Geometric frustration in a hexagonal lattice of plasmonic nanoelements

We introduce the concept of geometric frustration in plasmonic arrays of nanoelements. In particular, we present the case of a hexagonal lattice of Au nanoasterisks arranged so that the gaps between neighboring elements are small and lead to a strong near-field dipolar coupling. Besides, far-field interactions yield higher-order collective modes around the visible region that follow the translational symmetry of the lattice. However, dipolar excitations of the gaps in the hexagonal array are geometrically frustrated for interactions beyond nearest neighbors, yielding the destabilization of the low energy modes in the near infrared. This in turn results in a slow dynamics of the optical response and a complex interplay between localized and collective modes, a behavior that shares features with geometrically frustrated magnetic systems

Genomic insights on the ethno-history of the Maya and the ‘Ladinos’ from Guatemala

Background Guatemala is a multiethnic and multilingual country located in Central America. The main population groups separate ‘Ladinos’ (mixed Native American-African-Spanish), and Native indigenous people of Maya descent. Among the present-day Guatemalan Maya, there are more than 20 different ethnic groups separated by different languages and cultures. Genetic variation of these communities still remains largely unexplored. The principal aim of this study is to explore the genetic variability of the Maya and ‘Ladinos’ from Guatemala by means of uniparental and ancestry informative markers (AIMs). Results Analyses of uniparental genetic markers indicate that Maya have a dominant Native American ancestry (mitochondrial DNA [mtDNA]: 100%; Y-chromosome: 94%). ‘Ladino’, however, show a clear gender-bias as indicated by the large European ancestry observed in the Y-chromosome (75%) compared to the mtDNA (0%). Autosomal polymorphisms (AIMs) also mirror this marked gender-bias: (i) Native American ancestry: 92% for the Maya vs. 55% for the ‘Ladino’, and (ii) European ancestry: 8% for the Maya vs. 41% for the ‘Ladino’. In addition, the impact of the Trans-Atlantic slave trade on the present-day Guatemalan population is very low (and only occurs in the ‘Ladino’; mtDNA: 9%; AIMs: 4%), in part mirroring the fact that Guatemala has a predominant orientation to the Pacific Ocean instead of a Caribbean one. Sequencing of entire Guatemalan mitogenomes has led to improved Native American phylogeny via the addition of new haplogroups that are mainly observed in Mesoamerica and/or the North of South America. Conclusions The data reveal the existence of a fluid gene flow in the Mesoamerican area and a predominant unidirectional flow towards South America, most likely occurring during the Pre-Classic (1800 BC-200 AD) and the Classic (200–1000 AD) Eras of the Mesoamerican chronology, coinciding with development of the most distinctive and advanced Mesoamerican civilization, the Maya. Phylogenetic features of mtDNA data also suggest a demographic scenario that is compatible with moderate local endogamy and isolation in the Maya combined with episodes of gene exchange between ethnic groups, suggesting an ethno-genesis in the Guatemalan Maya that is recent and supported on a cultural rather than a biological basis.We greatly thank all the sample contributors in Guatemala. JS was supported by research grants from the German FAZIT-STIFTUNG and the German Academic Exchange Service (DAAD). VAI was supported by funding from the EUROFORGEN project and the Xunta de Galicia (EM 2012/045). The research leading to these results has received funding from the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program FP7/2007-2013/ under REA grant agreement n° 290344, and the grants from the “Ministerio de Ciencia e Innovación” (SAF2008-02971) from the Plan Galego IDT, Xunta de Galicia (EM 2012/045) given to ASS

L'índex de la Carpeta d'Aprenentatge com a evidència de la presa de decisions del professorat d'Educació Superior

Presentem els resultats d'un estudi sobre les carpetes d'aprenentatge dels estudiants en els graus d'Educació Infantil i Primària que indaga en l'índex. Aquest apartat de la carpeta és fonamental, perquè reflecteix la presa de decisions del docent sobre què vol ensenyar i com vol que ho facin els estudiants, afavorint-los la consciència sobre l'aprenentatge. Com estudioses d'aquesta eina observem que la seva implantació encara planteja molts reptes i la nostra recerca en posa de manifest algun

Geometric frustration in ordered lattices of plasmonic nanoelements

Inspired by geometrically frustrated magnetic systems, we present the optical response of three cases of hexagonal lattices of plasmonic nanoelements. All of them were designed using a metal-insulator-metal configuration to enhance absorption of light, with elements in close proximity to exploit near-field coupling, and with triangular symmetry to induce frustration of the dipolar polarization in the gaps between neighboring structures. Both simulations and experimental results demonstrate that these systems behave as perfect absorbers in the visible and/or the near infrared. Besides, the numerical study of the time evolution shows that they exhibit a relatively extended time response over which the system fluctuates between localized and collective modes. It is of particular interest the echoed excitation of surface lattice resonance modes, which are still present at long times because of the geometric frustration inherent to the triangular lattice. It is worth noting that the excitation of collective modes is also enhanced in other types of arrays where dipolar excitations of the nanoelements are hampered by the symmetry of the array. However, we would like to emphasize that the enhancement in triangular arrays can be significantly larger because of the inherent geometric incompatibility of dipolar excitations and three-fold symmetry axes

Changes in heart rate variability of flight phobics during a paced breathing task and exposure to fearful stimuli

The aim of this experiment was to explore changes in the vagally mediated heart rate variability (HRV) of flight phobics during exposure to feared stimuli. A paced breathing task was included to control for respiration effects. Sixty-one flight phobics (40 women) with a mean age of 39.07 years (SD = 11.24) participated in the study. The root mean of the squared successive interbeat intervals differences (RMSSD) was taken as the time domain measure of HRV. High frequency (HF: 0.15-0.4 Hz) and low frequency (LF: 0.04-0.15 Hz) band power was calculated on the ECG recordings obtained during free breathing baseline (BL), paced breathing (PB), and exposure (E) to fearful stimuli. Heart rate unexpectedly increased from BL to PB, and decreased from PB to E, while no differences were found between BL and E. No changes in the RMSSD were seen across conditions. HF band power increased, as expected, from BL to PB, and a significant decrease was found from PB to E. LF band power, as well as the LF/HF ratio, increased from BL to E. Discussion focuses on (a) the role of the parasympathetic and the sympathetic nervous systems in fear-related situations, and (b) the effects of paced breathing in preparing the system to cope with threatEn este estudio se analizan los cambios en la variabilidad de la tasa cardíaca (HRV) relacionada con el sistema vagal en sujetos fóbicos durante la exposición a estímulos temidos. Se ha introducido una tarea de respiración pautada para controlar los efectos de la misma en la medida de la HRV. Han participado en el estudio 61 pacientes con fobia a volar (40 mujeres) con una edad media de 39,07 años (SD =11,24). Como medida de la HRV en el dominio del tiempo se ha tomado la RMSSD (media cuadrática de las diferencias de los intervalos RR sucesivos). Se ha calculado la potencia espectral en las bandas de alta (HF: 0.15-0.4 Hz) y de baja frecuencia (LF: 0.04-0.15 Hz) sobre los registros de ECG obtenidos durante una línea base sin respiración controlada (BL), una fase de respiración pautada (PB) y la exposición (E) a estímulos temidos. La tasa cardíaca aumentó de forma inesperada de BL a PB, disminuyó de PB a E, y no se obtuvieron diferencias entre BL y E. No se observaron cambios en RMSSD entre las tres condiciones. La potencia espectral de HF aumentó, como se esperaba, de BL a PB, y disminuyó de forma significativa de PB a E. La potencia espectral de LF, así como la relación LF/HF, aumentó de BL a E. La discusión se centra en (a) el papel de los sistemas simpático y parasimpático en las situaciones de miedo, y (b) los efectos de la respiración pautada en la preparación del sistema para afrontar estímulos temido

Structure and dynamics of [Nb(η5-C5H4SiMe3) 2(η2-H2BR2)] (R2 = O2C6H4, C8H14, H2) complexes. A combined experimental and theoretical study

Dihydrogen elimination from the reaction of the niobocene trihydride Cp‘2NbH3 (Cp‘ = η5-C5H4SiMe3) and the appropriate borane provides a synthetic route to the new borate-containing niobocene complexes [Nb(η5-C5H4SiMe3)2(η2-H2BR2)] (R2 = O2C6H4 (1), C8H14 (2), H2 (3)). The reaction with H2BO2C6H4 or H2BC8H14 proceeds at mild temperature, and the BH3·THF adduct reacts even at low temperature. Complexes 2 and 3 show dynamic behavior in solution. Spectroscopic and theoretical studies were carried out in order to clarify these dynamic processes. In addition, X-ray diffraction studies of 2 were carried out and the results correlated with the theoretical data. Finally, reactions of Cp‘2Nb(H)(L) (L = CO, CN(2,6-Me2C6H3), tBuOOCHCHCOOtBu) with BH3·THF give rise to the complex 3, with the elimination of the appropriate ancillary ligand L.Financial support from the Spanish Comisión Interministerial de Ciencia y Tecnología (Projects PB98-0915, PB98-0916-CO2-01, and PB-95-0023-CO1-CO2) is acknowledged.Peer reviewe

Long-term follow-up of transjugular intrahepatic portosystemic shunt (TIPS) with stent-graft

PURPOSEWe aimed to retrospectively evaluate the long-term clinical and patency results after the placement of transjugular intrahepatic portosystemic shunts (TIPS) using stent-graft. Many studies show the clinical results and the patency follow-up of TIPS with stent-graft in the short and medium term. However, few studies show long-term results.METHODSBetween 2002 and 2016, TIPS with stent-grafts were placed in 132 patients. The median age was 59.5 years. The median Model for End-stage Liver Disease (MELD) score was 13, and 71% were Child-Pugh B. Indications for TIPS were bleeding (83%) and ascites or hydrothorax (17%). The technical and clinical success rates were calculated, as were the rates of patency, survival and complications. The median follow-up period was 43 months.RESULTSThe technical success rate was 98%, and the clinical success rates were 85% in patients with indication for bleeding and 95% in patients with indication for ascites or hydrothorax. Primary patency did not decrease from 66% after 6 years (95% confidence interval [CI], 56.2%–75.8%) primary assisted patency remained stable at 87% after 6 years (95% CI, 77.2%–96.8%) and secondary patency did not decrease from 98% after 4 years (95% CI, 95.1%–100%). The median overall survival was 42.8 months (95% CI, 33.8–51.8 months). A total of 54 patients suffered some type of complication, minor (28 patients) or major (26 patients), during the follow-up.CONCLUSIONThe clinical success rate was high. The choice of the maximum initial limit of portosystemic gradient and the diameter of the post-TIPS shunt, together with the number of shunt reductions, are important to be able to compare results between publications. In our study, the patency rates did not decrease after 6 years; hence, long-term follow-up of these patients may not be necessary

Social anxiety and negative early life events in university students

Abstract Introduction: There is substantial evidence regarding the impact of negative life events during childhood on the aetiology of psychiatric disorders. We examined the association between negative early life events and social anxiety in a sample of 571 Spanish University students. Methods: In a cross-sectional survey conducted in 2007, we collected data through a semistructured questionnaire of sociodemographic variables, personal and family psychiatric history, and substance abuse. We assessed the five early negative life events: (i) the loss of someone close, (ii) emotional abuse, (iii) physical abuse, (iv) family violence, and (v) sexual abuse. All participants completed the Liebowitz Social Anxiety Scale. Results: Mean (SD) age was 21 (4.5), 75% female, LSAS score was 40 (DP = 22), 14.2% had a psychiatric family history and 50.6% had negative life events during childhood. Linear regression analyses, after controlling for age, gender, and family psychiatric history, showed a positive association between family violence and social anxiety score (p = 0.03). None of the remaining stressors produced a significant increase in LSAS score (p > 0.05). Conclusion: University students with high levels of social anxiety presented higher prevalence of negative early life events. Thus, childhood family violence could be a risk factor for social anxiety in such a population