Spatial mode detection by frequency upconversion

The efficient creation and detection of spatial modes of light has become topical of late, driven by the need to increase photon-bit-rates in classical and quantum communications. Such mode creation/detection is traditionally achieved with tools based on linear optics. Here we put forward a new spatial mode detection technique based on the nonlinear optical process of sum-frequency generation. We outline the concept theoretically and demonstrate it experimentally with intense laser beams carrying orbital angular momentum and Hermite-Gaussian modes. Finally, we show that the method can be used to transfer an image from the infrared band to the visible, which implies the efficient conversion of many spatial modes.Comment: Published version, 4 pages, 5 figure

Pyhtään kunnan kuljetusten optimointi ja tarkistustyökalu

Pyhtään kunta on yli 5 000 asukkaan maalaiskunta Kymenlaaksossa Kaakkois-Suomessa. Kunnan toimeksiantona selvitettiin kuljetusten parantamismahdollisuudet. Pyhtään kunnan kuljetusselvitys koostui neljästä eri kuljetusosa-alueesta: koulukuljetuksesta, vammaispalvelusta, ruokakuljetuksesta ja Pyhtään palvelulinjasta. Selvityksen pääpaino oli koulukuljetuksissa. Tavoitteina oli löytää kuljetuksista kustannussäästöjä, selvittää vuoroliikenteen pysyvyys ja rakentaa tarkistustyökalu. Selvitystyö koostui myös Suomen lainsäädännön tarkastelusta, kuljetusten nykytilan selvittämisestä ja niiden mahdollisesta yhdistämisestä sekä koulukuljetuskustannusten laskemisesta. Työmenetelmät olivat tiedon keruu ja analysointi, yhteydenotot ja haastattelut sekä tarkistustyökalun luominen MS Excel -taulukkolaskentaohjelmalla. Työn tuloksena syntyivät koulukuljetuskartat ja ehdotus koulukuljetusportfolion laatimisesta sekä kaksi tarkistustyökalua. Lisäksi selvitystyössä päädyttiin siihen, että koulukuljetuskustannusten nousu on johtunut epäonnistuneesta kilpailutuksesta.The municipality of Pyhtää has over 5000 inhabitants and is located in Southern Finland. The aim of this thesis was to make a report to the municipality of Pyhtää, Finland. The report consisted of four different fields of transportation: school transport, services for the disabled, transport of perishable foodstuff and service line of Pyhtää. The main subject was the school transportation. The aims of the thesis were to find cost savings, clarify the permanence of bus lines and create a control tool to the municipality’s personnel. The report also consisted of Finnish legislation, monitoring the present state of transport, drawing the route maps from the school transportation and counting the transportation costs. The methods were finding and analyzing the available information, contacting and interviewing involved parties. The control tool was built with MS Office Excel –program. The results of the thesis were the school transport’s route maps, suggestion to create a portfolio from the school transportation and two different versions of the control tool. In addition the thesis concluded that the cost of the school transportation has increased from the unsuccessful tendering

Ultraflexible and robust graphene supercapacitors printed on textiles for wearable electronics applications

Printed graphene supercapacitors have the potential to empower tomorrow’s wearable electronics. We report a solid-state flexible supercapacitor device printed on textiles using graphene oxide ink and a screen-printing technique. After printing, graphene oxide was reduced in situ via a rapid electrochemical method avoiding the use of any reducing reagents that may damage the textile substrates. The printed electrodes exhibited excellent mechanical stability due to the strong interaction between the ink and textile substrate. The unique hierarchical porous structure of the electrodes facilitated ionic diffusion and maximised the surface area available for the electrolyte/ active material interface. The obtained device showed outstanding cyclic stability over 10 000 cycles and maintained excellent mechanical flexibility, which is necessary for wearable applications. The simple printing technique is readily scalable and avoids the problems associated with fabricating supercapacitor devices made of conductive yarn, as previously reported in the literature

A data-driven model on the thermal transfer mechanism of composite phase change materials

Phase change materials (PCMs) that are incorporated with highly conductive nanomaterials to fabricate composite phase change materials (CPCMs), received much focus as a promising energy strategy for latent heat storage and conversion systems, due to their excellent thermophysical properties such as oxidation resistance and large enthalpies of fusion. However, the correct prediction of the thermal conductivity of these CPCMs remains deficient, mainly due to the lack of knowledge on the microscopic heat transfer mechanisms between the nanofiller and matrix interphase. Herein, a data-driven, modified Maxwell model is proposed to determine the thermal conductivity of these CPCMs, using milled carbon fiber (MCF)-reinforced PCMs as validation. This new model incorporates the aspect ratio and morphology smoothness of MCFs and introduces compatibility factors for different types of PCM matrices, which are paraffin and polyethylene glycol (PEG) respectively. At filler loadings above 15 wt%, the theoretical model gave poorer forecasts (with an average prediction error of 0.075) due to the random agglomeration of MCF nanoparticles, which can obstruct the phonon pathway. Regardless, this model accurately estimated the thermal conductivities of MCF/PCMs up to 9 wt% and 11 wt% MCF loading, with percentage fit values being 0.983 and 0.996 for PEG and paraffin systems, respectively. This model also eliminates the limitations of existing models, that were only suitable for composites with low filler loadings

High-Valent Pyrazolate-Bridged Platinum Complexes: A Joint Experimental and Theoretical Study

Complexes {Pt(C^C*)(µ-pz)}2] (HC^C*A= 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene 1a, HC^C*B= 1-phenyl-3-methyl-1H-imidazol-2-ylidene 1b) react with methyl iodide (MeI) at room temperature in the dark to give compounds {PtIV(C^C*)Me(µ-pz)}2(µ-I)]I (C^C*A2a, C^C*B2b). The reaction of 1a with benzyl bromide (BnBr) in the same conditions afforded Br(C^C*A)PtIII(µ-pz)2PtIII(C^C*A)Bn] (5a), which by heating in BnBr(l) became {PtIV(C^C*A)Bn(µ-pz)}2(µ-Br)]Br (6a). Experimental investigations and density functional theory (DFT) calculations on the mechanisms of these reactions from 1a revealed that they follow a SN2 pathway in the two steps of the double oxidative addition (OA). Based on the DFT investigations, species such as (C^C*A)PtIII(µ-pz)2PtIII(C^C*A)R]X (RX = MeI Int-Me, BnBr Int-Bn) and (C^C*A)PtII(µ-pz)2PtIV(C^C*A)(R)X] (RX = MeI Int'-Me, BnBr Int'-Bn) were proposed as intermediates for the first and the second OA reactions, respectively. In order to put the mechanisms on firmer grounds, Int-Me was prepared as (C^C*A)PtIII(µ-pz)2PtIII(C^C*A)Me]BF4(3a') and used to get I(C^C*A)PtIII(µ-pz)2PtIII(C^C*A)Me](4a), (C^C*A)PtII(µ-pz)2PtIV(C^C*A)(Me)I](Int'-Me), and {PtIV(C^C*)Me(µ-pz)}2(µ-I)]BF4(2a'). The single-crystal X-ray structures of 2a, 2b, 3a', and 5a along with the mono- and bi-dimensional 1H and 195Pt{1H} NMR spectra of all the named species allowed us to compare structural and spectroscopic data for high-valent complexes with the same core {Pt(C^C*)(µ-pz)}2] but different oxidation states. © 2022 American Chemical Society. All rights reserved

Mineralogical characterization of silica sinters from the El Tatio geothermal field, Chile

11 páginas.Silica sinters, deposited from alkali chloride waters in the El Tatio geothermal field in northern Chile (22°20'S, 68°01'W), have been characterized by XRD, SEM, TG-DTA, and FTIR. The dominant silica phase is opal-A. Minor contents of opal-A/-CT and opal-CT are also present together with halite (NaCl), sylvite (KCl), and realgar (AsS). Accessory phases include teruggite [Ca4MgAs2B12O22(OH)12·12(H2O)], sassolite (H3BO3), and detrital quartz (SiO2). FWHM values reflect the immature nature of the studied opal-A. DTA heating experiments of opal-A show cristobalite crystallization at ~1000 °C, whereas DTA cooling experiments show the β -alfacristobalite transformation at ~200 °C. The total weight loss is related to changes in the sinter microtextures, mineral phases, and organic matter contents. FTIR spectra show the effects of silica maturation as consequence of the loss of trapped and absorbed water attached to silanols.Peer reviewe

Up-Converting Lanthanide-Doped YAG Nanospheres

The development of lanthanide-doped Y3Al5O12 (Ln:YAG) garnet nanostructures is a hot topic in the field of inorganic nanophosphors due to the current interest in developing small nanoparticles for solid-state lighting (SSL), displays, lasers and scintillation applications. In this study, we report the preparation of homogeneous Ln:YAG (Ln: Ho/Yb ions) nanospheres through a combined two-steps coprecipitationsolvothermal synthesis at low temperature. The crystal growth takes place in ethylene glycol, which is an inexpensive, non-toxic and easily available solvent. Monodisperse and crystalline spherical YAG particles of 80 nm in diameter were obtained. Furthermore, the protocol can be extended to other compositions (Tb/Yb, Tm/Yb. . .) to explore different luminescent properties, without affecting the morphology of the material, indicating the robustness and practical utility of the reported methodology. Thermal treatment of the nanogarnets at 1200◦C is necessary for making materials optically active upon both UV and NIR excitation. The spherical morphology of annealed samples is preserved, what helps their further dispersion in solvents, barbotines, inks or printing vehicles. The lanthanide-doped nanogarnets exhibited the characteristic blue, green and red emissions from lanthanide upconversion photoluminescence (UCPL) upon NIR excitation. The UCPL mechanism was studied and CIE chromate coordinates were obtained. These nanogarnets were further evaluated as functional ceramic phosphors by incorporating them into commercial glazes. The materials exhibited an exceptional chemical stability in a harsh medium such as a fused glaze. Consequently, the visible emissions of the nanoparticles were transferred to the whole glass matrix, thus providing a functional glaze that emits intense blue and green light upon NIR excitation. These luminescent nanogarnets have promising applications in smart enamels, but can also be useful for lighting displays (white LEDs. . .), smart paintings or plastics, and anti-counterfeiting systems

Driven Diffusive Systems: How Steady States Depend on Dynamics

In contrast to equilibrium systems, non-equilibrium steady states depend explicitly on the underlying dynamics. Using Monte Carlo simulations with Metropolis, Glauber and heat bath rates, we illustrate this expectation for an Ising lattice gas, driven far from equilibrium by an `electric' field. While heat bath and Glauber rates generate essentially identical data for structure factors and two-point correlations, Metropolis rates give noticeably weaker correlations, as if the `effective' temperature were higher in the latter case. We also measure energy histograms and define a simple ratio which is exactly known and closely related to the Boltzmann factor for the equilibrium case. For the driven system, the ratio probes a thermodynamic derivative which is found to be dependent on dynamics

Hydrophilic surface modification of acrylate-based biomaterials

[EN] Acrylic polymers have proved to be excellent with regard to cell adhesion, colonization and survival, in vitro and in vivo. Highly ordered and regular pore structures thereof can be produced with the help of polyamide templates, which are removed with nitric acid. This treatment converts a fraction of the ethyl acrylate side groups into acrylic acid, turning poly(ethyl acrylate) scaffolds into a more hydrophilic and pH-sensitive substrate, while its good biological performance remains intact. To quantify the extent of such a modification, and be able to characterize the degree of hydrophilicity of poly(ethyl acrylate), poly(ethyl acrylate) was treated with acid for different times (four, nine and 17 days), and compared with poly(acrylic acid) and a 90/10%wt. EA/AAc copolymer (P(EA-co-AAc)). The biological performance was also assessed for samples immersed in acid up to four days and the copolymer, and it was found that the incorporation of acidic units on the material surface was not prejudicial for cells. This surface modification of 3D porous hydrophobic scaffolds makes easier the wetting with culture medium and aqueous solutions in general, and thus represents an advantage in the manageability of the scaffolds.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors acknowledge financing through project FP7 NMP3-SL-2009-229239 'Regeneration of cardiac tissue assisted by bioactive implants' (RECATABI) and projects MAT2011-28791-C03-02 and -03 from the Spanish Ministerio de Ciencia e Innovacion. This work was also supported by the Spanish Ministry of Education through M. Arnal-Pastor FPU AP2009-1870 grant.Arnal Pastor, MP.; Comín-Cebrián, S.; Martínez-Ramos, C.; Monleón Pradas, M.; Vallés Lluch, A. (2016). Hydrophilic surface modification of acrylate-based biomaterials. Journal of Biomaterials Applications. 30(9):1429-1441. doi:10.1177/0885328215627414S1429144130

Dynamic behavior of anisotropic non-equilibrium driving lattice gases

It is shown that intrinsically anisotropic non-equilibrium systems relaxing by a dynamic process exhibit universal critical behavior during their evolution toward non-equilibrium stationary states. An anisotropic scaling anzats for the dynamics is proposed and tested numerically. Relevant critical exponents can be evaluated self-consistently using both the short- and long-time dynamics frameworks. The obtained results allow us to clarify a long-standing controversy about the theoretical description, the universality and the origin of the anisotropy of driven diffusive systems, showing that the standard field theory does not hold and supporting a recently proposed alternative theory.Comment: 4 pages, 2 figure