42 research outputs found
Twinning of Rhombic Colloidal Crystals
We observe twinning of two-dimensional (2D) rhombic colloidal
crystals
of hard Brownian rhombic platelets. By contrast to square particles,
which have higher symmetry but can also form rhombic lattices at high
densities, each rhombic particle has a distinguishable bidirectional
pointing axis. This key feature, which is not readily seen in rhombic
crystals of square colloids, facilitates observations of different
types of twinning: contact, polysynthetic, and cyclic. Moreover, we
find that the twinned crystals are slightly offset spatially along
their shared mirror line. In addition, the average pointing axis of
the particles in a single crystal is also offset on average by a small
angle, either clockwise or counterclockwise, from the average pointing
axis of the rhombic lattice yielding a form of nonlocal chiral symmetry
breaking. Because mirror lines between contact twins introduce only
a small reduction in the total number of accessible states, compared
to a perfect single crystal, twinning and piecewise linear defects
are commonly observed. Thus, twinning, which is usually associated
with complex compositions in certain minerals, also emerges in a simpler
2D system of entropically driven, hard, achiral objects
Enhanced Photocatalytic Removal of Sodium Pentachlorophenate with Self-Doped Bi<sub>2</sub>WO<sub>6</sub> under Visible Light by Generating More Superoxide Ions
In
this study, we demonstrate that the photocatalytic sodium
pentachlorophenate removal efficiency of Bi<sub>2</sub>WO<sub>6</sub> under visible light can be greatly enhanced by bismuth
self-doping through a simple soft-chemical method. Density functional
theory calculations and systematical characterization results revealed
that bismuth self-doping did not change the redox power of photogenerated
carriers but promoted the separation and transfer of photogenerated
electron–hole pairs of Bi<sub>2</sub>WO<sub>6</sub> to produce
more superoxide ions, which were confirmed by photocurrent generation
and electron spin resonance spectra as well as superoxide ion
measurement results. We employed gas chromatography–mass spectrometry
and total organic carbon analysis to probe the degradation and the
mineralization processes. It was found that more superoxide
ions promoted the dechlorination process to favor the subsequent
benzene ring cleavage and the final mineralization of sodium
pentachlorophenate during bismuth self-doped Bi<sub>2</sub>WO<sub>6</sub> photocatalysis by producing easily decomposable
quinone intermediates. This study provides new insight into the effects
of photogenerated reactive species on the degradation of sodium
pentachlorophenate and also sheds light on the design
of highly efficient visible-light-driven photocatalysts for
chlorophenol pollutant removal
Self-Powered Wireless Smart Sensor Node Enabled by an Ultrastable, Highly Efficient, and Superhydrophobic-Surface-Based Triboelectric Nanogenerator
Wireless
sensor networks will be responsible for a majority of
the fast growth in intelligent systems in the next decade. However,
most of the wireless smart sensor nodes require an external power
source such as a Li-ion battery, where the labor cost and environmental
waste issues of replacing batteries have largely limited the practical
applications. Instead of using a Li-ion battery, we report an ultrastable,
highly efficient, and superhydrophobic-surface-based triboelectric
nanogenerator (TENG) to scavenge wind energy for sustainably powering
a wireless smart temperature sensor node. There is no decrease in
the output voltage and current of the TENG after continuous working
for about 14 h at a wind speed of 12 m/s. Through a power management
circuit, the TENG can deliver a constant output voltage of 3.3 V and
a pulsed output current of about 100 mA to achieve highly efficient
energy storage in a capacitor. A wireless smart temperature sensor
node can be sustainably powered by the TENG for sending the real-time
temperature data to an iPhone under a working distance of 26 m, demonstrating
the feasibility of the self-powered wireless smart sensor networks
The histograms of the prevalence after one day under each null model.
<p>The histograms of the prevalence after one day under each null model.</p
A review of the acquisitions experience of major UK companies
SIGLEAvailable from British Library Document Supply Centre-DSC:98/08553 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Intersession time.
<p>The intersession time distribution for each node is clearly longer for all null models that break TN.</p
Session volume over time shows diurnal and weekday/weekend patterns.
<p>Session volume over time shows diurnal and weekday/weekend patterns.</p
Total contacts per node.
<p>Total contacts per node are comparable across null models.</p
Fraction of infected devices |<i>I</i>(<i>t</i>)|/<i>N</i> as a function of time, for the original contact trace and inducement-shuffled null models.
<p>Fraction of infected devices |<i>I</i>(<i>t</i>)|/<i>N</i> as a function of time, for the original contact trace and inducement-shuffled null models.</p
Characterization of Morphology and Structure of Wax Crystals in Waxy Crude Oils by Terahertz Time-Domain Spectroscopy
The
content, morphology, and structure of precipitated wax crystals
are major factors affecting crude oil rheology. In this paper, model
oils obtained by dissolving a realistic mixture of long-chain <i>n</i>-octacosane in diesel fuels were studied using terahertz
time-domain spectroscopy (THz-TDS) and microscopy to gain insight
into clusters composed of asphaltene and wax with increasing wax content.
The fractal dimension was used for quantitative characterization of
the morphology and structure of clusters in the model oils. From the
measured absorption and extinction coefficients in the THz region,
dynamic processes of the clusters in the model oils were analyzed
and identified. The extinction coefficient in the THz region strongly
depended on the dispersed and aggregated states of the asphaltene
and wax crystals. These observations suggest that the aggregation
state of the particles in model oils can be monitored with THz-TDS.
In the future, THz-TDS technology may be used to effectively analyze
particle dispersion or the aggregation state in crude oil and may
thus be useful for rapid assessment of the effect of pour-point depressant
on wax crystal aggregates