Search results for "artifacts"
showing 10 items of 105 documents
Potential pitfalls in fetal neurosonography
2005
Objective To present anatomic variants of the fetal brain and artifacts related to scanning techniques that could be misinterpreted as abnormalities on prenatal neurosonographic studies. Methods The findings were derived from fetal neurosonographic studies performed routinely from 16 to 36 weeks' gestation during the last 3 years, supervised by a sonologist specialized in neonatal cranial sonography. Results The pitfalls were divided into three groups: brain parenchyma, ventricular system and choroid plexus. We provide images of these pseudolesions and clues to their differentiation from true brain pathology. Conclusions Knowledge of misleading images seen on fetal neurosonographic studies …
Stones, Bones, and Hillfort: Radiocarbon Dating of Ķivutkalns Bronze-Working Center
2013
The Bronze Age site of ķivutkalns with its massive amount of archaeological artifacts and human remains is considered the largest bronze-working center in Latvia. The site is a unique combination of cemetery and hillfort believed to be built on top of each other. This work presents new radiocarbon dates on human and animal bone collagen that somewhat challenge this interpretation. Based on analyses using a Bayesian modeling framework, the present data suggest overlapping calendar year distributions for the contexts within the 1st millennium BC. The carbon and nitrogen isotopic ratios indicate mainly terrestrial dietary habits of studied individuals and nuclear family remains buried in one o…
Poggetti Vecchi (Tuscany, Italy): A late Middle Pleistocene case of human-elephant interaction
2019
Abstract A paleosurface with a concentration of wooden-, bone-, and stone-tools interspersed among an accumulation of fossil bones, largely belonging to the straight-tusked elephant Palaeoloxodon antiquus, was found at the bottom of a pool, fed by hot springs, that was excavated at Poggetti Vecchi, near Grosseto (Tuscany, Italy). The site is radiometrically dated to the late Middle Pleistocene, around 171,000 years BP. Notable is the association of the artifacts with the elephant bones, and in particular the presence of digging sticks made from boxwood (Buxus sp.). Although stone tools show evidence of use mainly on animal tissues, indicating some form of interaction between hominins and an…
Modified electrocardiograph-triggered black-blood turbo spin-echo technique to improve T1-weighting in contrast-enhanced MRI of atherosclerotic carot…
2008
Purpose To assess the efficacy of a modified electrocardiograph (EKG)-triggered black-blood T1W (T1W) spin-echo sequence in improving contrast on post-gadolinium high-resolution carotid plaque imaging by implementing heart-rate–independent contrast preparation. Materials and Methods We used a standard EKG-triggered double inversion-recovery (DIR) turbo spin-echo (TSE) sequence modified with the addition of an extra saturation (90°) radio frequency (RF) pulse placed immediately after the DIR module, shortening the repetition time to a fixed value of 400 msec. A total of 10 patients with atherosclerotic disease were included in the study. Postinjection intraplaque contrast measurements were p…
Zinc isotope variations in archeological human teeth (Lapa do Santo, Brazil) reveal dietary transitions in childhood and no contamination from gloves
2020
International audience; Zinc (Zn) isotope ratios of dental enamel are a promising tracer for dietary reconstruction in archeology, but its use is still in its infancy. A recent study demonstrated a high risk of Zn contamination from nitrile, and latex gloves used during chemical sample preparation. Here we assess the potential impact of the use of such gloves during enamel sampling on the Zn isotope composition of teeth from a population of early Holocene hunter gatherers from Lapa do Santo, Lagoa Santa, Minas Gerais, Brazil. We first examined the amount of Zn and its isotopic composition released from the gloves used in this study by soaking them in weak nitric acid and water. We compared …
Power estimation for non-standardized multisite studies
2016
A concern for researchers planning multisite studies is that scanner and T1-weighted sequence-related biases on regional volumes could overshadow true effects, especially for studies with a heterogeneous set of scanners and sequences. Current approaches attempt to harmonize data by standardizing hardware, pulse sequences, and protocols, or by calibrating across sites using phantom-based corrections to ensure the same raw image intensities. We propose to avoid harmonization and phantom-based correction entirely. We hypothesized that the bias of estimated regional volumes is scaled between sites due to the contrast and gradient distortion differences between scanners and sequences. Given this…
Tractional Motion Machines: Tangent-Managing Planar Mechanisms as Analog Computers and Educational Artifacts
2012
Concrete and virtual machines play a central role in the both Unconventional Computing (machines as computers) and in Math Education (influence of artifacts on reaching/producing abstract thought). Here we will examine some fallouts in these fields for the Tractional Motion Machines, planar mechanisms based on some devices used to plot the solutions of differential equations by the management of the tangent since the late 17th century.
Characterization of entropy measures against data loss: Application to EEG records
2012
This study is aimed at characterizing three signal entropy measures, Approximate Entropy (ApEn), Sample Entropy (SampEn) and Multiscale Entropy (MSE) over real EEG signals when a number of samples are randomly lost due to, for example, wireless data transmission. The experimental EEG database comprises two main signal groups: control EEGs and epileptic EEGs. Results show that both SampEn and ApEn enable a clear distinction between control and epileptic signals, but SampEn shows a more robust performance over a wide range of sample loss ratios. MSE exhibits a poor behavior for ratios over a 40% of sample loss. The EEG non-stationary and random trends are kept even when a great number of samp…
Bias artifact suppression on MR volumes.
2007
RF-Inhomogeneity correction is a relevant research topic in the field of Magnetic Resonance Imaging (MRI). A volume corrupted by this artifact exhibits nonuni- form illumination both inside a single slice and between adjacent ones. In this work a bias correction technique is presented, which suppresses this artifact on MR vol- umes scanned from different body parts without any a-priori hypothesis on the artifact model. Theoretical foundations of the method are reported together with experimental results and a comparison is presented with both the 2D version of the algorithm and other techniques that are widely used in MRI literature.
Genotoxicity investigations on nanomaterials: methods, preparation and characterization of test material, potential artifacts and limitations--many q…
2008
Nanomaterials display novel properties to which most toxicologists have not consciously been exposed before the advent of their practical use. The same properties, small size and particular shape, large surface area and surface activity, which make nanomaterials attractive in many applications, may contribute to their toxicological profile. This review describes what is known about genotoxicity investigations on nanomaterials published in the openly available scientific literature to-date. The most frequently used test was the Comet assay: 19 studies, 14 with positive outcome. The second most frequently used test was the micronucleus test: 14 studies, 12 of them with positive outcome. The A…