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In forest management planning, the dynamic treatment unit (DTU) approach has become an increasingly relevant alternative to the traditional planning approach using fixed stands, due to improved remote sensing techniques and optimization procedures, with the potential for the higher goal fulfillment of forest activities. For the DTU approach, the traditional concept of fixed stands is disregarded, and forest data are kept in units with a high spatial resolution. Forest operations are planned by clustering cells to form treatment units for harvest operations. This paper presents a new model with an exact optimization technique for forming DTUs in forest planning. In comparison with most previous models, this model aims for increased flexibility by modelling the spatial dimension according to cell proximity rather than immediate adjacency. The model is evaluated using a case study with harvest flow constraints for a forest estate in southern Sweden, represented by 3587 cells. The parameter settings differed between cases, resulting in varying degrees of clustered DTUs, which caused relative net present value losses of up to 4.3%. The case without clustering had the lowest net present value when considering entry costs. The solution times varied between 2.2 s and 42 min 6 s and grew rapidly with increasing problem size. Key words: dynamic treatment units, mixed integer programming, optimization, remote sensing, spatial forest planning. En planification de la gestion forestiere, l'approche par unite de traitement dynamique (UTD) est devenue une alternative de plus en plus pertinente a l'approche de gestion traditionnelle fondee sur des peuplements fixes. Cela est rendu possible grace a l'amelioration des techniques de teledetection et des procedures d'optimisation et offre la possibilite d'une meilleure realisation des objectifs des activites forestieres. Avec l'approche par UTD, on ignore le concept traditionnel de peuplements fixes et les donnees forestieres sont conservees dans des unites a grande resolution spatiale. Les operations forestieres sont planifiees en regroupant les cellules pour former des unites de traitement pour les operations de recolte. Cet article presente un nouveau modele avec une technique d'optimisation exacte pour former les UTD en planification forestiere. Comparativement a la plupart des modeles precedents, ce modele vise a augmenter la flexibilite en modelisant la dimension spatiale en fonction de la proximite des cellules plutot que de leur contigu'ite. Le modele est evalue a l'aide d'une etude de cas comportant des contraintes de flux de recolte sur un domaine forestier situe dans le sud de la Suede, represente par 3587 cellules. L'ajustement des parametres differait selon le cas, ce qui se traduit par differents degres de regroupement d'UTD, causant des pertes de valeur actualisee nette relative allant jusqu'a 4,3%. Le cas qui ne comporte aucun regroupement avait la plus faible valeur actualisee nette lorsqu'on considere les couts d'entree. Le temps requis pour trouver la solution variait de 2,2 s a 42 min 6 s et augmentait rapidement avec l'augmentation de la taille du probleme. Mots-cles : unites de traitement dynamiques, programmation partiellement en nombres entiers, optimisation, teledetection, gestion forestiere spatiale., Introduction In forest management planning, the concept of stands has been of central importance for a long time (e.g., af Strom 1829). In this context, a stand is a geographically [...]

Tularemia, caused by the bacterium Francisella tularensis, is a potentially severe disease that often causes unspecific symptoms; because of its low infectious dose and ease of dissemination, F. tularensis is [...]

Polybrominated diphenyl ether (PBDEs) flame retardant chemicals, used in the manufacture of furniture, infant products, and electronics, are ubiquitous in U.S. households (Sjodin et al. 2008). An unintended consequence of [...]

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants and are ubiquitous environmental contaminants. PBDEs have been linked to adverse neurodevelopment in animals and humans. OBJECTIVES: We [...]

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) are persistent, bioaccumulative, and endocrine-disrupting chemicals. OBJECNVES: We used handwipes to estimate exposure to PBDEs in house dust among toddlers and examined sex, age, breast-feeding, [...]

BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic environmental pollutants generated during incomplete combustion. After exposure and during metabolism, PAHs can form reactive epoxides that can covalently bind to DNA. These [...]

BACKGROUND: Polybrominated diphenyl ethers (PBDE), which are used as flame retardants, have been found to be higher in residents of California than of other parts of the United States. OBJECTIVES: [...]

BACKGROUND: Cooking with biomass fuels on open fires results in exposure to health-damaging pollutants such as carbon monoxide (CO), polycyclic aromatic hydrocarbons (PAHs), and particulate matter. OBJECTIVE: We compared CO [...]

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants in consumer products and are ubiquitous in residential indoor air and dust. However, little is known about exposure [...]

This article takes as its point of departure the question of how Wilhelm Halbfass, Daya Krishna, and Jitendranath Mohanty have conceptualized tradition in relation to 'Indian' philosophy. They have all [...]

BACKGROUND: Human exposure to polybrominated diphenyl ether (PBDE) flame retardants has increased exponentially over the last three decades. Animal and human studies suggest that PBDEs may disrupt thyroid function. Although [...]

BACKGROUND: Low doses of some persistent organic pollutants (POPs) associate cross-sectionally with type 2 diabetes, whereas associations with high POP exposures are inconsistent. OBJECTIVES: We investigated whether several POPs prospectively [...]

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) are widely used flame retardant compounds that are persistent and bioaccumulative and therefore have become ubiquitous environment contaminants. Animal studies suggest that prenatal PBDE exposure [...]

BACKGROUND: Exposure to polybrominated diphenyl ether (PBDE) flame retardants is widespread, with 97% of Americans having detectable levels. Although PBDEs have been associated with reproductive and hormonal effects in animals, [...]

BACKGROUND: Reported polybrominated diphenyl ether (PBDE) concentrations in human samples in the United States have been higher than in Europe and Asia. Little is known about factors that contribute to [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.comnet.2009.07.008 Byline: Jing Fu, Peter Sjodin, Gunnar Karlsson Keywords: Routing convergence; Centralized control; Link-state routing protocols Abstract: The decentralized control scheme for routing in current IP networks has been questioned, and a centralized routing scheme has been proposed as an alternative. In this paper, we compare the convergence of centralized control scheme with decentralized link-state routing protocols. We first review the architectural advantages and challenges of centralized control. Thereafter, we identify and discuss the components of the convergence time in both schemes. We present how to achieve fast routing convergence in networks with centralized control. In particular, we analyze how to distribute forwarding information efficiently. Finally, we perform simulation studies on the convergence time for both real and synthetic network topologies and study the impact of control element location, link weights, and number of failures on the convergence time. The results show that the centralized control scheme can provide faster routing convergence than link-state routing protocols. Author Affiliation: KTH, Royal Institute of Technology, SE-100 44 Stockholm, Sweden Article History: Received 9 July 2008; Revised 18 February 2009; Accepted 16 July 2009 Article Note: (miscellaneous) Responsible Editor: S. Kasera

BACKGROUND: Conventional wisdom regarding exposures to persistent organic chemicals via breastfeeding assumes that concentrations decline over the course of lactation and that the mother's body burden reflects her cumulative lifetime [...]

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in many producrs and have been detected in human samples worldwide. Limited data show that concentrations are elevated in young [...]

BACKGROUND: Developing infants may be especially sensitive to hormone disruption from chemicals including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). OBJECTIVE: We investigated relationships between cord serum levels of [...]

BACKGROUND: Prenatal polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) exposures may influence children's neurodevelopment. OBJECTIVE: We examined the association of prenatal PBDE and PCB exposures with children's reading skills at ages 5 and 8 years, Full-Scale Intelligence Quotient (FSIQ), and externalizing behavior problems at age 8 years. METHODS: From 239 mother-child pairs recruited (2003-2006) in Cincinnati, Ohio, we measured maternal serum PBDE and PCB concentrations, assessed child's reading skills using the Woodcock-Johnson Tests of Achievement III (WJ-III) at age 5 years and the Wide Range Achievement Test-4 (WRAT-4) at age 8 years, tested FSIQ using the Wechsler Intelligence Scale for Children-IV (WISC-IV), and externalizing behavior problems using the Behavioral Assessment System for Children-2 (BASC-2) at age 8 years. We used multiple linear regression to examine the association of prenatal PBDE and PCB concentrations and reading, FSIQ, and externalizing behavior problems after adjusting for covariates. RESULTS: An increase of [Sum.sub.4]PBDEs (BDE-47, BDE-99, BDE-100, and BDE-153) by 10 times was not significantly associated with reading scores at age 5 years at the p = 0.05 level but was inversely associated with Reading Composite scores ([beta]: -6.2, 95% CI: -11.7, -0.6) and FSIQ ([beta]: -5.3, 95% CI: -10.6, -0.02) at age 8 years; it was positively associated with the score for externalizing behavior problems ([beta]: 3.5, 95% CI: -0.1, 7.2) at age 8 years. Prenatal [Sum.sub.4]PCBs (PCB-118, -153, -138-158, and -180) was not significantly associated with a child's reading skills, FSIQ, and externalizing behavior problems. CONCLUSION: Prenatal PBDE concentration was inversely associated with reading skills and FSIQ and positively associated with externalizing behavior problems at age 8 years. No significant associations were found in prenatal PCB concentration., Introduction PBDEs were widely used as flame retardants in the manufacture of electronics, fUrniture, carpets, and textiles and are detectable in indoor dust, fish, birds, human serum, and adipose tissue. [...]

BACKGROUND: Recent studies have reported blood levels of polybrominated diphenyl ethers (PBDEs) in the U.S. population. Information about neonatal levels and about the relationship to polychlorinated biphenyls (PCBs) exposures is limited. OBJECTIVES: The objective was to characterize levels and determinants of fetal exposure to PBDEs and PCBs among newborns from Baltimore, Maryland. METHODS: We analyzed umbilical cord blood for eight PBDEs and 35 PCBs from infants delivered at the Johns Hopkins Hospital. Maternal and infant characteristics were abstracted from medical records. RESULTS: Ninety-four percent of cord serum samples had quantifiable levels of at least one PBDE congener, and > 99% had at least one detectable PCB congener. PBDE concentrations in cord blood were similar to those reported in other studies from North America. Strong correlations were observed within but not across PCB and PBDE classes. Multivariate models showed that many factors independently predicted exposure to BDE-47, BDE-100, and BDE-153 and CB-118, CB-138/158, CB-153, and CB-180. Generally, infants of Asian mothers had lower PBDE and PCB levels, and infants of smokers had higher levels. Increased maternal body mass index was associated with lower levels of PCBs but not PBDEs. Levels of PCBs but not PBDEs were lower in births from married and multiparous mothers. Increased maternal age was associated with higher PCB levels but lower PBDE levels. CONCLUSIONS: Although many of the factors we investigated were independent predictors of both PBDE and PCB levels, in some cases the direction of associations was different. More research is needed to better understand the sources and pathways of PBDE exposure. KEY WORDS: dichlorodiphenyldichloroethylene, dichlorodiphenyltrichloroethane, environmental exposure, epidemiology, fetal exposure, polychlorinated biphenyls, polybrominated diphenyl ethers, prenatal, urban. Environ Health Perspect 115:1794-1800 (2007). doi:10.1289/ehp.10333 available via http://dx.doi.org/Online 27 September 2007], Use of polybrominated diphenyl ethers (PBDEs) as flame retardants (FRs) in plastics, including electronic enclosures and polyurethane used in upholstery cushioning and carpet pads, has increased steadily in the past [...]

BACKGROUND: Recent studies have raised concerns about polybrominated diphenyl ether (PBDE) flame retardant exposures to pregnant women and women of child-bearing age in the United States. Few studies have measured [...]

BACKGROUND: Prenatal exposure to endocrine disruptors has been associated with increased risk of childhood obesity. However, epidemiologic studies on polybrominated diphenyl ethers (PBDEs) are limited despite animal studies indicating PBDEs' potential role as an obesogen. OBJECTIVES: We investigated whether maternal concentrations of BDEs 28, 47, 99, 100, 153, and ΣPBDEs during pregnancy were associated with anthropometric measures in children aged 1-8 years. METHODS: We examined 318 mother--child pairs in the Health Outcomes and Measures of the Environment (HOME) Study, a birth cohort enrolled from 2003 through 2006 (Cincinnati, OH). Serum PBDEs were measured at 16 ± 3 weeks gestation. We measured child height (1-8 years), weight (1-8 years), body mass index (BMI) (2-8 years), waist circumference (4-8 years), and body fat (8 years). To account for repeated measures, we used linear mixed models and generalized estimating equations to estimate associations between maternal PBDEs and child anthropometric measures. RESULTS: We found no statistically significant associations between prenatal PBDEs and height or weight z-score. A 10-fold increase in maternal serum BDE-153 was associated with lower BMI 2-score (β = -0.36; 95% CI: -0.60, -0.13) at 2-8 years, smaller waist circumference (β = -1.81 cm; 95% CI: -3.13, -0.50) at 4-8 years, and lower percent body fat (β = -2.37%; 95% CI: -4.21, -0.53) at 8 years. A decrease in waist circumference at 4-8 years was observed with a 10-fold increase in BDE-100 (β = -1.50 cm; 95% CI: -2.93, -0.08) and ΣPBDEs (β = -1.57 cm; 95% CI: -3.11, -0.02). CONCLUSIONS: Reverse causality may have resulted in prenatal PBDEs, particularly BDE-153, and decreased BMI, waist circumference, and body fat. Environ Health Perspect 124:1891-1897; http://dx.doi.org/10.1289/EHP139, Introduction Childhood obesity is associated with adverse health effects, including diabetes, dyslipidemia, fatty liver disease, and hypertension (Daniels 2009). Between 1980 and 2013, the global prevalence of childhood obesity increased [...]

A method for the measurement of 24 hydroxylated polycyclic aromatic hydrocarbon metabolites (OH-PAHs) in urine has been developed. The method is based on enzymatic deconjugation, automated liquid--liquid extraction, and gas chromatography/isotope dilution high-resolution mass spectrometry after derivatization of the OH-PAHs to the trimethylsilylated derivatives. The metabolites included in the current method are formed from eight different parent compounds. The limits of detection were below 7 pg/mL when using a sample size of 2 mL of urine, except for 1- and 2-naphthols (18 and 12 pg/mL, respectively). The enzymatic deconjugation efficiency, verified by deconjugation of urine samples spiked with [alpha]-naphthyl [beta]-D-glucuronide sodium salt (1-NAP-GLU) and pyrene-1-sulfate potassium salt (1-PYR-SULF), was determined to be 97% for 1-NAP-GLU conjugate and 84% for 1-PYR-SULF. The overall coefficients of variance for six batches of quality control samples (n = 42), was 2.9-11%. Mean method recoveries of the [sup.13]C-labeled internal standards were 66-72%, except for [sup.13][C.sub.6-1-naphthol (46%). The throughput of this method has been determined to be 40 samples per day per analyst. This method is currently applied to epidemiological studies, such as the National Exposure and Nutrition Examination Survey (NHANES), to measure human exposure to PAHs.

The aim of the present study was to model apparent serum half-lives of polybrominated diphenyl ethers (PBDEs) with 7-10 bromine substituents. Workers with occupational exposure to PBDEs have elevated serum [...]

Polybrominated diphenyl ethers (PBDEs) have been widely used in the United States and worldwide as flame retardants. Recent PBDE production figures show that worldwide use has increased. To determine whether [...]

We have characterized environmental exposures among 187 women who were pregnant, were at or near the World Trade Center (WTC) on or soon after 11 September 2001, and are enrolled [...]

We investigate conditions under which a model with stochastic demography or population structure converges to the coalescent with a linear change in timescale. We argue that this is a necessary condition for the existence of a meaningful effective population size. We find that such a linear timescale change is obtained when demographic fluctuations and coalescence events occur on different timescales. Simple models of population structure and randomly fluctuating population size are used to exemplify the ideas and provide an intuitive feel for the meaning of the conditions.

A new method using comprehensive two-dimensional gas chromatography and isotope dilution time-of-flight mass spectrometry (GC x GC-IDTOFMS) for the simultaneous measurement of selected polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and brominated flame retardants is presented. In contrast to the reference methods based on classical GC/MS, a single injection of the extract containing all compounds of interest results in accurate identification and quantification. Using GC x GC ensures the chromatographic separation of most compounds, and TOFMS allows mass spectral deconvolution of coeluting compounds as well as the use of [sup.13]C-labeled internal standards for quantification. Isotope ratio measurements of the most intense ions for both native and labels ensure the required specificity. The use of this new method with an automated sample preparation procedure developed at the Centers for Disease Control and Prevention (CDC) for the analysis of human serum and milk compared favorably to conventional isotope-dilution one-dimensional gas chromatography-high-resolution mass spectrometry (GC-IDHRMS) for the different human serum and milk pools tested. The instrumental detection limits ranged between 0.5 pg/[micro]L and 10 pg/[micro]L and the method detection limits ranged between 1 and 15 pg/[micro]L (N = 59 analytes). The reproducibility of the method was almost as good as with GC-IDHRMS, the relative standard deviations ranging between 1 and 11% for OCPs measured in human serum. OCP, PBDE, and PCB levels measured using the two methods were highly correlated, and the deviations between the two methods were below 20% for most analytes with concentrations above 1 ng/g milk lipids.

A study of different methods to account for change in greenhouse gas emissions due to a change in use or supply of electricity in the deregulated Nordic electricity market having hydropower, nuclear and fossil fuel types of power generation are discussed. A comprehensive accounting scheme facilitates cost-effective carbon dioxide mitigation procedures by providing an accurate link between the different energy measures and their related emissions and to reduce Greenhouse gases (GHG) in line with the Kyoto mechanisms is presented.

A semiautomated extraction and cleanup method has been developed to measure eight polybrominated diphenyl ethers (PBDEs), 2,2',4,4',5,5'-hexabromobiphenyl (BB-153), and 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153). The method employs solid-phase dispersion on diatomaceous earth in a solid-phase extraction cartridge followed by automated addition of internal standards ([sup.13]C-labeled). Extraction is then performed using an automated modular solid-phase extraction system. The extraction procedure includes drying the sample on diatomaceous earth by pressurized nitrogen and eluting target analytes and lipids with dichloromethane. Lipid content is determined gravimetrically. Lipid determinations performed using this method are compared with other standard methods and with a certified reference material. A relative standard deviation of 7.9% was obtained for 130 determinations of the lipid content in a breast milk quality control sample. Final analytical determination of target analytes was performed by gas chromatography-isotope dilution high-resolution mass spectrometry. Relative standard deviations for the measurements of target analytes for which a labeled internal standard was available were below 10% for analytes at concentrations above 1 ng/g of lipid. Mean recoveries of the [13.sup.]C-labeled internal standards ranged from 60 to 89% for the eight PBDE congeners; 74 and 113% were recovered for BB-153 and CB-153, respectively.