706 research outputs found
A Three Dimensional Analysis of Au-Silica Core-Shell Nanoparticles Using Medium Energy Ion Scattering
The medium energy ion scattering (MEIS) facility at the IIAA Huddersfield has been used
for the analysis of a monolayer of Au-silica core-shell nanoparticles deposited on Si substrate.
Both spherical and rod shape particles were investigated and the spectra produced by 100 keV He+
ions scattered through angles of 90º and 125º were compared with the results of RBS-MAST [1]
simulations performed on artificial 3D model cells containing the nanoparticles. The thickness of
the silica shell, the diameter of the Au spheres, and the diameter and length of the Au nano-rods
were determined from best fits of the measured set of MEIS spectra.
In addition, the effect of ion irradiation on the silica shell and gold core was monitored by
MEIS measurements in conjunction with RBS-MAST simulations. Ion bombardment was
performed under largely different conditions, i.e., by 30 keV Ar+, 150 keV Fe+, or 2.8 MeV N+
ions in the dose range of 2×1015 - 2×1016 cm-2. Significant changes in the particle geometry can be
observed due to ion beam-induced sputtering and recoil effects, the significance of which was
estimated from full-cascade SRIM simulations.
Rutherford backscattering spectrometry (RBS), Field emission scanning electron microscopy
(FESEM), and Atomic Force Microscopy (AFM) techniques have been applied as complementary
characterization tools to monitor the amount of gold and surface morphology on the un-irradiated
and irradiated sample areas. We show that MEIS can yield spatial information on the geometrical
changes of particulate systems at the nanometre scale
Dependence of the flux creep activation energy on current density and magnetic field for MgB2 superconductor
Systematic ac susceptibility measurements have been performed on a MgB
bulk sample. We demonstrate that the flux creep activation energy is a
nonlinear function of the current density , indicating a
nonlogarithmic relaxation of the current density in this material. The
dependence of the activation energy on the magnetic field is determined to be a
power law , showing a steep decline in the activation
energy with the magnetic field, which accounts for the steep drop in the
critical current density with magnetic field that is observed in MgB. The
irreversibility field is also found to be rather low, therefore, the pinning
properties of this new material will need to be enhanced for practical
applications.Comment: 11 pages, 6 figures, Revtex forma
Resummation in nonlinear equation for high energy factorizable gluon density and its extension to include coherence
Motivated by forthcoming p-Pb experiments at Large Hadron Collider which
require both knowledge of gluon densities accounting for saturation and for
processes at a wide range of we study basic momentum space evolution
equations of high energy QCD factorization. Solutions of those equations might
be used to form a set of gluon densities to calculate observables in
generalized high energy factorization. Moreover in order to provide a framework
for predictions for exclusive final states in p-Pb scattering with high
we rewrite the equation for the high energy factorizable gluon density in a
resummed form, similarly to what has been done in \cite{Kutak:2011fu} for the
BK equation. The resummed equation is then extended to account for colour
coherence. This introduces an external scale to the evolution of the gluon
density, and therefore makes it applicable in studies of final states.Comment: 14 pages, appendix added, accepted for publication in JHE
Bispecific PD1-IL2v and anti-PD-L1 break tumor immunity resistance by enhancing stem-like tumor-reactive CD8<sup>+</sup> T cells and reprogramming macrophages.
Immunotherapies have shown remarkable, albeit tumor-selective, therapeutic benefits in the clinic. Most patients respond transiently at best, highlighting the importance of understanding mechanisms underlying resistance. Herein, we evaluated the effects of the engineered immunocytokine PD1-IL2v in a mouse model of de novo pancreatic neuroendocrine cancer that is resistant to checkpoint and other immunotherapies. PD1-IL2v utilizes anti-PD-1 as a targeting moiety fused to an immuno-stimulatory IL-2 cytokine variant (IL2v) to precisely deliver IL2v to PD-1 <sup>+</sup> T cells in the tumor microenvironment. PD1-IL2v elicited substantial infiltration by stem-like CD8 <sup>+</sup> T cells, resulting in tumor regression and enhanced survival in mice. Combining anti-PD-L1 with PD1-IL2v sustained the response phase, improving therapeutic efficacy both by reprogramming immunosuppressive tumor-associated macrophages and enhancing T cell receptor (TCR) immune repertoire diversity. These data provide a rationale for clinical trials to evaluate the combination therapy of PD1-IL2v and anti-PD-L1, particularly in immunotherapy-resistant tumors infiltrated with PD-1 <sup>+</sup> stem-like T cells
On the quark component in prompt photon and electroweak gauge boson production at high energies
In the framework of the kt-factorization approach, we study the production of
prompt photons and electroweak gauge bosons in high energy proton-(anti)proton
collisions at modern colliders. Our consideration is based on the amplitude for
the production of a single photon or W/Z boson associated with a quark pair in
the fusion of two off-shell gluons. The quark component is taken into account
separately using the quark-gluon scaterring and quark-antiquark annihilation
QCD subprocesses. Special attention is put on the contributions from the quarks
involved into the earlier steps of the evolution cascade. Using the
Kimber-Martin-Ryskin formalism, we simulate this component and demonstrate that
it plays an important role at both the Tevatron and LHC energies. Our
theoretical results are compared with recent experimental data taken by the D0
and CDF collaborations at the Tevatron.Comment: 16 pages, 9 figure
Atomic-scale visualization of initial growth of homoepitaxial SrTiO3 thin film on an atomically ordered substrate
The initial homoepitaxial growth of SrTiO3 on a (\surd13\times\surd13) -
R33.7{\deg}SrTiO3(001) substrate surface, which can be prepared under oxide
growth conditions, is atomically resolved by scanning tunneling microscopy. The
identical (\surd13\times\surd13) atomic structure is clearly visualized on the
deposited SrTiO3 film surface as well as on the substrate. This result
indicates the transfer of the topmost Ti-rich (\surd13\times\surd13) structure
to the film surface and atomic-scale coherent epitaxy at the film/substrate
interface. Such atomically ordered SrTiO3 substrates can be applied to the
fabrication of atom-by-atom controlled oxide epitaxial films and
heterostructures
Terahertz underdamped vibrational motion governs protein-ligand binding in solution
Low-frequency collective vibrational modes in proteins have been proposed as being responsible for efficiently directing biochemical reactions and biological energy transport. However, evidence of the existence of delocalized vibrational modes is scarce and proof of their involvement in biological function absent. Here we apply extremely sensitive femtosecond optical Kerr-effect spectroscopy to study the depolarized Raman spectra of lysozyme and its complex with the inhibitor triacetylchitotriose in solution. Underdamped delocalized vibrational modes in the terahertz frequency domain are identified and shown to blue-shift and strengthen upon inhibitor binding. This demonstrates that the ligand-binding coordinate in proteins is underdamped and not simply solvent-controlled as previously assumed. The presence of such underdamped delocalized modes in proteins may have significant implications for the understanding of the efficiency of ligand binding and protein–molecule interactions, and has wider implications for biochemical reactivity and biological function
Lack of Matrilin-2 Favors Liver Tumor Development via Erk1/2 and GSK-3 beta Pathways In Vivo
Matrilin-2 (Matn2) is a multidomain adaptor protein which plays a role in the assembly of extracellular matrix (ECM). It is produced by oval cells during stem cell-driven liver regeneration. In our study, the impact of Matn2 on hepatocarcinogenesis was investigated in Matn2(-/-) mice comparing them with wild-type (WT) mice in a diethylnitrosamine (DEN) model. The liver tissue was analyzed macroscopically, histologically and immunohistochemically, at protein level by Proteome Profiler Arrays and Western blot analysis. Matn2(-/-) mice exhibited higher susceptibility to hepatocarcinogenesis compared to wild-type mice. In the liver of Matn2(-/-) mice, spontaneous microscopic tumor foci were detected without DEN treatment. After 15 mu g/g body weight DEN treatment, the liver of Matn2(-/-) mice contained macroscopic tumors of both larger number and size than the WT liver. In contrast with the WT liver, spontaneous phosphorylation of EGFR, Erk1/2 GSK-3 alpha/beta and retinoblastoma protein (p-Rb), decrease in p21/CIP1 level, and increase in beta-Catenin protein expression were detected in Matn2(-/-) livers. Focal Ki-67 positivity of these samples provided additional support to our presumption that the lack of Matn2 drives the liver into a pro-proliferatory state, making it prone to tumor development. This enhanced proliferative capacity was further increased in the tumor nodules of DEN-treated Matn2(-/-) livers. Our study suggests that Matn2 functions as a tumor suppressor in hepatocarcinogenesis, and in this process activation of EGFR together with that of Erk1/2, as well as inactivation of GSK-3 beta, play strategic roles
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