STUDY ON THE SENSITIVITY OF FUNCTIONALIZEDNANOWIRES USING VARIED CHEMICALS

Silicon nanowire-based metal-oxide-semiconductor field-effect transistors (SiNW MOSFETs) havebeen demonstrated excellent sensitivity and stability after surface modification and functionalization ofnanowires. Chemical molecules have been applied to functionalize the surface of silicon surface. Silanecoupling agents are good candidates for forming self-assembled monolayers (SAMs) by chemicallyinteracting with silicon oxide. Those chemically modified SAMs can provide a functional surface tofurther conjugate biomolecules on SiNW MOSFETs. After functionalization, SiNW MOSFETs withtunably biocompatible surface can sustain a functional biointerface for biological tests. In this work,SiNW MOSFETs were fabricated using the standard I-line stepper of MOS semiconducting process andthen visualized by scanning electron microscopy (SEM). The n-type SiNW MOSFETs devices werefabricated after the process of trimming, the scale of nanowire was down to a level of approximate 165 nm.3-aminopropyl trimethoxysilane (APTMS) and 3-mercaptopropyl trimethoxysilane (MPTMS) SAMs wereindependently used to modify the surface of SiNW MOSFETs for pH sensing in biological buffer solution.Atomic force microscopy (AFM) and electron spectroscopy for chemical analysis (ESCA) were appliedto characterize before and after surface modification. AFM found APTMS and MPTMS were successfullymodified on silicon substrates. The average vertical length of APTMS and MPTMS SAMs from our AFMobservation was around 2.628 nm and 2.698 nm, respectively. ESCA showed the specifically functionalamino (-NH2) groups and mercapto (-SH) groups on each APTMS and MPTMS modified silicon substrates.The specific amine functional group at 399.4 eV occurred after the modification of APTMS on siliconsubstrate in N1s spectra. S2p spectra showed the specific binding at 163.6 eV (C-SH) and 165.8 eV (-C-SS-C-) after the modification of MPTMS on silicon substrate. Those disulfide bonds further influenced theorganization of MPTMS-SAM on the surface; therefore, the APTMS had better SAM performance on oursilicon substrate. On the other hand, electrical measuring system was used for elucidating that the suitablesurface modification would have great impact on the sensing response and sensitivity. Varied biologicalPBS solutions at different pH values showed that unmodified SiNW MOSFETs were sensitive to theH+ ion change. When the pH level of the solution increased, the drain current of the unmodified SiNWMOSFETs decreased accordingly. In comparison with unmodified nanowires in current measurement,the changes of current of APTMS or MPTMS modified nanowires were enhanced in sensing of differentpH solutions. Our results also showed that amino and mercapto groups of APTMS and MPTMS canimprove the protonation and deprotonation reactions in different pH solutions. Both APTMS and MPTMSmodified SiNW MOSFETs in pH sensings possessed good electrical sensing response and sensitivity incontrast with unmodified one. Moreover, in consequence of lower mercaptal groups of MPTMS on NWs,the relatively minor signal responses to varied pH solutions in MPTMS modified SiNW MOSFETs. Theelectrical measurement showed that the amino groups of APTMS significantly improve the sensitivity ofSiNW MOSFET in different pH sensings. Our results showed that adequate modification could provide afunctionable surface for SiNW MOSFETs. We inferred the APTMS modified SiNW MOSFETs could be areal-time sensor for different pH levels detection and further applied in monitoring biological environmentin the future

The role of Omi/HtrA2 protease in neonatal postasphyxial serum-induced apoptosis in human kidney proximal tubule cells

Omi/HtrA2, a proapoptotic mitochondrial serine protease, is involved in both caspase-dependent and caspaseindependent apoptosis. A growing body of evidence indicates that Omi/HtrA2 plays an important role in the pathogenesis of a variety of ischemia-reperfusion (I/R) injuries. However, the role of Omi/HtrA2 in renal injuries that occur in neonates with asphyxia remains unknown. The present study was designed to investigate whether Omi/HtrA2 plays an important role in the types of renal injuries that are induced by neonatal postasphyxial serum. Human renal proximal tubular cell line (HK-2) cells were used as targets. A 20% serum taken from neonates one day after asphyxia was applied to target cells as an attacking factor. We initially included control and postasphyxial serum-attacked groups and later included a ucf-101 group in the study. In the postasphyxial serum-treated group, cytosolic Omi/HtrA2 and caspase-3 expression in HK-2 cells was significantly higher than in the control group. Moreover, the concentration of cytosolic caspase-3 was found to be markedly decreased in HK-2 cells in the ucf-101 group. Our results suggest both that postasphyxial serum has a potent apoptosis-inducing effect on HK-2 cells and that this effect can be partially blocked by ucf-101. Taken together, our results demonstrate for the first time that postasphyxial serum from neonates results in Omi/HtrA2 translocation from the mitochondria to the cytosol, where it promotes HK-2 cell apoptosis via a protease activity-dependent, caspase-mediated pathway

A Simple Model for Cavity Enhanced Slow Lights in Vertical Cavity Surface Emission Lasers

We develop a simple model for the slow lights in Vertical Cavity Surface Emission Lasers (VCSELs), with the combination of cavity and population pulsation effects. The dependences of probe signal power, injection bias current and wavelength detuning for the group delays are demonstrated numerically and experimentally. Up to 65 ps group delays and up to 10 GHz modulation frequency can be achieved in the room temperature at the wavelength of 1.3 $\mu$m. The most significant feature of our VCSEL device is that the length of active region is only several $\mu$m long. Based on the experimental parameters of quantum dot VCSEL structures, we show that the resonance effect of laser cavity plays a significant role to enhance the group delays

Validation of the Action Research Arm Test using item response theory in patients after stroke

Objective: To validate the unidimensionality of the Action Research Arm Test (ARAT) using Mokken analysis and to examine whether scores of the ARAT can be transformed into interval scores using Rasch analysis. Subjects and methods: A total of 351 patients with stroke were recruited from 5 rehabilitation departments located in 4 regions of Taiwan. The 19-item ARAT was administered to all the subjects by a physical therapist. The data were analysed using item response theory by non-parametric Mokken analysis followed by Rasch analysis. Results: The results supported a unidimensional scale of the 19-item ARAT by Mokken analysis, with the scalability coefficient H = 0.95. Except for the item pinch ball bearing 3rd finger and thumb'', the remaining 18 items have a consistently hierarchical order along the upper extremity function's continuum. In contrast, the Rasch analysis, with a stepwise deletion of misfit items, showed that only 4 items (grasp ball'', grasp block 5 cm(3)'', grasp block 2.5 cm(3)'', and grip tube 1 cm(3)'') fit the Rasch rating scale model's expectations. Conclusion: Our findings indicated that the 19-item ARAT constituted a unidimensional construct measuring upper extremity function in stroke patients. However, the results did not support the premise that the raw sum scores of the ARAT can be transformed into interval Rasch scores. Thus, the raw sum scores of the ARAT can provide information only about order of patients on their upper extremity functional abilities, but not represent each patient's exact functioning

Assessing the quality of steady-state visual-evoked potentials for moving humans using a mobile electroencephalogram headset.

Recent advances in mobile electroencephalogram (EEG) systems, featuring non-prep dry electrodes and wireless telemetry, have enabled and promoted the applications of mobile brain-computer interfaces (BCIs) in our daily life. Since the brain may behave differently while people are actively situated in ecologically-valid environments versus highly-controlled laboratory environments, it remains unclear how well the current laboratory-oriented BCI demonstrations can be translated into operational BCIs for users with naturalistic movements. Understanding inherent links between natural human behaviors and brain activities is the key to ensuring the applicability and stability of mobile BCIs. This study aims to assess the quality of steady-state visual-evoked potentials (SSVEPs), which is one of promising channels for functioning BCI systems, recorded using a mobile EEG system under challenging recording conditions, e.g., walking. To systematically explore the effects of walking locomotion on the SSVEPs, this study instructed subjects to stand or walk on a treadmill running at speeds of 1, 2, and 3 mile (s) per hour (MPH) while concurrently perceiving visual flickers (11 and 12 Hz). Empirical results of this study showed that the SSVEP amplitude tended to deteriorate when subjects switched from standing to walking. Such SSVEP suppression could be attributed to the walking locomotion, leading to distinctly deteriorated SSVEP detectability from standing (84.87 ± 13.55%) to walking (1 MPH: 83.03 ± 13.24%, 2 MPH: 79.47 ± 13.53%, and 3 MPH: 75.26 ± 17.89%). These findings not only demonstrated the applicability and limitations of SSVEPs recorded from freely behaving humans in realistic environments, but also provide useful methods and techniques for boosting the translation of the BCI technology from laboratory demonstrations to practical applications