Rumen metabolism, omasal flow of nutrients, and microbial dynamics in lactating dairy cows fed fresh perennial ryegrass (Lolium perenne L.) not supplemented or supplemented with rolled barley grain

peer-reviewedThe objective of this study was to evaluate the effect of rolled barley grain (RB) supplementation on rumen metabolism, omasal flow of nutrients, and microbial dynamics in lactating dairy cows fed fresh perennial ryegrass (Lolium perenne L.; PRG)-based diets. Ten ruminally cannulated Holstein cows averaging (mean ± standard deviation) 49 ± 23 d in milk and 513 ± 36 kg of body weight were assigned to 1 of 2 treatments in a switchback design. The treatment diets were PRG only (G) or PRG plus 3.5 kg of dry matter RB (G+RB). The study consisted of three 29-d periods where each period consisted of 21 d of diet adaptation and 8 d of data and sample collection. A double marker system was used to quantify nutrient flow entering the omasal canal along with labeled 15N-ammonium sulfate to measure bacterial, protozoal, and nonmicrobial N flow. Rumen evacuation techniques were used to determine nutrient and microbial pool size, allowing the calculation of fractional rates of digestion and microbial growth. There was no difference in daily milk yield or energy-corrected milk yield between treatments. Milk fat concentration and milk urea N decreased, whereas milk protein concentration increased in cows fed the G+RB diet. During the omasal sampling phase, dry matter intake was higher in cows fed the G+RB diet. Ruminal and total-tract neutral detergent fiber digestibility was lower in G+RB cows; however, no difference was observed in reticulorumen pH. The rumen pool size of fermentable carbohydrate was increased in cows fed the G+RB diet; however, the fractional rate of digestion was decreased. Flow of nonammonia N and bacterial N at the omasal canal increased in cows fed the G+RB diet compared with the G diet. Protozoa N flow was not different between diets; however, protozoa appeared to supply a much larger amount of microbial N and exhibited shorter generation time than previously considered. Feed N ruminal digestibility, corrected for microbial contribution, was similar for both treatments (88.4 and 89.0% for G and G+RB, respectively). In conclusion, RB supplementation did not benefit overall animal performance; however, it reduced ruminal neutral detergent fiber digestibility and increased bacterial N flow. The results demonstrate the large dependence of cows consuming PRG-based diets on microbial N as the main source of nonammonia N supply. Additional quantitative research is required to further describe the supply of nutrients and microbial dynamics in cows consuming PRG-based diets in an effort to determine most limiting nutrients

Hypoxic Pulmonary Vasoconstriction in Humans:Tale or Myth

Hypoxic Pulmonary vasoconstriction (HPV) describes the physiological adaptive process of lungs to preserves systemic oxygenation. It has clinical implications in the development of pulmonary hypertension which impacts on outcomes of patients undergoing cardiothoracic surgery. This review examines both acute and chronic hypoxic vasoconstriction focusing on the distinct clinical implications and highlights the role of calcium and mitochondria in acute versus the role of reactive oxygen species and Rho GTPases in chronic HPV. Furthermore it identifies gaps of knowledge and need for further research in humans to clearly define this phenomenon and the underlying mechanism

ELECTRICALLY CONDUCTIVE POLYMER-POLYMER COMPOSITES

Des composites conducteurs ont été préparés par polymérisation de l'acétylène dans des films de polyéthylène suivie par un dopage à l'iode. L'obtention de conductivités élevées (5-10 S/cm) à faible concentration en (CH)x (∼3% poids) est expliquée à l'aide d'un modèle simple de percolation.Conductive composites have been prepared by polymerization of acelene in polyethylene films followed by iodine doping. The attainment of high conductivity (5-10 S/cm) at low (CH)x concentrations (∼3 wt%) is explained with a simple percolation model

Defects and morphological concerns in electroluminescent polymers

The degradation of luminescence in phenylenevinylene polymers is due to exciton diffusion to quenching defects. The microscopic structure of these defects is identified by in-situ vibrational spectroscopy. The authors present evidence that the defect quenching is due to charge transfer by studies on model phenylenevinylene oligomer. In the absence of defect quenchers, the authors have achieved nearly exponential photoluminescence decay with observed lifetimes > 1 ns and a fourfold increase in electroluminescence. They have also utilized picosecond laser spectroscopy to study the formation yield of emissive excitons in the polymer PPVs with different morphology. They have found that increasing polymer chain separation would greatly increases the luminescent efficiency due to avoiding the interchain excitons (exciplexes). Clarification of the nature of photophysics of conjugated polymers suggests avenues for improvement in fabrication of emissive polymers and electroluminescent polymers devices

SYNTHESIS OF GRAFT AND BLOCK COPOLYMERS CONTAINING (CH)x SEGMENTS

Deux approches ont été étudiées pour étendre l'intérêt des dérivés polyacétyléniques, respectivement (1) l'usage du polyacétylène dopé comme initiateur macromoléculaire pour la synthèse de copolymères greffés, et (2) les réactions de transformation comme moyen de synthèse de copolymères en bloc.Two approaches have been investigated to expand the scope of polyacetylene derivatives, namely (1) the use of doped (CH)x as a macromolecular initiator for the synthesis of graft copolymers, and (2) transformation reactions as a route to block copolymer syntheses

MAGNETIC PROPERTIES OF POLYACETYLENE COMPOSITES

Des composites du polyéthylène basse densité, LDPE, et du trans-polyacétylène, t-(CH)x, préparés par polymérisation de l'acétylène dans des films de LDPE imprégnés de catalyseur Ziegler-Natta, ont été étudiés par double résonance (ENDOR) et échos de spins électroniques (ESE) et les résultats ont été comparés avec ceux obtenus dans les mêmes conditions sur des films de trans-polyacétylène. Les mesures par ENDOR indiquent que la fonction d'onde, une orbitale π pure fortement délocalisée, est essentiellement la même dans les composites que dans le polyacétylène pur mais qu'à une température donnée le coefficient de diffusion du spin électronique est significativement réduit. Les temps de mémoire de phase TM par ESE, mesurés à l'aide d'une séquence de pulses 90°-180° ont montré la même dépendance en température ; toutefois, les temps TM (donc le temps de corrélation de la diffusion de spin électronique) des composites sont substantiellement plus longs à chaque température. Ces résultats impliquent que le coefficient de diffusion de spin est réduit et l'énergie d'activation augmentée dans les composites comparé au polyacétylène pur. Les temps TM des composites apparaissent moins sensibles que ceux du polyacétylène pur à une exposition prolongée à l'oxygène ; toutefois, une exposition prolongée réduit le temps de mémoire de phase et l'énergie d'activation "effective" du ou des processus dynamique(s) qui déterminent la relaxation de phase par modulation des interactions magnétiques.Composites of low density polyethylene, LDPE, and trans-Polyacetylene, t-(CH)x, prepared by polymerization of acetylene in LDPE films impregnated with a Ziegler-Natta catalyst, have been studied by Electron Nuclear Double Resonance (ENDOR) and Electron Spin Echo (ESE) spectroscopies and the results compared with analogous studies conducted on trans-polyacetylene films. ENDOR measurements indicate that the wavefunction, a highly delocalized pure π-orbital, is essentially the same in composites as in pure polyacetylenes but at a given temperature the electron spin diffusion coefficient is substantially reduced. ESE phase memory times, TM, measured by a 90°-180° pulse technique exhibited the same general function dependence on temperature ; however, TM times (hence electron spin diffusion correlation times) for the composites were substantially longer at each temperature. These results imply a reduced spin diffusion coefficient and increased activation energy in the composites compared to pure polyacetylene. Phase memory times for the composites appear less sensitive to prolonged exposure to oxygen than is the case for pure polyacetylene ; however, prolonged exposure does shorten phase memory times and reduce the "effective" activation energy for the dynamic process or processes which determines phase relaxation by modulation of the magnetic interactions