Assessment of stiffness and strength of 4 different implants available for equine fracture treatment: a study on a 20 degrees oblique long-bone fracture model using a bone substitute

OBJECTIVE: To compare the mechanical properties of 4 stabilization methods for equine long-bone fractures: dynamic compression plate (DCP), limited contact-DCPlate (LC-DCP), locking compression plate (LCP), and the clamp-rod internal fixator (CRIF--formerly VetFix). STUDY DESIGN: In vitro mechanical study. SAMPLE POPULATION: Bone substitute material (24 tubes) was cut at 20 degrees to the long axis of the tube to simulate an oblique mid-shaft fracture. METHODS: Tubes were divided into 4 groups (n=6) and double plated in an orthogonal configuration, with 1 screw of 1 implant being inserted in lag fashion through the "fracture". Thus, the groups were: (1) 2 DCP implants (4.5, broad, 10 holes); (2) 2 LC-DCP implants (5.5, broad, 10 holes); (3) 2 LCP implants (4.5/5.0, broad, 10 holes) and 4 head locking screws/plate; and (4) 2 CRIF (4.5/5.0) and 10 clamps in alternating position left and right of the rod. All constructs were tested in 4-point bending with a quasi-static load until failure. The implant with the interfragmentary screw was always positioned on the tension side of the construct. Force, displacement, and angular displacement at the "fracture" line were determined. Construct stiffness under low and high loads, yield strength, ultimate strength, and maximum angular displacement were determined. RESULTS: None of the implants failed; the strength of the bone substitute was the limiting factor. At low loads, no differences in stiffness were found among groups, but LCP constructs were stiffer than other constructs under high loads (P=.004). Ultimate strength was lowest in the LCP group (P=.01), whereas yield strength was highest for LCP constructs (409 N m, P=.004). CRIF had the lowest yield strength (117 N m, P=.004); no differences in yield strength (250 N m) were found between DCP and LC-DCP constructs. Differences were found for maximum angular displacement at the "fracture" line, between groups: LPC相似文献   

Probing proton dynamics in molecules on an attosecond time scale

We demonstrate a technique that uses high-order harmonic generation in molecules to probe nuclear dynamics and structural rearrangement on a subfemtosecond time scale. The chirped nature of the electron wavepacket produced by laser ionization in a strong field gives rise to a similar chirp in the photons emitted upon electron-ion recombination. Use of this chirp in the emitted light allows information about nuclear dynamics to be gained with 100-attosecond temporal resolution, from excitation by an 8-femtosecond pulse, in a single laser shot. Measurements on molecular hydrogen and deuterium agreed well with calculations of ultrafast nuclear dynamics in the H2+ molecule, confirming the validity of the method. We then measured harmonic spectra from CH4 and CD4 to demonstrate a few-femtosecond time scale for the onset of proton rearrangement in methane upon ionization.     

Oxidant-antioxidant imbalance in horses infected with equine infectious anaemia virus

This study assesses the impact of equine infectious anaemia virus (EIAV) infection on the oxidant/antioxidant equilibrium of horses. Blood samples from 96 Romanian horses aged 1-25 years, were divided into different groups according to their EIAV-infection status, age, and time post-seroconversion. The effect of infection on oxidative stress was estimated by measuring enzymatic antioxidants (superoxide dismutase [SOD], glutathione peroxidase [GPx] and catalase), non-enzymatic antioxidants (uric acid and carotenoids), and lipid peroxidation (malondialdehyde [MDA]). Infection modified the oxidant/antioxidant equilibrium in the horses, influencing GPx and uric acid levels (P<0.05). Time post-seroconversion also contributed to oxidative stress imbalance, exhibiting a significant influence on both SOD and MDA concentrations in the blood (P<0.05). Animal age did not have a significant influence on oxidative stress. Recently infected horses (<1 year following seroconversion), and horses >5 years old, represented the most vulnerable category in terms of oxidative stress, followed by recently infected animals <5 years old. The results of this study are novel in implicating EIAV infection in the development of oxidative stress in horses.     

Clinical presentation, treatment, and outcome of dacryocystitis in rabbits: a retrospective study of 28 cases (2003–2007)

Objective  To document the clinical presentation, diagnostics, treatment, and clinical outcome of rabbits with dacryocystitis.
Materials and methods  This retrospective study included 28 rabbits diagnosed with dacryocystitis. Available records of clinical and ophthalmological examinations, bacteriological samplings, diagnostic imaging, and treatment were reviewed. A telephone survey of the owners was conducted to evaluate recovery and recurrences.
Results  The mean age of the 28 rabbits presenting with ocular discharge from the nasolacrimal duct was 4.4 years. In 25 rabbits (89%), dacryocystitis was a unilateral finding. No underlying cause could be determined in 10 animals (35%). Dental malocclusion was observed in 14 rabbits (50%) and rhinitis in two animals (7%), with one animal showing both symptoms (4%). One rabbit (4%) presented with panophthalmitis. Most animals (96%) received topical antibiotic treatment. If necessary, additional topical (acetylcysteine, vitamin A ointment, nonsteroidals) or systemic treatment (antibiotics, nonsteroidals, paramunity inducer, and glucocorticoids) was provided. The mean duration of therapy was 5.8 weeks. The nasolacrimal duct was flushed in 27 of 31 affected eyes (87%). Dentistry was performed in 80% of the animals suffering from malocclusion. Regarding the clinical outcome, 12 animals (43%) showed complete recovery, eight rabbits (28%) were euthanized, three (11%) died due to unrelated causes, and three (11%) were lost to follow-up. Two rabbits (7%) continue to display signs of dacryocystitis and are being treated symptomatically by the owners.
Conclusions  This study reports the clinical presentation, treatment, and outcome of dacryocystitis in rabbits and outlines the importance of examination of the oral cavity, diagnostic imaging, and bacteriologic sampling.     

Comment on "The human K-complex represents an isolated cortical down-state"

Cash et al. (Reports, 22 May 2009, p. 1084) argue that the human K-complex, a defining characteristic of slow-wave sleep, is a unipolar electroencephalogram (EEG) wave reflecting a simple neuronal hyperpolarizing event. We disagree with this conclusion and point to several confounding aspects of the study.     

Quantitative genetic analysis of condensed tannins in oilseed rape meal

Condensed tannins (proanthocyanidins, PAs) in the seed meal of oilseed rape can potentially have a negative impact on non-ruminant livestock nutrition, particularly because of their ability to form indigestible, astringent or bitter-tasting complexes with proteins. One option to overcome this problem is the breeding of oilseed rape varieties with reduced condensed tannins in the seed coat. This might be achievable via selection of genotypes with thinner seed coats and consequently reduced condensed tannin accumulation (seed coat structural cell mutants), or alternatively by selection of genotypes with reduced biosynthesis of condensed tannins (flavonoid biosynthesis mutants). Both types of transparent testa (TT) mutants are well-characterised in Arabidopsis; however the genetic basis of the yellow-seed trait in the polyploid genome of rapeseed is still not completely understood. In this study, genetic and chemical analyses of PAs were performed in 166 doubled haploid (DH) rapeseed lines from the segregating Brassica napus doubled haploid population YE2-DH (black seed × yellow seed). Using these analyses, the relationship between seed colour and PA fractions in B. napus was investigated with a view to improving the rapeseed meal quality. Proanthocyanidin contents were estimated by vanillin and HPLC assays and the obtained values were used to identify quantitative trait loci. Closely linked molecular markers that were identified during this study for the target traits (seed colour, condensed tannins) can be valuable tools for breeding of new oilseed rape cultivars with reduced levels of antinutritive PA compounds.     

Quantification and comparison of wheat yield variation across space and time

Research about spatio-temporal variation of crop yield does not abound. From a precision agriculture (PA) perspective and particularly considering site-specific crop management (SSCM), this is an aberration. There is a serious need to further question how temporal variation of crop yield impacts ones ability to manage spatial variation. The aim of this study is to consider and develop new and existing approaches to this question. Spatio-temporal analysis was undertaken for two wheat fields in South Australia with 3 and 4 years of wheat yield data. Temporal analysis included the calculation of semi-variance across each field between pairs of years for the creation of maps and the calculation of rank correlations between pairs of years. These analyses supported previous notions that the magnitude of temporal variation is large compared with spatial variation. However, some consistence of spatial patterns between years was also observed for each of the fields indicating that considering magnitudes of variation alone is not an exhaustive analysis. A long-term (100 years) temporal analysis using variograms was undertaken for a single point simulated using the Agricultural Production Simulator Model (APSIM). The long-term analysis overcame the fact that 3 or 4 years of yield data are an extremely small sample size for the time dimension. This analysis provided some useful insight into temporal variation such as a large nugget variance accounting for 75% of the temporal variation and the cyclical nature of temporal yield variation. A novel use of pseudo cross semi-variograms was applied to a spatio-temporal analysis of yield variation for the two fields. This analysis provides a preliminary insight into identifying space–time variance equivalents. With greater depth of temporal crop yield data this is a promising perspective from which to identify optimal spatial management strategies.     

Inferring spatial structure from population genetics and spatial synchrony in demography of Baltic Sea fishes: implications for management

The spatial structure of species is important for their dynamics and evolution, but also for management and conservation. There are numerous ways of inferring spatial structures, and information from multiple methods is becoming more common to examine how different processes shape the spatial structures of species to improve fish management. Here, we investigate the spatial structure of a suite of Baltic Sea fish species based on the following: (i) spatial (presumably neutral) genetic differentiation, reviewed from the literature, and (ii) spatial synchrony in abundance changes from time series of fishery‐independent surveys, which we currently find to be underused given the amount of data available. For each of these two methods, species were classified as having a distinct, continuous or no/weak spatial structure. In addition, based on each source of information, we estimated the spatial scale of management units for species. The results show that only among species confined to the coastal zone the two sources of information yielded a congruence of the spatial structure (displaying a continuous spatial structure). In contrast, offshore species show weak spatial genetic structure but stronger spatial structure of synchrony in abundance. Based on this, we suggest that population genetic structure and synchrony in abundance should be used as complementary information as they reflect different spatial processes and suggest that management actions should differ with respect to scale depending on the management targets applied. We propose similar analysis should be applied to areas outside the Baltic Sea, and other stock identification methods, to improve management of fish resources.