2,070 research outputs found
Low Levels of Physical Activity Increase Metabolic Responsiveness to Cold in a Rat (Rattus fuscipes)
Physical activity modulates expression of metabolic genes and may therefore be a prerequisite for metabolic responses to environmental stimuli. However, the extent to which exercise interacts with environmental conditions to modulate metabolism is unresolved. Hence, we tested the hypothesis that even low levels of physical activity are beneficial by improving metabolic responsiveness to temperatures below the thermal neutral zone, thereby increasing the capacity for substrate oxidation and energy expenditure.We used wild rats (Rattus fuscipes) to avoid potential effects of breeding on physiological phenotypes. Exercise acclimation (for 30 min/day on 5 days/week for 30 days at 60% of maximal performance) at 22°C increased mRNA concentrations of PGC1α, PPARδ, and NRF-1 in skeletal muscle and brown adipose tissue compared to sedentary animals. Lowering ambient temperature to 12°C caused further increases in relative expression of NRF-1 in skeletal muscle, and of PPARδ of brown adipose tissue. Surprisingly, relative expression of UCP1 increased only when both exercise and cold stimuli were present. Importantly, in sedentary animals cold acclimation (12°C) alone did not change any of the above variables. Similarly, cold alone did not increase maximum capacity for substrate oxidation in mitochondria (cytochrome c oxidase and citrate synthase activities) of either muscle or brown adipose tissue. Animals that exercised regularly had higher exercise induced metabolic rates in colder environments than sedentary rats, and temperature induced metabolic scope was greater in exercised rats.Physical activity is a necessary prerequisite for the expression of transcriptional regulators that influence a broad range of physiological functions from energy metabolism to cardiovascular function and nutrient uptake. A sedentary lifestyle leads to decreased daily energy expenditure because of a lack of direct use of energy and a muted metabolic response to ambient temperature, which can be reversed even by low levels of physical activity
Risk factors and costs of hospital admissions in first year of life: a population based study
Normalização do artigo cientĂfico agrĂcola.
bitstream/item/150979/1/NORMALIZ-ARTIGO-CIENTIFICO-AGRICOLA.pd
Bibliografia de solos.
Conceituação geral dos solos. FĂsica do solo. QuĂmica do solo. Biologia do solo. Fertilidade e fertilizantes do solo. Levantamento do solo. Conservação do solo. Solos de floresta. Mineralogia do solo. Localidades geográficas. Culturas. Economica. MĂ©todos analĂticos. Aerofotogrametria, fotointerpretação e cartografia. Instrumentos e equipamentos.bitstream/item/146139/1/BIBLIOGRAFIA-DE-SOLOS-.pd
Scaling Law for Criticality Conditions in Heterogeneous Energetic Materials under Shock Loading
Initiation in heterogeneous energetic material (HEM) subjected to shock
loading occurs due to the formation of hot spots. The criticality of the hot
spots governs the initiation and sensitivity of HEMs. In porous energetic
materials, collapse of pores under impact leads to the formation of hot spots.
Depending on the size and strength of the hot spots chemical reaction can
initiate. The criticality of the hot spots is dependent on the imposed shock
load, void morphology and the type of energetic material. This work evaluates
the relative importance of material constitutive and reactive properties on the
criticality condition of spots. Using a scaling-based approach, the criticality
criterion for cylindrical voids as a function of shock pressure, Ps and void
diameter, Dvoid is obtained for two different energetic material HMX and TATB.
It is shown that the criticality of different energetic materials is
significantly dependent on their reactive properties
- …