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1.
Chem Commun (Camb) ; 57(18): 2297-2300, 2021 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-33533350

RESUMO

We report here the first successful synthesis of planar triphenylborane 1 with the phenyl groups bridged by oxygen and nitrogen atoms via double nucleophilic aromatic substitution reaction. The hetero atom-bridged 1 has excellent planarity. Its structural and photophysical properties are tunable by altering the bridging atoms.

2.
J Clin Invest ; 99(10): 2351-7, 1997 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-9153276

RESUMO

Homeostasis of body fluid is maintained by the kidneys, which contain two million glomeruli for blood filtration. A glomerulus is formed by growth of Bowman's capsule harmonized with a capillary during kidney development. The vascular endothelial growth factor (VEGF) is an essential angiogenic cytokine, and VEGF deficiency is known to be fatal in mice in early embryonic stages. As secretions of VEGF from cultured kidneys vary according to developmental stages, the role of VEGF in kidney development was studied in vivo by blocking the endogenous VEGF activity with antibody in newborn mice, in which most organs are already developed but kidneys are still developing. The antibody-treated animals showed normal growth but systemic edema. Vessel formation in the superficial renal cortex was disturbed, nephrogenic areas were diminished, and the number of developing nephrons decreased significantly. Many abnormal glomeruli, lacking capillary tufts, were observed in the antibody-treated mice, and VEGF expression in their Bowman's capsule showed a compensatory increase. These results suggest that VEGF mediates communication between the Bowman's capsule and capillary endothelial cells for developing a glomerulus as well as promoting nephrogenesis. In conclusion, VEGF is likely to be an essential molecule for kidney development, and especially for glomerulogenesis.


Assuntos
Desenvolvimento Embrionário e Fetal , Fatores de Crescimento Endotelial/biossíntese , Glomérulos Renais/embriologia , Rim/embriologia , Linfocinas/biossíntese , Néfrons/embriologia , Animais , Animais Recém-Nascidos , Anticorpos , Membrana Basal/fisiologia , Membrana Basal/ultraestrutura , Capilares/embriologia , Capilares/fisiologia , Embrião de Mamíferos , Fatores de Crescimento Endotelial/metabolismo , Fatores de Crescimento Endotelial/fisiologia , Imuno-Histoquímica , Rim/irrigação sanguínea , Rim/metabolismo , Córtex Renal/irrigação sanguínea , Córtex Renal/embriologia , Glomérulos Renais/ultraestrutura , Linfocinas/metabolismo , Linfocinas/fisiologia , Camundongos , Microscopia Eletrônica , Técnicas de Cultura de Órgãos , Fator A de Crescimento do Endotélio Vascular , Fatores de Crescimento do Endotélio Vascular
3.
Int J Radiat Oncol Biol Phys ; 41(5): 1157-62, 1998 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-9719127

RESUMO

PURPOSE: Phosphorus-31 magnetic resonance spectra (31P-MRS) were obtained from highly apoptotic murine lymphoma xenografts before and up to 24 hr following graded doses of radiation ranging from 2 to 30 Gy. Radiation-induced apoptosis was also estimated up to 24 hr by scoring apoptotic cells in tumor tissue. METHODS AND MATERIALS: Highly apoptotic murine lymphoma cells, EL4, were subcutaneously transplanted into C57/BL mice. At 7 days after transplantation, radiation was given to the tumor with a single dose at 3, 10, and 30 Gy. The beta-ATP/Pi, PME/Pi, and beta-ATP/PME values were calculated from the peak area of each spectrum. Radiation-induced apoptosis was scored with counting apoptotic cells on hematoxylin and eosin stained specimens (% apoptosis). RESULTS: The values of % apoptosis 4, 8, and 24 hr after radiation were 21.8, 19.6, and 4.6% at 3 Gy, 35.1, 25.6, and 14.8% at 10 Gy, 38.4, 38.0, and 30.6% at 30 Gy, respectively (cf. 4.4% in control). There was no correlation between early change in beta-ATP/Pi and % apoptosis at 4 hr after radiation when most of the apoptosis occurred. An early decrease in PME/Pi was observed at 4 hr after radiation dose at 30 Gy. For each dose, the values of beta-ATP/Pi 24 hr after radiation were inversely related to radiation dose. CONCLUSION: The increase in beta-ATP/Pi observed by 31P-MRS was linked to the degree of histological recovery from radiation-induced apoptosis.


Assuntos
Apoptose/efeitos da radiação , Linfoma/radioterapia , Trifosfato de Adenosina/metabolismo , Animais , Linfoma/metabolismo , Linfoma/patologia , Espectroscopia de Ressonância Magnética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fósforo , Doses de Radiação , Fatores de Tempo , Transplante Heterólogo , Células Tumorais Cultivadas/efeitos da radiação
4.
Thromb Haemost ; 65(1): 73-6, 1991 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-2024241

RESUMO

Urokinase immobilized polymer is highly antithrombotic, which cannot be explained only by fibrinolysis. We immobilized 10 IU/cm2 of urokinase to polyurethane by using maleic anhydride methylvinyl ether copolymer as a carrier. Then we incubated blood in circular tubes made of this material, measured the clotting factors and observed the surface of the tubes after incubation by scanning electronmicroscopy and immunofluorescence microscopy. After 5 min incubation, the relative activities of factors V, VIII, IX, X and XII, fibrinogen, plasminogen and alpha 2 plasmin inhibitor decreased, but the activity of factor VII increased. No platelet adhesion to the surface of the urokinase immobilized polyurethane was observed and there was no significant adsorption of serum proteins, including fibrinogen, fibronectin and vWF antigen, on the surface. Urokinase-immobilized polyurethane catalyzed the digestion of clotting factors as well as fibrinolysis and also inhibited platelet adhesion on its surface probably by inhibiting protein adsorption and its clinical application including vessel prosthesis should be developed further.


Assuntos
Fatores de Coagulação Sanguínea/efeitos dos fármacos , Plaquetas/efeitos dos fármacos , Enzimas Imobilizadas/farmacologia , Fibrinolíticos , Ativador de Plasminogênio Tipo Uroquinase/farmacologia , Fatores de Coagulação Sanguínea/análise , Humanos , Fluoreto de Fenilmetilsulfonil/análogos & derivados , Poliuretanos , Ativador de Plasminogênio Tipo Uroquinase/antagonistas & inibidores
5.
J Biochem ; 87(5): 1519-30, 1980 May.
Artigo em Inglês | MEDLINE | ID: mdl-7390997

RESUMO

Many studies have been reported on the reaction of formaldehyde (FA) with amino acids or proteins, and FA is assumed to react with the alpha-amino group as well as some of the side chain groups. In most of these investigations a large excess of FA relative to amino acids or proteins was employed. In the present study, however, we carried out the reaction with a smaller excess of FA in order to clarify the reactivity, firstly with the alpha-amino groups, and secondly with specific side chain groups. No evidence for so-called Schiff base (-N = CH2) formation was obtained in the reaction with the alpha-amino groups, but the formation of an acid-labile N-hydroxymethyl compound as a major product was suggested by NMR and IR at greater than pH 9.2. There was no indication, however, of the presence of such a product below pH 9.2, and the amount of N-hydroxymethyl product increased in parallel with the reaction pH. The higher the reaction pH (greater than or equal to 9.2), the greater the consumption of FA, up to 2 mol/mol Ala. In addition, the larger the excess of FA, the smaller the amount of free amino group remaining (at pH 9.7). In the assignment of IR spectra, discrete absorption bands of the alpha-carboxyl group of Ala were observed, which reflected ionization states of the alpha-amino group, and these were utilized for analysis of the reaction mechanism. Furthermore, among amino acids with side chain groups, His, Trp, and Arg showed high reactivity and Asn showed moderate reactivity. The products were relatively stable and were purified and subjected to instrumental analyses. Sixteen other amino acids including Tyr and Lys did not yield stable products. The products from Arg were unique because of the non-involvement of the amino group, and were reversibly converted to the original Arg upon acid hydrolysis. The products from His, Trp and Asn all involved amino or amide nitrogen forming cyclic ring structures with methylene derived from FA. The chemical structures of these products were determined on the basis of elemental analyses, MS and NMR.


Assuntos
Aminoácidos , Formaldeído , Química Orgânica , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Fenômenos de Química Orgânica , Espectrofotometria Infravermelho , Relação Estrutura-Atividade
6.
Anticancer Res ; 18(4A): 2525-8, 1998.
Artigo em Inglês | MEDLINE | ID: mdl-9703904

RESUMO

PURPOSE: The aim of this study was to investigate the cell killing induced by low dose-rate irradiation (LDRI) simultaneously combined with long duration mild hyperthermia in LK87 human lung cancer cells. Cell cycle alteration due to this combined treatment was also observed. MATERIALS AND METHODS: Human lung adenocarcinoma cells, LK87, were treated with concurrent LDRI (50 cGy/hr) and mild hyperthermia (38 to 42 degrees C). Cell survival was estimated by clonogenic assay. Flow cytometry was performed with FACScan. The treatments were simultaneously performed for up to 48 hr (24 Gy). RESULTS: Survival curves of mild hyperthermia alone revealed development of chronic thermotolerance up to 48 hr, whereas LDRI plus hyperthermia caused an exponential decrease in survival. The LDRI cytotoxicities were enhanced by mild hyperthermia over a non-lethal temperature range. The Do values calculated from dose response curves at 37, 38, 39, 40, 41 41.5 and 42 degrees C were 6.55, 5.25, 4.24, 3.99, 3.46, 1.83 and 0.70 Gy, respectively. Cell cycle analysis demonstrated a remarkable G2 and a mild G1 block for LDRI alone, but only a G1 block was observed for LDRI combined with 41 degrees C hyperthermia. CONCLUSION: The LDRI cytotoxicity was enhanced by long duration mild temperature hyperthermia. The suppression of chronic thermotolerance was considered to be a mechanism involved in this sensitization.


Assuntos
Sobrevivência Celular/fisiologia , Hipertermia Induzida , Sobrevivência Celular/efeitos da radiação , Radioisótopos de Césio , DNA de Neoplasias/análise , DNA de Neoplasias/efeitos da radiação , Relação Dose-Resposta à Radiação , Citometria de Fluxo , Temperatura Alta , Humanos , Neoplasias Pulmonares , Reação em Cadeia da Polimerase , Polimorfismo Conformacional de Fita Simples , Fatores de Tempo , Células Tumorais Cultivadas , Ensaio Tumoral de Célula-Tronco
7.
Int J Radiat Biol ; 75(6): 739-45, 1999 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10405004

RESUMO

PURPOSE: To investigate cell killing by means of low dose-rate irradiation (LDRI) combined with concurrent mild hyperthermia and to determine the effect of low-dose caffeine on this combination treatment. MATERIALS AND METHODS: Human lung adenocarcinoma cells, LK87, were treated with LDRI (50 cGy/h) in combination with mild hyperthermia at 41 degrees C and low-dose caffeine (1 mM). Cell survival was estimated by clonogenic assay. Flow-cytometry was performed with PI staining using FACScan. Heat-shock protein (HSP72/73) was measured by the Western blotting method. All treatments were simultaneously performed for up to 48 h (24 Gy). RESULTS: LDRI cytotoxicities were enhanced by hyperthermia at 41 degrees C. D0 calculated from the dose-response curve for LDRI combined with 41 degrees C was 3.46 Gy whereas it was 6.55 Gy for LDRI alone. The survival curve for LDRI +41 degrees C demonstrated no chronic thermotolerance up to 48 h. For LDRI + simultaneous low-dose caffeine, cell killing was also enhanced, where D0 was 3.38 Gy at 37 degrees C. Radiosensitization caused by caffeine was enhanced by combination with simultaneous mild hyperthermia at 41 degrees C, where D0=1.78 Gy. Cell cycle analysis demonstrated remarkable G2 and mild G1 arrest for LDRI alone, but only G1 arrest was observed for LDRI combined with 41 degrees C and for LDRI combined with caffeine. Strong and early G1 arrest was observed in the treatment with LDRI + caffeine at 41 degrees C. The amount of HSP72/73 in the combination of LDRI with caffeine at 41 degrees C was less than that at 41 degrees C alone. CONCLUSION: LDRI cytotoxicity was enhanced by non-lethal hyperthermia. Low dose caffeine produced further cell killing in the combination of LDRI with mild hyperthermia.


Assuntos
Cafeína/farmacologia , Hipertermia Induzida , Neoplasias Pulmonares/terapia , Ciclo Celular/efeitos dos fármacos , Ciclo Celular/efeitos da radiação , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Terapia Combinada , Proteínas de Choque Térmico HSP72 , Proteínas de Choque Térmico/análise , Humanos , Neoplasias Pulmonares/patologia , Células Tumorais Cultivadas
8.
Clin Nephrol ; 37(2): 84-9, 1992 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-1551254

RESUMO

A new morphological classification of urinary erythrocytes was instituted in order to differentiate glomerular from urological hematuria. One hundred and thirteen hematuric patients including 73 glomerular and 40 urological disease patients were examined. The former group consisted of IgA nephropathy (n = 45), lupus nephritis (6), membrano-proliferative glomerulonephritis (5), non-IgA mesangial proliferative glomerulonephritis (4), Henoch-Schoenlein purpura nephritis (4), membranous nephropathy (4), endocapillary proliferative glomerulonephritis (3), and minimal change nephrotic syndrome (2). The latter group included bladder cancer (n = 15), renal calculi (15), prostate cancer (3), urethral cancer (1) and post-transurethral resection (6). In each urine sample, 100 urinary erythrocytes were observed under differential interference microscopy and classified into 10 concretely defined shapes (5 "glomerular" and 5 "urological" shapes) and unclassified shapes. Using percentage of "glomerular" shape erythrocytes and setting the cut-off at 15%, 90.4% of sensitivity and 97.5% of specificity for the diagnosis of glomerular disease were obtained. When percentage of one specific shape (G1), [i.e. doughnut-like cell with one or more blebs] was used at a cut-off of 1%, sensitivity and specificity were 89.0% and 95.0% respectively. These results were satisfactory as compared with most previous reports. Moreover, our classification is so concrete that it is more objective, accurate, and easily understandable, even for beginners. Distinct shape "G1" is particularly important for morphological investigation of hematuria.


Assuntos
Eritrócitos/patologia , Hematúria/diagnóstico , Diagnóstico Diferencial , Índices de Eritrócitos , Feminino , Glomerulonefrite/complicações , Hematúria/etiologia , Humanos , Masculino , Microscopia de Interferência , Pessoa de Meia-Idade , Sensibilidade e Especificidade , Doenças Urológicas/complicações
9.
Clin Nephrol ; 33(2): 61-5, 1990 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-2311307

RESUMO

Two patients with IgA nephritis associated with hereditary plasminogen abnormalities are described. One patient had dysplasminogenemia and the other had plasminogen deficiency. In both patients, renal biopsy specimens showed significant arteriosclerotic changes in addition to mesangial proliferation. Increased fibrinopeptide A concentration in their plasma suggested increased thrombin generation. In one patient, no systemic arteriosclerosis coexisted, judging from normal optic fundi and the absence of neurological and cardiac abnormalities. In IgA nephritis, renal vascular hyalinosis is often observed, probably resulting from vascular injury. Thus, it was suggested that the decreased fibrinolysis and renal vascular injury of these patients synergistically induced more fibrin thrombi and accelerated arteriosclerosis of the kidney. These cases imply the important role of fibrinolytic disorders in the progression of IgA nephritis.


Assuntos
Transtornos da Coagulação Sanguínea/complicações , Glomerulonefrite por IGA/complicações , Plasminogênio/deficiência , Adulto , Arteriosclerose/complicações , Arteriosclerose/patologia , Biópsia , Transtornos da Coagulação Sanguínea/sangue , Testes de Coagulação Sanguínea , Glomerulonefrite por IGA/sangue , Glomerulonefrite por IGA/patologia , Humanos , Rim/patologia , Masculino , Pessoa de Meia-Idade
10.
Intern Med ; 31(3): 426-30, 1992 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-1319248

RESUMO

The occurrence of rhabdomyolysis and acute renal failure associated with cytomegaloviral infection is rare. A 27-year-old housewife was admitted to our hospital with complaints of thirst, muscle weakness, abdominal pain and oliguria. There was no past history of diabetes, drinking, fever or drug habituation and a negative family history. Laboratory tests revealed myoglobinuria, hyper-pancreatic type amylaseuria, hyperglycemia, azotemia and highly increased creatine phosphokinase in the plasma. She was treated with hemodialysis and insulin therapy. Serological studies showed a 4-fold increase in cytomegalovirus antibody titers 4 weeks after admission. Muscle biopsy specimens showed hyaline degeneration and infiltration of T cell lymphocytes in the muscle. Renal biopsy specimens showed acute tubular necrosis and some myoglobin casts. No cytomegalovirus antigen was found in renal specimens by immunofluorescence study. From these results, it was determined that a systemic cytomegalovirus infection triggered pancreatitis which caused diabetic ketoacidosis, rhabdomyolysis and acute renal failure.


Assuntos
Injúria Renal Aguda/complicações , Infecções por Citomegalovirus/complicações , Pancreatite/complicações , Rabdomiólise/complicações , Doença Aguda , Injúria Renal Aguda/etiologia , Injúria Renal Aguda/patologia , Adulto , Cetoacidose Diabética/etiologia , Feminino , Humanos , Pancreatite/etiologia , Rabdomiólise/etiologia , Rabdomiólise/patologia
11.
ASAIO J ; 39(3): M581-3, 1993.
Artigo em Inglês | MEDLINE | ID: mdl-8268604

RESUMO

Effect of blood-air contact in the venous line air-trap chamber on blood clotting was studied. Fourteen chronic hemodialysis patients (six men, eight women; mean age, 49 years) with elevation of thrombin-antithrombin III were studied. To prevent blood-air contact, triglyceride (NOF-005) was floated over the blood in the chamber. Control hemodialysis was performed for 4 weeks and hemodialysis using NOF-005 followed for the next 4 weeks. Clot formation in the circuit was examined after each hemodialysis and clotting factors including thrombin-antithrombin III, FXII Antigen, vWF Antigen, PF4 and beta-thromboglobulin were measured before and after the last hemodialysis of each control and NOF-005 hemodialysis. Clotting in the chamber was improved when NOF-005 was used. Thrombin-antithrombin III increase during hemodialysis was suppressed to about 30% of control values by using NOF-005. blood-air contact seems to promote thrombin generation and accelerate clot formation.


Assuntos
Falência Renal Crônica/sangue , Diálise Renal , Trombina/biossíntese , Triglicerídeos/farmacologia , Adulto , Idoso , Antitrombina III/metabolismo , Testes de Coagulação Sanguínea , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Peptídeo Hidrolases/metabolismo
12.
Radiat Med ; 15(3): 177-80, 1997.
Artigo em Inglês | MEDLINE | ID: mdl-9278375

RESUMO

A case of embryonal rhabdomyosarcoma (RMS) arising from adult lower proximal extremity is described. Rhabdomyosarcoma (RMS) is most common among children, but adult embryonal RMS is rare. The patient was a 44-year-old man with a large tumor of the left extremity invading to the pelvis. The histological diagnosis was embryonal RMS. Radiation therapy was delivered a total dose of 50 Gy to the tumor. Although adult RMS, usually pleomorphic type, is considered to be radioresistant, the tumor showed marked response to radiotherapy and local control was achieved easily in this case.


Assuntos
Rabdomiossarcoma Embrionário/radioterapia , Adulto , Biópsia , Relação Dose-Resposta à Radiação , Seguimentos , Humanos , Perna (Membro) , Metástase Linfática/radioterapia , Masculino , Rabdomiossarcoma Embrionário/diagnóstico , Tomografia Computadorizada por Raios X
13.
Rinsho Byori ; 48(6): 485-90, 2000 Jun.
Artigo em Japonês | MEDLINE | ID: mdl-10897664

RESUMO

A glomerulus is a functional unit of the kidney, and endothelial cells in the glomerulus are often exposed to more than 5 times higher pressure than peripheral capillaries. Glomerular development proceeds through angiogenesis and VEGF was shown to mediate the angiogenesis. VEGF is constitutively expressed in the glomerulus from the embryo to adults. When VEGF signal was blocked by the antibody, glomerular endothelial cells were swollen and capillary lumen was interrupted. Changes were more prominent in the juxta-medullary than in the cortical glomerulus. A major VEGF receptor, Flk-1/KDR, is specifically localized to the glomerular endothelial cell among tissues and more predominantly in the juxta-medullary than in the cortical glomerulus. As capillary pressure is higher in the juxta-medullary than in the cortical glomeruli, endothelial cells in the former are exposed to more tension than those in the latter. VEGF might be a protective molecule for endothelial cells against tension. The effect of VEGF on the repair of an impaired glomerulus was evaluated in the rat Thy-1 glomerulonephritis. VEGF inhibited early endothelial injury and accelerated consequent remodeling of the glomerulus. In the patient study, VEGF excretion in the urine was independent from its serum or plasma level, but increased as renal function decreased. VEGF signaling is essential in glomerular development, maintenance and repair. VEGF excreted in the urine might reflect its generation in the kidney and be a unique marker of renal function.


Assuntos
Fatores de Crescimento Endotelial/urina , Glomerulonefrite/fisiopatologia , Linfocinas/urina , Animais , Biomarcadores/urina , Fatores de Crescimento Endotelial/fisiologia , Endotélio Vascular/citologia , Endotélio Vascular/fisiopatologia , Humanos , Glomérulos Renais/fisiopatologia , Linfocinas/fisiologia , Ratos , Regeneração , Fator A de Crescimento do Endotélio Vascular , Fatores de Crescimento do Endotélio Vascular
14.
Nihon Jinzo Gakkai Shi ; 33(1): 81-5, 1991 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-2038136

RESUMO

The renal disease in an adult woman with Type 1 glycogen storage disease (GSD) is reported. Since she was 15 years old, several episodes of gouty arthritis had developed. At the age of 18, proteinuria was pointed out. Hepatomegaly, renomegaly out of proportion to the impairment of renal function, hyperuricemia, hyperlipidemia, fasting hypoglycemia and lactic acidemia were observed. The diagnosis of GSD was established on the basis of a glucose tolerance test, glucagon test and liver biopsy. The findings of renal biopsies performed at the ages of 24 and 27 years old suggested that glomerular damage might have preceded the tubulo-interstitial lesion.


Assuntos
Doença de Depósito de Glicogênio Tipo I/patologia , Nefropatias/etiologia , Rim/patologia , Adulto , Biópsia , Feminino , Doença de Depósito de Glicogênio Tipo I/complicações , Humanos
15.
Nihon Jinzo Gakkai Shi ; 33(6): 623-8, 1991 Jun.
Artigo em Japonês | MEDLINE | ID: mdl-1920942

RESUMO

Although the etiology of systemic lupus erythematosus (SLE) is thought to be multifactorial, genetic factors may play some role in its pathogenesis. Supportive of this hypothesis are the studies of identical twins and familial cases of SLE. We describe below a family in which mother and son both developed SLE. The mother was diagnoged as SLE at age 25, and had been treated with prednisolone. In February 1989, she had massive proteinuria. The onset of the son's disease was at age 13 in 1988, when he noted erythema and photosensitivity. At admission to our hospital in 1989, he had polyarthralgia, proteinuria, positive antinuclear antibody, positive anti-DNA antibody. Both two patients had a same haplotype, HLA A2.BW61(40).DR9. Two asymptomatic members of this family were also studied, the younger son had positive antinuclear antibody and hypocomplementemia.


Assuntos
Lúpus Eritematoso Sistêmico/genética , Adolescente , Adulto , Anticorpos Antinucleares/análise , DNA/imunologia , Feminino , Antígeno HLA-A2/análise , Antígenos HLA-B/análise , Antígeno HLA-B40 , Antígenos HLA-DR/análise , Subtipos Sorológicos de HLA-DR , Haplótipos , Humanos , Lúpus Eritematoso Sistêmico/etiologia , Lúpus Eritematoso Sistêmico/imunologia , Masculino
16.
Artigo em Inglês | MEDLINE | ID: mdl-25314445

RESUMO

The distinguishable Brownian relaxation dynamics of a clustered-particle system of superparamagnetic iron oxide nanoparticle suspension compared to that of a dispersed-particle system has been experimentally investigated through characterization of the frequency and field strength dependences of complex magnetic susceptibility. We confirmed that the application of low sinusoidal magnetic field strength enables cluster rotation instead of individual particle rotations. Furthermore, we found that the cluster rotation was altered to individual particle rotations in higher field strength, resulting in a shorter Brownian relaxation time, which suggests a change in the hydrodynamic volume. This evolutional relaxation behavior was associated with a change in the fitting parameter which satisfies the empirical model of relaxation and further represents the significance of interparticle interactions in defining the nonlinearity of the magnetization response.


Assuntos
Hidrodinâmica , Nanopartículas de Magnetita/química , Fenômenos Magnéticos , Movimento (Física) , Tamanho da Partícula , Suspensões , Temperatura
19.
Nihon Rinsho ; 57 Suppl: 586-8, 1999 Aug.
Artigo em Japonês | MEDLINE | ID: mdl-10503508
20.
Phys Rev Lett ; 94(14): 147203, 2005 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-15904101

RESUMO

Two different ferromagnetic-paramagnetic transitions are detected in (Ga,Mn)As/GaAs(001) epilayers from ac susceptibility measurements: transition at a higher temperature results from (Ga,Mn)As cluster phases with [110] uniaxial anisotropy and that at a lower temperature is associated with a ferromagnetic (Ga,Mn)As matrix with 100 cubic anisotropy. A change in the magnetic easy axis from [100] to [110] with increasing temperature can be explained by the reduced contribution of 100 cubic anisotropy to the magnetic properties above the transition temperature of the (Ga,Mn)As matrix.

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