A framework for cumulative risk assessment in the 21st century

The ILSI Health and Environmental Sciences Institute (HESI) has developed a framework to support a transition in the way in which information for chemical risk assessment is obtained and used (RISK21). The approach is based on detailed problem formulation, where exposure drives the data acquisition process in order to enable informed decision-making on human health safety as soon as sufficient evidence is available. Information is evaluated in a transparent and consistent way with the aim of optimizing available resources. In the context of risk assessment, cumulative risk assessment (CRA) poses additional problems and questions that can be addressed using the RISK21 approach. The focus in CRA to date has generally been on chemicals that have common mechanisms of action. Recently, concern has also been expressed about chemicals acting on multiple pathways that lead to a common health outcome, and non-chemical other conditions (non-chemical stressors) that can lead to or modify a common outcome. Acknowledging that CRAs, as described above, are more conceptually, methodologically and computationally complex than traditional single-stressor risk assessments, RISK21 further developed the framework for implementation of workable processes and procedures for conducting assessments of combined effects from exposure to multiple chemicals and non-chemical stressors. As part of the problem formulation process, this evidence-based framework allows the identification of the circumstances in which it is appropriate to conduct a CRA for a group of compounds. A tiered approach is then proposed, where additional chemical stressors and/or non-chemical modulating factors (ModFs) are considered sequentially. Criteria are provided to facilitate the decision on whether or not to include ModFs in the formal quantitative assessment, with the intention to help focus the use of available resources to have the greatest potential to protect public health

On Unbounded Composition Operators in L2L^2-Spaces

Fundamental properties of unbounded composition operators in $L^2$-spaces are studied. Characterizations of normal and quasinormal composition operators are provided. Formally normal composition operators are shown to be normal. Composition operators generating Stieltjes moment sequences are completely characterized. The unbounded counterparts of the celebrated Lambert's characterizations of subnormality of bounded composition operators are shown to be false. Various illustrative examples are supplied

Problem formulation for risk assessment of combined exposures to chemicals and other stressors in humans

When the human health risk assessment/risk management paradigm was developed, it did not explicitly include a "problem formulation" phase. The concept of problem formulation was first introduced in the context of ecological risk assessment (ERA) for the pragmatic reason to constrain and focus ERAs on the key questions. However, this need also exists for human health risk assessment, particularly for cumulative risk assessment (CRA), because of its complexity. CRA encompasses the combined threats to health from exposure via all relevant routes to multiple stressors, including biological, chemical, physical and psychosocial stressors. As part of the HESI Risk Assessment in the 21st Century (RISK21) Project, a framework for CRA was developed in which problem formulation plays a critical role. The focus of this effort is primarily on a chemical CRA (i.e., two or more chemicals) with subsequent consideration of non-chemical stressors, defined as "modulating factors" (ModFs). Problem formulation is a systematic approach that identifies all factors critical to a specific risk assessment and considers the purpose of the assessment, scope and depth of the necessary analysis, analytical approach, available resources and outcomes, and overall risk management goal. There are numerous considerations that are specific to multiple stressors, and proper problem formulation can help to focus a CRA to the key factors in order to optimize resources. As part of the problem formulation, conceptual models for exposures and responses can be developed that address these factors, such as temporal relationships between stressors and consideration of the appropriate ModFs

Prevalence and predictors of post‐traumatic stress symptoms in adolescent and young adult cancer survivors: a 1‐year follow‐up study

Objectives Post‐traumatic stress symptoms (PTSS) have been identified as a meaningful indicator of distress in cancer survivors. Distinct from young adult survivors of childhood cancer, young people diagnosed with cancer as adolescents and young adults (AYAs) face unique psychosocial issues; however, there is little published research of PTSS in the AYA population. This study examines prevalence and predictors of PTSS among AYAs with cancer. Methods As part of a longitudinal study of AYAs with cancer, 151 patients aged 15–39 years completed mailed surveys at 6 and 12 months post‐diagnosis. Severity of PTSS was estimated at 6 and 12 months post‐diagnosis. Multiple regression analyses were conducted to investigate the predictive effects of socio‐demographic and clinical characteristics on changes in PTSS over time. Results At 6 and 12 months, respectively, 39% and 44% of participants reported moderate to severe levels of PTSS; 29% had PTSS levels suggestive of post‐traumatic stress disorder. No significant differences in severity of PTSS between 6 and 12 months were observed. Regression analyses suggested that a greater number of side effects were associated with higher levels of PTSS at 6 months. Currently receiving treatment, having surgical treatment, diagnosis of a cancer type with a 90–100% survival rate, remaining unemployed/not in school, and greater PTSS at 6 months were associated with higher levels of PTSS at 12 months. Conclusions Post‐traumatic stress symptoms were observed as early as 6 months following diagnosis and remained stable at 12‐month follow‐up. The development of early interventions for reducing distress among AYA patients in treatment is recommended. Copyright © 2012 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99033/1/pon3217.pd

Psychological distress and unsatisfied need for psychosocial support in adolescent and young adult cancer patients during the first year following diagnosis

Purpose Identifying at‐risk adolescent and young adult (AYA) cancer patients and referring them to age‐appropriate psychosocial support services may be instrumental in reducing psychological distress and promoting psychosocial adaptation. The purpose of this study is to identify trajectories of clinically significant levels of distress throughout the first year following diagnosis and to distinguish factors, including supportive care service use, that predict the extent to which AYAs report distress. Methods In this prospective multisite study, 215 AYAs aged 15–39 years were assessed for psychological distress and psychosocial support service use within the first 4 months of diagnosis and again 6 and 12 months later. On the basis of distress scores, respondents were assigned to one of four distress trajectory groups (Resilient, Recovery, Delayed, and Chronic). Multiple logistic regression analyses examined whether demographics, clinical variables, and reports of unsatisfied need for psychosocial support were associated with distress trajectories over 1 year. Results Twelve percent of AYAs reported clinically significant chronic distress throughout the first 12 months following diagnosis. An additional 15% reported delayed distress. Substantial proportions of AYAs reported that needs for information (57%), counseling (41%), and practical support (39%) remained unsatisfied at 12 months following diagnosis. Not getting counseling needs met, particularly with regard to professional mental health services, was observed to be significantly associated with distress over time. Conclusions Substantial proportions of AYAs are not utilizing psychosocial support services. Findings suggest the importance of identifying psychologically distressed AYAs and addressing their needs for mental health counseling throughout a continuum of care. Copyright © 2014 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109318/1/pon3533.pd

Data-adaptive harmonic spectra and multilayer Stuart-Landau models

Harmonic decompositions of multivariate time series are considered for which we adopt an integral operator approach with periodic semigroup kernels. Spectral decomposition theorems are derived that cover the important cases of two-time statistics drawn from a mixing invariant measure. The corresponding eigenvalues can be grouped per Fourier frequency, and are actually given, at each frequency, as the singular values of a cross-spectral matrix depending on the data. These eigenvalues obey furthermore a variational principle that allows us to define naturally a multidimensional power spectrum. The eigenmodes, as far as they are concerned, exhibit a data-adaptive character manifested in their phase which allows us in turn to define a multidimensional phase spectrum. The resulting data-adaptive harmonic (DAH) modes allow for reducing the data-driven modeling effort to elemental models stacked per frequency, only coupled at different frequencies by the same noise realization. In particular, the DAH decomposition extracts time-dependent coefficients stacked by Fourier frequency which can be efficiently modeled---provided the decay of temporal correlations is sufficiently well-resolved---within a class of multilayer stochastic models (MSMs) tailored here on stochastic Stuart-Landau oscillators. Applications to the Lorenz 96 model and to a stochastic heat equation driven by a space-time white noise, are considered. In both cases, the DAH decomposition allows for an extraction of spatio-temporal modes revealing key features of the dynamics in the embedded phase space. The multilayer Stuart-Landau models (MSLMs) are shown to successfully model the typical patterns of the corresponding time-evolving fields, as well as their statistics of occurrence.Comment: 26 pages, double columns; 15 figure

Contrasting carbonate depositional systems for Pliocene cool-water limestones cropping out in central Hawke's Bay, New Zealand

Pliocene limestone formations in central Hawke's Bay (eastern North Island, New Zealand) accumulated on and near the margins of a narrow forearc basin seaway within the convergent Australia/Pacific plate boundary zone. The active tectonic setting and varied paleogeographic features of the limestone units investigated, in association with probable glacioeustatic sea-level fluctuations, resulted in complex stratigraphic architectures and contrasting types of carbonate accumulation on either side of the seaway. Here, we recognise recurring patterns of sedimentary facies, and sequences and systems tracts bounded by key physical surfaces within the limestone sheets. The facies types range from Bioclastic (B) to Siliciclastic (S) end-members via Mixed (M) carbonate-siliciclastic deposits. Skeletal components are typical cool-water associations dominated by epifaunal calcitic bivalves, bryozoans, and especially barnacles. Siliciclastic contents vary from one formation to another, and highlight siliciclastic-rich limestone units in the western ranges versus siliciclastic-poor limestone units in the eastern coastal hills. Heterogeneities in facies types, stratal patterns, and also in diagenetic pathways between eastern and western limestone units are considered to originate in the coeval occurrence in different parts of the forearc basin of two main morphodynamic carbonate systems over time

Quantum Ballistic Evolution in Quantum Mechanics: Application to Quantum Computers

Quantum computers are important examples of processes whose evolution can be described in terms of iterations of single step operators or their adjoints. Based on this, Hamiltonian evolution of processes with associated step operators $T$ is investigated here. The main limitation of this paper is to processes which evolve quantum ballistically, i.e. motion restricted to a collection of nonintersecting or distinct paths on an arbitrary basis. The main goal of this paper is proof of a theorem which gives necessary and sufficient conditions that T must satisfy so that there exists a Hamiltonian description of quantum ballistic evolution for the process, namely, that T is a partial isometry and is orthogonality preserving and stable on some basis. Simple examples of quantum ballistic evolution for quantum Turing machines with one and with more than one type of elementary step are discussed. It is seen that for nondeterministic machines the basis set can be quite complex with much entanglement present. It is also proved that, given a step operator T for an arbitrary deterministic quantum Turing machine, it is decidable if T is stable and orthogonality preserving, and if quantum ballistic evolution is possible. The proof fails if T is a step operator for a nondeterministic machine. It is an open question if such a decision procedure exists for nondeterministic machines. This problem does not occur in classical mechanics.Comment: 37 pages Latexwith 2 postscript figures tar+gzip+uuencoded, to be published in Phys. Rev.

Types of Urea Supplement for Wintering Beef Calves

Previous research at the Cottonwood Station showed that calves fed low levels of urea during an adaptation period made faster gains than unadapted calves when fed higher levels of urea during the wintering period. Calves fed a corn-base urea supplement in pellet form gained faster than those fed a commercial, molasses-base urea supplement in liquid form. The following tow experiments were conducted as replications of those reported previously under this title