More on New Massive Gravity: Exact Solutions

We give a novel description of the recently proposed theory of new massive gravity (NMG) in three dimensions. We show that in terms of a Dirac type differential operator acting on the traceless Ricci tensor, the field equations of the theory reduce to the massive Klein-Gordon type equation with a curvature-squared source term and to a constraint equation. Under a certain relation between the source tensor and the traceless Ricci tensor, fulfilled for constant scalar curvature, the field equations of topologically massive gravity (TMG) can be thought of as the "square-root" of the massive Klein-Gordon type equation. Using this fact, we establish a simple framework for mapping all known algebraic types D and N solutions of TMG into NMG. We also present new exact solutions of algebraic types D and N which are only inherent in NMG.Comment: 4 pages, twocolumn REVTeX; Minor cosmetic changes made and new metric adde

Consideracoes gerais sobre as principais pragas dos produtos armazenados e seu controle.

Consideracoes das principais pragas dos produtos armazenados e seu controle.bitstream/item/140489/1/ID-7312.pd

Towards a historical ecology of intertidal foraging in the Mafia Archipelago: archaeomalacology and implications for marine resource management

Understanding the timing and nature of human influence on coastal and island ecosystems is becoming a central concern in archaeological research, particularly when investigated within a historical ecology framework. Unfortunately, the coast and islands of eastern Africa have not figured significantly within this growing body of literature, but are important given their historically contingent environmental, social, and political contexts, as well as the considerable threats now posed to marine ecosystems. Here, we begin developing a longer-term understanding of past marine resource use in the Mafia Archipelago (eastern Africa), an area of high ecological importance containing the Mafia Island Marine Park. Focusing on the comparatively less researched marine invertebrates provides a means for initiating discussion on potential past marine ecosystem structure, human foraging and environmental shifts, and the implications for contemporary marine resource management. The available evidence suggests that human-environment interactions over the last 2000 years were complex and dynamic; however, these data raise more questions than answers regarding the specific drivers of changes observed in the archaeomalacological record. This is encouraging as a baseline investigation and emphasizes the need for further engagement with historical ecology by a range of cognate disciplines to enhance our understanding of these complex issues

Quantitative determination of aflatoxin by high performance liquid chromatography in wheat silos in Golestan province, north of Iran

Background: Aflatoxins are the most common mycotoxins that contaminate crops. They are produced by fungi such as Aspergillus flavus and Aspergillus parasiticus. Wheat (Tricitumaestivum) is one of the most important staple foods used in Iran, and the environmental conditions in the north of Iran are favorable to fungal growth. This study was designed in order to determine the aflatoxin concentration in wheat samples from silos in Golestan Province north of Iran. Methods: Samples were collected from three silos of Golestan province. First, aflatoxins were isolated using immu-noaffinity chromatography. Then the aflatoxin concentrations were determined by High performance liquid chroma-tography (HPLC) method and fluorescence detector. Results: Ten out of 34 samples (29.4 of samples) were contaminated by aflatoxins.No concentration was found above permitted aflatoxin levels in Iran (15 ng/g). In one sample (2.9), aflatoxin B1 was seen over the permissible limits in Iran. The highest level found in samples for total aflatoxin, aflatoxin B1, aflatoxin B2, aflatoxin G1 and aflatox-in G2 were 7.08 ng/g, 6.91 ng/g, 0.29 ng/g, 1.37 ng/g and 0.23 ng/g, respectively. No correlation was found between humidity levels in wheat samples contained aflatoxin and wheat samples without aflatoxin. Conclusion: Despite the total aflatoxins determined in samples were below the permissible limits in Iran, the 29 aflatoxin contamination rate can negatively affect health factors and it should not be neglected. So, it is predictable that if the storage duration of samples increases, the aflatoxin contamination levels will increase. © 2015, Iranian Journal of Public Health. All rights reserved

A Dimension-Adaptive Multi-Index Monte Carlo Method Applied to a Model of a Heat Exchanger

We present an adaptive version of the Multi-Index Monte Carlo method, introduced by Haji-Ali, Nobile and Tempone (2016), for simulating PDEs with coefficients that are random fields. A classical technique for sampling from these random fields is the Karhunen-Lo\`eve expansion. Our adaptive algorithm is based on the adaptive algorithm used in sparse grid cubature as introduced by Gerstner and Griebel (2003), and automatically chooses the number of terms needed in this expansion, as well as the required spatial discretizations of the PDE model. We apply the method to a simplified model of a heat exchanger with random insulator material, where the stochastic characteristics are modeled as a lognormal random field, and we show consistent computational savings

An Improved Slant Path Attenuation Prediction Method in Tropical Climates

An improved method for predicting slant path attenuation in tropical climates is presented in this paper. The proposed approach is based on rain intensity data R_0.01 (mm/h) from 37 tropical and equatorial stations; and is validated by using the measurement data from a few localities in tropical climates. The new method seems to accurately predict the slant path attenuation in tropical localities, and the comparative tests seem to show significant improvement in terms of the RMS of the relative error variable compared to the RMS obtained with the SAM, Crane, and ITU-R prediction models

Scattering of the low-mode internal tide at the Line Islands Ridge

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2015The scattering of low-mode internal tides by ocean-floor topography is extensively studied through analytical models and field observations at the Line Islands Ridge (LIR). An existing Green function method is utilized to examine the generation of internal tides by idealized topographic shapes as well as realistic transects of the LIR. The method is also applied to examine the scattering of a mode-1 internal tide at these topographies to determine the relative high mode energy flux due to generated and scattered internal tides at the realistic transects. A method of determining the modal content of an internal wave field is advanced to account for arbitrary stratification and rotation. It is then adjusted to allow for image loss as is common to oceanographic studies. Its performance is compared to the existing regression method widely used by oceanographers to determine the modal content of internal tides. The results from this comparison are used to inform the analysis of the field observations. This thesis concludes by examining the modal content of the LIR as determined from measurements taken during the 150-day EXperiment on Internal Tide Scattering (EXITS) NSF field study. Motivated by satellite altimetry data and three-dimensional numerical model studies, the EXITS cruise sought to observe the internal tide scattering process in the ocean for the first time. The data from three moorings equipped with moored profilers, spanning total depths of 3000-5000 m is analyzed to determine the modal content of the southward propagating internal tide before and after it encounters the ridge for evidence of topographic scattering