Investigation of nanocomposite PNIPAm-g-graphene with pre-lower critical solution temperature rapid thermal response function for chip adaptive cooling: A molecular dynamics and computational fluid dynamics simulations

Temperature-sensitive hydrogels have been widely used for rapid adaptive cooling in electronic device thermal management with promising applications. However, existing temperature-sensitive hydrogels can only regulate the flow in the chip cooling system after the ambient temperature reaches their lower critical solution temperature (LCST). Before reaching LCST, effective rapid heat dissipation for electronic chips is not achievable. This study aims to develop a temperature-sensitive hydrogel that can provide assisted adaptive cooling for electronic chips before reaching its LCST. This requires the hydrogel to have a thermal conductivity far surpassing existing hydrogel materials. Using the temperature-sensitive hydrogel PNIPAm and graphene molecules as base materials, this research utilized molecular dynamics simulations to graft graphene molecules onto PNIPAm molecules in different ways, resulting in the temperature-sensitive hydrogel material PNIPAm-g-graphene. Non-equilibrium molecular dynamics (NEMD) was employed to calculate the thermal conductivity of this material under different temperature conditions. The results indicate that the thermal conductivity of PNIPAm-g-graphene can reach up to 1.95474 W/m K (graphene grafted at  CH₃ functional group, temperature at 280 K). Compared to the thermal conductivity of PNIPAm under the same conditions (0.45 W/m K), the increase in thermal conductivity is significant, demonstrating excellent thermal conductivity compared to PNIPAm. Subsequently, this study analyzed the underlying mechanisms of different thermal conductivities in materials obtained by grafting graphene molecules at different points using the method of overlap in Phonon Density of States Curves (PDOS) from the perspective of interfacial thermal conduction. Finally, through computational fluid dynamics (CFD) simulations, this study investigates the chip's adaptive cooling performance with PNIPAm-g-graphene material. The results show that, compared to traditional temperature-sensitive hydrogels, PNIPAm-g-graphene can achieve efficient adaptive cooling of chip hotspots before the cooling fluid temperature reaches its LCST value. This finding is significant for the field of chip cooling. The study proposes a new method for rapid, adaptive cooling of chip hotspots and explores its feasibility from the perspectives of molecular dynamics and CFD simulation. It holds importance in the thermal management of electronic devices and the rapid adaptive cooling of electronic chips.     

拓扑分子格的极不连通性和S－闭性

利用完备余ｃｏ－Ｈｅｙｔｉｎｇ代数上的伪补运算，在拓扑分子格上引入极不连通性和Ｓ－闭性，得到了每个Ｓ－闭的正则拓扑分子格是极不连通的以及同胚的广义序同态保持极不连通性和Ｓ－闭性．     

Photosynthetically active sunlight at high southern latitudes

A network of scanning spectroradiometers has acquired a multiyear database of visible solar irradiance, covering wavelengths from 400 to 600 nm, at four sites in the high-latitude Southern Hemisphere, from 55 degrees S to 90 degrees S. Monthly irradiations computed from the hourly measurements reveal the character of the seasonal cycle and illustrate the role of cloudiness as functions of latitude. Near summer solstice, the combined influences of solar elevation and the duration of daylight would produce a monthly irradiation with little latitude dependence under clear skies. However, the attenuation associated with local cloudiness varies geographically, with the greatest effect at the most northern locations, Ushuaia, Argentina and Palmer Station on the Antarctic Peninsula. Near summer solstice, the South Pole experiences the largest monthly irradiation of the sites studied, where relatively clear skies contribute to this result. Scaling factors derived from radiative-transfer calculations combined with the measured 400-600 nm irradiances allow estimating irradiances integrated over the wavelength band 400-700 nm. This produces a climatology of photosynthetically active radiation for each month of the year at each site.     

钾助催化剂与Fe3O4相互作用行为的XRD表征

XRD研究表明 ,作为乙苯脱氢催化剂中的氧化铁活性组分 ,具有反式尖晶石结构的Fe3O4 比刚玉型的α Fe2O3 更易与钾助催化剂发生相互作用 :α Fe2O3-K2O需经850℃煅烧才能生成多铁酸钾 ,但在Fe3O4 -K2O体系中只需700℃即可.而且 ,钾还可抑制Fe3O4 被氧化为α Fe2O3 的进程 ,在空气中 ,Fe3O4 只需300℃煅烧即可明显转化为α Fe2O3 ,但同样的转化在Fe3O4 K2O体系中要经700℃煅烧才会明显地发生.实验结果表明 ,某种形态的多铁酸钾可能是催化剂中的储钾相.     

Hg2+‐Induced In Situ Generated Radical Cation of (S)‐BINOL‐Based Polymer for Highly Enantioselective Recognition of Phenylalaninol

Phenylalaninol enantiomers are one of the most important chiral compounds due to its presence in biologically active molecules and pharmaceutical products. In this paper, a novel chiral fluorescence polymer sensor incorporating (S)‐BINOL and oligomeric aniline via a nucleophilic addition–elimination reaction is designed and synthesized. Polymer sensor exhibits “turn‐off” fluorescence quenching response upon the addition of Hg²⁺, and “turn‐on” moderate fluorescence enhancement behavior towards phenylalaninol enantiomers. Meanwhile, this kind of (S)‐BINOL‐based polymer sensor can exhibit highly selective enantioselective recognition response towards (L)‐phenylalaninol upon the addition of Hg²⁺ and the value of ef can reach as high as 5.4, which can be attributed to the formation of in situ generated radical cation arisen from oligomeric aniline moiety by Hg²⁺ induction.

     

Utilization of nonlinear vibrations of soft pipe conveying fluid for driving underwater bio-inspired robot

Creatures with longer bodies in nature like snakes and eels moving in water commonly generate a large swaying of their bodies or tails, with the purpose of producing significant frictions and collisions between body and fluid to provide the power of consecutive forward force. This swaying can be idealized by considering oscillations of a soft beam immersed in water when waves of vibration travel down at a constant speed. The present study employs a kind of large deformations induced by nonlinear vibrations of a soft pipe conveying fluid to design an underwater bio-inspired snake robot that consists of a rigid head and a soft tail. When the head is fixed, experiments show that a second mode vibration of the tail in water occurs as the internal flow velocity is beyond a critical value. Then the corresponding theoretical model based on the absolute nodal coordinate formulation (ANCF) is established to describe nonlinear vibrations of the tail. As the head is free, the theoretical modeling is combined with the computational fluid dynamics (CFD) analysis to construct a fluid-structure interaction (FSI) simulation model. The swimming speed and swaying shape of the snake robot are obtained through the FSI simulation model. They are in good agreement with experimental results. Most importantly, it is demonstrated that the propulsion speed can be improved by 21% for the robot with vibrations of the tail compared with that without oscillations in the pure jet mode. This research provides a new thought to design driving devices by using nonlinear flow-induced vibrations.

     

Achiral Dichroic Dyes-mediated Circularly Polarized Emission Regulated by Orientational Order Parameter through Cholesteric Liquid Crystals

It is noteworthy that cholesteric liquid crystal (CLC) platforms have been witnessed in high-performance circularly polarized luminescence (CPL) behaviors through the highly organized chiral co-assembled arrangement of achiral dyes. However, most CPL-active design strategies are closely relative to the helix co-assembly structure of CLC rather than achiral dyes. Herein, we developed an intriguing regulation strategy for CPL-active CLC materials. They were regulated using the orientational order parameter (S_F) of achiral dichroic dyes as an incisive probe for the order arrangement degree of achiral dyes in CLC media. The I-shaped phenothiazine derivative PHECN dye (S_F=0.30) emitted a strong CPL signal (|g_lum|=0.47). In contrast, the T-shaped derivative (PHEBen) dye (S_F=0.09) showed a weak circular polarization level (|g_lum|=0.07) at similar CLC textures. Most interestingly, this kind of dichroic PHECN dye with a higher S_F could greatly improve the contrast ratio of CPL (Δg_lum=0.47) and emission intensity (ΔFL=46.0 %) at direct-current electric field compared with the T-shaped PHEBen (Δg_lum=0.07 and ΔFL=1.0 %) in CLC. This work demonstrates that an induced CPL emission can be mediated using achiral dichroic dye, which will open a new avenue for developing excellent CPL-active display materials.     

高效液相色谱法测定硫酸伏拉帕沙原料药中杂质

建立了高效液相色谱法测定硫酸伏拉帕沙原料药中杂质的方法。采用ACE Excel C18(4.6 mm×250 mm,5μm)色谱柱;以pH 2.5的H3PO4溶液为流动相A,乙腈为流动相B,梯度洗脱;检测波长为260 nm;进样量为20μL。结果表明,主成分与各杂质的分离度良好,各已知杂质在测定的范围内具有良好的线性(r>0.9996)。方法可用于硫酸伏拉帕沙原料药的质量控制。     

A chiral perazamacrocyclic fluorescent sensor for cascade recognition of Cu(II) and the unmodified α-amino acids in protic solutions

A novel chiral Perazamacrocyclic fluorescent sensor (1) was designed and synthesized. It can serve as a fluorescent turn-off sensor with high selectivity toward Cu(II) among 14 metal ions. Furthermore, though 1 exhibits no enantioselectivity, after adding Cu(II), the in situ generated Cu(II)-containing complex of 1 (Cu(II)-1) can exhibit remarkable fluorescent enhancement responses and considerable enantioselectivities toward unmodified α-amino acids in protic solutions via a ligand displacement mechanism; i.e. a cascade recognition of Cu(II) and unmodified α-amino acids has been achieved.