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Showing papers by "University of Mons published in 2012"


Journal ArticleDOI
TL;DR: In this paper, results from searches for the standard model Higgs boson in proton-proton collisions at 7 and 8 TeV in the CMS experiment at the LHC, using data samples corresponding to integrated luminosities of up to 5.8 standard deviations.

8,857 citations


Journal ArticleDOI
TL;DR: A critical review of the biophysicochemical properties of various nanomaterials with emphasis on currently available toxicology data and methodologies for evaluating nanoparticle toxicity suggests that NPs may need to be sequestered into products so that the NPs are not released into the atmosphere during the product's life or during recycling.
Abstract: Nanoscience has matured significantly during the last decade as it has transitioned from bench top science to applied technology. Presently, nanomaterials are used in a wide variety of commercial products such as electronic components, sports equipment, sun creams and biomedical applications. There are few studies of the long-term consequences of nanoparticles on human health, but governmental agencies, including the United States National Institute for Occupational Safety and Health and Japan's Ministry of Health, have recently raised the question of whether seemingly innocuous materials such as carbon-based nanotubes should be treated with the same caution afforded known carcinogens such as asbestos. Since nanomaterials are increasing a part of everyday consumer products, manufacturing processes, and medical products, it is imperative that both workers and end-users be protected from inhalation of potentially toxic NPs. It also suggests that NPs may need to be sequestered into products so that the NPs are not released into the atmosphere during the product's life or during recycling. Further, non-inhalation routes of NP absorption, including dermal and medical injectables, must be studied in order to understand possible toxic effects. Fewer studies to date have addressed whether the body can eventually eliminate nanomaterials to prevent particle build-up in tissues or organs. This critical review discusses the biophysicochemical properties of various nanomaterials with emphasis on currently available toxicology data and methodologies for evaluating nanoparticle toxicity (286 references).

1,138 citations


Journal ArticleDOI
16 Mar 2012-Science
TL;DR: In this paper, the electron-hole pair created via photon absorption in organic photoconversion systems must overcome the Coulomb attraction to achieve long-range charge separation, and this process is facilitated through the formation of excited, delocalized band states.
Abstract: The electron-hole pair created via photon absorption in organic photoconversion systems must overcome the Coulomb attraction to achieve long-range charge separation. We show that this process is facilitated through the formation of excited, delocalized band states. In our experiments on organic photovoltaic cells, these states were accessed for a short time (

1,023 citations


Journal ArticleDOI
29 Mar 2012
TL;DR: In this article, the authors reported results from searches for the standard model Higgs boson in proton-proton collisions at square root(s) = 7 TeV in five decay modes: gamma pair, b-quark pair, tau lepton pair, W pair, and Z pair.
Abstract: Combined results are reported from searches for the standard model Higgs boson in proton-proton collisions at sqrt(s)=7 TeV in five Higgs boson decay modes: gamma pair, b-quark pair, tau lepton pair, W pair, and Z pair. The explored Higgs boson mass range is 110-600 GeV. The analysed data correspond to an integrated luminosity of 4.6-4.8 inverse femtobarns. The expected excluded mass range in the absence of the standard model Higgs boson is 118-543 GeV at 95% CL. The observed results exclude the standard model Higgs boson in the mass range 127-600 GeV at 95% CL, and in the mass range 129-525 GeV at 99% CL. An excess of events above the expected standard model background is observed at the low end of the explored mass range making the observed limits weaker than expected in the absence of a signal. The largest excess, with a local significance of 3.1 sigma, is observed for a Higgs boson mass hypothesis of 124 GeV. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-600 (110-145) GeV is estimated to be 1.5 sigma (2.1 sigma). More data are required to ascertain the origin of this excess.

786 citations


Journal ArticleDOI
TL;DR: In this article, the performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 inverse picobarns of data collected in pp collisions at the LHC in 2010.
Abstract: The performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 inverse picobarns of data collected in pp collisions at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection criteria covering a wide range of physics analysis needs have been examined. For all considered selections, the efficiency to reconstruct and identify a muon with a transverse momentum pT larger than a few GeV is above 95% over the whole region of pseudorapidity covered by the CMS muon system, abs(eta)<2.4, while the probability to misidentify a hadron as a muon is well below 1%. The efficiency to trigger on single muons with pT above a few GeV is higher than 90% over the full eta range, and typically substantially better. The overall momentum scale is measured to a precision of 0.2% with muons from Z decays. The transverse momentum resolution varies from 1% to 6% depending on pseudorapidity for muons with pT below 100 GeV and, using cosmic rays, it is shown to be better than 10% in the central region up to pT = 1 TeV. Observed distributions of all quantities are well reproduced by the Monte Carlo simulation.

568 citations


Journal ArticleDOI
TL;DR: This study reveals that tension in central stress fibres is gradually generated by anisotropic force contraction dipoles, which expand as the cell elongates and spreads and proposes a simple mechanical model that quantitatively accounts for the experimental data and provides a conceptual framework for the mechanistic coordination between cell and nuclear shape.
Abstract: Actin filaments are involved in the modulation of nuclear shape and function, but mechanistic understanding of these processes is lacking. Versaevel et al. show that orientation and deformation of the nucleus are regulated by lateral compressive forces driven by tension in central actomyosin fibres.

515 citations


Journal ArticleDOI
TL;DR: The transverse momentum spectra of charged particles have been measured in pp and PbPb collisions at 2.76 TeV by the CMS experiment at the LHC as mentioned in this paper.
Abstract: The transverse momentum spectra of charged particles have been measured in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV by the CMS experiment at the LHC. In the transverse momentum range pt = 5-10 GeV/c, the charged particle yield in the most central PbPb collisions is suppressed by up to a factor of 5 compared to the pp yield scaled by the number of incoherent nucleon-nucleon collisions. At higher pt, this suppression is significantly reduced, approaching roughly a factor of 2 for particles with pt in the range pt=40-100 GeV/c.

446 citations


Journal ArticleDOI
TL;DR: In this paper, the key mechanisms of higher-spin extensions of ordinary gravities in four dimensions and higher are explained, and an overview of various no-go theorems for low-energy scattering of massless particles in flat spacetime is given.
Abstract: Aiming at nonexperts, the key mechanisms of higher-spin extensions of ordinary gravities in four dimensions and higher are explained. An overview of various no-go theorems for low-energy scattering of massless particles in flat spacetime is given. In doing so, a connection between the $S$-matrix and the Lagrangian approaches is made, exhibiting their relative advantages and weaknesses, after which potential loopholes for nontrivial massless dynamics are highlighted. Positive yes-go results for non-Abelian cubic higher-derivative vertices in constantly curved backgrounds are reviewed. Finally, how higher-spin symmetry can be reconciled with the equivalence principle in the presence of a cosmological constant leading to the Fradkin-Vasiliev vertices and Vasiliev's higher-spin gravity with its double perturbative expansion (in terms of numbers of fields and derivatives) is outlined.

383 citations


Journal ArticleDOI
Rasha Abbasi1, Y. Abdou2, T. Abu-Zayyad3, Markus Ackermann  +266 moreInstitutions (41)
18 Apr 2012-Nature
TL;DR: An upper limit on the flux of energetic neutrinos associated with GRBs that is at least a factor of 3.7 below the predictions is reported, implying either that GRBs are not the only sources of cosmic rays with energies exceeding 1018 electronvolts or that the efficiency of neutrino production is much lower than has been predicted.
Abstract: Very energetic astrophysical events are required to accelerate cosmic rays to above 10(18) electronvolts. GRBs (c-ray bursts) have been proposed as possible candidate sources(1-3). In the GRB 'fireball' model, cosmic-ray acceleration should be accompanied by neutrinos produced in the decay of charged pions created in interactions between the high-energy cosmic-ray protons and gamma-rays(4). Previous searches for such neutrinos found none, but the constraints were weak because the sensitivity was at best approximately equal to the predicted flux(5-7). Here we report an upper limit on the flux of energetic neutrinos associated with GRBs that is at least a factor of 3.7 below the predictions(4,8-10). This implies either that GRBs are not the only sources of cosmic rays with energies exceeding 10(18) electronvolts or that the efficiency of neutrino production is much lower than has been predicted.

342 citations


Journal ArticleDOI
Rasha Abbasi1, Y. Abdou2, T. Abu-Zayyad3, Markus Ackermann  +265 moreInstitutions (39)
TL;DR: DeepCore as discussed by the authors was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking physics data in May 2010.

317 citations


Journal ArticleDOI
TL;DR: In this article, an in-depth study of bilayer cells consisting of a donor/acceptor interface between zinc phthalocyanine (ZnPc) and fullerene (C60) is conducted and devices with the typically deposited standing up (edge-on) orientation are compared to those with ZnPC lying flat (face-on).
Abstract: The anisotropy inherent to many planar organic molecules leads to a high sensitivity of various fundamental processes to the orientation of molecules within films and at heterojunctions. Such processes include absorption, charge and exciton transport, energy levels, and charge transfer, all of which are critical to organic solar cell operation. Here,an in-depth study of bilayer cells consisting of a donor/acceptor interface between zinc phthalocyanine (ZnPc) and fullerene (C60) is conducted and devices with the typically deposited standing up (edge-on) orientation are compared to those with ZnPc lying flat (face-on). The face-on ZnPc-based device allows for an increase in all solar cell parameters, substantially increasing power conversion efficiency from 1.5% to 2.8%. Spectrally resolved photocurrent measurements reveal a >50% increase in ZnPc signal, from which only 12% is accounted for by the increase in absorption associated with the face-on orientation. The increase in internal quantum efficiency is accounted for via an improved charge transfer. The results of this study indicate that proper consideration of the orientation between donor and acceptor needs to be taken in order to fully optimize the numerous processes required for photovoltaic energy conversion.

Journal ArticleDOI
TL;DR: This review focuses on control strategies for robotic ankle systems in active and semiactive lower-limb orthoses, prostheses, and exoskeletons, with special attention to algorithms for gait phase identification, adaptation to different walking conditions, and motion intention recognition.

Journal ArticleDOI
TL;DR: In this paper, the suppression of individual nS states in PbPb collisions with respect to their yields in pp data has been measured, and the results demonstrate the sequential suppression of the Υ(nS) states from the dimuon invariant mass spectra.
Abstract: The suppression of the individual Υ(nS) states in PbPb collisions with respect to their yields in pp data has been measured. The PbPb and pp data sets used in the analysis correspond to integrated luminosities of 150 μb^(-1) and 230 nb^(-1), respectively, collected in 2011 by the CMS experiment at the LHC, at a center-of-mass energy per nucleon pair of 2.76 TeV. The Υ(nS) yields are measured from the dimuon invariant mass spectra. The suppression of the Υ(nS) yields in PbPb relative to the yields in pp, scaled by the number of nucleon-nucleon collisions, R_(AA), is measured as a function of the collision centrality. Integrated over centrality, the R_(AA) values are 0.56±0.08(stat)±0.07(syst), 0.12±0.04(stat)±0.02(syst), and lower than 0.10 (at 95% confidence level), for the Υ(1S), Υ(2S), and Υ(3S) states, respectively. The results demonstrate the sequential suppression of the Υ(nS) states in PbPb collisions at LHC energies.

Journal ArticleDOI
06 Jun 2012
TL;DR: In this article, the dijet momentum balance and angular correlations are studied as a function of collision centrality and leading jet transverse momentum for PbPb collisions at a nucleon-nucleon center-of-mass energy of 276 TeV.
Abstract: Dijet production in PbPb collisions at a nucleon–nucleon center-of-mass energy of 276 TeV is studied with the CMS detector at the LHC A data sample corresponding to an integrated luminosity of 150 μb−1 is analyzed Jets are reconstructed using combined information from tracking and calorimetry, using the anti-kT algorithm with R=03 The dijet momentum balance and angular correlations are studied as a function of collision centrality and leading jet transverse momentum For the most peripheral PbPb collisions, good agreement of the dijet momentum balance distributions with pp data and reference calculations at the same collision energy is found, while more central collisions show a strong imbalance of leading and subleading jet transverse momenta attributed to the jet-quenching effect The dijets in central collisions are found to be more unbalanced than the reference, for leading jet transverse momenta up to the highest values studied

Journal ArticleDOI
TL;DR: In this paper, the yields of both prompt and non-prompt J/psi, as well as Y(1S) mesons, are measured by the CMS experiment via their dimuon decays in PbPb and pp collisions at sqrt(sNN) = 2.76 TeV.
Abstract: Yields of prompt and non-prompt J/psi, as well as Y(1S) mesons, are measured by the CMS experiment via their dimuon decays in PbPb and pp collisions at sqrt(sNN) = 2.76 TeV for quarkonium rapidity |y|<2.4. Differential cross sections and nuclear modification factors are reported as functions of y and transverse momentum pt, as well as collision centrality. For prompt J/psi with relatively high pt (6.5

Journal ArticleDOI
TL;DR: In this paper, five state-of-the-art GCI detection algorithms are compared using six different databases with contemporaneous electroglottographic recordings as ground truth, and containing many hours of speech by multiple speakers.
Abstract: The pseudo-periodicity of voiced speech can be exploited in several speech processing applications. This requires however that the precise locations of the glottal closure instants (GCIs) are available. The focus of this paper is the evaluation of automatic methods for the detection of GCIs directly from the speech waveform. Five state-of-the-art GCI detection algorithms are compared using six different databases with contemporaneous electroglottographic recordings as ground truth, and containing many hours of speech by multiple speakers. The five techniques compared are the Hilbert Envelope-based detection (HE), the Zero Frequency Resonator-based method (ZFR), the Dynamic Programming Phase Slope Algorithm (DYPSA), the Speech Event Detection using the Residual Excitation And a Mean-based Signal (SEDREAMS) and the Yet Another GCI Algorithm (YAGA). The efficacy of these methods is first evaluated on clean speech, both in terms of reliabililty and accuracy. Their robustness to additive noise and to reverberation is also assessed. A further contribution of the paper is the evaluation of their performance on a concrete application of speech processing: the causal-anticausal decomposition of speech. It is shown that for clean speech, SEDREAMS and YAGA are the best performing techniques, both in terms of identification rate and accuracy. ZFR and SEDREAMS also show a superior robustness to additive noise and reverberation.

Journal ArticleDOI
21 Sep 2012
TL;DR: In this paper, a search was made for events containing an energetic jet and an imbalance in transverse momentum using a data sample of pp collisions at a center-of-mass energy of 7 TeV.
Abstract: A search has been made for events containing an energetic jet and an imbalance in transverse momentum using a data sample of pp collisions at a center-of-mass energy of 7 TeV. This signature is common to both dark matter and extra dimensions models. The data were collected by the CMS detector at the LHC and correspond to an integrated luminosity of 5.0 inverse femtobarns. The number of observed events is consistent with the standard model expectation. Constraints on the dark matter-nucleon scattering cross sections are determined for both spin-independent and spin-dependent interaction models. For the spin-independent model, these are the most constraining limits for a dark matter particle with mass below 3.5 GeV, a region unexplored by direct detection experiments. For the spin-dependent model, these are the most stringent constraints over the 0.1-200 GeV mass range. The constraints on the Arkani-Hamed, Dimopoulos, and Dvali model parameter MD determined as a function of the number of extra dimensions are also an improvement over the previous results.

Journal ArticleDOI
S. Chatrchyan, Vardan Khachatryan, Albert M. Sirunyan, A. Tumasyan  +2247 moreInstitutions (138)
12 Apr 2012
TL;DR: In this article, a search for a Higgs boson decaying into two photons is described using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns.
Abstract: A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.

Journal ArticleDOI
TL;DR: In this article, the authors highlight recent and most important approaches to form monolayers and to subsequently elaborate homogeneous and heterogeneous coatings of polymer brushes by surface-initiated polymerization.

Journal ArticleDOI
TL;DR: In this article, bionanocomposites based on renewable cellulose nanowhiskers (CNWs) as nanofillers and renewable poly( l -lactide) (PLA) as polymeric matrix were successfully and straightforwardly prepared using melt-extrusion technique.

Journal ArticleDOI
S. Chatrchyan1, Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1  +3905 moreInstitutions (138)
TL;DR: Spectra of identified charged hadrons are measured in pp collisions at the LHC for sqrt(s) = 0.9, 2.76, and 7 TeV as mentioned in this paper.
Abstract: Spectra of identified charged hadrons are measured in pp collisions at the LHC for sqrt(s) = 0.9, 2.76, and 7 TeV. Charged pions, kaons, and protons in the transverse-momentum range pt approximately 0.1-1.7 GeV and for rapidities abs(y) < 1 are identified via their energy loss in the CMS silicon tracker. The average pt increases rapidly with the mass of the hadron and the event charged-particle multiplicity, independently of the center-of-mass energy. The fully corrected pt spectra and integrated yields are compared to various tunes of the PYTHIA6 and PYTHIA8 event generators.

Journal ArticleDOI
TL;DR: In this article, a search for a light charged Higgs boson that can be produced in the decay of the top quark to charged H and b quark and which, in turn, decays into tau and tau neutrino is presented.
Abstract: Results are presented on a search for a light charged Higgs boson that can be produced in the decay of the top quark to charged H and b quark and which, in turn, decays into tau and tau neutrino. The analysed data correspond to an integrated luminosity of about 2 inverse femtobarns recorded in proton-proton collisions at sqrt(s) = 7 TeV by the CMS experiment at the LHC. The search is sensitive to the decays of the top quark pairs t anti-t to charged Higgs W b anti-b and t anti-t to charged Higgs b anti-b. Various final states have been studied separately, all requiring presence of a tau lepton from charged Higgs decays, missing transverse energy, and multiple jets. Upper limits on the branching fraction B(t to charged Higgs b) in the range of 2-3% are established for charged Higgs boson masses between 80 and 160 GeV, under the assumption that B(charged Higgs to tau anti-tau neutrino) = 1.

Journal ArticleDOI
TL;DR: In this article, a measurement of the single-top-quark t-channel production cross section in pp collisions at s√=7 TeV with the CMS detector at the LHC is presented.
Abstract: A measurement of the single-top-quark t-channel production cross section in pp collisions at s√=7 TeV with the CMS detector at the LHC is presented. Two different and complementary approaches have been followed. The first approach exploits the distributions of the pseudorapidity of the recoil jet and reconstructed top-quark mass using background estimates determined from control samples in data. The second approach is based on multivariate analysis techniques that probe the compatibility of the candidate events with the signal. Data have been collected for the muon and electron final states, corresponding to integrated luminosities of 1.17 and 1.56 fb^(−1), respectively. The single-top-quark production cross section in the t-channel is measured to be 67.2±6.1 pb, in agreement with the approximate next-to-next-to-leading-order standard model prediction. Using the standard model electroweak couplings, the CKM matrix element |V_(tb)| is measured to be 1.020 ± 0.046 (meas.) ± 0.017 (theor.).

Journal ArticleDOI
21 Jun 2012
TL;DR: In this paper, a search for neutral Higgs bosons decaying to tau pairs at a center-of-mass energy of 7 TeV is performed using a dataset corresponding to an integrated luminosity of 4.6 fb^(−1) recorded by the CMS experiment at the LHC.
Abstract: A search for neutral Higgs bosons decaying to tau pairs at a center-of-mass energy of 7 TeV is performed using a dataset corresponding to an integrated luminosity of 4.6 fb^(−1) recorded by the CMS experiment at the LHC. The search is sensitive to both the standard model Higgs boson and to the neutral Higgs bosons predicted by the minimal supersymmetric extension of the standard model (MSSM). No excess of events is observed in the tau-pair invariant-mass spectrum. For a standard model Higgs boson in the mass range of 110–145 GeV upper limits at 95% confidence level (CL) on the production cross section are determined. We exclude a Higgs boson with m_H=115 GeV with a production cross section 3.2 times of that predicted by the standard model. In the MSSM, upper limits on the neutral Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, m_A, sets stringent new bounds in the parameter space, excluding at 95% CL values of tan β as low as 7.1 at m_A=160 GeV in the m^(max)_h benchmark scenario.

Journal ArticleDOI
S. Chatrchyan1, Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1  +4135 moreInstitutions (167)
TL;DR: In this article, measurements from the CMS experiment at the LHC of dihadron correlations for charged particles produced in PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV are presented.
Abstract: Measurements from the CMS experiment at the LHC of dihadron correlations for charged particles produced in PbPb collisions at a nucleon-nucleon centre-of-mass energy of 2.76 TeV are presented. The results are reported as a function of the particle transverse momenta (pt) and collision centrality over a broad range in relative pseudorapidity [Delta(eta)] and the full range of relative azimuthal angle [Delta(phi)]. The observed two-dimensional correlation structure in Delta(eta) and Delta(phi) is characterised by a narrow peak at Delta(eta), Delta(phi) approximately (0, 0) from jet-like correlations and a long-range structure that persists up to at least |Delta(eta)| = 4. An enhancement of the magnitude of the short-range jet peak is observed with increasing centrality, especially for particles of pt around 1-2 GeV/c. The long-range azimuthal dihadron correlations are extensively studied using a Fourier decomposition analysis. The extracted Fourier coefficients are found to factorise into a product of single-particle azimuthal anisotropies up to pt approximately 3-3.5 GeV/c for at least one particle from each pair, except for the second-order harmonics in the most central PbPb events. Various orders of the single-particle azimuthal anisotropy harmonics are extracted for associated particle pt of 1-3 GeV/c, as a function of the trigger particle pt up to 20 GeV/c and over the full centrality range.

Journal ArticleDOI
TL;DR: The structure and properties of PBSFs can be tuned ranging from crystalline polymers possessing good tensile modulus and strength to nearly amorphous polymer of low T(g) and high elongation (~600%), and therefore they may find applications in thermoplastics as well as elastomers or impact modifiers.

Journal ArticleDOI
TL;DR: In this paper, the normalized rapidity (y) and transverse momentum (qT) distributions of Drell-Yan muon and electron pairs in the Z-boson mass region (60
Abstract: Measurements of the normalized rapidity (y) and transverse momentum (qT) distributions of Drell-Yan muon and electron pairs in the Z-boson mass region (60

Journal ArticleDOI
TL;DR: This study is focused on the direct relationship between the size and magnetization of the particles and their nuclear magnetic resonance relaxation properties, which condition their efficiency.
Abstract: Magnetic particles are very efficient magnetic resonance imaging (MRI) contrast agents. In recent years, chemists have unleashed their imagination to design multi-functional nanoprobes for biomedical applications including MRI contrast enhancement. This study is focused on the direct relationship between the size and magnetization of the particles and their nuclear magnetic resonance relaxation properties, which condition their efficiency. Experimental relaxation results with maghemite particles exhibiting a wide range of sizes and magnetizations are compared to previously published data and to well-established relaxation theories with a good agreement. This allows deriving the experimental master curve of the transverse relaxivity versus particle size and to predict the MRI contrast efficiency of any type of magnetic nanoparticles. This prediction only requires the knowledge of the size of the particles impermeable to water protons and the saturation magnetization of the corresponding volume. To predict the T(2) relaxation efficiency of magnetic single crystals, the crystal size and magnetization - obtained through a single Langevin fit of a magnetization curve - is the only information needed. For contrast agents made of several magnetic cores assembled into various geometries (dilute fractal aggregates, dense spherical clusters, core-shell micelles, hollow vesicles…), one needs to know a third parameter, namely the intra-aggregate volume fraction occupied by the magnetic materials relatively to the whole (hydrodynamic) sphere. Finally a calculation of the maximum achievable relaxation effect - and the size needed to reach this maximum - is performed for different cases: maghemite single crystals and dense clusters, core-shell particles (oxide layer around a metallic core) and zinc-manganese ferrite crystals.

Journal ArticleDOI
10 Jan 2012-PLOS ONE
TL;DR: The modification of conventional toxicity assays and the consideration of the “cell vision” concept are crucial matters to obtain reliable, and reproducible nanotoxicology data and offer a suitable way to obtain a deep understanding on the cell-NP interactions.
Abstract: Until now, the results of nanotoxicology research have shown that the interactions between nanoparticles (NPs) and cells are remarkably complex. In order to get a deep understanding of the NP-cell interactions, scientists have focused on the physicochemical effects. However, there are still considerable debates about the regulation of nanomaterials and the reported results are usually in contradictions. Here, we are going to introduce the potential key reasons for these conflicts. In this case, modification of conventional in vitro toxicity assays, is one of the crucial ignored matter in nanotoxicological sciences. More specifically, the conventional methods neglect important factors such as the sedimentation of NPs and absorption of proteins and other essential biomolecules onto the surface of NPs. Another ignored matter in nanotoxicological sciences is the effect of cell “vision” (i.e., cell type). In order to show the effects of these ignored subjects, we probed the effect of superparamagnetic iron oxide NPs (SPIONs), with various surface chemistries, on various cell lines. We found thatthe modification of conventional toxicity assays and the consideration of the “cell vision” concept are crucial matters to obtain reliable, and reproducible nanotoxicology data. These new concepts offer a suitable way to obtain a deep understanding on the cell-NP interactions. In addition, by consideration of these ignored factors, the conflict of future toxicological reports would be significantly decreased.

Journal ArticleDOI
TL;DR: In this article, the UV/Vis properties of 33 polyphenols were systematically investigated, including mainly flavonoids, isoflavonoids and flavonolignans.