Combination of a modified quick,easy, cheap,efficient, rugged,and safe extraction method with a deep eutectic solvent based microwave‐assisted dispersive liquid–liquid microextraction: Application in extraction and preconcentration of multiclass pesticide residues in tomato samples

In this study, a new two–step extraction procedure based on the combination of a modified quick, easy, cheap, effective, rugged, and safe extraction method with a deep eutectic solvent based microwave‐assisted dispersive liquid–liquid microextraction has been developed for the extraction of multiclass pesticides in tomato samples before their analysis by gas chromatography with flame ionization detection. In this method, initially, an aliquot of tomato is crushed and diluted with deionized water. The mixture is then passed through a filter paper and its residue and aqueous phase are separated. Afterwards, acetonitrile as an extraction/disperser solvent is passed through the filter paper containing the refuse. The analytes remained in the refuse are extracted into the acetonitrile and then the obtained extract is mixed with a deep eutectic solvent. The obtained mixture is injected into the tomato juice and placed in a microwave oven for 15 s. Consequently, a cloudy state is formed and the extractant containing the analytes are sedimented at the bottom of the tube after centrifugation. Finally, 1 μL of the sedimented phase is removed and injected into the separation system. Under the optimum conditions, limits of detection and quantification were in the ranges of 0.42–0.74 and 1.4–2.5 ng/g, respectively.     

Theory of closed interacting strings

Using the equations of motion obtained from the Nambu Lagrangian, we study closed strings. Interactions are introduced in the system via certain topological transformations. using the method of functional integration. The Born term turns out to be equal to the Virasoro-Shapiro amplitude. Not all the variables used in the calculation are independent and the physical states therefore satisfy certain conditions. However the interactions are such that those states not satisfying the extra conditions decouple from the rest. The amplitude for the scattering of excited states, the vertex functions and the volume elements for tree aand one-loop amplitudes are calculated. The amplitude for tree or one-loop graphs can be simply obtained from the corresponding amplitude in open string theory.     

Quotient space solutions of 11-dimensional supergravity

All the Freund-Rubin type solutions of the 11-dimensional supergravity with a simply connected quotient spaceG/H as the compact 7-dimensional manifold are found. Their geometries depend only on the imbedding ofHG and the Riemannian structure ofG/H. In particular, SU₃×SU₂×U₁/SU₂×U₁×U₁, Einstein solutions are discussed in detail.     

Insight into diacetylene photopolymerization in Langmuir‐Blodgett films using simultaneous AFM and fluorescence microscopy imaging

A phase‐separated monolayer film comprised of a mixture of 10, 12‐pentacosadiynoic acid (PCDA) with perfluorotetradecanoic acid (PF; CF₃(CF₂)₁₂COOH) has been characterized using a microscope that is capable of simultaneous atomic force microscope (AFM) imaging and fluorescence imaging. Design criteria for this instrument are described, as well as its application to investigating the mixed film systems. The product of PCDA photopolymerization has two phases, a red phase with strong fluorescence and a blue phase with no fluorescence. With the help of the dual AFM‐fluorescence microscope, it was found that both the red and the blue phase polymers were produced in the same sample from photoillumination, and the relative quantities of the different phases were quantified. Further, the importance of intrinsic mechanical stress in the films is discussed in terms of its influence on selectivity towards the red polymer phase.     

Deposition and photopolymerization of phase-separated perfluorotetradecanoic acid-10,12-pentacosadiynoic acid Langmuir-Blodgett monolayer films

Mixed monolayer surfactant films of perfluorotetradecanoic acid and the photopolymerizable diacetylene molecule 10,12-pentacosadiynoic acid were prepared at the air-water interface and transferred onto solid supports via Langmuir-Blodgett (LB) deposition. The addition of the perfluoroacid to the diacetylene surfactant results in enhanced stabilization of the monolayer in comparison with the pure diacetylene alone, allowing film transfer onto a solid substrate without resorting to addition of cations in the subphase or photopolymerization prior to deposition. The resulting LB films consisted of well-defined phase-separated domains of the two film components, and the films were characterized by a combination of atomic force microscope (AFM) imaging and fluorescence emission microscopy both before and after photopolymerization into the highly emissive "red form" of the polydiacetylene. Photopolymerization of the monolayer films resulted in the formation of diacetylene bilayers, which were highly fluorescent, with the apparent rate of photopolymerization and the fluorescence emission of the films being largely unaffected by the presence of the perfluoroacid.     

Volume element for loop diagram in the string picture of dual models

Using perturbation theory and the vertex function for the joining and separation of strings, we calculate the momentum-independent part of the orientable loop diagram in the string picture of the orbital dual model. The calculation is done for the case where spacetime has the critical dimensionality.     

Double-horizon limit, AdS geometry and entropy function

We start from a generic metric which describes four-dimensional stationary black holes in an arbitrary theory of gravity and show that the AdS₂ part of the near-horizon geometry is a consequence of the double-horizon limit and finiteness. We also show that the field configurations of the near horizon are determined if the same conditions are applied to the equations of motion. This is done by showing that in the double-horizon limit field equations at the horizon decouple from the bulk of the space. Solving these equations gives the near-horizon field configurations. It is shown that these decoupled equations can be obtained from an action derived from the original action by applying the double-horizon condition. Our results agree with the entropy function method.