Kendall's tau for serial dependence

The authors show how Kendall's tau can be adapted to test against serial dependence in a univariate time series context. They provide formulas for the mean and variance of circular and noncircular versions of this statistic, and they prove its asymptotic normality under the hypothesis of independence. They present also a Monte Carlo study comparing the power and size of a test based on Kendall's tau with the power and size of competing procedures based on alternative parametric and nonparametric measures of serial dependence. In particular, their simulations indicate that Kendall's tau outperforms Spearman's rho in detecting first‐order autoregressive dependence, despite the fact that these two statistics are asymptotically equivalent under the null hypothesis, as well as under local alternatives.     

BlueLinx can benefit from innovative inventory management methods for commodity forward buys

Commodity prices often fluctuate significantly from one purchasing opportunity to the next. These fluctuations allow firms to benefit from forward buying (buying for future demand in addition to current demand) when prices are low. We propose a combined heuristic to determine the optimal number of future periods a firm should purchase at each ordering opportunity in order to maximize total expected profit when there is uncertainty in future demand and future buying price. We compare our heuristic with existing methods via simulation using real demand data from BlueLinx, a two-stage distributor of building products. The results show that our combined heuristic performs better than any existing methods considering forward buying or safety stock separately. We also compare our heuristic to the optimal inventory management policy by full enumeration for a smaller data set. The proposed heuristic is shown to be close to optimal. This study is the first to decide both the optimal number of future periods to buy for uncertain purchase price and the appropriate purchasing quantity with safety stock for uncertain demand simultaneously. The experience suggests that the proposed combined heuristic is simple and can be very beneficial for any company where forward buying is possible.     

Investment in health when health is stochastic

This paper applies stochastic control theory to the Grossman model of investment in health to characterize the case of a serious illness, i.e., one that permanently reduces the individual’s stock of health capital. Health itself is modelled as a stochastic variable, whose variation over time is determined partly by a deterministic factor and partly by a random factor with a Poisson distribution. After setting out the equations for the deterministic and stochastic approaches, phase diagrams illustrate how the introduction of uncertainty alters the model. The framework is also used to consider the effect of the introduction of a vaccine.

Enhancing strength and postocclusive calf blood flow in older people with training with blood-flow restriction

The response of calf-muscle strength, resting blood flow, and postocclusive blood flow (PObf) were investigated after 4 wk of low-load resistance training (LLRT) with and without blood-flow restriction in a matched-leg design. Ten untrained older individuals age 62-73 yr performed unilateral plantar-flexion LLRT at 25% 1-repetition maximum (1RM). One limb was trained with normal blood flow and the other had blood flow restricted using a pressure cuff above the knee. 1RM, isometric maximal voluntary contraction, and isokinetic strength at 0.52 rad/s increased (p < .05) more after LLRT with blood-flow restriction than with normal blood flow. Peak PObf increased (p < .05) after LLRT with blood-flow restriction, compared with no change after LLRT with normal blood flow. These results suggest that 4 wk of LLRT with blood-flow restriction may be beneficial to older individuals to improve strength and blood-flow parameters.     

Nursing home deficiency citations for safety

Deficiency citations for safety violations in U.S. nursing homes from 2000 to 2007 are examined (representing a panel of 119,472 observations). Internal (i.e., operating characteristics of the facility), organizational factors (i.e., characteristics of the facility itself), and external factors (i.e., characteristics outside of the influence of the organization) associated with these deficiency citations are examined. The findings show that nursing homes increasingly receive deficiency citations for resident safety issues. Low staffing levels, poor quality of care, and an unfavorable Medicaid mix (occupancy and reimbursement) are associated with the likelihood of receiving deficiency citations for safety violations. In many cases, this likely influences the quality of life and quality of care of residents.     

Protecting children in new times: child protection and the risk society

This paper examines the nature of late-modern child protection by placing it in the context of the paradigm of `risk society'. It traces out a structural transformation in the relationship between expertise and lay people that has occurred since the 1970s which resulted in the emergence of child abuse inquiries and new public disclosures of professional 'failures'. The dynamic and empowering features of social developments are identified in how institutions, professionals and lay people re-appropriate power, knowledge and reskill themselves. Traditionally repressed problems like child sexual abuse have gained recognition in a context where abused women and children – like all late-modern citizens – are reflexively engaged in constructing their own biographies and using expertise in the planning of their life projects. A radically new professional risk consciousness in child protection is traced to late-modern existential crises associated with death and sexuality and the emergence of manufactured risk, which is known and experienced by social workers as risk in the context of radically uncertain futures for children. Drawing on the work of sociologists of 'reflexive modernity', the paper aims to advance our understandings of social work and child protection beyond the one-dimensional focus of post-modernist critics on power, control and bureaucracy to recognize the new opportunities, as well as the dangers, involved in child protection in risk society.