Reciprocating motion is a widely existing form of mechanical motion in natural environment. In this work we reported a case-encapsulated triboelectric nanogenerator (cTENG) based on sliding ...electrification to convert reciprocating motion into electric energy. Patterned with multiple sets of grating electrodes and lubricated with polytetrafluoroethylene (PTFE) nanoparticles, the cTENG exported an average effective output power of 12.2 mW over 140 kΩ external load at a sliding velocity of 1 m/s, in corresponding to a power density of 1.36 W/m2. The sliding motion can be induced by direct-applied forces as well as inertia forces, enabling the applicability of the cTENG in addressing ambient vibration motions that feature large amplitude and low frequency. The cTENG was demonstrated to effectively harvest energy from human body motions and wavy water surface, indicating promising prospects of the cTENG in applications such as portable and stand-alone self-powered electronics.
Recently, commercial graphite and other carbon‐based materials have shown promising properties as the anode for potassium‐ion batteries. A fundamental problem related to those carbon electrodes, ...significant volume expansion, and structural instability/collapsing caused by cyclic K‐ion intercalation, remains unsolved and severely limits further development and applications of K‐ion batteries. Here, a multiwalled hierarchical carbon nanotube (HCNT) is reported to address the issue, and a reversible specific capacity of 232 mAh g−1, excellent rate capability, and cycling stability for 500 cycles are achieved. The key structure of the HCNTs consists of an inner CNT with dense‐stacked graphitic walls and a loose‐stacked outer CNT with more disordered walls, and individual HCNTs are further interconnected into a hyperporous bulk sponge with huge macropore volume, high conductivity, and tunable modulus. It is discovered that the inner dense‐CNT serves as a robust skeleton, and collectively, the outer loose‐CNT is beneficial for K‐ion accommodation; meanwhile the hyperporous sponge facilitates reaction kinetics and offers stable surface capacitive behavior. The hierarchical carbon nanotube structure has great potential in developing high‐performance and stable‐structure electrodes for next generation K and other metal‐ion batteries.
A hierarchical carbon nanotube (HCNT) consists of two coaxial, seamless arranged parts, including a dense‐stacked inner CNT and a loose‐stacked outer CNT. Those HCNTs are interconnected into a hyperporous bulk sponge with a huge macropore volume, high conductivity, and tunable modulus. Such unique materials have potential applications as high‐performance freestanding anodes for K‐ion batteries with excellent specific capacity and cycling stability.
Neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists because their attributes can be used to determine the properties of the dense matter in ...their cores. One of the most informative approaches for determining the equation of state (EoS) of this dense matter is to measure both a star's equatorial circumferential radius Re and its gravitational mass M. Here we report estimates of the mass and radius of the isolated 205.53 Hz millisecond pulsar PSR J0030+0451 obtained using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER). This approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. We explored a variety of emission patterns on the stellar surface. Our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using NICER. The radius and mass estimates given by this model are km and (68%). The independent analysis reported in the companion paper by Riley et al. explores different emitting spot models, but finds spot shapes and locations and estimates of Re and M that are consistent with those found in this work. We show that our measurements of Re and M for PSR J0030+0451 improve the astrophysical constraints on the EoS of cold, catalyzed matter above nuclear saturation density.
We report on Bayesian parameter estimation of the mass and equatorial radius of the millisecond pulsar PSR J0030+0451, conditional on pulse-profile modeling of Neutron Star Interior Composition ...Explorer X-ray spectral-timing event data. We perform relativistic ray-tracing of thermal emission from hot regions of the pulsar's surface. We assume two distinct hot regions based on two clear pulsed components in the phase-folded pulse-profile data; we explore a number of forms (morphologies and topologies) for each hot region, inferring their parameters in addition to the stellar mass and radius. For the family of models considered, the evidence (prior predictive probability of the data) strongly favors a model that permits both hot regions to be located in the same rotational hemisphere. Models wherein both hot regions are assumed to be simply connected circular single-temperature spots, in particular those where the spots are assumed to be reflection-symmetric with respect to the stellar origin, are strongly disfavored. For the inferred configuration, one hot region subtends an angular extent of only a few degrees (in spherical coordinates with origin at the stellar center) and we are insensitive to other structural details; the second hot region is far more azimuthally extended in the form of a narrow arc, thus requiring a larger number of parameters to describe. The inferred mass M and equatorial radius Req are, respectively, 1.34 − 0.16 + 0.15 M and 12.71 − 1.19 + 1.14 km , while the compactness GM R eq c 2 = 0.156 − 0.010 + 0.008 is more tightly constrained; the credible interval bounds reported here are approximately the 16% and 84% quantiles in marginal posterior mass.
Freestanding composite structures with embedded transition metal dichalcogenides (TMDCs) as the active material are highly attractive in the development of advanced electrodes for energy storage ...devices. Most 3D electrodes consist of a bilayer design involving a core–shell combination. To further enhance the gravimetric and areal capacities, a 3D trilayer design is proposed that has MoSe2 as the TMDC sandwiched in‐between an inner carbon nanotube (CNT) core and an outer carbon layer to form a CNT/MoSe2/C framework. The CNT core creates interconnected pathways for the e−/Na+ conduction, while the conductive inert carbon layer not only protects the corrosive environment between the electrolyte and MoSe2 but also is fully tunable for an optimized Na+ storage. This unique heterostructure is synthesized via a solvothermal‐carbonization approach. Due to annealing under a confined structural configuration, MoSe2 interlayer spaces are expanded to facilitate a faster Na+ diffusion. It is shown that an ≈3 nm thick carbon layer yielded an optimized anode for a sodium‐ion battery. The 3D porosity of the heterostructure remains intact after an intense densification process to produce a high areal capacity of 4.0 mAh cm−2 and a high mass loading of 13.9 mg cm−2 with a gravimetric capacity of 347 mAh g−1 at 500 mA g−1 after 500 cycles.
A 3D trilayer heterostructure (3D CNT/MoSe2/C) (CNT: carbon nanotube) is fabricated in which expanded MoSe2 is sandwiched in‐between the carbon nanotube and the carbon layer with a tunable thickness of outer carbon layer. The 3D CNT/MoSe2/C heterostructures are highly porous and can be densified by compaction. Representative CNT/MoSe2/C present adequately high mass loading, high areal capacity, and excellent cyclic stability for sodium‐ion batteries.
On Estimating Conditional Conservatism Ball, Ray; Kothari, S. P.; Nikolaev, Valeri V.
The Accounting review,
05/2013, Letnik:
88, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The concept of conditional conservatism (asymmetric earnings timeliness) has provided new insight into financial reporting and stimulated considerable research since Basu (1997). Patatoukas and ...Thomas (2011) report bias in firm-level cross-sectional asymmetry estimates that they attribute to scale effects. We do not agree with their advice that researchers should avoid conditional conservatism estimates and inferences from research based on such estimates. Our theoretical and empirical analyses suggest the explanation is a correlated omitted variables problem that can be addressed in a straightforward fashion, including fixed-effects regression. Correlation between the expected components of earnings and returns biases estimates of how earnings incorporate the information contained in returns. Further, the correlation varies with returns, biasing asymmetric timeliness estimates. When firm-specific effects are taken into account, estimates do not exhibit the bias, are statistically and economically significant, are consistent with priors, and behave as a predictable function of book-to-market, size, and leverage.
With wearable electronics rapidly coming into fashion, research into flexible energy storage devices and in particular, pliable electrodes, is attracting a lot of attention. Pliable electrodes are ...usually fabricated by intercalating an active material in a flexible matrix with superior mechano‐electrical properties, and can be grouped either as substrate‐supported or free‐standing. Depending on their mode of deformation the electrodes can be labeled as bendable, compressible or stretchable. Recent progress and challenges in the design and fabrication of pliable electrodes for constructing flexible lithium ion batteries and flexible supercapacitors are highlighted. 2 pliable core‐shell structure electrodes fabricated from: a) carbon nanotube sponge embedded with MoS2 nanoparticles and b) electrospun polyethylene terephthalate fibers impregnated with graphene nanoplatelets are also presented.
Pliable electrodes are usually fabricated by intercalating an active material in a flexible matrix with superior mechano‐electrical properties. Their implementation in flexible lithium ion batteries and flexible supercapacitors still face many challenges. Two promising pliable electrodes are highlighted: carbon nanotube sponge embedded with MoS2 nanoparticles, and electrospun polyethylene terephthalate fibers impregnated with graphene nanoplatelets.
Heterogeneous inorganic nanotube structures consisting of multiwalled carbon nanotubes coated by long, continuous MoS2 sheets with tunable sheet number are synthesized using a carbon‐nanotube sponge ...as a template. The resulting 3D porous hybrid sponges have potential applications as high‐performance freestanding anodes for Li‐ion batteries with excellent specific capacity and cycling stability.
Heterogeneous nanostructuring of MoSe2 over a carbon nanotube (CNT) sponge as a free-standing electrode not only brings higher performance but also eliminates the need for dead elements such as a ...binder, conductive carbon, and supportive current collectors. Further, the porous CNT sponge can be easily compacted via an intense densification of the active material MoSe2 to produce an electrode with a high mass loading for a significantly improved areal capacity. In this work, we present a tunable coating of MoSe2 on a CNT sponge to fabricate a core–shell MoSe2@CNT anode. The three-dimensional nanotubular sponge is synthesized via a solvothermal process, followed by thermal annealing to improve crystallization. Structural and morphological studies revealed that MoSe2 grew as a layered structure (d = 0.66 nm), where numbers of layers can be controlled to yield optimized results for Li+ storage. We showed that the 10-layer core–shell CNT@MoSe2 hybrid sponge delivered a discharge capacity of 820.5 mAh g–1 after 100 cycles at 100 mA g–1 with a high cyclic stability and rate capability. Further, an ex situ structural and morphological analysis revealed that ionic storage causes a phase change in MoSe2 from a crystalline to a partial amorphous state for a continuous increase in the capacity with extended cycling. We believe that the strategy developed here will assist users to tune the electrode materials for future energy-storage devices, especially how the materials are changing with the passage of time and their effects on the device performance.
Surgical resection constitutes the first choice of treatment for colorectal cancer (CRC). Despite advancements in intraoperative navigation, there remains a considerable lack of effective targeting ...probes for the imaging-guided surgical navigation of CRC owing to their high heterogeneity. Hence, developing a suitable fluorescent probe to detect the specific types of CRC populations is crucial. Herein, we labeled ABT-510, a small, CD36-targeting thrombospondin-1–mimetic peptide overexpressed in various cancer types, with fluorescein isothiocyanate or near-infrared dye MPA. We found that fluorescence-conjugated ABT-510 exhibited excellent selectivity and specificity toward cells or tissues with high CD36 expression. The tumor-to-colorectal signal ratios were 11.28 ± 0.61 (95% confidence interval) and 10.74 ± 0.07 (95% confidence interval) in subcutaneous HCT-116 and HT-29 tumor-bearing nude mice, respectively. Moreover, high signal contrast was observed in the orthotopic and liver metastatic CRC xenograft mouse models. Furthermore, MPA–PEG4–r-ABT-510 exhibited an antiangiogenic effect via tube information assay with human umbilical vein endothelial cells. Overall, MPA–PEG4–r-ABT-510 presents rapid and precise tumor delineation characteristics, thereby making it a desirable tool for CRC imaging and surgical navigation.
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