Observation of enhanced transmission for s-polarized light through a subwavelength slit

Enhanced optical transmission (EOT) through subwavelength apertures is usually obtained for p-polarized light. The present study experimentally investigates EOT for s-polarized light. A subwavelength slit surrounded on each side by periodic grooves has been fabricated in a gold film and covered by a thin dielectric layer. The excitation of s-polarized dielectric waveguide modes inside the dielectric film strongly increases the s-polarized transmission. Transmission measurements are compared with a coupled mode model and show good qualitative agreement. Adding a waveguide can improve light transmission through subwavelength apertures, as both s and p-polarization can be efficiently transmitted.Comment: 11 pages, 3 figures, submitted to Applied Physics Letter

Evaluation of the response of a Bonner Sphere Spectrometer with a (LiI)-Li-6 detector using 3D meshed MCNP6.1.1 models

[EN] In order to undertake further studies on neutron spectra deconvolution in radiotherapy LinAc bunkers after using high megavolts treatment beams, it has been calculated the theoretical Response Function for a widespread neutron Bonner Sphere Spectrometer (BSS) exposed to arbitrary neutron sources. The neutron response function of the Bonner spectrometer is of essential importance for its neutron spectrum unfolding procedure and is directly related to the quality of the unfolded spectrum. Response detector curves from 10 keV to 20 MeV have been obtained by Monte Carlo (MC) simulation with MCNP6.1.1, where the use of unstructured mesh geometries is introduced as a novelty. In order to validate the accuracy of the MCNP6 simulation, we have used the detector model to measure an 241Am-Be neutron source, and the obtained neutron counts of the spectrometer and simulated counts are found to be very consistent, with a relative error below 10%. This comparison shows that the estimation of the Bonner sphere neutron response by MCNP6 is highly precise.Morató-Rafet, S.; Juste Vidal, BJ.; Miró Herrero, R.; Verdú Martín, GJ.; Guàrdia, V. (2019). Evaluation of the response of a Bonner Sphere Spectrometer with a (LiI)-Li-6 detector using 3D meshed MCNP6.1.1 models. Radiation Physics and Chemistry. 155:221-224. https://doi.org/10.1016/j.radphyschem.2018.05.027S22122415

Microscopic Theory of Josephson Mesoscopic Constrictions

We present a microscopic theory for the d.c. Josephson effect in model mesoscopic constrictions. Our method is based on a non-equilibrium Green function formalism which allows for a self-consistent determination of the order parameter profile along the constriction. The various regimes defined by the different length scales (Fermi wavelength $\lambda_F$, coherence length $\xi_0$ and constriction length $L_C$) can be analyzed, including the case where all these lengths are comparable. For the case $\lambda_F \tilde{<} (L_C,\xi_0)$ phase oscillations with spatial period $\lambda_F/2$ can be observed. In the case of $L_C>\xi_0$ solutions with a phase-slip center inside the constriction can be found, in agreement with previous phenomenological theories.Comment: 4 pages (RevTex 3.0), 3 postscript figures available upon request, 312456-C

Interspecific Introgression in Cetaceans: DNA Markers Reveal Post-F1 Status of a Pilot Whale

Visual species identification of cetacean strandings is difficult, especially when dead specimens are degraded and/or species are morphologically similar. The two recognised pilot whale species (Globicephala melas and Globicephala macrorhynchus) are sympatric in the North Atlantic Ocean. These species are very similar in external appearance and their morphometric characteristics partially overlap; thus visual identification is not always reliable. Genetic species identification ensures correct identification of specimens. Here we have employed one mitochondrial (D-Loop region) and eight nuclear loci (microsatellites) as genetic markers to identify six stranded pilot whales found in Galicia (Northwest Spain), one of them of ambiguous phenotype. DNA analyses yielded positive amplification of all loci and enabled species identification. Nuclear microsatellite DNA genotypes revealed mixed ancestry for one individual, identified as a post-F1 interspecific hybrid employing two different Bayesian methods. From the mitochondrial sequence the maternal species was Globicephala melas. This is the first hybrid documented between Globicephala melas and G. macrorhynchus, and the first post-F1 hybrid genetically identified between cetaceans, revealing interspecific genetic introgression in marine mammals. We propose to add nuclear loci to genetic databases for cetacean species identification in order to detect hybrid individuals.

The absence of 5-HT4 receptors modulates depression- and anxiety-like responses and influences the response of fluoxetine in olfactory bulbectomised mice: Adaptive changes in hippocampal neuroplasticity markers and 5-HT1A autoreceptor

reclinical studies support a critical role of 5-HT4 receptors (5-HT4Rs) in depression and anxiety, but their influence in depression- and anxiety-like behaviours and the effects of antidepressants remain partly unknown. We evaluated 5-HT4R knockout (KO) mice in different anxiety and depression paradigms and mRNA expression of some neuroplasticity markers (BDNF, trkB and Arc) and the functionality of 5-HT1AR. Moreover, the implication of 5-HT4Rs in the behavioural and molecular effects of chronically administered fluoxetine was assessed in naïve and olfactory bulbectomized mice (OBX) of both genotypes. 5-HT4R KO mice displayed few specific behavioural impairments including reduced central activity in the open-field (anxiety), and decreased sucrose consumption and nesting behaviour (anhedonia). In these mice, we measured increased levels of BDNF and Arc mRNA and reduced levels of trkB mRNA in the hippocampus, and a desensitization of 5-HT1A autoreceptors. Chronic administration of fluoxetine elicited similar behavioural effects in WT and 5-HT4R KO mice on anxiety-and depression-related tests. Following OBX, locomotor hyperactivity and anxiety were similar in both genotypes. Interestingly, chronic fluoxetine failed to reverse this OBX-induced syndrome in 5-HT4R KO mice, a response associated with differential effects in hippocampal neuroplasticity biomarkers. Fluoxetine reduced hippocampal Arc and BDNF mRNA expressions in WT but not 5-HT4R KO mice subjected to OBX. These results demonstrate that the absence of 5-HT4Rs triggers adaptive changes that could maintain emotional states, and that the behavioural and molecular effects of fluoxetine under pathological depression appear to be critically dependent on 5-HT4RsThis research was supported by Spanish Ministry of Economy and Competitiveness (SAF2011-25020), and Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM)

Response to a Salmonella Typhimurium challenge in piglets supplemented with protected sodium butyrate or Bacillus licheniformis : effects on performance, intestinal health and behavior

Salmonella spp. is one of the worldwide leading causes of food-borne illnesses for which the inclusion of probiotics or organic acids in animal feeds can be useful control methods. Experimental models are utilized to test the efficacy of strategies against pathogens, but they exhibit limitations which may preclude finding sensible evaluation parameters. The objective of this work is to evaluate the efficacy of 2 different feed additives; a Bacillus licheniformis based probiotic and a protected sodium butyrate (SB) salt, using an experimental model of salmonellosis and, second, to explore if behavior analysis can be used as a sensible evaluation tool for additives evaluation. A total of 78 piglets weaned at 24 d, 8.3 kg BW, were used. Seventy-two were placed in 3 rooms of 8 pens (3 animals/pen) with evenly distributed treatments (n = 8): CON, control group with plain diet; PRO, plain diet with 1 kg/t of Proporc (10 9 cfu of B. licheniformis /kg of feed), and BUT, plain diet with 3 kg/t of Gustor BP70 (2.1 g of partially protected SB salt/kg of feed). Remaining piglets (n = 6) were separated and used as a challenge negative control. The experiment lasted 16 d. After 1 wk of adaptation, animals were challenged with 5 × 10 8 cfu of Salmonella Typhimurium. One pig per pen was euthanized and sampled at d 4 and 8 post-inoculation (PI). There were no significant differences among treatments for ADFI, ADG, G:F, rectal temperature, fecal consistency, pH, ammonia, short-chain fatty acids and lactic acid concentrations, cytokine TNF-α, Pig-MAP acute-phase proteins and histological parameters. However, both products were equally able to reduce colonization and shedding of Salmonella (P = 0.016 for PRO and BUT vs. CON). In addition, PRO treatment had a positive effect on behavioral displays, particularly exploring (P < 0.05 vs. CON), feeding (P < 0.05 vs. CON and BUT) and other active behaviors (P < 0.05 vs. CON and BUT) in the morning period (0830 to 1030 h). In the afternoon (1400 to 1600 h), the challenge effect was most significant. Pigs were less active after the challenge (P < 0.001), with a decrease in positive contacts (P = 0.004), exploration (P < 0.001) and feeding behaviors (P < 0.001) on d 3 PI, in comparison with before the challenge. Accordingly, many lying conducts increased at d 3 PI (P < 0.05). In conclusion, both treatments had positive effects against Salmonella, and behavior analysis appears to be a sensible tool to be considered

Self-Assembled Triply Periodic Minimal Surfaces as moulds for Photonic Band Gap Materials

We propose systems with structures defined by self-assembled triply periodic minimal surfaces (STPMS) as candidates for photonic bandgap materials. To support our proposal we have calculated the photonic bands for different STPMS and we have found that, at least, the double diamond and gyroid structures present full photonic bandgaps. Given the great variety of systems which crystalize in these structures, the diversity of possible materials that form them and the range of lattice constants they present, the construction of photonic bandgap materials with gaps in the visible range may be presently within reach.Comment: 3 pages, 2 figures, RevTe

Dosis recibida a partir de la generación de fotoneutrones en un maniquí antropomórfico sometido a un tratamiento de radioterapia

Normalmente, los sistemas de planificación de tratamientos en radioterapia no tienen en cuenta las posibles dosis recibidas por los pacientes debido a la contribución de neutrones inducida por los haces de fotones de alta energía. Esta información es especialmente importante para estimar posibles riesgos para la salud, incluida la posibilidad de desarrollar cánceres secundarios. El análisis de la dosis generada por los neutrones permitiría una optimización de los tratamientos del paciente, mejorando la temporización, secuenciación de tratamientos y evitando sobredosis. Las ventajas de utilizar las simulaciones Monte Carlo en este estudio se centran en que se trata de una metodología especialmente adecuada para estudiar todas las interacciones que contribuyen a la dosis del cuerpo de los pacientes modelados, incluida la producción de fotoneutrones, proporcionando una herramienta versátil y fiable para el estudio del transporte de partículas. Este trabajo ha desarrollado una simulación completa con MCNPX [1] para estudiar las distribuciones de dosis generadas en un maniquí por un haz de fotones emitido por un acelerador lineal con colimador multiláminas (Elekta Precise). Los puntos de cálculo de dosis se localizan en la cabeza y torso del maniquí RANDO PHANTOM. El modelo de simulación del acelerador lineal fue previamente validado con medidas experimentales tomadas en el Hospital Clínic Universitari de Valencia. Los resultados obtenidos reflejan que la dosis recibida debida a la contribución de fotoneutrones, aunque es baja (en torno al 0.5-1% de la máxima dosis) no debe ser despreciada por los sistemas de planificación.Juste Vidal, BJ.; Miró Herrero, R.; Abella, V.; Campayo Esteban, JM.; Díez, S.; Verdú Martín, GJ. (2012). Dosis recibida a partir de la generación de fotoneutrones en un maniquí antropomórfico sometido a un tratamiento de radioterapia. Sociedad Nuclear Española. http://hdl.handle.net/10251/71528

Monte Carlo flattening filter design to high energy intraoperative electron beam homogenization

[EN] Intraoperative radiotherapy using mobile linear accelerators is used for a wide variety of malignancies. However, when large fields are used in combination with high energies, a deterioration of the flatness dose profile is measured with respect to smaller fields and lower energies. Indeed, for the LIAC HWL of Sordina, this deterioration is observed for the 12 MeV beam combined with 10 cm (or larger) diameter applicator. Aimed to solve this problem, a flattening filter has been designed and validated evaluating the feasibility of its usage at the upper part of the applicator. The design of the filter was based on Monte Carlo simulations because of its accuracy in modeling components of clinical devices, among other purposes. The LIAC 10 cm diameter applicator was modeled and simulated independently by two different research groups using two different MC codes, reproducing the heterogeneity of the 12 MeV energy beam. Then, an iterative process of filter design was carried out. Finally, the MC designed conical filter with the optimal size and height to obtain the desired flattened beam was built in-house using a 3D printer. During the experimental validation of the applicator-filter, percentage depth dose, beam profiles, absolute and peripheral dose measurements were performed to demonstrate the effectiveness of the filter addition in the applicator. These measurements conclude that the beam has been flattened, from 5.9% with the standard configuration to 1.6% for the configuration with the filter, without significant increase of the peripheral dose. Consequently, the new filter-applicator LIAC configuration can be used also in a conventional surgery room. A reduction of 16% of the output dose and a reduction of 1.1 mm in the D50 of the percentage depth dose was measured with respect to the original configuration. This work is a proof-of-concept that demonstrates that it is possible to add a filter able to flatten the beam delivered by the Sordina LIAC HWL. Future studies will focus on more refined technical solutions fully compatible with the integrity of the applicator, including its sterilization, to be safely introduced in the clinical practice.The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Giuseppe Felici reports a relationship with S.I.T. Sordina IORT Technologies S.p.A. that includes: employment. We thank the professionals and facilities at the 3D printing and metrology department in the Mechanics Unit at IFIC. JV thanks I. Diaz for measuring the PLA density. We thank S.I.T. SORDINA IORT Tech-nologies SpA for providing the applicator used for testing the filter during the measurements. JV, FB, and JP would like to acknowledge the Spanish "Ministerio de Ciencia e Innovacion" (MCIN) grant PID2021-125096NB-I00 funded by MCIN/AEI/10.13039 and the "Generalitat Valenciana" (GVA) grant PROMETEO/2021/064.Oliver-Gil, S.; Vijande, J.; Tejedor-Aguilar, N.; Miró Herrero, R.; Rovira-Escutia, JJ.; Ballester, F.; Juste-Vidal, B.... (2023). Monte Carlo flattening filter design to high energy intraoperative electron beam homogenization. Radiation Physics and Chemistry. 212. https://doi.org/10.1016/j.radphyschem.2023.11110221

Astrophysical S factor for the He-4(He-3,gamma)Be-7 reaction at medium energies

3 pags., 1 tab. -- Nuclear Physics in Astrophysics V 3–8 April 2011, Eilat, IsraelThe astrophysical S factor for the He-4(He-3,gamma)Be-7 direct capture reaction plays a major role in the context of solar neutrino flux and primordial Li-7 abundances that demand accurate information on the reaction. We report here our recent cross section measurements using the activation method in the region of E-CM=900-2800 keV, that aim to shed light on the discrepancies in the existing data and lead to a more accurate extrapolation of the S factor