Showing papers by "Romanian Academy published in 2012"

Unsupervised Learning for Graph Matching

Abstract: Graph matching is an essential problem in computer vision that has been successfully applied to 2D and 3D feature matching and object recognition. Despite its importance, little has been published on learning the parameters that control graph matching, even though learning has been shown to be vital for improving the matching rate. In this paper we show how to perform parameter learning in an unsupervised fashion, that is when no correct correspondences between graphs are given during training. Our experiments reveal that unsupervised learning compares favorably to the supervised case, both in terms of efficiency and quality, while avoiding the tedious manual labeling of ground truth correspondences. We verify experimentally that our learning method can improve the performance of several state-of-the art graph matching algorithms. We also show that a similar method can be successfully applied to parameter learning for graphical models and demonstrate its effectiveness empirically.

The role of streamers in the deflection of coronal mass ejections: comparison between stereo three-dimensional reconstructions and numerical simulations

Abstract: On 2009 September 21, a filament eruption and the associated coronal mass ejection (CME) were observed by the Solar Terrestrial Relations Observatory (STEREO) spacecraft. The CME originated from the southern hemisphere and showed a deflection of about 15 ◦ toward the heliospheric current sheet (HCS) during the propagation in the COR1 field of view. The CME source region was near the central meridian, but no on-disk CME signatures could be seen from the Earth. The aim of this paper is to provide a physical explanation for the strong deflection of the CME observed on 2009 September 21. The two-sided view of the STEREO spacecraft allows us to reconstruct the three-dimensional travel path of the CME and the evolution of the CME source region. The observations are combined with a magnetohydrodynamic simulation, starting from a magneticfield configuration closely resembling the extrapolated potential field for that date. By applying localized shearing motions, a CME is initiated in the simulation, showing a similar non-radial evolution, structure, and velocity as the observed event. The CME gets deflected toward the current sheet of the larger northern helmet streamer due to an imbalance in the magnetic pressure and tension forces and finally gets into the streamer. This study shows that during solar minima, even CMEs originating from high latitude can be easily deflected toward the HCS, eventually resulting in geoeffective events. How rapidly they undergo this latitudinal migration depends on the strength of both the large-scale coronal magnetic field and the magnetic flux of the erupting filament.

Inflammation in atherosclerosis: a cause or a result of vascular disorders?

Abstract: Sound data support the concept that in atherosclerosis, inflammation and dyslipidemia intersect each other and that irrespective of the initiator, both participate from the early stages to the ultimate fate of the atheromatous plaque. The two partakers manoeuvre a vicious circle in atheroma formation: dyslipidaemia triggers an inflammatory process and inflammation elicits dyslipidaemia. Independent of the initial cause, the atherosclerotic lesions occur focally, in particular arterial-susceptible sites, by a process that, although continuous, can be arbitrarily divided into a sequence of consecutive stages that lead from fatty streak to the fibro-lipid plaque and ultimately to plaque rupture and thrombosis. In the process, the initial event is a change in endothelial cells (EC) constitutive properties. Then, the molecular alarm signals send by dysfunctional EC are decoded by specific blood immune cells (monocytes, T lymphocytes, neutrophils, mast cells) and by the resident vascular cells, that respond by initiating a robust inflammatory process, in which the cells and the factors they secrete hasten the atheroma development. Direct and indirect crosstalk between the cells housed within the nascent plaque, complemented by the increase in risk factors of atherosclerosis lead to atheroma development and outcome. The initial inflammatory response can be regarded as a defense/protective reaction mechanism, but its further amplification, speeds up atherosclerosis. In this review, we provide an overview on the role of inflammation and dyslipidaemia and their intersection in atherogenesis. The data may add to the foundation of a novel attitude in the diagnosis and treatment of atherosclerosis.

Unsteady Pressure Analysis of a Swirling Flow With Vortex Rope and Axial Water Injection in a Discharge Cone

Abstract: The variable demand of the energy market requires that hydraulic turbines operate atvariable conditions, which includes regimes far from the best efficiency point. The vortexrope developed at partial discharges in the conical diffuser is responsible for large pres-sure pulsations, runner blades breakdowns and may lead to power swing phenomena. Anovel method introduced by Resiga et al. (2006, “Jet Control of the Draft Tube in FrancisTurbines at Partial Discharge,” Proceedings of the 23rd IAHR Symposium on HydraulicMachinery and Systems, Yokohama, Japan, Paper No. F192) injects an axial water jetfrom the runner crown downstream in the draft tube cone to mitigate the vortex rope andits consequences. A special test rig was developed at “Politehnica” University of Timi-soara in order to investigate different flow control techniques. Consequently, a vortexrope similar to the one developed in a Francis turbine cone at 70% partial discharge isgenerated in the rig’s test section. In order to investigate the new jet control method anauxiliary hydraulic circuit was designed in order to supply the jet. The experimentalinvestigations presented in this paper are concerned with pressure measurements at thewall of the conical diffuser. The pressure fluctuations’ Fourier spectra are analyzed inorder to assess how the amplitude and dominating frequency are modified by the waterinjection. It is shown that the water jet injection significantly reduces both the amplitudeand the frequency of pressure fluctuations, while improving the pressure recovery in theconical diffuser. [DOI: 10.1115/1.4007074]Keywords: decelerated swirling flow, vortex rope, water injection method, unsteadypressure, experimental investigation

Modeling of asteroid spectra – M4AST

Abstract: Context. The interpretation of asteroid spectra provides the basis for determining the chemical composition and physical process that modified the surface of the asteroids. The increasing number of asteroid spectral measurements has lead to well-developed methods for analyzing asteroid spectra. There is however no centralized database for all the published data and a set of standard routines is also required. Aims. We present a public software tool that combines both data archives and analyses of asteroid spectra. Methods. Our project M4AST (Modeling for asteroids) consists of an asteroid spectral database and a set of applications for analyzing asteroid spectra. These applications cover aspects related to taxonomy, curve matching with laboratory spectra, space weathering models, and mineralogical diagnosis. Results. M4AST project is fully available via a web interface. The database contains around 2700 spectra that can be either processed in M4AST and/or downloaded. The paper presents the algorithms we developed for spectral analyses based on existing methods. The robustness of routines is proven by the solutions found for spectra of three different asteroids: (9147) Kourakuen, (99 942) Apophis, and (175 706) 1996 FG3. The available results confirm those in the literature. M4AST applications can also be used to characterize any new asteroid spectra. Conclusions. M4AST is a robust and reliable tool dedicated to asteroid spectra.

Efficient closed-form solution to generalized boundary detection

Abstract: Boundary detection is essential for a variety of computer vision tasks such as segmentation and recognition. We propose a unified formulation for boundary detection, with closed-form solution, which is applicable to the localization of different types of boundaries, such as intensity edges and occlusion boundaries from video and RGB-D cameras. Our algorithm simultaneously combines low- and mid-level image representations, in a single eigenvalue problem, and we solve over an infinite set of putative boundary orientations. Moreover, our method achieves state of the art results at a significantly lower computational cost than current methods. We also propose a novel method for soft-segmentation that can be used in conjunction with our boundary detection algorithm and improve its accuracy at a negligible extra computational cost.

Solution Combustion Synthesis and Characterization of Magnetite, Fe3O4, Nanopowders

Abstract: Combustion synthesis of Fe3O4 and properties of the resulted powders have been discussed in relation to reaction atmosphere (in air/in the absence of air) and used fuel (sucrose, citric acid and glucose). Conducting the combustion reactions in air caused the rapid oxidation of Fe2+ to Fe3+ under the influence of the atmospheric oxygen; therefore the final reaction product was a mixture of α-Fe2O3 and γ-Fe2O3. In order to avoid the oxidation of Fe2+ to Fe3+ a simple but efficient solution has been suggested: combustion reactions were carried out in a round bottom flask and the evolving gases were bubbled in a beaker filled with water. This solution allowed the preparation of Fe3O4 nanopowders, with crystallite size varying from 10 nm (glucose) to 18 nm (citric acid). Depending on the used fuel, the specific surface area of the magnetite powders varied between 56 m2/g (citric acid) and 106 m2/g (glucose). The saturation magnetization of Fe3O4 powders prepared in the absence of air ranged between 55.3 emu/g (glucose) and 59.4 emu/g (sucrose).

Targeted drugs by olefin metathesis: piperidine-based iminosugars

Abstract: Examining advances in the class of natural and non-natural piperidine azasugars, important therapeutic agents and potent glycosidase inhibitors, this review looks at syntheses applying olefin metathesis as a highly efficient key step and gateway strategy for discovery of better iminosugar leads for treatment of widespread affections like viral and metabolic diseases. Amply illustrated is how ring-closing metathesis (RCM and RCEYM), promoted by commercial ruthenium alkylidene catalysts, manage to construct the common tetrahydropyridine core while cross-metathesis (CM), starting from this generic scaffold, provides general access to families of novel azasugars. Special consideration is given to high-profile iminosugar drugs of this class (1-deoxynojirimycin and congeners, adenophorine, fagomine, isofagomine and some of their N- and C-substituted analogues) stressing upon newest trends for enhancing biological activity and modulating previously unexploited targets in multispecific therapies.

Proteomic analysis of plasma membranes isolated from undifferentiated and differentiated HepaRG cells

Abstract: Liver infection with hepatitis B virus (HBV), a DNA virus of the Hepadnaviridae family, leads to severe disease, such as fibrosis, cirrhosis and hepatocellular carcinoma. The early steps of the viral life cycle are largely obscure and the host cell plasma membrane receptors are not known. HepaRG is the only proliferating cell line supporting HBV infection in vitro, following specific differentiation, allowing for investigation of new host host-cell factors involved in viral entry, within a more robust and reproducible environment. Viral infection generally begins with receptor recognition at the host cell surface, following highly specific cell-virus interactions. Most of these interactions are expected to take place at the plasma membrane of the HepaRG cells. In the present study, we used this cell line to explore changes between the plasma membrane of undifferentiated (−) and differentiated (+) cells and to identify differentially-regulated proteins or signaling networks that might potentially be involved in HBV entry. Our initial study identified a series of proteins that are differentially expressed in the plasma membrane of (−) and (+) cells and are good candidates for potential cell-virus interactions. To our knowledge, this is the first study using functional proteomics to study plasma membrane proteins from HepaRG cells, providing a platform for future experiments that will allow us to understand the cell-virus interaction and mechanism of HBV viral infection.

Dual role of lipoproteins in endothelial cell dysfunction in atherosclerosis.

Abstract: The endothelium is a key constituent of the vascular wall, being actively involved in maintaining the structural integrity and proper functioning of blood vessels. Hyperlipidemia, diabetes, hypertension, smoking and aging are important risk factors for the dysfunction of endothelial cells (EC). Circulating lipoproteins (Lp) synthesized and secreted from the intestine or liver have an important role in supplying peripheral tissues with fatty acids from triglyceride rich lipoproteins (TGRLp) for energy production or storage, and cholesterol from low density lipoproteins (LDL) or high density lipoproteins (HDL) for the synthesis of cellular membranes and steroid hormones. Under pathological conditions, Lp may suffer alterations in concentration and composition and become aggressors for EC. Modified LDL, remnant Lp, TGRLp lipolysis products, dysfunctional HDL are involved in the changes induced in EC morphology (reduced glycocalyx, overdeveloped endoplasmic reticulum, Golgi apparatus and basement membrane), loose intercellular junctions, increased oxidative and inflammatory stress, nitric oxide/redox imbalance, excess Lp transport and storage, as well as loss of anti-thrombotic properties, all of these being characteristics of endothelial dysfunction. Normal HDL are able to counteract the harmful effects of atherogenic Lp in EC but under persistent pathological conditions they lose the protective properties and become pro-atherogenic. This review summarises recent advances in understanding the role of Lp in the induction of endothelial dysfunction and the initiation and progression of atherosclerotic lesions. Its main focus is the antagonistic role of atherogenic Lp (LDL, VLDL, dysfunctional HDL) versus anti-atherogenic Lp (HDL), also pointing out the potential targets for arresting or reversing this process.

Low density polyethylene composites containing cellulose pulp fibers

Abstract: Unbleached and bleached Kraft cellulose pulp fibers modified with a long chain carboxylic acid, i.e. oleic acid in cold plasma conditions have been used as reinforcements in low density polyethylene (LDPE). The purpose of the modification is to enhance the interfacial adhesion between cellulose and matrix and to increase the dispersability. Composites containing up to 10 wt.% of untreated and modified cellulose pulp fibers with LDPE were prepared by melt mixing. The samples were characterized by processing behavior, mechanical and rheological properties, SEM, contact angle measurements, TGA and DSC. It was found that when the modified pulp fibers were incorporated into composites matrix, most of the properties have been improved.

Activation of ERAD Pathway by Human Hepatitis B Virus Modulates Viral and Subviral Particle Production

Abstract: Hepatitis B virus (HBV) belongs to the Hepadnaviridae family of enveloped DNA viruses. It was previously shown that HBV can induce endoplasmic reticulum (ER) stress and activate the IRE1-XBP1 pathway of the unfolded protein response (UPR), through the expression of the viral regulatory protein X (HBx). However, it remained obscure whether or not this activation had any functional consequences on the target genes of the UPR pathway. Of these targets, the ER degradation-enhancing, mannosidase-like proteins (EDEMs) are thought to play an important role in relieving the ER stress during UPR, by recognizing terminally misfolded glycoproteins and delivering them to the ER-associated degradation (ERAD). In this study, we investigated the role of EDEMs in the HBV life-cycle. We found that synthesis of EDEMs (EDEM1 and its homologues, EDEM2 and EDEM3) is significantly up-regulated in cells with persistent or transient HBV replication. Co-expression of the wild-type HBV envelope proteins with EDEM1 resulted in their massive degradation, a process reversed by EDEM1 silencing. Surprisingly, the autophagy/lysosomes, rather than the proteasome were involved in disposal of the HBV envelope proteins. Importantly, inhibition of the endogenous EDEM1 expression in HBV replicating cells significantly increased secretion of both, enveloped virus and subviral particles. This is the first report showing that HBV activates the ERAD pathway, which, in turn, reduces the amount of envelope proteins, possibly as a mechanism to control the level of virus particles in infected cells and facilitate the establishment of chronic infections.

Quasilinear elliptic non-homogeneous Dirichlet problems through Orlicz-Sobolev spaces

Abstract: In this paper, we are interested in the existence of infinitely many weak solutions for a non-homogeneous eigenvalue Dirichlet problem. By using variational methods, in an appropriate Orlicz–Sobolev setting, we determine intervals of parameters such that our problem admits either a sequence of non-negative weak solutions strongly converging to zero provided that the non-linearity has a suitable behaviour at zero or an unbounded sequence of non-negative weak solutions if a similar behaviour occurs at infinity.

Behaviour of cold-formed steel perforated sections in compression. Part 1—Experimental investigations

Abstract: This paper is the first part of a study devoted to interactive buckling of steel pallet racks compression members, carried out at the CEMSIG Research Centre 〈 http://cemsig.ct.upt.ro 〉 from “Politehnica” University of Timisoara; this part summarizes the experimental program [1] , [2] . Upright members of two different cross-sections, with and without perforations, were tested according to the guidelines of European design code for pallet rack systems EN15512 [3] , in order to determine the ultimate strength for specimens of length corresponding to local buckling, i.e. stub columns, and of length equal to the distance between two subsequent nodes of an upright frame, i.e. upright members. The last set of tests was devoted, mainly, to the observation of distortional buckling of upright members. However, depending on the cross-section dimensions, the length between two subsequent nodes can be often larger than distortional critical length. In such cases the test results correspond rather to the distortional–global interaction, than to pure distortion. Consequently, additional specimens having the length calibrated to correspond to distortional buckling and to interactive distortional-overall buckling range, respectively, were tested. Material tests and imperfection measurements were also performed.

[W(bipy)(CN)6]−: A Suitable Metalloligand in the Design of Heterotrimetallic Complexes. The First CuIILnIIIWV Trinuclear Complexes

Abstract: The first 3d–4f–5d heterotrimetallic complexes using [WV(bipy)(CN)6]− as a metalloligand were synthesized (bipy = 2,2′-bipyridine). The structural and magnetic properties of three [CuIILnIIIWV] complexes (Ln = Gd, Ho, Tb) are discussed.

Explaining fast ejections of plasma and exotic X-ray emission from the solar corona

Abstract: Coronal mass ejections (CMEs) are the most energetic events in the solar system and can make near-Earth space a hazardous place. However, there is still no consensus as to what physical mechanisms are responsible for these solar eruptions. Here we demonstrate a fundamental connection between the emergence of magnetic flux into the solar atmosphere and the formation of solar eruptions. We present a model of the dynamics of the solar atmosphere and inner solar wind region using a realistic representation of the electric field at the photosphere, calculated from flux-emergence computer simulations, as the boundary conditions. From this, we show how magnetic flux and helicity injection leads to the reorganization of the solar corona. We show evidence for the in situ formation of a CME plasmoid, which is independent of the emerging flux tube, and we conclusively connect this process to the formation of a hot X-ray structure.

New national and regional bryophyte records, 31

Abstract: 1. Andreaea nitida Hook.f. & WilsonContributors: H. Bednarek-Ochyra, R. Ochyra and M. LebouvierIles Kerguelen: Grande Terre, Peninsule Courbet, southern side of Val Studer: plateau at the south-eas...

Ni–Al layered double hydroxides as catalyst precursors for CO2 removal by methanation

Abstract: The effect of nickel content on the structure and activity of co-precipitated Ni–Al layered double hydroxides (LDHs) as catalyst precursors for CO2 removal by methanation was studied by variation of the Ni2+/Al3+ molar ratio (Ni2+/Al3+ = 3.0, 1.5 and 0.5), and of the reduction and reaction temperatures as well as of the space velocities. Powder X-ray diffraction (PXRD), H2 chemisorption, and temperature programmed reduction (TPR) techniques were applied for physicochemical characterization of the samples. It was specified that the nano-scaled dimensions of the as-synthesized samples also generate nano-metrical metallic nickel particles (PXRD). The existence of readily and hardly reducible Ni2+–O species in the studied samples (TPR), affects catalytic performance. The studied catalysts hydrogenate CO2 effectively to residual concentrations of the latter in the range of 0–10 ppm at reaction temperatures from 400 to 220 °C and space velocities between 22,000 and 3000 h−1. The variation of the CO2 methanation activity with the changes of space velocities depends on the nickel content, and reduction and reaction temperatures. After reduction at 400 and 450 °C, a sample of Ni2+/Al3+ = 3.0 has demonstrated the highest conversion degree at all the reaction temperatures and space velocities, while a catalyst of Ni2+/Al3+ = 0.5 dominated in the methanation activity after reduction within 530–600 °C. The Ni2+/Al3+ = 1.5 catalyst data take intermediate position between Ni2+/Al3+ = 3.0 and Ni2+/Al3+ = 0.5 often closer to Ni2+/Al3+ = 3.0 ones. The studied Ni–Al LDH systems are found to be promising catalyst precursors for fine CO2 removal from hydrogen-rich gas streams through the methanation reaction, depending on the technological regime of catalyst activation.

Fourier Kernel Learning

Abstract: Approximations based on random Fourier embeddings have recently emerged as an efficient and formally consistent methodology to design large-scale kernel machines [23]. By expressing the kernel as a Fourier expansion, features are generated based on a finite set of random basis projections, sampled from the Fourier transform of the kernel, with inner products that are Monte Carlo approximations of the original non-linear model. Based on the observation that different kernel-induced Fourier sampling distributions correspond to different kernel parameters, we show that a scalable optimization process in the Fourier domain can be used to identify the different frequency bands that are useful for prediction on training data. This approach allows us to design a family of linear prediction models where we can learn the hyper-parameters of the kernel together with the weights of the feature vectors jointly. Under this methodology, we recover efficient and scalable linear reformulations for both single and multiple kernel learning. Experiments show that our linear models produce fast and accurate predictors for complex datasets such as the Visual Object Challenge 2011 and ImageNet ILSVRC 2011.

Evidence of exposure to aristolochic acid in patients with urothelial cancer from a Balkan endemic nephropathy region of Romania.

Abstract: Recently, chronic Aristolochia poisoning was found responsible for the aetiology of Balkan endemic nephropathy (BEN) in Croatia, Serbia, and Bosnia, and diet was the likely route of exposure to aristolochic acid (AA). BEN, often associated with an increased incidence of upper urinary tract carcinoma (UUC), also affects residents of certain rural villages in Romania. AA is a nephrotoxin and human carcinogen that forms DNA adducts after metabolic activation, which induce characteristic TP53 mutations in urothelial tumours. Here we present the first evidence linking AA exposure to UUC in residents of an endemic region in the Romanian Mehedinti County. DNA was extracted from kidney and tumour tissue of seven patients who underwent nephroureterectomy for UUC and resided in BEN villages (endemic group). Five patients with UUC from nonendemic villages served as controls. AA-DNA adducts (7-(deoxyadenosin-N6-yl)-aristolactam I), established biomarkers of AA exposure, were identified by 32P-postlabelling in renal DNA of six patients from the endemic group and in one of the nonendemic group (adduct levels ranged from 0.3 to 6.5 adducts per 108 nucleotides). Additionally, an A to T transversion in TP53, a base substitution characteristic of AA mutagenic activity was found in urothelial tumour DNA of one patient from the endemic group. Our results provide a molecular link to the cause of urothelial tumours in BEN regions of Romania indicating that AA is the common aetiological agent for BEN across its numerous geographical foci. Environ. Mol. Mutagen., 2012. (c) 2012 Wiley Periodicals, Inc.

Tracheal telocytes

Abstract: Recently, a novel type of stromal cell – the telocytes (TC) – was identified in mouse trachea. These cells are known to possess the ultrastructural characteristics, which support their role in intercellular signaling. We found TC in all stromal compartments of the tracheal wall. TC with long prolongations (telopodes, Tp) were lining longitudinally the collagen bundles, and were serially arranged (end-to-end connections of Tp were found). Noteworthy, Tp frequently establish stromal synapses with mast cells (MC). Primary cilia were also identified in TC. In conclusion, tracheal TC could be involved in the tracheal regulation (e.g. secretion, contractility). The tandem TC-MC deserves further investigations.

The Dwarf project: Eclipsing binaries – precise clocks to discover exoplanets

Abstract: We present a new observational campaign, Dwarf, aimed at detection of circumbinary extrasolar planets using the timing of the minima of low-mass eclipsing binaries. The observations will be performed within an extensive network of relatively small to medium-size telescopes with apertures of similar to 20-200 cm. The starting sample of the objects to be monitored contains (i) low-mass eclipsing binaries with M and K components, (ii) short-period binaries with a sdB or sdO component, and (iii) post-common-envelope systems containing a WD, which enable to determine minima with high precision. Since the amplitude of the timing signal increases with the orbital period of an invisible third component, the timescale of the project is long, at least 5-10 years. The paper gives simple formulas to estimate the suitability of individual eclipsing binaries for the circumbinary planet detection. Intrinsic variability of the binaries (photospheric spots, flares, pulsation etc.) limiting the accuracy of the minima timing is also discussed. The manuscript also describes the best observing strategy and methods to detect cyclic timing variability in the minima times indicating the presence of circumbinary planets. First test observations of the selected targets are presented ((c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)