584 research outputs found
AAS227 - Synthesizing Understanding from Data with yt
No full textThis is a talk I gave at the AAS227 about yt. yt is available at yt-project.org.<div><br></div><div>While I am listed as the author of this talk, the yt community is composed of more than a hundred code contributors and mailing list participants, and we are grateful to their involvement and support.</div><div><br></div><div>Additionally, the yt project is built on other members of the scientific software ecosystem such as Jupyter, NumPy, Cython, h5py and hdf5, Matplotlib, and Sympy.</div
Study of Anopheles gambiae s.l. vector populations by mark-release-recapture experiments in Banambani, Mali.
No full textCorrection to: Chemoradiation in elderly patients with glioblastoma from the multiinstitutional GBMmolRPA cohort: is shortcourse radiotherapy enough or is it a matter of selection?
No full textThe name of author Do Hoon Lim was incorrect in the initial online publication. The original article has been corrected
Spatial and temporal variation in malaria transmission in a low endemicity area in northern Tanzania.
No full textBACKGROUND: Spatial and longitudinal monitoring of transmission intensity will allow better targeting of malaria interventions. In this study, data on meteorological, demographic, entomological and parasitological data over the course of a year was collected to describe malaria epidemiology in a single village of low transmission intensity. METHODS: Entomological monitoring of malaria vectors was performed by weekly light trap catches in 10 houses. Each house in the village of Msitu wa Tembo, Lower Moshi, was mapped and censused. Malaria cases identified through passive case detection at the local health centre were mapped by residence using GIS software and the incidence of cases by season and distance to the main breeding site was calculated. RESULTS: The principle vector was Anopheles arabiensis and peak mosquito numbers followed peaks in recent rainfall. The entomological inoculation rate estimated was 3.4 (95% CI 0.7-9.9) infectious bites per person per year. The majority of malaria cases (85/130) occurred during the rainy season (chi2 = 62,3, p < 0.001). Living further away from the river (OR 0.96, CI 0.92-0.998, p = 0.04 every 50 m) and use of anti-insect window screens (OR 0.65, CI 0.44-0.94, p = 0.023) were independent protective factors for the risk of malaria infection. Children aged 1-5 years and 5-15 years were at greater risk of clinical episodes (OR 2.36, CI 1.41-3.97, p = 0.001 and OR 3.68, CI 2.42-5.61, p < 0.001 respectively). CONCLUSION: These data show that local malaria transmission is restricted to the rainy season and strongly associated with proximity to the river. Transmission reducing interventions should, therefore, be timed before the rain-associated increase in mosquito numbers and target households located near the river
Effect of donepezil on transcranial magnetic stimulation parameters in Alzheimer's disease
No full textIntroduction: There is a need for a reliable, noninvasive biomarker for Alzheimer's disease (AD). We assessed whether short-latency afferent inhibition (SAI), a transcranial magnetic stimulation paradigm that assesses cholinergic circuits of the brain, could become such a biomarker.
Methods: Nineteen patients with AD underwent four SAI testing sessions. The timing of their usual donepezil dose was altered to create different cholinergic states for each session. This was compared to the SAI results from 20 healthy subjects.
Results: SAI was not able to distinguish the different cholinergic states assessed in our study. There appeared to be a diurnal variation in cholinergic function in the control group, which was not present in the AD cohort.
Discussion: SAI does not appear to have a role in diagnosis and assessment of AD patients. The loss of diurnal variation, however, warrants further investigation as it may provide further biochemical insights about AD
Can Cause and Effect be Distinguised by Simple Regression? ESRI Memorandum Series No. 50 (revised) 1968(?)
No full textLet data be (Xt, Yt), t = 1, 2, ..., T. We assume throughout that T is "large". We try to evolve statistical tests for identifying whether X or Y is the cause, the other variable being the effect
Spatial distribution of malaria transmission in relationship to "Anopheles gambiae" complex members in Sudan savanna and irrigated rice cultivation areas of Mali
No full textMalaria remains a major public health problem that is exacerbated by poor
implementation of control measures, and by the spread of drug-resistant parasites and
insecticide resistant vectors. Preventive measures, including those targeted at vectors, are one
of the four basic elements of the global malaria control strategy. The control methods to use
should be selective and specific to the control area. The success of the approach of selective
and targeted interventions requires a good stratification of control areas, which should be
based on mapping of malaria risk and vector species distribution.
The goal of this thesis was to enhance our understanding of the relationship between
the distribution of members of Anopheles gambiae complex and climatic and environmental
conditions, to describe their spatial and temporal distribution, to quantify their unique
contribution to malaria transmission, and to produce attributed malaria risk maps of Mali. We
used Bayesian geostatistical modeling, implemented via Markov chain Monte Carlo
simulation (MCMC), which can quantify the relationship between environmental factors and
the species distribution by taking into account the spatial dependence present in the data in a
flexible way that allows simultaneous estimation of all model parameters. In addition,
Bayesian kriging enables model-based prediction together with the prediction error, a feature which is not possible in the classical kriging.
The analyses described in chapters 2 and 3 identified environmental factors related to
the distribution of a) the two major species (An. arabiensis and An. gambiae s.s.) which
compose the An. gambiae complex and b) the chromosomal (Bamako, Mopti, Savanna
Hybrids) forms of An. gambiae s.s., and produced maps of the geographical distribution of the
species and chromosomal forms. Estimation of the contribution of species and chromosomal
forms to malaria transmission in Mali is described in Chapter 4; the spatio-temporal
distribution of An. gambiae complex densities and its chromosomal (Mopti, Bamako, Savanna, Hybrids) forms in a Sudan savanna village is examined in Chapter 5; the
investigation of malaria vector ecology during the dry season and its implication for vector
control is described in Chapter 6, and Chapter 7 presents the spatial pattern of malaria
transmission in the rice cultivation area of the Office du Niger.
The maps produced in chapters 2 & 3 showed higher frequencies of An. arabiensis in
the drier Savanna areas and An. gambiae s.s. in the flooded/irrigated areas of the inner delta of
Niger river, the southern Savanna, along rivers and in the Sahel. The Mopti form was found in
the same ecological area as An. arabiensis. In addition, it occupied the flooded/irrigated areas
of the inner delta of Niger River. The Savanna form prefers the Sudan Savanna areas and the
Bamako form was confined around Bamako city and in part of Sikasso region (South of
Mali). Analyses in Chapter 4 indicated that high malaria risk was associated with insecticide
resistance gene (kdr) carriers (Bamako/Savanna chromosomal) and Hybrids compared to the
non-carriers An. arabiensis and the Mopti chromosomal form, although the association was
not significant. The attributed risk maps of the different species and subspecies indicated that
in the middle West and South East part of the country malaria transmission risk is mainly due
to An. arabiensis, in the irrigated/flooded areas malaria risk is attributed to the Mopti form, in the southern part to the Savanna/Bamako forms and in the southern areas of the region of
Kayes to the hybrids. Thus these results suggest that insecticide control measures must be
strengthened in the Sahelian (epidemic prone area) and irrigated/flooded areas where An.
arabiensis and the Mopti chromosomal form, which have no or lower frequency of insecticide
resistance gene, prevail. Any vector control by means of insecticides in the Southern part of
the country, where the S molecular form (Savanna and Bamako) predominates, must be
accompanied by a close insecticide resistance monitoring system. The analyses carried out in Chapter 5 and 6 on the spatial distribution of the sibling
species of An. gambiae complex in a savanna village showed that the distribution of mosquito
densities was concentric with higher densities clustering at the periphery of the village at the
beginning of the rainy season and during the dry season. This distribution was patchy during
the middle and the end of the rainy season. The chromosomal forms were sympatric
throughout the seasons. There was a spatial clustering in their relative frequency distribution
changing over time in the village. The Mopti chromosomal form was the most abundant at the
beginning and middle of the rainy season and the Bamako form at the end of the rainy season.
Larval habitats monitoring showed that in the main village of Bancoumana nearly all larval
habitats were human-made, rain-dependent and dried out 10-12 weeks after the end of the
rainy season. At the same time, numerous natural puddles highly productive for anopheline
larvae even during the dry season were located in the fishermen’s hamlets. These were
adjacent to the receding Niger River bed and 5 km away from the main village. Larval
habitats in Bancoumana were re-colonized shortly after rainfall suggesting that mosquitoes
emerging from the riverbed are an important source for the rain-fed water bodies of
Bancoumana. This observation indicates that control interventions targeting the Mopti form
should be implemented at the beginning and middle of the rainy season, while those targeting the Bamako form should be done at the end of the rainy season. In addition, appropriate
vector control implemented in the fishermen’s hamlet during the dry season and at the
periphery of the main village at the beginning of the rainy season may be feasible, sustainable
at low cost and may ameliorate malaria transmission in this area.
In chapter 7, the analyses of malaria transmission parameters in the rice cultivation
area of the Office du Niger indicated a strong spatial correlation in mosquito densities, which
is related to the rice cultivation environment. However, the spatial correlation observed in the
parous rate (PR) and human blood index (HBI) was weak suggesting that these parameters are more closely related to local conditions such as population behavior and economic status,
and/or the presence of animals rather than similar environment over large areas. Since both
the PR and HBI measure the vector-human contact rate, and hence the potential for malaria
transmission intensity, attention must be paid to the local variations when implementing
control strategies in rice cultivation areas.
This work makes a substantial contribution to the mapping of the spatial distribution
of malaria vector species and subspecies which was previously limited by the lack of field
data and appropriate statistical analyses. It also provides valuable information for
conventional vector control as well as future implementation for genetically manipulated
mosquitoes control method
Scaling relationships in indentation of power-law creep solids using self-similar indenters
No full textWe use dimensional analysis to derive scaling relationships for self-similar indenters indenting solids that exhibit power-law creep. We identify the parameter that represents the indentation strain rate. The scaling relationships are applied to several types of indentation creep experiment with constant displacement rate, constant loading rate or constant ratio of loading rate over load. The predictions compare favourably with experimental observations reported in the literature. Finally, a connection is found between creep and 'indentation-size effect' (i.e. changing hardness with indentation depth or load)
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