole agent injection and it mixing process. Liquid phase distribution of the agent injected inside the vessel is measured by means of Diffuse Back-Light Illumination (DBI) technique. Vapor phase distribution, when present, is measured through the single-pass Schlieren technique. Results show a poor performance in terms of spatial distribution (narrow jet with little atomization) of the two alternative agents injected through the nozzle actually used in the aircraft cargo cabin fire suppression systems. However, simply replacing the nozzle and using one with a swirler showed excellent performance in terms of spray penetration and spreading angle. This results ratify that the nozzles of the fire extinguisher system currently used in the aircraft cargo cabin does not work for the alternative agents tested.This research was performed in the frame of the project "Multi -physics methodology for phase change due to rapidly depressurized two-phase flows" reference 785549 from Clean Sky Joint Undertaking. The authors would also like to thankJose Enrique Del Rey for his help and participation in the test rig assembly as a lab technician.Payri, R.; Gimeno, J.; Marti-Aldaravi, P.; Carvallo-Garcia, C. (2020). Parametrical study of the dispersion of an alternative fire suppression agent through a real-size extinguisher system nozzle under realistic aircraft cargo cabin conditions. Process Safety and Environmental Protection. 141:110-122. https://doi.org/10.1016/j.psep.2020.04.022110122141Aleiferis, P. G., & van Romunde, Z. R. (2013). An analysis of spray development with iso-octane, n-pentane, gasoline, ethanol and n-butanol from a multi-hole injector under hot fuel conditions. Fuel, 105, 143-168. doi:10.1016/j.fuel.2012.07.044Amini, G. (2016). Liquid flow in a simplex swirl nozzle. International Journal of Multiphase Flow, 79, 225-235. doi:10.1016/j.ijmultiphaseflow.2015.09.004Chiu, C.-W., & Li, Y.-H. (2015). Full-scale experimental and numerical analysis of water mist system for sheltered fire sources in wind generator compartment. Process Safety and Environmental Protection, 98, 40-49. doi:10.1016/j.psep.2015.05.011Gann, R. G. (1998). Fire Technology, 34(4), 363-371. doi:10.1023/a:1015370628661Genzale, C. L., Reitz, R. D., & Musculus, M. P. B. (2009). Effects of spray targeting on mixture development and emissions formation in late-injection low-temperature heavy-duty diesel combustion. Proceedings of the Combustion Institute, 32(2), 2767-2774. doi:10.1016/j.proci.2008.06.072Gong, C., Jangi, M., & Bai, X.-S. (2014). Large eddy simulation of n-Dodecane spray combustion in a high pressure combustion vessel. Applied Energy, 136, 373-381. doi:10.1016/j.apenergy.2014.09.030Grosshandler, W., Presser, C., Lowe, D., & Rinkinen, W. (1995). Assessing Halon Alternatives for Aircraft Engine Nacelle Fire Suppression. Journal of Heat Transfer, 117(2), 489-494. doi:10.1115/1.2822548Kim, S. C., & Ryou, H. S. (2003). An experimental and numerical study on fire suppression using a water mist in an enclosure. Building and Environment, 38(11), 1309-1316. doi:10.1016/s0360-1323(03)00134-3Liang, T., Liu, M., Liu, Z., Zhong, W., Xiao, X., & Lo, S. (2015). A study of the probability distribution of pool fire extinguishing times using water mist. Process Safety and Environmental Protection, 93, 240-248. doi:10.1016/j.psep.2014.05.009McLinden, M. O., Perkins, R. A., Lemmon, E. W., & Fortin, T. J. (2015). Thermodynamic Properties of 1,1,1,2,2,4,5,5,5-Nonafluoro-4-(trifluoromethyl)-3-pentanone: Vapor Pressure, (p, ρ, T) Behavior, and Speed of Sound Measurements, and an Equation of State. Journal of Chemical & Engineering Data, 60(12), 3646-3659. doi:10.1021/acs.jced.5b00623Modak, A. U., Abbud-Madrid, A., Delplanque, J.-P., & Kee, R. J. (2006). The effect of mono-dispersed water mist on the suppression of laminar premixed hydrogen–, methane–, and propane–air flames. Combustion and Flame, 144(1-2), 103-111. doi:10.1016/j.combustflame.2005.07.003NDUBIZU, C. C., ANANTH, R., & TATEM, P. A. (2000). The Effects of Droplet Size and Injection Orientation on Water Mist Suppression of Low and High Boiling Point Liquid Pool Fires. Combustion Science and Technology, 157(1), 63-86. doi:10.1080/00102200008947310Pagliaro, J. L., & Linteris, G. T. (2017). Hydrocarbon flame inhibition by C6F12O (Novec 1230): Unstretched burning velocity measurements and predictions. Fire Safety Journal, 87, 10-17. doi:10.1016/j.firesaf.2016.11.002Payri, R., García-Oliver, J. M., Bardi, M., & Manin, J. (2012). Fuel temperature influence on diesel sprays in inert and reacting conditions. Applied Thermal Engineering, 35, 185-195. doi:10.1016/j.applthermaleng.2011.10.027Payri, R., Salvador, F. J., Bracho, G., & Viera, A. (2017). Differences between single and double-pass schlieren imaging on diesel vapor spray characteristics. Applied Thermal Engineering, 125, 220-231. doi:10.1016/j.applthermaleng.2017.06.140Prasad, K., Li, C., & Kailasanath, K. (1999). Simulation of water mist suppression of small scale methanol liquid pool fires. Fire Safety Journal, 33(3), 185-212. doi:10.1016/s0379-7112(99)00028-4Reitz, R. D. (1982). Mechanism of atomization of a liquid jet. Physics of Fluids, 25(10), 1730. doi:10.1063/1.863650Yang, P., Liu, T., & Qin, X. (2010). Experimental and numerical study on water mist suppression system on room fire. Building and Environment, 45(10), 2309-2316. doi:10.1016/j.buildenv.2010.04.017Yinshui, L., Zhuo, J., Dan, W., & Xiaohui, L. (2014). Experimental research on the water mist fire suppression performance in an enclosed space by changing the characteristics of nozzles. Experimental Thermal and Fluid Science, 52, 174-181. doi:10.1016/j.expthermflusci.2013.09.00

Pt-zeolites as active catalysts for the removal of chlorate in water by hydrogenation reactions

[EN] Catalytic hydrogenation is used to remove chlorate ions from water streams by using platinum catalysts supported on zeolites with different topologies (FAU, BEA, MWW, MFI and MOR), Si/Al ratio and compensating cation. It is observed that there is an important influence of the zeolite characteristics on the catalytic activity. The best results have been obtained with the catalyst supported on zeolites with a high number of acid centres, this is with a low Si/Al ratio and with protons, as counter-cation species compensating aluminium charge. The acid sites favour the interaction of the catalyst with the reactants and influence the neighbouring Pt species improving the redox properties of the catalyst. It is shown that with an adequate number of acid sites it is possible to decrease the metal content, keeping the same catalytic activity, by increasing the metal dispersion. The highest activity is obtained with an acidic FAU zeolite, with low Si/Al ratio and 1 wt% of Pt added by ion exchange. This catalyst is able to simultaneously reduce chlorate and chlorite ions and chlorate and bromate ions indicating that it is a multifunctional catalyst that can be utilized for removing different pollutants in water.The authors are grateful for the financial support by the Spanish Ministry of Science and Innovation (CEX2021-001230-S grant funded by MCIN/AEI/10.13039/501100011033, and TED2021-131715B-I00 grant funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe " by the European Union NextGenerationEU/PRTR) . Financial support by the Generalitat Valenciana (Prometeo 2021/077) is also acknowledged. A. Pla-Hernandez thanks Spanish Ministry of Science and Innovation for the pre-doctoral grant PRE2019-088100, associated with the project RTI2018-101784-B-I00.Plá-Hernandez, A.; Rey Garcia, F.; Palomares Gimeno, AE. (2024). Pt-zeolites as active catalysts for the removal of chlorate in water by hydrogenation reactions. Catalysis Today. 429. https://doi.org/10.1016/j.cattod.2023.11446142

Method to determine which quantum operations can be realized with linear optics with a constructive implementation recipe

The evolution of quantum light through linear optical devices can be described by the scattering matrix S of the system. For linear optical systems with m possible modes, the evolution of n input photons is given by a unitary matrix U=φm,M(S), derived from a known homomorphism, φm,M, which depends on the size of the resulting Hilbert space of the possible photon states, M. We present a method to decide whether a given unitary evolution U for n photons in m modes can be achieved with linear optics or not and the inverse transformation φ−1m,M when the transformation can be implemented. Together with previous results, the method can be used to find a simple optical system which implements any quantum operation within the reach of linear optics. The results come from studying the adjoint map between the Lie algebras corresponding to the Lie groups of the relevant unitary matrices

No-go theorems for photon state transformations in quantum linear optics

We give a necessary condition for photon state transformations in linear optical setups preserving the total number of photons. From an analysis of the algebra describing the quantum evolution, we find a conserved quantity that appears in all allowed optical transformations. We comment some examples and numerical applications, with example code, and give three general no-go results. These include (i) the impossibility of deterministic transformations which redistribute the photons from one to two different modes, (ii) a proof that it is impossible to generate a perfect Bell state in heralded schemes with a separable input for any number of ancillary photons and modes and a fixed herald and (iii) a restriction for the conversion between different types of entanglement (converting GHZ to W states).Comment: 18 pages. Comments welcome