Decoherence via the dynamical casimir effect

We derive a master equation for a mirror interacting with the vacuum field via radiation pressure. The dynamical Casimir effect leads to decoherence of a superposition state in a time scale that depends on the degree of "macroscopicity" of the state components, and which may be much shorter than the relaxation time scale. Coherent states are selected by the interaction as pointer states.     

A novel method for the determination of total 1,3-octanediols in apple juice via 1,3-dioxanes by solid-phase microextraction and high-speed gas chromatography

In this work, a novel, simple and fast method based on solid-phase microextraction (SPME) followed by high-speed gas chromatography (HSGC) was developed for the analysis of total 1,3-octanediols in apple juices by means of derivatization reaction to volatile 1,3-dioxanes. The derivatization reaction, SPME conditions, glycosidically bound fraction and 1,3-nonanediol as a surrogate standard were studied. The formation of 1,3-dioxanes from 1,3-diols was confirmed by GC–MS. The method was validated obtaining a regression coefficient (r²) of 0.9996, precisions between 0.3 and 9.8%, extraction recoveries in the range 94.7–112.2% and LOD of 2.9 μg l⁻¹. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The method was applied to the analysis of 21 Asturian apple varieties finding a double reciprocal relationship between the concentrations of saturated and unsaturated 1,3-octanediol.     

Experimental design applied to the analysis of volatile compounds in apple juice by headspace solid-phase microextraction

A simple and fast method based on solid-phase microextraction (SPME) followed by fast gas chromatography (Fast GC) has been developed for the analysis of volatile compounds in Asturian apple juices employed in the cider production. Three different fiber coatings have been checked (PDMS, PDMS-DVB and CAR-PDMS) and PDMS-DVB has been presented to be the most suitable one. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The use of Fast GC allowed the separation of 14 compounds (esters, aldehydes and alcohols) in approximately 4 min, clearly reducing the analysis time when compared to conventional GC. Good linearity, recoveries and repeatability of the solid-phase microextraction were obtained with r(2) values, recoveries and relative standard deviations ranging from 0.9822 to 0.9998, 83.2 to 109.8% and 0.5 to 11.7%, respectively, using standard solution.     

Characterization of hexacationic imidazolium ionic liquids as effective and highly stable gas chromatography stationary phases

Polycationic ionic liquids (ILs) are an attractive class of ILs with great potential applicability as gas chromatography stationary phases. A family of hexacationic imidazolium ILs derived from the cycloalkanol family was chemically first prepared in a straightforward manner and then applied for analytical separation purposes. Four tuneable engineering vectors, namely cation ring size structure, anion nature, spatial disposition of cycloalkanol substituents and O‐substitution, were considered as experimental parameters for the design of the desired ionic liquids. A total number of five new phases based on a common benzene core respectively exhibited column efficiencies around to 2500 plates/m, broad operating temperature ranges and also, even more importantly, good thermal stabilities (bleeding temperature between 260 and 365°C), finding variations in the selectivity and analytes elution orders depending on the IL structures. Their solvation characteristics were evaluated using the Abraham solvation parameter model, establishing clear correlations between their cation structure and retention capability with respect to certain analytes. The study of relationships between the ILs structure and solvation parameters gives us an idea of the IL stationary phase to be used for specific separations.     

Fluorimetric determination of ultratraces of lead by ion-pair extraction with cryptand 2.2.1 and eosin

A spectrofluorimetric study of the extraction of lead into 1,2-dichloroethane, as an ion-pair formed between the cryptand 2.2.1-lead complex and the eosinate counter-ion is described. Optimum conditions for the extraction have been established and a new spectrofluorimetric determination of ultratraces of lead is proposed (detection limit 0.8 ng/ml; relative standard deviation 2.4% at the 60 ng/ml level). The metal:ligand:counter-ion molecular ratio in the extracted mononuclear ion-pair is 1:1:1. The equilibrium constants involved in the extraction have been estimated and refined by the Letagrop-DISTR program.     

Fluorimetric determination of calcium by ion-pair extraction with cryptand 2.2.1 and eosin

A fluorimetric study on the extraction of calcium into 1,2-dichloroethane as an ion-pair, formed between the cryptand 2.2.1-calcium complex and the eosinate anion, is described. Optimum conditions for extraction are established and a new fluorimetric determination of ultratraces of calcium is proposed. A linear working range from 1.5 ng ml^–1 (detection limit) to 100 ng ml^–1 of calcium and a relative standard deviation of ± 2.9% at the 70 ng ml^–1 level are obtained. The equilibrium constants involved in the extraction process have been calculated and refined by the Letagrop-DISTR program. The proposed method has been tested for the direct determination of calcium in sugars.     

非平衡态/不可逆过程的热力学理论(Ⅱ)

<正> 7 解的唯一性 如果不考虑非平衡态和不可逆性,则等能密度理论中的基本命题与经典弹性理论中的在形式上完全相同。无论整个系统的动能是大还是小,图6中(sumform)_o上的面力T_i和在(sumform)_c和在的位移u_i将始终在空间坐标系x_i和时刻i下给出。与一般力学中相同,必须知道有关位移u_i及其时间导数的初始条件。它们的影响则可通过(38)和(39)向等能面转化,从而得到     

Dithienylethene-Based Single Molecular Photothermal Linear Actuator

By employing a mechanically controllable break junction technique, we have realized an ideal single molecular linear actuator based on dithienylethene (DTE) based molecular architecture, which undergoes reversible photothermal isomerization when subjected to UV irradiation under ambient conditions. As a result, open form (compressed, UV OFF) and closed form (elongated, UV ON) of dithienylethene-based molecular junctions are achieved. Interestingly, the mechanical actuation is achieved without changing the conductance of the molecular junction around the Fermi level over several cycles, which is an essential property required for an ideal single molecular actuator. Our study demonstrates a unique example of achieving a perfect balance between tunneling width and barrier height change upon photothermal isomerization, resulting in no change in conductance but a change in the molecular length, which results in mechanical actuation at the single molecular level.