Background:In Xuanwei County, Yunnan Province, China, lung cancer mortality rates in both males and females are among the highest in China.Methods:We evaluated differential effects of smoking on lung cancer mortality before and after household stove improvement with chimney to reduce exposure to smoky coal emissions in the unique cohort in Xuanwei, China. Effects of independent variables on lung cancer mortality were measured as hazard ratios and 95% confidence intervals using a multivariable Cox regression model that included separate time-dependent variables for smoking duration (years) before and after stove improvement.Results and conclusion:We found that the effect of smoking on lung cancer risk becomes considerably stronger after chimney installation and consequent reduction of indoor coal smoke exposure.
In the quest to develop ultrafine-grained ferrite steels, an external stress is often applied to control the austenite-to-ferrite transformation kinetics. To understand the role of an applied stress in diffusional ferrite nucleation, a micromechanics analysis was performed. It is well known that the austenite-to-ferrite transition is accompanied by a volume increase of up to 9% at absolute zero. The calculation due to the volume change alone shows that a coherent ferrite particle has less strain energy in the NishiyamaWasserman (NW) orientation than in the Kurdjumov-Sachs (KS) orientation, and preferred shapes of NW-oriented particles are disk-like, acicular, and spherical in the order. When an applied elastic stress is introduced, two interaction terms arise. The first one is an inhomogeneity term due to the difference in elastic constants between fcc and bcc Fe, and the other is an interaction term between the volume change and the applied stress. The interesting feature of the austenite elastic constants -high bulk modulus but soft shear modulus -combined with the strong elastic anisotropy of ferrite, reveals the diverse influence of applied stress upon the energetics of ferrite formation. In certain applied stress modes, both inhomogeneity and interaction energy terms are found to lower the free energy associated with the ferrite particle, promoting enhanced ferrite nucleation. As an example, coherency strain alone decreases, when compared to a strain-free case, the nucleation rate by an order of 10 À21 , but its interaction with an appropriate applied stress can increase the rate by a factor of about 30.
The behavior characterizing choice response decision-making was studied in monkeys to provide background information for ongoing neurophysiological studies of the neural mechanisms underlying saccadic choice decisions. Animals were trained to associate a specific color from a set of colored visual stimuli with a specific spatial location. The visual stimuli (colored disks) appeared briefly at equal eccentricity from a central fixation position and then were masked by gray disks. The correct target association was subsequently cued by the appearance of a colored stimulus at the fixation point. The animal indicated its choice by saccading to the remembered location of the eccentric stimulus, which had matched the color of the cue. The number of alternative associations (NA) varied from 1 to 4 and remained fixed within a block of trials. After the training period, performance (percent correct responses) declined modestly as NA increased (on average 96, 93 or 84% correct for 1, 2 or 4 NA, respectively). Response latency increased logarithmically as a function of NA, thus obeying Hick's law. The spatial extent of the learned association between color and location was investigated by rotating the array of colored stimuli that had remained fixed during the learning phase to various different angles. Error rates in choice saccades increased gradually as a function of the amount of rotation. The learned association biased the direction of the saccadic response toward the quadrant associated with the cue, but saccade direction was always toward one of the actual visual stimuli. This suggests that the learned associations between stimuli and responses were not spatially exact, but instead the association between color and location was distributed with declining strength from the trained locations. These results demonstrate that the saccade system in monkeys also displays the characteristic dependence on NA in choice response latencies, while more basic features of the eye movements are invariant from those in other tasks. The findings also provide behavioral evidence that spatially distributed regions are established for the sensory-to-motor associations during training which are later utilized for choice decisions.
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