Electrochemistry and electrogenerated chemiluminescence from silicon nanocrystal quantum dots

Reversible electrochemical injection of discrete numbers of electrons into sterically stabilized silicon nanocrystals (NCs) (approximately 2 to 4 nanometers in diameter) was observed by differential pulse voltammetry (DPV) in N,N'-dimethylformamide and acetonitrile. The electrochemical gap between the onset of electron injection and hole injection-related to the highest occupied and lowest unoccupied molecular orbitals-grew with decreasing nanocrystal size, and the DPV peak potentials above the onset for electron injection roughly correspond to expected Coulomb blockade or quantized double-layer charging energies. Electron transfer reactions between positively and negatively charged nanocrystals (or between charged nanocrystals and molecular redox-active coreactants) occurred that led to electron and hole annihilation, producing visible light. The electrogenerated chemiluminescence spectra exhibited a peak maximum at 640 nanometers, a significant red shift from the photoluminescence maximum (420 nanometers) of the same silicon NC solution. These results demonstrate that the chemical stability of silicon NCs could enable their use as redox-active macromolecular species with the combined optical and charging properties of semiconductor quantum dots.     

Sources of petroleum hydrocarbons in urban runoff

In an effort to provide a better understanding of the sources of petroleum hydrocarbons in urban runoff, petroleum products as well as probable source materials were analyzed for hydrocarbons and trace metals and then compared to urban runoff samples from four different land use areas. The petroleum products considered were No. 2 and No. 6 fuel oils, used and virgin crankcase oils, and gasoline. Source materials included street dust, roadside soil, roadside vegetation, and atmospheric fallout; and the land use categories were commercial, residential, interstate highway, and industrial areas. The samples were compared on the basis of hydrocarbon (saturated and aromatic) and trace metal (Cd, Pb, Mn, Cu, Fe, Zn) loadings and distributions. Results indicated that the hydrocarbon content in runoff at all four land use sites originated primarily from used crankcase oil, with a small amount of No. 2 fuel oil detected at the industrial site. Only a small portion of the crankcase oil component came from the sources surveyed, and the majority of this oil probably came from: (1) oil drops within the driving lanes on the road surfaces or deposits in parking areas, and/or (2) direct dumping of waste crankcase oil down storm drains.     

Effect of 1-methylcyclopropene on volatile emission and aroma in cv. Anna apples

The rapidly ripening summer apple cultivar Anna was treated with 0.1 micro L(-1) and 1 microL L(-1) 1-methylcyclopropene (MCP) at harvest and kept at 20 degrees C, or stored for 5 weeks at 0 degrees C and then transferred to 20 degrees C. Total volatiles were not reduced by treatment with 0.1 microL L(-1) MCP, but were 70% lower in fruits treated with 1 microL L(-1) MCP than in untreated fruits. Ethylene production was 50% and 95% inhibited by 0.1 microL L(-1) and 1 microL L(-1) MCP, respectively. The volatiles produced by fruit at harvest were predominantly aldehydes and alcohols, with some acetate esters as well as 2-methyl butyl acetate and beta-damascenone. During ripening, the acetate and butyrate esters increased greatly and alcohols and aldehydes decreased. MCP-treated apples retained more alcohols, aldehydes, and beta-damascenone volatiles than did untreated apples. Sensory evaluation found that control and 0.1 microL L(-1) treated apples developed more fruity, ripe, and overall aromas, but the preference was for the 1 microL L(-1) treated apples with a less ripe aroma.     

Effect of Geotrichum candidum protein substitution in pelleted fish feed on the growth of rainbow trout (Salmo gairdneri Rich.) and on utilization of the diet

Three experiments were conducted with rainbow trout to determine if Geotrichum candidum GC single cell protein could replace 100, 75 or 50% of fish meal in a pelleted diet. When the fish meal was completely replaced by GC the fish growth was retarded after 3 weeks of the experiment. With the larger fish (individual weight 47–54 g) in the short trial there were significant differences between fish fed the control diet (fish meal) and those fed the 75% substitution of GC diet. The most remarkable differences in fish growth appeared in a 42-day trial with small fish (5 g individual weight) when fish groups fed diets with 0.50 and 75% replacement gave significantly different results (P < 0.05), being 93,9, 46.6 and 34.2% gain, with feed coefficients of 1.49, 2.77 and 3.67, respectively. With large fish fed diets with 0,50 and 75% GC replacement, apparent digestibility of protein was 64.7, 68.2 and 37.5%, but fat digestibility was 79.5, 91.1 and 81.0%, respectively. No significant differences in amounts of free plasma amino acid (PAA) were found between rainbow trout fed diets with 0 or 50% substitution, but there was a marked decrease in PAA in the group fed the diet with 75% GC substitution. Analysis of chosen heavy metals was made on diets, fish and faeces, and Cu in particular was found not to be accumulated in the fish body.     

Effects of slow release gonadotropin releasing hormone analog on milt characteristics and plasma levels of gonadal steroids in greenback flounder, Rhombosolea tapirina

Spermiated male greenback flounder (Rhombosolea tapirina) were implanted with gonadotropin releasing hormone analog (GnRHa) pellets at different dosages to examine their effects on milt characteristics and plasma levels of testosterone (T), 11-ketotestosterone (11KT) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP). Milt and blood samples were collected for up to 28 or 42 days post-implantation (p.i.) in two separate experiments using fish that were slightly or moderately spermiated, respectively. In both experiments, fish treated with GnRHa pellets showed a consistent and significant increase in milt volume relative to controls, and the increase of milt volume was more rapid than the increase in numbers of spermatozoa. Spermatocrit (Sct) was significantly lower in GnRHa-treated fish than in controls. Plasma levels of T and 11KT were elevated at 7 and 14 days p.i. in slightly spermiated fish treated with GnRHa and elevated plasma T and 11KT levels were accompanied by increased milt volume early in the spermiation period. In contrast, there was no significant difference in plasma T levels between GnRHa-treated and control fish in fish that were moderately spermiated at the time of implant. Treatment with GnRHa tended to result in lower plasma levels of 11KT and higher levels of 17,20βP relative to controls, and there was a positive relationship between the elevation of plasma 17,20βP and the increase in milt volume in response to implantation of GnRHa pellet. Slow release GnRHa administration had no effect on sperm activity or pH and osmolality of seminal plasma in either experiment.     

Performance of finishing beef steers in response to anabolic implant and zilpaterol hydrochloride supplementation

Our objectives were to evaluate the dose/payout pattern of trenbolone acetate (TBA) and estradiol-17β (E(2)) implants and feeding of zilpaterol hydrochloride (ZH) on performance and carcass characteristics of finishing beef steers. A randomized complete block design was used with a 3 × 2 factorial arrangement of treatments. British × Continental steers (n = 168; initial BW = 362 kg) were blocked by BW and allotted randomly to 42 pens (7 pens/treatment; 6 pens/block; 4 steers/pen). The main effects of treatment were implant [no implant (NI); Revalor-S (REV-S; 120 mg of TBA + 24 mg of E(2)); and Revalor-XS (REV-X; 200 mg of TBA + 40 mg of E(2))] and ZH (0 or 8.3 mg/kg of DM for 20 d with a 3-d withdrawal before slaughter). Blocks were split into 2 groups, and block groups were fed for either 153 or 174 d. No implant × ZH interactions were noted for cumulative performance data. Overall, shrunk final BW (567, 606, and 624 kg for NI, REV-S, and REV-X, respectively), ADG (1.25, 1.51, and 1.60 kg), and G:F (0.14, 0.16, and 0.17) increased (P < 0.05) as TBA and E(2) dose increased. Implanting increased (P < 0.05) DMI, but DMI did not differ (P > 0.10) between REV-S and REV-X (8.8 for NI vs. 9.4 kg/d for the 2 implants). From d 1 to 112 of the feeding period, implanting increased (P < 0.05) ADG and G:F, but REV-S and REV-X did not differ (P > 0.10). From d 112 to end, ADG increased by 19% (P < 0.05) and G:F was 18% greater (P < 0.05) for REV-X vs. REV-S. Carcass-adjusted final BW (29-kg difference), ADG (0.2-kg/d difference), and G:F (0.02 difference) were increased (P < 0.05) by ZH, but daily DMI was not affected by feeding ZH. Hot carcass weight was increased (P < 0.05) by ZH (19-kg difference) and implant, with REV-X resulting in the greatest response (HCW of 376 for NI vs. 404 and 419 kg for REV-S and REV-X, respectively; P < 0.05). An implant × ZH interaction (P = 0.05) occurred for dressing percent (DP). Without ZH, implanting increased DP, but DP did not differ (P > 0.10) between REV-X and REV-S. With ZH, REV-X increased (1.7%; P < 0.05) DP vs. NI and REV-S. Marbling score, 12th-rib fat, and KPH were not affected (P > 0.10) by implant or ZH. Overall, treatment increased steer performance and HCW in an additive fashion, suggesting different mechanisms of action for ZH and steroidal implants. In addition, a greater dose of TBA + E(2) and extended payout improved steer performance and HCW.     

Association between skin surface pH, temperature and Staphylococcus pseudintermedius in dogs with immunomodulatory-responsive lymphocytic-plasmacytic pododermatitis

Secondary bacterial infection is a frequent complication in lesional skin of dogs with immunomodulatory‐responsive lymphocytic–plasmacytic pododermatitis (ImR‐LPP). However, the influence of skin pH and temperature in determining the composition of the cutaneous microflora at lesional sites has not been investigated. The association between ImR‐LPP and pedal skin temperature, pH and Staphylococcus pseudintermedius isolates was thus evaluated. Temperature and pH were measured in 20 dogs with ImR‐LPP and in 30 clinically healthy control dogs, and S. pseudintermedius was cultured from interdigital and palmoplantar swabs in both groups and scored semi‐quantitatively for bacterial growth. In the ImR‐LPP group, mean skin pH was slightly, but significantly, higher at both interdigital and palmoplantar sites. Staphylococcus pseudintermedius was isolated more frequently, and scores for bacterial growth were also significantly higher. However, mean skin temperatures were not significantly different from those in the control group. The isolation of S. pseudintermedius was significantly associated with ImR‐LPP, with the single exception of isolates on Columbia blood agar from the palmoplantar region. However, pH and temperature were not significantly associated with the disease, and were not associated with the isolation of S. pseudintermedius at most sites sampled. Staphylococcus pseudintermedius was not isolated from all feet sampled in dogs with ImR‐LPP. Taken together, these data would suggest that S. pseudintermedius infection is most likely to be a secondary phenomenon in dogs with ImR‐LPP, and that changes in skin pH and temperature are not significant risk factors for this disease.