3,910 research outputs found
The Minkowski metric in non-inertial observer radar coordinates
We give a closed expression for the Minkowski (1+1)-dimensional metric in the
radar coordinates of an arbitrary non-inertial observer O in terms of O's
proper acceleration. Knowledge of the metric allows the non-inertial observer
to perform experiments in spacetime without making reference to inertial
frames. To clarify the relation between inertial and non-inertial observers the
coordinate transformation between radar and inertial coordinates, also is
given. We show that every conformally flat coordinate system can be regarded as
the radar coordinate system of a suitable observer for a suitable
parametrization of the observer worldline. Therefore, the coordinate
transformation between arbitrarily moving observers is a conformal
transformation and conformally invariant (1+1)-dimensional theories lead to the
same physics for all observers, independently of their relative motion.Comment: Revtex4, 6 pages, 1 figur
Frequency and Circadian Timing of Eating May Influence Biomarkers of Inflammation and Insulin Resistance Associated with Breast Cancer Risk.
Emerging evidence suggests that there is interplay between the frequency and circadian timing of eating and metabolic health. We examined the associations of eating frequency and timing with metabolic and inflammatory biomarkers putatively associated with breast cancer risk in women participating in the National Health and Nutrition Examination 2009-2010 Survey. Eating frequency and timing variables were calculated from 24-hour food records and included (1) proportion of calories consumed in the evening (5 pm-midnight), (2) number of eating episodes per day, and (3) nighttime fasting duration. Linear regression models examined each eating frequency and timing exposure variable with C-reactive protein (CRP) concentrations and the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Each 10 percent increase in the proportion of calories consumed in the evening was associated with a 3 percent increase in CRP. Conversely, eating one additional meal or snack per day was associated with an 8 percent reduction in CRP. There was a significant interaction between proportion of calories consumed in the evening and fasting duration with CRP (p = 0.02). A longer nighttime fasting duration was associated with an 8 percent lower CRP only among women who ate less than 30% of their total daily calories in the evening (p = 0.01). None of the eating frequency and timing variables were significantly associated with HOMA-IR. These findings suggest that eating more frequently, reducing evening energy intake, and fasting for longer nightly intervals may lower systemic inflammation and subsequently reduce breast cancer risk. Randomized trials are needed to validate these associations
Loss of redundant gene expression after polyploidization in plants
Based on chromosomal location data of genes encoding 28 biochemical systems in allohexaploid wheat,Triticum aestivum L. (genomes AABBDD), it is concluded that the proportions of systems controlled by triplicate, duplicate, and single loci are 57%, 25%, and 18% respectively
An analytic expression for the electronic correlation term of the kinetic functional
We propose an analytic formula for the non-local Fisher information
functional, or electronic kinetic correlation term, appearing in the expression
of the kinetic density functional. Such an explicit formula is constructed on
the basis of well-founded physical arguments and a rigorous mathematical
prescription
Wrist-worn physical activity trackers progressively underestimate steps with increasing walking speeds
Model Reactions Involving Ester Functional Groups during ThermoâOxidative Degradation of Biodiesel
Biodiesel is a renewable fuel used in diesel engines that is typically blended with diesel fuel. However, biodiesel is susceptible to oxidation, which has the potential to produce higher molecular weight materials that may adversely impact vehicle fuelâsystem performance. To investigate the chemical reactions potentially important in biodiesel oxidation, four different types of chemical reactions involving esters were studied: (1) ester formation (reactions of acids with alcohols), (2) alcoholysis (reactions of alcohols with esters), (3) acidolysis (reaction of acids with esters), and (4) ester exchange (reactions between two esters). Experiments with representative model compounds were used to evaluate these reactions at 90â°C with aeration; conditions previously used to simulate thermoâoxidative degradation during biodiesel aging. Reactions were monitored using gas chromatography, fourier transform infrared (FTIR) spectroscopy, and total acid number (TAN). Evidence is presented suggesting that alcoholysis and ester formation (Reactions 1 and 2), catalyzed by carboxylic acids, are important reactions of esters that could lead to larger molecules. Acidolysis (Reaction 3) proceeded at a comparatively slow rate and ester exchange reaction products (Reaction 4) were not detected under these aging conditions.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151841/1/aocs12277_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151841/2/aocs12277.pd
Development Of Core Ion Temperature Gradients And Edge Sheared Flows In A Helicon Plasma Device Investigated By Laser Induced Fluorescence Measurements
- âŠ