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A Study on Nonthermal Irreversible Electroporation of the Thyroid.
BackgroundNonthermal irreversible electroporation is a minimally invasive surgery technology that employs high and brief electric fields to ablate undesirable tissues. Nonthermal irreversible electroporation can ablate only cells while preserving intact functional properties of the extracellular structures. Therefore, nonthermal irreversible electroporation can be used to ablate tissues safely near large blood vessels, the esophagus, or nerves. This suggests that it could be used for thyroid ablation abutting the esophagus. This study examines the feasibility of using nonthermal irreversible electroporation for thyroid ablation.MethodsRats were used to evaluate the effects of nonthermal irreversible electroporation on the thyroid. The procedure entails the delivery of high electric field pulses (1-3 kV/cm, 100 microseconds) between 2 surface electrodes bracing the thyroid. The right lobe was treated with various nonthermal irreversible electroporation pulse sequences, and the left was the control. After 24 hours of the nonthermal irreversible electroporation treatment, the thyroid was examined with hemotoxylin and eosin histological analysis. Mathematical models of electric fields and the Joule heating-induced temperature raise in the thyroid were developed to examine the experimental results.ResultsTreatment with nonthermal irreversible electroporation leads to follicular cells damage, associated with cell swelling, inflammatory cell infiltration, and cell ablation. Nonthermal irreversible electroporation spares the trachea structure. Unusually high electric fields, for these types of tissue, 3000 V/cm, are needed for thyroid ablation. The mathematical model suggests that this may be related to the heterogeneous structure of the thyroid-induced distortion of local electric fields. Moreover, most of the tissue does not experience thermal damage inducing temperature elevation. However, the heterogeneous structure of the thyroid may cause local hot spots with the potential for local thermal damage.ConclusionNonthermal irreversible electroporation with 3000 V/cm can be used for thyroid ablation. Possible applications are treatment of hyperthyroidism and thyroid cancer. The highly heterogeneous structure of the thyroid distorts the electric fields and temperature distribution in the thyroid must be considered when designing treatment protocols for this tissue type
Development of Powder-in-Tube Processed Iron Pnictide Wires and Tapes
The development of the PIT fabrication process of iron pnictide
superconducting wires and tapes has been carried out in order to enhance their
transport properties. Silver was found to be the best sheath material, since no
reaction layer was observed between the silver sheath and the superconducting
core. The grain connectivity of iron pnictide wires and tapes has been markedly
improved by employing Ag or Pb as dopants. At present, critical current
densities in excess of 3750 A/cm^2 (Ic = 37.5 A) at 4.2 K have been achieved on
Ag-sheathed SrKFeAs wires prepared with the above techniques, which is the
highest in iron-based wires and tapes so far. Moreover, Ag-sheathed Sm-1111
superconducting tapes were successfully prepared by PIT method at temperatures
as low as 900C, instead of commonly used temperatures of 1200C. These results
demonstrate the feasibility of producing superconducting pnictide composite
wires, even grain boundary properties require much more attention.Comment: 4 pages, 6 figures. Submitted to ASC2010 proceeding
Enhanced critical current properties in Ba0.6K0.4+xFe2As2 superconductor by over-doping of potassium
Phase-pure polycrystalline Ba0.6K0.4+xFe2As2 with were prepared using a
one-step solid-state reaction method. We found that over-doping of potassium
can improve critical current density (Jc). High-field Jc for samples with x =
0.1 is three times higher than that for samples with x = 0. Over-doping of K
has minimal effect on the critical transition temperature (Tc). Less than 0.5 K
degradations in Tc was measured for samples with x = 0.1. TEM revealed high
concentration of dislocations in samples with x = 0.1, resulting in enhanced
flux pining. Further analyses on magnetization loops for powder samples confirm
that K over-doping can promote intra-grain Jc. Our results indicate that slight
excess of K in Ba0.6K0.4Fe2As2 samples is beneficial to high-field
applications.Comment: 13 pages, 4 figure
High transport critical current densities in textured Fe-sheathed Sr1-xKxFe2As2+Sn superconducting tapes
We report the realization of grain alignment in Sn-added Sr1-xKxFe2As2
superconducting tapes prepared by ex-situ powder-in-tube method. At 4.2 K, high
transport critical current densities Jc of 2.5x10^4 A/cm^2 (Ic = 180 A) in
self-field and 3.5x10^3 A/cm^2 (Ic = 25.5 A) in 10 T have been measured. These
values are the highest ever reported so far for Fe-based superconducting wires
and tapes. We believe the superior Jc in our tape samples are due to well
textured grains and strengthened intergrain coupling achieved by Sn addition.
Our results demonstrated an encouraging prospect for application of iron based
superconductors.Comment: 14 pages, 4 figure
Perfect sets in Cayley graphs
In a graph with vertex set , a subset of is called an
-perfect set if every vertex in has exactly neighbors in and
every vertex in has exactly neighbors in , where and
are nonnegative integers. In the literature -perfect sets are known
as perfect codes and -perfect sets are known as total perfect codes. In
this paper we prove that, for any finite group , if a non-trivial normal
subgroup of is a perfect code in some Cayley graph of , then it is
also an -perfect set in some Cayley graph of for any pair of
integers and with and such that divides . A similar result
involving total perfect codes is also proved in the paper
Direct observation of nanometer-scale amorphous layers and oxide crystallites at grain boundaries in polycrystalline Sr1-xKxFe2As2 superconductors
We report here an atomic resolution study of the structure and composition of
the grain boundaries in polycrystalline Sr0.6K0.4Fe2As2 superconductor. A large
fraction of grain boundaries contain amorphous layers larger than the coherence
length, while some others contain nanometer-scale particles sandwiched in
between amorphous layers. We also find that there is significant oxygen
enrichment at the grain boundaries. Such results explain the relatively low
transport critical current density (Jc) of polycrystalline samples with respect
to that of bicrystal films.Comment: 12 pages, 4 figure
Disorder Improves Light Absorption in Thin Film Silicon Solar Cells with Hybrid Light Trapping Structure
We present a systematic simulation study on the impact of disorder in thin film silicon solar cells with hybrid light trapping structure. For the periodical structures introducing certain randomness in some parameters, the nanophotonic light trapping effect is demonstrated to be superior to their periodic counterparts. The nanophotonic light trapping effect can be associated with the increased modes induced by the structural disorders. Our study is a systematic proof that certain disorder is conceptually an advantage for nanophotonic light trapping concepts in thin film solar cells. The result is relevant to the large field of research on nanophotonic light trapping which currently investigates and prototypes a number of new concepts including disordered periodic and quasiperiodic textures. The random effect on the shape of the pattern (position, height, and radius) investigated in this paper could be a good approach to estimate the influence of experimental inaccuracies for periodic or quasi-periodic structures
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