4,808 research outputs found

    Correlation amplitude and entanglement entropy in random spin chains

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    Using strong-disorder renormalization group, numerical exact diagonalization, and quantum Monte Carlo methods, we revisit the random antiferromagnetic XXZ spin-1/2 chain focusing on the long-length and ground-state behavior of the average time-independent spin-spin correlation function C(l)=\upsilon l^{-\eta}. In addition to the well-known universal (disorder-independent) power-law exponent \eta=2, we find interesting universal features displayed by the prefactor \upsilon=\upsilon_o/3, if l is odd, and \upsilon=\upsilon_e/3, otherwise. Although \upsilon_o and \upsilon_e are nonuniversal (disorder dependent) and distinct in magnitude, the combination \upsilon_o + \upsilon_e = -1/4 is universal if C is computed along the symmetric (longitudinal) axis. The origin of the nonuniversalities of the prefactors is discussed in the renormalization-group framework where a solvable toy model is considered. Moreover, we relate the average correlation function with the average entanglement entropy, whose amplitude has been recently shown to be universal. The nonuniversalities of the prefactors are shown to contribute only to surface terms of the entropy. Finally, we discuss the experimental relevance of our results by computing the structure factor whose scaling properties, interestingly, depend on the correlation prefactors.Comment: v1: 16 pages, 15 figures; v2: 17 pages, improved discussions and statistics, references added, published versio

    Electrochemistry combined-surface plasmon resonance biosensors: A review

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    Over the years, most of the literature reported applications of electrochemical and surface plasmon resonance (SPR) immunoassays for biosensing but, so far, the combination of the two methods in the same sensing spot for analytical purposes is much less explored and discussed. The aim of this Review is to highlight the great potential of electrochemistry combined-SPR (eSPR) as analytical tool for screening chemically and biologically relevant (bio)molecules by combining the unique features of SPR integrated with electrochemical readout. In the first part of the Review, we describe the urgent need of innovative methods for screening clinical biological markers (General Introduction), briefly discuss general concepts of SPR and electrochemical sensing (Concepts behind eSPR biosensors) and highlight the hyphenation of two methods to developed combined biosensing systems (Set-up configuration and eSPR principles). Firstly, we briefly give an overview of the setup for implementation of eSPR technique and discuss some relevant experimental conditions to perform the combined optical and electrochemical measurements. Then, the principles and fundamentals of eSPR biosensors are presented and described. We also present representative examples of eSPR biosensors in the literature (Applications of eSPR biosensors). In the second part, we review studies on how combined electrical and plasmonic detection contributed to the biosensing field, in particular, for the successful screening of clinically relevant biomolecules, namely proteins (Detection of proteins), nucleic acids (Detection of nucleic acids), small size chemical species (Detection of small molecules) and cells (Living-cell Analysis). Finally, we discuss the current limitations of eSPR biosensors performance and suggest possible ways to overcome these limitations (Limitations and optimization) and then we explore aspects about the development of the method and its applications and discuss areas of likely future growth (Conclusions and perspectives).This research had the financial support of FCT (Fundação para a Ciência e Tecnologia) and co-financed by the European Union (FEDER funds) under the Partnership Agreement PT2020, Research Grant Pest-C/QUI/UIDB/00081/2020 (CIQUP). J.A. Ribeiro (ref. SFRH/BPD/105395/2014) and C.M. Pereira (ref. SFRH/BSAB/150320/2019) acknowledge FCT under the QREN – POPH – Advanced Training, subsidized by European Union and national MEC funds. The authors acknowledge the research project MyTag (ref. PTDC/EEI-EEE/4832/2021), funded by FCT, for financial support.info:eu-repo/semantics/publishedVersio

    Computational Fluid Dynamics Modeling of Ammonia Concentration in a Commercial Broiler Building

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    In the present study, a numerical model was developed to predict the flow pattern inside a broiler building. The model intends to predict the velocities fields inside the domain and am-monia (NH3) emitted or released by litter from poultry housing. The numerical model developed in Computational Fluid Dynamics (CFD) commercial code, intends to represent a commercial broiler building, and intends to simulate the 3D and heat transfer, in steady state flow. The evaporative cooling pads were also included in the model. The validation of the model was based in experimental measurements obtained in previous studies. The simulations were fo-cused on Summer, Winter and also Mid-Season situation. The numerical results of NH3 concen-tration were compared with the experimental measurements, and a quite good agreement was verified. The numerical results allowed the characterization of: the inside flow pattern devel-oped for the summer and winter situation; the inside NH3 distribution, and the velocity field distribution inside the broiler building. It was found that NH3 concentration increases along the tunnel, especially in low flow rate imposed from the exhaust fan. Also, it was verified that the low velocities inside domain are no sufficient to remove the gaseous pollutants.info:eu-repo/semantics/publishedVersio
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