Traffic and Related Self-Driven Many-Particle Systems

Since the subject of traffic dynamics has captured the interest of physicists, many astonishing effects have been revealed and explained. Some of the questions now understood are the following: Why are vehicles sometimes stopped by so-called ``phantom traffic jams'', although they all like to drive fast? What are the mechanisms behind stop-and-go traffic? Why are there several different kinds of congestion, and how are they related? Why do most traffic jams occur considerably before the road capacity is reached? Can a temporary reduction of the traffic volume cause a lasting traffic jam? Under which conditions can speed limits speed up traffic? Why do pedestrians moving in opposite directions normally organize in lanes, while similar systems are ``freezing by heating''? Why do self-organizing systems tend to reach an optimal state? Why do panicking pedestrians produce dangerous deadlocks? All these questions have been answered by applying and extending methods from statistical physics and non-linear dynamics to self-driven many-particle systems. This review article on traffic introduces (i) empirically data, facts, and observations, (ii) the main approaches to pedestrian, highway, and city traffic, (iii) microscopic (particle-based), mesoscopic (gas-kinetic), and macroscopic (fluid-dynamic) models. Attention is also paid to the formulation of a micro-macro link, to aspects of universality, and to other unifying concepts like a general modelling framework for self-driven many-particle systems, including spin systems. Subjects such as the optimization of traffic flows and relations to biological or socio-economic systems such as bacterial colonies, flocks of birds, panics, and stock market dynamics are discussed as well.Comment: A shortened version of this article will appear in Reviews of Modern Physics, an extended one as a book. The 63 figures were omitted because of storage capacity. For related work see http://www.helbing.org

Randomized trial of a phone- and web-based weight loss program for women at elevated breast cancer risk: the HELP study

Excess weight and physical inactivity are modifiable risk factors for breast cancer. Behavioral intervention is particularly important among women with an elevated risk profile. This trial tested an intervention that trained women to use a self-monitoring website to increase activity and lose weight. Women with BMI≥27.5 kg/m(2) at elevated breast cancer risk were randomized to the intervention (N=71) or usual care (N=34). The intervention group received telephone-based coaching and used web-based self-monitoring tools. At 6 months, significant weight loss was observed in the intervention group (4.7% loss from starting weight; SD=4.7%) relative to usual care (0.4% gain; SD=3.0%) (p<.0001). By 12 months, the intervention group had lost 3.7% of weight (SD=5.4%), compared to 1.3% (SD=4.2) for usual care (p=.003). At 12 months, accelerometer-measured moderate-to-vigorous physical activity increased by 12 min/day (SD=24) compared to no change in usual care (p=.04. In summary, this web- and phone-based approach produced modest but significant improvements in weight and physical activity for women at elevated breast cancer risk

Sleep duration and breast cancer prognosis: perspectives from the Women's Healthy Eating and Living Study.

PurposeTo examine whether baseline sleep duration or changes in sleep duration are associated with breast cancer prognosis among early-stage breast cancer survivors in the multi-center Women's Healthy Eating and Living Study.MethodsData were collected from 1995 to 2010. Analysis included 3047 women. Sleep duration was self-reported at baseline and follow-up intervals. Cox proportional hazard models were used to investigate whether baseline sleep duration was associated with breast cancer recurrence, breast cancer-specific mortality, and all-cause mortality. Time-varying models investigated whether changes in sleep duration were associated with breast cancer prognosis.ResultsCompared to women who slept 7-8&nbsp;h/night at baseline, sleeping ≥9&nbsp;h/night was associated with a 48% increased risk of breast cancer recurrence (Hazard ratio [HR] 1.48, 95% Confidence interval [CI] 1.01, 2.00), a 52% increased risk of breast cancer-specific mortality (HR 1.52, 95% CI 1.09, 2.13), and a 43% greater risk of all-cause mortality (HR 1.43, 95% CI 1.07, 1.92). Time-varying models showed analogous increased risk in those who inconsistently slept ≥9&nbsp;h/night (all P&nbsp;&lt;&nbsp;0.05), but not in those who consistently slept ≥9&nbsp;h/night.ConclusionsConsistent long or short sleep, which may reflect inter-individual variability in the need for sleep, does not appear to influence prognosis among early-stage breast cancer survivors

Randomized trial of a phone- and web-based weight loss program for women at elevated breast cancer risk: the HELP study.

Excess weight and physical inactivity are modifiable risk factors for breast cancer. Behavioral intervention is particularly important among women with an elevated risk profile. This trial tested an intervention that trained women to use a self-monitoring website to increase activity and lose weight. Women with BMI ≥27.5&nbsp;kg/m(2) at elevated breast cancer risk were randomized to the intervention (N&nbsp;=&nbsp;71) or usual care (N&nbsp;=&nbsp;34). The intervention group received telephone-based coaching and used web-based self-monitoring tools. At 6&nbsp;months, significant weight loss was observed in the intervention group (4.7&nbsp;% loss from starting weight; SD&nbsp;=&nbsp;4.7&nbsp;%) relative to usual care (0.4&nbsp;% gain; SD&nbsp;=&nbsp;3.0&nbsp;%) (p&nbsp;&lt;&nbsp;0.0001). By 12&nbsp;months, the intervention group had lost 3.7&nbsp;% of weight (SD&nbsp;=&nbsp;5.4&nbsp;%), compared to 1.3&nbsp;% (SD&nbsp;=&nbsp;4.2) for usual care (p&nbsp;=&nbsp;0.003). At 12&nbsp;months, accelerometer-measured moderate-to-vigorous physical activity increased by 12&nbsp;min/day (SD&nbsp;=&nbsp;24) compared to no change in usual care (p&nbsp;=&nbsp;0.04. In summary, this web- and phone-based approach produced modest but significant improvements in weight and physical activity for women at elevated breast cancer risk

The effects of weight loss and metformin on cognition among breast cancer survivors: Evidence from the Reach for Health study.

ObjectiveBreast cancer survivors experience problems with cognition that interfere with daily life and can last for years. In the general population, obesity and diabetes are risk factors for cognitive decline, and weight loss can improve cognition; however, the impact of intentional weight loss on cancer survivors' cognition has not been tested. We investigated the impact of weight loss and metformin on changes in cognitive function in a sample of breast cancer survivors.MethodsOverweight/obese postmenopausal breast cancer survivors (n&nbsp;=&nbsp;333) were randomized to a weight loss intervention versus control and metformin versus placebo in a 2&nbsp;×&nbsp;2 factorial design. Outcomes were changes in five cognitive domains from baseline to 6&nbsp;months measured by objective neurocognitive tests.ResultsThere were no statistically significant intervention effects for the metformin or weight loss interventions in five neurocognitive domains. Baseline body mass index (BMI) was a significant effect modifier of the changes in verbal functioning for the weight loss (P&nbsp;=&nbsp;0.009) and metformin interventions (P&nbsp;=&nbsp;0.0125). These effect modifications were independent of percent weight loss achieved during the 6-month study period.ConclusionsThis randomized controlled trial of weight loss and metformin interventions that examined changes to cognition among breast cancer survivors suggests that these interventions may not improve cognitive functioning among breast cancer survivors in general. However, weight loss may improve verbal functioning among individuals with a higher BMI

Breast cancer survivors reduce accelerometer-measured sedentary time in an exercise intervention.

PurposeCancer survivors are highly sedentary and have low physical activity. How physical activity interventions impact sedentary behavior remains unclear. This secondary analysis examined changes in sedentary behavior among breast cancer survivors participating in a physical activity intervention that significantly increased moderate-to-vigorous physical activity (MVPA).MethodsInsufficiently active breast cancer survivors were randomized to a 12-week physical activity intervention (exercise arm) or control arm. The intervention focused solely on increasing MVPA with no content targeting sedentary behavior. Total sedentary behavior, light physical activity (LPA), and MVPA were measured at baseline and 12 weeks (ActiGraph GT3X+ accelerometer). Separate linear mixed-effects models tested intervention effects on sedentary behavior, intervention effects on LPA, the relationship between change in MVPA and change in sedentary behavior, and potential moderators of intervention effects on sedentary behavior.ResultsThe exercise arm had significantly greater reductions in sedentary behavior than the control arm (mean - 24.9 min/day (SD = 5.9) vs. - 4.8 min/day (SD = 5.9), b = - 20.1 (SE = 8.4), p = 0.02). Larger increases in MVPA were associated with larger decreases in sedentary behavior (b = - 1.9 (SE = 0.21), p &lt; 0.001). Women farther out from surgery had significantly greater reductions in sedentary behavior than women closer to surgery (b = - 0.91 (SE = 0.5), p = 0.07). There was no significant group difference in change in LPA from baseline to 12 weeks (b = 5.64 (SE = 7.69), p = 0.48).ConclusionsBreast cancer survivors in a physical activity intervention reduced total sedentary time in addition to increasing MVPA.Implications for cancer survivorsBoth increasing physical activity and reducing sedentary behavior are needed to promote optimal health in cancer survivors. These results show that MVPA and sedentary behavior could be successfully targeted together, particularly among longer-term cancer survivors.Clinical trial registrationThis study is registered at www.ClinicalTrials.gov (NCT02332876)