Use of \u3cem\u3eN\u3c/em\u3e-Alkane Technique to Estimate Sheep Dry Matter Intake

Given the complexity of evaluating intake on grazing, some compounds have been studied to promote qualitative and quantitative estimates of animal physiology. In this sense, the technique using n-alkanes as a marker has been used in several animal species, especially in grazing ruminants (Dove and Mayes 1996). By definition, validation under grazing or browsing conditions is not possible, because actual intakes are unknown (Dove and Mayes 2005). Thus, the aim of the study was to evaluate the methodology of n-alkanes to estimate herbage intake by sheep in metabolic cages

Deslocamento e estimativa de gasto energético de ovinos manejados com diferentes métodos de pastoreio e ofertas de forragem em campo natural

The Trial was conducted at an 8.4ha natural grassland area, subdivided into 12 experimental units of 0.7 each in the Universidade Federal do Rio Grande do Sul, when were tested two grazing methods (continuous and rotational(CS and RS) and two herbage allowances (HA; 12 and 18 kg dry matter/100 kg live weight; 12 and 18%), resulting in four treatments: CS12, CS18, RS12 and RS18. The displacement was measured during a 24h period using GPS devices fixed on the ewes back. Together with this evaluation was made a grazing behavior evaluation to synchronize the displacement with the grazing activity. With the GPS data (total and grazing displacement) the energy expenditure was predicted using equations reported in the literature. The herbage allowance did not influence the displacement and the estimations of energy expenditure. The CS presented a higher displacement than RS. Under the assumptions of estimations of energy expenditure, a higher level along all day and during grazing would be expected in the CS. Depending of the pasture quality, variations in the grazing methods could become an important management tool.O ensaio foi conduzido em 8,4ha de campo nativo, dividido em 12 unidades experimentais com 0,7ha, testando dois métodos de pastoreio (lotação contínua e rotativa; LC e LR) e duas ofertas de forragem (12 e 18 kg MS/100 kg PV; 12 e 18%) com ovelhas em gestação, gerando quatro tratamentos: LC12, LC18, LR12 e LR18. Foram medidos os deslocamentos durante um período de 24h utilizando-se aparelhos de GPS fixado na região das cruzes dos animais e o deslocamento na atividade de pastejo e procura de alimento, por meio de sincronização dos dados dos GPS e comportamento ingestivo, qual foi avaliado na ocasião. Com os deslocamentos medidos os gastos energéticos foram estimados por meio de formulas matemáticas repostadas na literatura. As OF não modificaram o deslocamento dos animais durante 24 horas ou em pastejo. O deslocamento só foi influenciado pelos métodos de pastoreio, onde os animais sob lotação contínua se deslocaram mais. Assumindo as estimativas de gasto energético, um alto nível de gasto durante o dia e na atividade de pastejo é observada no método contínuo. Dependendo da qualidade da pastagem, variações no método de pastoreio podem se tornar importantes ferramentas de manejo

Visible photodissociation spectroscopy of PAH cations and derivatives in the PIRENEA experiment

The electronic spectra of gas-phase cationic polycyclic aromatic hydrocarbons (PAHs), trapped in the Fourier Transform Ion Cyclotron Resonance cell of the PIRENEA experiment, have been measured by multiphoton dissociation spectroscopy in the 430-480 nm spectral range using the radiation of a mid-band optical parametric oscillator laser. We present here the spectra recorded for different species of increasing size, namely the pyrene cation (C16H10+), the 1-methylpyrene cation (CH3-C16H9+), the coronene cation (C24H12+), and its dehydrogenated derivative C24H10+. The experimental results are interpreted with the help of time-dependent density functional theory calculations and analysed using spectral information on the same species obtained from matrix isolation spectroscopy data. A kinetic Monte Carlo code has also been used, in the case of pyrene and coronene cations, to estimate the absorption cross-sections of the measured electronic transitions. Gas-phase spectra of highly reactive species such as dehydrogenated PAH cations are reported for the first time

Desempenho de ovelhas e cordeiros manejados com diferentes métodos de pastoreio e ofertas de forragem em campo natural

The objective of was to determine the influence of grazing methods with a relatively low or high herbage allowance in the first 84 gestation days on ewes/lambs daily weight gain (DWG) and area production. The study was conducted at an 8.4 ha natural grassland in South Brazil. During the winter, early pregnancy ewes were submitted to two grazing methods (continuous (CS) and rotative (RS) stoking) and two herbage allowances (HA; 12 and 18% live weight)), resulting in four treatments: CS18, CS12, RS18 and RS12. It was measured the DWG and body condition score (BCS) from ewes and from ewes and lambs after born, as well lambs area production. During the winter only the HA change the DWG from the ewes. During the spring differences were found only in the lambs DWG from grazing method, been higher in CS. A grazing method × HA interaction indicate that the higher lambs area production was achieved in the CS12 treatment. The results indicate that the grazing methods and HA had a little influence in the animal performance over winter and the herbage could be better used in this period.O objetivo foi determinar a influência dos métodos de pastoreio com uma relativa baixa e alta oferta de forragem nos primeiros 84 dias de gestação no desempenho de ovelhas e seus cordeiros após o nascimento. O trabalho foi conduzido em 8,4 ha de campo natural, quando os animais foram submetidos a diferentes métodos de pastoreio (lotação contínua (LC) e rotativa (LR)) e ofertas de forragem (OF, 12 e 18% do peso vivo (PV)), gerando quatro tratamentos: LC12, LC18, LR12 e LR18. Foi medido o ganho médio diário (GMD) das ovelhas e cordeiros e a condição corporal das ovelhas assim como a produção de cordeiros por área. No inverno o GMD somente foi modificado pelas OF. Na primavera, somente o GMD dos cordeiros apresentou efeito e somente para métodos de pastoreio, sendo o melhor desempenho encontrado nos cordeiros nascidos de ovelhas manejadas no inverno sob LC. Uma interação métodos × OF indicou que a maior produção por área de cordeiros foi no obtida em LC12. Os resultados indicam que os métodos de pastoreio e as OF tem pouca influência no desempenho animal no inverno e pode-se fazer uma melhor utilização da forragem neste período

The CH out-of-plane bending modes of PAH molecules in astrophysical environments

We present 10-15 micron spectra of a sample of H II regions, YSOs and evolved stars that show strong unidentified infrared emission features, obtained with the ISO/SWS spectrograph on-board ISO. These spectra reveal a plethora of emission features with bands at 11.0, 11.2, 12.0, 12.7, 13.5 and 14.2 micron. These features are observed to vary considerably in relative strength to each-other from source to source. In particular, the 10-15 micron spectra of the evolved stars are dominated by the 11.2 micron band while for H II regions the 12.7 is typically as strong as the 11.2 micron band. Analysing the ISO data we find a good correlation between the 11.2 micron band and the 3.3 micron band, and between the 12.7 micron and the 6.2 micron band. There is also a correlation between the ratio of the UIR bands to the total dust emission and the 12.7 over 11.2 micron ratio. Bands in the 10-15 micron spectral region are due to CH out-of-plane (OOP) bending modes of polycyclic aromatic hydrocarbons (PAHs). We summarise existing laboratory data and theoretical quantum chemical calculations of these modes for neutral and cationic PAHs. Due to mode coupling, the exact peak position of these bands depends on the number of adjacent CH groups and hence the observed interstellar 10-15 micron spectra can be used to determine the molecular structure of the interstellar PAHs emitting in the different regions. We conclude that evolved stars predominantly inject compact ~100-200 C-atom PAHs into the ISM where they are subsequently processed, resulting in more open and uneven PAH structures.Comment: 14 pages, 9 figures, accepted for A&

Time-dependent density functional study of the electronic spectra of oligoacenes in the charge states -1, 0, +1, and +2

We present a systematic theoretical study of the five smallest oligoacenes (naphthalene, anthracene, tetracene, pentacene, and hexacene) in their anionic,neutral, cationic, and dicationic charge states. We used density functional theory (DFT) to obtain the ground-state optimised geometries, and time-dependent DFT (TD-DFT) to evaluate the electronic absorption spectra. Total-energy differences enabled us to evaluate the electron affinities and first and second ionisation energies, the quasiparticle correction to the HOMO-LUMO energy gap and an estimate of the excitonic effects in the neutral molecules. Electronic absorption spectra have been computed by combining two different implementations of TD-DFT: the frequency-space method to study general trends as a function of charge-state and molecular size for the lowest-lying in-plane long-polarised and short-polarised $\pi\to\pi^\star$ electronic transitions, and the real-time propagation scheme to obtain the whole photo-absorption cross-section up to the far-UV. Doubly-ionised PAHs are found to display strong electronic transitions of $\pi\to\pi^\star$ character in the near-IR, visible, and near-UV spectral ranges, like their singly-charged counterparts. While, as expected, the broad plasmon-like structure with its maximum at about 17-18 eV is relatively insensitive to the charge-state of the molecule, a systematic decrease with increasing positive charge of the absorption cross-section between about 6 and about 12 eV is observed for each member of the class.Comment: 38 pages, 11 figures, 7 tables, accepted for publication in Chemical Physic

ISM properties in low-metallicity environments I. mid-infrared spectra of dwarf galaxies

We present new ISOCAM mid-infrared spectra of three starbursting nearby dwarf galaxies, NGC1569, IIZw40, NGC1140 and the 30Dor region of the LMC and explore the properties of the ISM in low-metallicity environments, also using additional sources from the literature. We analyse the various components of the ISM probed by the mid-infrared observations and compare them with other Galactic and extragalactic objects. The MIR spectra of the low-metallicity starburst sources are dominated by the [NeIII] and [SIV] lines, as well as a steeply rising dust continuum. PAH bands are generaly faint, both locally and averaged over the full galaxy, in stark contrast to dustier starburst galaxies, where the PAH features are very prominant and even dominate on global scales. The hardness of the modeled interstellar radiation fields for the dwarf galaxies increases as the presence of PAH band emission becomes less pronounced. The [NeIII]/[NeII] ratios averaged over the full galaxy are strikingly high, often >10. Thus, the hard radiation fields are pronounced and pervasive. We find a prominent correlation between the PAHs/VSGs and the [NeIII]/[NeII] ratios for a wide range of objects, including the low metallicity galaxies as well as Galactic HII regions and other metal-rich galaxies. This effect is consistent with the hardness of the interstellar radiation field playing a major role in the destruction of PAHs in the low metallicity ISM. We see a PAHs/VSGs and metallicity correlation, also found by Engelbracht et al. (2005) for a larger survey. Combined effects of metallicity and radiation field seem to be playing important roles in the observed behavior of PAHs in the low metallicity systems.Comment: accepted by A&

Multi-photon and electron impact ionisation studies of reactivity in adenine–water clusters

Multi-photon ionisation (MPI) and electron impact ionisation (EII) mass spectrometry experiments have been carried out to probe unimolecular and intermolecular reactivities in hydrated adenine clusters. The effects of clustering with water on fragment ion production from adenine have been studied for the first time. While the observation of NH4+ fragments indicated the dissociation of protonated adenine, the dominant hydration effects were enhanced C4H4N4+ production and the suppression of dissociative ionisation pathways with high activation energies. These observations can be attributed to energy removal from the excited adenine radical cation via cluster dissociation. Comparisons of MPI and EII measurements provided the first experimental evidence supporting hypoxanthine formation in adenine–water clusters via theoretically predicted barrierless deamination reactions in closed shell complexes

Fragmentation processes of ionized 5-fluorouracil in the gas phase and within clusters

We have measured mass spectra for positive ions produced from neutral 5-fluorouracil by electron impact at energies from 0 to 100 eV. Fragment ion appearance energies of this (radio-)chemotherapy agent have been determined for the first time and we have identified several new fragment ions of low abundance. The main fragmentations are similar to uracil, involving HNCO loss and subsequent HCN loss, CO loss, or FCCO loss. The features adjacent to these prominent peaks in the mass spectra are attributed to tautomerization preceding the fragmentation and/or the loss of one or two additional hydrogen atoms. A few fragmentions are distinct for 5-fluorouracil compared to uracil, most notably the production of the reactive moiety CF+. Finally, multiphoton ionization mass spectra are compared for 5-fluorouracil from a laser thermal desorption source and from a supersonic expansion source. The detection of a new fragment ion at 114 u in the supersonic expansion experiments provides the first evidence for a clustering effect on the radiation response of 5-fluorouracil. By analogy with previous experiments and calculations on protonated uracil, this is assigned to NH3 loss from protonated 5-fluorouracil