14,444 research outputs found
Cold quarks in medium: an equation of state
We derive a compact, semi-algebraic expression for the cold quark matter
equation of state (EoS) in a covariant model that exhibits coincident
deconfinement and chiral symmetry restoring transitions in-medium. Along the
way we obtain algebraic expressions for: the number- and scalar-density
distributions in both the confining Nambu and deconfined Wigner phases; and the
vacuum-pressure difference between these phases, which defines a bag constant.
The confining interaction materially alters the distribution functions from
those of a Fermi gas and consequently has a significant impact on the model's
thermodynamic properties, which is apparent in the EoS.Comment: 5 pages, 5 figure
On the Rozansky-Witten weight systems
Ideas of Rozansky and Witten, as developed by Kapranov, show that a complex
symplectic manifold X gives rise to Vassiliev weight systems. In this paper we
study these weight systems by using D(X), the derived category of coherent
sheaves on X. The main idea (stated here a little imprecisely) is that D(X) is
the category of modules over the shifted tangent sheaf, which is a Lie algebra
object in D(X); the weight systems then arise from this Lie algebra in a
standard way. The other main results are a description of the symmetric
algebra, universal enveloping algebra, and Duflo isomorphism in this context,
and the fact that a slight modification of D(X) has the structure of a braided
ribbon category, which gives another way to look at the associated invariants
of links. Our original motivation for this work was to try to gain insight into
the Jacobi diagram algebras used in Vassiliev theory by looking at them in a
new light, but there are other potential applications, in particular to the
rigorous construction of the (1+1+1)-dimensional Rozansky-Witten TQFT, and to
hyperkaehler geometry
The effect of a decaffeinated green tea extract formula on fat oxidation, body composition and exercise performance
Background:
The cardio-metabolic and antioxidant health benefits of caffeinated green tea (GT) relate to its catechin polyphenol content. Less is known about decaffeinated extracts, particularly in combination with exercise. The aim of this study was therefore to determine whether a decaffeinated green tea extract (dGTE) positively influenced fat oxidation, body composition and exercise performance in recreationally active participants.
Methods:
Fourteen, recreationally active males participated in a double-blind, placebo-controlled, parallel design intervention (mean±SE; age = 21.4±0.3 yrs; weight = 76.37±1.73 kg; body fat = 16.84±0.97 %, peak oxygen consumption [V̇O2peak] = 3.00±0.10 L·min-1). Participants were randomly assigned capsulated dGTE (571 mg·d-1; n=7) or placebo (PL; n=7) for 4 weeks. Following body composition and resting cardiovascular measures, participants cycled for 1 hour at 50% V̇O2peak, followed by a 40 minute performance trial at week 0, 2 and 4. Fat and carbohydrate oxidation was assessed via indirect calorimetry. Pre-post exercise blood samples were collected for determination of total fatty acids (TFA). Distance covered (km) and average power output (W) were assessed as exercise performance criteria.
Results:
Total fat oxidation rates increased by 24.9 % from 0.241±0.025 to 0.301±0.009 g·min-1 with dGTE (P=0.05; ηp2 = 0.45) by week 4, whereas substrate utilisation was unaltered with PL. Body fat significantly decreased with dGTE by 1.63±0.16 % in contrast to PL over the intervention period (P<0.001; ηp2 = 0.84). No significant changes for FFA or blood pressure between groups were observed. dGTE resulted in a 10.9 % improvement in performance distance covered from 20.23±0.54 km to 22.43 ± 0.40 km by week 4 (P<0.001; ηp2 = 0.85).
Conclusions:
A 4 week dGTE intervention favourably enhanced substrate utilisation and subsequent performance indices, but did not alter TFA concentrations in comparison to PL. The results support the use of catechin polyphenols from dGTE in combination with exercise training in recreationally active volunteers
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