Higher-Derivative Two-Dimensional Massive Fermion Theories

We consider the canonical quantization of a generalized two-dimensional massive fermion theory containing higher odd-order derivatives. The requirements of Lorentz invariance, hermiticity of the Hamiltonian and absence of tachyon excitations suffice to fix the mass term, which contains a derivative coupling. We show that the basic quantum excitations of a higher-derivative theory of order 2N+1 consist of a physical usual massive fermion, quantized with positive metric, plus 2N unphysical massless fermions, quantized with opposite metrics. The positive metric Hilbert subspace, which is isomorphic to the space of states of a massive free fermion theory, is selected by a subsidiary-like condition. Employing the standard bosonization scheme, the equivalent boson theory is derived. The results obtained are used as a guideline to discuss the solution of a theory including a current-current interaction.Comment: 23 pages, Late

Ab-initio study of the relation between electric polarization and electric field gradients in ferroelectrics

The hyperfine interaction between the quadrupole moment of atomic nuclei and the electric field gradient (EFG) provides information on the electronic charge distribution close to a given atomic site. In ferroelectric materials, the loss of inversion symmetry of the electronic charge distribution is necessary for the appearance of the electric polarization. We present first-principles density functional theory calculations of ferroelectrics such as BaTiO3, KNbO3, PbTiO3 and other oxides with perovskite structures, by focusing on both EFG tensors and polarization. We analyze the EFG tensor properties such as orientation and correlation between components and their link with electric polarization. This work supports previous studies of ferroelectric materials where a relation between EFG tensors and polarization was observed, which may be exploited to study ferroelectric order when standard techniques to measure polarization are not easily applied.Comment: 9 pages, 6 figures, 5 tables, corrected typos, as published in Phys. Rev.

Self-sustainable bio-methanol & bio-char coproduction from 2nd generation biomass gasification

Methanol is an important intermediate in the synthesis of different chemicals. It is mainly produced by reforming of natural gas in centralized facilities with productive capacities on the order of 109 tons per day. Production of methanol from biomass suffers from the cost and logistics of the transportation of biomass and it has not yet maturated into commercial scale. The techno-economic feasibility of the co-production of bio-methanol and bio-char is assessed through detailed computer simulations using process simulator Aspen HYSYS® together with the gasification simulator GASDS. This work further elaborates the previous results on the bio-methanol production process, presenting particularities and updates on previously reported values. The production model is seen to be valid, with payback times that go from 3 to 6 years according to the capacity of the plant (100 to 1000 kt of biomass per year). Self-sustainability is possible but a 50/50 mix of producing and buying electricity yields the most economic choice. © Copyright 2017, AIDIC Servizi S.r.l

Avaliação da produtividade de girassol semeado em janeiro em Pelotas - RS.

Com o objetivo de avaliar a produtividade de girassol foram realizados dois experimentos na safrinha, experimento 1 (2008) e experimento 2 (2009). Os experimentos foram conduzidos na área experimental da Embrapa Clima Temperado, com delineamento experimental em blocos casualizados com quatro repetições. A produtividade média do experimento 1 foi de 1190 kg.ha-1, onde foram avaliados os genótipos: Agrobel 960, Aguará 3, Embrapa 122, BRHS 01, Hélio 358 e M 733.No experimento 2, onde foram avaliados os genótipos Agrobel 962, Aguará 4, BRHS 01, Hélio 251, MG 2, Olisum 3 e Zenit, obteve-se produtividade média de 379 kg.ha-1. A diferença na produtividade média entre os experimentos, foi devida as diferentes condições climáticas ocorridas durante a execução dos dois experimentos, principalmente após a floração na fase de enchimento de aquênio, onde as precipitações ocorridas nessa fase foram diferentes, com 4,8 mm no experimento 2 ( 2009) e 135,9 mm no experimento 1 (2008)

Compact QED3_3 - a simple example of a variational calculation in a gauge theory

We apply a simple mean field like variational calculation to compact QED in 2+1 dimensions. Our variational ansatz explicitly preserves compact gauge invariance of the theory. We reproduce in this framework all the known results, including dynamical mass generation, Polyakov scaling and the nonzero string tension. It is hoped that this simple example can be a useful reference point for applying similar approximation techniques to nonabelian gauge theories.Comment: 18 pages, OUTP- 94-23 P, TPI-MINN-94/37-

Pathogens inactivation kinetics in co-digestion of swine manure and swine carcass.

ABSTRACT: Swine intensive production increases the necessity of efficient manure management and treatment. Additionally, animal carcasses disposal inside or outside animal rearing farms is under concern and object of discussion because biosecurity protocols. Anaerobic digestion has a potential to convert biodegradable organic carbon into biogas. Swine manure and swine carcass co-digestion could be a feasible alternative to treat these residues and generate a renovable energy source. However, biodigestion has limited capacity to remove pathogenic micro-organisms and this must be studied to minimize the biologic risks and assure safe disposal and use of digestate. Considering this, the objective of this study was to evaluate the Escherichia coli (E. coli) and Salmonella enterica ? serovar Senftenberg (S. Senftenberg) inactivation kinetics during swine manure and swine carcass co-digestion. The inactivation experiments were conducted in triplicates, where different inactivation strategies were performed at two temperatures (24ºC and 37ºC).Two swine carcass/swine manure ratios were studied(3kgcarcass.m-3 manureand 15 kgcarcass.m-3 manure). S. Senftenberg was total inactivated after 10 days for both temperature and both ratios of swine carcass/swine manure. At 37ºC and ratio of 3kgcarcass.m-3 manureE.coli was total inactivated after 10 days and at ratio 15 kgcarcass.m-3 manureafter 8 days. At 24ºC it were necessary 25 days and 31 days for relations 15kg.m-3 and 3kg.m-3 respectively. Digestion temperature influenced the inactivation process being more pronounced for E. coli. In batch reactors operating at 37ºC it is suggested hydraulic retention time (HRT) greater than 10 days for total elimination of E.coli and S. Senftenberg, while at 24ºC for at least 30 days