ABSTRACT
PURPOSE: We have previously observed substantially higher oxygen uptake in soldiers walking on terrain at night than when performing the same walk in bright daylight. The aims of the present study were to investigate the influence of vision on mechanical efficiency during slow, horizontal, constant-speed walking, and to determine whether any vision influence is modified by load carriage. METHODS: Each subject (n = 15) walked (3.3 km/h) for 10 min on a treadmill in four different conditions: (1) full vision, no carried load, (2) no vision, no carried load, (3) full vision with a 25.5-kg rucksack, (4) no vision with a 25.5-kg rucksack. RESULTS: Oxygen uptake was 0.94 ± 0.12 l/min in condition (1), 1.15 ± 0.20 l/min in (2), 1.15 ± 0.12 l/min in (3) and 1.35 ± 0.19 l/min in (4). Thus, lack of vision increased oxygen uptake by about 19%. Analyses of movement pattern, by use of optical markers attached to the limbs and torso, revealed considerably shorter step length (12 and 10%) in the no vision (2 and 4) than full vision conditions (1 and 3). No vision conditions (2 and 4) increased step width by 6 and 6%, and increased vertical foot clearance by 20 and 16% compared to full vision conditions (1 and 3). CONCLUSION: The results suggest that vision has a marked influence on mechanical efficiency even during entrained, repetitive movements performed on an obstacle-free horizontal surface under highly predictable conditions.
Subject(s)
Energy Metabolism , Walking , Biomechanical Phenomena , Exercise Test , Gait , Humans , OxygenABSTRACT
Recent developments in string compactifications demonstrate obstructions to the simplest constructions of low energy cosmologies with positive vacuum energy. The existence of obstacles to creating scale-separated de Sitter solutions indicates a UV/IR puzzle for embedding cosmological vacua in a unitary theory of quantum gravity. Motivated by this puzzle, we propose an embedding of positive energy Friedmann-Lemaître-Robertson-Walker cosmology within string theory. Our proposal involves confining 4D gravity on a brane which mediates the decay from a nonsupersymmetric five-dimensional anti-de Sitter false vacuum to a true vacuum. In this way, it is natural for a 4D observer to experience an effective positive cosmological constant coupled to matter and radiation, avoiding the need for scale separation or a fundamental de Sitter vacuum.
ABSTRACT
We combine the principle of gauge invariance with extrinsic string geometry to develop a lattice model that can be employed to theoretically describe properties of chiral, unbranched homopolymers. We find that in its low temperature phase the model is in the same universality class with proteins that are deposited in the Protein Data Bank, in the sense of the compactness index. We apply the model to analyze various statistical aspects of folded proteins. Curiously we find that it can produce results that are a very good good match to the data in the Protein Data Bank.
Subject(s)
Models, Chemical , Models, Molecular , Polymers/chemistry , Proteins/chemistry , Proteins/ultrastructure , Computer Simulation , Protein Conformation , Protein FoldingABSTRACT
A chemical warfare (CW) protective bag for babies, younger than 1 year, has been evaluated in respect of thermal load. Heat and water vapour dissipating from the baby make the climate in the protective bag more demanding than outside. The thermal strain on a baby was estimated from heat and mass transfer data using an electrically heated baby manikin and a water-filled tray. Furthermore, a theoretical baby model was developed based on relations valid for heat and mass transfer rates from a cylinder and flat surface. Convective and radiative (dry) and evaporative heat transfer coefficients calculated from this model agreed well with the measured values. The maximum heat dissipation from a baby was calculated for combinations of air temperatures (22-30 degrees C) and relative humidities (70-90% rh). The results indicate that a naked baby can dissipate about 100% more heat than is produced during basal conditions when the bag is ventilated (70 1 min(-1)) and the ambient climate is 30 degrees C and 90% rh. If the ventilation rate is 40 1 min(-1), the margin is reduced to 50%. Clothing reduces the margin further. Ventilating the bag with 70 1 min(-1), a dressed baby can dissipate only 10-20% more heat than is produced during basal conditions in a climate (27 degrees C and 80% rh) that is obtained in a crowded shelter after about 24 h of occupation.
