148 research outputs found
Anomalous Couplings in the Process
No full textWe discuss experimental aspects related to the possible existence of anomalous ZZV couplings (V=Z,gamma) in the ee->ZZ process. We find that, among several options, the optimal procedure to quantify their presence requires the inclusion of anomalous couplings in a complete four-fermion final-state generator. Various comparisons and checks proof the correctness of our calculations at the percent level.We discuss experimental aspects related to the process and to the search for anomalous ZZV couplings (V) at LEP2 and future colliders. We present two possible approaches for a realistic study of the reaction and discuss the differences between them. We find that the optimal method to study double Z resonant production and to quantify the presence of anomalous couplings requires the use of a complete four-fermion final-state calculation
Investigating the impact of gold nanoparticles on cells: from transcription to behavior
No full textGold nanoparticles (Au NPs) are being research extensively for various biomedical applications; their applicability arises from a unique set of optical and physical properties brought on by their nanoscale dimensions.1 Furthermore, facile and scalable synthetic and surface functionalization strategies for Au NPs make these properties highly tunable.1 These areas of research are still relatively new and the number of publications per year referring to gold nanomaterials has skyrocketed from 11 in 1990, to 673 in 2000, to more than 31,400 in 2015 (Web of Science database, topic search = “gold nano*”, accessed March 2, 2016). The potential application of Au NPs for disease detection, diagnosis and therapy has motivated numerous analyses of their interactions with biomolecules, cells, animals, humans and the environment.1,2 A vast majority of studies aimed at gaining a better understanding of how cells interact with and are influenced by Au NPs have focused mainly on measuring cytotoxicity and simple cell processes like proliferation or NP uptake. While Au NPs larger than 4-5 nm in diameter (with appropriate, non-toxic surface coatings) have been shown to be largely non-cytotoxic, there can be subtle non-toxic effects induced by Au NPs.3 The adsorption of soluble proteins onto NP surfaces (the protein corona) is highly studied, but little attention has been paid to how those interactions perturb gene expression of cells or to understanding NP interactions with other types of biomolecules. This thesis aims to look deeper into how molecular level effects of NPs in cells and cellular environments can lead to down-stream changes to cell gene expression and behavior.
Firstly, the impact of Au nanorods (Au NRs) on 3D cancer cell migration via interactions between Au NRs and extracellular matrix (ECM) structural proteins was examined.4 While experiments on the influence of NPs on cell behaviors exist, nearly all of these studies neglect the impact of the ECM. In vivo cells exist in complex, fibrous 3D environments and series of intricate biochemical, cell-cell and cell-ECM interactions govern behaviors such as migration. Cancer cell migration allows tumor cells to spread and metastasize to new areas of the body, but little is known about how Au NR interaction with the ECM after injection and targeting to tumors may affect this process. The inevitable contact of in vivo Au NRs with the ECM presents a possible source of unintended side effects. In order to study how gold nanoparticles can influence ECM properties and cell-ECM interactions, we have created a nested-gel type I collagen matrix for measuring whether Au NRs alter the migration of MDA-MB-231 human breast cancer cells in 3D collagen environments. In contrast to the few studies of Au NR-induced migration changes in 2D environments, our results show that Au NRs in a model ECM increase the frequency of spontaneous cellular migration. The presence of negatively-charged polyelectrolyte-coated Au NRs during the collagen self-assembly process was shown to induce mechanical and structural changes, to alter molecular diffusion, and to affect cellular adhesion, morphology, locomotion strategy and protease expression. The results demonstrate the indirect impact nanoparticles can exert on cell behaviors within three-dimensional ECMs.
The shape and surface chemistry of Au NPs was also investigated in terms of the role of these factors in cellular transcriptomic (gene expression) responses after both short- and long-term exposures.5 Respectively, human dermal fibroblasts (HDF) and prostate cancer (PC3) cells were exposed to 0.1 nM (24 hours) and 1.0 nM (48 hours) concentrations of Au NPs of four different, but related surface chemistries. A combination of microarray gene expression analysis techniques and typical cellular characterization was used to learn more about how the nature of the Au NP surface coating influences cells on a molecular level. Identity, charge and lability of surface coatings (and cell type and dosing parameters) were all implicated as important factors to consider in order to predict gene expression responses. In a separate study, HDF cells were exposed to 0.1 nM (low-dose) Au NPs of different shapes and surface coatings for 20 weeks. The long-term effects of acute (24 hour) and chronic (20 weeks) exposure were measured by viability, proliferation, NP uptake, and morphology studies combined with gene expression analysis of genes related to stress and toxicity pathways. It is rare to find chronic exposure studies, especially with Au NPs, and these experiments showed that acute, sub-cytotoxic doses of NPs may induce long-term stress on cells. These cells were found to react very differently to acute versus chronic doses of the same NPs after 20 weeks. Additionally, surface coating was shown to have a much larger impact on determining NP-cell interactions than shape of Au NPs. In all, we have expanded the collective understanding of the molecular interactions Au NPs experience inside cells based on surface chemistry, shape, dosage and exposure time and parameters.
References
1. Dreaden, E.C.; Alkilany, A.M.; Huang, X.; Murphy, C.J.; El-Sayed, M.A. The Golden Age: Gold Nanoparticles for Biomedicine. Chem. Soc. Rev. 2012, 41, 2740–2779.
2. Yang, X.; Yang, M.; Pang, B.; Vara, M.; Xia, Y. Gold Nanomaterials at Work in Biomedicine. Chem. Rev. 2015, 115, 10410–10488.
3. Alkilany, A.M.; Lohse, S.E.; Murphy, C.J. The Gold Standard: Gold Nanoparticle Libraries to Understand the Nano-Bio Interface. Acc. Chem. Res. 2013, 46, 650–661.
4. Grzincic, E.M.; Murphy, C.J. Gold Nanorods Indirectly Promote Migration of Metastatic Human Breast Cancer Cells in Three-Dimensional Cultures. ACS Nano 2015, 9, 6801–6816.
5. Grzincic, E.M.; Yang, J.A.; Drnevich, J.; Falagan-Lotsch, P.; Murphy, C.J. Global Transcriptomic Analysis of Model Human Cell Lines Exposed to Surface-Modified Gold Nanoparticles: The Effect of Surface Chemistry. Nanoscale 2015, 7, 1349–1362.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-05-01The student, Elissa Grzincic, accepted the attached license on 2016-04-14 at 19:38.The student, Elissa Grzincic, submitted this Dissertation for approval on 2016-04-14 at 19:46.This Dissertation was approved for publication on 2016-04-19 at 08:16.DSpace SAF Submission Ingestion Package generated from Vireo submission #9234 on 2016-07-07 at 14:16:45Made available in DSpace on 2016-07-07T21:14:44Z (GMT). No. of bitstreams: 3
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Test of the tau-model of Bose-Einstein correlations and reconstruction of the source function in hadronic Z-boson decay at LEP
No full textBose–Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using a Lévy stable distribution in conjunction with a model where a particle’s momentum is correlated with its space–time point of production, the τ-model. Using this description and the measured rapidity and transverse momentum distributions, the space–time evolution of particle emission in two-jet events is reconstructed. However, the elongation of the particle emission region previously observed is not accommodated in the τ-model, and this is investigated using an ad hoc modification
Search for scalar leptons and scalar quarks at LEP
No full textScalar partners of quarks and leptons, predicted in supersymmetric models, are searched for in e(+)e(-) collisions at centre-of-mass energies between 192 and 209 GeV at LEP. No evidence for any such particle is found in a data sample of 450 pb(-1). Upper limits on their production cross sections are set and lower limits on their masses are derived in the framework of the Minimal Supersymmetric Standard Model. (C) 2003 Published by Elsevier B.V
Measurement of the mass and the width of the W boson at LEP
No full textThe mass and the total decay width of the W boson are measured with the L3 detector at the LEP e(+)e(-) collider using W-boson pairs produced in 0.7 fb(-1) of data collected at centre-of-mass energies between 161 and 209 GeV. Combining semi-leptonic and fully-hadronic final states, the mass and the width of the W boson are determined to be m(W) = 80.270 +/- 0.046 +/- 0.031 GeV and Gamma(W) = 2.18 +/- 0.11 +/- 0.09 GeV , where the first uncertainty is statistical and the second systematic
Study of inclusive strange-baryon production and search for pentaquarks in two-photon collisions at LEP
No full textMeasurements of inclusive production of the Lambda, Xi(-) and Xi*(1530) baryons in two-photon collisions with the L3 detector at LEP are presented. The inclusive differential cross sections for Lambda and Xi(-) are measured as a function of the baryon transverse momentum, p(t), and pseudo-rapidity, eta. The mean number of Lambda, Xi(-) and Xi*(1530) baryons per hadronic two-photon event is determined in the kinematic range 0.4 GeV \u3c p(t) \u3c 2.5GeV, vertical bar eta vertical bar \u3c 1.2. Overall agreement with the theoretical models and Monte Carlo predictions is observed. A search for inclusive production of the pentaquark theta(+)(1540) in two-photon collisions through the decay theta(+) -\u3e pK(S)(0) is also presented. No evidence for production of this state is found
Measurement of hadron and lepton-pair production in e(+)e(-) collisions at root s=192-208 GeV at LEP
No full textHadron production and lepton-pair production in e(+)e(-) collisions are studied with data collected with the L3 detector at LEP at centre-of-mass energies root s = 192-208 GeV. Using a total integrated luminosity of 453 pb(-1), 36057 hadronic events and 12863 lepton-pair events are selected. The cross sections for hadron production and lepton-pair production are measured for the full sample and for events where no high-energy initial-state-radiation photon is emitted prior to the collisions. Lepton-pair events are further investigated and forward-backward asymmetries are measured. Finally, the differential cross sections for electron-positron pair-production is determined as a function of the scattering angle. An overall good agreement is found with Standard Model predictions
Analysis of the pi(+) pi(-) pi(+)pi(-) and pi(+)pi(0) pi(-) pi(0) final states in quasi-real two-photon collisions at LEP
No full textThe reactions gamma gamma -\u3e pi(+)pi(-)pi(+)pi(-) and gamma gamma -\u3e pi(+)pi(0)pi(-)pi(0) are studied with the L3 detector at LEP in a data sample collected at centre-of-mass energies from 161 GeV to 209 GeV with a total integrated luminosity of 698 pb(-1). A spin-parity-helicity analysis of the rho(0)rho(0) and p(+)p(-) systems for two-photon centre-of-mass energies between 1 and 3 GeV shows the dominance of the spin-parity state 2(+) with helicity 2. The contribution of 0(+) and 0(-) spin-parity states is also observed, whereas contributions of 2(-) states and of a state with spin-parity 2(+) and zero helicity are found to be negligible. (c) 2006 Elsevier B.V. All rights reserved
Generalized event shape and energy flow studies in e+e− annihilation at √s=912−2080 GeV
No full textWe present results from a study of hadronic event structure in high energy e(+)e(-') interactions using the L3 detector at LEP. A new class of event shape distributions are measured at and above the Z boson pole for light quark (u, d, s, c) flavours. Energy flow correlations are studied for all hadronic events. Next-to-leading-log QCD calculations and QCD models with improved leading-log approximations are compared to data and good agreement is found at the Z-pole whereas some discrepancies are observed at higher centre-of-mass energies
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