THE RELATIONSHIP BETWEEN ENVIRONMENT CHANGE AND SE MONSOON STRENGTH, DAIHAI LAKE, INNER MONGOLIA

Daihai Lake, located in NW margin of SE monsoon region, belongs to the sensitive area for climatic fluctuation. The analysis of continuous sedimentary column with an age of 100 ka indicates that there exists the different quasiperiodicity in time scales for monsoon shift. The climatic fluctuation in the Daihai Basin shows all along the alternation of cold and dry with a warm and wet climatic pattern, suggesting that the strength and drift of SE monsoon play a controllable role in the climatic change.     

High pressure optical measurements on BP III and the isotropic phase of a highly chiral liquid crystal

The optical activity and light transmission of the blue phases and isotropic phase of 4'-(2-methylbutylphenyl)-4'-(2-methylbutyl)-4-biphenylcarboxylate (CE2) are investigated under high pressure. The temperature ranges of the first (BP I) and third (BP III) blue phases show only the slightest change, if any, with increasing pressure. This is the first time BP III, a phase which is not understood at all, has been investigated under pressure. In addition, an alternative analysis to the one reported previously is reported which confirms that the pretransitional optical activity in the isotropic phase changes very slightly due to pressure, and even this small change seems to be due to small changes in pitch and index of refraction. Taken together, these observations indicate that high pressure has little effect on both the BP III phase and the transition to the isotropic phase in highly chiral systems, even though the BP III phase differs significantly from the other blue phases and strong short range fluctuations make the transition appear continuous optically.     

CLIMATIC CHANGE SINCE LITTLE ICE AGE RECORDED BY DUNDE ICE CAP

The climatic change since the Little Ice Age recorded in the Dunde Ice Cap is presentedin this paper. There have been three cold periods and three warm periods since 1400AD.Among them, the coldest one was in the 17th century. Many evidences verified the three coldand warm variations recorded in the Dundc Ice Cap. But it was found from the comparison between the Dunde Icc Cap climatic record and thewinter temperature record in Shanghai that there was a temporal dfference in climatic changebetween East China and West China. The general trend is that the cooling and warmingprocesses in West China were earlier than that in East China. In the Dunde Ice Cap, it isnow in an anomalous warm period, while it is not as warm as in Dunde Ice Cap recordaccording to the winter temperature in Shanghai. In addition to the possible cause of temporaldifference in climatic change between West China and East China, another possible cause isthat the greenhouse effect of CO_2 may already be recognizable in the Dunde Ice Cap a     

The role of counterions on the elasticity of highly charged lamellar phases: a small-angle x-ray and neutron-scattering determination

The structure and fluctuations of the swollen L(alpha) lamellar phase of highly charged surfactant didodecyldimethylammonium halide fluid bilayers (DDA+X-) are studied using high-resolution small-angle x-ray scattering and medium-resolution, high-contrast small-angle neutron-scattering. The Caille parameter eta, as a function of the swelling (L(alpha) periodicity d), was determined from the full q-range fits of the measured scattering profiles for three different counterions (X- = Cl-, Br-, and NO3-). This parameter quantifies the amplitude of the membrane fluctuations within the Landau-de Gennes smectic-A linear elasticity theory. The different anions used gave strong specific effects at the maximum swelling of the L(alpha) phase, while at lower swellings a two-phase coexistence of swollen and collapsed lamellae (d approximately 30 and approximately 80 angstroms) was observed for bromide and nitrate ions. Over the intermediate dilution range for all three counterions, a single L(alpha) phase can be continuously swollen with pure water which is governed by an equation of state (i.e., osmotic pressure versus period) and thermally excited fluctuation amplitudes that can be well described by the same Poisson-Boltzmann calculation. The membranes were found to be slightly stiffer than predicted by purely electrostatic repulsions, and this is tentatively attributed to an extra bending rigidity contribution from the surfactant chains.     

Determination of rare earth, major and trace elements in authigenic fraction of Andaman Sea (Northeastern Indian Ocean) sediments by Inductively Coupled Plasma-Mass Spectrometry

Downcore variation of rare earth elements (REEs) in the authigenic Fe-Mn oxides of a sediment core (covering a record of last ∼ 40 kyr) from the Andaman Sea, a part of the Indian Ocean shows distinctive positive Ce and Eu anomalies. These positive Ce anomalies (Ce* = 1.1 ∼ 1.8) are ascribed to be due to oxidation of deep sea sediments. The large positive Eu anomalies (i.e., Eu* >1.8 to 3.2) occur within a time span near the glacial/interglacial transition (∼ 7000-14,000 yr BP) which could be due to the past hydrothermal activity or to the effects arising from sea level changes. During glacial times, the Andaman Sea was almost completely isolated due to low sea level, leading to a reduction in sediment supply from the Ayeyarwady River. The variations of metal abundances (i.e., Ca, Al, Mn, and Fe) in the authigenic fraction provided independent information to evaluate the water column physicochemical changes during the glacial/interglacial transition period. The studied sediment core records changes in riverine inputs and reflects depositional changes related to sea level fluctuations and climatic events over the past 40 kyr in the Andaman Sea.     

Inducing monodomain blue phase liquid crystals by long-lasting voltage application during temperature variation

We demonstrate a new successful technique for inducing a monodomain in blue phase (BP) liquid crystals (BPLCs). By application of an AC voltage during the cooling or heating of the material into the BP temperature range, a fairly homogeneous BP area was obtained, compared to the case without voltage. We determined that applying a voltage of 3.3 V/µm was very effective in terms of obtaining a monodomain: for four of the seven different applied cooling/heating rates an area ratio of more than 99% was obtained for one particular BP orientation. This study describes a successful and replicable technique to make a BPLC monodomain, which is important for the development of BPLCs and other applications.     

Interplay between cubic and hexagonal phases in block copolymer solutions

The phase behavior of a symmetric styrene-isoprene (SI) diblock copolymer in a styrene-selective solvent, diethylphthalate, was investigated by in situ small-angle X-ray scattering on isotropic and shear-oriented solutions and by rheology and birefringence. A remarkable new feature in this phase diagram is the coexistence of both body-centered cubic (bcc) and hexagonally close-packed (hcp) sphere phases, in a region between close-packed spheres (cps) and hexagonally packed cylinders (hex) over the concentration range phi approximately 0.33-0.45. By focusing on the transitions among these various ordered phases during heating and cooling cycles, we observed a strong hysteresis: supercooled cylinders persisted upon cooling. The stability of these supercooled cylinders is quite dependent on concentration, and for phi > or = 0.40, the supercooled cylinders do not revert to spheres even after quiescent annealing for 1 month. The spontaneous formation of spheres due to the dissociation of cylinders is kinetically hindered in this case, and the system is apparently not amenable to any pretransitional fluctuations of cylinders prior to the cylinder-to-sphere transition. This contrasts with the case of cylinders transforming to spheres upon heating in the melt. The application of large amplitude shear to the supercooled cylinders is effective in restoring the equilibrium sphere phases.     

THE STUDY ON FEATURES OF PALEOCLIMATIC VARIATION OF DRY AND COLD AREAS (Ⅱ)——PRELIMINARY STUDY ON FLUCTUATING MODEL OF PALEOCLIMATE OF QARHAN SALT LAKE REGION IN QAIDAM BASIN

Depositing ages of sediment in core CK6 of Qarhan Salt Lake were determined by usingmethods of ~(14)C, ~(230)Th and paleo-terrestrial-magnetism. Based on synthetic analyses for thevariation of the content of organic carbon, sporo-pollen composition and lithofacies, the fluc-tuating model of paleo-climate since 750 ka B.P. was set up. It is divided into 21 fluctua-ting epochs of climate, among them, 11 are warm and humid epochs, and 10 are dry andcold epochs.     

Synthesis and study the liquid crystalline properties of compounds containing benzoxazole core and terminal vinyl group

Terminal vinyl-based benzoxazole liquid crystalline compounds, 2-(3-fluoro-4?-alkoxy-1,1?-biphenyl ?4-yl)-5-(2-propenyloxymethyl)-benzoxazole (nPPF(2)BP), were synthesised and their structures were confirmed by infrared (IR) spectra, proton nuclear magnetic resonance (¹H-NMR) spectra, gas chromatography with electron impact-mass spectrometry (GC/EI-MS), matrix-assisted laser desorption/ionisation-time of flight (MALDI-TOF) mass spectrometry and elemental analysis (EA). The compounds show enantiotropic smectic/nematic phases with mesophase ranges are 71–97 °C and 87–136°C on heating and cooling processes for nPPF(2)BP, respectively. They give low melting points due to lateral fluoro substituent and flexible terminal 2-propenyloxymethyl chain. It is found that the compounds nPPF(2)BP with shorter alkoxy chain (n = 3, 4) exhibit a wide range of nematic mesophase, which is ascribed to enhanced π–π interaction caused by terminal vinyl moiety, whereas further elongation of the terminal alkoxy chain results in supressing nematic phase and increasing smectic mesophase. Compared with methyl terminated analogues, 2-propenyloxymethyl terminated compounds nPPF(2)BP display much lower melting points and wider or comparable mesophase range both in heating and cooling.     

Communication: Critical dynamics and nuclear relaxation in lipid bilayers

Membrane composition fluctuations affect deuterium nuclear magnetic relaxation in lipid bilayers. The time dependence of the fluctuations depends on lipid diffusion. Near a miscibility critical point this diffusion involves an advective hydrodynamic coupling to the aqueous phase. The corresponding diffusion coefficient depends on both the critical length and the fluctuation wavelength. We calculate the effects of these dynamics on transverse deuterium nuclear relaxation in the 0.1(o)-10(o) range above the critical temperature.     

Application of Calcite Veins to Study of Newly-activated Faulting

The study of period and chronology of fault activity in major worksites in an area with exposed basement rocks is quite difficult. The authors have applied the combinative techniques of field investigation, microscopic observation and isotopic dating to studying the calcite veins filled in the fault zones in several major engineering regions and got successful results. The following conclusions are reached: (i) The last period of strong activity of fault F8 in the Tianshengqiao Hydropower Station, Nanpan River is 200 ka B. P. , and there has been, no obvious activity since 150 ka. (ii) The last period of strong activity for 5 faults in Shixiali Reservoir, Yangyuan County, Hebei Province is 200-300 ka B. P. , and there has been no obvious activity since 200 ka. The research results provide a sound basis of engineering geology for project designers.     

Influence of metal cations on the intramolecular hydrogen-bonding network and pKa in phosphorylated compounds

The binding of the most common metal cations of cytoplasm (Li+, Na+, K+, Mg2+ and Ca2+) to a model molecule having an intramolecular hydrogen-bonding network, myo-inositol-2-monophosphate, was studied using first principles. A strong correlation between the conformation of metal inositol phosphate complexes with the type of metal cation, degree of deprotonation state, and the surrounding environment has been observed. On the basis of the hydrogen-bonding network analysis of the cation-phosphate complexes (Mn+-Ins(2)P1), the alkali cations show little effect on the conformational preference while the conformational preference for the binding of the alkaline earth cations is pH-dependent and solvent-dependent. For example, these calculations predict that Mg2+-Ins(2)P1(0) and Mg2+-Ins(2)P1(2-) favor the 1a/5e form while Mg2+-Ins(2)P1(1-) favors the 5a/1e conformation. The Ca2+-Ins(2)P1(2-) complex prefers the 1a/5e conformation in the gas phase and in a nonpolar protein environment, but inverts to the 5a/1e conformation upon entering the polar aqueous phase. The binding affinities of the cations and the pK(a) values for the cation-phosphate complexes are derived from thermodynamical analysis.     

Crystal–nematic phase separation in an asymmetric liquid crystal dimer possessing a terminal hydroxyl group

We prepared an asymmetric liquid crystal dimer possessing a terminal hydroxyl group, 2-{4-{7-[4-(4-cyanophenyl)phenyloxy]heptyloxy}phenyl}-5-(6-hydroxyhexyloxy)pyrimidine, and investigated the phase transition behaviour using polarising optical microscopy and differential scanning calorimetry. The compound exhibited an enantiotropic nematic phase. On cooling, two distinct domains were formed during the nematic-to-crystal phase transition. During heating, one domain melted at 126.4°C to the N phase, whereas the other domain changed to the N phase at 144.6°C. Therefore, the crystal and nematic phases coexisted at a temperature of 18.2 K. The coexistence behaviour characteristics depend on the cooling rate. We discuss the manner in which intermolecular interactions affect the phase transition behaviour.     

Fluorescence blinking, exciton dynamics, and energy transfer domains in single conjugated polymer chains

In order to understand exciton migration and fluorescence intensity fluctuation mechanisms in conjugated polymer single molecules, we studied fluorescence decay dynamics at "on" and "off" fluorescence intensity levels with 20 ps time resolution using MEH-PPV [poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] dispersed in PMMA. Two types of intensity fluctuations were distinguished for single chains of conjugated polymers. Abrupt intensity fluctuations (blinking) were found to be always accompanied by corresponding changes in fluorescence lifetime. On the contrary, during "smooth" intensity fluctuations no lifetime change was observed. Time-resolved data in combination with data on fluorescence emission and excitation anisotropy lead to a picture where a single polymer molecule is seen as consisting of several energy transfer domains. Exciton migration is efficient within a domain and not efficient between domains. Each domain can have several emitting low-energy sites over which the exciton continuously migrates until it decays. Emission of individual domains is often highly polarized. Fluorescence from a domain can be strongly quenched by Forster energy transfer to a quencher (hole polaron) if the domain overlaps with the quenching sphere.     

Monotropic smectic A to double layer smectic C transition of biphenyl containing liquid crystal acetylene

5-[（4’-Heptoxy-4-biphenylyl）carbonyloxy]-1-pentyne（A-3,7） was synthesized and the phase structures and transitions were investigated by differential scanning calorimetry（DSC）,wide angle X-ray diffraction（WAXD）,polarized light microscopy（PLM） and the molecular packing in the crystal and liquid crystalline phases were simulated by molecular dynamic simulation.The results showed that the sample formed thermodynamically metastable SmA and SmC₂ phases before crystallized during cooling and the crystal phase directly transformed into isotropic phase during heating.     

Synthesis and characterization of new liquid crystalline monomers for non-linear optics. X-ray study of re-entrant nematic behaviour with smectic-like fluctuations of C-type

The syntheses and structural properties of four liquid crystalline monomers are presented. They were prepared by two different reaction pathways. Transition temperatures and phase characterization were done by DSC, polarization microscopy and X-ray diffractometry. The dependence of phase transition temperatures on substitution of the aromatic core are discussed. Two of the compounds investigated highly ordered smectic phases. The improvement of the conjugation by means of a lateral hydroxy group disturbs the occurrence of the E re-entrant phase with smectic-like fluctuations of the C-type was observed in a compound with a lateral hydroxy group. The existence of this re-entrant nematic phase was confirmed by X-ray measurements both on cooling and heating of the sample. the alkyl chain lengths and the lateral show and B phases. The presence of a nematic     

X-ray study of the nematic and smectic A phases of the cyano-substituted pyridines

We report an X-ray study of lamellar ordering in the nematic and smectic A phases of a homologous series of polar liquid crystals, the 2-(4-alkylphenyl)-5-cyanopyridines (nCP). Experiments were carried out using a diffractometer with a linear position sensitive detector. In the nematic and smectic A phases of the nCP and their mixtures with non-polar 4-n-butyl-4'-methoxyazoxybenzene two types of layering were found. One corresponds to the fluctuations of the smectic density wave with a monolayer wavevector q₁, and the other is due to the partial bilayer fluctuations with the incommensurate wavevector q₂ ≠ q₁/2. The temperature dependences of the X-ray scattering intensity and the longitudinal correlation length for both types of layering in the nematic phase are presented. The critical behaviour in the vicinity of the smectic A-nematic phase transition occurs for a fluctuation mode, either q₁ or q₂, depending on the position on the liquid crystal phase diagram. The influence of the molecular structure of cyano-substituted pyridines on the formation of layered structures of different types is also discussed.     

Bipolar Tribocharging Signal During Friction Force Fluctuations at Metal–Insulator Interfaces

Friction and triboelectrification of materials show a strong correlation during sliding contacts. Friction force fluctuations are always accompanied by two tribocharging events at metal–insulator [e.g., polytetrafluoroethylene (PTFE)] interfaces: injection of charged species from the metal into PTFE followed by the flow of charges from PTFE to the metal surface. Adhesion maps that were obtained by atomic force microscopy (AFM) show that the region of contact increases the pull‐off force from 10 to 150 nN, reflecting on a resilient electrostatic adhesion between PTFE and the metallic surface. The reported results suggest that friction and triboelectrification have a common origin that must be associated with the occurrence of strong electrostatic interactions at the interface.     

Visco-elastic properties of reentrant nematic liquid crystalline mixtures

The visco-elastic properties for binary mixtures of 4- n -hexyloxy-4'-cyanobiphenyl (6OCB) and 4- n -octyloxy-4'-cyanobiphenyl (8OCB) are investigated in detail by a light scattering technique. The mixtures exhibit a reentrant nematic (RN) phase between the smectic A (SmA) and crystal phases in the range 22.0-29.5 wt % of 6OCB. The viscosity and the elastic constant increase with cooling in both the nematic and reentrant nematic phases. It is also found that the mixtures exhibit anomalously large values of viscosity and elastic constant near the phase transition, i.e. a pretransitional phenomenon can be observed. The activation energy for viscosity is smaller in the RN phase than in the ordinary nematic phase appearing at higher temperatures, while the normalized elastic constant (defined as the ratio of the elastic constant to the square of the dielectric anisotropy) is larger. Moreover, the visco-elastic behaviour depends on the specific time during which the sample has been kept in the SmA phase. These results confirm that the SmA phase has a strong influence on the formation of molecular aggregates, which plays an important role in the reentrant phenomenon of these systems.     

Monte Carlo Simulation of the Reactive Formation of Co‐Continuous Nanostructured Polymers

Structure formation during high‐temperature reactive blending of randomly functionalized poly‐disperse backbone polymers (such as polyethylene) with end‐functionalized graft polymers (such as polyamide 6) forming co‐continuous nanostructured microphases was investigated by means of MC simulations using the bond fluctuation algorithm. We compared reacted and non‐reacted systems under the same conditions. For the non‐reacted system at low temperatures, phase separation was observed. In the system with grafting reactions, macroscopic phase separation was inhibited even if the consumption of reactive sites was only 50%. The calculated structure factor indicates a distinct difference between the two simulation states in accordance with the 3D visualization of the system and the box‐counting method.