15,863 research outputs found
Dominant negative phenotype of Bacillus thuringiensis Cry1Ab, Cry11Aa and Cry4Ba mutants suggest hetero-oligomer formation among different Cry toxins.
Background - Bacillus thuringiensis Cry toxins are used worldwide in the control of different insect pests important in agriculture or in human health. The Cry proteins are pore-forming toxins that affect the midgut cell of target insects. It was shown that non-toxic Cry1Ab helix a-4 mutants had a dominant negative (DN) phenotype inhibiting the toxicity of wildtype Cry1Ab when used in equimolar or sub-stoichiometric ratios (1:1, 0.5:1, mutant:wt) indicating that oligomer formation is a key step in toxicity of Cry toxins. Methodology/Principal Findings - The DN Cry1Ab-D136N/T143D mutant that is able to block toxicity of Cry1Ab toxin, was used to analyze its capacity to block the activity against Manduca sexta larvae of other Cry1 toxins, such as Cry1Aa, Cry1Ac, Cry1Ca, Cry1Da, Cry1Ea and Cry1Fa. Cry1Ab-DN mutant inhibited toxicity of Cry1Aa, Cry1Ac and Cry1Fa. In addition, we isolated mutants in helix a-4 of Cry4Ba and Cry11Aa, and demonstrate that Cry4Ba-E159K and Cry11Aa-V142D are inactive and completely block the toxicity against Aedes aegypti of both wildtype toxins, when used at sub-stoichiometric ratios, confirming a DN phenotype. As controls we analyzed Cry1Ab-R99A or Cry11Aa-E97A mutants that are located in helix a-3 and are affected in toxin oligomerization. These mutants do not show a DN phenotype but were able to block toxicity when used in 10:1 or 100:1 ratios (mutant:wt) probably by competition of binding with toxin receptors. Conclusions/Significance - We show that DN phenotype can be observed among different Cry toxins suggesting that may interact in vivo forming hetero-oligomers. The DN phenotype cannot be observed in mutants affected in oligomerization, suggesting that this step is important to inhibit toxicity of other toxin
Formation of S0 galaxies through mergers. Morphological properties: tidal relics, lenses, ovals, and other inner components
Major mergers are popularly considered too destructive to produce the relaxed
regular structures and the morphological inner components (ICs) usually
observed in lenticular (S0) galaxies. We aim to test if major mergers can
produce remnants with realistic S0 morphologies. We have selected a sample of
relaxed discy remnants resulting from the dissipative merger simulations of the
GalMer database and derived their properties mimicking the typical conditions
of current observational data. We compare their global morphologies, visual
components, and merger relics in mock photometric images with their real
counterparts. Only 1-2 Gyr after the full merger, we find that: 1) many
remnants (67 major and 29 minor events) present relaxed structures and typical
S0 or E/S0 morphologies, for a wide variety of orbits and even in gas-poor
cases. 2) Contrary to popular expectations, most of them do not exhibit any
morphological traces of their past merger origin under typical observing
conditions and at distances as nearby as 30 Mpc. 3) The merger relics are more
persistent in minor mergers than in major ones for similar relaxing time
periods. 4) No major-merger S0-like remnant develops a significant bar. 5)
Nearly 58% of the major-merger S0 remnants host visually detectable ICs, such
as embedded inner discs, rings, pseudo-rings, inner spirals, nuclear bars, and
compact sources, very frequent in real S0s too. 6) All remnants contain a lens
or oval, identically ubiquitous in local S0s. 7) These lenses and ovals do not
come from bar dilution in major merger cases, but are associated with stellar
halos or embedded inner discs instead (thick or thin). We conclude that the
relaxed morphologies, lenses, ovals, and other ICs of real S0s do not
necessarily come from internal secular evolution, gas infall or environmental
mechanisms, as traditionally assumed, but they can result from major mergers as
well.Comment: Accepted for publication in A&A, 37 pages, 21 figures, 9 tables.
Version with better resolution and language edited. A version with full
Appendices is available at:
https://www.researchgate.net/publication/325905181_Formation_of_S0_galaxies_through_mergers_Morphological_properties_tidal_relics_lenses_ovals_and_other_inner_components_-_Version_of_the_corresponding_AA_paper_with_full_Appendice
A virtual object-location task for children: Gender and videogame experience influence navigation; age impacts memory and completion time
The use of virtual reality-based tasks for studying memory has increased considerably. Most of the studies that have looked at child population factors that influence performance on such tasks have been focused on cognitive variables. However, little attention has been paid to the impact of non-cognitive skills. In the present paper, we tested 52 typically-developing children aged 5-12 years in a virtual object-location task. The task assessed their spatial short-term memory for the location of three objects in a virtual city. The virtual task environment was presented using a 3D application consisting of a 120" stereoscopic screen and a gamepad interface. Measures of learning and displacement indicators in the virtual environment, 3D perception, satisfaction, and usability were obtained. We assessed the children's videogame experience, their visuospatial span, their ability to build blocks, and emotional and behavioral outcomes. The results indicate that learning improved with age. Significant effects on the speed of navigation were found favoring boys and those more experienced with videogames. Visuospatial skills correlated mainly with ability to recall object positions, but the correlation was weak. Longer paths were related with higher scores of withdrawal behavior, attention problems, and a lower visuospatial span. Aggressiveness and experience with the device used for interaction were related with faster navigation. However, the correlations indicated only weak associations among these variables
The Low Redshift survey at Calar Alto (LoRCA)
The Baryon Acoustic Oscillation (BAO) feature in the power spectrum of
galaxies provides a standard ruler to measure the accelerated expansion of the
Universe. To extract all available information about dark energy, it is
necessary to measure a standard ruler in the local, z<0.2, universe where dark
energy dominates most the energy density of the Universe. Though the volume
available in the local universe is limited, it is just big enough to measure
accurately the long 100 Mpc/h wave-mode of the BAO. Using cosmological N-body
simulations and approximate methods based on Lagrangian perturbation theory, we
construct a suite of a thousand light-cones to evaluate the precision at which
one can measure the BAO standard ruler in the local universe. We find that
using the most massive galaxies on the full sky (34,000 sq. deg.), i.e. a
K(2MASS)<14 magnitude-limited sample, one can measure the BAO scale up to a
precision of 4\% and 1.2\% using reconstruction). We also find that such a
survey would help to detect the dynamics of dark energy.Therefore, we propose a
3-year long observational project, named the Low Redshift survey at Calar Alto
(LoRCA), to observe spectroscopically about 200,000 galaxies in the northern
sky to contribute to the construction of aforementioned galaxy sample. The
suite of light-cones is made available to the public.Comment: 15 pages. Accepted in MNRAS. Please visit our website:
http://lorca-survey.ft.uam.es
In vitro monitoring of surface mechanical properties of poly(L-lactic acid) using microhardness
Poly(L-lactic acid) (PLLA) was immersed in
a simulated body fluid (SBF) solution at 37.58C for distinct
times. The variation of the surface mechanical properties
of PLLA samples with immersion time was followed by
microhardness. These measurements showed that PLLA
microhardness decreased significantly ( 60%) after only
30 days of immersion. The results were explained in terms
of hydrolytic degradation of the samples. The dependence
of microhardness with the applied dwell time was also analyzed.
The creep curves were successfully described by a
power law. A decrease of the creep constant k as the
immersion time increased was found. Differential scanning
calorimetry was also used to analyze the changes in the
physical properties of PLLA, namely in crystallinity degree
(Xc) and glass transition temperature (Tg), as a function of
the immersion time in SBF. A significant variation in the
crystallinity degree of PLLA, initially nearly amorphous
(Xc 5 9%), was detected after only 3 days of immersion
(Xc 5 37%). The interpretation of this behavior was based
on the hydrolysis process suffered by PLLA
Microhardness of starch based biomaterials in simulated physiological conditions
In this work the variation of the surface mechanical properties of starch-based biomaterials with immersion time was followed using
microhardness measurements. Two blends with very distinct water uptake capabilities, starch/cellulose acetate (SCA) and starch/poly-
(e-caprolactone) (SPCL), were immersed in a phosphate buffer solution (PBS) at 37.5 C for various times. The microhardness of the
blends decreased significantly ( 50% for SPCL and 94% for SCA), within a time period of 30 days of immersion, reflecting the different
hydrophilic character of the synthetic components of the blends. The dependence of microhardness on the applied loading time and load
was also analysed and showed a power law dependency for SCA. Water uptake and weight loss measurements were performed for the
same immersion times used in the microhardness experiments. The different swelling/degradation behaviour presented by the blends was
related to the respective variation in microhardness. Moreover, complementary characterization of the mechanical properties of SCA
and SPCL was accomplished by dynamic mechanical analysis (DMA) and creep measurements. Microhardness measurements proved
to be a useful technique for characterizing the mechanical behaviour near the surface of polymeric biomaterials, including in simulated
physiological conditions
Comparative study of the environmental footprints of marinas on European Islands
Ports have been key elements in Europe's economic development. This situation is even more relevant on islands, which are highly dependent on the maritime sector. Consequently, over the years, ports with diverse functionalities have been established both in mainland Europe and on its outlying islands. This article discusses the environmental impact of leisure marinas on European islands, especially as they are closely linked to economic development through tourism. The aim is to study the environmental impact of these infrastructures by determining the carbon and water footprints of marinas on European islands in the Atlantic and the Mediterranean. The results obtained enable the authors to make recommendations in order to reduce the overall environmental footprint of marinas on islands, considering that these territories are much more vulnerable to climate change than mainland locations in Europe
On the Reliability of Cross Correlation Function Lag Determinations in Active Galactic Nuclei
Many AGN exhibit a highly variable luminosity. Some AGN also show a
pronounced time delay between variations seen in their optical continuum and in
their emission lines. In effect, the emission lines are light echoes of the
continuum. This light travel-time delay provides a characteristic radius of the
region producing the emission lines. The cross correlation function (CCF) is
the standard tool used to measure the time lag between the continuum and line
variations. For the few well-sampled AGN, the lag ranges from 1-100 days,
depending upon which line is used and the luminosity of the AGN. In the best
sampled AGN, NGC 5548, the H_beta lag shows year-to-year changes, ranging from
about 8.7 days to about 22.9 days over a span of 8 years. In this paper it is
demonstrated that, in the context of AGN variability studies, the lag estimate
using the CCF is biased too low and subject to a large variance. Thus the
year-to-year changes of the measured lag in NGC 5548 do not necessarily imply
changes in the AGN structure. The bias and large variance are consequences of
finite duration sampling and the dominance of long timescale trends in the
light curves, not due to noise or irregular sampling. Lag estimates can be
substantially improved by removing low frequency power from the light curves
prior to computing the CCF.Comment: To appear in the PASP, vol 111, 1999 Nov; 37 pages; 10 figure
Prevalence and Incidence of Parkinson\u27s Disease in Latin America: A Meta-Analysis
\ua9 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. Background: Parkinson\u27s disease (PD) is a rapidly growing neurodegenerative disorder, but up-to-date epidemiological data are lacking in Latin America. We sought to estimate the prevalence and incidence of PD and parkinsonism in Latin America. Methods: We searched Medline, Embase, Scopus, Web of Science, Scientific Electronic Library Online, and Literatura Latino-Americana e do Caribe em Ci\ueancias da Sa\ufade or the Latin American and Caribbean Health Science Literature databases for epidemiological studies reporting the prevalence or incidence of PD or parkinsonism in Latin America from their inception to 2022. Quality of studies was assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist. Data were pooled via random-effects meta-analysis and analyzed by data source (cohort studies or administrative databases), sex, and age group. Significant differences between groups were determined by meta-regression. Results: Eighteen studies from 13 Latin American countries were included in the review. Meta-analyses of 17 studies (nearly 4 million participants) found a prevalence of 472 (95% CI, 271–820) per 100,000 and three studies an incidence of 31 (95% CI, 23–40) per 100,000 person-years for PD; and seven studies found a prevalence of 4300 (95% CI, 1863–9613) per 100,000 for parkinsonism. The prevalence of PD differed by data source (cohort studies, 733 [95% CI, 427–1255] vs. administrative databases. 114 [95% CI, 63–209] per 100,000, P < 0.01), age group (P < 0.01), but not sex (P = 0.73). PD prevalence in ≥60 years also differed significantly by data source (cohort studies. 1229 [95% CI, 741–2032] vs. administrative databases, 593 [95% CI, 480–733] per 100,000, P < 0.01). Similar patterns were observed for parkinsonism. Conclusions: The overall prevalence and incidence of PD in Latin America were estimated. PD prevalence differed significantly by the data source and age, but not sex. \ua9 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society
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