Structure and magnetic properties of Mn_(1.2)Fe_(0.8)P_(0.76)Ge_(0.24) annealed alloy

Bulk Mn_(1.2)Fe_(0.8)P_(0.76)Ge_(0.24) alloy was prepared by mechanical milling and subsequent spark plasma sintering technique.Effect of annealing on the structure and magneto-caloric properties of the alloy was investigated.XRD results show that both sintered and annealed samples possess a hexagonal Fe_2P-type crystal structure.After annealing,ferromagnetic impurity Fe_3Mn_4Ge_6,which exists in the sintered sample,was eliminated from the alloy.Furthermore,the lattice constants a and c change noticeably,leading to a decrease in c/a ratio,while the cell volume almost remains invariable.As a result,the Curie temperature of the alloy increases from 253 K to 298 K,but the maximum magnetic entropy change decreases from 37.5 to 11.7 J·kg·K^(-1) for 2 T magnetic field change.On the other hand,the thermal hysteresis of M-T curves around T_C upon heating and cooling is 14 and 8 K for the as-sintered and the annealed sample,respectively,showing evident change.

MnFe(PGe) compounds: Preparation, structural evolution,and magnetocaloric effects

The interdependences of preparation conditions, magnetic and crystal structures, and magnetocaloric effects （MCE） of the MnFePGe-based compounds are reviewed. Based upon those findings, a new method for the evaluation of the MCE in these compounds, based on differential scanning calorimetry （DSC）, is proposed. The MnFePGe-based compounds are a group of magnetic refrigerants with giant magnetocaloric effect （GMCE）, and as such, have drawn tremendous attention, especially due to their many advantages for practical applications. Structural evolution and phase transformation in the compounds as functions of temperature, pressure, and magnetic field are reported. Influences of preparation conditions upon the homogeneity of the compounds＇ chemical composition and microstructure, both of which play a key role in the MCE and thermal hysteresis of the compounds, are introduced. Lastly, the origin of the ＂virgin effect＂ in the MnFePGe- based compounds is discussed.

Thermodynamic Properties of Linear Protein Solutions:an Application to Type Ⅰ Antifreeze Protein Solutions

A statistical thermodynamic theory of linear protein solutions was proposed with the aid of a lattice model and applied to type Ⅰ antifreeze protein（AFPI） solutions.The numerical results for several AFPI solutions show that the Gibbs function of the solution has a minimum at a certain protein concentration,but the protein chemical potential increases with increasing the concentration.The influences of temperature and protein chain length on the AFPI chemical potential were also discussed.The evaluation for the colligative depression of the freezing point confirms that the antifreeze action should be recognized as non-colligative.The theoretical deduction for the concentration dependence of the thermal hysteresis activity coincides qualitatively with the previous experimental and theoretical results.

Plant Antifreeze Proteins and Their Expression Regulatory Mechanism

Low temperature is one of the major limiting environmental factors which constitutes the growth, development, productivity and distribution of plants. Over the past several years, the proteins and genes associated with freezing resistance of plants have been widely studied. The recent progress of domestic and foreign research on plant antifreeze proteins and the identifica- tion and characterization of plant antifreeze protein genes, especially on expression regulatory mechanism of plant antifreeze proteins are reviewed in this paper. Finally, some unsolved problems and the trend of research in physiological functions and gene expression regulatory mechanism of plant antifreeze proteins are discussed.

Effect of Annealing Duration and Substrates on Structure and Property of Vanadium Dioxide Films

Using the oxidation method from vanadium metal thin films by magnetron sputtering, under the fixed annealing parameters of temperature（400 ℃） and oxygen pressure（103 Pa）, we fabricated a series of vanadium dioxide thin films through the change of annealing durations or substrates（quartz glass or AZOcovered glass）. Characterization of the thermochromic properties together with the X-ray diffraction（XRD） and field emission scanning electron microscopy（FE-SEM） indicates that appropriate annealing duration is a key factor to obtain pure VO2 films and AZO-covered glass is more suitable to obtain the VO2 films with high visible transmittance, good crystallinity and larger near-infrared switching efficiencies（maximum 34% at 2000 nm） compared with the substrate of quartz glass. However, VO2 films on quartz glass exhibit narrower loop（7 ℃） with smart reversible response to temperature. Depth profile XPS spectra further indicate that for the films fabricated on quartz glass from thicker V metal films, the existence of low valence vanadium oxides is inevitable and leads to a lower transmittance in the region of visible light.

Transcriptomic and proteomic analyses on the supercooling ability and mining of antifreeze proteins of the Chinese white wax scale insect

The Chinese white wax scale insect, Ericerus pela, can survive at extremely low temperatures, and some overwintering individuals exhibit supercooling at tempera- tures below -30℃. To investigate the deep supercooling ability ofE. pela, transcriptomic and proteomic analyses were performed to delineate the major gene and protein families responsible for the deep supercooling ability of overwintering females. Gene Ontology （GO） classification and Kyoto Encyclopedia of Genes and Genomes （KEGG） analysis indicated that genes involved in the mitogen-activated protein kinase, calcium, and PI3K-Akt signaling pathways and pathways associated with the biosynthesis of soluble sugars, sugar alcohols and free amino acids were dominant. Proteins responsible for low-temperature stress, such as cold acclimation proteins, glycerol biosynthesis-related enzymes and heat shock proteins （HSPs） were identified. However, no antifreeze proteins （AFPs） were identified through sequence similarity search methods. A random forest approach identified 388 putative AFPs in the proteome. The AFP gene ep-afp was expressed in Escherichia coli, and the expressed protein exhibited a thermal hysteresis activity of 0.97℃, suggesting its potential role in the deep supercooling ability ofE. pela.

Renormalization group theory for temperature-driven first-order phase transitions in scalar models

We study the scaling and universal behavior of temperature-driven first-order phase transitions in scalar models. These transitions are found to exhibit rich phenomena, though they are controlled by a single complex-conjugate pair of imaginary fixed points of φ3 theory. Scaling theories and renormalization group theories are developed to account for the phenomena, and three universality classes with their own hysteresis exponents are found： a field-like thermal class, a partly thermal class, and a purely thermal class, designated, respectively, as Thermal Classes I, II, and III. The first two classes arise from the opposite limits of the scaling forms proposed and may cross over to each other depending on the temperature sweep rate. They are both described by a massless model and a purely massive model, both of which are equivalent and are derived from φ3 theory via symmetry. Thermal Class III characterizes the cooling transitions in the absence of applied external fields and is described by purely thermal models, which include cases in which the order parameters possess different symmetries and thus exhibit different universality classes. For the purely thermal models whose free energies contain odd-symmetry terms, Thermal Class III emerges only at the mean-field level and is identical to Thermal Class II. Fluctuations change the model into the other two models. Using the extant three- and two- loop results for the static and dynamic exponents for the Yang-Lee edge singularity, respectively, which falls into the same universality class as φ3 theory, we estimate the thermal hysteresis exponents of the various classes to the same precision. Comparisons with numerical results and experiments are briefly discussed.

Microstructure,magnetic and magnetocaloric properties of Fe_(2-x)Mn_xP_(0.4)Si_(0.6) alloys

The present work is devoted to investigating the microstructure,magnetism and magnetocaloric effects of Si- and Mn-rich FeMn(P,Si) alloys.The Mn-substituted alloys with Fe_(2-x)Mn_xP_(0.4)Si_(0.6)(x=1.25,1.30,1.35,1.40,1.45 and 1.50) were prepared by high-energy ball milling and solid-state reaction.Experimental results show that the alloys crystallized into a majority Fe_2P-type hexagonal structure,coexisting with minor amounts of(Mn,Fe)_3Si and(Mn,Fe)_5Si_3 phases.The Curie temperature decreased linearly from 321 to 266 K with increasing Mn content from 1.25 to 1.50 in Fe_(2-x)Mn_xP_(0.4)Si_(0.6) alloys.The first-order magnetic phase transition became weakened and the second-order magnetic phase transition became dominated with increasing Mn content.Fe_(0.75)Mn_(1.25)P_(0.4)Si_(0.6) alloy presents a maximum isothermal magnetic-entropy changes of 7.2 J(kg K)^(-1) in a magnetic field change of 0-1.5 T.The direct measurement shows that Fe_(0.7)Mn_(1.3)P_(0.4)Si_(0.6) and Fe_(0.65)Mn_(1.35)P_(0.4)Si_(0.6) alloys exhibit a maximum adiabatic temperature change of 1.8 K in a magnetic field change of 0-1.48 T.The thermal hysteresis for all alloys is less than 4 K.These experimental results reveal that Fe_(2-x)Mn_xP_(0.4)Si_(0.6) alloys could be a candidate material for magnetic refrigeration.

A study on mechanical properties of equal wall thickness rubber bushing of positive displacement motor based on hydrogenated nitrile butadiene rubber aging test

Shale gas production has become the main driver of global gas production growth.Deep shale gas is difficult to extract,which puts forward higher requirements for drilling speed increase.The downhole power drilling tools are mainly screw drilling tools.Conventional screw drill tool stator bushing has poor heat dissipation,which is prone to thermal hysteresis failure,shortening drilling tool life,and is not suitable for high temperature and high pressure environment of deep shale gas wells.Equal wall thickness screw drilling tools and hydrogenated nitrile rubber have better high temperature resistance.Therefore,based on the thermal aging experiment and constitutive model of the rubber changes the displacement of the inner cavity of the stator bushing and the difference between the front and the back is up to 21.6%.The increase of the interference and eccentricity between rotor and motor leads to the increase of the maximum von Mises stress of the stator bushing and the thermal hysteresis temperature.The influence of the interference is greater than the influence of the eccentricity so that the interference should be given priority in the design.This paper provides a theoretical reference for the design and optimization of equal wall thickness bushing of positive displacement motor.