Fabrication of Efficient Single-Emitter Plasmonic Patch Antennas by Deterministic In Situ Optical Lithography using Spatially Modulated Light

Single-emitter plasmonic patch antennas are room-temperature deterministic single-photon sources, which exhibit highly accelerated and directed single-photon emission. However, for efficient operation these structures require 3D nanoscale deterministic control of emitter positioning within the device, which is a demanding task, especially when emitter damage during fabrication is a major concern. To overcome this limitation, the deterministic room-temperature in situ optical lithography protocol uses spatially modulated light to position a plasmonic structure nondestructively on any selected single-emitter with 3D nanoscale control. Herein, the emission statistics of such plasmonic antennas that embed a deterministically positioned single colloidal CdSe/CdS quantum dot, which highlight acceleration and brightness of emission, are analyzed. It is demonstrated that the presented antenna induces a 1000-fold effective increase in the absorption cross-section, and, under high pumping, these antennas show nonlinearly enhanced emission.

Tailoring Experimental Configurations to Probe Transition Dipoles of Fluorescent Nanoemitters by Polarimetry or Fourier Imaging with Enhanced Sensitivity

Probing the transition dipoles responsible for the luminescence of a nanoemitter is essential to understanding its physical properties, its interactions with its environment, and its potential applications. Various methods in photoluminescence microscopy, based on polarimetry or Fourier imaging, have been developed to measure an emitter's dipole properties: the number of radiating dipoles, the oscillator strength ratio between them, and their orientation. In this article, we model the most used of these protocols and show that their sensitivity depends crucially on the experimental conditions: substrate material, presence of another lower or upper layer, and objective numerical aperture. We develop guidelines to optimize the measurement sensitivity by tailoring the experimental conditions, depending on the type of protocol used and the dipole property to be measured.

Experimental measurement of local high temperature at the surface of gold nanorods using doped ZnGa2O4 as a nanothermometer

Heat measurement induced by photoexcitation of a plasmonic metal nanoparticle assembly under environmental conditions is of primary importance for the further development of applications in the fields of (photo)catalysis, nanoelectronics and nanomedicine. Nevertheless, the fine control of the rise in temperature remains difficult and limits the use of this technology due to the lack of local temperature measurement tools working under environmental conditions. Luminescence nanothermometers are an alternative solution to the limitations of conventional contact thermometers since they are able to give an absolute temperature value with high spatial resolution using common optical equipment. As a proof of concept of this nanothermometry approach, a high local temperature exceeding one hundred degrees is measured on the thermalized photoexcited aggregate of gold nanorods using ZnGa₂O₄:Cr³⁺,Bi³⁺ nanothermometers that have a strong temperature dependence on the luminescence lifetime of chromium(iii) and high sensitivity over an extensive range of temperatures. A study on the influence of the average distance between nanosensors and nanoheaters on the measured temperature is carried out by coating the nanosensors with a silica layer of tunable thickness, highlighting the temperature gradient at the vicinity of the nanoheater as the theory predicts. The variation of the optical nanosensor response is relevant and promising, and it could be further envisioned as a potential candidate for local temperature measurement at the nanoscale since no plasmonic effect on Cr³⁺ lifetime is observed. The results reported here open up an even wider field of application for high temperature nanothermometry on real samples such as aggregate particles for many applications including catalysis and nanoelectronics. Thermometry using luminescent nanoprobes, which is complementary to thermal microscopy techniques, will allow in situ and in operando temperature monitoring at very small scales.

Single Gold Bipyramid Nanoparticle Orientation Measured by Plasmon-Resonant Scattering Polarimetry

The 3D orientation of a single gold nanoparticle is probed experimentally by light scattering polarimetry. We choose high-quality gold bipyramids (AuBPs) that support around 700 nm a well-defined narrow longitudinal localized surface plasmonic resonance (LSPR) which can be considered as a linear radiating dipole. A specific spectroscopic dark-field technique was used to control the collection angles of the scattered light. The in-plane as well as the out-of-plane angles are determined by analyzing the polarization of the scattered radiation. The data are compared with a previously developed model where the environment and the angular collection both play crucial roles. We show that most of the single AuBPs present an out-of-plane orientation consistent with their geometry. Finally, the fundamental role of the collection angles on the determination of the orientation is investigated for the first time. Several features are then deduced: we validate the choice of the analytical 1D model, an accurate 3D orientation is obtained, and the critical contribution of the evanescent waves is highlighted.

Polariton fluids for analogue gravity physics

Analogue gravity enables the study of fields on curved space-times in the laboratory. There are numerous experimental platforms in which amplification at the event horizon or the ergoregion has been observed. Here, we demonstrate how optically generating a defect in a polariton microcavity enables the creation of one- and two-dimensional, transsonic fluid flows. We show that this highly tuneable method permits the creation of horizons. Furthermore, we present a rotating geometry akin to the water-wave bathtub vortex. These experiments usher in the possibility of observing stimulated as well as spontaneous amplification by the Hawking, Penrose and Zeld'ovich effects in fluids of light. This article is part of a discussion meeting issue 'The next generation of analogue gravity experiments'.

Extreme multiexciton emission from deterministically assembled single-emitter subwavelength plasmonic patch antennas

Coupling nano-emitters to plasmonic antennas is a key milestone for the development of nanoscale quantum light sources. One challenge, however, is the precise nanoscale positioning of the emitter in the structure. Here, we present a laser etching protocol that deterministically positions a single colloidal CdSe/CdS core/shell quantum dot emitter inside a subwavelength plasmonic patch antenna with three-dimensional nanoscale control. By exploiting the properties of metal-insulator-metal structures at the nanoscale, the fabricated single-emitter antenna exhibits a very high-Purcell factor (>72) and a brightness enhancement of a factor of 70. Due to the unprecedented quenching of Auger processes and the strong acceleration of the multiexciton emission, more than 4 photons per pulse can be emitted by a single quantum dot, thus increasing the device yield. Our technology can be applied to a wide range of photonic nanostructures and emitters, paving the way for scalable and reliable fabrication of ultra-compact light sources.

Imprinted Photonic Hydrogels for the Size- and Shell-Selective Recognition of Nanoparticles

Sensors based on responsive photonic hydrogels have recently attracted considerable attention for visual medical diagnostics, pharmaceutical bioassays, and environmental monitoring. However, the use of these promising materials for the detection of nanoparticles (NPs) has never been explored so far, although the sensing of nanoobjects is a rapidly evolving area of research. To address this issue, we have combined the concepts of inverse-opal hydrogels and nanoparticle-imprinted polymers. In this way, we could obtain a NP-imprinted photonic hydrogel consisting of a three-dimensional, highly ordered poly(methacrylic acid) macroporous array, in which nanocavities complementary to the target NPs, in this case colloidal quantum dots, are distributed. This novel type of NP-imprinted photonic hydrogel sensor was shown to display high sensitivity and selectivity, thus opening new prospects for the development of equipment-free and cost-efficient sensing devices for NPs.

Rats can acquire conditional fear of faint light leaking through the acrylic resin used to mount fiber optic cannulas

Rodents are exquisitely sensitive to light and optogenetic behavioral experiments routinely introduce light-delivery materials into experimental situations, which raises the possibility that light could leak and influence behavioral performance. We examined whether rats respond to a faint diffusion of light, termed caplight, which emanated through the translucent dental acrylic resin used to affix deep-brain optical cannulas in place. Although rats did not display significant changes in locomotion or rearing to caplight in a darkened open field, they did acquire conditional fear via caplight-footshock pairings. These findings highlight the potential confounding influence of extraneous light emanating from light-delivery materials during optogenetic analyses.

Near-field to far-field characterization of speckle patterns generated by disordered nanomaterials

We study the intensity spatial correlation function of optical speckle patterns above a disordered dielectric medium in the multiple scattering regime. The intensity distributions are recorded by scanning near-field optical microscopy (SNOM) with sub-wavelength spatial resolution at variable distances from the surface in a range which spans continuously from the near-field (distance ≪ λ) to the far-field regime (distance ≫ λ). The non-universal behavior at sub-wavelength distances reveals the connection between the near-field speckle pattern and the internal structure of the medium.

Experimental investigation and thermodynamic evaluation of the C–O–Zr ternary system

Experimental and thermodynamic modelling of the ZrC_xO_y solid solution.

Quantum dot-imprinted polymers with size and shell-selective recognition properties

The emergence of nanotechnology has stimulated a great deal of research to detect engineered nanoparticles spread out in the environment. We address this issue here by designing quantum dot-imprinted polymers for the speciation of nanoparticles based on their size, shape and surface chemistry.

Correction: Quantum dot-imprinted polymers with size and shell-selective recognition properties

Correction for ‘Quantum dot-imprinted polymers with size and shell-selective recognition properties’ by S. Gam-Derouich et al., Chem. Commun., 2015, DOI: 10.1039/c5cc05203c.

Inverse opals of molecularly imprinted hydrogels for the detection of bisphenol A and pH sensing

Inverse opal films of molecularly imprinted polymers (MIP) were elaborated using the colloidal crystal template method. The colloidal crystals of silica particles were built by the Langmuir-Blodgett technique, allowing a perfect control of the film thickness. Polymerization in the interspaces of the colloidal crystal in the presence of bisphenol A (BPA) and removal of the used template provides 3D-ordered macroporous methacrylic acid-based hydrogel films in which nanocavities derived from bisphenol A are distributed within the thin walls of the inverse opal hydrogel. The equilibrium swelling properties of the nonimprinted (NIPs) and molecularly imprinted polymers (MIPs) were studied as a function of pH and bisphenol A concentration, while the molecular structures of the bulk hydrogels were analyzed using a cross-linked network structure theory. This study showed an increase in nanopore (mesh) size in the MIPs after BPA extraction as compared to NIPs, in agreement with the presence of nanocavities left by the molecular imprints of the template molecule. The resulting inverse opals were found to display large responses to external stimuli (pH or BPA) with Bragg diffraction peak shifts depending upon the hydrogel film thickness. The film thickness was therefore shown to be a critical parameter for improving the sensing capacities of inverse opal hydrogel films deposited on a substrate.

Isotropic broadband absorption by a macroscopic self-organized plasmonic crystal

We describe the plasmonic properties of a two-dimensional periodic metallic grating of macroscopic size obtained by gold deposition on a self-assembled silica opal. Structural characterization shows a transition from microscopic order to isotropy at macroscopic scale. Optical reflection spectra exhibit a dip of almost complete absorption due to coupling to surface-plasmon-polaritons (SPP). This is explained by theoretical calculations introducing a density of coupled SPP modes. We demonstrate, at a given incidence angle, a broad continuum of coupled wavelengths over the visible spectrum. This opens new possibilities in fields where light-plasmon coupling is required over a broad range of wavelengths and incidence orientations.

Experimental Determination of the Fluorescence Quantum Yield of Semiconductor Nanocrystals

Many studies have considered the luminescence of colloidal II–VI nanocrystals, both in solution at a collective scale and at an individual scale by confocal microscopy. The quantum yield is an important figure of merit for the optical quality of a fluorophore. We detail here a simple method to determine the quantum yield of nanocrystals in solution as a function of the absorption. For this purpose, we choose rhodamine 101 as a reference dye to measure the nanocrystal fluorescence quantum yield. The influence of the concentration on quantum yield is therefore studied for both the reference and the solutions of nanocrystals and is found to be critical for the acuity of the method. Different types of nanocrystals are studied to illustrate different quantum yield evolutions with the concentration.

Thermoresponsive colloidal crystals built from core-shell poly(styrene/alpha-tert-butoxy-omega-vinylbenzylpolyglycidol) microspheres

Core-shell particles of poly(styrene/alpha-tert-butoxy-omega-vinylbenzylpolyglycidol) P(S/PGL) were used as new building blocks for the assembly of a colloidal crystal. The added-value properties of these particles for photonic crystal architectures are their high hydrophilicity together with their thermoresponsivity. Indeed, the poglycidol-rich shell undergoes a phase transition above 45 degrees C, which leads to its collapse at the particle surface accompanied by a decrease in the particle diameter. The three-dimensional crystalline arrays display Bragg diffraction properties, as judged by angle-resolved reflectance spectroscopy. The thermoresponsivity of the colloidal assemblies was observed through modifications of their optical properties with respect to the temperature used during the assembly process. The wetting properties of the crystalline material were also shown to reversibly switch from hydrophilic to hydrophobic as a function of the assembly temperature, thus evidencing the reorganization of the surface polyglycidol chains during the polymer phase transition. This work shows conclusively that P(S/PGL) particles are promising alternatives to poly(N-isopropylacrylamide) and poly(ethylene glycol) particles for the elaboration of thermoresponsive colloidal crystals, with a phase transition situated in between those of these two polymers.

Light scattering by pores in transparent Nd:YAG ceramics for lasers: correlations between microstructure and optical properties

Nd:YAG ceramics for laser applications were elaborated with various residual porosities by reaction-sintering process. The porosity analysis with CLSM and SEM led to the determination of the pore volume fraction after sintering. This study revealed that the mean pore size of Nd:YAG ceramics was around 0.7 microm while the residual porosity was ranging between 10(-1)% and 10(-4)%. These pore contents affect the transparency and laser efficiency of ceramics. The analytical model based on the Mie light scattering fairly fits the experimental data. This demonstrates that the porosity in Nd:YAG ceramics should be lower than 10(-4)% to reach single-crystal laser efficiency.

Frequency doubling of low power images using a self-imaging cavity

A self-imaging resonator can be simultaneously resonant for many transverse modes and therefore allows cavity build-up for images of various shapes. The stability properties of such a cavity are reviewed. We have used this device for the first time to enhance the efficiency of second harmonic generation of weak images. We characterize the global and local efficiency of the second harmonic generation, and discuss its limitation due to the spatial bandwidth of the cavity and the diffraction along the crystal length.

Controlled modification of single colloidal CdSe/ZnS nanocrystal fluorescence through interactions with a gold surface

Single colloidal CdSe/ZnS nanocrystals are deposited at various distances from a gold film in order to improve their performance as single photon sources. Photon antibunching is demonstrated and the experimental curves are accurately fitted by theoretical equations. Emission lifetime and intensity are measured and found in excellent agreement with theoretical values. The various effects of a neighbouring gold film are discussed : interferences of the excitation beam, interferences of the fluorescence light, opening of plasmon and lossy-surface-wave modes, modification of the radiation pattern leading to a modified objective collection efficiency. At 80 nm from the gold film, when using an objective with 0.75 numerical aperture, about a 2.4-fold increase of the detected intensity is evidenced.

Quantum processing of images by continuous wave optical parametric amplification

We have experimentally shown that a degenerate optical parametric oscillator pumped by a cw laser, inserted in a cavity having degenerate transverse modes such as a hemiconfocal or confocal cavity, and operating below the oscillation threshold in the regime of phase sensitive amplification, is able to process input images of various shapes in the quantum regime. More precisely, when deamplified, the image is amplitude squeezed; when amplified, its two polarization components are intensity correlated at the quantum level. In addition, the amplification process of the images is shown to take place in the noiseless regime.

Conditional preparation of a quantum state in the continuous variable regime: generation of a sub-Poissonian state from twin beams

We report the first experimental demonstration of conditional preparation of a nonclassical state of light in the continuous variable regime. Starting from a nondegenerate optical parametric oscillator which generates above threshold quantum intensity correlated signal and idler "twin beams," we keep the recorded values of the signal intensity only when the idler intensity falls inside a band narrower than its standard deviation. By this very simple technique, we generate a sub-Poissonian state 4.4 dB (64%) below shot noise from twin beams exhibiting 7.5 dB (82%) of noise reduction in the intensity difference.

Municipal waste incinerators: air and biological monitoring of workers for exposure to particles, metals, and organic compounds

AIMS

To evaluate occupational exposure to toxic pollutants at municipal waste incinerators (MWIs).

METHODS

Twenty nine male subjects working near the furnaces in two MWIs, and 17 subjects not occupationally exposed to combustion generated pollutants were studied. Individual air samples were taken throughout the shift; urine samples were collected before and after. Stationary air samples were taken near potential sources of emission.

RESULTS

Occupational exposure did not result in the infringement of any occupational threshold limit value. Atmospheric exposure levels to particles and metals were 10-100 times higher in MWIs than at the control site. The main sources were cleaning operations for particles, and residue transfer and disposal operations for metals. MWI workers were not exposed to higher levels of polycyclic aromatic hydrocarbons than workers who are routinely in contact with vehicle exhaust. The air concentrations of volatile organic compounds and aldehydes were low and did not appear to pose any significant threat to human health. Only the measurement of chlorinated hydrocarbon levels would seem to be a reliable marker for the combustion of plastics. Urine metal levels were significantly higher at plant 1 than at plant 2 because of high levels of pollutants emanating from one old furnace.

CONCLUSION

While biological monitoring is an easy way of acquiring data on long term personal exposure, air monitoring remains the only method that makes it possible to identify the primary sources of pollutant emission which need to be controlled if occupational exposure and environmental pollution are to be reduced.

Surpassing the standard quantum limit for optical imaging using nonclassical multimode light

Using continuous wave superposition of spatial modes, we demonstrate experimentally displacement measurement of a light beam below the standard quantum limit. Multimode squeezed light is obtained by mixing a vacuum squeezed beam and a coherent beam that are spatially orthogonal. Although the resultant beam is not squeezed, it is shown to have strong internal spatial correlations. We show that the position of such a light beam can be measured using a split detector with an increased precision compared to a classical beam. This method can be used to improve the sensitivity of small displacement measurements.

[How do we reduce the under-reporting of occupational primary lung cancer]

The under-reporting of occupational lung cancer is due to insufficient recognition of occupational exposure and inadequate medico-legal action.

MATERIALS AND METHODS

All cases of primary bronchial carcinoma seen at the University Hospital of Grenoble between October 1996 and December 1998 completed a standardised questionnaire set by a physician in occupational medicine. When evidence of exposure to occupational carcinogens was established a claim for occupational disease was made and the outcomes of these claims were obtained from the Department of Social Security at the end of 2000.

RESULTS

Asbestos was the most common carcinogenic agent found, followed by crystalline silica, diesel fumes, metals, paints and ionising radiation. Among the 305 patients in the study with primary bronchial carcinoma 20% were able to make a claim for occupational disease whereas only 2% would have claimed otherwise. The Department of Social Security accepted 77% of the 39 claims for occupational disease submitted, thus giving a 12% incidence of occupational bronchial carcinoma in this group.

CONCLUSION

It is important to inform and instruct doctors of the environmental risks that are additional to those of tobacco smoking and of the need of inquire into any exposure to carcinogenic agents in order to ensure that the victims receive the appropriate medico-legal benefits. Improved primary prevention alone might eventually avoid the development of up to 3 500 cases of occupation bronchial carcinoma per year in France.

Method for confirmation of synthetic corticosteroids in doping urine samples by liquid chromatography-electrospray ionisation mass spectrometry

In this study, we report on the development of a method to confirm simultaneously nine of the most commonly abused synthetic corticosteroids in urine based on liquid chromatography-electrospray ionisation mass spectrometry. A considerable simplified sample preparation procedure, including liquid-liquid phase extraction with Extrelut-NT3 columns, provided both excellent sample purification and high overall recoveries. Complete HPLC separations were obtained on a reversed-phase column with 1 mM ammonium acetate-acetonitrile (60:40, v/v) as mobile phase. Mass spectral acquisition was done in the negative ion, and selected ion monitoring modes to identify the drugs with at least three characteristic ions. Detection limits were determined at < or =1 ng/ml and the confirmation limits at 1 to 5 ng/ml.

Ambulatory blood pressure variation in normotensive subjects in relation to the sitting or standing position

OBJECTIVE

To evaluate the physiological variations in arterial blood pressure in normotensive subjects during activity and in relation to the sitting or lying position.

METHODS

The subjects were 30 healthy volunteers who were normotensive and receiving no treatment. Blood pressure was measured using the validated monitor Diasys Integra (NOVACOR SA, Rueil-Malmaison, France) with an integral position sensor. Blood pressure was recorded every 15min over a 24h period, additional measurements being made in the first, third and sixth minutes after standing up.

RESULTS

During the active period (1000-2000h), 53% of the measures were made in the standing position. Over this period, the values of systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate were significantly elevated in the standing position in comparison to the sitting position. The difference was of the order of 5mmHg for the SBP, 3.5mmHg for the DBP and 9beats/min for the heart rate. The SBP, DBP and heart rate measured in the first, third and sixth minutes after standing up were not significantly different.

CONCLUSION

When measuring the blood pressure and heart rate in ambulatory patients, it seems justified to evaluate the patient's position during monitoring in order to achieve a better reproducibility and also to uncover any problems of blood pressure control with positional change, as could exist in patients with autonomic dysfunction. This might also aid in evaluating antihypertensive treatment and also any deleterious hypotensive effects.

Quantum limits in the measurement of very small displacements in optical images

We consider the problem of the measurement of very small displacements in the transverse plane of an optical image with a split photodetector. We show that the standard quantum limit for such a measurement, which is equal to the diffraction limit divided by the square root of the number of photons used in the measurement, cannot be overcome by use of ordinary single-mode squeezed light. We give the form of possible multimode nonclassical states of light, enabling us to enhance by orders of magnitude the resolution of such a measurement beyond the standard quantum limit.

Sub-shot-noise high-sensitivity spectroscopy with optical parametric oscillator twin beams

Nondegenerate optical parametric oscillators generate above-threshold signal and idler beams that have intensity fluctuations correlated at the quantum level (twin beams). We describe what is to our knowledge the first high-sensitivity spectroscopy experiment using twin beams emitted by a cw optical parametric oscillator: a very weak two-photon absorption signal, in the 10(-7) range, is recorded on the 4S(1/2)-5S(1/2) transition of atomic potassium with a noise background that is reduced by 1.9 dB with respect to the shot-noise limit of the light used in the experiment.

Urinary hexane diamine as an indicator of occupational exposure to hexamethylene diisocyanate

The occupational exposure of 19 men to hexamethylene diisocyanate (HDI) vapour was monitored during one 8-h shift. It ranged from 0.30 to 97.7 micrograms/m3. This was compared with the urinary output of hexane diamine (HDA) liberated by acid hydrolysis from its conjugates in post-shift samples. The excretion varied from 1.36 to 27.7 micrograms g creatinine, and there was a linear association of HDI air concentration with urinary HDA excretion. The validity of the urinary analysis was confirmed by simultaneous blind analysis in another laboratory. The results had an excellent linear concordance. Thus, it seems that while the gas chromatographic-mass spectrometric detection method requires sophisticated apparatus, the results are very useful to occupational health practices. A biological exposure index limit of 19 micrograms HDA/g creatinine in a post-shift urine specimen is proposed as an occupational limit level of HDI monomer (time-weighted average = 75 micrograms/m3). Most importantly, biological monitoring of HDA is sensitive enough to be used at and below the current allowable exposure limit levels.

Biological monitoring of occupational exposure to toluene diisocyanate

The study validated the use of urinary toluene diamine (TDA) in postshift samples as an indicator of preceding 8-h exposure to toluene diisocyanate (TDI). Nine workers exposed in TDI-based polyurethane foam production were studied. Their exposure levels varied in 8-h time-averaged samples from 9.5 to 94 micrograms/m3. The urinary TDA concentrations varied from 6.5 to 31.7 micrograms/g creatinine and they were linearly related to the atmospheric TDI levels. Approximately 20% of TDI is metabolized to diamines but their specificity is remarkable to the extent that by analysis for the 2,4- and 2,6-diamino isomers an idea of the percutaneous absorption may be had.

[Nyctohemeral changes of blood pressure. Diagnostic and prognostic value]

The blood pressure shows circadian variation in normal subjects with higher diurnal than nocturnal values: the difference between day and night time blood pressure is about 10-20 mmHg for systolic and for diastolic blood pressure. These variations are mainly related to physical and/or psychosensorial stress: the physician is himself a cause of increased blood pressure (the "white coat" effect). The degree of the nocturnal decrease in blood pressure which is maximal 2 and 3 o'clock is related to the quality and depth of sleep. The nocturnal decrease is followed by an increase in blood pressure when the person wakes up (early morning peak). Diagnostic signs: a physiological inversion of the circadian rhythm may be observed in people who sleep during the daytime and work at night. There would seem to be less of a nocturnal fall in black persons in the United States. Some pathological conditions can inverse or at least disturb the ciacadian variation: apart from hypertension, this has been reported in autonomic nervous system disease, in diabetics with autonomic neuropathy in some elderly patients, in Cushing's syndrome, after cardiac transplantation, etc... In hypertensives, the lack of nocturnal decrease of the blood pressure or an inversion in circadian rhythm should be looked for in severe and secondary hypertension such as associated with pheochromocytoma, or in renal dialysis patients. In toxaemia of pregnancy, this abnormality may herald an eclamptic crisis. Prognostic signs: in normotensives (especially in black persons) and hypertensives, inversion of the circadian rhythm is associated with more severe left ventricular hypertrophy and a higher morbidity.