155 research outputs found
A CASE STUDY: READING A STORY BOOK WITH YOUNG ENGLISH LANGUAGE LEARNERS AT THE SILENT PERIOD
Reading a story book is considered as an effective way to promote language skills because it has been shown to foster enjoyment and pleasure in reading among language learners, however, there is still insufficient evidence about the effect of the reading on students’ motivation during the silent period to learn a foreign second language. The purpose of this study is to investigate second language learners’ reading motivation, and their language growth among interactions as reading a book during the silent period. Furthermore, this study has an implication to understand how reading a book affects young students when learning a foreign second language as English
GHz nanomechanical resonator in an ultraclean suspended graphene p-n junction
We demonstrate high-frequency mechanical resonators in ballistic graphene p-n
junctions. Fully suspended graphene devices with two bottom gates exhibit
ballistic bipolar behavior after current annealing. We determine the graphene
mass density and built-in tension for different current annealing steps by
comparing the measured mechanical resonant response to a simplified membrane
model. We consistently find that after the last annealing step the mass density
compares well with the expected density of pure graphene. In a graphene
membrane with high built-in tension, but still of macroscopic size with
dimensions 3 1 , a record resonance frequency of 1.17 GHz
is observed after the final current annealing step. We further compare the
resonance response measured in the unipolar with the one in the bipolar regime.
Remarkably, the resonant signals are strongly enhanced in the bipolar regime.
This enhancement is caused in part by the Fabry-Perot resonances that appear in
the bipolar regime and possibly also by the photothermoelectric effect that can
be very pronounced in graphene p-n junctions under microwave irradiation.Comment: 16 pages, 4 figures, 1 tabl
AC Josephson effect in a gate-tunable CdAs nanowire superconducting weak link
Three-dimensional topological Dirac semimetals have recently gained
significant attention, since they possess exotic quantum states. When
constructing Josephson junctions utilizing these materials as the weak link,
the fractional ac Josephson effect emerges in the presence of a topological
supercurrent contribution. We investigate the ac Josephson effect in a Dirac
semimetal CdAs nanowire using two complementary methods: by probing the
radiation spectrum and by measuring Shapiro patterns. With both techniques, we
find that conventional supercurrent dominates at all investigated doping levels
and that any potentially present topological contribution falls below our
detection threshold. The inclusion of thermal noise in a resistively and
capacitively shunted junction (RCSJ) model allows us to reproduce the microwave
characteristics of the junction. With this refinement, we explain how weak
superconducting features can be masked and provide a framework to account for
elevated electronic temperatures present in realistic experimental scenarios
Quantum dots formed in three-dimensional Dirac semimetal CdAs nanowires
We demonstrate quantum dot (QD) formation in three-dimensional Dirac
semimetal CdAs nanowires using two electrostatically tuned pn
junctions with a gate and magnetic fields. The linear conductance measured as a
function of gate voltage under high magnetic fields is strongly suppressed at
the Dirac point close to zero conductance, showing strong conductance
oscillations. Remarkably, in this regime, the CdAs nanowire device
exhibits Coulomb diamond features, indicating that a clean single QD forms in
the Dirac semimetal nanowire. Our results show that a ptype QD can be formed
between two ntype leads underneath metal contacts in the nanowire by
applying gate voltages under strong magnetic fields. Analysis of the quantum
confinement in the gapless band structure confirms that pn junctions formed
between the ptype QD and two neighboring ntype leads under high magnetic
fields behave as resistive tunnel barriers due to cyclotron motion, resulting
in the suppression of Klein tunneling. The ptype QD with magnetic
field-induced confinement shows a single hole filling. Our results will open up
a route to quantum devices such as QDs or quantum point contacts based on Dirac
and Weyl semimetals
The COOH-terminus of TM4SF5 in hepatoma cell lines regulates c-Src to form invasive protrusions via EGFR Tyr845 phosphorylation
AbstractTransmembrane 4 L six family member 5 (TM4SF5) enhances cell migration and invasion, although how TM4SF5 mechanistically mediates these effects remains unknown. In the study, during efforts to understand TM4SF5-mediated signal transduction, TM4SF5 was shown to bind c-Src and thus hepatoma cell lines expressing TM4SF5 were analyzed for the significance of the interaction in cell invasion. The C-terminus of TM4SF5 bound both inactive c-Src that might be sequestered to certain cellular areas and active c-Src that might form invasive protrusions. Wildtype (WT) TM4SF5 expression enhanced migration and invasive protrusion formation in a c-Src-dependent manner, compared with TM4SF5-null control hepatoma cell lines. However, tailless TM4SF5ΔC cells were more efficient than WT TM4SF5 cells, suggesting a negative regulatory role by the C-terminus. TM4SF5 WT- or TM4SF5ΔC-mediated formation of invasive protrusions was dependent or independent on serum or epidermal growth factor treatment, respectively, although they both were dependent on c-Src. The c-Src activity of TM4SF5 WT- or TM4SF5ΔC-expressing cells correlated with enhanced Tyr845 phosphorylation of epidermal growth factor receptor. Y845F EGFR mutation abolished the TM4SF5-mediated invasive protrusions, but not c-Src phosphorylation. Our findings demonstrate that TM4SF5 modulates c-Src activity during TM4SF5-mediated invasion through a TM4SF5/c-Src/EGFR signaling pathway, differentially along the leading protrusive edges of an invasive cancer cell
Integrated Piezoelectric AlN Thin Film with SU-8/PDMS Supporting Layer for Flexible Sensor Array
This research focuses on the development of a flexible tactile sensor array consisting of aluminum nitride (AlN) based on micro-electro-mechanical system (MEMS) technology. A total of 2304 tactile sensors were integrated into a small area of 2.5 × 2.5 cm2. Five hundred nm thick AlN film with strong c-axis texture was sputtered on Cr/Au/Cr (50/50/5 nm) layers as the sacrificial layer coated on a Si wafer. To achieve device flexibility, polydimethylsiloxane (PDMS) polymer and SU-8 photoresist layer were used as the supporting layers after etching away a release layer. Twenty-five mM (3-mercaptopropyl) trimethoxysilane (MPTMS) improves the adhesion between metal and polymers due to formation of a self-assembled monolayer (SAM) on the surface of the top electrode. The flexible tactile sensor has 8 × 8 channels and each channel has 36 sensor elements with nine SU-8 bump blocks. The tactile sensor array was demonstrated to be flexible by bending 90 degrees. The tactile sensor array was demonstrated to show clear spatial resolution through detecting the distinct electrical response of each channel under local mechanical stimulus. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.1
GHz nanomechanical resonator in an ultraclean suspended graphene p-n junction
We demonstrate high-frequency mechanical resonators in ballistic graphene p-n junctions. Fully suspended graphene devices with two bottom gates exhibit ballistic bipolar behavior after current annealing. We determine the graphene mass density and built-in tension for different current annealing steps by comparing the measured mechanical resonant response to a simplified membrane model. In a graphene membrane with high built-in tension, but still of macroscopic size with dimensions 3 x 1 m(2), a record resonance frequency of 1.17 GHz is observed after the final current annealing step. We further compare the resonance response measured in the unipolar with the one in the bipolar regime. Remarkably, the resonant signals are strongly enhanced in the bipolar regime
Problematic Use of Alcohol and Online Gaming as Coping Strategies During the COVID-19 Pandemic: A Mini Review
The COVID-19 (coronavirus disease 2019) pandemic has dramatically changed our daily lives and activities, including those originally intended to serve for leisure and pleasure. Drinking and online gaming became coping behaviors used to rescue ourselves from the stress and restricted lifestyle during the COVID-19 pandemic. However, frequent drinking and gaming can result in the pathological consequences of addiction. Those affected use the stimuli not to obtain pleasure, but rather to avoid the displeasure induced by stress and previous use, often unsuccessfully. This review aims to provide an overview of recent longitudinal cohort studies on alcohol and gaming use during the COVID-19 pandemic, as well as to analyze how the pandemic has affected alcohol and gaming use. There was a substantial risk of alcohol and online gaming overuse during the lockdown, which may depend on the pandemic's duration or overuse patterns. Previous studies have shown that increased alcohol consumption and online gaming are associated with heightened stress and anxiety levels caused by social isolation/quarantine. Over time, frequent or excessive alcohol consumption and gaming could lead to an increased risk of more serious mental health problems. Every effort should be made to mitigate mental health problems and ensure adequate adaptation to these exceptional circumstances. Therefore, it would be helpful to encourage physical activity, social interaction, and collaboration to facilitate psychological and physical health. © Copyright © 2021 Xu, Park, Kang, Choi and Koo.1
Impact of the gate geometry on adiabatic charge pumping in InAs double quantum dots
We compare the adiabatic quantized charge pumping performed in two types of InAs nanowire double quantum dots (DQDs), either with tunnel barriers defined by closely spaced narrow bottom gates, or by well-separated side gates. In the device with an array of bottom gates of 100 nm pitch and 10 mu m lengths, the pump current is quantized only up to frequencies of a few MHz due to the strong capacitive coupling between the bottom gates. In contrast, in devices with well-separated side gates with reduced mutual gate capacitances, we find well-defined pump currents up to 30 MHz. Our experiments demonstrate that high frequency quantized charge pumping requires careful optimization of the device geometry, including the typically neglected gate feed lines
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