Science.gov

Sample records for bony heterogeneity effects

  1. The Effects of Latarjet Reconstruction on Glenohumeral Instability in the Presence of Combined Bony Defects

    PubMed Central

    Patel, Ronak M.; Walia, Piyush; Gottschalk, Lionel; Jones, Morgan H.; Fening, Stephen D.; Miniaci, Anthony

    2015-01-01

    Objectives: Recurrent glenohumeral instability is often a result of underlying bony defects in the glenoid and/or humeral head. Anterior glenoid augmentation with a bone block (i.e. Latarjet) has been recommended for glenoid bone loss in the face of recurrent instability. However, no study has investigated the effect of Latarjet augmentation in the setting of both glenoid and humeral head defects (Hill-Sachs Defects (HSD)). The purpose of this study was to evaluate the stability achieved through a Latarjet procedure in the presence of combined bony defects. Our hypothesis was that Latarjet augmentation would increase shoulder stability for glenoid defects with small HSD, but have limited success in cases with large concomitant HSD. Methods: Eighteen fresh-frozen cadaveric specimens were tested at combinations of glenohumeral abduction (ABD) angles of 20°, 40°, and 60° and external rotation (ER) angles of 0°, 40°, and 80°. Each experiment applied a 50N medial load on the humerus to replicate the static load of soft tissues, and then simulated anterior dislocation by translating the glenoid in an anterior direction. Translational distance and medial-lateral displacement of the humeral head, along with horizontal reaction forces, were recorded for every trial. Specimens were tested in an intact condition (no defect), different combinations of defects, and with Latarjet augmentation. The Latarjet was performed for 20% and 30% glenoid defects by transferring the specimen’s coracoid process anterior to the glenoid flush with the articulating surface. Results: Results are summarized in Fig. 1. The vertical axis represents the normalized distance to dislocation with respect to the values of the intact joint. The horizontal axis represents the varying sizes and combinations of bony defects. Latarjet augmentation improved stability for every combination of bony defects. At 20° ABD, 0°ER, and 20% glenoid defect size, the percentage of intact translation did not

  2. The Effects of Latarjet Reconstruction on Glenohumeral Instability in the Presence of Combined Bony Defects

    PubMed Central

    Patel, Ronak Maneklal; Walia, Piyush; Gottschalk, Lionel; Jones, Morgan H.; Fening, Stephen D.; Miniaci, Anthony

    2015-01-01

    Objectives: Recurrent glenohumeral instability is often as a result of underlying bony defects in the glenoid and/or humeral head. Anterior glenoid augmentation with a bone block (i.e. Latarjet) has been recommended for glenoid bone loss in the face of recurrent instability. However, no study has investigated the effect of Latarjet augmentation in the setting of both glenoid and humeral head defects (Hill-Sachs Defects (HSD)). The purpose of this study was to evaluate the stability achieved through a Latarjet procedure in the presence of combined bony defects. Methods: Eighteen fresh-frozen cadaveric specimens were tested at all combinations of glenohumeral abduction (ABD) angles of 20°, 40°, and 60° and three external rotation (ER) levels (0°, 40°, and 80°). Each experiment comprised of anterior dislocation by translating the glenoid under a 50N medial load applied on the humerus, simulating the static load of soft tissues. Translational distance and medial-lateral displacement of the humeral head, along with horizontal reaction forces were recorded for every trial. Specimens were tested in an intact condition (no defect), different combinations of defects, and with Latarjet augmentation. The Latarjet was performed for 20% and 30% glenoid defects by transferring the specimen's coracoid process anterior to the glenoid flush with the articulating surface. Four different humeral head defects were created of sizes 6%, 19%, 31%, and 44% of humeral diameter. Repeated measures analysis of variance (ANOVA) was performed with statistical significance set at p <0.05. Results: Results are summarized in Fig. 1. The vertical axis represents the normalized distance to dislocation with respect to the values of the intact joint. The horizontal axis represents the varying sizes and combinations of bony defects. At 20° ABD and 0°ER, increasing HSD size did not affect percentage of intact translation with a constant glenoid defect of 20% before and after Latarjet

  3. The Cardiovascular and Neurotoxic Effects of the Venoms of Six Bony and Cartilaginous Fish Species

    PubMed Central

    Han, Han; Baumann, Kate; Casewell, Nicholas R.; Ali, Syed A.; Dobson, James; Koludarov, Ivan; Debono, Jordan; Cutmore, Scott C.; Rajapakse, Niwanthi W.; Jackson, Timothy N. W.; Jones, Rob; Hodgson, Wayne C.; Fry, Bryan G.; Kuruppu, Sanjaya

    2017-01-01

    Fish venoms are often poorly studied, in part due to the difficulty in obtaining, extracting, and storing them. In this study, we characterize the cardiovascular and neurotoxic effects of the venoms from the following six species of fish: the cartilaginous stingrays Neotrygon kuhlii and Himantura toshi, and the bony fish Platycephalus fucus, Girella tricuspidata, Mugil cephalus, and Dentex tumifrons. All venoms (10–100 µg/kg, i.v.), except G. tricuspidata and P. fuscus, induced a biphasic response on mean arterial pressure (MAP) in the anesthetised rat. P. fucus venom exhibited a hypotensive response, while venom from G. tricuspidata displayed a single depressor response. All venoms induced cardiovascular collapse at 200 µg/kg, i.v. The in vitro neurotoxic effects of venom were examined using the chick biventer cervicis nerve-muscle (CBCNM) preparation. N. kuhlii, H. toshi, and P. fucus venoms caused concentration-dependent inhibition of indirect twitches in the CBCNM preparation. These three venoms also inhibited responses to exogenous acetylcholine (ACh) and carbachol (CCh), but not potassium chloride (KCl), indicating a post-synaptic mode of action. Venom from G. tricuspidata, M. cephalus, and D. tumifrons had no significant effect on indirect twitches or agonist responses in the CBCNM. Our results demonstrate that envenoming by these species of fish may result in moderate cardiovascular and/or neurotoxic effects. Future studies aimed at identifying the molecules responsible for these effects could uncover potentially novel lead compounds for future pharmaceuticals, in addition to generating new knowledge about the evolutionary relationships between venomous animals. PMID:28212333

  4. Effect of antiresorptive drugs on bony turnover in the jaw: denosumab compared with bisphosphonates.

    PubMed

    Ristow, Oliver; Gerngroß, Carlos; Schwaiger, Markus; Hohlweg-Majert, Bettina; Kehl, Victoria; Jansen, Heike; Hahnefeld, Lilian; Koerdt, Steffen; Otto, Sven; Pautke, Christoph

    2014-04-01

    Osteonecrosis of the jaw as a result of treatment with receptor activators of nuclear factor kappa-B ligand (RANKL) inhibitors (denosumab) is a new type of bony necrosis, the exact pathogenesis of which is unknown. Our aim was to find out whether the turnover of bone in the jaw is increased after denosumab has been given compared with other skeletal sites, and if that turnover might have a role in denosumab-related osteonecrosis of the jaw (DRONJ). Bone scintigraphic images of 45 female patients with breast cancer and bone metastases were analysed retrospectively, and divided into 3 groups: those given denosumab, those given a bisphosphonate, and a control group (n=15 in each). All patients had bone scintigraphy before treatment (T0) and during the course of treatment after 12 (T1) and 24 (T2) months. The data were analysed quantitatively using 6 preset bony regions of interest. There was similar turnover of bone in the mandible compared with other skeletal sites (such as the femur), while the maxilla showed significantly higher turnover. None of the bony regions investigated showed any significant changes after the bisphosphonate had been given. There was a tendency to increase bone turnover in those patients taking denosumab. The bone turnover of the jawbone is not overtly changed either by a bisphosphonate or denosumab, so it seems unlikely that oversuppression of bony turnover in the jawbones plays an important part either in the pathogenesis of DRONJ or in the bisphosphonate-related osteonecrosis of the jaw (BRONJ).

  5. The effect of violin playing on the bony facial structures in adolescents.

    PubMed

    Kovero, O; Könönen, M; Pirinen, S

    1997-08-01

    Holding a violin between shoulder and chin needs a special kind of muscle function. The purpose of this investigation was to determine whether this kind of muscular activity is a modifying factor for facial growth in adolescence. The bony facial dimensions of 24 adolescent violin students attending colleges of music with a playing history of 5-11 years were measured from lateral and posteroanterior cephalograms and panoramic tomograms of the jaws. The dimensions were compared with those of sex- and age-matched controls. Significant differences were found between violin players and controls. The players had higher faces, especially on the right side of the lower face and in the right mandibular ramus. The players also had more proclined upper and lower incisors than the controls. It is concluded that the overall greater facial height in violinists reflects the increased face muscle activity and the higher bony dimensions of the right side of the face are due to the muscular activity produced on that side to balance the load caused by the violin on the left. The greater proclination of the incisors is the result of an altered balance of muscular activity between tongue and lip, and the pressure of the violin to the chin.

  6. The effect of professional violin and viola playing on the bony facial structures.

    PubMed

    Kovero, O; Könönen, M; Pirinen, S

    1997-02-01

    Professional violin and viola playing involves a particular kind of asymmetric face, neck and shoulder muscle activity. The aim of this study was to find out whether players' facial morphology is influenced by this occupational orofacial muscle activity. Lateral and posteroanterior cephalograms and panoramic tomograms of 26 adult professional violin and viola players were evaluated and compared with those of age, sex and dentition matched controls. Significant differences were found between the players and the controls. The players had smaller facial heights, more proclined maxillary incisors and greater mandibular lengths. Thus, intense long-term violin/viola playing has the effect of modifying facial morphology.

  7. Effect of prenatal alcohol exposure on bony craniofacial development: a mouse MicroCT study.

    PubMed

    Shen, Li; Ai, Huisi; Liang, Yun; Ren, Xiaowei; Anthony, Charles Bruce; Goodlett, Charles R; Ward, Richard; Zhou, Feng C

    2013-08-01

    Craniofacial bone dysmorphology is an important but under-explored potential diagnostic feature of fetal alcohol spectrum disorders. This study used longitudinal MicroCT 3D imaging to examine the effect of prenatal alcohol exposure on craniofacial bone growth in a mouse model. C57BL/6J dams were divided into 3 groups: alcohol 4.2% v/v in PMI® liquid diet (ALC), 2 weeks prior to and during pregnancy from embryonic (E) days 7-E16; pair-fed controls (PF), isocalorically matched to the ALC group; chow controls (CHOW), given ad libitum chow and water. The MicroCT scans were performed on pups on postnatal days 7 (P7) and P21. The volumes of the neurocranium (volume encased by the frontal, parietal, and occipital bones) and the viscerocranium (volume encased by the mandible and nasal bone), along with total skull bone volume, head size, and head circumference were evaluated using general linear models and discriminant analyses. The pups in the alcohol-treated group, when compared to the chow-fed controls (ALC vs CHOW) and the isocaloric-fed controls (ALC vs PF), showed differences in head size and circumference at P7 and P21, the total skull volume and parietal bone volume at P7, and volume of all the tested bones except nasal at P21. There was a growth trend of ALC < CHOW and ALC < PF. While covarying for gender and head size or circumference, the treatment affected the total skull and mandible at P7 (ALC > CHOW), and the total skull, parietal bone, and occipital bone at P21 (ALC < CHOW, ALC < PF). While covarying for the P7 measures, the treatment affected only the 3 neurocranial bones at P21 (ALC < CHOW, ALC < PF). Discriminant analysis sensitively selected between ALC and CHOW (AUC = 0.967), between ALC and PF (AUC = 0.995), and between PF and CHOW (AUC = 0.805). These results supported our hypothesis that craniofacial bones might be a reliable and sensitive indicator for the diagnosis of prenatal alcohol exposure. Significantly, we found that the neurocranium (upper

  8. Bony anomaly of Meckel's cave.

    PubMed

    Tubbs, R Shane; Salter, E George; Oakes, W Jerry

    2006-01-01

    This study describes the seemingly rare occurrence of bone formation within the proximal superior aspect of Meckel's cave thus forming a bony foramen for the proximal trigeminal nerve to traverse. The anatomy of Meckel's cave is reviewed and the clinical potential for nerve compression from this bony anomaly discussed.

  9. Bony instability of the shoulder.

    PubMed

    Bushnell, Brandon D; Creighton, R Alexander; Herring, Marion M

    2008-09-01

    Instability of the shoulder is a common problem treated by many orthopaedists. Instability can result from baseline intrinsic ligamentous laxity or a traumatic event-often a dislocation that injures the stabilizing structures of the glenohumeral joint. Many cases involve soft-tissue injury only and can be treated successfully with repair of the labrum and ligamentous tissues. Both open and arthroscopic approaches have been well described, with recent studies of arthroscopic soft-tissue techniques reporting results equal to those of the more traditional open techniques. Over the last decade, attention has focused on the concept of instability of the shoulder mediated by bony pathology such as a large bony Bankart lesion or an engaging Hill-Sachs lesion. Recent literature has identified unrecognized large bony lesions as a primary cause of failure of arthroscopic reconstruction for instability, a major cause of recurrent instability, and a difficult diagnosis to make. Thus, although such bony lesions may be relatively rare compared with soft-tissue pathology, they constitute a critically important entity in the management of shoulder instability. Smaller bony lesions may be amenable to arthroscopic treatment, but larger lesions often require open surgery to prevent recurrent instability. This article reviews recent developments in the diagnosis and treatment of bony instability.

  10. Long-term effect on tooth vitality of regenerative therapy in deep periodontal bony defects: a retrospective study.

    PubMed

    de Sanctis, Massimo; Goracci, Cecilia; Zucchelli, Giovanni

    2013-01-01

    Over the last few decades, many authors have investigated the effect of periodontal disease and treatment on pulpal status with controversial results. This study was conducted to verify whether periodontal disease in a deep intrabony defect and complex therapy, including aggressive root planing such as in periodontal regeneration, have an influence on tooth vitality. One hundred thirty-seven patients who fulfilled the requirements were included. The collected data did not support the need for "preventive" root canal treatment in severely compromised teeth that are planned to undergo periodontal regenerative surgery.

  11. Role of effective canal diameter in assessing the pre-operative and the post-operative status of patients with bony cranio-vertebral anomalies

    PubMed Central

    Mehrotra, Anant; Srivastava, Arun; Sahu, Rabi N.; Kumar, Raj

    2016-01-01

    Introduction: The effective canal diameter (ECD) for the cranio-vertebral junction is measured from the posterior surface of the dens to the nearest posterior bony structure (foramen magnum or the posterior arch of the atlas). The ECD is the space which is occupied by the buffer space (which can be compromised without producing any signs or symptoms) and the cord itself. We intend to study the role of the ECD (especially in patients with markedly reduced ECD) in producing the symptoms and also the outcome of surgery in patients with bony cranio-vertebral junction (CVJ) anomalies. Materials and Methods: A total of 67 consecutive patients from the period of January 2009 through June 2010 were prospectively included in the study. These patients were operated by a single experienced surgeon (the senior author) at the Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow. The ECD and the pre-operative Kumar and Kalra score (K and K score) (4) was calculated for all patients. The K and K score was also calculated at the time of discharge, at three months and six months follow-up. The patients were divided into three groups based on the ECD into 5 mm to 10 mm group, 10 mm to 15 mm group, and >15 mm group. Results: There were 53 male (79.1%) patients and 14 female patients (20.9%) with mean age of presentation 27.10 years (±15.01 years) with range of 4-59 years. The duration of symptoms in our series varied from 1-120 months with mean of 23.79 months. The mean effective canal diameter was 9.027 mm (±2.23 mm) with range of 5-16 mm. The mean pre-operative K and K score was 19.27 (±4.19). There were 39 patients who had an ECD between 5 mm to 10 mm, 24 patients with ECD between 10 mm to 15 mm, and 4 patients with ECD more than 15 mm. The correlation coefficients between the effective canal diameter and the pre-operative and the post-operative Kumar and Kalra score at the time of discharge, 3 months and 6 months were 0.404 (P < 0.001), 0.320 (P < 0.008), 0

  12. Values for bony acetabular roof angle and percentage femoral head cover in a selective ultrasound neonatal hip-screening programme: effect of age, sex and side.

    PubMed

    Wilkinson, A Graham; Wilkinson, Sally; Elton, Robert A

    2017-02-22

    Published maturation curves for bony acetabular roof or α angle (AA) and percentage femoral head cover (FHC) with age are sparse. We aimed to determine typical values for AA and FHC in 2236 infants referred to a selective ultrasound screening programme. There was increase in the values of first measurement of AA and FHC related to the logarithm of age. Males had greater values than females (P<0.001) and right hips had greater values than left (P<0.001) for both measurements. Significant side differences have not been reported previously. Treatment decisions should be made on the basis of sex, side and age-specific data.

  13. Recursive partitioning for heterogeneous causal effects.

    PubMed

    Athey, Susan; Imbens, Guido

    2016-07-05

    In this paper we propose methods for estimating heterogeneity in causal effects in experimental and observational studies and for conducting hypothesis tests about the magnitude of differences in treatment effects across subsets of the population. We provide a data-driven approach to partition the data into subpopulations that differ in the magnitude of their treatment effects. The approach enables the construction of valid confidence intervals for treatment effects, even with many covariates relative to the sample size, and without "sparsity" assumptions. We propose an "honest" approach to estimation, whereby one sample is used to construct the partition and another to estimate treatment effects for each subpopulation. Our approach builds on regression tree methods, modified to optimize for goodness of fit in treatment effects and to account for honest estimation. Our model selection criterion anticipates that bias will be eliminated by honest estimation and also accounts for the effect of making additional splits on the variance of treatment effect estimates within each subpopulation. We address the challenge that the "ground truth" for a causal effect is not observed for any individual unit, so that standard approaches to cross-validation must be modified. Through a simulation study, we show that for our preferred method honest estimation results in nominal coverage for 90% confidence intervals, whereas coverage ranges between 74% and 84% for nonhonest approaches. Honest estimation requires estimating the model with a smaller sample size; the cost in terms of mean squared error of treatment effects for our preferred method ranges between 7-22%.

  14. Effects of Population Heterogeneity on Accuracy of DIF Detection

    ERIC Educational Resources Information Center

    Oliveri, María Elena; Ercikan, Kadriye; Zumbo, Bruno D.

    2014-01-01

    Heterogeneity within English language learners (ELLs) groups has been documented. Previous research on differential item functioning (DIF) analyses suggests that accurate DIF detection rates are reduced greatly when groups are heterogeneous. In this simulation study, we investigated the effects of heterogeneity within linguistic (ELL) groups on…

  15. Estimating Heterogeneous Treatment Effects with Observational Data*

    PubMed Central

    Xie, Yu; Brand, Jennie E.; Jann, Ben

    2011-01-01

    Individuals differ not only in their background characteristics, but also in how they respond to a particular treatment, intervention, or stimulation. In particular, treatment effects may vary systematically by the propensity for treatment. In this paper, we discuss a practical approach to studying heterogeneous treatment effects as a function of the treatment propensity, under the same assumption commonly underlying regression analysis: ignorability. We describe one parametric method and two non-parametric methods for estimating interactions between treatment and the propensity for treatment. For the first method, we begin by estimating propensity scores for the probability of treatment given a set of observed covariates for each unit and construct balanced propensity score strata; we then estimate propensity score stratum-specific average treatment effects and evaluate a trend across them. For the second method, we match control units to treated units based on the propensity score and transform the data into treatment-control comparisons at the most elementary level at which such comparisons can be constructed; we then estimate treatment effects as a function of the propensity score by fitting a non-parametric model as a smoothing device. For the third method, we first estimate non-parametric regressions of the outcome variable as a function of the propensity score separately for treated units and for control units and then take the difference between the two non-parametric regressions. We illustrate the application of these methods with an empirical example of the effects of college attendance on womens fertility. PMID:23482633

  16. Recursive partitioning for heterogeneous causal effects

    PubMed Central

    Athey, Susan; Imbens, Guido

    2016-01-01

    In this paper we propose methods for estimating heterogeneity in causal effects in experimental and observational studies and for conducting hypothesis tests about the magnitude of differences in treatment effects across subsets of the population. We provide a data-driven approach to partition the data into subpopulations that differ in the magnitude of their treatment effects. The approach enables the construction of valid confidence intervals for treatment effects, even with many covariates relative to the sample size, and without “sparsity” assumptions. We propose an “honest” approach to estimation, whereby one sample is used to construct the partition and another to estimate treatment effects for each subpopulation. Our approach builds on regression tree methods, modified to optimize for goodness of fit in treatment effects and to account for honest estimation. Our model selection criterion anticipates that bias will be eliminated by honest estimation and also accounts for the effect of making additional splits on the variance of treatment effect estimates within each subpopulation. We address the challenge that the “ground truth” for a causal effect is not observed for any individual unit, so that standard approaches to cross-validation must be modified. Through a simulation study, we show that for our preferred method honest estimation results in nominal coverage for 90% confidence intervals, whereas coverage ranges between 74% and 84% for nonhonest approaches. Honest estimation requires estimating the model with a smaller sample size; the cost in terms of mean squared error of treatment effects for our preferred method ranges between 7–22%. PMID:27382149

  17. Functional Heterogeneity and Senior Management Team Effectiveness

    ERIC Educational Resources Information Center

    Benoliel, Pascale; Somech, Anit

    2016-01-01

    Purpose: There has been an increasing trend toward the creation of senior management teams (SMTs) which are characterized by a high degree of functional heterogeneity. Although such teams may create better linkages to information, along with the benefits of functional heterogeneity comes the potential for conflicts that stem from the value…

  18. Biology of Bony Fish Macrophages

    PubMed Central

    Hodgkinson, Jordan W.; Grayfer, Leon; Belosevic, Miodrag

    2015-01-01

    Macrophages are found across all vertebrate species, reside in virtually all animal tissues, and play critical roles in host protection and homeostasis. Various mechanisms determine and regulate the highly plastic functional phenotypes of macrophages, including antimicrobial host defenses (pro-inflammatory, M1-type), and resolution and repair functions (anti-inflammatory/regulatory, M2-type). The study of inflammatory macrophages in immune defense of teleosts has garnered much attention, and antimicrobial mechanisms of these cells have been extensively studied in various fish models. Intriguingly, both similarities and differences have been documented for the regulation of lower vertebrate macrophage antimicrobial defenses, as compared to what has been described in mammals. Advances in our understanding of the teleost macrophage M2 phenotypes likewise suggest functional conservation through similar and distinct regulatory strategies, compared to their mammalian counterparts. In this review, we discuss the current understanding of the molecular mechanisms governing teleost macrophage functional heterogeneity, including monopoetic development, classical macrophage inflammatory and antimicrobial responses as well as alternative macrophage polarization towards tissues repair and resolution of inflammation. PMID:26633534

  19. Heterogeneity Effects in Plutonium Contaminated Soil

    DTIC Science & Technology

    2009-03-01

    lodged in the lung, a partition coefficient specific to the BOMARC missile site contamination might be developed. The question of long-term...activity heterogeneity using dual counting methods with gamma spectroscopy using a hyper pure germanium (HpGe) counter. Each sample was partitioned ... partition off onto bone surfaces and to the liver with the remaining fraction distributing to other tissues in the body (Cember, 1996). As the routes of

  20. Landscape heterogeneity-biodiversity relationship: effect of range size.

    PubMed

    Katayama, Naoki; Amano, Tatsuya; Naoe, Shoji; Yamakita, Takehisa; Komatsu, Isamu; Takagawa, Shin-ichi; Sato, Naoto; Ueta, Mutsuyuki; Miyashita, Tadashi

    2014-01-01

    The importance of landscape heterogeneity to biodiversity may depend on the size of the geographic range of species, which in turn can reflect species traits (such as habitat generalization) and the effects of historical and contemporary land covers. We used nationwide bird survey data from Japan, where heterogeneous landscapes predominate, to test the hypothesis that wide-ranging species are positively associated with landscape heterogeneity in terms of species richness and abundance, whereas narrow-ranging species are positively associated with landscape homogeneity in the form of either open or forest habitats. We used simultaneous autoregressive models to explore the effects of climate, evapotranspiration, and landscape heterogeneity on the richness and abundance of breeding land-bird species. The richness of wide-ranging species and the total species richness were highest in heterogeneous landscapes, where many wide-ranging species showed the highest abundance. In contrast, the richness of narrow-ranging species was not highest in heterogeneous landscapes; most of those species were abundant in either open or forest landscapes. Moreover, in open landscapes, narrow-ranging species increased their species richness with decreasing temperature. These results indicate that heterogeneous landscapes are associated with rich bird diversity but that most narrow-ranging species prefer homogeneous landscapes--particularly open habitats in colder regions, where grasslands have historically predominated. There is a need to reassess the generality of the heterogeneity-biodiversity relationship, with attention to the characteristics of species assemblages determined by environments at large spatiotemporal scales.

  1. Effects of microstructural heterogeneity on BGA reliability

    SciTech Connect

    Neilsen, M.K.; Burchett, S.N.; Fang, H.E.; Vianco, P.T.

    1998-07-01

    The near eutectic 60Sn-40Pb alloy is the most commonly used solder for electrical interconnections in electronic packages. This alloy has a number of processing advantages (suitable melting point of 183 C and good wetting behavior). However, under conditions of cyclic strain and temperature (thermomechanical fatigue), the microstructure of this alloy undergoes a heterogeneous coarsening and failure process that makes the prediction of solder joint lifetime complex. A viscoplastic constitutive model for solder with an internal state variable that tracks microstructural evolution is currently under development. This constitutive model was implemented in to several finite element codes. With this computational capability, the thermomechanical response of solder interconnects, including microstructural evolution, can be predicted. This capability was applied to predict the thermomechanical response of a ball grid array (BGA) solder interconnect. BGAs with both homogeneous and heterogeneous initial microstructures were evaluated. In this paper, the constitutive model used to describe the solder will first be briefly discussed. The results of computational studies to determine the thermomechanical response of BGA solder interconnects will then be presented.

  2. Estimation of effective hydrogeological parameters in heterogeneous and anisotropic aquifers

    NASA Astrophysics Data System (ADS)

    Lin, Hsien-Tsung; Tan, Yih-Chi; Chen, Chu-Hui; Yu, Hwa-Lung; Wu, Shih-Ching; Ke, Kai-Yuan

    2010-07-01

    SummaryObtaining reasonable hydrological input parameters is a key challenge in groundwater modeling. Analysis of temporal evolution during pump-induced drawdown is one common approach used to estimate the effective transmissivity and storage coefficients in a heterogeneous aquifer. In this study, we propose a Modified Tabu search Method (MTM), an improvement drawn from an alliance between the Tabu Search (TS) and the Adjoint State Method (ASM) developed by Tan et al. (2008). The latter is employed to estimate effective parameters for anisotropic, heterogeneous aquifers. MTM is validated by several numerical pumping tests. Comparisons are made to other well-known techniques, such as the type-curve method (TCM) and the straight-line method (SLM), to provide insight into the challenge of determining the most effective parameter for an anisotropic, heterogeneous aquifer. The results reveal that MTM can efficiently obtain the best representative and effective aquifer parameters in terms of the least mean square errors of the drawdown estimations. The use of MTM may involve less artificial errors than occur with TCM and SLM, and lead to better solutions. Therefore, effective transmissivity is more likely to be comprised of the geometric mean of all transmissivities within the cone of depression based on a precise estimation of MTM. Further investigation into the applicability of MTM shows that a higher level of heterogeneity in an aquifer can induce an uncertainty in estimations, while the changes in correlation length will affect the accuracy of MTM only once the degree of heterogeneity has also risen.

  3. Local heterogeneity effects on small-sample worths

    SciTech Connect

    Schaefer, R.W.

    1986-01-01

    One of the parameters usually measured in a fast reactor critical assembly is the reactivity associated with inserting a small sample of a material into the core (sample worth). Local heterogeneities introduced by the worth measurement techniques can have a significant effect on the sample worth. Unfortunately, the capability is lacking to model some of the heterogeneity effects associated with the experimental technique traditionally used at ANL (the radial tube technique). It has been suggested that these effects could account for a large portion of what remains of the longstanding central worth discrepancy. The purpose of this paper is to describe a large body of experimental data - most of which has never been reported - that shows the effect of radial tube-related local heterogeneities.

  4. Effects of Heterogeneous Diffuse Fibrosis on Arrhythmia Dynamics and Mechanism

    NASA Astrophysics Data System (ADS)

    Kazbanov, Ivan V.; Ten Tusscher, Kirsten H. W. J.; Panfilov, Alexander V.

    2016-02-01

    Myocardial fibrosis is an important risk factor for cardiac arrhythmias. Previous experimental and numerical studies have shown that the texture and spatial distribution of fibrosis may play an important role in arrhythmia onset. Here, we investigate how spatial heterogeneity of fibrosis affects arrhythmia onset using numerical methods. We generate various tissue textures that differ by the mean amount of fibrosis, the degree of heterogeneity and the characteristic size of heterogeneity. We study the onset of arrhythmias using a burst pacing protocol. We confirm that spatial heterogeneity of fibrosis increases the probability of arrhythmia induction. This effect is more pronounced with the increase of both the spatial size and the degree of heterogeneity. The induced arrhythmias have a regular structure with the period being mostly determined by the maximal local fibrosis level. We perform ablations of the induced fibrillatory patterns to classify their type. We show that in fibrotic tissue fibrillation is usually of the mother rotor type but becomes of the multiple wavelet type with increase in tissue size. Overall, we conclude that the most important factor determining the formation and dynamics of arrhythmia in heterogeneous fibrotic tissue is the value of maximal local fibrosis.

  5. The Cardiovascular and Neurotoxic Effects of the  Venoms of Six Bony and Cartilaginous Fish Species.

    PubMed

    Han, Han; Baumann, Kate; Casewell, Nicholas R; Ali, Syed A; Dobson, James; Koludarov, Ivan; Debono, Jordan; Cutmore, Scott C; Rajapakse, Niwanthi W; Jackson, Timothy N W; Jones, Rob; Hodgson, Wayne C; Fry, Bryan G; Kuruppu, Sanjaya

    2017-02-16

    Fish venoms are often poorly studied, in part due to the difficulty in obtaining, extracting, and storing them. In this study, we characterize the cardiovascular and neurotoxic effects of the venoms from the following six species of fish: the cartilaginous stingrays Neotrygon kuhlii and Himantura toshi, and the bony fish Platycephalus fucus, Girella tricuspidata, Mugil cephalus, and Dentex tumifrons. All venoms (10-100 μg/kg, i.v.), except G. tricuspidata and P. fuscus, induced a biphasic response on mean arterial pressure (MAP) in the anesthetised rat. P. fucus venom exhibited a hypotensive response, while venom from G. tricuspidata displayed a single depressor response. All venoms induced cardiovascular collapse at 200 μg/kg, i.v. The in vitro neurotoxic effects of venom were examined using the chick biventer cervicis nerve-muscle (CBCNM) preparation. N. kuhlii, H. toshi, and P. fucus venoms caused concentration-dependent inhibition of indirect twitches in the CBCNM preparation. These three venoms also inhibited responses to exogenous acetylcholine (ACh) and carbachol (CCh), but not potassium chloride (KCl), indicating a post-synaptic mode of action. Venom from G. tricuspidata, M. cephalus, and D. tumifrons had no significant effect on indirect twitches or agonist responses in the CBCNM. Our results demonstrate that envenoming by these species of fish may result in moderate cardiovascular and/or neurotoxic effects. Future studies aimed at identifying the molecules responsible for these effects could uncover potentially novel lead compounds for future pharmaceuticals, in addition to generating new knowledge about the evolutionary relationships between venomous animals.

  6. An effective cache algorithm for heterogeneous storage systems.

    PubMed

    Li, Yong; Feng, Dan; Shi, Zhan

    2013-01-01

    Modern storage environment is commonly composed of heterogeneous storage devices. However, traditional cache algorithms exhibit performance degradation in heterogeneous storage systems because they were not designed to work with the diverse performance characteristics. In this paper, we present a new cache algorithm called HCM for heterogeneous storage systems. The HCM algorithm partitions the cache among the disks and adopts an effective scheme to balance the work across the disks. Furthermore, it applies benefit-cost analysis to choose the best allocation of cache block to improve the performance. Conducting simulations with a variety of traces and a wide range of cache size, our experiments show that HCM significantly outperforms the existing state-of-the-art storage-aware cache algorithms.

  7. Advances in genomics of bony fish

    PubMed Central

    Jansen, Hans J.; Dirks, Ron P.

    2014-01-01

    In this review, we present an overview of the recent advances of genomic technologies applied to studies of fish species belonging to the superclass of Osteichthyes (bony fish) with a major emphasis on the infraclass of Teleostei, also called teleosts. This superclass that represents more than 50% of all known vertebrate species has gained considerable attention from genome researchers in the last decade. We discuss many examples that demonstrate that this highly deserved attention is currently leading to new opportunities for answering important biological questions on gene function and evolutionary processes. In addition to giving an overview of the technologies that have been applied for studying various fish species we put the recent advances in genome research on the model species zebrafish and medaka in the context of its impact for studies of all fish of the superclass of Osteichthyes. We thereby want to illustrate how the combined value of research on model species together with a broad angle perspective on all bony fish species will have a huge impact on research in all fields of fundamental science and will speed up applications in many societally important areas such as the development of new medicines, toxicology test systems, environmental sensing systems and sustainable aquaculture strategies. PMID:24291769

  8. Pediatric bony craniovertebral junction abnormalities: Institutional experience of 10 years

    PubMed Central

    Kale, S. S.; Ailawadhi, Pankaj; Yerramneni, Vamsi Krishna; Chandra, P. S.; Kumar, Rajender; Sharma, B. S.; Mahapatra, A. K.

    2011-01-01

    Objective: To study the clinical features and treatment outcome of pediatric patients with bony craniovertebral abnormalities. Materials and Methods: The authors studied 189 consecutive cases of pediatric bony craniovertebral junction abnormalities operated between 2001 and March, 2010. Results: The pathologies were developmental (n = 162), traumatic (n = 18) and tuberculous (n = 9). Surgical procedures included transoral decompression (n = 118), occipitocervical fusion (OCF, n = 139), C 1 -C 2 fusion (n = 45), and posterior fossa decompression (n = 5). Methods for OCF included contoured stainless steel rods (n = 86), titanium lateral mass screws and plates (n = 47) and steel wires (n = 6). Constructs of all patients of posterior fixation with contoured rods and wires or lateral mass screw and rod who could be followed up were either stable/fused or were fused and stable. No implant failure was noticed among these two surgical procedures. However, 6 patients with C 1-C 2 fusion had broken wires on follow-up requiring repeat posterior fixation. Good neurological outcome was observed even in poor-grade patients. No significant effect on the curvature or growth of the spine was observed at follow-up. Conclusions: Pediatric craniovertebral junction anomalies can be managed successfully with good outcomes using a low cost contoured rod and wires. PMID:22069436

  9. The Effect of Surface Heterogeneity on Cloud Absorption Estimates

    NASA Technical Reports Server (NTRS)

    Chiu, Jui-Yuan C.; Marshak, Alexander; Wiscombe, Warren J.

    2004-01-01

    This study presents a systematic and quantitative analysis of the effect of inhomogeneous surface albedo on shortwave cloud absorption estimates. We use 3D radiative transfer modeling with gradually complex clouds over a simplified surface to calculate cloud absorption. We find that averaging surface albedo always underestimates cloud absorption, and thus accounting for surface heterogeneity always enhances cloud absorption. However, the impact on cloud absorption estimates is not enough to explain the discrepancy between measured and model calculated shortwave cloud absorptions.

  10. TRAPEZE: a randomised controlled trial of the clinical effectiveness and cost-effectiveness of chemotherapy with zoledronic acid, strontium-89, or both, in men with bony metastatic castration-refractory prostate cancer.

    PubMed Central

    James, Nicholas; Pirrie, Sarah; Pope, Ann; Barton, Darren; Andronis, Lazaros; Goranitis, Ilias; Collins, Stuart; McLaren, Duncan; O'Sullivan, Joe; Parker, Chris; Porfiri, Emilio; Staffurth, John; Stanley, Andrew; Wylie, James; Beesley, Sharon; Birtle, Alison; Brown, Janet; Chakraborti, Prabir; Russell, Martin; Billingham, Lucinda

    2016-01-01

    BACKGROUND: Bony metastatic castration-refractory prostate cancer is associated with a poor prognosis and high morbidity. TRAPEZE was a two-by-two factorial randomised controlled trial of zoledronic acid (ZA) and strontium-89 (Sr-89), each combined with docetaxel. All have palliative benefits, are used to control bone symptoms and are used with docetaxel to prolong survival. ZA, approved on the basis of reducing skeletal-related events (SREs), is commonly combined with docetaxel in practice, although evidence of efficacy and cost-effectiveness is lacking. Sr-89, approved for controlling metastatic pain and reducing need for subsequent bone treatments, is generally palliatively used in patients unfit for chemotherapy. Phase II analysis confirmed the safety and feasibility of combining these agents. TRAPEZE aimed to determine the clinical effectiveness and cost-effectiveness of each agent. METHODS: Patients were randomised to receive six cycles of docetaxel plus prednisolone: alone, with ZA, with a single Sr-89 dose after cycle 6, or with both. Primary outcomes were clinical progression-free survival (CPFS: time to pain progression, SRE or death) and cost-effectiveness. Secondary outcomes were SRE-free interval (SREFI), total SREs, overall survival (OS) and quality of life (QoL). Log-rank test and Cox regression modelling were used to determine clinical effectiveness. Cost-effectiveness was assessed from the NHS perspective and expressed as cost per additional quality-adjusted life-year (QALY). An additional analysis was carried out for ZA to reflect the availability of generic ZA. RESULTS: PATIENTS: 757 randomised (median age 68.7 years; Eastern Cooperative Oncology Group scale score 0, 40%; 1, 52%; 2, 8%; prior radiotherapy, 45%); median prostate-specific antigen 143.78 ng/ml (interquartile range 50.8-353.9 ng/ml). Stratified log-rank analysis of CPFS was statistically non-significant for either agent (Sr-89, p = 0.11; ZA, p = 0.45). Cox regression

  11. Effects of spatial heterogeneity on land-atmosphere interactions

    NASA Astrophysics Data System (ADS)

    Hu, Zhenglin

    1998-08-01

    A well-coordinated modeling and observational data analysis approach is designed to address various aspects of the impact of surface heterogeneity on land-atmosphere interactions with following specific objectives: (1) Understanding and quantifying the feedback between land and atmosphere by using a partially coupled model and concepts of factorial experiment design. (2) Developing a parsimonious parameterization for surface temperature and soil moisture content. (3) Developing a semi-analytical approach to quantify and parameterize the effects of surface heterogeneity on land surface model and remote sensing algorithms. Using a factorial experiment framework, a systematic relationship is developed between uncoupled and coupled land surface model sensitivities. It is shown that the relative sensitivity of a coupled model can be partitioned into the relative sensitivity of the corresponding uncoupled model, a term related to interactive effects, and a product term involving main effects of land and atmosphere processes. The proposed framework is used to explain why sensitivities to certain parameters are enhanced (damped) when the land surface model is coupled with an atmospheric model. The aforementioned study used a detailed land surface model which needs dozens of land surface parameters that cannot be measured directly. A parsimonious and computationally efficient parameterization of land surface processes is achieved by the force-restore method. An improved version of the force-restore method is developed and tested. This refined version of the force-restore method can be used for modeling surface temperature and soil moisture content. Above studies assume homogeneous surface conditions over a grid. However, the land surface is usually very heterogeneous at the mesoscale and climate model scales. A computationally efficient analytical approach is developed to evaluate effects of surface heterogeneity on and scaling properties of land surface representations

  12. The Value of Heterogeneity for Cost-Effectiveness Subgroup Analysis

    PubMed Central

    Manca, Andrea; Claxton, Karl; Sculpher, Mark J.

    2014-01-01

    This article develops a general framework to guide the use of subgroup cost-effectiveness analysis for decision making in a collectively funded health system. In doing so, it addresses 2 key policy questions, namely, the identification and selection of subgroups, while distinguishing 2 sources of potential value associated with heterogeneity. These are 1) the value of revealing the factors associated with heterogeneity in costs and outcomes using existing evidence (static value) and 2) the value of acquiring further subgroup-related evidence to resolve the uncertainty given the current understanding of heterogeneity (dynamic value). Consideration of these 2 sources of value can guide subgroup-specific treatment decisions and inform whether further research should be conducted to resolve uncertainty to explain variability in costs and outcomes. We apply the proposed methods to a cost-effectiveness analysis for the management of patients with acute coronary syndrome. This study presents the expected net benefits under current and perfect information when subgroups are defined based on the use and combination of 6 binary covariates. The results of the case study confirm the theoretical expectations. As more subgroups are considered, the marginal net benefit gains obtained under the current information show diminishing marginal returns, and the expected value of perfect information shows a decreasing trend. We present a suggested algorithm that synthesizes the results to guide policy. PMID:24944196

  13. Understanding the effect of retirement on health: Mechanisms and heterogeneity.

    PubMed

    Eibich, Peter

    2015-09-01

    This paper investigates the mechanisms behind the health effects of retirement. Using a Regression Discontinuity Design to exploit financial incentives in the German pension system for identification, I find that retirement improves subjective health status and mental health, while also reducing outpatient care utilization. I explore a wide range of health behaviors, time use, and effect heterogeneity as potential mechanisms. Relief from work-related stress and strain, increased sleep duration as well as more frequent physical exercise seem to be key mechanisms through which retirement affects health.

  14. Frequency-dependent effective hydraulic conductivity of strongly heterogeneous media.

    PubMed

    Caspari, E; Gurevich, B; Müller, T M

    2013-10-01

    The determination of the transport properties of heterogeneous porous rocks, such as an effective hydraulic conductivity, arises in a range of geoscience problems, from groundwater flow analysis to hydrocarbon reservoir modeling. In the presence of formation-scale heterogeneities, nonstationary flows, induced by pumping tests or propagating elastic waves, entail localized pressure diffusion processes with a characteristic frequency depending on the pressure diffusivity and size of the heterogeneity. Then, on a macroscale, a homogeneous equivalent medium exists, which has a frequency-dependent effective conductivity. The frequency dependence of the conductivity can be analyzed with Biot's equations of poroelasticity. In the quasistatic frequency regime of this framework, the slow compressional wave is a proxy for pressure diffusion processes. This slow compressional wave is associated with the out-of-phase motion of the fluid and solid phase, thereby creating a relative fluid-solid displacement vector field. Decoupling of the poroelasticity equations gives a diffusion equation for the fluid-solid displacement field valid in a poroelastic medium with spatial fluctuations in hydraulic conductivity. Then, an effective conductivity is found by a Green's function approach followed by a strong-contrast perturbation theory suggested earlier in the context of random dielectrics. This theory leads to closed-form expressions for the frequency-dependent effective conductivity as a function of the one- and two-point probability functions of the conductivity fluctuations. In one dimension, these expressions are consistent with exact solutions in both low- and high-frequency limits for arbitrary conductivity contrast. In 3D, the low-frequency limit depends on the details of the microstructure. However, the derived approximation for the effective conductivity is consistent with the Hashin-Shtrikman bounds.

  15. Dosimetric effect of tissue heterogeneity for 125I prostate implants

    PubMed Central

    Oliveira, Susana Maria; Teixeira, Nuno José; Fernandes, Lisete; Teles, Pedro; Vaz, Pedro

    2014-01-01

    Aim To use Monte Carlo (MC) together with voxel phantoms to analyze the tissue heterogeneity effect in the dose distributions and equivalent uniform dose (EUD) for 125I prostate implants. Background Dose distribution calculations in low dose-rate brachytherapy are based on the dose deposition around a single source in a water phantom. This formalism does not take into account tissue heterogeneities, interseed attenuation, or finite patient dimensions effects. Tissue composition is especially important due to the photoelectric effect. Materials and methods The computed tomographies (CT) of two patients with prostate cancer were used to create voxel phantoms for the MC simulations. An elemental composition and density were assigned to each structure. Densities of the prostate, vesicles, rectum and bladder were determined through the CT electronic densities of 100 patients. The same simulations were performed considering the same phantom as pure water. Results were compared via dose–volume histograms and EUD for the prostate and rectum. Results The mean absorbed doses presented deviations of 3.3–4.0% for the prostate and of 2.3–4.9% for the rectum, when comparing calculations in water with calculations in the heterogeneous phantom. In the calculations in water, the prostate D90 was overestimated by 2.8–3.9% and the rectum D0.1cc resulted in dose differences of 6–8%. The EUD resulted in an overestimation of 3.5–3.7% for the prostate and of 7.7–8.3% for the rectum. Conclusions The deposited dose was consistently overestimated for the simulation in water. In order to increase the accuracy in the determination of dose distributions, especially around the rectum, the introduction of the model-based algorithms is recommended. PMID:25337412

  16. Heterogeneous structure and its effect on properties and electrochemical behavior of ion-exchange membrane

    NASA Astrophysics Data System (ADS)

    Ariono, D.; Khoiruddin; Subagjo; Wenten, I. G.

    2017-02-01

    Generally, commercially available ion-exchange membrane (IEM) can be classified into homogeneous and heterogeneous membranes. The classification is based on degree of heterogeneity in membrane structure. It is well known that the heterogeneity greatly affects the properties of IEM, such as conductivity, permselectivity, chemical and mechanical stability. The heterogeneity also influences ionic and electrical current transfer behavior of IEM-based processes during their operation. Therefore, understanding the role of heterogeneity in IEM properties is important to provide preliminary information on their operability and applicability. In this paper, the heterogeneity and its effect on IEM properties are reviewed. Some models for describing the heterogeneity of IEM and methods for characterizing the degree of heterogeneity are discussed. In addition, the influence of heterogeneity on the performance of IEM-based processes and their electrochemical behavior are described.

  17. Effective reaction parameters for mixing controlled reactions in heterogeneous media

    NASA Astrophysics Data System (ADS)

    Luo, Jian; Dentz, Marco; Carrera, Jesus; Kitanidis, Peter

    2008-02-01

    Sound understanding of mixing-controlled reactions in heterogeneous media is needed for the realistic modeling of contaminant transport in aquifers and is a precondition for the evaluation of natural attenuation processes, the design of nuclear waste disposal, and the engineered remediation of contaminated sites. In this work, we study the bimolecular dissolution-precipitation equilibrium reaction, adapted after De Simoni et al. (2005). Because of advective and dispersive transport of the reacting species, the system is globally in nonequilibrium because the effective reaction rate is limited by the finite rate of transport and thus is affected by the heterogeneity of the formation. We study the macroscopic formulation of such a reactive transport system in terms of mixing-controlled reaction parameters which integrate the impact of spatial heterogeneity. The apparent chemical saturation is found to be a function of the concentration variance and is generally greater than its local-scale equivalent. This explains why water samples taken from pumping wells are normally nonequilibrium with respect to minerals existing in the aquifer, even when local equilibrium is to be expected. The reaction rate is given by the product of a reaction factor, associated with the local equilibrium constant and concentration variance, and a mixing factor, which is the product of the microdispersion coefficient and the square gradient of the mean and perturbation concentration fields. The mixing factor dominates the description of the reaction rate in the upscaled macroscopic models. The reaction rate predicted by macroscopic models is controlled by two competing effects: The large heterogeneity-induced macrodispersion coefficient leads to an increase of reaction rate, while a more smoothed concentration gradient may lead to a decrease of the reaction rate. Macroscopic models may only give a good approximation at large time and away from the plume center of mass because of the balanced

  18. Effects of incomplete mixing on chemical reactions under flow heterogeneities.

    NASA Astrophysics Data System (ADS)

    Perez, Lazaro; Hidalgo, Juan J.; Dentz, Marco

    2016-04-01

    Evaluation of the mixing process in aquifers is of primary importance when assessing attenuation of pollutants. In aquifers different hydraulic and chemical properties can increase mixing and spreading of the transported species. Mixing processes control biogeochemical transformations such as precipitation/dissolution reactions or degradation reactions that are fast compared to mass transfer processes. Reactions are local phenomena that fluctuate at the pore scale, but predictions are often made at much larger scales. However, aquifer heterogeities are found at all scales and generates flow heterogeneities which creates complex concentration distributions that enhances mixing. In order to assess the impact of spatial flow heterogeneities at pore scale we study concentration profiles, gradients and reaction rates using a random walk particle tracking (RWPT) method and kernel density estimators to reconstruct concentrations and gradients in two setups. First, we focus on a irreversible bimolecular reaction A+B → C under homogeneous flow to distinguish phenomena of incomplete mixing of reactants from finite-size sampling effects. Second, we analise a fast reversible bimolecular chemical reaction A+B rightleftharpoons C in a laminar Poiseuille flow reactor to determine the difference between local and global reaction rates caused by the incomplete mixing under flow heterogeneities. Simulation results for the first setup differ from the analytical solution of the continuum scale advection-dispersion-reaction equation studied by Gramling et al. (2002), which results in an overstimation quantity of reaction product (C). In the second setup, results show that actual reaction rates are bigger than the obtained from artificially mixing the system by averaging the concentration vertically. - LITERATURE Gramling, C. M.,Harvey, C. F., Meigs, and L. C., (2002). Reactive transport in porous media: A comparison of model prediction with laboratory visualization, Environ. Sci

  19. An effective medium theory for three-dimensional elastic heterogeneities

    NASA Astrophysics Data System (ADS)

    Jordan, Thomas H.

    2015-11-01

    A second-order Born approximation is used to formulate a self-consistent theory for the effective elastic parameters of stochastic media with ellipsoidal distributions of small-scale heterogeneity. The covariance of the stiffness tensor is represented as the product of a one-point tensor variance and a two-point scalar correlation function with ellipsoidal symmetry, which separates the statistical properties of the local anisotropy from those of the geometric anisotropy. The spatial variations can then be rescaled to an isotropic distribution by a simple metric transformation; the spherical average of the strain Green's function in the transformed space reduces to a constant Kneer tensor, and the second-order corrections to the effective elastic parameters are given by the contraction of the rescaled Kneer tensor against the single-point variance of the stiffness tensor. Explicit results are derived for stochastic models in which the heterogeneity is transversely isotropic and its second moments are characterized by a horizontal-to-vertical aspect ratio η. If medium is locally isotropic, the expressions for the anisotropic effective moduli reduce in the limit η → ∞ to Backus's second-order expressions for a 1-D stochastic laminate. Comparisons with the exact Backus theory show that the second-order approximation predicts the effective anisotropy for non-Gaussian media fairly well for relative rms fluctuations in the moduli smaller than about 30 per cent. A locally anisotropic model is formulated in which the local elastic properties have hexagonal symmetry, guided by a Gaussian random vector field that is transversely isotropic and specified by a horizontal-to-vertical orientation ratio ξ. The self-consistent theory provides closed-form expressions for the dependence of the effective moduli on 0 < ξ < ∞ and 0 < η < ∞. The effective-medium parametrizations described here appear to be suitable for incorporation into tomographic modelling.

  20. DIAGNOSTIC CRITERIA FOR PROLIFERATIVE THYROID LESIONS IN BONY FISHES

    EPA Science Inventory

    Criteria for distinguishing hyperplastic thyroid lesions from thyroid neoplasia in bony fishes have long been debated by scientists. Confusion exists because the thyroid tissue in most teleosts is unencapsulated, is occasionally found in ectopic sites, and is frequently predispos...

  1. DIAGNOSTIC CRITERIA FOR PROLIFERATIVE THYROID LESIONS IN BONY FISHES

    EPA Science Inventory

    Thyroid proliferative lesions are rather common in bony fishes but disagreement exists in the fish pathology community concerning diagnostic criteria for hyperplastic versus neoplastic lesions. To simplify the diagnosis of proliferative thyroid lesions and to reduce confusion reg...

  2. Analysis of Surface Heterogeneity Effects with Mesoscale Terrestrial Modeling Platforms

    NASA Astrophysics Data System (ADS)

    Simmer, C.

    2015-12-01

    An improved understanding of the full variability in the weather and climate system is crucial for reducing the uncertainty in weather forecasting and climate prediction, and to aid policy makers to develop adaptation and mitigation strategies. A yet unknown part of uncertainty in the predictions from the numerical models is caused by the negligence of non-resolved land surface heterogeneity and the sub-surface dynamics and their potential impact on the state of the atmosphere. At the same time, mesoscale numerical models using finer horizontal grid resolution [O(1)km] can suffer from inconsistencies and neglected scale-dependencies in ABL parameterizations and non-resolved effects of integrated surface-subsurface lateral flow at this scale. Our present knowledge suggests large-eddy-simulation (LES) as an eventual solution to overcome the inadequacy of the physical parameterizations in the atmosphere in this transition scale, yet we are constrained by the computational resources, memory management, big-data, when using LES for regional domains. For the present, there is a need for scale-aware parameterizations not only in the atmosphere but also in the land surface and subsurface model components. In this study, we use the recently developed Terrestrial Systems Modeling Platform (TerrSysMP) as a numerical tool to analyze the uncertainty in the simulation of surface exchange fluxes and boundary layer circulations at grid resolutions of the order of 1km, and explore the sensitivity of the atmospheric boundary layer evolution and convective rainfall processes on land surface heterogeneity.

  3. Effects of Along-strike Fault Heterogeneity on Rupture Propagation

    NASA Astrophysics Data System (ADS)

    Weng, H.; Yang, H.

    2015-12-01

    Fault zone materials have been suggested to be heterogeneous, such as along-strike variations of low velocity zone and stress conditions. How these fault heterogeneities affect earthquake rupture propagation is important to advance our understanding of earthquake physics, and yet remains poorly understood. Here we investigate the effects of along-strike fault heterogeneity on rupture propagation through numerical modeling on a strike-slip planar fault governed by a linear slip-weakening friction law. We first implement along-strike variations of fault zone materials based on field observations, which have shown the velocities of P and S waves of the low velocity zones can be reduced up to 50% compared to intact rocks. The rupture speed is decreased if the rupture propagates into materials with lower shear modulus and keeps at a stable speed quickly. In contrast, the rupture speed is increased if the rupture propagates into materials with higher shear modulus and accelerates into a steady speed more slowly. If this material boundary is very close to the nucleation zone, it may inhibit the nucleation process. In addition, there is always a perturbation on the rupture speed near the boundary due to the reflected energy. We then investigate the effects of a patch with elevated effective normal stress (barrier) on rupture propagation. Except for the distance d between the barrier and the nucleation zone, its width w, and the additional effective normal stress Δσn, all other parameters are kept constant for all the simulated models. Our results confirm that the barrier may slow down or stop coseismic ruptures, but may also induce supershear ruptures. Moreover, there is a sharp boundary between stopping the rupture and making very strong supershear ruptures. Furthermore, we demonstrate that the supershear rupture may emerge in a region that is delineated by two approximate linear boundaries for parameters d and w. The duration of supershear ruptures increases as the

  4. Multiple bony overgrowths in the mouth - report of two cases

    PubMed Central

    Kannan, Sathya; Muthusamy, Senthilkumar; Muthu, Kavitha; Sidhu, Preena

    2015-01-01

    Summary Tori and exostoses are benign bony protuberances that arise from bone surfaces in the oral cavity. The etiology of these growths has been implicated as multifactorial, but no consensus has been reached so far. These painless overgrowths seldom present as a complaint in the dental office unless functional or esthetic complications set in, and there is a fear for cancer. Here we discuss two rare cases where bony overgrowths present in the mouth were extensive and multiple. PMID:26811708

  5. Effective heterogeneity controlling premonitory slip on laboratory faults

    NASA Astrophysics Data System (ADS)

    Selvadurai, P. A.; Glaser, S.; Parker, J.

    2015-12-01

    Using a direct shear friction apparatus, we characterize factors controlling rheological differences along a PMMA-PMMA fault in the laboratory. Rheological differences on natural faults are believed to be a controlling factor to aseismic transients (slow slip) in nature. Asperity sizes and locations were measured using a pressure sensitive film at high (σn = 0.8 MPa) and low (σn = 0.4 MPa) nominal normal stress levels. Faults confined to low and high normal stress experienced lower and higher 'effective heterogeneity,' quantified using a characteristic elastic correlation length λc [Braun and Peyrard, 2012]. The fault was sheared at a constant far-field velocity VLP under constant normal stress σn. Non-uniform premonitory slip accumulated along the fault prior to rapid sliding. Slow events (SE), which were characterized as local increases in slip rate, were observed when the effective heterogeneity was increased. These events nucleated from the weaker central section of the fault propagating outwards at speeds between 0.84 mm/s to 26.5 mm/s over times 406 s and 11 s. The rupture growth rates were dependent on the load-point velocity VLP driving the system to failure. Slip rates, which increased within the SE, were also dependent on the load-point velocity. The evolution of slip rates versus time was similar to the 2013-2014 Boso slow slip event [Fukuda et al., 2014]. The slow event culminated with rapid slip rate deceleration sufficient to generate seismicity measured by an array of acoustic emission sensors. Deceleration of the SE (left panel of figure) shows a lower-frequency event (~ 60 - 350 Hz). In Detail A, we show the smaller, high-frequency events (~ 300 - 500 kHz) were superimposed on the larger, low-frequency signal. These events only occurred at higher levels of effective heterogeneity and demonstrate interactions between larger/slow and localized/fast slip. References: Braun, O. M. & M. Peyrard (2012), 'Crack in the frictional interface as a

  6. Effective IPTV channel management method over heterogeneous environments

    NASA Astrophysics Data System (ADS)

    Joo, Hyunchul; Lee, Dai-boong; Song, Hwangjun

    2007-09-01

    This paper presents an effective IPTV channel management method using SVC (scalable video coding) that considers concurrently both channel zapping time and network utilization. A broadcasting channel is encoded in two-layered bitstream (base-layer channel and enhancement-layer channel) to supply for heterogeneous environments. The proposed algorithm locates only a limited numbers of base-layer channels close to users to reduce the network delay part of channel zapping time and adjusts the length of GOP (group of picture) into each base-layer channel to decrease the video decoding delay part of channel zapping time, which are performed based on user's channel preference information. Finally, the experimental results are provided to show the performance of the proposed schemes.

  7. A bony foreign body found in a patient with no bony injury: a case report.

    PubMed

    Kaushik, Devwart; Joshi, Narendra; Kumar, Rakesh; Goyal, Shiv Kumar; Kumar, Kamlesh; Gaba, Sahil

    2014-01-01

    Open fractures with bone loss are a common occurrence following high energy trauma. But usually the bone fragments are lost on the roadside and are not usable. We report a patient who was involved in a head-on collision between two wheelers and presented with a bone fragment embedded in his thigh. Radiological survey revealed no bony injury in that patient. Another patient, who presented at the same time, sustained a segmental fracture of shaft femur and was found to have lost a bone fragment that was similar to the one found in previous patient. CT scan with 3D reconstruction revealed this missing fragment to be the same as that found in previous patient. Both patients had a history of head-on collision while travelling on a two-wheeler. Present case report throws some highlights on the probable mechanism of injury.

  8. Contamination, risk, and heterogeneity: on the effectiveness of aquifer remediation

    NASA Astrophysics Data System (ADS)

    Maxwell, Reed M.; Carle, Steven F.; Tompson, Andrew F. B.

    2008-06-01

    The effectiveness of aquifer remediation is typically expressed in terms of a reduction in contaminant concentrations relative to a regulated maximum contaminant level (MCL), and is usually confirmed by sparse monitoring data and/or simple model calculations. Here, the effectiveness of remediation is re-examined from a more thorough risk-based perspective that goes beyond the traditional MCL concept. A methodology is employed to evaluate the health risk to individuals exposed to contaminated household water that is produced from groundwater. This approach explicitly accounts for differences in risk arising from variability in individual physiology and water use, the uncertainty in estimating chemical carcinogenesis for different individuals, and the uncertainties and variability in contaminant concentrations within groundwater as affected by transport through heterogeneous geologic media. A hypothetical contamination scenario is developed as a case study in a saturated, alluvial aquifer underlying an actual Superfund site. A baseline (unremediated) human exposure and health risk scenario, as induced by contaminated groundwater pumped from this site, is predicted and compared with a similar estimate based upon pump-and-treat exposure intervention. The predicted reduction in risk in the remediation scenario is not an equitable one—that is, it is not uniform to all individuals within a population and varies according to the level of uncertainty in prediction. The importance of understanding the detailed hydrogeologic connections that are established in the heterogeneous geologic regime between the contaminated source, municipal receptors, and remediation wells, and its relationship to this uncertainty is demonstrated. Using two alternative pumping rates, we develop cost-benefit curves based upon reduced exposure and risk to different individuals within the population, under the presence of uncertainty.

  9. Neutronic double heterogeneity effect in particle dispersed type inert matrix fuels

    NASA Astrophysics Data System (ADS)

    Akie, H.; Takano, H.

    2006-06-01

    Rock-like oxide (ROX) fuel concept is studied in Japan for effective plutonium burning in light water reactors (LWRs). ROX is a heterogeneous fuel, where Pu containing yttria stabilized zirconia (YSZ) particles are dispersed in spinel matrix, and similar to the high temperature gas cooled reactor (HTR) fuel. The effect of such a 'double' heterogeneity (fuel, structure and coolant heterogeneity in reactor core, plus fuel heterogeneity) on HTR neutronic characteristics is important, while the effect was not taken into account in the ROX fueled LWR neutronics calculations. Here, this double heterogeneity effect is estimated for ROX fueled LWR, and compared with the Pu containing YSZ particle fueled HTR. As a result, the heterogeneity effect was negligible in the ROX-LWR system, while it is notable in YSZ-HTR system. The volume fraction of YSZ particle in the fuel region is one of the important parameter to cause the difference.

  10. Heterogenization of Homogeneous Catalysts: the Effect of the Support

    SciTech Connect

    Earl, W.L.; Ott, K.C.; Hall, K.A.; de Rege, F.M.; Morita, D.K.; Tumas, W.; Brown, G.H.; Broene, R.D.

    1999-06-29

    We have studied the influence of placing a soluble, homogeneous catalyst onto a solid support. We determined that such a 'heterogenized' homogeneous catalyst can have improved activity and selectivity for the asymmetric hydrogenation of enamides to amino acid derivatives. The route of heterogenization of RhDuPhos(COD){sup +} cations occurs via electrostatic interactions with anions that are capable of strong hydrogen bonding to silica surfaces. This is a novel approach to supported catalysis. Supported RhDuPhos(COD){sup +} is a recyclable, non-leaching catalyst in non-polar media. This is one of the few heterogenized catalysts that exhibits improved catalytic performance as compared to its homogeneous analog.

  11. Effects of reservoir heterogeneity on scaling of effective mass transfer coefficient for solute transport.

    PubMed

    Leung, Juliana Y; Srinivasan, Sanjay

    2016-09-01

    Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It

  12. Effects of reservoir heterogeneity on scaling of effective mass transfer coefficient for solute transport

    NASA Astrophysics Data System (ADS)

    Leung, Juliana Y.; Srinivasan, Sanjay

    2016-09-01

    Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It

  13. Effect of heterogeneous catalyst during combustion of diesel fuel

    NASA Astrophysics Data System (ADS)

    Arefeen, Quamrul

    1999-11-01

    With the increase in number of vehicles using diesel engines, the contributions to environmental pollution made by diesel engines is also on the rise. Carbon monoxide, oxides of nitrogen and sulfur, hydrocarbons, and particulates are currently regulated as harmful emissions from diesel engines. Recent technologies to control harmful engine emissions have been almost exclusively directed towards gasoline engines. It is generally held that fuel quality will have to play an important role with all IC engines to meet future stringent regulations. The objective of the present study was to determine the effects of heterogeneous catalyst on combustion. Micron sized solid catalyst, suspended in a specific organic peroxide, has been found to promote better combustion by modifying kinetics and changing the thermodynamics of the reactions. The catalyst reduces emissions without dramatically changing the properties of the fuel. The characteristic parameters of a baseline fuel, and the same fuel with the additive, were analyzed. The dosage of additive used was found to be compatible with commercial diesel. Diesel vehicles were driven unloaded at normal road conditions during the experiments. Exhaust emissions were measured when the trucks were at static conditions and the engine running on idle and at 2000 rpm. The gaseous components in the exhaust, O2, CO2, CO, NO, NO2, NOx, SO2, and CxH y were monitored. Particulates were trapped on a pre-weighed glass filter. Some of the filters were sent to an independent laboratory for microscopic and elemental analysis of the collected debris. Zinc oxide/peroxide suspended in tert-butyl hydro peroxide were used as the heterogeneous fuel catalyst. This combination increased the cetane rating of a commercial diesel fuel from 45 to a level of 70 depending on treatment ratio. A treatment ratio of one ounce additive per 5 gallons of diesel increased cetane number by an average of 5 points. Road mileage with the additive increased by an average

  14. Viscoelastic effective properties of two types of heterogeneous materials.

    NASA Astrophysics Data System (ADS)

    Cornet, Jan; Dabrowski, Marcin; Schmid, Daniel

    2015-04-01

    In the past, a lot of efforts have been put to describe two end cases of rock behaviors: elasticity and viscosity. In recent years, more focus has been brought on the intermediate viscoelastic cases which describe better the rheology of rocks such as shales. Shales are typically heterogeneous and the question arises as to how to derive their effective properties so that they can be approximated as homogeneous media. This question has already been dealt with at the elastic and viscous limit but still remains for some cases in between. Using MILAMIN, a fast finite element solver for large problems, we numerically investigate different approaches to derive the effective properties of several viscoelastic media. Two types of geometries are considered: layered and inclusion based media. We focus on two dimensional plane strain problems considering two phase composites deformed under pure shear. We start by investigating the case of transversely isotropic layered media made of two Maxwell materials. Using the Backus averaging method we discuss the degree of relevance of this averaging by considering some parameters as: layer periodicity, layer thickness and layer interface roughness. Other averaging methods are also discussed which provide a broader perspective on the performances of Backus averaging. In a second part we move on to inclusion based models. The advantage of these models compared to the previous one is that they provide a better approximation to real microstructures in rocks. The setup we consider in this part is the following: some viscous circular inclusions are embedded in an elastic matrix. Both the inclusions and the matrix are homogeneous but the inclusions are purely isotropic while the matrix can also be anisotropic. In order to derive the effective viscoelastic properties of the medium we use two approaches: the self-consistent averaging and the differential effective medium theory. The idea behind self-consistency is to assume that the inclusions

  15. Effects of Diffusive Property Heterogeneity on Effective MatrixDiffusion Coefficient for Fractured Rock

    SciTech Connect

    Zhang, Yingqi; Liu, Hui-hai; Zhou, Quanlin; Finsterle, Stefan

    2005-08-16

    Heterogeneities of diffusion properties are likely toinfluence the effective matrix diffusion coefficient determined fromtracer breakthrough curves. The objectives of this study are (1) toexamine if it is appropriate to use a single, effective matrix diffusioncoefficient to predict breakthrough curves in a fractured formation, (2)to examine if a postulated scale dependence of the effective matrixdiffusion coefficient is caused by heterogeneity in diffusion properties,and (3) to examine whether multirate diffusion results in the previouslyobserved time dependence of the effective matrix diffusion coefficient.The results show that the use of a single effective matrix diffusioncoefficient is appropriate only if the interchannel and intrachannelvariability of diffusion properties is small. The scale dependence of theeffective matrix diffusion coefficient is not caused by the studied typesof heterogeneity. Finally, the multirate diffusion process does notresult in the time dependence of the effective matrix diffusioncoefficient. oefficient is appropriate only if the inter- andintrachannel variability of diffusion properties is small. The scaledependence of the effective matrix diffusion coefficient is not caused byeither type of the studied heterogeneity. Finally, the multi-ratediffusion process does not result in the time dependence of the effectivematrix diffusion coefficient.

  16. DIAGNOSTIC CRITERIA FOR PROLIFERATIVE THYROID LESIONS IN BONY FISHES II

    EPA Science Inventory

    Thyroid proliferative lesions are rather common in bony fishes but diagnostic terminology and criteria for these lesions are inconsistent in the literature. The diagnosis of proliferative thyroid lesions is especially challenging in fish due to the fact that the thyroid is not a ...

  17. PROPOSED DIAGNOSTIC CRITERIA FOR PROLIFERATIVE THYROID LESIONS IN BONY FISHES

    EPA Science Inventory

    Distinguishing hyperplastic lesions from neoplasia in the thyroid of bony fishes has been debated by scientists for about one hundred years. As early as the first decade of the last century, the histological interpretation of some of the striking proliferative lesions observed in...

  18. 1. GENERAL VIEW FROM BONY PILE LOOKING SOUTH. WASH HOUSE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. GENERAL VIEW FROM BONY PILE LOOKING SOUTH. WASH HOUSE IN LEFT BACKGROUND. TIPPLE AND CLEANING PLANT TO RIGHT. IN CENTER IS A TANK USED FOR TREATING MINE REFUSE AND ACID RUNOFF. - Eureka No. 40, Tipple & Cleaning Plant, East of State Route 56, north of Little Paint Creek, Scalp Level, Cambria County, PA

  19. Soil spatial heterogeneity effect on soil electrical resistivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Electrical resistivity (ER) is growing in popularity due to its ease of use and because of its non-invasive techniques, which are used to reveal and map soil heterogeneity. The objective of this work was to evaluate how differing soil properties affect the electric resistivity and to observe these e...

  20. The Effect of Heterogeneity on Numerical Ordering in Rhesus Monkeys

    ERIC Educational Resources Information Center

    Cantlon, Jessica F.; Brannon, Elizabeth M.

    2006-01-01

    We investigated how within-stimulus heterogeneity affects the ability of rhesus monkeys to order pairs of the numerosities 1 through 9. Two rhesus monkeys were tested in a touch screen task where the variability of elements within each visual array was systematically varied by allowing elements to vary in color, size, shape, or any combination of…

  1. The Heterogeneous Effects of Income Changes on Happiness

    ERIC Educational Resources Information Center

    Becchetti, Leonardo; Corrado, Luisa; Rossetti, Fiammetta

    2011-01-01

    We investigate the relationship between money and happiness across the waves of the British Household Panel Study by using a latent class approach which accounts for slope heterogeneity. Our findings reveal the presence of a vast majority of "Easterlin-type" individuals with positive but very weak relationship between changes in income…

  2. Long-term Formation of Aggressive Bony Lesions in Dogs with Mid-Diaphyseal Fractures Stabilized with Metallic Plates: Incidence in a Tertiary Referral Hospital Population

    PubMed Central

    Gilley, Robert S.; Hiebert, Elizabeth; Clapp, Kemba; Bartl-Wilson, Lara; Nappier, Michael; Werre, Stephen; Barnes, Katherine

    2017-01-01

    The incidence of complications secondary to fracture stabilization, particularly osteolytic lesions and bony tumor formation, has long been difficult to evaluate. The objective of this study was to describe the long-term incidence of aggressive bony changes developing in dogs with long bone diaphyseal fractures stabilized by metallic bone plates compared to a breed-, sex-, and age-matched control group. The medical records of a tertiary referral center were retrospectively reviewed for dogs that matched each respective criterion. Signalment, history, cause of death (if applicable), and aggressive bony changes at previous fracture sites were recorded. Ninety dogs met the criteria for inclusion in the fracture group and were matched with appropriate control dogs. Four of the dogs in the fracture group developed aggressive bony changes at the site of previous fracture repairs most consistent with osseous neoplasia. One lesion was confirmed with cytology as neoplastic. The population of dogs was mixed with regard to breed and body weight, but all dogs with aggressive bony lesions were male. Incidence of aggressive bony lesion formation in the fracture group was 4 (4.4%) and was 0 (0%) in the control group; three (75%) of the affected dogs in the fracture group included cerclage as a component of their primary fracture stabilizations. Incidence of aggressive bony lesions in the fracture group compared to the control group was determined to be statistically significant (p = 0.0455), as was the incidence of cerclage among dogs affected by aggressive bony lesions compared to the rest of the fracture group (p = 0.0499). Development of aggressive bony lesions is an uncommon complication of fracture fixation. Additional research is needed to further identify and elucidate the long-term effects of metallic implants in dogs. PMID:28197406

  3. Long-term Formation of Aggressive Bony Lesions in Dogs with Mid-Diaphyseal Fractures Stabilized with Metallic Plates: Incidence in a Tertiary Referral Hospital Population.

    PubMed

    Gilley, Robert S; Hiebert, Elizabeth; Clapp, Kemba; Bartl-Wilson, Lara; Nappier, Michael; Werre, Stephen; Barnes, Katherine

    2017-01-01

    The incidence of complications secondary to fracture stabilization, particularly osteolytic lesions and bony tumor formation, has long been difficult to evaluate. The objective of this study was to describe the long-term incidence of aggressive bony changes developing in dogs with long bone diaphyseal fractures stabilized by metallic bone plates compared to a breed-, sex-, and age-matched control group. The medical records of a tertiary referral center were retrospectively reviewed for dogs that matched each respective criterion. Signalment, history, cause of death (if applicable), and aggressive bony changes at previous fracture sites were recorded. Ninety dogs met the criteria for inclusion in the fracture group and were matched with appropriate control dogs. Four of the dogs in the fracture group developed aggressive bony changes at the site of previous fracture repairs most consistent with osseous neoplasia. One lesion was confirmed with cytology as neoplastic. The population of dogs was mixed with regard to breed and body weight, but all dogs with aggressive bony lesions were male. Incidence of aggressive bony lesion formation in the fracture group was 4 (4.4%) and was 0 (0%) in the control group; three (75%) of the affected dogs in the fracture group included cerclage as a component of their primary fracture stabilizations. Incidence of aggressive bony lesions in the fracture group compared to the control group was determined to be statistically significant (p = 0.0455), as was the incidence of cerclage among dogs affected by aggressive bony lesions compared to the rest of the fracture group (p = 0.0499). Development of aggressive bony lesions is an uncommon complication of fracture fixation. Additional research is needed to further identify and elucidate the long-term effects of metallic implants in dogs.

  4. Effect of edema, relative biological effectiveness, and dose heterogeneity on prostate brachytherapy

    SciTech Connect

    Wang, Jian Z.; Mayr, Nina A.; Nag, Subir; Montebello, Joseph; Gupta, Nilendu; Samsami, Nina; Kanellitsas, Christos

    2006-04-15

    Many factors influence response in low-dose-rate (LDR) brachytherapy of prostate cancer. Among them, edema, relative biological effectiveness (RBE), and dose heterogeneity have not been fully modeled previously. In this work, the generalized linear-quadratic (LQ) model, extended to account for the effects of edema, RBE, and dose heterogeneity, was used to assess these factors and their combination effect. Published clinical data have shown that prostate edema after seed implant has a magnitude (ratio of post- to preimplant volume) of 1.3-2.0 and resolves exponentially with a half-life of 4-25 days over the duration of the implant dose delivery. Based on these parameters and a representative dose-volume histogram (DVH), we investigated the influence of edema on the implant dose distribution. The LQ parameters ({alpha}=0.15 Gy{sup -1} and {alpha}/{beta}=3.1 Gy) determined in earlier studies were used to calculate the equivalent uniform dose in 2 Gy fractions (EUD{sub 2}) with respect to three effects: edema, RBE, and dose heterogeneity for {sup 125}I and {sup 103}Pd implants. The EUD{sub 2} analysis shows a negative effect of edema and dose heterogeneity on tumor cell killing because the prostate edema degrades the dose coverage to tumor target. For the representative DVH, the V{sub 100} (volume covered by 100% of prescription dose) decreases from 93% to 91% and 86%, and the D{sub 90} (dose covering 90% of target volume) decrease from 107% to 102% and 94% of prescription dose for {sup 125}I and {sup 103}Pd implants, respectively. Conversely, the RBE effect of LDR brachytherapy [versus external-beam radiotherapy (EBRT) and high-dose-rate (HDR) brachytherapy] enhances dose effect on tumor cell kill. In order to balance the negative effects of edema and dose heterogeneity, the RBE of prostate brachytherapy was determined to be approximately 1.2-1.4 for {sup 125}I and 1.3-1.6 for {sup 103}Pd implants. These RBE values are consistent with the RBE data published in the

  5. Power reactor and critical experiment heterogeneity effects assessment for bias factors definition

    SciTech Connect

    Salvatores, M.; Soule, R.; Carta, M.

    1988-09-01

    Heterogeneity effects are compared in a power reactor subassembly of the Superphenix type and in the lattices of the critical experiments performed in the Masurca critical facility. Both the fuel in heterogeneity and the structure tube heterogeneity are evaluated with a two-step method based on the subgroup technique for self-shielding effect evaluation and on the Benoist method for streaming effect evaluation (the DHARMA method). Besides validation with reference calculations for simple geometries, experimental evidence confirms the good performance of the method proposed.

  6. Percutaneous embolization of bony pelvic neoplasms with tissue adhesive

    SciTech Connect

    Keller, F.S.; Rosch, J.; Bird, C.B.

    1983-04-01

    Eight patients with tumors of the bony pelvis underwent embolization with isobutyl-2-cyanoacrylate (IBCA). Five patients had primary bone tumors, of which 2 were malignant and 3 were benign; 3 patients had metastases to the bony pelvis from the thyroid gland, kidney, and femur, respectively. Embolization was performed to minimize blood loss during resection of a giant-cell tumor in one patient and insertion of a hip prosthesis in another who had metastatic renal carcinoma. It was also done prior to scheduled surgery in one of the patients with aneurysmal bone cyst, but healing was sufficient to cancel the operation; in the other patient, embolization was the only therapy. Palliative embolization was performed in 4 patients with malignant tumors after other means failed to control pain or slow progression. IBCA appears to be an efficient means of occluding the vessels feeding selected primary bone tumors and metastases.

  7. [Ultrastructure of granulocytes of bony fishes (orders Salmoniformes, Cypriniformes, Perciformes)].

    PubMed

    Flerova, E A; Balabanova, L V

    2013-01-01

    Analysis of data on utrastructure of granulocytes of freshwater and marine bony fish of orders Salmoniformes, Cypriniformes, and Perciformes showed that in all studied species there were revealed two types of granulocytes - neutrophils and eosinophils. The exception was the bluefish Pomatomus saltatrix L. whose pronephros hemopoietic tissue was found to contain one type of the granulocytic line - neutrophils. The identification parameters of granular leukocytes are specific granules filling the cytoplasm. The main form of specific granules in neutrophils of bony fish of various phylogenetic groups is an elongated granule with different distribution of fibrils or a granule that has crystalloid formed from fibrils. The main form of eosinophil granules - large, electron-dense, homogenous.

  8. Effect of surface and subsurface heterogeneity on the hydrological response of a grassed buffer zone

    NASA Astrophysics Data System (ADS)

    Gatel, Laura; Lauvernet, Claire; Carluer, Nadia; Paniconi, Claudio

    2016-11-01

    Grassed buffer zones are an effective method to reduce contaminant impacts on aquatic environments. The general objective of this study is to explore the impact of both surface and subsurface heterogeneity on the hydrological responses of a vegetative buffer strip. Heterogeneity is described by two variables, microtopography and saturated hydraulic conductivity. Numerous surface and subsurface heterogeneity scenarios were simulated with a physically-based numerical model of coupled surface/subsurface processes. The scenarios were evaluated relative to data from an experimental vegetative filter in a Beaujolais vineyard, France. The subsurface scenarios show that conductivity heterogeneity plays a key role on the buffer strip's capacity to infiltrate incoming surface runoff and on the ensuing runoff pathways. The conjunctive surface and subsurface scenarios indicate that microtopography variability is comparatively less influential on the hydrological interactions and pathways within the buffer strip, and that representing this heterogeneity via appropriate statistical distributions can be a good assumption in practice.

  9. Geometric heterogeneity of the lattice and its effect on the kinetics phase transitions of surface reactions

    NASA Astrophysics Data System (ADS)

    Cortés, Joaquín.; Valencia, Eliana

    1999-04-01

    Two novel phenomena are discussed in this paper. The first one refers to the effect of the catalyst's surface heterogeneity on the smoothing of the first-order transition observed in the ( A+ B2) reaction (ZGB model). The second effect corresponds to obtaining information on the surface heterogeneity from the shape of the transition curve. Two types of heterogeneity were considered: the structure obtained by the random blocking of reactive sites, and the existence of a distribution in independent strips or terraces on the catalyst's surface.

  10. Capillary effects in drainage in heterogeneous porous media: Continuum modeling, experiments and pore network simulations

    SciTech Connect

    Xu, Baomin; Yortsos, Y.C.

    1993-04-01

    We investigate effects of capillary heterogeneity induced by variations in permeability in the direction of displacement in heterogeneous porous media under drainage conditions. The investigation is three-pronged and uses macroscopic simulation, based on the standard continuum equations, experiments with the use of an acoustic technique and pore network numerical models. It is found that heterogeneity affects significantly the saturation profiles, the effect being stronger at lower rates. A good agreement is found between the continuum model predictions and the experimental results based on which it can be concluded that capillary heterogeneity effects in the direction of displacement act much like a body force (e.g. gravity). A qualitative agreement is also found between the continuum approach and the pore network numerical models, which is expected to improve when finite size effects in the pore network simulations diminish. The results are interpreted with the use of invasion percolation concepts.

  11. Homogeneous-heterogeneous reaction effects in peristalsis through curved geometry

    SciTech Connect

    Hayat, Tasawar; Tanveer, Anum Alsaadi, Fuad; Alotaibi, Naif D.

    2015-06-15

    This paper looks at the influence of homogeneous-heterogeneous reactions on the peristaltic transport of non-Newtonian fluid in a curved channel with wall properties. Constitutive relations for thermodynamic third grade material are utilized in the problem development. An electrically conducting fluid in the presence of radial applied magnetic field is considered. The governing flow equations are developed in the presence of viscous heating. Mathematical computations are simplified employing long wavelength and low Reynolds number considerations. The solutions for velocity, temperature, concentration and heat transfer coefficient are obtained and examined. The features of sundry parameters are analyzed by plotting graphs.

  12. Effect of heterogeneous investments on the evolution of cooperation in spatial public goods game.

    PubMed

    Huang, Keke; Wang, Tao; Cheng, Yuan; Zheng, Xiaoping

    2015-01-01

    Understanding the emergence of cooperation in spatial public goods game remains a grand challenge across disciplines. In most previous studies, it is assumed that the investments of all the cooperators are identical, and often equal to 1. However, it is worth mentioning that players are diverse and heterogeneous when choosing actions in the rapidly developing modern society and researchers have shown more interest to the heterogeneity of players recently. For modeling the heterogeneous players without loss of generality, it is assumed in this work that the investment of a cooperator is a random variable with uniform distribution, the mean value of which is equal to 1. The results of extensive numerical simulations convincingly indicate that heterogeneous investments can promote cooperation. Specifically, a large value of the variance of the random variable can decrease the two critical values for the result of behavioral evolution effectively. Moreover, the larger the variance is, the better the promotion effect will be. In addition, this article has discussed the impact of heterogeneous investments when the coevolution of both strategy and investment is taken into account. Comparing the promotion effect of coevolution of strategy and investment with that of strategy imitation only, we can conclude that the coevolution of strategy and investment decreases the asymptotic fraction of cooperators by weakening the heterogeneity of investments, which further demonstrates that heterogeneous investments can promote cooperation in spatial public goods game.

  13. Effect of Heterogeneous Investments on the Evolution of Cooperation in Spatial Public Goods Game

    PubMed Central

    Huang, Keke; Wang, Tao; Cheng, Yuan; Zheng, Xiaoping

    2015-01-01

    Understanding the emergence of cooperation in spatial public goods game remains a grand challenge across disciplines. In most previous studies, it is assumed that the investments of all the cooperators are identical, and often equal to 1. However, it is worth mentioning that players are diverse and heterogeneous when choosing actions in the rapidly developing modern society and researchers have shown more interest to the heterogeneity of players recently. For modeling the heterogeneous players without loss of generality, it is assumed in this work that the investment of a cooperator is a random variable with uniform distribution, the mean value of which is equal to 1. The results of extensive numerical simulations convincingly indicate that heterogeneous investments can promote cooperation. Specifically, a large value of the variance of the random variable can decrease the two critical values for the result of behavioral evolution effectively. Moreover, the larger the variance is, the better the promotion effect will be. In addition, this article has discussed the impact of heterogeneous investments when the coevolution of both strategy and investment is taken into account. Comparing the promotion effect of coevolution of strategy and investment with that of strategy imitation only, we can conclude that the coevolution of strategy and investment decreases the asymptotic fraction of cooperators by weakening the heterogeneity of investments, which further demonstrates that heterogeneous investments can promote cooperation in spatial public goods game. PMID:25781345

  14. Effect of salt concentration on the stability of heterogeneous DNA

    NASA Astrophysics Data System (ADS)

    Singh, Amar; Singh, Navin

    2015-02-01

    We study the role of cations on the stability of double stranded DNA (dsDNA) molecules. It is known that the two strands of double stranded DNA (dsDNA) have negative charge due to phosphate group. Cations in the form of salt in the solution, act as shielding agents thereby reducing the repulsion between these strands. We study several heterogeneous DNA molecules. We calculate the phase diagrams for DNA molecules in thermal as well as in force ensembles using Peyrard-Bishop-Dauxois (PBD) model. The dissociation and the stacking energies are the two most important factors that play an important role in the DNA stability. With suitable modifications in the model parameters we investigate the role of cation concentration on the stability of different heterogeneous DNA molecules. The objective of this work is to understand how these cations modify the strength of different pairs or bases along the strand. The phase diagram for the force ensemble case (a dsDNA is pulled from an end) is compared with the experimental results.

  15. Numerical Simulations of Floodplain Heterogeneity Effects on Meanders Migration

    NASA Astrophysics Data System (ADS)

    Bogoni, M.; Lanzoni, S.; Putti, M.

    2014-12-01

    Floodplains and sinuous rivers have a close relationship with each other, mutually influencing their evolutions in time and space. The heterogeneity in erosional resistance has a crucial role on meander planform evolution. It depends on external factors, like land use and cover, but also on the composition of the floodplain, which is due to the ancient geological composition and to the processes associated to long-term river migration. In particular, banks erosion and deposition cause a variation of the superficial composition of the soil, therefore the river patterns are influenced by the previous trends. Based on some recent works, the aim of this contribution is to collect numerical information on the relations between meander migration and the heterogeneity of floodplains caused by oxbow lakes. Numerical simulations have been performed to analyze the temporal and spatial behavior of meanders with a range of values of the erosional resistance of the plain. These values are set as a function of some factors: the characteristic grain size of sediment transported by the flow, the deposition age of the sediments, the eventual presence of vegetation on the banks. The statistical analysis of characteristic geometrical quantities of meanders are able to show the dependence of the simulation results on the meander history. In particular we try to answer to the following questions: how do the rivers affect themselves during their spatial and temporal evolution, modifying the distribution of the floodplain erodibility? Do the migration history plays a main role on the meanders migration modeling?

  16. Charge Transfer and Support Effects in Heterogeneous Catalysis

    SciTech Connect

    Hervier, Antoine

    2011-12-21

    the band bending at the interface, gives rise to a steady-state flow of hot holes to the surface. This leads to a decrease in turnover on the surface, an effect which is enhanced when a reverse bias is applied to the diode. Similar experiments were carried out for CO oxidation. On Pt/Si diodes, the reaction rate was found to increase when a forward bias was applied. When the diode was exposed to visible light and a reverse bias was applied, the rate was instead decreased. This implies that a flow of negative charges to the surface increases turnover, while positive charges decrease it. Charge flow in an oxide supported metal catalyst can be modified even without designing the catalyst as a solid state electronic device. This was done by doping stoichiometric and nonstoichiometric TiO2 films with F, and using the resulting oxides as supports for Pt films. In the case of stoichiometric TiO2, F was found to act as an n-type dopant, creating a population of filled electronic states just below the conduction band, and dramatically increasing the conductivity of the oxide film. The electrons in those states can transfer to surface O, activating it for reaction with CO, and leading to increased turnover for CO oxidation. This reinforces the hypothesis that CO oxidation is activated by a flow of negative charges to the surface. The same set of catalysts was used for methanol oxidation. The electronic properties of the TiO2 films again correlated with the turnover rates, but also with selectivity. With stoichiometric TiO2 as the support, F-doping caused an increase in selectivity toward the formation of partial oxidation products, formaldehyde and methyl formate, versus the total oxidation product, CO2. With non-stoichiometric TiO2, F-doping had the reverse effect. Ambient Pressure X-Ray Photoelectron Spectroscopy was used to investigate this F-doping effect in reaction conditions. In O2 alone, and in

  17. Composite catalyst surfaces: Effect of inert and active heterogeneities on pattern formation

    SciTech Connect

    Baer, M.; Bangia, A.K.; Kevrekidis, I.G.; Haas, G.; Rotermund, H.H.; Ertl, G.

    1996-12-05

    Spatiotemporal dynamics in reaction-diffusion systems can be altered through the properties (reactivity, diffusivity) of the medium in which they occur. We construct active heterogeneous media (composite catalytic surfaces with inert as well as active illusions) using microelectronics fabrication techniques and study the spatiotemporal dynamics of heterogeneous catalytic reactions on these catalysts. In parallel, we perform simulations as well as numerical stability and bifurcation analysis of these patterns using mechanistic models. At the limit of large heterogeneity `grain size` (compared to the wavelength of spontaneously arising structures) the interaction patterns with inert or active boundaries dominates (e.g., pinning, transmission, and boundary breakup of spirals, interaction of pulses with corners, `pacemaker` effects). At the opposite limit of very small or very finely distributed heterogeneity, effective behavior is observed (slight modulation of pulses, nearly uniform oscillations, effective spirals). Some representative studies of transitions between the two limits are presented. 48 refs., 11 figs.

  18. Quantitative study of cellular heterogeneity in doxorubicin uptake and its pharmacological effect on cancer cells.

    PubMed

    Deng, Bin; Wang, Zhi-Ming; Zhou, Zi-Hao; Liu, Yi-Meng; Yang, Xi-Liang; Song, Jian; Xiao, Yu-Xiu

    2014-10-01

    Cellular heterogeneity in doxorubicin (DOX) uptake and its relationship with pharmacological effect on cancer cells were quantitatively investigated for the first time. An in vitro experimental model was established by treating human leukemia K562 and breast cancer MCF-7 cells with different schedules of DOX with or without surface P-glycoprotein (P-gp) inhibitor verapamil (VER). The cellular heterogeneity in DOX uptake was quantitatively examined by single-cell analysis using capillary electrophoresis coupled with laser-induced fluorescence detection. The corresponding cytotoxic effect was tested by cellular morphology, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium and flow cytometry assays. The expression of cellular membrane surface P-gp was determined by flow cytometry. Results showed that the cellular heterogeneity exists in DOX uptake. The single-high DOX schedule leads to lower uptake heterogeneity and higher mean drug uptake. The cellular heterogeneity in DOX uptake was found to be negatively correlated with drug cytotoxicity and surface P-gp expression, with r = -0.7680 to ~ -0.9587. VER reduces the cellular variation in DOX uptake, suggesting that surface P-gp may be one of the causes of the cellular heterogeneity in DOX uptake. This research demonstrates the importance of quantitative study of cellular heterogeneity in drug uptake and its potential application in drug schedule design, response prediction and therapy modulation.

  19. The effect and correction of reference heterogeneity in diffuse optical tomography

    NASA Astrophysics Data System (ADS)

    Vavadi, Hamed; Xu, Chen; Zhu, Quing

    2015-03-01

    Near infrared (NIR) diffuse optical tomography has demonstrated great potential in the initial diagnosis of tumor and in the assessment of tumor vasculature response to neoadjuvant chemotherapy. To reconstruct the absorption map of a breast lesion, perturbation is needed which is the normalized difference between the measurements of lesion-side breast and contralateral reference breast. However, the heterogeneity in the reference breast can produce unwanted perturbation which will result in distortion of the reconstructed target absorption map. This report introduces a filtering method to overcome the reference heterogeneity. This method corrects affected source-detector measurements obtained from the reference side by using averages of unaffected measurements. As a result, the filtered perturbation has decreased the effect of heterogeneity on the reconstructed absorption maps. To evaluate the performance of this filtering method, we have compared the reconstructed results with and without the filtering algorithm using simulated heterogeneous reference with heterogeneous absorbers ranging from 0.05 to 0.20 cm-1 and heterogeneous scatters ranging from 10 to 20cm-1. The results show that the algorithm can improve the maximum reconstructed target value up to 99% of the value with homogeneous reference. In the worst case of high absorption heterogeneity in reference breast, the maximum reconstructed value was around 30.85% of the true absorption without filtering correction and was improved to 60.4% of the true absorption value, which is 95% of the reconstructed value when using the homogeneous reference.

  20. Resource heterogeneity, soil fertility, and species diversity: effects of clonal species on plant communities.

    PubMed

    Eilts, J Alexander; Mittelbach, Gary G; Reynolds, Heather L; Gross, Katherine L

    2011-05-01

    Spatial heterogeneity in soil resources is widely thought to promote plant species coexistence, and this mechanism figures prominently in resource-ratio models of competition. However, most experimental studies have found that nutrient enhancements depress diversity regardless of whether nutrients are uniformly or heterogeneously applied. This mismatch between theory and empirical pattern is potentially due to an interaction between plant size and the scale of resource heterogeneity. Clonal plants that spread vegetatively via rhizomes or stolons can grow large and may integrate across resource patches, thus reducing the positive effect of small-scale resource heterogeneity on plant species richness. Many rhizomatous clonal species respond strongly to increased soil fertility, and they have been hypothesized to drive the descending arm of the hump-shaped productivity-diversity relationship in grasslands. We tested whether clonals reduce species richness in a grassland community by manipulating nutrient heterogeneity, soil fertility, and the presence of rhizomatous clonal species in a 6-year field experiment. We found strong and consistent negative effects of clonals on species richness. These effects were greatest at high fertility and when soil resources were applied at a scale at which rhizomatous clonals could integrate across resource patches. Thus, we find support for the hypothesis that plant size and resource heterogeneity interact to determine species diversity.

  1. The evaluation of bony union after frontofacial distraction.

    PubMed

    Eley, Karen A; Witherow, Helen; Hayward, Richard; Evans, Robert; Young, Karen; Clark, Allan; Dunaway, David

    2009-03-01

    Frontofacial advancement by distraction osteogenesis using the rigid external distraction device has become an accepted treatment for the deformity associated with craniofacial dysostoses (e.g., Crouzon, Apert, and Pfeiffer syndromes). The technical and physiological principles of osteogenesis distraction are well understood. This study documents the pattern of calcification at the osteotomy sites after distraction by analysis of serial three-dimensional computed tomography (CT) scans. The CT scans of 25 patients (11 with Crouzon, 6 with Apert, and 8 with Pfeiffer syndrome) were analyzed. Eleven individual areas along the osteotomy lines were assessed for evidence of bone formation. Scores were assigned within 4 categories ranging from no bone, calcification without bridge formation, a bony bridge, to complete bony infill (>95%). The scans were reviewed on 2 separate occasions by 2 independent assessors. There was high concordance both for intraobserver and interobserver scores. Rigid external distraction frame removal was undertaken after a 6-week consolidation period. All CT scan timings were calculated from this date. Of the 25 patients studied, 16 patients had CT scans available at 3 to 6 months, 12 at 9 to 12 months, and 7 at or more than 18 months. The scans were available in standard coronal slices with three-dimensional reconstructions. Bone formation is most consistently seen in the pterygoid region with calcification consistently occurring earlier and more completely in this area. Bone formation was often delayed in the orbital region and severely delayed or absent in the frontal region and zygomatic arches. There was no significant difference in the order or quality of bony union for the 3 underlying craniofacial dysostoses. This preliminary study confirms the clinical impression that bone formation after distraction is greatest in the pterygoid regions. The clinical implications of these findings are discussed.

  2. Treatment Effect Heterogeneity in a Science Professional Development Initiative: The Case for School Capacity

    ERIC Educational Resources Information Center

    Bruch, Sarah; Grigg, Jeffrey; Hanselman, Paul

    2010-01-01

    This study focuses on how the treatment effects of a teacher professional development initiative in science differed by school capacity. In other words, the authors are primarily concerned with treatment effect heterogeneity. As such, this paper complements ongoing evaluation of the average treatment effects of the initiative over time. The…

  3. Effect of the heterogeneous neuron and information transmission delay on stochastic resonance of neuronal networks

    NASA Astrophysics Data System (ADS)

    Wang, Qingyun; Zhang, Honghui; Chen, Guanrong

    2012-12-01

    We study the effect of heterogeneous neuron and information transmission delay on stochastic resonance of scale-free neuronal networks. For this purpose, we introduce the heterogeneity to the specified neuron with the highest degree. It is shown that in the absence of delay, an intermediate noise level can optimally assist spike firings of collective neurons so as to achieve stochastic resonance on scale-free neuronal networks for small and intermediate αh, which plays a heterogeneous role. Maxima of stochastic resonance measure are enhanced as αh increases, which implies that the heterogeneity can improve stochastic resonance. However, as αh is beyond a certain large value, no obvious stochastic resonance can be observed. If the information transmission delay is introduced to neuronal networks, stochastic resonance is dramatically affected. In particular, the tuned information transmission delay can induce multiple stochastic resonance, which can be manifested as well-expressed maximum in the measure for stochastic resonance, appearing every multiple of one half of the subthreshold stimulus period. Furthermore, we can observe that stochastic resonance at odd multiple of one half of the subthreshold stimulus period is subharmonic, as opposed to the case of even multiple of one half of the subthreshold stimulus period. More interestingly, multiple stochastic resonance can also be improved by the suitable heterogeneous neuron. Presented results can provide good insights into the understanding of the heterogeneous neuron and information transmission delay on realistic neuronal networks.

  4. Effect of the heterogeneous neuron and information transmission delay on stochastic resonance of neuronal networks.

    PubMed

    Wang, Qingyun; Zhang, Honghui; Chen, Guanrong

    2012-12-01

    We study the effect of heterogeneous neuron and information transmission delay on stochastic resonance of scale-free neuronal networks. For this purpose, we introduce the heterogeneity to the specified neuron with the highest degree. It is shown that in the absence of delay, an intermediate noise level can optimally assist spike firings of collective neurons so as to achieve stochastic resonance on scale-free neuronal networks for small and intermediate α(h), which plays a heterogeneous role. Maxima of stochastic resonance measure are enhanced as α(h) increases, which implies that the heterogeneity can improve stochastic resonance. However, as α(h) is beyond a certain large value, no obvious stochastic resonance can be observed. If the information transmission delay is introduced to neuronal networks, stochastic resonance is dramatically affected. In particular, the tuned information transmission delay can induce multiple stochastic resonance, which can be manifested as well-expressed maximum in the measure for stochastic resonance, appearing every multiple of one half of the subthreshold stimulus period. Furthermore, we can observe that stochastic resonance at odd multiple of one half of the subthreshold stimulus period is subharmonic, as opposed to the case of even multiple of one half of the subthreshold stimulus period. More interestingly, multiple stochastic resonance can also be improved by the suitable heterogeneous neuron. Presented results can provide good insights into the understanding of the heterogeneous neuron and information transmission delay on realistic neuronal networks.

  5. Comparative testicular structure and spermatogenesis in bony fishes

    PubMed Central

    Uribe, Mari Carmen; Grier, Harry J; Mejía-Roa, Víctor

    2014-01-01

    In most bony fishes, testes are paired elongated organs that are attached to the dorsal wall of the body by a mesorchium. Histological examination of teleost testes, and also in all vertebrates, shows that the testes are formed of germ cells and somatic cells, comprising the germinal and interstitial compartments. Both compartments are separated by a basement membrane. The germ cells may be spermatogonia, meiotic spermatocytes and haploid spermatids that differentiate into spermatozoa. The process of spermatogenesis includes a sequence of morphological and physiological changes of germ cells that begin with the differentiation of spermatogonia that become meiotic spermatocytes. After the second meiotic division, through a process of spermiogenesis, these differentiate into spermatozoa. Spermatogonia associate with Sertoli cells to form spermatocysts or cysts. The cyst is the unit of spermatogenic function, composed of a cohort of isogenic germ cells surrounded by encompassing Sertoli cells. The teleost testis is organized morphologically into 3 types of testis: 1) tubular testis type, present in lower bony fishes as salmonids, cyprinids and lepisosteids; 2) unrestricted spermatogonial testis type, found in neoteleosts except Atherinomorpha; and 3) restricted spermatogonial testis type, characteristic of all Atherinomorpha. The morphology of the testicular germinal epithelium changes during the annual reproductive cycle, reflecting reproductive seasonality. PMID:26413405

  6. Allergenicity of bony and cartilaginous fish - molecular and immunological properties.

    PubMed

    Stephen, J N; Sharp, M F; Ruethers, T; Taki, A; Campbell, D E; Lopata, A L

    2017-03-01

    Allergy to bony fish is common and probably increasing world-wide. The major heat-stable pan-fish allergen, parvalbumin (PV), has been identified and characterized for numerous fish species. In contrast, there are very few reports of allergic reactions to cartilaginous fish despite widespread consumption. The molecular basis for this seemingly low clinical cross-reactivity between these two fish groups has not been elucidated. PV consists of two distinct protein lineages, α and β. The α-lineage of this protein is predominant in muscle tissue of cartilaginous fish (Chondrichthyes), while β-PV is abundant in muscle tissue of bony fish (Osteichthyes). The low incidence of allergic reactions to ingested rays and sharks is likely due to the lack of molecular similarity, resulting in reduced immunological cross-reactivity between the two PV lineages. Structurally and physiologically, both protein lineages are very similar; however, the amino acid homology is very low with 47-54%. Furthermore, PV from ancient fish species such as the coelacanth demonstrates 62% sequence homology to leopard shark α-PV and 70% to carp β-PV. This indicates the extent of conservation of the PV isoforms lineages across millennia. This review highlights prevalence data on fish allergy and sensitization to fish, and details the molecular diversity of the two protein lineages of the major fish allergen PV among different fish groups, emphasizing the immunological and clinical differences in allergenicity.

  7. Characteristics of Supplemental Educational Services Providers That Explain Heterogeneity of Effects on Achievement

    ERIC Educational Resources Information Center

    Jones, Curtis J.

    2015-01-01

    This study used a mixed-methods approach to explore the heterogeneity of effectiveness between supplemental educational services (SES) providers in the Chicago Public Schools (CPS). Using surveys of schools and SES providers, and statistical modeling, providers using college graduates and teachers as tutors were found to be more effective than…

  8. Evaluating Heterogeneous Conservation Effects of Forest Protection in Indonesia

    PubMed Central

    Shah, Payal; Baylis, Kathy

    2015-01-01

    Establishing legal protection for forest areas is the most common policy used to limit forest loss. This article evaluates the effectiveness of seven Indonesian forest protected areas introduced between 1999 and 2012. Specifically, we explore how the effectiveness of these parks varies over space. Protected areas have mixed success in preserving forest, and it is important for conservationists to understand where they work and where they do not. Observed differences in the estimated treatment effect of protection may be driven by several factors. Indonesia is particularly diverse, with the landscape, forest and forest threats varying greatly from region to region, and this diversity may drive differences in the effectiveness of protected areas in conserving forest. However, the observed variation may also be spurious and arise from differing degrees of bias in the estimated treatment effect over space. In this paper, we use a difference-in-differences approach comparing treated observations and matched controls to estimate the effect of each protected area. We then distinguish the true variation in protected area effectiveness from spurious variation driven by several sources of estimation bias. Based on our most flexible method that allows the data generating process to vary across space, we find that the national average effect of protection preserves an additional 1.1% of forest cover; however the effect of individual parks range from a decrease of 3.4% to an increase of 5.3% and the effect of most parks differ from the national average. Potential biases may affect estimates in two parks, but results consistently show Sebangau National Park is more effective while two parks are substantially less able to protect forest cover than the national average. PMID:26039754

  9. Scaling Effects of Cr(VI) Reduction Kinetics. The Role of Geochemical Heterogeneity

    SciTech Connect

    Wang, Li; Li, Li

    2015-10-22

    The natural subsurface is highly heterogeneous with minerals distributed in different spatial patterns. Fundamental understanding of how mineral spatial distribution patterns regulate sorption process is important for predicting the transport and fate of chemicals. Existing studies about the sorption was carried out in well-mixed batch reactors or uniformly packed columns, with few data available on the effects of spatial heterogeneities. As a result, there is a lack of data and understanding on how spatial heterogeneities control sorption processes. In this project, we aim to understand and develop modeling capabilities to predict the sorption of Cr(VI), an omnipresent contaminant in natural systems due to its natural occurrence and industrial utilization. We systematically examine the role of spatial patterns of illite, a common clay, in determining the extent of transport limitation and scaling effects associated with Cr(VI) sorption capacity and kinetics using column experiments and reactive transport modeling. Our results showed that the sorbed mass and rates can differ by an order of magnitude due to of the illite spatial heterogeneities and transport limitation. With constraints from data, we also developed the capabilities of modeling Cr(VI) in heterogeneous media. The developed model is then utilized to understand the general principles that govern the relationship between sorption and connectivity, a key measure of the spatial pattern characteristics. This correlation can be used to estimate Cr(VI) sorption characteristics in heterogeneous porous media. Insights gained here bridge gaps between laboratory and field application in hydrogeology and geochemical field, and advance predictive understanding of reactive transport processes in the natural heterogeneous subsurface. We believe that these findings will be of interest to a large number of environmental geochemists and engineers, hydrogeologists, and those interested in contaminant fate and transport

  10. Effect of material property heterogeneity on biomechanical modeling of prostate under deformation.

    PubMed

    Samavati, Navid; McGrath, Deirdre M; Jewett, Michael A S; van der Kwast, Theo; Ménard, Cynthia; Brock, Kristy K

    2015-01-07

    Biomechanical model based deformable image registration has been widely used to account for prostate deformation in various medical imaging procedures. Biomechanical material properties are important components of a biomechanical model. In this study, the effect of incorporating tumor-specific material properties in the prostate biomechanical model was investigated to provide insight into the potential impact of material heterogeneity on the prostate deformation calculations. First, a simple spherical prostate and tumor model was used to analytically describe the deformations and demonstrate the fundamental effect of changes in the tumor volume and stiffness in the modeled deformation. Next, using a clinical prostate model, a parametric approach was used to describe the variations in the heterogeneous prostate model by changing tumor volume, stiffness, and location, to show the differences in the modeled deformation between heterogeneous and homogeneous prostate models. Finally, five clinical prostatectomy examples were used in separately performed homogeneous and heterogeneous biomechanical model based registrations to describe the deformations between 3D reconstructed histopathology images and ex vivo magnetic resonance imaging, and examine the potential clinical impact of modeling biomechanical heterogeneity of the prostate. The analytical formulation showed that increasing the tumor volume and stiffness could significantly increase the impact of the heterogeneous prostate model in the calculated displacement differences compared to the homogeneous model. The parametric approach using a single prostate model indicated up to 4.8 mm of displacement difference at the tumor boundary compared to a homogeneous model. Such differences in the deformation of the prostate could be potentially clinically significant given the voxel size of the ex vivo MR images (0.3  ×  0.3  ×  0.3 mm). However, no significant changes in the registration accuracy were

  11. Nonlinear effects of locally heterogeneous hydraulic conductivity fields on regional stream-aquifer exchanges

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Winter, C. L.; Wang, Z.

    2015-11-01

    Computational experiments are performed to evaluate the effects of locally heterogeneous conductivity fields on regional exchanges of water between stream and aquifer systems in the Middle Heihe River basin (MHRB) of northwestern China. The effects are found to be nonlinear in the sense that simulated discharges from aquifers to streams are systematically lower than discharges produced by a base model parameterized with relatively coarse effective conductivity. A similar, but weaker, effect is observed for stream leakage. The study is organized around three hypotheses: (H1) small-scale spatial variations of conductivity significantly affect regional exchanges of water between streams and aquifers in river basins, (H2) aggregating small-scale heterogeneities into regional effective parameters systematically biases estimates of stream-aquifer exchanges, and (H3) the biases result from slow paths in groundwater flow that emerge due to small-scale heterogeneities. The hypotheses are evaluated by comparing stream-aquifer fluxes produced by the base model to fluxes simulated using realizations of the MHRB characterized by local (grid-scale) heterogeneity. Levels of local heterogeneity are manipulated as control variables by adjusting coefficients of variation. All models are implemented using the MODFLOW (Modular Three-dimensional Finite-difference Groundwater Flow Model) simulation environment, and the PEST (parameter estimation) tool is used to calibrate effective conductivities defined over 16 zones within the MHRB. The effective parameters are also used as expected values to develop lognormally distributed conductivity (K) fields on local grid scales. Stream-aquifer exchanges are simulated with K fields at both scales and then compared. Results show that the effects of small-scale heterogeneities significantly influence exchanges with simulations based on local-scale heterogeneities always producing discharges that are less than those produced by the base model

  12. Effect of Heterogeneity on Decorrelation Mechanisms in Spiking Neural Networks: A Neuromorphic-Hardware Study

    NASA Astrophysics Data System (ADS)

    Pfeil, Thomas; Jordan, Jakob; Tetzlaff, Tom; Grübl, Andreas; Schemmel, Johannes; Diesmann, Markus; Meier, Karlheinz

    2016-04-01

    High-level brain function, such as memory, classification, or reasoning, can be realized by means of recurrent networks of simplified model neurons. Analog neuromorphic hardware constitutes a fast and energy-efficient substrate for the implementation of such neural computing architectures in technical applications and neuroscientific research. The functional performance of neural networks is often critically dependent on the level of correlations in the neural activity. In finite networks, correlations are typically inevitable due to shared presynaptic input. Recent theoretical studies have shown that inhibitory feedback, abundant in biological neural networks, can actively suppress these shared-input correlations and thereby enable neurons to fire nearly independently. For networks of spiking neurons, the decorrelating effect of inhibitory feedback has so far been explicitly demonstrated only for homogeneous networks of neurons with linear subthreshold dynamics. Theory, however, suggests that the effect is a general phenomenon, present in any system with sufficient inhibitory feedback, irrespective of the details of the network structure or the neuronal and synaptic properties. Here, we investigate the effect of network heterogeneity on correlations in sparse, random networks of inhibitory neurons with nonlinear, conductance-based synapses. Emulations of these networks on the analog neuromorphic-hardware system Spikey allow us to test the efficiency of decorrelation by inhibitory feedback in the presence of hardware-specific heterogeneities. The configurability of the hardware substrate enables us to modulate the extent of heterogeneity in a systematic manner. We selectively study the effects of shared input and recurrent connections on correlations in membrane potentials and spike trains. Our results confirm that shared-input correlations are actively suppressed by inhibitory feedback also in highly heterogeneous networks exhibiting broad, heavy-tailed firing

  13. The impact of breathing motion versus heterogeneity effects in lung cancer treatment planning

    SciTech Connect

    Rosu, Mihaela; Chetty, Indrin J.; Tatro, Daniel S.; Haken, Randall K. ten

    2007-04-15

    The purpose of this study is to investigate the effects of tissue heterogeneity and breathing-induced motion/deformation on conformal treatment planning for pulmonary tumors and to compare the magnitude and the clinical importance of changes induced by these effects. Treatment planning scans were acquired at normal exhale/inhale breathing states for fifteen patients. The internal target volume (ITV) was defined as the union of exhale and inhale gross tumor volumes uniformly expanded by 5 mm. Anterior/posterior opposed beams (AP/PA) and three-dimensional (3D)-conformal plans were designed using the unit-density exhale (''static'') dataset. These plans were further used to calculate (a) density-corrected (''heterogeneous'') static dose and (b) heterogeneous cumulative dose, including breathing deformations. The DPM Monte Carlo code was used for dose computations. For larger than coin-sized tumors, relative to unit-density plans, tumor and lung doses increased in the heterogeneity-corrected plans. In comparing cumulative and static plans, larger normal tissue complication probability changes were observed for tumors with larger motion amplitudes and uncompensated breathing-induced hot/cold spots in lung. Accounting for tissue heterogeneity resulted in average increases of 9% and 7% in mean lung dose (MLD) for the 6 MV and 15 MV photon beams, respectively. Breathing-induced effects resulted in approximately 1% and 2% average decreases in MLD from the static value, for the 6 and 15 MV photon beams, respectively. The magnitude of these effects was not found to correlate with the treatment plan technique, i.e., AP/PA versus 3D-CRT. Given a properly designed ITV, tissue heterogeneity effects are likely to have a larger clinical significance on tumor and normal lung treatment evaluation metrics than four-dimensional respiratory-induced changes.

  14. Heterogeneous treatment effects of speed cameras on road safety.

    PubMed

    Li, Haojie; Graham, Daniel J

    2016-12-01

    This paper analyses how the effects of fixed speed cameras on road casualties vary across sites with different characteristics and evaluates the criteria for selecting camera sites. A total of 771 camera sites and 4787 potential control sites are observed for a period of 9 years across England. Site characteristics such as road class, crash history and site length are combined into a single index, referred to as a propensity score. We first estimate the average effect at each camera site using propensity score matching. The effects are then estimated as a function of propensity scores using local polynomial regression. The results show that the reduction in personal injury collisions ranges from 10% to 40% whilst the average effect is 25.9%, indicating that the effects of speed cameras are not uniform across camera sites and are dependent on site characteristics, as measured by propensity scores. We further evaluate the criteria for selecting camera sites in the UK by comparing the effects at camera sites meeting and not meeting the criteria. The results show that camera sites which meet the criteria perform better in reducing casualties, implying the current site selection criteria are rational.

  15. The effect of material heterogeneity in curved composite beams for use in aircraft structures

    NASA Technical Reports Server (NTRS)

    Otoole, Brendan J.; Santare, Michael H.

    1992-01-01

    A design tool is presented for predicting the effect of material heterogeneity on the performance of curved composite beams for use in aircraft fuselage structures. Material heterogeneity can be induced during processes such as sheet forming and stretch forming of thermoplastic composites. This heterogeneity can be introduced in the form of fiber realignment and spreading during the manufacturing process causing a gradient in material properties in both the radial and tangential directions. The analysis procedure uses a separate two-dimensional elasticity solution for the stresses in the flanges and web sections of the beam. The separate solutions are coupled by requiring the forces and displacements match at the section boundaries. Analysis is performed for curved beams loaded in pure bending and uniform pressure. The beams can be of any general cross-section such as a hat, T-, I-, or J-beam. Preliminary results show that geometry of the beam dictates the effect of heterogeneity on performance. Heterogeneity plays a much larger role in beams with a small average radius to depth ratio, R/t, where R is the average radius of the beam and t is the difference between the inside and outside radius. Results of the analysis are in the form of stresses and displacements, and they are compared to both mechanics of materials and numerical solutions obtained using finite element analysis.

  16. Quantifying effects of soil heterogeneity on groundwater pollution at four sites in USA.

    PubMed

    Vuurens, Saskia; Stagnitti, Frank; de Rooij, Gerrit; Boll, Jan; Li, Ling; LeBlanc, Marc; Ierodiaconou, Daniel; Versace, Vince; Salzman, Scott

    2005-05-01

    Four sites located in the north-eastern region of the United States of America have been chosen to investigate the impacts of soil heterogeneity in the transport of solutes (bromide and chloride) through the vadose zone (the zone in the soil that lies below the root zone and above the permanent saturated groundwater). A recently proposed mathematical model based on the cumulative beta distribution has been deployed to compare and contrast the regions' heterogeneity from multiple sample percolation experiments. Significant differences in patterns of solute leaching were observed even over a small spatial scale, indicating that traditional sampling methods for solute transport, for example the gravity pan or suction lysimeters, or more recent inventions such as the multiple sample percolation systems may not be effective in estimating solute fluxes in soils when a significant degree of soil heterogeneity is present. Consequently, ignoring soil heterogeneity in solute transport studies will likely result in under- or overprediction of leached fluxes and potentially lead to serious pollution of soils and/or groundwater. The cumulative beta distribution technique is found to be a versatile and simple technique of gaining valuable information regarding soil heterogeneity effects on solute transport. It is also an excellent tool for guiding future decisions of experimental designs particularly in regard to the number of samples within one site and the number of sampling locations between sites required to obtain a representative estimate of field solute or drainage flux.

  17. Petersen estimator, Chapman adjustment, list effects, and heterogeneity.

    PubMed

    Mao, Chang Xuan; Huang, Ruochen; Zhang, Sijia

    2017-03-01

    We use a nonparametric mixture model for the purpose of estimating the size of a population from multiple lists in which both the individual effects and list effects are allowed to vary. We propose a lower bound of the population size that admits an analytic expression. The lower bound can be estimated without the necessity of model-fitting. The asymptotical normality of the estimator is established. Both the estimator itself and that for the estimable bound of its variance are adjusted. These adjusted versions are shown to be unbiased in the limit. Simulation experiments are performed to assess the proposed approach and real applications are studied.

  18. Using Dirichlet Processes for Modeling Heterogeneous Treatment Effects across Sites

    ERIC Educational Resources Information Center

    Miratrix, Luke; Feller, Avi; Pillai, Natesh; Pati, Debdeep

    2016-01-01

    Modeling the distribution of site level effects is an important problem, but it is also an incredibly difficult one. Current methods rely on distributional assumptions in multilevel models for estimation. There it is hoped that the partial pooling of site level estimates with overall estimates, designed to take into account individual variation as…

  19. Heterogeneous patterns on block copolymer thin film via solvent annealing: Effect on protein adsorption

    NASA Astrophysics Data System (ADS)

    Shen, Lei; Zhu, Jintao; Liang, Haojun

    2015-03-01

    Heterogeneous patterns consisting of nanometer-scaled hydrophobic/hydrophilic domains were generated by self-assembly of poly(styrene)-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) block copolymer thin film. The effect of the heterogeneity of the polymer film surface on the nonspecific adsorption of the protein human plasma fibrinogen (FBN, 5.0 × 5.0 × 47.5 nm3) was investigated. The kinetics of the FBN adsorption varies from a single-component Langmuir model on homogeneous hydrophilic PHEMA to a two-stage spreading relaxation model on homogeneous hydrophobic PS surface. On a heterogeneous PS-b-PHEMA surface with majority PS part, the initial FBN adsorption rate remains the same as that on the homogeneous PS surface. However, hydrophilic PHEMA microdomains on the heterogeneous surface slow down the second spreading stage of the FBN adsorption process, leading to a surface excess of adsorbed FBN molecules less than the presumed one simply calculated as adsorption onto multiple domains. Importantly, when the PS-b-PHEMA surface is annealed to form minority domelike PS domains (diameter: ˜50-100 nm) surrounded by a majority PHEMA matrix, such surface morphology proves to be strongly protein-repulsive. These interesting findings can be attributed to the enhancement of the spread FBN molecule in a mobile state by the heterogeneity of polymer film surface before irreversible adsorption occurs.

  20. Heterogeneous growth fingerlings of the Nile tilapia Oreochromis niloticus: effects of density and initial size variability.

    PubMed

    Barbosa, J M; Brugiolo, S S S; Carolsfeld, J; Leitão, S S

    2006-05-01

    In this study, the effect of initial heterogeneity of weight and density on heterogeneous growth (HetG) evaluated by the coefficient of the variation of weight in the young Nile tilapia Oreochromis niloticus of the territorial species was tested. Fish were maintained in a glass aquarium (8 and 2 L of water) with two levels of initial heterogeneity of weight: low and high, under two density conditions: low and high, thus constituting four conditions (six replications for each). Initially, the weights of the animals were taken after 8, 16, 22 and 30 days (end of experiment). The results, evaluated by the non-parametric test of Kruskal- Wallis, demonstrated that in the groups where the animals were stored under high initial HetG, there was a reduction of the same and that in the groups where the animals were stored under high density, there was exacerbation or maintained high values of HetG. High density in association with high initial heterogeneity caused more exacerbation of HetG in such a way that the density appeared to be a determining factor for exacerbation or the maintenance of high values of HetG, whereas the initial heterogeneity of the weight could be a secondary factor.

  1. Effects of spatially heterogeneous porosity on matrix diffusion as investigated by X-ray absorption imaging

    NASA Astrophysics Data System (ADS)

    Tidwell, Vincent C.; Meigs, Lucy C.; Christian-Frear, Tracy; Boney, Craig M.

    2000-03-01

    High-resolution X-ray absorption imaging was used to investigate the effects of spatially heterogeneous porosity on matrix diffusion. Experiments were performed on four, centimeter-scale slabs of Culebra dolomite taken from the Waste Isolation Pilot Plant (WIPP) site. These tests involved the diffusion of potassium iodide into a single edge of each brine-saturated rock slab, while X-ray absorption imaging was used to measure the two-dimensional relative concentration distribution at different times during the experiment. X-ray imaging was also used to measure the heterogeneous, two-dimensional porosity distribution of each rock slab. The resulting high-resolution data provide unique insight into the spatially varying diffusion characteristics of each heterogeneous rock sample, which traditional methods such as through-diffusion experiments cannot. In these tests, significant variations in the diffusion coefficient were calculated over the relatively small length (centimeter) and time scales (months) investigated. Results also indicated that these variations were related to the heterogeneous porosity characteristics of each rock sample. Not only were the diffusion coefficients found to depend on the magnitude of the porosity but also on its spatial distribution. Specifically, the geometry, position, and orientation of the heterogeneous porosity features populating each rock slab appeared to influence the diffusion characteristics.

  2. Facile Hydrothermal Preparation of ZNO/CO3O4 Heterogeneous Nanostructures and its Photovoltaic Effect

    NASA Astrophysics Data System (ADS)

    Wei, Fanan; Jiang, Minlin; Liu, Lianqing

    2015-07-01

    Photovoltaic technology offers great potential in the replacement of fossil fuel resources, but still suffers from high device fabrication cost. Herein, we attempted to provide a solution to these issues with heterogeneous nanostructures. Firstly, Zinc oxide (ZnO)/cobalt oxide (Co3O4) heterojunction nanowires are prepared through facile fabrication methods. By assembling Co(OH)2 nanoplates on ZnO nanowire arrays, the ZnO/Co3O4 heterogeneous nanostructures are uniformly synthesized on ITO coated glass and wafer. Current (I)-voltage (V) measurement through conductive atomic force microscope shows excellent photovoltaic effect. And, the heterojunction nanostructures shows unprecedented high open circuit voltage. Therefore, the potential application of the heterogeneous nanostructures in solar cells is demonstrated.

  3. Pore-Scale Process Coupling and Effective Surface Reaction Rates in Heterogeneous Subsurface Materials

    SciTech Connect

    Liu, Chongxuan; Liu, Yuanyuan; Kerisit, Sebastien N.; Zachara, John M.

    2015-09-01

    This manuscript provides a review of pore-scale researches in literature including experimental and numerical approaches, and scale-dependent behavior of geochemical and biogeochemical reaction rates in heterogeneous porous media. A mathematical equation that can be used to predict the scale-dependent behavior of geochemical reaction rates in heterogeneous porous media has been derived. The derived effective rate expression explicitly links the effective reaction rate constant to the intrinsic rate constant, and to the pore-scale variations in reactant concentrations in porous media. Molecular simulations to calculate the intrinsic rate constants were provided. A few examples of pore-scale simulations were used to demonstrate the application of the equation to calculate effective rate constants in heterogeneous materials. The results indicate that the deviation of effective rate constant from the intrinsic rate in heterogeneous porous media is caused by the pore-scale distributions of reactants and their correlation, which are affected by the pore-scale coupling of reactions and transport.

  4. Effect of heterogeneous microvasculature distribution on drug delivery to solid tumour

    NASA Astrophysics Data System (ADS)

    Zhan, Wenbo; Gedroyc, Wladyslaw; Xu, Xiao Yun

    2014-11-01

    Most of the computational models of drug transport in vascular tumours assume a uniform distribution of blood vessels through which anti-cancer drugs are delivered. However, it is well known that solid tumours are characterized by dilated microvasculature with non-uniform diameters and irregular branching patterns. In this study, the effect of heterogeneous vasculature on drug transport and uptake is investigated by means of mathematical modelling of the key physical and biochemical processes in drug delivery. An anatomically realistic tumour model accounting for heterogeneous distribution of blood vessels is reconstructed based on magnetic resonance images of a liver tumour. Numerical simulations are performed for different drug delivery modes, including direct continuous infusion and thermosensitive liposome-mediated delivery, and the anti-cancer effectiveness is evaluated through changes in tumour cell density based on predicted intracellular concentrations. Comparisons are made between regions of different vascular density, and between the two drug delivery modes. Our numerical results show that both extra- and intra-cellular concentrations in the liver tumour are non-uniform owing to the heterogeneous distribution of tumour vasculature. Drugs accumulate faster in well-vascularized regions, where they are also cleared out more quickly, resulting in less effective tumour cell killing in these regions. Compared with direct continuous infusion, the influence of heterogeneous vasculature on anti-cancer effectiveness is more pronounced for thermosensitive liposome-mediated delivery.

  5. Heterogeneous Effects of Charter Schools: Unpacking Family Selection and Achievement Growth in Los Angeles

    ERIC Educational Resources Information Center

    Shin, Hyo Jeong; Fuller, Bruce; Dauter, Luke

    2017-01-01

    Disparate findings on whether students attending charter schools outperform peers in traditional public schools (TPS) may stem from mixing differing types of charters or inadequately accounting for pupil background. To gauge prior family selection and heterogeneous effects, we distinguish between conversion and start-up charter schools, along with…

  6. Effects of Constructivist and Computer-Facilitated Strategies on Achievement in Heterogeneous Secondary Biology.

    ERIC Educational Resources Information Center

    Duffy, Maryellen; Barowy, William

    This paper describes the effects of the implementation of constructivist techniques with interactive computer simulations on conceptual understanding of plant nutrition and critical thinking skills in heterogeneously grouped secondary biology classrooms. The study focused on three strategies for teaching plant nutrition: (1) traditional; (2)…

  7. Heterogeneous photocatalytic degradation of rose bengal: Effect of operational parameters

    NASA Astrophysics Data System (ADS)

    Kaur, Japinder; Singhal, Sonal

    2014-10-01

    The photocatalytic degradation of rose bengal dye has been investigated using ZnO nanoparticles as photocatalyst. ZnO nanoparticles were found to be efficient catalyst for the degradation of dye and 98% degradation was observed in 90 min. Effect of various operational parameters such as amount of catalyst (0.25-2.00 g/L), concentration of dye (0.01-0.05 mM) and pH (3-11) of dye solution on the rate of dye degradation was studied. The most favorable results for the degradation of rose bengal were observed at pH 5 at a catalyst loading of 1 g/L. Moreover, hydroxyl radicals have been detected in the photocatalytic reaction mixture by using terephthalic acid photoluminescence probing technique. The reusability of the catalyst has also been studied and catalyst was found to be active even after being used for 5 times.

  8. The effect of losing and gaining flow conditions on hyporheic exchange in heterogeneous streambeds

    NASA Astrophysics Data System (ADS)

    Fox, A.; Laube, G.; Schmidt, C.; Fleckenstein, J. H.; Arnon, S.

    2016-09-01

    Bed form-induced hyporheic exchange flux (qH) is increasingly viewed as a key process controlling water fluxes and biogeochemical processes in river networks. Despite the fact that streambeds are inherently heterogeneous, the majority of bed form flume-scale studies were done on homogeneous systems. We conducted salt and dye tracer experiments to study the effects of losing and gaining flow conditions on qH using a laboratory recirculating flume system packed with a heterogeneous streambed, and equipped with a drainage system that enabled us to apply losing or gaining fluxes. We found that when either losing or gaining fluxes increased (regardless of whether the flux was upward or downward), qH followed an exponential decline, the volume of the hyporheic flow cell drastically reduced, and the mean residence times declined moderately. A numerical flow model for the heterogeneous streambed was set up and fitted against the experimental data in order to test whether an equivalent homogeneous case exists. The measured qH were accurately predicted with the heterogeneous model, while it was underestimated using a homogeneous model characterized by the geometric mean of the hydraulic conductivity. It was also shown that in order to produce the results of the heterogeneous model with an equivalent hydraulic conductivity, the latter had to be increased as the losing or gaining fluxes increase. The results strongly suggest that it is critical to adequately account for the heterogeneous streambed structure in order to accurately predict the effect of vertical exchange fluxes between the stream and groundwater on hyporheic exchange.

  9. Size and heterogeneity effects on the strength of fibrous composites

    NASA Astrophysics Data System (ADS)

    Mahesh, Sivasambu; Beyerlein, Irene J.; Phoenix, S. Leigh

    Probabilistic fiber composite strength distributions and size scalings depend heavily on both the stress redistribution mechanism around broken fibers and properties of the fiber strength distribution. In this study we perform large scale Monte Carlo simulations to study the fracture process in a fiber composite material in which fibers are arranged in parallel in a hexagonal array and their strengths are given by a two-parameter Weibull distribution function. To calculate the stress redistribution due to several broken fibers, a realistic 3D shear-lag theory is applied to rhombus-shaped domains with periodic boundary conditions. Empirical composite strength distributions are generated from several hundred Monte Carlo replications, particularly for much lower values of fiber Weibull modulus γ, and larger composite sizes than studied previously. Despite the localized stress enhancements due to fiber failures, predicted by the shear-lag model, composite response displays a transition to equal load sharing like behavior for approximately γ≤1. Accordingly, the results reveal distinct alterations in size effect, failure mode, and weak-link scaling behavior, associated with a transition from stress-driven to fiber strength-driven breakdown.

  10. The short-term outcome of the modified Sauvé-Kapandji procedure regarding range of motion, carpal bone translation and bony shelf size.

    PubMed

    Toyama, Shogo; Tamai, Kazuo; Sakamoto, Atsuto; Hirashima, Toshiko

    2011-02-01

    The Sauvé-Kapandji (S-K) procedure is a common treatment for rheumatoid wrists, but in some cases severe bone destruction makes this operative modality difficult to perform, while also resulting in a poor outcome. A modified S-K procedure for these wrists has been reported, but the clinical outcomes of the modified procedure are unclear. This study evaluated 24 wrists in 20 patients who underwent the modified S-K procedure. The mean follow-up period was 34.5 months. The clinical assessments were range of motion, carpal bone translation and bony shelf size. The range of motion and carpal bone translation were similar to those produced by the S-K procedure. In regard to bony shelf size, wrists with an excessively large bony shelf tended to have a progression of carpal bone translation toward the palmar direction due to the residual malposition of the ECU tendon. The modified S-K procedure appears to be a safe and effective surgical alternative for the treatment of severely destroyed rheumatoid wrists. Although the modified procedure allows for the adjustment of the bony shelf size, it should not be used with wrists that have an excessively large bony shelf.

  11. Effects of three-dimensional geometric field focusing on concentration polarization in a heterogeneous permselective system

    NASA Astrophysics Data System (ADS)

    Green, Yoav; Yossifon, Gilad

    2014-01-01

    The current study extends previous two-dimensional (2D) analysis of concentration polarization to account for three-dimensional effects in realistic heterogeneous ion-permselective systems, e.g., microchamber-nanoslot devices. An analytical solution of the electrodiffusive problem, decoupled from electroconvection along with the local electroneutrality approximation, was obtained using the separation of variables technique. It is able to account for the previously neglected effects of microchamber and nanoslot heights on concentration polarization in terms of concentration profiles, limiting current, and current-voltage curves. The resultant heterogeneity in the third dimension adds to that already existing in the 2D in plane problem to further increase geometric field-focusing effects. As a result the currents no longer scale linearly with the nanoslot area, but rather depend on its shape and relative size compared to that of the nonconducting region (i.e., level of heterogeneity). This is turn leads to pronounced current density intensification with increased system heterogeneity found to be in qualitative agreement with previously reported experiments in which both microchamber and nanoslot geometries were varied.

  12. The heterogeneity of the cigarette price effect on body mass index.

    PubMed

    Wehby, George L; Courtemanche, Charles J

    2012-09-01

    Previous studies estimate the average effect of cigarette price on body mass index (BMI), with recent research showing that their different methodologies all point to a negative effect after several years. This literature, however, ignores the possibility that the effect could vary throughout the BMI distribution or across socioeconomic and demographic groups due to differences in underlying obesity risks or preferences for health. We evaluate heterogeneity in the long-run impact of cigarette price on BMI by performing quantile regressions and stratifying the sample by race, education, age, and sex. Cigarette price has a highly heterogeneous negative effect that is more than three times as strong at high BMI levels--where weight loss is most beneficial for health--than at low levels. The effects are also strongest for blacks, college graduates, middle-aged adults, and women. We also assess the implications for disparities, conduct robustness checks, and evaluate potential mechanisms.

  13. Minimally Invasive Surgery Combined with Regenerative Biomaterials in Treating Intra-Bony Defects: A Meta-Analysis

    PubMed Central

    Zhang, Yuanyuan; Li, Wenyang; Song, Jinlin

    2016-01-01

    Background With the popularity of minimally invasive surgery (MIS) in periodontics, numerous publications have evaluated the benefits of MIS with or without various regenerative biomaterials in the treatment of periodontal intra-bony defects. However, it is unclear if it is necessary to use biomaterials in MIS. Thus, we conducted a meta-analysis of randomized clinical trials in patients with intra-bony defects to compare the clinical outcomes of MIS with regenerative biomaterials for MIS alone. Methods The authors retrieved English publications on relevant studies from Cochrane CENTRAL, PubMed, Medline, Embase, Clinical Evidence, and ClinicalTrails.gov (up to June 30, 2015). The main clinical outcomes were the reduction of probing pocket depths (PPDs), gain of clinical attachment level (CAL), recession of gingival margin (REC) and radiographic bone fill. Review Manager 5.2 (Cochrane Collaboration, Oxford, England) was used to calculate the heterogeneity and mean differences of the main clinical outcomes. Results In total, 464 studies in the literature were identified but only four were ultimately feasible. The results showed no significant difference regarding CAL gain (P = 0.32) and PPD reduction (P = 0.40) as well as REC increase (P = 0.81) and radiographic bone fill (P = 0.64) between the MIS plus biomaterials group and the MIS alone group. Conclusions The meta-analysis suggested no significant difference in treatment of intra-bony defects between the MIS plus biomaterials group and the MIS alone group, indicating that it is important to take costs and benefits into consideration when a decision is made about a therapeutic approach. There needs to be an in-depth exploration of the induction of intrinsic tissue healing of MIS without biomaterials to achieve optimal outcomes. PMID:26785405

  14. Model-based definition of population heterogeneity and its effects on metabolism in sporulating Bacillus subtilis.

    PubMed

    Morohashi, Mineo; Ohashi, Yoshiaki; Tani, Saeka; Ishii, Kotaro; Itaya, Mitsuhiro; Nanamiya, Hideaki; Kawamura, Fujio; Tomita, Masaru; Soga, Tomoyoshi

    2007-08-01

    The soil bacterium Bacillus subtilis forms dormant, robust spores as a tactic to ensure survival under conditions of starvation. However, the sporulating culture includes sporulating and non-sporulating cells, because a portion of the cell population initiates sporulation in wild-type strain. We anticipated that the population effect must be considered carefully to analyse samples yielding population heterogeneity. We first built a mathematical model and simulated for signal transduction of the sporulation cue to see what mechanisms are responsible for generating the heterogeneity. The simulated results were confirmed experimentally, where heterogeneity is primarily modulated by negative feedback circuits, resulting in generation of a bistable response within the sporulating culture. We also confirmed that mutants relevant to negative feedback yield either sporulating or non-sporulating subpopulations. To see the effect of molecular mechanism between sporulating and non-sporulating cells in distinct manner, metabolome analysis was conducted using the above mutants. The metabolic profiles exhibited distinct characteristics with time regardless of whether sporulation was initiated or not. In addition, several distinct characteristics of metabolites were observed between strains, which was inconsistent with previously reported data. The results imply that careful consideration must be made in the interpretation of data obtained from cells yielding population heterogeneity.

  15. Inclusive fitness in finite populations-effects of heterogeneity and synergy.

    PubMed

    Taylor, Peter

    2017-03-01

    I review recent results concerning the relationship between the inclusive fitness (IF) effect and standard measures of allele fitness in a finite-population, with attention to the effect of heterogeneity in population structure and nonadditive fitness effects. In both cases, existing theoretical work is somewhat technical and I try to provide a more transparent account. In a heterogeneous population it is known that inclusive fitness will generally fail to incorporate the effects of selection on the distribution of alleles among states unless a reproductive-value weighting is used. But even given that, recent work shows that under certain updating rules, the IF effect can fail to be equivalent to standard measures such as fixation probability. In terms of synergistic fitness effects, I review the result that in the finite population model, the IF effect can be calculated using only "additive" relatedness coefficients so that computational difficulties found in the infinite-population model do not arise. In my own work, there is an interaction here in that my 2012 work on synergy with Maciejewski made an assumption about inclusive fitness that my 2014 work on heterogeneity with Tarnita showed to be wrong. I include (Appendix C) a corrected argument for the 2012 result.

  16. Effects of matrix heterogeneity on animal dispersal: from individual behavior to metapopulation-level parameters.

    PubMed

    Revilla, Eloy; Wiegand, Thorsten; Palomares, Francisco; Ferreras, Pablo; Delibes, Miguel

    2004-11-01

    Mounting theoretical and empirical evidence shows that matrix heterogeneity may have contrasting effects on metapopulation dynamics by contributing to patch isolation in nontrivial ways. We analyze the movement properties during interpatch dispersal in a metapopulation of Iberian lynx (Lynx pardinus). On a daily temporal scale, lynx habitat selection defines two types of matrix habitats where individuals may move: open and dispersal habitats (avoided and used as available, respectively). There was a strong and complex impact of matrix heterogeneity on movement properties at several temporal scales (hourly and daily radiolocations and the entire dispersal event). We use the movement properties on the hourly temporal scale to build a simulation model to reconstruct individual dispersal events. The two most important parameters affecting model predictions at both the individual (daily) and metapopulation scales were related to the movement capacity (number of movement steps per day and autocorrelation in dispersal habitat) followed by the parameters representing the habitat selection in the matrix. The model adequately reproduced field estimates of population-level parameters (e.g., interpatch connectivity, maximum and final dispersal distances), and its performance was clearly improved when including the effect of matrix heterogeneity on movement properties. To assume there is a homogeneous matrix results in large errors in the estimate of interpatch connectivity, especially for close patches separated by open habitat or corridors of dispersal habitat, showing how important it is to consider matrix heterogeneity when it is present. Movement properties affect the interaction of dispersing individuals with the landscape and can be used as a mechanistic representation of dispersal at the metapopulation level. This is so when the effect of matrix heterogeneity on movement properties is evaluated under biologically meaningful spatial and temporal scales.

  17. Ultrasonographic appearance of bony abnormalities at the dorsal aspect of the fetlock joint in geriatric cadaver horses.

    PubMed

    Vanderperren, K; Gielen, I; Van Caelenberg, A; Van der Vekens, E; Raes, E V; Hauspie, S; van Bree, H; Saunders, J H

    2012-07-01

    This article describes the ultrasonographic (US) appearance of bony abnormalities on the dorsal aspect of the third metacarpal/metatarsal bone of the equine fetlock in cadavers with radiographic signs of osteoarthrosis. After US, computed tomography was undertaken to better characterise the lesions. Twelve fetlock joints were collected and all had more than one bone abnormality on US. Normal subchondral bone appeared on US as a well-defined and regular hyperechoic line with distal acoustic shadowing. Bone abnormalities detected on US included (1) gaps in the proximal subchondral bone filled with material of heterogeneous echogenicity, (2) bone fragments represented as small straight smoothly delineated hyperechoic lines with distal shadowing located superficial to the surface of the adjacent bone, (3) proximal new bone formation visible as mild to severe cortical protrusions, (4) marginal osteophytoses seen as an elevation of the hyperechoic surface of the subchondral bone at the edges of the joint surfaces, (5) indentations in subchondral bone seen as a concave deviation of the hyperechoic line without interruption, (6) focal or diffuse irregularities of the subchondral bone seen as disruptions of the normal smooth bony contours, and (7) focal hyperechoic spikes originating from the subchondral plate and invading the articular cartilage. These findings are discussed.

  18. Bony fish and their contribution to marine inorganic carbon cycling

    NASA Astrophysics Data System (ADS)

    Salter, Michael; Perry, Chris; Wilson, Rod; Harborne, Alistair

    2016-04-01

    Conventional understanding of the marine inorganic carbon cycle holds that CaCO3 (mostly as low Mg-calcite and aragonite) precipitates in the upper reaches of the ocean and sinks to a point where it either dissolves or is deposited as sediment. Thus, it plays a key role controlling the distribution of DIC in the oceans and in regulating their capacity to absorb atmospheric CO2. However, several aspects of this cycle remain poorly understood and have long perplexed oceanographers, such as the positive alkalinity anomaly observed in the upper water column of many of the world's oceans, above the aragonite and calcite saturation horizons. This anomaly would be explained by extensive dissolution of a carbonate phase more soluble than low Mg-calcite or aragonite, but major sources for such phases remain elusive. Here we highlight marine bony fish as a potentially important primary source of this 'missing' high-solubility CaCO3. Precipitation of CaCO3 takes place within the intestines of all marine bony fish as part of their normal physiological functioning, and global production models suggest it could account for up to 45 % of total new marine CaCO3 production. Moreover, high Mg-calcite containing >25 % mol% MgCO3 - a more soluble phase than aragonite - is a major component of these precipitates. Thus, fish CaCO3 may at least partially explain the alkalinity anomaly in the upper water column. However, the issue is complicated by the fact that carbonate mineralogy actually varies among fish species, with high Mg-calcite (HMC), low Mg-calcite (LMC), aragonite, and amorphous calcium carbonate (ACC) all being common products. Using data from 22 Caribbean fish species, we have generated a novel production model that resolves phase proportions. We evaluate the preservation/dissolution potential of these phases and consider potential implications for marine inorganic carbon cycling. In addition, we consider the dramatic changes in fish biomass structure that have resulted

  19. Experimental study on effects of geologic heterogeneity in enhancing dissolution trapping of supercritical CO2

    NASA Astrophysics Data System (ADS)

    Agartan, Elif; Trevisan, Luca; Cihan, Abdullah; Birkholzer, Jens; Zhou, Quanlin; Illangasekare, Tissa H.

    2015-03-01

    Dissolution trapping is one of the primary mechanisms that enhance the storage security of supercritical carbon dioxide (scCO2) in saline geologic formations. When scCO2 dissolves in formation brine produces an aqueous solution that is denser than formation brine, which leads to convective mixing driven by gravitational instabilities. Convective mixing can enhance the dissolution of CO2 and thus it can contribute to stable trapping of dissolved CO2. However, in the presence of geologic heterogeneities, diffusive mixing may also contribute to dissolution trapping. The effects of heterogeneity on mixing and its contribution to stable trapping are not well understood. The goal of this experimental study is to investigate the effects of geologic heterogeneity on mixing and stable trapping of dissolved CO2. Homogeneous and heterogeneous media experiments were conducted in a two-dimensional test tank with various packing configurations using surrogates for scCO2 (water) and brine (propylene glycol) under ambient pressure and temperature conditions. The results show that the density-driven flow in heterogeneous formations may not always cause significant convective mixing especially in layered systems containing low-permeability zones. In homogeneous formations, density-driven fingering enhances both storage in the deeper parts of the formation and contact between the host rock and dissolved CO2 for the potential mineralization. On the other hand, for layered systems, dissolved CO2 becomes immobilized in low-permeability zones with low-diffusion rates, which reduces the risk of leakage through any fault or fracture. Both cases contribute to the permanence of the dissolved plume in the formation.

  20. The impact of ignoring population heterogeneity when Markov models are used in cost-effectiveness analysis.

    PubMed

    Zaric, Gregory S

    2003-01-01

    Many factors related to the spread and progression of diseases vary throughout a population. This heterogeneity is frequently ignored in cost-effectiveness analyses by using average or representative values or by considering multiple risk groups. The author explores the impact that such simplifying assumptions may have on the results and interpretation of cost-effectiveness analyses when Markov models are used to calculate the costs and health impact of interventions. A discrete-time Markov model for a disease is defined, and 5 potential interventions are considered. Health benefits, costs, and incremental cost-effectiveness ratios are calculated for each intervention. It is assumed that the population is heterogeneous with respect to the probability of becoming sick. Ignoring this heterogeneity may lead to optimistic or pessimistic estimates of cost-effectiveness ratios, depending on the intervention and, in some cases, the parameter values. Implications are discussed of this finding on the use of league tables and on comparisons of cost-effectiveness ratios versus commonly accepted threshold values.

  1. The effects of racial heterogeneity on mental health: A study of detained youth across multiple counties.

    PubMed

    Lau, Katherine S L; Aalsma, Matthew C; Holloway, Evan D; Wiehe, Sarah E; Vachon, David D

    2015-09-01

    A majority of detained adolescents experience mental health and substance use problems. Limited research has examined the interaction between the race/ethnicity of an individual youth and county-level racial heterogeneity on adolescent mental health outcomes. Participants were identified through a statewide mental health screening project that took place in detention centers across 11 different counties in a Midwestern state during January 1, 2008, to May 10, 2010. A total of 23,831 detained youth (ages 11-18 years), identified as non-Hispanic White (46.6%), Black (43.5%), or Hispanic (9.8%), completed a mental health screener that assessed problems in alcohol/drug use, depression-anxiety, anger-irritability, trauma, somatic complaints, and suicide ideation. Census data were gathered to determine the racial heterogeneity of each county and other county-level variables. Hierarchical linear regression analyses were used to test the independent and interactive effects of youth race/ethnicity and county-level variables (including racial heterogeneity of the county) on adolescent mental health. Independent of other community characteristics, as county-level racial heterogeneity increased, mental health problems among detained youth decreased. In future research on the development and persistence of mental health problems in detained youth, both community and individual-level factors should be considered.

  2. Estimation of the advection effects induced by surface heterogeneities in the surface energy budget

    NASA Astrophysics Data System (ADS)

    Cuxart, Joan; Wrenger, Burkhard; Martínez-Villagrasa, Daniel; Reuder, Joachim; Jonassen, Marius O.; Jiménez, Maria A.; Lothon, Marie; Lohou, Fabienne; Hartogensis, Oscar; Dünnermann, Jens; Conangla, Laura; Garai, Anirban

    2016-07-01

    The effect of terrain heterogeneities in one-point measurements is a continuous subject of discussion. Here we focus on the order of magnitude of the advection term in the equation of the evolution of temperature as generated by documented terrain heterogeneities and we estimate its importance as a term in the surface energy budget (SEB), for which the turbulent fluxes are computed using the eddy-correlation method. The heterogeneities are estimated from satellite and model fields for scales near 1 km or broader, while the smaller scales are estimated through direct measurements with remotely piloted aircraft and thermal cameras and also by high-resolution modelling. The variability of the surface temperature fields is not found to decrease clearly with increasing resolution, and consequently the advection term becomes more important as the scales become finer. The advection term provides non-significant values to the SEB at scales larger than a few kilometres. In contrast, surface heterogeneities at the metre scale yield large values of the advection, which are probably only significant in the first centimetres above the ground. The motions that seem to contribute significantly to the advection term in the SEB equation in our case are roughly those around the hectometre scales.

  3. Ancient origin of lubricated joints in bony vertebrates

    PubMed Central

    Askary, Amjad; Smeeton, Joanna; Paul, Sandeep; Schindler, Simone; Braasch, Ingo; Ellis, Nicholas A; Postlethwait, John; Miller, Craig T; Crump, J Gage

    2016-01-01

    Synovial joints are the lubricated connections between the bones of our body that are commonly affected in arthritis. It is assumed that synovial joints first evolved as vertebrates came to land, with ray-finned fishes lacking lubricated joints. Here, we examine the expression and function of a critical lubricating protein of mammalian synovial joints, Prg4/Lubricin, in diverse ray-finned fishes. We find that Prg4 homologs are specifically enriched at the jaw and pectoral fin joints of zebrafish, stickleback, and gar, with genetic deletion of the zebrafish prg4b gene resulting in the same age-related degeneration of joints as seen in lubricin-deficient mice and humans. Our data support lubricated synovial joints evolving much earlier than currently accepted, at least in the common ancestor of all bony vertebrates. Establishment of the first arthritis model in the highly regenerative zebrafish will offer unique opportunities to understand the aetiology and possible treatment of synovial joint disease. DOI: http://dx.doi.org/10.7554/eLife.16415.001 PMID:27434666

  4. Jaws and teeth of the earliest bony fishes.

    PubMed

    Botella, Hector; Blom, Henning; Dorka, Markus; Ahlberg, Per Erik; Janvier, Philippe

    2007-08-02

    Extant jawed vertebrates, or gnathostomes, fall into two major monophyletic groups, namely chondrichthyans (cartilaginous fishes) and osteichthyans (bony fishes and tetrapods). Fossil representatives of the osteichthyan crown group are known from the latest Silurian period, 418 million years (Myr) ago, to the present. By contrast, stem chondrichthyans and stem osteichthyans are still largely unknown. Two extinct Palaeozoic groups, the acanthodians and placoderms, may fall into these stem groups or the common stem group of gnathostomes, but their relationships and monophyletic status are both debated. Here we report unambiguous evidence for osteichthyan characters in jaw bones referred to the late Silurian (423-416-Myr-old) fishes Andreolepis hedei and Lophosteus superbus, long known from isolated bone fragments, scales and teeth, and whose affinities to, or within, osteichthyans have been debated. The bones are a characteristic osteichthyan maxillary and dentary, but the organization of the tooth-like denticles they bear differs from the large, conical teeth of crown-group osteichthyans, indicating that they can be assigned to the stem group. Andreolepis and Lophosteus are thus not only the oldest but also the most phylogenetically basal securely identified osteichthyans known so far.

  5. Effects of heterogeneity in aquifer permeability and biomass on biodegradation rate calculations - Results from numerical simulations

    USGS Publications Warehouse

    Scholl, M.A.

    2000-01-01

    Numerical simulations were used to examine the effects of heterogeneity in hydraulic conductivity (K) and intrinsic biodegradation rate on the accuracy of contaminant plume-scale biodegradation rates obtained from field data. The simulations were based on a steady-state BTEX contaminant plume-scale biodegradation under sulfate-reducing conditions, with the electron acceptor in excess. Biomass was either uniform or correlated with K to model spatially variable intrinsic biodegradation rates. A hydraulic conductivity data set from an alluvial aquifer was used to generate three sets of 10 realizations with different degrees of heterogeneity, and contaminant transport with biodegradation was simulated with BIOMOC. Biodegradation rates were calculated from the steady-state contaminant plumes using decreases in concentration with distance downgradient and a single flow velocity estimate, as is commonly done in site characterization to support the interpretation of natural attenuation. The observed rates were found to underestimate the actual rate specified in the heterogeneous model in all cases. The discrepancy between the observed rate and the 'true' rate depended on the ground water flow velocity estimate, and increased with increasing heterogeneity in the aquifer. For a lognormal K distribution with variance of 0.46, the estimate was no more than a factor of 1.4 slower than the true rate. For aquifer with 20% silt/clay lenses, the rate estimate was as much as nine times slower than the true rate. Homogeneous-permeability, uniform-degradation rate simulations were used to generate predictions of remediation time with the rates estimated from heterogeneous models. The homogeneous models were generally overestimated the extent of remediation or underestimated remediation time, due to delayed degradation of contaminants in the low-K areas. Results suggest that aquifer characterization for natural attenuation at contaminated sites should include assessment of the presence

  6. Effective velocity for transport in heterogeneous compressible flows with mean drift

    NASA Astrophysics Data System (ADS)

    Attinger, Sabine; Abdulle, Assyr

    2008-01-01

    Solving transport equations in heterogeneous flows might give rise to scale dependent transport behavior with effective large scale transport parameters differing from those found on smaller scales. For incompressible velocity fields, homogenization methods have proven to be powerful in describing the effective transport parameters. In this paper, we aim at studying the effective drift of transport problems in heterogeneous compressible flows. Such a study was done by Vergassola and Avellaneda in Physica D 106, 148 (1997). There, it was shown that for static compressible flow without mean drift, impacts on the large scale drift do not occur. We will first discuss the impact of a mean drift and show that static compressible flow with mean drift can produce a heterogeneity driven large scale drift (or ballistic transport). For the case of Gaussian stationary random processes, we derive explicit results for the large scale drift. Moreover, we show that the large scale or effective drift depends on the small scale diffusion coefficients and thus on the molecular weights of the particles. This study could be applied to weight-based particle separation. Numerical simulations are presented to illustrate these phenomena.

  7. The effect of heterogeneous dynamics of online users on information filtering

    NASA Astrophysics Data System (ADS)

    Chen, Bo-Lun; Zeng, An; Chen, Ling

    2015-11-01

    The rapid expansion of the Internet requires effective information filtering techniques to extract the most essential and relevant information for online users. Many recommendation algorithms have been proposed to predict the future items that a given user might be interested in. However, there is an important issue that has always been ignored so far in related works, namely the heterogeneous dynamics of online users. The interest of active users changes more often than that of less active users, which asks for different update frequency of their recommendation lists. In this paper, we develop a framework to study the effect of heterogeneous dynamics of users on the recommendation performance. We find that the personalized application of recommendation algorithms results in remarkable improvement in the recommendation accuracy and diversity. Our findings may help online retailers make better use of the existing recommendation methods.

  8. Heterogeneity and the Effect of Mental Health Parity Mandates on the Labor Market*

    PubMed Central

    Andersen, Martin

    2015-01-01

    Health insurance benefit mandates are believed to have adverse effects on the labor market, but efforts to document such effects for mental health parity mandates have had limited success. I show that one reason for this failure is that the association between parity mandates and labor market outcomes vary with mental distress. Accounting for this heterogeneity, I find adverse labor market effects for non-distressed individuals, but favorable effects for moderately distressed individuals and individuals with a moderately distressed family member. On net, I conclude that the mandates are welfare increasing for moderately distressed workers and their families, but may be welfare decreasing for non-distressed individuals. PMID:26210944

  9. Detection of irrigation timing using MODIS and SAR: Effect of land cover heterogeneity

    NASA Astrophysics Data System (ADS)

    Seungtaek, J.; Keunchang, J.; Lee, H.; Seokyeong, H.; Kang, S.

    2010-12-01

    Rice is one of the world’s major staple foods. Paddy rice fields had unique biophysical characteristics that the rice is grown on flooded soils unlike other crops. Distribution and timing of irrigation of paddy rice fields are of importance to determine hydrological balance and efficiency of water resource. In this paper, we detected the distribution and timing of irrigation of paddy rice fields using the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the NASA EOS Aqua satellite. Previous researches demonstrated that MODIS data can be utilized to detect timing of irrigation by combining vegetation index and Land Surface Water Index (LSWI). Land cover heterogeneity, however, causes considerable uncertainty of the satellite-based detections. To evaluate and quantify the effect of land cover heterogeneity, Radarsat-1 Synthetic Aperture Radar (SAR) images were applied together with the MODIS images. Sub-pixel heterogeneity of MODIS image on land cover and irrigation was evaluated and quantified by using the Radarsat-1 SAR images. The degree of sub-pixel heterogeneity was related with detection of a threshold value of LSWI to determine the timing of irrigation. The threshold value with the degree of heterogeneity increased (R2=0.95), which was applied to detect the timing of irrigation over complex land cover areas. Reliable detecting of timing of irrigation could enhance reliability of MODIS-based estimation on evapotranspiration from paddy rice fields. In this presentation, we will demonstrate the enhancement of MODIS-based evapotranspiration by using our new algorithm on detection of timing of irrigation. Acknowledgement: This study was supported by National Academy of Agricultural Science, RDA, Republic of Korea.

  10. Effect of heterogeneity on the quantitative determination of trace elements in concrete.

    PubMed

    Weritz, Friederike; Schaurich, Dieter; Taffe, Alexander; Wilsch, Gerd

    2006-05-01

    Laser-induced breakdown spectroscopy has been used for quantitative measurement of trace elements, e.g. sulfur and chlorine, in concrete. Chloride and sulfate ions have a large effect on the durability of concrete structures, and quantitative measurement is important for condition assessment and quality assurance. Concrete is a highly heterogeneous material in composition and grain-size distribution, i.e. the spatial distribution of elements. Calibration plots were determined by use of laboratory-made reference samples consisting of pressings of cement powder, hydrated cement, cement mortar, and concrete, in which the heterogeneity of the material is increasing because of the aggregates. Coarse aggregate and cement paste are distinguishable by the intensity of the Ca spectral lines. More advanced evaluation is necessary to account for the effect of the fine aggregate. The three series of reference samples enable systematic study of the effects of heterogeneity on spectral intensity, signal fluctuation, uncertainty, and limits of detection. Spatially resolved measurements and many spectra enable statistical evaluation of the data. The heterogeneity has an effect on measurement of the sulfur and chlorine content, because both occur mainly in the cement matrix. Critical chloride concentrations are approximately 0.04% (m/m). The chlorine spectral line at 837.6 nm is evaluated. The natural sulfur content of concrete is approximately 0.1% (m/m). The spectral line at 921.3 nm is evaluated. One future application may be simultaneous determination of the amount of damaging trace elements and the cement content of the concrete.

  11. Application of Effective Medium Theory to the Three-Dimensional Heterogeneity of Mantle Anisotropy

    NASA Astrophysics Data System (ADS)

    Song, X.; Jordan, T. H.

    2015-12-01

    A self-consistent theory for the effective elastic parameters of stochastic media with small-scale 3D heterogeneities has been developed using a 2nd-order Born approximation to the scattered wavefield (T. H. Jordan, GJI, in press). Here we apply the theory to assess how small-scale variations in the local anisotropy of the upper mantle affect seismic wave propagation. We formulate a anisotropic model in which the local elastic properties are specified by a constant stiffness tensor with hexagonal symmetry of arbitrary orientation. This orientation is guided by a Gaussian random vector field with transversely isotropic (TI) statistics. If the outer scale of the statistical variability is small compared to a wavelength, then the effective seismic velocities are TI and depend on two parameters, a horizontal-to-vertical orientation ratio ξ and a horizontal-to-vertical aspect ratio, η. If ξ = 1, the symmetry axis is isotropically distributed; if ξ < 1, it is vertical biased (bipolar distribution), and if ξ > 1, it is horizontally biased (girdle distribution). If η = 1, the heterogeneity is geometrically isotropic; as η à∞, the medium becomes a horizontal stochastic laminate; as η à0, the medium becomes a vertical stochastic bundle. Using stiffness tensors constrained by laboratory measurements of mantle xenoliths, we explore the dependence of the effective P and S velocities on ξ and η. The effective velocities are strongly controlled by the orientation ratio ξ; e.g., if the hexagonal symmetry axis of the local anisotropy is the fast direction of propagation, then vPH > vPV and vSH > vSV for ξ > 1. A more surprising result is the 2nd-order insensitivity of the velocities to the heterogeneity aspect ratio η. Consequently, the geometrical anisotropy of upper-mantle heterogeneity significantly enhances seismic-wave anisotropy only through local variations in the Voigt-averaged velocities, which depend primarily on rock composition and not deformation

  12. Effect of permeability heterogeneity on CO2 injectivity and sweep efficiency based on numerical simulations

    NASA Astrophysics Data System (ADS)

    Tian, Liang; Yang, Zhibing; Fagerlund, Fritjof; Niemi, Auli

    2015-04-01

    We study effect of geological heterogeneity on the injection of supercritical CO2 into a deep saline aquifer at the scale of a pilot test site, based on numerical modeling. The effect of heterogeneity on storage capacity is investigated by assessing the effect on sweep efficiency and on injectivity. Log-normally distributed random permeability fields characterized by their standard deviation (σ) and correlation length (λ) are generated and injection simulations conducted for each realization of the permeability fields with TOUGH2/ECO2N code. A range of injection pressures is tested as well. The results indicate that injectivity increases with the increased horizontal correlation length given that the vertical correlation length is fixed and significant inter-realization variation is seen when changing the standard deviation. Sweep efficiency is favored by smaller horizontal correlation length. For cases with increased standard deviation, the sweep efficiency shows significant inter-realization variability. Finally, it can be shown that both sweep efficiency and injectivity can be expressed as simple functions of medium heterogeneity characteristics, standard deviation (σ) and correlation length (λ).

  13. Estimating effective model parameters for heterogeneous unsaturated flow using error models for bias correction

    NASA Astrophysics Data System (ADS)

    Erdal, D.; Neuweiler, I.; Huisman, J. A.

    2012-06-01

    Estimates of effective parameters for unsaturated flow models are typically based on observations taken on length scales smaller than the modeling scale. This complicates parameter estimation for heterogeneous soil structures. In this paper we attempt to account for soil structure not present in the flow model by using so-called external error models, which correct for bias in the likelihood function of a parameter estimation algorithm. The performance of external error models are investigated using data from three virtual reality experiments and one real world experiment. All experiments are multistep outflow and inflow experiments in columns packed with two sand types with different structures. First, effective parameters for equivalent homogeneous models for the different columns were estimated using soil moisture measurements taken at a few locations. This resulted in parameters that had a low predictive power for the averaged states of the soil moisture if the measurements did not adequately capture a representative elementary volume of the heterogeneous soil column. Second, parameter estimation was performed using error models that attempted to correct for bias introduced by soil structure not taken into account in the first estimation. Three different error models that required different amounts of prior knowledge about the heterogeneous structure were considered. The results showed that the introduction of an error model can help to obtain effective parameters with more predictive power with respect to the average soil water content in the system. This was especially true when the dynamic behavior of the flow process was analyzed.

  14. Effects of the investigation scale on pumping test results in heterogeneous porous aquifers

    NASA Astrophysics Data System (ADS)

    Schad, Hermann; Teutsch, Georg

    1994-07-01

    At the environmental field site Horkheimer Insel numerous pumping tests were performed at different investigation scales. The measured time-drawdown curves exhibit a characteristic segmentation into two or three drawdown phases. Since the site is highly heterogeneous it was intended to take advantage of the non-stationarity of the flow field during pumping tests in order to determine the effective length scale of the subsurface heterogeneity structure. The time-drawdown curves were evaluated using the Theis' analytical solution, which, however, yields different aquifer parameters for the different drawdown phases. Because this solution does not satisfy the properties of the test site aquifer totally, some of the inferred parameter distributions are regarded as suitable only for a relative comparison rather than representing 'true' effective parameters. Based on a definition of spatial and temporal scale, a statistical description along with a qualitative interpretation of the parameter distributions determined is provided. The results indicate that the effective length scale of the heterogeneity structure can be estimated from pumping test data. However, it is believed that for a quantitative interpretation of the field data, the application of numerical methods is necessary.

  15. Effects of temporal heterogeneity of water supply on the growth of Perilla frutescens depend on plant density

    PubMed Central

    Hagiwara, Yousuke; Kachi, Naoki; Suzuki, Jun-Ichirou

    2010-01-01

    Background and Aims Plants respond to the spatial and temporal heterogeneity of a resource supply. However, their responses will depend on intraspecific competition for resource acquisition. Although plants are subject to various intensities of intraspecific competition, most studies of resource heterogeneity have been carried out under a single density so that the effects of intraspecific competition on plant responses to resource heterogeneity are largely unknown. Methods A growth experiment was performed to investigate plant responses to the temporal heterogeneity of water supply and nutrient levels under multiple plant densities. The annual plant Perilla frutescens was grown using different combinations of frequency of water supply, nutrient level and density, while providing the same total amount of water under all conditions. The effects of the treatments on biomass, allocation to roots and intensity of competition were analysed after 48 d. Key Results Biomass and allocation to roots were larger under homogeneous than under heterogeneous water supply, and the effects of water heterogeneity were greater at high density than at low density. The effects of water heterogeneity were greater at high nutrient level than at low level for biomass, while the effects were greater at low nutrient level than high level for allocation to roots. Competition was severer under homogeneous than under heterogeneous water supply. Conclusions Competition for water probably makes plants more sensitive to the water heterogeneity. In addition, the intensity of intraspecific competition can be affected by the temporal patterns of water supply. Because both resource heterogeneity and intraspecific competition affect resource acquisition and growth of plants, their interactive effects should be evaluated more carefully under future studies. PMID:20495200

  16. Effects of heterogeneity and friction on the deformation and strength of rock

    SciTech Connect

    Nihei, K.T.; Myer, L.R.; Liu, Z.; Cook, N.G.W.; Kemeny, J.M.

    1994-03-01

    Experimental observations of the evolution of damage in rocks during compressive loading indicate that macroscopic failure occurs predominantly by extensile crack growth parallel or subparallel to the maximum principal stress. Extensile microcracks initiate at grain boundaries and open pores by a variety of micromechanical processes which may include grain bending, Brazilian type fracture and grain boundary sliding. Microstructural heterogeneity in grain size, strength and shape determines the magnitude of the local tensile stresses which produce extensile microcracking and the stability with which these microcracks coalesce to form macrocracks. Friction at grain boundaries and between the surfaces of microcracks reduces the strain energy available for extensile crack growth and increases the stability of microcrack growth. In clastic rocks, frictional forces may improve the conditions for extensile microcrack growth by constraining the amount of sliding and rotation of individual grains. Micromechanical models are used to investigate the effects of heterogeneity and friction on the deformation and strength of crystalline and clastic rocks.

  17. Reduced negativity effect in older adults' memory for emotional pictures: the heterogeneity-homogeneity list paradigm.

    PubMed

    Grühn, Daniel; Scheibe, Susanne; Baltes, Paul B

    2007-09-01

    Using the heterogeneity-homogeneity list paradigm, the authors investigated 48 young adults' (20-30 years) and 48 older adults' (65-75 years) recognition memory for emotional pictures. The authors obtained no evidence for a positivity bias in older adults' memory: Age differences were primarily driven by older adults' diminished ability to remember negative pictures. The authors further found a strong effect of list types: Pictures, particularly neutral ones, were better recognized in homogeneous (blocked) lists than in heterogeneous (mixed) ones. Results confirm those of a previous study by D. Grühn, J. Smith, and P. B. Baltes (2005) that used a different type of to-be-remembered material, that is, pictures instead of words.

  18. New heterogeneous test statistics for the unbalanced fixed-effect nested design.

    PubMed

    Guo, Jiin-Huarng; Billard, L; Luh, Wei-Ming

    2011-05-01

    When the underlying variances are unknown or/and unequal, using the conventional F test is problematic in the two-factor hierarchical data structure. Prompted by the approximate test statistics (Welch and Alexander-Govern methods), the authors develop four new heterogeneous test statistics to test factor A and factor B nested within A for the unbalanced fixed-effect two-stage nested design under variance heterogeneity. The actual significance levels and statistical power of the test statistics were compared in a simulation study. The results show that the proposed procedures maintain better Type I error rate control and have greater statistical power than those obtained by the conventional F test in various conditions. Therefore, the proposed test statistics are recommended in terms of robustness and easy implementation.

  19. The value of heterogeneity for cost-effectiveness subgroup analysis: conceptual framework and application.

    PubMed

    Espinoza, Manuel A; Manca, Andrea; Claxton, Karl; Sculpher, Mark J

    2014-11-01

    This article develops a general framework to guide the use of subgroup cost-effectiveness analysis for decision making in a collectively funded health system. In doing so, it addresses 2 key policy questions, namely, the identification and selection of subgroups, while distinguishing 2 sources of potential value associated with heterogeneity. These are 1) the value of revealing the factors associated with heterogeneity in costs and outcomes using existing evidence (static value) and 2) the value of acquiring further subgroup-related evidence to resolve the uncertainty given the current understanding of heterogeneity (dynamic value). Consideration of these 2 sources of value can guide subgroup-specific treatment decisions and inform whether further research should be conducted to resolve uncertainty to explain variability in costs and outcomes. We apply the proposed methods to a cost-effectiveness analysis for the management of patients with acute coronary syndrome. This study presents the expected net benefits under current and perfect information when subgroups are defined based on the use and combination of 6 binary covariates. The results of the case study confirm the theoretical expectations. As more subgroups are considered, the marginal net benefit gains obtained under the current information show diminishing marginal returns, and the expected value of perfect information shows a decreasing trend. We present a suggested algorithm that synthesizes the results to guide policy.

  20. The effective surface energy of heterogeneous solids measured by inverse gas chromatography at infinite dilution.

    PubMed

    Sun, Chenhang; Berg, John C

    2003-04-15

    Inverse gas chromatography (IGC) at infinite dilution has been widely used to access the nonspecific surface free energy of solid materials. Since most practical surfaces are heterogeneous, the effective surface energy given by IGC at infinite dilution is somehow averaged over the whole sample surface, but the rule of averaging has thus far not been established. To address this problem, infinite dilution IGC analysis was carried out on mixtures of known heterogeneity. These materials are obtained by mixing two types of solid particles with significantly different surface energies as characterized individually with IGC, and results are obtained for binary combinations in varying proportions. It is found that when all surface components have the same accessibility by probe molecules, the effective surface energy of such a heterogeneous surface is related to the surface energy distribution by a square root linear relationship, square root sigma(eff)(LW)= summation operator (i)phi(i) square root sigma(i)(LW), where sigma(i)(LW) refers to the nonspecific (Lifshitz-van der Waals) surface energy of patches i, and phi(i) to their area fraction.

  1. Differential effects of excitatory and inhibitory heterogeneity on the gain and asynchronous state of sparse cortical networks

    PubMed Central

    Mejias, Jorge F.; Longtin, André

    2014-01-01

    Recent experimental and theoretical studies have highlighted the importance of cell-to-cell differences in the dynamics and functions of neural networks, such as in different types of neural coding or synchronization. It is still not known, however, how neural heterogeneity can affect cortical computations, or impact the dynamics of typical cortical circuits constituted of sparse excitatory and inhibitory networks. In this work, we analytically and numerically study the dynamics of a typical cortical circuit with a certain level of neural heterogeneity. Our circuit includes realistic features found in real cortical populations, such as network sparseness, excitatory, and inhibitory subpopulations of neurons, and different cell-to-cell heterogeneities for each type of population in the system. We find highly differentiated roles for heterogeneity, depending on the subpopulation in which it is found. In particular, while heterogeneity among excitatory neurons non-linearly increases the mean firing rate and linearizes the f-I curves, heterogeneity among inhibitory neurons may decrease the network activity level and induces divisive gain effects in the f-I curves of the excitatory cells, providing an effective gain control mechanism to influence information flow. In addition, we compute the conditions for stability of the network activity, finding that the synchronization onset is robust to inhibitory heterogeneity, but it shifts to lower input levels for higher excitatory heterogeneity. Finally, we provide an extension of recently reported heterogeneity-induced mechanisms for signal detection under rate coding, and we explore the validity of our findings when multiple sources of heterogeneity are present. These results allow for a detailed characterization of the role of neural heterogeneity in asynchronous cortical networks. PMID:25309409

  2. Protein-nanoparticle interactions: the effects of surface compositional and structural heterogeneity are scale dependent

    NASA Astrophysics Data System (ADS)

    Huang, Rixiang; Carney, Randy P.; Stellacci, Francesco; Lau, Boris L. T.

    2013-07-01

    Nanoparticles (NPs) in the biological environment are exposed to a large variety and concentration of proteins. Proteins are known to adsorb in a `corona' like structure on the surface of NPs. In this study, we focus on the effects of surface compositional and structural heterogeneity on protein adsorption by examining the interaction of self-assembled monolayer coated gold NPs (AuNPs) with two types of proteins: ubiquitin and fibrinogen. This work was designed to systematically investigate the role of surface heterogeneity in nanoparticle-protein interaction. We have chosen the particles as well as the proteins to provide different types (in distribution and length-scale) of heterogeneity. The goal was to unveil the role of heterogeneity and of its length-scale in the particle-protein interaction. Dynamic light scattering and circular dichroism spectroscopy were used to reveal different interactions at pH above and below the isoelectric points of the proteins, which is related to the charge heterogeneity on the protein surface. At pH 7.4, there was only a monolayer of proteins adsorbed onto the NPs and the secondary structure of proteins remained intact. At pH 4.0, large aggregates of nanoparticle-protein complexes were formed and the secondary structures of the proteins were significantly disrupted. In terms of interaction thermodynamics, results from isothermal titration calorimetry showed that ubiquitin adsorbed differently onto (1) AuNPs with charged and nonpolar terminals organized into nano-scale structure (66-34 OT), (2) AuNPs with randomly distributed terminals (66-34 brOT), and (3) AuNPs with homogeneously charged terminals (MUS). This difference in adsorption behavior was not observed when AuNPs interacted with fibrinogen. The results suggested that the interaction between the proteins and AuNPs was influenced by the surface heterogeneity on the AuNPs, and this influence depends on the scale of surface heterogeneity and the size of the proteins

  3. Structural heterogeneity modulates effective refractory period: a mechanism of focal arrhythmia initiation.

    PubMed

    Bishop, Martin J; Connolly, Adam; Plank, Gernot

    2014-01-01

    Reductions in electrotonic loading around regions of structural and electrophysiological heterogeneity may facilitate capture of focal triggered activity, initiating reentrant arrhythmias. How electrotonic loading, refractoriness and capture of focal ectopics depend upon the intricate nature of physiological structural anatomy, as well as pathological tissue remodelling, however, is not well understood. In this study, we performed computational bidomain simulations with anatomically-detailed models representing the rabbit left ventricle. We used these models to quantify the relationship between local structural anatomy and spatial heterogeneity in action potential (AP) characteristics, electrotonic currents and effective refractory periods (ERPs) under pacing and restitution protocols. Regions surrounding vessel cavities, in addition to tissue surfaces, had significantly lower peak downstream electrotonic currents than well coupled myocardium (72.6 vs 220.4 μA/cm2), with faster maximum AP upstroke velocities (257.3 vs 147.3 mV/ms), although noticeably very similar APDs (167.7 vs 168.4 ms) and AP restitution properties. Despite similarities in APDs, ERPs in regions of low electrotonic load in the vicinity of surfaces, intramural vessel cavities and endocardial structures were up to 40 ms shorter compared to neighbouring well-coupled tissue, leading to regions of sharp ERP gradients. Consequently, focal extra-stimuli timed within this window of ERP heterogeneity between neighbouring regions readily induced uni-directional block, inducing reentry. Most effective induction sites were within channels of low ERPs between large vessels and epicardium. Significant differences in ERP driven by reductions in electrotonic loading due to fine-scale physiological structural heterogeneity provides an important mechanism of capture of focal activity and reentry induction. Application to pathological ventricles, particularly myocardial infarction, will have important implications

  4. Heterogeneous Suppression of Sequential Effects in Random Sequence Generation, but Not in Operant Learning

    PubMed Central

    Shteingart, Hanan; Loewenstein, Yonatan

    2016-01-01

    There is a long history of experiments in which participants are instructed to generate a long sequence of binary random numbers. The scope of this line of research has shifted over the years from identifying the basic psychological principles and/or the heuristics that lead to deviations from randomness, to one of predicting future choices. In this paper, we used generalized linear regression and the framework of Reinforcement Learning in order to address both points. In particular, we used logistic regression analysis in order to characterize the temporal sequence of participants’ choices. Surprisingly, a population analysis indicated that the contribution of the most recent trial has only a weak effect on behavior, compared to more preceding trials, a result that seems irreconcilable with standard sequential effects that decay monotonously with the delay. However, when considering each participant separately, we found that the magnitudes of the sequential effect are a monotonous decreasing function of the delay, yet these individual sequential effects are largely averaged out in a population analysis because of heterogeneity. The substantial behavioral heterogeneity in this task is further demonstrated quantitatively by considering the predictive power of the model. We show that a heterogeneous model of sequential dependencies captures the structure available in random sequence generation. Finally, we show that the results of the logistic regression analysis can be interpreted in the framework of reinforcement learning, allowing us to compare the sequential effects in the random sequence generation task to those in an operant learning task. We show that in contrast to the random sequence generation task, sequential effects in operant learning are far more homogenous across the population. These results suggest that in the random sequence generation task, different participants adopt different cognitive strategies to suppress sequential dependencies when

  5. A heterogeneous chemistry model for acid rain`s effect on ozone

    SciTech Connect

    Ye, Tao

    1995-11-01

    A computer model for simulating heterogeneous reactions in cloud is developed to determine the S(IV) species` effect on ozone. Crutzen claims that NO{sub x}, HO{sub x} families and H{sub 2}CO in the troposphere can decrease ozone by 5 to 10%. However, is this claim valid for a SO{sub x} polluted atmosphere? The SO{sub x} family reacts with the ozone destroyers. These reactions seem to be significant enough to reduce the H{sub 2}CO`s destructive effect on ozone.

  6. Control rod heterogeneity effects in liquid-metal fast breeder reactors: Method developments and experimental validation

    SciTech Connect

    Carta, M.; Granget, G.; Palmiotti, G.; Salvatores, M.; Soule, R.

    1988-11-01

    The control rod worth assessment in a large liquid-metal fast breeder reactor is strongly dependent on the actual arrangement of the absorber pins inside the control rod subassemblies. The so-called heterogeneity effects (i.e., the effects on the rod reactivity of the actual rod internal geometry versus homogenization of the absorber atoms over all the subassembly volume) have been evaluated, using explicit and variational methods to derive appropriate cross sections. An experimental program performed at the MASURCA facility has been used to validate these methods.

  7. Effect of crustal heterogeneities and effective rock strength on the formation of HP and UHP rocks.

    NASA Astrophysics Data System (ADS)

    Reuber, Georg; Kaus, Boris; Schmalholz, Stefan; White, Richard

    2015-04-01

    next step, we performed several hundred numerical simulations to understand the effects of km-scale heterogeneities and material parameters on pressure magnitudes, using a model setup that is otherwise very similar to the one of Li et al. (2010). Results show that significant non-lithostatic pressures occur if (lower) crustal rocks are dry or if km-scale (nappe-sized) heterogeneities with dryer rocks are present within the crust. Overpressure magnitudes can be up to 1 GPa or 100% and in some cases rock assemblages are temporarily in the coesite stability field at a depth of only 40 km, followed by rapid exhumation to the surface. Tectonic overpressures can vary strongly in magnitude versus time, but peak pressures are present sufficiently long for metamorphic reactions to occur. The presence of heterogeneities can affect the crustal-scaled deformation pattern, and the effective friction angle of crustal-scale rocks (or the dryness of these rocks) is a key parameter that determines the magnitude of non-lithostatic pressures. Our results thus reconcile previous findings and highlight the importance of having an accurate knowledge of the fluid-pressure, initial crustal structure and rock composition during continental collision. If rocks are dry by the time they enter a subduction zone, or are stronger/dryer than surrounding rocks, they are likely to develop significantly higher pressures than nearby rocks. This might explain the puzzling observation that some nappes have very high peak pressures, while juxtaposed nappes have much lower values, without clear structural evidence for deep burial and exhumation along a subduction channel of the high-pressure nappe. Our models might also give a partial explanation of why the reported timescales for high and ultra-high pressure stages of peak metamorphism are often very short. References: Burov, E., Francois, T., Agard, P., Le Pourhiet, L., Meyer, B., Tirel, C., Lebedev, S., Yamato, P., Brun, J.-P., 2014. Tectonophysics

  8. Effects of spanwise topographic heterogeneity on amplitude and frequency modulation of streamwise velocity fluctuations

    NASA Astrophysics Data System (ADS)

    Awasthi, Ankit; Subdberg, Matthew; Anderson, William

    2016-11-01

    We present results on the effects of topographic height, and spanwise heterogeneity, on amplitude and frequency modulation of small-scale structures in the roughness sublayer due to large-scale structures in the logarithmic region of turbulent channel flows. This work follows preceding contributions on amplitude and frequency modulation in smooth wall turbulent boundary layers. We have considered three topographic cases with different characteristics from homogeneous (sandpaper), to two spanwise heterogeneous cases where the height amplitude is increased (this topographic configuration induces turbulent secondary flows, which are known to alter the outer-layer flow characteristics). Indeed, pre-multiplied energy spectra across wavelength and elevation (so-called spectrograms) illustrate how turbulent energy is redistributed with systematic modification to the underlying topography. We have determined how the large-scale (low-pass filtered) streamwise velocity modulates the amplitude and frequency response of small-scale (high-pass filtered) signal. We find that outer-layer topographic-induced perturbations completely alter the intensity of amplitude and frequency modulation. This highlights the passive-actuator-like role of roughness heterogeneity, and underpins the need to incorporate such functional dependence in the development of wall models for LES. Air Force Office of Scientific Research, Grant # FA9550-14-1-0101.

  9. CHIMERA: Clustering of Heterogeneous Disease Effects via Distribution Matching of Imaging Patterns.

    PubMed

    Dong, Aoyan; Honnorat, Nicolas; Gaonkar, Bilwaj; Davatzikos, Christos

    2016-02-01

    Many brain disorders and diseases exhibit heterogeneous symptoms and imaging characteristics. This heterogeneity is typically not captured by commonly adopted neuroimaging analyses that seek only a main imaging pattern when two groups need to be differentiated (e.g., patients and controls, or clinical progressors and non-progressors). We propose a novel probabilistic clustering approach, CHIMERA, modeling the pathological process by a combination of multiple regularized transformations from normal/control population to the patient population, thereby seeking to identify multiple imaging patterns that relate to disease effects and to better characterize disease heterogeneity. In our framework, normal and patient populations are considered as point distributions that are matched by a variant of the coherent point drift algorithm. We explain how the posterior probabilities produced during the MAP optimization of CHIMERA can be used for clustering the patients into groups and identifying disease subtypes. CHIMERA was first validated on a synthetic dataset and then on a clinical dataset mixing 317 control subjects and patients suffering from Alzheimer's Disease (AD) and Parkison's Disease (PD). CHIMERA produced better clustering results compared to two standard clustering approaches. We further analyzed 390 T1 MRI scans from Alzheimer's patients. We discovered two main and reproducible AD subtypes displaying significant differences in cognitive performance.

  10. Effects of the heterogeneous landscape on a predator-prey system

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Hee

    2010-01-01

    In order to understand how a heterogeneous landscape affects a predator-prey system, a spatially explicit lattice model consisting of predators, prey, grass, and landscape was constructed. The predators and preys randomly move on the lattice space and the grass grows in its neighboring site according to its growth probability. When predators and preys meet at the same site at the same time, a number of prey, equal to the number of predators are eaten. This rule was also applied to the relationship between the prey and grass. The predator (prey) could give birth to an offspring when it ate prey (grass), with a birth probability. When a predator or prey animal was initially introduced, or newly born, its health state was set at a given high value. This health state decreased by one with every time step. When the state of an animal decreased to less than zero, the animal died and was removed from the system. The heterogeneous landscape was characterized by parameter H, which controlled the heterogeneity according to the neutral model. The simulation results showed that H positively or negatively affected a predator’s survival, while its effect on prey and grass was less pronounced. The results can be understood by the disturbance of the balance between the prey and predator densities in the areas where the animals aggregated.

  11. A Comparative Dosimetric Analysis of the Effect of Heterogeneity Corrections Used in Three Treatment Planning Algorithms

    NASA Astrophysics Data System (ADS)

    Herrick, Andrea Celeste

    Successful treatment in radiation oncology relies on the evaluation of a plan for each individual patient based on delivering the maximum dose to the tumor while sparing the surrounding normal tissue (organs at risk) in the patient. Organs at risk (OAR) typically considered include the heart, the spinal cord, healthy lung tissue, and any other organ in the vicinity of the target that is not affected by the disease being treated. Depending on the location of the tumor and its proximity to these OARs, several plans may be created and evaluated in order to assess which "solution" most closely meets all of the specified criteria. In order to successfully review a treatment plan and take the correct course of action, a physician needs to rely on the computer model (treatment planning algorithm) of dose distribution to reconstruct CT scan data to proceed with the plan that best achieves all of the goals. There are many available treatment planning systems from which a Radiation Oncology center can choose from. While the radiation interactions considered are identical among clinics, the way the chosen algorithm handles these interactions can vary immensely. The goal of this study was to provide a comparison between two commonly used treatment planning systems (Pinnacle and Eclipse) and their associated dose calculation algorithms. In order to this, heterogeneity correction models were evaluated via test plans, and the effects of going from heterogeneity uncorrected patient representation to a heterogeneity correction representation were studied. The results of this study indicate that the actual dose delivered to the patient varies greatly between treatment planning algorithms in areas of low density tissue such as in the lungs. Although treatment planning algorithms are attempting to come to the same result with heterogeneity corrections, the reality is that the results depend strongly on the algorithm used in the situations studied. While the Anisotropic Analytic Method

  12. Heterogeneous Effects of Fructose on Blood Lipids in Individuals With Type 2 Diabetes

    PubMed Central

    Sievenpiper, John L.; Carleton, Amanda J.; Chatha, Sheena; Jiang, Henry Y.; de Souza, Russell J.; Beyene, Joseph; Kendall, Cyril W.C.; Jenkins, David J.A.

    2009-01-01

    OBJECTIVE Because of blood lipid concerns, diabetes associations discourage fructose at high intakes. To quantify the effect of fructose on blood lipids in diabetes, we conducted a systematic review and meta-analysis of experimental clinical trials investigating the effect of isocaloric fructose exchange for carbohydrate on triglycerides, total cholesterol, LDL cholesterol, and HDL cholesterol in type 1 and 2 diabetes. RESEARCH DESIGN AND METHODS We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Library for relevant trials of ≥7 days. Data were pooled by the generic inverse variance method and expressed as standardized mean differences with 95% CI. Heterogeneity was assessed by χ2 tests and quantified by I2. Meta-regression models identified dose threshold and independent predictors of effects. RESULTS Sixteen trials (236 subjects) met the eligibility criteria. Isocaloric fructose exchange for carbohydrate raised triglycerides and lowered total cholesterol under specific conditions without affecting LDL cholesterol or HDL cholesterol. A triglyceride-raising effect without heterogeneity was seen only in type 2 diabetes when the reference carbohydrate was starch (mean difference 0.24 [95% CI 0.05–0.44]), dose was >60 g/day (0.18 [0.00–0.37]), or follow-up was ≤4 weeks (0.18 [0.00–0.35]). Piecewise meta-regression confirmed a dose threshold of 60 g/day (R2 = 0.13)/10% energy (R2 = 0.36). A total cholesterol–lowering effect without heterogeneity was seen only in type 2 diabetes under the following conditions: no randomization and poor study quality (−0.19 [−0.34 to −0.05]), dietary fat >30% energy (−0.33 [−0.52 to −0.15]), or crystalline fructose (−0.28 [−0.47 to −0.09]). Multivariate meta-regression analyses were largely in agreement. CONCLUSIONS Pooled analyses demonstrated conditional triglyceride-raising and total cholesterol–lowering effects of isocaloric fructose exchange for carbohydrate in type 2 diabetes. Recommendations

  13. Accounting for Heterogeneity in Relative Treatment Effects for Use in Cost-Effectiveness Models and Value-of-Information Analyses

    PubMed Central

    Soares, Marta O.; Palmer, Stephen; Ades, Anthony E.; Harrison, David; Shankar-Hari, Manu; Rowan, Kathy M.

    2015-01-01

    Cost-effectiveness analysis (CEA) models are routinely used to inform health care policy. Key model inputs include relative effectiveness of competing treatments, typically informed by meta-analysis. Heterogeneity is ubiquitous in meta-analysis, and random effects models are usually used when there is variability in effects across studies. In the absence of observed treatment effect modifiers, various summaries from the random effects distribution (random effects mean, predictive distribution, random effects distribution, or study-specific estimate [shrunken or independent of other studies]) can be used depending on the relationship between the setting for the decision (population characteristics, treatment definitions, and other contextual factors) and the included studies. If covariates have been measured that could potentially explain the heterogeneity, then these can be included in a meta-regression model. We describe how covariates can be included in a network meta-analysis model and how the output from such an analysis can be used in a CEA model. We outline a model selection procedure to help choose between competing models and stress the importance of clinical input. We illustrate the approach with a health technology assessment of intravenous immunoglobulin for the management of adult patients with severe sepsis in an intensive care setting, which exemplifies how risk of bias information can be incorporated into CEA models. We show that the results of the CEA and value-of-information analyses are sensitive to the model and highlight the importance of sensitivity analyses when conducting CEA in the presence of heterogeneity. The methods presented extend naturally to heterogeneity in other model inputs, such as baseline risk. PMID:25712447

  14. Multidimensional Modeling of Atmospheric Effects and Surface Heterogeneities on Remote Sensing

    NASA Technical Reports Server (NTRS)

    Gerstl, S. A. W.; Simmer, C.; Zardecki, A. (Principal Investigator)

    1985-01-01

    The overall goal of this project is to establish a modeling capability that allows a quantitative determination of atmospheric effects on remote sensing including the effects of surface heterogeneities. This includes an improved understanding of aerosol and haze effects in connection with structural, angular, and spatial surface heterogeneities. One important objective of the research is the possible identification of intrinsic surface or canopy characteristics that might be invariant to atmospheric perturbations so that they could be used for scene identification. Conversely, an equally important objective is to find a correction algorithm for atmospheric effects in satellite-sensed surface reflectances. The technical approach is centered around a systematic model and code development effort based on existing, highly advanced computer codes that were originally developed for nuclear radiation shielding applications. Computational techniques for the numerical solution of the radiative transfer equation are adapted on the basis of the discrete-ordinates finite-element method which proved highly successful for one and two-dimensional radiative transfer problems with fully resolved angular representation of the radiation field.

  15. A mathematical model of mortality dynamics across the lifespan combining heterogeneity and stochastic effects.

    PubMed

    Avraam, Demetris; de Magalhaes, Joao Pedro; Vasiev, Bakhtier

    2013-08-01

    The mortality patterns in human populations reflect biological, social and medical factors affecting our lives, and mathematical modelling is an important tool for the analysis of these patterns. It is known that the mortality rate in all human populations increases with age after sexual maturity. This increase is predominantly exponential and satisfies the Gompertz equation. Although the exponential growth of mortality rates is observed over a wide range of ages, it excludes early- and late-life intervals. In this work we accept the fact that the mortality rate is an exponential function of age and analyse possible mechanisms underlying the deviations from the exponential law across the human lifespan. We consider the effect of heterogeneity as well as stochastic factors in altering the exponential law and compare our results to publicly available age-dependent mortality data for Swedish and US populations. In a model of heterogeneous populations we study how differences in parameters of the Gompertz equation describing different subpopulations account for mortality dynamics at different ages. Particularly, we show that the mortality data on Swedish populations can be reproduced fairly well by a model comprising four subpopulations. We then analyse the influence of stochastic effects on the mortality dynamics to show that they play a role only at early and late ages, when only a few individuals contribute to mortality. We conclude that the deviations from exponential law at young ages can be explained by heterogeneity, namely by the presence of a subpopulation with high initial mortality rate presumably due to congenital defects, while those for old ages can be viewed as fluctuations and explained by stochastic effects.

  16. Design and analysis of large-effective-area heterogeneous trench-assisted multi-core fiber.

    PubMed

    Tu, Jiajing; Saitoh, Kunimasa; Koshiba, Masanori; Takenaga, Katsuhiro; Matsuo, Shoichiro

    2012-07-02

    Based on the overlap integral of electromagnetic fields in neighboring cores, a calculating method is proposed for obtaining the coupling coefficient between two adjacent trench-assisted non-identical cores. And a kind of heterogeneous trench-assisted multi-core fiber (Hetero-TA-MCF) with 12 cores is proposed to achieve large effective area (A(eff)) and high density of cores. As bending radius becomes larger than 50 mm, the crosstalk value at 1550-nm wavelength of the Hetero-TA-MCF is about -42 dB after 100-km propagation and the A(eff) of this Hetero-TA-MCF can reach 100 µm(2).

  17. The problem of effect size heterogeneity in meta-analytic structural equation modeling.

    PubMed

    Yu, Jia Joya; Downes, Patrick E; Carter, Kameron M; O'Boyle, Ernest H

    2016-10-01

    Scholars increasingly recognize the potential of meta-analytic structural equation modeling (MASEM) as a way to build and test theory (Bergh et al., 2016). Yet, 1 of the greatest challenges facing MASEM researchers is how to incorporate and model meaningful effect size heterogeneity identified in the bivariate meta-analysis into MASEM. Unfortunately, common MASEM approaches in applied psychology (i.e., Viswesvaran & Ones, 1995) fail to account for effect size heterogeneity. This means that MASEM effect sizes, path estimates, and overall fit values may only generalize to a small segment of the population. In this research, we quantify this problem and introduce a set of techniques that retain both the true score relationships and the variability surrounding those relationships in estimating model parameters and fit indices. We report our findings from simulated data as well as from a reanalysis of published MASEM studies. Results demonstrate that both path estimates and overall model fit indices are less representative of the population than existing MASEM research would suggest. We suggest 2 extension MASEM techniques that can be conducted using online software or in R, to quantify the stability of model estimates across the population and allow researchers to better build and test theory. (PsycINFO Database Record

  18. Effective Block-Scale Dispersion and Its Self-Averaging Behavior in Heterogeneous Porous Media

    NASA Astrophysics Data System (ADS)

    de Barros, Felipe; Dentz, Marco

    2015-04-01

    Upscaled (effective) dispersion coefficients in spatially heterogeneous flow fields must (1) account for the sub-scale variability that is filtered out by homogenization and (2) be modeled as a random function to incorporate the uncertainty associated with non-ergodic solute bodies. In this study, we use the framework developed in de Barros and Rubin (2011) [de Barros F.P.J. and Rubin Y., Modelling of block-scale macrodispersion as a random function. Journal of Fluid Mechanics 676 (2011): 514-545] to develop novel semi-analytical expressions for the first two statistical moments of the block-effective dispersion coefficients in three-dimensional spatially random flow fields as a function of the key characteristic length scales defining the transport problem. The derived expressions are based on perturbation theory and limited to weak-to-mild heterogeneity and uniform-in-the-mean steady state flow fields. The semi-analytical solutions provide physical insights of the main controlling factors influencing the temporal scaling of the dispersion coefficient of the solute body and its self-averaging dispersion behavior. Our results illustrate the relevance of the joint influence of the block-scale and local-scale dispersion in diminishing the macrodispersion variance under non-ergodic conditions. The impact of the statistical anisotropy ratio in the block-effective macrodispersion self-averaging behavior is also investigated. The analysis performed in this work has implications in numerical modeling and grid design.

  19. Modeling electrostatic and heterogeneity effects on proton dissociation from humic substances

    USGS Publications Warehouse

    Tipping, E.; Reddy, M.M.; Hurley, M.A.

    1990-01-01

    The apparent acid dissociation constant of humic substances increases by 2-4 pK units as ionization of the humic carboxylate groups proceeds. This change in apparent acid strength is due in part to the increase in electrical charge on the humic molecules as protons are shed. In addition, proton dissociation reactions are complicated because humic substances are heterogeneous with respect to proton dissociating groups and molecular size. In this paper, we use the Debye-Hu??ckel theory to describe the effects of electrostatic interactions on proton dissociation of humic substances. Simulations show that, for a size-heterogeneous system of molecules, the weight-average molecular weight is preferable to the number-average value for averaging the effects of electrostatic interactions. Analysis of published data on the proton dissociation of fulvic acid from the Suwannee River shows that the electrostatic interactions can be satisfactorily described by a hypothetical homogeneous compound having a molecular weight of 1000 (similar to the experimentally determined weight-average value). Titration data at three ionic strengths, for several fulvic acid concentrations, and in the pH range from 2.9 to 6.4 can be fitted with three adjustable parameters (pK??int values), given information on molecular size and carboxylate group content. ?? 1990 American Chemical Society.

  20. Effects of treatment or/and vaccination on HIV transmission in homosexuals with genetic heterogeneity.

    PubMed

    Hsu Schmitz, S

    2000-09-01

    Several mutant genes in HIV co-receptors (e.g., CCR5, CCR2 and CXCR4) have been correlated with susceptibility to HIV or/and rate of progression to AIDS. Some of these genes have high allele frequencies in general populations. Their effects on the HIV/AIDS dynamics may be significant. To study such genetic heterogeneity, Hsu Schmitz [S.-F. Hsu Schmitz, A mathematical model of HIV transmission in homosexuals with genetic heterogeneity, J. Theoret. Med. (to appear)] proposed a one-sex model with susceptibles classified by genotype as having no, partial or full natural resistance to HIV infection and infecteds classified as rapid, normal or slow progressors. The example of CCR5-Delta32 mutation in San Francisco gay men indicated that the normal progressors are most responsible for disease spread. The per-partnership transmission rates of rapid and slow progressors are identified as key parameters. The present manuscript extends the previous one by considering the intervention of treatment or/and vaccination. Detailed investigations are illustrated by using the same example of CCR5-Delta32 mutation in San Francisco gay men. Treating only newly infected individuals or vaccinating only newly recruited susceptibles is not effective enough for disease control. When both measures are applied, the epidemic may be eradicated if the transmission rate of slow progressors is not too large, and treatments and vaccines in use are of decent quality.

  1. Effects of heterogeneous traffic with speed limit zone on the car accidents

    NASA Astrophysics Data System (ADS)

    Marzoug, R.; Lakouari, N.; Bentaleb, K.; Ez-Zahraouy, H.; Benyoussef, A.

    2016-06-01

    Using the extended Nagel-Schreckenberg (NS) model, we numerically study the impact of the heterogeneity of traffic with speed limit zone (SLZ) on the probability of occurrence of car accidents (Pac). SLZ in the heterogeneous traffic has an important effect, typically in the mixture velocities case. In the deterministic case, SLZ leads to the appearance of car accidents even in the low densities, in this region Pac increases with increasing of fraction of fast vehicles (Ff). In the nondeterministic case, SLZ decreases the effect of braking probability Pb in the low densities. Furthermore, the impact of multi-SLZ on the probability Pac is also studied. In contrast with the homogeneous case [X. Li, H. Kuang, Y. Fan and G. Zhang, Int. J. Mod. Phys. C 25 (2014) 1450036], it is found that in the low densities the probability Pac without SLZ (n = 0) is low than Pac with multi-SLZ (n > 0). However, the existence of multi-SLZ in the road decreases the risk of collision in the congestion phase.

  2. Effect of distance-related heterogeneity on population size estimates from point counts

    USGS Publications Warehouse

    Efford, Murray G.; Dawson, Deanna K.

    2009-01-01

    Point counts are used widely to index bird populations. Variation in the proportion of birds counted is a known source of error, and for robust inference it has been advocated that counts be converted to estimates of absolute population size. We used simulation to assess nine methods for the conduct and analysis of point counts when the data included distance-related heterogeneity of individual detection probability. Distance from the observer is a ubiquitous source of heterogeneity, because nearby birds are more easily detected than distant ones. Several recent methods (dependent double-observer, time of first detection, time of detection, independent multiple-observer, and repeated counts) do not account for distance-related heterogeneity, at least in their simpler forms. We assessed bias in estimates of population size by simulating counts with fixed radius w over four time intervals (occasions). Detection probability per occasion was modeled as a half-normal function of distance with scale parameter sigma and intercept g(0) = 1.0. Bias varied with sigma/w; values of sigma inferred from published studies were often 50% for a 100-m fixed-radius count. More critically, the bias of adjusted counts sometimes varied more than that of unadjusted counts, and inference from adjusted counts would be less robust. The problem was not solved by using mixture models or including distance as a covariate. Conventional distance sampling performed well in simulations, but its assumptions are difficult to meet in the field. We conclude that no existing method allows effective estimation of population size from point counts.

  3. Effects of small-scale heterogeneities on the bulk mechanical properties of sea ice

    NASA Astrophysics Data System (ADS)

    Song, A.

    2015-12-01

    The Arctic ice cover is riddled with cracks, ridges, and melt ponds leading to spatial heterogeneities that manifest as sharp transitions in thickness, porosity, salinity, etc., that in turn affect the bulk mechanical behavior of the ice pack. In regions within and near the marginal ice zone, where ice survives the summer melt and break-up as discrete floes with length scales on the order of hundreds of meters to a kilometer, the freeze up subsequent to the melt season forms a patchwork of thick perennial ice bound together by thinner and smoother first-year ice with a coherence of varying length scales. Remote sensing has shown that the fracture patterns in these patchy ice regions, which may be more representative of marginal ice zone and coastal areas, tend to form in preferential pathways in the thinner ice, therefore modifying the rhomboidal pattern that is characteristic of more homogeneous ice. Using a sea ice model based on the discrete element method (DEM) and remotely sensed images, we examine the effect that heterogeneities in the ice cover have on the derivation of constitutive behavior at scales relevant to climate models by representing the observed heterogeneities explicitly. This model allows us to not only measure the mechanical response of a sample domain, but to also look at the break-up behavior for regions of varying melt pond coverage, thickness, etc. Our hope is that our results can be used to extend existing sea ice rheologies that already incorporate the spatial discontinuities of the ice cover due to lead formation [Moritz & Ukita, 2000; Schreyer et al., 2006; Wilchinsky & Feltham, 2004; Sedlacek et al., 2007].

  4. Heterogeneous Effects of Housing Vouchers on the Mental Health of US Adolescents

    PubMed Central

    Nguyen, Quynh C.; Rehkopf, David H.; Schmidt, Nicole M.

    2016-01-01

    Objectives. To assess the mental health effects on adolescents of low-income families residing in high-poverty public housing who received housing vouchers to assist relocation. Methods. We defined treatment effects to compare 2829 adolescents aged 12 to 19 years in families offered housing vouchers versus those living in public housing in the Moving to Opportunity experiment (1994–1997; Boston, MA; Baltimore, MD; Chicago, IL; Los Angeles, CA; New York, NY). We employed model-based recursive partitioning to identify subgroups with heterogeneous treatment effects on psychological distress and behavior problems measured in 2002. We tested 35 potential baseline treatment modifiers. Results. For psychological distress, Chicago participants experienced null treatment effects. Outside Chicago, boys experienced detrimental effects, whereas girls experienced beneficial effects. Behavior problems effects were null for adolescents who were aged 10 years or younger at baseline. For adolescents who were older than 10 years at baseline, violent crime victimization, unmarried parents, and unsafe neighborhoods increased adverse treatment effects. Adolescents who were older than 10 years at baseline without learning problems or violent crime victimization, and whose parents moved for better schools, experienced beneficial effects. Conclusions. Health effects of housing vouchers varied across subgroups. Supplemental services may be necessary for vulnerable subgroups for whom housing vouchers alone may not be beneficial. PMID:26794179

  5. Effect of Hierarchical, Multi-Scale Heterogeneity on Long-Term Nitrate Transport in a Deep Vadose Zone

    NASA Astrophysics Data System (ADS)

    Harter, T.; Botros, F.

    2008-12-01

    Worldwide, unconsolidated sedimentary basins provide a significant groundwater resource. Deep unsaturated zones are common within these sedimentary basins, particularly within arid and semi-arid climate zones with strong groundwater development. For the vertical flow and transport through these unsaturated sediments, two to three hierarchical heterogeneity scales can readily be identified: sedimentary sequences, sedimentary strata within a sequence, and within-stratum heterogeneity. Based on a detailed field reconnaissance, we developed three different representations of two-dimensional and three-dimensional water flow and nitrate transport in a 16 m thick alluvial unsaturated zone below an irrigated orchard in semi- arid Fresno County, California: The first model representation is a homogeneous lithofacies representation which explicitly identifies major textural facies within the unsaturated zone. The second is a heterogeneous lithofacies model which includes heterogeneity within each facies, where heterogeneity is represented by the scaling factor technique (single-parameter heterogeneity). The third is also a heterogeneous model where the heterogeneity in each lithofacies is characterized by random fields of each parameter in the van Genuchten soil hydraulic function (multi-parameter heterogeneity). Scaling factors and van Genuchten parameters are generated using a geostatistical model that is based on extensive field site borehole data and undisturbed core analyses. We compared the effect of the different modeling representations on water flow and nitrate transport during seven years of two different fertilization treatments. Estimated nitrate levels in the vadose zone and nitrate leaching to groundwater differ significantly between fertilizer treatments, yet are nearly identical between the three model representations and model dimensionality. In all cases, the deep vadose zone nitrate mass is at least four times larger than the measured nitrate mass at the

  6. Effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events

    NASA Astrophysics Data System (ADS)

    Quan, Jiannong; Liu, Quan; Li, Xia; Gao, Yang; Jia, Xingcan; Sheng, Jiujiang; Liu, Yangang

    2015-12-01

    The effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events was investigated by analysis of comprehensive measurements of aerosol composition and concentrations [e.g., particular matters (PM2.5), nitrate (NO3), sulfate (SO4), ammonium (NH4)], gas-phase precursors [e.g., nitrogen oxides (NOx), sulfur dioxide (SO2), and ozone (O3)], and relevant meteorological parameters [e.g., visibility and relative humidity (RH)]. The measurements were conducted in Beijing, China from Sep. 07, 2012 to Jan. 16, 2013. The results show that the conversion ratios of N from NOx to nitrate (Nratio) and S from SO2 to sulfate (Sratio) both significantly increased in haze events, suggesting enhanced conversions from NOx and SO2 to their corresponding particle phases in the late haze period. Further analysis shows that Nratio and Sratio increased with increasing RH, with Nratio and Sratio being only 0.04 and 0.03, respectively, when RH < 40%, and increasing up to 0.16 and 0.12 when RH reached 60-80%, respectively. The enhanced conversion ratios of N and S in the late haze period is likely due to heterogeneous aqueous reactions, because solar radiation and thus the photochemical capacity are reduced by the increases in aerosols and RH. This point was further affirmed by the relationships of Nratio and Sratio to O3: the conversion ratios increase with decreasing O3 concentration when O3 concentration is lower than <15 ppb but increased with increasing O3 when O3 concentration is higher than 15 ppb. The results suggest that heterogeneous aqueous reactions likely changed aerosols and their precursors during the haze events: in the beginning of haze events, the precursor gases accumulated quickly due to high emission and low reaction rate; the occurrence of heterogeneous aqueous reactions in the late haze period, together with the accumulated high concentrations of precursor gases such as SO2 and NOx, accelerated the formation of secondary

  7. Effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events

    SciTech Connect

    Quan, Jiannong; Liu, Yangang; Liu, Quan; Li, Xia; Gao, Yang; Jia, Xingcan; Sheng, Jiujiang

    2015-09-30

    In this study, the effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events was investigated by analysis of comprehensive measurements of aerosol composition and concentrations [e.g., particular matters (PM2.5), nitrate (NO3), sulfate (SO4), ammonium (NH4)], gas-phase precursors [e.g., nitrogen oxides (NOx), sulfur dioxide (SO2), and ozone (O3)], and relevant meteorological parameters [e.g., visibility and relative humidity (RH)]. The measurements were conducted in Beijing, China from Sep. 07, 2012 to Jan. 16, 2013. The results show that the conversion ratios of N from NOx to nitrate (Nratio) and S from SO2 to sulfate (Sratio) both significantly increased in haze events, suggesting enhanced conversions from NOx and SO2 to their corresponding particle phases in the late haze period. Further analysis shows that Nratio and Sratio increased with increasing RH, with Nratio and Sratio being only 0.04 and 0.03, respectively, when RH < 40%, and increasing up to 0.16 and 0.12 when RH reached 60–80%, respectively. The enhanced conversion ratios of N and S in the late haze period is likely due to heterogeneous aqueous reactions, because solar radiation and thus the photochemical capacity are reduced by the increases in aerosols and RH. This point was further affirmed by the relationships of Nratio and Sratio to O3: the conversion ratios increase with decreasing O3 concentration when O3 concentration is lower than <15 ppb but increased with increasing O3 when O3 concentration is higher than 15 ppb. The results suggest that heterogeneous aqueous reactions likely changed aerosols and their precursors during the haze events: in the beginning of haze events, the precursor gases accumulated quickly

  8. Effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events

    DOE PAGES

    Quan, Jiannong; Liu, Yangang; Liu, Quan; ...

    2015-09-30

    In this study, the effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events was investigated by analysis of comprehensive measurements of aerosol composition and concentrations [e.g., particular matters (PM2.5), nitrate (NO3), sulfate (SO4), ammonium (NH4)], gas-phase precursors [e.g., nitrogen oxides (NOx), sulfur dioxide (SO2), and ozone (O3)], and relevant meteorological parameters [e.g., visibility and relative humidity (RH)]. The measurements were conducted in Beijing, China from Sep. 07, 2012 to Jan. 16, 2013. The results show that the conversion ratios of N from NOx to nitrate (Nratio) and S from SO2 to sulfate (Sratio) bothmore » significantly increased in haze events, suggesting enhanced conversions from NOx and SO2 to their corresponding particle phases in the late haze period. Further analysis shows that Nratio and Sratio increased with increasing RH, with Nratio and Sratio being only 0.04 and 0.03, respectively, when RH < 40%, and increasing up to 0.16 and 0.12 when RH reached 60–80%, respectively. The enhanced conversion ratios of N and S in the late haze period is likely due to heterogeneous aqueous reactions, because solar radiation and thus the photochemical capacity are reduced by the increases in aerosols and RH. This point was further affirmed by the relationships of Nratio and Sratio to O3: the conversion ratios increase with decreasing O3 concentration when O3 concentration is lower than <15 ppb but increased with increasing O3 when O3 concentration is higher than 15 ppb. The results suggest that heterogeneous aqueous reactions likely changed aerosols and their precursors during the haze events: in the beginning of haze events, the precursor gases accumulated quickly due to high emission and low reaction rate; the occurrence of heterogeneous aqueous reactions in the late haze period, together with the accumulated high concentrations of precursor gases such as SO2 and NOx, accelerated the

  9. Surface heterogeneity effects of activated carbons on the kinetics of paracetamol removal from aqueous solution

    NASA Astrophysics Data System (ADS)

    Ruiz, B.; Cabrita, I.; Mestre, A. S.; Parra, J. B.; Pires, J.; Carvalho, A. P.; Ania, C. O.

    2010-06-01

    The removal of a compound with therapeutic activity (paracetamol) from aqueous solutions using chemically modified activated carbons has been investigated. The chemical nature of the activated carbon material was modified by wet oxidation, so as to study the effect of the carbon surface chemistry and composition on the removal of paracetamol. The surface heterogeneity of the carbon created upon oxidation was found to be a determinant in the adsorption capability of the modified adsorbents, as well as in the rate of paracetamol removal. The experimental kinetic data were fitted to the pseudo-second order and intraparticle diffusion models. The parameters obtained were linked to the textural and chemical features of the activated carbons. After oxidation the wettability of the carbon is enhanced, which favors the transfer of paracetamol molecules to the carbon pores (smaller boundary layer thickness). At the same time the overall adsorption rate and removal efficiency are reduced in the oxidized carbon due to the competitive effect of water molecules.

  10. Heterogeneous effects of oil shocks on exchange rates: evidence from a quantile regression approach.

    PubMed

    Su, Xianfang; Zhu, Huiming; You, Wanhai; Ren, Yinghua

    2016-01-01

    The determinants of exchange rates have attracted considerable attention among researchers over the past several decades. Most studies, however, ignore the possibility that the impact of oil shocks on exchange rates could vary across the exchange rate returns distribution. We employ a quantile regression approach to address this issue. Our results indicate that the effect of oil shocks on exchange rates is heterogeneous across quantiles. A large US depreciation or appreciation tends to heighten the effects of oil shocks on exchange rate returns. Positive oil demand shocks lead to appreciation pressures in oil-exporting countries and this result is robust across lower and upper return distributions. These results offer rich and useful information for investors and decision-makers.

  11. Evidence-Based Medicine, Heterogeneity of Treatment Effects, and the Trouble with Averages

    PubMed Central

    Kravitz, Richard L; Duan, Naihua; Braslow, Joel

    2004-01-01

    Evidence-based medicine is the application of scientific evidence to clinical practice. This article discusses the difficulties of applying global evidence (“average effects” measured as population means) to local problems (individual patients or groups who might depart from the population average). It argues that the benefit or harm of most treatments in clinical trials can be misleading and fail to reveal the potentially complex mixture of substantial benefits for some, little benefit for many, and harm for a few. Heterogeneity of treatment effects reflects patient diversity in risk of disease, responsiveness to treatment, vulnerability to adverse effects, and utility for different outcomes. Recognizing these factors, researchers can design studies that better characterize who will benefit from medical treatments, and clinicians and policymakers can make better use of the results. PMID:15595946

  12. Pore and Continuum Scale Study of the Effect of Subgrid Transport Heterogeneity on Redox Reaction Rates

    SciTech Connect

    Liu, Yuanyuan; Liu, Chongxuan; Zhang, Changyong; Yang, Xiaofan; Zachara, John M.

    2015-08-01

    A micromodel system with a pore structure for heterogeneous flow and transport was used to investigate the effect of subgrid transport heterogeneity on redox reaction rates. Hematite reductive dissolution by injecting a reduced form of flavin mononucleotide (FMNH2) at variable flow rates was used as an example to probe the variations of redox reaction rates in different subgrid transport domains. Experiments, pore-scale simulations, and macroscopic modeling were performed to measure and simulate in-situ hematite reduction and to evaluate the scaling behavior of the redox reaction rates from the pore to macroscopic scales. The results indicated that the measured pore-scale rates of hematite reduction were consistent with the predictions from a pore scale reactive transport model. A general trend is that hematite reduction followed reductant transport pathways, starting from the advection-dominated pores toward the interior of diffusion-dominated domains. Two types of diffusion domains were considered in the micromodel: a micropore diffusion domain, which locates inside solid grains or aggregates where reactant transport is limited by diffusion; and a macropore diffusion domain, which locates at wedged, dead-end pore spaces created by the grain-grain contacts. The rate of hematite reduction in the advection-dominated domain was faster than those in the diffusion-controlled domains, and the rate in the macropore diffusion domain was faster than that in the micropore domain. The reduction rates in the advection and macropore diffusion domains increased with increasing flow rate, but were affected by different mechanisms. The rate increase in the advection domain was controlled by the mass action effect as a faster flow supplied more reactants, and the rate increase in the macropore domain was more affected by the rate of mass exchange with the advection domain, which increased with increasing flow rate. The hematite reduction rate in the micropore domain was, however

  13. Effects of Porous Medium Heterogeneity on Vadose Zone Desiccation: Intermediate-scale Laboratory Experiments and Simulations

    SciTech Connect

    Oostrom, Martinus; Freedman, Vicky L.; Wietsma, Thomas W.; Dane, Jacob H.; Truex, Michael J.

    2012-11-01

    Soil desiccation (drying), involving water evaporation induced by dry gas injection, is a potentially robust vadose zone remediation process to limit contaminant transport through the vadose zone. A series of four intermediate-scale flow cell experiments was conducted in homogeneous and simple layered heterogeneous porous medium systems to investigate the effects of heterogeneity on desiccation of unsaturated porous media. The permeability ratios of porous medium layers ranged from about five to almost two orders of magnitude. The insulated flow cell was equipped with twenty humidity and temperature sensors and a dual-energy gamma system was used to determine water saturations at various times. The multiphase code STOMP was used to simulate the desiccation process. Results show that injected dry gas flowed predominantly in the higher permeability layer and delayed water removal from the lower permeability material. For the configurations tested, water vapor diffusion from the lower to the higher permeability zone was considerable over the duration of the experiments, resulting in much larger relative humidity values of the outgoing air than based on permeability ratios alone. Acceptable numerical matches with the experimental data were obtained when an extension of the saturation-capillary pressure relation below the residual water saturation was used. The agreements between numerical and experimental results suggest that the correct physics are implemented in the simulator and that the thermal and hydraulic properties of the porous media, flow cell wall and insulation materials were properly represented.

  14. Nanoparticle-enhanced spectral photoacoustic tomography: effect of oxygen saturation and tissue heterogeneity

    NASA Astrophysics Data System (ADS)

    Vogt, William C.; Jia, Congxian; Wear, Keith A.; Garra, Brian S.; Pfefer, T. Joshua

    2016-03-01

    Molecular imaging for breast cancer detection, infectious disease diagnostics and preclinical animal research may be achievable through combined use of targeted exogenous agents - such as nanoparticles - and spectral Photoacoustic Tomography (PAT). However, tissue heterogeneity can alter fluence distributions and acoustic propagation, corrupting measured PAT absorption spectra and complicating in vivo nanoparticle detection and quantitation. Highly absorptive vascular structures represent a common confounding factor, and variations in vessel hemoglobin saturation (SO2) may alter spectral content of signals from adjacent/deeper regions. To evaluate the impact of this effect on PAT nanoparticle detectability, we constructed heterogeneous phantoms with well-characterized channel-inclusion geometries and biologically relevant optical and acoustic properties. Phantoms contained an array of tubes at several depths filled with hemoglobin solutions doped with varying concentrations of gold nanorods with an absorption peak at 780 nm. Both overlying and target network SO2 was tuned using sodium dithionite. Phantoms were imaged from 700 to 900 nm using a custom PAT system comprised of a tunable pulsed laser and a research-grade ultrasound system. Recovered nanoparticle spectra were analyzed and compared with results from both spectrophotometry and PAT data from waterimmersed tubes containing blood and nanoparticle solutions. Results suggested that nanoparticle selection for a given PAT application should take into account expected oxygenation states of both target blood vessel and background tissue oxygenation to achieve optimal performance.

  15. Effects of geographical heterogeneity in species interactions on the evolution of venom genes

    PubMed Central

    Chang, Dan; Olenzek, Amy M.; Duda, Thomas F.

    2015-01-01

    Geographical heterogeneity in the composition of biotic interactions can create a mosaic of selection regimes that may drive the differentiation of phenotypes that operate at the interface of these interactions. Nonetheless, little is known about effects of these geographical mosaics on the evolution of genes encoding traits associated with species interactions. Predatory marine snails of the family Conidae use venom, a cocktail of conotoxins, to capture prey. We characterized patterns of geographical variation at five conotoxin genes of a vermivorous species, Conus ebraeus, at Hawaii, Guam and American Samoa, and evaluated how these patterns of variation are associated with geographical heterogeneity in prey utilization. All populations show distinct patterns of prey utilization. Three ‘highly polymorphic’ conotoxin genes showed significant geographical differences in allelic frequency, and appear to be affected by different modes of selection among populations. Two genes exhibited low levels of diversity and a general lack of differentiation among populations. Levels of diversity of ‘highly polymorphic’ genes exhibit a positive relationship with dietary breadth. The different patterns of evolution exhibited by conotoxin genes suggest that these genes play different roles in prey capture, and that some genes are more greatly affected by differences in predator–prey interactions than others. Moreover, differences in dietary breadth appear to have a greater influence on the differentiation of venoms than differences in the species of prey. PMID:25788600

  16. Cirrus heterogeneity effects on cloud optical properties retrieved with an optimal estimation method from MODIS VIS to TIR channels

    NASA Astrophysics Data System (ADS)

    Fauchez, T.; Platnick, S.; Sourdeval, O.; Meyer, K.; Cornet, C.; Zhang, Z.; Szczap, F.

    2017-02-01

    This study presents preliminary results on the effect of cirrus heterogeneities on top-of-atmosphere (TOA) simulated radiances or reflectances for MODIS channels centered at 0.86, 2.21, 8.56, 11.01 and 12.03 µm, and on cloud optical properties retrieved with a research-level optimal estimation method (OEM). Synthetic cirrus cloud fields are generated using a 3D cloud generator (3DCLOUD) and radiances/reflectances are simulated using a 3D radiative transfer code (3DMCPOL). We find significant differences between the heterogeneity effects on either visible and near-infrared (VNIR) or thermal infrared (TIR) radiances. However, when both wavelength ranges are combined, heterogeneity effects are dominated by the VNIR horizontal radiative transport effect. As a result, small optical thicknesses are overestimated and large ones are underestimated. Retrieved effective diameter are found to be slightly affected, contrarily to retrievals using TIR channels only.

  17. Distance-to-Agreement Investigation of Tomotherapy's Bony Anatomy-Based Autoregistration and Planning Target Volume Contour-Based Optimization

    SciTech Connect

    Suh, Steve; Schultheiss, Timothy E.

    2013-03-01

    Purpose: To compare Tomotherapy's megavoltage computed tomography bony anatomy autoregistration with the best achievable registration, assuming no deformation and perfect knowledge of planning target volume (PTV) location. Methods and Materials: Distance-to-agreement (DTA) of the PTV was determined by applying a rigid-body shift to the PTV region of interest of the prostate from its reference position, assuming no deformations. Planning target volume region of interest of the prostate was extracted from the patient archives. The reference position was set by the 6 degrees of freedom (dof)—x, y, z, roll, pitch, and yaw—optimization results from the previous study at this institution. The DTA and the compensating parameters were calculated by the shift of the PTV from the reference 6-dof to the 4-dof—x, y, z, and roll—optimization. In this study, the effectiveness of Tomotherapy's 4-dof bony anatomy–based autoregistration was compared with the idealized 4-dof PTV contour-based optimization. Results: The maximum DTA (maxDTA) of the bony anatomy-based autoregistration was 3.2 ± 1.9 mm, with the maximum value of 8.0 mm. The maxDTA of the contour-based optimization was 1.8 ± 1.3 mm, with the maximum value of 5.7 mm. Comparison of Pearson correlation of the compensating parameters between the 2 4-dof optimization algorithms shows that there is a small but statistically significant correlation in y and z (0.236 and 0.300, respectively), whereas there is very weak correlation in x and roll (0.062 and 0.025, respectively). Conclusions: We find that there is an average improvement of approximately 1 mm in terms of maxDTA on the PTV going from 4-dof bony anatomy-based autoregistration to the 4-dof contour-based optimization. Pearson correlation analysis of the 2 4-dof optimizations suggests that uncertainties due to deformation and inadequate resolution account for much of the compensating parameters, but pitch variation also makes a statistically significant

  18. Mixing effects on apparent reaction rates and isotope fractionation during denitrification in a heterogeneous aquifer

    USGS Publications Warehouse

    Green, C.T.; Böhlke, J.K.; Bekins, B.A.; Phillips, S.P.

    2010-01-01

    Gradients in contaminant concentrations and isotopic compositions commonly are used to derive reaction parameters for natural attenuation in aquifers. Differences between field-scale (apparent) estimated reaction rates and isotopic fractionations and local-scale (intrinsic) effects are poorly understood for complex natural systems. For a heterogeneous alluvial fan aquifer, numerical models and field observations were used to study the effects of physical heterogeneity on reaction parameter estimates. Field measurements included major ions, age tracers, stable isotopes, and dissolved gases. Parameters were estimated for the O2 reduction rate, denitrification rate, O 2 threshold for denitrification, and stable N isotope fractionation during denitrification. For multiple geostatistical realizations of the aquifer, inverse modeling was used to establish reactive transport simulations that were consistent with field observations and served as a basis for numerical experiments to compare sample-based estimates of "apparent" parameters with "true" (intrinsic) values. For this aquifer, non-Gaussian dispersion reduced the magnitudes of apparent reaction rates and isotope fractionations to a greater extent than Gaussian mixing alone. Apparent and true rate constants and fractionation parameters can differ by an order of magnitude or more, especially for samples subject to slow transport, long travel times, or rapid reactions. The effect of mixing on apparent N isotope fractionation potentially explains differences between previous laboratory and field estimates. Similarly, predicted effects on apparent O2 threshold values for denitrification are consistent with previous reports of higher values in aquifers than in the laboratory. These results show that hydrogeological complexity substantially influences the interpretation and prediction of reactive transport. ?? 2010 by the American Geophysical Union.

  19. Methods for exploring treatment effect heterogeneity in subgroup analysis: an application to global clinical trials.

    PubMed

    Schou, I Manjula; C Marschner, Ian

    2015-01-01

    Multi-country randomised clinical trials (MRCTs) are common in the medical literature, and their interpretation has been the subject of extensive recent discussion. In many MRCTs, an evaluation of treatment effect homogeneity across countries or regions is conducted. Subgroup analysis principles require a significant test of interaction in order to claim heterogeneity of treatment effect across subgroups, such as countries in an MRCT. As clinical trials are typically underpowered for tests of interaction, overly optimistic expectations of treatment effect homogeneity can lead researchers, regulators and other stakeholders to over-interpret apparent differences between subgroups even when heterogeneity tests are insignificant. In this paper, we consider some exploratory analysis tools to address this issue. We present three measures derived using the theory of order statistics, which can be used to understand the magnitude and the nature of the variation in treatment effects that can arise merely as an artefact of chance. These measures are not intended to replace a formal test of interaction but instead provide non-inferential visual aids, which allow comparison of the observed and expected differences between regions or other subgroups and are a useful supplement to a formal test of interaction. We discuss how our methodology differs from recently published methods addressing the same issue. A case study of our approach is presented using data from the Study of Platelet Inhibition and Patient Outcomes (PLATO), which was a large cardiovascular MRCT that has been the subject of controversy in the literature. An R package is available that implements the proposed methods.

  20. On the biology of the bony otic capsule and the pathogenesis of otosclerosis.

    PubMed

    Bloch, Sune Land

    2012-10-01

    In human otosclerosis, focal pathological bone remodeling occurs in significant amounts inside the normally anti-resorptive perilabyrinthine domain of the bony otic capsule. Otosclerosis causes hearing loss in 0.2-0.5% of the population by ankylosis of the footplate. The disease cannot be predicted, avoided or medically reversed as the pathogenesis remains unknown. Previously genetic research has failed to identify a specific otosclerosis-gene and earlier theories of virus infections, autoimmunity or association to generalized bone diseases have been unable to explain why otosclerosis only occurs in the bony otic capsule while the rest of the skeleton remains completely normal. Studies from the otopathological laboratory (RH) have revealed how the bone turnover rates increase centrifugally from a sub-normal 0.1% adjacent to the inner ear space towards a normal 10% per year at the capsular periphery. This graded restriction of bone remodeling is most likely caused by the anti-resorptive action of the cytokine osteoprotegerin (OPG), which is expressed in high levels (1000 x normal bone levels) by inner ear structures to inhibit perilabyrinthine osteoclast formation and function. OPG knockout mice develop excessive, irregular bone remodeling, stapes fixation and progressive hearing loss. The lacuno-canalicular porosity is the candidate anatomical routes for the transmission of OPG-derived signals to the surrounding bone. This extracellular signaling pathway depends crucially on the viability of individual osteocytes. When bone remodeling is low, the average age of the bone matrix and osteocytes increases. We detected a high fetal density of labyrinthine osteocytes, which may secure a life-long anatomical route for inner ear OPG despite accumulation of non-viable osteocytes. Moreover, 3-D reconstructions and vector-based stereology revealed a co-existence between non-viable osteocytes and otosclerosis. We suggest that bone remodeling may commence when the effect of

  1. Person Heterogeneity of the BDI-II-C and Its Effects on Dimensionality and Construct Validity: Using Mixture Item Response Models

    ERIC Educational Resources Information Center

    Wu, Pei-Chen; Huang, Tsai-Wei

    2010-01-01

    This study was to apply the mixed Rasch model to investigate person heterogeneity of Beck Depression Inventory-II-Chinese version (BDI-II-C) and its effects on dimensionality and construct validity. Person heterogeneity was reflected by two latent classes that differ qualitatively. Additionally, person heterogeneity adversely affected the…

  2. Response function theories that account for size distribution effects - A review. [mathematical models concerning composite propellant heterogeneity effects on combustion instability

    NASA Technical Reports Server (NTRS)

    Cohen, N. S.

    1980-01-01

    The paper presents theoretical models developed to account for the heterogeneity of composite propellants in expressing the pressure-coupled combustion response function. It is noted that the model of Lengelle and Williams (1968) furnishes a viable basis to explain the effects of heterogeneity.

  3. Association of evaluation methods of the effective permittivity of heterogeneous media on the basis of a generalized singular approximation

    NASA Astrophysics Data System (ADS)

    Kolesnikov, V. I.; Yakovlev, V. B.; Bardushkin, V. V.; Lavrov, I. V.; Sychev, A. P.; Yakovleva, E. N.

    2013-09-01

    Various methods for evaluation of the effective permittivity of heterogeneous media, namely, the effective medium approximation (Bruggeman's approximation), the Maxwell-Garnett approximation, Wiener's bounds, and the Hashin-Shtrikman variational bounds (for effective static characteristics) are combined on the basis of a generalized singular approximation.

  4. Bony labyrinth shape variation in extant Carnivora: a case study of Musteloidea.

    PubMed

    Grohé, Camille; Tseng, Z Jack; Lebrun, Renaud; Boistel, Renaud; Flynn, John J

    2016-03-01

    The bony labyrinth provides a proxy for the morphology of the inner ear, a primary cognitive organ involved in hearing, body perception in space, and balance in vertebrates. Bony labyrinth shape variations often are attributed to phylogenetic and ecological factors. Here we use three-dimensional (3D) geometric morphometrics to examine the phylogenetic and ecological patterns of variation in the bony labyrinth morphology of the most species-rich and ecologically diversified traditionally recognized superfamily of Carnivora, the Musteloidea (e.g. weasels, otters, badgers, red panda, skunks, raccoons, coatis). We scanned the basicrania of specimens belonging to 31 species using high-resolution X-ray computed micro-tomography (μCT) to virtually reconstruct 3D models of the bony labyrinths. Labyrinth morphology is captured by a set of six fixed landmarks on the vestibular and cochlear systems, and 120 sliding semilandmarks, slid at the center of the semicircular canals and the cochlea. We found that the morphology of this sensory structure is not significantly influenced by bony labyrinth size, in comparisons across all musteloids or in any of the individual traditionally recognized families (Mephitidae, Procyonidae, Mustelidae). PCA (principal components analysis) of shape data revealed that bony labyrinth morphology is clearly distinguishable between musteloid families, and permutation tests of the Kmult statistic confirmed that the bony labyrinth shows a phylogenetic signal in musteloids and in most mustelids. Both the vestibular and cochlear regions display morphological differences among the musteloids sampled, associated with the size and curvature of the semicircular canals, angles between canals, presence or absence of a secondary common crus, degree of lateral compression of the vestibule, orientation of the cochlea relative to the semicircular canals, proportions of the cochlea, and degree of curvature of its turns. We detected a significant ecological signal

  5. Effects of Heterogeneous Adsorption Affinity on Natural Organic Matter (NOM) Transport in Laboratory Sand Columns

    NASA Astrophysics Data System (ADS)

    McInnis, D. P.; Bolster, D.; Maurice, P. A.

    2012-12-01

    Transport of reactive sorbing solutes through porous media is commonly quantified by implementing an effective retardation coefficient in the advection-dispersion equation (ADE), which describes dispersion in accordance with Fick's law. However, anomalous (non-Fickian) transport behavior can be observed in systems with heterogeneous retardation coefficients (Dentz & Castro, 2009). In such systems, the ADE is unable to reproduce the non-Fickian nature of plume shapes and breakthrough curves, motivating the development and application of alternative solute transport theories, such as the continuous time random walk (CTRW) or multi-rate mass transfer (MRMT). Heterogeneity in retardation coefficients in practice arises from variability in the geochemical properties controlling sorption-desorption kinetics between the solute and mineral surfaces. These distributions have been described in the context of heterogeneity of the porous medium, but to date little attention has been given to the potential role of a geochemically heterogeneous solute. In this work, we consider a system in which anomalous transport arises during the passage of natural organic matter (NOM), a polydisperse mixture of compounds derived from the breakdown of plants and microorganisms in the environment, through homogeneous laboratory sand columns. NOM solutions were passed through columns containing either hematite, corundum, or a naturally-coated quartz sand at a variety of pH and ionic strength conditions. Influent and effluent NOM concentration was measured as UV absorbance at 254 nm. The resulting breakthrough curves are non-Fickian, displaying power-law tailing at late times. Such curves cannot be predicted by the ADE model. Reactivity of NOM components is known to be related to their molecular weight (MW), which tends to be log-normally distributed in aquatic NOM isolates (Cabaniss et al., 2000). Low-MW compounds are more water-soluble, have a higher diffusion coefficient, and due to their

  6. Evaluation of PET texture features with heterogeneous phantoms: complementarity and effect of motion and segmentation method

    NASA Astrophysics Data System (ADS)

    Carles, M.; Torres-Espallardo, I.; Alberich-Bayarri, A.; Olivas, C.; Bello, P.; Nestle, U.; Martí-Bonmatí, L.

    2017-01-01

    A major source of error in quantitative PET/CT scans of lung cancer tumors is respiratory motion. Regarding the variability of PET texture features (TF), the impact of respiratory motion has not been properly studied with experimental phantoms. The primary aim of this work was to evaluate the current use of PET texture analysis for heterogeneity characterization in lesions affected by respiratory motion. Twenty-eight heterogeneous lesions were simulated by a mixture of alginate and 18 F-fluoro-2-deoxy-D-glucose (FDG). Sixteen respiratory patterns were applied. Firstly, the TF response for different heterogeneous phantoms and its robustness with respect to the segmentation method were calculated. Secondly, the variability for TF derived from PET image with (gated, G-) and without (ungated, U-) motion compensation was analyzed. Finally, TF complementarity was assessed. In the comparison of TF derived from the ideal contour with respect to TF derived from 40%-threshold and adaptive-threshold PET contours, 7/8 TF showed strong linear correlation (LC) (p  <  0.001, r  >  0.75), despite a significant volume underestimation. Independence of lesion movement (LC in 100% of the combined pairs of movements, p  <  0.05) was obtained for 1/8 TF with U-image (width of the volume-activity histogram, WH) and 4/8 TF with G-image (WH and energy (ENG), local-homogeneity (LH) and entropy (ENT), derived from the co-ocurrence matrix). Their variability in terms of the coefficient of variance ({{C}\\text{V}} ) resulted in {{C}\\text{V}} (WH)  =  0.18 on the U-image and {{C}\\text{V}} (WH)  =  0.24, {{C}\\text{V}} (ENG)  =  0.15, {{C}\\text{V}} (LH)  =  0.07 and {{C}\\text{V}} (ENT)  =  0.06 on the G-image. Apart from WH (r  >  0.9, p  <  0.001), not one of these TF has shown LC with C max. Complementarity was observed for the TF pairs: ENG-LH, CONT (contrast)-ENT and LH-ENT. In conclusion, the effect of

  7. Effects of vegetation heterogeneity and surface topography on spatial scaling of net primary productivity

    NASA Astrophysics Data System (ADS)

    Chen, J. M.; Chen, X.; Ju, W.

    2013-07-01

    Due to the heterogeneous nature of the land surface, spatial scaling is an inevitable issue in the development of land models coupled with low-resolution Earth system models (ESMs) for predicting land-atmosphere interactions and carbon-climate feedbacks. In this study, a simple spatial scaling algorithm is developed to correct errors in net primary productivity (NPP) estimates made at a coarse spatial resolution based on sub-pixel information of vegetation heterogeneity and surface topography. An eco-hydrological model BEPS-TerrainLab, which considers both vegetation and topographical effects on the vertical and lateral water flows and the carbon cycle, is used to simulate NPP at 30 m and 1 km resolutions for a 5700 km2 watershed with an elevation range from 518 m to 3767 m in the Qinling Mountain, Shanxi Province, China. Assuming that the NPP simulated at 30 m resolution represents the reality and that at 1 km resolution is subject to errors due to sub-pixel heterogeneity, a spatial scaling index (SSI) is developed to correct the coarse resolution NPP values pixel by pixel. The agreement between the NPP values at these two resolutions is improved considerably from R2 = 0.782 to R2 = 0.884 after the correction. The mean bias error (MBE) in NPP modelled at the 1 km resolution is reduced from 14.8 g C m-2 yr-1 to 4.8 g C m-2 yr-1 in comparison with NPP modelled at 30 m resolution, where the mean NPP is 668 g C m-2 yr-1. The range of spatial variations of NPP at 30 m resolution is larger than that at 1 km resolution. Land cover fraction is the most important vegetation factor to be considered in NPP spatial scaling, and slope is the most important topographical factor for NPP spatial scaling especially in mountainous areas, because of its influence on the lateral water redistribution, affecting water table, soil moisture and plant growth. Other factors including leaf area index (LAI) and elevation have small and additive effects on improving the spatial scaling

  8. Effects of vegetation heterogeneity and surface topography on spatial scaling of net primary productivity

    NASA Astrophysics Data System (ADS)

    Chen, J. M.; Chen, X.; Ju, W.

    2013-03-01

    Due to the heterogeneous nature of the land surface, spatial scaling is an inevitable issue in the development of land models coupled with low-resolution Earth system models (ESMs) for predicting land-atmosphere interactions and carbon-climate feedbacks. In this study, a simple spatial scaling algorithm is developed to correct errors in net primary productivity (NPP) estimates made at a coarse spatial resolution based on sub-pixel information of vegetation heterogeneity and surface topography. An eco-hydrological model BEPS-TerrainLab, which considers both vegetation and topographical effects on the vertical and lateral water flows and the carbon cycle, is used to simulate NPP at 30 m and 1 km resolutions for a 5700 km2 watershed with an elevation range from 518 m to 3767 m in the Qinling Mountain, Shaanxi Province, China. Assuming that the NPP simulated at 30 m resolution represents the reality and that at 1 km resolution is subject to errors due to sub-pixel heterogeneity, a spatial scaling index (SSI) is developed to correct the coarse resolution NPP values pixel by pixel. The agreement between the NPP values at these two resolutions is improved considerably from R2 = 0.782 to R2 = 0.884 after the correction. The mean bias error (MBE) in NPP modeled at the 1 km resolution is reduced from 14.8 g C m-2 yr-1 to 4.8 g C m-2 yr-1 in comparison with NPP modeled at 30 m resolution, where the mean NPP is 668 g C m-2 yr-1. The range of spatial variations of NPP at 30 m resolution is larger than that at 1 km resolution. Land cover fraction is the most important vegetation factor to be considered in NPP spatial scaling, and slope is the most important topographical factor for NPP spatial scaling especially in mountainous areas, because of its influence on the lateral water redistribution, affecting water table, soil moisture and plant growth. Other factors including leaf area index (LAI), elevation and aspect have small and additive effects on improving the spatial scaling

  9. Antral bony wall erosion, trigeminal nerve injury, and enophthalmos after root canal surgery

    PubMed Central

    Ferreira, Eduardo; Antunes, Luís; Dinis, Paulo Borges

    2016-01-01

    Introduction: The frequently used irrigant in dental surgery, sodium hypochlorite, is occasionally the cause of minor, usually circumscribed, adverse effects. Severe, extensive complications, with lasting sequelae, however, also can occur, as in the case we report herein. Case Report: A 55-year-old woman underwent an endodontic procedure on a maxillary molar, whose roots, unknown to the surgeon, were protruding into the maxillary sinus. After sodium hypochlorite root canal irrigation, the patient immediately developed intense facial pain, facial edema, and periorbital cellulitis. An emergency department evaluation diagnosed an intense inflammatory disease of the maxillary sinus, with significant destruction of its bony walls, accompanied by midface paraesthesia due to infraorbital nerve injury. In the following weeks, the patient slowly developed enophthalmos due to bone erosion of the orbit floor. Treatment, besides prolonged oral steroids, required the endoscopic endonasal opening of the maxillary sinus for profuse irrigation. Two years later, the patient maintained a complete loss of function of the maxillary sinus, anesthesia-paraesthesia of the midface, and inferior dystonia of the eye with an enophthalmos. Conclusion: Dentists, maxillofacial surgeons, and otorhinolaryngologists should all be aware of the whole spectrum of complications of even the simplest dental work. Sodium hypochlorite irrigations should be used cautiously in root canal surgery, with the full awareness of its potential for causing soft-tissue damage. PMID:27465790

  10. Geometric effects of global lateral heterogeneity on long-period surface wave propagation

    NASA Technical Reports Server (NTRS)

    Lay, T.; Kanamori, H.

    1985-01-01

    The present investigation has the objective to document examples of anomalous long-period surface wave amplitude behavior and to provide a preliminary appraisal of the effects of global lateral heterogeneity on surface wave propagation from a ray theory perspective. Attention is given to remarkable long-period surface wave anomalies described in literature, an equidistance azimuthal plot centered on the Iranian source region, Rayleigh wave and Love wave spectra for the 256-s period arrivals for the Tabas earthquake, constrained moment tensor and fault model inversion solutions ofr Iranian earthquakes, aspects of surface wave ray tracing, and a table of Rayleigh wave amplitude anomalies for Iranian earthquakes. Surface wave ray-tracing calculations for models of global phase velocity variations proposed by Nakanishi and Anderson (1984) are found to show that large-amplitude anomalies will be observed for Love and Rayleigh waves with periods of 100-250 s.

  11. Effects of tissue heterogeneity on the optical estimate of breast density

    PubMed Central

    Taroni, Paola; Pifferi, Antonio; Quarto, Giovanna; Spinelli, Lorenzo; Torricelli, Alessandro; Abbate, Francesca; Balestreri, Nicola; Ganino, Serena; Menna, Simona; Cassano, Enrico; Cubeddu, Rinaldo

    2012-01-01

    Breast density is a recognized strong and independent risk factor for developing breast cancer. At present, breast density is assessed based on the radiological appearance of breast tissue, thus relying on the use of ionizing radiation. We have previously obtained encouraging preliminary results with our portable instrument for time domain optical mammography performed at 7 wavelengths (635–1060 nm). In that case, information was averaged over four images (cranio-caudal and oblique views of both breasts) available for each subject. In the present work, we tested the effectiveness of just one or few point measurements, to investigate if tissue heterogeneity significantly affects the correlation between optically derived parameters and mammographic density. Data show that parameters estimated through a single optical measurement correlate strongly with mammographic density estimated by using BIRADS categories. A central position is optimal for the measurement, but its exact location is not critical. PMID:23082283

  12. The good, the bad, and the different: a primer on aspects of heterogeneity of treatment effects.

    PubMed

    Malone, Daniel C; Hines, Lisa E; Graff, Jennifer S

    2014-06-01

    The concept of heterogeneity is concerned with understanding differences within and across patients and studies. Heterogeneity of treatment effects is nonrandom variability in response to treatment and includes both benefits and harms. Because not all patients respond the same way, treatment decisions applied in a "one size fits all" fashion based on the average response observed in clinical trials may lead to suboptimal outcomes for some patients. Variation in outcomes among patients may be caused by observable and nonobservable factors. Changes in patients' health status over time can contribute to variability among patients. Assuming that the results from clinical trials are homogeneous across patients may fail to take into account clinically significant variability where some patients may receive benefit and others harm. Subgroup analyses and prediction models are 2 tools to explain variability observed within a study. Evidence synthesis with meta-analysis can provide useful information on the overall effectiveness and response among groups of patients undersampled in individual studies. Yet caution is warranted if the meta-analysis is missing studies or the individual studies comprising the meta-analysis are inherently different.For those making clinical, coverage, and reimbursement decisions at a population level, such as clinicians and pharmacy and therapeutics committee members, understanding the variation among patients, among subpopulations or populations of patients, among clinical studies, or within a meta-analysis is important to ensuring optimal patient outcomes. This article presents a variety of tools and resources to aid decision makers as they evaluate the literature to determine when clinically relevant differences exist.

  13. Severe bony ankylosis of the temporomandibular joint on one side and contralateral adhesion: A case report

    PubMed Central

    Kim, Seong-Gon; Choi, Hang-Moon; Kim, Hyun Jung

    2015-01-01

    Bony fusion between the mandibular condyle and skull base involves temporomandibular joint (TMJ) bony ankylosis. This condition might originate from trauma, infection, or systemic disease. TMJ adhesion can develop after synovial damage. Both TMJ ankylosis and adhesion lead to functional impairment and pain. Here, we present a case of a 50-year-old female who had bony ankylosis of the right TMJ and adhesion of the left TMJ. She had otitis media in the right ear. A large mass in the right TMJ was observed on computed tomograph. Magnetic resonance image showed a large fused bone mass with normal bone marrow in the right TMJ and flattening of the condyle with a thin disk in the left TMJ. Gap arthroplasty with temporal fascia was performed on the right TMJ, and discectomy, high condylectomy, and coronoidectomy were performed on the left TMJ. During a 2-year follow-up after surgery, the patient had no recurrence. PMID:26125005

  14. Low effect of young afforestations on bird communities inhabiting heterogeneous Mediterranean cropland

    PubMed Central

    Rey Benayas, José M.; Carrascal, Luis M.

    2015-01-01

    Afforestation programs such as the one promoted by the EU Common Agricultural Policy have spread tree plantations on former cropland. These afforestations attract generalist forest and ubiquitous species but may cause severe damage to open habitat species, especially birds of high conservation value. We investigated the effects of young (<20 yr) tree plantations dominated by pine P. halepensis on bird communities inhabiting the adjacent open farmland habitat in central Spain. We hypothesize that pine plantations located at shorter distances from open fields and with larger surface would affect species richness and conservation value of bird communities. Regression models controlling for the influence of land use types around plantations revealed positive effects of higher distance to pine plantation edge on community species richness in winter, and negative effects on an index of conservation concern (SPEC) during the breeding season. However, plantation area did not have any effect on species richness or community conservation value. Our results indicate that the effects of pine afforestation on bird communities inhabiting Mediterranean cropland are diluted by heterogeneous agricultural landscapes. PMID:26664801

  15. Allocating Sample Sizes to Reduce Budget for Fixed-Effect 2×2 Heterogeneous Analysis of Variance

    ERIC Educational Resources Information Center

    Luh, Wei-Ming; Guo, Jiin-Huarng

    2016-01-01

    This article discusses the sample size requirements for the interaction, row, and column effects, respectively, by forming a linear contrast for a 2×2 factorial design for fixed-effects heterogeneous analysis of variance. The proposed method uses the Welch t test and its corresponding degrees of freedom to calculate the final sample size in a…

  16. Effect of meter-scale heterogeneities inside 67P nucleus on CONSERT data

    NASA Astrophysics Data System (ADS)

    Ciarletti, Valérie; Lasue, Jérémie; Lemonnier, Florentin; Kofman, Wlodek; Levasseur-Regourd, Anny-Chantal; Herique, Alain; Guiffaut, Christophe

    2016-10-01

    Since their arrival at comet 67P in August 2014, a number of instruments onboard Rosetta's main spacecraft and Philae lander have been observing the surface of the nucleus and revealed details of amazing surficial structures (hundreds of meters deep pits and cliffs, surface roughness of the order of a couple of meters in size, non-continuous apparent layers on both lobes of the comet). After two years of observations, the activity of the comet has also been better constrained, while the origin of sporadic jet activities remains debated. This surficial information is complemented by relevant measurements assessing the nucleus internal structure that have been collected by the CONSERT (Comet Nucleus Sounding Experiment by Radiowave Transmission) experiment in order to constrain the nucleus formation and evolution.The CONSERT experiment is a bistatic radar with receivers and transmitters on-board both Rosetta's main spacecraft and the Philae lander. The instrument transmits electromagnetic waves at 90 MHz (10 MHz bandwidth) between Philae and Rosetta. The signal propagated through the small lobe of 67P over distances ranging from approximately 200 to 800 meters depending on the spacecraft location and probed a maximum depth of about one hundred meters in the vicinity of the final landing site Abydos. The CONSERT data have been used to obtain an estimate of the permittivity mean value. Thanks to the 10 MHz frequency bandwidth of the signal used by the instrument, a spatial resolution around 10m is obtained inside the sounded volume of the nucleus.In this work, we analyze the effect of internal heterogeneities of 67P on the CONSERT data by simulating the propagation of the signal through a fractal model of the comet interior. We considered for the simulations a range of realistic permittivity values and characteristic sizes of the material heterogeneities. The different parameters values used have an impact on the width of the signal propagating through the modeled

  17. Bony expansion in skeletal metastases from carcinoma of the prostate as seen by bone scintigraphy

    SciTech Connect

    Resnik, C.S.; Garver, P.; Resnick, D.

    1984-10-01

    Carcinoma of the prostate often metastasizes to the skeletal system, the usual radiologic pattern being widespread patchy areas of increased density without change in the contour of the involved bones. Radionuclide correlation generally shows multiple foci of increased tracer activity. Less commonly, there is bony sclerosis with expansion of the diameter of the involved bone. Several cases of expansile skeletal metastases from carcinoma of the prostate have appeared in the literature but we know of no published descriptions of the radionuclide findings. We present three patients with carcinoma of the prostate who had skeletal metastases with evidence of bony expansion on both roentgenographic and radionuclide examination. 15 references, 8 figures.

  18. A case of atlas assimilation: description of bony and soft structures.

    PubMed

    Ciołkowski, Maciej K; Krajewski, Paweł; Ciszek, Bogdan

    2014-10-01

    A case of atlas assimilation revealed during serial study of suboccipital region is presented. The specimen was harvested from the body of 31-year-old woman. Images of the computed tomography scans are correlated with classic dissection. Asymmetrical bony assimilation is accompanied by asymmetrical development of the suboccipital musculature. In the presented case, the atlantic segments of both vertebral arteries preserved their usual course between bony elements derived from the atlas and proatlas. Development of the soft tissues must be influenced by similar factors as development of the skeleton. Detailed radiologic studies, possibly with volumetric reconstructions, are necessary in cases of atlas assimilation before surgical interventions in the region of craniovertebral junction.

  19. Substrate effect on the formation of hydrogels with heterogeneous network structure.

    PubMed

    Peng, Mao; Ping Gong, Jian; Osada, Yoshihito

    2003-01-01

    It was found that when an aqueous solution of vinyl monomers is polymerized on a hydrophobic substrate, obvious heterogeneity occurs in the region of the interface. This substrate effect was observed on polytetrafluroethylene (Teflon), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyvinylchloride (PVC), but not on hydrophilic substrates. Compared with synthesis on hydrophilic surfaces, the surfaces of hydrogels synthesized on a hydrophobic substrate exhibit a larger degree of swelling, a lower surface coefficient of friction and elastic modulus, weaker interfacial adhesion, and reduced interaction with biological cells. This substrate effect has been observed for many types of aqueous monomer solutions. It was found that the above properties are related to the loosely cross-linked architecture, containing some graft-like polymer chains, that is formed on the gel surface when the gel is prepared on a hydrophobic substrate. To understand the mechanism of the substrate effect, two novel optical methods, electric speckle pattern interferometry (ESPI) and real-time laser sheet refraction (RT-LSR), were developed. It was found that oxygen trapped in the composite interface between the monomer solution and rough hydrophobic substrates played an important role in the substrate effect.

  20. Effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography

    PubMed Central

    Jin, Xing; Li, Changhui; Wang, Lihong V.

    2008-01-01

    The effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography were studied. A numerical model for calculating the propagation of thermoacoustic waves through the skull was developed and experimentally examined. The model takes into account wave reflection and refraction at the skull surfaces and therefore provides improved accuracy for the reconstruction. To evaluate when the skull-induced effects could be ignored in reconstruction, the reconstructed images obtained by the proposed method were further compared with those obtained with the method based on homogeneous acoustic properties. From simulation and experimental results, it was found that when the target region is close to the center of the brain, the effects caused by the skull layer are minimal and both reconstruction methods work well. As the target region becomes closer to the interface between the skull and brain tissue, however, the skull-induced distortion becomes increasingly severe, and the reconstructed image would be strongly distorted without correcting those effects. In this case, the proposed numerical method can improve image quality by taking into consideration the wave refraction and mode conversion at the skull surfaces. This work is important for obtaining good brain images when the thickness of the skull cannot be ignored. PMID:18697545

  1. Effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography.

    PubMed

    Jin, Xing; Li, Changhui; Wang, Lihong V

    2008-07-01

    The effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography were studied. A numerical model for calculating the propagation of thermoacoustic waves through the skull was developed and experimentally examined. The model takes into account wave reflection and refraction at the skull surfaces and therefore provides improved accuracy for the reconstruction. To evaluate when the skull-induced effects could be ignored in reconstruction, the reconstructed images obtained by the proposed method were further compared with those obtained with the method based on homogeneous acoustic properties. From simulation and experimental results, it was found that when the target region is close to the center of the brain, the effects caused by the skull layer are minimal and both reconstruction methods work well. As the target region becomes closer to the interface between the skull and brain tissue, however, the skull-induced distortion becomes increasingly severe, and the reconstructed image would be strongly distorted without correcting those effects. In this case, the proposed numerical method can improve image quality by taking into consideration the wave refraction and mode conversion at the skull surfaces. This work is important for obtaining good brain images when the thickness of the skull cannot be ignored.

  2. Effects of heterogeneities on capillary pressure-saturation-relative permeability relationships.

    PubMed

    Ataie-Ashtiani, Behzad; Hassanizadeh, S Majid; Celia, Michael A

    2002-06-01

    In theories of multiphase flow through porous media, capillary pressure-saturation and relative permeability-saturation curves are assumed to be intrinsic properties of the medium. Moreover, relative permeability is assumed to be a scalar property. However, numerous theoretical and experimental works have shown that these basic assumptions may not be valid. For example, relative permeability is known to be affected by the flow velocity (or pressure gradient) at which the measurements are carried out. In this article, it is suggested that the nonuniqueness of capillary pressure-relative permeability-saturation relationships is due to the presence of microheterogeneities within a laboratory sample. In order to investigate this hypothesis, a large number of "numerical experiments" are carried out. A numerical multiphase flow model is used to simulate the procedures that are commonly used in the laboratory for the measurement of capillary pressure and relative permeability curves. The dimensions of the simulation domain are similar to those of a typical laboratory sample (a few centimeters in each direction). Various combinations of boundary conditions and soil heterogeneity are simulated and average capillary pressure, saturation, and relative permeability for the "soil sample" are obtained. It is found that the irreducible water saturation is a function of the capillary number; the smaller the capillary number, the larger the irreducible water saturation. Both drainage and imbibition capillary pressure curves are found to be strongly affected by heterogeneities and boundary conditions. Relative permeability is also found to be affected by the boundary conditions; this is especially true about the nonaqueous phase permeability. Our results reveal that there is much need for laboratory experiments aimed at investigating the interplay of boundary conditions and microheterogeneities and their effect on capillary pressure and relative permeability.

  3. Effect of heterogeneity on enhanced reductive dechlorination: Analysis of remediation efficiency and groundwater acidification

    NASA Astrophysics Data System (ADS)

    Brovelli, A.; Lacroix, E.; Robinson, C. E.; Gerhard, J.; Holliger, C.; Barry, D. A.

    2011-12-01

    Enhanced reductive dehalogenation is an attractive in situ treatment technology for chlorinated contaminants. The process includes two acid-forming microbial reactions: fermentation of an organic substrate resulting in short-chain fatty acids, and dehalogenation resulting in hydrochloric acid. The accumulation of acids and the resulting drop of groundwater pH are controlled by the mass and distribution of chlorinated solvents in the source zone, type of electron donor, alternative terminal electron acceptors available and presence of soil mineral phases able to buffer the pH (such as carbonates). Groundwater acidification may reduce or halt microbial activity, and thus dehalogenation, significantly increasing the time and costs required to remediate the aquifer. In previous work a detailed geochemical and groundwater flow simulator able to model the fermentation-dechlorination reactions and associated pH change was developed. The model accounts for the main processes influencing microbial activity and groundwater pH, including the groundwater composition, the electron donor used and soil mineral phase interactions. In this study, the model was applied to investigate how spatial variability occurring at the field scale affects dechlorination rates, groundwater pH and ultimately the remediation efficiency. Numerical simulations were conducted to examine the influence of heterogeneous hydraulic conductivity on the distribution of the injected, fermentable substrate and on the accumulation/dilution of the acidic products of reductive dehalogenation. The influence of the geometry of the DNAPL source zone was studied, as well as the spatial distribution of soil minerals. The results of this study showed that the heterogeneous distribution of the soil properties have a potentially large effect on the remediation efficiency. For examples, zones of high hydraulic conductivity can prevent the accumulation of acids and alleviate the problem of groundwater acidification. The

  4. Peripheral Dose Heterogeneity Due to the Thread Effect in Total Marrow Irradiation With Helical Tomotherapy

    SciTech Connect

    Takahashi, Yutaka; Verneris, Michael R.; Dusenbery, Kathryn E.; Wilke, Christopher T.; Storme, Guy; Weisdorf, Daniel J.; Hui, Susanta K.

    2013-11-15

    Purpose: To report potential dose heterogeneity leading to underdosing at different skeletal sites in total marrow irradiation (TMI) with helical tomotherapy due to the thread effect and provide possible solutions to reduce this effect. Methods and Materials: Nine cases were divided into 2 groups based on patient size, defined as maximum left-to-right arm distance (mLRD): small mLRD (≤47 cm) and large mLRD (>47 cm). TMI treatment planning was conducted by varying the pitch and modulation factor while a jaw size (5 cm) was kept fixed. Ripple amplitude, defined as the peak-to-trough dose relative to the average dose due to the thread effect, and the dose–volume histogram (DVH) parameters for 9 cases with various mLRD was analyzed in different skeletal regions at off-axis (eg, bones of the arm or femur), at the central axis (eg, vertebrae), and planning target volume (PTV), defined as the entire skeleton plus 1-cm margin. Results: Average ripple amplitude for a pitch of 0.430, known as one of the magic pitches that reduce thread effect, was 9.2% at 20 cm off-axis. No significant differences in DVH parameters of PTV, vertebrae, or femur were observed between small and large mLRD groups for a pitch of ≤0.287. Conversely, in the bones of the arm, average differences in the volume receiving 95% and 107% dose (V95 and V107, respectively) between large and small mLRD groups were 4.2% (P=.016) and 16% (P=.016), respectively. Strong correlations were found between mLRD and ripple amplitude (rs=.965), mLRD and V95 (rs=−.742), and mLRD and V107 (rs=.870) of bones of the arm. Conclusions: Thread effect significantly influences DVH parameters in the bones of the arm for large mLRD patients. By implementing a favorable pitch value and adjusting arm position, peripheral dose heterogeneity could be reduced.

  5. Effect of methacholine on peripheral lung mechanics and ventilation heterogeneity in asthma.

    PubMed

    Downie, Sue R; Salome, Cheryl M; Verbanck, Sylvia; Thompson, Bruce R; Berend, Norbert; King, Gregory G

    2013-03-15

    The forced oscillation technique (FOT) and multiple-breath nitrogen washout (MBNW) are noninvasive tests that are potentially sensitive to peripheral airways, with MBNW indexes being especially sensitive to heterogeneous changes in ventilation. The objective was to study methacholine-induced changes in the lung periphery of asthmatic patients and determine how changes in FOT variables of respiratory system reactance (Xrs) and resistance (Rrs) and frequency dependence of resistance (Rrs5-Rrs19) can be linked to changes in ventilation heterogeneity. The contributions of air trapping and airway closure, as extreme forms of heterogeneity, were also investigated. Xrs5, Rrs5, Rrs19, Rrs5-Rrs19, and inspiratory capacity (IC) were calculated from the FOT. Ventilation heterogeneity in acinar and conducting airways, and trapped gas (percent volume of trapped gas at functional residual capacity/vital capacity), were calculated from the MBNW. Measurements were repeated following methacholine. Methacholine-induced airway closure (percent change in forced vital capacity) and hyperinflation (change in IC) were also recorded. In 40 mild to moderate asthmatic patients, increase in Xrs5 after methacholine was predicted by increases in ventilation heterogeneity in acinar airways and forced vital capacity (r(2) = 0.37, P < 0.001), but had no correlation with ventilation heterogeneity in conducting airway increase or IC decrease. Increases in Rrs5 and Rrs5-Rrs19 after methacholine were not correlated with increases in ventilation heterogeneity, trapped gas, hyperinflation, or airway closure. Increased reactance in asthmatic patients after methacholine was indicative of heterogeneous changes in the lung periphery and airway closure. By contrast, increases in resistance and frequency dependence of resistance were not related to ventilation heterogeneity or airway closure and were more indicative of changes in central airway caliber than of heterogeneity.

  6. Applicability of the Effective-Medium Approximation to Heterogeneous Aerosol Particles.

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael I.; Dlugach, Janna M.; Liu, Li

    2016-01-01

    The effective-medium approximation (EMA) is based on the assumption that a heterogeneous particle can have a homogeneous counterpart possessing similar scattering and absorption properties. We analyze the numerical accuracy of the EMA by comparing superposition T-matrix computations for spherical aerosol particles filled with numerous randomly distributed small inclusions and Lorenz-Mie computations based on the Maxwell-Garnett mixing rule. We verify numerically that the EMA can indeed be realized for inclusion size parameters smaller than a threshold value. The threshold size parameter depends on the refractive-index contrast between the host and inclusion materials and quite often does not exceed several tenths, especially in calculations of the scattering matrix and the absorption cross section. As the inclusion size parameter approaches the threshold value, the scattering-matrix errors of the EMA start to grow with increasing the host size parameter and or the number of inclusions. We confirm, in particular, the existence of the effective-medium regime in the important case of dust aerosols with hematite or air-bubble inclusions, but then the large refractive-index contrast necessitates inclusion size parameters of the order of a few tenths. Irrespective of the highly restricted conditions of applicability of the EMA, our results provide further evidence that the effective-medium regime must be a direct corollary of the macroscopic Maxwell equations under specific assumptions.

  7. Applicability of the effective-medium approximation to heterogeneous aerosol particles

    NASA Astrophysics Data System (ADS)

    Mishchenko, Michael I.; Dlugach, Janna M.; Liu, Li

    2016-07-01

    The effective-medium approximation (EMA) is based on the assumption that a heterogeneous particle can have a homogeneous counterpart possessing similar scattering and absorption properties. We analyze the numerical accuracy of the EMA by comparing superposition T-matrix computations for spherical aerosol particles filled with numerous randomly distributed small inclusions and Lorenz-Mie computations based on the Maxwell-Garnett mixing rule. We verify numerically that the EMA can indeed be realized for inclusion size parameters smaller than a threshold value. The threshold size parameter depends on the refractive-index contrast between the host and inclusion materials and quite often does not exceed several tenths, especially in calculations of the scattering matrix and the absorption cross section. As the inclusion size parameter approaches the threshold value, the scattering-matrix errors of the EMA start to grow with increasing the host size parameter and/or the number of inclusions. We confirm, in particular, the existence of the effective-medium regime in the important case of dust aerosols with hematite or air-bubble inclusions, but then the large refractive-index contrast necessitates inclusion size parameters of the order of a few tenths. Irrespective of the highly restricted conditions of applicability of the EMA, our results provide further evidence that the effective-medium regime must be a direct corollary of the macroscopic Maxwell equations under specific assumptions.

  8. Assessing and reporting heterogeneity in treatment effects in clinical trials: a proposal

    PubMed Central

    2010-01-01

    Mounting evidence suggests that there is frequently considerable variation in the risk of the outcome of interest in clinical trial populations. These differences in risk will often cause clinically important heterogeneity in treatment effects (HTE) across the trial population, such that the balance between treatment risks and benefits may differ substantially between large identifiable patient subgroups; the "average" benefit observed in the summary result may even be non-representative of the treatment effect for a typical patient in the trial. Conventional subgroup analyses, which examine whether specific patient characteristics modify the effects of treatment, are usually unable to detect even large variations in treatment benefit (and harm) across risk groups because they do not account for the fact that patients have multiple characteristics simultaneously that affect the likelihood of treatment benefit. Based upon recent evidence on optimal statistical approaches to assessing HTE, we propose a framework that prioritizes the analysis and reporting of multivariate risk-based HTE and suggests that other subgroup analyses should be explicitly labeled either as primary subgroup analyses (well-motivated by prior evidence and intended to produce clinically actionable results) or secondary (exploratory) subgroup analyses (performed to inform future research). A standardized and transparent approach to HTE assessment and reporting could substantially improve clinical trial utility and interpretability. PMID:20704705

  9. Effect of electrical forepaw stimulation on capillary transit-time heterogeneity (CTH).

    PubMed

    Gutiérrez-Jiménez, Eugenio; Cai, Changsi; Mikkelsen, Irene Klærke; Rasmussen, Peter Mondrup; Angleys, Hugo; Merrild, Mads; Mouridsen, Kim; Jespersen, Sune Nørhøj; Lee, Jonghwan; Iversen, Nina Kerting; Sakadzic, Sava; Østergaard, Leif

    2016-12-01

    Functional hyperemia reduces oxygen extraction efficacy unless counteracted by a reduction of capillary transit-time heterogeneity of blood. We adapted a bolus tracking approach to capillary transit-time heterogeneity estimation for two-photon microscopy and then quantified changes in plasma mean transit time and capillary transit-time heterogeneity during forepaw stimulation in anesthetized mice (C57BL/6NTac). In addition, we analyzed transit time coefficient of variance = capillary transit-time heterogeneity/mean transit time, which we expect to remain constant in passive, compliant microvascular networks. Electrical forepaw stimulation reduced, both mean transit time (11.3% ± 1.3%) and capillary transit-time heterogeneity (24.1% ± 3.3%), consistent with earlier literature and model predictions. We observed a coefficient of variance reduction (14.3% ± 3.5%) during functional activation, especially for the arteriolar-to-venular passage. Such coefficient of variance reduction during functional activation suggests homogenization of capillary flows beyond that expected as a passive response to increased blood flow by other stimuli. This finding is consistent with an active neurocapillary coupling mechanism, for example via pericyte dilation. Mean transit time and capillary transit-time heterogeneity reductions were consistent with the relative change inferred from capillary hemodynamics (cell velocity and flux). Our findings support the important role of capillary transit-time heterogeneity in flow-metabolism coupling during functional activation.

  10. Effect of heterogenous and homogenous air gaps on dry heat loss through the garment.

    PubMed

    Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M

    2015-11-01

    In real life conditions, the trapped air between the human body and the garment has uneven shape and vary over the body parts as a consequence of the complex geometry of the human body. However, the existing clothing models assume uniform air layer between the human body and the garment or its full contact, which may cause large error in the output of simulations. Therefore, the aim of this study was to investigate the effect of a heterogeneous vertical air gap with different configuration of folds (size and frequency) on dry heat loss using a heated cylinder (Torso). It was found that the presence of folds in the garment led to an increased heat loss from the body in comparison to a homogeneous air gap of comparable size. Interestingly, the size of folds did not have an influence on the dry heat loss. Additionally, the effect of the contact area on dry heat loss became important when exceeding a threshold of about 42%. The results from this study are useful for modelling of a realistic dry heat loss through the clothing and contribute to the improvement of design of protective and active sport garments.

  11. Effect of heterogenous and homogenous air gaps on dry heat loss through the garment

    NASA Astrophysics Data System (ADS)

    Mert, Emel; Psikuta, Agnes; Bueno, Marie-Ange; Rossi, René M.

    2015-11-01

    In real life conditions, the trapped air between the human body and the garment has uneven shape and vary over the body parts as a consequence of the complex geometry of the human body. However, the existing clothing models assume uniform air layer between the human body and the garment or its full contact, which may cause large error in the output of simulations. Therefore, the aim of this study was to investigate the effect of a heterogeneous vertical air gap with different configuration of folds (size and frequency) on dry heat loss using a heated cylinder (Torso). It was found that the presence of folds in the garment led to an increased heat loss from the body in comparison to a homogeneous air gap of comparable size. Interestingly, the size of folds did not have an influence on the dry heat loss. Additionally, the effect of the contact area on dry heat loss became important when exceeding a threshold of about 42 %. The results from this study are useful for modelling of a realistic dry heat loss through the clothing and contribute to the improvement of design of protective and active sport garments.

  12. The effects of capillary transit time heterogeneity (CTH) on brain oxygenation

    PubMed Central

    Angleys, Hugo; Østergaard, Leif; Jespersen, Sune N

    2015-01-01

    We recently extended the classic flow–diffusion equation, which relates blood flow to tissue oxygenation, to take capillary transit time heterogeneity (CTH) into account. Realizing that cerebral oxygen availability depends on both cerebral blood flow (CBF) and capillary flow patterns, we have speculated that CTH may be actively regulated and that changes in the capillary morphology and function, as well as in blood rheology, may be involved in the pathogenesis of conditions such as dementia and ischemia-reperfusion injury. The first extended flow–diffusion equation involved simplifying assumptions which may not hold in tissue. Here, we explicitly incorporate the effects of oxygen metabolism on tissue oxygen tension and extraction efficacy, and assess the extent to which the type of capillary transit time distribution affects the overall effects of CTH on flow–metabolism coupling reported earlier. After incorporating tissue oxygen metabolism, our model predicts changes in oxygen consumption and tissue oxygen tension during functional activation in accordance with literature reports. We find that, for large CTH values, a blood flow increase fails to cause significant improvements in oxygen delivery, and can even decrease it; a condition of malignant CTH. These results are found to be largely insensitive to the choice of the transit time distribution. PMID:25669911

  13. Effects of Spatially Heterogeneous Porosity on Matrix-Diffusion as Investigated by X ray Absorption Imaging

    SciTech Connect

    Boney, C.; Christian-Frear, T.; Meigs, L.C.; Tidwell, V.C.

    1998-10-20

    Laboratory experiments were performed to investigate the effects of spatial variation in porosity on matrix-diffusion processes. Four centimeter-scale slabs of Culebra dolomite taken from the Waste Isolation Pilot Plant site were used in the tests. Experiments involved the simple diffusion of iodine into a single edge of each rock slab while X ray absorption imaging was used to measure the resulting two-dmensional solute concentration field as a function of time. X ray imaging was also used to quantify the two-dimensional porosity field of each rock slab. Image analysis provided a unique opportunity to both visuake and quantifj the effects of the spatially variable porosi~ on matrixdMusion. Four key results were obtained. First, significant variation in rates of diffusion were realized over the relatively small length (centimeter) and time scales (months) investigated. Second, clear evidence of diffusion preferentially following zones of relatively higher porosity was noted. Third, rate of difhion was found to vary as tracer diffused into the rock slabs encountering changing porosity conditions. Fourth, strong correlation between porosi~ and the calculated diffusion coefficients was found. In fact, the nature of the correlation can be related to the geometry, position, and orientation of the heterogeneous porosity features populating each rock slab.

  14. Bayesian analysis of nonlinear mixed-effects mixture models for longitudinal data with heterogeneity and skewness.

    PubMed

    Lu, Xiaosun; Huang, Yangxin

    2014-07-20

    It is a common practice to analyze complex longitudinal data using nonlinear mixed-effects (NLME) models with normality assumption. The NLME models with normal distributions provide the most popular framework for modeling continuous longitudinal outcomes, assuming individuals are from a homogeneous population and relying on random-effects to accommodate inter-individual variation. However, the following two issues may standout: (i) normality assumption for model errors may cause lack of robustness and subsequently lead to invalid inference and unreasonable estimates, particularly, if the data exhibit skewness and (ii) a homogeneous population assumption may be unrealistically obscuring important features of between-subject and within-subject variations, which may result in unreliable modeling results. There has been relatively few studies concerning longitudinal data with both heterogeneity and skewness features. In the last two decades, the skew distributions have shown beneficial in dealing with asymmetric data in various applications. In this article, our objective is to address the simultaneous impact of both features arisen from longitudinal data by developing a flexible finite mixture of NLME models with skew distributions under Bayesian framework that allows estimates of both model parameters and class membership probabilities for longitudinal data. Simulation studies are conducted to assess the performance of the proposed models and methods, and a real example from an AIDS clinical trial illustrates the methodology by modeling the viral dynamics to compare potential models with different distribution specifications; the analysis results are reported.

  15. The effects of laser welding on heterogeneous immunoassay performance in a microfluidic cartridge

    PubMed Central

    Mäntymaa, Anne; Halme, Jussi; Välimaa, Lasse; Kallio, Pasi

    2011-01-01

    Sealing of a microfluidic cartridge is a challenge, because the cartridge commonly contains heat-sensitive biomolecules that must also be protected from contamination. In addition, the objective is usually to obtain a sealing method suitable for mass production. Laser welding is a rapid technique that can be accomplished with low unit costs. Even though the technique has been widely adopted in industry, the literature on its use in microfluidic applications is not large. This paper is the first to report the effects of laser welding on the performance of the heterogeneous immunoassay in a polystyrene microfluidic cartridge in which biomolecules are immobilized into the reaction surface of the cartridge before sealing. The paper compares the immunoassay performance of microfluidic cartridges that are sealed either with an adhesive tape or by use of laser transmission welding. The model analyte used is thyroid stimulating hormone (TSH). The results show that the concentration curves in the laser-welded cartridges are very close to the curves in the taped cartridges. This indicates, first, that laser welding does not cause any significant reduction in immunoassay performance, and second, that the polystyrene cover does not have significant effect on the signal levels. Interestingly, the coefficients of variance between parallel samples were lower in the laser-welded cartridges than in the taped cartridges. PMID:22685505

  16. The Community College Effect Revisited: The Importance of Attending to Heterogeneity and Complex Counterfactuals*

    PubMed Central

    Brand, Jennie E.; Pfeffer, Fabian T.; Goldrick-Rab, Sara

    2015-01-01

    Community colleges are controversial educational institutions, often said to simultaneously expand college opportunities and diminish baccalaureate attainment. We assess the seemingly contradictory functions of community colleges by attending to effect heterogeneity and to alternative counterfactual conditions. Using data on postsecondary outcomes of high school graduates of Chicago Public Schools, we find that enrolling at a community college penalizes more advantaged students who otherwise would have attended four-year colleges, particularly highly selective schools; however, these students represent a relatively small portion of the community college population, and these estimates are almost certainly biased. On the other hand, enrolling at a community college has a modest positive effect on bachelor's degree completion for disadvantaged students who otherwise would not have attended college; these students represent the majority of community college goers. We conclude that discussions among scholars, policymakers, and practitioners should move beyond considering the pros and cons of community college attendance for students in general to attending to the implications of community college attendance for targeted groups of students. PMID:25825705

  17. A general joint model for longitudinal measurements and competing risks survival data with heterogeneous random effects

    PubMed Central

    Li, Gang; Elashoff, Robert M.; Pan, Jianxin

    2011-01-01

    This article studies a general joint model for longitudinal measurements and competing risks survival data. The model consists of a linear mixed effects sub-model for the longitudinal outcome, a proportional cause-specific hazards frailty sub-model for the competing risks survival data, and a regression sub-model for the variance–covariance matrix of the multivariate latent random effects based on a modified Cholesky decomposition. The model provides a useful approach to adjust for non-ignorable missing data due to dropout for the longitudinal outcome, enables analysis of the survival outcome with informative censoring and intermittently measured time-dependent covariates, as well as joint analysis of the longitudinal and survival outcomes. Unlike previously studied joint models, our model allows for heterogeneous random covariance matrices. It also offers a framework to assess the homogeneous covariance assumption of existing joint models. A Bayesian MCMC procedure is developed for parameter estimation and inference. Its performances and frequentist properties are investigated using simulations. A real data example is used to illustrate the usefulness of the approach. PMID:20549344

  18. Lakeshore zoning has heterogeneous ecological effects: an application of a coupled economic-ecological model.

    PubMed

    Butsic, Van; Lewis, David J; Radeloff, Volker C

    2010-04-01

    Housing growth has been widely shown to be negatively correlated with wildlife populations, avian richness, anadromous fish, and exotic invasion. Zoning is the most frequently used public policy to manage housing development and is often motivated by a desire to protect the environment. Zoning is also pervasive, taking place in all 50 states. One relevant question that has received little research concerns the effectiveness of zoning to meet ecological goals. In this paper, we examined whether minimum frontage zoning policies have made a positive impact on the lakes they were aimed to protect in Vilas County, Wisconsin, U.S.A. We used an economic model that estimated when a given lot will be subdivided and how many new lots will be created as a function of zoning. Using the economic model, we simulated the effects of multiple zoning scenarios on lakeshore development. The simulated development patterns were then input to ecological models that predicted the amount of coarse woody debris (CWD) and the growth rate of bluegills as a function of residential density. Comparison of the ecological outcomes under different simulated zoning scenarios quantified the effect of zoning policies on residential density, CWD, and bluegill growth rates. Our results showed that zoning significantly affected residential density, CWD counts, and bluegill growth rates across our study area, although the effect was less clear at the scale of individual lake. Our results suggest that homogeneous zoning (i.e., for a county) is likely to have mixed results when applied to a heterogeneous landscape. Further, our results suggest that zoning regimes with a higher minimum shoreline frontage are likely to have larger ecological effects when applied to lakes that are less developed.

  19. Prenatal growth stages show the development of the ruminant bony labyrinth and petrosal bone.

    PubMed

    Costeur, Loïc; Mennecart, Bastien; Müller, Bert; Schulz, Georg

    2017-02-01

    Foetuses are a source of scientific information to understand the development and evolution of anatomical structures. The bony labyrinth, surrounding the organ of balance and hearing, is a phylogenetically and ecologically informative structure for which still little concerning growth and shape variability is known in many groups of vertebrates. Except in humans, it is poorly known in many other placentals and its prenatal growth has almost never been studied. Ruminants are a diversified group of placentals and represent an interesting case study to understand the prenatal growth of the ear region. We computed tomography -scanned five cow foetuses and an adult petrosal bone (Bos taurus, Artiodactyla, Mammalia), and describe the bony labyrinth when already ossified. The foetuses encompass the second half of the 9.3-month-long gestation period of the cow. They were sampled at different ontogenetic stages to understand how and when the petrosal bone and bony labyrinth ossify in ruminants. The petrosal bone and bony labyrinth ossify within about 20 days in the fourth month of gestation. The bony labyrinth is already fully ossified at least in the 6th month, while only the cochlea, most of the vestibule and the common crus are already ossified at the beginning of the 4th month. The pars canalicularis of the petrosal thus ossifies at last. The size and volume of the bony labyrinth stay similar from the 6th month (possibly even from the 5th). From the end of the 4th month of gestation, a progressive lengthening of the cochlear aqueduct and endolymphatic sac occurs, culminating in the adult form and partly explaining the larger volume of the later. The inner ear in the cow ossifies quickly during the gestation period, being fully ossified around mid-gestation time, as in humans. The adult size and most of its volume are reached by mid-gestation time while the petrosal bone and skull still grow. A negative ontogenetic allometry between the bony labyrinth and the petrosal

  20. The Effect of Point-spread Function Interaction with Radiance from Heterogeneous Scenes on Multitemporal Signature Analysis. [soybean stress

    NASA Technical Reports Server (NTRS)

    Duggin, M. J.; Schoch, L. B.

    1984-01-01

    The point-spread function is an important factor in determining the nature of feature types on the basis of multispectral recorded radiance, particularly from heterogeneous scenes and particularly from scenes which are imaged repetitively, in order to provide thematic characterization by means of multitemporal signature. To demonstrate the effect of the interaction of scene heterogeneity with the point spread function (PSF)1, a template was constructed from the line spread function (LSF) data for the thematic mapper photoflight model. The template was in 0.25 (nominal) pixel increments in the scan line direction across three scenes of different heterogeneity. The sensor output was calculated by considering the calculated scene radiance from each scene element occurring between the contours of the PSF template, plotted on a movable mylar sheet while it was located at a given position.

  1. Development of kink bands in granodiorite: Effect of mechanical heterogeneities, fault geometry, and friction

    NASA Astrophysics Data System (ADS)

    Chheda, T. D.; Nevitt, J. M.; Pollard, D. D.

    2014-12-01

    The formation of monoclinal right-lateral kink bands in Lake Edison granodiorite (central Sierra Nevada, CA) is investigated through field observations and mechanics based numerical modeling. Vertical faults act as weak surfaces within the granodiorite, and vertical granodiorite slabs bounded by closely-spaced faults curve into a kink. Leucocratic dikes are observed in association with kinking. Measurements were made on maps of Hilgard, Waterfall, Trail Fork, Kip Camp (Pollard and Segall, 1983b) and Bear Creek kink bands (Martel, 1998). Outcrop scale geometric parameters such as fault length andspacing, kink angle, and dike width are used to construct a representative geometry to be used in a finite element model. Three orders of fault were classified, length = 1.8, 7.2 and 28.8 m, and spacing = 0.3, 1.2 and 3.6 m, respectively. The model faults are oriented at 25° to the direction of shortening (horizontal most compressive stress), consistent with measurements of wing crack orientations in the field area. The model also includes a vertical leucocratic dike, oriented perpendicular to the faults and with material properties consistent with aplite. Curvature of the deformed faults across the kink band was used to compare the effects of material properties, strain, and fault and dike geometry. Model results indicate that the presence of the dike, which provides a mechanical heterogeneity, is critical to kinking in these rocks. Keeping properties of the model granodiorite constant, curvature increased with decrease in yield strength and Young's modulus of the dike. Curvature increased significantly as yield strength decreased from 95 to 90 MPa, and below this threshold value, limb rotation for the kink band was restricted to the dike. Changing Poisson's ratio had no significant effect. The addition of small faults between bounding faults, decreasing fault spacing or increasing dike width increases the curvature. Increasing friction along the faults decreases slip, so

  2. Effective grid-dependent dispersion coefficient for conservative and reactive transport simulations in heterogeneous porous media

    NASA Astrophysics Data System (ADS)

    Cortinez, J. M.; Valocchi, A. J.; Herrera, P. A.

    2013-12-01

    Because of the finite size of numerical grids, it is very difficult to correctly account for processes that occur at different spatial scales to accurately simulate the migration of conservative and reactive compounds dissolved in groundwater. In one hand, transport processes in heterogeneous porous media are controlled by local-scale dispersion associated to transport processes at the pore-scale. On the other hand, variations of velocity at the continuum- or Darcy-scale produce spreading of the contaminant plume, which is referred to as macro-dispersion. Furthermore, under some conditions both effects interact, so that spreading may enhance the action of local-scale dispersion resulting in higher mixing, dilution and reaction rates. Traditionally, transport processes at different spatial scales have been included in numerical simulations by using a single dispersion coefficient. This approach implicitly assumes that the separate effects of local-dispersion and macro-dispersion can be added and represented by a unique effective dispersion coefficient. Moreover, the selection of the effective dispersion coefficient for numerical simulations usually do not consider the filtering effect of the grid size over the small-scale flow features. We have developed a multi-scale Lagragian numerical method that allows using two different dispersion coefficients to represent local- and macro-scale dispersion. This technique considers fluid particles that carry solute mass and whose locations evolve according to a deterministic component given by the grid-scale velocity and a stochastic component that corresponds to a block-effective macro-dispersion coefficient. Mass transfer between particles due to local-scale dispersion is approximated by a meshless method. We use our model to test under which transport conditions the combined effect of local- and macro-dispersion are additive and can be represented by a single effective dispersion coefficient. We also demonstrate that for

  3. The Effect of Incorporation of HNO(sub 3) Into Liquid Sulfuric Acid on Heterogeneous Reaction Probabilities

    NASA Technical Reports Server (NTRS)

    Zhang, R.; Leu, M-T.; Keyser, L.

    1994-01-01

    Using a fast-flow reactor coupled to a quadrupole mass spectrometer, the heterogeneous reactions of C1ONO2 + HCl and HOCl + HCl as well as hydrolysis of N2O5 and C1ONO2 were investigated on liquid sulfuric acid, with particular emphasis on the effect of incorporation of HNO3 on the reaction probabilities.

  4. Expanding the Scope of Mindfulness-Based Cognitive Therapy: Evidence for Effectiveness in a Heterogeneous Psychiatric Sample

    ERIC Educational Resources Information Center

    Green, Sheryl M.; Bieling, Peter J.

    2012-01-01

    Mindfulness-based interventions (e.g., MBSR; Kabat-Zinn, 1990; MBCT; Segal, Williams, & Teasdale, 2002) have demonstrated effectiveness in a number of distinct clinical populations. However, few studies have evaluated MBCT within a heterogeneous group of psychiatric adult outpatients. This study examined whether a wider variety of patients…

  5. Systematic Analysis of the Effect of Small Scale Permeability Heterogeneity on Hyporheic Exchange Flux and Residence Times

    NASA Astrophysics Data System (ADS)

    Laube, G.; Schmidt, C.; Fleckenstein, J. H.

    2014-12-01

    The hyporheic zone (HZ) contributes significantly to whole stream biogeochemical cycling. Biogeochemical reactions within the HZ are often transport limited, thus, understanding these reactions requires knowledge about the magnitude of hyporheic fluxes (HF) and the residence time (RT) of these fluxes within the HZ. While the hydraulics of HF are relatively well understood, studies addressing the influence of permeability heterogeneity lack systematic analysis and have even produced contradictory results (e.g. [1] vs. [2]). In order to close this gap, this study uses a statistical numerical approach to elucidate the influence of permeability heterogeneity on HF and RT. We simulated and evaluated 3750 2D-scenarios of sediment heterogeneity by means of Gaussian random fields with focus on total HF and RT distribution. The scenarios were based on ten realizations of each of all possible combinations of 15 different correlation lengths, 5 dipping angles and 5 permeability variances. Roughly 500 hyporheic stream traces were analyzed per simulation, for a total of almost two million stream traces analyzed for correlations between permeability heterogeneity, HF, and RT. Total HF and the RT variance positively correlated with permeability variance while the mean RT negatively correlated with permeability variance. In contrast, changes in correlation lengths and dipping angles had little effect on the examined properties RT and HF. These results provide a possible explanation of the seemingly contradictory conclusions of recent studies, given that the permeability variances in these studies differ by several orders of magnitude. [1] Bardini, L., Boano, F., Cardenas, M.B, Sawyer, A.H, Revelli, R. and Ridolfi, L. "Small-Scale Permeability Heterogeneity Has Negligible Effects on Nutrient Cycling in Streambeds." Geophysical Research Letters, 2013. doi:10.1002/grl.50224. [2] Zhou, Y., Ritzi, R. W., Soltanian, M. R. and Dominic, D. F. "The Influence of Streambed Heterogeneity on

  6. First Record of Eocene Bony Fishes and Crocodyliforms from Canada’s Western Arctic

    PubMed Central

    Eberle, Jaelyn J.; Gottfried, Michael D.; Hutchison, J. Howard; Brochu, Christopher A.

    2014-01-01

    Background Discovery of Eocene non-marine vertebrates, including crocodylians, turtles, bony fishes, and mammals in Canada’s High Arctic was a critical paleontological contribution of the last century because it indicated that this region of the Arctic had been mild, temperate, and ice-free during the early – middle Eocene (∼53–50 Ma), despite being well above the Arctic Circle. To date, these discoveries have been restricted to Canada’s easternmost Arctic – Ellesmere and Axel Heiberg Islands (Nunavut). Although temporally correlative strata crop out over 1,000 km west, on Canada’s westernmost Arctic Island – Banks Island, Northwest Territories – they have been interpreted as predominantly marine. We document the first Eocene bony fish and crocodyliform fossils from Banks Island. Principal Findings We describe fossils of bony fishes, including lepisosteid (Atractosteus), esocid (pike), and amiid, and a crocodyliform, from lower – middle Eocene strata of the Cyclic Member, Eureka Sound Formation within Aulavik National Park (∼76°N. paleolat.). Palynology suggests the sediments are late early to middle Eocene in age, and likely spanned the Early Eocene Climatic Optimum (EECO). Conclusions/Significance These fossils extend the geographic range of Eocene Arctic lepisosteids, esocids, amiids, and crocodyliforms west by approximately 40° of longitude or ∼1100 km. The low diversity bony fish fauna, at least at the family level, is essentially identical on Ellesmere and Banks Islands, suggesting a pan-High Arctic bony fish fauna of relatively basal groups around the margin of the Eocene Arctic Ocean. From a paleoclimatic perspective, presence of a crocodyliform, gar and amiid fishes on northern Banks provides further evidence that mild, year-round temperatures extended across the Canadian Arctic during early – middle Eocene time. Additionally, the Banks Island crocodyliform is consistent with the phylogenetic hypothesis of a Paleogene divergence

  7. Treatment effect heterogeneity for univariate subgroups in clinical trials: Shrinkage, standardization, or else.

    PubMed

    Varadhan, Ravi; Wang, Sue-Jane

    2016-01-01

    Treatment effect heterogeneity is a well-recognized phenomenon in randomized controlled clinical trials. In this paper, we discuss subgroup analyses with prespecified subgroups of clinical or biological importance. We explore various alternatives to the naive (the traditional univariate) subgroup analyses to address the issues of multiplicity and confounding. Specifically, we consider a model-based Bayesian shrinkage (Bayes-DS) and a nonparametric, empirical Bayes shrinkage approach (Emp-Bayes) to temper the optimism of traditional univariate subgroup analyses; a standardization approach (standardization) that accounts for correlation between baseline covariates; and a model-based maximum likelihood estimation (MLE) approach. The Bayes-DS and Emp-Bayes methods model the variation in subgroup-specific treatment effect rather than testing the null hypothesis of no difference between subgroups. The standardization approach addresses the issue of confounding in subgroup analyses. The MLE approach is considered only for comparison in simulation studies as the "truth" since the data were generated from the same model. Using the characteristics of a hypothetical large outcome trial, we perform simulation studies and articulate the utilities and potential limitations of these estimators. Simulation results indicate that Bayes-DS and Emp-Bayes can protect against optimism present in the naïve approach. Due to its simplicity, the naïve approach should be the reference for reporting univariate subgroup-specific treatment effect estimates from exploratory subgroup analyses. Standardization, although it tends to have a larger variance, is suggested when it is important to address the confounding of univariate subgroup effects due to correlation between baseline covariates. The Bayes-DS approach is available as an R package (DSBayes).

  8. Effect of droplet size distribution on reaction heat in a liquid-liquid heterogeneous reaction process.

    PubMed

    Yasuhiro, Fujimoto

    2004-11-11

    In heterogeneous liquid-liquid reaction processes, explosions have been reported. An aim of this study is to simulate the accident stories, which might be caused by inappropriate mixing conditions in the heterogeneous reaction process. The reaction of water-insoluble anhydride and water was selected as a model process. The experimental trend data of droplet size with agitation in a batch reactor were fitted to an empirical equation. The good fittings show the applicability of the equation in our reaction conditions.

  9. Effects of Heterogeneity on Transport of Graphene Oxide in Saturated and Unsaturated Porous Media

    NASA Astrophysics Data System (ADS)

    Dong, S.; Sun, Y.; Shi, X.; Wu, J.; Gao, B.

    2015-12-01

    Graphene oxide (GO) has received increasing attention in many fields with its wide applications and rapid growth in production. Therefore, it is expected that GO nanoparticles will inevitably be released into the subsurface and cause the environmental risk subsequently. In view of this, knowledge of the fate for GO in the vadose zone and groundwater systems is indispensable. So far most research has focused on the deposition and transport of GO nanoparticles in one-dimensional homogenous porous media; nonetheless, the complex heterogeneous system is extensively distributed in natural subsurface environment and may not be well represented by the homogeneous packed columns. However, little investigations have been directed toward understanding the transport of GO in heterogeneous porous media. The overarching objective of this study is to advance current understanding of GO transport in structured heterogeneous porous media. The saturated and unsaturated columns packed with different sand combinations and solution ionic strength, were used to examine the breakthrough behavior of GO in heterogeneous porous media. A two-domain model considering GO exchange between zones was developed to describe GO transport in structured, heterogeneous porous media. The experimental data indicate that volumetric moisture content and water flow are the critical factors that control GO transport in heterogeneous porous media. And higher ionic strength decrease the mobility of GO particles in both saturated and unsaturated heterogeneous pore media. Simulations of this two-domain nanoparticle transport model matched experimental breakthrough data well for all the experimental conditions. Experimental and model results show that under saturated conditions, both fast-flow and slow-flow domains affect colloid transport in heterogeneous media. Under unsaturated conditions, however, our results indicate that flows in the fast flow domain dominate the colloid transport and retention processes.

  10. The Effect of a Heterogeneous Thin Electrically Conducting Lower Mantle Layer on Secular Variation in the Geodynamo

    NASA Astrophysics Data System (ADS)

    Vilim, R.; Dumberry, M.; Stanley, S.

    2013-12-01

    Recent studies have shown that the rate of secular variation is not constant over the Earth. Particularly, the Pacific Ocean is remarkably devoid of any quickly time varying magnetic field components. While this could be due to factors intrinsic to the dynamo, the Earth's lowest mantle displays a remarkable heterogeneity that could also help explain the pattern of secular variation if this deep mantle heterogeneity can couple to the dynamo. There have been several recent studies that discuss the possibility of an electrically conducting lower mantle, either because of the metallization of FeO, or from the deep penetration of iron into the mantle due to morphological instabilities. If a thin lower mantle layer is heterogeneous in electrical conductivity it could couple to the flow via the Lorenz force and brake the eddies which contribute to secular variation, lowering both the field amplitude and the rate of secular variation. A conducting mantle layer will also preferentially damp the quickly time varying components of the magnetic field via the electromagnetic screening effect, reducing the secular variation we observe at the surface of the Earth. While other studies have investigated the thermal effects of a heterogeneous lower mantle on the dynamo, we investigate the effects of a thin electrically conducting lower mantle layer. We use a numerical geodynamo model to determine whether this layer can cause the spatial pattern of secular variation rates observed for the Earth.

  11. Pyrite cinder as a cost-effective heterogeneous catalyst in heterogeneous Fenton reaction: decomposition of H(2)O(2) and degradation of Acid Red B.

    PubMed

    Wu, Deli; Liu, Yanxia; Duan, Dong; Ma, Luming

    2014-01-01

    Pyrite cinder (PyC) was employed as a heterogeneous Fenton-like catalyst, and its catalytic activity was evaluated in view of the effects of catalyst dosage, pH and leaching metal ions. PyC showed significant reactivity, and the pseudo-first-order kinetic rate constant for decomposition of H(2)O(2) and degradation of Acid Red B (ARB) were 3.4 and 14.89 (10⁻³ min⁻¹) respectively when pH = 5. When 20 g/L PyC was added into 10 mM H(2)O(2) solution in neutral pH, H(2)O(2) could be completely degraded within 4 h, and more than 90% ARB was removed. Leaching metal ions from PyC were found to have little effect on decomposition of H(2)O(2) or on degradation of ARB. PyC still had high catalytic activity after five successive runs. The decomposition mechanism of H(2)O(2) was analyzed and the Haber-Weiss mechanism was employed in this paper. The electron spin resonance image showed •OH was produced and increased between 3 and 5 min in the PyC catalyzing H(2)O(2) reaction, which demonstrated that PyC had a durable ability to produce •OH.

  12. Effects of physical and chemical heterogeneity on water-quality samples obtained from wells

    USGS Publications Warehouse

    Reilly, Thomas E.; Gibs, Jacob

    1993-01-01

    Factors that affect the mass of chemical constituents entering a well include the distributions of flow rate and chemical concentrations along and near the screened or open section of the well. Assuming a layered porous medium (with each layer being characterized by a uniform hydraulic conductivity and chemical concentration), a knowledge of the flow from each layer along the screened zone and of the chemical concentrations in each layer enables the total mass entering the well to be determined. Analyses of hypothetical systems and a site at Galloway, NJ, provide insight into the temporal variation of water-quality data observed when withdrawing water from screened wells in heterogeneous ground-water systems.The analyses of hypothetical systems quantitatively indicate the cause-and-effect relations that cause temporal variability in water samples obtained from wells. Chemical constituents that have relatively uniform concentrations with depth may not show variations in concentrations in the water discharged from a well after the well is purged (evacuation of standing water in the well casing). However, chemical constituents that do not have uniform concentrations near the screened interval of the well may show variations in concentrations in the well discharge water after purging because of the physics of ground-water flow in the vicinity of the screen.Water-quality samples were obtained through time over a 30 minute period from a site at Galloway, NJ. The water samples were analyzed for aromatic hydrocarbons, and the data for benzene, toluene, and meta+para xylene were evaluated for temporal variations. Samples were taken from seven discrete zones, and the flow-weighted concentrations of benzene, toluene, and meta+para xylene all indicate an increase in concentration over time during pumping. These observed trends in time were reproduced numerically based on the estimated concentration distribution in the aquifer and the flow rates from each zone.The results of

  13. The Effect of Spatial Heterogeneities on Nucleation Kinetics in Amorphous Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Shen, Ye

    The mechanical property of the Al based metallic glass could be enhanced significantly by introducing the high number density of Al-fcc nanocrystals (1021 ˜1023 m-3) to the amorphous matrix through annealing treatments, which motivates the study of the nucleation kinetics for the microstructure control. With the presence of a high number density (1025 m-3) of aluminum-like medium range order (MRO), the Al-Y-Fe metallic glass is considered to be spatially heterogeneous. Combining the classical nucleation theory with the structural configuration, a MRO seeded nucleation model has been proposed and yields theoretical steady state nucleation rates consistent with the experimental results. In addition, this model satisfies all the thermodynamic and kinetic constraints to be reasonable. Compared with the Al-Y-Fe system, the primary crystallization onset temperature decreases significantly and the transient delay time (tau) is shorter in the Al-Y-Fe-Pb(In) systems because the insoluble Pb and In nanoparticles in the amorphous matrix served as extrinsic spatial heterogeneity to provide the nucleation sites for Al-fcc precipitation and the high-resolution transmission electron microscopy (HRTEM) images of the Pb-Al interface revealed a good wetting behavior between the Al and Pb nanoparticles. The study of the transient delay time (tau) could provide insight on the transport behavior during the nucleation and a more convenient approach to evaluate the delay time has been developed by measuring the Al-Y-Fe amorphous alloy glass transition temperature (Tg) shift with the increasing annealing time (tannealing) in FlashDSC. The break point in the Tg vs. log(tannealing) plot has been identified to correspond to the delay time by the TEM characterization. FlashDSC tests with different heating rates and different compositions (Al-Y-Fe-Pb and Zn-Mg-Ca-Yb amorphous alloys) further confirmed the break point and delay time relationship. The amorphous matrix composition and the

  14. The effect of spatial heterogenity on the aggregation of ticks on white-footed mice

    PubMed Central

    Devevey, G.; Brisson, D.

    2013-01-01

    SUMMARY Parasites are often aggregated on a minority of the individuals in their host populations. Although host characteristics are commonly presumed to explain parasite aggregation on hosts, spatio-temporal aggregation of parasites during their host-seeking stages may have a dominant effect on the aggregation on hosts. We aimed to quantify, using mixed models, repeatability and autocorrelation analyses, the degree to which the aggregation of blacklegged ticks (Ixodes scapularis) on white-footed mice (Peromyscus leucopus) is influenced by spatio-temporal distributions of the host-seeking ticks and by heterogeneity among mice. Host-seeking ticks were spatially aggregated at both the larval and nymphal life-stages. However, this spatial aggregation accounted for little of the variation in larval and nymphal burdens observed on mice (3% and 0%, respectively). Conversely, mouse identity accounted for a substantial proportion of the variance in tick burdens. Mouse identity was a significant explanatory factor as the majority of ticks parasitized a consistent set of mice throughout the activity seasons. Of the characteristics associated with mouse identity investigated, only gender affected larval burdens, and body mass and home range sizes in males were correlated with nymphal burdens. These analyses suggest that aggregation of ticks on a minority of mice does not result from the distribution of host-seeking ticks but from characteristics of the hosts. PMID:22409977

  15. Effect of chemical heterogeneity on photoluminescence of graphite oxide treated with S-/N-containing modifiers

    NASA Astrophysics Data System (ADS)

    Ebrahim, Amani M.; Rodríguez-Castellón, Enrique; Montenegro, José María; Bandosz, Teresa J.

    2015-03-01

    Graphite oxide (GO) obtained using Hummers method was modified by hydrothermal treatment either with sulfanilic acid or polystyrene (3-ammonium) sulfonate at 100 °C or 85 °C, respectively. Both modifiers contain sulfur in the oxidized forms and nitrogen in the reduced forms. The materials were characterized using FTIR, XPS, thermal analysis, potentiometric titration and SEM. Their photoluminescent properties and their alteration with an addition of Ag+ were also measured. As a result of these modifications nitrogen was introduced to the graphene layers as amines, imides, amides, and sulfur as sulfones and sulfonic acids. Moreover, the presence of polyaniline was detected. This significantly affected the polarity, acid-base character, and conductivity of the materials. Apparently carboxylic groups of GO were involved in the surface reactions. The modified GOs lost their layered structure and the modifications resulted in the high degree of structural and chemical heterogeneity. Photoluminescence in visible light was recorded and linked to the presence of heteroatoms. For the polystyrene (3-ammonium) sulfonate modified sample addition of Ag+ quenched the photoluminescence at low wavelength showing sensitivity as a possible optical detector. No apparent effect was found for the sulfanilic acid modified sample.

  16. Effects of electrical heterogeneity on transmural reentry during acute global ischemia.

    PubMed

    Zhang, Hong; Jin, Yin-Bin; Zhang, Zhen-Xi; Yang, Lin; Huang, Ye-Cho

    2010-03-01

    Ventricular arrhythmias are commonly observed in patients with ischemia. It is reported that the electrophysiological changes evoked by ischemia are greater in the epicardium than in the endocardium. To investigate the effects of this heterogeneity on transmural reentry, the computer simulation method is used. A two-dimensional model which can reproduce the endocardial, epicardial and middle cell types, approximate the ischemic characteristics and distribution of the ischemic severity is developed by setting different ratios of the maximum conductance of the rapid and slow inward rectifier potassium currents and considering the three major component conditions of acute ischemia at the ionic level. The results demonstrate that action potentials of the ischemic cells have elevated resting potential, shortened duration, slowed upstroke and declined amplitude. Conduction velocity is much more depressed in the epicardium because of the ischemia-induced transmural gradient of excitability. The epicardially initiated activation has wider vulnerable window and more possibility to cause unidirectional propagation even reentry. Dispersion of the excitability is proposed to be the underlying mechanism.

  17. Specificity and Heterogeneity of Terahertz Radiation Effect on Gene Expression in Mouse Mesenchymal Stem Cells

    DOE PAGES

    Alexandrov, Boian S.; Phipps, M. Lisa; Alexandrov, Ludmil B.; ...

    2013-01-31

    In this paper, we report that terahertz (THz) irradiation of mouse mesenchymal stem cells (mMSCs) with a single-frequency (SF) 2.52 THz laser or pulsed broadband (centered at 10 THz) source results in irradiation specific heterogenic changes in gene expression. The THz effect depends on irradiation parameters such as the duration and type of THz source, and on the degree of stem cell differentiation. Our microarray survey and RT-PCR experiments demonstrate that prolonged broadband THz irradiation drives mMSCs toward differentiation, while 2-hour irradiation (regardless of THz sources) affects genes transcriptionally active in pluripotent stem cells. The strictly controlled experimental environment indicatesmore » minimal temperature changes and the absence of any discernable response to heat shock and cellular stress genes imply a non-thermal response. Computer simulations of the core promoters of two pluripotency markers reveal association between gene upregulation and propensity for DNA breathing. Finally, we propose that THz radiation has potential for non-contact control of cellular gene expression.« less

  18. Specificity and Heterogeneity of Terahertz Radiation Effect on Gene Expression in Mouse Mesenchymal Stem Cells

    PubMed Central

    Alexandrov, Boian S.; Phipps, M. Lisa; Alexandrov, Ludmil B.; Booshehri, Layla G.; Erat, Anna; Zabolotny, Janice; Mielke, Charles H.; Chen, Hou-Tong; Rodriguez, George; Rasmussen, Kim Ø.; Martinez, Jennifer S.; Bishop, Alan R.; Usheva, Anny

    2013-01-01

    We report that terahertz (THz) irradiation of mouse mesenchymal stem cells (mMSCs) with a single-frequency (SF) 2.52 THz laser or pulsed broadband (centered at 10 THz) source results in irradiation specific heterogenic changes in gene expression. The THz effect depends on irradiation parameters such as the duration and type of THz source, and on the degree of stem cell differentiation. Our microarray survey and RT-PCR experiments demonstrate that prolonged broadband THz irradiation drives mMSCs toward differentiation, while 2-hour irradiation (regardless of THz sources) affects genes transcriptionally active in pluripotent stem cells. The strictly controlled experimental environment indicates minimal temperature changes and the absence of any discernable response to heat shock and cellular stress genes imply a non-thermal response. Computer simulations of the core promoters of two pluripotency markers reveal association between gene upregulation and propensity for DNA breathing. We propose that THz radiation has potential for non-contact control of cellular gene expression. PMID:23378916

  19. Scheduling in Heterogeneous Grid Environments: The Effects of DataMigration

    SciTech Connect

    Oliker, Leonid; Biswas, Rupak; Shan, Hongzhang; Smith, Warren

    2004-01-01

    Computational grids have the potential for solving large-scale scientific problems using heterogeneous and geographically distributed resources. However, a number of major technical hurdles must be overcome before this goal can be fully realized. One problem critical to the effective utilization of computational grids is efficient job scheduling. Our prior work addressed this challenge by defining a grid scheduling architecture and several job migration strategies. The focus of this study is to explore the impact of data migration under a variety of demanding grid conditions. We evaluate our grid scheduling algorithms by simulating compute servers, various groupings of servers into sites, and inter-server networks, using real workloads obtained from leading supercomputing centers. Several key performance metrics are used to compare the behavior of our algorithms against reference local and centralized scheduling schemes. Results show the tremendous benefits of grid scheduling, even in the presence of input/output data migration - while highlighting the importance of utilizing communication-aware scheduling schemes.

  20. Cost-effective hydraulic tomography surveys for predicting flow and transport in heterogeneous aquifers.

    PubMed

    Ni, Chuen-Fa; Yeh, Tian-Chyi Jim; Chent, Jui-Sheng

    2009-05-15

    This study shows how a cost-effective hydraulic tomography survey (HTS) and the associated data estimator can be used to characterize flow and transport in heterogeneous aquifers. The HTS is an improved field hydraulic test that accounts for responses of hydraulic stresses caused by pumping or injection events at different locations of an aquifer. A sequential data assimilation method based on a cokriging algorithm is then used to map the aquifer hydraulic conductivity (K). This study uses a synthetic two-dimensional aquifer to assess the accuracy of predicted concentration breakthrough curves (BTCs) on the basis of the Kfields estimated by geometric mean, kriging, and HTS. Such Kfields represent different degrees of flow resolutions as compared with the synthetically generated one. Without intensive experimentsto calibrate accurate dispersivities at sites, the flow field based on the HTS Kfield can yield accurate predictions of BTC peaks and phases. On the basis of calculating mean absolute and square errors for estimated K fields, numerical assessments on the HTS operation strategy show that more pumping events will generally lead to more accurate estimations of Kfields, and the pump locations need to be installed in high Kzones to maximize the delivery of head information from pumps to measurement points. Additionally, the appropriate distances of installed wells are suggested to be less than one-third of the ln(K) correlation length in x direction.

  1. Effect of alkali cations on heterogeneous photo-Fenton process mediated by Prussian blue colloids.

    PubMed

    Liu, Shou-Qing; Cheng, Shi; Feng, Lian-Rong; Wang, Xiao-Mei; Chen, Zhi-Gang

    2010-10-15

    This article evaluates Prussian blue (iron hexacyanoferrate) colloids as a heterogeneous photo-Fenton catalyst for the degradation of Rhodamine B. The emphasis is laid on the effects of alkali metal cations on the photo-Fenton process. The facts show that alkali cations strongly affect the degradation rate of organic species. The degradation rates of Rhodamine B, Malachite Green, and Methyl Orange in the presence of KCl, KNO(3), and K(2)SO(4), respectively, are faster than their degradation rates in the presence of the corresponding sodium salts. The average degradation rates of Rhodamine B in 0.2 M KCl, NaCl, RbCl, and CsCl solution, decline in sequence, and the rate in KCl solution is greater than that without any salt added deliberately. Thus, potassium ions accelerate the degradation rate, but sodium, rubidium, and cesium ions slow the rate. The order of the rates is R(K)>R>R(Na)>R(Rb)>R(Cs), which is consistent with that of the voltammetric oxidation currents of Prussian blue in the corresponding cation solutions. This phenomenon is attributed to the molecular recognition of the microstructure in Prussian blue nanoparticles to the alkali cations. The reaction mechanism of the photo-Fenton process has also been explored.

  2. Specificity and Heterogeneity of Terahertz Radiation Effect on Gene Expression in Mouse Mesenchymal Stem Cells

    SciTech Connect

    Alexandrov, Boian S.; Phipps, M. Lisa; Alexandrov, Ludmil B.; Booshehri, Layla G.; Erat, Anna; Zabolotny, Janice; Mielke, Charles H.; Chen, Hou-Tong; Rodriguez, George; Rasmussen, Kim O.; Martinez, Jennifer S.; Bishop, Alan R.; Usheva, Anny

    2013-01-31

    In this paper, we report that terahertz (THz) irradiation of mouse mesenchymal stem cells (mMSCs) with a single-frequency (SF) 2.52 THz laser or pulsed broadband (centered at 10 THz) source results in irradiation specific heterogenic changes in gene expression. The THz effect depends on irradiation parameters such as the duration and type of THz source, and on the degree of stem cell differentiation. Our microarray survey and RT-PCR experiments demonstrate that prolonged broadband THz irradiation drives mMSCs toward differentiation, while 2-hour irradiation (regardless of THz sources) affects genes transcriptionally active in pluripotent stem cells. The strictly controlled experimental environment indicates minimal temperature changes and the absence of any discernable response to heat shock and cellular stress genes imply a non-thermal response. Computer simulations of the core promoters of two pluripotency markers reveal association between gene upregulation and propensity for DNA breathing. Finally, we propose that THz radiation has potential for non-contact control of cellular gene expression.

  3. Autosomal dominant ataxia: Genetic evidence for locus heterogeneity from a cuban founder-effect population

    PubMed Central

    Auburger, Georg; Diaz, Guillermo Orozco; Capote, Raul Ferreira; Sanchez, Suzana Gispert; Perez, Marta Paradoa; del Cueto, Marianela Estrada; Meneses, Mirna Garcia; Farrall, Martin; Williamson, Robert; Chamberlain, Susan; Baute, Luis Heredero

    1990-01-01

    The locus for autosomal dominant ataxia with a diagnosis of olivo-ponto-cerebellar atrophy at autopsy has been previously assigned to chromosome 6p. However, evidence for two alternative locations has been reported. We have recently described a large potential founder-effect population of such patients in the Holguin province of Cuba. With an estimated 1,000 patients available for analysis, this extensive cluster of families provides a unique opportunity for the definitive localization of the genetic mutation. Linkage analysis between the disease locus in this population and markers within and flanking the HLA region on chromosome 6 were undertaken in 12 families comprising over 100 affected individuals. Despite similarity in the clinical phenotype between those families where the disease locus has been reported to be linked to the HLA locus and the Cuban patients, no evidence of linkage to this region could be demonstrated in the latter. The disease locus was excluded from a 96-cM genetic interval of the short arm of chromosome 6, encompassing the F13A1–HLA–GLO1–MUT/D6S4 loci. These data strongly support the existence of genetic heterogeneity for the disease. PMID:1971152

  4. Methylparaben removal using heterogeneous photocatalysis: effect of operational parameters and mineralization/biodegradability studies.

    PubMed

    Zúñiga-Benítez, Henry; Peñuela, Gustavo A

    2016-03-18

    Methylparaben (MePB) is an organic compound employed mainly in the manufacture of different personal care products. However, it has been recently listed as a potential endocrine disrupter chemical. Therefore, the main objective of this work was to evaluate the degradation of MePB in aqueous solutions using heterogeneous photocatalysis with TiO2 and hydrogen peroxide. In this way, effects of pH and the initial concentrations of catalyst, H2O2, and pollutant on treatment were analyzed. A face centered, central composite design was used for determination of the influence of each parameter in the process and the conditions under which the pollutant suffers the highest rates of degradation were selected. In general, results indicate that combination TiO2/H2O2/light irradiation leads to ∼90 % of substrate removal after 30 min of reaction and that hydroxyl free radicals are the main specie responsible for organic matter elimination. Finally, in terms of mineralization and biodegradability, experimental results indicated that part of the organic matter was transformed into CO2 and water and the photo-treatment promoted an increase in samples biodegradability.

  5. Targeting P38 Pathway Regulates Bony Formation via MSC Recruitment during Mandibular Distraction Osteogenesis in Rats

    PubMed Central

    Yang, Zi-hui; Wu, Bao-lei; Ye, Chen; Jia, Sen; Yang, Xin-jie; Hou, Rui; Lei, De-lin; Wang, Lei

    2016-01-01

    Distraction osteogenesis (DO) is a widely used self-tissue engineering. However, complications and discomfort due to the long treatment period are still the bottleneck of DO. Novel strategies to accelerate bone formation in DO are still needed. P38 is capable of regulating the osteogenic differentiation of both mesenchymal stem cells (MSCs) and osteoblasts, which are crucial to bone regeneration. However, it is not clear whether targeting p38 could regulate bony formation in DO. The purpose of the current work was to investigate the effects of local application of either p38 agonist anisomycin or p38 inhibitor SB203580 in a rat model of DO. 30 adult rats were randomly divided into 3 groups: (A) rats injected with DMSO served as the control group; (B) rats injected with p38 agonist anisomycin; (C) rats injected with p38 inhibitor SB203580. All the rats were subjected to mandibular distraction and the injection was performed daily during this period. The distracted mandibles were harvested on days 15 and 30 after surgery and subjected to the following analysis. Micro-computed tomography and histological evaluation results showed that local application of p38 agonist anisomycin increased new bone formation in DO, whereas p38 inhibitor SB203580 decreased it. Immunohistochemical analysis suggested that anisomycin promoted MSC recruitment in the distraction gap. In conclusion, this study demonstrated that local application of p38 agonist anisomycin can increase new bone formation during DO. This study may lead to a novel cell-based strategy for the improvement of bone regeneration. PMID:27766028

  6. Endocrine and Local IGF-I in the Bony Fish Immune System

    PubMed Central

    Franz, Anne-Constance; Faass, Oliver; Köllner, Bernd; Shved, Natallia; Link, Karl; Casanova, Ayako; Wenger, Michael; D’Cotta, Helena; Baroiller, Jean-François; Ullrich, Oliver; Reinecke, Manfred; Eppler, Elisabeth

    2016-01-01

    A role for GH and IGF-I in the modulation of the immune system has been under discussion for decades. Generally, GH is considered a stimulator of innate immune parameters in mammals and teleost fish. The stimulatory effects in humans as well as in bony fish often appear to be correlated with elevated endocrine IGF-I (liver-derived), which has also been shown to be suppressed during infection in some studies. Nevertheless, data are still fragmentary. Some studies point to an important role of GH and IGF-I particularly during immune organ development and constitution. Even less is known about the potential relevance of local (autocrine/paracrine) IGF-I within adult and developing immune organs, and the distinct localization of IGF-I in immune cells and tissues of mammals and fish has not been systematically defined. Thus far, IGF-I has been localized in different mammalian immune cell types, particularly macrophages and granulocytes, and in supporting cells, but not in T-lymphocytes. In the present study, we detected IGF-I in phagocytic cells isolated from rainbow trout head kidney and, in contrast to some findings in mammals, in T-cells of a channel catfish cell line. Thus, although numerous analogies among mammals and teleosts exist not only for the GH/IGF-system, but also for the immune system, there are differences that should be further investigated. For instance, it is unclear whether the primarily reported role of GH/IGF-I in the innate immune response is due to the lack of studies focusing on the adaptive immune system, or whether it truly preferentially concerns innate immune parameters. Infectious challenges in combination with GH/IGF-I manipulations are another important topic that has not been sufficiently addressed to date, particularly with respect to developmental and environmental influences on fish growth and health. PMID:26821056

  7. Endocrine and Local IGF-I in the Bony Fish Immune System.

    PubMed

    Franz, Anne-Constance; Faass, Oliver; Köllner, Bernd; Shved, Natallia; Link, Karl; Casanova, Ayako; Wenger, Michael; D'Cotta, Helena; Baroiller, Jean-François; Ullrich, Oliver; Reinecke, Manfred; Eppler, Elisabeth

    2016-01-26

    A role for GH and IGF-I in the modulation of the immune system has been under discussion for decades. Generally, GH is considered a stimulator of innate immune parameters in mammals and teleost fish. The stimulatory effects in humans as well as in bony fish often appear to be correlated with elevated endocrine IGF-I (liver-derived), which has also been shown to be suppressed during infection in some studies. Nevertheless, data are still fragmentary. Some studies point to an important role of GH and IGF-I particularly during immune organ development and constitution. Even less is known about the potential relevance of local (autocrine/paracrine) IGF-I within adult and developing immune organs, and the distinct localization of IGF-I in immune cells and tissues of mammals and fish has not been systematically defined. Thus far, IGF-I has been localized in different mammalian immune cell types, particularly macrophages and granulocytes, and in supporting cells, but not in T-lymphocytes. In the present study, we detected IGF-I in phagocytic cells isolated from rainbow trout head kidney and, in contrast to some findings in mammals, in T-cells of a channel catfish cell line. Thus, although numerous analogies among mammals and teleosts exist not only for the GH/IGF-system, but also for the immune system, there are differences that should be further investigated. For instance, it is unclear whether the primarily reported role of GH/IGF-I in the innate immune response is due to the lack of studies focusing on the adaptive immune system, or whether it truly preferentially concerns innate immune parameters. Infectious challenges in combination with GH/IGF-I manipulations are another important topic that has not been sufficiently addressed to date, particularly with respect to developmental and environmental influences on fish growth and health.

  8. Clinical and Microcomputed Topography Evaluation of the Concentrated Growth Factors as a Sole Material in a Cystic Bony Defect in Alveolar Bone Followed by Dental Implantation: A Case Report.

    PubMed

    Shyu, Shih-Shiun; Fu, Earl; Shen, E-Chin

    2016-10-01

    Concentrated growth factors (CGFs) can be used to enhance wound healing. This case report describes a short-term effect of CGF grafting followed by implant placement in a cystic bony defect within the mandible. Healing conditions were monitored by 2 implant-related surgeries, radiographs, and a microcomputed topography examination. Continuous increase of radiopacity in radiographs was noticed till 6 months after grafting. Bone core specimen was taken at 3.5 months after grafting, and percent bone volume reached 32.7% analyzed by microcomputed topography. In conclusion, the present case showed bone regeneration in the cystic bony defect grafted by CGFs alone.

  9. Effects of topography and crustal heterogeneities on the source estimation of LP event at Kilauea volcano

    USGS Publications Warehouse

    Cesca, S.; Battaglia, J.; Dahm, T.; Tessmer, E.; Heimann, S.; Okubo, P.

    2008-01-01

    The main goal of this study is to improve the modelling of the source mechanism associated with the generation of long period (LP) signals in volcanic areas. Our intent is to evaluate the effects that detailed structural features of the volcanic models play in the generation of LP signal and the consequent retrieval of LP source characteristics. In particular, effects associated with the presence of topography and crustal heterogeneities are here studied in detail. We focus our study on a LP event observed at Kilauea volcano, Hawaii, in 2001 May. A detailed analysis of this event and its source modelling is accompanied by a set of synthetic tests, which aim to evaluate the effects of topography and the presence of low velocity shallow layers in the source region. The forward problem of Green's function generation is solved numerically following a pseudo-spectral approach, assuming different 3-D models. The inversion is done in the frequency domain and the resulting source mechanism is represented by the sum of two time-dependent terms: a full moment tensor and a single force. Synthetic tests show how characteristic velocity structures, associated with shallow sources, may be partially responsible for the generation of the observed long-lasting ringing waveforms. When applying the inversion technique to Kilauea LP data set, inversions carried out for different crustal models led to very similar source geometries, indicating a subhorizontal cracks. On the other hand, the source time function and its duration are significantly different for different models. These results support the indication of a strong influence of crustal layering on the generation of the LP signal, while the assumption of homogeneous velocity model may bring to misleading results. ?? 2008 The Authors Journal compilation ?? 2008 RAS.

  10. Reducing the effects of acoustic heterogeneity with an iterative reconstruction method from experimental data in microwave induced thermoacoustic tomography

    SciTech Connect

    Wang, Jinguo; Zhao, Zhiqin Song, Jian; Chen, Guoping; Nie, Zaiping; Liu, Qing-Huo

    2015-05-15

    Purpose: An iterative reconstruction method has been previously reported by the authors of this paper. However, the iterative reconstruction method was demonstrated by solely using the numerical simulations. It is essential to apply the iterative reconstruction method to practice conditions. The objective of this work is to validate the capability of the iterative reconstruction method for reducing the effects of acoustic heterogeneity with the experimental data in microwave induced thermoacoustic tomography. Methods: Most existing reconstruction methods need to combine the ultrasonic measurement technology to quantitatively measure the velocity distribution of heterogeneity, which increases the system complexity. Different to existing reconstruction methods, the iterative reconstruction method combines time reversal mirror technique, fast marching method, and simultaneous algebraic reconstruction technique to iteratively estimate the velocity distribution of heterogeneous tissue by solely using the measured data. Then, the estimated velocity distribution is used subsequently to reconstruct the highly accurate image of microwave absorption distribution. Experiments that a target placed in an acoustic heterogeneous environment are performed to validate the iterative reconstruction method. Results: By using the estimated velocity distribution, the target in an acoustic heterogeneous environment can be reconstructed with better shape and higher image contrast than targets that are reconstructed with a homogeneous velocity distribution. Conclusions: The distortions caused by the acoustic heterogeneity can be efficiently corrected by utilizing the velocity distribution estimated by the iterative reconstruction method. The advantage of the iterative reconstruction method over the existing correction methods is that it is successful in improving the quality of the image of microwave absorption distribution without increasing the system complexity.

  11. The effect of heterogeneity identifying the leakage of carbon dioxide in a shallow aquifer: an experimental study

    NASA Astrophysics Data System (ADS)

    Ha, S. W.; Lee, S. H.; Jeon, W. T.; Joo, Y. J.; Lee, K. K.

    2014-12-01

    Carbon dioxide (CO2) leakage into the shallow aquifer is one of the main concerns at a CO2 sequestration site. Various hydrogeochemical parameters have been suggested to determine the leakage (i.e., pH, EC, Alkalinity, Ca and δ13C). For the practical point of view, direct and continuous measurement of the dissolved CO2 concentration at the proper location can be the most useful strategy for the CO2 leakage detection in a shallow aquifer. In order to enhance possibility of identifying leaked CO2, monitoring location should be determined with regard to the shallow aquifer heterogeneity. In this study, a series of experiments were conducted to investigate the effects of heterogeneity on the dissolved CO2 concentrations. A 2-D sand tank of homogeneous medium sands including a single heterogeneity layer was designed. Two NDIR CO2 sensors, modified for continuous measuring in aquatic system, were installed above and below the single heterogeneous layer (clay, fine and medium sand lenses). Also, temperature and water contents were measured continuously at a same position. Bromocresol purple which is one of the acid-base indicator was used to visualize CO2 migration. During the gas phase CO2 injection at the bottom of the sand tank, dissolved CO2 in the water is continuously measured. In the results, significant differences of concentrations were observed due to the presence of heterogeneity layer, even the locations were close. These results suggested that monitoring location should be determined considering vertical heterogeneity of shallow aquifer at a CO2 leakage site.

  12. Effects of heterogeneous competitor distribution and ramet aggregation on the growth and size structure of a clonal plant.

    PubMed

    Dong, Bi-Cheng; Wang, Jiu-Zhong; Liu, Rui-Hua; Zhang, Ming-Xiang; Yu, Fei-Hai

    2013-01-01

    Spatially heterogeneous distribution of interspecific competitors and intraspecific aggregation of offspring ramets may affect the growth and size structure of clonal plant populations, but these have been rarely studied. We conducted a greenhouse experiment in which we grew a population of eight offspring ramets (plants) of the stoloniferous clonal plant Hydrocotyle vulgaris aggregately or segregately in two homogeneous treatments with or without a competing grass Festuca elata and a heterogeneous treatment with a patchy distribution of the grass. In patchy grass treatments, H. vulgaris produced markedly more biomass, ramets and stolons in open patches (without grasses) than in grass patches, but displayed lower size variations as measured by coefficient of variation of biomass, ramets and stolons among the eight plants. In open areas, H. vulgaris produced statistically the same amounts of biomass and even more stolons and showed higher size variations in patchy grass treatments than in open (no grass) treatments. In grass areas, H. vulgaris grew much worse and displayed higher size variations in patchy grass treatments than in full grass treatments. Ramet aggregation decreased the growth of H. vulgaris in open treatments and in both open and grass patches in patchy grass treatments, but had little effect in full grass treatments. Ramet aggregation had little effect on size variations. Therefore, heterogeneous distribution of competitors can affect the growth and size structure of clonal plant populations, and ramet aggregation may decrease population growth when they grow in open environments or heterogeneous environments with a patchy distribution of interspecific competitors.

  13. Effect of Subgrid Heterogeneity on Scaling Geochemical and Biogeochemical Reactions: A Case of U(VI) Desorption

    SciTech Connect

    Liu, Chongxuan; Shang, Jianying; Shan, Huimei; Zachara, John M.

    2014-02-04

    The effect of subgrid heterogeneity in sediment properties on the rate of uranyl[U(VI)] desorption was investigated using a sediment collected from the US Department of Energy Hanford site. The sediment was sieved into 7 grain size fractions that each exhibited different U(VI) desorption properties. Six columns were assembled using the sediment with its grain size fractions arranged in different spatial configurations to mimic subgrid heterogeneity in reactive transport properties. The apparent rate of U(VI) desorption varied significantly in the columns. Those columns with sediment structures leading to preferential transport had much lower rates of U(VI) desorption than those with relatively homogeneous transport. Modeling analysis indicated that the U(VI) desorption model and parameters characterized from well-mixed reactors significantly over-predicted the measured U(VI) desorption in the columns with preferential transport. A dual domain model, which operationally separates reactive transport properties into two subgrid domains improved the predictions significantly. A similar effect of subgrid heterogeneity, albeit at a less degree, was observed for denitrification, which also occurred in the columns. The results imply that subgrid heterogeneity is an important consideration in extrapolating reaction rates from the laboratory to field.

  14. Slope stability of bioreactor landfills during leachate injection: effects of heterogeneous and anisotropic municipal solid waste conditions.

    PubMed

    Giri, Rajiv K; Reddy, Krishna R

    2014-03-01

    In bioreactor landfills, leachate recirculation can significantly affect the stability of landfill slope due to generation and distribution of excessive pore fluid pressures near side slope. The current design and operation of leachate recirculation systems do not consider the effects of heterogeneous and anisotropic nature of municipal solid waste (MSW) and the increased pore gas pressures in landfilled waste caused due to leachate recirculation on the physical stability of landfill slope. In this study, a numerical two-phase flow model (landfill leachate and gas as immiscible phases) was used to investigate the effects of heterogeneous and anisotropic nature of MSW on moisture distribution and pore-water and capillary pressures and their resulting impacts on the stability of a simplified bioreactor landfill during leachate recirculation using horizontal trench system. The unsaturated hydraulic properties of MSW were considered based on the van Genuchten model. The strength reduction technique was used for slope stability analyses as it takes into account of the transient and spatially varying pore-water and gas pressures. It was concluded that heterogeneous and anisotropic MSW with varied unit weight and saturated hydraulic conductivity significantly influenced the moisture distribution and generation and distribution of pore fluid pressures in landfill and considerably reduced the stability of bioreactor landfill slope. It is recommended that heterogeneous and anisotropic MSW must be considered as it provides a more reliable approach for the design and leachate operations in bioreactor landfills.

  15. The effect of reservoir heterogeneity on gas production from hydrate accumulations in the permafrost

    SciTech Connect

    Reagan, M. T.; Kowalsky, M B.; Moridis, G. J.; Silpngarmlert, S.

    2010-05-01

    The quantity of hydrocarbon gases trapped in natural hydrate accumulations is enormous, leading to significant interest in the evaluation of their potential as an energy source. Large volumes of gas can be readily produced at high rates for long times from methane hydrate accumulations in the permafrost by means of depressurization-induced dissociation combined with conventional technologies and horizontal or vertical well configurations. Initial studies on the possibility of natural gas production from permafrost hydrates assumed homogeneity in intrinsic reservoir properties and in the initial condition of the hydrate-bearing layers (either due to the coarseness of the model or due to simplifications in the definition of the system). These results showed great promise for gas recovery from Class 1, 2, and 3 systems in the permafrost. This work examines the consequences of inevitable heterogeneity in intrinsic properties, such as in the porosity of the hydrate-bearing formation, or heterogeneity in the initial state of hydrate saturation. Heterogeneous configurations are generated through multiple methods: (1) through defining heterogeneous layers via existing well-log data, (2) through randomized initialization of reservoir properties and initial conditions, and (3) through the use of geostatistical methods to create heterogeneous fields that extrapolate from the limited data available from cores and well-log data. These extrapolations use available information and established geophysical methods to capture a range of deposit properties and hydrate configurations. The results show that some forms of heterogeneity, such as horizontal stratification, can assist in production of hydrate-derived gas. However, more heterogeneous structures can lead to complex physical behavior within the deposit and near the wellbore that may obstruct the flow of fluids to the well, necessitating revised production strategies. The need for fine discretization is crucial in all cases to

  16. Magnetic pyrite cinder as an efficient heterogeneous ozonation catalyst and synergetic effect of deposited Ce.

    PubMed

    Wu, Deli; Liu, Ying; He, Hongping; Zhang, Yalei

    2016-07-01

    Heterogeneous catalytic ozonation was emerged to be a promising alternative in the mineralization of various persistent organic pollutants in recent decades. Magnetic pyrite cinder (PyC), which was employed as the catalyst in our investigation, was further deposited by Ce (Ce-PyC) to enhance its catalytic activity in the degradation of aqueous reactive black 5 (RB5). The results showed that additional 17.39%, 42.12% mineralization efficiency was obtained by O3/PyC, O3/Ce-PyC, respectively, in the degradation of RB5 compared to that of O3 alone under identical experimental condition. The reaction mechanism involved the enhanced mineralization of aqueous RB5 at the catalyst-solution interface via hydroxyl radicals produced by the reaction between O3 and catalyst surface. Besides surface hydroxyl, surface Ce(Ⅲ) was crucial for Ce-PyC in the enhanced generation of hydroxyl radicals. More surprisingly, it was found that both PyC and Ce-PyC could exert quite stable catalytic activity in a wide pH range from 3 to 10, which was supposed to be combined with inherently comprised various metal oxide, such as Fe2O3, Fe3O4, MnO2 and CuO. Ozone utilization evaluation demonstrated that PyC and Ce-PyC facilitated effective ozone decomposition, as ozone utilization efficiency (mgTOC/mgO3) of O3/PyC and O3/Ce-PyC increased 64.0%, 155.0%, respectively, compared to that of O3 alone. This investigation provided an effective alternative in the resource utilization of PyC, which was traditionally characterized as a waste material.

  17. Neurotrophin-3 Induces BMP-2 and VEGF Activities and Promotes the Bony Repair of Injured Growth Plate Cartilage and Bone in Rats.

    PubMed

    Su, Yu-Wen; Chung, Rosa; Ruan, Chun-Sheng; Chim, Shek Man; Kuek, Vincent; Dwivedi, Prem P; Hassanshahi, Mohammadhossein; Chen, Ke-Ming; Xie, Yangli; Chen, Lin; Foster, Bruce K; Rosen, Vicki; Zhou, Xin-Fu; Xu, Jiake; Xian, Cory J

    2016-06-01

    Injured growth plate is often repaired by bony tissue causing bone growth defects, for which the mechanisms remain unclear. Because neurotrophins have been implicated in bone fracture repair, here we investigated their potential roles in growth plate bony repair in rats. After a drill-hole injury was made in the tibial growth plate and bone, increased injury site mRNA expression was observed for neurotrophins NGF, BDNF, NT-3, and NT-4 and their Trk receptors. NT-3 and its receptor TrkC showed the highest induction. NT-3 was localized to repairing cells, whereas TrkC was observed in stromal cells, osteoblasts, and blood vessel cells at the injury site. Moreover, systemic NT-3 immunoneutralization reduced bone volume at injury sites and also reduced vascularization at the injured growth plate, whereas recombinant NT-3 treatment promoted bony repair with elevated levels of mRNA for osteogenic markers and bone morphogenetic protein (BMP-2) and increased vascularization and mRNA for vascular endothelial growth factor (VEGF) and endothelial cell marker CD31 at the injured growth plate. When examined in vitro, NT-3 promoted osteogenesis in rat bone marrow stromal cells, induced Erk1/2 and Akt phosphorylation, and enhanced expression of BMPs (particularly BMP-2) and VEGF in the mineralizing cells. It also induced CD31 and VEGF mRNA in rat primary endothelial cell culture. BMP activity appears critical for NT-3 osteogenic effect in vitro because it can be almost completely abrogated by co-addition of the BMP inhibitor noggin. Consistent with its angiogenic effect in vivo, NT-3 promoted angiogenesis in metatarsal bone explants, an effect abolished by co-treatment with anti-VEGF. This study suggests that NT-3 may be an osteogenic and angiogenic factor upstream of BMP-2 and VEGF in bony repair, and further studies are required to investigate whether NT-3 may be a potential target for preventing growth plate faulty bony repair or for promoting bone fracture healing. © 2016

  18. Combined effects of climatic gradient and domestic livestock grazing on reptile community structure in a heterogeneous agroecosystem.

    PubMed

    Rotem, Guy; Gavish, Yoni; Shacham, Boaz; Giladi, Itamar; Bouskila, Amos; Ziv, Yaron

    2016-01-01

    Grazing plays an important role in shaping ecological communities in human-related ecosystems. Although myriad studies have explored the joint effect of grazing and climate on plant communities, this interactive effect has rarely been studied in animals. We hypothesized that the effect of grazing on the reptile community varies along a climatic gradient in relation to the effect of grazing on habitat characteristics, and that grazing differentially affects reptiles of different biogeographic regions. We tested our hypotheses by collecting data on environmental characteristics and by trapping reptiles in four heterogeneous landscapes experiencing differing grazing intensities and distributed along a sharp climatic gradient. We found that while reptile diversity increased with grazing intensity at the mesic end of the gradient, it decreased with grazing intensity at the arid end. Moreover, the proportion of reptile species of differing biogeographic origins varied with the interactive effect of climate and grazing. The representation of species originating in arid biogeographic zones was highest at the arid end of the climatic gradient, and representation increased with grazing intensity within this area. Regardless of the climatic context, increased grazing pressure results in a reduction in vegetation cover and thus in changes in habitat characteristics. By reducing vegetation cover, grazing increased habitat heterogeneity in the dense mesic sites and decreased habitat heterogeneity in the arid sites. Thus, our results suggest that the same direction of habitat alteration caused by grazing may have opposite effects on biodiversity and community composition in different climatic contexts.

  19. Aquifer heterogeneity controls on adverse human health effects and the concept of the hazard attenuation factor

    NASA Astrophysics Data System (ADS)

    de Barros, F. P. J.; Bellin, A.; Cvetkovic, V.; Dagan, G.; Fiori, A.

    2016-08-01

    We analyze the probability distribution of the hazard attenuation factor for a noncarcinogenic reactive compound captured by a well in heterogeneous porous formations. The hazard attenuation factor is defined as the ratio between the hazard index HI at a detection well and at the source. Heterogeneity of the aquifer is represented through the multi-indicator model (a collection of blocks of independent permeability) while flow and transport are solved by the means of the self-consistent approach that is able to deal with any degree of heterogeneity. Due to formation heterogeneity, HI is a random variable and similar for hazard attenuation index. The latter can be fully characterized by its cumulative distribution function (CDF), which in turn can be related to the statistics of the travel time of solute particles, from the source to the detection well. The approach is applied to the case of a solute which undergoes decay and a well with a screen much smaller than the correlation scale of hydraulic conductivity. The results show that the probability of exceeding a given acceptable threshold of the hazard index is significantly affected by the level of heterogeneity comparable to the one observed for the MADE site, and the distance between the source and the well.

  20. Heterogeneous nanometer-scale Joule and Peltier effects in sub-25 nm thin phase change memory devices

    NASA Astrophysics Data System (ADS)

    Grosse, Kyle L.; Pop, Eric; King, William P.

    2014-09-01

    We measure heterogeneous power dissipation in phase change memory (PCM) films of 11 and 22 nm thin Ge2Sb2Te5 (GST) by scanning Joule expansion microscopy (SJEM), with sub-50 nm spatial and ˜0.2 K temperature resolution. The heterogeneous Joule and Peltier effects are explained using a finite element analysis (FEA) model with a mixture of hexagonal close-packed and face-centered cubic GST phases. Transfer length method measurements and effective media theory calculations yield the GST resistivity, GST-TiW contact resistivity, and crystal fraction of the GST films at different annealing temperatures. Further comparison of SJEM measurements and FEA modeling also predicts the thermopower of thin GST films. These measurements of nanometer-scale Joule, thermoelectric, and interface effects in PCM films could lead to energy-efficient designs of highly scaled PCM technology.

  1. Bony Versus Soft Tissue Reconstruction for Anterior Shoulder Instability

    PubMed Central

    McLaughlin, Richard James; Miniaci, Anthony; Jones, Morgan H.

    2015-01-01

    effect on the model. When the rate of no complication after open surgery is 97.6%, open surgery becomes the patient’s preferred treatment. Conclusion: Arthroscopic surgery is an acceptable treatment if recurrent instability occurs consistently at ≤23.8%. This has important implications given the technical difficulty of successfully performing arthroscopic fixation to resolve recurrent anteroinferior glenohumeral dislocations associated with critical osseous defects. However, due to a lack of clinical outcomes studies, more research is needed to better predict the optimal operative treatment. PMID:26779552

  2. Effects of heterogeneities on the partitioning of airway and tissue properties in normal mice.

    PubMed

    Ito, Satoru; Lutchen, Kenneth R; Suki, Béla

    2007-03-01

    We measured the mechanical properties of the respiratory system of C57BL/6 mice using the optimal ventilation waveform method in closed- and open-chest conditions at different positive end-expiratory pressures. The tissue damping (G), tissue elastance (H), airway resistance (Raw), and hysteresivity were obtained by fitting the impedance data to three different models: a constant-phase model by Hantos et al. (Hantos Z, Daroczy B, Suki B, Nagy S, Fredberg JJ. J Appl Physiol 72: 168-178, 1992), a heterogeneous Raw model by Suki et al. (Suki B, Yuan H, Zhang Q, Lutchen KR. J Appl Physiol 82: 1349-1359, 1997), and a heterogeneous H model by Ito et al. (Ito S, Ingenito EP, Arold SP, Parameswaran H, Tgavalekos NT, Lutchen KR, Suki B. J Appl Physiol 97: 204-212, 2004). Both in the closed- and open-chest conditions, G and hysteresivity were the lowest and Raw the highest in the heterogeneous Raw model, and G and H were the largest in the heterogeneous H model. Values of G, Raw, and hysteresivity were significantly higher in the closed-chest than in the open-chest condition. However, H was not affected by the conditions. When the tidal volume of the optimal ventilation waveform was decreased from 8 to 4 ml/kg in the closed-chest condition, G and hysteresivity significantly increased, but there were smaller changes in H or Raw. In summary, values of the obtained mechanical properties varied among these models, primarily due to heterogeneity. Moreover, the mechanical parameters were significantly affected by the chest wall and tidal volume in mice. Contribution of the chest wall and heterogeneity to the mechanical properties should be carefully considered in physiological studies in which partitioning of airway and tissue properties are attempted.

  3. The Effects of Realistic Geological Heterogeneity on Seismic Modeling: Applications in Shear Wave Generation and Near-Surface Tunnel Detection

    NASA Astrophysics Data System (ADS)

    Sherman, Christopher Scott

    Naturally occurring geologic heterogeneity is an important, but often overlooked, aspect of seismic wave propagation. This dissertation presents a strategy for modeling the effects of heterogeneity using a combination of geostatistics and Finite Difference simulation. In the first chapter, I discuss my motivations for studying geologic heterogeneity and seis- mic wave propagation. Models based upon fractal statistics are powerful tools in geophysics for modeling heterogeneity. The important features of these fractal models are illustrated using borehole log data from an oil well and geomorphological observations from a site in Death Valley, California. A large part of the computational work presented in this disserta- tion was completed using the Finite Difference Code E3D. I discuss the Python-based user interface for E3D and the computational strategies for working with heterogeneous models developed over the course of this research. The second chapter explores a phenomenon observed for wave propagation in heteroge- neous media - the generation of unexpected shear wave phases in the near-source region. In spite of their popularity amongst seismic researchers, approximate methods for modeling wave propagation in these media, such as the Born and Rytov methods or Radiative Trans- fer Theory, are incapable of explaining these shear waves. This is primarily due to these method's assumptions regarding the coupling of near-source terms with the heterogeneities and mode conversion. To determine the source of these shear waves, I generate a suite of 3D synthetic heterogeneous fractal geologic models and use E3D to simulate the wave propaga- tion for a vertical point force on the surface of the models. I also present a methodology for calculating the effective source radiation patterns from the models. The numerical results show that, due to a combination of mode conversion and coupling with near-source hetero- geneity, shear wave energy on the order of 10% of the

  4. From concepts, theory, and evidence of heterogeneity of treatment effects to methodological approaches: a primer

    PubMed Central

    2012-01-01

    Implicit in the growing interest in patient-centered outcomes research is a growing need for better evidence regarding how responses to a given intervention or treatment may vary across patients, referred to as heterogeneity of treatment effect (HTE). A variety of methods are available for exploring HTE, each associated with unique strengths and limitations. This paper reviews a selected set of methodological approaches to understanding HTE, focusing largely but not exclusively on their uses with randomized trial data. It is oriented for the “intermediate” outcomes researcher, who may already be familiar with some methods, but would value a systematic overview of both more and less familiar methods with attention to when and why they may be used. Drawing from the biomedical, statistical, epidemiological and econometrics literature, we describe the steps involved in choosing an HTE approach, focusing on whether the intent of the analysis is for exploratory, initial testing, or confirmatory testing purposes. We also map HTE methodological approaches to data considerations as well as the strengths and limitations of each approach. Methods reviewed include formal subgroup analysis, meta-analysis and meta-regression, various types of predictive risk modeling including classification and regression tree analysis, series of n-of-1 trials, latent growth and growth mixture models, quantile regression, and selected non-parametric methods. In addition to an overview of each HTE method, examples and references are provided for further reading. By guiding the selection of the methods and analysis, this review is meant to better enable outcomes researchers to understand and explore aspects of HTE in the context of patient-centered outcomes research. PMID:23234603

  5. Spatial and Temporal Analysis of Drought Effects in a Heterogeneous Semi-Arid Forest Ecosystem

    NASA Astrophysics Data System (ADS)

    Assal, T.; Anderson, P. J.; Sibold, J.

    2015-12-01

    Drought-induced forest mortality has been documented across genera in recent years in western North America. Understanding patterns of mortality and plant response to severe drought is important to resource managers, given the frequency of these events are expected to increase in the future. Remote sensing studies have documented changes in forest properties due to direct and indirect effects of drought; however, few have addressed this at local scales needed to characterize highly heterogeneous ecosystems in the forest-shrubland ecotone. We analyzed a 22-year Landsat time series (1985-2012) to determine changes in forest that experienced a relatively dry decade punctuated by two years of extreme drought. We assessed the relationship between vegetation indices and field measures, applied the index to trend analysis to uncover the location, direction and timing of change, and assessed the interaction of climate on topography. The Normalized Difference Moisture Index (NDMI) had the strongest correlation with plant area index (R2 = 0.64) and canopy gap fraction (R2 = 0.65). During the study period, 25% of the forested area experienced a significant (p < 0.05) negative trend in NDMI, compared to less than 10% in a positive trend. Trends were not consistent across forest type as a larger amount of coniferous forest was impacted by negative trends than deciduous forest. Southern aspects were least likely to exhibit a negative trend and north aspects were most prevalent. Field plots with a negative trend had a lower live density, and higher amounts of standing dead and down trees compared to plots with no trend. Our analysis identifies spatially explicit patterns of long-term trends anchored with ground based evidence to highlight areas of forest that are resistant, persistent and vulnerable to severe drought. The results provide a long-term perspective for the resource management of this area and can be applied to similar ecosystems throughout western North America.

  6. The use of helical computed tomographic scan to assess bony physeal bridges.

    PubMed

    Loder, R T; Swinford, A E; Kuhns, L R

    1997-01-01

    Coronal and sagittal reformatted images of the physis obtained with the helical computed tomography (CT) scanner were studied in five children. This technique allows tomographic slices at 1.0-mm thickness and can be performed in approximately 20 s. The distal femora were studied in two children, the distal tibia in two children, and the distal radius in one child. In three children, after physeal mapping, bar resections were performed. In all cases, the location and size of the bar was accurately predicted by the map constructed from the helical CT scan. We recommend the helical CT scan to prepare physeal maps to determine the extent and location of physeal bony bars because of excellent bony detail, radiation doses one half to one quarter those of conventional tomography, and the rapidity of scanning, which bypasses the need for sedation.

  7. Effect of phosphate on heterogeneous Fenton oxidation of catechol by nano-Fe₃O₄ Inhibitor or stabilizer?

    PubMed

    Yang, Xiaofang; He, Jie; Sun, Zhongxi; Holmgren, Allan; Wang, Dongsheng

    2016-01-01

    The effect of phosphate on adsorption and oxidation of catechol, 1,2-dihydroxybenzene, in a heterogeneous Fenton system was investigated. In situ attenuated total reflectance infrared spectroscopy (ATR-FTIR) was used to monitor the surface speciation at the nano-Fe3O4 catalyst surface. The presence of phosphate decreased the removal rate of catechol and the abatement of dissolved organic compounds, as well as the decomposition of H2O2. This effect of phosphate was mainly due to its strong reaction with surface sites on the iron oxide catalyst. At neutral and acid pH, phosphate could displace the adsorbed catechol from the surface of catalyst and also could compete for surface sites with H2O2. In situ IR spectra indicated the formation of iron phosphate precipitation at the catalyst surface. The iron phosphate surface species may affect the amount of iron atoms taking part in the catalytic decomposition of H2O2 and formation of hydroxyl radicals, and inhibit the catalytic ability of Fe3O4 catalyst. Therefore, phosphate ions worked as stabilizer and inhibitor in a heterogeneous Fenton reaction at the same time, in effect leading to an increase in oxidation efficiency in this study. However, before use of phosphate as pH buffer or H2O2 stabilizer in a heterogeneous Fenton system, the possible inhibitory effect of phosphate on the actual removal of organic pollutants should be fully considered.

  8. Upper cervical spinal cord compression due to bony stenosis of the spinal canal.

    PubMed

    Benitah, S; Raftopoulos, C; Balériaux, D; Levivier, M; Dedeire, S

    1994-04-01

    Compression of the upper cervical spinal cord due to stenosis of the bony spinal canal is infrequent. In the first case reported here, stenosis was due to acquired extensive, unilateral osteophytes centered on the left apophyseal joints of C1-C2 in an elderly professional violinist. In the second case, stenosis was secondary to isolated congenital hypertrophy of the laminae of C1 and C2.

  9. [Effects of cutting intensity on spatial heterogeneity of topsoil temperature in secondary forest in Maoershan region of Heilongjian Province].

    PubMed

    Gu, Jiacun; Wang, Zhengquan; Han, Youzhi; Wang, Xiangrong; Mei, Li; Zhang, Xiujuan; Cheng, Yunhuan

    2006-12-01

    This paper studied the effects of different cutting intensity on the spatial heterogeneity of topsoil (3 - 5 cm) temperature in the secondary forest in Maoershan region of Heilongjiang Province. Three treatments were installed, i.e., no cutting (treatment A), 50% of randomly cutting (treatment B), and clear cutting (treatment C). Based on the requirements of geostatistic analysis, there were 160, 154 and 154 sampling points with a spatial distance of 0.5 - 56 m in the treatments A, B and C, respectively. Topsoil temperature was measured by thermometer in spring and summer during the two years after cutting, and the spatial heterogeneity of the temperature was analyzed by semivariogram and Kriging arithmetic. The results showed that after cutting, the mean value of topsoil temperature had an increase of 0.6 - 4.2 degrees C (P < 0.001), and correlated positively with cutting intensity. The spatial heterogeneity and variation degree of topsoil temperature also increased with the increasing intensity of cutting. As for the small scale spatial heterogeneity of topsoil temperature, it was also increased after cutting, but the scale was mainly within the range of < 20 m and the composition of spatial heterogeneity was slightly affected. The comparison of Kriging maps suggested that in treatments B and C, the spatial pattern strength of topsoil temperature was enhanced, and the difference between treatments B and C and treatment A was larger in spring than in summer. In treatments B and C, topsoil temperature fluctuated and had similar distribution patterns in the same seasons; while in treatment A, the temperature had a relatively even distribution within the year.

  10. Effect of interaction heterogeneity on colloidal arrangements at a curved oil-water interface.

    PubMed

    Lee, Mina; Lee, Daeyeon; Park, Bum Jun

    2015-01-14

    We report the unique arrangement behaviour of colloidal particles at a curved oil-water interface. Particles trapped at a centrosymmetrically curved oil-water interface, formed by placing an oil lens at a neat air-water interface, organize into diverse arrangement structures due to electrostatic repulsion under the gravitational field. To reveal a possible mechanism behind the observed diversity, we investigate the interactions between pairs of particles at the curved oil-water interface. The magnitude of electrostatic repulsive interactions between pairs of particles is determined by minimizing the total potential of the particle pairs. We show that the pair interactions are quite heterogeneous, following a Gamma distribution. Using the experimentally determined pair potential and the heterogeneity in the potential as input parameters for Monte Carlo simulations, we show that such interaction heterogeneity affects the particle arrangements at the curved interface and results in an observed diversity in the particle arrangement structures. We believe that this work prompts further experimental and simulation studies to extensively understand hierarchical relations from small scale measurements (e.g., pair interactions and heterogeneity) to bulk scale properties (e.g., microstructure and interfacial rheology).

  11. Effects of heterogeneity in synaptic conductance between weakly coupled identical neurons.

    PubMed

    Bradley, Patrick J; Wiesenfeld, Kurt; Butera, Robert J

    2011-04-01

    A significant degree of heterogeneity in synaptic conductance is present in neuron to neuron connections. We study the dynamics of weakly coupled pairs of neurons with heterogeneities in synaptic conductance using Wang-Buzsaki and Hodgkin-Huxley model neurons which have Types I and II excitability, respectively. This type of heterogeneity breaks a symmetry in the bifurcation diagrams of equilibrium phase difference versus the synaptic rate constant when compared to the identical case. For weakly coupled neurons coupled with identical values of synaptic conductance a phase locked solution exists for all values of the synaptic rate constant, α. In particular, in-phase and anti-phase solutions are guaranteed to exist for all α. Heterogeneity in synaptic conductance results in regions where no phase locked solution exists and the general loss of the ubiquitous in-phase and anti-phase solutions of the identically coupled case. We explain these results through examination of interaction functions using the weak coupling approximation and an in-depth analysis of the underlying multiple cusp bifurcation structure of the systems of coupled neurons.

  12. Restructuring for Caring and Effective Education: An Administrative Guide to Creating Heterogeneous Schools.

    ERIC Educational Resources Information Center

    Villa, Richard A.; And Others

    This collection of papers offers advice on restructuring education to create heterogeneous schools, with the goal of creating happy, comfortable, and successful learning environments for all the children and adults who learn and teach in them. Section I, titled "A Rationale for Restructuring and the Change Process," contains the following papers:…

  13. Effects of Current Velocity, Particle Size, and Substrate Heterogeneity on Crayfish (Orconectes propinquus) Activity

    NASA Astrophysics Data System (ADS)

    Clark, J. M.; Kershner, M. W.

    2005-05-01

    The use of flow refugia (e.g., substrate) by lotic invertebrates often increases their likelihood of survival during flood events. Movement to potential refugia becomes risky as velocities increase, and the range of velocities that benthic invertebrates can withstand is variable. In this study, activity time and slip velocities of small [carapace length (CL)=10-20 mm] and large (CL=20-30 mm) Orconectes propinquus were measured in an artificial flume across ranges of current velocity and substrate heterogeneity. Particle sizes included small pebbles (16-32 mm), large pebbles (32-64 mm), and small cobble (64-128 mm). Water velocity was increased by 0.1 m/s increments from 0.1-1.5 m/s at 5-minute intervals or until the crayfish was dislodged from the substrate. As current velocity increased, the probability of slipping increased for all crayfish. Regardless of the degree of substrate heterogeneity, small crayfish held their position at higher velocities than large crayfish and were also less active. Slip rates were generally lower for both sizes as substrate heterogeneity increased. Essentially, the availability and probability of finding refugia increased with increased habitat heterogeneity and allowed crayfish to avoid being swept into the drift.

  14. Reliability of the Bony Anatomy in Image-Guided Stereotactic Radiotherapy of Brain Metastases

    SciTech Connect

    Guckenberger, Matthias Baier, Kurt; Guenther, Iris; Richter, Anne; Wilbert, Juergen; Sauer, Otto; Vordermark, Dirk; Flentje, Michael

    2007-09-01

    Purpose: To evaluate whether the position of brain metastases remains stable between planning and treatment in cranial stereotactic radiotherapy (SRT). Methods and Materials: Eighteen patients with 20 brain metastases were treated with single-fraction (17 lesions) or hypofractionated (3 lesions) image-guided SRT. Median time interval between planning and treatment was 8 days. Before treatment a cone-beam CT (CBCT) and a conventional CT after application of i.v. contrast were acquired. Setup errors using automatic bone registration (CBCT) and manual soft-tissue registration of the brain metastases (conventional CT) were compared. Results: Tumor size was not significantly different between planning and treatment. The three-dimensional setup error (mean {+-} SD) was 4.0 {+-} 2.1 mm and 3.5 {+-} 2.2 mm according to the bony anatomy and the lesion itself, respectively. A highly significant correlation between automatic bone match and soft-tissue registration was seen in all three directions (r {>=} 0.88). The three-dimensional distance between the isocenter according to bone match and soft-tissue registration was 1.7 {+-} 0.7 mm, maximum 2.8 mm. Treatment of intracranial pressure with steroids did not influence the position of the lesion relative to the bony anatomy. Conclusion: With a time interval of approximately 1 week between planning and treatment, the bony anatomy of the skull proved to be an excellent surrogate for the target position in image-guided SRT.

  15. Heterogeneous Catalysis.

    ERIC Educational Resources Information Center

    Miranda, R.

    1989-01-01

    Described is a heterogeneous catalysis course which has elements of materials processing embedded in the classical format of catalytic mechanisms and surface chemistry. A course outline and list of examples of recent review papers written by students are provided. (MVL)

  16. Heterogeneous catalysis.

    PubMed

    Schlögl, Robert

    2015-03-09

    A heterogeneous catalyst is a functional material that continually creates active sites with its reactants under reaction conditions. These sites change the rates of chemical reactions of the reactants localized on them without changing the thermodynamic equilibrium between the materials.

  17. Multilevel Models for Intensive Longitudinal Data with Heterogeneous Autoregressive Errors: The Effect of Misspecification and Correction with Cholesky Transformation

    PubMed Central

    Jahng, Seungmin; Wood, Phillip K.

    2017-01-01

    Intensive longitudinal studies, such as ecological momentary assessment studies using electronic diaries, are gaining popularity across many areas of psychology. Multilevel models (MLMs) are most widely used analytical tools for intensive longitudinal data (ILD). Although ILD often have individually distinct patterns of serial correlation of measures over time, inferences of the fixed effects, and random components in MLMs are made under the assumption that all variance and autocovariance components are homogenous across individuals. In the present study, we introduced a multilevel model with Cholesky transformation to model ILD with individually heterogeneous covariance structure. In addition, the performance of the transformation method and the effects of misspecification of heterogeneous covariance structure were investigated through a Monte Carlo simulation. We found that, if individually heterogeneous covariances are incorrectly assumed as homogenous independent or homogenous autoregressive, MLMs produce highly biased estimates of the variance of random intercepts and the standard errors of the fixed intercept and the fixed effect of a level 2 covariate when the average autocorrelation is high. For intensive longitudinal data with individual specific residual covariance, the suggested transformation method showed lower bias in those estimates than the misspecified models when the number of repeated observations within individuals is 50 or more. PMID:28286490

  18. Clinical Evaluation of Autologous Platelet Rich Fibrin in Horizontal Alveolar Bony Defects

    PubMed Central

    Sam, George; Amol, Nagrale Vijay

    2014-01-01

    Background: Horizontal bone loss is the most common periodontal problem confronting the clinician but has received little attention. Platelet rich fibrin (PRF) is a second generation platelet concentrate. The platelets, leucocytes, growth factors and cytokines contained within PRF make it a healing biomaterial with tremendous potential for bone and soft tissue regeneration. Aim: This interventional clinical trial evaluates the clinical effectiveness of Autologous Platelet Rich Fibrin (PRF) in the management of horizontal bony defects. Settings and Design: Department of Periodontics. Design was Non Randomized Clinical Trial with split mouth design. Materials and Methods: A total of 45 sites with horizontal bone loss in 15 patients were studied, 15 sites were treated with PRF gel (experimental group I) and 15 sites were treated with PRF gel and PRF membrane (experimental group II). Control group (15 sites) were treated with open flap debridement. Statistical Analysis: All the parameters were assessed at baseline and after nine months which included Pocket Depth (PD), Clinical Attachment level (CAL), Gingival Recession (REC) and Relative Crest Height (RCH). The mean changes at baseline and after 9 months within each group were compared using Wilcoxon Signed Ranks Test. The mean changes for each parameter between groups were compared using Kruskal Wallis Test. Results: Re-evaluation at nine months revealed that all groups showed a significant reduction in probing depth (1.1±0.38 mm in control, 1.73±0.53 mm in group I, 1.7±0.45 mm in group II)(p<0.05) and clinical attachment gain (0.86±0.58 mm in control, 1.56±0.62 mm in group I, 1.7±0.52 in group II)(p<0.05) as compared to baseline. Intergroup comparisons of reduction in probing depth and clinical attachment gain showed significant differences in the experimental groups as compared to control (p<0.05), but there was no significant difference between the experimental groups (p>0.05). There was no significant

  19. Spatial and temporal trends of drought effects in a heterogeneous semi-arid forest ecosystem

    USGS Publications Warehouse

    Assal, Timothy J.; Anderson, Patrick J.; Sibold, Jason

    2016-01-01

    Drought has long been recognized as a driving mechanism in the forests of western North America and drought-induced mortality has been documented across genera in recent years. Given the frequency of these events are expected to increase in the future, understanding patterns of mortality and plant response to severe drought is important to resource managers. Drought can affect the functional, physiological, structural, and demographic properties of forest ecosystems. Remote sensing studies have documented changes in forest properties due to direct and indirect effects of drought; however, few studies have addressed this at local scales needed to characterize highly heterogeneous ecosystems in the forest-shrubland ecotone. We analyzed a 22-year Landsat time series (1985–2012) to determine changes in forest in an area that experienced a relatively dry decade punctuated by two years of extreme drought. We assessed the relationship between several vegetation indices and field measured characteristics (e.g. plant area index and canopy gap fraction) and applied these indices to trend analysis to uncover the location, direction and timing of change. Finally, we assessed the interaction of climate and topography by forest functional type. The Normalized Difference Moisture Index (NDMI), a measure of canopy water content, had the strongest correlation with short-term field measures of plant area index (R2 = 0.64) and canopy gap fraction (R2 = 0.65). Over the entire time period, 25% of the forested area experienced a significant (p-value < 0.05) negative trend in NDMI, compared to less than 10% in a positive trend. Coniferous forests were more likely to be associated with a negative NDMI trend than deciduous forest. Forests on southern aspects were least likely to exhibit a negative trend while north aspects were most prevalent. Field plots with a negative trend had a lower live density, and higher amounts of standing dead and down trees compared to plots with no

  20. The effects of selective history and environmental heterogeneity on inbreeding depression in experimental populations of Drosophila melanogaster.

    PubMed

    Long, Tristan A F; Rowe, Locke; Agrawal, Aneil F

    2013-04-01

    Inbreeding depression varies considerably among populations, but only some aspects of this variation have been thoroughly studied. Because inbreeding depression requires genetic variation, factors that influence the amount of standing variation can affect the magnitude of inbreeding depression. Environmental heterogeneity has long been considered an important contributor to the maintenance of genetic variation, but its effects on inbreeding depression have been largely ignored by empiricists. Here we compare inbreeding depression, measured in two environments, for 20 experimental populations of Drosophila melanogaster that have been maintained under four different selection regimes, including two types of environmentally homogeneous selection and two types environmentally heterogeneous selection. In line with theory, we find considerably higher inbreeding depression in populations from heterogeneous selection regimes. We also use our data set to test whether inbreeding depression is correlated with either stress or the phenotypic coefficient of variation (CV), as suggested by some recent studies. Though both of these factors are significant predictors of inbreeding depression in our study, there is an effect of assay environment on inbreeding depression that cannot be explained by either stress or CV.

  1. A beaklike bony extension of the medial aspect of the greater sciatic notch: a radiographic appearance sexually influenced.

    PubMed

    Gülekon, I N; Turgut, H B

    2002-05-01

    The bony pelvis provides more obvious sex differences than any other bone in the human skeleton. This study evaluates a bony extension of the medial aspect of the greater sciatic notch, which extends caudad to the arcuate line as seen on pelvic radiographs. A total of 2620 randomly selected supine pelvic radiographs (anteroposterior view) of adult females and males were reviewed. The subjects belonged to a central Anatolian population and their age ranged between 18 and 77 years in females and between 18 and 81 years in males. Only 22 (1.7%) of the 1337 female pelvic radiographs showed a bony extension, whereas 882 (68.8%) of the males had one. All these bony extensions were bilateral and symmetric. The results were statistically significant (P < 0.001). We assert that this radiographic appearance is a male characteristic.

  2. The simple wire interosseous fixation technique (SWIFT) for reattachment of FDP avulsions with a large bony fragment.

    PubMed

    Markeson, Daniel B; Mughal, Maleeha; Subramanian, Padmanabhan; Iyer, Srinivasan

    2012-12-01

    Avulsion injuries of the flexor digitorum profundus tendon can be with or without a bony fragment. Types 3, 4, and 5 injuries often have a sizeable bony fragment. In the past, they have been repaired with either a screw, plate, or pull-out wire with a dorsal button, often in combination with a K wire to immobilize the distal interphalangeal joint. We illustrate with 2 cases a simple technique for secure repair of the flexor digitorum profundus avulsions with a bony fragment. In contrast to previously described techniques, our technique involves minimal dissection, has a significantly reduced risk of fracture to the bony fragment, is completely internalized thereby reducing the risk of postoperative infection and allows immediate mobilization.

  3. Effect of the spatial heterogeneity of soil properties on the growth and productivity of soybeans

    NASA Astrophysics Data System (ADS)

    Kutuzova, N. D.; Kust, G. S.; Rozov, S. Yu.; Stoma, G. V.

    2015-01-01

    The joint study of the spatial heterogeneity and dynamics of the biometric parameters of soybean growth and productivity and the soil properties has shown that the thickness and bulk density of the subsurface horizon, which determine the accumulation of water in the root-inhabited layer and its dynamics at the critical stages of soybean growing during the vegetation period, mainly affect the growth dynamics of soybean plants on chernozems in Krasnodar region.

  4. Monte Carlo Investigation on the Effect of Heterogeneities on Strut Adjusted Volume Implant (SAVI) Dosimetry

    NASA Astrophysics Data System (ADS)

    Koontz, Craig

    Breast cancer is the most prevalent cancer for women with more than 225,000 new cases diagnosed in the United States in 2012 (ACS, 2012). With the high prevalence, comes an increased emphasis on researching new techniques to treat this disease. Accelerated partial breast irradiation (APBI) has been used as an alternative to whole breast irradiation (WBI) in order to treat occult disease after lumpectomy. Similar recurrence rates have been found using ABPI after lumpectomy as with mastectomy alone, but with the added benefit of improved cosmetic and psychological results. Intracavitary brachytherapy devices have been used to deliver the APBI prescription. However, inability to produce asymmetric dose distributions in order to avoid overdosing skin and chest wall has been an issue with these devices. Multi-lumen devices were introduced to overcome this problem. Of these, the Strut-Adjusted Volume Implant (SAVI) has demonstrated the greatest ability to produce an asymmetric dose distribution, which would have greater ability to avoid skin and chest wall dose, and thus allow more women to receive this type of treatment. However, SAVI treatments come with inherent heterogeneities including variable backscatter due to the proximity to the tissue-air and tissue-lung interfaces and variable contents within the cavity created by the SAVI. The dose calculation protocol based on TG-43 does not account for heterogeneities and thus will not produce accurate dosimetry; however Acuros, a model-based dose calculation algorithm manufactured by Varian Medical Systems, claims to accurately account for heterogeneities. Monte Carlo simulation can calculate the dosimetry with high accuracy. In this thesis, a model of the SAVI will be created for Monte Carlo, specifically using MCNP code, in order to explore the affects of heterogeneities on the dose distribution. This data will be compared to TG-43 and Acuros calculated dosimetry to explore their accuracy.

  5. Macroscopic geometric heterogeneity effects in radiation dose distribution analysis for boron neutron capture therapy.

    PubMed

    Moran, J M; Nigg, D W; Wheeler, F J; Bauer, W F

    1992-01-01

    Calculations of radiation flux and dose distributions for boron neutron capture therapy (BNCT) of brain tumors are typically performed using sophisticated three-dimensional analytical models based on either a homogeneous approximation or a simplified few-region approximation to the actual highly heterogeneous geometry of the irradiation volume. Such models should be validated by comparison with calculations using detailed models in which all significant macroscopic tissue heterogeneities and geometric structures are explicitly represented as faithfully as possible. This paper describes such a validation exercise for BNCT of canine brain tumors. Geometric measurements of the canine anatomical structures of interest for this work were performed by dissecting and examining two essentially identical Labrador retriever heads. Chemical analyses of various tissue samples taken during the dissections were conducted to obtain measurements of elemental compositions for the tissues of interest. The resulting geometry and tissue composition data were then used to construct a detailed heterogeneous calculational model of the Labrador head. Calculations of three-dimensional radiation flux distributions pertinent to BNCT were performed for this model using the TORT discrete-ordinates radiation transport code. The calculations were repeated for a corresponding volume-weighted homogeneous-tissue model. Comparison of the results showed that peak neutron and photon flux magnitudes were quite similar for the two models (within 5%), but that the spatial flux profiles were shifted in the heterogeneous model such that the fluxes in some locations away from the peak differed from the corresponding fluxes in the homogeneous model by as much as 10%-20%. Differences of this magnitude can be therapeutically significant, emphasizing the need for proper validation of simplified treatment planning models.

  6. Scale-Dependent Effects of a Heterogeneous Landscape on Genetic Differentiation in the Central American Squirrel Monkey (Saimiri oerstedii)

    PubMed Central

    Blair, Mary E.; Melnick, Don J.

    2012-01-01

    Landscape genetic studies offer a fine-scale understanding of how habitat heterogeneity influences population genetic structure. We examined population genetic structure and conducted a landscape genetic analysis for the endangered Central American Squirrel Monkey (Saimiri oerstedii) that lives in the fragmented, human-modified habitats of the Central Pacific region of Costa Rica. We analyzed non-invasively collected fecal samples from 244 individuals from 14 groups for 16 microsatellite markers. We found two geographically separate genetic clusters in the Central Pacific region with evidence of recent gene flow among them. We also found significant differentiation among groups of S. o. citrinellus using pairwise FST comparisons. These groups are in fragments of secondary forest separated by unsuitable “matrix” habitats such as cattle pasture, commercial African oil palm plantations, and human residential areas. We used an individual-based landscape genetic approach to measure spatial patterns of genetic variance while taking into account landscape heterogeneity. We found that large, commercial oil palm plantations represent moderate barriers to gene flow between populations, but cattle pastures, rivers, and residential areas do not. However, the influence of oil palm plantations on genetic variance was diminished when we restricted analyses to within population pairs, suggesting that their effect is scale-dependent and manifests during longer dispersal events among populations. We show that when landscape genetic methods are applied rigorously and at the right scale, they are sensitive enough to track population processes even in species with long, overlapping generations such as primates. Thus landscape genetic approaches are extremely valuable for the conservation management of a diverse array of endangered species in heterogeneous, human-modified habitats. Our results also stress the importance of explicitly considering the heterogeneity of matrix habitats

  7. Scale-dependent effects of a heterogeneous landscape on genetic differentiation in the Central American squirrel monkey (Saimiri oerstedii).

    PubMed

    Blair, Mary E; Melnick, Don J

    2012-01-01

    Landscape genetic studies offer a fine-scale understanding of how habitat heterogeneity influences population genetic structure. We examined population genetic structure and conducted a landscape genetic analysis for the endangered Central American Squirrel Monkey (Saimiri oerstedii) that lives in the fragmented, human-modified habitats of the Central Pacific region of Costa Rica. We analyzed non-invasively collected fecal samples from 244 individuals from 14 groups for 16 microsatellite markers. We found two geographically separate genetic clusters in the Central Pacific region with evidence of recent gene flow among them. We also found significant differentiation among groups of S. o. citrinellus using pairwise F(ST) comparisons. These groups are in fragments of secondary forest separated by unsuitable "matrix" habitats such as cattle pasture, commercial African oil palm plantations, and human residential areas. We used an individual-based landscape genetic approach to measure spatial patterns of genetic variance while taking into account landscape heterogeneity. We found that large, commercial oil palm plantations represent moderate barriers to gene flow between populations, but cattle pastures, rivers, and residential areas do not. However, the influence of oil palm plantations on genetic variance was diminished when we restricted analyses to within population pairs, suggesting that their effect is scale-dependent and manifests during longer dispersal events among populations. We show that when landscape genetic methods are applied rigorously and at the right scale, they are sensitive enough to track population processes even in species with long, overlapping generations such as primates. Thus landscape genetic approaches are extremely valuable for the conservation management of a diverse array of endangered species in heterogeneous, human-modified habitats. Our results also stress the importance of explicitly considering the heterogeneity of matrix habitats in

  8. The dual effect of ephaptic coupling on cardiac conduction with heterogeneous expression of connexin 43.

    PubMed

    Wei, Ning; Mori, Yoichiro; Tolkacheva, Elena G

    2016-05-21

    Decreased and heterogeneous expression of connexin 43 (Cx43) are common features in animal heart failure models. Ephpatic coupling, which relies on the presence of junctional cleft space between the ends of adjacent cells, has been suggested to play a more active role in mediating intercellular electrical communication when gap junctions are reduced. To better understand the interplay of Cx43 expression and ephaptic coupling on cardiac conduction during heart failure, we performed numerical simulations on our model when Cx43 expression is reduced and heterogeneous. Under severely reduced Cx43 expression, we identified three new phenomena in the presence of ephaptic coupling: alternating conduction, in which ephaptic and gap junction-mediated mechanisms alternate; instability of planar fronts; and small amplitude action potential (SAP), which has a smaller potential amplitude than the normal action potential. In the presence of heterogeneous Cx43 expression, ephaptic coupling can either prevent or promote conduction block (CB) depending on the Cx43 knockout (Cx43KO) content. When Cx43KO content is relatively high, ephaptic coupling reduces the probabilities of CB. However, ephaptic coupling promotes CB when Cx43KO and wild type cells are mixed in roughly equal proportion, which can be attributed to an increase in current-to-load mismatch.

  9. Modeling the Heterogeneous Effects of GHG Mitigation Policies on Global Agriculture and Forestry

    NASA Astrophysics Data System (ADS)

    Golub, A.; Henderson, B.; Hertel, T. W.; Rose, S. K.; Sohngen, B.

    2010-12-01

    Agriculture and forestry are envisioned as potentially key sectors for climate change mitigation policy, yet the depth of analysis of mitigation options and their economic consequences remains remarkably shallow in comparison to that for industrial mitigation. Farming and land use change - much of it induced by agriculture -account for one-third of global greenhouse gas (GHG) emissions. Any serious attempt to curtail these emissions will involve changes in the way farming is conducted, as well as placing limits on agricultural expansion into areas currently under more carbon-intensive land cover. However, agriculture and forestry are extremely heterogeneous, both in the technology and intensity of production, as well as in the GHG emissions intensity of these activities. And these differences, in turn, give rise to significant changes in the distribution of agricultural production, trade and consumption in the wake of mitigation policies. This paper assesses such distributional impacts via a global economic analysis undertaken with a modified version of the GTAP model. The paper builds on a global general equilibrium GTAP-AEZ-GHG model (Golub et al., 2009). This is a unified modeling framework that links the agricultural, forestry, food processing and other sectors through land, and other factor markets and international trade, and incorporates different land-types, land uses and related CO2 and non-CO2 GHG emissions and sequestration. The economic data underlying this work is the global GTAP data base aggregated up to 19 regions and 29 sectors. The model incorporates mitigation cost curves for different regions and sectors based on information from the US-EPA. The forestry component of the model is calibrated to the results of the state of the art partial equilibrium global forestry model of Sohngen and Mendelson (2007). Forest carbon sequestration at both the extensive and intensive margins are modeled separately to better isolate land competition between

  10. The Effects of Heterogeneities on Seismic Wave Propagation in the Climax Stock

    SciTech Connect

    Hagan Webb, C., Snelson, C. M., White, R., Emmitt, R., Barker, D., Abbott, R., Bonal, N.

    2011-12-01

    The Comprehensive Nuclear Test-Ban Treaty requires the ability to detect low-yield (less than 150kton) nuclear events. This kind of monitoring can only be done seismically on a regional scale (within 2000km). At this level, it is difficult to distinguish between low-yield nuclear events and non-nuclear events of similar magnitude. In order to confidently identify a nuclear event, a more detailed understanding of nuclear seismic sources is needed. In particular, it is important to know the effects of local geology on the seismic signal. This study focuses on P-wave velocity in heterogeneous granitoid. The Source Physics Experiment (SPE) is currently performing low-yield tests with chemical explosives at the Nevada National Security Site (NNSS). The exact test site was chosen to be in the Climax Stock, a cretaceous granodiorite and quartz-monzonite pluton located in Area 15 of the NNSS. It has been used in the past for the Hard Hat and Pile Driver nuclear tests, which provided legacy data that can be used to simulate wave propagation. The Climax Stock was originally chosen as the site of the SPE partly because of its assumed homogeneity. It has since been discovered that the area of the stock where the SPE tests are being performed contains a perched water table. In addition, the stock is known to contain an extensive network of faults, joints, and fractures, but the exact effect of these structural features on seismic wave velocity is not fully understood. The SPE tests are designed to seismically capture the explosion phenomena from the near- to the far-field transition of the seismic waveform. In the first SPE experiment, 100kg of chemical explosives were set off at a depth of 55m. The blast was recorded with an array of sensors and diagnostics, including accelerometers, geophones, rotational sensors, short-period and broadband seismic sensors, Continuous Reflectometry for Radius vs. Time Experiment, Time of Arrival, Velocity of Detonation, and infrasound sensors

  11. Effect of pattern formation on C and N turnover heterogeneity in initial soils

    NASA Astrophysics Data System (ADS)

    Schaaf, Wolfgang; Zimmermann, Claudia

    2013-04-01

    The formation of vegetation patterns and hydrological processes, among others, result in soil heterogeneity in newly exposed land surfaces. We studied the effect of these developling structures on carbon and nitrogen trunover in soils of the artificial catchment Chicken Creek (Schaaf et al. 2011, 2012). Substrates with different physical and geochemical properties in combination with different labelled plant litter materials were studied in a microcosm experiment over a period of 80 weeks. Main objectives of the microcosm experiment were to determine the transformation processes of C and N from litter decomposition within the gaseous, liquid and solid phase, the interaction with mineral surfaces and its role for the establishment of biogeochemical cycles. The microcosm experiments were established in a climate chamber at constant 10 °C. In total, 48 soil columns (diameter: 14.4 cm; height: 30 cm) were filled with two different quaternary substrates (sand and loamy sand) representing the textural variation within the catchment at a bulk density of 1.4-1.5 g cm-3. The columns were automatically irrigated with artificial rainwater four times a day with 6.6 ml each (corresponding to 600 mm yr-1). The gaseous phase in the headspace of the microcosms was analyzed continuously for CO2 and N2O concentrations. C and N transformation processes were studied using 13C and 15N labelled litter of two different plant species occurring at the catchment (Lotus corniculatus, Calamagrostis epigejos) that was incorporated into the microcosm surface. By including litter from species with wide distribution within the catchment and soil substrates representing the main variation types of the sediments used for catchment construction we were able to characterize the general function of these sub-patches within the catchment with respect to litter decomposition, soil solution composition, DOC and nutrient leaching, and impact on the mineral soil phase. The results suggest that initial

  12. The Effects of Heterogeneities on Seismic Wave Propagation in the Climax Stock

    NASA Astrophysics Data System (ADS)

    Webb, C. H.; Snelson, C. M.; White, R. L.; Emmitt, R. F.; Barker, D. L.; Abbott, R. E.; Bonal, N. D.

    2011-12-01

    The Comprehensive Nuclear Test-Ban Treaty requires the ability to detect low-yield (less than 150kton) nuclear events. This kind of monitoring can only be done seismically on a regional scale (within 2000km). At this level, it is difficult to distinguish between low-yield nuclear events and non-nuclear events of similar magnitude. In order to confidently identify a nuclear event, a more detailed understanding of nuclear seismic sources is needed. In particular, it is important to know the effects of local geology on the seismic signal. This study focuses on P-wave velocity in heterogeneous granitoid. The Source Physics Experiment (SPE) is currently performing low-yield tests with chemical explosives at the Nevada National Security Site (NNSS). The exact test site was chosen to be in the Climax Stock, a cretaceous granodiorite and quartz-monzonite pluton located in Area 15 of the NNSS. It has been used in the past for the Hard Hat and Pile Driver nuclear tests, which provided legacy data that can be used to simulate wave propagation. The Climax Stock was originally chosen as the site of the SPE partly because of its assumed homogeneity. It has since been discovered that the area of the stock where the SPE tests are being performed contains a perched water table. In addition, the stock is known to contain an extensive network of faults, joints, and fractures, but the exact effect of these structural features on seismic wave velocity is not fully understood. The SPE tests are designed to seismically capture the explosion phenomena from the near- to the far-field transition of the seismic waveform. In the first SPE experiment, 100kg of chemical explosives were set off at a depth of 55m. The blast was recorded with an array of sensors and diagnostics, including accelerometers, geophones, rotational sensors, short-period and broadband seismic sensors, Continuous Reflectometry for Radius vs. Time Experiment, Time of Arrival, Velocity of Detonation, and infrasound sensors

  13. Monte Carlo simulation of the Leksell Gamma Knife®: II. Effects of heterogeneous versus homogeneous media for stereotactic radiosurgery

    NASA Astrophysics Data System (ADS)

    Moskvin, Vadim; Timmerman, Robert; DesRosiers, Colleen; Randall, Marcus; DesRosiers, Paul; Dittmer, Phil; Papiez, Lech

    2004-11-01

    The absence of electronic equilibrium in the vicinity of bone-tissue or air-tissue heterogeneity in the head can misrepresent deposited dose with treatment planning algorithms that assume all treatment volume as homogeneous media. In this paper, Monte Carlo simulation (PENELOPE) and measurements with a specially designed heterogeneous phantom were applied to investigate the effect of air-tissue and bone-tissue heterogeneity on dose perturbation with the Leksell Gamma Knife®. The dose fall-off near the air-tissue interface caused by secondary electron disequilibrium leads to overestimation of dose by the vendor supplied treatment planning software (GammaPlan®) at up to 4 mm from an interface. The dose delivered to the target area away from an air-tissue interface may be underestimated by up to 7% by GammaPlan® due to overestimation of attenuation of photon beams passing through air cavities. While the underdosing near the air-tissue interface cannot be eliminated with any plug pattern, the overdosage due to under-attenuation of the photon beams in air cavities can be eliminated by plugging the sources whose beams intersect the air cavity. Little perturbation was observed next to bone-tissue interfaces. Monte Carlo results were confirmed by measurements. This study shows that the employed Monte Carlo treatment planning is more accurate for precise dosimetry of stereotactic radiosurgery with the Leksell Gamma Knife® for targets in the vicinity of air-filled cavities.

  14. Heterogeneity in a room-temperature ionic liquid: persistent local environments and the red-edge effect.

    PubMed

    Hu, Zhonghan; Margulis, Claudio J

    2006-01-24

    In this work, we investigate the slow dynamics of 1-butyl-3-methylimidazolium hexafluorophosphate, a very popular room-temperature ionic solvent. Our study predicts the existence of heterogeneity in the liquid and shows that this heterogeneity is the underlying microscopic cause for the recently reported "red-edge effect" (REE) observed in the study of fluorescence of the organic probe 2-amino-7-nitrofluorene. This theoretical work explains in microscopic terms the relation between REE and dynamic heterogeneity in a room-temperature ionic liquid (IL). The REE is typical of micellar or colloidal systems, which are characterized by microscopic environments that are structurally very different. In contrast, in the case of this room-temperature IL, the REE occurs because of the long period during which molecules are trapped in quasistatic local solvent cages. This trapping time, which is longer than the lifetime of the excited-state probe, together with the inability of the surroundings to adiabatically relax, induces a set of site-specific spectroscopic responses. Subensembles of fluorescent molecules associated with particular local environments absorb and emit at different frequencies. We describe in detail the absorption wavelength-dependent emission spectra of 2-amino-7-nitrofluorene and show that this dependence on lambda(ex) is characteristic of the IL and, as is to be expected, is absent in the case of a normal solvent such as methanol.

  15. Coupling Between Flow and Precipitation In Heterogeneous Subsurface Environments and Effects on Contaminant Fate and Transport (Project no. 99272)

    SciTech Connect

    Redden, G.D.; Fujita, Y.; Scheibe, T.D.; Tartakovsky, A.M.; Smith, R.W.; Reddy, M.M.; Kelly, S.D.

    2006-04-05

    This project is aimed at understanding how contaminant transport in heterogeneous porous media is impacted by precipitation and dissolution events through chemical interactions with precipitates and as a consequence of coupling between precipitation and flow. We hypothesize that precipitation/coprecipitation, encapsulation, isolation from flow and alteration of reactive surfaces will contribute to altering contaminant mobility during precipitation events, and that predicting the release of contaminants during precipitate dissolution requires an understanding of how precipitates are distributed and how contaminants are released from the different compartments over time. Using calcium carbonate as a model system, physical experiments and modeling at the pore-scale and continuum-scale will be used to improve the conceptual approach to predicting the impact of flow-precipitation coupling on solute migration. Column and 2-dimensional intermediate-scale experiments with constructed physical and chemical heterogeneities will be used to investigate the movement of fluids and reactive solutes during different types of mixing events that lead to calcium carbonate supersaturation and precipitation. Smoothed particle hydrodynamic modeling will be used to simulate pore-scale mixing and precipitation in heterogeneous porous media and estimate continuum-scale parameters. Continuum-scale modeling will be used to test conceptual models and associated effective parameters that simulate the macroscopic behavior of the experimental domains.

  16. SU-E-J-63: Estimating the Effects of Respiratory Motion On Dose Heterogeneity for ITV-Based Treatments

    SciTech Connect

    Williams, C; Lewis, J

    2014-06-01

    Purpose: To quantify the relationship between the amount of dose heterogeneity in a treatment plan that uses an internal target volume (ITV) to account for respiratory motion and the true amount of heterogeneity in the dose delivered to the tumor contained within that ITV. Methods: We develop a convolution-based framework for calculating dose delivered to a tumor moving inside an ITV according to a common sinusoid-based breathing model including asymmetry. We model the planned ITV dose distribution as a centrally peaked analytic function approximating the profile of clinical stereotactic body radiotherapy treatments. Expressions for the minimum and maximum dose received by the tumor are derived and evaluated for a range of clinically relevant parameters. Results of the model are validated with phantom measurements using an ion chamber array. Results: An analytic expression is presented for the maximum and minimum doses received by the tumor relative to the planned ITV dose. The tumor dose heterogeneity depends solely on the ratio of tumor size to ITV size, the peak dose in the planned ITV dose distribution, and the respiratory asymmetry parameter. Under the assumptions of this model, using a typical breathing asymmetry parameter and a dose distribution with a fixed size ITV covered by the 100% line and with a 130% hotspot, the maximum dose to the tumor varies between 113%–130%, and the minimum dose varies between 100%–116% depending on the amount of tumor motion. Conclusion: This modeling exercise demonstrates the interplay between motion and dose heterogeneity. Tumors that exhibit large amounts of respiratory motion relative to their size will receive a more homogeneous dose and a larger minimum dose than would be inferred from the ITV dose distribution. This effect is not captured in current clinical treatment planning methods unless 4D dose calculation techniques are used. This work was partially supported by a Varian Medical Systems research grant.

  17. Effects of spatial heterogeneity on butterfly species richness in Rocky Mountain National Park, CO, USA

    USGS Publications Warehouse

    Kumar, S.; Simonson, S.E.; Stohlgren, T.J.

    2009-01-01

    We investigated butterfly responses to plot-level characteristics (plant species richness, vegetation height, and range in NDVI [normalized difference vegetation index]) and spatial heterogeneity in topography and landscape patterns (composition and configuration) at multiple spatial scales. Stratified random sampling was used to collect data on butterfly species richness from seventy-six 20 ?? 50 m plots. The plant species richness and average vegetation height data were collected from 76 modified-Whittaker plots overlaid on 76 butterfly plots. Spatial heterogeneity around sample plots was quantified by measuring topographic variables and landscape metrics at eight spatial extents (radii of 300, 600 to 2,400 m). The number of butterfly species recorded was strongly positively correlated with plant species richness, proportion of shrubland and mean patch size of shrubland. Patterns in butterfly species richness were negatively correlated with other variables including mean patch size, average vegetation height, elevation, and range in NDVI. The best predictive model selected using Akaike's Information Criterion corrected for small sample size (AICc), explained 62% of the variation in butterfly species richness at the 2,100 m spatial extent. Average vegetation height and mean patch size were among the best predictors of butterfly species richness. The models that included plot-level information and topographic variables explained relatively less variation in butterfly species richness, and were improved significantly after including landscape metrics. Our results suggest that spatial heterogeneity greatly influences patterns in butterfly species richness, and that it should be explicitly considered in conservation and management actions. ?? 2008 Springer Science+Business Media B.V.

  18. Optimization of the Implementation of Managed Aquifer Recharge - Effects of Aquifer Heterogeneity

    NASA Astrophysics Data System (ADS)

    Maliva, Robert; Missimer, Thomas; Kneppers, Angeline

    2010-05-01

    Managed aquifer recharge (MAR) has become a key component of integrated water resources management, especially in water scarce regions. MAR can serve the dual role of increasing the supply of available water and improving the quality of recharged water through natural attenuation processes. The performance of MAR systems is highly dependent upon site-specific hydrogeological conditions. Aquifer heterogeneity, such as the presence of high-permeability preferential flow zones and dual or even the so-called triple-porosity conditions, has been responsible for the under performance or failure of some MAR systems. Aquifer heterogeneity can result in much more rapid and unpredictable movement and mixing of recharged water and the bypassing of natural attenuation processes. A critical element of MAR projects is a detailed aquifer characterization and the development of groundwater flow and solute transport models at the appropriate spatial and temporal scales that accurately simulate local heterogeneous flow systems. Geochemical modeling based on high-quality, site-specific mineralogical and water chemistry data can also be used to predict the potential for adverse water-rock interactions such as the leaching of arsenic and trace metals into recharged water. Hydrogeological conditions that could lead to poor system performance should be identified early in the project development before the investment is made to construct a full-scale system. Hydrogeological conditions that have lead to poor MAR system performance are typically identifiable at the exploratory well stage of projects. Early detection of adverse hydrogeological conditions provides an opportunity to either abandon a likely under-performing project, select an alternative site with more favorable conditions, or modify the system design to be more compatible with local hydrogeology. Advanced borehole geophysical techniques and workflow software can allow for enhanced aquifer characterization and thus allow for

  19. Shear zone nucleation and deformation transient: effect of heterogeneities and loading conditions in experimentally deformed calcite

    NASA Astrophysics Data System (ADS)

    Morales, L. F. G.; Rybacki, E.; Dresen, G. H.; Kilian, R.

    2015-12-01

    In the Earth's middle to lower crust, strain is frequently localized along ductile shear zones, which commonly nucleate at structural and material heterogeneities. To investigate shear zone nucleation and development due to heterogeneities, we performed constant strain-rate (CSR) and constant stress (CS) simple shear (torsion) deformation experiments on Carrara marble samples containing weak (limestone) inclusions. The experiments were conducted in a Paterson-type gas deformation apparatus at 900 °C temperature and 400 MPa confining pressure and maximum bulk shear strains of 3. Peak shear stress was about 20 MPa for all the samples, followed by smooth weakening and steady state behavior. The strain is predominantly localized in the host marble within the process zone in front of the inclusion, defined by a zone of intense grain size reduction due to dynamic recrystallization. In CS tests a narrow shear zone developed in front of the inclusion, whereas in CSR experiments the deformation is more heterogeneously distributed, up to g=3.. In the later, secondary foliations oblique to the process zone and alternating thin, high-strain layers are common. In samples deformed at the same shear strain (g=1), the average recrystallized grain size in the process zone is similar for CS and CSR conditions. Crystallographic preferred orientation (CPO) measurements shows that different grain sizes have slightly different CPO patterns. CPO strength varies for different grain sizes, with a CPO strength peak between 40-50 μm, decreasing progressively within smaller grain size, but with secondary peaks for different coarse-grained sizes. Our observations suggest that the initial formation and transient deformation of shear zones is strongly affected by loading conditions.

  20. Using patient self-reports to study heterogeneity of treatment effects in major depressive disorder

    PubMed Central

    Kessler, R.C.; van Loo, H.M.; Wardenaar, K.J.; Bossarte, R.M.; Brenner, L.A.; Ebert, D.D; de Jonge, P.; Nierenberg, A.A.; Rosellini, A.J.; Sampson, N.A.; Schoevers, R.A.; Wilcox, M.A.; Zaslavsky, A.M.

    2016-01-01

    Aims Clinicians need guidance to address the heterogeneity of treatment responses of patients with major depressive disorder (MDD). While prediction schemes based on symptom clustering and biomarkers have so far not yielded results of sufficient strength to inform clinical decision-making, prediction schemes based on big data predictive analytic models might be more practically useful. Methods We review evidence suggesting that prediction equations based on symptoms and other easily-assessed clinical features found in previous research to predict MDD treatment outcomes might provide a foundation for developing predictive analytic clinical decision support models that could help clinicians select optimal (personalized) MDD treatments. These methods could also be useful in targeting patient subsamples for more expensive biomarker assessments. Results Approximately two dozen baseline variables obtained from medical records or patient reports have been found repeatedly in MDD treatment trials to predict overall treatment outcomes (i.e., intervention versus control) or differential treatment outcomes (i.e., intervention A versus intervention B). Similar evidence has been found in observational studies of MDD persistence-severity. However, no treatment studies have yet attempted to develop treatment outcome equations using the full set of these predictors. Promising preliminary empirical results coupled with recent developments in statistical methodology suggest that models could be developed to provide useful clinical decision support in personalized treatment selection. These tools could also provide a strong foundation to increase statistical power in focused studies of biomarkers and MDD heterogeneity of treatment response in subsequent controlled trials. Conclusions Coordinated efforts are needed to develop a protocol for systematically collecting information about established predictors of heterogeneity of MDD treatment response in large observational treatment

  1. Analyzing heterogeneity in the effects of physical activity in children on social network structure and peer selection dynamics

    PubMed Central

    Henry, Teague; Gesell, Sabina B.; Ip, Edward H.

    2016-01-01

    Background Social networks influence children and adolescents’ physical activity. The focus of this paper is to examine the differences in the effects of physical activity on friendship selection, with eye to the implications on physical activity interventions for young children. Network interventions to increase physical activity are warranted but have not been conducted. Prior to implementing a network intervention in the field, it is important to understand potential heterogeneities in the effects that activity level have on network structure. In this study, the associations between activity level and cross sectional network structure, and activity level and change in network structure are assessed. Methods We studied a real-world friendship network among 81 children (average age 7.96 years) who lived in low SES neighborhoods, attended public schools, and attended one of two structured aftercare programs, of which one has existed and the other was new. We used the exponential random graph model (ERGMs) and its longitudinal extension to evaluate the association between activity level and various demographic factors in having, forming, and dissolving friendship. Due to heterogeneity between the friendship networks within the aftercare programs, separate analyses were conducted for each network. Results There was heterogeneity in the effect of physical activity on both cross sectional network structure and the formation and dissolution processes, both across time and between networks. Conclusions Network analysis could be used to assess the unique structure and dynamics of a social network before an intervention is implemented, so as to optimize the effects of the network intervention for increasing childhood physical activity. Additionally, if peer selection processes are changing within a network, a static network intervention strategy for childhood physical activity could become inefficient as the network evolves. PMID:27867518

  2. The Effect of Mantle Heterogeneity on Tidal Gravity and Surface Deformations

    NASA Astrophysics Data System (ADS)

    Metivier, L.; Conrad, C. P.

    2007-12-01

    Precise knowledge of Earth tides is crucial for correcting the signal from satellite gravity surveys or superconducting gravimeters with nanoGal precision. Some local observations show unexplained perturbations to the tidal gravity signal. This noise is generally considered to result from unmodeled loading induced by oceanic tides, but it is possible that an unmodeled component of Earth's body tides contributes to this noise. In fact, the strain and gravity responses of the Earth to body tides are generally computed assuming a radially (or elliptically) stratified Earth. However, seismic tomography surveys and fluid dynamic studies show that thermal convection in Earth's mantle produces significant heterogeneity. Superplumes beneath the Pacific and South Africa superswells, and descending slabs that ring the Pacific are examples of this internal heterogeneity. We have determined body tides for a non-radially symmetric earth model using a spectral element method. The structure of the laterally-heterogeneous mantle interior has been inferred from a tomographic model. We couple this heterogeneity to a viscous convection model to compute dynamic topography on surface and CMB, and verify the complete Earth model using geoid observations. We investigated semi-diurnal, diurnal and a few longer periods wave tides. We show that laterally-varying mantle structure induces perturbations in surface tidal response of the solid Earth of about 1 per mil. Using a tidal catalogue, we show that the maximum perturbation of radial tidal and geoid displacements are about 0.25 mm and about 0.1 mm, respectively, and the maximum perturbation of tidal gravity variation is about 120 nanoGal. This gravity perturbation is 100 times larger than the present precision of superconducting gravimeters and is at the level of the observed tidal noise. However, the amplitudes of tidal perturbations depend strongly on location, and are particularly high above large dense slabs (such as those near South

  3. The Tree of Life and a New Classification of Bony Fishes

    PubMed Central

    Betancur-R., Ricardo; Broughton, Richard E.; Wiley, Edward O.; Carpenter, Kent; López, J. Andrés; Li, Chenhong; Holcroft, Nancy I.; Arcila, Dahiana; Sanciangco, Millicent; Cureton II, James C; Zhang, Feifei; Buser, Thaddaeus; Campbell, Matthew A.; Ballesteros, Jesus A; Roa-Varon, Adela; Willis, Stuart; Borden, W. Calvin; Rowley, Thaine; Reneau, Paulette C.; Hough, Daniel J.; Lu, Guoqing; Grande, Terry; Arratia, Gloria; Ortí, Guillermo

    2013-01-01

    The tree of life of fishes is in a state of flux because we still lack a comprehensive phylogeny that includes all major groups. The situation is most critical for a large clade of spiny-finned fishes, traditionally referred to as percomorphs, whose uncertain relationships have plagued ichthyologists for over a century. Most of what we know about the higher-level relationships among fish lineages has been based on morphology, but rapid influx of molecular studies is changing many established systematic concepts. We report a comprehensive molecular phylogeny for bony fishes that includes representatives of all major lineages. DNA sequence data for 21 molecular markers (one mitochondrial and 20 nuclear genes) were collected for 1410 bony fish taxa, plus four tetrapod species and two chondrichthyan outgroups (total 1416 terminals). Bony fish diversity is represented by 1093 genera, 369 families, and all traditionally recognized orders. The maximum likelihood tree provides unprecedented resolution and high bootstrap support for most backbone nodes, defining for the first time a global phylogeny of fishes. The general structure of the tree is in agreement with expectations from previous morphological and molecular studies, but significant new clades arise. Most interestingly, the high degree of uncertainty among percomorphs is now resolved into nine well-supported supraordinal groups. The order Perciformes, considered by many a polyphyletic taxonomic waste basket, is defined for the first time as a monophyletic group in the global phylogeny. A new classification that reflects our phylogenetic hypothesis is proposed to facilitate communication about the newly found structure of the tree of life of fishes. Finally, the molecular phylogeny is calibrated using 60 fossil constraints to produce a comprehensive time tree. The new time-calibrated phylogeny will provide the basis for and stimulate new comparative studies to better understand the evolution of the amazing

  4. Comparative study of notoungulate (Placentalia, Mammalia) bony labyrinths and new phylogenetically informative inner ear characters

    PubMed Central

    Macrini, Thomas E; Flynn, John J; Ni, Xijun; Croft, Darin A; Wyss, André R

    2013-01-01

    The phylogenetic relationships of notoungulates, an extinct group of predominantly South American herbivores, remain poorly resolved with respect to both other placental mammals and among one another. Most previous phylogenetic analyses of notoungulates have not included characters of the internal cranium, not least because few such features, including the bony labyrinth, have been described for members of the group. Here we describe the inner ears of the notoungulates Altitypotherium chucalensis (Mesotheriidae), Pachyrukhos moyani (Hegetotheriidae) and Cochilius sp. (Interatheriidae) based on reconstructions of bony labyrinths obtained from computed tomography imagery. Comparisons of the bony labyrinths of these taxa with the basally diverging notoungulate Notostylops murinus (Notostylopidae), an isolated petrosal from Itaboraí, Brazil, referred to Notoungulata, and six therian outgroups, yielded an inner ear character matrix of 25 potentially phylogenetically informative characters, 14 of them novel to this study. Two equivocally optimized character states potentially support a pairing of Mesotheriidae and Hegetotheriidae, whereas four others may be diagnostic of Notoungulata. Three additional characters are potentially informative for diagnosing more inclusive clades: one for crown Placentalia; another for a clade containing Kulbeckia, Zalambdalestes, and Placentalia; and a third for Eutheria (crown Placentalia plus stem taxa). Several other characters are apomorphic for at least one notoungulate in our study and are of potential interest for broader taxonomic sampling within Notoungulata to clarify currently enigmatic interrelationships. Measures of the semicircular canals were used to infer agility (e.g. capable of quick movements vs. lethargic movements) of these taxa. Agility scores calculated from these data generally corroborate interpretations based on postcranial remains of these or closely related species. We provide estimates of the low

  5. Comparative Anatomy of the Bony Labyrinth (Inner Ear) of Placental Mammals

    PubMed Central

    Ekdale, Eric G.

    2013-01-01

    Background Variation is a naturally occurring phenomenon that is observable at all levels of morphology, from anatomical variations of DNA molecules to gross variations between whole organisms. The structure of the otic region is no exception. The present paper documents the broad morphological diversity exhibited by the inner ear region of placental mammals using digital endocasts constructed from high-resolution X-ray computed tomography (CT). Descriptions cover the major placental clades, and linear, angular, and volumetric dimensions are reported. Principal Findings The size of the labyrinth is correlated to the overall body mass of individuals, such that large bodied mammals have absolutely larger labyrinths. The ratio between the average arc radius of curvature of the three semicircular canals and body mass of aquatic species is substantially lower than the ratios of related terrestrial taxa, and the volume percentage of the vestibular apparatus of aquatic mammals tends to be less than that calculated for terrestrial species. Aspects of the bony labyrinth are phylogenetically informative, including vestibular reduction in Cetacea, a tall cochlear spiral in caviomorph rodents, a low position of the plane of the lateral semicircular canal compared to the posterior canal in Cetacea and Carnivora, and a low cochlear aspect ratio in Primatomorpha. Significance The morphological descriptions that are presented add a broad baseline of anatomy of the inner ear across many placental mammal clades, for many of which the structure of the bony labyrinth is largely unknown. The data included here complement the growing body of literature on the physiological and phylogenetic significance of bony labyrinth structures in mammals, and they serve as a source of data for future studies on the evolution and function of the vertebrate ear. PMID:23805251

  6. Anatomical study of suboccipital vertebral arteries and surrounding bony structures using virtual reality technology

    PubMed Central

    Ha, Wenbo; Yang, DeLin; Gu, Shixin; Xu, Qi-Wu; Che, Xiaoming; Wu, Jin-Song; Li, Wensheng

    2014-01-01

    Background This work aimed to evaluate the efficacy of virtual reality (VR) technology in neurosurgical anatomy through a comparison of the virtual 3D microanatomy of the suboccipital vertebral arteries and their bony structures as part of the resection of tumors in the craniovertebral junction (CVJ) of 20 patients compared to the actual microanatomy of the vertebral arteries of 15 cadaveric headsets. Material/Methods The study was conducted with 2 groups of data: a VR group composed of 20 clinical cases and a physical body group (PB group) composed of 15 cadaveric headsets. In the VR group, the dissection and measurements of the vertebral arteries were simulated on a Dextroscope. In the PB group, the vertebral arteries in the cadaver heads were examined under a microscope and anatomical measurements of VA and bony structures were performed. The length and course of the vertebral arteries and its surrounding bony structures in each group were compared. Results The distances from the inferior part of the transverse process foramen (TPF) of C1 to the inferior part of TPF of C2 were 17.68±2.86 mm and 18.4±1.82 mm in the PB and VR groups, respectively. The distances between the middle point of the posterior arch of the atlas and the medial intersection of VA on the groove were 17.35±2.23 mm in the PB group and 18.13±2.58 mm in the VR group. The distances between the middle line and the entrance of VA to the lower rim of TPF of Atlas were 28.64±2.67 mm in PB group and 29.23±2.89 mm in VR group. The diameters of the vertebral artery (VA) at the end of the groove and foramen of C2 transverse process were 4.02±046 mm and 4.25±0.51 mm, respectively, in the PB group and 3.54±0.44 mm and 4.47±0.62 mm, respectively, in VR group. The distances between the VA lumen center and midline of the foramen magnum at the level of dural penetration was 10.4±1.13 mm in the PB group and 11.5±1.34 mm in the VR group (P>0.05). Conclusions VR technology can accurately simulate the

  7. Bony fusion of the maxilla and mandible as a sequelae of noma: A rare case report

    PubMed Central

    Awasthi, Ujjwala Rastogi; Mody, Bharat M.; Suma, Gundareddy N.; Garg, Shruti

    2015-01-01

    Noma is a gangrenous disease of the orofacial region that leads to severe facial tissue destruction and is a significant cause of death among children. With the advent of modern antibiotics and improved nutrition, children with noma may survive into adulthood, but must face the challenge of undergoing repair of the sequelae of noma. This report describes a case of bony fusion of the maxilla and mandible in a 28-year-old female patient, which was a sequelae of a childhood case of noma. PMID:26389063

  8. Effects of outcome devaluation on instrumental behaviors in a discriminated heterogeneous chain.

    PubMed

    Thrailkill, Eric A; Bouton, Mark E

    2017-01-01

    Operant behavior often takes place in a sequence, or chain, of linked responses that lead to a reinforcer. We have recently studied rats performing a discriminated heterogeneous behavior chain that involves the presentation of a discriminative stimulus (e.g., a panel light) to set the occasion for a procurement behavior (e.g., a lever press) that leads to a second stimulus (e.g., a second panel light) that indicates that a consumption response (e.g., a chain pull) will be reinforced. The present study assessed the role played by a representation of the reinforcer in controlling the performance of the responses in this chain. After acquisition of the chain, rats received a reinforcer devaluation treatment in the form of repeated paired, or unpaired, presentations of the food-pellet outcome and lithium-chloride illness. Once paired rats came to reject the pellets, half the animals in each group were tested on procurement, and the other half were tested on consumption. Neither response was affected by the outcome devaluation treatment, although entries into the food cup were suppressed. Combined with other results, the findings suggest that the "goal" for goal-directed procurement responding in a discriminated heterogeneous chain may be the consumption response rather than the primary reinforcer. (PsycINFO Database Record

  9. Mechanical measurements of heterogeneity and length scale effects in PEG-based hydrogels

    PubMed Central

    Bush, Brian G.; Shapiro, Jenna M.; DelRio, Frank W.; Cook, Robert F.; Oyen, Michelle L.

    2015-01-01

    Colloidal-probe spherical indentation load-relaxation experiments with a probe radius of 3 μm are conducted on poly(ethylene glycol) (PEG) hydrogel materials to quantify their steady-state mechanical properties and time-dependent transport properties via a single experiment. PEG-based hydrogels are shown to be heterogeneous in both morphology and mechanical stiffness at this scale; a linear-harmonic interpolation of hyperelastic Mooney-Rivlin and Boussinesq flat-punch indentation models was used to describe the steady-state response of the hydrogels and determine upper and lower bounds for indentation moduli. Analysis of the transient load-relaxation response during displacement-controlled hold periods provides a means of extracting two time constants τ1 and τ2, where τ1 and τ2 are assigned to the viscoelastic and poroelastic properties, respectively. Large τ2 values at small indentation depths provide evidence of a non-equilibrium state characterized by a phenomenon that restricts poroelastic fluid flow through the material; for larger indentations, the variability in τ2 values decreases and pore sizes estimated from τ2 via indentation approach those measured via macroscopic swelling experiments. The contact probe methodology developed here provides a means of assessing hydrogel heterogeneity, including time-dependent mechanical and transport properties, and has potential implications in hydrogel biomedical and engineering applications. PMID:26255839

  10. Mechanical measurements of heterogeneity and length scale effects in PEG-based hydrogels.

    PubMed

    Bush, Brian G; Shapiro, Jenna M; DelRio, Frank W; Cook, Robert F; Oyen, Michelle L

    2015-09-28

    Colloidal-probe spherical indentation load-relaxation experiments with a probe radius of 3 μm are conducted on poly(ethylene glycol) (PEG) hydrogel materials to quantify their steady-state mechanical properties and time-dependent transport properties via a single experiment. PEG-based hydrogels are shown to be heterogeneous in both morphology and mechanical stiffness at this scale; a linear-harmonic interpolation of hyperelastic Mooney-Rivlin and Boussinesq flat-punch indentation models was used to describe the steady-state response of the hydrogels and determine upper and lower bounds for indentation moduli. Analysis of the transient load-relaxation response during displacement-controlled hold periods provides a means of extracting two time constants τ1 and τ2, where τ1 and τ2 are assigned to the viscoelastic and poroelastic properties, respectively. Large τ2 values at small indentation depths provide evidence of a non-equilibrium state characterized by a phenomenon that restricts poroelastic fluid flow through the material; for larger indentations, the variability in τ2 values decreases and pore sizes estimated from τ2via indentation approach those measured via macroscopic swelling experiments. The contact probe methodology developed here provides a means of assessing hydrogel heterogeneity, including time-dependent mechanical and transport properties, and has potential implications in hydrogel biomedical and engineering applications.

  11. Discriminating effects of heterogeneity and matrix diffusion by alternative tracer designs

    SciTech Connect

    Tsang, Y.Y.W.

    1995-03-01

    Flow and transport calculations are carried out by numerical simulation for different tracer designs: single-well radially diverging/converging (huff-puff), single well radially converging, and two-well injection-withdrawal (doublet) in a 2D fracture zone. The fractured rocks are conceptualized as a dual-continuum: the well-connected fractures forming a heterogeneous continuum for advective transport, and the less permeable matrix forming a second continuum for tracer diffusion. Results show that the huff-puff design can be a good diagnostic test for matrix diffusion. The two-well doublet design averages over a large volume and corrects for the extreme sensitivity to spatial heterogeneities of the single well converging test, but requires prior knowledge of presence or absence of matrix diffusion to give reliable estimate of transport parameters. Results of this study demonstrate that using a suite of different tracer designs is important to reduce the uncertainty in association with solving the inverse problem of tracer test interpretation to characterize transport in fractured rocks.

  12. Effects of diffusion on total biomass in heterogeneous continuous and discrete-patch systems

    USGS Publications Warehouse

    DeAngelis, Don; Ming Ni, Wei; Zhang, Bo

    2016-01-01

    Theoretical models of populations on a system of two connected patches previously have shown that when the two patches differ in maximum growth rate and carrying capacity, and in the limit of high diffusion, conditions exist for which the total population size at equilibrium exceeds that of the ideal free distribution, which predicts that the total population would equal the total carrying capacity of the two patches. However, this result has only been shown for the Pearl-Verhulst growth function on two patches and for a single-parameter growth function in continuous space. Here, we provide a general criterion for total population size to exceed total carrying capacity for three commonly used population growth rates for both heterogeneous continuous and multi-patch heterogeneous landscapes with high population diffusion. We show that a sufficient condition for this situation is that there is a convex positive relationship between the maximum growth rate and the parameter that, by itself or together with the maximum growth rate, determines the carrying capacity, as both vary across a spatial region. This relationship occurs in some biological populations, though not in others, so the result has ecological implications.

  13. Meta-analysis of heterogeneous Down Syndrome data reveals consistent genome-wide dosage effects related to neurological processes

    PubMed Central

    2011-01-01

    Background Down syndrome (DS; trisomy 21) is the most common genetic cause of mental retardation in the human population and key molecular networks dysregulated in DS are still unknown. Many different experimental techniques have been applied to analyse the effects of dosage imbalance at the molecular and phenotypical level, however, currently no integrative approach exists that attempts to extract the common information. Results We have performed a statistical meta-analysis from 45 heterogeneous publicly available DS data sets in order to identify consistent dosage effects from these studies. We identified 324 genes with significant genome-wide dosage effects, including well investigated genes like SOD1, APP, RUNX1 and DYRK1A as well as a large proportion of novel genes (N = 62). Furthermore, we characterized these genes using gene ontology, molecular interactions and promoter sequence analysis. In order to judge relevance of the 324 genes for more general cerebral pathologies we used independent publicly available microarry data from brain studies not related with DS and identified a subset of 79 genes with potential impact for neurocognitive processes. All results have been made available through a web server under http://ds-geneminer.molgen.mpg.de/. Conclusions Our study represents a comprehensive integrative analysis of heterogeneous data including genome-wide transcript levels in the domain of trisomy 21. The detected dosage effects build a resource for further studies of DS pathology and the development of new therapies. PMID:21569303

  14. Strong Effects of Vs30 Heterogeneity on Physics-Based Scenario Ground-Shaking Computations

    NASA Astrophysics Data System (ADS)

    Louie, J. N.; Pullammanappallil, S. K.

    2014-12-01

    Hazard mapping and building codes worldwide use the vertically time-averaged shear-wave velocity between the surface and 30 meters depth, Vs30, as one predictor of earthquake ground shaking. Intensive field campaigns a decade ago in Reno, Los Angeles, and Las Vegas measured urban Vs30 transects with 0.3-km spacing. The Clark County, Nevada, Parcel Map includes urban Las Vegas and comprises over 10,000 site measurements over 1500 km2, completed in 2010. All of these data demonstrate fractal spatial statistics, with a fractal dimension of 1.5-1.8 at scale lengths from 0.5 km to 50 km. Vs measurements in boreholes up to 400 m deep show very similar statistics at 1 m to 200 m lengths. When included in physics-based earthquake-scenario ground-shaking computations, the highly heterogeneous Vs30 maps exhibit unexpectedly strong influence. In sensitivity tests (image below), low-frequency computations at 0.1 Hz display amplifications (as well as de-amplifications) of 20% due solely to Vs30. In 0.5-1.0 Hz computations, the amplifications are a factor of two or more. At 0.5 Hz and higher frequencies the amplifications can be larger than what the 1-d Building Code equations would predict from the Vs30 variations. Vs30 heterogeneities at one location have strong influence on amplifications at other locations, stretching out in the predominant direction of wave propagation for that scenario. The sensitivity tests show that shaking and amplifications are highly scenario-dependent. Animations of computed ground motions and how they evolve with time suggest that the fractal Vs30 variance acts to trap wave energy and increases the duration of shaking. Validations of the computations against recorded ground motions, possible in Las Vegas Valley due to the measurements of the Clark County Parcel Map, show that ground motion levels and amplifications match, while recorded shaking has longer duration than computed shaking. Several mechanisms may explain the amplification and increased

  15. Palaeobiology of Hyaenodon exiguus (Hyaenodonta, Mammalia) based on morphometric analysis of the bony labyrinth.

    PubMed

    Pfaff, Cathrin; Nagel, Doris; Gunnell, Gregg; Weber, Gerhard W; Kriwet, Jürgen; Morlo, Michael; Bastl, Katharina

    2017-02-01

    Species of the extinct genus Hyaenodon were among the largest carnivorous mammals from the Late Eocene through Early Miocene in North America, Europe and Asia. The origin, phylogeny and palaeobiology of Hyaenodonta are still ambiguous. Most previous studies focused on teeth and dental function in these highly adapted species, which might be influenced by convergent morphologies. The anatomy of the bony labyrinth in vertebrates is generally quite conservative and, additionally, was used in functional-morphological studies. This study provides the first anatomical description of the bony labyrinth of the extinct European species Hyaenodon exiguus in comparison to selected extant carnivoran taxa discussed from a functional-morphological perspective. Hyaenodon exiguus may have occupied a hyaena-like dietary niche with a semi-arboreal lifestyle, based on the relative height, width and length of the semicircular canals of the inner ear. However, this contradicts previous functional-morphological studies focusing on the diameter of the canals, which presumably represent the signal of locomotion mode.

  16. Bony labyrinth morphometry indicates locomotor adaptations in the squirrel-related clade (Rodentia, Mammalia).

    PubMed

    Pfaff, Cathrin; Martin, Thomas; Ruf, Irina

    2015-06-22

    The semicircular canals (SCs) of the inner ear detect angular acceleration and are located in the bony labyrinth of the petrosal bone. Based on high-resolution computed tomography, we created a size-independent database of the bony labyrinth of 50 mammalian species especially rodents of the squirrel-related clade comprising taxa with fossorial, arboreal and gliding adaptations. Our sampling also includes gliding marsupials, actively flying bats, the arboreal tree shrew and subterranean species. The morphometric anatomy of the SCs was correlated to the locomotion mode. Even if the phylogenetic signal cannot entirely be excluded, the main significance for functional morphological studies has been found in the diameter of the SCs, whereas the radius of curvature is of minor interest. Additionally, we found clear differences in the bias angle of the canals between subterranean and gliding taxa, but also between sciurids and glirids. The sensitivity of the inner ear correlates with the locomotion mode, with a higher sensitivity of the SCs in fossorial species than in flying taxa. We conclude that the inner ear of flying and gliding mammals is less sensitive due to the large information flow into this sense organ during locomotion.

  17. Electrosensory ampullary organs are lateral line placode-derived in bony fishes

    PubMed Central

    Modrell, Melinda S.; Bemis, William E.; Northcutt, R. Glenn; Davis, Marcus C.; Baker, Clare V. H.

    2014-01-01

    Electroreception is an ancient subdivision of the lateral line sensory system, found in all major vertebrate groups (though lost in frogs, amniotes, and most ray-finned fishes). Electroreception is mediated by “hair cells” in ampullary organs, distributed in fields flanking lines of mechanosensory hair cell-containing neuromasts that detect local water movement. Neuromasts, and afferent neurons for both neuromasts and ampullary organs, develop from lateral line placodes. Although ampullary organs in the axolotl (a representative of the lobe-finned clade of bony fishes) are lateral line placode-derived, non-placodal origins have been proposed for electroreceptors in other taxa. Here we show morphological and molecular data describing lateral line system development in the basal ray-finned fish Polyodon spathula, and present fate-mapping data that conclusively demonstrate a lateral line placode origin for ampullary organs and neuromasts. Together with the axolotl data, this confirms that ampullary organs are ancestrally lateral line placode-derived in bony fishes. PMID:21988912

  18. Bony labyrinth morphometry indicates locomotor adaptations in the squirrel-related clade (Rodentia, Mammalia)

    PubMed Central

    Pfaff, Cathrin; Martin, Thomas; Ruf, Irina

    2015-01-01

    The semicircular canals (SCs) of the inner ear detect angular acceleration and are located in the bony labyrinth of the petrosal bone. Based on high-resolution computed tomography, we created a size-independent database of the bony labyrinth of 50 mammalian species especially rodents of the squirrel-related clade comprising taxa with fossorial, arboreal and gliding adaptations. Our sampling also includes gliding marsupials, actively flying bats, the arboreal tree shrew and subterranean species. The morphometric anatomy of the SCs was correlated to the locomotion mode. Even if the phylogenetic signal cannot entirely be excluded, the main significance for functional morphological studies has been found in the diameter of the SCs, whereas the radius of curvature is of minor interest. Additionally, we found clear differences in the bias angle of the canals between subterranean and gliding taxa, but also between sciurids and glirids. The sensitivity of the inner ear correlates with the locomotion mode, with a higher sensitivity of the SCs in fossorial species than in flying taxa. We conclude that the inner ear of flying and gliding mammals is less sensitive due to the large information flow into this sense organ during locomotion. PMID:26019162

  19. Multi-locus phylogenetic analysis reveals the pattern and tempo of bony fish evolution

    PubMed Central

    Broughton, Richard E.; Betancur-R., Ricardo; Li, Chenhong; Arratia, Gloria; Ortí, Guillermo

    2013-01-01

    Over half of all vertebrates are “fishes”, which exhibit enormous diversity in morphology, physiology, behavior, reproductive biology, and ecology. Investigation of fundamental areas of vertebrate biology depend critically on a robust phylogeny of fishes, yet evolutionary relationships among the major actinopterygian and sarcopterygian lineages have not been conclusively resolved. Although a consensus phylogeny of teleosts has been emerging recently, it has been based on analyses of various subsets of actinopterygian taxa, but not on a full sample of all bony fishes. Here we conducted a comprehensive phylogenetic study on a broad taxonomic sample of 61 actinopterygian and sarcopterygian lineages (with a chondrichthyan outgroup) using a molecular data set of 21 independent loci. These data yielded a resolved phylogenetic hypothesis for extant Osteichthyes, including 1) reciprocally monophyletic Sarcopterygii and Actinopterygii, as currently understood, with polypteriforms as the first diverging lineage within Actinopterygii; 2) a monophyletic group containing gars and bowfin (= Holostei) as sister group to teleosts; and 3) the earliest diverging lineage among teleosts being Elopomorpha, rather than Osteoglossomorpha. Relaxed-clock dating analysis employing a set of 24 newly applied fossil calibrations reveals divergence times that are more consistent with paleontological estimates than previous studies. Establishing a new phylogenetic pattern with accurate divergence dates for bony fishes illustrates several areas where the fossil record is incomplete and provides critical new insights on diversification of this important vertebrate group. PMID:23788273

  20. Effect of reservior heterogeneities on waterflood and EOR chemical flood performance

    SciTech Connect

    Tomutsa, L.; Knight, J.

    1988-10-01

    Simulations were performed to study the capability of a modified version of the black oil simulator BOAST to handle reservoir heterogeneities of the type encountered in the barrier bar depositional system studied in the geoscience research program being performed for the Department of Energy as project BE1. The cases studied consisted of two-dimensional and three-dimensional simulations of layered reservoirs with different permeability contracts between the layers, different vertical permeability/horizontal permeability ratios and continuous and discontinuous shale layers. Software was developed to show graphically the residual oil saturation in the reservoir grid blocks at selected time intervals during the simulation. BOAST was modified for the residual oil saturation displays as well as for graphical displays of production rates and cumulative production versus time of oil, water and gas. 40 refs., 32 figs., 9 tabs.

  1. Viscoelastic relaxations of high alcohols and alkanes: Effects of heterogeneous structure and translation-orientation coupling

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tsuyoshi

    2017-03-01

    The frequency-dependent shear viscosity of high alcohols and linear alkanes, including 1-butanol, 1-octanol, 1-dodecanol, n-hexane, n-decane, and n-tetradecane, was calculated using molecular dynamics simulation. The relaxation of all the liquids was bimodal. The correlation functions of the collective orientation were also evaluated. The analysis of these functions showed that the slower relaxation mode of alkanes is assigned to the translation-orientation coupling, while that of high alcohols is not. The X-ray structure factors of all the alcohols showed prepeaks, as have been reported in the literature, and the intermediate scattering functions were calculated at the prepeak. Comparing the intermediate scattering function with the frequency-dependent shear viscosity based on the mode-coupling theory, it was demonstrated that the slower viscoelastic relaxation of the alcohols is assigned to the relaxation of the heterogeneous structure described by the prepeak.

  2. Effect of method of heterogenization of ephedrine and reaction conditions on the enantioselectivity of Michael additions

    SciTech Connect

    Krotov, V.V.; Staroverov, S.M.; Nesterenko, P.N.; Lisichkin. G.V.

    1987-11-10

    A series of heterogeneous catalysts for asymmetric Michael additions was synthesized based on ephedrine chemically bound to the surface of silica. The length of the hydrocarbon chain binding the active center to the support surface affects the sign of rotation of the reaction product from the asymmetric addition of thiophenol to benzylideneacetophenone. Grafting ephedrine to the silica surface via a short hydrocarbon chain results in a change in the configuration of the reaction product. Silanol groups on the silica surface are involved in the transition state, as evidenced by data obtained using silica which has been exhaustively treated with trimethylchlorosilane. The absolute specific rotation of 1,3-diphenyl-3-thiophenylpropan-1-one has been established.

  3. Effects of heterogeneous wind fields and vegetation composition on modeled estimates of pollen source area

    NASA Astrophysics Data System (ADS)

    Burke, K. D.; Goring, S. J.; Williams, J. W.; Holloway, T.

    2015-12-01

    Fossil pollen records from lakes, bogs, and small hollows offer the main source of information about vegetation responses to climate change and land use over timescales of decades to millennia. Millions of pollen grains are released from individual trees each year, and are transported by wind before settling out of the atmosphere. Reconstructing past vegetation from sedimentary pollen records, however, requires careful modeling of pollen production, transport, and deposition. The atmosphere is turbulent, and regional wind patterns shift from day to day. In accordance with this, it is necessary for pollen transport models to adequately account for variable, non-uniform wind patterns and vegetation heterogeneity. Using a simulation approach, with both simulated vegetation patterns and vegetation gradients, as well as simulated wind fields, we show the inconsistency in pollen loading proportions and local vegetation proportions when non-uniform wind patterns are incorporated. Vegetation upwind from the lake is over-represented due to the increased prevalence of winds transporting pollen from that area. The inclusion of North American Regional Reanalysis (NARR) wind records affirms this finding. Of the lake sites explored in this study, none had uniform wind patterns. The use of a settlement-era gridded vegetation dataset, compiled by the PalEON project and based on Public Land Survey System (PLSS) records allows us to model pollen source area with realistic vegetation heterogeneity. Due to differences in productivity, pollen fall speeds, and neighboring vegetation, there exist patterns of vegetation that may be poorly characterized due to over/under representation of different taxa. Better understanding these differences in representation allows for more accurate reconstruction of historical vegetation, and pollen-vegetation relationships.

  4. Effects of soil heterogeneity on steady state soil water pressure head under a surface line source

    NASA Astrophysics Data System (ADS)

    Zhang, Z. Fred; Parkin, Gary W.; Kachanoski, R. Gary; Smith, James E.

    2002-07-01

    There are numerous analytical solutions available for flow in unsaturated homogeneous porous media. In this paper, the stream tube model for one-dimensional water movement is extended to two-dimensional (2-D) water movement from a line source as the stream plane model. As well, new solutions are derived to predict the mean and variance of pressure head of water movement under a surface line source in heterogeneous soil using the perturbation method with first-order approximation (PM1) and with second-order approximation (PM2). A variance expression was also developed based on the spectral relationship presented by Yeh et al. [1985a]. The new solutions were tested using the 2-D stream plane model with parameters A = ln(α) and Y = ln(KS) and measurements from field experiments. Results show that the mean of steady state pressure head below the line source is not only a function of the mean parameter values but also a function of the variances of A and Y and the linear cross-correlation coefficient (ρ) between A and Y. The PM2 model can predict the mean pressure head accurately in heterogeneous soils at any level of correlation between A and Y, except when both the soil variability and ρ are high. The pressure head variance estimation based on the PM1 model predicts the measured variance well only when both the soil variability and ρ are low. The field experimental results show that both the PM1 and the spectral models give reasonable predictions of the pressure head variance. Both the measured and predicted values of the variance of pressure head using the two models increase with the depth of soil. Both models show that the variance of pressure head decreases as the source strength increases, but on average, the pressure head variance was underestimated by both models.

  5. Effect of tissue heterogeneity on an in vivo range verification technique for proton therapy

    NASA Astrophysics Data System (ADS)

    Hassane Bentefour, El; Shikui, Tang; Prieels, Damien; Lu, Hsiao-Ming

    2012-09-01

    It was proposed recently that time-resolved dose measurements during proton therapy treatment by passively scattered beams may be used for in vivo range verification. The method was shown to work accurately in a water tank. In this paper, we further evaluated the potential of the method for more clinically relevant situations where proton beams must pass through regions with significant tissue heterogeneities. Specifically, we considered prostate treatment where the use of anterior or anterior- oblique fields was recently proposed in order to reduce rectal dose by taking advantage of the sharp distal fall-off of the Bragg peak. These beam portals pass through various parts of pubic bone and potential air cavities in the bladder and bowels. Using blocks of materials with densities equivalent to bone, air, etc, arranged in the water tank in relevant configurations, we tested the robustness of the method against range shifting and range mixing. In the former, the beam range is changed uniformly by changes in tissue density in the beam path, while in the latter, variations in tissue heterogeneities across the beam cross section causes the mixing of beam energies downstream, as often occurs when the beam travels along the interface of materials with significantly different densities. We demonstrated that in the region of interest, the method can measure water-equivalent path length with accuracy better than ±0.5 mm for pure range shifting and still reasonable accuracy for range mixing between close beam energies. In situations with range mixing between significantly different beam energies, the dose rate profiles may be simulated for verifying the beam range. We also found that the above performances can be obtained with very small amount of dose (<0.5 cGy), if silicon diodes are used as detectors. This makes the method suitable for in vivo range verification prior to each treatment delivery.

  6. EFFECTS OF DOBUTAMINE ON INTESTINAL MICROVASCULAR BLOOD FLOW HETEROGENEITY AND OXYGEN EXTRACTION DURING SEPTIC SHOCK.

    PubMed

    Ospina-Tascón, Gustavo Adolfo; García Marín, Alberto Federico; Echeverri, Gabriel J; Bermúdez, William Fernando; Madriñán Navia, Humberto José; Valencia, Juan David; Quiñones, Edgardo; Rodríguez, Fernando; Marulanda, Angela; Arango Davila, César Augusto; Bruhn, Alejandro; Hernández, Glenn; De Backer, Daniel

    2017-03-23

    Derangements of microvascular blood flow distribution might contribute to disturbing oxygen extraction by peripheral tissues. We evaluated the dynamic relationships between the mesenteric oxygen extraction ratio (mes-ERO2) and the heterogeneity of microvascular blood flow at the gut and sublingual mucosa, during the development and resuscitation of septic shock in a swine model of fecal peritonitis. Jejunal-villi and sublingual microcirculation were evaluated using a portable intravital-microscopy technique. Simultaneously, we obtained arterial, mixed-venous and mesenteric blood gases, and jejunal-tonometric measurements. During resuscitation, pigs were randomly allocated to fixed-dose of dobutamine (5 µgr/kg/min) or placebo, while three sham models with identical monitoring served as controls. At the time-of-shock, we observed a significant decreased proportion of perfused intestinal-villi (villi-PPV) and sublingual percentage of perfused small-vessels (SL-PPV), paralleling an increase in mes-ERO2 in both dobutamine and placebo groups. After starting resuscitation, villi-PPV and SL-PPV significantly increased in the dobutamine group with subsequent improvement of functional capillary density, while mes-ERO2 exhibited a corresponding significant decrease (repeated-measures ANOVA, p=0.02 and p=0.04 for time*group-interactions and inter-group differences for villi-PPV and mes-ERO2, respectively). Variations in villi-PPV were paralleled by variations in mes-ERO2 (R(2)=0.88, p<0.001) and these, in turn, by mesenteric lactate changes (R(2)=0.86, p<0.001). There were no significant differences in cardiac output and systemic oxygen delivery throughout the experiment. In conclusion, dynamic changes in microvascular blood flow heterogeneity at jejunal mucosa are closely related to the mesenteric oxygen extraction ratio, suggesting a crucial role for microvascular blood flow distribution on oxygen uptake during development and resuscitation from septic shock.

  7. MR imaging of heterogeneity in partially frozen brine and their effect on ultrasonic wave propagation

    NASA Astrophysics Data System (ADS)

    Pradhan, O.; Matsushima, J.; Suzuki, M.

    2012-12-01

    Methane hydrate bearing sediment possesses unique seismic wave propagation properties. Both high seismic wave velocity and high wave attenuation are observed in methane hydrate bearing sediment. We used brine with salinity 2% in analogous to methane hydrate for conducting laboratory waveform measurement and characterization by using nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) technique. When brine undergoes freezing, only pure water freezes into ice and salt remains in solution with successively increasing salinity and decreasing freezing point of the solution. Unfrozen brine is enclosed inside micro pores in ice, with exhibiting solid-liquid coexisting system. We used conventional pulse transmission technique to measure compressional wave velocity in partially frozen brine when brine is subjected cooling down to -12oC. Waveform measurement shows sudden increase in compressional wave velocity at temperature -3oC. Below -3oC, velocity increases slightly. Largest wave attenuation is observed at around -3oC. We conducted MRI experiment by using instrument Varian Unity Inova 4.7T. T1 weighted and diffusion weighted (DW) MR images were prepared by applying magnetic field gradient of 0.3 gauss/cm. We observe the spatial distribution of pores, microstructures and heterogeneity in partially frozen brine sample slices. Two dimensional apparent diffusion coefficient (ADC) maps are prepared from DW images with b-values 0 and 81 s/mm2 respectively. We estimate porosity quantitatively from each MR slices at temperature -3, -5, -7 and -12oC by using image analysis technique. Gassmann equation is applied to calculate compressional wave velocity from the porosity data and compared with the measured velocity obtained by waveform analysis technique. The NMR results show the existence of high and low mobility unfrozen brine in the pore space. MR imaging shows the heterogeneously distributed porosity values within a single slice with low porosity and high

  8. Clinical and Radiologic Evaluation of Regenerative Potential of NHA Paste and DBM in the Treatment of Periodontal Intra-bony Defects -A Randomized Control Trial

    PubMed Central

    Jain, Deepti; Gupta, Bharat; Sharma, Saurabh; Juneja, Saurabh; Juneja, Manjushree; Sharma, Shruti; Patil, Neha

    2016-01-01

    .64% (p<0.05). Conclusion Overall, both therapies led to significant improvements of the investigated parameters. The NHA paste was as effective in terms of improving clinical and radiographic parameters as DBM-Xenograft, which is an already established bone graft. There is a need for further long term controlled studies evaluating the adjunctive benefits of usage of NHA paste in the treatment of periodontal intra-bony defects. PMID:27790585

  9. Underestimating the effects of spatial heterogeneity due to individual movement and spatial scale: infectious disease as an example

    USGS Publications Warehouse

    Cross, Paul C.; Caillaud, Damien; Heisey, Dennis M.

    2013-01-01

    Many ecological and epidemiological studies occur in systems with mobile individuals and heterogeneous landscapes. Using a simulation model, we show that the accuracy of inferring an underlying biological process from observational data depends on movement and spatial scale of the analysis. As an example, we focused on estimating the relationship between host density and pathogen transmission. Observational data can result in highly biased inference about the underlying process when individuals move among sampling areas. Even without sampling error, the effect of host density on disease transmission is underestimated by approximately 50 % when one in ten hosts move among sampling areas per lifetime. Aggregating data across larger regions causes minimal bias when host movement is low, and results in less biased inference when movement rates are high. However, increasing data aggregation reduces the observed spatial variation, which would lead to the misperception that a spatially targeted control effort may not be very effective. In addition, averaging over the local heterogeneity will result in underestimating the importance of spatial covariates. Minimizing the bias due to movement is not just about choosing the best spatial scale for analysis, but also about reducing the error associated with using the sampling location as a proxy for an individual’s spatial history. This error associated with the exposure covariate can be reduced by choosing sampling regions with less movement, including longitudinal information of individuals’ movements, or reducing the window of exposure by using repeated sampling or younger individuals.

  10. Sacro-Iliac Joint Sensory Block and Radiofrequency Ablation: Assessment of Bony Landmarks Relevant for Image-Guided Procedures.

    PubMed

    Robinson, Trevor J G; Roberts, Shannon L; Burnham, Robert S; Loh, Eldon; Agur, Anne M

    2016-01-01

    Image-guided sensory block and radiofrequency ablation of the nerves innervating the sacro-iliac joint require readily identifiable bony landmarks for accurate needle/electrode placement. Understanding the relative locations of the transverse sacral tubercles along the lateral sacral crest is important for ultrasound guidance, as they demarcate the position of the posterior sacral network (S1-S3 ± L5/S4) innervating the posterior sacro-iliac joint. No studies were found that investigated the spatial relationships of these bony landmarks. The purpose of this study was to visualize and quantify the interrelationships of the transverse sacral tubercles and posterior sacral foramina to inform image-guided block and radiofrequency ablation of the sacro-iliac joint. The posterior and lateral surfaces of 30 dry sacra (15 M/15 F) were digitized and modeled in 3D and the distances between bony landmarks quantified. The relationships of bony landmarks (S1-S4) were not uniform. The mean intertubercular and interforaminal distances decreased from S1 to S4, whereas the distance from the lateral margin of the posterior sacral foramina to the transverse sacral tubercles increased from S1 to S3. The mean intertubercular distance from S1 to S3 was significantly (p < 0.05) larger in males. The interrelationships of the sacral bony landmarks should be taken into consideration when estimating the site and length of an image-guided strip lesion targeting the posterior sacral network.

  11. 'Junction-Level' Heterogeneous Integration of III-V Materials with Si CMOS for Novel Asymmetric Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Chang, Yoon Jung

    Driven by Moore's law, semiconductor chips have become faster, denser and cheaper through aggressive dimension scaling. The continued scaling not only led to dramatic performance improvements in digital logic applications but also in mixed-mode and/or communication applications. Moreover, size/weight/power (SWAP) restrictions on all high-performance system components have resulted in multi-functional integration of multiple integrated circuits (ICs)/dies in 3D packages/ICs by various system-level approaches. However, these approaches still possess shortcomings and in order to truly benefit from the most advanced digital technologies, the future high-speed/high power devices for communication applications need to be fully integrated into a single CMOS chip. Due to limitations in Si device performance in high-frequency/power applications as well as expensive III-V compound semiconductor devices with low integration density, heterogeneous integration of compound semiconductor materials/devices with Si CMOS platform has emerged as a viable solution to low-cost high-performance ICs. In this study, we first discuss on channel and drain engineering approaches in the state-of-the-art multiple-gate field-effect transistor to integrate III-V compound semiconductor materials with Si CMOS for improved device performance in mixed-mode and/or communication applications. Then, growth, characterization and electrical analysis on small-area (diameter < 100nm) complete selective-area epitaxy of GaAs/GaN will be demonstrated for achieving 'dislocation-free' III-V compound semiconductor film on a Si(001) substrate. Based on a success in dislocation-free heterogeneous III-V film growth, we propose a novel ultra-scaled 'junction-level' heterogeneous integration onto mainstream Si CMOS platform. Device architecture and its key features to overcome aforementioned challenges will be given to demonstrate the potential to improve the overall system performance with diverse functionality.

  12. Intensification of heterogeneously catalyzed Suzuki-Miyaura cross-coupling reaction using ultrasound: Understanding effect of operating parameters.

    PubMed

    Sancheti, Sonam V; Gogate, Parag R

    2017-01-27

    Palladium-catalyzed Suzuki-Miyaura cross-coupling reaction is a significant reaction for obtaining industrially important products. The current research work deals with intensification of reaction of 4-bromoanisole and phenylboronic acid catalyzed with 5wt% Pd/C (5% by weight Pd supported on C available as commercial catalyst) using ultrasound and more importantly, without use of any additional phase transfer catalyst. Heterogeneous catalyst has been selected in the present work so as to harness the benefits of easy separation and the possible limitations of heterogeneous operation are minimized by introducing ultrasonic irradiations. The effect of operating parameters such as ultrasound power, temperature, catalyst loading and molar ratio on the progress of reaction has been investigated. It has been observed that an optimum power, temperature and catalyst loading exist for maximum benefits whereas higher molar ratio was found to be favourable for the progress of the reaction. Also, the use of ultrasound reduced the reaction time from 70min required in conventional approach to only 35min under conditions of frequency of 22kHz, power dissipation of 40W and catalyst loading as 1.5mol% (refers to total quantum of catalyst used in the work) in ethanol-water system under ambient conditions. The work also demonstrated successful results at ten times higher volume as compared to the normally used volumes in the case of simple ultrasonic horn. Overall, the work has successfully demonstrated process intensification benefits obtained due to the use of ultrasound for heterogeneously catalyzed Suzuki-Miyaura cross-coupling reaction.

  13. Characterization of Paper Heterogeneity

    NASA Astrophysics Data System (ADS)

    Considine, John M.

    Paper and paperboard are the most widely-used green materials in the world because they are renewable, recyclable, reusable, and compostable. Continued and expanded use of these materials and their potential use in new products requires a comprehensive understanding of the variability of their mechanical properties. This work develops new methods to characterize the mechanical properties of heterogeneous materials through a combination of techniques in experimental mechanics, materials science and numerical analysis. Current methods to analyze heterogeneous materials focus on crystalline materials or polymer-crystalline composites, where material boundaries are usually distinct. This work creates a methodology to analyze small, continuously-varying stiffness gradients in 100% polymer systems and is especially relevant to paper materials where factors influencing heterogeneity include local mass, fiber orientation, individual pulp fiber properties, local density, and drying restraint. A unique approach was used to understand the effect of heterogeneity on paper tensile strength. Additional variation was intentionally introduced, in the form of different size holes, and their effect on strength was measured. By modifying two strength criteria, an estimate of strength in the absence of heterogeneity was determined. In order to characterize stiffness heterogeneity, a novel load fixture was developed to excite full-field normal and shear strains for anisotropic stiffness determination. Surface strains were measured with digital image correlation and were analyzed with the VFM (Virtual Fields Method). This approach led to VFM-identified stiffnesses that were similar to values determined by conventional tests. The load fixture and VFM analyses were used to measure local stiffness and local stiffness variation on heterogeneous anisotropic materials. The approach was validated on simulated heterogeneous materials and was applied experimentally to three different paperboards

  14. Interconnecting heterogeneous database management systems

    NASA Technical Reports Server (NTRS)

    Gligor, V. D.; Luckenbaugh, G. L.

    1984-01-01

    It is pointed out that there is still a great need for the development of improved communication between remote, heterogeneous database management systems (DBMS). Problems regarding the effective communication between distributed DBMSs are primarily related to significant differences between local data managers, local data models and representations, and local transaction managers. A system of interconnected DBMSs which exhibit such differences is called a network of distributed, heterogeneous DBMSs. In order to achieve effective interconnection of remote, heterogeneous DBMSs, the users must have uniform, integrated access to the different DBMs. The present investigation is mainly concerned with an analysis of the existing approaches to interconnecting heterogeneous DBMSs, taking into account four experimental DBMS projects.

  15. Effect of surface free energies on the heterogeneous nucleation of water droplet: A molecular dynamics simulation approach

    SciTech Connect

    Xu, W.; Lan, Z.; Peng, B. L.; Wen, R. F.; Ma, X. H.

    2015-02-07

    Heterogeneous nucleation of water droplet on surfaces with different solid-liquid interaction intensities is investigated by molecular dynamics simulation. The interaction potentials between surface atoms and vapor molecules are adjusted to obtain various surface free energies, and the nucleation process and wetting state of nuclei on surfaces are investigated. The results indicate that near-constant contact angles are already established for nano-scale nuclei on various surfaces, with the contact angle decreasing with solid-liquid interaction intensities linearly. Meanwhile, noticeable fluctuation of vapor-liquid interfaces can be observed for the nuclei that deposited on surfaces, which is caused by the asymmetric forces from vapor molecules. The formation and growth rate of nuclei are increasing with the solid-liquid interaction intensities. For low energy surface, the attraction of surface atoms to water molecules is comparably weak, and the pre-existing clusters can depart from the surface and enter into the bulk vapor phase. The distribution of clusters within the bulk vapor phase becomes competitive as compared with that absorbed on surface. For moderate energy surfaces, heterogeneous nucleation predominates and the formation of clusters within bulk vapor phase is suppressed. The effect of high energy particles that embedded in low energy surface is also discussed under the same simulation system. The nucleation preferably initiates on the high energy particles, and the clusters that formed on the heterogeneous particles are trapped around their original positions instead of migrating around as that observed on smooth surfaces. This feature makes it possible for the heterogeneous particles to act as fixed nucleation sites, and simulation results also suggest that the number of nuclei increases monotonously with the number of high energy particles. The growth of nuclei on high energy particles can be divided into three sub-stages, beginning with the formation

  16. Inclusion of line tension effect in classical nucleation theory for heterogeneous nucleation: A rigorous thermodynamic formulation and some unique conclusions

    SciTech Connect

    Singha, Sanat K.; Das, Prasanta K. Maiti, Biswajit

    2015-03-14

    A rigorous thermodynamic formulation of the geometric model for heterogeneous nucleation including line tension effect is missing till date due to the associated mathematical hurdles. In this work, we develop a novel thermodynamic formulation based on Classical Nucleation Theory (CNT), which is supposed to illustrate a systematic and a more plausible analysis for the heterogeneous nucleation on a planar surface including the line tension effect. The appreciable range of the critical microscopic contact angle (θ{sub c}), obtained from the generalized Young’s equation and the stability analysis, is θ{sub ∞} < θ{sub c} < θ′ for positive line tension and is θ{sub M} < θ{sub c} < θ{sub ∞} for negative line tension. θ{sub ∞} is the macroscopic contact angle, θ′ is the contact angle for which the Helmholtz free energy has the minimum value for the positive line tension, and θ{sub M} is the local minima of the nondimensional line tension effect for the negative line tension. The shape factor f, which is basically the dimensionless critical free energy barrier, becomes higher for lower values of θ{sub ∞} and higher values of θ{sub c} for positive line tension. The combined effect due to the presence of the triple line and the interfacial areas (f{sup L} + f{sup S}) in shape factor is always within (0, 3.2), resulting f in the range of (0, 1.7) for positive line tension. A formerly presumed appreciable range for θ{sub c}(0 < θ{sub c} < θ{sub ∞}) is found not to be true when the effect of negative line tension is considered for CNT. Estimation based on the property values of some real fluids confirms the relevance of the present analysis.

  17. Heterogeneous effects of old age on human muscle oxidative capacity in vivo: a systematic review and meta-analysis.

    PubMed

    Fitzgerald, Liam F; Christie, Anita D; Kent, Jane A

    2016-11-01

    Despite intensive efforts to understand the extent to which skeletal muscle mitochondrial capacity changes in older humans, the answer to this important question remains unclear. To determine what the preponderance of evidence from in vivo studies suggests, we conducted a systematic review and meta-analysis of the effects of age on muscle oxidative capacity as measured noninvasively by magnetic resonance spectroscopy. A secondary aim was to examine potential moderators contributing to differences in results across studies, including muscle group, physical activity status, and sex. Candidate papers were identified from PubMed searches (n = 3561 papers) and the reference lists of relevant papers. Standardized effects (Hedges' g) were calculated for age and each moderator using data from the 22 studies that met the inclusion criteria (n = 28 effects). Effects were coded as positive when older (age, ≥55 years) adults had higher muscle oxidative capacity than younger (age, 20-45 years) adults. The overall effect of age on oxidative capacity was positive (g = 0.171, p < 0.001), indicating modestly greater oxidative capacity in old. Notably, there was significant heterogeneity in this result (Q = 245.8, p < 0.001; I(2) = ∼70%-90%). Muscle group, physical activity, and sex were all significant moderators of oxidative capacity (p ≤ 0.029). This analysis indicates that the current body of literature does not support a de facto decrease of in vivo muscle oxidative capacity in old age. The heterogeneity of study results and identification of significant moderators provide clarity regarding apparent discrepancies in the literature, and indicate the importance of accounting for these variables when examining purported age-related differences in muscle oxidative capacity.

  18. Effects of dispersal on total biomass in a patchy, heterogeneous system: Analysis and experiment.

    PubMed

    Zhang, Bo; Liu, Xin; DeAngelis, D L; Ni, Wei-Ming; Wang, G Geoff

    2015-06-01

    An intriguing recent result from mathematics is that a population diffusing at an intermediate rate in an environment in which resources vary spatially will reach a higher total equilibrium biomass than the population in an environment in which the same total resources are distributed homogeneously. We extended the current mathematical theory to apply to logistic growth and also showed that the result applies to patchy systems with dispersal among patches, both for continuous and discrete time. This allowed us to make specific predictions, through simulations, concerning the biomass dynamics, which were verified by a laboratory experiment. The experiment was a study of biomass growth of duckweed (Lemna minor Linn.), where the resources (nutrients added to water) were distributed homogeneously among a discrete series of water-filled containers in one treatment, and distributed heterogeneously in another treatment. The experimental results showed that total biomass peaked at an intermediate, relatively low, diffusion rate, higher than the total carrying capacity of the system and agreeing with the simulation model. The implications of the experiment to dynamics of source, sink, and pseudo-sink dynamics are discussed.

  19. The Effects of Spatially Heterogeneous Prey Distributions on Detection Patterns in Foraging Seabirds

    PubMed Central

    Miramontes, Octavio; Boyer, Denis; Bartumeus, Frederic

    2012-01-01

    Many attempts to relate animal foraging patterns to landscape heterogeneity are focused on the analysis of foragers movements. Resource detection patterns in space and time are not commonly studied, yet they are tightly coupled to landscape properties and add relevant information on foraging behavior. By exploring simple foraging models in unpredictable environments we show that the distribution of intervals between detected prey (detection statistics) is mostly determined by the spatial structure of the prey field and essentially distinct from predator displacement statistics. Detections are expected to be Poissonian in uniform random environments for markedly different foraging movements (e.g. Lévy and ballistic). This prediction is supported by data on the time intervals between diving events on short-range foraging seabirds such as the thick-billed murre (Uria lomvia). However, Poissonian detection statistics is not observed in long-range seabirds such as the wandering albatross (Diomedea exulans) due to the fractal nature of the prey field, covering a wide range of spatial scales. For this scenario, models of fractal prey fields induce non-Poissonian patterns of detection in good agreement with two albatross data sets. We find that the specific shape of the distribution of time intervals between prey detection is mainly driven by meso and submeso-scale landscape structures and depends little on the forager strategy or behavioral responses. PMID:22514629

  20. Forage digestibility and intake by lesser snow geese: effects of dominance and resource heterogeneity

    USGS Publications Warehouse

    Hupp, Jerry W.; White, Robert G.; Sedinger, James S.; Robertson, Donna G.

    1996-01-01

    We measured forage intake, digestibility, and retention time for 11 free-ranging, human-imprinted lesser snow geese (Chen caerulescens caerulescens) as they consumed underground stembases of tall cotton-grass (Eriophorum angustifolium) on an arctic staging area in northeastern Alaska. Geese fed in small patches (x̄=21.5 m2) of forage that made up ≤3% of the study area and consisted of high-quality “aquatic graminoid” and intermediate-quality “wet sedge” vegetation types. Dominant geese spent more time feeding in aquatic graminoid areas (r=0.61), but less total time feeding and more time resting than subdominant geese. Subdominant geese were displaced to areas of wet sedge where cotton-grass was a smaller proportion of underground biomass. Geese metabolized an average of 48% of the organic matter in stembases and there was a positive correlation between dominance and organic matter metabolizability (r=0.61). Total mean retention time of forage was 1.37 h and dry matter intake was 14.3 g/h. Snow geese that stage on the coastal plain of the Beaufort Sea likely use an extensive area because they consume a large mass of forage and exploit habitats that are patchily distributed and make up a small percentage of the landscape. Individual variation in nutrient absorption may result from agonistic interactions in an environment where resources are heterogeneously distributed.

  1. The effect of mesostructure heterogeneity on cracks initiation and the displacement distribution in NCF composites

    NASA Astrophysics Data System (ADS)

    Zrida, H.; Giannadis, K.; Varna, J.; Ayadi, Z.

    2012-02-01

    Non Crimp Fabrics (NCF) are promising new generation composite materials. They are now being used in some sections of composite industry, for example in wind turbine blades and boat hulls. The aerospace industry also shows an increasing interest in this material, thanks to the low cost of its manufacturing process. NCFs are special types of textile composites, made of layers of parallel fiber bundles oriented in different directions and separated by resin. Due to the manufacturing process the fiber bundles are not perfectly straight. They show a certain degree of waviness which decreases the stiffness and the strength of the material. The heterogeneous mesostructure affects the mechanical properties of the material and the failure mechanisms. This was studied using both numerical and experimental methods. In our experimental approach, a carbon fiber/epoxy resin laminate with uniform fiber distribution was manufactured by voluntarily introducing waviness to simulate the NCF composites. The displacement map was studied against the thickness of a sample loaded in tension, using ESPI (Electronic Speckle Pattern Interferometry). This can give us a primary idea of the micro damage initiation and the cracks' shapes.

  2. Heterogeneity of Notch signaling in astrocytes and the effects of GFAP and vimentin deficiency.

    PubMed

    Lebkuechner, Isabell; Wilhelmsson, Ulrika; Möllerström, Elin; Pekna, Marcela; Pekny, Milos

    2015-10-01

    Astrocytes have multiple roles in the CNS including control of adult neurogenesis. We recently showed that astrocyte inhibition of neurogenesis through Notch signaling depends on the intermediate filament proteins glial fibrillary acidic protein (GFAP) and vimentin. Here, we used real-time quantitative PCR to analyze gene expression in individual mouse astrocytes in primary cultures and in GFAP(POS) or Aldh1L1(POS) astrocytes freshly isolated from uninjured, contralesional and lesioned hippocampus 4 days after entorhinal cortex lesion. To determine the Notch signaling competence of individual astrocytes, we measured the mRNA levels of Notch ligands and Notch1 receptor. We found that whereas most cultured and freshly isolated astrocytes were competent to receive Notch signals, only a minority of astrocytes were competent to send Notch signals. Injury increased the fraction of astrocyte subpopulation unable to send and receive Notch signals, thus resembling primary astrocytes in vitro. Astrocytes deficient of GFAP and vimentin showed decreased Notch signal sending competence and altered expression of Notch signaling pathway-related genes Dlk2, Notch1, and Sox2. Furthermore, we identified astrocyte subpopulations based on their mRNA and protein expression of nestin and HB-EGF. This study improves our understanding of astrocyte heterogeneity, and points to astrocyte cytoplasmic intermediate filaments as targets for neural cell replacement strategies.

  3. Heterogeneous Reactions of Acetic Acid with Oxide Surfaces: Effects of Mineralogy and Relative Humidity.

    PubMed

    Tang, Mingjin; Larish, Whitney A; Fang, Yuan; Gankanda, Aruni; Grassian, Vicki H

    2016-07-21

    We have investigated the heterogeneous uptake of gaseous acetic acid on different oxides including γ-Al2O3, SiO2, and CaO under a range of relative humidity conditions. Under dry conditions, the uptake of acetic acid leads to the formation of both acetate and molecularly adsorbed acetic acid on γ-Al2O3 and CaO and only molecularly adsorbed acetic acid on SiO2. More importantly, under the conditions of this study, dimers are the major form for molecularly adsorbed acetic acid on all three particle surfaces investigated, even at low acetic acid pressures under which monomers are the dominant species in the gas phase. We have also determined saturation surface coverages for acetic acid adsorption on these three oxides under dry conditions as well as Langmuir adsorption constants in some cases. Kinetic analysis shows that the reaction rate of acetic acid increases by a factor of 3-5 for γ-Al2O3 when relative humidity increases from 0% to 15%, whereas for SiO2 particles, acetic acid and water are found to compete for surface adsorption sites.

  4. Effective Suppression of Pathological Synchronization in Cortical Networks by Highly Heterogeneous Distribution of Inhibitory Connections

    PubMed Central

    Kada, Hisashi; Teramae, Jun-Nosuke; Tokuda, Isao T.

    2016-01-01

    Even without external random input, cortical networks in vivo sustain asynchronous irregular firing with low firing rate. In addition to detailed balance between excitatory and inhibitory activities, recent theoretical studies have revealed that another feature commonly observed in cortical networks, i.e., long-tailed distribution of excitatory synapses implying coexistence of many weak and a few extremely strong excitatory synapses, plays an essential role in realizing the self-sustained activity in recurrent networks of biologically plausible spiking neurons. The previous studies, however, have not considered highly non-random features of the synaptic connectivity, namely, bidirectional connections between cortical neurons are more common than expected by chance and strengths of synapses are positively correlated between pre- and postsynaptic neurons. The positive correlation of synaptic connections may destabilize asynchronous activity of networks with the long-tailed synaptic distribution and induce pathological synchronized firing among neurons. It remains unclear how the cortical network avoids such pathological synchronization. Here, we demonstrate that introduction of the correlated connections indeed gives rise to synchronized firings in a cortical network model with the long-tailed distribution. By using a simplified feed-forward network model of spiking neurons, we clarify the underlying mechanism of the synchronization. We then show that the synchronization can be efficiently suppressed by highly heterogeneous distribution, typically a lognormal distribution, of inhibitory-to-excitatory connection strengths in a recurrent network model of cortical neurons. PMID:27803659

  5. Hardening anisotropy of {gamma}/{gamma}{prime} superalloy single crystals. 2: Numerical analysis of heterogeneity effects

    SciTech Connect

    Estevez, R.; Hoinard, G.; Franciosi, P.

    1997-04-01

    In the first part of this study, the {gamma}/{gamma}{prime} superalloy single crystals yield stress and hardening anisotropy were experimentally estimated at 650 C, assuming homogeneous plasticity, G. Hoinard, R. Estevez and P. Franciosi, Acta Metall. 43, 1593 (1995). Here alloy morphology is regarded in two different ways: first as a two-phase anisotropic material with a uniform {gamma} matrix, describing the {gamma}{prime} precipitates arrangement with the help of an elementary pattern of inclusions; then treating the {gamma} matrix as a three (geometrical) phase medium, i.e., the three families of orthogonal {gamma} layers separating the precipitates, to estimate the matrix behavior heterogeneity in a 4-phase modelling of the alloy. Both {gamma} and {gamma}{prime} phases are treated as elastic-plastic crystalline media deforming by octahedral and cubic slip, and the models are based on the self consistent approximation. The alloy elasticity limit, internal stresses and hardening anisotropy are discussed with regard to the chosen behavior description for each phase, and behavior simulations are compared to experimental information.

  6. Sensing Home: A Cost-Effective Design for Smart Home via Heterogeneous Wireless Networks.

    PubMed

    Fan, Xiaohu; Huang, Hao; Qi, Shipeng; Luo, Xincheng; Zeng, Jing; Xie, Qubo; Xie, Changsheng

    2015-12-03

    The aging population has inspired the marketing of advanced real time devices for home health care, more and more wearable devices and mobile applications, which have emerged in this field. However, to properly collect behavior information, accurately recognize human activities, and deploy the whole system in a real living environment is a challenging task. In this paper, we propose a feasible wireless-based solution to deploy a data collection scheme, activity recognition model, feedback control and mobile integration via heterogeneous networks. We compared and found a suitable algorithm that can be run on cost-efficient embedded devices. Specifically, we use the Super Set Transformation method to map the raw data into a sparse binary matrix. Furthermore, designed front-end devices of low power consumption gather the living data of the habitant via ZigBee to reduce the burden of wiring work. Finally, we evaluated our approach and show it can achieve a theoretical time-slice accuracy of 98%. The mapping solution we propose is compatible with more wearable devices and mobile apps.

  7. Sensing Home: A Cost-Effective Design for Smart Home via Heterogeneous Wireless Networks

    PubMed Central

    Fan, Xiaohu; Huang, Hao; Qi, Shipeng; Luo, Xincheng; Zeng, Jing; Xie, Qubo; Xie, Changsheng

    2015-01-01

    The aging population has inspired the marketing of advanced real time devices for home health care, more and more wearable devices and mobile applications, which have emerged in this field. However, to properly collect behavior information, accurately recognize human activities, and deploy the whole system in a real living environment is a challenging task. In this paper, we propose a feasible wireless-based solution to deploy a data collection scheme, activity recognition model, feedback control and mobile integration via heterogeneous networks. We compared and found a suitable algorithm that can be run on cost-efficient embedded devices. Specifically, we use the Super Set Transformation method to map the raw data into a sparse binary matrix. Furthermore, designed front-end devices of low power consumption gather the living data of the habitant via ZigBee to reduce the burden of wiring work. Finally, we evaluated our approach and show it can achieve a theoretical time-slice accuracy of 98%. The mapping solution we propose is compatible with more wearable devices and mobile apps. PMID:26633424

  8. The effect of line tension on the shape of liquid menisci near stripwise heterogeneous walls.

    PubMed

    Hoorfar, M; Amirfazli, A; Gaydos, J A; Neumann, A W

    2005-06-30

    Most attempts for the measurement of line tension in solid-liquid-vapor systems are based on the drop size dependence of contact angles of sessile drops on smooth, homogeneous solid surfaces. Despite being a well-defined thermodynamic quantity, there are still significant discrepancies in both the magnitude and sign of line tension reported in different experimental arrangements and theoretical studies. In order to broaden the scope of experimental studies of line tension, a non-axisymmetric system, i.e., a stripwise heterogeneous wall arrangement, was considered. A numerical scheme has been developed to solve simultaneously both the modified Young equation and the Laplace equation of capillarity for such a stripwise wall and to generate a series of theoretical contact lines for non-zero line tension values. These theoretical curves can be compared to experimental profiles to determine line tension. The preliminary comparison of these curves with an experimental curve suggests that the line tension value is on the order of 10(-6) (J/m), in agreement with values obtained from drop size dependence of contact angle studies. The comparison also shows that line tension in such systems cannot be as low as 10(-10) (J/m), i.e., the order of the magnitude obtained from some theoretical studies and experimental approaches.

  9. Effect of geometry on concentration polarization in realistic heterogeneous permselective systems

    NASA Astrophysics Data System (ADS)

    Green, Yoav; Shloush, Shahar; Yossifon, Gilad

    2014-04-01

    This study extends previous analytical solutions of concentration polarization occurring solely in the depleted region, to the more realistic geometry consisting of a three-dimensional (3D) heterogeneous ion-permselective medium connecting two opposite microchambers (i.e., a three-layer system). Under the local electroneutrality approximation, the separation of variable methods is used to derive an analytical solution of the electrodiffusive problem for the two opposing asymmetric microchambers. The assumption of an ideal permselective medium allows for the analytic calculation of the 3D concentration and electric potential distributions as well as a current-voltage relation. It is shown that any asymmetry in the microchamber geometries will result in current rectification. Moreover, it is demonstrated that for non-negligible microchamber resistances, the conductance does not exhibit the expected saturation at low concentrations but instead shows a continuous decrease. The results are intended to facilitate a more direct comparison between theory and experiments, as now the voltage drop is across a realistic 3D and three-layer system.

  10. Risks at the DNA Replication Fork: Effects upon Carcinogenesis and Tumor Heterogeneity

    PubMed Central

    Mertz, Tony M.; Harcy, Victoria; Roberts, Steven A.

    2017-01-01

    The ability of all organisms to copy their genetic information via DNA replication is a prerequisite for cell division and a biological imperative of life. In multicellular organisms, however, mutations arising from DNA replication errors in the germline and somatic cells are the basis of genetic diseases and cancer, respectively. Within human tumors, replication errors additionally contribute to mutator phenotypes and tumor heterogeneity, which are major confounding factors for cancer therapeutics. Successful DNA replication involves the coordination of many large-scale, complex cellular processes. In this review, we focus on the roles that defects in enzymes that normally act at the replication fork and dysregulation of enzymes that inappropriately damage single-stranded DNA at the fork play in causing mutations that contribute to carcinogenesis. We focus on tumor data and experimental evidence that error-prone variants of replicative polymerases promote carcinogenesis and on research indicating that the primary target mutated by APOBEC (apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like) cytidine deaminases is ssDNA present at the replication fork. Furthermore, we discuss evidence from model systems that indicate replication stress and other cancer-associated metabolic changes may modulate mutagenic enzymatic activities at the replication fork. PMID:28117753

  11. Effects of dispersal on total biomass in a patchy, heterogeneous system: analysis and experiment.

    USGS Publications Warehouse

    Zhang, Bo; Liu, Xin; DeAngelis, Donald L.; Ni, Wei-Ming; Wang, G Geoff

    2015-01-01

    An intriguing recent result from mathematics is that a population diffusing at an intermediate rate in an environment in which resources vary spatially will reach a higher total equilibrium biomass than the population in an environment in which the same total resources are distributed homogeneously. We extended the current mathematical theory to apply to logistic growth and also showed that the result applies to patchy systems with dispersal among patches, both for continuous and discrete time. This allowed us to make specific predictions, through simulations, concerning the biomass dynamics, which were verified by a laboratory experiment. The experiment was a study of biomass growth of duckweed (Lemna minor Linn.), where the resources (nutrients added to water) were distributed homogeneously among a discrete series of water-filled containers in one treatment, and distributed heterogeneously in another treatment. The experimental results showed that total biomass peaked at an intermediate, relatively low, diffusion rate, higher than the total carrying capacity of the system and agreeing with the simulation model. The implications of the experiment to dynamics of source, sink, and pseudo-sink dynamics are discussed.

  12. Effects of cirrus spatial heterogeneity and ice particle shape on remote sensing of cirrus optical thickness and effective crystal radius - A case study

    NASA Astrophysics Data System (ADS)

    Eichler, Heike; Schmidt, Konrad Sebastian; Buras, Robert; Wendisch, Manfred; Mayer, Bernhard; Emde, Claudia; Pilewskie, Peter; King, Michael; Platnick, Steven

    2010-05-01

    The relative importance of three-dimensional (3D) effects and ice crystal shape of spatially heterogeneous cirrus on the remote-sensing of optical thickness and effective crystal radius is evaluated. In current ice cloud retrievals, the single-scattering properties of ice crystals have to be assumed a-priori. Likewise, the effects of spatial cloud heterogeneity are ignored in current techniques. Both simplifications introduce errors in the retrievals. The study is based on 3D and independent pixel approximation (IPA) radiative transfer calculations. As model input a cloud case that was generated from data collected during the NASA Tropical Composition, Cloud, and Climate Coupling (TC4) experiment is used. First, spectral upwelling radiance fields from the input cloud as they would be sensed by airborne or spaceborne radiometers were determined with 3D radiative transfer simulations. Then the cirrus optical thickness and ice particle effective radius that would be obtained in standard satellite techniques under the IPA assumption were retrieved. The ratios between retrieved and original fields are used as a metric for cloud heterogeneity effects on retrievals. Second, in the retrieval single-scattering properties (crystal shapes) different from those in the radiance calculations were used. In order to isolate ice crystal habit effects, the net horizontal photon transport was disabled here. Thus, the ratios between retrieved and original values of optical thickness and effective radius serve as metric for ice crystal habit effects. When comparing the two metrics, it is found that locally both can be of the same magnitude (up to 50% over- and underestimation), with different dependencies on cirrus optical thickness, effective radius, and optical thickness variability. On domain average, shape effects bias the retrievals more strongly than 3D effects.

  13. Bony protuberances on the anterior and posterior clinoid processes lead to traumatic internal carotid artery aneurysm following craniofacial injury.

    PubMed

    Cheong, Jin Hwan; Kim, Jae Min; Kim, Choong Hyun

    2011-01-01

    Traumatic intracranial aneurysms are rare, comprising 1% or less of all cerebral aneurysms. The majority of these aneurysms arise at the skull base or in the distal anterior and middle cerebral arteries or their branches following direct mural injury or acceleration-induced shearing force. We present a 50-year-old patient in whom subarachnoid hemorrhage (SAH) was developed as a result of traumatic aneurysm rupture after a closed craniofacial injury. Through careful evaluation of the three-dimensional computed tomography and conventional angiographies, the possible mechanism of the traumatic internal carotid artery trunk aneurysm is correlated with a hit injury by the bony protuberances on the anterior and posterior clinoid processes. This traumatic aneurysm was successfully obliterated with clipping and wrapping technique. The possibility of a traumatic intracranial aneurysm should be considered when patient with SAH demonstrates bony protuberances on the clinoid process as a traumatic aneurysm may result from mechanical injury by the sharp bony edges.

  14. Enhancement of Bacterial Transport in Aerobic and Anaerobic Environments: Assessing the Effect of Metal Oxide Chemical Heterogeneities

    SciTech Connect

    T.C. Onstott

    2005-09-30

    The goal of our research was to understand the fundamental processes that control microbial transport in physically and chemically heterogeneous aquifers and from this enhanced understanding determine the requirements for successful, field-scale delivery of microorganisms to metal contaminated subsurface sites. Our specific research goals were to determine; (1) the circumstances under which the preferential adsorption of bacteria to Fe, Mn, and Al oxyhydroxides influences field-scale bacterial transport, (2) the extent to which the adhesion properties of bacterial cells affect field-scale bacterial transport, (3) whether microbial Fe(III) reduction can enhance field-scale transport of Fe reducing bacteria (IRB) and other microorganisms and (4) the effect of field-scale physical and chemical heterogeneity on all three processes. Some of the spin-offs from this basic research that can improve biostimulation and bioaugmentation remediation efforts at contaminated DOE sites have included; (1) new bacterial tracking tools for viable bacteria; (2) an integrated protocol which combines subsurface characterization, laboratory-scale experimentation, and scale-up techniques to accurately predict field-scale bacterial transport; and (3) innovative and inexpensive field equipment and methods that can be employed to enhance Fe(III) reduction and microbial transport and to target microbial deposition under both aerobic and anaerobic conditions.

  15. An Uncertainty Quantification Framework for Studying the Effect of Spatial Heterogeneity in Reservoir Permeability on CO2 Sequestration

    SciTech Connect

    Hou, Zhangshuan; Engel, David W.; Lin, Guang; Fang, Yilin; Fang, Zhufeng

    2013-10-01

    In this paper, we introduce an uncertainty quantification (UQ) software framework for carbon sequestration, focused on the effect of spatial heterogeneity of reservoir properties on CO2 migration. We use a sequential Gaussian method (SGSIM) to generate realizations of permeability fields with various spatial statistical attributes. To deal with the computational difficulties, we integrate the following ideas/approaches. First, we use three different sampling approaches (probabilistic collocation, quasi-Monte Carlo, and adaptive sampling) to reduce the number of forward calculations while trying to explore the parameter space and quantify the input uncertainty. Second, we use eSTOMP as the forward modeling simulator. eSTOMP is implemented with the Global Arrays toolkit that is based on one-sided inter-processor communication and supports a shared memory programming style on distributed memory platforms, providing a highly-scalable performance. Third, we built an adaptive system infrastructure to select the best possible data transfer mechanisms, to optimally allocate system resources to improve performance and to integrate software packages and data for composing carbon sequestration simulation, computation, analysis, estimation and visualization. We demonstrate the framework with a given CO2 injection scenario in heterogeneous sandstone reservoirs.

  16. Using Simulation to Examine the Effect of Physician Heterogeneity on the Operational Efficiency of an Overcrowded Hospital Emergency Department

    NASA Astrophysics Data System (ADS)

    Kuo, Y.-H.; Leung, J. M. Y.; Graham, C. A.

    2015-05-01

    In this paper, we present a case study of modelling and analyzing the patient flow of a hospital emergency department in Hong Kong. The emergency department is facing the challenge of overcrowding and the patients there usually experience a long waiting time. Our project team was requested by a senior consultant of the emergency department to analyze the patient flow and provide a decision support tool to help improve their operations. We adopt a simulation approach to mimic their daily operations. With the simulation model, we conduct a computational study to examine the effect of physician heterogeneity on the emergency department performance. We found that physician heterogeneity has a great impact on the operational efficiency and thus should be considered when developing simulation models. Our computational results show that, with the same average of service rates among the physicians, variation in the rates can improve overcrowding situation. This suggests that emergency departments may consider having some efficient physicians to speed up the overall service rate in return for more time for patients who need extra medical care.

  17. Transport and deposition of polymer-modified Fe0 nanoparticles in 2-D heterogeneous porous media: effects of particle concentration, Fe0 content, and coatings.

    PubMed

    Phenrat, Tanapon; Cihan, Abdullah; Kim, Hye-Jin; Mital, Menka; Illangasekare, Tissa; Lowry, Gregory V

    2010-12-01

    Concentrated suspensions of polymer-modified Fe(0) nanoparticles (NZVI) are injected into heterogeneous porous media for groundwater remediation. This study evaluated the effect of porous media heterogeneity and the dispersion properties including particle concentration, Fe(0) content, and adsorbed polymer mass and layer thickness which are expected to affect the delivery and emplacement of NZVI in heterogeneous porous media in a two-dimensional (2-D) cell. Heterogeneity in hydraulic conductivity had a significant impact on the deposition of NZVI. Polymer modified NZVI followed preferential flow paths and deposited in the regions where fluid shear is insufficient to prevent NZVI agglomeration and deposition. NZVI transported in heterogeneous porous media better at low particle concentration (0.3 g/L) than at high particle concentrations (3 and 6 g/L) due to greater particle agglomeration at high concentration. High Fe(0) content decreased transport during injection due to agglomeration promoted by magnetic attraction. NZVI with a flat adsorbed polymeric layer (thickness ∼30 nm) could not be transported effectively due to pore clogging and deposition near the inlet, while NZVI with a more extended adsorbed layer thickness (i.e., ∼70 nm) were mobile in porous media. This study indicates the importance of characterizing porous media heterogeneity and NZVI dispersion properties as part of the design of a robust delivery strategy for NZVI in the subsurface.

  18. The Effect of Heterogeneous Lithospheric Structure on Surface Stress and Tectonics on Mercury

    NASA Astrophysics Data System (ADS)

    Rosenburg, M. A.; Williams, J.; Aharonson, O.

    2008-12-01

    Observations of Mercury's surface from the Mariner 10 and MESSENGER spacecraft reveal a planet-wide distribution of lobate scarps, which are interpreted to be the surface expression of thrust faults due to global contraction. Statistical analysis of scarps mapped in images from both missions suggests that the orientations of these features are not consistent with a uniform distribution, the expected outcome for a contracting lithosphere of constant thickness. One possible explanation for this observation considers Mercury's thermal state, which is driven by the insolation pattern. Mercury's 3:2 spin-orbit resonance, in concert with its substantial orbital eccentricity of e = 0.20, causes long-wavelength surface temperature variations of more than 130 K. Corresponding variations in lithospheric thickness are hence expected. If the contraction occurred while Mercury was in this dynamical state, the resulting stress distribution recorded on the surface during global cooling and inner core solidification may reflect this heterogeneity. We seek to determine whether contraction of a lithosphere with lateral thickness variations can explain the observed lobate scarp orientations on Mercury's surface. We employ the three-dimensional, viscoelastic, finite element model CitcomSVE along with a thermal evolution model to study Mercury's response to cooling, inner core formation, and lithosphere growth and to track the accumulation of stress in the lithosphere. The resulting stress pattern can then be compared to the orientations and distribution of scarps mapped on the surface of Mercury. Preliminary results indicate systematic variations between the expected orientation of faults in the "cold poles," where the lithosphere is thicker and the "hot poles," where the lithosphere is weaker. As MESSENGER returns more data, comparisons between model results and surface features will be refined.

  19. Heterogeneous Heat Flow and Groundwater Effects on East Antarctic Ice Sheet Dynamics

    NASA Astrophysics Data System (ADS)

    Gooch, B. T.; Soderlund, K. M.; Young, D. A.; Blankenship, D. D.

    2015-12-01

    We present the results numerical models describing the potential contributions groundwater and heterogeneous heat sources might have on ice dynamics. A two-phase, 1D hydrothermal model demonstrates the importance of groundwater flow in heat flux advection near the ice-bed interface. Typical, conservative vertical groundwater volume fluxes on the order of +/- 1-10 mm/yr can alter vertical heat flux by +/- 50-500 mW/m2 that could produce considerable volumes of meltwater depending on basin geometry and geothermal heat production. A 1D hydromechanical model demonstrates that during ice advance groundwater is mainly recharged into saturated sedimentary aquifers and during retreat groundwater discharges into the ice-bed interface, potentially contributing to subglacial water budgets on the order of 0.1-1 mm/yr during ice retreat. A map of most-likely elevated heat production provinces, estimated sedimentary basin depths, and radar-derived bed roughness are compared together to delineate areas of greatest potential to ice sheet instability in East Antarctica. Finally, a 2D numerical model of crustal fluid and heat flow typical to recently estimated sedimentary basins under the East Antarctic Ice Sheet is coupled to a 2.5D Full Stokes ice sheet model (with simple basal hydrology) to test for the sensitivity of hydrodynamic processes on ice sheet dynamics. Preliminary results show that the enhanced fluid flow can dramatically alter the basal heating of the ice and its temperature profile, as well as, the sliding rate, which heavily alter ice dynamics.

  20. Geometric effects in microfluidics on heterogeneous cell stress using an Eulerian-Lagrangian approach.

    PubMed

    Warren, K M; Mpagazehe, J N; LeDuc, P R; Higgs, C F

    2016-02-07

    The response of individual cells at the micro-scale in cell mechanics is important in understanding how they are affected by changing environments. To control cell stresses, microfluidics can be implemented since there is tremendous control over the geometry of the devices. Designing microfluidic devices to induce and manipulate stress levels on biological cells can be aided by computational modeling approaches. Such approaches serve as an efficient precursor to fabricating various microfluidic geometries that induce predictable levels of stress on biological cells, based on their mechanical properties. Here, a three-dimensional, multiphase computational fluid dynamics (CFD) modeling approach was implemented for soft biological materials. The computational model incorporates the physics of the particle dynamics, fluid dynamics and solid mechanics, which allows us to study how stresses affect the cells. By using an Eulerian-Lagrangian approach to treat the fluid domain as a continuum in the microfluidics, we are conducting studies of the cells' movement and the stresses applied to the cell. As a result of our studies, we were able to determine that a channel with periodically alternating columns of obstacles was capable of stressing cells at the highest rate, and that microfluidic systems can be engineered to impose heterogenous cell stresses through geometric configuring. We found that when using controlled geometries of the microfluidics channels with staggered obstructions, we could increase the maximum cell stress by nearly 200 times over cells flowing through microfluidic channels with no obstructions. Incorporating computational modeling in the design of microfluidic configurations for controllable cell stressing could help in the design of microfludic devices for stressing cells such as cell homogenizers.

  1. The Heterogeneous Effects of Cigarette Prices on Brand Choice in China: Implications for Tobacco Control Policy

    PubMed Central

    Li, Jing; White, Justin S.; Hu, Teh-wei; Fong, Geoffrey T.; Jiang, Yuan

    2015-01-01

    Background China has long kept its tobacco taxes below international standards. The Chinese government has cited as two rationales against raising tobacco tax, namely the unfair burden it places on low-income smokers and the ability of consumers to switch to cheaper brands. Objective This study examines how different socioeconomic subgroups of Chinese smokers switch brands in response to cigarette price changes. Methods We model smokers’ choice of cigarette tier as a function of tier-specific prices. We examine heterogeneous responses to prices by estimating mixed logit models for different income and education subgroups that allow for random variation in smokers’ preferences. We use data from three waves of the longitudinal ITC China Survey, collected in six large Chinese cities between 2006 and 2009. Findings Low-income and less educated smokers are considerably more likely to switch tiers (including both up-trading and down-trading) than are their high-socioeconomic status (SES) counterparts. For those in the second-to-lowest tier, a ¥1 ($0.16, or roughly 25%) rise in prices increases the likelihood of switching tiers by 5.6% points for low-income smokers and 7.2% points for less educated smokers, compared to 1.6% and 3.0% points for the corresponding high-SES groups. Low-income and less educated groups are also more likely to trade down compared to their high-SES counterparts. Conclusion Only a small percentage of low-income and less educated Chinese smokers switched to cheaper brands in response to price increases. Hence, the concern of the Chinese government that a cigarette tax increase will lead to large-scale brand switching is not supported by this study. PMID:25855642

  2. Bony cranial ornamentation linked to rapid evolution of gigantic theropod dinosaurs

    NASA Astrophysics Data System (ADS)

    Gates, Terry A.; Organ, Chris; Zanno, Lindsay E.

    2016-09-01

    Exaggerated cranial structures such as crests and horns, hereafter referred to collectively as ornaments, are pervasive across animal species. These structures perform vital roles in visual communication and physical interactions within and between species. Yet the origin and influence of ornamentation on speciation and ecology across macroevolutionary time scales remains poorly understood for virtually all animals. Here, we explore correlative evolution of osseous cranial ornaments with large body size in theropod dinosaurs using a phylogenetic comparative framework. We find that body size evolved directionally toward phyletic giantism an order of magnitude faster in theropod species possessing ornaments compared with unadorned lineages. In addition, we find a body mass threshold below which bony cranial ornaments do not originate. Maniraptoriform dinosaurs generally lack osseous cranial ornaments despite repeatedly crossing this body size threshold. Our study provides novel, quantitative support for a shift in selective pressures on socio-sexual display mechanisms in theropods coincident with the evolution of pennaceous feathers.

  3. 100-million-year dynasty of giant planktivorous bony fishes in the Mesozoic seas.

    PubMed

    Friedman, Matt; Shimada, Kenshu; Martin, Larry D; Everhart, Michael J; Liston, Jeff; Maltese, Anthony; Triebold, Michael

    2010-02-19

    Large-bodied suspension feeders (planktivores), which include the most massive animals to have ever lived, are conspicuously absent from Mesozoic marine environments. The only clear representatives of this trophic guild in the Mesozoic have been an enigmatic and apparently short-lived Jurassic group of extinct pachycormid fishes. Here, we report several new examples of these giant bony fishes from Asia, Europe, and North America. These fossils provide the first detailed anatomical information on this poorly understood clade and extend its range from the lower Middle Jurassic to the end of the Cretaceous, showing that this group persisted for more than 100 million years. Modern large-bodied, planktivorous vertebrates diversified after the extinction of pachycormids at the Cretaceous-Paleogene boundary, which is consistent with an opportunistic refilling of vacated ecospace.

  4. Bony cranial ornamentation linked to rapid evolution of gigantic theropod dinosaurs.

    PubMed

    Gates, Terry A; Organ, Chris; Zanno, Lindsay E

    2016-09-27

    Exaggerated cranial structures such as crests and horns, hereafter referred to collectively as ornaments, are pervasive across animal species. These structures perform vital roles in visual communication and physical interactions within and between species. Yet the origin and influence of ornamentation on speciation and ecology across macroevolutionary time scales remains poorly understood for virtually all animals. Here, we explore correlative evolution of osseous cranial ornaments with large body size in theropod dinosaurs using a phylogenetic comparative framework. We find that body size evolved directionally toward phyletic giantism an order of magnitude faster in theropod species possessing ornaments compared with unadorned lineages. In addition, we find a body mass threshold below which bony cranial ornaments do not originate. Maniraptoriform dinosaurs generally lack osseous cranial ornaments despite repeatedly crossing this body size threshold. Our study provides novel, quantitative support for a shift in selective pressures on socio-sexual display mechanisms in theropods coincident with the evolution of pennaceous feathers.

  5. A rare combination of fractures around the elbow: Bony variant of terrible triad.

    PubMed

    Kumar, Vishal; Kumar, Avinash; Aggarwal, Sameer

    2015-01-01

    Radial head and coronoid fractures without posterior dislocation of the elbow have not been recorded in the literature. There is no literature documenting the combined fractures of the radial head, capitellum and coronoid process together in the same elbow. This is a case report highlighting this combination of fractures in a 30 year old patient treated with open reduction and internal fixation of all three fractures. The patient was followed up for 28 months and had a good range of motion of the elbow without any instability. Thus such a triad with no ligamentous injuries could depict a bony variant of terrible triad and a mechanism for such an injury has also been explained.

  6. Morphometry of the primate bony labyrinth: a new method based on high-resolution computed tomography.

    PubMed Central

    Spoor, F; Zonneveld, F

    1995-01-01

    A method is described for taking accurate measurements of the bony labyrinth of humans and other primates using high-resolution computed tomography (CT). The measurements comprise 8 dimensions, 14 orientations and 2 indices of the labyrinth, as well as 7 orientations of related structures of the petrous pyramid. Comparison of the measurements taken from CT scans with those taken from subsequently made casts and cryosections demonstrates that the method is sufficiently accurate to permit the morphometric analysis of labyrinthine size and shape. Since the CT method is nondestructive, fast and easy to perform, it is applicable to large samples and to rare or precious anthropological specimens. Images Fig. 1 Fig. 2 Fig. 4 PMID:7649826

  7. Reconstruction of bony facial contour deficiencies with polymethylmethacrylate implants: case report

    PubMed Central

    ABDO FILHO, Ruy C. C.; OLIVEIRA, Thais M.; LOURENÇO, Natalino; GURGEL, Carla; ABDO, Ruy C.C.

    2011-01-01

    Facial trauma can be considered one of the most serious aggressions found in the medical centers due to the emotional consequences and the possibility of deformity. In craniofacial surgery, the use of autologous bone is still the first choice for reconstructing bony defects or irregularities. When there is a shortage of donor bone or a patient refuses an intracranial operation, alloplastic materials such as polymethylmethacrylate (PMMA) can be used. The PMMA prosthesis can be pre-fabricated, bringing advantages such as reduction of surgical time, easy technical handling and good esthetic results. This paper describes the procedures for rehabilitating a patient with PMMA implants in the region of the face, recovering the facial contours and esthetics of the patient. PMID:21952926

  8. Bony cranial ornamentation linked to rapid evolution of gigantic theropod dinosaurs

    PubMed Central

    Gates, Terry A.; Organ, Chris; Zanno, Lindsay E.

    2016-01-01

    Exaggerated cranial structures such as crests and horns, hereafter referred to collectively as ornaments, are pervasive across animal species. These structures perform vital roles in visual communication and physical interactions within and between species. Yet the origin and influence of ornamentation on speciation and ecology across macroevolutionary time scales remains poorly understood for virtually all animals. Here, we explore correlative evolution of osseous cranial ornaments with large body size in theropod dinosaurs using a phylogenetic comparative framework. We find that body size evolved directionally toward phyletic giantism an order of magnitude faster in theropod species possessing ornaments compared with unadorned lineages. In addition, we find a body mass threshold below which bony cranial ornaments do not originate. Maniraptoriform dinosaurs generally lack osseous cranial ornaments despite repeatedly crossing this body size threshold. Our study provides novel, quantitative support for a shift in selective pressures on socio-sexual display mechanisms in theropods coincident with the evolution of pennaceous feathers. PMID:27676310

  9. Heterogeneity in the spatial receptive field architecture of multisensory neurons of the superior colliculus and its effects on multisensory integration.

    PubMed

    Ghose, D; Wallace, M T

    2014-01-03

    Multisensory integration has been widely studied in neurons of the mammalian superior colliculus (SC). This has led to the description of various determinants of multisensory integration, including those based on stimulus- and neuron-specific factors. The most widely characterized of these illustrate the importance of the spatial and temporal relationships of the paired stimuli as well as their relative effectiveness in eliciting a response in determining the final integrated output. Although these stimulus-specific factors have generally been considered in isolation (i.e., manipulating stimulus location while holding all other factors constant), they have an intrinsic interdependency that has yet to be fully elucidated. For example, changes in stimulus location will likely also impact both the temporal profile of response and the effectiveness of the stimulus. The importance of better describing this interdependency is further reinforced by the fact that SC neurons have large receptive fields, and that responses at different locations within these receptive fields are far from equivalent. To address these issues, the current study was designed to examine the interdependency between the stimulus factors of space and effectiveness in dictating the multisensory responses of SC neurons. The results show that neuronal responsiveness changes dramatically with changes in stimulus location - highlighting a marked heterogeneity in the spatial receptive fields of SC neurons. More importantly, this receptive field heterogeneity played a major role in the integrative product exhibited by stimulus pairings, such that pairings at weakly responsive locations of the receptive fields resulted in the largest multisensory interactions. Together these results provide greater insight into the interrelationship of the factors underlying multisensory integration in SC neurons, and may have important mechanistic implications for multisensory integration and the role it plays in shaping

  10. Skin thickness on bony prominences measured by ultrasonography in patients with spinal cord injury

    PubMed Central

    Yalcin, Elif; Akyuz, Mufit; Onder, Burcu; Unalan, Halil; Degirmenci, Ibrahim

    2013-01-01

    Objective The detailed assessment of soft tissues over bony prominences and identification of methods of predicting pressure sores would improve the quality of care for patients with spinal cord injury (SCI). Comparing skin thicknesses on bony prominences in patients with SCI to those in healthy individuals will represent, to our knowledge, the first study aimed at determining whether differences in skin thicknesses between these groups can be detected by ultrasound. Design In both patients and controls, skin thicknesses on the sites at risk for pressure ulcers – sacrum, greater trochanter, and ischium – were evaluated using high-frequency ultrasound. The waist was also evaluated by the same method for control as it was considered to be a pressure-free region. Participants Thirty-two patients with complete thoracic SCI and 34 able-bodied individuals. Results The skin was significantly thinner over the sacrum and ischial tuberosity in individuals with SCI compared with healthy individuals. No significant differences were observed in skin thicknesses over the greater trochanter or the waist between the two groups. Conclusions Protecting skin integrity in patients with paraplegia is challenging due to many contributing factors, such as prolonged pressure, frictional/shearing forces, and poor nutrition. Thinning of the skin can increase the risk of soft tissue damage, leading to pressure ulcers. The significant differences in skin thickness at the sacrum and ischium provide the basis for establishing the early signs of pressure damage. Measuring skin thickness by ultrasound is a reliable non-invasive method that could be a promising tool for predicting pressure ulcers. PMID:23809593

  11. Spatial heterogeneity in medulloblastoma.

    PubMed

    Morrissy, A Sorana; Cavalli, Florence M G; Remke, Marc; Ramaswamy, Vijay; Shih, David J H; Holgado, Borja L; Farooq, Hamza; Donovan, Laura K; Garzia, Livia; Agnihotri, Sameer; Kiehna, Erin N; Mercier, Eloi; Mayoh, Chelsea; Papillon-Cavanagh, Simon; Nikbakht, Hamid; Gayden, Tenzin; Torchia, Jonathon; Picard, Daniel; Merino, Diana M; Vladoiu, Maria; Luu, Betty; Wu, Xiaochong; Daniels, Craig; Horswell, Stuart; Thompson, Yuan Yao; Hovestadt, Volker; Northcott, Paul A; Jones, David T W; Peacock, John; Wang, Xin; Mack, Stephen C; Reimand, Jüri; Albrecht, Steffen; Fontebasso, Adam M; Thiessen, Nina; Li, Yisu; Schein, Jacqueline E; Lee, Darlene; Carlsen, Rebecca; Mayo, Michael; Tse, Kane; Tam, Angela; Dhalla, Noreen; Ally, Adrian; Chuah, Eric; Cheng, Young; Plettner, Patrick; Li, Haiyan I; Corbett, Richard D; Wong, Tina; Long, William; Loukides, James; Buczkowicz, Pawel; Hawkins, Cynthia E; Tabori, Uri; Rood, Brian R; Myseros, John S; Packer, Roger J; Korshunov, Andrey; Lichter, Peter; Kool, Marcel; Pfister, Stefan M; Schüller, Ulrich; Dirks, Peter; Huang, Annie; Bouffet, Eric; Rutka, James T; Bader, Gary D; Swanton, Charles; Ma, Yusanne; Moore, Richard A; Mungall, Andrew J; Majewski, Jacek; Jones, Steven J M; Das, Sunit; Malkin, David; Jabado, Nada; Marra, Marco A; Taylor, Michael D

    2017-04-10

    Spatial heterogeneity of transcriptional and genetic markers between physically isolated biopsies of a single tumor poses major barriers to the identification of biomarkers and the development of targeted therapies that will be effective against the entire tumor. We analyzed the spatial heterogeneity of multiregional biopsies from 35 patients, using a combination of transcriptomic and genomic profiles. Medulloblastomas (MBs), but not high-grade gliomas (HGGs), demonstrated spatially homogeneous transcriptomes, which allowed for accurate subgrouping of tumors from a single biopsy. Conversely, somatic mutations that affect genes suitable for targeted therapeutics demonstrated high levels of spatial heterogeneity in MB, malignant glioma, and renal cell carcinoma (RCC). Actionable targets found in a single MB biopsy were seldom clonal across the entire tumor, which brings the efficacy of monotherapies against a single target into question. Clinical trials of targeted therapies for MB should first ensure the spatially ubiquitous nature of the target mutation.

  12. The effect of heterogeneous variance on efficiency and power of cluster randomized trials with a balanced 2 × 2 factorial design.

    PubMed

    Lemme, Francesca; van Breukelen, Gerard J P; Candel, Math J J M; Berger, Martijn P F

    2015-10-01

    Sample size calculation for cluster randomized trials (CRTs) with a [Formula: see text] factorial design is complicated due to the combination of nesting (of individuals within clusters) with crossing (of two treatments). Typically, clusters and individuals are allocated across treatment conditions in a balanced fashion, which is optimal under homogeneity of variance. However, the variance is likely to be heterogeneous if there is a treatment effect. An unbalanced allocation is then more efficient, but impractical because the optimal allocation depends on the unknown variances. Focusing on CRTs with a [Formula: see text] design, this paper addresses two questions: How much efficiency is lost by having a balanced design when the outcome variance is heterogeneous? How large must the sample size be for a balanced allocation to have sufficient power under heterogeneity of variance? We consider different scenarios of heterogeneous variance. Within each scenario, we determine the relative efficiency of a balanced design, as a function of the level (cluster, individual, both) and amount of heterogeneity of the variance. We then provide a simple correction of the sample size for the loss of power due to heterogeneity of variance when a balanced allocation is used. The theory is illustrated with an example of a published 2 x2 CRT.

  13. Effect of adding nanometre-sized heterogeneities on the structural dynamics and the excess wing of a molecular glass former

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Fischer, J. K. H.; Lunkenheimer, P.; Loidl, A.; Novak, E.; Jalarvo, N.; Ohl, M.

    2016-10-01

    We present the relaxation dynamics of glass-forming glycerol mixed with 1.1 nm sized polyhedral oligomeric silsesquioxane (POSS) molecules using dielectric spectroscopy (DS) and two different neutron scattering (NS) techniques. Both, the reorientational dynamics as measured by DS and the density fluctuations detected by NS reveal a broadening of the α relaxation when POSS molecules are added. Moreover, we find a significant slowing down of the α-relaxation time. These effects are in accord with the heterogeneity scenario considered for the dynamics of glasses and supercooled liquids. The addition of POSS also affects the excess wing in glycerol arising from a secondary relaxation process, which seems to exhibit a dramatic increase in relative strength compared to the α relaxation.

  14. Effect of adding nanometre-sized heterogeneities on the structural dynamics and the excess wing of a molecular glass former

    PubMed Central

    Gupta, S.; Fischer, J. K. H.; Lunkenheimer, P.; Loidl, A.; Novak, E.; Jalarvo, N.; Ohl, M.

    2016-01-01

    We present the relaxation dynamics of glass-forming glycerol mixed with 1.1 nm sized polyhedral oligomeric silsesquioxane (POSS) molecules using dielectric spectroscopy (DS) and two different neutron scattering (NS) techniques. Both, the reorientational dynamics as measured by DS and the density fluctuations detected by NS reveal a broadening of the α relaxation when POSS molecules are added. Moreover, we find a significant slowing down of the α-relaxation time. These effects are in accord with the heterogeneity scenario considered for the dynamics of glasses and supercooled liquids. The addition of POSS also affects the excess wing in glycerol arising from a secondary relaxation process, which seems to exhibit a dramatic increase in relative strength compared to the α relaxation. PMID:27725747

  15. Effects of the thermal heterogeneity of the column on chromatographic results.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2006-10-27

    The influence of the thermal heterogeneity of HPLC columns on retention data was investigated. The retention factor of the retained compound phenol was measured at 24 increasing values of the flow rate, from 0.025 to 4.9 mL/min, on six different packing materials prepared with the same batch of silica particles (5 microm diameter, 90 A pore size). One column was packed with the neat silica particles, another with the silica endcapped with trimethylchlorosilane (TMS)(C(1), 3.92 micromol/m(2)), and the other four with silica first derivatized with octadecyl-dimethyl-chlorosilane (C(18), 0.42, 1.01, 2.03, and 3.15 micromol/m(2)), and second endcapped with TMS. Four different sources of heat contributing to raise the column temperature were considered: (1) the heat supplied by the hot high-pressure pump chamber to the solvent; (2) the adiabatic (dS=0) compression of the solvent in the high-pressure pump; (3) the isenthalpic (dH=0) decompression of the solvent during its migration along the porous chromatographic bed; and (4) the heat released by the friction of the solvent percolating through the column bed. The main contributions appear to be the heat supplied to the solvent by the HP pump and the friction heat. The average column temperature (ACT) was indirectly derived from the measurements of the first moment, mu(1), of phenol peak, of the column pressure drop, DeltaP, and of the retention factors of the phenol peak apices as a function of the flow rate applied. If the column is placed in a still-air bath at 298 K (and its temperature is not externally controlled), a longitudinal temperature gradient is established along the column and the average column temperature is about 6 K higher when this column is operated at 4.9 mL/min than when the flow rate is only 0.025 mL/min. If the column is placed in a heated air bath (temperature controlled at 316 or 338 K), the ACT changes by less than 3 K over the whole flow rate range applied.

  16. Effect of spatial forcing data and landscape heterogeneity on performance and consistency of model structures

    NASA Astrophysics Data System (ADS)

    Euser, Tanja; Winsemius, Hessel; Hrachowitz, Markus; Savenije, Hubert

    2014-05-01

    One of the main questions in hydrological modelling is how to design conceptual rainfall-runoff models with a higher degree of realism. It is expected that if models have a higher degree of realism, their predictive power will increase. One frequently discussed option is the use of more spatial information, which is increasingly available. Information with spatial variability can be found for example for forcing data, elevation, land use, etc. The abundance of spatially variable data requires the modeller to carefully select which data add realism to the model and which data only add complexity. An additional complication is further that the spatial detail required is a function of the time scales of the forcing data and the required output. The amount of spatially variable data available can guide the choice of an adequate distribution level of a model. As it is often difficult to determine the most suitable level of distribution for a certain catchment, this study systematically evaluates the value of incorporating distributed forcing data and distributed model structures in a stepwise approach for the Ourthe catchment (Belgium). The distribution of the model structures is based on landscape heterogeneity, using both elevation data and land use data. Eight different model configurations are tested: a lumped and a distributed model structure, each with lumped and stepwise distributed fluxes and stocks. To stepwise distribute the fluxes and stocks, the distributed forcing data is sequentially kept distributed for each reservoir of the model. To compare the degree of realism of the different configurations, both model performance and consistency are compared. Performance describes the ability of a model configuration to mimic a specific part of the hydrological behaviour in a specific catchment. Consistency describes the ability of a model configuration to adequately reproduce several hydrological signatures simultaneously. FARM (Framework to Assess the Realism of

  17. Effect of heterogeneity and anisotropy related to the construction method on transfer processes in waste rock piles.

    PubMed

    Lahmira, Belkacem; Lefebvre, René; Aubertin, Michel; Bussière, Bruno

    2016-01-01

    Waste rock piles producing acid mine drainage (AMD) are partially saturated systems involving multiphase (gas and liquid) flow and coupled transfer processes. Their internal structure and heterogeneous properties are inherited from their wide-ranging material grain sizes, their modes of deposition, and the underlying topography. This paper aims at assessing the effect of physical heterogeneity and anisotropy of waste rock piles on the physical processes involved in the generation of AMD. Generic waste rock pile conditions were represented with the numerical simulator TOUGH AMD based on those found at the Doyon mine waste rock pile (Canada). Models included four randomly distributed material types (coarse, intermediate, fine and very fine-grained). The term "randomly" as used in this study means that the vertical profile and spatial distribution of materials in waste rock piles (internal structure) defy stratigraphy principles applicable to natural sediments (superposition and continuity). The materials have different permeability and capillary properties, covering the typical range of materials found in waste rock piles. Anisotropy with a larger horizontal than vertical permeability was used to represent the effect of pile construction by benches, while the construction by end-dumping was presumed to induce a higher vertical than horizontal permeability. Results show that infiltrated precipitation preferentially flows in fine-grained materials, which remain almost saturated, whereas gas flows preferentially through the most permeable coarse materials, which have higher volumetric gas saturation. Anisotropy, which depends on pile construction methods, often controls global gas flow paths. Construction by benches favours lateral air entry close to the pile slope, whereas end-dumping leads to air entry from the surface to the interior of the pile by secondary gas convection cells. These results can be useful to construct and rehabilitate waste rock piles to minimize

  18. The effects of scale and spatial heterogeneities on diffusion in volcanic breccias and basalts: Amchitka Island, Alaska.

    PubMed

    Benning, Jennifer L; Barnes, David L

    2009-05-12

    Knowledge of the factors that influence the diffusion of contaminants, such as the diffusivity and the connected porosity, is crucial to modeling the long-term fate and transport of contaminants in subsurface systems with small or negligible advective flow, such as in fractured crystalline rock. Fractured rock is naturally heterogeneous, and hence, understanding the diffusivity of a molecule through this material (or the formation factor of the medium) becomes a complex problem, with critical concerns about the scale of laboratory measurements and about the spatial variability of these measurements relative to the scale needed for fate and transport modeling. This study employed both electrical and tracer-based laboratory methods to investigate the effects of scale and pore system connectivity on the diffusivity for volcanic matrix rock derived from the study site, a former underground nuclear test site at Amchitka Island, Alaska. The results of these investigations indicate a relatively well-connected pore system with scale effects generally limited to approximately 6 cm lengths and well-correlated to observed heterogeneous features. An important conclusion resulting from this study, however, is that there is a potential for the estimated diffusivity to be misrepresented by an order of magnitude if multiple samples or longer sample lengths are not used. Given the relatively large number of measurements resulting from these investigations, an analysis of the probability density function (PDF) of the diffusivity was possible. The PDF of the diffusivity was shown to generally follow a normal distribution for individual geologic layers. However, when all of the geologic layers are considered together, the distribution of the subsurface as a whole was shown to follow a lognormal distribution due to the order of magnitude differences amongst the layers. An understanding of these distributions is essential for future stochastic modeling efforts.

  19. Impacts of surface adsorbed catechol on tropospheric aerosol surrogates: heterogeneous ozonolysis and its effects on water uptake.

    PubMed

    Woodill, Laurie A; O'Neill, Erinn M; Hinrichs, Ryan Z

    2013-07-11

    Surface adsorbed organics are ubiquitous components of inorganic tropospheric aerosols and have the potential to alter aerosol chemical and physical properties. To assess the impact of adsorbed organics on water uptake by inorganic substrates, we used diffuse reflectance infrared spectroscopy to compared water adsorption isotherms for uncoated NaCl and α-Al2O3 samples, samples containing a monolayer of adsorbed catechol, and adsorbed catechol samples following ozonolysis. Adsorption of gaseous catechol on to the inorganic substrates produced vibrational features indicating physisorption on NaCl and displacement of surface hydroxyl groups forming binuclear bidentate catecholate on α-Al2O3, with surface concentrations of 2-3 × 10(18) molecules m(-2). Subsequent heterogeneous ozonolysis produced muconic acid at a rate 4-5 times faster on NaCl compared to α-Al2O3, with predicted atmospheric lifetimes of 4.3 and 18 h, respectively, assuming a tropospheric ozone concentration of 40 ppb. Water adsorption isotherms for all NaCl samples were indistinguishable within experimental uncertainty, indicating that these organic monolayers had negligible impact on coadsorbed water surface concentrations for these systems. α-Al2O3-catechol samples exhibited dramatically less water uptake compared to uncoated α-Al2O3, while oxidation of surface adsorbed catechol had no effect on the extent of water uptake. For both substrates, adsorbed organics increased the relative abundance of "ice-like" versus "liquid-like" water, with the effect larger for catechol than oxidized ozonolysis products. These results highlight the importance of aerosol substrate in understanding the heterogeneous ozonolysis of adsorbed polyphenols and suggest such coatings may impair ice nucleation by aluminosilicate mineral aerosol.

  20. Nutrient Availability and Atmospheric CO2 Partial Pressure Modulate the Effects of Nutrient Heterogeneity on the Size Structure of Populations in Grassland Species

    PubMed Central

    MAESTRE, FERNANDO T.; REYNOLDS, JAMES F.

    2006-01-01

    • Background and Aims Size-asymmetric competition occurs when larger plants have a disproportionate advantage in competition with smaller plants. It has been hypothesized that nutrient heterogeneity may promote it. Experiments testing this hypothesis are inconclusive, and in most cases have evaluated the effects of nutrient heterogeneity separately from other environmental factors. The aim of this study was to test, using populations of Lolium perenne, Plantago lanceolata and Holcus lanatus, two hypotheses: (a) nutrient heterogeneity promotes size-asymmetric competition; and (b) nutrient heterogeneity interacts with both atmospheric CO2 partial pressure (PCO2) and nutrient availability to determine the magnitude of this response. • Methods Microcosms consisting of monocultures of the three species were grown for 90 d in a factorial experiment with the following treatments: PCO2 (37·5 and 70 Pa) and nutrient availability (NA; 40 and 120  mg of N added as organic material) combined with different spatial distribution of the organic material (NH; homogeneous and heterogeneous). Differences in the size of individual plants within populations (size inequality) were quantified using the coefficient of variation of individual above-ground biomass and the combined biomass of the two largest individuals in each microcosm. Increases in size inequality were associated with size-asymmetric competition. • Key Results Size inequality increased when the nutrients were heterogeneously supplied in the three species. The effects of NH on this response were more pronounced under high nutrient supply in both Plantago and Holcus (significant NA × NH interactions) and under elevated PCO2 in Plantago (significant PCO2 × NA × NH interaction). No significant two- and three-way interactions were found for Lolium. • Conclusions Our first hypothesis was supported by our results, as nutrient heterogeneity promoted size-asymmetric competition in the three species evaluated

  1. Achondrogenesis II-hypochondrogenesis: variability versus heterogeneity.

    PubMed

    Borochowitz, Z; Ornoy, A; Lachman, R; Rimoin, D L

    1986-06-01

    Recently hypochondrogenesis was described as a form of neonatally lethal dwarfism said to resemble spondyloepiphyseal dysplasia congenita radiographically and achondrogenesis II morphologically. Because of the difficulty in distinguishing radiographically between mild achondrogenesis II and severe hypochondrogenesis, we performed a clinical, radiographic, and morphologic study of 24 cases originally classified as either achondrogenesis II or hypochondrogenesis, in an attempt to distinguish between heterogeneity and clinical variability. Review of the radiographic findings in these cases show a fairly continuous spectrum of bony defects, rather than two distinct radiographic syndromes. Chondro-osseous histology and ultrastructure was similar in all cases regardless of severity and was characterized by hypervascularity and hypercellularity of the cartilage with multiple small, round dilated cysternae of rough endoplasmic reticulum. These findings suggest that hypochondrogenesis and achondrogenesis type II represent a spectrum with marked phenotypic variability.

  2. Fine Mapping Seronegative and Seropositive Rheumatoid Arthritis to Shared and Distinct HLA Alleles by Adjusting for the Effects of Heterogeneity

    PubMed Central

    Han, Buhm; Diogo, Dorothée; Eyre, Steve; Kallberg, Henrik; Zhernakova, Alexandra; Bowes, John; Padyukov, Leonid; Okada, Yukinori; González-Gay, Miguel A.; Rantapää-Dahlqvist, Solbritt; Martin, Javier; Huizinga, Tom W.J.; Plenge, Robert M.; Worthington, Jane; Gregersen, Peter K.; Klareskog, Lars; de Bakker, Paul I.W.; Raychaudhuri, Soumya

    2014-01-01

    Despite progress in defining human leukocyte antigen (HLA) alleles for anti-citrullinated-protein-autoantibody-positive (ACPA+) rheumatoid arthritis (RA), identifying HLA alleles for ACPA-negative (ACPA−) RA has been challenging because of clinical heterogeneity within clinical cohorts. We imputed 8,961 classical HLA alleles, amino acids, and SNPs from Immunochip data in a discovery set of 2,406 ACPA− RA case and 13,930 control individuals. We developed a statistical approach to identify and adjust for clinical heterogeneity within ACPA− RA and observed independent associations for serine and leucine at position 11 in HLA-DRβ1 (p = 1.4 × 10−13, odds ratio [OR] = 1.30) and for aspartate at position 9 in HLA-B (p = 2.7 × 10−12, OR = 1.39) within the peptide binding grooves. These amino acid positions induced associations at HLA-DRB1∗03 (encoding serine at 11) and HLA-B∗08 (encoding aspartate at 9). We validated these findings in an independent set of 427 ACPA− case subjects, carefully phenotyped with a highly sensitive ACPA assay, and 1,691 control subjects (HLA-DRβ1 Ser11+Leu11: p = 5.8 × 10−4, OR = 1.28; HLA-B Asp9: p = 2.6 × 10−3, OR = 1.34). Although both amino acid sites drove risk of ACPA+ and ACPA− disease, the effects of individual residues at HLA-DRβ1 position 11 were distinct (p < 2.9 × 10−107). We also identified an association with ACPA+ RA at HLA-A position 77 (p = 2.7 × 10−8, OR = 0.85) in 7,279 ACPA+ RA case and 15,870 control subjects. These results contribute to mounting evidence that ACPA+ and ACPA− RA are genetically distinct and potentially have separate autoantigens contributing to pathogenesis. We expect that our approach might have broad applications in analyzing clinical conditions with heterogeneity at both major histocompatibility complex (MHC) and non-MHC regions. PMID:24656864

  3. Closing the Gap: Modeling Within-School Variance Heterogeneity in School Effect Studies. CSE Report 689

    ERIC Educational Resources Information Center

    Choi, Kilchan; Kim, Junyeop

    2006-01-01

    Effective schools should be superior in both enhancing students' achievement levels and reducing the gap between high- and low-achieving students in the school. However, the focus has been placed mainly on schools' achievement levels in most school effect studies. In this article, we attend to the school-specific achievement dispersion as well as…

  4. Class Size Effects on Student Achievement: Heterogeneity across Abilities and Fields

    ERIC Educational Resources Information Center

    De Paola, Maria; Ponzo, Michela; Scoppa, Vincenzo

    2013-01-01

    In this paper, we analyze class size effects on college students exploiting data from a project offering special remedial courses in mathematics and language skills to freshmen enrolled at an Italian medium-sized public university. To estimate the effects of class size, we exploit the fact that students and teachers are virtually randomly assigned…

  5. Examining Heterogeneity in the Effect of Taking Algebra in Eighth Grade

    ERIC Educational Resources Information Center

    Rickles, Jordan H.

    2013-01-01

    Increased access to algebra was a focal point of the National Mathematics Advisory Panel's 2008 report on improving mathematics learning in the United States. Past research found positive effects for early access to algebra, but the focus on average effects may mask important variation across student subgroups. The author addresses whether these…

  6. Closing the Gap: Modeling Within-School Variance Heterogeneity in School Effect Studies

    ERIC Educational Resources Information Center

    Kim, Junyeop; Choi, Kilchan

    2008-01-01

    Effective schools should be superior in both enhancing students' achievement levels and reducing the gap between high- and low-achieving students in the school. However, the focus has been placed mainly on schools' achievement levels in most school effect studies. In this article, we focused our attention upon the school-specific achievement…

  7. Heterogeneous effects in the process of ozone synthesis in electrical discharges

    SciTech Connect

    Schmidt-Szalowski, K.; Borucka, A. )

    1989-06-01

    Catalytic effects of solid surfaces in the synthesis of ozone have been examined under semicorona discharges conditions. It was found out that in the presence of a granular dielectric (silica) in the discharge gap, the ozone formation was accelerated and higher ozone concentrations were obtained. The mechanism of catalytic effects of silica is discussed.

  8. Interface coupling-induced enhancement of magnetoimpedance effect in heterogeneous nanobrush by adjusting textures of Co nanowires

    PubMed Central

    2013-01-01

    Interface coupling-induced and interface coupling-enhanced magnetoimpedance (MI) effect in heterogeneous nanobrush has been investigated. The nanobrush is composed of Fe25Ni75 nanofilm and textured hexagonal close-packed cobalt nanowire array, respectively fabricated by RF magnetron sputtering and electrochemical deposition. The design of this structure is based on the vortex distribution of magnetic moments in thin film, which can be induced by the exchange coupling effect at the interfaces of the nanobrush. The texture of nanowires plays an important role in the MI effect of the nanobrush, which is regulated by controlling the pH values and temperatures of the deposition process. The ‘parallel’ and ‘perpendicular’ coupling models were used to explain the different MI results of the nanobrush with cobalt nanowires, which have (100) and (002) textures, respectively. The optimized MI effect of the nanobrush brought by (100) nanowires can be magnified by 300% with more than 80%/Oe magnetic sensitivity at a low frequency, which has great application potentials in low-frequency MI sensors. PMID:24207011

  9. Dual-tracer transport experiments in a physically and chemically heterogeneous porous aquifer: effective transport parameters and spatial variability

    NASA Astrophysics Data System (ADS)

    Ptak, T.; Schmid, G.

    1996-08-01

    In order to investigate the effects of reactive transport processes within a heterogeneous porous aquifer, two small-scale forced gradient tracer tests were conducted at the 'Horkheimer Insel' field site. During the experiments, two fluorescent tracers were injected simultaneously in the same fully penetrating groundwater monitoring well, located approximately 10 m from the pumping well. Fluoresceine and Rhodamine WT were used to represent the classes of practically non-sorbing and sorbing solutes, respectively. Multilevel breakthrough curves with a temporal resolution of 1 min were measured for both tracers at different depths within the pumping well using fibre-optic fluorimeters. This paper presents the tracer test design, the fibre-optic fluorimetry instrumentation, the experimental results and the interpretation of the measured multilevel breakthrough curves in terms of temporal moments and effective transport parameters. Significant sorption of Rhodamine WT is apparent from the effective retardation factors. Furthermore, an enhanced tailing of Rhodamine WT breakthrough curves is observed, which is possibly caused by a variability of aquifer sorption properties. The determined effective parameters are spatially variable, suggesting that a complex numerical flow and transport modelling approach within a stochastic framework will be needed to adequately describe the transport behaviour observed in the two experiments. Therefore, the tracer test results will serve in future work for the validation of numerical stochastic transport simulations taking into account the spatial variability of hydraulic conductivity and sorption-related aquifer properties.

  10. Effects of Relative Humidity and Particle Phase Water on the Heterogeneous OH Oxidation of 2-Methylglutaric Acid Aqueous Droplets.

    PubMed

    Chim, Man Mei; Chow, Chun Yin; Davies, James F; Chan, Man Nin

    2017-03-02

    Organic aerosols can exist as aqueous droplets, with variable water content depending on their composition and environmental conditions (e.g., relative humidity (RH)). Recent laboratory studies have revealed that oxidation kinetics in highly concentrated droplets can be much slower than those in dilute solutions. However, it remains unclear whether aerosol phase water affects the formation of reaction products physically and/or chemically. In this work, we investigate the role of aerosol phase water on the heterogeneous chemistry of aqueous organic droplets consisting of 2-methylglutaric acid (2-MGA), measuring the reaction kinetics and the reaction products upon heterogeneous OH oxidation over a range of RH. An atmospheric pressure soft ionization source (direct analysis in real time, DART) coupled with a high-resolution mass spectrometer is used to obtain real-time molecular information on the reaction products. Aerosol mass spectra show that the same reaction products are formed at all measured RH. At a given reaction extent of the parent 2-MGA, the aerosol composition is independent of RH. These results suggest the aerosol phase water does not alter reaction mechanisms significantly. Kinetic measurements find that the effective OH uptake coefficient, γeff, decreases with decreasing RH below 72%. Isotopic exchange measurements performed using aerosol optical tweezers reveal water diffusion coefficients in the 2-MGA droplets to be 3.0 × 10(-13) to 8.0 × 10(-13) m(2) s(-1) over the RH range of 47-58%. These values are comparable to those of other viscous organic aerosols (e.g., citric acid), indicating that 2-MGA droplets are likely to be viscous at low humidity. Smaller γeff at low RH is likely attributed to the slower diffusion of reactants within the droplets. Taken together, the observed relationship between the γeff and RH is likely attributed to changes in aerosol viscosity rather than changes in reaction mechanisms.

  11. Heterogeneous road networks have no apparent effect on the genetic structure of small mammal populations.

    PubMed

    Grilo, Clara; Del Cerro, Irene; Centeno-Cuadros, Alejandro; Ramiro, Victor; Román, Jacinto; Molina-Vacas, Guillem; Fernández-Aguilar, Xavier; Rodríguez, Juan; Porto-Peter, Flávia; Fonseca, Carlos; Revilla, Eloy; Godoy, José A

    2016-09-15

    Roads are widely recognized to represent a barrier to individual movements and, conversely, verges can act as potential corridors for the dispersal of many small mammals. Both barrier and corridor effects should generate a clear spatial pattern in genetic structure. Nevertheless, the effect of roads on the genetic structure of small mammal populations still remains unclear. In this study, we examine the barrier effect that different road types (4-lane highway, 2-lane roads and single-lane unpaved roads) may have on the population genetic structure of three species differing in relevant life history traits: southern water vole Arvicola sapidus, the Mediterranean pine vole Microtus duodecimcostatus and the Algerian mouse Mus spretus. We also examine the corridor effect of highway verges on the Mediterranean pine vole and the Algerian mouse. We analysed the population structure through pairwise estimates of FST among subpopulations bisected by roads, identified genetic clusters through Bayesian assignment approaches, and used simple and partial Mantel tests to evaluate the relative barrier or corridor effect of roads. No strong evidences were found for an effect of roads on population structure of these three species. The barrier effect of roads seems to be site-specific and no corridor effect of verges was found for the pine vole and Algerian mouse populations. The lack of consistent results among species and for each road type lead us to believe that the ability of individual dispersers to use those crossing structures or the habitat quality in the highway verges may have a relatively higher influence on gene flow among populations than the presence of crossing structures per se. Further research should include microhabitat analysis and the estimates of species abundance to understand the mechanisms that underlie the genetic structure observed at some sites.

  12. Guided Bayesian imputation to adjust for confounding when combining heterogeneous data sources in comparative effectiveness research.

    PubMed

    Antonelli, Joseph; Zigler, Corwin; Dominici, Francesca

    2017-03-03

    In comparative effectiveness research, we are often interested in the estimation of an average causal effect from large observational data (the main study). Often this data does not measure all the necessary confounders. In many occasions, an extensive set of additional covariates is measured for a smaller and non-representative population (the validation study). In this setting, standard approaches for missing data imputation might not be adequate due to the large number of missing covariates in the main data relative to the smaller sample size of the validation data. We propose a Bayesian approach to estimate the average causal effect in the main study that borrows information from the validation study to improve confounding adjustment. Our approach combines ideas of Bayesian model averaging, confounder selection, and missing data imputation into a single framework. It allows for different treatment effects in the main study and in the validation study, and propagates the uncertainty due to the missing data imputation and confounder selection when estimating the average causal effect (ACE) in the main study. We compare our method to several existing approaches via simulation. We apply our method to a study examining the effect of surgical resection on survival among 10 396 Medicare beneficiaries with a brain tumor when additional covariate information is available on 2220 patients in SEER-Medicare. We find that the estimated ACE decreases by 30% when incorporating additional information from SEER-Medicare.

  13. The relationship between the lizard eye and associated bony features: a cautionary note for interpreting fossil activity patterns.

    PubMed

    Hall, Margaret I

    2009-06-01

    Activity pattern, the time of day when an animal is active, is associated with ecology. There are two major activity patterns: diurnal (awake during the day in a photopic environment) and nocturnal (awake at night in a scotopic environment). Lizards exhibit characteristic eye shapes associated with activity pattern, with scotopic-adapted lizard eyes optimized for visual sensitivity with large corneal diameters relative to their eye axial lengths, and photopic-adapted lizards optimized for visual acuity, with larger axial lengths of the eye relative to their corneal diameters. This study: (1) quantifies the relationship between the lizard eye and its associated bony anatomy (the orbit, sclerotic ring, and associated skull widths); (2) investigates how activity pattern is reflected in that bony anatomy; and (3) determines if it is possible to reliably interpret activity pattern for a lizard that does not have the soft tissue available for study, specifically, for a fossil. Knowledge of extinct lizards' activity patterns would be useful in making paleoecological interpretations. Here, 96 scotopic- and photopic-adapted lizard species are analyzed in a phylogenetic context. Although there is a close relationship between the lepidosaur eye and associated bony anatomy, based on these data activity pattern cannot be reliably interpreted for bony-only specimens, such as a fossil, possibly because of the limited ossification of the lepidosaur skull. Caution should be exercised when utilizing lizard bony anatomy to interpret light-level adaptation, either for a fossil lizard or as part of an extant phylogenetic bracket to interpret other extinct animals with sclerotic rings, such as dinosaurs.

  14. Sacro-Iliac Joint Sensory Block and Radiofrequency Ablation: Assessment of Bony Landmarks Relevant for Image-Guided Procedures

    PubMed Central

    Roberts, Shannon L.; Burnham, Robert S.; Loh, Eldon; Agur, Anne M.

    2016-01-01

    Image-guided sensory block and radiofrequency ablation of the nerves innervating the sacro-iliac joint require readily identifiable bony landmarks for accurate needle/electrode placement. Understanding the relative locations of the transverse sacral tubercles along the lateral sacral crest is important for ultrasound guidance, as they demarcate the position of the posterior sacral network (S1–S3 ± L5/S4) innervating the posterior sacro-iliac joint. No studies were found that investigated the spatial relationships of these bony landmarks. The purpose of this study was to visualize and quantify the interrelationships of the transverse sacral tubercles and posterior sacral foramina to inform image-guided block and radiofrequency ablation of the sacro-iliac joint. The posterior and lateral surfaces of 30 dry sacra (15 M/15 F) were digitized and modeled in 3D and the distances between bony landmarks quantified. The relationships of bony landmarks (S1–S4) were not uniform. The mean intertubercular and interforaminal distances decreased from S1 to S4, whereas the distance from the lateral margin of the posterior sacral foramina to the transverse sacral tubercles increased from S1 to S3. The mean intertubercular distance from S1 to S3 was significantly (p < 0.05) larger in males. The interrelationships of the sacral bony landmarks should be taken into consideration when estimating the site and length of an image-guided strip lesion targeting the posterior sacral network. PMID:27747222

  15. The bony labyrinth of the middle Pleistocene Sima de los Huesos hominins (Sierra de Atapuerca, Spain).

    PubMed

    Quam, Rolf; Lorenzo, Carlos; Martínez, Ignacio; Gracia-Téllez, Ana; Arsuaga, Juan Luis

    2016-01-01

    We performed 3D virtual reconstructions based on CT scans to study the bony labyrinth morphology in 14 individuals from the large middle Pleistocene hominin sample from the site of the Sima de los Huesos (SH) in the Sierra de Atapuerca in northern Spain. The Atapuerca (SH) hominins represent early members of the Neandertal clade and provide an opportunity to compare the data with the later in time Neandertals, as well as Pleistocene and recent humans more broadly. The Atapuerca (SH) hominins do not differ from the Neandertals in any of the variables related to the absolute and relative sizes and shape of the semicircular canals. Indeed, the entire Neandertal clade seems to be characterized by a derived pattern of canal proportions, including a relatively small posterior canal and a relatively large lateral canal. In contrast, one of the most distinctive features observed in Neandertals, the low placement of the posterior canal (i.e., high sagittal labyrinthine index), is generally not present in the Atapuerca (SH) hominins. This low placement is considered a derived feature in Neandertals and is correlated with a more vertical orientation of the ampullar line (LSCm < APA), posterior surface of the petrous pyramid (LSCm > PPp), and third part of the facial canal (LSCm < FC3). Some variation is present within the Atapuerca (SH) sample, however, with a few individuals approaching the Neandertal condition more closely. In addition, the cochlear shape index in the Atapuerca (SH) hominins is low, indicating a reduction in the height of the cochlea. Although the phylogenetic polarity of this feature is less clear, the low shape index in the Atapuerca (SH) hominins may be a derived feature. Regardless, cochlear height subsequently increased in Neandertals. In contrast to previous suggestions, the expanded data in the present study indicate no difference across the genus Homo in the angle of inclination of the cochlear basal turn (COs < LSCm). Principal components

  16. Numerical simulation of heterogeneous fractured gas reservoir systems with turbulence and closure stress effects

    SciTech Connect

    Allam, A.M.; Crichlow, H.B.; Soliman, M.Y.

    1981-01-01

    A numerical technique for analyzing the behavior of a fractured gas reservoir system is presented. The reservoir is simulated by a fully implicit three-dimensional model that incorporates the effects of turbulent flow and closure stress in a finite conductivity fracture. The model utilizes the real gas pseudo-pressure, two-point upstream transmissibilities and a stable iterative process based on a sparse matrix approach to solving the equation systems. This paper presents a description of the model and applications to various reservoirs to illustrate the effects of fracture heights, turbulence and closure pressure on well performance. 16 refs.

  17. Influence of heterogeneous sulfur atoms on the negative differential resistance effect in polythiophene

    SciTech Connect

    Liu, Xiao Jing; Dong, Kang Liang; An, Zhong

    2014-09-07

    In this work, we have carried out theoretical investigations aiming to clarify the effects of sulfur heteroatoms on the transport characteristics in polythiophene. Sulfur atoms in polythiophene are demonstrated to influence the structure and transport process by two aspects: the electron hopping between carbon atoms on both sides of the sulfur atom as well as the effective confinement of π electrons from the sulfur atom. Based on the static Su-Schrieffer-Heeger model and the nonequilibrium Green's function formalism, we simulate the electron transportation in a metal/polythiophene/metal structure. The simulation results show that the electron hopping via sulfur atoms is responsible for the observed negative differential resistance (NDR) behavior in the I-V curves. The NDR disappears if the electron transport channels from carbon to carbon via sulfur atoms are forbidden. The weaker the effective confinement of π electrons and the electron hopping between carbon atoms on both sides of the sulfur atom are, the higher is the peak-to-valley ratio of the NDR and the wider the voltage range where the current remains at low levels. These results can help in understanding the NDR effect in polythiophene.

  18. Bias and Bias Correction in Multi-Site Instrumental Variables Analysis of Heterogeneous Mediator Effects

    ERIC Educational Resources Information Center

    Reardon, Sean F.; Unlu, Faith; Zhu, Pei; Bloom, Howard

    2013-01-01

    We explore the use of instrumental variables (IV) analysis with a multi-site randomized trial to estimate the effect of a mediating variable on an outcome in cases where it can be assumed that the observed mediator is the only mechanism linking treatment assignment to outcomes, as assumption known in the instrumental variables literature as the…

  19. Bias and Bias Correction in Multisite Instrumental Variables Analysis of Heterogeneous Mediator Effects

    ERIC Educational Resources Information Center

    Reardon, Sean F.; Unlu, Fatih; Zhu, Pei; Bloom, Howard S.

    2014-01-01

    We explore the use of instrumental variables (IV) analysis with a multisite randomized trial to estimate the effect of a mediating variable on an outcome in cases where it can be assumed that the observed mediator is the only mechanism linking treatment assignment to outcomes, an assumption known in the IV literature as the exclusion restriction.…

  20. Heterogenous Effects of Sports Participation on Education and Labor Market Outcomes

    ERIC Educational Resources Information Center

    Gorry, Devon

    2016-01-01

    This paper analyzes the distribution of education and labor market benefits from sports participation. Results show that effects are similar across gender, but differ on other dimensions. In particular, participants in team sports show greater gains than those in individual sports. Quantile regressions show that educational gains are larger for…

  1. Examining the Foundations of Methods That Assess Treatment Effect Heterogeneity across Intermediate Outcomes

    ERIC Educational Resources Information Center

    Feller, Avi; Miratrix, Luke

    2015-01-01

    The goal of this study is to better understand how methods for estimating treatment effects of latent groups operate. In particular, the authors identify where violations of assumptions can lead to biased estimates, and explore how covariates can be critical in the estimation process. For each set of approaches, the authors first review the…

  2. The Effects of Homogeneous versus Heterogeneous Stimuli on the Confrontation-Naming Performance of Aphasics.

    ERIC Educational Resources Information Center

    Williams, Sarah E.; Wright, Judith M.

    1985-01-01

    The effect of semantic grouping on confrontation-naming performances of 16 fluent and 10 nonfluent aphasic adults was examined. Performances were not uniformly facilitated in one naming condition over the other. Some patients, however, did appear to display performance discrepancies between the two conditions. (Author/CL)

  3. Interval Estimates of Multivariate Effect Sizes: Coverage and Interval Width Estimates under Variance Heterogeneity and Nonnormality

    ERIC Educational Resources Information Center

    Hess, Melinda R.; Hogarty, Kristine Y.; Ferron, John M.; Kromrey, Jeffrey D.

    2007-01-01

    Monte Carlo methods were used to examine techniques for constructing confidence intervals around multivariate effect sizes. Using interval inversion and bootstrapping methods, confidence intervals were constructed around the standard estimate of Mahalanobis distance (D[superscript 2]), two bias-adjusted estimates of D[superscript 2], and Huberty's…

  4. The Effects of Sand Sediment Volume Heterogeneities on Sound Propagation and Scattering

    DTIC Science & Technology

    2013-08-19

    the Nearly Constant Q (NCQ) model developed originally for seismology [10]. In the NCQ model, the attenuation is modeled as a sum of relaxation... seismology and mantle composition. Geophys. J. R. Astron. Soc., 47(1): pp. 41–58, 1976. 11. K. L. Williams. An effective density fluid model for

  5. Influence of heterogeneous sulfur atoms on the negative differential resistance effect in polythiophene

    NASA Astrophysics Data System (ADS)

    Liu, Xiao Jing; Dong, Kang Liang; An, Zhong

    2014-09-01

    In this work, we have carried out theoretical investigations aiming to clarify the effects of sulfur heteroatoms on the transport characteristics in polythiophene. Sulfur atoms in polythiophene are demonstrated to influence the structure and transport process by two aspects: the electron hopping between carbon atoms on both sides of the sulfur atom as well as the effective confinement of π electrons from the sulfur atom. Based on the static Su-Schrieffer-Heeger model and the nonequilibrium Green's function formalism, we simulate the electron transportation in a metal/polythiophene/metal structure. The simulation results show that the electron hopping via sulfur atoms is responsible for the observed negative differential resistance (NDR) behavior in the I-V curves. The NDR disappears if the electron transport channels from carbon to carbon via sulfur atoms are forbidden. The weaker the effective confinement of π electrons and the electron hopping between carbon atoms on both sides of the sulfur atom are, the higher is the peak-to-valley ratio of the NDR and the wider the voltage range where the current remains at low levels. These results can help in understanding the NDR effect in polythiophene.

  6. Numerical simulation of heterogeneous fractured gas reservoir systems with turbulence and closure stress effects

    SciTech Connect

    Allam, A.M.

    1982-01-01

    Although techniques for designing a fracture treatment are available, the intended results of these techniques are often not attained. The evaluation of fracturing treatments on low permeability gas wells is required to both optimize the fracturing design and form prediction calculations of a treatments effect. This study primarily investigates the effect of fracture height on the performance of vertically fractured wells. The effects of layered media, turbulance, and closure pressure are included in this work. Consider that a well, intercepted by a vertical fracture, is in the center of a squared drainage system with closed outer boundary. Any increase in well productivity will be determined by fracture parameters, which are: fracture length, height, fracture conductivity, and location of the fracture in the formaton. On the basis of the analysis of fluid flow in porous media, the problem solving technique used in this study is the numerical method. A three-dimensional finite difference fully implicit model was written for this. In addition, the Sparse Matrix technique was used as a solver. Furthermore, Slices Source Over Relaxation was used as an iterative method for solving routines. Presented here are the numerical results of the three-dimensional model for a well intercepting a vertical fracture wth finite conductivity. The results are presented in the general form of dimensionless variables. Type curves considering the effect of fracture height on well performance are included. In addition, type curves for turbulent flow in the fracture are also obtained. Finally, other important contributions of this work are the data showing the effect of layered formation on fractured well performance.

  7. Heterogeneous effects of exogenous IL-2 on HIV-specific cell-mediated immunity (CMI).

    PubMed Central

    Bell, S J; Cooper, D A; Kemp, B E; Doherty, R R; Penny, R

    1992-01-01

    A characteristic feature associated with HIV-1 infection of the human host is a chronic decline in circulating CD4+ T helper/inducer cell numbers. Impaired cell-mediated immune functions usually occur in parallel with the decline in CD4+ T cells. Activated CD4+ T helper cells are a major source of endogenous IL-2 which is required for the immunoregulation of both antigen-specific B cells and CD8+ T cells. HIV-specific T cell proliferative responses are said to be weak and inconsistent, even during the asymptomatic phase of disease. We thus wished to determine how exogenous IL-2 affected HIV-specific T cell proliferation at different stages of the disease. Our cohort of 81 included both asymptomatic and symptomatic HIV-infected patients as well as uninfected normal donors. Proliferative responses of peripheral blood mononuclear cells (PBMC) that were elicited during culture with an immunodominant gp41-derived synthetic peptide, gp41[8], and which were known to be CD8+ cell-associated in asymptomatics only, were used to analyse the effects of exogenous IL-2. IL-2 had three main effects on HIV-specific proliferation, namely (i) an additive effect, (ii) a synergistic effect, and (iii) an induced effect. More specifically, low dose exogenous IL-2 frequently augmented lymphoproliferation in both asymptomatic and symptomatic gp41[8] responders. In most symptomatics, however, who were predominantly gp41[8] non-responders, exogenous IL-2 induced lymphoproliferation. Flow cytometric analyses using dual immunofluorescence were used to analyse the T cell subset distribution of proliferating PBMC cultures. During culture with gp41[8], both CD4+ and CD8+ T cell numbers increased. However, after the addition of exogenous IL-2 to gp41[8]-containing cultures, CD8+ cell-associated lymphoproliferative responses were preferentially augmented. These results suggest that in symptomatics there is an inadequate supply of endogenous IL-2 to help maintain the strong and effective CD8+ cell

  8. Heterogeneous photocatalysis of methylene blue over titanate nanotubes: effect of adsorption.

    PubMed

    Xiong, Lin; Sun, Weiling; Yang, Ye; Chen, Cheng; Ni, Jinren

    2011-04-01

    Titanate nanotubes were synthesized with hydrothermal reaction using TiO(2) and NaOH as the precursors and subsequent calcination at 400°C for 2h. The products were characterized with SEM and XRD. Adsorption and photocatalysis of methylene blue over titanate nanotubes and TiO(2) were investigated. The results indicated that titanate nanotubes exhibited a better photocatalytic degradation of methylene blue in a simultaneous adsorption and photodegradation system than that in equilibrium adsorption followed by a photodegradation system, whereas TiO(2) showed no significant differences in photocatalytic activity in the two systems. The methylene blue overall removal efficiency over TNTs in the first system even exceeded that over TiO(2). The different catalytic performances of titanate nanotubes in the two systems were tentatively attributed to different effects of adsorption of methylene blue, i.e., the promoting effect in the former and the inhibition effect in the latter. Decantation experiments showed that the titanate nanotube photocatalyst could be easily separated from the reaction medium by sedimentation. Thus titanate nanotubes with high sedimentation rates and concurrent adsorption represent a new catalyst system with a strong potential for commercial applications.

  9. Neotropical primate communities: Effects of disturbance, resource production and forest type heterogeneity.

    PubMed

    Stevenson, Pablo R

    2015-12-18

    Undisturbed primate communities in the Neotropics are bottom-up structured as their biomass and species richness can be predicted from fruit production. However, the effects of fruit scarcity and the availability of forest types have not been fully analyzed, and seasonality is expected to differently affect small and large monkeys. The first aim of this study was to examine the effect of contrasting forest types within a location on the temporal variation in fruit production. The second was to assess the relative roles of disturbance, climate, patterns of fruit and leaf production, and plant composition on determining Neotropical primate communities. I compiled population density data for diurnal primate species from 154 sites to calculate species richness and assemblage biomass. Fruit abundance in the study sites was estimated from fruit trap data and phenology transects, and fruit variability was calculated as the monthly coefficient of variation (CV) and the length of the fruit scarcity period (LFSP). The results indicate that fruit production in floodplain forests is generally more variable than in terra firme forests, and this variation decreases in habitats with mixed forest types. Endozoochorous fruit production (based on fruit traps) and litter productivity were good predictors of the biomass of Neotropical primates (R(2)  = 0.83 and R(2)  = 0.59, respectively), but neither CV nor LFSP were good predictors. The biomass of large primates was independent of rainfall variation, but the biomass of small and medium sized monkeys was negatively correlated with temporal rainfall variability. Varzea forests tended to show higher biomass than those from terra firme and igapó. These results suggest that the production of fleshy fruits is the best predictor of the structure of primate assemblages in the Neotropics, but the effect of leaf quality and productivity remains to be investigated. Am. J. Primatol. © 2015 Wiley Periodicals, Inc.

  10. Target Promiscuity and Heterogeneous Effects of Tarantula Venom Peptides Affecting Na+ and K+ Ion Channels*

    PubMed Central

    Redaelli, Elisa; Cassulini, Rita Restano; Silva, Deyanira Fuentes; Clement, Herlinda; Schiavon, Emanuele; Zamudio, Fernando Z.; Odell, George; Arcangeli, Annarosa; Clare, Jeffrey J.; Alagón, Alejandro; de la Vega, Ricardo C. Rodríguez; Possani, Lourival D.; Wanke, Enzo

    2010-01-01

    Venom-derived peptide modulators of ion channel gating are regarded as essential tools for understanding the molecular motions that occur during the opening and closing of ion channels. In this study, we present the characterization of five spider toxins on 12 human voltage-gated ion channels, following observations about the target promiscuity of some spider toxins and the ongoing revision of their “canonical” gating-modifying mode of action. The peptides were purified de novo from the venom of Grammostola rosea tarantulas, and their sequences were confirmed by Edman degradation and mass spectrometry analysis. Their effects on seven tetrodotoxin-sensitive Na+ channels, the three human ether-à-go-go (hERG)-related K+ channels, and two human Shaker-related K+ channels were extensively characterized by electrophysiological techniques. All the peptides inhibited ion conduction through all the Na+ channels tested, although with distinctive patterns. The peptides also affected the three pharmaceutically relevant hERG isoforms differently. At higher concentrations, all peptides also modified the gating of the Na+ channels by shifting the activation to more positive potentials, whereas more complex effects were recorded on hERG channels. No effects were evident on the two Shaker-related K+ channels at concentrations well above the IC50 value for the affected channels. Given the sequence diversity of the tested peptides, we propose that tarantula toxins should be considered both as multimode and target-promiscuous ion channel modulators; both features should not be ignored when extracting mechanistic interpretations about ion channel gating. Our observations could also aid in future structure-function studies and might help the development of novel ion channel-specific drugs. PMID:19955179

  11. Effects of spatial habitat heterogeneity on habitat selection and annual fecundity for a migratory forest songbird

    USGS Publications Warehouse

    Cornell, K.L.; Donovan, T.M.

    2010-01-01

    Understanding how spatial habitat patterns influence abundance and dynamics of animal populations is a primary goal in landscape ecology. We used an information-theoretic approach to investigate the association between habitat patterns at multiple spatial scales and demographic patterns for black-throated blue warblers (Dendroica caerulescens) at 20 study sites in west-central Vermont, USA from 2002 to 2005. Sites were characterized by: (1) territory-scale shrub density, (2) patch-scale shrub density occurring within 25 ha of territories, and (3) landscape-scale habitat patterns occurring within 5 km radius extents of territories. We considered multiple population parameters including abundance, age ratios, and annual fecundity. Territory-scale shrub density was most important for determining abundance and age ratios, but landscape-scale habitat structure strongly influenced reproductive output. Sites with higher territory-scale shrub density had higher abundance, and were more likely to be occupied by older, more experienced individuals compared to sites with lower shrub density. However, annual fecundity was higher on sites located in contiguously forested landscapes where shrub density was lower than the fragmented sites. Further, effects of habitat pattern at one spatial scale depended on habitat conditions at different scales. For example, abundance increased with increasing territory-scale shrub density, but this effect was much stronger in fragmented landscapes than in contiguously forested landscapes. These results suggest that habitat pattern at different spatial scales affect demographic parameters in different ways, and that effects of habitat patterns at one spatial scale depends on habitat conditions at other scales. ?? Springer Science+Business Media B.V. 2009.

  12. Effects of tissue heterogeneity on single-coil, scanning MIT imaging

    NASA Astrophysics Data System (ADS)

    Feldkamp, J. R.; Quirk, S.

    2016-03-01

    We recently reported on the use of a single induction coil to accomplish imaging of the electrical conductivity in human tissues via magnetic induction tomography (MIT). A key to the method was the development of a mapping equation that quantitatively relates an arbitrary electrical conductivity distribution to ohmic loss in a coil consisting of concentric circular loops in a plane. By making multiple coil loss measurements at a number of locations in the vicinity of the target (scan), this mapping equation can be used to build an algorithm for 3D image construction of electrical conductivity. Important assumptions behind the mathematical formula included uniform relative permittivity throughout all space and continuous variation in conductivity. In this paper, these two assumptions were tested in a series of experiments involving the use of human tissue phantoms created from agarose, doped with sufficient sodium chloride to yield physiological conductivities. Inclusions of doped agarose were scanned both while isolated and also while embedded in a matrix of agarose gel having lowered conductivity - to help evaluate the effects of abrupt permittivity change. The effects of discontinuous conductivity change were simulated by filling 5 cm diameter petri dishes with 1.4% aqueous KCl and placing them in a much larger, 14 cm diameter petri dish - gap distance varied from about 3 mm to 30 mm. In either case, we will show that these effects are minimal on resultant images, helping to further validate the mapping equation used to construct MIT images. Because of their simplicity, scans reported here did not include coil rotation. To acknowledge the importance of rotation, however, we have devoted a section of this work to illustrate the profound benefits of coil rotation during a scan - though virtual data are used, where coil rotation is more easily specified.

  13. Effects of various poisoning compounds on the activity and stereospecificity of heterogeneous Ziegler–Natta catalyst

    PubMed Central

    Tangjituabun, Kitti; Yull Kim, Sang; Hiraoka, Yuichi; Taniike, Toshiaki; Terano, Minoru; Jongsomjit, Bunjerd; Praserthdam, Piyasan

    2008-01-01

    A TiCl4/ethylbenzoate/MgCl2 Ziegler–Natta catalyst was pretreated with chemically different poisoning compounds to investigate their effects on the catalyst activity and stereospecificity for propylene polymerization. The poisoning power on the activity was in the order of methanol > acetone > ethyl acetate. A kinetic analysis using the stopped-flow method revealed that addition of the poisoning materials decreased the activity through the reduction of the number of active sites, whereas the catalyst isospecificity was hardly affected by these materials. PMID:27877969

  14. Study of void sizes and loading configurations effects on shock initiation due to void collapse in heterogeneous energetic materials

    NASA Astrophysics Data System (ADS)

    Roy, Sidhartha; Rai, Nirmal; Udaykumar, H. S.

    2015-06-01

    In heterogeneous energetic materials, presence of porosity has been seen to increase its sensitivity towards shock initiation and ignition. Under the application of shock load, the viscoplastic deformation of voids and its collapse leads to the formation of local high temperature regions known as hot spots. The chemical reaction triggers at the hot spot depending on the local temperature and grows eventually leading to ignition and formation of detonation waves in the material. The temperature of the hot spot depends on various factors such as shock strength, void size, void arrangements, loading configuration etc. Hence, to gain deeper understanding on shock initiation and ignition study due to void collapse, a parametric study involving various factors which can affect the hot spot temperature is desired. In the current work, effects of void sizes, shock strength and loading configurations has been studied for shock initiation in HMX using massively parallel Eulerian code, SCIMITAR3D. The chemical reaction and decomposition for HMX has been modeled using Henson-Smilowitz multi step mechanism. The effect of heat conduction has also been taken into consideration. Ignition threshold criterion has been established for various factors as mentioned. The critical hot spot temperature and its size which can lead to ignition has been obtained from numerical experiments.

  15. Determination of the relative power density distribution in a heterogeneous reactor from the results of measurements of the reactivity effects and the neutron importance function

    SciTech Connect

    Bobrov, A. A.; Glushkov, E. S.; Zimin, A. A.; Kapitonova, A. V.; Kompaniets, G. V.; Nosov, V. I. Petrushenko, R. P.; Smirnov, O. N.

    2012-12-15

    A method for experimental determination of the relative power density distribution in a heterogeneous reactor based on measurements of fuel reactivity effects and importance of neutrons from a californium source is proposed. The method was perfected on two critical assembly configurations at the NARCISS facility of the Kurchatov Institute, which simulated a small-size heterogeneous nuclear reactor. The neutron importance measurements were performed on subcritical and critical assemblies. It is shown that, along with traditionally used activation methods, the developed method can be applied to experimental studies of special features of the power density distribution in critical assemblies and reactors.

  16. Determination of the relative power density distribution in a heterogeneous reactor from the results of measurements of the reactivity effects and the neutron importance function

    NASA Astrophysics Data System (ADS)

    Bobrov, A. A.; Glushkov, E. S.; Zimin, A. A.; Kapitonova, A. V.; Kompaniets, G. V.; Nosov, V. I.; Petrushenko, R. P.; Smirnov, O. N.

    2012-12-01

    A method for experimental determination of the relative power density distribution in a heterogeneous reactor based on measurements of fuel reactivity effects and importance of neutrons from a californium source is proposed. The method was perfected on two critical assembly configurations at the NARCISS facility of the Kurchatov Institute, which simulated a small-size heterogeneous nuclear reactor. The neutron importance measurements were performed on subcritical and critical assemblies. It is shown that, along with traditionally used activation methods, the developed method can be applied to experimental studies of special features of the power density distribution in critical assemblies and reactors.

  17. Attention and memory evaluation across the life span: heterogeneous effects of age and education.

    PubMed

    Gómez-Pérez, Esther; Ostrosky-Solís, Feggy

    2006-05-01

    The developmental sequences of attention and memory were studied by utilizing normative data derived from the neuropsychological battery named NEUROPSI ATTENTION AND MEMORY. A sample of 521 Spanish-speaking individuals, aged 6 to 85 years, participated in this study. In the adult sample, educational level ranged from 0 to 22 years of education. Data from subtests measuring orientation, attention and concentration, executive functions, working memory, immediate and delayed verbal memory, and immediate and delayed visual memory were included. The factor structure of the analyzed battery is presented. The effects of age and education on this structure were analyzed. Results suggested that although attention and memory are related, their developmental sequences are separated from one another. During childhood, the development of selective and sustained attention, attentional-working memory, and executive functions showed a fast improvement in performance. Development of verbal memory and place and person orientation showed a slower increment in scores. In the adult sample it was found that factors related to memory are sensitive to age, whereas those related to attention and executive functions are sensitive to education. The consideration of both the developmental sequence, as well as differential effects of education, can improve the sensitivity and specificity of neuropsychological measures, allowing early diagnosis of cognitive dysfunction and implementation of adequate rehabilitation programs.

  18. Assessing heterogeneity of treatment effect in a clinical trial with the proportional interactions model.

    PubMed

    Kovalchik, Stephanie A; Varadhan, Ravi; Weiss, Carlos O

    2013-12-10

    Understanding how individuals vary in their response to treatment is an important task of clinical research. For standard regression models, a proportional interactions model first described by Follmann and Proschan (1999) offers a powerful approach for identifying effect modification in a randomized clinical trial when multiple variables influence treatment response. In this paper, we present a framework for using the proportional interactions model in the context of a parallel-arm clinical trial with multiple prespecified candidate effect modifiers. To protect against model misspecification, we propose a selection strategy that considers all possible proportional interactions models. We develop a modified Bonferroni correction for multiple testing that accounts for the positive correlation among candidate models. We describe methods for constructing a confidence interval for the proportionality parameter. In simulation studies, we show that our modified Bonferroni adjustment controls familywise error and has greater power to detect proportional interactions compared with multiplcity-corrected subgroup analyses. We demonstrate our methodology by using the Studies of Left Ventricular Dysfunction Treatment trial, a placebo-controlled randomized clinical trial of the efficacy of enalapril to reduce the risk of death or hospitalization in chronic heart failure patients. An R package called anoint is available for implementing the proportional interactions methodology.

  19. Understanding Treatment Effects Heterogeneities Using Multi-Site Regression Discontinuity Designs: Example from a "Double-Dose" Algebra Study in Chicago

    ERIC Educational Resources Information Center

    Nomi, Takako; Raudenbush, Stephen W.

    2012-01-01

    To understand heterogeneity in the effects of double-dose algebra across schools, the authors focus on two policy implementation features and their variation across schools. The first source of variation is the degree to which schools followed the cutoff-based course assignment policy. The second source of variation is the degree to which schools…

  20. The Effects of Homogeneous versus Heterogeneous Reading-Style Grouping on EFL Students' Non-Preferred Reading Style and Reading Comprehension

    ERIC Educational Resources Information Center

    El-Koumy, Abdel Salam Abdel Khalek

    2009-01-01

    The purpose of this study was to investigate the effects of homogeneous versus heterogeneous reading-style grouping on EFL students' non-preferred reading style and reading comprehension. The study used a pretest-posttest experimental design. The original subjects of the study (N=86) were Egyptian English major senior students during the 2005/2006…

  1. Primary bony non-Hodgkin lymphoma of the cervical spine: a case report

    PubMed Central

    2010-01-01

    Introduction Non-Hodgkin lymphoma primarily originating from the bone is exceedingly rare. To our knowledge, this is the first report of primary bone lymphoma presenting with progressive cord compression from an origin in the cervical spine. Herein, we discuss the unusual location in this case, the presenting symptoms, and the management of this disease. Case presentation We report on a 23-year-old Caucasian-American man who presented with two months of night sweats, fatigue, parasthesias, and progressive weakness that had progressed to near quadriplegia. Magnetic resonance (MR) imaging demonstrated significant cord compression seen primarily at C7. Surgical management, with corpectomy and dorsal segmental fusion, in combination with adjuvant chemotherapy and radiation therapy, halted the progression of the primary disease and preserved neurological function. Histological analysis demonstrated an aggressive anaplastic large cell lymphoma. Conclusion Isolated primary bony lymphoma of the spine is exceedingly rare. As in our case, the initial symptoms may be the result of progressive cervical cord compression. Anterior corpectomy with posterolateral decompression and fusion succeeded in preventing progressive neurologic decline and maintaining quality of life. The reader should be aware of the unique presentation of this disease and that surgical management is a successful treatment strategy. PMID:20205845

  2. The Bony Bankart Lesion: How to Measure the Glenoid Bone Loss

    PubMed Central

    Skupiński, Jarosław; Piechota, Małgorzata Zofia; Wawrzynek, Wojciech; Maczuch, Jarosław; Babińska, Anna

    2017-01-01

    Summary An osseous Bankart lesion is commonly seen in patients with an anterior shoulder dislocation. It is defined as a detachment of the anteroinferior labrum associated with a glenoid rim fracture. Radiological studies are crucial not only for detecting glenoid bone defects but also for measuring the amount of bone loss. The precise quantification of the bony defect is crucial for the therapeutic desicion-making and clinical outcomes. Although we know that major glenoid bone loss requires surgical intervention, none of the studies performed so far answered the question what size of the defect should be an indication for open surgery procedures. Moreover, there is still no consensus on the exact percentage of glenoid loss that results in a higher risk of re-dislocations. In our opinion, there is a strong need for a consensus on universally accepted measuring techniques of the glenoid defect as well as on algorithms with validated glenoid bone loss threshold values for therapeutic decision-making. In this study, we review the techniques described so far in the literature and try to assess if any of these techniques should be treated as a leading method of detecting and quantifying osseous glenoid lesions. PMID:28243338

  3. Effect of compositional heterogeneity on dissolution of non-ideal LNAPL mixtures.

    PubMed

    Vasudevan, M; Johnston, C D; Bastow, T P; Lekmine, G; Rayner, J L; Nambi, I M; Suresh Kumar, G; Ravi Krishna, R; Davis, G B

    2016-11-01

    The extent of dissolution of petroleum hydrocarbon fuels into groundwater depends greatly on fuel composition. Petroleum fuels can consist of thousands of compounds creating different interactions within the non-aqueous phase liquid (NAPL), thereby affecting the relative dissolution of the components and hence a groundwater plume's composition over long periods. Laboratory experiments were conducted to study the variability in the effective solubilities and activity coefficients for common constituents of gasoline fuels (benzene, toluene, p-xylene and 1,2,4-trimethylbenzene) (BTX) in matrices with an extreme range of molar volumes and chemical affinities. Four synthetic mixtures were investigated comprising BTX with the bulk of the NAPL mixtures made up of either, ethylbenzene (an aromatic like BTX with similar molar volume); 1,3,5-trimethylbenzene (an aromatic with a greater molar volume); n-hexane (an aliphatic with a low molar volume); and n-decane (an aliphatic with a high molar volume). Equilibrium solubility values for the constituents were under-predicted by Raoult's law by up to 30% (higher experimental concentrations) for the mixture with n-hexane as a filler and over-predicted by up to 12% (lower experimental concentrations) for the aromatic mixtures with ethylbenzene and 1,3,5-trimethylbenzene as fillers. Application of PP-LFER (poly-parameter linear free energy relationship) model for non-ideal mixtures also resulted in poor correlation between experimentally measured and predicted concentrations, indicating that differences in chemical affinities can be the major cause of deviation from ideal behavior. Synthetic mixtures were compared with the dissolution behavior of fresh and naturally weathered unleaded gasoline. The presence of lighter aliphatic components in the gasoline had a profound effect on estimating effective solubility due to chemical affinity differences (estimated at 0.0055 per percentage increase in the molar proportion of aliphatic) as

  4. Effect of compositional heterogeneity on dissolution of non-ideal LNAPL mixtures

    NASA Astrophysics Data System (ADS)

    Vasudevan, M.; Johnston, C. D.; Bastow, T. P.; Lekmine, G.; Rayner, J. L.; Nambi, I. M.; Suresh Kumar, G.; Ravi Krishna, R.; Davis, G. B.

    2016-11-01

    The extent of dissolution of petroleum hydrocarbon fuels into groundwater depends greatly on fuel composition. Petroleum fuels can consist of thousands of compounds creating different interactions within the non-aqueous phase liquid (NAPL), thereby affecting the relative dissolution of the components and hence a groundwater plume's composition over long periods. Laboratory experiments were conducted to study the variability in the effective solubilities and activity coefficients for common constituents of gasoline fuels (benzene, toluene, p-xylene and 1,2,4-trimethylbenzene) (BTX) in matrices with an extreme range of molar volumes and chemical affinities. Four synthetic mixtures were investigated comprising BTX with the bulk of the NAPL mixtures made up of either, ethylbenzene (an aromatic like BTX with similar molar volume); 1,3,5-trimethylbenzene (an aromatic with a greater molar volume); n-hexane (an aliphatic with a low molar volume); and n-decane (an aliphatic with a high molar volume). Equilibrium solubility values for the constituents were under-predicted by Raoult's law by up to 30% (higher experimental concentrations) for the mixture with n-hexane as a filler and over-predicted by up to 12% (lower experimental concentrations) for the aromatic mixtures with ethylbenzene and 1,3,5-trimethylbenzene as fillers. Application of PP-LFER (poly-parameter linear free energy relationship) model for non-ideal mixtures also resulted in poor correlation between experimentally measured and predicted concentrations, indicating that differences in chemical affinities can be the major cause of deviation from ideal behavior. Synthetic mixtures were compared with the dissolution behavior of fresh and naturally weathered unleaded gasoline. The presence of lighter aliphatic components in the gasoline had a profound effect on estimating effective solubility due to chemical affinity differences (estimated at 0.0055 per percentage increase in the molar proportion of aliphatic) as

  5. Effects of simplifying choice tasks on estimates of taste heterogeneity in stated-choice surveys.

    PubMed

    Johnson, F Reed; Ozdemir, Semra; Phillips, Kathryn A

    2010-01-01

    Researchers usually employ orthogonal arrays or D-optimal designs with little or no attribute overlap in stated-choice surveys. The challenge is to balance statistical efficiency and respondent burden to minimize the overall error in the survey responses. This study examined whether simplifying the choice task, by using a design with more overlap, provides advantages over standard minimum-overlap methods. We administered two designs for eliciting HIV test preferences to split samples. Surveys were undertaken at four HIV testing locations in San Francisco, California. Personal characteristics had different effects on willingness to pay for the two treatments, and gains in statistical efficiency in the minimal-overlap version more than compensated for possible imprecision from increased measurement error.

  6. Atrial natriuretic peptide receptor heterogeneity and effects on cyclic GMP accumulation

    SciTech Connect

    Leitman, D.C.

    1988-01-01

    The effects of atrial natriuretic peptide (ANP), oxytocin (OT) and vasopressin (AVP) on guanylate cyclase activity and cyclic GMP accumulation were examined, since these hormones appear to be intimately associated with blood pressure and intravascular volume homeostasis. ANP was found to increase cyclic GMP accumulation in ten cell culture systems, which were derived from blood vessels, adrenal cortex, kidney, lung, testes and mammary gland. ANP receptors were characterized in intact cultured cells using {sup 125}I-ANP{sub 8-33}. Specific {sup 125}I-ANP binding was saturable and of high affinity. Scratchard analysis of the binding data for all cell types exhibited a straight line, indicating that these cells possessed a single class of binding sites. Despite the presence of linear Scatchard plots, these studies demonstrated that cultured cells possess two functionally and physically distinct ANP-binding sites. Most of the ANP-binding sites in cultured cells have a molecular size of 66,000 daltons under reducing conditions. The identification of cultured cell types in which hormones (ANP and oxytocin) regulate guanylate cyclase activity and increase cyclic GMP synthesis will provide valuable systems to determine the mechanisms of hormone-receptor coupling to guanylate cyclase and the cellular processes regulated by cyclic GMP.

  7. Heterogeneous effects of dopamine on highly localized, voltage-induced Ca2+ accumulation in identified motoneurons.

    PubMed

    Kloppenburg, Peter; Zipfel, Warren R; Webb, Watt W; Harris-Warrick, Ronald M

    2007-11-01

    Modulation of synaptic transmission is a major mechanism for the functional reconfiguration of neuronal circuits. Neurotransmitter release and, consequently, synaptic strength are regulated by intracellular Ca(2+) levels in presynaptic terminals. In identified neurons of the lobster pyloric network, we studied localized, voltage-induced Ca(2+) accumulation and its modulation in varicosities on distal neuritic arborizations, which have previously been shown to be sites of synaptic contacts. We previously demonstrated that dopamine (DA) weakens synaptic output from the pyloric dilator (PD) neuron and strengthens synaptic output from the lateral pyloric (LP) and pyloric constrictor (PY) neurons. Here we show that DA modifies voltage-activated Ca(2+) accumulation in many varicosities in ways that are consistent with DA's effects on synaptic transmission: DA elevates Ca(2+) accumulation in LP and PY varicosities and reduces Ca(2+) accumulation in PD varicosities. However, in all three neuron types, we also found varicosities that were unaffected by DA. In the PY neurons, we found that DA can simultaneously increase and decrease voltage-evoked Ca(2+) accumulation at different varicosities, even within the same neuron. These results suggest that regulation of Ca(2+) entry is a common mechanism to regulate synaptic strength in the pyloric network. However, voltage-evoked local Ca(2+) accumulation can be differentially modulated to control Ca(2+)-dependent processes in functionally separate varicosities of a single neuron.

  8. Effect of regional lung inflation on ventilation heterogeneity at different length scales during mechanical ventilation of normal sheep lungs.

    PubMed

    Wellman, Tyler J; Winkler, Tilo; Costa, Eduardo L V; Musch, Guido; Harris, R Scott; Venegas, Jose G; Vidal Melo, Marcos F

    2012-09-01

    Heterogeneous, small-airway diameters and alveolar derecruitment in poorly aerated regions of normal lungs could produce ventilation heterogeneity at those anatomic levels. We modeled the washout kinetics of (13)NN with positron emission tomography to examine how specific ventilation (sV) heterogeneity at different length scales is influenced by lung aeration. Three groups of anesthetized, supine sheep were studied: high tidal volume (Vt; 18.4 ± 4.2 ml/kg) and zero end-expiratory pressure (ZEEP) (n = 6); low Vt (9.2 ± 1.0 ml/kg) and ZEEP (n = 6); and low Vt (8.2 ± 0.2 ml/kg) and positive end-expiratory pressure (PEEP; 19 ± 1 cmH(2)O) (n = 4). We quantified fractional gas content with transmission scans, and sV with emission scans of infused (13)NN-saline. Voxel (13)NN-washout curves were fit with one- or two-compartment models to estimate sV. Total heterogeneity, measured as SD[log(10)(sV)], was divided into length-scale ranges by measuring changes in variance of log(10)(sV), resulting from progressive filtering of sV images. High-Vt ZEEP showed higher sV heterogeneity at <12- (P < 0.01), 12- to 36- (P < 0.01), and 36- to 60-mm (P < 0.05) length scales compared with low-Vt PEEP, with low-Vt ZEEP in between. Increased heterogeneity was associated with the emergence of low sV units in poorly aerated regions, with a high correlation (r = 0.95, P < 0.001) between total heterogeneity and the fraction of lung with slow washout. Regional mean fractional gas content was inversely correlated with regional sV heterogeneity at <12- (r = -0.67), 12- to 36- (r = -0.74), and >36-mm (r = -0.72) length scales (P < 0.001). We conclude that sV heterogeneity at length scales <60 mm increases in poorly aerated regions of mechanically ventilated normal lungs, likely due to heterogeneous small-airway narrowing and alveolar derecruitment. PEEP reduces sV heterogeneity by maintaining lung expansion and airway patency at those small length scales.

  9. Exploiting P-S converted waves. Part 1: Modeling the effects of anisotropy and heterogeneities

    SciTech Connect

    Michelena, R.J.; Ata, E.; Sierra, J.

    1994-12-31

    The authors performed extensive modeling studies to evaluate P-S converted waves effectiveness and limitations in the estimation of both cracks orientation and density. The target area is a fractured, carbonate reservoir located in south-west Venezuela. The reservoir depth is on the order of 3000 m, which implies that high quality P-S data are needed to obtain detectable information about the anisotropy at this depth. They focused their analysis on P-S converted waves because only explosives charges were available as energy sources. The modeling was performed prior to and after the data acquisition to help both design of the experiment and interpretation of the data. Synthetic seismograms were generated using 2D, elastic finite difference, along with a 3D-3C, paraxial ray tracing codes. They conducted also a noise-spread test to complement this study and determine the acquisition parameters. A 3D velocity model of the subsurface was built based on previous P-wave seismic sections, well logs (dual-sonic, density, check-shots and FMS), geological maps, and production information. This model was perturbed in a layer stripping fashion until an acceptable match was obtained around the depth of interest between synthetic and multicomponent field data. The anisotropy produced measurable differences in traveltimes and amplitudes between in-line and cross-line components. These differences (which are comparable to those observed on the field data) suggest that it is feasible to map fractures at depths around the reservoir area by using P-S converted waves.

  10. Effects of spatial heterogeneity in moisture content on the horizontal spread of peat fires.

    PubMed

    Prat-Guitart, Nuria; Rein, Guillermo; Hadden, Rory M; Belcher, Claire M; Yearsley, Jon M

    2016-12-01

    The gravimetric moisture content of peat is the main factor limiting the ignition and spread propagation of smouldering fires. Our aim is to use controlled laboratory experiments to better understand how the spread of smouldering fires is influenced in natural landscape conditions where the moisture content of the top peat layer is not homogeneous. In this paper, we study for the first time the spread of peat fires across a spatial matrix of two moisture contents (dry/wet) in the laboratory. The experiments were undertaken using an open-top insulated box (22×18×6cm) filled with milled peat. The peat was ignited at one side of the box initiating smouldering and horizontal spread. Measurements of the peak temperature inside the peat, fire duration and longwave thermal radiation from the burning samples revealed important local changes of the smouldering behaviour in response to sharp gradients in moisture content. Both, peak temperatures and radiation in wetter peat (after the moisture gradient) were sensitive to the drier moisture condition (preceding the moisture gradient). Drier peat conditions before the moisture gradient led to higher temperatures and higher radiation flux from the fire during the first 6cm of horizontal spread into a wet peat patch. The total spread distance into a wet peat patch was affected by the moisture content gradient. We predicted that in most peat moisture gradients of relevance to natural ecosystems the fire self-extinguishes within the first 10cm of horizontal spread into a wet peat patch. Spread distances of more than 10cm are limited to wet peat patches below 160% moisture content (mass of water per mass of dry peat). We found that spatial gradients of moisture content have important local effects on the horizontal spread and should be considered in field and modelling studies.

  11. Genetic heterogeneity in the apolipoprotein C-III promoter and effects of insulin.

    PubMed

    Dallinga-Thie, G M; Groenendijk, M; Blom, R N; De Bruin, T W; De Kant, E

    2001-09-01

    In the present study, we have investigated the in vivo and in vitro role of two newly identified variants (G(-)944A and A(-)1180C) located in the upstream promoter region of the apolipoprotein C-III (apoC-III) gene. These variants were studied in 30 probands diagnosed with FCHL, their relatives, and spouses. The allele frequencies of both variants were not different between the groups. No significant associations between plasma lipid traits and DNA variants were observed. We further analyzed the effect of the presence of these variants in the upstream enhancing region of the apoC-III gene, as five different in vivo occurring haplotypes, on the transcriptional activity of apoC-III in both HepG2 and Caco-2 cells. All five promoter constructs, including the wild type, showed similar enhancing activity of the apoC-III gene. The average transcription efficiency was enhanced 19-fold in HepG2 cells and 11-fold in Caco-2 cells. Previous studies have shown in vitro insulin-dependent down-regulation of the apoC-III gene transcription in HepG2 cells by DNA variation in an insulin response element (IRE) in the apoC-III promoter. We observed a 30% insulin-dependent down-regulation of apoC-III expression that was, however, independent of the presence of the two IRE variants. In contrast, in Caco-2 cells, a more variable insulin-dependent up-regulation was found that was also independent of the presence of the IRE variants.In conclusion, our data suggested that the apoC-III gene transcription in vitro is regulated by insulin but independent of the presence of the two IRE variants at -455 and -482. We were unable to detect associations between these apoC-III variants and plasma lipids and insulin in our FCHL population. This means that in vivo apoC-III transcription not only depends upon insulin but appears to be mediated by other mechanisms.

  12. Regulation of platelet heterogeneity: effects of thrombocytopenia on platelet volume and density.

    PubMed

    Corash, L; Mok, Y; Levin, J; Baker, G

    1990-03-01

    We have examined the effects of variable degrees of acute thrombocytopenia on platelet levels, mean platelet volume (MPV), and buoyant density after induction of thrombocytopenia by platelet antiserum (PAS) in mice with or without spleens. Mice were studied serially 10-16, 36, 48, 60-64, 84, 108, 144, 180, 228, 276, 348-360, 372, and 516 h after PAS treatment. MPV and platelet count (PC) x 10(6)/microliters for normal intact mice (n = 136) were 4.7 +/- 0.3 fl (SD) and 1.69 +/- 0.52 (SD), respectively. Twelve hours after PAS-induced severe thrombocytopenia (PC less than 0.05 x 10(6)/microliters), MPV increased significantly (p less than 0.01) to 6.4 fl, was maximal at 36 h (8.2 fl), remained elevated until 144 h following PAS treatment, and then returned to normal. Platelet density decreased significantly (p less than 0.05) 64 h after PAS treatment and returned to normal at 144 h. Hematocrits of repeatedly bled intact control mice decreased from 45% to 30%, accompanied by thrombocytosis (maximal PC 2.24 x 10(6)/microliters) without significant changes in either MPV or platelet density. Moderate thrombocytopenia (PC 0.1-0.2 x 10(6)/microliters) in intact mice produced significantly (p less than 0.05) increased MPV, at 5.7 fl 12 h after PAS treatment, with a peak MPV of 7.6 fl (p less than 0.001) at 36 h; MPV returned to normal at 84 h. Platelet density decreased (p less than 0.001) 12 h after PAS treatment and returned to baseline at 228 h. Control splenectomized mice (n = 185) had an MPV of 5.0 fl +/- 0.7 fl and a PC of 2.14 +/- 0.6 x 10(6)/microliters. Comparably severe and moderate thrombocytopenia in splenectomized mice produced alterations in platelet count, MPV, and density similar to those in intact mice, although maximal MPV and the degree of rebound thrombocytosis after severe thrombocytopenia were more marked in splenectomized mice. In response to reduction of the platelet mass in both intact and splenectomized mice, MPV increased in proportion to the

  13. The effect of ozone on nicotine desorption from model surfaces:evidence for heterogeneous chemistry

    SciTech Connect

    Destaillats, Hugo; Singer, Brett C.; Lee, Sharon K.; Gundel, LaraA.

    2005-05-01

    Assessment of secondhand tobacco smoke exposure using nicotine as a tracer or biomarker is affected by sorption of the alkaloid to indoor surfaces and by its long-term re-emission into the gas phase. However, surface chemical interactions of nicotine have not been sufficiently characterized. Here, the reaction of ozone with nicotine sorbed to Teflon and cotton surfaces was investigated in an environmental chamber by monitoring nicotine desorption over a week following equilibration in dry or humid air (65-70 % RH). The Teflon and cotton surfaces had N{sub 2}-BET surface areas of 0.19 and 1.17 m{sup 2} g{sup -1}, and water mass uptakes (at 70 % RH) of 0 and 7.1 % respectively. Compared with dry air baseline levels in the absence of O{sub 3}, gas phase nicotine concentrations decrease, by 2 orders of magnitude for Teflon after 50 h at 20-45 ppb O{sub 3}, and by a factor of 10 for cotton after 100 h with 13-15 ppb O{sub 3}. The ratios of pseudo first-order rate constants for surface reaction (r) to long-term desorption (k) were r/k = 3.5 and 2.0 for Teflon and cotton surfaces, respectively. These results show that surface oxidation was competitive with desorption. Hence, oxidative losses could significantly reduce long-term re-emissions of nicotine from indoor surfaces. Formaldehyde, N-methylformamide, nicotinaldehyde and cotinine were identified as oxidation products, indicating that the pyrrolidinic N was the site of electrophilic attack by O{sub 3}. The presence of water vapor had no effect on the nicotine-O{sub 3} reaction on Teflon surfaces. By contrast, nicotine desorption from cotton in humid air was unaffected by the presence of ozone. These observations are consistent with complete inhibition of ozone-nicotine surface reactions in an aqueous surface film present in cotton but not in Teflon surfaces.

  14. Modeling the hydrologicEffects of Spatial Heterogeneity in Soil Hydraulic Properties in a Mountainous Watershed, Northwest China

    NASA Astrophysics Data System (ADS)

    He, C.; Jin, X.; Zhang, L.; Zhang, X.

    2014-12-01

    Heterogeneity of soil hydraulic properties directly affects variations of hydrological processes at corresponding scales. Understanding spatial variation of soil hydraulic properties such as soil moisture is therefore fundamental for modeling watershed ecohydrological processes. As part of the National Science Foundation of China (NSFC) funded ''Integrated Ecohydrological Research Plan of the Heihe River Watershed'', this study established an observation network that consists of sampling points, zones, and tributaries to analyze spatial variations of soil hydraulic properties in the Upper Reach of the Heihe River Watershed, a second largest inland river (terminal lake) with a drainage area of over 128,000 km2 in Northwest China. Spatial heterogeneity of soil properties was analyzed based on the large number of soil sampling and in situ observations. The spatial clustering method, Full-Order-CLK was employed to derive five soil heterogeneous zones (Configuration 97, 80, 65, 40, and 20). Subsequently, SWAT model was used to quantify the impact of the spatial heterogeneity of soil hydraulic properties on hydrologic process in the study watershed. Results show the simulations by the SWAT model with the spatially clustered soil hydraulic information from the field sampling data had much better representation of the soil heterogeneity and more accurate performance than the model using the average soil property values for each soil type derived from the coarse soil datasets (Gansu Soil Handbook at 1:1,000,000 scale). Thus, incorporating detailed field sampling soil heterogeneity data greatly improves performance in hydrologic modeling.

  15. The interactions of squalene, alkanes and other mineral oils with model membranes; effects on membrane heterogeneity and function.

    PubMed

    Richens, Joanna L; Lane, Jordan S; Mather, Melissa L; O'Shea, Paul

    2015-11-01

    Droplet interface bilayers (DIBs) offer many favourable facets as an artificial membrane system but the influence of any residual oil that remains in the bilayer following preparation is ill-defined. In this study the fluorescent membrane probes di-8-butyl-amino-naphthyl-ethylene-pyridinium-propyl-sulfonate (Di-8-ANEPPS) and Fluoresceinphosphatidylethanolamine (FPE) were used to help understand the nature of the phospholipid-oil interaction and to examine any structural and functional consequences of such interactions on membrane bilayer properties. Concentration-dependent modifications of the membrane dipole potential were found to occur in phospholipid vesicles exposed to a variety of different oils. Incorporation of oil into the lipid bilayer was shown to have no significant effect on the movement of fatty acids across the lipid bilayer. Changes in membrane heterogeneity were, however, demonstrated with increased microdomain formation being visible in the bilayer following exposure to mineral oil, pentadecane and squalene. As it is important that artificial systems provide an accurate representation of the membrane environment, careful consideration should be taken prior to the application of DIBs in studies of membrane structure and organisation.

  16. Effect of chemical heterogeneity of biodegradable polymers on surface energy: A static contact angle analysis of polyester model films.

    PubMed

    Belibel, R; Avramoglou, T; Garcia, A; Barbaud, C; Mora, L

    2016-02-01

    Biodegradable and bioassimilable poly((R,S)-3,3 dimethylmalic acid) (PDMMLA) derivatives were synthesized and characterized in order to develop a new coating for coronary endoprosthesis enabling the reduction of restenosis. The PDMMLA was chemically modified to form different custom groups in its side chain. Three side groups were chosen: the hexyl group for its hydrophobic nature, the carboxylic acid and alcohol groups for their acid and neutral hydrophilic character, respectively. The sessile drop method was applied to characterize the wettability of biodegradable polymer film coatings. Surface energy and components were calculated. The van Oss approach helped reach not only the dispersive and polar acid-base components of surface energy but also acid and basic components. Surface topography was quantified by atomic force microscopy (AFM) and subnanometer average values of roughness (Ra) were obtained for all the analyzed surfaces. Thus, roughness was considered to have a negligible effect on wettability measurements. In contrast, heterogeneous surfaces had to be corrected by the Cassie-Baxter equation for copolymers (10/90, 20/80 and 30/70). The impact of this correction was quantified for all the wettability parameters. Very high relative corrections (%) were found, reaching 100% for energies and 30% for contact angles.

  17. Coalescent Times and Patterns of Genetic Diversity in Species with Facultative Sex: Effects of Gene Conversion, Population Structure, and Heterogeneity

    PubMed Central

    Hartfield, Matthew; Wright, Stephen I.; Agrawal, Aneil F.

    2016-01-01

    Many diploid organisms undergo facultative sexual reproduction. However, little is currently known concerning the distribution of neutral genetic variation among facultative sexual organisms except in very simple cases. Understanding this distribution is important when making inferences about rates of sexual reproduction, effective population size, and demographic history. Here we extend coalescent theory in diploids with facultative sex to consider gene conversion, selfing, population subdivision, and temporal and spatial heterogeneity in rates of sex. In addition to analytical results for two-sample coalescent times, we outline a coalescent algorithm that accommodates the complexities arising from partial sex; this algorithm can be used to generate multisample coalescent distributions. A key result is that when sex is rare, gene conversion becomes a significant force in reducing diversity within individuals. This can reduce genomic signatures of infrequent sex (i.e., elevated within-individual allelic sequence divergence) or entirely reverse the predicted patterns. These models offer improved methods for assessing null patterns of molecular variation in facultative sexual organisms. PMID:26584902

  18. Fine root mercury heterogeneity: metabolism of lower-order roots as an effective route for mercury removal.

    PubMed

    Wang, Jun-Jian; Guo, Ying-Ying; Guo, Da-Li; Yin, Sen-Lu; Kong, De-Liang; Liu, Yang-Sheng; Zeng, Hui

    2012-01-17

    Fine roots are critical components for plant mercury (Hg) uptake and removal, but the patterns of Hg distribution and turnover within the heterogeneous fine root components and their potential limiting factors are poorly understood. Based on root branching structure, we studied the total Hg (THg) and its cellular partitioning in fine roots in 6 Chinese subtropical trees species and the impacts of root morphological and stoichiometric traits on Hg partitioning. The THg concentration generally decreased with increasing root order, and was higher in cortex than in stele. This concentration significantly correlated with root length, diameter, specific root length, specific root area, and nitrogen concentration, whereas its cytosolic fraction (accounting for <10% of THg) correlated with root carbon and sulfur concentrations. The estimated Hg return flux from dead fine roots outweighed that from leaf litter, and ephemeral first-order roots that constituted 7.2-22.3% of total fine root biomass may have contributed most to this flux (39-71%, depending on tree species and environmental substrate). Our results highlight the high capacity of Hg stabilization and Hg return by lower-order roots and demonstrate that turnover of lower-order roots may be an effective strategy of detoxification in perennial tree species.

  19. Coalescent Times and Patterns of Genetic Diversity in Species with Facultative Sex: Effects of Gene Conversion, Population Structure, and Heterogeneity.

    PubMed

    Hartfield, Matthew; Wright, Stephen I; Agrawal, Aneil F

    2016-01-01

    Many diploid organisms undergo facultative sexual reproduction. However, little is currently known concerning the distribution of neutral genetic variation among facultative sexual organisms except in very simple cases. Understanding this distribution is important when making inferences about rates of sexual reproduction, effective population size, and demographic history. Here we extend coalescent theory in diploids with facultative sex to consider gene conversion, selfing, population subdivision, and temporal and spatial heterogeneity in rates of sex. In addition to analytical results for two-sample coalescent times, we outline a coalescent algorithm that accommodates the complexities arising from partial sex; this algorithm can be used to generate multisample coalescent distributions. A key result is that when sex is rare, gene conversion becomes a significant force in reducing diversity within individuals. This can reduce genomic signatures of infrequent sex (i.e., elevated within-individual allelic sequence divergence) or entirely reverse the predicted patterns. These models offer improved methods for assessing null patterns of molecular variation in facultative sexual organisms.

  20. Meso-Scale Heterogeneity Effects on the Bulk Shock Response of Ti+Al+B Reactive Powder Mixtures

    NASA Astrophysics Data System (ADS)

    Gonzales, Manny; Gurumurthy, Ashok; Kennedy, Gregory; Gokhale, Arun; Thadhani, Naresh

    2015-06-01

    Highly heterogeneous reactive powder mixtures including Ti+2B (Stoichiometric 1:2) and an Al-containing mixture (Ti+2B+50%Al by vol.) are studied to ascertain the shock compression response and potential reaction behavior. The transit time through the pressed powder mixture compacts is monitored using poly-vinylidene fluoride (PVDF) stress gauges and used to compute a wave speed through the compact. The stress states at the back of the powder (measuring the state of the compacted and potentially transformed powder) are compared with thermodynamic mixture theories as well as meso scale microstructure-based simulations to identify the onset of anomalous behavior which can be traced to highly exothermic reaction in this system. Shock compression experiments show highly dispersive wave fronts when measured from the back surface of the powder compact, which are compared with meso scale simulations considering varying starting mixture states. These simulations also provide microstructure evolution parameters during shock compression which are stereologically evaluated to establish the state of the material present under the experimental conditions. An analysis of the effects of starting mixture conditions on the stress at the back surface is also presented. We gratefully acknowledge support and funding from DTRA through Grant No. HDTRA1-10-1-0038.

  1. Meso-scale heterogeneity effects on the bulk shock response of Ti+2B reactive powder mixtures

    NASA Astrophysics Data System (ADS)

    Gonzales, Manny; Gurumurthy, Ashok; Kennedy, Gregory B.; Gokhale, Arun M.; Thadhani, Naresh N.

    2017-01-01

    Highly heterogeneous reactive powder mixtures containing Ti+2B (Stoichiometric 1:2) are studied to ascertain the shock compression response and potential reaction behavior. The transit time through the pressed powder mixture compacts is monitored using poly-vinylidene fluoride (PVDF) stress gauges and used to compute a wave speed through the compact. The stress states at the back of the powder (measuring the state of the compacted and potentially transformed powder) are compared with thermodynamic mixture theories as well as meso-scale microstructure-based simulations to identify the onset of anomalous behavior which can be traced to highly exothermic reaction in this system. Shock compression experiments show highly dispersive wave fronts when measured from the back surface of the powder compact, which are compared with meso-scale simulations considering varying starting mixture states. These simulations also provide microstructure evolution parameters during shock compression which are stereologically evaluated to establish the state of the material present under the experimental conditions. An analysis of the effects of starting mixture conditions on the stress at the back surface is also presented.

  2. A safe, efficient and cost effective process for removing petroleum hydrocarbons from a highly heterogeneous and relatively inaccessible shoreline.

    PubMed

    Guerin, Turlough F

    2015-10-01

    A rocky, intractable and highly heterogeneous, intertidal zone, was contaminated from a diesel fuel spill that occurred during refuelling of a grader used in road construction, on an operational mine's shiploading facility. A practical, cost-effective, and safer (to personnel by avoiding drilling and earthworks), and non-invasive sampling and remediation strategy was designed and implemented since the location and nature of the impacted geology (rock fill) and sediment, precluded conventional ex-situ and any in-situ treatment where drilling would be required. Enhanced biostimulation with surfactant, available N & P (which were highly constrained), and increased aeration, increased the degradation rate from no discernable change for 2 years post-spill, to 170 mg/kg/day; the maximum degradation rate after intervention. While natural attenuation was ineffective in this application, the low-cost, biostimulation intervention proved successful, allowing the site owner to meet their regulatory obligations. Petroleum hydrocarbons (aliphatic fraction) decreased from ∼20,000 mg/kg to <200 mg/kg at the completion of 180 weeks of treatment.

  3. Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source.

    PubMed

    Shi, Chengyu; Guo, Bingqi; Cheng, Chih-Yao; Eng, Tony; Papanikolaou, Nikos

    2010-09-21

    A low-energy electronic brachytherapy source (EBS), the model S700 Axxent x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V(100) reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95

  4. [Morphofunctional disturbances in kidneys of sturgeons and bony fishes of the Volga-Caspian reservoir under natural conditions].

    PubMed

    Romanov, Al A; Lepilina, I N; Romanov, An A

    2006-01-01

    By light microscopy, the morphofunctional state of mesonephros was studied for various sturgeons and bony fishes taken from natural waters. Different changes were recorded in structural-functional elements of nephrons of the mesonephros. The most frequent disturbances are hemorrhages in the intertubule tissue of kidneys, hyalinosis of vessel walls, swollen epithelium, inflammations. The revealed disturbances may be regarded as a response to negative environmental impacts.

  5. Fetal Growth Restriction Induces Heterogeneous Effects on Vascular Biomechanical and Functional Properties in Guinea Pigs (Cavia porcellus)

    PubMed Central

    Cañas, Daniel; Herrera, Emilio A.; García-Herrera, Claudio; Celentano, Diego; Krause, Bernardo J.

    2017-01-01

    Aim: Fetal growth restriction (FGR) is associated with a variety of cardiometabolic diseases in adulthood which could involve remodeling processes of the vascular walls that could start in the fetal period. However, there is no consensus whether this remodeling affects in a similar way the whole vascular system. We aimed to determine the effects of FGR on the vasoactive and biomechanical properties of umbilical and systemic vessels in fetal guinea pigs. Methods: FGR was induced by implanting ameroid occluders at mid-gestation in uterine arteries of pregnant guinea pigs, whilst the control group was exposed to simulated surgery. At the term of gestation, systemic arteries (aorta, carotid and femoral) and umbilical vessels were isolated to determine ex vivo contractile and biomechanical responses (stretch-stress until rupture) on a wire myograph, as well as opening angle and residual stresses. Histological characteristics in tissue samples were measured by van Gieson staining. Results: Aorta and femoral arteries from FGR showed an increased in biomechanical markers of stiffness (p < 0.01), contractile capacity (p < 0.05) and relative media thickness (p < 0.01), but a reduced internal diameter (p < 0.001), compared with controls. There were no differences in the biomechanical properties of carotid and umbilical from control and FGR fetuses, but FGR umbilical arteries had a decreased contractile response to KCl (p < 0.05) along with a reduced relative media thickness (p < 0.05). Conclusion: Altogether, these changes in functional, mechanical and morphological properties suggest that FGR is associated with a heterogeneous pro-constrictive vascular remodeling affecting mainly the lower body fetal arteries. These effects would be set during a pathologic pregnancy in order to sustain the fetal blood redistribution in the FGR and may persist up to adulthood increasing the risk of a cardiovascular disease. PMID:28344561

  6. Fetal Growth Restriction Induces Heterogeneous Effects on Vascular Biomechanical and Functional Properties in Guinea Pigs (Cavia porcellus).

    PubMed

    Cañas, Daniel; Herrera, Emilio A; García-Herrera, Claudio; Celentano, Diego; Krause, Bernardo J

    2017-01-01

    Aim: Fetal growth restriction (FGR) is associated with a variety of cardiometabolic diseases in adulthood which could involve remodeling processes of the vascular walls that could start in the fetal period. However, there is no consensus whether this remodeling affects in a similar way the whole vascular system. We aimed to determine the effects of FGR on the vasoactive and biomechanical properties of umbilical and systemic vessels in fetal guinea pigs. Methods: FGR was induced by implanting ameroid occluders at mid-gestation in uterine arteries of pregnant guinea pigs, whilst the control group was exposed to simulated surgery. At the term of gestation, systemic arteries (aorta, carotid and femoral) and umbilical vessels were isolated to determine ex vivo contractile and biomechanical responses (stretch-stress until rupture) on a wire myograph, as well as opening angle and residual stresses. Histological characteristics in tissue samples were measured by van Gieson staining. Results: Aorta and femoral arteries from FGR showed an increased in biomechanical markers of stiffness (p < 0.01), contractile capacity (p < 0.05) and relative media thickness (p < 0.01), but a reduced internal diameter (p < 0.001), compared with controls. There were no differences in the biomechanical properties of carotid and umbilical from control and FGR fetuses, but FGR umbilical arteries had a decreased contractile response to KCl (p < 0.05) along with a reduced relative media thickness (p < 0.05). Conclusion: Altogether, these changes in functional, mechanical and morphological properties suggest that FGR is associated with a heterogeneous pro-constrictive vascular remodeling affecting mainly the lower body fetal arteries. These effects would be set during a pathologic pregnancy in order to sustain the fetal blood redistribution in the FGR and may persist up to adulthood increasing the risk of a cardiovascular disease.

  7. Morphoscopic analysis of experimentally produced bony wounds from low-velocity ballistic impact.

    PubMed

    Kieser, Jules A; Tahere, Joy; Agnew, Caitlin; Kieser, David C; Duncan, Warwick; Swain, Michael V; Reeves, Matthew T

    2011-12-01

    Understanding how bone behaves when subjected to ballistic impact is of critical importance for forensic questions, such as the reconstruction of shooting events. Yet the literature addressing microscopic anatomical features of gunshot wounds to different types of bone is sparse. Moreover, a biomechanical framework for describing how the complex architecture of bone affects its failure during such impact is lacking. The aim of this study was to examine the morphological features associated with experimental gunshot wounds in slaughtered pig ribs. We shot the 4th rib of 12 adult pigs with .22 mm subsonic bullets at close range (5 cm) and examined resultant wounds under the light microscope, scanning electron microscope SEM and micro tomograph μCT. In all cases there was a narrow shot channel followed by spall region, with evidence of plastic deformation with burnishing of the surface bone in the former, and brittle fracture around and through individual Haversian systems in the latter. In all but one case, the entrance wounds were characterized by superficially fractured cortical bone in the form of a well-defined collar, while the exit wounds showed delamination of the periosteum. Inorganic residue was evident in all cases, with electron energy dispersive spectroscopy EDS confirming the presence of carbon, phosphate, lead and calcium. This material appeared to be especially concentrated within the fractured bony collar at the entrance. We conclude that gunshot wounds in flat bones may be morphologically divided into a thin burnished zone at the entry site, and a fracture zone at the exit.

  8. Three-Dimensional Reconstruction of the Bony Nasolacrimal Canal by Automated Segmentation of Computed Tomography Images

    PubMed Central

    Jañez-Garcia, Lucia; Ramirez-Sebastian, Jose M.; Toledano-Fernandez, Nicolas; Urbasos-Pascual, Maria; Jañez-Escalada, Luis

    2016-01-01

    Objective To apply a fully automated method to quantify the 3D structure of the bony nasolacrimal canal (NLC) from CT scans whereby the size and main morphometric characteristics of the canal can be determined. Design Cross-sectional study. Subjects 36 eyes of 18 healthy individuals. Methods Using software designed to detect the boundaries of the NLC on CT images, 36 NLC reconstructions were prepared. These reconstructions were then used to calculate NLC volume. The NLC axis in each case was determined according to a polygonal model and to 2nd, 3rd and 4th degree polynomials. From these models, NLC sectional areas and length were determined. For each variable, descriptive statistics and normality tests (Kolmogorov-Smirnov and Shapiro-Wilk) were established. Main Outcome Measures Time for segmentation, NLC volume, axis, sectional areas and length. Results Mean processing time was around 30 seconds for segmenting each canal. All the variables generated were normally distributed. Measurements obtained using the four models polygonal, 2nd, 3rd and 4th degree polynomial, respectively, were: mean canal length 14.74, 14.3, 14.80, and 15.03 mm; mean sectional area 15.15, 11.77, 11.43, and 11.56 mm2; minimum sectional area 8.69, 7.62, 7.40, and 7.19 mm2; and mean depth of minimum sectional area (craniocaudal) 7.85, 7.71, 8.19, and 8.08 mm. Conclusion The method proposed automatically reconstructs the NLC on CT scans. Using these reconstructions, morphometric measurements can be calculated from NLC axis estimates based on polygonal and 2nd, 3rd and 4th polynomial models. PMID:27187800

  9. Comparison of bony dimensions at the level of the pelvic floor in women with and without pelvic organ prolapse

    PubMed Central

    Stein, Tamara A.; Kaur, Gurpreet; Summers, Aimee; Larson, Kindra A.; Delancey, John O. L.

    2010-01-01

    Objective Compare bony pelvis dimensions at the level of pelvic support in women with and without pelvic organ prolapse (POP). Study Design Pelvic floor dimensions of 42 Caucasian women with POP ≥ 1cm beyond the hymen were compared to 42 age and parity-matched women with normal support. Bony landmarks relevant to connective tissue and levator attachments were identified on MRI. Dimensions were independently measured by two examiners and averaged for each subject. Results Measurements (cms) for cases and controls are as follows: Interspinous Diameter, 11.2±0.8 vs. 11.1±0.7, p=0.19; Anterior-Posterior Outlet Diameter, 11.7±0.7 vs. 11.7±0.8, p=0.71; Pubic Symphysis to Ischial Spine - Left, 9.5±0.5 vs. 9.5±0.4, p=0.91; -Right, 9.5±0.4 vs. 9.5±0.5, p=0.81; Sacrococcygeal junction to Ischial Spine - Left, 7.0±0.6 vs. 7.0±0.5, p=0.54; - Right, 7.0±0.6 vs. 6.9±0.4, p=0.32. Conclusion Bony pelvis dimensions are similar at the level of the muscular pelvic floor in Caucasian women with and without POP. PMID:19254580

  10. Ontogenetic variation in the bony labyrinth of Monodelphis domestica (Mammalia: Marsupialia) following ossification of the inner ear cavities.

    PubMed

    Ekdale, Eric G

    2010-11-01

    Ontogeny, or the development of an individual from conception to death, is a major source of variation in vertebrate morphology. All anatomical systems are affected by ontogeny, and knowledge of the ontogenetic history of these systems is important to understand when formulating biological interpretations of evolutionary history and physiology. The present study is focused on how variation affects the bony labyrinth across a growth series of an extant mammal after ossification of the inner ear chambers. Digital endocasts of the bony labyrinth were constructed using CT data across an ontogenetic sequence of Monodelphis domestica, an important experimental animal. Various aspects of the labyrinth were measured, including angles between the semicircular canals, number of turns of the cochlea, volumes of inner ear constituents, as well as linear dimensions of semicircular canals. There is a strong correlation between skull length and age, but from 27 days after birth onward, there is no correlation with age among most of the inner ear measurements. Exceptions are the height of the arc of the lateral semicircular canal, the angular deviation of the lateral canal from planarity, the length of the slender portion of the posterior semicircular canal, and the length of the canaliculus cochleae. Adult dimensions of several of the inner ear structures, such as the arcs of the semicircular canals, are achieved before the inner ear is functional, and the non-ontogenetic variation in the bony labyrinth serves as an important source for behavioral, physiological, and possibly phylogenetic information.

  11. Hedgehog and TGFβ signaling converge on Gli2 to control bony invasion and bone destruction in oral squamous cell carcinoma

    PubMed Central

    Cannonier, Shellese A.; Gonzales, Cara B.; Ely, Kim; Guelcher, Scott A.; Sterling, Julie A.

    2016-01-01

    Oral Squamous Cell Carcinoma (OSCC) is the sixth most common cancer worldwide. OSCC invasion into the lymph nodes and mandible correlates with increased rates of recurrence and lower overall survival. Tumors that infiltrate mandibular bone proliferate rapidly and induce bone destruction. While survival rates have increased 12% over the last 20 years, this improvement is attributed to general advances in prevention, earlier detection, and updated treatments. Additionally, despite decades of research, the molecular mechanisms of OSCC invasion into the mandible are not well understood. Parathyroid Hormone-related Protein (PTHrP), has been shown to be essential for mandibular invasion in OSCC animal models, and our previous studies demonstrate that the transcription factor Gli2 increases PTHrP expression in tumor metastasis to bone. In OSCC, we investigated regulators of Gli2, including Hedgehog, TGFβ, and Wnt signaling to elucidate how PTHrP expression is controlled. Here we show that canonical Hedgehog and TGFβ signaling cooperate to increase PTHrP expression and mandibular invasion in a Gli2-dependent manner. Additionally, in an orthotopic model of mandibular invasion, inhibition of Gli2 using shRNA resulted in a significant decrease of both PTHrP expression and bony invasion. Collectively, our findings demonstrate that multiple signaling pathways converge on Gli2 to mediate PTHrP expression and bony invasion, highlighting Gli2 as a therapeutic target to prevent bony invasion in OSCC. PMID:27738315

  12. Comparison of outcome of microvascular bony head and neck reconstructions using the fibular free flap and the iliac crest flap.

    PubMed

    Mücke, Thomas; Loeffelbein, Denys J; Kolk, Andreas; Wagenpfeil, Stefan; Kanatas, Anastasios; Wolff, Klaus-Dietrich; Mitchell, David A; Kesting, Marco R

    2013-09-01

    Several microvascular free flaps are available for reconstruction of the osseous components after resections for head and neck cancer. We have prospectively evaluated patients treated by bony microsurgical reconstruction to identify predictors of adverse outcomes for delayed wound healing and failure of free flaps. All patients from July 2007 to June 2011 who had reconstructions with microvascular fibular or iliac crest flaps immediately after resection of the tumour were evaluated. There were a total of 156 bony free flaps: 120 (77%) fibular and 36 (23%) iliac crest flaps. A total of 133 (85%) were successful. Delayed wound healing was more common with the iliac crest flap (p=0.01) at the intraoral site (p=0.04). Significantly more iliac crest free flaps failed (p=0.02). Anastomosis to the facial artery (p=0.05) and facial vein (p=0.04), and duration of overall operating time were associated with a significantly higher risk of failure of the flap. Patients with cancer of the head and neck who require microsurgical bony reconstruction are at increased risk of postoperative complications. Significantly more complications were found with the iliac crest flap, whereas the fibular flap was associated with a significantly longer operating time.

  13. Highly effective heterogeneous chemosensors of luminescent silica@coordination polymer core-shell micro-structures for metal ion sensing

    PubMed Central

    Cho, Won; Lee, Hee Jung; Choi, Sora; Kim, Yoona; Oh, Moonhyun

    2014-01-01

    Heterogeneous solid sensors are regarded as promising next-generation sensor due to their excellent chemical stability, low contamination, and excellent recyclability, despite their low sensitivity and weak signal. The dispersity and signals specifically from the exterior of solid sensors are critical aspects which define the sensing sensitivity and selectivity. A novel strategy for the preparation of ideal heterogeneous sensors based upon luminescent lanthanide coordination polymers (LnCP) has been demonstrated. Ideal heterogeneous sensors are systematically achieved by p