381 research outputs found
Electrodynamic formulation of special relativity from the first postulate
This work presents the form that the special theory of relativity takes when only the first postulate and the properties of homogeneity and isotropy of space and time are considered valid. The transformations of Lorentz coordinates are obtained in terms of a universal constant parameter k, developing from these the relativistic kinematics, dynamics and electrodynamics and their respective invariances before these transformations
A Framework to Evaluate Software Developerâs Productivity The VALORTIA Project
Currently, there is a lack in companies developing software in relation to assessing their staffâs productivity
before executing software projects, with the aim of improving effectiveness and efficiency. QuEF (Quality
Evaluation Framework) is a framework that allows defining quality management tasks based on a model.
The main purpose of this framework is twofold: improve an entityâs continuous quality, and given a context,
decide between a set of entityâs instances on the most appropriate one. Thus, the aim of this paper is to
make this framework available to evaluate productivity of professionals along software development and
select the most appropriate experts to implement the suggested project. For this goal, Valortia platform,
capable of carrying out this task by following the QuEF framework guidelines, is designed. Valortia is a
platform to certify users' knowledge on a specific area and centralize all certification management in its
model by means of providing protocols and methods for a suitable management, improving efficiency and
effectiveness, reducing cost and ensuring continuous quality.Ministerio de Ciencia e InnovaciĂłn TIN2013-46928-C3-3-
Characterization of Palladium Nanoparticles Produced by Healthy and Microwave-Injured Cells of Desulfovibrio desulfuricans and Escherichia coli
Numerous studies have focused on the bacterial synthesis of palladium nanoparticles
(bio-Pd NPs), via uptake of Pd (II) ions and their enzymatically-mediated reduction to Pd (0).
Cells of Desulfovibrio desulfuricans (obligate anaerobe) and Escherichia coli (facultative anaerobe,
grown anaerobically) were exposed to low-dose radiofrequency (RF) radiation(microwave (MW)
energy) and the biosynthesized Pd NPs were compared. Resting cells were exposed to microwave
energy before Pd (II)-challenge. MW-injured Pd (II)-treated cells (and non MW-treated controls)
were contacted with H2 to promote Pd(II) reduction. By using scanning transmission electron
microscopy (STEM) associated with a high-angle annular dark field (HAADF) detector and energy
dispersive X-ray (EDX) spectrometry, the respective Pd NPs were compared with respect to their mean
sizes, size distribution, location, composition, and structure. Differences were observed following
MWinjury prior to Pd(II) exposure versus uninjured controls. With D. desulfuricans the bio-Pd NPs
formed post-injury showed two NP populations with different sizes and morphologies. The first,
mainly periplasmically-located, showed polycrystalline Pd nano-branches with different crystal
orientations and sizes ranging between 20 and 30 nm. The second NPpopulation, mainly located
intracellularly, comprised single crystals with sizes between 1 and 5 nm. Bio-Pd NPs were produced
mainly intracellularly by injured cells of E. coli and comprised single crystals with a size distribution
between 1 and 3 nm. The polydispersity index was reduced in the bio-Pd made by injured cells of
E. coli and D. desulfuricans to 32% and 39%, respectively, of the values of uninjured controls, indicating
an increase in NP homogeneity of 30â40% as a result of the prior MWinjury. The observations are
discussed with respect to the different locations of Pd(II)-reducing hydrogenases in the two organisms
and with respect to potential implications for the catalytic activity of the produced NPs following
injury-associated altered NP patterning.The study was supported by NERC (grant NE/L014076/1) to LEM
Sobre las concepciones en DinĂĄmica elemental de los adolescentes formales y concretos y el cambio metodolĂłgico
Depositional fluxes and concentrations of \u3csup\u3e7\u3c/sup\u3eBe and \u3csup\u3e210\u3c/sup\u3ePb in bulk precipitation and aerosols at the interface of Atlantic and Mediterranean coasts in Spain
Bulk depositional fluxes of 7Be and 210Pb in precipitation measured over a period of 16 months (April 2009âJuly 2010) in Huelva, Spain varied between 5.6 and 186 Bq mâ2 monthâ1 (annual mean: 834 Bq mâ2 yearâ1) and 0.8 and 8.1 Bq mâ2 monthâ1 (annual mean: 59 Bq mâ2 yearâ1), respectively, with the lowest depositional fluxes occurring during dry summer months. Quantitative evaluation of the precipitation-normalized seasonal depositional fluxes of 7Be and 210Pb indicates that the enrichment factor in winter is \u3c 1.0 while in 2010 spring, it is significantly higher than 1, possibly indicating input of air from the stratosphere-troposphere exchange (for 7Be). The specific activities of 7Be and 210Pb varied from 0.03 to 7.42 Bq Lâ1 (mean = 2.5 Bq Lâ1) and 0.005 to 1.07 BqLâ1 (mean = 0.23 Bq Lâ1), respectively, with the highest values corresponding to the spring season. The spatial and temporal variations of 7Be and 210Pb in aerosols from three stations are evaluated and compared to their monthly depositional fluxes. The mean depositional velocity of aerosols using 7Be and 210Pb are similar, âŒ0.5 cm sâ1 and are compared to other published values. This is the first time the fractional amounts of 7Be and 210Pb in monthly bulk precipitation are compared to the fractional amount of precipitation and provides insight on how the amount of precipitation plays a key role on the scavenging of these nuclides. The importance of dry fallout is evaluated for the study site which has direct implications for other areas in the Mediterranean Climate Zone
Valorisation of ilmenite mud waste in the manufacture of commercial ceramic
This paper reports the results of a study focused on the production of ceramic tiles from ilmenite mud (MUD), a waste generated by the industry devoted to the TiO2 pigment production. Ceramic tiles were produced from mixtures of a commercial red stoneware mixture (RSM) with different concentrations of mud (3, 5, 7, 10, 30 and 50 wt.%). The samples were sintered to simulate a fast-firing process. The sintering behaviour of the fired samples was evaluated according to ISO methodologies by linear shrinkage, water absorption and porosity measurements. Both green powder and fired samples were characterised by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC/TG), field emission scanning electron microscopy (FESEM) and bending strength measurements. Moreover, since this activity is a NORM (Naturally Occurring Radioactive Material) industry, the radionuclides activity concentrations were measured by both gamma and alpha spectrometry techniques. Finally, the TCLP leaching test (Toxicity Characteristic Leaching Procedure, USEPA) was performed to assess the risks of the use of undissolved mud tiles from an environmental perspective. The results obtained demonstrated that ilmenite mud can be successfully valorisated in the manufacture of red stoneware ceramic bodies, with even better technological properties than commercial ones. The addition of mud as additive (from 3% to 10%) had a beneficial effect to the sintering processes, improving the bending strength (up to 15%) and reducing both apparent porosity and water absorption (up to 50%).This research has been partially supported by the Government of AndalusiĂĄs Project âCharacterization and modelling of the phosphogypsum stacks from Huelva for their environmental management and controlâ (Ref.: RNM-6300) and by National Institution of Higher Education, Science, Technology and Innovation of the Republic of Ecuador â (SENESCYT for its acronym in Spanish), Prometeo Project. Dr. M.I. MartĂn expresses her gratitude for the contract JAE-Doc_08-00032 to the Spanish National Research Council (CSIC), co-financed by the European Social Fund Operational Programme 2007â2013 Adaptability and Employment Multiregional.Peer reviewe
Amplified Nanoscale Detection of Labelled Molecules via Surface Electrons on Diamond
The detection of individual molecules and their dynamics has been a
long-standing challenge in the field of nanotechnology. In this work, we
present a method that utilizes a nitrogen vacancy (NV) center and a
dangling-bond on the diamond surface to measure the coupling between two
electronic targets tagged on a macromolecule. To achieve this, we design a
multi-tone dynamical decoupling sequence that leverages the strong interaction
between the nitrogen vacancy center and the dangling bond. In addition, this
sequence minimizes the impact of decoherence finally resulting in an increased
signal-to-noise ratio. This proposal has the potential to open up new avenues
for fundamental research and technological innovation in distinct areas such as
biophysics and biochemistry.Comment: 9 pages, 6 figure
Corrigendum to âPhylogeography of the Variable Antshrike (Thamnophilus caerulescens), a South American passerine distributed along multiple environmental gradientsâ [Mol. Phylogenet. Evol. 148 (2020) 106810](S1055790320300828)(10.1016/j.ympev.2020.106810)
© 2020 Elsevier Inc. The authors regret: (a) The information of Table 2 has incorrect values in column 6. The following table has the correct values. (b) Also, there is a minor typo in the section âData accessibilityâ, in the word: âalignmentsareâ. The correct words are: âalignments areâ. The authors would like to apologize for any inconvenience caused
Phylogeography of the Variable Antshrike (Thamnophilus caerulescens), a South American passerine distributed along multiple environmental gradients
© 2020 Elsevier Inc. The Neotropics show a wealth of distributional patterns shared by many co-distributed species. A distinctive pattern is the so-called âcircum-Amazonian distribution,â which is observed in species that do not occur in Amazonia but rather along a belt of forested habitats spanning south and east of Amazonia, the Andean foothills, and often into the Venezuelan Coastal Range and the Tepuis. Although this pattern is widespread across animals and plants, its underlying biogeographic mechanisms remain poorly understood. The Variable Antshrike (Thamnophilus caerulescens) is a sexually dimorphic suboscine passerine that exhibits extreme plumage variation and occurs along the southern portion of the circum-Amazonian belt. We describe broad-scale phylogeographic patterns of T. caerulescens and assess its demographic history using DNA sequences from the mitochondrion and ultraconserved elements (UCEs). We identified three genomic clusters: a) northern Atlantic Forest; b) southeastern Cerrado and central-southern Atlantic Forest, and c) Chaco and Andes. Our results were consistent with Pleistocene divergence followed by gene flow, mainly between the latter two clusters. There were no genetic signatures of rapid population expansions or bottlenecks. The population from the northern Atlantic Forest was the most genetically divergent group within the species. The demographic history of T. caerulescens was probably affected by series of humid and dry periods throughout the Quaternary that generated subtle population expansions and contractions allowing the intermittent connection of habitats along the circum-Amazonian belt. Recognizing the dynamic history of climate-mediated forest expansions, contractions, and connections during the South American Pleistocene is central toward a mechanistic understanding of circum-Amazonian distributions
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