58 research outputs found
Quantitative and qualitative differences in subcutaneous adipose tissue stores across lipodystrophy types shown by magnetic resonance imaging
BACKGROUND: Lipodystrophies are characterized by redistributed subcutaneous fat stores. We previously quantified subcutaneous fat by magnetic resonance imaging (MRI) in the legs of two patients with familial partial lipodystrophy subtypes 2 and 3 (FPLD2 and FPLD3, respectively). We now extend the MRI analysis across the whole body of patients with different forms of lipodystrophy. METHODS: We studied five subcutaneous fat stores (supraclavicular, abdominal, gluteal, thigh and calf) and the abdominal visceral fat stores in 10, 2, 1, 1 and 2 female subjects with, respectively, FPLD2, FPLD3, HIV-related partial lipodystrophy (HIVPL), acquired partial lipodystrophy (APL), congenital generalized lipodystrophy (CGL) and in six normal control subjects. RESULTS: Compared with normal controls, FPLD2 subjects had significantly increased supraclavicular fat, with decreased abdominal, gluteal, thigh and calf subcutaneous fat. FPLD3 subjects had increased supraclavicular and abdominal subcutaneous fat, with less severe reductions in gluteal, thigh and calf fat compared to FPLD2 subjects. The repartitioning of fat in the HIVPL subject closely resembled that of FPLD3 subjects. APL and CGL subjects had reduced upper body, gluteal and thigh subcutaneous fat; the APL subject had increased, while CGL subjects had decreased subcutaneous calf fat. Visceral fat was markedly increased in FPLD2 and APL subjects. CONCLUSION: Semi-automated MRI-based adipose tissue quantification indicates differences between various lipodystrophy types in these studied clinical cases and is a potentially useful tool for extended quantitative phenomic analysis of genetic metabolic disorders. Further studies with a larger sample size are essential for confirming these preliminary findings
Phonons in a one-dimensional microfluidic crystal
The development of a general theoretical framework for describing the
behaviour of a crystal driven far from equilibrium has proved difficult1.
Microfluidic crystals, formed by the introduction of droplets of immiscible
fluid into a liquid-filled channel, provide a convenient means to explore and
develop models to describe non-equilibrium dynamics2, 3, 4, 5, 6, 7, 8, 9, 10,
11. Owing to the fact that these systems operate at low Reynolds number (Re),
in which viscous dissipation of energy dominates inertial effects, vibrations
are expected to be over-damped and contribute little to their dynamics12, 13,
14. Against such expectations, we report the emergence of collective normal
vibrational modes (equivalent to acoustic 'phonons') in a one-dimensional
microfluidic crystal of water-in-oil droplets at Reapprox10-4. These phonons
propagate at an ultra-low sound velocity of approx100 mum s-1 and frequencies
of a few hertz, exhibit unusual dispersion relations markedly different to
those of harmonic crystals, and give rise to a variety of crystal instabilities
that could have implications for the design of commercial microfluidic systems.
First-principles theory shows that these phonons are an outcome of the
symmetry-breaking flow field that induces long-range inter-droplet
interactions, similar in nature to those observed in many other systems
including dusty plasma crystals15, 16, vortices in superconductors17, 18,
active membranes19 and nucleoprotein filaments20.Comment: https://www.weizmann.ac.il/complex/tlusty/papers/NaturePhys2006.pd
Superfluid transport of information in turning flocks of starlings
Collective decision-making in biological systems requires all individuals in
the group to go through a behavioural change of state. During this transition,
the efficiency of information transport is a key factor to prevent cohesion
loss and preserve robustness. The precise mechanism by which natural groups
achieve such efficiency, though, is currently not fully understood. Here, we
present an experimental study of starling flocks performing collective turns in
the field. We find that the information to change direction propagates across
the flock linearly in time with negligible attenuation, hence keeping group
decoherence to a minimum. This result contrasts with current theories of
collective motion, which predict a slower and dissipative transport of
directional information. We propose a novel theory whose cornerstone is the
existence of a conserved spin current generated by the gauge symmetry of the
system. The theory turns out to be mathematically identical to that of
superfluid transport in liquid helium and it explains the dissipationless
propagating mode observed in turning flocks. Superfluidity also provides a
quantitative expression for the speed of propagation of the information,
according to which transport must be swifter the stronger the group's
orientational order. This prediction is verified by the data. We argue that the
link between strong order and efficient decision-making required by
superfluidity may be the adaptive drive for the high degree of behavioural
polarization observed in many living groups. The mathematical equivalence
between superfluid liquids and turning flocks is a compelling demonstration of
the far-reaching consequences of symmetry and conservation laws across
different natural systems
Predicting youth participation in urban agriculture in Malaysia: insights from the theory of planned behavior and the functional approach to volunteer motivation
This study examines factors associated with the decision of Malaysian youth to participate in a voluntary urban agriculture program. Urban agriculture has generated significant interest in developing countries to address concerns over food security, growing urbanization and employment. While an abundance of data shows attracting the participation of young people in traditional agriculture has become a challenge for many countries, few empirical studies have been conducted on youth motivation to participate in urban agriculture programs, particularly in non-Western settings. Drawing on the theories of planned behavior and the functional approach to volunteer motivation, we surveyed 890 students from a public university in Malaysia about their intention to join a new urban agriculture program. Hierarchical regression findings indicated that the strongest predictor of participation was students’ attitude toward urban agriculture, followed by subjective norms, career motives and perceived barriers to participation. The findings from this study may provide useful information to the university program planners in Malaysia in identifying mechanisms for future students’ involvement in the program
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