Studies of the friction and wetting behavior of polymer surfaces with controlled surface structures/

Reaction of poly(chlorotrifluoroethylene) (PCTFE) with trimethyl 4-lithioorthobutyrate and hydrolysis produces a surface containing carboxylic acids (PCTFE-CO\sb2H). The advancing water contact angle (\Theta\sb{\rm A}) varies from {\sim56}\sp\circ at low pH to {\sim30}\sp\circ at high pH. The receding water contact angle (\Theta\sb{\rm R}) is 0\sp\circ at all pH values. PCTFE-CO2H could be reduced to the alcohol, creating a less hydrophilic surface \rm (\Theta\sb{A}/\Theta\sb{R} = 62\sp\circ/22\sp\circ) or converted to the n-octyl ester, rendering a hydrophobic surface \rm (\Theta\sb{A}/\Theta\sb{R} = 99\sp\circ/47\sp\circ). PCTFE reacts with acetaldehyde 3-lithiopropyl ethyl acetal at $-$78-$-$15\sp\circC to introduce the acetal into the outer $\sim$30-1000 A of the surface (PCTFE-PEAA). Hydrolysis produces a hydrophilic \rm (\Theta\sb{A}/\Theta\sb{R} = 67\sp\circ/17\sp\circ), alcohol-functionalized surface (PCTFE-OH) which was derivatized to prepare a series of linear hydrocarbon and fluorocarbon ester surfaces. Reactions with multifunctional reagents produced crosslinked surfaces. Gravimetric, XPS, ATR-IR and contact angles results are consistent with the proposed surface structures and high reaction yields. Water contact angles on the hydrocarbon ester surfaces range from 82\sp\circ/46\sp\circ (acetate) to 108\sp\circ/90\sp\circ (stearate), while those on the fluorocarbon esters range from 92\sp\circ/51\sp\circ (trifluoroacetate) to 120\sp\circ/69\sp\circ (perfluorodecanoate). Hexadecane contact angles and XPS results show that the stearate and perfluorodecanoate esters form ordered surfaces. Friction properties of these modified surfaces were also investigated. The effects of varying the ester chain length, crosslinking the surface and varying the modification depth were studied. Contrary to expectations, the perfluorinated surfaces exhibited greater friction than their hydrocarbon analogs. The results show that chemical interactions at the sliding interface have little influence on friction and that it is the deformation behavior of the polymer near the interface that dictates the magnitude of the energy losses. Mixed surfaces were prepared to study the effect of surface composition on wetting. Randomly mixed hydroxyl/hydrocarbon ester surfaces were prepared by kinetic control of the esterification of PCTFE-OH, while compositionally similar, patchy surfaces were prepared by kinetic control of the hydrolysis of PCTFE-Esters. Esterification of the alcohol groups in these two sets of mixed surfaces was utilized to prepare the corresponding hydrocarbon ester/fluorocarbon ester mixed surfaces. As expected, greater contact angle hysteresis was observed on the patchy surfaces

Effects of dietary l-arginine supplementation to gilts during early gestation on foetal survival, growth and myofiber formation

The effects of l-arginine on porcine foetal development and myogenesis were determined. Twenty Swiss Large White gilts were randomly allocated to either the control (C) or l-arginine treatment (A). In addition to the standard gestation diet, A-sows received 26 g l-arginine daily from days 14 to 28 of gestation. At day 75 of pregnancy, sows were sacrificed and the number and weight of foetuses were recorded. From each litter, the lightest, heaviest and the ones with an average foetal weight (FtW) were selected. Primary (P), secondary (S) and total myofiber number as well as S/P ratio were determined in the semitendinosus (ST) and rhomboideus (RH) muscles. In A-sows, the number of viable foetuses (13.0 v. 9.3) and total FtW (4925 v. 3729 g) was greater (P ⩽ 0.04) than in C-sows. Compared to C-sow foetuses, the ST of A-sow foetuses had 7% more (17 699 v. 16 477; P = 0.04) P myofibers and the S/P ratio in both muscles was lower (ST = 20.3 v. 21.5; RH = 24.1 v. 27.1; P ⩽ 0.07). Regardless of the maternal diet, the S myofiber number and the S/P ratio in both muscles were greater (P ⩽ 0.01) in foetuses with a high FtW compared to low FtW. These data suggest that l-arginine supplemented to gilts during early gestation enhanced foetal survival and in the ST positively affected the primary phase of myofiber formatio

Effects of two supplementation levels of linseed combined with CLA or tallow on meat quality traits and fatty acid profile of adipose and different muscle tissues in slaughter pigs

Dietary linseed supply efficiently elevates the linolenic acid concentration of pork. The main problem of increasing the n-3 fatty acid tissue levels arises from a higher susceptibility to lipid oxidation. Increasing the saturation level of tissue lipids by the dietary inclusion of conjugated linoleic acids (CLA) or tallow might prevent oxidation. Thus, the aim of the study was to evaluate the impact of dietary CLA or tallow supplementation combined with extruded linseed on the growth performance, carcass characteristics and fatty acid profile of muscles (longissimus, semimembranosus, biceps femoris) and subcutaneous fat (SF). The enzyme activity of the de novo lipogenesis and stearoyl-CoA desaturase in the SF was also assessed. From 18 to 104 kg BW, 32 Swiss Large White barrows were fed a diet supplemented with either: (1) 2% linseed (L2); (2) 3% linseed (L3); (3) 2% linseed + 1% CLA (L2-C) or (4) 2% linseed + 1% tallow (L2-T). The linolenic and eicosatrienoic acid concentrations were higher (P 0.05) affected by the dietary fats, whereas Δ9-desaturase activity was depressed (P < 0.05) by CLA inclusion (L2-C). Only when oxidation was challenged by cooking and subsequent storage for 4 days at 4°C values of thiobarbituric acid-reactive substances were lower (P < 0.05) in longissimus muscle chops of L2-C compared with L2, L3 and L2-T barrows. The present findings revealed that CLA, but not tallow, combined with extruded linseed enhanced the oxidative stability of pork probably by lowering the degree of unsaturation of the lipids without affecting the improved ∑n-6/∑n-3 rati

Effect of average litter weight in pigs on growth performance, carcass characteristics and meat quality of the offspring as depending on birth weight

Offspring born from normal litter size (10 to 15 piglets) but classified as having lower than average birth weight (average of the sow herd used: 1.46 ± 0.2 kg; mean ± s.d.) carry at birth negative phenotypic traits normally associated with intrauterine growth restriction, such as brain-sparing and impaired myofiber hyperplasia. The objective of the study was to assess long-term effects of intrauterine crowding by comparing postnatal performance, carcass characteristics and pork quality of offspring born from litters with higher (>1.7 kg) or lower ( 0.05). These pigs were fattened in group pen and slaughtered at 165 days of age. Pre-weaning performance of the litters and growth performance, carcass and meat quality traits of the selected pigs were assessed. Number of stillborn and pig mortality were greater (P 0.05) slaughter weight at 165 days of age. However, HL-gilts were more feed efficient and had leaner carcasses than HI-, LH- and LI-pigs (birth weight class × gender interaction P < 0.05). Meat quality traits were mostly similar between groups. The marked between-litter birth weight variation observed in normal size litters had therefore no evident negative impact on growth potential and quality of pigs from the lower birth weight grou

Decreasing the level of hemicelluloses in sow’s lactation diet affects the milk composition and post-weaning performance of low birthweight piglets

Hemicelluloses (HC) are polysaccharides constituents of the cell walls of plants. They are fermented in the gut to produce volatile fatty acids (VFA). The present study investigated the effects of decreasing HC level in a sow’s lactation diet on sow performances, offspring development and milk composition. From 110 days (d) of gestation until weaning (26 ± 0.4 d post-farrowing), 40 Swiss Large White sows were assigned to one of the four dietary treatments: (1) T13 (HC: 127 g/kg), (2) T11 (HC: 114 g/kg), (3) T9 (HC: 94 g/kg) and (4) T8 (HC: 80 g/kg). Milk was collected at 3 and 17d of lactation. At birth, piglets were divided into two groups according to their birthweight (BtW): normal (N-BtW; BtW &gt;1.20 kg) or low (L-BtW; BtW ≤1.20 kg). Decreased HC levels in the maternal diet linearly increased (p ≤.05) the body weight of L-BtW piglets at two weeks post-weaning and linearly decreased (p ≤.05) diarrhoea incidence and duration in this category. The concentrations of copper, threonine and VFA, as well as the proportion of butyrate, in milk linearly increased (p ≤.05), whereas lactose content linearly decreased (p ≤.05) with decreased HC in the maternal diet. The present study provides evidence that decreasing HC level in a sow’s lactation diet can positively affect the composition and VFA profile of milk and ultimately favour the growth and health of L-BtW piglets.Highlights The results of this study showed that decreasing the level of hemicelluloses in a sow’s lactation diet modified milk composition and had positive effects on the post-weaning performance of low birthweight piglets. This study highlighted the role of dietary fibres in the maternal diet to alleviate body weight variations at two weeks post-weaning. Nevertheless, before advising pig producers, further research should elucidate the optimal level of hemicelluloses for lactating sows

Intrauterine crowding impairs formation and growth of secondary myofibers in pigs

There are indications that intrauterine crowding may cause intrauterine growth retardation with the possibility of an impaired myofiber hyperplasia. The aim of the study was to confirm this by generating large differences in uterine space using sows that were unilaterally hysterectomized-ovariectomized (HO; crowded) or unilaterally oviduct ligated (OL; non-crowded). In the study, seven HO and seven OL Swiss Large White third parity sows were used. At farrowing, litter size and litter birth weight were determined. Subsequently, within each litter two male and two female progenies each with the respectively lowest (L) and highest (H) birth weight were sacrificed. Internal organs and brain were weighed, and longissimus (LM) and semitendinosus muscle (SM) samples were collected. Histological analyses were performed in both muscles using mATPase staining after preincubation at pH 4.3 and 10.2. Myosin heavy chain (MyHC) polymorphism was determined in the LM by means of SDS-PAGE. The number of piglets born alive was similar in both sow groups, but litter size expressed per uterine horn was lower (P < 0.05) in OL than HO sows. Consequently, OL progeny were markedly heavier (P < 0.01). Regardless of gender, the organs, the brain and the SM were heavier (P < 0.001) in OL and H compared with HO and L offspring, respectively. Compared with HO pigs, the SM of OL offspring tended (P < 0.1) to have more myofibers, which were of larger (P < 0.05) size. However, myofiber density appeared to be lower (P < 0.1) in the SM of OL than HO pigs. The impact of birth weight on myofiber characteristics was limited to the lower (P < 0.05) myofiber density in the SM and the larger (P < 0.01) myofiber size in the light portion of the SM of H than L offspring, whereas myofiber hyperplasia did not differ between birth weight categories. The SM, but not the LM, of male offspring had a greater (P < 0.05) myofiber density. This did not affect total SM myofiber number. The relative abundance of fetal and type I MyHC in the LM was lower (P < 0.05) and that of type II MyHC was greater (P < 0.001) in OL than HO pigs. The current data suggest that regardless of birth weight and gender, in the LM and SM of individuals born from a crowded environment, not only hyperplasia but also hypertrophy of myofibers is impaired and their maturity seems delaye

May 2020 School of Graduate Studies Newsletter

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