The genotoxic effects of DNA lesions induced by artificial UV-radiation and sunlight

Solar radiation sustains and affects all life forms on Earth. The increase in solar UV-radiation at environmental levels, due to depletion of the stratospheric ozone layer, highlights serious issues of social concern. This becomes still more dramatic in tropical and subtropical regions where radiation-intensity is still higher. Thus, there is the need to evaluate the harmful effects of solar UV-radiation on the DNA molecule as a basis for assessing the risks involved for human health, biological productivity and ecosystems. In order to evaluate the profile of DNA damage induced by this form of radiation and its genotoxic effects, plasmid DNA samples were exposed to artificial-UV lamps and directly to sunlight. The induction of cyclobutane pyrimidine dimer photoproducts (CPDs) and oxidative DNA damage in these molecules were evaluated by means of specific DNA repair enzymes. On the other hand, the biological effects of such lesions were determined through the analysis of the DNA inactivation rate and mutation frequency, after replication of the damaged pCMUT vector in an Escherichia coli MBL50 strain. The results indicated the induction of a significant number of CPDs after exposure to increasing doses of UVC, UVB, UVA radiation and sunlight. Interestingly, these photoproducts are those lesions that better correlate with plasmid inactivation as well as mutagenesis, and the oxidative DNA damages induced present very low correlation with these effects. The results indicated that DNA photoproducts play the main role in the induction of genotoxic effects by artificial UV-radiation sources and sunlight. (C) 2010 Elsevier B.V. All rights reserved.

p53 Mutant Human Glioma Cells Are Sensitive to UV-C-Induced Apoptosis Due to Impaired Cyclobutane Pyrimidine Dimer Removal

The p53 protein is a key regulator of cell responses to DNA damage, and it has been shown that It sensitizes glioma cells to the alkylating agent temozolomide by up-regulating the extrinsic apoptotic pathway, whereas it increases the resistance to chloroethylating agents, such as ACNU and BCNU, probably by enhancing the efficiency of DNA repair. However, because these agents induce a wide variety of distinct DNA lesions, the direct Importance of DNA repair is hard to access. Here, it is shown that the Induction of photoproducts by UV light (UV-C) significantly Induces apoptosis In a p53-mutated glioma background. This Is caused by a reduced level of photoproduct repair, resulting In the persistence of DNA lesions in p53-mutated glioma cells. UV-C-Induced apoptosis in p53 mutant glioma cells Is preceded by strong transcription and replication inhibition due to blockage by unrepaired photolesions. Moreover, the results Indicate that UV-C-induced apoptosis of p53 mutant glioma cells Is executed through the intrinsic apoptotic pathway, with Bcl-2 degradation and sustained Bax and Bak up-regulation. Collectively, the data Indicate that unrepaired DNA lesions Induce apoptosis In p53 mutant gliomas despite the resistance of these gliomas to temozolomide, suggesting that efficiency of treatment of p53 mutant gliomas might be higher with agents that Induce the formation of DNA lesions whose global genomic repair is dependent on p53. (Mol Cancer Res 2009;7(2):237-46)

Towards improving cluster-based feature selection with a simplified silhouette filter

This paper proposes a filter-based algorithm for feature selection. The filter is based on the partitioning of the set of features into clusters. The number of clusters, and consequently the cardinality of the subset of selected features, is automatically estimated from data. The computational complexity of the proposed algorithm is also investigated. A variant of this filter that considers feature-class correlations is also proposed for classification problems. Empirical results involving ten datasets illustrate the performance of the developed algorithm, which in general has obtained competitive results in terms of classification accuracy when compared to state of the art algorithms that find clusters of features. We show that, if computational efficiency is an important issue, then the proposed filter May be preferred over their counterparts, thus becoming eligible to join a pool of feature selection algorithms to be used in practice. As an additional contribution of this work, a theoretical framework is used to formally analyze some properties of feature selection methods that rely on finding clusters of features. (C) 2011 Elsevier Inc. All rights reserved.

A Floating-point Extended Kalman Filter Implementation for Autonomous Mobile Robots

Localization and Mapping are two of the most important capabilities for autonomous mobile robots and have been receiving considerable attention from the scientific computing community over the last 10 years. One of the most efficient methods to address these problems is based on the use of the Extended Kalman Filter (EKF). The EKF simultaneously estimates a model of the environment (map) and the position of the robot based on odometric and exteroceptive sensor information. As this algorithm demands a considerable amount of computation, it is usually executed on high end PCs coupled to the robot. In this work we present an FPGA-based architecture for the EKF algorithm that is capable of processing two-dimensional maps containing up to 1.8 k features at real time (14 Hz), a three-fold improvement over a Pentium M 1.6 GHz, and a 13-fold improvement over an ARM920T 200 MHz. The proposed architecture also consumes only 1.3% of the Pentium and 12.3% of the ARM energy per feature.

Aerosol inorganic composition at a tropical site: Discrepancies between filter-based sampling and a semi-continuous method

The concentrations of the water-soluble inorganic aerosol species, ammonium (NH4+), nitrate (NO3-), chloride (Cl-), and sulfate (SO42-), were measured from September to November 2002 at a pasture site in the Amazon Basin (Rondnia, Brazil) (LBA-SMOCC). Measurements were conducted using a semi-continuous technique (Wet-annular denuder/Steam-Jet Aerosol Collector: WAD/SJAC) and three integrating filter-based methods, namely (1) a denuder-filter pack (DFP: Teflon and impregnated Whatman filters), (2) a stacked-filter unit (SFU: polycarbonate filters), and (3) a High Volume dichotomous sampler (HiVol: quartz fiber filters). Measurements covered the late dry season (biomass burning), a transition period, and the onset of the wet season (clean conditions). Analyses of the particles collected on filters were performed using ion chromatography (IC) and Particle-Induced X-ray Emission spectrometry (PIXE). Season-dependent discrepancies were observed between the WAD/SJAC system and the filter-based samplers. During the dry season, when PM2.5 (D-p <= 2.5 mu m) concentrations were similar to 100 mu g m(-3), aerosol NH4+ and SO42- measured by the filter-based samplers were on average two times higher than those determined by the WAD/SJAC. Concentrations of aerosol NO3- and Cl- measured with the HiVol during daytime, and with the DFP during day- and nighttime also exceeded those of the WAD/SJAC by a factor of two. In contrast, aerosol NO3- and Cl- measured with the SFU during the dry season were nearly two times lower than those measured by the WAD/SJAC. These differences declined markedly during the transition period and towards the cleaner conditions during the onset of the wet season (PM2.5 similar to 5 mu g m(-3)); when filter-based samplers measured on average 40-90% less than the WAD/SJAC. The differences were not due to consistent systematic biases of the analytical techniques, but were apparently a result of prevailing environmental conditions and different sampling procedures. For the transition period and wet season, the significance of our results is reduced by a low number of data points. We argue that the observed differences are mainly attributable to (a) positive and negative filter sampling artifacts, (b) presence of organic compounds and organosulfates on filter substrates, and (c) a SJAC sampling efficiency of less than 100%.

UV optical absorption spectra analysis of beryl crystals from Brazil

The spectral decomposition analysis was applied to the optical absorption spectra of green and colorless beryl crystals from the Brazilian Eastern Pegmatitic province in the natural state, Submitted to heat treatment and irradiated with UV light The attributions of the lines were made taking into account highly accurate quantum mechanical calculations The deconvolution of the green beryl spectra revealed four lines, two of them around 12,000 cm(-1) (1 5eV) and two of them around 34,000 cm(-1) (4.2 eV) attributed to Fe(2+) and Fe(3+), respectively The deconvolution of the colorless beryl spectra without any treatment, after heating and for the same heat treatment followed by UV light irradiation revealed five lines The analysis of ratio relations showed that the lines at 36,400 cm(-1) (4.5 eV) and 41,400 cm(-1) (5 1 eV) belongs to a single defect attributed to a silicon dangling bond defect (=Si). Discussions and comparison with reported defects in quartz have supported the allocation of the lines at 61,000 cm(-1) (7.6 eV) and 43,800 cm(-1) (5 4 eV) to diamagnetic oxygen vacancy defect ( Si-Si ) and unrelaxed ( Si Si ) defect, respectively Finally, the line at 39.100 cm(-1) (4.8 eV), quite polarized along the c-axis, was attributed to a (Fe(2+) OH(-)) defect in the structural channels (C) 2009 Elsevier B V All rights reserved

Dosimetric properties of UV irradiated calcium co-doped borate glass-ceramic

The thermoluminescence (TL) response of Dy and Li doped 20CaB(4)O(7)-80CaB(2)O(4) (Wt%) glass-ceramic irradiated with ultraviolet (UV) radiation was studied. In order to act as TL activator ions, the Dy and Li ions were included in the matrix during the melting process to increase its TL efficiency. A single crystalline CaB2O4 phase was present in the glass-ceramic as determined by X-ray diffraction (XRD). The glass-ceramic 20CaB(4)O(7)-80CaB(2)O(4):Dy,Li wt% (named 20CBO7:Dy,Li) is a newly prepared TL material. Its thermoluminescent dosimetric characteristics have shown a linear response under UV radiation exposure and a good TL signal reproducibility, thus proving to be a promising material for using as an ultraviolet radiation dosimeter. (C) 2007 Elsevier B.V. All rights reserved.

Mice and larvae tracking using a particle filter with an auto-adjustable observation model

This paper proposes a novel way to combine different observation models in a particle filter framework. This, so called, auto-adjustable observation model, enhance the particle filter accuracy when the tracked objects overlap without infringing a great runtime penalty to the whole tracking system. The approach has been tested under two important real world situations related to animal behavior: mice and larvae tracking. The proposal was compared to some state-of-art approaches and the results show, under the datasets tested, that a good trade-off between accuracy and runtime can be achieved using an auto-adjustable observation model. (C) 2009 Elsevier B.V. All rights reserved.

A note on a practical relationship between filter coefficients and scaling and wavelet functions of Discrete Wavelet Transforms

In this paper, the relationship between the filter coefficients and the scaling and wavelet functions of the Discrete Wavelet Transform is presented and exemplified from a practical point-of-view. The explanations complement the wavelet theory, that is well documented in the literature, being important for researchers who work with this tool for time-frequency analysis. (c) 2011 Elsevier Ltd. All rights reserved.

The transcriptional response to cadmium, organic hydroperoxide, singlet oxygen and UV-A mediated by the sigma(E)-ChrR system in Caulobacter crescentus

Caulobacter crescentus sigma(E) belongs to the ECF (extracytoplasmic function) subfamily of RNA polymerase sigma factors, whose members regulate gene expression in response to distinct environmental stresses. During physiological growth conditions, data indicate that sigma(E) is maintained in reduced levels due to the action of ChrR, a negative regulator of rpoE gene expression and function. However, once bacterial cells are exposed to cadmium, organic hydroperoxide, singlet oxygen or UV-A irradiation, transcription of rpoE is induced in a sigma(E)-dependent manner. Site-directed mutagenesis indicated that residue C188 in ChrR is critical for the cadmium response while residues H140 and H142 are required for the bacterial response to organic hydroperoxide, singlet oxygen and UV-A. Global transcriptional analysis showed that sigma(E) regulates genes involved in protecting cells against oxidative damages. A combination of transcriptional start site identification and promoter prediction revealed that some of these genes contain a putative sigma(E)-dependent motif in their upstream regions. Furthermore, deletion of rpoE and two sigma(E)-dependent genes (cfaS and hsp20) impairs Caulobacter survival when singlet oxygen is constantly generated in the cells.

Biflavonoids from Araucaria angustifolia protect against DNA UV-Induced damage

Ultraviolet radiation is one of the most deleterious forms of radiation to terrestrial organisms and is involved in formation of mutagenic pyrimidine dimers and oxidized nucleotides. The biflavonoid fraction (BFF), extracted from needles of Araucaria angustifolia was capable of protecting calf thymus DNA from damage induced by UV radiation. This occurred through prevention of cyclobutane thymine dimer and 8-oxo-7,8-dihydro-2`-deoxyguanosine formation, this being quantified by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) in a multiple reaction monitoring mode (MRM) and by HPLC-coulometric detection, respectively. (C) 2009 Elsevier Ltd. All rights reserved.

In vitro evaluation of Cu and Fe bioavailability in cashew nuts by off-line coupled SEC-UV and SIMAAS

In this work Cu and Fe bioavailability in cashew nuts was evaluated using in vitro method. Extractions with simulated gastric and intestinal fluids and dialysis procedures were applied for this purpose. The proteins separation and quantification were performed by size exclusion chromatography (SEC) coupled on-line to ultra-violet (UV) and off-line to simultaneous multielement atomic absorption spectrometry (SIMAAS). The SEC-UV and SIMAAS profiles of the protein fractions obtained by alkaline extraction (NaOH) and precipitation with HCl indicated the presence of high and low molecular weight species in the range between >75 kDa and 9.3 kDa. Almost 83% of Cu and 78% of Fe were extracted during cashew nut digestion and 90% of both elements were dialyzed. With these results it is possible to assume that 75% of Cu and 70% of Fe present in cashew nut could be bioavailable. The SEC-UV and SIMAAS chromatographic profiles obtained after in vitro gastrointestinal digestion reveal that Cu and Fe not dialyzed can be associated to a compound of 9.2 kDa. (C) 2010 Elsevier B.V. All rights reserved.

Reliable and fast sensor for in vitro evaluation of solar protection factor based on the photobleaching kinetics of a nanocrystalline TiO(2)/dye UV-dosimeter

A reliable and fast sensor for in vitro evaluation of solar protection factors (SPFs) of cosmetic products, based on the photobleaching kinetics of a nanocrystalline TiO(2)/dye UV-dosimeter, has been devised. The accuracy, robustness and suitability of the new device was demonstrated by the excellent matching of the predicted and the in vivo results up to SPF 70, for four standard samples analyzed in blind. These results strongly suggest that our device can be useful for routine SPF evaluation in laboratories devoted to the development or production of cosmetic formulations, since the conventional in vitro methods tend to exhibit unacceptably high errors above SPF similar to 30 and the conventional in vivo methods tend to be expensive and exceedingly time consuming. (C) 2011 Elsevier B.V. All rights reserved.

Flow injection analysis of ethyl xanthate by gas diffusion and UV detection as CS(2) for process monitoring of sulfide ore flotation

A sensitive and robust analytical method for spectrophotometric determination of ethyl xanthate, CH(3)CH(2)OCS(2)(-) at trace concentrations in pulp solutions from froth flotation process is proposed. The analytical method is based on the decomposition of ethyl xanthate. EtX(-), with 2.0 mol L(-1) HCl generating ethanol and carbon disulfide. CS(2). A gas diffusion cell assures that only the volatile compounds diffuse through a PTFE membrane towards an acceptor stream of deionized water, thus avoiding the interferences of non-volatile compounds and suspended particles. The CS(2) is selectively detected by UV absorbance at 206 nm (epsilon = 65,000 L mol(-1) cm(-1)). The measured absorbance is directly proportional to EtX(-) concentration present in the sample solutions. The Beer`s law is obeyed in a 1 x 10(-6) to 2 x 10(-4) mol L(-1) concentration range of ethyl xanthate in the pulp with an excellent correlation coefficient (r = 0.999) and a detection limit of 3.1 x 10(-7) mol L(-1), corresponding to 38 mu g L. At flow rates of 200 mu L min(-1) of the donor stream and 100 mu L min(-1) of the acceptor channel a sampling rate of 15 injections per hour could be achieved with RSD < 2.3% (n = 10, 300 mu L injections of 1 x 10(-5) mol L(-1) EtX(-)). Two practical applications demonstrate the versatility of the FIA method: (i) evaluation the free EtX(-) concentration during a laboratory study of the EtX(-) adsorption capacity on pulverized sulfide ore (pyrite) and (ii) monitoring of EtX(-) at different stages (from starting load to washing effluents) of a flotation pilot plant processing a Cu-Zn sulfide ore. (C) 2010 Elsevier By. All rights reserved.

Identification of lift-off mechanism failure for salt drill-in drilling fluid containing polymer filter cake through adsorption/desorption studies

Drilling fluid`s contact with the productive zone of horizontal or complex wells can reduce well productivity by fluid invasion in the borehole wall. Salted drilling drill-in fluid containing polymers has often been applied in horizontal or complex petroleum wells in the poorly consolidated sandstone reservoirs of the Campos basin, Rio de Janeiro, Brazil. This fluid usually consists of natural polymers such as starch and xanthan gum, which are deposited as a filter cake on the wellbore wall during the drilling. Therefore, the identification of a lift-off mechanism failure, which can be detachment or blistering and pinholing, will enable formulation improvements. increasing the chances of success during filter cake removal in open hole operations. Likewise, knowledge of drill-in drilling fluid adsorption/desorption onto sand can help understand the filter cake-rock adhesion mechanism and consequently filter cake lift-off mechanism failures. The present study aimed to identify the lift-off failure mechanism for this type of fluid filter cake studying adsorption/desorption onto SiO(2) using solutions of natural polymers, lubricants, besides the fluid itself. Ellipsometry was employed to measure this process. The adsorption/desorption studies showed that the adsorbed layer of drilling fluid onto the walls of the rock pores is made up of clusters of polymers, linked by hydrogen bonds, which results in a force of lower cohesion compared to the electrostatic interaction between silica and polymers. Consequently, it was found that the most probable filter cake failure mechanism is rupture (blistering and pinholing), which results in the formation of ducts within the filter cake. (C) 2009 Elsevier B.V. All rights reserved.