Living tissues, such as muscle, autonomously grow and remodel themselves to adapt to their surrounding mechanical environment through metabolic processes. By contrast, typical synthetic materials ...cannot grow and reconstruct their structures once formed. We propose a strategy for developing "self-growing" polymeric materials that respond to repetitive mechanical stress through an effective mechanochemical transduction. Robust double-network hydrogels provided with a sustained monomer supply undergo self-growth, and the materials are substantially strengthened under repetitive loading through a structural destruction-reconstruction process. This strategy also endows the hydrogels with tailored functions at desired positions by mechanical stamping. This work may pave the way for the development of self-growing gel materials for applications such as soft robots and intelligent devices.
The double-network (DN) structure is a state-of-the-art strategy used for toughening soft materials. The challenge for widespread applications, however, is the difficulty in synthesizing the two ...interpenetrating networks with contrasting architecture, i.e., one network is brittle and sparse and the other is stretchable and dense. Such structures are formed to toughen hydrogels via two-step sequential synthesis of a highly swellable polyelectrolyte network and a subsequent stretchable network in aqueous media; however, this approach is not directly applicable for fabricating tough DN elastomers from low-polar polymers. Herein, we propose a polyelectrolyte approach to fabricate tough solvent-free DN elastomers comprising a hybridized brittle polyelectrolyte network and a stretchable low-polar polyacrylic network. Because polyelectrolyte networks swell significantly in high-dielectric media, the contrasting DN structure can be fabricated using an organic cosolvent with an extremely high dielectric constant. By removing the solvent, we obtained polyelectrolyte–elastomeric polyacrylate DN elastomers, which exhibit a moderate elastic modulus (∼1 MPa), distinct yielding, high strength (∼5 MPa nominal stress), and large stretchability (∼2000% strain) accompanied by strain-hardening and high fracture toughness (∼104 J m–2). The volume ratio of the two networks is a key parameter governing mechanical performance. This approach broadens polymer choices for developing robust elastomers.
A rain-gauge-adjusted algorithm for global satellite mapping of precipitation (GSMaP) that estimates the surface precipitation rate with resolutions of 0.1° and 1 h over the globe is described ...herein. Precipitation is one of the most important parameters of the earth's system, and its global distribution and changes are essential data for modeling the water cycle, maintaining ecosystems, increasing agricultural production, improving weather forecasting precision, and implementing flood warning systems. In the Global Precipitation Measurement project, integrated products of high-resolution mapping of precipitation, obtained from microwave measurements made by a constellation satellite and infrared radiometers in geostationary orbit, are developed and supplied to the public. However, these high-resolution products, such as GSMaP_MVK, sometimes underestimate surface precipitation, introducing large errors into hydrological modeling. This paper combines the global gauge data set with GSMaP_MVK, using a new algorithm gauge-adjusted GSMaP (GSMaP_Gauge), described and evaluated herein using local radar and rain-gauge data sets. This algorithm outperforms other GSMaP products in all validation tests.
Living organisms share the ability to grow various microstructures on their surface to achieve functions. Here we present a force stamp method to grow microstructures on the surface of hydrogels ...based on a force-triggered polymerisation mechanism of double-network hydrogels. This method allows fast spatial modulation of the morphology and chemistry of the hydrogel surface within seconds for on-demand functions. We demonstrate the oriented growth of cells and directional transportation of water droplets on the engineered hydrogel surfaces. This force-triggered method to chemically engineer the hydrogel surfaces provides a new tool in addition to the conventional methods using light or heat, and will promote the wide application of hydrogels in various fields.
We study the relationship among public-key encryption (PKE) satisfying indistinguishability against chosen plaintext attacks (IND-CPA security), that against chosen ciphertext attacks (IND-CCA ...security), and trapdoor functions (TDF). Specifically, we aim at finding a unified approach and some additional requirement to realize IND-CCA secure PKE and TDF based on IND-CPA secure PKE, and show the following two main results. As the first main result, we show how to achieve IND-CCA security via a weak form of key-dependent-message (KDM) security. More specifically, we construct an IND-CCA secure PKE scheme based on an IND-CPA secure PKE scheme and a secret-key encryption (SKE) scheme satisfying one-time KDM security with respect to projection functions (projection-KDM security). Projection functions are elementary functions with respect to which KDM security has been widely studied. Since the existence of projection-KDM secure PKE implies that of the above two building blocks, as a corollary of this result, we see that the existence of IND-CCA secure PKE is implied by that of projection-KDM secure PKE. As the second main result, we extend the above construction of IND-CCA secure PKE into that of TDF by additionally requiring a mild requirement for each building block. Our TDF satisfies adaptive one-wayness. We can instantiate our TDF based on a wide variety of computational assumptions. Especially, we obtain the first TDF (with adaptive one-wayness) based on the sub-exponential hardness of the constant-noise learning-parity-with-noise (LPN) problem. In addition, we show that by extending the above constructions, we can obtain PKE schemes satisfying advanced security notions under CCA, that is, optimal rate leakage-resilience under CCA and selective-opening security under CCA. As a result, we obtain the first PKE schemes satisfying these security notions based on the computational Diffie–Hellman (CDH) assumption or the low-noise LPN assumption.
NIZK from SNARGs Kitagawa, Fuyuki; Matsuda, Takahiro; Yamakawa, Takashi
Journal of cryptology,
04/2023, Letnik:
36, Številka:
2
Journal Article
Recenzirano
We give a construction of a non-interactive zero-knowledge (NIZK) argument for all
NP
languages based on a succinct non-interactive argument (SNARG) for all
NP
languages and a one-way function. The ...succinctness requirement for the SNARG is rather mild: We only require that the proof size be
|
π
|
=
poly
(
λ
)
(
|
x
|
+
|
w
|
)
δ
for some constant
δ
<
1
, where |
x
| is the statement length, |
w
| is the witness length, and
λ
is the security parameter. Especially, we do not require the efficiency of the verification to be sublinear in |
x
| or |
w
|. As a corollary, we give a generic conversion from a SNARK to a zero-knowledge SNARG assuming the existence of one-way functions where SNARK is a SNARG with knowledge-extractability. For this conversion, we require the SNARK to be fully succinct, i.e., the proof size is
poly
(
λ
)
(
|
x
|
+
|
w
|
)
o
(
1
)
. Before this work, such a conversion was only known if we additionally assume the existence of a NIZK. Along the way of obtaining our result, we give a generic compiler to upgrade a NIZK for all
NP
languages with non-adaptive zero-knowledge to one with adaptive zero-knowledge. Though this can be shown by carefully combining known results, to the best of our knowledge, no explicit proof of this generic conversion has been presented.
High modulus, toughness, and fatigue resistance are usually difficult to be obtained simultaneously in rubbery materials. Here, we report that by superimposing the nanophase separation structure in ...double network (DN) elastomers using immiscible polymers, the modulus, fracture energy, and energy release rate of fatigue threshold are enhanced all together by 13, 5, and 5 times, respectively. We reveal that the interplay between the DN structure and the nanophase separation structure brings two effects synergistically: (1) formation of nanoclusters overstresses and homogenizes the sacrificial network, thereby remarkably increasing the modulus and yielding stress and (2) the nanoclusters act as viscoelastic nanofillers dissipating energy and pinning the crack propagation, thereby significantly enhancing toughness and fatigue resistance. This work provides a facile approach to superimpose high-order structures in DN materials for excellent mechanical performance. The clarified synergetic effects should be universal for DN materials made of immiscible polymers. We believe that this work will facilitate more studies on elastomers and gels along this line.
Macromolecular crowding (MMC) in cells is a hot topic in biology; therefore, well-characterized measurement standards for the evaluation of the nano-environment in MMC solutions are necessary. We ...propose to use polarization-dependent fluorescence correlation spectroscopy (Pol-FCS) for evaluation of macromolecular crowding in solutions. Pol-FCS can simultaneously measure the relaxation times of rotational and translational diffusion of fluorescent molecules at the same position, even in living cells with low damage. In this report, the differences in the nano-environment among solutions of small molecules, gels, and MMC solutions were evaluated by comparing their rotational and translational diffusion using Pol-FCS. Moreover, this method could distinguish the phase shift in the polyethylene glycol solution. Finally, we separately evaluated the nano-environment in the cytosol and nucleus of living cells in different cell lines and cell cycles. We expect this evaluation method to be useful in characterizing the nano-environment in MMC studies. In addition, the proposed method may be useful for other nano-environments such as liquid-liquid phase separation.
Double-network gels are a class of tough soft materials comprising two elastic networks with contrasting structures. The formation of a large internal damage zone ahead of the crack tip by the ...rupturing of the brittle network accounts for the large crack resistance of the materials. Understanding what determines the damage zone is the central question of the fracture mechanics of double-network gels. In this work, we found that at the onset of crack propagation, the size of necking zone, in which the brittle network breaks into fragments and the stretchable network is highly stretched, distinctly decreases with the increase of the solvent viscosity, resulting in a reduction in the fracture toughness of the material. This is in sharp contrast to the tensile behavior of the material that does not change with the solvent viscosity. This result suggests that the dynamics of stretchable network strands, triggered by the rupture of the brittle network, plays a role. To account for this solvent viscosity effect on the crack initiation, a delayed blunting mechanism regarding the polymer dynamics effect is proposed. The discovery on the role of the polymer dynamic adds an important missing piece to the fracture mechanism of this unique material.
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