1,728 research outputs found
Modelling Oscillator synchronisation during vertebrate axis segmentation
he somitogenesis clock regulates the periodicity with which somites form in the posterior pre-somitic mesoderm. Whilst cell heterogeneity results in noisy oscillation rates amongst constituent cells, synchrony within the population is maintained as oscillators are entrained via juxtracine signalling mechanisms. Here we consider a population of phase-coupled oscillators and investigate how biologically motivated perturbations to the entrained state can perturb synchrony within the population. We find that the ratio of mitosis length to clock period can influence levels of desynchronisation. Moreover, we observe that random cell movement, and hence change of local neighbourhoods, increases synchronisation
Do all roads lead to rome? The potential of different approaches to diagnose Aelurostrongylus abstrusus infection in cats
An infection with the cat lungworm, Aelurostrongylus abstrusus, can be subclinical, but it can also cause severe respiratory clinical signs. Larvae excretion, antibody levels, clinical assessment findings of the respiratory system and diagnostic imaging findings were recorded and compared for six cats with experimental aelurostrongylosis. In five cats, patency started 33–47 days post infection (pi), but two cats excreted larvae only in long intervals and low numbers. Positive ELISA results were observed in four cats with patent aelurostrongylosis, starting between five days before and 85 days after onset of patency. One seropositive cat remained copromicroscopically negative. Mild respiratory signs were observed in all cats examined. A computed tomographic (CT) examination of the lungs displayed distinct alterations, even in absence of evident clinical signs or when larvae excretion was low or negative. The thoracic radiograph evaluation correlated with the CT results, but CT was more distinctive. After anthelmintic treatment in the 25th week post infection, pulmonary imaging findings improved back to normal within 6–24 weeks. This study shows that a multifaceted approach, including diagnostic imaging, can provide a clearer diagnosis and monitoring of disease progression. Furthermore, a CT examination provides an alternative to post mortem examination and worm counts in anthelmintic efficacy studies
Thermal Conductivity of Isotopically Enriched 28Si Revisited
The thermal conductivity of isotopically enriched 28Si (enrichment better
than 99.9%) was redetermined independently in three laboratories by high
precision experiments on a total of 4 samples of different shape and degree of
isotope enrichment in the range from 5 to 300 K with particular emphasis on the
range near room temperature. The results obtained in the different laboratories
are in good agreement with each other. They indicate that at room temperature
the thermal conductivity of isotopically enriched 28Si exceeds the thermal
conductivity of Si with a natural, unmodified isotope mixture by 102 %.
This finding is in disagreement with an earlier report by Ruf et al. At
26 K the thermal conductivity of 28Si reaches a maximum. The maximum
value depends on sample shape and the degree of isotope enrichment and exceeds
the thermal conductivity of natural Si by a factor of 8 for a 99.982%
28Si enriched sample. The thermal conductivity of Si with natural isotope
composition is consistently found to be 3% lower than the values
recommended in the literature
Comparative analysis of intestinal helminth infections in colic and non-colic control equine patients
All around the world, intestinal helminths constitute one of the most prevalent life-long occurring infections and re-infections affecting all horse age groups. A range of parasite species among strongyles, ascarids, and tapeworms is known to have the potential to cause colic in horses. However, there is a lack of current scientific evidence on the actual relevance of helminth infection levels in the context of colic in horses kept during prevailing epidemiological conditions. Thus, a prospective case-control study on the occurrence of intestinal helminths in a total of 620 mainly adult equine clinic patients was conducted to investigate the association between colic and helminth infection. For each horse, a range of copromicroscopic, serological, and clinical data was obtained, in addition to a questionnaire on relevant anamnestic data, including previous anthelmintic treatment and husbandry. Using a FLOTAC-based copromicroscopic diagnosis, the highest infection rates were seen for strongyles (41.8%), followed by Anoplocephala perfoliata and Parascaris spp. (both 0.8%), with no significant difference between the two study groups. Employing a real-time PCR a 1.1% S. vulgaris DNA prevalence was found. Considerably higher seroprevalences were observed using S. vulgaris and A. perfoliata ELISAs, with 32.3% and 10.7%, respectively. It was noteworthy that no association concerning either serologic status was encountered with colic status. The shedding of strongyle eggs was associated with a 1.8-times increased risk of S. vulgaris seropositivity. Recent anthelmintic treatment was associated with the onset of colic, as animals who had received an anthelmintic during the previous week had a 2.4-times higher risk of signs of colic compared to those who had been treated at least eight weeks prior. Another noteworthy observation was that ponies were significantly less often affected by colic than warmbloods. The high S. vulgaris and considerable A. perfoliata seroprevalences encountered in this investigation should prompt veterinarians, farm managers, and horse owners to maintain consequent and effective worm control measures
Computing stationary distributions in equilibrium and non-equilibrium systems with Forward Flux Sampling
We present a method for computing stationary distributions for activated
processes in equilibrium and non-equilibrium systems using Forward Flux
Sampling (FFS). In this method, the stationary distributions are obtained
directly from the rate constant calculations for the forward and backward
reactions; there is no need to perform separate calculations for the stationary
distribution and the rate constant. We apply the method to the non-equilibrium
rare event problem proposed by Maier and Stein, to nucleation in a
2-dimensional Ising system, and to the flipping of a genetic switch
A time-domain control signal detection technique for OFDM
Transmission of system-critical control information plays a key role in efficient management of limited wireless network resources and successful reception of payload data information. This paper uses an orthogonal frequency division multiplexing (OFDM) architecture to investigate the detection performance of a time-domain approach used to detect deterministic control signalling information. It considers a type of control information chosen from a finite set of information, which is known at both transmitting and receiving wireless terminals. Unlike the maximum likelihood (ML) estimation method, which is often used, the time-domain detection technique requires no channel estimation and no pilots as it uses a form of time-domain correlation as the means of detection. Results show that when compared with the ML method, the time-domain approach improves detection performance even in the presence of synchronisation error caused by carrier frequency offset
Spectral Identification of an Ancient Supernova using Light Echoes in the LMC
We report the successful identification of the type of the supernova
responsible for the supernova remnant SNR 0509-675 in the Large Magellanic
Cloud (LMC) using Gemini spectra of surrounding light echoes. The ability to
classify outbursts associated with centuries-old remnants provides a new window
into several aspects of supernova research and is likely to be successful in
providing new constraints on additional LMC supernovae as well as their
historical counterparts in the Milky Way Galaxy (MWG). The combined spectrum of
echo light from SNR 0509-675 shows broad emission and absorption lines
consistent with a supernova (SN) spectrum. We create a spectral library
consisting of 26 SNe Ia and 6 SN Ib/c that are time-integrated, dust-scattered
by LMC dust, and reddened by the LMC and MWG. We fit these SN templates to the
observed light echo spectrum using minimization as well as correlation
techniques, and we find that overluminous 91T-like SNe Ia with \dm15<0.9
match the observed spectrum best.Comment: 12 pages, 18 Figures, to be published in Ap
Pushing the Boundaries of Conventional Core-Collapse Supernovae: The Extremely Energetic Supernova SN 2003ma
We report the discovery of a supernova (SN) with the highest apparent energy
output to date and conclude that it represents an extreme example of the Type
IIn subclass. The SN, which was discovered behind the Large Magellanic Cloud at
z = 0.289 by the SuperMACHO microlensing survey, peaked at M_R = -21.5 mag and
only declined by 2.9 mag over 4.7 years after the peak. Over this period, SN
2003ma had an integrated bolometric luminosity of 4 x 10^51 ergs, more than any
other SN to date. The radiated energy is close to the limit allowed by
conventional core-collapse explosions. Optical spectra reveal that SN 2003ma
has persistent single-peaked intermediate-width hydrogen lines, a signature of
interaction between the SN and a dense circumstellar medium. The light curves
show further evidence for circumstellar interaction, including a long plateau
with a shape very similar to the classic SN IIn 1988Z -- however, SN 2003ma is
ten times more luminous at all epochs. The fast velocity measured for the
intermediate-width H_alpha component (~6000 km/s) points towards an extremely
energetic explosion (> 10^52 ergs), which imparts a faster blast-wave speed to
the post-shock material and a higher luminosity from the interaction than is
observed in typical SNe IIn. Mid-infrared observations of SN 2003ma suggest an
infrared light echo is produced by normal interstellar dust at a distance ~0.5
pc from the SN.Comment: 21 pages, 15 figures, accepted for publication in Ap
Dirofilaria spp. And angiostrongylus vasorum: Current risk of spreading in central and northern europe
In the past few decades, the relevance of Dirofilaria immitis and Dirofilaria repens, causing cardiopulmonary and subcutaneous dirofilariosis in dogs and cats, and of Angiostrongylus vasorum, causing canine angiostrongylosis, has steadily increased in Central and Northern Europe. In this review, a summary of published articles and additional reports dealing with imported or autoch-thonous cases of these parasites is provided for Central (Austria, Czechia, Germany, Hungary, Lux-emburg, Poland, Slovakia, Slovenia, and Switzerland) and Northern (Denmark, Finland, Iceland, Norway, and Sweden) Europe. Research efforts focusing on Dirofilaria spp. and A. vasorum have varied by country, and cross-border studies are few. The housing conditions of dogs, pet move-ments, the spread of competent vectors, and climate change are important factors in the spread of these nematodes. Dogs kept outside overnight are a major factor for the establishment of Dirofilaria spp. However, the establishment of invasive, diurnal, synanthropic, competent mosquito vectors such as Aedes albopictus may also influence the establishment of Dirofilaria spp. The drivers of the spread of A. vasorum remain not fully understood, but it seems to be influenced by habitats shared with wild canids, dog relocation, and possibly climatic changes; its pattern of spreading appears to be similar in different countries. Both Dirofilaria spp. and A. vasorum merit further monitoring and research focus in Europe
Low thermal conductivity of the layered oxide (Na,Ca)Co_2O_4: Another example of a phonon glass and an electron crystal
The thermal conductivity of polycrystalline samples of (Na,Ca)Co_2O_4 is
found to be unusually low, 20 mW/cmK at 280 K. On the assumption of the
Wiedemann-Franz law, the lattice thermal conductivity is estimated to be 18
mW/cmK at 280 K, and it does not change appreciably with the substitution of Ca
for Na. A quantitative analysis has revealed that the phonon mean free path is
comparable with the lattice parameters, where the point-defect scattering plays
an important role. Electronically the same samples show a metallic conduction
down to 4.2 K, which strongly suggests that NaCo_2O_4 exhibits a glass-like
poor thermal conduction together with a metal-like good electrical conduction.
The present study further suggests that a strongly correlated system with
layered structure can act as a material of a phonon glass and an electron
crystal.Comment: 5 pages 3 figures, to be published in Phys. Rev.
- …