4,647 research outputs found
Low-Temperature Excitations of Dilute Lattice Spin Glasses
A new approach to exploring low-temperature excitations in finite-dimensional
lattice spin glasses is proposed. By focusing on bond-diluted lattices just
above the percolation threshold, large system sizes can be obtained which
lead to enhanced scaling regimes and more accurate exponents. Furthermore, this
method in principle remains practical for any dimension, yielding exponents
that so far have been elusive. This approach is demonstrated by determining the
stiffness exponent for dimensions , (the upper critical dimension),
and . Key is the application of an exact reduction algorithm, which
eliminates a large fraction of spins, so that the reduced lattices never exceed
variables for sizes as large as L=30 in , L=9 in , or L=8
in . Finite size scaling analysis gives for ,
significantly improving on previous work. The results for and ,
and , are entirely new and are compared with
mean-field predictions made for d>=6.Comment: 7 pages, LaTex, 7 ps-figures included, added result for stiffness in
d=7, as to appear in Europhysics Letters (see
http://www.physics.emory.edu/faculty/boettcher/ for related information
Z_2-vortex ordering of the triangular-lattice Heisenberg antiferromagnet
Ordering of the classical Heisenberg antiferromagnet on the triangular
lattice is studied by means of a mean-field calculation, a scaling argument and
a Monte Carlo simulation, with special attention to its vortex degree of
freedom. The model exhibits a thermodynamic transition driven by the Z_2-vortex
binding-unbinding, at which various thermodynamic quantities exhibit an
essential singularity. The low-temperature state is a "spin-gel" state with a
long but finite spin correlation length where the ergodicity is broken
topologically. Implications to recent experiments on triangular-lattice
Heisenberg antiferromagnets are discussed
Monte Carlo Study of the Anisotropic Heisenberg Antiferromagnet on the Triangular Lattice
We report a Monte Carlo study of the classical antiferromagnetic Heisenberg
model with easy axis anisotropy on the triangular lattice. Both the free energy
cost for long wavelength spin waves as well as for the formation of free
vortices are obtained from the spin stiffness and vorticity modulus
respectively. Evidence for two distinct Kosterlitz-Thouless types of
defect-mediated phase transitions at finite temperatures is presented.Comment: 8 pages, 10 figure
In vitro exploration of the synergistic effect of alternating magnetic field mediated thermo-chemotherapy with doxorubicin loaded dual pH- and thermo-responsive magnetic nanocomposite carriers
Nanoparticle induced hyperthermia has been considered as a promising approach for cancer treatment for decades. The local heating ability and drug delivery potential highlight a diversified possibility in clinical application, therefore a variety of nanoparticles has been developed accordingly. However, currently, only a few of them are translated into the clinical stage indicating a 'medically underexplored nanoparticles' situation, which encourages their comprehensive biomedical exploration. This study presents a thorough biological evaluation of previous well-developed dual pH- and thermo-responsive magnetic doxorubicin-nanocarriers (MNC-DOX) in multiple cancer cell lines. The cytotoxicity of the nanocomposites has been determined by the MTT assay on primary cell lines. Histology and fluorescence microscopy imaging revealed the efficiency of cellular uptake of nanocarriers in different cell lines. The IC50 of MNC-DOX is significantly higher than that of free DOX without an alternating magnetic field (AMF), which implied the potential to lower the systemic cytotoxicity in clinical research. The concurrent thermo-chemotherapy generated by this platform has been successfully achieved under an AMF. Promising effective synergistic results have been demonstrated through in vitro study in multi-model cancer cell lines via both trypan blue exclusion and bioluminescence imaging methods. Furthermore, the two most used magnetic hyperthermia modalities, namely intracellular and extracellular treatments, have been compared on the same nanocarriers in all 3 cell lines, which showed that treatment after internalization is not required but preferable. These results lead to the conclusion that this dual responsive nanocarrier has extraordinary potential to serve as a novel broad-spectrum anticancer drug and worth pursuing for potential clinical applications
Evidence for the droplet/scaling picture of spin glasses
We have studied the Parisi overlap distribution for the three dimensional
Ising spin glass in the Migdal-Kadanoff approximation. For temperatures T
around 0.7Tc and system sizes upto L=32, we found a P(q) as expected for the
full Parisi replica symmetry breaking, just as was also observed in recent
Monte Carlo simulations on a cubic lattice. However, for lower temperatures our
data agree with predictions from the droplet or scaling picture. The failure to
see droplet model behaviour in Monte Carlo simulations is due to the fact that
all existing simulations have been done at temperatures too close to the
transition temperature so that sytem sizes larger than the correlation length
have not been achieved.Comment: 4 pages, 6 figure
In vitro exploration of the synergistic effect of alternating magnetic field mediated thermo-chemotherapy with doxorubicin loaded dual pH- and thermo-responsive magnetic nanocomposite carriers
Nanoparticle induced hyperthermia has been considered as a promising approach for cancer treatment for decades. The local heating ability and drug delivery potential highlight a diversified possibility in clinical application, therefore a variety of nanoparticles has been developed accordingly. However, currently, only a few of them are translated into the clinical stage indicating a 'medically underexplored nanoparticles' situation, which encourages their comprehensive biomedical exploration. This study presents a thorough biological evaluation of previous well-developed dual pH- and thermo-responsive magnetic doxorubicin-nanocarriers (MNC-DOX) in multiple cancer cell lines. The cytotoxicity of the nanocomposites has been determined by the MTT assay on primary cell lines. Histology and fluorescence microscopy imaging revealed the efficiency of cellular uptake of nanocarriers in different cell lines. The IC50 of MNC-DOX is significantly higher than that of free DOX without an alternating magnetic field (AMF), which implied the potential to lower the systemic cytotoxicity in clinical research. The concurrent thermo-chemotherapy generated by this platform has been successfully achieved under an AMF. Promising effective synergistic results have been demonstrated through in vitro study in multi-model cancer cell lines via both trypan blue exclusion and bioluminescence imaging methods. Furthermore, the two most used magnetic hyperthermia modalities, namely intracellular and extracellular treatments, have been compared on the same nanocarriers in all 3 cell lines, which showed that treatment after internalization is not required but preferable. These results lead to the conclusion that this dual responsive nanocarrier has extraordinary potential to serve as a novel broad-spectrum anticancer drug and worth pursuing for potential clinical applications
The nature of the different zero-temperature phases in discrete two-dimensional spin glasses: Entropy, universality, chaos and cascades in the renormalization group flow
The properties of discrete two-dimensional spin glasses depend strongly on
the way the zero-temperature limit is taken. We discuss this phenomenon in the
context of the Migdal-Kadanoff renormalization group. We see, in particular,
how these properties are connected with the presence of a cascade of fixed
points in the renormalization group flow. Of particular interest are two
unstable fixed points that correspond to two different spin-glass phases at
zero temperature. We discuss how these phenomena are related with the presence
of entropy fluctuations and temperature chaos, and universality in this model.Comment: 14 pages, 5 figures, 2 table
Reactive trityl derivatives: stabilised carbocation mass-tags for life sciences applications
The rational design of novel triarylmethyl (trityl)-based mass tags (MT) for mass-spectrometric (MS) applications is described. We propose a "pKR+ rule" to correlate the stability of trityl carbocations with their MS performance: trityls with higher pKR+ values ionise and desorb better. Trityl blocks were synthesised that have high pKR+ values and are stable in conditions of MS analysis; these MTs can be ionised by matrix as well as irradiation with a 337 nm nitrogen laser. 13C-Labelled tags were prepared for MS quantitation applications. Moreover, the tags were equipped with a variety of functional groups allowing conjugation with different functionalities within (bio)molecules to enhance the MS characteristics of the latter. The MS behaviour of model polycationic trityl compounds with and without the matrix was studied to reveal that poly-trityl clusters are always singly charged under the (MA)LDI-TOF conditions. Several peptide-trityl conjugates were prepared and comparisons revealed a beneficial effect of trityl tags on the conjugate detection in MS. Trityl compounds containing para-methoxy- and dimethylamine groups, as well as a xanthene fragment, showed considerable enhancement in MS detection of model peptides; thus they are promising tools for proteomic applications. Dimethoxytrityl derivatives allow one to distinguish between Arg- and Lys-containing peptides. Maleimido trityl derivatives are suitable for the efficient derivatisation of thiol-containing peptides in pyridine
Absence of aging in the remanent magnetization in Migdal-Kadanoff spin glasses
We study the non-equilibrium behavior of three-dimensional spin glasses in
the Migdal-Kadanoff approximation, that is on a hierarchical lattice. In this
approximation the model has an unique ground state and equilibrium properties
correctly described by the droplet model. Extensive numerical simulations show
that this model lacks aging in the remanent magnetization as well as a maximum
in the magnetic viscosity in disagreement with experiments as well as with
numerical studies of the Edwards-Anderson model. This result strongly limits
the validity of the droplet model (at least in its simplest form) as a good
model for real spin glasses.Comment: 4 pages and 3 figures. References update
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