74 research outputs found
Reliability of fluctuation-induced transport in a Maxwell-demon-type engine
We study the transport properties of an overdamped Brownian particle which is
simultaneously in contact with two thermal baths. The first bath is modeled by
an additive thermal noise at temperature . The second bath is associated
with a multiplicative thermal noise at temperature . The analytical
expressions for the particle velocity and diffusion constant are derived for
this system, and the reliability or coherence of transport is analyzed by means
of their ratio in terms of a dimensionless P\'{e}clet number. We find that the
transport is not very coherent, though one can get significantly higher
currents.Comment: 14 pages, 5 figure
Copper(II) complexes with 2-ethylpyridine and related hydroxyl pyridine derivatives : structural, spectroscopic, magnetic and anticancer in vitro studies
Copper(ii) complexes with 2-ethylpyridine (1 and 2), 2-(hydroxyethyl)pyridine (3) and 2-(hydroxymethyl)pyridine (4) have been synthesized and characterized. All inorganic compounds have been studied by X-ray diffraction, thermogravimetry, vibrational and EPR spectroscopy as well as theoretical methods. The geometry of the complexes 1, 3 and 4 adopts nearly perfect geometry close to square planar (1, 4) or square pyramid (3) stereochemistry, respectively. The distortion of five coordinated copper(ii) ions in complex 2 indicates intermediate geometry between square pyramidal and trigonal pyramidal geometry. Further, the magnetic measurements have shown antiferromagnetic behaviour of the prepared complexes in a wide range of temperatures. The antiferromagnetic behaviour of 2 should originate from the superexchange interactions between each copper(ii) ion by the mixed chloride and μ(4)-O ion pathways. Besides, the weak antiferromagnetic character of 2 can be also attributed to the presence of intrachain exchange between dimeric units through double oxide ion. In complex 3, strong antiferromagnetic coupling between Cu(ii) centres in the Cu(2)O(2)Cl(2) moiety is found. The cytotoxicity of all compounds was tested in vitro against various cancer cell lines: human lung adenocarcinoma (A549), human breast adenocarcinoma (MCF7), human prostate carcinoma; derived from metastatic site: brain (DU-145) and two normal cell lines: human embryonic kidney (HEK293T) and human keratinocyte (HaCat). Furthermore, Pluronic P-123 micelles loaded with selected complexes (1 and 3) were proposed to overcome low solubility and to minimize systemic side effects. More detailed study revealed that complex 3 loaded inside micelles causes DU-145 cells' death with simultaneous decrease of mitochondrial membrane potential and a high level of reactive oxygen species generation. The stability of the compounds 1–4 in DMSO was confirmed by UV-Vis and FT-IR spectra studies
Copper(II) complexes of functionalized 2,2’:6’,2’’-terpyridines and 2,6-di(thiazol-2-yl)pyridine : structure, spectroscopy, cytotoxicity and catalytic activity
Six new copper(II) complexes with 2,2’:6’,2’’-terpyridine (4’-Rn-terpy) [1 (R1 = furan-2-yl), 2 (R2 = thiophen-
2-yl), and 3 (R3 = 1-methyl-1H-pyrrol-2-yl)] and 2,6-di(thiazol-2-yl)pyridine derivatives (Rn-dtpy)
[4 (R1), 5 (R2), and 6 (R3)] have been synthesized by a reaction between copper(II) chloride and the corresponding
ligand. The complexes have been characterized by UV-vis and IR spectroscopy, and their structures
have been determined by X-ray analysis. The antiproliferative potential of copper(II) complexes of
2,2’:6’,2’’-terpyridine and 2,6-di(thiazol-2-yl)pyridine derivatives towards human colorectal (HCT116) and
ovarian (A2780) carcinoma as well as towards lung (A549) and breast adenocarcinoma (MCF7) cell lines
was examined. Complex 1 and complex 6 were found to have the highest antiproliferative effect on
A2780 ovarian carcinoma cells, particularly when compared with complex 2, 3 with no antiproliferative
effect. The order of cytotoxicity in this cell line is 6 > 1 > 5 > 4 > 2 ≈ 3. Complex 2 seems to be much
more specific towards colorectal carcinoma HCT116 and lung adenocarcinoma A549 cells. The viability
loss induced by the complexes agrees with Hoechst 33258 staining and typical morphological apoptotic
characteristics like chromatin condensation and nuclear fragmentation. The specificity towards different
types of cell lines and the low cytotoxic activity towards healthy cells are of particular interest and are a
positive feature for further developments. Complexes 1–6 were also tested in the oxidation of alkanes
and alcohols with hydrogen peroxide and tert-butyl-hydroperoxide (TBHP). The most active catalyst 4
gave, after 120 min, 0.105 M of cyclohexanol + cyclohexanone after reduction with PPh3. This concentration
corresponds to a yield of 23% and TON = 210. Oxidation of cis-1,2-dimethylcyclohexane with
m-CPBA catalyzed by 4 in the presence of HNO3 gave a product of a stereoselective reaction (trans/cis =
0.47). Oxidation of secondary alcohols afforded the target ketones in yields up to 98% and TON = 630
The combinatorics of the Baer-Specker group
Denote the integers by Z and the positive integers by N.
The groups Z^k (k a natural number) are discrete, and the classification up
to isomorphism of their (topological) subgroups is trivial. But already for the
countably infinite power Z^N of Z, the situation is different. Here the product
topology is nontrivial, and the subgroups of Z^N make a rich source of examples
of non-isomorphic topological groups. Z^N is the Baer-Specker group.
We study subgroups of the Baer-Specker group which possess group theoretic
properties analogous to properties introduced by Menger (1924), Hurewicz
(1925), Rothberger (1938), and Scheepers (1996). The studied properties were
introduced independently by Ko\v{c}inac and Okunev. We obtain purely
combinatorial characterizations of these properties, and combine them with
other techniques to solve several questions of Babinkostova, Ko\v{c}inac, and
Scheepers.Comment: To appear in IJ
Reorganization of a 2D disordered granular medium due to a small local cyclic perturbation
We measure experimentally the rearrangements due to a small localized cyclic
displacement applied to a packing of rigid grains under gravity in a 2D
geometry. We analyze the evolution of the response to this perturbation by
considering the individual particle displacement and the coarse grained
displacement field, as well as the mean packing fraction and coordination
number. We find that the displacement response is rather long ranged, and
evolves considerably with the number of cycles. We show that a small difference
in the preparation method (induced by tapping the container) leads to a
significant modification in the response though the packing fraction changes
are minute. Not only the initial response but also its further evolution change
with preparation, demonstrating that the system still retains a memory of the
initial preparation after many cycles. Nevertheless, after a sufficient number
of cycles, the displacement response for both preparation methods converges to
a nearly radial field with a 1/r decay from the perturbation source. The
observed differences between the preparation methods seem to be related to the
changes in the coordination number (which is more sensitive to the evolution of
the packing than the packing fraction). Specifically, it may be understood as
an effect of the breaking of local arches, which affects the lateral
transmission of forces.Comment: 13 pages, revised and resubmitted to J. Stat. Mech.: Theory and Exp.
(JSTAT
Artificial Brownian motors: Controlling transport on the nanoscale
In systems possessing spatial or dynamical symmetry breaking, Brownian motion
combined with symmetric external input signals, deterministic or random, alike,
can assist directed motion of particles at the submicron scales. In such cases,
one speaks of "Brownian motors". In this review the constructive role of
Brownian motion is exemplified for various one-dimensional setups, mostly
inspired by the cell molecular machinery: working principles and
characteristics of stylized devices are discussed to show how fluctuations,
either thermal or extrinsic, can be used to control diffusive particle
transport. Recent experimental demonstrations of this concept are reviewed with
particular attention to transport in artificial nanopores and optical traps,
where single particle currents have been first measured. Much emphasis is given
to two- and three-dimensional devices containing many interacting particles of
one or more species; for this class of artificial motors, noise rectification
results also from the interplay of particle Brownian motion and geometric
constraints. Recently, selective control and optimization of the transport of
interacting colloidal particles and magnetic vortices have been successfully
achieved, thus leading to the new generation of microfluidic and
superconducting devices presented hereby. Another area with promising potential
for realization of artificial Brownian motors are microfluidic or granular
set-ups.....Comment: 57 pages, 39 figures; submitted to Reviews Modern Physics, revised
versio
Jury Systems Around the World
Lay citizens participate as decision makers in the legal systems of many countries. This review describes the different approaches that countries employ to integrate lay decision makers, contrasting in particular the use of juries composed of all citizens with mixed decision-making bodies of lay and law-trained judges. The review discusses research on the benefits and drawbacks of lay legal decision making as well as international support for the use of ordinary citizens as legal decision makers, with an eye to explaining a recent increase in new jury systems around the world. The review calls for more comparative work on diverse approaches to lay participation, examining how different methods of including lay participation promote or detract from fact finding, legal consciousness, civic engagement, and citizen power
Occupational asthma follow-up — which markers are elevated in exhaled breath condensate and plasma?
Objectives: To search for optimal markers in the exhaled breath condensate (EBC), plasma and urine that would reflect the activity/ severity of occupational asthma (OA) after the withdrawal from the exposure to the allergen. Material and Methods: Markers of oxidative stress: 8-iso-prostaglandin F2α (8-isoprostane, 8-ISO), malondialdehyde (MDA), 4-hydroxy-trans-2-nonenale (HNE), cysteinyl leukotrienes (LT) and LTB4 were determined using liquid chromatography and mass spectrometry in 43 subjects with immunological OA (49.3±11.8 years), removed from the exposure to the sensitizing agent 10.5±6.5 years ago; and in 20 healthy subjects (49.0±14.9 years). EBC was harvested both before and after the methacholine challenge test. In parallel, identical markers were collected in plasma and urine. The results were analyzed together with forced expiratory volume in one second (FEV1), blood eosinophils, immunoglobulin E (IgE) and eosinophilic cationic protein (ECP) and statistically evaluated (Spearman rank correlation rS, two- or one-sample t tests and alternatively Kruskal Wallis or pair Wilcoxon tests). Results: Several parameters of lung functions were lower in the patients (FEV1% predicted, MEF25% and MEF50%, Rtot%, p < 0.001). Shorter time interval since the removal from the allergen exposure correlated with higher ECP (rS = 0.375) and lower FEV1%, MEF25% and MEF50% after methacholine challenge (rS = -0.404, -0.425 and -0.532, respectively). In the patients, IgE (p < 0.001) and ECP (p = 0.009) was increased compared to controls. In EBC, 8-ISO and cysteinyl LTs were elevated in the asthmatics initially and after the challenge. Initial 8-ISO in plasma correlated negatively with FEV1 (rS = -0.409) and with methacholine PD20 (rS = -0.474). 8-ISO in plasma after the challenge correlated with IgE (rS = 0.396). Conclusions: The improvement in OA is very slow and objective impairments persist years after removal from the exposure. Cysteinyl LTs and 8-ISO in EBC and 8-ISO in plasma might enrich the spectrum of useful objective tests for the follow-up of OA
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