Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities having ...the optical mode volume close to or below the diffraction limit. Recently, it has become possible to make all-dielectric nano-cavities with reduced mode volumes and negligible non-radiative losses. Here, we realise low-loss high-refractive-index dielectric gallium phosphide (GaP) nano-antennas with small mode volumes coupled to atomic mono- and bilayers of WSeFormula: see text. We observe a photoluminescence enhancement exceeding 10Formula: see text compared with WSeFormula: see text placed on planar GaP, and trace its origin to a combination of enhancement of the spontaneous emission rate, favourable modification of the photoluminescence directionality and enhanced optical excitation efficiency. A further effect of the coupling is observed in the photoluminescence polarisation dependence and in the Raman scattering signal enhancement exceeding 10Formula: see text. Our findings reveal dielectric nano-antennas as a promising platform for engineering light-matter coupling in two-dimensional semiconductors.
Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities having ...the optical mode volume close to or below the diffraction limit. Recently, it has become possible to make all-dielectric nano-cavities with reduced mode volumes and negligible non-radiative losses. Here, we realise low-loss high-refractive-index dielectric gallium phosphide (GaP) nano-antennas with small mode volumes coupled to atomic mono- and bilayers of WSe2. We observe a photoluminescence enhancement exceeding 10(4) compared with WSe2 placed on planar GaP, and trace its origin to a combination of enhancement of the spontaneous emission rate, favourable modification of the photoluminescence directionality and enhanced optical excitation efficiency. A further effect of the coupling is observed in the photoluminescence polarisation dependence and in the Raman scattering signal enhancement exceeding 10(3). Our findings reveal dielectric nano-antennas as a promising platform for engineering light-matter coupling in two-dimensional semiconductors.
Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities with ...optical modes volumes close to or below the diffraction limit. Recently, it has become possible to make all-dielectric nano-cavities with reduced mode volumes and negligible non-radiative losses. Here, we realise low-loss high-refractive-index dielectric gallium phosphide (GaP) nano-antennas with small mode volumes coupled to atomic mono- and bilayers of WSe\(_2\). We observe a photoluminescence enhancement exceeding 10\(^4\) compared with WSe\(_2\) placed on planar GaP, and trace its origin to a combination of enhancement of the spontaneous emission rate, favourable modification of the photoluminescence directionality and enhanced optical excitation efficiency. A further effect of the coupling is observed in the photoluminescence polarisation dependence and in the Raman scattering signal enhancement exceeding 10\(^3\). Our findings reveal dielectric nano-antennas as a promising platform for engineering light-matter coupling in two-dimensional semiconductors.
The escalation of health care costs through the 1970s and 1980s led to rapid changes in the structure of the health care environment. As a profession, psychology has much in its current scope of ...practice to help it thrive in the evolving health care system. The changes in the health care system and the evolution of managed care are presented. The resistance of psychologists to adapt to the changing environment is discussed as a detriment to the further development of the profession. Opportunities for expanding the realm of clinical practice in the evolving health care system are examined. A scientist-practitioner-administrator model is presented as an alternative to traditional training of psychologists. It is suggested that such a model will provide psychologists with more of the skills needed to succeed in the new health care environment. Recommendations are made as to how clinical psychologists can contribute to the future of the profession by supporting changes in training, effective outcome studies, and expanding their clinical practices.
Abstract
Single photon emitters in atomically-thin semiconductors can be deterministically positioned using strain induced by underlying nano-structures. Here, we couple monolayer WSe
2
to ...high-refractive-index gallium phosphide dielectric nano-antennas providing both optical enhancement and monolayer deformation. For single photon emitters formed on such nano-antennas, we find very low (femto-Joule) saturation pulse energies and up to 10
4
times brighter photoluminescence than in WSe
2
placed on low-refractive-index SiO
2
pillars. We show that the key to these observations is the increase on average by a factor of 5 of the quantum efficiency of the emitters coupled to the nano-antennas. This further allows us to gain new insights into their photoluminescence dynamics, revealing the roles of the dark exciton reservoir and Auger processes. We also find that the coherence time of such emitters is limited by intrinsic dephasing processes. Our work establishes dielectric nano-antennas as a platform for high-efficiency quantum light generation in monolayer semiconductors.
In 2011–2012, Santorini was characterized by seismic‐geodetic‐geochemical unrest, which was unprecedented since the most‐recent eruption occurred in 1950 and led to fear an eruption was imminent. ...This unrest offered a chance for investigating the processes leading to volcanic reactivation and the compositional characteristics of involved magma. We have thus analyzed the He‐Ne‐Ar‐isotope composition of fluid inclusions in olivines and clinopyroxenes from cumulate mafic enclaves hosted in cogenetic dacitic lavas of the 1570–1573 and 1925–1928 eruptions of Nea Kameni. These unique data on Aegean volcanism were compared with those of gases collected in quiescent periods and during the unrest. The 3He/4He ratios (3.1–4.0 Ra) are significantly lower than the typical arc‐volcano values (R/Ra ∼ 7–8), suggesting the occurrence of magma contamination in Santorini plumbing system, which would further modify the 3He/4He ratio of parental magmas generated in the local metasomatized mantle. The 3He/4He values of enclaves (3.1–3.6 Ra) are comparable to those measured in gases during quiescent periods, confirming that enclaves reflect the He‐isotope signature of magma residing at shallow depths and feeding passive degassing. A significant increase in soil CO2 flux from Nea Kameni and anomalous compositional variations in the fumaroles were identified during the unrest, accordingly with previous studies. Simultaneously, 3He/4He ratios up to 4.0 Ra were also measured, demonstrating that the unrest was due to the intrusion into the shallow plumbing system of a more‐primitive 3He‐rich magma, which is even volatile richer and less contaminated than mafic magma erupted as enclaves. This new intrusion did not however trigger an eruption.
Key Points:
We studied the He‐Ne‐Ar isotopes in mafic enclaves and in gases from Santorini
The 3He/4He ratios of gases and enclaves is in the range 3.0–4.0 Ra
The 2011–2012 unrest at Santorini was due to the intrusion of a new mafic magma
The dopamine D2 and D3 receptors are implicated in schizophrenia and its pharmacological treatments. These receptors undergo intracellular trafficking processes that are modulated by dysbindin-1 ...(Dys). Indeed, Dys variants alter cognitive responses to antipsychotic drugs through D2-mediated mechanisms. However, the mechanism by which Dys might selectively interfere with the D3 receptor subtype is unknown. Here, we revealed an interaction between functional genetic variants altering Dys and D3. Specifically, both in patients with schizophrenia and in genetically modified mice, concomitant reduction in D3 and Dys functionality was associated with improved executive and working memory abilities. This D3/Dys interaction produced a D2/D3 imbalance favoring increased D2 signaling in the prefrontal cortex (PFC) but not in the striatum. No epistatic effects on the clinical positive and negative syndrome scale (PANSS) scores were evident, while only marginal effects on sensorimotor gating, locomotor functions, and social behavior were observed in mice. This genetic interaction between D3 and Dys suggests the D2/D3 imbalance in the PFC as a target for patient stratification and procognitive treatments in schizophrenia.
Tectonic and magmatic activity may couple at volcanic arcs, even though any relationship is less defined in smaller arcs, experiencing limited activity. Here we use gas geochemistry data collected ...during the 2011–2012 unrest at Santorini (Greece) to understand better the dynamics of the Aegean Volcanic Arc with regard to its tectonic setting. Since the most recent eruption in 1950 and before the unrest, minor seismicity and CO2 degassing (mainly from the fumaroles of Nea Kameni islet) were observed at Santorini. On January 2011, anomalous seismicity along the NE‐SW trending Kameni Line was accompanied by an inflation north of Nea Kameni. Fumarolic gas composition changed and gas release notably increased. We carried out geochemical study on both Kameni and Thera islands from January 2012 to June 2013. We repeated surveys of diffuse soil CO2 degassing and of in‐soil gas concentration, and we analyzed fumaroles and gas dissolved in thermal waters for chemical and isotopic composition. In agreement with previous studies, our geochemical data, particularly the diffuse soil CO2 flux increase, the increase of H2 content, and of CO2/CH4 and 3He/4He ratios in fumarolic gases, support geophysical data in indicating that unrest was associated with the emplacement of new mafic magma. This unrest had limited effect on the regional setting, with gas emissions focusing along the regional NE‐SW structures, without triggering by any seismic event, conversely to the 1950 eruption, which probably occurred in a frame of general tectonic reorganization of the Aegean microplate.
Key Points
Extensive and systematic geochemical surveys followed the anomalous degassing during Santorini unrest, both in the caldera center and on the inner caldera walls
Gas ratios and isotopic composition indicate deep mafic magma refilling into the shallow dacitic plumbing system
Unrest has limited apparent relations with the longer‐term tectonic evolution of the Arc, conversely to the 1950 eruption
•The Crash Momentum Index (CMI) is employed to represent impact eccentricity.•ReliefF algorithm provides a ranking of the most in influential variables on injury risk.•CMI affects injury risk, ...regardless of the used statistical or machine learning model.•Impact-related variables are more in influential than occupant/vehicle-related features.•By CMI and closing velocity, injury risk can be predicted before collision occurrence.
Thorough evaluations on injury risk (IR) are fundamental for guiding interventions toward the enhancement of both the road infrastructure and the active/passive safety of vehicles. Well-established estimates are currently based on IR functions modeled on post-crash variables, such as velocity change sustained by the vehicle (ΔV); thence, these analyses do not directly suggest how pre-crash conditions can be modified to allow for IR reduction. Nevertheless, ΔV can be disaggregated into two contributions which enable its apriori calculation, based only on the information available at the impact instant: the Crash Momentum Index (CMI), representing impact eccentricity at collision, and the closing velocity at collision (Vr).
By extensively employing the CMI indicator, this work assesses the overall influence of impact eccentricity and closing velocity on the risk for occupants to sustain a serious injury. As CMI synthesizes indications regarding ΔV, its use can be disjointed from the ΔV itself for the derivation of high-quality IR models. This feature distinguishes CMI from the other eccentricity indicators available at the state-of-the-art, allowing for the contribution of eccentricity on IR to be completely isolated. Because of this element of originality, special attention is given to the CMI variable throughout the present work.
Based on data extracted from the NASS/CDS database, the influence of the CMI and Vr variables on IR is specifically highlighted and analyzed from several perspectives. The feature ranking algorithm ReliefF, whose use is unprecedented in the accident analysis field, is first employed to assess importance of such impact-related variables in determining the injury outcome: if compared to vehicle-related and occupant-related variables (as category and age, respectively), the higher influence of CMI and Vr is initially highlighted. Secondly, the relevance of CMI and Vr is confirmed by fitting different predictive models: the fitted models which include the CMI predictor perform better than models which neglect the CMI, in terms of classical evaluation metrics. As a whole, considering the high predictive power of the proposed CMI-based models, this work provides valuable tools for the apriori assessment of IR.
We synthesized five fluorophore–photochrome dyads designed to switch reversibly between nonfluorescent and fluorescent isomers under optical control. These compounds pair an oxazine photochrome to a ...biphenyl, fluorene, pyrene, coumarin, or cyanine fluorophore in their molecular skeleton and can be prepared in a single step from known precursors in yields ranging from 30 to 63%. Nuclear magnetic resonance spectroscopy indicates that the oxazine ring of these compounds opens and closes spontaneously on a millisecond time scale in acetonitrile at ambient temperature. Under these conditions, the fraction of ring-open isomer at equilibrium is negligible in all instances with the exception of the cyanine derivative, which instead is almost exclusively in this form. Absorption and emission spectroscopies demonstrate, however, that the fraction of ring-open isomer is sensitive to solvent polarity and increases with a transition from acetonitrile to methanol. Alternatively, the ring-open isomer can be populated photochemically or trapped with the addition of acid. In both instances, the characteristic absorption and emission bands of the 3H-indolium chromophores, embedded within the ring-open species, can clearly be observed in the visible region. In the case of the coumarin derivative, the brightness of this chromophoric fragment is sufficiently high to permit the imaging of individual molecules with excellent signal-to-noise ratios. In fact, the fluorescence of single fluorophore–photochrome dyads can be activated under the influence of ultraviolet inputs and the resulting species can be localized with nanoscale precision under visible illumination. Indeed, subdiffraction images of polymer nanoparticles, doped with this particular dyad, can be reconstructed with nanoscale resolution. Thus, our operating principles for fluorescence switching at the single-molecule level can offer the opportunity to overcome diffraction and, eventually, lead to the development of an entire family of probes for super-resolution fluorescence imaging.
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