Photoperiodic control of reproduction and patterns of melatonin secretion in the rainbow trout, Oncorhynchus mykiss

Reproduction In salmonids is an annual event with spawning confined to a brief (typically 6 week) period each year. The reproductive cycle appears to be controlled by on endogenous circannual rhythm or •clock' which, under natural conditions, is entrained by the seasonal changes in daylength. This thesis Investigates the mechanisms by which photoperiod entrains the circannual clock which, it is proposed, controls maturation In the rainbow trout, Oncorhynchus mykiss, Abrupt changes m photoperiod can either advance or delay spawning and the timing of changes m serum calcium, oestradol-178 and testosterone which accompany maturation in the female rainbow trout. These effects can be interpreted as corrective phase advances or phase delays of a circannual dock. 'Long' photoperiods of between 12 and 22 hours applied in January, followed by shorter photoperiods of between 3.5 and 13.5 hours from May were equally effective tor the advancement of maturation In December-spawning female rainbow trout. Maturation was also advanced, though to a lesser extent, in fish which remained on typical winter photoperiods (8.5 or 10 hours), provided they received a decrease to an even shorter photoperiod prior to the summer solstice. In contrast, maturation was delayed in fish maintained under a constant winter photoperiod (8.5 hours), and these fish also exhibited a desynchronization of spawning times characteristic of endogenous circannual rhythms in free-run. Collectively, these results indicate that direction of change of daylength is the feature of the photoperiodic signal responsible for the entrainment of the endogenous circannual clock; the same photoperiod may be interpreted as 'long' or 'short’ providing it is longer or shorter than that to which the fish have been previously exposed. The concept of a rigid critical' daylength for reproductive function it therefore untenable in the rainbow trout. The liming of the increase to a 'long' photoperiod was also on important determinant of spawning lime; maturation occurred in sequence In December-spawning female rainbow trout maintained on constant 'long' days from January and February, and in fish exposed to 'long' days from December, January and February, followed by 'short' days in May. Maturation can also be advanced or delayed by exposing rainbow trout to short (S2 months) periods of continuous light at different phases of the reproductive cycle. These effects can be described in the form of a partial phase-response curve. The proportion of fish responding to short periods of continuous light was dependent on both the duration of the light period, and. most importantly, its position in relation to the phase of the reproductive cycle. A high proportion (285%) of fish responded with an advance in spawning time only when the period of exposure to continuous light occurred close to the preceding natural breeding season. The minimum period of exposure capable of advancing maturation in a majority (280%) of rainbow trout was 1 month. In 3 consecutive experiments over 90% of female rainbow trout exposed to continuous light for 2 months from January to March spawned again in a 6-wook period In July and August, approximately 5 months in advance of their natural spawning period. Exposure of rainbow trout to short periods of continuous light therefore provides a simple, cheap and predictable method for the production of out- of-season eggs on commercial fish farms. Patterns of melatonin secretion In the rainbow trout accurately reflected the prevailing photoperiod, with levels elevated for the duration of darkness under both long (16L:8D or 18L:6D) and short (8L:16D or 6L:18D) daylengths. Distinct diurnal rhythms in circulating melatonin were also detected in the Atlantic salmon. Salmo salar and Nile tilapia. nranr.hrnmi« niinticiis. Melatonin production in the rainbow trout is not under endogenous circadian control; changes in melatonin levels always coincided with the light to dark or dark to light transitions, and the melatonin rhythm did not persist in constant darkness. Additionally, the melatonin rhythm Immediately re adjusted to the new photoperiod when rainbow trout were transferred from long (t8L:6D) to short (6L:18D) days. Those results indicate that melatonin production in the rainbow trout is a direct response to darkness. Although the seasonally-changing patterns of melatonin secretion clearly provide the rainbow trout with accurate information on both daily and calendar lime the results of experiments designed to lest the hypothesis that melatonin conveys photic Information to the reproductive axis were inconclusive

The application of contact mechanics to the numerical simulation of particulate material

Particulate solids are complex redundant systems which consist of discrete particles. The interactions between the particles are complex and have been the subject of many theoretical and experimental investigations. Invetigations of particulate material have been restricted by the lack of quantitative information on the mechanisms occurring within an assembly. Laboratory experimentation is limited as information on the internal behaviour can only be inferred from measurements on the assembly boundary, or the use of intrusive measuring devices. In addition comparisons between test data are uncertain due to the difficulty in reproducing exact replicas of physical systems. Nevertheless, theoretical and technological advances require more detailed material information. However, numerical simulation affords access to information on every particle and hence the micro-mechanical behaviour within an assembly, and can replicate desired systems. To use a computer program to numerically simulate material behaviour accurately it is necessary to incorporte realistic interaction laws. This research programme used the finite difference simulation program `BALL', developed by Cundall (1971), which employed linear spring force-displacement laws. It was thus necessary to incorporate more realistic interaction laws. Therefore, this research programme was primarily concerned with the implementation of the normal force-displacement law of Hertz (1882) and the tangential force-displacement laws of Mindlin and Deresiewicz (1953). Within this thesis the contact mechanics theories employed in the program are developed and the adaptations which were necessary to incorporate these laws are detailed. Verification of the new contact force-displacement laws was achieved by simulating a quasi-static oblique contact and single particle oblique impact. Applications of the program to the simulation of large assemblies of particles is given, and the problems in undertaking quasi-static shear tests along with the results from two successful shear tests are described

Shape-changing architectural skins: a review on materials, design and fabrication strategies and performance analysis

In recent years, there has been an increasing interest in shape-changing smart materials in design fields. The ability to design responsive architectures that adapt to different climatic conditions is, without doubt, an appealing idea. One area in which shape-changing materials are applied is in the design of building skins or envelopes. This paper presents a systematic review of the literature on the use of shape-changing materials in the development of active skin systems, identifying patterns in design and manufacturing strategies. We also note the stage of development of the proposed designs and whether performance analysis was conducted to predict their behaviour. The results show that the most commonly used materials are SMA (Shape Memory Alloys) and wood-based bio-composites. Other shape-changing materials used for developing skin systems are, in order of popularity, thermo bimetals, electroactive polymers, composite bimetals, shape memory polymers, and hydrogels. The patterns identified among the studies are (1) design strategies: smart material as the skin, smart material as the actuator, combination with other non-responsive materials, responsive structures, geometric amplification; and (2) manufacturing strategies: bilayer systems and additive manufacturing.   Finally, while the argument for the development of responsive skin systems is often based on the idea of efficiency and improved performance, we found that few studies can predict the performance of such skin systems

Stabilized antiferroelectricity in xBiScO3-(1-x)NaNbO3 lead-free ceramics with established double hysteresis loops

We previously reported various solid solution systems that demonstrated the stabilized antiferroelectric (P) phases in NaNbO 3 through lowering the tolerance factor. However, all those reported modifications were achieved by adding A 2+ B 4+ O 3 type solid solutions. A lead-free antiferroelectric (AFE) solid solution xBiScO 3 -(1-x)NaNbO 3 was rationalized by adopting the tolerance factor design rule. Specifically, adding BiScO 3 was found to effectively stabilize the AFE phase without changing the crystal symmetry of NaNbO 3 . Microstructure and electron zone axis diffraction patterns from transmission electron microscopy revealed the stabilized AFE (P) phase in this solid solution. Besides, the electric-field-induced polarization with a double-hysteresis loop was observed. The present results pointed out that the strategy could also be applied while adding A 3+ B 3+ O 3 type solid solutions. In addition, it expanded the compositional design that can be applied to antiferroelectric materials

The unusual case of plastic deformation and high dislocation densities with the cold sintering of the piezoelectric ceramic K0.5Na0.5NbO3

K0.5Na0.5NbO3 (KNN) can be readily densified using the cold sintering process, but despite observing high relative permittivity, the ferroelectric hysteresis is strongly suppressed along with a major suppression in the all-important piezoelectric properties. In this study, KNN is fabricated using a NaOH+KOH transient flux under a uniaxial pressure of 400 MPa and heating to 300 °C for 2 h to drive densification to 93% theoretical. It is only after a secondary heat treatment that we observe improvements of the ferroelectric hysteresis and piezoelectric properties. From a detailed structural-property-processing study using analytical transmission electron microscopy (TEM), X-ray line broadening and high field dielectric characterization methodologies we conclude that there is an unusual in-situ plastic deformation process that takes place in addition to the densification under the cold sintering process. High densities of dislocations within grains were observed that lead to multiple pinning sites that impact both the intrinsic and extrinsic contributions to the high field dielectric and piezoelectric properties. Annealing significantly reduced the dislocation density in the highly defective crystallites, observed directly from the TEM and from the sharpening of the X-ray diffraction peaks, resulting in piezoelectric and ferroelectric properties that approached those of conventionally sintered KNN

Dielectric relaxation and localized electron hopping in colossal dielectric (Nb,In)-doped TiO2 rutile nanoceramics

Dielectric spectroscopy was performed on a Nb and In co-doped rutile TiO2 nano-crystalline ceramic (n-NITO) synthesized by a low-temperature spark plasma sintering (SPS) technique. The dielectric properties of the n-NITO were not largely affected by the metal electrode contacts. Huge dielectric relaxation was observed at a very low temperature below 35 K. Both the activation energy and relaxation time suggested that the electronic hopping motion is the underlying mechanism responsible for the colossal dielectric permittivity (CP) and its relaxation, instead of the internal barrier layer effect or a dipolar relaxation. With Havriliak–Negami (H–N) fitting, a relaxation time with a large distribution of dielectric relaxations was revealed. The broad distributed relaxation phenomena indicated that Nb and In were involved, controlling the dielectric relaxation by modifying the polarization mechanism and localized states. The associated distribution function is calculated and presented. The frequency-dependent a.c. conductance is successfully explained by a hopping conduction model of the localized electrons with the distribution function. It is demonstrated that the dielectric relaxation is strongly correlated with the hopping electrons in the localized states. The CP in SPS n-NITO is then ascribed to a hopping polarization

Contrasting conduction mechanisms of two internal barrier layer capacitors: (Mn, Nb)-doped SrTiO3 and CaCu3Ti4O12

The d.c. conduction is investigated in the two different types of internal barrier layer capacitors, namely, (Mn, Nb)-doped SrTiO3 (STO) and CaCu3Ti4O12 (CCTO). Scanning electron microscopy (SEM) and Capacitance - Voltage (C-V) analysis are performed to estimate the effective electric field at a grain boundary, EGB. Then, the d.c. conduction mechanism is discussed based on the J (Current density)-EGB characteristics. Three different conduction mechanisms are successively observed with the increase of EGB in both systems. In (Mn, Nb)-doped STO, non-linear J-EGB characteristics is temperature dependent at the intermediate EGB and becomes relatively insensitive to the temperature at the higher EGB. The J- EGB at each regime is explained by the Schottky emission (SE) followed by Fowler-Nordheim (F-N) tunneling. Based on the F-N tunneling, the breakdown voltage is then scaled by the function of the depletion layer thickness and Schottky barrier height at the average grain boundary. The proposed function shows a clear linear relationship with the breakdown. On the other hand, F-N tunneling was not observed in CCTO in our measurement. Ohmic, Poole-Frenkel (P-F), and SE are successively observed in CCTO. The transition point from P-F and SE depends on EGB and temperature. A charge-based deep level transient spectroscopy study reveals that 3 types of trap states exist in CCTO. The trap one with Et ∼ 0.65 eV below the conduction band is found to be responsible for the P-F conduction

Survival rates for Nephrops norvegicus discarded from Northern European trawl fisheries

When discarded from bottom trawl fisheries, survival of Nephrops norvegicus may be sufficiently high that this species can be exempted from the EU Landing Obligation. In three studies, Nephrops were sampled from trawlers in northern European waters, and the fate of individuals monitored for a minimum of 13 days in onshore tanks. Winter estimates of captive survival (means ± 95% confidence intervals), including immediate mortality during catch sorting, were 62 ± 2.8% for the West of Scotland, 57 ± 1.8% for the Farne Deeps (North Sea), and 67 ± 5.4% for the Skagerrak. The Farne Deeps fishery is not active in summer, but captive survival rates in summer in the other two areas were reduced to 47 ± 3.4% for West of Scotland and 40 ± 4.8% for the Skagerrak. Linear modelling of the West of Scotland and Skagerrak data suggested that higher survivals in winter were related to colder water or air temperatures, although temperatures during captive observation may also have had an impact. Net modifications in the Skagerrak study had an effect on survival, which was higher for Nephrops sampled from nets equipped with the more selective Swedish sorting grid compared to Seltra trawls

Investigation of Electric Field–Induced Structural Changes at Fe-Doped SrTiO3 Anode Interfaces by Second Harmonic Generation

We report on the detection of electric field–induced second harmonic generation (EFISHG) from the anode interfaces of reduced and oxidized Fe-doped SrTiO3 (Fe:STO) single crystals. For the reduced crystal, we observe steady enhancements of the susceptibility components as the imposed dc-voltage increases. The enhancements are attributed to a field-stabilized electrostriction, leading to Fe:Ti-O bond stretching and bending in Fe:Ti-O6 octahedra. For the oxidized crystal, no obvious structural changes are observed below 16 kV/cm. Above 16 kV/cm, a sharp enhancement of the susceptibilities occurs due to local electrostrictive deformations in response to oxygen vacancy migrations away from the anode. Differences between the reduced and oxidized crystals are explained by their relative oxygen vacancy and free carrier concentrations which alter internal electric fields present at the Pt/Fe:STO interfaces. Our results show that the optical SHG technique is a powerful tool for detecting structural changes near perovskite-based oxide interfaces due to field-driven oxygen vacancy migration

Systematic Association Mapping Identifies NELL1 as a Novel IBD Disease Gene

Crohn disease (CD), a sub-entity of inflammatory bowel disease (IBD), is a complex polygenic disorder. Although recent studies have successfully identified CD-associated genetic variants, these susceptibility loci explain only a fraction of the heritability of the disease. Here, we report on a multi-stage genome-wide scan of 393 German CD cases and 399 controls. Among the 116,161 single-nucleotide polymorphisms tested, an association with the known CD susceptibility gene NOD2, the 5q31 haplotype, and the recently reported CD locus at 5p13.1 was confirmed. In addition, SNP rs1793004 in the gene encoding nel-like 1 precursor (NELL1, chromosome 11p15.1) showed a consistent disease-association in independent German population- and family-based samples (942 cases, 1082 controls, 375 trios). Subsequent fine mapping and replication in an independent sample of 454 French/Canadian CD trios supported the authenticity of the NELL1 association. Further confirmation in a large German ulcerative colitis (UC) sample indicated that NELL1 is a ubiquitous IBD susceptibility locus (combined p<10−6; OR = 1.66, 95% CI: 1.30–2.11). The novel 5p13.1 locus was also replicated in the French/Canadian sample and in an independent UK CD patient panel (453 cases, 521 controls, combined p<10−6 for SNP rs1992660). Several associations were replicated in at least one independent sample, point to an involvement of ITGB6 (upstream), GRM8 (downstream), OR5V1 (downstream), PPP3R2 (downstream), NM_152575 (upstream) and HNF4G (intron)