Increasing valence pushes DNA nanostar networks to the isostatic point

The classic picture of soft material mechanics is that of rubber elasticity, in which material modulus is related to the entropic elasticity of flexible polymeric linkers. The rubber model, however, largely ignores the role of valence (i.e., the number of network chains emanating from a junction). Recent work predicts that valence, and particularly the Maxwell isostatic point, plays a key role in determining the mechanics of semiflexible polymer networks. Here, we report a series of experiments confirming the prominent role of valence in determining the mechanics of a model system. The system is based on DNA nanostars (DNAns): multiarmed, self-assembled nanostructures that form thermoreversible equilibrium gels through base pair-controlled cross-linking. We measure the linear and nonlinear elastic properties of these gels as a function of DNAns arm number, f, and concentration [DNAns]. We find that, as f increases from three to six, the gel’s high-frequency plateau modulus strongly increases, and its dependence on [DNAns] transitions from nonlinear to linear. Additionally, higher-valence gels exhibit less strain hardening, indicating that they have less configurational freedom. Minimal strain hardening and linear dependence of shear modulus on concentration at high f are consistent with predictions for isostatic systems. Evident strain hardening and nonlinear concentration dependence of shear modulus suggest that the low-f networks are subisostatic and have a transient, potentially fractal percolated structure. Overall, our observations indicate that network elasticity is sensitive both to entropic elasticity of network chains and to junction valence, with an apparent isostatic point 5<fc≤6 in agreement with the Maxwell prediction.

KONTRIBUSI AGROFORESTRI DALAM MITIGASI GAS RUMAH KACA MELALUI PENYERAPAN KARBON Contribution Of Agroforestry Mitigation Greenhouse Gases Through The Carbon Sequestration

Agroforestri memiliki kemampuan dalam mitigasi iklim melalui dalam penyerapan karbon. Dengan kondisi tegakan agroforestry menyerupai hutan skunder sehingga memiliki kemampuan dalam menyerap karbon yang cukup besar. Tujuan dari penelitian ini adalah untuk mengetahui karbon yang dapat diserap pada setiap model agroforestri yang ada di Kecamatan XIII Koto Kampar. Model agroforestri Karet-GaharuDurian memiliki biomassa adalah 135,35 ton/ha dan potensi karbon 62,26 C ton/ha sedangkan Model KaretDurian memiliki biomassa 82,14 ton/ha dan karbon 37,78 ton/ha. Biomassa model Karet-Gaharu adalah 93,70 ton/ha dengan potensi karbon 43,10 ton/haKata Kunci : model agroforestri; biomassa; karbon Agroforestry has the ability to mitigate climate through in carbon sequestration. With the condition of agroforestry stands resembling a secondary forest that has the ability to absorb considerable carbon. The purpose of this research is to know the carbon that can be absorbed in every model of agroforestry in District XIII Koto Kampar. The agroforestry model of Rubber-Gaharu-Durian has biomass is 135.35 ton / ha and carbon potential is 62.26 C t / ha while the Durian-Rubber Model has 82.14 ton / ha biomass and 37.78 ton / ha of carbon. Rubber-Gaharu model biomass is 93,70 ton / ha with carbon potential 43,10 ton / h