Probing the Dark Exciton in Monolayer MoS2_2 by Quantum Interference in Second Harmonic Generation Spectroscopy

We report resonant second harmonic generation (SHG) spectroscopy of an hBN-encapsulated monolayer of MoS$_2$. By tuning the energy of the excitation laser, we identify a dark state transition (D) that is blue detuned by +25 meV from the neutral exciton X$^0$. We observe a splitting of the SHG spectrum into two distinct peaks and a clear anticrossing between them as the SHG resonance is tuned through the energy of the dark exciton D. This observation is indicative of quantum interference arising from the strong two-photon light-matter interaction. We further probe the incoherent relaxation from the dark state to the bright excitons, including X$^0$ and localized excitons LX, by the resonant enhancement of their intensities at the SHG-D resonance. The relaxation of D to bright excitons is strongly suppressed on the bare substrate whilst enabled when the hBN/MoS$_2$/hBN heterostructure is integrated in a nanobeam cavity. The relaxation enabled by the cavity is explained by the phonon scattering enhanced by the cavity phononic effects. Our work reveals the two-photon quantum interference with long-lived dark states and enables the control through nanostructuring of the substrate. These results indicate the great potential of dark excitons in 2D-material based nonlinear quantum devices

Selective Exciton-Phonon-Phonon Coupling and Anharmonicity with Cavity Vibrational Phonons and MoS2_2 Lattice Phonons in Hybrid Nanobeam Cavities

We report selective coupling between neutral excitons X$^0$, vibrational phonon modes of a freestanding nanobeam cavity and lattice phonons of a MoS$_2$ monolayer fully encapsulated by hBN. Our experimental findings demonstrate that the cavity vibrational phonons selectively couple to neutral excitons (X$^0$), and the coupling to negatively charged trion (X$^-$) being significantly weaker. We establish this result by studying the lattice temperature induced broadening of exciton linewidths, where the contribution from the X$^0$-cavity phonon coupling is clearly observed while the X$^-$-cavity phonon coupling is not. Furthermore, when the Raman modes of MoS$_2$ lattice phonons A$_{1g}$ and 2LA are tuned into an outgoing resonance with exciton emissions, we observe the X$^0$-cavity phonon-lattice phonon coupling which inherits the characteristics rule the of X$^0$-cavity phonon coupling. As a result, X$^0$-induced Raman scatterings are enhanced, while X$^-$-induced scatterings are suppressed, revealed by the detuning-dependent Raman intensities and the ratio of X$^-$/X$^0$ emission intensities. The phonon anharmonicity from the coupling between cavity vibrational phonons and MoS$_2$ lattice phonons is further demonstrated by the observed Raman linewidth. Such hybrid couplings between materials and nanostructures enable the control of phonon-induced processes in nanophotonic and nanomechanical systems incorporating 2D semiconductors

Effects of ischemic compression on trigger points in the first dorsal interosseous muscle in patients with thumb carpometacarpal osteoarthritis

Background: Thumb carpometacarpal osteoarthritis (CMC OA) is a common disorder that interferes with the ability to perform the activities of daily life. The purpose of this study was to investigate the immediate effects of ischemic compression on myofascial trigger points (MTrPs) in the first dorsal interosseous (FDI) muscle in patients with the diagnosis of thumb CMC OA. Methods: In a quasi-experimental clinical trial, thirty-one patients, 87% female (age: 82 ± 9.4 years), with thumb CMC OA, were consecutively assigned to either an experimental treatment that included the ischemic compression of the FDI MTrP or a sham treatment of the FDI MTrP for one session. The main outcome considered in the study was the pressure pain threshold (PPT). Measurements were taken pre-and post-treatment and at a 1-week follow-up period. Results: The PPT over the right (affected) FDI muscle showed statistically significant differences between groups at 1-week follow up (F = 3.518; p = 0.04) in favor of the experimental group. Conclusions: The ischemic compression of FDI-MTrPs is an appropriate part of a multimodal treatment to decrease local pain sensitivity in patients with CMC OA

Synergistic effects of UVR and simulated stratification on commensalistic phytoplankton–bacteria relationship in two optically contrasting oligotrophic Mediterranean lakes

An indirect effect of global warming is a reduction in the depth of the upper mixed layer (UML) causing organisms to be exposed to higher levels of ultraviolet (UVR, 280–400 nm) and photosynthetically active radiation (PAR, 400–700 nm). This can affect primary and bacterial production as well as the commensalistic phytoplankton–bacteria relationship. The combined effects of UVR and reduction in the depth of the UML were assessed on variables related to the metabolism of phytoplankton and bacteria, during in situ experiments performed with natural pico- and nanoplankton communities from two oligotrophic lakes with contrasting UVR transparency (high-UVR versus low-UVR waters) of southern Spain. The negative UVR effects on epilimnetic primary production (PP) and on heterotrophic bacterial production (HBP), intensified under increased stratification, were higher in the low-UVR than in the high-UVR lake, and stronger on the phytoplanktonic than on the heterotrophic bacterial communities. Under UVR and increased stratification, the commensalistic phytoplankton–bacteria relationship was strengthened in the high-UVR lake where excretion of organic carbon (EOC) rates exceeded the bacterial carbon demand (BCD; i.e., BCD : EOC(%) ratio 100). The greater UVR damage to phytoplankton and bacteria and the weakening of their commensalistic interaction found in the low-UVR lake indicates that these ecosystems would be especially vulnerable to UVR and increased stratification as stressors related to global climate change. Thus, our findings may have important implications for the carbon cycle in oligotrophic lakes of the Mediterranean region.This study was supported by the Ministerio Español de Medio Ambiente, Rural y Marino (PN2009/067), Ciencia e Innovación (CGL2011-23681), Junta de Andalucía (Excelencia CVI-02598 and P09-RNM-5376), Consejo Nacional de Investigaciones Científicas y Técnicas – CONICET (PIP no. 112-201001-00228), and Fundación Playa Unión. G. Herrera and C. Durán were supported by a Formación de Profesorado Universitario grant from the Spanish government. The authors are indebted to the staff of Sierra Nevada National Park and Lagunas de Ruidera Natural Park for permission to work, to E. Jiménez-Coll for the bacterial production analysis, and to D. Nesbitt for writing assistance in English

Interactive effects of vertical mixing, nutrients and ultraviolet radiation: in situ photosynthetic responses of phytoplankton from high mountain lakes in Southern Europe

Global change, together with human activities, has resulted in increasing amounts of organic material (including nutrients) that water bodies receive. This input further attenuates the penetration of solar radiation, leading to the view that opaque lakes are more "protected" from solar ultraviolet radiation (UVR) than clear ones. Vertical mixing, however, complicates this view as cells are exposed to fluctuating radiation regimes, for which the effects have, in general, been neglected. Furthermore, the combined impacts of mixing, together with those of UVR and nutrient inputs are virtually unknown. In this study, we carried out complex in situ experiments in three high mountain lakes of Spain (Lake Enol in the National Park Picos de Europa, Asturias, and lakes Las Yeguas and La Caldera in the National Park Sierra Nevada, Granada), used as model ecosystems to evaluate the joint impact of these climate change variables. The main goal of this study was to address the question of how short-term pulses of nutrient inputs, together with vertical mixing and increased UVR fluxes modify the photosynthetic responses of phytoplankton. The experimentation consisted in all possible combinations of the following treatments: (a) solar radiation: UVR + PAR (280–700 nm) versus PAR (photosynthetically active radiation) alone (400–700 nm); (b) nutrient addition (phosphorus (P) and nitrogen (N)): ambient versus addition (P to reach to a final concentration of 30 μg P L−1, and N to reach N:P molar ratio of 31); and (c) mixing: mixed (one rotation from surface to 3 m depth (speed of 1 m 4 min−1, total of 10 cycles)) versus static. Our findings suggest that under ambient nutrient conditions there is a synergistic effect between vertical mixing and UVR, increasing phytoplankton photosynthetic inhibition and excretion of organic carbon (EOC) from opaque lakes as compared to algae that received constant mean irradiance within the epilimnion. The opposite occurs in clear lakes where antagonistic effects were determined, with mixing partially counteracting the negative effects of UVR. Nutrient input, mimicking atmospheric pulses from Saharan dust, reversed this effect and clear lakes became more inhibited during mixing, while opaque lakes benefited from the fluctuating irradiance regime. These climate change related scenarios of nutrient input and increased mixing, would not only affect photosynthesis and production in lakes, but might also further influence the microbial loop and trophic interactions via enhanced EOC under fluctuating UVR exposure.This work was supported by Ministerio Español de Medio Ambiente, Rural y Marino (PN2009/067) and Ciencia e Innovación (GLC2008-01127/BOS and CGL2011-23681), Junta de Andalucía (Excelencia CVI-02598), Agencia Nacional de Promoción Científica y Tecnológica (PICT 2007-1651) and Fundación Playa Unión; GH and CD were supported by the Spanish Government – Formación de Profesorado Universitario Grant

Non-Local Exciton-Photon Interactions in Hybrid High-Q Beam Nanocavities with Encapsulated MoS2 Monolayers

Atomically thin semiconductors can be readily integrated into a wide range of nanophotonic architectures for applications in quantum photonics and novel optoelectronic devices. We report the observation of non-local interactions of \textit{free} trions in pristine hBN/MoS$_2$/hBN heterostructures coupled to single mode (Q $>10^4$) quasi 0D nanocavities. The high excitonic and photonic quality of the interaction system stem from our integrated nanofabrication approach simultaneously with the hBN encapsulation and the maximized local cavity field amplitude within the MoS$_2$ monolayer. We observe a non-monotonic temperature dependence of the cavity-trion interaction strength, consistent with the non-local light-matter interactions in which the extent of the center-of-mass wavefunction is comparable to the cavity mode volume in space. Our approach can be generalized to other optically active 2D materials, opening the way towards harnessing novel light-matter interaction regimes for applications in quantum photonics

Caracterización epidemiológica de la hematuria vesical bovina en Caldas, Risaralda y Quindío

Se realizó el estudio de la epidemiologia de la Hematuria Vesical Bovina (HVB) en Caldas, Risaralda y Quindío. La investigación se efectuó a través de La resolución de encuestas practicadas en 45 fincas de la zona. Por los resultados obtenidos se concluye que Ia HVB solo afecta a los bovinos con una prevalencia instantánea de 1,16% para Ia zona y de 3,83% para las fincas, determinándose que las vacas mayores de cuatro años son las más afectadas y estableciéndose que las razas puras y los cruces son más susceptibles que el ganado criollo y que algunas razas rústicas como el normando. Se determinó que la HVB se ve favorecida en su presentación por precipitaciones pluviales anuales alrededor de los 2.500 mm y por el pH menor o igual a 5,0 y el color amarillento de los suelos, como también por un manejo deficiente de praderas, representado por un control de malezas anual a mayor que determina Ia abundancia de malezas en general y de helechos en particular con las fincas afectadas, las cuales a su vez se caracterizan por ser explotaciones más de tipo extensivo donde no suministran a los animales sales a premezclas minerales. Finalmente se calculan algunas pérdidas económicas y se discute que la HVB es ante todo producto de las características ecológicas y del sistema de explotación y manejo animal, a la vez que se plantean medidas tendientes a su prevención y control.An epidemiological study on Bovine Vesical Haematuria (HVB) was carried out based on the evaluation of a survey on 45 farms of Caldas, Risaralda and QuindIo regions in Colombia. The results indicated the prevalence of the disease was of 1.16% for the whole region and 3.83% for farms. It also indicated that BVH affects mainly cows older than four years and that pure breed or cross breeds are more susceptible than "criollo" and rustic breeds like Normando cattle. The annual rainfall around 2.500 mm., pH values equal or under 5.0 and yellowish color of the soil, as well as inadecuate weed's control that leads to an 341 excees of them, particulary braken fern were considered the most important factors that contributed to the presentation of the disease. The affected farms were also caracterized by lack of mineral supplies on the animals ration. Discussion of the importance of ecological and animal handling factors, evaluation of economical losses and recommendations on prevention and control are presented.Ganado de doble propósito-Ganaderia doble proposit

Lasing of Moir\'e Trapped MoSe2_2/WSe2_2 Interlayer Excitons Coupled to a Nanocavity

Moir\'e trapped interlayer excitons (IXs) in heterobilayer transition metal dichalcogenides currently attract strong interest due to their potential for non-classical light generation, coherent spin-photon interfaces and exploring novel correlated phases of electrons. Here, we report lasing of moir\'e trapped IXs by integrating a pristine hBN-encapsulated MoSe$_2$/WSe$_2$ heterobilayer in a high-Q ($>10^4$) nanophotonic cavity. We control the detuning between the IX line and the cavity mode with a magnetic field and measure the dipolar coupling strength to the cavity mode to be $78 \pm 4\ \mathrm{\mu eV}$, fully consistent with the 82 $\mathrm{\mu eV}$ predicted by theory. The emission from the cavity mode shows clear threshold-like behaviour. We observe a superlinear power dependence accompanied by a narrowing of the linewidth as the distinct features of lasing. The onset and prominence of these threshold-like behaviours are significant at resonance whilst weak off-resonance. Our results show that a lasing transition can be induced in interacting moir\'e trapped IXs with macroscopic coherence extending over the lengthscale of the cavity mode. Such systems raise interesting perspectives for low-power switching and synaptic nanophotonic devices using 2D materials

Do UK universities communicate their brands effectively through their websites?

This paper attempts to explore the effectiveness of UK universities’ websites. The area of branding in higher education has received increasing academic investigation, but little work has researched how universities demonstrate their brand promises through their websites. The quest to differentiate through branding can be challenging in the university context, however. It is argued that those institutions that have a strong distinctive image will be in a better position to face a changing future. Employing a multistage methodology, the web pages of twenty UK universities were investigated by using a combination of content and multivariable analysis. Results indicated ‘traditional values’ such as teaching and research were often well communicated in terms of online brand but ‘emotional values’ like social responsibility and the universities’ environments were less consistently communicated, despite their increased topicality. It is therefore suggested that emotional values may offer a basis for possible future online differentiation