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Surface sediments (n=85) from a 160-km river-estuarine transect of the Clyde, UK, were analysed for total mercury (Hg), saturated hydrocarbons and unresolved complex mixtures (UCMs) of hydrocarbons. Results show that sediment-Hg concentration ranges from 0.01 to 1.38mgkg–1 (mean 0.20mgkg–1) and a spatial trend in Hg-content low–high–low–high, from freshwater source, to Glasgow, to estuary, is evident. In summary, sediment-Hg content is low in the upper Clyde (mean of 0.05Hg mgkg–1), whereas sediments from the Clyde in urbanised Glasgow have higher Hg concentrations (0.04 to 1.26mgkg–1; mean 0.45mgkg–1), and the inner estuary sediments contain less Hg (mean 0.06mgkg–1). The highest mean sediment Hg (0.65mgkg–1) found in the outer estuary is attributed to historical anthropogenic activities. A significant positive Spearman correlation between Hg and total organic carbon is observed throughout the river estuary (0.86; P<0.001). Comparison with Marine Scotland guidelines suggests that no sites exceed the 1.5mgkg–1 criterion (Action Level 2); 22 fall between 0.25 and 1.5mgkg–1 dry wt. (Action Level 1) and 63 are of no immediate concern (<0.25mgkg–1 dry wt.). Saturated (n-alkane) hydrocarbons in the upper Clyde are of natural terrestrial origin. By contrast, the urbanised Glasgow reaches and outer estuary are characterised by pronounced and potentially toxic UCM concentrations in sediments (380–914mg/kg and 103–247mgkg–1, respectively), suggesting anthropogenic inputs such as biodegraded crude oil, sewage discharge and/or urban run-off.
An experiment was carried out to examine the effects of offering beef cattle five silage diets. These were perennial ryegrass silage (PRGS) as the sole forage, tall fescue/perennial ryegrass silage (FGS) as the sole forage, PRGS in a 50:50 ratio on a dry matter (DM) basis with lupin/triticale silage (LTS), lupin/wheat silage (LWS) and pea/oat silage (POS). Each of the five silage diets was supplemented with 4 and 7 kg of concentrates/head/day in a five silages × two concentrate intakes factorial design. A total of 90 cattle were used in the 121-day experiment. The grass silages were of medium digestibility and were well preserved. The legume/cereal silages had high ammonia N, high acetic acid, low lactic acid, low butyric acid and low digestible organic matter concentrations (542, 562 and 502 g/kg DM for LTS, LWS and POS, respectively). Silage treatment did not significantly affect liveweight gain, carcass gain, carcass characteristics, the instrumental assessment of meat quality or fatty acid composition of the M. longissimus dorsi muscle. In view of the low yields of the legume/cereal crops, it is concluded that the inclusion of spring-sown legume/cereal silages in the diets of beef cattle is unlikely to be advantageous.
An experiment was carried out to examine the effects of offering beef steers grass silage (GS) as the sole forage, lupins/triticale silage (LTS) as the sole forage, a mixture of LTS and GS at a ratio of 70:30 on a dry matter (DM) basis, vetch/barley silage (VBS) as the sole forage, a mixture of VBS and GS at a ratio of 70:30 on a DM basis, giving a total of five silage diets. Each of the five silage diets was supplemented with 2 and 5 kg of concentrates/head/day in a 5 × 2 factorial design to evaluate the five silages at two levels of concentrate intake and to examine possible interactions between silage type and concentrate intake. A total of 80 beef steers were used in the 122-day experiment. The GS was well preserved while the whole crop cereal/legume silages had high ammonia-nitrogen (N) concentrations, low lactic acid concentrations and low butyric acid concentrations For GS, LTS, LTS/GS, VBS and VBS/GS, respectively, silage DM intakes were 6.5, 7.0, 7.2, 6.1 and 6.6 (s.e.d. 0.55) kg/day and live weight gains were 0.94, 0.72, 0.63, 0.65 and 0.73 (s.e.d. 0.076) kg/day. Silage type did not affect carcass fatness, the colour or tenderness of meat or the fatty acid composition of the intramuscular fat in the longissimus dorsi muscle.
Tenderness can be considered as a function of three components: connective tissue content/composition, sarcomere length and proteolysis of the myofibrillar proteins (ageing) (Koohmaraie, 2002). Improvement of sarcomere length and proteolysis can be achieved through optimal processing (e.g. hanging and aging; Thompson, 2006). The main technique that improves the sarcomere length is tenderstretch hanging. This technique increases the tension of the hindlimb and loin muscles avoiding the contraction of the fibers at rigor (Bouton, 1973). In this experiment the aim was, under commercial conditions, to compare two methods of tenderstretch hanging and to examine the potential to improve the tenderness of lamb muscles.
A considerable proportion of beef produced in the UK is a byproduct of the dairy industry. Young animals from this source are generally regarded as low in quality and meat from animals of this type is usually destined for the commodity minced beef market. The objective of the present study was to evaluate the effect of slaughter weight on sensory characteristics of meat from Holstein-Friesian bulls and steers offered a cereal-based ration.
Meat from Holstein-Friesian bulls, which are bred for dairy traits, is generally regarded as low quality and is usually destined for the commodity (mince) market. However, given their ready availability as a by-product from the dairy herd, it is important to determine if meat from these animals would be suited to higher-priced markets. Furthermore, meat from bulls is generally considered to be lower quality than that from steers, though there is a paucity of data comparing meat from both sources. Hence, the objective of this study was to evaluate the effect of slaughter weight on meat quality characteristics of Holstein-Friesian bulls and steers offered a cereal-based ration.
This study was based on research to identify particular pig breeds, which produce high quality eating pork. Duroc in particular is thought to improve meat quality of progeny when crossed with Large White/Landrace (LW/Lr) hybrid dams by altering the intra-muscular fat (IMF) content of the lean, which is positively related to eating quality (McGloughlin et al., 1988). The extraction of IMF is slow and laborious with harmful solvents involved. Eichinger and Beck (1991) have successfully used NIRS to measure IMF ranging from 1-11% in 39 beef carcases. Ground beef and pork samples have also been predicted for fat, water and protein by NIRS, with prediction errors of 0.82-1.49%, 0.94-1.33% and 0.35-0.70% respectively (Togersen et al.,1999). Instrumental measurements of pork are accepted as indicators of tenderness. Sensory variables such as juiciness, tenderness and flavour are important characteristics for the consumer. Therefore the objective of this study was to explore the potential of NIRS to estimate the chemical, physical and sensory parameters of homogenized fresh pork eye muscle.
Under- and over-nutrition during gestation may influence fetal hypothalamic development resulting in individuals predisposed to adverse health effects. This study examined fetuses from obese and control ewes to determine whether dam obesity alters hypothalamic expression of fetal appetite regulatory genes. A second objective was to contrast the expression of appetite regulatory genes in ewes that become the most obese to those that remained in moderate body condition on the same energy-rich diet. Multiparous, western white-faced ewes were weighed and individually fed 100% (control) or 150% (obese) of National Research Council requirements from day 60 before mating until day 75 of gestation. At day 75 of gestation, fetuses were collected and weighed. Hypothalamic tissue from fetal lambs and dams was collected and frozen for mRNA extraction. Dam obesity (P ⩾ 0.16), fetal sex (P ⩾ 0.44) or their interaction (P ⩾ 0.42) did not affect the relative expression of fetal hypothalamic regulators of appetite, including neuropeptide Y, agouti-related protein, pro-opiomelanocortin, cocaine- and amphetamine-regulated transcript and receptors for leptin. Maternal obesity at day 75 of gestation in ewes did not affect developmental mechanisms responsible for the expression of fetal appetite regulatory genes and would not be expected to predispose offspring to adult-onset obesity through disrupted appetite regulation at this developmental time point. In the ewe, appetite regulatory genes did not differ (P > 0.20) with ewe adiposity; however, expression of estrogen receptor α, but not β (P = 0.37), in the medial basal hypothalamus was greater (P = 0.04) in obese than in control ewes.
Photochemical methods were developed to obtain a variation of the refractive index in aromatic polymer surfaces and a change in the photoluminescence characteristics of phenylene-vinylene-based polymers. Films of aromatic polymers, among them polystyrene (PS), poly(2-vinylnaphthalene) (PVN) and derivatives of poly(-phenylene-vinylene) (PPV) were UV irradiated in the presence of gaseous hydrazine (N2H4). The photoreaction led to a strongreduction of the refractive index of the polymers due to a hydrogenation of the aromatic units. In the case of PPV, we observed reductive photobleaching. This new technique was employed to produce photogenerated patterns in PPV. The results are compared to oxidative bleaching.
The interaction between thin films of ethylenedioxythiophene (EDOT) and polycrystalline copper and gold surfaces has been studied using photoelectron spectroscopy. Thick films of EDOT (∼100 Å) have been prepared by vapor deposition onto clean gold surfaces, which were cooled down to a temperature of 170 K during the deposition process. Monolayers were prepared by slowly heating the thick films up to 300 K. At 300 K most of the material has evaporated from the surface and about one monolayer remains chemisorbed on the gold surface. This shows that there is an interaction between EDOT and Au. This chemisorption causes a shift of around -0.5 eV of the binding energies for the core level electrons, presumably because of screening of the core-hole by the metal. An experimental and theoretical analysis of the valence level electrons suggests that two molecular orbitals, localized at the thiophene part of the molecule, are involved in the interaction with the metal atoms of the surface. The most likely orientation of the EDOT molecules is parallel to the Au surface. Upon adsorption the work function is changed from 5.2 eV for the clean gold surface to 4.0 eV for the EDOT monolayer. In the case of EDOT adsorbed on clean copper surfaces, no interaction was observed.
Ion implantation has become a versatile and powerful technique for
synthesizing nanometer-scale clusters and crystals embedded in the
near-surface region of a variety of hosts. The resulting nanocomposite
materials often show unique optical, magnetic, and electronic properties.
Here we review some of the principal features of this nanophase materials
synthesis technique and discuss the outstanding experimental difficulties
that currently hamper the development of devices based on the many unique
properties of these nanocomposite materials. Possible solutions to these
problems and future research directions are discussed.
A main limitation of biomedical devices is the inability to start, stop, and control cell growth making it crucial to develop biomaterial surfaces that induce a desired cellular response. Micropatterns of ridges and pillars were created in a siloxane elastomer (Dow Corning) by casting against epoxy replicates of a micromachined silicon wafer. Silicone oils were incorporated to determine the change in modulus and surface energy caused by these additives. SEM and white light interference profilometry verified that the micropatterning process produced high fidelity, low defect micropatterns. Mechanical analysis indicated that varying the viscosity, weight percent and functionality of the added silicone oil could change the elastic modulus by over an order of magnitude (0.1-2.3 MPa). As a self-wetting resin, silicone oils migrate to the surface, hence changing the surface properties from the bulk. Both topographical and chemical features define the surface energy, which in combination with elastic modulus, dictate biological activity. The results imply that the morphology, mechanical properties and surface energy of the siloxane elastomer can be modified to elicit a specific cell response as a function of engineered topographical and chemical functionalization.
H+-implantation is the basis for an ion-cut process, which
combines hydrophilic wafer bonding, to produce heterostructures over a wide
range of materials. This process has been successfully applied in Si to
produce a commercial silicon-on-insulator material. The efficacy of
implantation to produce thin-film separation was studied by investigation of
H+-induced exfoliation in Si and SiC. Experiments were done to
isolate the effects of the hydrogen chemistry from that of implant damage.
Damage is manipulated independently of H+ dosage by a variety of
techniques ranging from elevated temperature irradiation to a two-step
implantation scheme in Si, and the use of channeled-ion implantation in SiC.
The results will demonstrate that such schemes can significantly reduce the
critical dose for exfoliation.
The effects of laser energy fluence on the growth of pulsed laser deposited ZnO thin films on c-plane sapphire substrates were systematically investigated by using x-ray diffraction, Rutherford backscattering spectrometry with ion channeling, and scanning electron microscopy techniques. Optical and electrical properties of the ZnO epilayers were characterized by using ultraviolet-visible transmission spectroscopy and Van der Pauw measurements, respectively. It was found that the laser fluence has strong effects on the crystalline, optical and electrical qualities of the ZnO films. At low laser fluence, ZnO film grows via 3D-island mode with low deposition rate, loss of Zn near the surface and particulates on top of the film. High laser fluence may also cause simultaneous multi-layer growth and the degradation of crystalline, electrical, and optical quality of the ZnO films. The optimal laser fluence window was found between 1.2J/cm2 and 2.5 J/cm2 for obtaining high quality ZnO films for optoelectronic applications. The dependence of laser fluence on the ZnO growth mode, surface morphology and electrical and optical properties is discussed.
We describe detailed studies of ionically self-assembled monolayer (ISAM) photovoltaic (PV) devices incorporating various electron acceptor materials, such as fullerenes and phthalocyanines. Excitons are generated when the conducting polymer is irradiated, and the electron acceptors aid in dissociating the electron/hole pairs before they can radiatively recombine, thus improving the efficiency of the PV process. The ISAM technique allows the deposition of conducting polymer and electron acceptor materials in alternating layers of nanometer-scale thickness. This ensures that every photoexcited electron-hole pair is in proximity to an electron acceptor, thus minimizing electron-hole recombination and increasing the photocurrent. The individual thickness of each monolayer and the interpenetration of adjacent layers can be precisely controlled through the parameters of the electrolyte solutions. Using the ISAM technique, we have demonstrated that it is possible to create ultrathin films (100 nm) of PV material that have enhanced efficiencies.
Measurements and theory are presented examining the relationship between mobility and doping in regioregular poly(3-hexylthiophene) (P3HT). Mobility is found to increase super-linearly with doping and is comparable to models reported for other conjugated polymers. Schottky measurements have been used to calculate the doping density and bulk mobility of regioregular P3HT. Aluminium Schottky contacts showed signs of native oxide disrupting current flow through the device. This effect was observed to degrade further with the introduction of dopant into the polymer. Titanium devices show a general shift of the Schottky characteristic to higher current levels with increased dopant. Field effect mobility of P3HT films was also calculated using thin-film transistor (TFT) structures. The field effect mobility values were observed to be more than two orders of magnitude higher than the bulk mobility value. The addition of dopant also increased gate leakage currents in TFT devices. The increased conductivity in doped polymer can increase off currents in the device; this is avoided by using Schottky contacts as the source and drain. Preliminary results on Schottky contact TFTs are also presented as well as a description of the operation of such a device.
Photochemical methods were developed to obtain a variation of the refractive index in aromatic polymer surfaces and a change in the photoluminescence characteristics of phenylenevinylene-based polymers. Films of aromatic polymers, among them polystyrene (PS), poly(2-vinylnaphthalene) (PVN) and derivatives of poly(p-phenylene-vinylene) (PPV) were UV irradiated in the presence of gaseous hydrazine (N2H4). The photoreaction led to a strong reduction of the refractive index of the polymers due to a hydrogenation of the aromatic units. In the case of PPV, we observed reductive photobleaching. This new technique was employed to produce photogenerated patterns in PPV. The results are compared to oxidative bleaching.