S. Y. Yang

A nationwide survey of mild cognitive impairment and dementia, including very mild dementia, in Taiwan.

An increasing population of dementia patients produces substantial societal impacts. We assessed the prevalence of mild cognitive impairment (MCI) and all-cause dementia, including very mild dementia (VMD), in Taiwan. In a nationwide population-based cross-sectional survey, participants were selected by computerized random sampling from all 19 Taiwan counties and were enrolled between December 2011 and March 2013. Cases were identified through in-person interviews based on the National Institute on Aging-Alzheimer’s Association clinical criteria. Demographic data and histories involving mental status and function in daily living were collected. The principal objective assessments were the Taiwanese Mental Status Examination and Clinical Dementia Rating. In all, 10,432 people aged 65 years or older (mean age 76.2±6.7, 52.3% women) were interviewed. The age-adjusted prevalence of all-cause dementia was 8.04% (95% CI 7.47–8.61), including a 3.25% (95% CI 2.89–3.61) prevalence of VMD; that of MCI was 18.76% (95% CI 17.91–19.61). Women had a higher prevalence than men of both all-cause dementia (9.71% vs. 6.36%) and MCI (21.63% vs. 15.57%). MCI affects a considerable portion of the population aged 65 and above in Taiwan. The inclusion of VMD yields dementia prevalence rates higher than those previously reported from Taiwan. Old age, female gender, and a low educational level are significant associated factors.

Magnetochromatics of the magnetic fluid film under a dynamic magnetic field

The structure and the corresponding magnetochromatics of homogeneous magnetic fluid films under dynamic magnetic fields perpendicular to the film surfaces are investigated in this letter. During the application of a magnetic field from 0 up to 200 Oe, the structure in the magnetic fluid film evolves from a monodispersed state to a disordered-column state, and then to an ordered hexagonal structure. The column spacing for the instant hexagonal structure during the dynamic process was measured and found to vary from 2.41 to 1.83 μm when the field strength was raised from 60 to 200 Oe. Within this range, the hexagonal structure diffracts the visible light like an optical grating. Due to the dynamic variation of the column spacing with the increasing field strength, the color of the diffracted light changed unceasingly from red to blue when observed from a fixed point above the film. The results strongly suggest the possibility that optical devices may be developed by utilizing the magnetochromatics of magnet...

Enhancement of nuclear magnetic resonance in microtesla magnetic field with prepolarization field detected with high-Tc superconducting quantum interference device

We applied prepolarization field and high-Tc superconducting quantum interference device (SQUID) detector to enhance nuclear magnetic resonance signal in a microtesla magnetic field. The minimum measuring magnetic field is 8.9μT at which the proton resonance frequency is 380Hz. The specificity instrumentation and the difficulty of using a high-Tc SQUID with prepolarization field were investigated. We applied gradient field to perform one-dimensional proton imaging in a microtesla magnetic field. Additionally, low field high-Tc SQUID-based NMR systems are promising in biomagnetic research due to its use, for example, in imaging with hyperpolarized noble gas.

Nanomagnetic particles for SQUID-based magnetically labeled immunoassay

With the increasing importance of SQUID-based magnetically labeled immunoassay, the study on the synthesis of controllable sizes of magnetic nanoparticles plays a role to promote the accuracy of the immunoassay. In this work, Fe/sub 3/O/sub 4/ nano-particles coated with a suitable bio-probe (biotin) are synthesized through chemical co-precipitation process to probe the bio-target (avidin). Through the synthesis developed here, the particle hydrodynamic diameter can be adjusted from 30 to 90 nm, which provide candidates for probing various bio-targets in the future. The amount of the magnetically labeled avidin is then analyzed via measuring the saturated magnetization or the remanence of the sample by using a SQUID magnetometer.

Magnetic relaxation measurement in immunoassay using high-transition-temperature superconducting quantum interference device system

Due to their ultrahigh sensitivity to magnetic flux, superconducting quantum interference devices (SQUIDs) are able to detect biomagnetic signals. By labeling biotargets with magnetic nanoparticles, several groups have shown that SQUIDs are promising as quantitative probes of biotargets by measuring their magnetic properties. In this work, we describe the design and construction of a high-transition-temperature radio-frequency SQUID magnetometer system for measuring the magnetic relaxation of labeled avidin. We also describe the synthesis of magnetic nanoparticles coated with biotin for use in labeling the avidin. Furthermore, the specifications of the SQUID-based magnetically labeled immunoassay of avidin are explored.

Ultra-highly sensitive and wash-free bio-detection of H5N1 virus by immunomagnetic reduction assays

A platform for assaying avian influenza H5N1 viruses that involves measuring the ac immunomagnetic reduction of a magnetic reagent mixed with a detected sample is developed. The magnetic reagent contained magnetic nanoparticles coated with antibodies. To achieve an ultra-high sensitivity assay, a system utilizing a high-transition-temperature superconducting quantum interference device was used to sense the immunomagnetic reduction of the reagents. The results confirmed the ultra-high sensitivity of the immunomagnetic reduction assay on H5N1.

Multi-Channel SQUID-Based Ultra-High-Sensitivity In-Vitro Detections for Bio-Markers of Alzheimer's Disease Via Immunomagnetic Reduction

Via immunomagnetic reduction assay, bio-molecules can be quantitatively detected with the aid of bio-functionalized magnetic nanoparticles, which are used as labeling markers for specific bio-molecules. To achieve an ultra-high sensitivity in the detection of bio-molecules, the superconducting quantum interference device (SQUID) looks very promising as a sensor for the magnetic signal that are related to the concentration of the detected bio-molecules. We had developed a single channel SQUID-based magnetosusceptometer, but for increasing the detection through-put, we have developed a multi-channel SQUID-based magnetosusceptometer. In this work, the design and the working principle of a 4-channel SQUID-based magnetosusceptometer are introduced. By utilizing scanning technology, 4 samples can be logged into a SQUID-based magnetosusceptometer simultaneously. Be noted that only one single SQUID magnetometer has been used in the magnetosusceptometer. The precision and the sensitivity of detecting bio-molecules by using a 4-channel SQUID-based magnetosusceptometer have been investigated. The detected bio-molecules are biomarkers for Alzheimers disease.

Magnetically enhanced high-specificity virus detection using bio-activated magnetic nanoparticles with antibodies as labeling markers

This study describes magnetically driven suppression of cross-reactions among molecules. First, the magnetic nanoparticles are coated with bio-probes and dispersed in liquid. The bio-probes can then bind with homologous or heterologous bio-targets. When alternating-current (ac) magnetic fields are applied, magnetic nanoparticles rotate driven by ac magnetic fields. Thus, the bio-targets bound on the surface of magnetic nanoparticles experience a centrifugal force. The centrifugal force can be manipulated by adjusting the angular frequency of the rotating magnetic nanoparticles. The angular frequency is determined by the applied ac magnetic field frequency. Since the binding force for good binding is much higher than that of poor binding, frequency manipulation is needed for the centrifugal force to be higher than the poor-binding force but lower than the good-binding force. Therefore, poor binding which contributes to cross reactions between molecules can be suppressed efficiently by control of the ac magnetic field frequency.

Detection of deep flaws by using a HTS-SQUID in unshielded environment

We reported the nondestructive evaluation of flaws in conductive samples with the high-T/sub c/ SQUID operated at 77 K. By nulling the SQUID with an additional compensation, we can sensitively detect the excited magnetic field due to the eddy current around a deep flaw. To investigate the effects of the size and the depth of flaws on the induced magnetic field, the excited magnetic fields as a function of the depth were measured for buried slots with various widths and thickness. Besides, the amplitude and the phase with different excitation frequencies for a fixed slot size are also studied. It was found that for a fixed excitation frequency, the phase of the measured signal linearly responds to the depth of the slot, while the amplitude correlates with the height of the slot. The results are valuable for quantitative evaluation of flaws.

Effect of molecule-particle binding on the reduction in the mixed-frequency alternating current magnetic susceptibility of magnetic bio-reagents

By specifically bio-functionalizing magnetic nanoparticles, magnetic nanoparticles are able to label target bio-molecules. This property can be applied to quantitatively detect molecules invitro by measuring the related magnetic signals of nanoparticles bound with target molecules. One of the magnetic signals is the reduction in the mixed-frequency ac magnetic susceptibility of suspended magnetic nanoparticles due to the molecule-particle association. Many experimental results show empirically that the molecular-concentration dependent reduction in ac magnetic susceptibility follows the logistic function. In this study, it has been demonstrated that the logistic behavior is originated from the growth of particle sizes due to the molecule-particle association. The analytic relationship between the growth of particle sizes and the reduction in ac magnetic susceptibility is developed.