Energy-Efficient Framework for Virtual Machine Consolidation in Cloud Data Centers

With the advent of the era of cloud computing, the high energy consumption of cloud computing data centers has become a prominent problem, and how to reduce the energy consumption of cloud computing data center and improve the efficiency of data center has become the research focus of researchers all the world. In a cloud environment, virtual machine consolidation(VMC) is an effective strategy that can improve the energy efficiency. However, at the same time, in the process of virtual machine consolidation, we need to deal with the tradeoff between energy consumption and excellent service performance to meet service level agreement(SLA). In this paper, we propose a new virtual machine consolidation framework for achieving better energy efficiency-Improved Underloaded Decision(IUD) algorithm and Minimum Average Utilization Difference(MAUD) algorithm. Finally, based on real workload data on Planet Lab, experiments have been done with the cloud simulation platform Cloud Sim. The experimental result shows that the proposed algorithm can reduce the energy consumption and SLA violation of data centers compared with existing algorithms, improving the energy efficiency of data centers.

Recent progress in Li and Mn rich layered oxide cathodes for Li-ion batteries

Li and Mn rich(LMR)layered oxides,written as xLi_(2) MnO_(3)·(1-x)LiMO_(2)(M=Mn,Ni,Co,Fe,etc.),have been widely reported in recent years due to their high capacity and high energy density.The stable structure and superior performance of LMR oxides make them one of the most promising candidates for the next-generation cathode materials.However,the commercialization of these materials is hindered by several drawbacks,such as low initial Coulombic efficiency,the degradation of voltage and capacity during cycling,and poor rate performance.This review summarizes research progress in solving these concerns of LMR cathodes over the past decade by following three classes of strategies:morphology design,bulk design,and surface modification.We elaborate on the processing procedures,electrochemical performance,mechanisms,and limitations of each approach,and finally put forward the concerns left and the possible solutions for the commercialization of LMR cathodes.

丁二烯丙烯腈共聚序列结构与玻璃化转变温度

使用核磁共振氢谱对乳液聚合法制备的丁腈橡胶序列结构进行表征,使用差示扫描量热仪表征丁腈橡胶的玻璃化转变温度(Tg)。结果表明,对乳液聚合的丁腈橡胶,丁腈橡胶呈现ABA\BBA\BAB\BBB 4种序列结构,反应过程中随转化率的增长,ABA\BBA\BAB\BBB不同序列结构的含量也呈现规律性变化,序列结构ABA\BBA\BAB的含量逐渐下降、BBB序列结构含量呈上升趋势。对不同丙烯腈含量的丁腈橡胶序列结构进行表征发现,序列结构BAB\BBA\BAB的含量逐渐上升、BBB序列结构的含量呈下降趋势。丁腈橡胶BBB序列中的1,2-丁二烯结构含量的提高影响到丁腈橡胶的玻璃化转变温度。

低分子量聚异戊二烯液体橡胶的结构表征及燃烧特性

以正丁基锂为引发剂,四氢呋喃(THF)为调节剂,通过核磁共振技术(NMR)研究了不同溶液体系对低分子量聚异戊二烯(LIR)结构的影响及LIR液体橡胶的燃烧行为。结果表明,在40℃,反应时间为4 h,异戊二烯单体浓度为30%的实验条件下,THF能够有效地调控LIR的结构,且能够稳定合成高cis-1,4-结构含量的低分子量液体异戊二烯橡胶。以微型量热仪(MCC)等研究了不同构型LIR的燃烧特性,LIR的3,4-结构能够提高LIR的燃烧性能,结果显示,3,4-结构含量每增加5%,热释放速率(HRR)值升高36 W/g。

A highly ionic reaction environment achieving low-temperature polyethylene upcycling

Plastic products have been indispensable in modern life,but90%of them are not recycled after use.The majority of discarded plastics ends up in landfills or is incinerated,which has generated large resource loss and environmental pollution.Therefore,“plastic upcycling”has been proposed to refer to the processes that convert waste plastics into new products with higher values[1].

Stimuli-Responsive Polypeptide-Based Supramolecular Hydrogels Mediated by Ca^2+ Ion Cross-Linking

Background and Originality Content Hydrogels,which retain a large amount of water,possess tunable porous three-dimensional nanostructure.They are known to resemble human tissue that can offer many advantages in biomedical applications such as tissue engineering,drug delivery and surgical dressings.1141 Stimuli-responsive hydrogels,referred as smart hydrogels can rapidly respond in a controlled manner to external stimuli,such as temperature,pH,light,etc.[s]In particular,the thermal-responsive hydrogels exhibit sol-to-gel phase transi­tion upon heating up to lower critical gelation temperatures(CGTs).

Embedding ultrasmall Ag nanoclusters in Luria-Bertani extract via light irradiation for enhanced antibacterial activity

Ultrasmall silver nanoclusters(Ag NCs)with rich surface chemistry and good biocompatibility are promising in antibacterial application,however,further development of Ag NCs for practical settings has been constrained by their relatively weak antibacterial activity.Using the nutritionally-rich medium for bacteria(e.g.,Luria-Bertani(LB)medium)to coat active Ag NCs could further improve their antibacterial activity.Here,we provide a delicate design of a highly efficient Ag NCs@ELB antibacterial agent(ELB denotes the extract of LB medium)by anchoring Ag NCs inside the ELB species via light irradiation.The as-designed Ag NCs with bacterium-favored nutrients on the surface can be easily swallowed by the bacteria,boosting the production of the intracellular reactive oxygen species(ROS,about 2-fold of that in the pristine Ag NCs).Subsequently,a higher concentration of ROS generated in Ag NCs@ELB leads to enhanced antibacterial activity,and enables to reduce the colony forming units(CFU)of both gram-positive and gram-negative bacteria with 3–4 orders of magnitude less than that treated with the pristine Ag NCs.In addition,the Ag NCs@ELB also shows good biocompatibility.This study suggests that surface engineering of active species(e.g.,Ag NCs)with nutritionally-rich medium of the bacteria is an efficient way to improve their antibacterial activity.

Titanium Complexes Bearing NNO-Tridentate Ligands: Highly Active Olefin Polymerization Catalysts with Great Control on Molecular Weight and Distribution

A series of titanium amido complexes (1-Ti(NMe_(2))_(2) to 4-Ti(NMe_(2))_(2)) bearing NNO-tridentate ligands was synthesized from the reactions of phenoxy-imine-amine ligands with one equivalent of Ti(NMe_(2))_(4). Subsequently, titanium dichloride complexes (1-TiCl_(2) to 4-TiCl_(2)) were prepared by treatment of titanium amido complexes with excess Me3SiCl in toluene. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes of 2-Ti(NMe_(2))_(2), 2-TiCl_(2), and 4-TiCl_(2) in the solid state were determined by single-crystal X-ray diffraction. Upon activation with MAO, titanium dichloride complexes as single-site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3-TiCl_(2)/MAO exhibited an activity as high as 1.35 × 108 g(PE)·mol−1(Ti)·h−1 at 70°C and produced polyethylene with high molecular weight (41.7 × 10^(4) g∙mol^(−1)) and very narrow distribution (Đ = 1.23). In the presence of 1-octene as comonomer, linear low-density polyethylenes (LLDPEs) with ultrahigh molecular weights (Mw = 136—326 × 10^(4) g∙mol^(−1)) and narrow distributions (Đ = 1.20—1.50) were successfully synthesized.

Direct Synthesis of Crystalline Graphtetrayne-A New Graphyne Allotrope

We report a bottom-up synthesis of a new graphyne allotrope-graphtetrayne(GTTY),which features four acetylene linkages between the adjacent benzene on the surface of copper under low temperature.The as-prepared GTTY exhibited nanosheet morphology with an average thickness of 4.5 nm.Structural analysis based on high-resolution transmission electron microscopy(HR-TEM)/selected area electron diffraction(SAED)characterizations revealed high crystallinity formed with a ninefold stacking structure.The GTTY displayed excellent semiconductor properties bearing a band gap of 1.3 eV and a conductivity of 0.285 S m^(−1)at room temperature.Moreover,by the space-charge-limited current(SCLC)method,the measured hole and electron mobilities of the GTTY films reached up to 1.47×10^(3) cm^(2) V^(−1)S^(−1)and 2.98×10^(3)cm^(2)V^(−1)S^(−1),respectively.

Pyrophosphate-Mediated On-Off-On Oxidase-Like Activity Switching of Nanosized MnFe_(2)O_(4) for Alkaline Phosphatase Sensing

Developing reliable and facile approaches for alkaline phosphatase(ALP)sensing is important due to its role as a clinical biomarker for many diseases.In this study,we proposed a new and convenient colorimetric assay based on the pyrophosphate(PPi)-mediated oxidase-mimicking activity switching of nanosized MnFe_(2)O_(4) for the detection of ALP.The synthesized MnFe_(2)O_(4) exhibited high oxidase-like activity to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine(TMB)to its blue product TMBox in the presence of dissolved O2,leading to a color reaction rapidly and remarkably;PPi could significantly inhibit the activity of the MnFe_(2)O_(4) nanozyme via the strong interaction between PPi and the Fe(III)species in MnFe_(2)O_(4),resulting in the suppression of the TMB color reaction;when ALP was added,it hydrolyzed the PPi substrate to phosphate(Pi)that had no obvious effect on the MnFe_(2)O_(4) activity,and such that the TMB color reaction catalyzed by the nanozyme could be observed again.With the above principle,linear colorimetric determination of ALP in the scope of 0.6-55 U L−1 was achieved,giving the limit of detection down to 0.27 U L−1.Besides,the developed assay could provide selective response toward ALP against other co-existing biological species.Furthermore,reliable detection of ALP in human serum samples was verified by our assay,revealing its great promise as an effective and facile tool for ALP monitoring in clinical practice.

Nanoscale Crystalline Sheets and Vesicles Assembled from Nonplanar Cyclic π-Conjugated Molecules

A fundamental challenge in chemistry and materials science is to create new carbon nanomaterials by assembling structurally unique carbon building blocks,such as nonplanar π-conjugated cyclic molecules.However,self-assembly of such cyclic π-molecules to form organized nanostructures has been rarely explored despite intensive studies on their chemical synthesis.Here we synthesized a family of new cycloparaphenylenes and found that these fully hydrophobic and nonplanar cyclic π-molecules could self-assemble into structurally distinct two-dimensional crystalline multilayer nanosheets.Moreover,these crystalline multilayer nanosheets could overcome inherent rigidity to curve into closed crystalline vesicles in solution.Tese supramolecular assemblies show that the cyclic molecular scafolds are homogeneously arranged on the surface of nanosheets and vesicles with their molecular isotropic x-y plane standing obliquely on the surface.Tese supramolecular architectures that combined exact crystalline order,orientation-specifc arrangement of π-conjugated cycles,controllable morphology,uniform molecular pore,superior forescence quench ability,and photoluminescence are expected to give rise to a new class of functional materials displaying unique photonic,electronic,and biological functions.

Self-Assembly of Crystalline Vesicles from Nonplanarπ-Conjugated Nanocycles

There is a great demand for self-assembled carbon nanomaterials because of their importance in optoelectronics,biomaterials,and so forth.Herein,we report a novel type of self-assembled,nanoscale,crystalline vesicle from nonplanarπ-conjugated nanocycles.We designed four different structural[8]cycloparaphenylenes([8]CPPs)molecules and demonstrated that these nonplanarπ-conjugated CPP nanocycles could self-assemble into multilamellar,crystalline vesicles in tetrahydrofuran(THF)/H2O mixed solvent.

Anion-π interactions:From concept to application

Anion-π interactions as a new member of supramolecular weak interactions are still in the young stage,but they already attract considerable attentions. Now the concerns are shifting from recognition to construction of functional systems. In this review, the anion-π functional systems especially anion-πcatalysis and self-assembly were highlighted and summarized together with several solid and recent examples of host-guest recognition. These applications suggest that the great potential of these new interactions.

Boost photothermal theranostics via self-assembly-induced crystallization(SAIC)

Owing to the intrinsic advantages of spatiotemporal selectivity,photothermal theranostics have become the advancing edge of precision medicine for cancer.Developing photothermal transduction agents(PTAs)with near-infrared(NIR)absorption,high photothermal conversion efficiency,robust photothermal stability,and good accumulation in tumors,is particularly valuable.Herein,we report a new concept,self-assembly-induced crystallization(SAIC),which can serve as a mechanism that dramatically boosts photothermal behaviors of PTA in NIR region.As a proof of concept,three heptamethine cyanine molecules with internal degrees of freedom(geometry and intramolecular interaction)are designed to fine-tune their crystallinity.Notably,Cy7-TCF-EMBI molecules with rigid and planar skeletons self-assemble into a crystalline state to maximize their packing density and improve the charge transfer,both of which contribute to nonradiative decay for energy dissipation as heat.The high packing density also renders an ideal scaffold for controlling intermolecular interactions to exhibit better photothermal stability,and endows an anisotropic three-dimensional architecture for passive tumor targeting.This“SAIC”strategy may offer a conceptually novel,practically simple but effective approach to unveil the structure–property relationship that could provide some general rules in rational design of PTAs,and paves the way for a next generation of supramolecular medicine for photothermal theranostics.

Spirobifluorene-Based Three-Dimensional Covalent Organic Frameworks with Rigid Topological Channels as Efficient Heterogeneous Catalyst

Although the past decade has witnessed tremendous progress in the development of covalent organic frameworks(COFs),three-dimensional(3D)COFs fabrications and characterizations are still much less studied compared with two-dimensional(2D)COFs,due to their complicated topology structures caused by interpenetration and limited choices of node-building blocks.In this work,we constructed a novel 3D COF(SP-3D-COF-BPY)successfully using orthogonal dual-planar spirobifluorene and bipyridine as building blocks.Also,we demonstrated the application of 3D COF-supported Pd(II)catalyst in heterogeneous catalysis.A sevenfold interpenetrated dia structure was revealed for SP-3DCOF-BPY by powder X-ray diffraction(PXRD)in conjunction with structural simulation and Pawley refinement.The bipyridine-linked frameworks bear one-dimensional(1D)unobstructed rigid channels and offer a high density of discrete coordination sites for chelating Pd(II)species.Very high loading of Pd(II)(∼15 wt%)was achieved in the asymmetric(as)-prepared Pd(II)@3D-COF-BYP.The generated highly ordered porous channels and easily accessible catalytic sites,such as COF-supported Pd(II)complex,serves as a highly active and stable microporous heterogeneous catalyst in Suzuki–Miyaura coupling reactions.The observed catalytic efficiency was high and the catalyst could be conveniently reused multiple times without any noticeable decay in catalytic performance.

Tunable supramolecular hydrogels from polypeptidePEG-polypeptide triblock copolymers

A series of ABA triblock copolymers of poly(?-(2-methoxy ethoxy)esteryl-glutamate)-block-poly(ethylene glycol)-blockpoly(?-(2-methoxy ethoxy)esteryl-glutamate) with poly(ethylene glycol) as middle hydrophilic B block and oligo(ethylene glycol)-functionalized polyglutamate(poly-L-EG2Glu) as terminal A blocks were prepared via ring-opening polymerization of EG2 Glu N-carboxyanhydride(NCA). The resulting P(EG2Glu)-b-PEG-b-P(EG2Glu) triblocks can spontaneously form hydrogels in water. The intermolecular hydrogen bonding interactions between polypeptides blocks were responsible for the formation of gel network structure. These hydrogels displayed shear-thinning and rapid recovery properties, which endowed them potential application as injectable drug delivery system. The mechanical strength of hydrogels can be modulated by copolymer composition, molecular weight and concentrations. Also, it was found that the hydrogels' strength decreased with temperature due to dehydration of polypeptide segments. Atomic force microscopy and scanning electron microscopy images revealed that these hydrogels were formed through micelle packing mechanism. Circular dichroism and Fourier transform infrared spectroscopy characterizations suggested the poly-L-EG2 Glu block adopted mixed conformation. A preliminary assessment of drug release in vitro demonstrated the hydrogels can offer a sustained release of doxorubicin(DOX) and the release rate could be controlled by varying chemical composition.

Chemoselective Polymerization of Fully Biorenewableα-Methylene-γ-Butyrolactone Using Organophosphazene/Urea Binary Catalysts Toward Sustainable Polyesters

Despite the great potential of biorenewableα-methylene-γ-butyrolactone(MBL)to produce functional,recyclable polyester,the ring-opening polymerization(ROP)of MBL remains a challenge due to the competing polymerization of the highly reactive exocyclic double bond and low-strained five-membered ring.In this contribution,we present the first organocatalytic chemoselective ROP of MBL to exclusively produce functional unsaturated polyester by utilizing a phosphazene base/urea binary catalyst.We show that delicate chemoselectivity can be realized by controlling the temperature and using selected urea catalysts.The obtained polyester can be completely recycled back to its monomer by chemolysis under mild conditions.Experimental and theoretical calculations provide mechanistic insights and indicate that the ROP pathway is kinetically favored by using urea with stronger acidity at low temperatures.

Enzyme responsive supramolecular hydrogels assembled from nonionic peptide amphiphiles

Smart peptide hydrogels are of great interest for their great potential applications. Here, we report a facile approach to prepare a class of enzyme-responsive hydrogels in a scalable manner. These hydrogels self-assemble from a family of nonionic peptide amphiphiles(PAs) synthesized by sequential ring-opening polymerization(ROP) of γ-benzyl-L-glutamate N-carboxyanhydride(BLG-NCA) and L-tyrosine N-carboxyanhydride(Tyr-NCA), followed by subsequent aminolysis. These PA samples can readily form a clear hydrogel with a critical gelation concentration as low as 0.5 wt%. The incorporation of tyrosine residues offers hydrophobicity, hydrogen-bonding interaction and enzyme-responsive properties. The hydrogel-to-nanogel transition is observed under physiological conditions in the presence of horseradish peroxidase(HRP) and hydrogen peroxide(H2 O2). The obtained PA hydrogels are ideal candidates for the new generation of smart scaffolds.

Stereoselective Ring-Opening Polymerization of rac-Lactide Catalyzed by Squaramide Derived Organocatalysts at Room Temperature

Substa ntial progresses have bee n made toward the developme nt of meta I-free catalysts for stereoselective rin g-ope ning polymeriza-tion(ROP)of rac-lactide.Yet the discovery of organic catalysts effective at ambient temperature remains a major challenge.Here,the bifunctional H-bonding catalyst SQ-1 containing a basic tertiary amine and squaramide motif proved to be good candidate for the stereoselective ROP of rac-lactide at room temperature,yielding stereoregular polylactide with controlled molecular weights(up to 21.1 kg/mol)and high tacticity(PjESC up to 0.88).Furthermore,binary H-b on ding catalytic system con sisti ng of squaramides(SQ-2 to SQ-6)and 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU)could efficiently promote the ROP of rac-lactide at room temperature within short reaction time.Among them,the most bulky squaramide SQ-2 exhibited the best steroselectivity towards the ROP of rac-lactide without transesterification side reactions during the polymerization process.The resulting polylactides were proved to have controlled molecular weights as high as 22.2 kg/mol and narrow distributions(1.10-1.24).

PREFACE

Hydrogels are classical soft and wet materials that have been extensively studied over the past several decades. Recently, with the development of supramolecular science, nanotechnology and precisely synthetic chemistry, various novel hydrogels have been designed and fabricated, which show emerging applications in tissue engineering, drug delivery, anti-fouling coatings, flexible electronics and soft robotics. Through tailoring their two-dimensional surface structures and three- dimensional networks, unique properties such as ultra-high mechanical strength, responsiveness to various kinds of stimuli, biocompatibility, special wettability and adhesion can be achieved.