Approximated Perspective Relaxations: a Project&Lift Approach

The Perspective Reformulation (PR) of a Mixed-Integer NonLinear Program with semi-continuous variables is obtained by replacing each term in the (separable) objective function with its convex envelope. Solving the corresponding continuous relaxation requires appropriate techniques. Under some rather restrictive assumptions, the Projected PR (P^2R) can be defined where the integer variables are eliminated by projecting the solution set onto the space of the continuous variables only. This approach produces a simple piecewise-convex problem with the same structure as the original one; however, this prevents the use of general-purpose solvers, in that some variables are then only implicitly represented in the formulation. We show how to construct an Approximated Projected PR (AP^2R) whereby the projected formulation is "lifted" back to the original variable space, with each integer variable expressing one piece of the obtained piecewise-convex function. In some cases, this produces a reformulation of the original problem with exactly the same size and structure as the standard continuous relaxation, but providing substantially improved bounds. In the process we also substantially extend the approach beyond the original P^2R development by relaxing the requirement that the objective function be quadratic and the left endpoint of the domain of the variables be non-negative. While the AP^2R bound can be weaker than that of the PR, this approach can be applied in many more cases and allows direct use of off-the-shelf MINLP software; this is shown to be competitive with previously proposed approaches in some applications

THE PROMOTER OF VACUOLAR METAL TRANSPORTER IN ARABIDOPSIS HALLERI: AN EXAMPLE OF EVOLUTION FOR METAL HYPERTOLERANCE/HYPERACCUMULATION

In the metal hyperaccumulator Arabidopsis halleri, the metal vacuolar transporter (VMT) isinvolved in hyperaccumulation and hypertolerance. Three VMT promoter sequences have beenidentified in the genome of A. halleri; expression analysis, conducted by GUS assay, showed thateach promoter sequence of A. halleri induced higher expression than the promoter sequence of theVMT orthologous gene in A. thaliana. Moreover, it was observed that A. halleri VTM members areexpressed in leaf trichomes, whereas VTM of A. thaliana is not present in these organs. In silicoanalysis revealed that the 5\u2019 UTR region of VTM is highly conserved between the two Arabidopsisspecies, although a dimer of MYB-binding motifs harboured by the A. halleri promoters is mutatedin a single nucleotide in the sequence of A. thaliana. Site-specific mutagenesis of these motifs in thepromoter of A. halleri indicates that they are likely involved in trichome-specific expression. Therole of these MYB-binding motifs in the A. halleri VMT promoter was tested in A. thaliana,considering their effect in both metal tolerance and accumulation. Transgenic A. thaliana plantsexpressing VMT under the control of the native A. halleri VMT promoter are more tolerant, in termsof root length, biomass production and chlorophyll content, to high metal concentrations, than theones bearing the same construct with the mutated MYB-binding motifs. Differences in shoots andin roots were also observed regarding metal accumulation. These results underline the divergentevolution of the VMT promoter, conferring higher metal tolerance, accompanied by expression intrichomes, in the hyperaccumulator A. halleri and protection to heavy metal stress in transgenic A.thaliana. Furthermore, a possible biotechnological approach might be applied in phytoremediationor biofortification programs to modulate metal content in plants

Identification via numerical computation of transcriptional determinants of a cell phenotype decision making

Complex cellular processes, such as phenotype decision making, are exceedingly difficult to analyze experimentally, due to the multiple-layer regulation of gene expression and the intercellular variability referred to as biological noise. Moreover, the heterogeneous experimental approaches used to investigate distinct macromolecular species, and their intrinsic differential time-scale dynamics, add further intricacy to the general picture of the physiological phenomenon. In this respect, a computational representation of the cellular functions of interest can be used to extract relevant information, being able to highlight meaningful active markers within the plethora of actors forming an active molecular network. The multiscale power of such an approach can also provide meaningful descriptions for both population and single-cell level events. To validate this paradigm a Boolean and a Markov model were combined to identify, in an objective and user-independent manner, a signature of genes recapitulating epithelial to mesenchymal transition in-vitro. The predictions of the model are in agreement with experimental data and revealed how the expression of specific molecular markers is related to distinct cell behaviors. The presented method strengthens the evidence of a role for computational representation of active molecular networks to gain insight into cellular physiology and as a general approach for integrating in-silico/in-vitro study of complex cell population dynamics to identify their most relevant drivers

accuracy of cultural heritage 3d models by rpas and terrestrial photogrammetry

The combined use of high-resolution digital images taken from ground as well as from RPAS (Remotely Piloted Aircraft Systems) have significantly increased the potential of close range digital photogrammetry applications in Cultural Heritage surveying and modeling. It is in fact possible, thanks to SfM (Structure from Motion), to simultaneously process great numbers of aerial and terrestrial images for the production of a dense point cloud of an object. In order to analyze the accuracy of results, we started numerous tests based on the comparison between 3D digital models of a monumental complex realized by the integration of aerial and terrestrial photogrammetry and an accurate TLS (Terrestrial Laser Scanner) reference model of the same object. A lot of digital images of a renaissance castle, assumed as test site, have been taken both by ground level and by RPAS at different distances and flight altitudes and with different flight patterns. As first step of the experimentation, the images were previously processed with Agisoft PhotoScan, one of the most popular photogrammetric software. The comparison between the photogrammetric DSM of the monument and a TLS reference one was carried out by evaluating the average deviation between the points belonging to the two entities, both globally and locally, on individual façades and architectural elements (sections and particular). In this paper the results of the first test are presented. A good agreement between photogrammetric and TLS digital models of the castle is pointed out

Heavy Metal Pollutions: State of the Art and Innovation in Phytoremediation

Mineral nutrition of plants greatly depends on both environmental conditions, particularly of soils, and the genetic background of the plant itself. Being sessile, plants adopted a range of strategies for sensing and responding to nutrient availability to optimize development and growth, as well as to protect their metabolisms from heavy metal toxicity. Such mechanisms, together with the soil environment, meaning the soil microorganisms and their interaction with plant roots, have been extensively studied with the goal of exploiting them to reclaim polluted lands; this approach, defined phytoremediation, will be the subject of this review. The main aspects and innovations in this field are considered, in particular with respect to the selection of efficient plant genotypes, the application of improved cultural strategies, and the symbiotic interaction with soil microorganisms, to manage heavy metal polluted soils

Endomembrane reorganization induced by heavy metals

Plant cells maintain plasmatic concentrations of essential heavy metal ions, such as iron, zinc, and copper, within the optimal functional range. To do so, several molecular mechanisms have to be committed to maintain concentrations of non-essential heavy metals and metalloids, such as cadmium, mercury and arsenic below their toxicity threshold levels. Compartmentalization is central to heavy metals homeostasis and secretory compartments, finely interconnected by traffic mechanisms, are determinant. Endomembrane reorganization can have unexpected effects on heavy metals tolerance altering in a complex way membrane permeability, storage, and detoxification ability beyond gene\u2019s expression regulation. The full understanding of endomembrane role is propaedeutic to the comprehension of translocation and hyper-accumulation mechanisms and their applicative employment. It is evident that further studies on dynamic localization of these and many more proteins may significantly contribute to the understanding of heavy metals tolerance mechanisms. The aim of this review is to provide an overview about the endomembrane alterations involved in heavy metals compartmentalization and tolerance in plants

The role of ABC1K7 and ABC1K8, two ABC1K kinases of Arabidopsis thaliana

The activity of bc1 complex kinases (ABC1K) belong to a large group of atypical protein kinases found in prokaryotes and eukaryotes. In bacteria and mitochondria, ABC1K kinases are involved in the respiratory pathway, being necessary for the synthesis of the coenzyme Q. In chloroplasts, ABC1K proteins play a role in prenylquinone synthesis and stress responses, but their precise function remains unclear. A functional characterization was carried out for ABC1K7 and ABC1K8, two ABC1K proteins of the Arabidopsis thaliana plastome. The comparison of abc1k7 and abc1k8 mutants, abc1k7/abc1k8 double mutant and wild-type plants revealed a reduction in plastidial ironcontaining proteins of the Cytb6f complex in the mutants. Iron uptake from soil is not hampered in mutant lines, suggesting that ABC1K7 and ABC1K8 affect iron distribution within the chloroplast. Moreover, mutant plants accumulated more ferritin and superoxide, and showed reduced tolerance to reactive oxygen species (ROS). Because ROS take part in abscisic acid (ABA) signaling, we investigated the relation between ABA and ABC1K7 and ABC1K8 and found that both genes were upregulated by ABA treatment, while expression of several ABA-responsive genes resulted affected in mutants. Moreover, analyzing ABA-mediated processes, we determined that germination was more affected by ABA treatment and osmotic and salt stress in the single and double mutants than in wild-type plants. Stomatal aperture was also reduced in the mutants under standard growth conditions and was not further reduced by exogenous ABA application. Furthermore, ABA-induced senescence symptoms were more severe in the leaves of the mutants compared to wild type leaves. Taken together, these data suggest that ABC1K7 and ABC1K8 probably act in signaling pathways that influence responses to ROS production and oxidative stress, such as ABA signaling, probably by influencing the cellular redox state and chloroplast lipid metabolism

VSCAN: An Enhanced Video Summarization using Density-based Spatial Clustering

In this paper, we present VSCAN, a novel approach for generating static video summaries. This approach is based on a modified DBSCAN clustering algorithm to summarize the video content utilizing both color and texture features of the video frames. The paper also introduces an enhanced evaluation method that depends on color and texture features. Video Summaries generated by VSCAN are compared with summaries generated by other approaches found in the literature and those created by users. Experimental results indicate that the video summaries generated by VSCAN have a higher quality than those generated by other approaches.Comment: arXiv admin note: substantial text overlap with arXiv:1401.3590 by other authors without attributio