A numerical study of the thermodynamic properties of a superconducting quantum cylinder in a longitudinal magnetic field is carried out. Closed-form expressions for the critical temperature, the free energy, the heat capacity jump, and the magnetization difference between the superconducting and normal phases as functions of the nanotube parameters are obtained in limit cases.
Authors:Y. Ichiyanagi, T. Uehashi, S. Yamada, Y. Kanazawa, and T. Yamada
Summary Ni1-xZnxFe2O4 (0≤x≤1) mixed ferrite nanoparticles encapsulated with amorphous-SiO2 were prepared by a wet chemical method. Particle sizes were controlled to range from 2.6 to 33.7 nm by heat treatment, and the particle size dependence of saturation magnetization Ms was investigated for the x=0.5 region. The Ms value decreased abruptly for particle sizes below about 6 nm. From the temperature dependence of the magnetization under field-cooled and zero-field-cooled conditions, blocking temperatures Tb were observed to be between 28 and 245 K depending on the particle size. At the blocking temperature, the superparamagnetic spins in the particle are supposed to be blocked against the thermal fluctuation energy. A smaller particle volume causes a lower blocking temperature; so an extremely small particle would be strongly affected by thermal fluctuation.
Hauser H., Melikhov Y., Jiles D. C. Examination of the equivalence of ferromagnetic hysteresis models describing the dependence of magnetization on magnetic field and stress,
IEEE Trans. Magn
, Vol. 45, No. 4, 2009, pp. 1940
Authors:S. Paradkar, C. Vrinda, N. Jyotsna, and N. Sivaprasad
A simple immunoradiometric assay for human follicle stimulating hormone (hFSH) was developed using a pair of monoclonal antibodies
obtained from commercial sources. The system developed makes use of a capture antibody covalently coupled to magnetisable
cellulose, which is a more economical and stable immunosorbent as compared to the other solid phases. The detector antibody
is labeled with125I using the chloramine-T oxidation method and purified by gel filtration. After initial cross-matching of the capture and
detector antibodies, various assay parameters have been optimised. This assay does not show any significant cross reactivity
with homologous hormones. A number of serum samples from men and women from reproductive age group was screened and compared
with another commercially available kit (r=0.98). Sensitivity of the assay is 1.4 mIU/ml, interassay variation is <5% and intraassay variation around 15%. The assay
is reproducible and sensitive enough for regular estimation of serum hFSH and is relatively inexpensive.
Authors:M. Kubota, Y. Kanazawa, K. Nasu, S. Moritake, H. Kawaji, T. Atake, and Y. Ichiyanagi
MgFe2O4 (Mg-ferrite) nanoparticles encapsulated in amorphous SiO2 were prepared by the wet chemical method. The particle sizes were estimated, based on the X-ray diffraction peaks, to be
between 3 and 8 nm, depending on the annealing temperature. The particle size increased as the annealing temperature increased.
From the magnetization measurements, the blocking temperature, Tb, was found to be between 30 and 60 K. The magnetization values varied with the annealing or quenching conditions. To clarify
the process of crystal growth, thermogravimetric and differential thermal analysis (TG-DTA) measurements were performed and
the results were compared with the X-ray diffraction patterns.
The radioimmunoessay of human placental lactogen (HPL) with separation of antibody bound and free hormone was achieved by the magnetizable solid phase coupled to antibody. The precision, accuracy, sensitivity and specificity of the method has been carefully checked in this study and the procedure of the assay was performed at room temperature. The above parameters were evaluated by recovery test (99%); within assays (4%), between assays (5%), sensitivity (0.04 g/ml) and there was no obvious cross reactivity with human growth hormone (hGH) and human chorionic gonadotropin (hCG).
Authors:R. K. Mohan, V. Kadwad, G. Samuel, M. Venkatesh, and N. Sivaprasad
A simple user-friendly, solid phase radioimmunoassay for testosterone in human serum based on magnetic particles is described.
IgG fractions precipitated from polyclonal testosterone antiserum were coupled to magnetizable cellulose particles using carbonyl
diimidazole. The prepared antibody solid phase was stable for one year when stored at 4 °C. The optimized assay involves the
incubation of 50 ml of testosterone standards (0.3-10 ng/ml), 100 ml of magnetizable cellulose particle coupled antibody suspension
and 100 ml of 125I-testosterone derivative for 4 hours at 37 °C. At the end of the incubation, the tubes were placed on a magnetic rack for
10 minutes after the addition of wash buffer and decanted. The sensitivity of the assay is 0.2 ng/ml. The intra-assay variation
was <15% throughout the assay range. The recovery varied from 88 to 115%. On dilution of samples having high levels of testosterone,
linearity ranged between 87 and 125%. Correlation coefficient of 0.978 was obtained when the developed solid phase assay was
compared to the earlier established liquid phase assay.
Authors:V. Kadwad, N. Jyotsna, N. Sivaprasad, and P. Sinha
An easy adoptable technique has been developed to prepare magnetizable cellulose by the process of wet grinding of a mixture of iron oxide (magnetite) and cellulose in a stirred ball mill. Anti rabbit IgG was covalently coupled to this magnetizable cellulose. The immunosorbent thus prepared has been used in radioimmunoassays of T3 and T4 for the separation of bound and free antigens. The reliability of the above immunosorbent has been validated by studying assay parameters such as non-specific binding (NSB), maximum binding (B0), CV etc. The single step process of wet grinding adopted here not only firmly binds magnetite and cellulose physically, but also lowers the size of the resulting magnetizable cellulose. The conventional method of preparation involves the coprecipitation of cellulose dissolved in cuprammonium hydroxide solution along with iron oxide, followed by extensive grinding and sieving of the iron oxide impregnated cellulose.