The state-to-state vibrational predissociation dynamics of the hydrogen fluoride dimer has been investigated in detail using a newly developed instrument which gives both initial state selection and photofragment state determination. Results are reported for a wide variety of initial states associated with the ν1 and ν2 vibrations. The final state distributions universally indicate that the preferred dissociation channels correspond to the production of one HF fragment that is highly rotationally excited and another that is not. This is explained in terms of an impulsive dissociation mechanism which proceeds from a geometry close to that of the equilibrium structure of the dimer. We find that nearly degenerate initial states can have rather different final state distributions. In particular, there is a distinct difference between the upper and lower members of the tunneling doublet, which is most likely attributable to their related symmetries. The dissociation energy (D0) is determined to be 1062±1 cm−1.

BackgroundPeriodontal disease (PD) is the most widespread oral disease in dogs and has been associated with serious systemic diseases. The disease is more prevalent in small breeds compared to large breeds and incidence increases with advancing age. In prevalence studies 84% of beagles over the age of 3 and 100% of poodles over the age of 4 were diagnosed with PD. Current knowledge of the rate of progression of PD is limited. The objective of this study was to determine the rate of PD progression in miniature schnauzers, an at risk small breed of dog.Dogs (n = 52, age 1.3-6.9 years) who had received a regular oral care regime prior to this study were assessed for levels of gingivitis and periodontitis around the whole gingival margin in every tooth under general anaesthetic. Assessments were conducted approximately every six weeks for up to 60 weeks following the cessation of the oral care regime.ResultsAll of the 2155 teeth assessed entered the study with some level of gingivitis. 23 teeth entered the study with periodontitis, observed across 12 dogs aged between 1.3 and 6.9 years. 35 dogs had at least 12 teeth progress to periodontitis within 60 weeks. Of the teeth that progressed to periodontitis, 54% were incisors. The lingual aspect of the incisors was significantly more likely to be affected (p < 0.001). The severity of gingivitis in periodontitis-affected teeth was variable with 24% of the aspects affected having very mild gingivitis, 36% mild gingivitis and 40% moderate gingivitis. Periodontitis progression rate was significantly faster in older dogs. Only one dog (age 3.5) did not have any teeth progress to periodontitis after 60 weeks.ConclusionsThis is the first study to have assessed the progression rate of periodontitis in miniature schnauzers and highlights that with no oral care regime, the early stages of periodontitis develop rapidly in this breed. An oral care regime and twice yearly veterinary dental health checks should be provided from an early age for this breed and other breeds with similar periodontitis incidence rates.

Periodontal disease is the most widespread oral disease in dogs. Whilst the involvement of bacteria in the aetiology of periodontitis is well established the role of individual species and their complex interactions with the host is not well understood. The objective of this research was therefore to perform a longitudinal study in dogs to identify the changes that occur in subgingival bacterial communities during the transition from mild gingivitis to the early stages of periodontitis (<25% attachment loss). Subgingival plaque samples were collected from individual teeth of 52 miniature schnauzer dogs every six weeks for up to 60 weeks. The microbial composition of plaque samples was determined using 454-pyrosequencing of the 16S rDNA. A group of aerobic Gram negative species, including Bergeyella zoohelcum COT-186, Moraxella sp. COT-017, Pasteurellaceae sp. COT-080, and Neisseria shayeganii COT-090 decreased in proportion as teeth progressed to mild periodontitis. In contrast, there was less evidence that increases in the proportion of individual species were associated with the onset of periodontitis, although a number of species (particularly members of the Firmicutes) became more abundant as gingivitis severity increased. There were small increases in Shannon diversity, suggesting that plaque community membership remains relatively stable but that bacterial proportions change during progression into periodontitis. This is the first study to demonstrate the temporal dynamics of the canine oral microbiota; it showed that periodontitis results from a microbial succession predominantly characterised by a reduction of previously abundant, health associated taxa.

The a-type, K=0 microwave spectrum of the N2–H2O complex has been observed using a pulsed molecular beam Fabry–Perot cavity microwave spectrometer. Seven isotopic species have been studied in the range of 5–23 GHz.The N2–H2O complex exhibits tunneling motions similar to the 1→2 tunneling motion of the H2O–DOD complex which gives rise to four components for each rotational transition. The molecular constants obtained for the ground tunneling (A1) state of 14N2–HOH are: B̄=2906.9252(2) MHz, DJ =0.043 486(15) MHz, and eQq(14N)=−4.253(2) MHz. The structure has a nearly linear N–N–HO geometry with a N–H distance of 2.42(4) Å and an OHN angle of 169° [RO–N=3.37(4) Å]. The electric dipole moment along the a principal axis of inertia was determined for the 15N2–HOH species with μa =0.833(3) D.

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