1,371 research outputs found
Influence of Deae-Dextran, Polybrene, Dextran and Dextran Sulphate on Spontaneous Leukaemia Development in AKR Mice and Virus Induced Leukaemia in BALB/c Mice
AKR mice of which more than 90% die of lymphatic thymus leukaemia, had their mean survival time increased by weekly intraperitoneal inoculation of either of the two polycations DEAE-dextran and polybrene. Administration of the neutral dextran had no effect, whereas the polyanion dextran sulphate accelerated leukaemia development
SPONTANEOUS AMYLOIDOSIS IN DIFFERENTLY GROUPED AND TREATED DBA/2, BALB/c, AND CBA MICE AND THYMUS FIBROSIS IN ESTROGEN-TREATED BALB/c MALES
Sex-segregated grouping of DBA/2, BALB/c, and CBA males caused rapid amyloid development and early death as compared with segregated grouped females or with males living individually in cages with several females. Grouping of several males in a cage with females also caused early death in amyloidosis indicating that the exposure of males to males and not the sexual isolation was important for the amyloid development. Both reserpine treatment and castration prolonged the survival time of sex-segregated grouped males. Estrogen treatment retarded amyloid development in sex-segregated males while spayed and androgen-treated spayed females showed only small amounts of amyloid. Treatment with chlortetracycline did not prevent amyloid development in grouped males. Thymectomy of sex-segregated males at 1 month of age gave inconclusive evidence of a prolongation of survival time. Egg-transferred DBA/2 mice reacted as conventional DBA/2 mice when grouped by sex segregation. Cells with abundant PAS-positive cytoplasm were found in the spleen, liver, and ovaries of mice of all strains but most prominently in CBA mice. Evidence for a direct conversion of these cells to amyloid was found. Estrogen-treated BALB/c males developed testicular tumors and thymus alterations including necrosis and depletion of lymphocytes, depletion of PAS cells, formation of large cysts containing necrotic nuclei, and intralobular fibrosis
Life span, leukaemia and amyloid incidences of untreated and polycation-treated AKR mice.
AKR mice, which have a short mean survival time and usually die with leukaemia, were studied from one month of age for correlation between these two parameters. For untreated animals we found the same mean survival time whether or not leukaemia occurred. By treating sucklings with the polycations diethylaminoethyl-dextran or hexadimethrine bromide the leukaemia incidence was significantly reduced. However, the mean survival time was unchanged, and remained the same in leukaemic and non-leukaemic animals. It is therefore suggested that the early death of AKR mice results from an ageing process and does not require leukaemia for implementation. Our prophylactic polycation treatment was furthermore found to induce spleen amyloid in some but not all of the mice that remained non-leukaemic
Specificity of the inhibition of DNA synthesis by extracts from cloned normal, sarcoma-virus-transformed and revertant 3T3 cells.
Extracts containing tissue-specific DNA-inhibitory activity were prepared from normal FL (Swiss) and BALBc3T3 cells, from these cells transformed with sarcoma virus and from revertants cloned from the transformed cell lines. By testing all extracts on all cell lines we found that (1) production of and susceptibility to the inhibitors were decreased in transformed BALB/c cells (2) specificity varied with expression of the transforming genome, as an extract from a given cell line inhibited the growth of its cell of origin, e.g. revertant, more than normal or transformed cells, and (3) there was also a DNA-synthesis stimulator
Huygens description of resonance phenomena in subwavelength hole arrays
We develop a point-scattering approach to the plane-wave optical transmission
of subwavelength metal hole arrays. We present a real space description instead
of the more conventional reciprocal space description; this naturally produces
interfering resonant features in the transmission spectra and makes explicit
the tensorial properties of the transmission matrix. We give transmission
spectra simulations for both square and hexagonal arrays; these can be
evaluated at arbitrary angles and polarizations.Comment: 5 pages, 3 figure
Observation of Enhanced Beaming from Photonic Crystal Waveguides
We report on the experimental observation of the beaming effect in photonic
crystals enhanced via surface modes. We experimentally map the spatial field
distribution of energy emitted from a subwavelength photonic crystal waveguide
into free-space, rendering with crisp clarity the diffractionless beaming of
energy. Our experimental data agree well with our numerical studies of the
beaming enhancement in photonic crystals with modulated surfaces. Without loss
of generality, we study the beaming effect in a photonic crystal scaled to
microwave frequencies and demonstrate the technological capacity to deliver
long-range, wavelength-scaled beaming of energy.Comment: 4 pages, 6 figure
Torsional response and stiffening of individual multi-walled carbon nanotubes
We report on the characterization of torsional oscillators which use
multi-walled carbon nanotubes as the spring elements. Through
atomic-force-microscope force-distance measurements we are able to apply
torsional strains to the nanotubes and measure their torsional spring constants
and effective shear moduli. We find that the effective shear moduli cover a
broad range, with the largest values near the theoretically predicted value.
The data also suggest that the nanotubes are stiffened by repeated flexing.Comment: 4 page
Conductivity in organic semiconductors hybridized with the vacuum field
Organic semiconductors have generated considerable interest for their
potential for creating inexpensive and flexible devices easily processed on a
large scale [1-11]. However technological applications are currently limited by
the low mobility of the charge carriers associated with the disorder in these
materials [5-8]. Much effort over the past decades has therefore been focused
on optimizing the organisation of the material or the devices to improve
carrier mobility. Here we take a radically different path to solving this
problem, namely by injecting carriers into states that are hybridized to the
vacuum electromagnetic field. These are coherent states that can extend over as
many as 10^5 molecules and should thereby favour conductivity in such
materials. To test this idea, organic semiconductors were strongly coupled to
the vacuum electromagnetic field on plasmonic structures to form polaritonic
states with large Rabi splittings ca. 0.7 eV. Conductivity experiments show
that indeed the current does increase by an order of magnitude at resonance in
the coupled state, reflecting mostly a change in field-effect mobility as
revealed when the structure is gated in a transistor configuration. A
theoretical quantum model is presented that confirms the delocalization of the
wave-functions of the hybridized states and the consequences on the
conductivity. While this is a proof-of-principle study, in practice
conductivity mediated by light-matter hybridized states is easy to implement
and we therefore expect that it will be used to improve organic devices. More
broadly our findings illustrate the potential of engineering the vacuum
electromagnetic environment to modify and to improve properties of materials.Comment: 16 pages, 13 figure
Polarization tomography of metallic nanohole arrays
We report polarization tomography experiments on metallic nanohole arrays
with square and hexagonal symmetry. As a main result, we find that a fully
polarized input beam is partly depolarized after transmission through a
nanohole array. This loss of polarization coherence is found to be anisotropic,
i.e. it depends on the polarization state of the input beam. The depolarization
is ascribed to a combination of two factors: i) the nonlocal response of the
array due to surface plasmon propagation, ii) the non-plane wave nature of a
practical input beam.Comment: 4 pages, 3 figures, 1 table, submitted to PR
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