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La Paz, Bolivia

Telmo C.,Royal University | Lousada J.,Center for the Research and Technology of Agro Environment
Biomass and Bioenergy | Year: 2011

The calorific values of wood pellets from different wood species were determined using a Parr 6300 bomb calorimeter, following the CEN/TS 14918:2005. The aim of this study was the thermo characterization of the wood pellets. Softwoods had a high calorific value between 19660.02 and 20360.45 kJ/kg, and the hardwoods had a ranging interval between 17631.66 and 20809.47 kJ/kg, in accordance to Phyllis distribution of HHV. The highest HHV (Higher Heating Value) and LHV (Low Heating Value) were obtained by Bowdichia nitida (20809.47-17907.85 kJ/kg). Cedrus atlantica was the softwood with the highest HHV (20360.45 kJ/kg). Pinus pinaster was the softwood with the highest LHV (16935.72 kJ/kg). Fagus sylvatica was the National hardwood with the highest HHV (19132.47 kJ/kg). Fraxinus angustifolia was the National hardwood with the highest LHV (16450.82 kJ/kg). Eucalyptus globulus obtained the lowest HHV and LHV (17631.66-14411.54 kJ/kg). © 2011 Elsevier Ltd.

A numerical technique is presented whereby aquifer hydraulic diffusivities (D) and macrodispersivities (α) are calculated by linear equations rewritten from flow and solute transport differential equations. The approach requires a GIS to calculate spatial and temporal hydraulic head (h) and solute concentration gradients. The model is tested in Portugal, in a semi-confined aquifer periodically monitored for h and chloride/sulphate concentrations. Average D (0.46 m2/s) and α (1975 m) compare favourably with literature results. The relationship between α and scale (L) is also investigated. In this context, two aquifer groups could be identified: the first group is heterogeneous at the "macroscopic" scale (solute travelled distances <1 km), but homogeneous at the "megascopic" scale. The overall scale dependency in this case is given by an equation of logarithmic type. The second group is heterogeneous at the macroscopic and megascopic scales, with a scale dependency of linear type. © 2013 Copyright 2013 IAHS Press.

Belan E.,Royal University
Biology Direct | Year: 2013

LINE-1 (L1) retrotransposons are repetitive elements in mammalian genomes. They are capable of synthesizing DNA on their own RNA templates by harnessing reverse transcriptase (RT) that they encode. Abundantly expressed full-length L1s and their RT are found to globally influence gene expression profiles, differentiation state, and proliferation capacity of early embryos and many types of cancer, albeit by yet unknown mechanisms. They are essential for the progression of early development and the establishment of a cancer-related undifferentiated state. This raises important questions regarding the functional significance of L1 RT in these cell systems. Massive nuclear L1-linked reverse transcription has been shown to occur in mouse zygotes and two-cell embryos, and this phenomenon is purported to be DNA replication independent. This review argues against this claim with the goal of understanding the nature of this phenomenon and the role of L1 RT in early embryos and cancers. Available L1 data are revisited and integrated with relevant findings accumulated in the fields of replication timing, chromatin organization, and epigenetics, bringing together evidence that strongly supports two new concepts. First, noncanonical replication of a portion of genomic full-length L1s by means of L1 RNP-driven reverse transcription is proposed to co-exist with DNA polymerase-dependent replication of the rest of the genome during the same round of DNA replication in embryonic and cancer cell systems. Second, the role of this mechanism is thought to be epigenetic; it might promote transcriptional competence of neighboring genes linked to undifferentiated states through the prevention of tethering of involved L1s to the nuclear periphery. From the standpoint of these concepts, several hitherto inexplicable phenomena can be explained. Testing methods for the model are proposed. © 2013 Belan; licensee BioMed Central Ltd.

Hussain A.,Royal University
Surgical Laparoscopy, Endoscopy and Percutaneous Techniques | Year: 2011

Laparoscopic cholecystectomy is the treatment of choice for gall bladder stone disease. Difficult cholecystectomy is associated with serious complications and a high conversion rate. The aim of this study was to review the current strategies to manage difficult cholecystectomy. Methods: A Medline search was conducted to review all published English literatures relevant to difficult cholecystectomy through 1993 to 2009. The search words were "laparoscopic cholecystectomy," "difficult cholecystectomy," "difficult laparoscopy," "subtotal laparoscopic cholecystectomy," "fundus first cholecystectomy," and "causes of conversion of laparoscopic cholecystectomy." Results: Ninety-one studies, which included 324,553 patients, were selected for this review. Five major categories of difficulty were identified. Conversion rate and iatrogenic injuries during laparoscopic cholecystectomy are still high despite significant improvement over the last 10 years. Depending on the technique of cholecystectomy, the degree of gall bladder inflammation, patient comorbidities, and surgical experience, the conversion rate was reported between 0.18% and 30%, whereas the incidence of iatrogenic injuries was from 0% to 0.6%. Subtotal cholecystectomy, antegrade and fundus first techniques, and peroperative cholangiogram were associated with lower complications and conversion rate. Risk factors for difficulty were male sex, increased age, acute and thick wall chronic cholecystitis, wide and short cystic duct, cholecystodigestive fistula, previous upper abdominal surgery, obesity, liver cirrhosis, anatomic variation, cholangiocarcinoma, and low surgeon's caseload. Conclusions: No consensus is found among surgeons on how to manage difficult laparoscopic cholecystectomy. Iatrogenic injuries and conversion rate can be reduced depending on the surgeon's experience, special techniques, and intraoperative investigations. Subtotal cholecystectomy, antegrade or fundus first techniques, and peroperative cholangiogram significantly reduced the complications and conversion rate. Copyright © 2011 by Lippincott Williams & Wilkins.

Perry E.,University of Alberta | Perry E.,Royal University
Rheumatology (Oxford, England) | Year: 2014

Recent findings have highlighted the potential initiation of ACPA in sites away from the joint. Periodontitis is an example of this concept. This process in the gums appears to be independent of smoking, the main environmental risk factor for ACPA-positive RA. There is extensive literature regarding the potential role of smoking in the pathogenesis of ACPA-positive RA. As a consequence of this strong association, the lung has become the focus of research to determine whether processes within the lung are linked to the generation of ACPA. Here we outline the current body of evidence and explore the hypothesis that the lung as an organ of immune defence has a role in the pathogenesis of the autoimmune disease ACPA-positive RA. © The Author 2014. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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