Defective Interfering Viral Particles in Acute Dengue Infections

While much of the genetic variation in RNA viruses arises because of the error-prone nature of their RNA-dependent RNA polymerases, much larger changes may occur as a result of recombination. An extreme example of genetic change is found in defective interfering (DI) viral particles, where large sections of the genome of a parental virus have been deleted and the residual sub-genome fragment is replicated by complementation by co-infecting functional viruses. While most reports of DI particles have referred to studies in vitro, there is some evidence for the presence of DI particles in chronic viral infections in vivo. In this study, short fragments of dengue virus (DENV) RNA containing only key regulatory elements at the 3′ and 5′ ends of the genome were recovered from the sera of patients infected with any of the four DENV serotypes. Identical RNA fragments were detected in the supernatant from cultures of Aedes mosquito cells that were infected by the addition of sera from dengue patients, suggesting that the sub-genomic RNA might be transmitted between human and mosquito hosts in defective interfering (DI) viral particles. In vitro transcribed sub-genomic RNA corresponding to that detected in vivo could be packaged in virus like particles in the presence of wild type virus and transmitted for at least three passages in cell culture. DENV preparations enriched for these putative DI particles reduced the yield of wild type dengue virus following co-infections of C6–36 cells. This is the first report of DI particles in an acute arboviral infection in nature. The internal genomic deletions described here are the most extensive defects observed in DENV and may be part of a much broader disease attenuating process that is mediated by defective viruses

Characterization of Portland cements by X-ray spectrometry allied to chemometrics

This work reports the use of X-ray spectrometry (XRS) allied to chemometric techniques to easily distinguish types of Portland cements, as well as to quantify some of their constituent elements. The samples were irradiated as powders for 200 s using two distinct irradiation conditions, one more adequate for heavier elements (condition 1) and the other (condition 2) for lighter elements, using a conventional bench top energy dispersive X-ray fluorescence (EDXRF) equipment. The spectra were processed via the software The Unscrambler, version 9.2. The PLS 1 LV1 X LV2 scores graph shows a classification into five groups, in accordance with the calcium concentration, using condition 2. The classification of the cements by producer was feasible using the PLS1 LV1 X LV3 scores graph, with condition 1. The elements Ca, Si, Al and Mg were successfully quantified using multivariate calibration of the whole spectra. However, for Fe, S and K, better results were obtained by correlating their corresponding K alpha peaks with concentrations in a univariate procedure, using irradiation condition 2. Chemometric tools allied to XRS are powerful techniques to classify Portland cements, regarding to their origins and their calcium concentration, which is related to the cement type. The PLS chemometric tool was very useful to easily quantify light elements, such as Al, Si and Mg, a challenge in most X-ray analytical methods, since their Ka emission peaks are very close to each other. Copyright (C) 2007 John Wiley & Sons, Ltd.204198445546

What's in a Name? Patterns, Trends, and Suggestions for Defining Non-Perennial Rivers and Streams

Rivers that cease to flow are globally prevalent. Although many epithets have been used for these rivers, a consensus on terminology has not yet been reached. Doing so would facilitate a marked increase in interdisciplinary interest as well as critical need for clear regulations. Here we reviewed literature from Web of Science database searches of 12 epithets to learn (Objective 1-O1) if epithet topics are consistent across Web of Science categories using latent Dirichlet allocation topic modeling. We also analyzed publication rates and topics over time to (O2) assess changes in epithet use. We compiled literature definitions to (O3) identify how epithets have been delineated and, lastly, suggest universal terms and definitions. We found a lack of consensus in epithet use between and among various fields. We also found that epithet usage has changed over time, as research focus has shifted from description to modeling. We conclude that multiple epithets are redundant. We offer specific definitions for three epithets (non-perennial, intermittent, and ephemeral) to guide consensus on epithet use. Limiting the number of epithets used in non-perennial river research can facilitate more effective communication among research fields and provide clear guidelines for writing regulatory documents