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CeAlGe, a proposed type-II Weyl semimetal, orders antiferromagnetically below 5 K. At 2 K, spin-flop and a spin-flip transitions to less than 1 $\mu_B$/Ce are observed in the $M(H)$ data below 30 kOe, ($\bf{H}\|\bf{a}$ and $\bf{b}$, and 4.3 kOe, $\bf{H}\|\langle110\rangle$, respectively, indicating a four-fold symmetry of the $M(H)$ data along the principal directions in the tetragonal $\it{ab}$ plane with $\langle110\rangle$ set of easy directions. However, anomalously robust and complex twofold symmetry is observed in the angular dependence of resistivity and magnetic torque data in the magnetically ordered state once the field is swept in the $\it{ab}$ plane. This twofold symmetry is independent of temperature and field hystereses and suggests a magnetic phase transition that separates two different magnetic structures in the $\it{ab}$ plane. The boundary of this magnetic phase transition and possibly the type of low-field magnetic structure can be tuned by an Al deficiency.

From an engineering standpoint, the magnetic field (B), temperature (T), and strain dependence (e) of the critical current density (JC) in practical superconducting wires/tapes is critical for optimizing device design using superconducting technology. The highly anisotropic and brittle nature of YBa2Cu3O7-δ (YBCO) coated conductor tapes means a detailed investigation of the parameters that affect the critical current is a challenging experimental task to achieve within a single strain apparatus. Here we present critical current measurements as a function of strain on YBCO coated conductors made using a bending apparatus designed for use in horizontal split-pair magnet systems with a 40 mm diameter bore. The design and configuration of the apparatus allows different compressive and tensile strain between -1.4%

High critical current density (Jc) DI-BSCCO Bi-2223 superconducting tape has been developed by Sumitomo Electric Industries (SEI) using the Controlled Over-Pressure (CT-OP) technique to improve the texturing and densification. Further enhancement of the mechanical properties has been obtained using lamination. We have investigated the effect of magnetic field and field orientation on Jc for a series of test DI-BSCCO tapes at 77 K and 4.2 K under tensile and compressive strains. These critical current data are strongly influenced by the anisotropy of Bi-2223, the texturing of the tape and its architecture. The magnetic field and angular dependence of Jc at 77 K can be described using a simple anisotropic exponential magnetic field model which includes the effects of the two-dimensionality and grain misalignment in these composites. The variation in the normalized Jc with respect to the strain is linear over the reversible range of strain where the gradient of the strain dependence is independent of temperature and field. The reversibility of Jc is extended further into the compressive regime after Jc degradation by compression.

Genes near adenosine monophosphate-activated protein kinase-α1 (PRKAA1) have been implicated in the greater uterine artery (UtA) blood flow and relative protection from fetal growth restriction seen in altitude-adapted Andean populations. Adenosine monophosphate-activated protein kinase (AMPK) activation vasodilates multiple vessels but whether AMPK is present in UtA or placental tissue and influences UtA vasoreactivity during normal or hypoxic pregnancy remains unknown. We studied isolated UtA and placenta from near-term C57BL/6J mice housed in normoxia (n = 8) or hypoxia (10% oxygen, n = 7-9) from day 14 to day 19, and placentas from non-labouring sea level (n = 3) or 3100 m (n = 3) women. Hypoxia increased AMPK immunostaining in near-term murine UtA and placental tissue. RT-PCR products for AMPK-α1 and -α2 isoforms and liver kinase B1 (LKB1; the upstream kinase activating AMPK) were present in murine and human placenta, and hypoxia increased LKB1 and AMPK-α1 and -α2 expression in the high- compared with low-altitude human placentas. Pharmacological AMPK activation by A769662 caused phenylephrine pre-constricted UtA from normoxic or hypoxic pregnant mice to dilate and this dilatation was partially reversed by the NOS inhibitor l-NAME. Hypoxic pregnancy sufficient to restrict fetal growth markedly augmented the UtA vasodilator effect of AMPK activation in opposition to PE constriction as the result of both NO-dependent and NO-independent mechanisms. We conclude that AMPK is activated during hypoxic pregnancy and that AMPK activation vasodilates the UtA, especially in hypoxic pregnancy. AMPK activation may be playing an adaptive role by limiting cellular energy depletion and helping to maintain utero-placental blood flow in hypoxic pregnancy.

We present the designs of probes for making critical current density (Jc) measurements on anisotropic high-temperature superconducting tapes as a function of field, field orientation, temperature and strain in our 40 mm bore, split-pair 15 T horizontal magnet. Emphasis is placed on the design of three components: the vapour-cooled current leads, the variable temperature enclosure, and the springboard-shaped bending beam sample holder. The vapour-cooled brass critical-current leads used superconducting tapes and in operation ran hot with a duty cycle (D) of ~0.2. This work provides formulae for optimising cryogenic consumption and calculating cryogenic boil-off, associated with current leads used to make J(c) measurements, made by uniformly ramping the current up to a maximum current (I(max)) and then reducing the current very quickly to zero. They include consideration of the effects of duty cycle, static helium boil-off from the magnet and Dewar (b'), and the maximum safe temperature for the critical-current leads (T(max)). Our optimized critical-current leads have a boil-off that is about 30% less than leads optimized for magnet operation at the same maximum current. Numerical calculations show that the optimum cross-sectional area (A) for each current lead can be parameterized by LI(max)/A = [1.46D(-0.18)L(0.4)(T(max) - 300)(0.25D(-0.09)) + 750(b'/I(max))D(10(-3)I(max)-2.87b') × 10⁶ A m⁻¹ where L is the current lead's length and the current lead is operated in liquid helium. An optimum A of 132 mm(2) is obtained when I(max) = 1000 A, T(max) = 400 K, D = 0.2, b' = 0.3 l h(-1) and L = 1.0 m. The optimized helium consumption was found to be 0.7 l h(-1). When the static boil-off is small, optimized leads have a boil-off that can be roughly parameterized by: b/I(max) ≈ (1.35 × 10(-3))D(0.41) l h(‑1) A(-1). A split-current-lead design is employed to minimize the rotation of the probes during the high current measurements in our high-field horizontal magnet. The variable-temperature system is based on the use of an inverted insulating cup that operates above 4.2 K in liquid helium and above 77.4 K in liquid nitrogen, with a stability of ±80 mK to ±150 mK. Uniaxial strains of -1.4% to 1.0% can be applied to the sample, with a total uncertainty of better than ±0.02%, using a modified bending beam apparatus which includes a copper beryllium springboard-shaped sample holder.

The microstructure and morphology of a mixture of polymeric materials depends on factors in both the thermal and rheological history of a sample as well as on its equilibrium thermodynamics. Concentrating largely on systems which are partly miscible we explore the effects of molecular, rheological and thermodynamic parameters on phase diagrams of binary polymer blends and show how these interact with sample preparation in determining the final sample morphology.

Flux pinning scaling laws were developed to explain the observed increase in the critical current density Jc caused by increased density of grain boundaries in polycrystalline low temperature superconductors (LTS) such as Nb3Sn. For four decades they have provided the framework for the successful development of the LTS materials that carry high Jc in high magnetic fields. However, the discovery of the weak-link problem suggested that transmission of supercurrent flow through the grain boundaries limited Jc in high temperature superconductors (HTS) such as YBa2Cu3O7-{\delta} (YBCO). Here we provide evidence that a single mechanism - flux flow along grain boundaries - confirmed by time-dependent Ginzburg-Landau (TDGL) computational visualisation in LTS materials, explains the functional form of Jc in polycrystalline LTS Nb3Sn and HTS YBCO and (Bi,Pb)2Sr2Can-1CunOx (BiSCCO) materials in low and high magnetic fields. Data presented show that standard flux pinning theory cannot explain comprehensive Jc data for YBCO because Jc is a function of strain but the superconducting properties are not. We conclude that grain boundaries are narrow and metallic in Nb3Sn and YBCO but wide and semiconducting in BiSCCO. Strain alters Jc by changing the superconducting properties of the grains in Nb3Sn but by changing the grain boundaries in YBCO

Controlled Over-Pressure is used by Sumitomo Electric Industries Ltd. to process so-called DI-BSCCO Bi-2223 superconducting tape reaching high critical current (IC) in high magnetic fields. This paper reports the critical current of DI-BSCCO tape at 77 K in low fields and at 4.2 K in our horizontal split-pair magnet in fields up to 13 T at various angles between the surface of the tape and the direction of the magnetic field. These critical current data are strongly influenced by the anisotropy of Bi-2223, the texturing of the tape and the magnetic history of the magnetic field. The magnetic field and angular dependence of IC at 77 K can be parameterised with a simple anisotropic Kim model. For 4.2 K measurements where large currents and magnetic fields are required, it is demonstrated that a split-current-lead design can be used to reduce rotation of the probe during the IC measurements.

The late stages of phase separation by spinodal decomposition have been studied by light scattering in an oligomeric blend of polystyrene (PS) with polybutadiene (PB) as a function of both quench depth and composition. The scattering function I(q,t) follows a dynamical scaling law of the form S(q,t)=qm(t)−3S[q/qm(t)] where the wave vector qm corresponds to the maximum in I(q,t). The profiles of the normalized scaled structure functions are compared with that predicted by Furukawa for critical mixtures (percolation regime) which is given by S(x)=4x2/(3+x8)[S(1)=1]. Apart from one exception, Furukawa’s function adequately describes the form of the normalized structure functions for a 60% PS mixture. However there are problems with some of the comparisons with the 50% and 70% PS blends. These disparities may in part be attributable to the fact that some of the data may lie outside the ‘‘true’’ late stages.

Room-temperature ultrasonic compressional wave velocity and attenuation measurements have been carried out on commercial poly-methyl methacrylate (PMMA) and fully deuterated PMMA. Deuteration was found to reduce the velocity by 4.4 ± 1.2% which can be completely accounted for by the density change of 8.0%, assuming no changes in atomic force constants or molar volume. The attenuation was 17% higher in the deuterated sample. Making reasonable assumptions about the distribution function for the relaxation times of molecular groupings moving in two-well potentials, the attenuation increase is attributed to a reduction in the attempt frequency for barrier hopping of main chain and/or ester methyl groups.

La theorie de l'influence de l'agregation des paires d'ions sur les dimensions de la chaine est comparee avec les mesures du rayon de giration

Influence du temps de dissolution et de la vitesse de cisaillement sur la viscosite de polystyrenesulfonate dans le xylene

Etude des systemes polystyrene/polybutadiene et polyoxyde d'ethylene methoxyle/polyoxyde de propene methoxyle

Recent advances in the small-angle scattering of X-rays, neutrons and light by polymers are reviewed. The three techniques are compared, from both experimental and theoretical points of view. Applications are discussed for the study of homophase and heterophase polymers, both in solution and in the solid state, as well as for unoriented and oriented crystalline polymers.

High-resolution neutron scattering experiments on deuterium-labelled model trifunctional networks show that the junction points move more slowly than the free chain centres by a factor of about two.

The theory is developed in terms of monatomic systems in order to demonstrate the relationships between the momentum and energy profiles of the scattered neutrons and the properties of the scattering nuclei. An indication is then given of how this framework may be expanded to deal with molecular systems. A brief discussion of the more commonly used experimental methods is included. Because of difficulties of interpretation and the lower resolution compared to other spectroscopic techniques, neutron scattering methods have been most successfully applied to certain well defined problems in molecular spectroscopy. A detailed discussion of low energy neutron scattering in the energy range of molecular translation and hindered rotation demonstrates both the difficulties involved and several instances where this technique has shed new light on the problem of molecular motions. The review concludes with a survey of neutron scattering of the dynamics of macromolecules.

The following is an account of a method of addition and some methods of subtraction which may appeal to teachers who like to lace their teaching with enrichment material, but who sometimes refrain from doing so because of a fear that an “off beat” treatment of a topic may confuse rather than clarify.

The first presentation by Dr. Lundberg, giving an overview of ionomer solution behaviour, prompted discussion on the surprising range of behaviour observed for even low levels of ionic substitution. At less than 2 mole% in polar solvents substantial molecular extension characteristic of polyeletrolytes may be observed by a number of techniques including neutron scattering and dipole moment measurements.

1. Thermodynamic Theory and Experimental Techniques for Polymer Blends.- 2. Glass Transitions and Compatibility Phase Behavior in Copolymer Containing Blends.- 3. Microscopy and other Methods of Studying Blends.- 4. Preparation of Blends.- 5. Light, Neutron and X-Ray Scattering Techniques for Studying Polymer Blends.- 6. Liquid-Liquid Phase Equilibria in Polymer Blends.- 7. Polymer Blend Modification of PVC.- 8. Synthesis of Block and Graft Copolymers.- 9. Block Copolymers Morphological and Physical Properties.- 10. Colloidal Behaviour and Surface Activity of Block Copolymers.- 11. Relationships between Morphology, Structure, Composition and Properties in Isotactic Polypropylene Based Blends.- 12. Rubber-Rubber Blends.- 13. Pure and Applied Research on Interpenetrating Polymer Networks and Related Materials.- 14. Fracture Toughness Evaluation of Blends and Mixtures and the Use of the J Method.- 15. Crazing and Cracking in Glassy Homopolymers.- 16. The Mechanical Properties of Homogeneous Glassy Polymer Blends.- 17. Mechanical Properties of High-Impact Polymers.- 18. Fatigue of High-Impact Polymers.- 19. Yielding and Failure Criteria for Rubber Modified Polymers, Part 1.- 20. Yielding and Failure Criteria for Rubber Modified Polymers, Part 2.- 21. Multiphase Thermosetting Polymers.- 22. Processing and Phase Morphology of Incompatible Polymer Blends.- Seminars.- 1. Pulse-Induced Critical Scattering.- 2. Phase Separation in Polymer Blends.- 3. Thermodynamics of Compatibility in Binary Polymeric Mixtures.- 4. PVC Blending Resins: Properties and Appllications.- 5. Block Copolymers as Homogenizing Agents in Blends of Amorphous and Semicrystalline Polymers.- 6. Study of Copolymer-Homopolymer Blends.- 7. Rubber-Plastics Blends.- 8. Isotactic Polypropylene/Rubber Blends: Effect of Crystallization Conditions and Composition on Properties.- 9. Ethylene-Propylene Rubber and Polyolefin Polymer Blends: Present Situation and Future Trends.

Most polymer pairs are incompatible, or at best partially compatible over limited ranges of temperature and concentration. A number of systems showing lower or upper critical solution temperatures have been studied in our laboratory by a variety of techniques and the phase boundaries determined. Labelling by partial deuteration of one component allows us to investigate chain dimensions and interaction parameters by small angle neutron scattering from the single phase mixture close to the phase boundary and thus to extend our understanding of the limited compatibility to a molecular level. It has been found that both chain expansion and chain contraction may occur in different systems as the phase boundary is approached from the single phase side.

Using the latest high resolution spectrometers, neutron scattering explores molecular motion at frequencies between 107 and 1014 Hz. This includes vibrations and rotations of side groups, phonon modes in crystals and high frequency conformational changes in solutions, melts and networks. The random variation in scattering power from nuclide to nuclide allows labelling techniques to be used to advantage, while the large neutron mass leads to a relatively short wavelength at low energies (compared to electromagnetic radiation) and gives spatial information simultaneously with the frequency information.

The neutron is a heavy particle compared to photons and therefore scattering spectroscopy using neutrons covers a unique range of frequency-spatial correlations. For inelastic experiments the far infra-red spectroscopic range up to ∼1000 cm-1 may be observed with sizeable wave vector transfers and phonon dispersion curves mapped out. In quasielastic experiments motion of main chain and side groups may be followed at frequencies from 107 Hz upwards, again with simultaneous information about the spatial characteristics of the motion in question.

Ionomers give rise to peaks in small angle scattering experiments. The structures inferred involve clustering of the ionic side groups. SANS has been used to investigate the effect of this structure on the molecular dimensions as well as the behaviour of the observed peak itself especially as a function of added water.

It is not the purpose of this chapter to enter into the details of scattering theory but rather to outline the principles and explain the applications to study of blends. All scattering experiments are based on the existence of variations in the homogeneity of the scattering medium. These may arise either because a few molecules of one type are embedded in a matrix of others as in dilute solutions, or because of concentration fluctuations in a high concentration mixture or from density fluctuations in a single component system. If these inhomogeneities also cause variation in the physical property relevant for scattering a particular type of radiation, a scattering pattern may result. These relevant properties are the polarisability (or refractive index) for light, the electron density for X-rays and the scattering length density (a nuclear property) for neutrons.

We modify the Cahn-Hilliard theory of concentration fluctuation dynamics to account for the short-time networklike nature of high molecular weight polymers. We propose an additional term in the free energy, due to elastic energy arising from the finite lifetime of entanglements. If we assume a single-exponential decay time for the entanglements, the equation of motion is governed by two exponential modes. For quenches into the two-phase region, the faster mode always decays with time, and the slower mode grows. The theory successfully accounts for data from spinodal decomposition of polymer blends containing at least one component of very high molecular weight.