3,215 research outputs found
Transverse voltage in high-Tc superconductors in zero magnetic fields
Longitudinal and transverse voltages have been measured in zero external
magnetic fields. In close vicinity of the superconducting transition nonzero
transverse voltage has been observed while far away from Tc, both above and
below no such voltage has been detected. The value of the transverse
resistivity depends on the value of the transport current. Several models have
been discussed taking into account also the penetration of self field due to
the applied transport current. It seems that observed results can be explained
using the Kosterlitz-Thouless model as a result of an unpairing of
vortex-antivortex pairs created below Tkt due to fluctuations. At Tkt free
vortices and antivortices are created and can contribute to a dissipation of
energy. Their movement should also be responsible for the observed nonzero
transverse voltage.Comment: 3 pages in Latex, 3 figs.ep
PARTIAL-PURIFICATION AND CHARACTERIZATION OF AN INHIBITOR (KCHI) PRODUCED BY KUPFFER CELLS IN CULTURE WHICH INHIBITS HEPATOCYTE PROLIFERATION INVITRO
Scaling of resistivities and guided vortex motion in MgB2 thin films
Longitudinal and transverse voltages have been measured on thin films of MgB2
with different superconducting transition widths. The study has been performed
in zero and non-zero external magnetic fields. The non-zero transverse voltage
has been observed in close vicinity of the critical temperature in zero
external magnetic field, while further away from Tc this voltage becomes zero.
In magnetic field it becomes a transverse voltage which is an even function
with respect to the direction of the field. The usual Hall voltage starts to
appear with increasing magnetic field and in large fields the even voltage
disappears and only the Hall voltage is measurable (i.e. the transverse even
voltage is suppressed with increasing magnetic field and increasing transport
current). New scaling between transverse and longitudinal resistivities has
been observed. This correlation is valid not only in the zero magnetic field
but also in nonzero magnetic field where transverse even voltage is detected.
Several models trying to explain observed results are discussed. The most
promising one seems to be guided motion of the vortices, though further
theoretical work will be required to confirm this
Estrogen Binding Protein Activity in Morris Hepatoma 7777 Compared With Normal Rat Liver
Estrogen binding protein activities were determined in the cytosol from adult male Buffalo rat liver and Morris hepatoma 7777. Estrogen receptors were prepared using the protamine sulfate precipitation technique of Chamness. The ability of various unlabeled steroids competing with [3H]estradiol was examined to establish the binding specificity. Estradiol binding in Morris hepatoma 7777 cytosol was greatly decreased compared with that present in hepatic cytosol prepared from normal rat liver. The receptor concentration expressed as femtomoles per milligram of cytoplasmic protein was 31.1 ± 2.9 SD for normal rat liver and 0.41 ± 0.88 SD for the hepatoma. Gel filtration chromatography revealed the presence of an estrogen binder in hepatoma cytosol which was not present in either normal liver or in the protamine sulfate precipitates of hepatoma cytosol. The molecular weight, binding specificity, and precipitation of this protein by specific antiserum suggests that it is α-fetoprotein. © 1984, American Gastroenterological Association. All rights reserved
The effect of estrogen and tamoxifen on hepatocyte proliferation in Vivo and in Vitro
We have previously shown that changes in estrogenâhepatocyte interaction occur during liver regeneration. Following 70% hepatectomy, estrogen levels in the blood were elevated, the number of estrogen receptors in the liver was increased and there was an active translocation of estrogen receptors from the cytosol to the nucleus. The injection of tamoxifen, an estrogen antagonist, inhibits hepatocyte proliferation following partial hepatectomy. The administration of 1 ÎŒg tamoxifen per gm body weight at zero time or 6 hr after the operation resulted in a significant inhibition both of DNA synthesis and of the number of cells in mitosis. Injections of tamoxifen 12 hr or later after the operation had no effect. Concomitant injections of equimolar amounts of estrogen abolished the inhibition by tamoxifen. The effects of estrogen and tamoxifen were also tested on hepatocytes in primary culture. Estrogens in the presence of 5% normal rat serum stimulated hepatocyte DNA synthesis as determined by [3H]thymidine incorporation and the labeling index, whereas epidermal growth factorâinduced DNA synthesis in the absence of normal rat serum was strongly inhibited. Tamoxifen, in contrast, inhibited DNA synthesis of hepatocytes in the presence of 5% normal rat serum and reversed the stimulatory effect of estrogen in the same system. Attempts to elucidate the mechanism of tamoxifen inhibition in vitro indicated that one effect of tamoxifen is to prevent the amilorideâsensitive Na+ influx necessary to initiate hepatocyte proliferation. Copyright © 1989 American Association for the Study of Liver Disease
Estradiol and testosterone levels in patients undergoing partial hepatectomy - A possible signal for hepatic regeneration?
In five adult male patients undergoing a 40-60% partial hepatectomy, serum sex hormone levels before and after hepatic resection were determined. Blood was drawn immediately prior to each surgical procedure and at specified time points postoperatively. Compared to hormone levels found prior to surgery, following major hepatic resection, estradiol levels increase at 24 and 48 hr, while testosterone levels decline, being significantly reduced at 96 and 144 hr. These data demonstrate that adult males who undergo a 40-60% partial hepatectomy experience alterations in their sex hormone levels similar to those observed in male rats following a 70% hepatectomy. These changes in sex hormone levels have been associated in animals with an alteration of the sex hormone receptor status of the liver that is thought to participate in the initiation of the regenerative response. These studies suggest, but do not prove, that in man, as in the case of the rat, sex hormones may participate in the initiation of or at least modulate in part the regenerative response that occurs following a major hepatic resection. © 1989 Plenum Publishing Corporation
Artichoke biorefinery: From food to advanced technological applications
A sequential extraction process has been designed for valorizing globe artichoke plant residues and waste (heads, leaves, stalks, and roots left in the field) by means of green extraction techniques according to a biorefinery approach. We investigated two cascading extractions based on microwave-assisted extractions (MAE) and green solvents (water and ethanol) that have been optimized for varying temperature, solvent and extraction time. In the first step, phenols were extracted with yields that ranged between 6.94 mg gâ1 dw (in leaves) and 3.28 mg gâ1 dw (in roots), and a phenols productivity of 175.74 kg Haâ1. In the second step, inulin was extracted with impressive yields (42% dw), higher than other conventional inulin sources, corresponding to an inulin productivity of 4883.58 kg Haâ1. The remaining residues were found to be valuable feedstocks both for bioenergy production and green manure (back to the field), closing the loop according to the Circular Economy paradigm
Smart fibrous structures produced by electrospinning using the combined effect of PCL/graphene nanoplatelets
Over the years, the development of adaptable monitoring systems to be integrated into soldiersâ body gear, making them as comfortable and lightweight as possible (avoiding the use of rigid electronics), has become essential. Electrospun microfibers are a great material for this application due to their excellent properties, especially their flexibility and lightness. Their functionalization with graphene nanoplatelets (GNPs) makes them a fantastic alternative for the development of innovative conductive materials. In this work, electrospun membranes based on polycaprolactone (PCL) were impregnated with different GNPs concentrations in order to create an electrically conductive surface with piezoresistive behavior. All the samples were properly characterized, demonstrating the homogeneous distribution and the GNPsâ adsorption onto the membraneâs surfaces. Additionally, the electrical performance of the developed systems was studied, including the electrical conductivity, piezoresistive behavior, and Gauge Factor (GF). A maximum electrical conductivity value of 0.079 S/m was obtained for the 2%GNPs-PCL sample. The developed piezoresistive sensor showed high sensitivity to external pressures and excellent durability to repetitive pressing. The best value of GF (3.20) was obtained for the membranes with 0.5% of GNPs. Hence, this work presents the development of a flexible piezoresistive sensor, based on electrospun PCL microfibers and GNPs, utilizing simple methods.The authors are thankful to TSSiPRO project, operation code NORTE 01-0145-FEDER000015, supported by the âPrograma Operacional Regional do Norteâ number NORTE-45-2015-
02 and Project UID/CTM/00264/2019 of 2C2TâCentro de CiĂȘncia e Tecnologia TĂȘxtil. Diana P.
Ferreira is thankful to CEECIND/02803/2017 and Joana C. AraĂșjo to the FCT PhD Scholarship
(SFRH/BD/147812/2019), founded by National Founds through FCT/MCTES
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