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A series of liquid crystalline polyethers has been synthesized from 1-(4-hydroxy-4‘-biphenylyl)-2-(4-hydroxyphenyl)propane and α,ω-dibromoalkanes [TPP(n)]. From the differential scanning calorimetry experiments, the TPP(n=odd)s show multiple phase transitions during cooling and heating. For each TPP(n=odd) the supercooling dependence of these transitions is found to be small. A phase diagram of the transition temperatures and the enthalpy and entropy changes of the transitions with respect to the number of methylene units (n) for TPP(n=odd)s have been obtained. Analyses have been conducted regarding the contributions of both the mesogenic groups and the methylene units to the differently ordered structures. Identification of the ordered structures in each phase has been carried out by combining wide angle X-ray powder and fiber diffraction experiments at different temperatures with polarized light and transmission electron microscopy experiments on the liquid crystal morphology and defects. It is found that for TPP(n≤13)s the highest temperature transition is from the isotropic melt to a nematic phase. However, for TPP(n≥15)s, the isotropic melt directly converts to a smectic F phase having a monoclinic unit cell (a pseudohexagonal packing tilted toward a side). The WAXD fiber patterns for this phase show that the chain orientation is parallel to the fiber direction. For TPP(n≤13)s formation of a smectic F phase with a monoclinic unit cell from the nematic phase can also be determined and the WAXD fiber pattern shows that the chain orientation is at an angle ranging between 0 and 20° with respect to the fiber direction. With an increase in the number of methylene units, this angle gradually decreases until n = 15, where this angle becomes zero. Further cooling leads to a smectic crystal G phase for all TPP(n=odd)s, and the different chain orientations with respect to the fiber direction in the WAXD fiber patterns still exist. TPP(n≤9)s remain in the smectic crystal G phase down to their glass transition temperatures, while TPP(n≥11)s form a smectic crystal H phase (a tilted herringbone, orthorhombic packing tilted toward the b-axis side, and a > b) in a low temperature range.

The synthesis and characterization of the AB2 monomers 6-bromo-l-(4-hydroxy-4'-biphenylyl)-2-(4-hydroxyphenyl)hexane (8 or TPH-b), 13-bromo-l-(4-hydroxyphenyl)-2-[4-(6-hydroxy-2-naphthalenylyl)-phenyl1 tridecane (22 or BPNT-b), and 13-bromo-l-(4hydroxyphenyl)-2-(4-hy~oxy-4''-p-~~henylyl)~ide~e (30 or TPT-b) are described. The phase-transfer-catalyzed polyetherification of all monomers followed by in situ alkylation of their phenolate chain ends with bromoalkanes, benzyl chloride, or allyl chloride led to the soluble hyperbranched polymers TPH-b-X, BPNT-b-X, and TPT-b-X (where X refers to the nature of their chain ends, for example, when X = Bz = benzyl, X = All = allyl, and, when X = numeral, it represents the number of carbons in the alkyl chain end). The minimum energy conformations of the flexible branching points of these polymers are anti and gauche. The gauche conformer leads to a hyperbranched polymer with a conventional treelike architecture. By analogy with the behavior of the corresponding linear polymers, above their glass transition temperature, these hyperbranched polymers are considered to minimize their free energy by lowering their free volume via a conventional nematic mesophase which is generated by the conformational change of their structural units from gauche to anti. The overall change in the architecture of these hyperbranched polymers via the anti-gauche conformational change of their structural units resembles that of a willow. Regardless of the nature of X, TPH-b-X and BPNT-b-X display only a very narrow enantiotropic nematic mesophase. TPT-b-8 with M,, = 11 800 and M,IM,, = 2.42 exhibits an enantiotropic nematic mesophase over a range of 82 O C . The degree of branching of TPT-b-A11 is 0.82. Thus TPT-b is of extreme interest for further investigations on this novel class of hyperbranched polymers and for the synthesis of thermotropic liquid crystalline dendrimers.

The recently discovered inverse magnetic catalysis around the critical temperature indicates that some important information is missing in our current understanding of conventional chiral dynamics of QCD, which is enhanced by the magnetic field. In this work, we provide a mechanism to explain that the inverse magnetic catalysis around the critical temperature is induced by sphalerons. At high temperatures, sphaleron transitions between distinct classical vacua cause an asymmetry between the number of right- and left-handed quarks due to the axial anomaly of QCD. In the presence of a strong magnetic field, the chiral imbalance is enhanced and destroys the right- and left-handed pairings, which naturally induces a decreasing critical temperature of the chiral phase transition for increasing magnetic field. The inverse magnetic catalysis at finite baryon density, and the critical end point in the presence of a strong magnetic field is also explored in this work.Comment: 5 pages, 3 figure

Belowground communities exert major controls over the carbon and nitrogen balances of terrestrial ecosystems by regulating decomposition and nutrient availability for plants. Yet little is known about the patterns of belowground communities and their relationships with environmental factors, particularly at the regional scale where multiple environmental gradients co‐vary. Here, we describe the patterns of belowground communities (microbes and nematodes) and their relationships with environmental factors based on two parallel studies: a field survey with two regional‐scale transects across the Mongolia plateau and a water‐addition experiment in a typical steppe. In the field survey, soils and plants were collected across two large‐scale transects (a 2000‐km east–west transect and a 900‐km south–north transect). At the regional‐scale, the variations in soil microbes (e.g. bacterial PLFA, fungal PLFA, and F/B ratio) were mainly explained by precipitation and soil factors. In contrast, the variation in soil nematodes (e.g. density of trophic groups and the bacterial‐feeding/fungal‐feeding nematode ratio) were primarily explained by precipitation. These variations of microbe or nematode variables explained by environmental factors at regional scale were derived from different vegetation types. Along the gradient from nutrient‐poor to nutrient‐rich vegetation types, the total variation in soil microbes explained by precipitation increased and that explained by plant and soil decreased, while the opposite was true for soil nematodes. Experimental water addition, which increased rainfall by 30% during the growing season, increased biomass or density of belowground communities, with the nematodes being more responsive than the microbes. The different responses of soil microbial and nematode communities to environmental gradients at the regional scale likely reflect their different adaptations to climate, soil nutrients, and plants. Our findings suggest that the soil nematode and microbial communities are strongly controlled by bottom‐up effects of precipitation alone or in combination with soil conditions.

We extend the confined-density-dependent-mass (CDDM) model to include isospin dependence of the equivalent quark mass. Within the confined-isospin-density-dependent-mass (CIDDM) model, we study the quark matter symmetry energy, the stability of strange quark matter, and the properties of quark stars. We find that including isospin dependence of the equivalent quark mass can significantly influence the quark matter symmetry energy as well as the properties of strange quark matter and quark stars. While the recently discovered large mass pulsars PSR J1614-2230 and PSR J0348+0432 with masses around 2M ⊙ cannot be quark stars within the CDDM model, they can be well described by quark stars in the CIDDM model. In particular, our results indicate that the two-flavor u-d quark matter symmetry energy should be at least about twice that of a free quark gas or normal quark matter within conventional Nambu-Jona-Lasinio model in order to describe the PSR J1614-2230 and PSR J0348+0432 as quark stars. Subject headings: dense matter -equation of state -stars: neutron

Liquid crystalline polyethers have been synthesized from 1-(4-hydroxy-4‘-biphenylyl)-2-(4-hydroxyphenyl)propane and α,ω-dibromoalkanes with even-numbers of methylene units [TPP(n = even)s]. Multiple phase transitions are found during cooling and heating via differential scanning calorimetry (DSC), and they show little undercooling dependence. Ordered structure identifications are based on experimental observations of wide angle X-ray powder and fiber diffraction experiments at different temperatures. Polarized light and transmission electron microscopy observations on mesophase morphology combined with DSC results on thermodynamic transition properties also provide additional evidence for these phase assignments. Moreover, the contributions of the mesogenic groups and the methylene units to each ordering process are obtained based on the changes of transition enthalpy and entropy. In TPP(n ≤ 8)s the highest temperature transition is from the isotropic melt to a nematic phase. This nematic phase is only stable in a narrow temperature range. For instance, it is 12 °C for TPP(n = 4) and 6 °C for TPP(n = 8). When the number of methylene units n ≥ 10, the isotropic melt directly enters a smectic F phase. The second transition in TPP(n ≤ 8)s is from the nematic to the smectic F phase. As a result, the smectic F phase exists for all TPP(n = even)s. Decreasing the temperature further leads to another transition in TPP(n = even)s to form a smectic crystal G phase which is followed by a transition to a smectic crystal H phase. This smectic crystal H phase remains for TPP(n ≤ 8)s down to their glass transition temperatures, while in TPP(n ≥ 10)s further ordering processes occur and crystal phases are observed. A phase diagram of TPP(n = even)s is constructed.

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