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The HOSTS Survey—Exozodiacal Dust Measurements for 30 Stars
摘要： The Hunt for Observable Signatures of Terrestrial Systems survey searches for dust near the habitable zones (HZs) around nearby, bright main-sequence stars. We use nulling interferometry in the N band to suppress the bright stellar light and to probe for low levels of HZ dust around the 30 stars observed so far. Our overall detection rate is 18%, including four new detections, among which are the first three around Sun-like stars and the first two around stars without any previously known circumstellar dust. The inferred occurrence rates are comparable for early-type and Sun-like stars, but decrease from 16% for stars with previously detected cold dust to 8% for stars without such excess, confirming earlier results at higher sensitivity. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal excess luminosity function, we put upper limits on the median HZ dust level of 13 zodis (95% confidence) for a sample of stars without cold dust and of 26 zodis when focusing on Sun-like stars without cold dust. However, our data suggest that a more complex luminosity function may be more appropriate. For stars without detectable Large Binocular Telescope Interferometer (LBTI) excess, our upper limits are almost reduced by a factor of two, demonstrating the strength of LBTI target vetting for future exo-Earth imaging missions. Our statistics are limited so far, and extending the survey is critical to informing the design of future exo-Earth imaging surveys.
关键词： planetary systems,zodiacal dust,techniques: interferometric,infrared: stars,circumstellar matter
更新于2025-09-23 15:22:29
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Photoswitchable Host-Guest Systems Incorporating Hemithioindigo and Spiropyran Units
摘要： We cover selected examples of the incorporation of hemithioindigo and spiropyran units in one of the binding partners of synthetic host-guest systems. In some of the simplest systems, isomerization of the switch simply modulates the thermodynamic stability of the two isomeric host-guest complexes. In the presence of more than two binding partners, the isomerization of the molecular switch alters the composition of the multicomponent host-guest system producing a shuttling process of one of the components between different hosts. In others, the isomerization process controls the uptake and release of some of the components from/to the bulk solution. We show that the understanding of the isomerization mechanisms of the molecular switches and the effects produced by the external stimuli are essential for the design of complex and responsive supramolecular host-guest systems. The physicochemical properties of the hemithioindigo and spiropyran molecular photoswitches are complementary, providing different avenues to their applications in solution and material science.
关键词： Spiropyrans,Hemithioindigos,Host-Guest Systems,Supramolecular Assemblies,Photoswitches
更新于2025-09-23 15:22:29
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Interactions between M-typed solitons based on nonlinear optimization in dispersion management systems
摘要： Investigations on soliton interactions in dispersion management systems are beneficial to improving the communication capacity. In this paper, the variable-coefficient fifth-order nonlinear Schr?dinger equation, which can be used to describe the soliton interactions in dispersion management systems, is studied analytically. M-typed soliton interactions are presented based on the obtained soliton solutions. Influences of nonlinear effects on M-typed soliton interactions are analyzed. Results indicate that we can effectively control soliton interactions by means of nonlinear optimization of dispersion management systems.
关键词： Soliton interactions,Solitons,Dispersion management systems
更新于2025-09-23 15:22:29
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Fluorescent Calixarene Scaffolds for NO Detection in Protic Media
摘要： Here, we present the first fluorescent water-soluble conjugated calixarene scaffolds that are capable of detection of NO gas. Two different scaffolds, one based on a 5,5’-Bicalixarene structure and its isomer bearing two distantly conjugated calixarene moieties, have been synthesized. While the fluorescence of both isomers is quenched upon either passing of NO gas or generating it in-situ from diethylamine NONOate, the bicalixarene-based scaffold showed a significantly stronger response. We also present an example of a dye encapsulation strategy to achieve the detection of NO at longer wavelengths than in the parent calixarene host. Finally, a conjugated polymer bearing 5,5’-Bicalixarene scaffold has also been prepared and demonstrated enhanced sensitivity compared with the monomer due to the molecular wire effect.
关键词： conjugated systems,nitric oxide,host-guest chemistry,fluorescent probes,Calixarene
更新于2025-09-23 15:22:29
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Enzymatic method of urea determination in LTCC microfluidic system based on absorption photometry
摘要： In this paper a novel microanalytical system based on absorption photometry for urea determination in small-volume biological samples is described. The developed microsystem with built-in microreactor with urease immobilised on its surface was fabricated using low temperature co-fired ceramics (LTCC) technology. For detection of the ammonium ions – product of urea hydrolysis, the modified Berthelot’s reaction was applied and conditions of this reaction were optimised in a way to be suitable for analysis in microsystems and for particular application, with special regards to very small alternation of urea concentration in culture medium. The best results were obtained for reagent R1 composed of: 180 mM sodium salicylate, 15 mM sodium nitroprusside, 2 mM EDTA in phosphate buffer solution of pH 7 and reagent R2 containing 16.9 mM sodium hypochlorite in phosphate buffer solution of pH 12. Linear concentration range of urea detection with the use of the developed LTCC microfluidic system for the selected flow rate of 4 μl/min, was in the range up to 1 mM, and the calculated lower limit of detection – 0.002 mM. The developed microsystem enables urea determination in samples of post-culture medium and of cells lysates of minimised volume c.a. 1 μl. Preliminary studies related to determination of urea in real samples, performed using hepatic cells lysates and post-culture medium were successful. As reference methods, commercially available tests were applied. The determined urea concentration measured by means of the QuantiChrom? and BioMaxima test and by the developed method based on the LTCC microanalytical system differs by c.a. 9% and 2% respectively. To the best of our knowledge, this is the first urea analysis microsystem for use in cells culture studies characterised by: the smallest volume of sample – 1 μl, long lifetime with stable response - reduced by 14%, through experimental time span of 30 days as well as suitability for quasi-monitoring of cells in vitro with sampling rate - 6 samples per hour.
关键词： LTCC technology,enzymatic microreactor,microfluidic systems,lab-on-a-chip,enzymatic urea determination,absorption photometry
更新于2025-09-23 15:22:29
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GravityCam: Wide-field high-resolution high-cadence imaging surveys in the visible from the ground
摘要： GravityCam is a new concept of ground-based imaging instrument capable of delivering significantly sharper images from the ground than is normally possible without adaptive optics. Advances in optical and near-infrared imaging technologies allow images to be acquired at high speed without significant noise penalty. Aligning these images before they are combined can yield a 2.5–3-fold improvement in image resolution. By using arrays of such detectors, survey fields may be as wide as the telescope optics allows. Consequently, GravityCam enables both wide-field high-resolution imaging and high-speed photometry. We describe the instrument and detail its application to provide demographics of planets and satellites down to Lunar mass (or even below) across the Milky Way. GravityCam is also suited to improve the quality of weak shear studies of dark matter distribution in distant clusters of galaxies and multiwavelength follow-ups of background sources that are strongly lensed by galaxy clusters. The photometric data arising from an extensive microlensing survey will also be useful for asteroseismology studies, while GravityCam can be used to monitor fast multiwavelength flaring in accreting compact objects and promises to generate a unique data set on the population of the Kuiper belt and possibly the Oort cloud.
关键词： asteroseismology,gravitational lensing: micro,Kuiper belt: general,(stars:) planetary systems,gravitational lensing: weak
更新于2025-09-23 15:22:29
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Optomechanical damping basis
摘要： We present a closed-form analytical solution to the eigenvalue problem of the Liouville operator generating the dissipative dynamics of the standard optomechanical system. The corresponding Lindblad master equation describes the dynamics of a single-mode field inside an optical cavity coupled by radiation pressure to its moving mirror. The optical field and the mirror are in contact with separate environments, which are assumed at zero and finite temperature, respectively. The optomechanical damping basis refers to the exact set of eigenvectors of the generator that, together with the exact eigenvalues, are explicitly derived. Both the weak- and the strong-coupling regime, which includes combined decay mechanisms, are solved in this work.
关键词： Open quantum systems,Decoherence,Optomechanics
更新于2025-09-23 15:22:29
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Robust high-fidelity coherent control of two-state systems by detuning pulses
摘要： Coherent control of two-state systems is traditionally achieved by resonant pulses of specific Rabi frequency and duration, by adiabatic techniques using level crossings or delayed pulses, or by sequences of pulses with precise relative phases (composite pulses). Here we develop a method for high-fidelity coherent control which uses a sequence of detuning pulses. By using the detuning pulse areas as control parameters, and driving on an analogy with composite pulses, we report a great variety of detuning pulse sequences for broadband and narrow-band transition probability profiles.
关键词： composite pulses,narrow-band,coherent control,broadband,detuning pulses,two-state systems
更新于2025-09-23 15:22:29
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Decoherence of the Radiation from an Accelerated Quantum Source
摘要： Decoherence is the process via which quantum superposition states are reduced to classical mixtures. Decoherence has been predicted for relativistically accelerated quantum systems; however, examples to date have involved restricting the detected field modes to particular regions of space-time. If the global state over all space-time is measured, then unitarity returns and the decoherence is removed. Here, we study a decoherence effect associated with accelerated systems that cannot be explained in this way. In particular, we study a uniformly accelerated source of a quantum field state—a single-mode squeezer. Even though the initial state of the field is vacuum (a pure state) and the interaction with the quantum source in the accelerated frame is unitary, we find that the final state detected by inertial observers appears to be decohered, i.e., in a mixed state. This unexpected result may indicate new directions in resolving inconsistencies between relativity and quantum theory. We extend this result to a two-mode state and find that entanglement is also decohered.
关键词： Unruh Effect,Quantum Field Theory,Accelerated Systems,Decoherence,Quantum Source
更新于2025-09-23 15:22:29
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Interfacial Tensions and Viscosities in Multiphase Systems by Surface Light Scattering (SLS)
摘要： Hypothesis Multiphase systems are relevant in many fields of process engineering. For process and product design in connection with multiphase systems, knowledge on the thermophysical properties of the individual phases such as viscosity and on the interfacial tension between these is required but often lacking in literature. Experiments In the present study, the applicability of surface light scattering (SLS) for the simultaneous measurement of interfacial tensions and viscosities in multiphase systems in macroscopic thermodynamic equilibrium is demonstrated. For two model systems consisting of n-decane and methanol as well as n-dodecane and methanol forming a vapor-liquid-liquid equilibrium at atmospheric pressure, surface fluctuations which show an oscillatory behavior at the vapor-liquid and liquid-liquid interface could be associated with hydrodynamic modes. Findings From an exact theoretical description of the dynamics of the surface fluctuations, absolute data for the dynamic viscosities of the two liquid phases as well as the vapor-liquid and liquid-liquid interfacial tensions could be determined at temperatures between (333 and 358) K with total measurement uncertainties (k = 2) down to about 2%. For both systems studied at temperatures close to the upper critical solution temperature, the viscosities of the two liquid phases approach each other and the liquid-liquid interfacial tension tends to zero.
关键词： liquid-liquid systems,interfacial tension,multiphase systems,interfaces,upper critical solution temperature,vapor-liquid systems,viscosity,surface light scattering
更新于2025-09-23 15:21:21