Associations have been shown between father’s absence and menarcheal age, but most studies have focused on absence resulting from divorce, abandonment or death. Little research has been conducted to evaluate the effect on menarcheal age of paternal absence through migrant work. In a sample of 400 middle school students, this study examined the association between paternal migrant work and menarcheal age against a backdrop of extensive rural-to-urban migration in China. Data were collected through a self-reported questionnaire, including social-demographic characteristics, aspects of family relationships, information about father’s migrant work and age at menarche. After adjusting for BMI, parent marital status and perceived relationship with mother, lower self-perceived quality of father–daughter relationship (both ‘father present, relationship poor’ and ‘father absent, relationship poor’) and lower frequency of contact with the father were associated with higher odds for early menarche. These findings suggest that the assumption that father’s absence for work influences the timing of menarche needs to be examined in the context of the quality of the father–daughter relationship and paternal care, which appear to play a critical role in the timing of menarche. These findings also emphasize the importance of enhancing paternal involvement and improving father–daughter relationships in the development of appropriate reproductive strategy in daughters.

Freestanding, strip-shaped magnetoelastic (ME) biosensors are a class ofwireless, mass-based biosensors that are being developed for the real-timedetection of pathogenic bacteria for food safety and bio-security. The masssensitivity of these biosensors operating in longitudinal-vibration modes isknown to be largely dependent on the position of masses attached to thesensor surfaces. Hence, considering this dependence is crucial to thedetection of low-concentration target pathogens, including single pathogenicbacteria, because their local attachment may cause varying sensor responses.In a worst case scenario, the resultant sensor responses (i.e., mass-inducedresonance frequency changes of the sensor) may be too small to be detecteddespite the attachment of the target pathogenic masses. To address theissue, phage-coated ME biosensors (magnetostrictive strips (4 mm × 0.8 mm ×30 μm) coated with a phage probe specifically binding streptavidin protein)with localized masses (streptavidin-coated polystyrene beads) werefabricated, and mass-position-dependence of the sensor’s sensitivity underthe fundamental-mode vibration was experimentally measured. In addition,three-dimensional finite element (FE) modal analysis was performed using theCalculiX software to simulate the phenomena. The experimental andtheoretical results show close agreement: (1) the mass sensitivity was lowwhen the mass was positioned in the middle of the sensor’s longest dimensionand (2) a much higher mass sensitivity was, by contrast, obtained for theequivalent masses placed at both ends of the strip-shaped sensor.Furthermore, FE models were constructed for differently sized, phage-coatedME biosensors (100 – 500 μm in length with different widths and thicknesses)loaded with a single bacterial mass (2 μm × 0.4 μm × 0.4 μm, 1.05 g/cm3) at varying longitudinal positions. The mass sensitivitywas found to be approximated by a mass-position-dependent Boltzmann functionwhose amplitude is inversely proportional to the length squared, width, andthickness of the sensor.

Individual magnetostrictive nanobars and arrays comprised of magnetostrictive nanobars were recently introduced as a high performance biosensor platform. In this paper, we report the fabrication and characterization of magnetostrictive nanobars based on Fe-B alloy. The nanobars were synthesized using a template-based electrochemical deposition method. The composition and microstructure of the Fe-B nanobars are directly related to their performance as a biosensor platform. The Fe-B nanobar arrays and individual nanobar were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as Auger electron spectroscopy (AES). Morphologically, nanobars have a very flat top and a smooth cylindrical surface, which are critical factors for obtaining high performance as sensor platforms. Structurally, electron diffraction reveals that the Fe-B nanobars are amorphous. AES analysis indicates that Fe-B nanobars show no significant compositional variation along the length direction. It is found that the nanobars were covered by an oxidation layer of a typical thickness of ∼ 10 nm. It is believed that this oxidation layer is related to the passivation of nanobars in air. High temperature annealing and subsequent structural analysis indicate that the Fe-B nanobars possess a good thermal stability.

Recently, the magnetostrictive microcantilever (MSMC) as a high performance biosensor platform was introduced. The MSMC is a wireless acoustic wave (AW) sensor and exhibits a high Q value. More importantly, the MSMC works well in liquid. In this paper, the detection of Bacillus anthracis spores using MSMCs with filamentous phage as the bioprobe is reported. The phased-coated MSMC biosensors were exposed to cultures containing target spores with increasing concentrations ranging from 5 × 104 to 5 × 108 spores/mL. By monitoring the shift in the resonance frequency of the MSMCs, the spores were detected in a real-time manner and a detection limit of 105 spores/mL was obtained for the MSMCs used in this research. Higher sensitivity is expected for the MSMCs with smaller size.

P(VDF-CTFE) based nanocomposites were prepared by mixing the polymer with carbon nanotube (CNT) or C60 using solution cast method. The volume fraction of the CNT or C60 was from 0.1 % to 1.0%. The influence of CNT and C60 on the crystallization behavior of P(VDF-CTFE) was determined using XRD and DSC as well as the P-E loop. It is found that the CNT or C60 enhances the β-phase and the crystallinity. The crystallinity process in the composites was studied using DSC.

Magnetostrictive nanobars as sensor platform were induced. Based on the resonance behavior of strips made from thin films, it is identified that the amorphous Fe-B alloy is a good candidate for fabricating high performance sensor platform. The fabrication process of amorphous Fe-B nanobars using electrochemical deposition is reported. The magnetization hysteresis loop of Fe-B nanobars with the diameters of 50, 100 and 200 nm, respectively, was characterized. It is found that, for all nanobars, the coercive field measured along length direction is smaller than the coercive field measured perpendicular to length direction. The physics behind the phenomena is discussed.

Piezopolymer PVDF and P(VDF-TrFE) based diaphragms were fabricated. The diaphragm can be used as a high performance sensor platform for employing in liquid. The microelectronic process for fabricating microdiaphragm and its array is established. The performance of the PVDF based diaphragm in air and liquid was tested. It is found that the diaphragm works well in liquid.

In this paper, a novel micro-biosensor platform - magnetostrictive microcantilever (MSMC) - is reported. The resonance behavior and the sensitivity of MSMC as sensor platform were characterized and compared to the theoretical calculation. The detection of yeast cells using the biosensor made of MSMC was reported. The results demonstrate the feasibility of MSMC as a high performance biosensor platform. Compare to current microcantilevers, which is widely considered as the state-of-art sensor platform, the MSMCs have following advantages: 1) remote/wireless driving and sensing; 2) easy to fabricate. More importantly, it is experimentally found that the quality merit factor (Q value) of MSMC can reach more than 250, which is much higher than other cantilevers.

A micro-electromechanical diaphragm (MEMD) as micro-sensor platform is introduced. The performance of a MEMD is compared with that of a microcantilever (MC). It is theoretically found that the sensitivity of a MEMD is about 50 times higher than that of a MC. The measured resonance frequencies in air proved the validity of the MEMD design. More importantly, the quality merit factor (Q value) of MEMD is higher than that of MC. The damping effect of liquid medium on a MEMD is much smaller than on a MC. It is experimentally demonstrated that the MEMD works well in both air and liquid.