Review on the epidemiology and dynamics of BSE epidemics

The paper describes how the comprehensive surveillance of bovine spongiform encephalopathy (BSE) and studies carried out on these data has enhanced our knowledge of the epidemiology of BSE. Around 7 000 BSE cases were detected through the screening of about 50 million cattle with rapid tests in Europe. It confirmed that the clinical surveillance had a poor capacity to detect cases, and also showed the discrepancy of this passive surveillance efficiency between regions and production types (dairy/beef). Other risk factors for BSE were being in a dairy herd (three times more than beef), having a young age at first calving (for dairy cattle), being autumn-born (dairy and beef), and being in a herd with a very high milk yield. These findings focus the risk on the feeding regimen of calves/heifers. Several epidemiological studies across countries suggest that the feedborne source related to meat and bone meal (MBM) is the only substantiated route of infection ¿ even after the feed ban ¿, while it is not possible to exclude maternal transmission or milk replacers as a source of some infections. In most European countries, the average age of the cases is increasing over time and the prevalence decreasing, which reflects the effectiveness of control measures. Consistent results on the trend of the epidemic were obtained using back-calculation modelling, the R0 approach and Age-Period-Cohort models. Furthermore, active surveillance also resulted in the finding of atypical cases. These are distinct from previously found BSE and classified in two different forms based on biochemical characteristics; their prevalence is very low (36 cases up to 1st September 2007), affected animals were old and some of them displayed clinical signs. The origin and possibility of natural transmission is unknown

Non-detection of Contamination by Stellar Activity in the Spitzer Transit Light Curves of TRAPPIST-1

We apply the transit light curve self-contamination technique of Morris et al. (2018) to search for the effect of stellar activity on the transits of the ultracool dwarf TRAPPIST-1 with 2018 Spitzer photometry. The self-contamination method fits the transit light curves of planets orbiting spotted stars, allowing the host star to be a source of contaminating positive or negative flux which influences the transit depths but not the ingress/egress durations. We find that none of the planets show statistically significant evidence for self-contamination by bright or dark regions of the stellar photosphere. However, we show that small-scale magnetic activity, analogous in size to the smallest sunspots, could still be lurking in the transit photometry undetected.Comment: Accepted for publication in ApJ

Ground-based follow-up observations of TRAPPIST-1 transits in the near-infrared

The TRAPPIST-1 planetary system is a favorable target for the atmospheric characterization of temperate earth-sized exoplanets by means of transmission spectroscopy with the forthcoming James Webb Space Telescope (JWST). A possible obstacle to this technique could come from the photospheric heterogeneity of the host star that could affect planetary signatures in the transit transmission spectra. To constrain further this possibility, we gathered an extensive photometric data set of 25 TRAPPIST-1 transits observed in the near-IR J band (1.2 $\mu$m) with the UKIRT and the AAT, and in the NB2090 band (2.1 $\mu$m) with the VLT during the period 2015-2018. In our analysis of these data, we used a special strategy aiming to ensure uniformity in our measurements and robustness in our conclusions. We reach a photometric precision of $\sim0.003$ (RMS of the residuals), and we detect no significant temporal variations of transit depths of TRAPPIST-1 b, c, e, and g over the period of three years. The few transit depths measured for planets d and f hint towards some level of variability, but more measurements will be required for confirmation. Our depth measurements for planets b and c disagree with the stellar contamination spectra originating from the possible existence of bright spots of temperature 4500 K. We report updated transmission spectra for the six inner planets of the system which are globally flat for planets b and g and some structures are seen for planets c, d, e, and f.Comment: accepted for publication in MNRA

Complex fractures of the distal humerus in the elderly: Is primary total elbow arthroplasty a valid treatment alternative? A series of 20 cases

SummaryIntroductionDistal humerus fractures are fairly rare. But as our population ages, these fractures become more complex and the choice of treatment more delicate. Poor bone quality results in many technical problems and the fixation hardware stability remains at risk. The goal of this study was to evaluate the functional recovery and morbidity of complex distal humerus fractures in elderly patients when treated with elbow prosthesis.HypothesisGood functional recovery can be achieved with a total joint replacement.Patients and methodsThis series consisted of 20 patients (18 women and two men) having an average age of 80years (range 65–93, median 80). Based on the AO classification, there were two Type A2 fractures, two Type B fractures, 15 Type C fractures and one fracture that could not be classified because of previous rheumatoid disease history at this elbow. Two fractures were open. In two cases, the olecranon was also fractured. Treatment consisted of the implantation of a Coonrad-Morrey, hinge-type total elbow prosthesis (Zimmer®, Warsaw, IN, USA). The Mayo Clinic surgical approach was used 17 times and the transolecranon approach was used three times. Primary arthroplasty was performed in 19 cases and the surgery was performed after six weeks of conservative treatment (diagnostic delay) in one case. Unrestricted motion was allowed after surgery, but a maximum of 0.5kg could be carried during the first 3months; this was subsequently increased to 2.5kg.ResultsFifteen of the 20 patients were available for reevaluation with an average follow-up of 3.6years (range 1.7–5.5, median 3.4). Four patients had died and one was lost to follow-up. The average range of motion was 97° (range 60–130°), comprising an average flexion of 130° (range 110–140°) and average loss of extension of 33° (range 0–80°). Pronation and supination were normal. The average Mayo Elbow Performance Score (MEPS) was 83 (range 60–100, median 80). X-rays revealed seven cases of radiolucent lines, with two being progressive. There was no visible wear of the polyethylene bushings at the hinge. Six patients had moderate periarticular heterotopic ossification. The two cases of olecranon osteotomy and one case of olecranon fracture had healed. There were no surgical site infections but two cases of ulnar compression, one of which required neurolysis. There was one case of humeral component loosening after 6years, but the implant was not changed.DiscussionThe clinical range of motion results were comparable to published data. The functional scores were slightly lower, mainly because of the pain factor. The initial results were encouraging and consistent with published data as long as the indications were well-chosen. Based on this retrospective study, total elbow arthroplasty can be a valid alternative in the surgeon's treatment armamentarium for complex distal humerus fractures in elderly patients who have moderate functional demands. Our results support our hypothesis, since we found good functional recovery without associated morbidity.Level of evidenceLevel IV retrospective study without comparator

Crystallization of DNA-coated colloids

DNA-coated colloids hold great promise for self-assembly of programmed heterogeneous microstructures, provided they not only bind when cooled below their melting temperature, but also rearrange so that aggregated particles can anneal into the structure that minimizes the free energy. Unfortunately, DNA-coated colloids generally collide and stick forming kinetically arrested random aggregates when the thickness of the DNA coating is much smaller than the particles. Here we report DNA-coated colloids that can rearrange and anneal, thus enabling the growth of large colloidal crystals from a wide range of micrometresized DNA-coated colloids for the first time. The kinetics of aggregation, crystallization and defect formation are followed in real time. The crystallization rate exhibits the familiar maximum for intermediate temperature quenches observed in metallic alloys, but over a temperature range smaller by two orders of magnitude, owing to the highly temperaturesensitive diffusion between aggregated DNA-coated colloids.link_to_OA_fulltex

Identification of target-specific bioisosteric fragments from ligand-protein crystallographic data

Bioisosteres are functional groups or atoms that are structurally different but that can form similar intermolecular interactions. Potential bioisosteres were identified here from analysing the X-ray crystallographic structures for sets of different ligands complexed with a fixed protein. The protein was used to align the ligands with each other, and then pairs of ligands compared to identify substructural features with high volume overlap that occurred in approximately the same region of geometric space. The resulting pairs of substructural features can suggest potential bioisosteric replacements for use in lead-optimisation studies. Experiments with 12 sets of ligand-protein complexes from the Protein Data Bank demonstrate the effectiveness of the procedure