A
bstract
We show that the spectrum of the SYK model can be interpreted as that of a 3D scalar coupled to gravity. The scalar has a mass which is at the Breitenholer-Freedman bound of AdS
2
, and ...subject to a delta function potential at the center of the interval along the third direction. This, through Kaluza-Klein procedure on AdS
2
× (
S
1
)
/Z
2
, generates the spectrum reproducing the bi-local propagator at strong coupling. Furthermore, the leading 1
/J
correction calculated in this picture reproduces the known correction to the poles of the SYK propagator, providing credence to a conjecture that the bulk dual of this model can be interpreted as a three dimensional theory.
In this study, graphene oxide (GO) nanosheets have been used for the adsorption of methyl green, a cationic dye from aqueous solution. GO nanosheets consist of single layered graphite structure ...decorated with a number of oxygen containing functionalities such as carboxyl, epoxy, ketone, and hydroxyl groups which impart a negative charge density to it in aqueous solution at a wide range of pH. Thus, GO nanosheets can be predicted as a good adsorbent material for the adsorption of cationic species. The adsorption of the methyl green onto the GO nanosheets has been carried out at different experimental conditions such as adsorption kinetics, concentration of adsorbate, pH, and temperature. The kinetics of the adsorption data were analyzed using four kinetic models such as the pseudofirst-order model, pseudosecond-order model, intraparticle diffusion, and the Boyd model to understand the adsorption behavior of methyl green onto the GO nanosheets and the mechanism of adsorption. The kinetics of adsorption result shows that the adsorption maximum was reached at 60 min and follows the linear form of pseudosecond-order kinetics. The adsorption isotherm of adsorption of the methyl green onto the GO nanosheets has been investigated in the pH range of 4 to 9 at 25 °C. The equilibrium data were fitted well to the Langmuir model. Various thermodynamic parameters such as the Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) change were also evaluated. The negative value of ΔG indicates spontaneity of the adsorption process of the methyl green–GO system. The interaction of methyl green onto the GO nanosheets has been investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy.
Giant Piezoelectricity on Si for Hyperactive MEMS Baek, S. H.; Park, J.; Kim, D. M. ...
Science (American Association for the Advancement of Science),
11/2011, Letnik:
334, Številka:
6058
Journal Article
Recenzirano
Microelectromechanical systems (MEMS) incorporating active piezoelectric layers offer integrated actuation, sensing, and transduction. The broad implementation of such active MEMS has long been ...constrained by the inability to integrate materials with giant piezoelectric response, such as Pb(MG 1/3 Nb 2/3 )O₃-PbTiO₃ (PMN-PT). We synthesized high-quality PMN-PT epitaxial thin films on vicinal (001) Si wafers with the use of an epitaxial (001) SrTiO₃ template layer with superior piezoelectric coefficients (e 31,f = -27 ± 3 coulombs per square meter) and figures of merit for piezoelectric energy-harvesting systems. We have incorporated these heterostructures into microcantilevers that are actuated with extremely low drive voltage due to thin-film piezoelectric properties that rival bulk PMN-PT single crystals. These epitaxial heterostructures exhibit very large electromechanical coupling for ultrasound medical imaging, microfluidic control, mechanical sensing, and energy harvesting.
Path-integral complexity for perturbed CFTs Bhattacharyya, Arpan; Caputa, Pawel; Das, Sumit R. ...
The journal of high energy physics,
07/2018, Letnik:
2018, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
In this work, we formulate a path-integral optimization for two dimensional conformal field theories perturbed by relevant operators. We present several evidences how this optimization ...mechanism works, based on calculations in free field theories as well as general arguments of RG flows in field theories. Our optimization is performed by minimizing the path-integral complexity functional that depends on the metric and also on the relevant couplings. Then, we compute the optimal metric perturbatively and find that it agrees with the time slice of the hyperbolic metric perturbed by a scalar field in the AdS/CFT correspondence. Last but not the least, we estimate contributions to complexity from relevant perturbations.
Spillage of effluents containing high concentration levels of pesticides into water has been considered as one of the serious environmental problems. In this study Fe3O4/reduced graphene oxide (rGO) ...nanocomposite has been efficiently utilized for the adsorption of five harmful pesticides namely ametryn, prometryn, simazine, simeton and atrazine in an aqueous medium. Electrostatic interaction between the pesticides and Fe3O4/rGO nanocomposite was analyzed by the zeta potential analysis, which is strongly related to the adsorption capacity of the adsorbent. The kinetics parameters of adsorption followed the pseudo second-order linear model. The adsorption isotherm studies show that, the maximum adsorption capacity of 54.8 mg g−1 is achieved at pH 5 and it was enhanced in the presence of different ions (Mg2+, Ca2+, Na+ and SO42) and maximum (63.7 mg g−1) for ametryn adsorption was found in seawater medium. Thermodynamic parameter shows that, the adsorption process is physisorption and spontaneity in nature. The mechanism of the adsorption process was established by the DRIFT spectroscopy analysis. Efficient adsorption (93.61%) of pesticides was observed due to electrostatic, hydrophobic and π–π interactions of composite towards the heterocyclic conjugation of pesticide molecules. Further, Fe3O4/rGO nanocomposite was easily and rapidly separated from an aqueous medium using the external magnet for reuse and 88.66% adsorption efficiency was observed up to seven cycles.
Display omitted
•A feasible and eco-friendly route for the removal of five triazine pesticides.•Magnetic Fe3O4/rGO shows efficient triazine pesticides removal property.•Specific ion effect plays an important role in pesticide adsorption onto Fe3O4/rGO.•The reusability and magnetic reparability of Fe3O4/rGO is added advantage.
A
bstract
We explore properties of path integral complexity in field theories on time dependent backgrounds using its dual description in terms of Hartle-Hawking wavefunctions. In particular, we ...consider boundary theories with time dependent couplings which are dual to Kasner-AdS metrics in the bulk with a time dependent dilaton. We show that holographic path integral complexity decreases as we approach the singularity, consistent with earlier results from holographic complexity conjectures. Furthermore, we find examples where the complexity becomes universal i.e., independent of the Kasner exponents, but the properties of the path integral tensor networks depend sensitively on this data.
Space-time in the SYK model Das, Sumit R.; Ghosh, Animik; Jevicki, Antal ...
The journal of high energy physics,
07/2018, Letnik:
2018, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
We consider the question of identifying the bulk space-time of the SYK model. Focusing on the signature of emergent space-time of the (Euclidean) model, we explain the need for non-local ...(Radon-type) transformations on external legs of
n
-point Green’s functions. This results in a dual theory with Euclidean AdS signature with additional legfactors. We speculate that these factors incorporate the coupling of additional bulk states similar to the discrete states of 2d string theory.
Extracting sentiment from text is a hard semantic problem. We develop a methodology for extracting small investor sentiment from stock message boards. The algorithm comprises different classifier ...algorithms coupled together by a voting scheme. Accuracy levels are similar to widely used Bayes classifiers, but false positives are lower and sentiment accuracy higher. Time series and cross-sectional aggregation of message information improves the quality of the resultant sentiment index, particularly in the presence of slang and ambiguity. Empirical applications evidence a relationship with stock values—tech-sector postings are related to stock index levels, and to volumes and volatility. The algorithms may be used to assess the impact on investor opinion of management announcements, press releases, third-party news, and regulatory changes.
Efficacious protocols have been established to synthesize a structurally privileged Π-extended coumarin-fused pyridone nucleus by activating the vinylic C(sp
2
)-H bond of coumarin-3-carboxamide ...under the influence of inexpensive Ru(
ii
)-metal. Here an
N
-methoxy carboxamide entity has been exploited as the chelating fragment to manifest C(sp
2
)-H bond functionalization with a concomitant (4 + 2) annulation reaction, resulting in heterocyclic ring-forming protocols along with sulfoxonium ylide and iodonium ylide as representative bench-stable carbene surrogates. This diverse heterocycle formation
via
carbene insertion strategies, is further expanded to activate the
ortho
-C(sp
2
)-H bonds of different heterocycles by employing the sp
2
-N moiety as the directing group to develop acyl-alkylated/alkenylated quinazolines, isoxazoles and highly fluorescent pyridone-
N
-oxides. Intriguingly, during an evaluation of the versatility of the current protocols, a one-pot double C-H activation has been rationalized in the presence of iodonium ylide, which results in biologically potent benzimidazole-fused coumarin-centered bridge-headed polycyclic heteroarenes. Furthermore, a chemo-selective late-stage synthetic transformation is being designed to develop differently substituted pyridone analogues by switching the nature of the reducing agent. In addition, a photophysical experiment was done on one pyridine-
N
-oxide compound (
7e
) and delightfully it exhibited fluorescence quenching activity selectively in the presence of Al
3+
ions, which appears to be a unique feature of our methodology. Finally, upon correlation of the merit of the developed pathways, the iodonium ylide mediated strategy appears to be superior.
Ru(
ii
)-assisted C(sp
2
)-H functionalization along with (4 + 2) annulation leads to coumarin-fused pyridone, highly decorated N-heteroarenes and pyridine-
N
-oxides; the protocol also induces double C-H activation to the benzimidazole-coumarin conjugates.
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