7 research outputs found
Effects of p-Synephrine during Exercise: A Brief Narrative Review
p-Synephrine is the principal phytochemical found in bitter orange (Citrus aurantium). This substance is widely included in dietary supplements for weight loss/body fat reduction due to its potential benefits of increasing fat oxidation. For years, p-synephrine-containing dietary supplements have been marketed without proper knowledge of their true effectiveness to enhance fat utilization, especially when combined with exercise. However, the effects of p-synephrine on fat oxidation during exercise have been investigated in the last few years. The aim of the current discussion is to summarize the evidence on the effects of p-synephrine intake on fat oxidation and performance during exercise. Previous investigations have demonstrated that the acute intake of p-synephrine does not modify running sprint performance, jumping capacity, or aerobic capacity. However, the acute intake of p-synephrine, in a dose of 2–3 mg/kg of body mass, has been effective to enhance the rate of fat oxidation during incremental and continuous exercise. This effect has been observed in a range of exercise workloads between 30% and 80% of VO2peak. p-Synephrine has the ability to increase the maximal rate of fat oxidation during exercise of increasing intensity without affecting the workload at which maximal fat oxidation is obtained (Fatmax). The effect of p-synephrine of fat oxidation is normally accompanied by a concomitant reduction of carbohydrate utilization during exercise, without modifying the energy expended during exercise. The shifting in substrate oxidation is obtained without any effect on heart rate during exercise and the prevalence of adverse effects is negligible. Thus, the acute use of p-synephrine, or p-synephrine containing products, might offer some benefits for those individuals seeking higher fat utilisation during exercise at low-to-moderate intensities. However, more research is still necessary to determine if the effect of p-synephrine on fat oxidation during exercise is maintained with chronic ingestion, in order to ascertain the utility of this substance in conjunction with exercise pro-grammes to produce an effective body fat/weight loss reduction
A self-consistent stellar and 3D nebular model for Planetary Nebula IC418
We present a coherent stellar and nebular model reproducing the observations
of the Planetary Nebula IC418. We want to test whether a stellar model obtained
by fitting the stellar observations is able to satisfactory ionize the nebula
and reproduce the nebular observations, which is by no mean evident. This
allows us to determine all the physical parameters of both the star and the
nebula, including the abundances and the distance. We used all the
observational material available (FUSE, IUE, STIS and optical spectra) to
constrain the stellar atmosphere model performed using the CMFGEN code. The
photoionization model is done with Cloudy_3D, and is based on CTIO, Lick, SPM,
IUE and ISO spectra as well as HST images. More than 140 nebular emission lines
are compared to the observed intensities. We reproduce all the observations for
the star and the nebula. The 3D morphology of the gas distribution is
determined. The effective temperature of the star is 36.7kK. Its luminosity is
7700 solar luminosity. We describe an original method to determine the distance
of the nebula using evolutionary tracks. No clumping factor is need to
reproduce the age-luminosity relation. The distance of 1.25 kpc is found in
very good agreement with recent determination using parallax method. The
chemical composition of both the star and the nebula are determined. Both are
Carbon-rich. The nebula presents evidence of depletion of elements Mg, Si, S,
Cl (0.5 dex lower than solar) and Fe (2.9 dex lower than solar). This is the
first self-consistent stellar and nebular model for a Planetary Nebula that
reproduces all the available observations ranging from IR to UV, showing that
the combined approach for the modeling process leads to more restrictive
constraints and, in principle, more trustworthy results.Comment: Accepted for publication in Astronomy and Astrophysics. V2: after
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