Second harmonic generation from metallic arrays of rectangular holes

The generation process of second harmonic (SH) radiation from holes periodically arranged on a metal surface is investigated. Three main modulating factors affecting the optical response are identified: the near-field distribution at the wavelength of the fundamental harmonic, how SH light couples to the diffraction orders of the lattice, and its propagation properties inside the holes. It is shown that light generated at the second harmonic can excite electromagnetic modes otherwise inaccessible in the linear regime under normal incidence illumination. It is demonstrated that the emission of SH radiation is only allowed along off-normal paths precisely due to that symmetry. Two different regimes are studied in the context of extraordinary optical transmission, where enhanced linear transmission either occurs through localized electromagnetic modes or is aided by surface plasmon polaritons (SPPs). While localized resonances in metallic hole arrays have been previously investigated, the role played by SPPs in SH generation has not been addressed so far. In general, good agreement is found between our calculations (based on the finite difference time domain method) and the experimental results on localized resonances, even though no free fitting parameters were used in describing the materials. It is found that SH emission is strongly modulated by enhanced fields at the fundamental wavelength (either localized or surface plasmon modes) on the glass metal interface. This is so in the transmission side but also in reflection, where emission can only be explained by an efficient tunneling of SH photons through the holes from the output to the input side. Finally, the existence of a dark SPP at the fundamental field is identified through a noninvasive method for the first time, by analyzing the efficiency and far-field pattern distribution in transmission at the second harmonic.Comment: This paper was published in JOSA B and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/josab/abstract.cfm?URI=josab-32-1-15. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under la

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

Impact of using new commercial glutathione enriched inactive dry yeast oenological preparations on the aroma and sensory properties of wines

The effect of the addition of a commercial enriched glutathione inactive dry yeast oenological preparation in the volatile and sensory properties of industrially manufactured rosé Grenache wines was evaluated during their shelf-life. In addition, triangle tests were performed at different times during wine aging (among 1 and 9 months) to determine the sensory differences between wines with and without glutathione inactive dry yeast preparations. Descriptive sensory analysis with a trained panel was carried out when sensory differences in the triangle test were noticed. In addition, consumer tests were performed in order to investigate consumers’ acceptability of wines. Results revealed significant sensory differences between control and glutathione inactive dry yeast wines after 9 months of aging. At that time, glutathione inactive dry yeast wines were more intense in fruity aromas (strawberry, banana) and less intense in yeast notes than control wine. The impact of the glutathione inactive dry yeast in the aroma might be the consequence of different effects that these preparations could induce in wine composition: modification of yeast byproducts during fermentation, release of volatile compounds from inactive dry yeast, interaction of wine volatile compounds with yeast macromolecules from inactive dry yeast and a possible antioxidant effect of the glutathione released by the inactive dry yeast preparation on some specific volatile compounds

Alkyl and alkylidene imido cyclopentadienyl tungsten complexes

This paper reports the alkylation of the cyclopentadienyl imido tungsten complexes [WCp′(NtBu)Cl3] (Cp′=η5-C5H5, η5-C5Me5) with β-hydrogen containing alkyl groups to render halo alkyl and trialkyl complexes [WCp′(NtBu)Cl3−nRn] (R=Et, n-Pr). Thermal decomposition of the trialkyl compounds gives the alkylidene derivatives [WCp′(NtBu)(CHR)(CH2R)] (R=Me, Et) by α-hydrogen elimination. All of the compounds were characterized by NMR spectroscopy and the molecular structure of [W(η5-C5Me5)(NtBu)Et3] was determined by X-ray diffraction methods.The authors acknowledge DGICYT (project PB97-0677) for financial support

Regioselective formation of\ud [2-(η5-cyclopentadienyl)-2-fluorenylpropane]-titanium complexes:\ud precursors, synthesis, structure and reactivity

The 2-cyclopentadienyl-2-fluorenylpropane ligand has been converted into the monometalated derivatives M[CMe2(C5H4)(C13H9)] (M=Li, Tl,) and CMe2[C5H4(SiMe3)](C13H9). These alkylating reagents have been characterized, and used to synthesize a new series of organotitanium (IV) complexes. The trimethylsilyl derivative was treated with TiCl4 to give the monocyclopentadienyl compound [Ti{CMe2(η5-C5H4)(C13H9)}Cl3]. Reaction of the thallium derivative with [Ti(η5-C5R5)Cl3] afforded the ‘mixed-ring’ dicyclopentadienyl complexes [Ti{CMe2(η5-C5H4)(C13H9)}(η5-C5R5)Cl2] (R=H, Me), whereas the reaction of TiCl4 with two equivalents of the lithium compound led to the dicyclopentadienyl complex [Ti{CMe2(η5-C5H4)(C13H9)}2Cl2]. The monocyclopentadienyl compound [Ti{CMe2(η5-C5H4)(C13H9)}Cl3] was readily hydrolyzed to give [Ti{CMe2(η5-C5H4)(C13H9)}Cl2]2(μ-O) in wet acetone (0.5% H2O). The dicyclopentadienyl derivative [Ti{CMe2(η5-C5H4)(C13H9)}(η5-C5Me5)Cl2] was further converted into [Ti{CMe2(η5-C5H4)(C13H9)}(η5-C5Me5)Me2] by alkylation with LiMe. Structural data of the titanium complexes demonstrate the η5-coordination of the cyclopentadienyl ring of the ancillary ligand, whereas the fluorenyl ring is not coordinated to the metal center. This mode of coordination is confirmed by the X-ray crystal structure analysis of [Ti{CMe2(η5-C5H4)(C13H9)}2Cl2]

Canted ground state in artificial molecules at high magnetic fields

We analyze the transitions that a magnetic field provokes in the ground state of an artificial homonuclear diatomic molecule. For that purpose, we have performed numerical diagonalizations for a double quantum dot around the regime of filling factor 2. We present phase diagrams in terms of tunneling and Zeeman couplings, and confinement strength. We identify a series of transitions from ferromagnetic to symmetric states through a set of canted states with antiferromagnetic couping between the two quantum dots

Late Holocene climate variability in the southwestern Mediterranean region: an integrated marine and terrestrial geochemical approach

A combination of marine (Alboran Sea cores, ODP 976 and TTR 300 G) and terrestrial (Zoñar Lake, Andalucia, Spain) geochemical proxies provides a high-resolution reconstruction of climate variability and human influence in the southwestern Mediterranean region for the last 4000 years at inter-centennial resolution. Proxies respond to changes in precipitation rather than temperature alone. Our combined terrestrial and marine archive documents a succession of dry and wet periods coherent with the North Atlantic climate signal. A dry period occurred prior to 2.7 cal ka BP – synchronously to the global aridity crisis of the third-millennium BC – and during the Medieval Climate Anomaly (1.4–0.7 cal ka BP). Wetter conditions prevailed from 2.7 to 1.4 cal ka BP. Hydrological signatures during the Little Ice Age are highly variable but consistent with more humidity than the Medieval Climate Anomaly. Additionally, Pb anomalies in sediments at the end of the Bronze Age suggest anthropogenic pollution earlier than the Roman Empire development in the Iberian Peninsula. The Late Holocene climate evolution of the in the study area confirms the see-saw pattern between the eastern and western Mediterranean regions and the higher influence of the North Atlantic dynamics in the western Mediterranean

Expression profiling of chromatin-modifying enzymes and global DNA methylation in CD4+ T cells from patients with chronic HIV infection at different HIV control and progression states

Abstract Background Integration of human immunodeficiency virus type 1 (HIV-1) into the host genome causes global disruption of the chromatin environment. The abundance level of various chromatin-modifying enzymes produces these alterations and affects both the provirus and cellular gene expression. Here, we investigated potential changes in enzyme expression and global DNA methylation in chronically infected individuals with HIV-1 and compared these changes with non-HIV infected individuals. We also evaluated the effect of viral replication and degree of disease progression over these changes. Results Individuals with HIV-1 had a significant surge in the expression of DNA and histone methyltransferases (DNMT3A and DNMT3B, SETDB1, SUV39H1) compared with non-infected individuals, with the exception of PRMT6, which was downregulated. Some histone deacetylases (HDAC2 and HDAC3) were also upregulated in patients with HIV. Among individuals with HIV-1 with various degrees of progression and HIV control, the group of treated patients with undetectable viremia showed greater differences with the other two groups (untreated HIV-1 controllers and non-controllers). These latter two groups exhibited a similar behavior between them. Of interest, the overexpression of genes that associate with viral protein Tat (such as SETDB1 along with DNMT3A and HDAC1, and SIRT-1) was more prevalent in treated patients. We also observed elevated levels of global DNA methylation in individuals with HIV-1 in an inverse correlation with the CD4/CD8 ratio. Conclusions The current study shows an increase in chromatin-modifying enzymes and remodelers and in global DNA methylation in patients with chronic HIV-1 infection, modulated by various levels of viral control and progression

Validación del monitor de medición de la grasa corporal por impedancia bioeléctrica OMRON BF 300

ObjetivosValorar la precisión del monitor de grasa corporal por impedancia bioeléctrica OMRON BF 300 y validar su medición del porcentaje de grasa corporal (%GC) frente a la ecuación de Siri. Diseño. Estudio descriptivo, transversal.EmplazamientoAtención primaria. Centros de Salud Coronel de Palma y San Fernando, Móstoles.ParticipantesEn la valoración de la precisión del monitor participaron 88 personas y 91 en la validación.Mediciones y resultados principalesLas determinaciones de %GC se realizaron por triplicado, anotándose la media. La precisión se evaluó mediante el coeficiente de correlación intraclase (CCI) y el coeficiente de variación (CV). La validez, mediante el error técnico, el CCI y el método de Bland-Altman. En la ecuación de Siri la densidad corporal se calculó con la ecuación de Durnin-Womersley. Precisión: el CCI fue de 0,999 y el CV de 0,4 ± 0,03. Validación: la diferencia de %GC monitor (26,6 ± 9,1%) – ecuación de Siri (27,8 ± 8,2%) fue de –1,27% (p < 0,01; IC del 95%, –1,97 a –0,57), el error técnico del monitor del 2,2% y el CCI de 0,956 (IC del 95%, 0,9335–0,9710), situándose un 80,2% de las diferencias monitor – ecuación por debajo del 5%, con un intervalo de concordancia por el método de Bland-Altman de +5,45 a –7,99%.ConclusionesEl monitor OMRON BF 300 satisface los criterios de precisión (CCI > 0,95 y CV bajo) y validación (error técnico excelente, CCI > 0,75 y diferencias clínicamente aceptables) y supone una alternativa válida a los pliegues cutáneos en la valoración nutricional del paciente.ObjectivesTo assess the accuracy of the OMRON BF 300 body fat monitor using bioelectric impedance and to validate its measurement of body fat percentage (BF%) against the Siri equation.DesignCross-sectional descriptive study.SettingPrimary care. Coronel de Palma and San Fernando Health Centres, Móstoles.Participants88 people took part in the assessment of the accuracy of the monitor, and 91 in the validation.Measurements and main resultsThe BF% were recorded in triplicate, with the mean being the figure noted. Precision was evaluated through the intra-class correlation coefficient (ICC) and the coefficient of variation (CV); validity, through technical error, the ICC and the Bland-Altman method. In the Siri equation, body density was calculated through the Durnin-Womersley equation. Precision: ICC was 0.999 and CV 0.4 ± 0.03. Validation: the difference between the BF% monitor (26.6 ± 9.1%) and the Siri equation (27.8 ± 8.2%) was –1.27% (p < 0.01; 95% CI –1.97 to –0.57); the technical error of the monitor was 2.2% and of the ICC 0.956 (95% CI, 0.9335–0.9710). Thus, 80.2% of the monitor-equation differences were below 5%, with a concordance interval under the Bland-Altman method of +5.45 to –7.99%.ConclusionsThe OMRON BF 300 monitor satisfies the precision criteria (ICC > 0.95 and low CV) and validation (excellent technical error, ICC > 0.75 and clinically acceptable differences) and is a valid alternative to cutaneous folds as a method of assessing nutrition of the patient