31 research outputs found
Minkowski Tensors of Anisotropic Spatial Structure
This article describes the theoretical foundation of and explicit algorithms
for a novel approach to morphology and anisotropy analysis of complex spatial
structure using tensor-valued Minkowski functionals, the so-called Minkowski
tensors. Minkowski tensors are generalisations of the well-known scalar
Minkowski functionals and are explicitly sensitive to anisotropic aspects of
morphology, relevant for example for elastic moduli or permeability of
microstructured materials. Here we derive explicit linear-time algorithms to
compute these tensorial measures for three-dimensional shapes. These apply to
representations of any object that can be represented by a triangulation of its
bounding surface; their application is illustrated for the polyhedral Voronoi
cellular complexes of jammed sphere configurations, and for triangulations of a
biopolymer fibre network obtained by confocal microscopy. The article further
bridges the substantial notational and conceptual gap between the different but
equivalent approaches to scalar or tensorial Minkowski functionals in
mathematics and in physics, hence making the mathematical measure theoretic
method more readily accessible for future application in the physical sciences
Generic Escherichia coli Contamination of Spinach at the Preharvest Stage: Effects of Farm Management and Environmental Factors
The objective of this study was to determine the effects of farm management and environmental factors on preharvest spinach contamination with generic Escherichia coli as an indicator of fecal contamination. A repeated cross-sectional study was conducted by visiting spinach farms up to four times per growing season over a period of 2 years (2010 to 2011). Spinach samples (n = 955) were collected from 12 spinach farms in Colorado and Texas as representative states of the Western and Southwestern United States, respectively. During each farm visit, farmers were surveyed about farm-related management and environmental factors using a questionnaire. Associations between the prevalence of generic E. coli in spinach and farm-related factors were assessed by using a multivariable logistic regression model including random effects for farm and farm visit. Overall, 6.6% of spinach samples were positive for generic E. coli. Significant risk factors for spinach contamination with generic E. coli were the proximity (within 10 miles) of a poultry farm, the use of pond water for irrigation, a >66-day period since the planting of spinach, farming on fields previously used for grazing, the production of hay before spinach planting, and the farm location in the Southwestern United States. Contamination with generic E. coli was significantly reduced with an irrigation lapse time of >5 days as well as by several factors related to field workers, including the use of portable toilets, training to use portable toilets, and the use of hand-washing stations. To our knowledge, this is the first report of an association between field workers' personal hygiene and produce contamination with generic E. coli at the preharvest level. Collectively, our findings support that practice of good personal hygiene and other good farm management practices may reduce produce contamination with generic E. coli at the preharvest level
Disposable Microfluidic Immunoarray Device for Sensitive Breast Cancer Biomarker Detection
Breast
cancer is the most common cancer in women worldwide. The detection
of biomarkers has played a significant role in the early diagnosis
and prognosis of breast cancer. Herein, we describe the construction
of a disposable microfluidic immunoarray device (DμID) for the
rapid and low-cost detection of CA15-3 (carbohydrate antigen 15-3),
a protein biomarker for breast cancer. The DμID was constructed
using a simple and rapid prototyping technique and was applied to
detect CA15-3 in cancer patients. The DμID construction was
based on the use of a double-sided adhesive card with a microfluidic
channel and a screen-printed array with 8 electrodes. Both the immunoarray
and microfluidic channel were designed using an inexpensive home cutter
printer and using low-cost materials. The immunoarray was modified
using the layer-by-layer technique aiming at immobilizing the primary
antibody. For the biomarker detection, magnetic particles (MPs) modified
with polyclonal antibodies and peroxidase enzymes were used as a strategy
for capture, separation, and preconcentration of the biomarker, in
addition to amplification of the electroanalytical signal. The preconcentration
and amplification strategies integrated with the nanostructured immunosensors
of the DμID meaningfully contributed toward the detection of
CA15-3 with a limit of detection (LoD) of 6 μU mL<sup>–1</sup>, requiring as low as 2 μL of serum samples for 8 simultaneous
detections. The obtained LoD was 1200 times lower compared to those
of other immunosensors previously reported in the literature. The
DμID was applied for the detection of CA15-3 in real samples
of breast cancer patients and was found to present an excellent correlation
with the well-established commercial electrochemiluminescence immunoassay.
The association of the DμID with nanostructured surfaces and
analyte capturing with bioconjugated paramagnetic particles is essentially
a promising breakthrough for the low-cost and accurate detection of
cancer biomarkers