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Biomedical subjects

A Hernando

Publications and source records attributed to A Hernando.

At least 19 recordsLinked to original sources
PubMed2006

Fe impurities weaken the ferromagnetic behavior in Au nanoparticles.

In this Letter, we report on a crucial experiment showing that magnetic impurities reduce the ferromagnetic order temperature in thiol-capped Au glyconanoparticles (GNPs). The spontaneous magnetization of AuFe GNPs exhibits a fast decrease with temperature that contrasts with the almost constant value of the magnetization observed in Au NPs. Moreover, hysteresis disappears below 300 K. Both features indicate that Fe impurities reduce the high local anisotropy field responsible for the ferromagnetic behavior in Au GNPs. As a consequence, the amazing ferromagnetism in Au NPs should not be associated with the presence of magnetic impurities.

Journal Article↗
PubMed2006

Origin of orbital ferromagnetism and giant magnetic anisotropy at the nanoscale.

The origin of orbital magnetism recently observed in different nanostructured films and particles is discussed as a consequence of spin-orbit coupling. It is shown that contact potentials induced at the thin film surface by broken symmetries, as domain boundaries in self-assembled monolayers, lead to orbital states that in some cases are of large radius. The component of the angular momentum normal to the surface can reach very high values that decrease the total energy by decreasing spin-orbit interaction energy. Intraorbital ferromagnetic spin correlations induce orbital momenta alignment. The estimated values of the magnetic moments per atom are in good agreement with the experimental observations in thiol capped gold films and nanoparticles.

Journal Article↗
PubMed2006

Immunochemical determination of gluten in malts and beers.

The gluten content in different varieties of barley and malts, and in different types of beers, was determined by a 'sandwich' enzyme immunoassay (RIDASCREEN Gliadin kit). The gluten levels in barley wheat, rye and spelt malts ranged 18.8-45.0, 44.0-68.0, 41.6 and 21.2 g kg-1, respectively. When various types of beer were compared, the gluten concentration increased as follows: alcohol-free beer (<3.0), lager beers (<3.0-8.7 mg l-1), stouts (9.0-15.2 mg l-1) and wheat beers (10.6-41.2 mg l-1). When 10 Czech lager beers were analysed, using both sandwich and competitive ELISA, the results showed that the latter method provided values several times higher than the former. Gluten balance was carried out during the brewing process, starting from the raw materials and terminating at the final beer. Gluten levels decreased due to precipitation during the mashing process, primary and secondary fermentation and, lastly, as a result of adsorption during beer stabilization. The gluten content in beer is, thus, approximately three orders of magnitude lower than in the raw malt.

Alcoholic Beverages↗
PubMed2005

Metallic magnetic nanoparticles.

In this paper, we reviewed some relevant aspects of the magnetic properties of metallic nanoparticles with small size (below 4 nm), covering the size effects in nanoparticles of magnetic materials, as well as the appearance of magnetism at the nanoscale in materials that are nonferromagnetic in bulk. These results are distributed along the text that has been organized around three important items: fundamental magnetic properties, different fabrication procedures, and characterization techniques. A general introduction and some experimental results recently obtained in Pd and Au nanoparticles have also been included. Finally, the more promising applications of magnetic nanoparticles in biomedicine are indicated. Special care was taken to complete the literature available on the subject.

Anisotropy↗
PubMed2005

Interface double-exchange ferromagnetism in the Mn-Zn-O system: new class of biphase magnetism.

In this Letter, we experimentally show that the room temperature ferromagnetism in the Mn-Zn-O system recently observed is associated with the coexistence of Mn(3+) and Mn(4+) via a double-exchange mechanism. The presence of the ZnO around MnO(2) modifies the kinetics of MnO(2)-->Mn(2)O(3) reduction and favors the coexistence of both Mn oxidation states. The ferromagnetic phase is associated with the interface formed at the Zn diffusion front into Mn oxide, corroborated by preparing thin film multilayers that exhibit saturation magnetization 2 orders of magnitude higher than bulk samples.

Journal Article↗
PubMed2004

Permanent magnetism, magnetic anisotropy, and hysteresis of thiol-capped gold nanoparticles.

We report on the experimental observation of magnetic hysteresis up to room temperature in thiol-capped Au nanoparticles with 1.4 nm size. The coercive field ranges from 860 Oe at 5 K to 250 Oe at 300 K. It is estimated that the Au atoms exhibit a magnetic moment of mu=0.036mu(B). However, Au nanoparticles with similar size but stabilized by means of a surfactant, i.e., weak interaction between protective molecules and Au surface atoms, are diamagnetic, as bulk Au samples are. The apparent ferromagnetism is consequently associated with 5d localized holes generated through Au-S bonds. These holes give rise to localized magnetic moments that are frozen in due to the combination of the high spin-orbit coupling (1.5 eV) of gold and the symmetry reduction associated with two types of bonding: Au-Au and Au-S.

Journal Article↗
PubMed2003

Ferromagnetism in fcc twinned 2.4 nm size Pd nanoparticles.

The onset of ferromagnetism has been experimentally observed in small Pd particles of average diameter 2.4 nm. High-resolution studies reveal that a high percentage of the fcc particle exhibits single and multiple twinning boundaries. The spontaneous magnetization close to 0.02 emu/g seems to indicate that only a small fraction of atoms holds a permanent magnetic moment and contributes to ferromagnetism. The possible origin of ferromagnetism is briefly discussed according to different models recently reported.

Journal Article↗
PubMed2000

[Influence of a day care hospital on the incidence of hospital admission of AIDS patients].

BACKGROUND: Day care units have become an usual way of medical care for AIDS patients. However, their influence on the incidence of hospital admissions has not been evaluated. METHODS: Observational and longitudinal study of a cohort of 308 patients with aids diagnosed between 1990 and 1994 and followed-up to June 1996. The incidence of hospital admissions according to the hospital of follow-up (with or without day care unit) was analyzed. A multivariate analysis of the number of hospital admissions was performed using regression model adjusted to a distribution of Poisson. RESULTS: After AIDS diagnosis, the incidence of hospital admissions was 108 per 100 patient-years of follow up (21 days as inpatient per patient-year). Those patients controlled in the hospital with day care unit have less hospital admissions (relative risk after adjusting by CD4+ cells count and type of diagnostic disease: 0.64; CI95% 0.55-0.76), and less days as inpatient through their follow-up (11 to 31 days less). There was no difference in survival among patients followed in both hospitals. CONCLUSIONS: A day care unit decrease the incidence of hospital admissions in aids patients. This positive impact is more evident in patients with lesser CD4+ cell counts.

Acquired Immunodeficiency Syndrome↗
PubMed1998

[Comparison of chemotherapy CHOP vs. CHOP/VIA in the treatment of aggressive non-Hodgkin's lymphoma: a randomized multicenter study of 132 patients. The PETHEMA group. Program for Study and Therapeutics of malignant hemopathies. Spanish Association of Hematology and Hemotherapy].

BACKGROUND: To compare standard chemotherapy CHOP (cyclophosphamide, adriamycin, vincristine and prednisone) with the regimen CHOP/VIA (VP-16, iphosphamide and cytarabine) in terms of response to therapy, response duration, survival and toxicity in patients with aggressive lymphoma. PATIENTS AND METHODS: 132 patients (84 males and 48 females; median age, 55 years) were included from 12 Spanish Institutions, diagnosed of non-Hodgkin's lymphoma of intermediate or high grade, in stages II-IV and previously untreated. Patients were randomized to receive CHOP or CHOP/VIA. RESULTS: After excluding 14 not assessable cases, 62 patients (52.5%) received CHOP, and 56 (47.5%) CHOP/VIA. No significant differences were found on main prognostic factors between such groups. Response was assessable in 114 cases (CHOP: 61; CHOP/VIA: 53) 39 patients (64%) receiving CHOP achieved complete response (CR), and 2 (3%) partial response (PR), whereas in the CHOP/VIA group CR and PR rates were 63% (34/53), and 7% (4/53), respectively. 14 patients (36%) treated with CHOP and 12 (35%) treated with CHOP/VIA eventually relapsed, with an actuarial risk of relapse at 36 months of 43% and 40%, respectively. Median survival was 37 months. No differences were found between both therapeutic groups, with an overall survival at 36 months from diagnosis of 53.5% (CI 95%: 40-67) for CHOP and 48% (CI 95%: 34-62) for CHOP/VIA. Finally, toxicity was not different for both arms. CONCLUSION: In the present study in patients with aggressive NHL chemotherapy regimens CHOP and CHOP/VIA showed similar results in terms of response, response duration, survival and toxicity.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1998

Long-term evaluation of the behavior of a polytetrafluoroethylene microprosthesis in the rat iliac artery: myointimal regression.

The present study represents a long-term investigation of polytetrafluoroethylene (PTFE) vascular microprostheses implanted in the right common iliac artery of rats, with the aim of evaluating the degree of intimal hyperplasia and the changes produced in the vascular prosthesis. A follow-up study was performed between 3 months and 1 year post-implantation, using immunohistochemical techniques, light, and electron microscopy. Three months after implantation, the PTFE segment appeared sandwiched between two cell layers. A general endothelialization was observed on the luminal surface. The underlying myointima appeared as an irregular lining of decreasing thickness, from the distal anastomosis with the receptor artery to the proximal suture. A large number of white blood cells were found adherent to and infiltrating the endothelium. A neoformed adventitia covered the prosthesis on the external surface. At 4 months post-implantation, a destabilization of the luminal surface was observed induced by white blood cells. A progressive reduction in the thickness of the myointimal layer was also apparent, so that 1 year after implantation, the luminal surface of the PTFE prosthesis was fully lined by a thin cell covering. There is good long-term tolerance to implanted PTFE microprostheses. The white blood cells present in the implant region appeared to play an important role in the long-term regression of intimal hyperplasia.

Animals↗