Sc Value Research Articles

Synthesis and applications of novel acceptor–donor–acceptor organic dyes with dithienopyrrole- and fluorene-cores for dye-sensitized solar cells

Four novel symmetrical organic dyes ( S1– S4) configured with acceptor–donor–acceptor (A–D–A) structures containing electron donating fluorene ( S1 and S2) and N-alkyl dithieno[3,2- b:2′,3′- d]pyrrole (DTP) ( S3 and S4) cores terminated with two anchoring cyanoacrylic acids (as electron acceptors) were synthesized and applied to dye-sensitized solar cells (DSSCs). The DSSC device based on S2 dye showed the best photovoltaic performance among S1– S4 dyes: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 76%, a short circuit current ( J SC) of 12.27 mA/cm 2, an open circuit voltage ( V OC) of 0.61 V, a fill factor (FF) of 0.63, and an overall power conversion efficiency ( η) of 4.73%. Besides, the utilization of chenodoxycholic acid (CDCA) as a co-adsorbent in the DSSC device based on S3 dye showed a significant improvement in its η value (from 3.70% to 4.31%), which is attributed to the suppression of dye aggregation on TiO 2 surface and thus to increase the J SC value eventually.

Synthesis and characterization of low-bandgap copolymers based on dihexyl-2 H-benzimidazole and terthiophene

A series of new semiconducting polymers with 3-(hexyloxy)thiophene, 2,2-dihexyl-2 H-benzimidazole ( HBI) and thiophene units was synthesized using Stille polymerization. These random copolymers show good solubility at room temperature in organic solvents owing to the long alkyl chain in new acceptor, 2,2-dihexyl-2 H-benzimidazole. In HBI, the sulfur at 2-position of 2,1,3-benzothiadiazole ( BT) unit was replaced with the carbon to make a highly soluble electron deficient moiety while keeping the 1,2-quinoid form of BT unit. The spectra of the solid films show absorption bands with maximum peaks at about 408–526 nm and the absorption onsets at 550–692 nm, corresponding to band gaps of 1.79–2.25 eV. The onset wavelengths of the absorption spectra in thin films exhibit a gradual red-shift with decreased amount of dihexyl-2 H-benzimidazol unit, that is, from 550 nm with PHOTDTHBI-9 to 692 nm with PHOTDTHBI-1. Under white light illumination (AM 1.5 G, 100 mW/cm 2), the device with PHOTDTHBI-3:PCBM blend demonstrated a V OC value of 0.36 V, a J SC value of 1.20 mA/cm 2, and a FF of 0.37, leading to the efficiency of 0.16%.

Novel Organic Sensitizers with a Quinoline Unit for Efficient Dye-sensitized Solar Cells

Three organic sensitizers, JK-128, JK-129, and JK-130 containing quinoline unit are designed and synthesized. Under standard global AM 1.5 solar condition, the JK-130 sensitized solar cell gave a short circuit photocurrent density of 11.52 mA cm -2 , an open circuit voltage of 0.70 V, and a fill factor of 0.75, corresponding to an overall conversion efficiency of 6.07%. We found that the η of JK-130 was higher than those of other two cells due to the higher photocurrent. The higher J sc value is attributed to the broad and intense absorption spectrum of JK 130.

TiO 2- and ZnO-based solar cells using a chlorophyll a derivative sensitizer for light-harvesting and energy conversion

TiO 2- and ZnO-based solar cells sensitized by a chlorophyll a derivative (methyl trans-3 2-carboxy-pyropheophorbide a) were fabricated and compared. The TiO 2-based solar cell produces higher values for the short-circuit photocurrent ( J sc), open-circuit photovoltage ( V oc), and energy-to-electricity conversion efficiency ( η) than the ZnO-based solar cell. The observed ATR-FTIR data on the dye-sensitized semiconductor electrodes and the spectra estimated from the density functional theory (DFT) suggest that the dye sensitizer is bound to TiO 2 with both the bidentate chelating and monodentate modes but is bound to ZnO with the monodentate mode exclusively. The frontier orbitals of the dye molecule bound to semiconductors suggest that the HOMO-2 and LUMO + 2 orbitals of the dye sensitizer do not participate in electron transfer processes for the dye–ZnO system, resulting in a lower J sc value and a relatively narrow response for the incident photon-to-current conversion efficiency in the solar cell. Transition component analysis based upon the time-dependent DFT results explains well the experimental UV–vis spectra and difference in the η values between the dye-sensitized solar cells based upon TiO 2 and ZnO nanocrystalline electrode materials.

Surface morphology and light scattering properties of plasma etched ZnO:B films grown by LP-MOCVD for silicon thin film solar cells

LP-MOCVD deposited ZnO:B thin films, post-etched by argon plasma processes, were investigated in this study in order to optimise the ZnO:B/p-layer interface when the ZnO:B is used as front electrode of p–i–n a-Si:H solar cells. At varying etching time different surface roughness was obtained and the evolution of the surface morphology was correlated with the texture characteristic and its scattering properties. Atomic force microscopy data were analysed and discussed together with the scattering properties, which are haze parameter and angular resolved scattering (ARS) distribution. The presence of several preferential scattering angles was hypothesized and a deconvolution approach was applied to each angular scattering curve. For each fixed preferential scattering angle θ i we associated a Gaussian distribution of the scattered light amount related to a well-defined scattering surface. The different preferential scattering angles were correlated to different scattering phenomena, the modifications of the angular scattering curves well agreed with SEM and AFM images. It is well known that a:Si–H solar cells fabricated on MOCVD deposited ZnO:B substrates show poor FF and V oc values with good J sc value. We demonstrated that only an effective sharp edge rounding off produced by an appropriately long plasma etching treatment is able to make MOCVD deposited ZnO:B perfectly suitable for high quality a-Si:H based devices.

Novel organic sensitizers containing a bulky spirobifluorene unit for solar cell

Three organic sensitizers JK-87, JK-88, and JK-89 containing a bulky spirobifluorene unit in the bridged group are designed and synthesized. Under standard global A.M. 1.5 solar condition, the JK-89 sensitized cell gave a short-circuit photocurrent density ( J sc) of 13.02 mA cm −2, an open-circuit voltage ( V oc) of 0.75 V, and a fill factor of 0.70, corresponding to an overall conversion efficiency η of 6.83%. The η of JK-89 is higher than those of other two cells due to the larger J sc. The improved J sc value is mainly attributed to the broad and red-shifted absorption band.

A new class of natural glycopeptides with sugar moiety-dependent antioxidant activities derived from Ganoderma lucidum fruiting bodies.

A water-soluble glycopeptide (PGY), fractionated and purified from the aqueous extract of the fruiting bodies of Ganoderma lucidum via two-step dialysis, anion exchange, and gel permeation chromatography, was constituted of two moieties of carbohydrate and peptide. Carbohydrate characterization with component analysis, methylation analysis, periodate oxidation, Smith degradation, enzymic hydrolysis, and IR and NMR experiments demonstrated that the carbohydrate moiety possessed a backbone of approximately 33 (1-->3)-linked beta-d-glucopyranosyl residues and side chains, at positions 6, of single alpha-l-arabinofuranosyl residues for every three Glcp residues in the main chain. On the basis of the results of amino acid composition and trypsin digestion, the peptide moiety, shown to consist of Arg, Ser, Ala, and Gly in a ratio of 1:1:2:2, exhibited the sequence of Ser-Arg-[(Ala)2(Gly)2] and was O-attached to the carbohydrate moiety via Ser. To contribute toward our understanding of the structure-activity relationship, a series of expected derivatives generated from PGY by trypsin digestion, debranching, and NaIO4 oxidation following reduction experiments, including PTC, DB-PGY, and PPP, were obtained. All of them, as well as PGY and a reference compound (butylated hydroxytoluene, BHT), were evaluated with two conventional antioxidant testing systems of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide radical scavenging and found to have their respective antioxidant activities in a concentration-dependent manner. Comparable radical-scavenging activities observed between PTC and PGY demonstrated that the removal of Ala and Gly in a peptide moiety did not result in the variation of biological functions of PGY. However, it was very interesting to note that the scavenging activity of PPP was higher for DPPH radicals, with an SC(50) value of 116.4 +/- 5.1 microg/mL, and lower for superoxide radicals, with an SC(50) value of 205.2 +/- 14.4 microg/mL, than that of PGY with corresponding SC(50) values of 133.5 +/- 5.5 and 140.5 +/- 7.7 microg/mL, and, moreover, DB-PGY displayed the weakest scavenging potency in the tested samples, indicating that the carbohydrate moiety, in particular the side chain of nonreducing end units of Araf residues as the functional region, played a vital role in the structure and antioxidant activity. In addition, compared with the SC(50) value of BHT, PGY showed lower DPPH radical-scavenging activity but possessed higher superoxide radical-quenching potency, suggesting that it could be presented as a possible new source of natural antioxidants.

On designing and testing transformations for derivation of standard 12-lead/18-lead electrocardiograms and vectorcardiograms from reduced sets of predictor leads

The aim of this study was to develop and evaluate transformation coefficients for deriving the standard 12-lead electrocardiogram (ECG), 18-lead ECG (with additional leads V7, V8, V9, V3R, V4R, V5R), and Frank vectorcardiogram (VCG) from reduced lead sets using 3 “limb” electrodes at Mason-Likar torso sites combined with 2 chest electrodes at precordial sites V1 to V6; 15 such lead sets exist and each can be recorded with 6-wire cable. As a study population, we used Dalhousie Superset (n = 892) that includes healthy subjects, postinfarction patients, and patients with a history of ventricular tachycardia. For each subject, 120-lead ECG recordings of 15-second duration were averaged, and all samples of the QRST complex for leads of interest were extracted; these data were used to derive—by regression analysis—general and patient-specific coefficients for lead transformations. These coefficients were then used to predict 12-lead/18-lead ECG sets and 3-lead VCG from 15 reduced lead sets, and the success of these predictions was assessed by 3 goodness-of-fit measures applied to the entire QRST waveform and to the ST deviation at J point; these 3 measures were similarity coefficient (SC in percentage), relative error (in percentage), and RMS error (in microvolts). Our results show that the best pair for predicting the standard 12-lead ECG by either general coefficients (mean SC = 95.56) or patient-specific coefficients (mean SC = 99.11) is V2 and V4; the best pair for deriving the 18-lead set by general coefficients (mean SC = 93.74) or by patient-specific coefficients (mean SC = 98.71) is V1 and V4; the best pair for deriving the Frank X, Y, Z leads is V1 and V3 for general coefficients (mean SC = 95.76) and V3 and V6 for patient-specific coefficients (mean SC = 99.05). The differences in mean SC among the first 8 to 10 predictor sets in each ranking table are within 1% of the highest SC value. Thus, in conclusion, there are several near-equivalent choices of reduced lead set using 6-wire cable that offer a good prediction of 12-lead/18-lead ECG and VCG; a pair most appropriate for the clinical application can be selected.

Influence of texture feature size on spherical silicon solar cells

The effects of surface texturing on spherical silicon solar cells were investigated. Surface texturing for spherical Si solar cells was prepared by immersing p-type spherical Si crystals in KOH solution with stirring. Two kinds of texture feature sizes (1 and 5 μm pyramids) were prepared by changing stirring speed. After fabrication through our baseline processes, these cells were evaluated by solar cell performance and external quantum efficiency. The cell with 1 and 5 μm pyramids shows the short circuit current density ( J sc) value of 31.9 and 33.2 mA·cm −2, which is 9% and 13% relative increase compared to the cell without texturing. Furthermore, the cell with 5 μm pyramids has a higher open-circuit voltage (0.589 V) than the cell with 1 μm pyramids (0.577 V). As a result, the conversion efficiency was improved from 11.4% for the cell without texturing to 12.1% for the cell with 5 μm pyramids.

Influence of pyrazole derivatives in I−/I3− redox electrolyte solution on Ru(II)-dye-sensitized TiO2 solar cell performance

Abstract The influence of pyrazole additives in an I − /I 3 − redox electrolyte solution on the performance of a bis(tetrabutylammonium) cis -bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II) (N719) dye-sensitized TiO 2 solar cell was studied. The current–voltage characteristics of the cell were measured using 18 different pyrazole derivatives. All of the pyrazole additives enhanced the open-circuit photovoltage ( V oc ) and the solar energy conversion efficiency ( η ), but reduced the short-circuit photocurrent density ( J sc ). Most of the pyrazoles improved fill factor (ff). The physical and chemical properties of the pyrazoles were computationally calculated in order to elucidate the reasons for the additive effects on cell performance. The greater the partial charge of the nitrogen atom at position 2 in the pyrazole group, the larger the V oc, but the smaller the J sc values. As the dipole moment of the pyrazole derivatives increased, the V oc value increased, but the J sc value decreased. The V oc of the cell also increased as the ionization energy of the pyrazoles decreased. These results suggest that the electron donicity of the pyrazole additives affected the interaction with the nanocrystalline TiO 2 photoelectrode, the I − /I 3 − electrolyte, and the acetonitrile solvent, which changed the Ru(II)-dye-sensitized solar cell performance.

Influence of quinoline derivatives in I −/I 3− redox electrolyte solution on the performance of Ru(II)-dye-sensitized nanocrystalline TiO 2 solar cell

The influence of quinoline additives in an I −/I 3 − redox electrolyte solution on the performance of a bis(tetra-butylammonium) cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II) (N719) dye-sensitized TiO 2 solar cell was studied. The I– V characteristics were measured for the cells with 20 types of quinoline derivatives. All of the quinoline additives enhanced the open-circuit photovoltage ( V oc) and fill factor (ff), but reduced the short circuit photocurrent density ( J sc) of the solar cell. Most of the quinolines also improved the solar energy conversion efficiency ( η). The physical and chemical properties of the quinolines were computationally calculated in order to elucidate the reasons for the additive effects on the cell performance. The greater the lowest partial charge of the atoms in the quinoline derivatives, namely nitrogen, the larger the V oc, but the smaller the J sc values. As the dipole moment of the quinoline derivatives increased, the V oc value increased, but the J sc value decreased. The V oc of the cell also increased as the ionization energy of the quinolines decreased. These results suggest that the electron donicity of the quinoline additives affected the interaction with the nanocrystalline TiO 2 photoelectrode, the I −/I 3 − electrolyte, and the acetonitrile solvent, which changed the Ru(II)-dye-sensitized solar cell performance.

Influence of aminotriazole additives in electrolytic solution on dye-sensitized solar cell performance

The influence of aminotriazole additives in acetonitrile solution of an I −/I 3 − redox electrolyte on the performance of a bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II) (N719) dye-sensitized TiO 2 solar cell was studied. The current–voltage characteristics were investigated under AM 1.5 (100 mW/cm 2) for 10 different aminotriazole compounds. The aminotriazole additives tested had varying effects on the solar cell performance. Most of the additives enhanced the open-circuit photovoltage ( V oc), fill factor (ff) and the solar energy conversion efficiency ( η), but reduced the short circuit photocurrent density ( J sc) of the solar cell. The highest η of 7.6% was obtained by adding 3-amino-1H-1,2,4-triazole and η was comparable to that of 4- t-butylpyridine (TBP). Both the physical and chemical properties of the aminotriazoles were computationally calculated in order to determine the reasons why the additive affects the solar cell performance. The greater the calculated partial charge of the nitrogen atoms in the molecule, the larger the V oc value. The V oc of the solar cell also increased as the size of the aminotriazole molecules decreased. The J sc value increased with increasing the absolute difference in the dipole moments between the calculated aminotriazoles and acetonitrile. These results suggest that the electron donicity of the aminotriazole additives influenced the interaction with the TiO 2 photoelectrode and the solvent, which altered the dye-sensitized solar cell performance.

Influence of benzimidazole additives in electrolytic solution on dye-sensitized solar cell performance

The influence of benzimidazole additives on the performance of a bis(tetrabutylammonium)- cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II) dye-sensitized TiO 2 solar cell with an I −/I 3 − redox electrolyte in acetonitrile was investigated by measuring the current–voltage characteristics of more than 20 different benzimidazole derivatives under AM 1.5 (100 mW/cm 2). The benzimidazole additives tested had varying effects on the cell performance. Adding benzimidazole drastically enhanced the open-circuit photovoltage ( V oc) and the fill factor (ff), but reduced the short-circuit photocurrent density ( J sc) of the solar cell. In order to determine the reasons for the additive effects on cell performance the physical and chemical properties of the benzimidazoles were computationally calculated. Consequently, the greater the calculated partial charge of the nitrogen atoms in position 3 of the benzimidazole groups, the larger the V oc, but the smaller the J sc values. The V oc values also increased as the molecular size of the benzimidazole derivatives decreased. Moreover, the greater the absolute difference between the calculated dipole moment of the benzimidazole and acetonitrile, the larger the J sc value. These results suggest that these properties of the benzimidazoles influenced the extent of interaction between the TiO 2 electrode and electrolyte solvent, which changed the dye-sensitized solar cell performance.

Influence of pyrimidine additives in electrolytic solution on dye-sensitized solar cell performance

The influence of pyrimidine additives on the performance of a bis(tetrabutylammonium) cis-bis(thiocyanato)bis(2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate)ruthenium(II) dye-sensitized TiO 2 solar cell with an I −/I 3 − redox electrolyte in acetonitrile was studied. The current–voltage characteristics were measured for more than 10 different pyrimidine derivatives under AM 1.5 (100 mW/cm 2). The pyrimidine additives tested had varying effects on the performance of the cell. The additives drastically enhanced the open-circuit photovoltage ( V oc) and the solar energy conversion efficiency ( η), but usually reduced the short circuit photocurrent density ( J sc) of the solar cell. Physical and chemical properties of the pyrimidines were computationally calculated in order to determine the reasons for the additive effects on cell performance. Consequently, the greater the calculated partial charge of the nitrogen atoms in the pyrimidine groups, the larger the V oc but the smaller the J sc values. The V oc of the cell also increased as the ionization energy of the pyrimidine molecules decreased. Moreover, as the calculated dipole moment of the pyrimidine derivatives increased, the J sc value was reduced, but the V oc value was enhanced. These results suggest that the electron donicity of pyrimidine additives influenced the interaction with TiO 2 electrode and I −/I 3 − electrolyte, which lead to the changes in dye-sensitized solar cell performance.

Finite element analysis of bubbly flow around an oscillating square-section cylinder

The bubbly flow around a square-section cylinder, which is forced to oscillate normal to a uniform flow, is simulated by an incompressible two-fluid model. The model is solved by the Arbitrary Lagrangian–Eulerian (ALE) finite element method. The width of the cylinder is 30 mm . A bubbly flow is assumed, and the bubble diameter is set as 1 mm . The volumetric fraction of the gas-phase upstream of the cylinder is 0.05, where the Reynolds number defined by the volumetric velocity of the liquid-phase is 200. With an increment in the cylinder oscillation frequency Sc, the vortex shedding frequency St approaches the Sc value. When the Sc is increased beyond a critical value, the lock-in occurs, in which the vortex shedding is synchronized with the cylinder oscillation. The time-averaged drag coefficient and the root-mean-square of the lift coefficient for the cylinder take their maximum values at the lock-in state. The volumetric fraction of the gas-phase α g is higher in the wake of the cylinder, irrespective of the Sc value. The α g value is lower below the lock-in state and higher in the lock-in state than the value for the stationary cylinder.

Enhanced quantum yield in porphyrin/electron-donor double-layer solar cells

When the layer of 3-carboxymethyl-5-[(3-ethyl-2(3H)-benzothiazolylidine)ethylidene (MC(COOH)) is inserted into the Au/Zntpyp interface in Al/Zntpyp/Au sandwich-type solar cell (Zntpyp: 5,10,15,20-tetra(3-pyridyl)porphyrinatozinc), the photovoltaic properties are remarkably improved. For the Al/Zntpyp(thickness 10 nm)/MC(COOH)(20 nm)/Au cell, a short-circuit photocurrent ( J sc) of 0.93 μ Acm −2, open-circuit photovoltage ( V oc) of 0.71 V, fill factor (ff) of 0.41, and energy conversion yield (η) of 3.6% are obtained when illuminated at the Al/Zntpyp interface with 455 nm monochromatic light of 7.5 μ Wcm −2 intensity. A rapid electron-transfer from the donor MC(COOH) to photogenerated holes in Zntpyp suppresses the charge recombination of the photogenerated carriers. The energetically well-arranged valence band levels eventually enhance the η value about 9 times compared with the Al/Zntpyp/Au cell. Further the Al/HD(9 nm)/MC(COOH)(20 nm)/Au cell using a longer-lived sensitizer (HD) instead of Zntpyp gives a J sc value of 2.36 μ Acm −2, V oc value of 0.69 V, ff value of 0.34, and η value of 4.8% when illuminated with 445 nm monochromatic light of 11.7 μ Wcm −2 intensity at the Al/HD interface, where HD represents a heterodimer consisting of 5,10,15-tri(4-chlorophenyl)-20-(3-pyridyl)porphyrin(H 2pyp 3p(Cl)) and 5,10,15,20-tetra(2,5-dimethoxyphenyl)porphyrinatozinc(Zntpp(OMe) 2).

Pharmacokinetics and bioequivalence of parenterally administered doramectin in cattle

Plasma concentrations of doramectin in 40 cattle dosed by subcutaneous (sc) or intramuscular (i.m.) injection (200 micrograms/kg) were compared to assess the bioequivalence of the two routes of administration. Peak concentration (Cmax), and areas under the concentration curve (AUC0-infinity) were determined from plasma concentrations. Animals treated by the sc route showed a mean AUC0-infinity of 457 +/- 66 ng.day/mL (+/- SD) and a mean Cmax of 27.8 +/- 7.9 ng/mL. Results from the i.m. treatment group showed a mean AUC0-infinity of 475 +/- 82 ng.day/mL and a mean Cmax of 33.1 +/- 9.0 ng/mL. Absorption constants (ka) determined by modelling were 0.542 +/- 0.336 day-1 after sc administration and 0.710 +/- 0.357 day-1 after i.m. administration. The 90% confidence limits on the difference between mean AUC0-infinity values for the sc and i.m. groups fell within 20% of the mean value for the subcutaneous group. Cmax was somewhat greater for the i.m. route. The 90% confidence limits on the difference in mean In(Tmax +1) also fell within 20% of the mean sc value. Based on this analysis, bioequivalence of the sc and i.m. formulation has been established.

The effect of non-steroidal anti-inflammatory drugs on the electrical properties of cultured dog tracheal epithelial cells

The effect of non-steroidal anti-inflammatory drugs (NSAIDs) on the electrical properties of primary cultures of dog tracheal epithelium has been studied. The cells used were grown with an air interface in a serum-free medium on membranes coated with human placental collagen. When mounted in Ussing chambers at 37°C, mean values for the baseline short circuit current ( I sc) and the transepithelial resistance of 65 tissue specimens from 18 dogs were 24.0 ± 3.2 μ A/cm 2 and 458 ± 128 Ω · cm 2 , respectively. These tissues had been pretreated with amiloride to abolish active Na + absorption. Under these conditions, the I sc value serves as a measure of active Cl − secretion. The results of this study revealed that the I sc across a cultured monolayer of trachea was attenuated by the tested NSAIDs, indomethacin, fulfenamic acid, mefenamic acid, aspirin, and acetaminophen, with K i's that ranged from 6.0 × 10 −5 to 2.51 × 10 −3 M. Salicylic acid had no effect on baselin I sc. Cl − channel inhibitors tested was: fulfenamic acid ⪢ indomethacin > mefenamic acid ⪢ aspirin > acetaminophen > salicylic acid. The NSAIDs also significantly inhibited both the transient, Ca 2+-dependent and the sustained, cAMP-dependent increases in I sc elicited by isoproterenol. Thus, the tested NSAIDs appeared to have an effect on the electrical properties of the cells. A similar effect of NSAIDs on ion transport across the human airway epithelium may help to reduce airway fluid secretion.

Secondary production by siphon regeneration in a tidal flat population of Macoma balthica

The share of cropped siphon tips in the secondary production of the bivalve Macoma balthica (L.) was estimated in a tidal flat area in the westernmost part of the Dutch Wadden Sea. Basic data were year-round measurements of siphon- and body weights in the field and regeneration rates of siphons in the laboratory. The completeness of the inhalant siphon was expressed as the Siphon Condition: SC = siphon weight divided by the square root of the body weight. In field populations the SC values showed a seasonal pattern, viz. low in summer and high in winter. Regeneration of the siphons was rapid under simulated tidal flat conditions, hardly depended on temperature and season and was faster as siphons were lighter. Siphon growth stopped when a SC value of 0.36 was reached. In tidal flat animals, SC values between 0.03 and 0.36 were observed. The estimated amounts of Macoma siphon tissue lost during 1975 at 4 tidal flat transects varied from 0.31 to 1.66 g ADW·m −2·a −1, i.e. nearly half of the annual mean biomass of the soft parts and hardly different from elimination in the form of whole Macoma. Only about 13% of the siphon tip biomass lost was consumed by flatfish. Other epibenthic predators, like gobies, shrimps and shore crabs will have cropped the rest. Individual Macoma will have lost an average of several siphon tips per day. The loss and subsequent regeneration of siphon tips must be an important factor in the ecology of Macoma, affecting feeding behaviour, burying depth and body weight. In tidal flat ecosystems, regeneration of siphon tips and other cropped body parts will significantly contribute to benthic secondary production.

A multi-test piece approach to the fracture characterisation of linepipe steels

The energy for fully shear fracture in CT tests has been measured for controlled rolled, normalised and also quenched and tempered materials. Equations have been derived relating the energy per unit area for fracture to the ligament length, (W−a), of the test piece, both at ambient temperature and also at lower temperatures; these are of the form: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaaca% WGvbaabaGaamOqamaabmaabaGaam4vaiabgkHiTiaadggaaiaawIca% caGLPaaaaaGaeyypa0JaamOuamaaBaaaleaacaWGJbaabeaakiabgU% caRiaadofadaWgaaWcbaGaam4yaaqabaGccaGGOaGaam4vaiabgkHi% TiaadggacaGGPaaaaa!47C3!\[\frac{U}{{B\left( {W - a} \right)}} = R_c + S_c (W - a)\] where B is the thickness and Rc and Sc are constants. The first term is the energy absorbed per unit area of fracture whereas the second term is the energy absorbed per unit volume of plastic deformation remote from the fracture surface. Increasing the strain rate or decreasing the temperature slightly increased the energy for fracture; however, there was an increase in the maximum contraction with increasing strain rate whereas there was a decrease with decreasing temperature. This indicated that high strain rate tests could not be correctly simulated by testing at lower temperatures. Similar equation constants were obtained from the results of SENB tests, but for tension tests there was a significantly higher Rc value although the Sc value was similar. Results of impact tests were also found to fit the same expression, with Rc and Sc values greater than for the slow rate tests. A number of sub-thickness CT test pieces were tested, but only a small, if any, decrease in toughness was observed.