273 research outputs found
Custos de transação e comportamento da base para o preço do milho em Rio Verde, GO.
O objetivo deste trabalho foi analisar o comportamento da base, que é a diferença entre o preço do milho de Rio Verde, GO, e o preço futuro do milho na BM&FBovespa de 3/1/2005 até 15/3/2011. Por conseguinte, a hipótese do estudo é que os custos de transação e as características regionais da comercialização do milho fazem que ocorra elevada divergência de preços entre os mercados. O modelo autorregressivo com threshold (TAR) foi usado para captar as importantes dimensões dos custos de transação. Os resultados estimados para o parâmetro TAR de 7,78% mostram uma fraca convergência entre os preços dos mercados e, por consequência, o enfraquecimento da base na região. Isso evidencia que os produtores minimizam custos de transação regionais e, por isso, estão mais preocupados com as transações de hedging privado no mercado físico, não recorrendo à bolsa de valores para proteção contra oscilação de preços
First observational evidence of a relation between globular clusters' internal rotation and stellar masses
Several observational studies have shown that many Galactic globular clusters
(GCs) are characterised by internal rotation. Theoretical studies of the
dynamical evolution of rotating clusters have predicted that, during their
long-term evolution, these stellar systems should develop a dependence of the
rotational velocity around the cluster's centre on the mass of stars, with the
internal rotation increasing for more massive stars. In this paper we present
the first observational evidence of the predicted rotation-mass trend. In our
investigation, we exploited the Data Release 3 catalogue of
three GCs: NGC 104 (47 Tuc), NGC 5139 ( Cen) and NGC 5904 (M 5). We
found clear evidence of a cluster rotation-mass relation in 47 Tuc and M 5,
while in Cen, the dynamically youngest system among the three clusters
studied here, no such trend was detected.Comment: 6 pages, 4 figures, 1 table. Accepted for publication in MNRAS
Letter
Photometry and astrometry with JWST -- III. A NIRCam-Gaia DR3 analysis of the open cluster NGC 2506
In the third paper of this series aimed at developing the tools for analysing
resolved stellar populations using the cameras on board of the James Webb Space
Telescope (JWST), we present a detailed multi-band study of the 2 Gyr Galactic
open cluster NGC 2506. We employ public calibration data-sets collected in
multiple filters to: (i) derive improved effective Point Spread Functions
(ePSFs) for ten NIRCam filters; (ii) extract high-precision photometry and
astrometry for stars in the cluster, approaching the main-sequence (MS) lower
mass of ~0.1 Msun; and (iii) take advantage of the synergy between JWST and
Gaia DR3 to perform a comprehensive analysis of the cluster's global and local
properties. We derived a MS binary fraction of ~57.5 %, extending the Gaia
limit (~0.8 Msun) to lower masses (~0.4 Msun) with JWST. We conducted a study
on the mass functions (MFs) of NGC 2506, mapping the mass segregation with Gaia
data, and extending MFs to lower masses with the JWST field. We also combined
information on the derived MFs to infer an estimate of the cluster present-day
total mass. Lastly, we investigated the presence of white dwarfs (WDs) and
identified a strong candidate. However, to firmly establish its cluster
membership, as well as that of four other WD candidates and of the majority of
faint low-mass MS stars, further JWST equally deep observations will be
required. We make publicly available catalogues, atlases, and the improved
ePSFs.Comment: 20 pages, 17 figures (5 in low resolution), 4 tables. Accepted for
publication in MNRAS on August 5, 2023. PSF models, catalogs and stacked
images are publicly available at
https://web.oapd.inaf.it/bedin/files/PAPERs_eMATERIALs/JWST/Paper_03
Resistance Exercise Training in McArdle Disease: Myth or Reality?
McArdle disease is a metabolic myopathy mainly characterised by symptom onset during physical activities or isometric muscle
contraction. Resistance (also termed strength) training is a type of physical exercise focusing on the use of resistance (e.g., lifing
weights) to induce muscular contraction, which builds muscle mass and strength. Historically people with McArdle disease were
advised to avoid resistance exercises and any other form of physical activity involving high mechanical loads such as prolonged
isometric contraction. Paradoxically, a clinical trial exploring the benefts of strength training in this patient population was
published. Te theory supporting strength training relied on the use of the ATP molecule and the creatine phosphate (ATPphosphocreatine
system) as energy sources for skeletal muscles. Here, we report two patients with McArdle disease who performed
weight training at local gyms. A single set of repetitions lasted for maximum 10 seconds with minimum of 30 seconds of rest period
in between sets of exercises. Benefts of this type of training included improvement in quality of life and amelioration of McArdle
disease symptoms. We provide further safety evidence of this type of exercise in people with McArdle disease. We emphasise the
importance of using a specifc protocol developed for people afected by this condition
Rhabdomyolysis: a genetic perspective
Rhabdomyolysis (RM) is a clinical emergency characterized by fulminant skeletal muscle damage and release of intracellular muscle components into the blood stream leading to myoglobinuria and, in severe cases, acute renal failure. Apart from trauma, a wide range of causes have been reported including drug abuse and infections. Underlying genetic disorders are also a cause of RM and can often pose a diagnostic challenge, considering their marked heterogeneity and comparative rarity.In this paper we review the range of rare genetic defects known to be associated with RM. Each gene has been reviewed for the following: clinical phenotype, typical triggers for RM and recommended diagnostic approach. The purpose of this review is to highlight the most important features associated with specific genetic defects in order to aid the diagnosis of patients presenting with hereditary causes of recurrent RM
The Large Programme on NGC6752 -- V. Differences in Luminosity and Mass Functions among Multiple Stellar Populations
We exploit the astro-photometric dataset of the multi-epoch infrared parallel
field of a Large Programme aimed at studying
the faintest stars of the globular cluster NGC6752 to determine the
luminosity and mass functions of the multiple stellar populations of this
cluster. Thanks to the measurement of proper motions and deeper completeness,
the results presented in this paper represent a significant improvement over
those of previous studies. We successfully derived membership probabilities
reaching stars as faint as , allowing us to reliably
distinguish the three main stellar populations detected within this cluster. We
employed a new set of model isochrones that have been individually fit to the
colour-magnitude diagram of each population. We present a comprehensive
analysis of the luminosity and mass functions for three stellar populations
within NGC6752. Notably, our findings reveal differences in the present-day
luminosity and mass functions of first-generation and second-generation stars;
these differences are consistent with the manifestation of the effects of
dynamical processes acting on populations with different initial spatial
distributions. Finally, we publicly release the catalogues with positions,
photometry, proper motions, and memberships probabilities, as well as the
stacked-image atlases and all newly calculated stellar models.Comment: 25 pages, 17 figures, 5 tables. Accepted for publication in A
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