3,854 research outputs found
Use of accelerometry to investigate physical activity in dogs receiving chemotherapy
Objectives:
To perform a preliminary study to assess whether single-agent palliative or adjuvant chemotherapy has an impact on objectively measured physical activity in dogs.
Methods:
Fifteen dogs with neoplasia (treatment group) wore ActiGraph™ accelerometers for 5-day periods before, during and after receiving single-agent adjuvant or palliative chemotherapy. Mean 5-day total physical activity and time spent in three different intensities of activity (sedentary, light-moderate and vigorous) before, during and after receiving chemotherapy were compared to a group of 15 healthy dogs (control group). Results were also compared within the treatment group across time.
Results:
Prior to chemotherapy, treated dogs tended to be less active than control dogs. Treatment group dogs were slightly more active at restaging than they were prior to treatment but had similar activity levels to control dogs. Marked effects of chemotherapy on physical activity were not detected. Physical activity was slightly lower in treated dogs during chemotherapy when compared to control dogs but there was a slight increase in physical activity of treated dogs during chemotherapy when compared with pretreatment recordings. There was little change in the mean 5-day total physical activity between treated dogs during chemotherapy and at restaging but a mild decrease in time spent sedentary and increase in time spent in light-moderate activity at this comparison of time points.
Clinical Significance:
Single-agent adjuvant or palliative chemotherapy had minimal impact on physical activity levels in dogs with neoplasia
Spectral Analysis and the Dynamic Response of Complex Networks
The eigenvalues and eigenvectors of the connectivity matrix of complex
networks contain information about its topology and its collective behavior. In
particular, the spectral density of this matrix reveals
important network characteristics: random networks follow Wigner's semicircular
law whereas scale-free networks exhibit a triangular distribution. In this
paper we show that the spectral density of hierarchical networks follow a very
different pattern, which can be used as a fingerprint of modularity. Of
particular importance is the value , related to the homeostatic
response of the network: it is maximum for random and scale free networks but
very small for hierarchical modular networks. It is also large for an actual
biological protein-protein interaction network, demonstrating that the current
leading model for such networks is not adequate.Comment: 4 pages 14 figure
An analytically solvable model of probabilistic network dynamics
We present a simple model of network dynamics that can be solved analytically
for uniform networks. We obtain the dynamics of response of the system to
perturbations. The analytical solution is an excellent approximation for random
networks. A comparison with the scale-free network, though qualitatively
similar, shows the effect of distinct topology.Comment: 4 pages, 1 figur
Variable sequence of events during the past seven terminations in two deep-sea cores from the Southern Ocean
The relationships among internally consistent records of summer sea-surface temperature (SSST), winter sea
ice (WSI), and diatomaceous stable isotopes were studied across seven terminations over the last 660 ka in
sedimentary cores from ODP sites 1093 and 1094. The sequence of events at both sites indicates that SSST
and WSI changes led the carbon and nitrogen isotopic changes in three Terminations (TI, TII and TVI) and followed
them in the other four Terminations (TIII, TIV, TV and TVII). In both TIII and TIV, the leads and lags between
the proxies were related to weak glacial mode, while in TV and TVII they were due to the influence of
the mid-Pleistocene transition. We show that the sequence of events is not unique and does not follow the
same pattern across terminations, implying that the processes that initiated climate change in the Southern
Ocean has varied through time
Real-time Detection and Rapid Multiwavelength Follow-up Observations of a Highly Subluminous Type II-P Supernova from the Palomar Transient Factory Survey
The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 deg^2 field of view mounted on the 48 inch Oschin Schmidt telescope at Palomar Observatory. One of the key goals of this survey is to conduct high-cadence monitoring of the sky in order to detect optical transient sources shortly after they occur. Here, we describe the real-time capabilities of the PTF and our related rapid multiwavelength follow-up programs, extending from the radio to the γ-ray bands. We present as a case study observations of the optical transient PTF10vdl (SN 2010id), revealed to be a very young core-collapse (Type II-P) supernova having a remarkably low luminosity. Our results demonstrate that the PTF now provides for optical transients the real-time discovery and rapid-response follow-up capabilities previously reserved only for high-energy transients like gamma-ray bursts
The luminous late-time emission of the type Ic supernova iPTF15dtg - evidence for powering from a magnetar?
iPTF15dtg is a Type Ic supernova (SN) showing a broad light curve around
maximum light, consistent with massive ejecta if we assume a
radioactive-powering scenario. We study the late-time light curve of iPTF15dtg,
which turned out to be extraordinarily luminous for a stripped-envelope (SE)
SN. We compare the observed light curves to those of other SE SNe and also with
models for the Co decay. We analyze and compare the spectra to nebular
spectra of other SE SNe. We build a bolometric light curve and fit it with
different models, including powering by radioactivity, magnetar powering, as
well as a combination of the two. Between 150 d and 750 d past explosion,
iPTF15dtg's luminosity declined by merely two magnitudes instead of the six
magnitudes expected from Co decay. This is the first
spectroscopically-regular SE SN showing this behavior. The model with both
radioactivity and magnetar powering provides the best fit to the light curve
and appears to be the more realistic powering mechanism. An alternative
mechanism might be CSM interaction. However, the spectra of iPTF15dtg are very
similar to those of other SE SNe, and do not show signs of strong CSM
interaction. iPTF15dtg is the first spectroscopically-regular SE SN whose light
curve displays such clear signs of a magnetar contributing to the powering of
the late time light curve. Given this result, the mass of the ejecta needs to
be revised to a lower value, and therefore the progenitor mass could be
significantly lower than the previously estimated 35 .Comment: 9 pages, 8 figures, accepted for publication in Astronomy and
Astrophysic
Validity and practical utility of accelerometry for the measurement of in-hand physical activity in horses
Background:
Accelerometers are valid, practical and reliable tools for the measurement of habitual physical activity (PA). Quantification of PA in horses is desirable for use in research and clinical settings. The objective of this study was to evaluate a triaxial accelerometer for objective measurement of PA in the horse by assessment of their practical utility and validity.
Horses were recruited to establish both the optimal site of accelerometer attachment and questionnaire designed to explore owner acceptance. Validity and cut-off values were obtained by assessing PA at various gaits. Validation study- 20 horses wore the accelerometer while being filmed for 10 min each of rest, walking and trotting and 5 mins of canter work. Practical utility study- five horses wore accelerometers on polls and withers for 18 h; compliance and relative data losses were quantified.
Results:
Accelerometry output differed significantly between the four PA levels (P <0•001) for both wither and poll placement. For withers placement, ROC analyses found optimal sensitivity and specificity at a cut-off of <47 counts per minute (cpm) for rest (sensitivity 99.5 %, specificity 100 %), 967–2424 cpm for trotting (sensitivity 96.7 %, specificity 100 %) and ≥2425 cpm for cantering (sensitivity 96.0 %, specificity 97.0 %). Attachment at the poll resulted in optimal sensitivity and specificity at a cut-off of <707 counts per minute (cpm) for rest (sensitivity 97.5 %, specificity 99.6 %), 1546–2609 cpm for trotting (sensitivity 90.33 %, specificity 79.25 %) and ≥2610 cpm for cantering (sensitivity 100 %, specificity 100 %) In terms of practical utility, accelerometry was well tolerated and owner acceptance high.
Conclusion:
Accelerometry data correlated well with varying levels of in-hand equine activity. The use of accelerometers is a valid method for objective measurement of controlled PA in the horse
SN2007ax : An Extremely Faint Type Ia Supernova
We present multi-band photometric and optical spectroscopic observations of
SN2007ax, the faintest and reddest Type Ia supernova (SNIa) yet observed. With
M_B = -15.9 and (B-V)max = 1.2, this SN is over half a magnitude fainter at
maximum light than any other SNIa. Similar to subluminous SN2005ke, SN2007ax
also appears to show excess in UV emission at late time. Traditionally,
Delta-m_15(B) has been used to parameterize the decline rate for SNeIa.
However, the B-band transition from fast to slow decline occurs sooner than 15
days for faint SNeIa. Therefore we suggest that a more physically motivated
parameter, the time of intersection of the two slopes, be used instead. Only by
explaining the faintest (and the brightest) supernovae, we can thoroughly
understand the physics of thermonuclear explosions. We suggest that future
surveys should carefully design their cadence, depth, pointings and follow-up
to find an unbiased sample of extremely faint members of this subclass of faint
SNeIa.Comment: Accepted for publication in ApJ
Oriental Theileriosis
Theileria orientalis, the causative agent of oriental theileriosis, is an apicomplexan haemoparasite and is one of several tick-borne Theileria spp. infecting cattle. Unlike the highly pathogenic transforming Theileria species (T. annulata and T. parva) which induce uncontrolled lymphocytic proliferation, T. orientalis is a non-transforming strain exerting its major pathogenic effects via erythrocyte destruction. Clinical symptoms associated with oriental theileriosis are largely consequences of the underlying anaemia. Because of its non-transforming nature, T. orientalis was previously considered a benign parasite, however, in the recent years, clinical outbreaks of T. orientalis have been increasingly observed throughout Asia and Australasia. Recent rapid spread of clinical theileriosis has been linked to a pathogenic genotype of the parasite, genotype Ikeda (Type 2). The geographic distribution of clinical outbreaks correlates to the range of the major vector tick, Haemaphysalis longicornis, although other vectors and modes of transmission are possible. This review includes discussion of T. orientalis epidemiology, transmission, pathogenesis, treatment and control and provides an update on the taxonomy of this organism which is still under debate
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