41 research outputs found
Surface magnetic canting in a ferromagnet
The surface magnetic canting (SMC) of a semi-infinite film with ferromagnetic
exchange interaction and competing bulk and surface anisotropies is
investigated via a nonlinear mapping formulation of mean-field theory
previously developed by our group [L. Trallori et al., Int. J. Mod. Phys. B 10,
1935-1988 (1996)], and extended to the case where an external magnetic field is
applied to the system. When the field H is parallel to the film plane, the
condition for SMC is found to be the same as that recently reported by Popov
and Pappas [Phys. Rev. B 64, 184401 (2001)]. The case of a field H applied
perpendicularly to the film plane is also investigated. In both cases, the
zero-temperature equilibrium configuration is easily determined by our
theoretical approach.Comment: 4 pages, 3 figure
Surface spin-flop and discommensuration transitions in antiferromagnets
Phase diagrams as a function of anisotropy and magnetic field are
obtained for discommensurations and surface states for an antiferromagnet in
which is parallel to the easy axis, by modeling it using the ground states
of a one-dimensional chain of classical XY spins. A surface spin-flop phase
exists for all , but the interval in over which it is stable becomes
extremely small as goes to zero. First-order transitions, separating
different surface states and ending in critical points, exist inside the
surface spin-flop region. They accumulate at a field (depending on )
significantly less than the value for a bulk spin-flop transition. For
there is no surface spin-flop phase in the strict sense;
instead, the surface restructures by, in effect, producing a discommensuration
infinitely far away in the bulk. The results are used to explain in detail the
phase transitions occurring in systems consisting of a finite, even number of
layers.Comment: Revtex 17 pages, 15 figure
Surface spin-flop transition in a uniaxial antiferromagnetic Fe/Cr superlattice induced by a magnetic field of arbitrary direction
We studied the transition between the antiferromagnetic and the surface
spin-flop phases of a uniaxial antiferromagnetic [Fe(14 \AA)/Cr(11 \AA] superlattice. For external fields applied parallel to the in-plane easy
axis, the layer-by-layer configuration, calculated in the framework of a
mean-field one-dimensional model, was benchmarked against published polarized
neutron reflectivity data. For an in-plane field applied at an angle with the easy axis, magnetometry shows that the magnetization
vanishes at H=0, then increases slowly with increasing . At a critical value
of , a finite jump in is observed for , while a
smooth increase of is found for . A dramatic
increase in the full width at half maximum of the magnetic susceptibility is
observed for . The phase diagram obtained from
micromagnetic calculations displays a first-order transition to a surface
spin-flop phase for low values, while the transition becomes continuous
for greater than a critical angle, . This is in fair agreement with the experimentally observed results.Comment: 24 pages, 7 figure
Surface spin-flop phases and bulk discommensurations in antiferromagnets
Phase diagrams as a function of anisotropy D and magnetic field H are
obtained for discommensurations and surface states for a model antiferromagnet
in which is parallel to the easy axis. The surface spin-flop phase exists
for all . We show that there is a region where the penetration length of the
surface spin-flop phase diverges. Introducing a discommensuration of even
length then becomes preferable to reconstructing the surface. The results are
used to clarify and correct previous studies in which discommensurations have
been confused with genuine surface spin-flop states.Comment: 4 pages, RevTeX, 2 Postscript figure
Phaseolus vulgaris L. Extract: Alpha-amylase inhibition against metabolic syndrome in mice
To examine the effects of the alpha-amylase inhibitor isoform 1 called phaseolamin, a standardized extract from white kidney beans (Phaseolus vulgaris L) was tested against the hallmarks of metabolic syndrome. The efficacy of a per os repeated treatment with P. vulgaris extract (500 mg/kg) was compared with metformin (100 mg/kg) and atorvastatin (10 mg/kg) in a model of metabolic syndrome evoked by prolonged high fat diet (HFD; week 1 to week 19) in C57BL/6 mice. Bean extract and compounds administration started after metabolic syndrome establishment (week 11). P. vulgaris extract reduced the body weight overtime, as well as effectively lowered glycaemia, triglycerides, and cholesterol. On week 19, bean extract normalized the HFD-evoked tolerance to glucose and insulin. According to the phytochemical characterization, it inhibited the alpha-amylase activity. Animals treated with the extract were rescued from motor impairments and nociceptive threshold alterations induced by HFD. Specific organs analysis revealed that P. vulgaris extract decreased hepatic steatosis and lipid peroxidation in liver. It protected the heart from HFD oxidative alterations increasing the expression of the detoxifying enzymes catalase and glutathione reductase, and normalizing NADH dehydrogenase level. The histological analysis of aorta showed a protection about the development of fatty streaks in the muscular layers. In conclusion, a prolonged treatment with the standardized extract of P. vulgaris significantly reduced several pathological features related to a metabolic syndrome-like condition; a multifactorial approach that candidates this vegetal product as a possible therapeutic option against metabolic syndrome
4-Hydroxy-3-nitro-5-ureido-benzenesulfonamides selectively target the tumor-associated carbonic anhydrase isoforms IX and XII showing hypoxia-enhanced anti-proliferative profiles.
Human carbonic anhydrases
(CA, EC, 4.2.1.1) IX and XII are overexpressed
in cancer cells as adaptive response to hypoxia and acidic conditions
characteristic of many tumors. In addition, hypoxia facilitates the
activity of specific oxido-reductases that may be exploited to selectively
activate bioreductive prodrugs. Here, new selective CA IX/XII inhibitors,
as analogues of the antitumor phase II drug SLC-0111 are described,
namely ureido-substituted benzenesulfonamides appended with a nitro-aromatic
moiety to yield an antiproliferative action increased by hypoxia.
These compounds were screened for the inhibition of the ubiquitous
hCA I/II and the target hCA IX/XII. Six X-ray crystallographies with
CA II and IX/mimic allowed for the rationalization of the compounds
inhibitory activity. The effects of some such compounds on the viability
of HT-29, MDA-MB-231, and PC-3 human cancer cell lines in both normoxic
and hypoxic conditions were examined, providing the initiation toward
the development of hypoxia-activated antitumor CAIs
Characterization of tumor antigen peptide-specific T cells isolated from the neoplastic tissue of patients with gastric adenocarcinoma.
Gastric cancer is a significant cause of morbidity and mortality worldwide. Surgical resection remains the primary curative treatment for gastric adenocarcinoma, but the poor (15-35%) survival rate at 5 years has prompted many studies for new therapeutic strategies, such as specific immunotherapy. The aim of this study was to analyze the functional properties of the T cell response to different antigen peptides related to gastric cancer in patients with gastric adenocarcinoma. To this purpose, we have cloned and characterized tumor-infiltrating T cells (TILs) isolated from the neoplastic gastric tissue samples. A T cell response specific to different peptides of gastric cancer antigens tested was documented in 17 out of 20 patients, selected for their HLA-A02 and/or -A24 alleles. Most of the cancer peptide-specific TILs expressed a Th1/Tc1 profile and cytotoxic activity against target cells. The effector functions of cancer peptide-specific T cells obtained from the peripheral blood of the same patients were also studied. The majority of peripheral blood peptide-specific T cells also expressed the Th1/Tc1 functional profile. In conclusion, in most of the patients with gastric adenocarcinoma, a specific type-1 T cell response to gastric cancer antigens was detectable and would have the potential of hamper tumor cell growth. However, in order to get tumor cell killing in vivo, the activity and the number of cancer peptide-specific Th1/Tc1 cells probably need to be enhanced by vaccination with the appropriate cancer antigenic peptides or by injection of the autologus tumor peptide-specific T cells expanded in vitro