118 research outputs found
Ionic blockade in a charged single-file water channel
The classical continuum theories fail to describe the ionic transport in
Angstrom channels, where conduction deviates from Ohm's law, as attributed to
dehydration/self-energy barrier and dissociation of Bjerrum ion-pairs in
previous work. Here we found that the cations are strongly bound to the surface
charge that blockade the ionic transport in a single-file water channel,
causing nonlinear current-voltage responses. The presence of free ions
significantly increased the probability of bound ions being released, resulting
in an ionic current. We found that ionic conduction gradually becomes Ohmic as
surface charge density increases, but the conduction amplitude decreased due to
increased friction from bound ions. We rationalized the ionic transport by 1D
Kramers' escape theory framework, which well described nonlinear ionic current,
and the impact of surface charge density on turning to Ohmic system. Our
results possibly provide an alternative view of ionic blockade in Angstrom
channels
Liquid-solid slip on charged walls: dramatic impact of charge distribution
Nanofluidic systems show great promises for applications in energy
conversion, where their performance can be enhanced by nanoscale liquid-solid
slip. However, efficiency is also controlled by surface charge, which is known
to reduce slip. Combining molecular dynamics simulations and analytical
developments, we show the dramatic impact of surface charge distribution on the
slip-charge coupling. Homogeneously charged graphene exhibits a very favorable
slip-charge relation (rationalized with a new theoretical model correcting some
weaknesses of the existing ones), leading to giant electrokinetic energy
conversion. In contrast, slip is strongly affected on heterogeneously charged
surfaces, due to the viscous drag induced by counter-ions trapped on the
surface. In that case slip should depend on the detailed physical chemistry of
the interface controlling the fraction of bound ions. Our numerical results and
theoretical models provide new fundamental insight on the molecular mechanisms
of liquid-solid slip, and practical guidelines for searching new functional
interfaces with optimal energy conversion properties, e.g. for blue energy or
waste heat harvesting.Comment: Main text: 7 pages, 3 figures; supplemental material: 22 pages, 5
figures; to be published in Physical Review Letter
Rethinking Data Distillation: Do Not Overlook Calibration
Neural networks trained on distilled data often produce over-confident output
and require correction by calibration methods. Existing calibration methods
such as temperature scaling and mixup work well for networks trained on
original large-scale data. However, we find that these methods fail to
calibrate networks trained on data distilled from large source datasets. In
this paper, we show that distilled data lead to networks that are not
calibratable due to (i) a more concentrated distribution of the maximum logits
and (ii) the loss of information that is semantically meaningful but unrelated
to classification tasks. To address this problem, we propose Masked Temperature
Scaling (MTS) and Masked Distillation Training (MDT) which mitigate the
limitations of distilled data and achieve better calibration results while
maintaining the efficiency of dataset distillation.Comment: ICCV 202
A multifunctional nanoplatform based on MoS2-nanosheets for targeted drug delivery and chemo-photothermal therapy
Synergistic tumor treatment has recently attracted more and more attention due to its remarkable therapeutic effect. Herein, a multifunctional drug delivery system based on hyaluronic acid (HA) targeted dual stimulation responsive MoS2 nanosheets (HA-PEI-LA-MoS2-PEG, HPMP) for active interaction with CD44 receptor positive MCF-7 cells is reported. Melanin (Mel), a new type of photothermal agent and doxorubicin (DOX) are both loaded onto the HPMP nanocomposite and can be released by mild acid or hyperthermia. The prepared HPMP nanocomposite has a uniform hydrodynamic diameter (104 nm), a high drug loading (944.3 mg.g-1 HPMP), a remarkable photothermal effect (photothermal conversion efficiency: 55.3%) and excellent biocompatibility. The DOX release from HPMP@(DOX/Mel) can be precisely controlled by the dual stimuli of utilizing the acidic environment in the tumor cells and external laser irradiation. Meanwhile, loading of Mel onto the surface can enhance the photothermal effect of the MoS2 nanosheets. In vitro experiments showed that the HPMP@(DOX/Mel) nanoplatform could efficiently deliver DOX into MCF-7 cells and demonstrated enhanced cytotoxicity compared to that of the non-targeted nanoplatform. In vivo experiments in a breast cancer model of nude mice further confirmed that the HPMP@(DOX/Mel) significantly inhibited tumor growth under near infrared (NIR) laser irradiation, which is superior to any single therapy. In summary, this flexible nanoplatform, based on multi-faceted loaded MoS2 nanosheets, exhibits considerable potential for efficient pH/NIR-responsive targeted drug delivery and chemo-photothermal synergistic tumor therapy
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