3,838 research outputs found
Status of populations and fisheries of Strombus gigas in Cuba, with some results of juvenile rearing in pens
Sampling bias in systems with structural heterogeneity and limited internal diffusion
Complex systems research is becomingly increasingly data-driven, particularly
in the social and biological domains. Many of the systems from which sample
data are collected feature structural heterogeneity at the mesoscopic scale
(i.e. communities) and limited inter-community diffusion. Here we show that the
interplay between these two features can yield a significant bias in the global
characteristics inferred from the data. We present a general framework to
quantify this bias, and derive an explicit corrective factor for a wide class
of systems. Applying our analysis to a recent high-profile survey of conflict
mortality in Iraq suggests a significant overestimate of deaths
Nuevo grillo (Orthoptera, Gryllidae) para Castilla-La Mancha y la península Ibérica
We report Tartarogryllus tartarus (Saussure, 1874), a species with disjunct distribution in the Mediterranean-Turanean area, for the first time in the Iberian Peninsula. We summarize morphological charateristics for the species identification adding some new relevant traits to distinguish it from Acheta domesticus and Eumodicogryllus bordigalensis, particularly the interior tympanic opening that is shaped like a narrow slot whereas it is almost rounded in Acheta and Eumodicogryllus. We have found the species in cereal crops and vegetation around hiper-saline lagoons of arid lands (Castilla-La Mancha, Spain). Adult emergence occurs in May with maximum sexual activity at the end of this month and in June. We suspect that this species may be more widely distributed in other regions of the Iberian Peninsula with appropriate habitat.Encontramos por primera vez en la península Ibérica Tartarogryllus tartarus (Saussure, 1874), especie de distribución disjunta en el área Turano-Mediterránea. Resumimos los distintos caracteres morfológicos utilizados para identificar esta especie y añadimos algunos nuevos para distinguirla de especies similares como Acheta domesticus y Eumodicogryllus bordigalensis. Destacamos la apertura timpánica interior en forma de ranura estrecha y poco perceptible en esta especie mientras que es redondeada en Acheta y en Eumodicogryllus. Habita cultivos de cereal y vegetación en zonas áridas alrededor de lagunas hipersalinas (Castilla-La Mancha, España). Los adultos emergen a partir de mediados de mayo con máxima actividad reproductiva a finales de este mes y en junio. Sugerimos que la especie puede tener una distribución más amplia en la península Ibérica en aquellas regiones que presentan el hábitat adecuado
Size-Controlled Water-Soluble Ag Nanoparticles
Ag nanoparticles of two different sizes (1 and 4 nm) were prepared within an apoferritin cavity by using an Ag+-loaded apoferritin as a nanoconfined environment for their construction. The initial amount of Ag' ions injected in the apoferritin cavity dictates the size of the final Ag particles. The protein shell prevents bulk aggregation of the metal particles, which renders them water soluble and extremely stable
Composite SUVR: a new method for boosting Alzheimer's disease monitoring and diagnostic performance, applied to tau PET
Background: Abnormal brain tau protein accumulation is strongly linked to multiple neurodegenerative disorders. Currently, brain tau pathology is quantified in vivo using tau PET by calculating the Standardized Uptake Value Ratio (SUVR) of target and reference regions of interest (ROIs).
Recent work (Schwarz et al., 2021) in Alzheimer’s Disease (AD) explored various target and reference ROIs to report performance of SUVR as a biomarker for diagnosis, disease monitoring, and clinical trial efficacy/eligibility (sample size estimate, SSE). Here we introduce a new method and biomarker: Composite SUVR (CUVR). /
Methods: We analyzed longitudinal SUV data from ADNI in the available 103 participants having three or more tau PET scans ([18F]AV-1451): 58 cognitively normal (CN); 21 mild cognitive impairment; 24 probable AD. In the spirit of SUVR and statistical ROIs (Chen, et al., NeuroImage 2010), we calculate CUVR as the SUV ratio of two composite regions. Our novel method is that the composite regions are determined by a genetic algorithm that searches the possible 3^96 combinations of regions from FreeSurfer’s default atlas. We compare performance of SUVR with CUVR.
Performance metrics follow Schwarz et al.: a linear mixed-effects model quantifies longitudinal group separation by tau accumulation rate (t statistic between fixed effects for CN and AD) and longitudinal precision (model residuals’ standard deviation). CUVR and SUVR values were log-transformed before model fitting.
We calculated SSE for a hypothetical clinical trial designed for 80% power to reduce tau PET accumulation by 20% (vs. placebo) in non-CN individuals. /
Results: Our method identified a CUVR biomarker involving 60 regions. Figure-1 shows the vast performance improvement of CUVR versus the best-performing SUVR (inferior-temporal target; eroded subcortical white matter reference). Group separation improved by 2.9x (t = 9.57 vs 3.32); longitudinal precision by 6.5x (residual std = 0.331% vs 2.14%); and CUVR required a smaller sample size by 3.9x (83 vs 318). /
Conclusions: Our simple data-driven approach discovered a new tau PET biomarker called CUVR. Experimental results show state-of-the-art longitudinal group separation, longitudinal precision, and clinical trial enrichment. The remarkable performance improvements provide compelling evidence for using CUVR for both eligibility and efficacy in Alzheimer’s disease clinical trials, particularly of anti-tau therapies
Far Ultraviolet Spectra of B Stars near the Ecliptic
Spectra of B stars in the wavelength range of 911-1100 A have been obtained
with the EURD spectrograph onboard the Spanish satellite MINISAT-01 with ~5 A
spectral resolution. IUE spectra of the same stars have been used to normalize
Kurucz models to the distance, reddening and spectral type of the corresponding
star. The comparison of 8 main-sequence stars studied in detail (alpha Vir,
epsilon Tau, lambda Tau, tau Tau, alpha Leo, zeta Lib, theta Oph, and sigma
Sgr) shows agreement with Kurucz models, but observed fluxes are 10-40% higher
than the models in most cases. The difference in flux between observations and
models is higher in the wavelength range between Lyman alpha and Lyman beta. We
suggest that Kurucz models underestimate the FUV flux of main-sequence B stars
between these two Lyman lines. Computation of flux distributions of
line-blanketed model atmospheres including non-LTE effects suggests that this
flux underestimate could be due to departures from LTE, although other causes
cannot be ruled out. We found the common assumption of solar metallicity for
young disk stars should be made with care, since small deviations can have a
significant impact on FUV model fluxes. Two peculiar stars (rho Leo and epsilon
Aqr), and two emission line stars (epsilon Cap and pi Aqr) were also studied.
Of these, only epsilon Aqr has a flux in agreement with the models. The rest
have strong variability in the IUE range and/or uncertain reddening, which
makes the comparison with models difficult.Comment: 25 pages, 6 figures, to be published in The Astrophysical Journa
Distributional inequalities for non harmonic functions
The relationship between the non-tangential maximal function and convenient versions of the area function of a general (non harmonic) function in a upper-half space are studied
Experiments on a videotape atom chip: fragmentation and transport studies
This paper reports on experiments with ultra-cold rubidium atoms confined in
microscopic magnetic traps created using a piece of periodically-magnetized
videotape mounted on an atom chip. The roughness of the confining potential is
studied with atomic clouds at temperatures of a few microKelvin and at
distances between 30 and 80 microns from the videotape-chip surface. The
inhomogeneities in the magnetic field created by the magnetized videotape close
to the central region of the chip are characterized in this way. In addition,
we demonstrate a novel transport mechanism whereby we convey cold atoms
confined in arrays of videotape magnetic micro-traps over distances as large as
~ 1 cm parallel to the chip surface. This conveying mechanism enables us to
survey the surface of the chip and observe potential-roughness effects across
different regions.Comment: 29 pages, 22 figures
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