Antiferroelectric and ferroelectric smectic C side chain liquid crystal polymers

Chirality in liquid crystals has been of increasing interest over the past twenty five years. More recently interesting results have been obtained in the area of chiral smectic liquid crystals with the discovery of Twist Grain Boundary (TGB), antiferroelectric and ferrielectric liquid crystal phases.The thesis is concerned mainly with the investigation into the incidence of novel smectic phases in Side Chain Liquid Crystal Polymers (SCLCPs), and the effect structural variation has on the appearance of these phases.A study of the effect of lateral fluoro substitution in the rigid core of the molecule on the formation of chiral smectic C phases showed how the position of the fluoro substituent affected the thermal stability of the polymeric material. This study also led to the discovery of an antiferroelectric-like structure in a polymer containing an achiral, swallow-tailed terminal chain.The thesis also describes an "odd / even" effect when altering the length of the flexible spacer connecting the polymer backbone to the rigid core of the side chain; a polymer with a flexible spacer containing an odd number of carbon atoms exhibits an antiferroelectric phase and the corresponding analogue with an even number of carbon atoms in the flexible spacer exhibits a ferroelectric phase.The effect of altering the moiety which connects the polymer backbone to the flexible spacer is also examined. Polymers which contain an ether functionality as the linking moiety retain their antiferroelectric properties. However, in polymers where the linking group is a "reverse ester", a smectic C phase was not observed*The final structural feature examined in this thesis involved an examination of the effect of changing the substituent on the polymer backbone. It was found that in polymers where the linking group was an ether moiety, or a reversed ester, increasing the size and polarity of the backbone substituent did not alter the phase sequence, but the liquid crystal phase was thermally stabilised. In polymers where the backbone was linked by an ester group, markedly increasing the polarity of the backbone substituent caused the resulting SCLCP to become more glass-like; the mesophase was thermally stabilised and gave poor alignment of the side chains

Magnetism and Superconductivity in (Er₀.₁₆Ho₀.₈₄)Rh₄B₄

The superconducting and ferromagnetic phase boundaries in the (Er1-xHox)Rh4B4 mixed ternary alloy system meet in a multicritical point at xcr ≈ 0.9. For xcr, the compounds first become superconducting as the temperature is lowered, and then lose superconductivity in a transition to ferromagnetism. The coexistence of superconductivity and ferromagnetism for alloys near the erbium-rich end of the phase diagram is well established. It has also been suggested that ferromagnetism and superconductivity coexist in alloys with x just below xcr. We have carried out neutron-diffraction, ac magnetic susceptibility, and heat-capacity measurements on a sample of (Er0.16Ho0.84)Rh4B4 to investigate the possibility of coexistence of ferromagnetism and superconductivity for x ≈ xcr. We find that there are minor discrepancies in the superconducting and magnetic transition temperatures reported for different samples of (Er0.16Ho0.84)Rh4B4, but that ferromagnetism and superconductivity do occur simultaneously over a narrow temperature range in this sample. We suggest that an inhomogeneous state occurs, consisting of separate ferromagnetic and superconducting regions, rather than microscopic coexistence

Time-dependent Magnetic Structures of the Superconducting Mixed Ternary System Ho(Rh₁₋ₓIrₓ)₄B₄

Magnetic structures have been determined by netron diffraction for several compositions in the superconducting mixed ternary system Ho(Rh1-xIrx)4B4. Two features previously reported to occur in the heat capacity for some compositions are shown to correspond to successive magnetic transitions. For x=0.30 and 0.45, neutron diffraction peaks for the lowest temperature structure develop over a timescale of many hours. The results are discussed in terms of magnetic frustration

Torque, power and muscle activation of eccentric and concentric isokinetic cycling

This study aimed to establish the effect of cycling mode and cadence on torque, external power output, and lower limb muscle activation during maximal, recumbent, isokinetic cycling. After familiarisation, twelve healthy males completed 6 × 10 s of maximal eccentric (ECC) and concentric (CON) cycling at 20, 40, 60, 80, 100, and 120 rpm with five minutes recovery. Vastus lateralis, medial gastrocnemius, rectus femoris, and biceps femoris surface electromyography was recorded throughout. As cadence increased, peak torque linearly decreased during ECC (350-248 N·m) and CON (239-117 N·m) and peak power increased in a parabolic manner. Crank angle at peak torque increased with cadence in CON (+13°) and decreased in ECC (-9.0°). At all cadences, peak torque (mean +129 N·m, range 111-143 N·m), and power (mean +871 W, range 181-1406 W), were greater during ECC compared to CON. For all recorded muscles the crank angle at peak muscle activation was greater during ECC compared to CON. This difference increased with cadence in all muscles except the vastus lateralis. Additionally, peak vastus laterallis and biceps femoris activation was greater during CON compared to ECC. Eccentric cycling offers a greater mechanical stimulus compared to concentric cycling but the effect of cadence is similar between modalities. Markers of technique (muscle activation, crank angle at peak activation and torque) were different between eccentric and concentric cycling and respond differently to changes in cadence. Such data should be considered when comparing between, and selecting cadences for, recumbent, isokinetic, eccentric and concentric cycling

BDNF val66met polymorphism is associated with modified experience-dependent plasticity in human motor cortex.

Motor training can induce profound physiological plasticity within primary motor cortex, including changes in corticospinal output and motor map topography. Using transcranial magnetic stimulation, we show that training-dependent increases in the amplitude of motor-evoked potentials and motor map reorganization are reduced in healthy subjects with a val66met polymorphism in the brain-derived neurotrophic factor gene (BDNF), as compared to subjects without the polymorphism. The results suggest that BDNF is involved in mediating experience-dependent plasticity of human motor cortex

A Simple Model of Global Aerosol Indirect Effects

Most estimates of the global mean indirect effect of anthropogenic aerosol on the Earth's energy balance are from simulations by global models of the aerosol lifecycle coupled with global models of clouds and the hydrologic cycle. Extremely simple models have been developed for integrated assessment models, but lack the flexibility to distinguish between primary and secondary sources of aerosol. Here a simple but more physically based model expresses the aerosol indirect effect (AIE) using analytic representations of cloud and aerosol distributions and processes. Although the simple model is able to produce estimates of AIEs that are comparable to those from some global aerosol models using the same global mean aerosol properties, the estimates by the simple model are sensitive to preindustrial cloud condensation nuclei concentration, preindustrial accumulation mode radius, width of the accumulation mode, size of primary particles, cloud thickness, primary and secondary anthropogenic emissions, the fraction of the secondary anthropogenic emissions that accumulates on the coarse mode, the fraction of the secondary mass that forms new particles, and the sensitivity of liquid water path to droplet number concentration. Estimates of present-day AIEs as low as 5 W/sq m and as high as 0.3 W/sq m are obtained for plausible sets of parameter values. Estimates are surprisingly linear in emissions. The estimates depend on parameter values in ways that are consistent with results from detailed global aerosol-climate simulation models, which adds to understanding of the dependence on AIE uncertainty on uncertainty in parameter values

Temporal Response of Rabbits to β-Adrenergic Agonist Feeding: Tissue Weight, Calpains and Calpastatin Activities, and Nucleic Acid and Protein Concentrations

Forty-eight crossbred rabbits were used in three replications of a 2 x 4 factorial arrangement to investigate the short-term responses of tissue accretion, calpains and calpastatin activity, and nucleic acid and protein concentrations to β- adrenergic agonist (BAA) feeding. Rabbits were fed a 17% CP diet with or without 7 ppm of L644,969 and slaughtered after 1, 4, 8, or 16 d of treatment. Empty body dressing percentage and biceps femoris weight (as a percentage of empty body weight [EBWI) were significantly higher in the treated rabbits than in the controls after 16 d of treatment. Heart and liver weights (as a percentage of EBW) were higher ( P \u3c .05) after 1 d and liver weight (as a percentage of EBW) was lower (P \u3c .05) after 16 d in treated vs controls. Except for an elevation of skeletal muscle m-calpain after 16 d, BAA-supplementation did not affect the calpain-calpastatin system. Muscle RNA concentrations and RNA:DNA ratios were higher (P \u3c .05) in treated rabbits after 1 d and remained higher thereafter. Protein:RNA ratios were lower ( P \u3c .0 1) in treated than in control rabbits after 4 d and remained lower throughout the trial. Muscle DNA content was lower after 4 d and higher after 16 d; RNA content was higher after 4, 8, and 16 d; and protein content was higher after 16 d in treated vs control rabbits. Liver nucleic acid and protein concentrations were not affected by BAA treatment. Heart RNA:DNA ratios were higher ( P \u3c .0 1) after 1 d and protein:RNA ratios were lower (P \u3c .05) after 4 d in the treated rabbits than in the controls. Collectively, these data imply that BAA-induced muscle growth in rabbits occurs through hyperplasia and seems to be related to elevated protein synthetic capacity

At-line boar taint classification by means of Rapid Evaporative Ionisation Mass Spectrometry (REIMS)

Increasing awareness of animal welfare has led to a European incentive to ban the surgical castration of piglets. A valid alternative for castration is the rearing of entire male pigs, but this allows the (re)occurrence of boar taint, an off-odour in meat from entire boars (1). Hence, due to adverse consumer reactions to pork with boar taint, the rearing of entire boars requires valid boar taint mitigation strategies. However, the introduction of Rapid Evaporative Ionisation MS (REIMS) offers compelling perspectives for the rapid as well as accurate at-line detection of boar taint by significantly reducing analysis time and workload, yet enhancing research output and efficiency (2). In this study, REIMS was used as a direct analysis technique to train predictive models for identification of boar taint above the odour threshold (based on sensory (soldering iron method) as well as chemical analysis (UHPLC-HRMS analysis of indole, skatole and androstenone levels) 3. Adipose tissue was sampled using a prototype bipolar handheld sampling device connected directly to a Xevo G2-XS Q-TOF system equipped with REIMS source (Fig. 1). The results demonstrate that untargeted mass spectrometric profiling in negative ionisation mode enables the construction of predictive models using LiveID, AMX and Simca (Q2 = 0.547, R2Y = 0.652 and p = 0) for the classification of carcasses according to boar taint status based on alterations in lipid profiles. As REIMS eliminates sample pre-treatment with analysis taking < 10 seconds, it offers significant potential as the first technique enabling accurate in-situ detection of boar taint. REIMS is a promising and highly innovative tool for several types of food quality and safety applications, furthermore allowing us to move state-of-the-art equipment and applications from bench to production site. Acknowledgments: This research was partly funded by the Flemish Government, department of animal welfare (LNE/STG/DWZ/16/11). References: [1] K. Verplanken, Ghent University PhD dissertation, (2018) 1-15. [2] K. Verplanken et al., Talanta, 169 (2017) 30–36. [3] K. Bekaert et al., Journal of Chromatography A, 1239 (2012) 49-55