Direct Observation of Polaritonic Chemistry by Nuclear Magnetic Resonance Spectroscopy.

Polaritonic chemistry is emerging as a powerful approach to modifying the properties and reactivity of molecules and materials. However, probing how the electronics and dynamics of molecular systems change under strong coupling has been challenging due to the narrow range of spectroscopic techniques that can be applied in situ. Here we develop microfluidic optical cavities for vibrational strong coupling (VSC) that are compatible with nuclear magnetic resonance (NMR) spectroscopy using standard liquid NMR tubes. VSC is shown to influence the equilibrium between two conformations of a molecular balance sensitive to London dispersion forces, revealing an apparent change in the equilibrium constant under VSC. In all compounds studied, VSC does not induce detectable changes in chemical shifts, J-couplings, or spin-lattice relaxation times. This unexpected finding indicates that VSC does not substantially affect molecular electron density distributions, and in turn has profound implications for the possible mechanisms at play in polaritonic chemistry under VSC and suggests that the emergence of collective behavior is critical.

Tilting a ground-state reactivity landscape by vibrational strong coupling.

Many chemical methods have been developed to favor a particular product in transformations of compounds that have two or more reactive sites. We explored a different approach to site selectivity using vibrational strong coupling (VSC) between a reactant and the vacuum field of a microfluidic optical cavity. Specifically, we studied the reactivity of a compound bearing two possible silyl bond cleavage sites-Si-C and Si-O, respectively-as a function of VSC of three distinct vibrational modes in the dark. The results show that VSC can indeed tilt the reactivity landscape to favor one product over the other. Thermodynamic parameters reveal the presence of a large activation barrier and substantial changes to the activation entropy, confirming the modified chemical landscape under strong coupling.

Conductivity in organic semiconductors hybridized with the vacuum field.

Much effort over the past decades has been focused on improving carrier mobility in organic thin-film transistors by optimizing the organization of the material or the device architecture. Here we take a different path to solving this problem, by injecting carriers into states that are hybridized to the vacuum electromagnetic field. To test this idea, organic semiconductors were strongly coupled to plasmonic modes to form coherent states that can extend over as many as 10(5) molecules and should thereby favour conductivity. Experiments show that indeed the current does increase by an order of magnitude at resonance in the coupled state, reflecting mostly a change in field-effect mobility. A theoretical quantum model confirms the delocalization of the wavefunctions of the hybridized states and its effect on the conductivity. Our findings illustrate the potential of engineering the vacuum electromagnetic environment to modify and to improve properties of materials.

Coherent coupling of molecular resonators with a microcavity mode.

The optical hybridization of the electronic states in strongly coupled molecule-cavity systems have revealed unique properties, such as lasing, room temperature polariton condensation and the modification of excited electronic landscapes involved in molecular isomerization. Here we show that molecular vibrational modes of the electronic ground state can also be coherently coupled with a microcavity mode at room temperature, given the low vibrational thermal occupation factors associated with molecular vibrations, and the collective coupling of a large ensemble of molecules immersed within the cavity-mode volume. This enables the enhancement of the collective Rabi-exchange rate with respect to the single-oscillator coupling strength. The possibility of inducing large shifts in the vibrational frequency of selected molecular bonds should have immediate consequences for chemistry.

Spectrum of advice and curbside consultations of infectious diseases specialists.

OBJECTIVES: Curbside consultation (CC) of infectious diseases specialists for advice is very frequent but the corresponding workload has rarely been assessed. This activity is mostly oral (phone or direct contact) and poorly quantifiable because it is not charged. We had for aim to evaluate this activity in a French teaching hospital. METHODS: We recorded all CCs given during a 2.5-year period, from mid-2011 to the end of 2013. RESULTS: During the study period, 6789 CCs were recorded (2715 per year), or slightly more than 10 per day. These CCs were divided in 676 travel recommendations and 6113 for other reasons. They were mostly given by phone (77.4%). Most demands came from our hospital (61.4%), followed by community family physicians and specialist (27.1%), other local hospitals (6.5%) and clinics (4.3%). All the departments in our hospital consulted us for advice at least once and answers were mainly given by phone (70.1%) and at bedside (30.5%). The answers were principally advice (50.8%), modification of antibiotic prescription (22.9%), initiation of antibiotic course (14.8%), maintaining the same treatment (6.2%), and stopping antibiotics (4.3%). CCs accounted for 20% of clinical work for 1 physician. If the CCs in our hospital had been paid, our department would have received an additional 77,000€ in revenue. CONCLUSION: This curbside activity is very important and time-consuming for infectious diseases specialists, but it is currently not acknowledged or rewarded.

Sorting nanoparticles with intertwined plasmonic and thermo-hydrodynamical forces.

We exploit plasmonic and thermo-hydrodynamical forces to sort gold nanoparticles in a microfluidic environment. In the appropriate regime, the experimental data extracted from a Brownian statistical analysis of the kinetic motions are in good agreement with Mie-type theoretical evaluations of the optical forces acting on the nanoparticles in the plasmonic near field. This analysis enables us to demonstrate the importance of thermal and hydrodynamical effects in a sorting perspective.

Detection of QTL controlling metabolism, meat quality, and liver quality traits of the overfed interspecific hybrid mule duck.

The mule duck, an interspecific hybrid obtained by crossing common duck (Anas platyrhynchos) females with Muscovy (Cairina moschata) drakes, is widely used for fatty liver production. The purpose of the present study was to detect and map single and pleiotropic QTL that segregate in the common duck species, and influence the expression of traits in their overfed mule duck offspring. To this end, we generated a common duck backcross (BC) population by crossing Kaiya and heavy Pekin experimental lines, which differ notably in regard to the BW and overfeeding ability of their mule progeny. The BC females were mated to Muscovy drakes and, on average, 4 male mule ducks hatched per BC female (1600 in total) and were measured for growth, metabolism during growth and the overfeeding period, overfeeding ability, and the quality of their breast meat and fatty liver. The phenotypic value of BC females was estimated for each trait by assigning to each female the mean value of the phenotypes of her offspring. Estimations allowed for variance, which depended on the number of male offspring per BC and the heritability of the trait considered. The genetic map used for QTL detection consisted of 91 microsatellite markers aggregated into 16 linkage groups (LG) covering a total of 778 cM. Twenty-two QTL were found to be significant at the 1% chromosome-wide threshold level using the single-trait detection option of the QTLMap software. Most of the QTL detected were related to the quality of breast meat and fatty liver: QTL for meat pH 20 min post mortem were mapped to LG4 (at the 1% genome-wide significance level), and QTL for meat lipid content and cooking losses were mapped to LG2a. The QTL related to fatty liver weight and liver protein and lipid content were for the most part detected on LG2c and LG9. Multitrait analysis highlighted the pleiotropic effects of QTL in these chromosome regions. Apart from the strong QTL for plasma triglyceride content at the end of the overfeeding period mapped to chromosome Z using single-trait analysis, all metabolic trait QTL were detected with the multitrait approach: the QTL mapped to LG14 and LG21 affected the plasma cholesterol and triglyceride contents, whereas the QTL mapped to LG2a seemed to impact glycemia and the basal plasma corticosterone content. A greater density genetic map will be needed to further fine map the QTL.

Diffraction regimes of single holes.

We investigate both experimentally and theoretically the far-field diffraction patterns of single circular apertures as a function of their diameters d and at a given illumination wavelength λ. We observe the transition between the well-known pseudoscalar regime of large holes (d≫λ) and the less-known vectorial regime of subwavelength ones (d≪λ). Four different diffraction regimes are identified for different d/λ regions, each one with its polarization dependence. A thorough comparison with a theoretical model, which takes into account both finite hole size and the dielectric properties of the metal, allows us to explain and understand the physical processes leading to this behavior. Our results reveal the subtle interplay between two competing factors, one related to polarization symmetries associated with surface-plasmon excitations and the other originating in the coupling of the field to the waveguide mode of the aperture.

Weak measurements of light chirality with a plasmonic slit.

We examine, both experimentally and theoretically, an interaction of tightly focused polarized light with a slit on a metal surface supporting plasmon-polariton modes. Remarkably, this simple system can be highly sensitive to the polarization of the incident light and offers a perfect quantum weak measurement tool with a built-in postselection in the plasmon-polariton mode. We observe the plasmonic spin Hall effect in both coordinate and momentum spaces which is interpreted as weak measurements of the helicity of light with real and imaginary weak values determined by the input polarization. Our experiment combines the advantages of (i) quantum weak measurements, (ii) near-field plasmonic systems, and (iii) high-numerical aperture microscopy in employing the spin-orbit interaction of light and probing light chirality.

Brownian motion in a designer force field: dynamical effects of negative refraction on nanoparticles.

Photonic crystals (PC) have demonstrated unique features that have renewed the fields of classical and quantum optics. Although holding great promises, associated mechanical effects have proven challenging to observe. We demonstrate for the first time that one of the most salient properties of PC, namely negative refraction, can induce specific forces on metal nanoparticles. By integrating a periodically patterned metal film in a fluidic cell, we show that near-field optical forces associated with negatively refracted surface plasmons are capable of controlling particle trajectories. Coupling particle motions to PC band structures draws new approaches and strategies for parallel and high resolution all-optical control of particle flows with applications for micro- and nanofluidic systems.

Self-collimation of surface plasmon beams.

We generate self-collimating surface plasmon beams in a doubly periodic plasmonic grating. The self-collimation effect is understood from the local anisotropy of the isofrequency surface of the grating in the vicinity of the bandgap. The properties of the beams are analyzed by leakage radiation microscopy and show to an unprecedented level significantly reduced diffraction as compared with plasmon beams propagating on a flat metal film.

Telomere length, comorbidity, functional, nutritional and cognitive status as predictors of 5 years post hospital discharge survival in the oldest old.

BACKGROUND: Telomere length has been considered in many cross-sectional studies as a biomarker of aging. However the association between shorter telomeres with lower survival at advanced ages remains a controversial issue. This association could reflect the impact of other health conditions than a direct biological effect. OBJECTIVE: To test whether leukocyte telomere length is associated with 5-year survival beyond the impact of other risk factors of mortality like comorbidity, functional, nutritional and cognitive status. DESIGN: Prospective study. SETTING AND PARTICIPANTS: A population representative sample of 444 patients (mean age 85 years; 74% female) discharged from the acute geriatric hospital of Geneva University Hospitals (January-December 2004), since then 263 (59.2%) had died (December 2009). MEASUREMENTS: Telomere length in leukocytes by flow cytometry. RESULTS: In univariate model, telomere length at baseline and cognitive status were not significantly associated with mortality even when adjusting for age (R²=9.5%) and gender (R²=1.9%). The best prognostic predictor was the geriatric index of comorbidity (GIC) (R²=8.8%; HR=3.85) followed by more dependence in instrumental (R²=5.9%; HR=3.85) and based (R²=2.3%; HR=0.84) activities of daily living and lower albumin levels (R²=1.5%; HR=0.97). Obesity (BMI>30: R²=1.6%; HR=0.55) was significantly associated with a two-fold decrease in the risk of mortality compared to BMI between 20-25. When all independent variables were entered in a full multiple Cox regression model (R²=21.4%), the GIC was the strongest risk predictor followed by the nutritional and functional variables. CONCLUSION: Neither telomeres length nor the presence of dementia are predictors of survival whereas the weight of multiple comorbidity conditions, nutritional and functional impairment are significantly associated with 5-year mortality in the oldest old.

Plasmonic coherent drive of an optical trap.

We demonstrate that optical trapping can be driven by delocalized surface plasmon modes resonantly excited within a standing wave trap. Dynamical modifications are shown to be determined by the near-field symmetry of the plasmonic modes with negligible thermal effect. With low trapping powers and polarization control, remarkable stiffness enhancements are recorded, the larger the smaller the particle. The results can be simply modeled accounting for a coherent interaction between the plasmon field and the Gaussian standing wave of the trap.

Mechanisms for extraordinary optical transmission through bull's eye structures.

We analyze both experimentally and theoretically the physical mechanisms that determine the optical transmission through deep sub-wavelength bull's eye structures (concentric annular grooves surrounding a circular hole). Our analysis focus on the transmission resonance as a function of the distance between the central hole and its nearest groove. We find that, for that resonance, each groove behaves almost independently, acting as an optical cavity that couples to incident radiation, and reflecting the surface plasmons radiated by the other side of the same cavity. It is the constructive contribution at the central hole of these standing waves emitted by independent grooves which ends up enhancing transmission. Also for each groove the coupling and reflection coefficients for surface plasmons are incorporated into a phenomenological Huygens-Fresnel model that gathers the main mechanisms to enhance transmission. Additionally, it is shown that the system presents a collective resonance in the electric field that does not lead to resonant transmission, because the fields radiated by the grooves do not interfere constructively at the central hole.

Reversible switching of ultrastrong light-molecule coupling.

We demonstrate that photochromic molecules enable switching from the weak- to ultrastrong-coupling regime reversibly, by using all-optical control. This switch is achieved by photochemically inducing conformational changes in the molecule. Remarkably, a Rabi splitting of 700 meV is measured at room temperature, corresponding to 32% of the molecular transition energy. A similar coupling strength is demonstrated in a plasmonic structure. Such systems present a unique combination of coupling strength and functional capacities.

Surface plasmon leakage radiation microscopy at the diffraction limit.

This paper describes the image formation process in optical leakage radiation microscopy of surface plasmon-polaritons with diffraction limited spatial resolution. The comparison of experimentally recorded images with simulations of point-like surface plasmon-polariton emitters allows for an assignment of the observed fringe patterns. A simple formula for the prediction of the fringe periodicity is presented and practically relevant effects of abberations in the imaging system are discussed.

The high prevalence of malnutrition in elderly diabetic patients: implications for anti-diabetic drug treatments.

BACKGROUND: Type 2 diabetes usually occurs in the context of obesity and associated insulin resistance. Current treatment recommendations are based on lifestyle modifications and incremental drug therapy. However, this approach could lead to inappropriate priorities upon ageing, when diabetes may be compounded by malnutrition and reduced insulin resistance. METHODS: We prospectively evaluated glycaemic and nutritional parameters in 146 consecutive diabetic patients (age 82.5 +/- 7.3 years, mean +/- sd) admitted to our geriatric service. We also implemented nutritional support therapy and a drug therapy adjustment protocol. Oral hypoglycaemic agent withdrawal was attempted in cases of good glycaemic control (HbA(1c) < 7.5% (<47 mmol/mol) or fasting blood glucose < 7.5 mmol/l). RESULTS: Mean BMI and HbA(1c) were 29.6 +/- 7.1 kg/m(2) and 6.9 +/- 1.2% (52 +/- 9 mmol/mol), respectively. Of the patients, 51.4% were taking 1-3 oral hypoglycaemic agents, 30.8% were on insulin and 9.6% on were on insulin and oral hypoglycaemic therapy. Low Mini Nutritional Assessment scores and serum marker levels indicated a high prevalence of malnutrition and/or chronic disease, even in obese patients. Mini Nutritional Assessment scores were positively associated with HbA(1c) values. Among patients treated by oral hypoglycaemic agents, complete drug withdrawal was achieved in 65.8%, much more often than new treatments were added (P = 0.002). Glycaemic control did not worsen after approximately 30 days, despite in-hospital nutritional therapy. Successful oral hypoglycaemic therapy withdrawal was associated with lower Mini Nutritional Assessment scores. CONCLUSIONS: Malnutrition is highly prevalent in elderly diabetic inpatients and, paradoxically, contributes to 'good' glycaemic control. Malnutrition should be screened for in these patients and, when present, should prompt a revision in diet and drug therapy. In particular, the possibility of reducing unnecessary drug therapy should be considered.

Optimization of bull's eye structures for transmission enhancement.

We present an exhaustive exploration of the parameter space defining the optical properties of a bull's eye structure, both experimentally and theoretically. By studying the resonance intensity variations associated with the different geometrical features, several parameters are seen to be interlinked and scale laws emerge. From the results it is possible to give a simple recipe to design a bull's eye structure with optimal transmission properties.

Enhanced optical transmission at the cutoff transition.

The phenomenon of extraordinary transmission in the optical regime for circular hole arrays in optically thick metal films is studied as a function of hole size and depth. In the limit of small holes compared to the depth, the transmission properties follow a waveguide type behavior. By describing the transmission process as resulting from the interference between a resonant and a non-resonant contribution, a transition is clearly revealed through the specific spectral variations of the resonance at a given hole depth. This transition is associated to a change in the attenuation through the hole as its size increases, and corresponds to the optimal condition for surface plasmon excitation.

Efficiency and finite size effects in enhanced transmission through subwavelength apertures.

We investigate transmission efficiency and finite size effects for the subwavelength hole arrays. Experiments and simulations show how the finite size effects depend strongly on the hole diameter. The transmission efficiency reaches an asymptotic upper value when the array is larger than the surface plasmon propagation length on the corrugated surface. By comparing the transmission of arrays with that of the corresponding single holes, the relative enhancement is found to increase as the hole diameter decreases. In the conditions of the experiments the enhancement is one to two orders of magnitude but there is no fundamental upper limit to this value.