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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. Effect of low-power laser irradiation on bony implant sites.

    PubMed

    Dörtbudak, Orhun; Haas, Robert; Mailath-Pokorny, Georg

    2002-06-01

    This study was designed to examine the effects of low-energy laser irradiation on osteocytes and bone resorption at bony implant sites. Five male baboons with a mean age of 6.5 years were used in the study. Four holes for accommodating implants were drilled in each iliac crest. Sites on the left side were irradiated with a 100 mW low-energy laser (690 nm) for 1 min (6 Joule) immediately after drilling and insertion of four sandblasted and etched (Frialit-2 Synchro) implants. Five days later, the bone was removed en bloc and was evaluated histomorphometrically. The mean osteocyte count per unit area was 109.8 cells in the irradiated group vs. 94.8 cells in the control group. As intra-individual cell counts varied substantially, osteocyte viability was used for evaluation. In the irradiated group, viable osteocytes were found in 41.7% of the lacuna vs. 34.4% in the non-irradiated group. This difference was statistically significant at P < 0.027. The total resorption area, eroded surface, was found to be 24.9% in the control group vs. 24.6% in the irradiated group. This difference was not statistically significant. This study showed that osteocyte viability was significantly higher in the samples that were subjected to laser irradiation immediately after implant site drilling and implant insertion, in comparison to control sites. This may have positive effects on the integration of implants. The bone resorption rate, in contrast, was not affected by laser irradiation.

  6. 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.

  7. The Effects of Latarjet Reconstruction on Glenohumeral Kinematics in the Presence of Combined Bony Defects: A Cadaveric Model.

    PubMed

    Patel, Ronak M; Walia, Piyush; Gottschalk, Lionel; Kuklis, Matthew; Jones, Morgan H; Fening, Steve D; Miniaci, Anthony

    2016-07-01

    Recurrent glenohumeral instability is often a result of underlying bony defects in the glenoid and/or humeral head. Anterior glenoid augmentation with a coracoid bone block (ie, Latarjet procedure) 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). To evaluate the glenohumeral kinematics of the Latarjet procedure in the presence of combined bony defects. Controlled laboratory study. Eighteen fresh-frozen cadaveric specimens void of all surrounding soft tissue were tested at all combinations of glenohumeral abduction (ABD) angles of 20°, 40°, and 60° and 3 external rotation (ER) levels of 0°, 40°, and 80°. Each experiment comprised anterior dislocation by translating the glenoid under a 50-N medial load applied on the humerus, simulating the static load of soft tissue. The primary outcome measurement was defined as the percentage of intact translation (normalized distance to dislocation). Specimens were tested in an intact condition (no defect), with different combinations of defects, and with Latarjet augmentation. The Latarjet procedure was performed for 20% and 30% glenoid defects by transferring the specimen's coracoid process anterior to the glenoid so that it was flush with the articulating surface. Results depended on the position of the arm. At 20° of ABD and 0° of ER, a 20% glenoid defect decreased the percentage of intact translation regardless of the humeral head defect size (P ≤ .0001). In this same setting, Latarjet reconstruction restored translation to dislocation greater than the native intact joint for all sizes of humeral head defects. At 60° of ABD and 80° of ER, a 20% glenoid defect led to an overall decrease in translation to dislocation with increasing humeral head defects. While Latarjet augmentation resulted in increased translation to dislocation for all

  8. 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.

  9. 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

  10. [Bony Bankart lesions].

    PubMed

    Spiegl, U J; Braun, S; Euler, S A; Warth, R J; Millett, P J

    2014-12-01

    Fractures of the anteroinferior glenoid rim, termed bony Bankart lesions, have been reported to occur in up to 22% of first time anterior shoulder dislocations. The primary goal of treatment is to create a stable glenohumeral joint and a good shoulder function. Options for therapeutic intervention are largely dependent on the chronicity of the lesion, the activity level of the patient and postreduction fracture characteristics, such as the size, location and number of fracture fragments. Non-operative treatment can be successful for small, acute fractures, which are anatomically reduced after shoulder reduction. However, in patients with a high risk profile for recurrent instability initial Bankart repair is recommended. Additionally, bony fixation is recommended for acute fractures that involve more than 15-20% of the inferior glenoid diameter. On the other hand chronic fractures are generally managed on a case-by-case basis depending on the amount of fragment resorption and bony erosion of the anterior glenoid with high recurrence rates under conservative therapy. When significant bone loss of the anterior glenoid is present, anatomical (e.g. iliac crest bone graft and osteoarticular allograft) or non-anatomical (e.g. Latarjet and Bristow) reconstruction of the anterior glenoid is often indicated.

  11. Arthroscopic Transosseous Bony Bankart Repair

    PubMed Central

    Driscoll, Matthew D.; Burns, Joseph P.; Snyder, Stephen J.

    2015-01-01

    Restoration of glenoid bony integrity is critical to minimizing the risk of recurrence and re-creating normal kinematics in the setting of anterior glenohumeral instability. We present an arthroscopic suture anchor–based technique for treating large bony Bankart fractures in which the fragment is secured to the intact glenoid using mattress sutures placed through the bony fragment and augmented with soft-tissue repair proximal and distal to the bony lesion. This straightforward technique has led to excellent fragment reduction and good outcomes in our experience. PMID:25973373

  12. 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.

  13. 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.

  14. Effect of exercise and environmental terrain on development of the digital cushion and bony structures of the bovine foot.

    PubMed

    Gard, Julie A; Taylor, Debra R; Wilhite, Dewey R; Rodning, Soren P; Schnuelle, Megan L; Sanders, Richard K; Beyers, Ronald J; Edmondson, Misty A; DeGraves, Fred J; van Santen, Edzard

    2015-03-01

    To determine whether exercise on alternative terrain affects the development of the digital cushion and bony structures of the bovine foot. 20 weaned bull calves. Two-month-old calves were randomly allocated to an exercise or control group. For 4 months, the control group was maintained in grass paddocks, and the exercise group was maintained in a 0.8-km lane with a mixed terrain of dirt, stones (0.32- to 0.95-cm pea gravel and 5-cm crusher run), and grass. Water and food for the exercise group were located at opposite ends of the lane; calves were fed twice daily, which ensured they walked 3.2 km/d. Pedometers were applied to all calves to measure distance traveled. All calves were slaughtered at 6 months of age. The right forefeet and hind feet were harvested for MRI and CT evaluation. Control calves walked a mean of 1.1 km daily, whereas the exercised calves walked a mean of 3.2 km daily. Mean digital cushion volume and surface area were 25,335 mm(3) and 15,647 mm(2), respectively, for the exercised calves and 17,026 mm(3) and 12,745 mm(2), respectively, for the control calves. When weight was controlled, mean digital cushion volume and surface area for the exercise group were increased by 37.10% and 18.25%, respectively, from those for the control group. Results indicated that exercise on alternative terrain increased the volume and surface area of the digital cushion of the feet of dairy calves, which should make them less susceptible to lameness.

  15. Arthroscopic bony bankart repair using double-threaded headless screw: a case report.

    PubMed

    Kokubu, Takeshi; Nagura, Issei; Mifune, Yutaka; Kurosaka, Masahiro

    2012-01-01

    We present a case of arthroscopic fixation for bony Bankart lesion using a double-threaded cannulated screw. A 39-year-old man sustained a left shoulder injury from a motorcycle accident. Radiographs showed bony Bankart lesion and CT revealed 40% defect of glenoid articular surface. Arthroscopic fixation was performed using double-threaded cannulated screw after the bony fragment was reduced by suturing the labrum at the edge with a suture anchor. Arthroscopic bony Bankart repair using double-threaded cannulated screw fixation is effective because compression force could be applied between bony fragments and the screw head is not exposed in the glenohumeral joint.

  16. 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.

  17. 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

  18. Phylogenetic classification of bony fishes.

    PubMed

    Betancur-R, Ricardo; Wiley, Edward O; Arratia, Gloria; Acero, Arturo; Bailly, Nicolas; Miya, Masaki; Lecointre, Guillaume; Ortí, Guillermo

    2017-07-06

    Fish classifications, as those of most other taxonomic groups, are being transformed drastically as new molecular phylogenies provide support for natural groups that were unanticipated by previous studies. A brief review of the main criteria used by ichthyologists to define their classifications during the last 50 years, however, reveals slow progress towards using an explicit phylogenetic framework. Instead, the trend has been to rely, in varying degrees, on deep-rooted anatomical concepts and authority, often mixing taxa with explicit phylogenetic support with arbitrary groupings. Two leading sources in ichthyology frequently used for fish classifications (JS Nelson's volumes of Fishes of the World and W. Eschmeyer's Catalog of Fishes) fail to adopt a global phylogenetic framework despite much recent progress made towards the resolution of the fish Tree of Life. The first explicit phylogenetic classification of bony fishes was published in 2013, based on a comprehensive molecular phylogeny ( www.deepfin.org ). We here update the first version of that classification by incorporating the most recent phylogenetic results. The updated classification presented here is based on phylogenies inferred using molecular and genomic data for nearly 2000 fishes. A total of 72 orders (and 79 suborders) are recognized in this version, compared with 66 orders in version 1. The phylogeny resolves placement of 410 families, or ~80% of the total of 514 families of bony fishes currently recognized. The ordinal status of 30 percomorph families included in this study, however, remains uncertain (incertae sedis in the series Carangaria, Ovalentaria, or Eupercaria). Comments to support taxonomic decisions and comparisons with conflicting taxonomic groups proposed by others are presented. We also highlight cases were morphological support exist for the groups being classified. This version of the phylogenetic classification of bony fishes is substantially improved, providing resolution

  19. ORV Arthroscopic Transosseous Bony Bankart Repair.

    PubMed

    Myer, Daniel M; Caldwell, Paul E

    2012-12-01

    The arthroscopic treatment of the "bony Bankart lesion" continues to evolve. We present a novel technique that we developed at Orthopaedic Research of Virginia, the "transosseous bony Bankart repair," which incorporates several essential concepts to provide for optimal healing and rehabilitation. We promote arthroscopic repair emphasizing bone preservation, a fracture interface without interposing sutures, the ability to reduce capsular volume, and multiple points of stable glenolabral fixation. Our technique positions suture anchors within the subchondral bone of the intact glenoid to allow for an anatomic reduction of the bony fragment. By use of an arthroscopic drill, spinal needle, and nitinol suture passing wire, the sutures are passed in a retrograde fashion through the bony Bankart fragment and anterior capsule in a mattress configuration. Additional inferior and superior anchors are placed to further provide stability and reduce capsular volume. While maximizing fracture surface area and optimizing bony healing, the end result is an anatomic reduction of the bony fragment and the glenoid articular surface.

  20. 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%.

  1. The bony labyrinth of Neanderthals.

    PubMed

    Spoor, Fred; Hublin, Jean-Jacques; Braun, Marc; Zonneveld, Frans

    2003-02-01

    This paper presents a comprehensive comparative analysis of the Neanderthal bony labyrinth, a structure located inside the petrous temporal bone. Fifteen Neanderthal specimens are compared with a Holocene human sample, as well as with a small number of European Middle Pleistocene hominins, and early anatomically modern and European Upper Palaeolithic humans. Compared with Holocene humans the bony labyrinth of Neanderthals can be characterized by an anterior semicircular canal arc which is smaller in absolute and relative size, is relatively narrow, and shows more torsion. The posterior semicircular canal arc is smaller in absolute and relative size as well, it is more circular in shape, and is positioned more inferiorly relative to the lateral canal plane. The lateral semicircular canal arc is absolutely and relatively larger. Finally, the Neanderthal ampullar line is more vertically inclined relative to the planar orientation of the lateral canal. The European Upper Palaeolithic and early modern humans are most similar, although not fully identical to Holocene humans in labyrinthine morphology. The European Middle Pleistocene hominins show the typical semicircular canal morphology of Neanderthals, with the exception of the arc shape and inferiorly position of the posterior canal and the strongly inclined ampullar line. The marked difference between the labyrinths of Neanderthals and modern humans can be used to assess the phylogenetic affinities of fragmentary temporal bone fossils. However, this application is limited by a degree of overlap between the morphologies. The typical shape of the Neanderthal labyrinth appears to mirror aspects of the surrounding petrous pyramid, and both may follow from the phylogenetic impact of Neanderthal brain morphology moulding the shape of the posterior cranial fossa. The functionally important arc sizes of the Neanderthal semicircular canals may reflect a pattern of head movements different from that of modern humans, possibly

  2. 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…

  3. 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…

  4. 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

  5. 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

  6. 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…

  7. 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…

  8. 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.

  9. A pulled sutures technique for bony Bankart lesion.

    PubMed

    Lee, Byung Ill; Choi, Hyung Suk; Min, Kyung Dae; Kwon, Sai Won; Kim, Jun Bum; Kim, Yong-Beom; Chun, Dong-Il

    2014-05-01

    In an attempt to present a new surgical technique for arthroscopic bony Bankart fixation, the authors developed the pulled sutures technique. In executing the new method, the authors first passed several non-absorbable sutures through labroligamentous tissue with displaced articular fragment by mimicking transglenoid suture technique. Aimed at achieving a safe and stable fixation, using a knotless anchor rather than transglenoid suture, was deployed. Overall, this pulled sutures technique was shown to be effective with the result of direct reduction, stable, and safe fixation for bony Bankart's lesion.

  10. Acute bony bankart lesion and surgical fixation.

    PubMed

    Rosenthal, Michael D; Provencher, Matthew T

    2009-10-01

    The patient was a 25-year-old man who sustained a traumatic left anterior shoulder dislocation. After self-reducing the first time, as well as in subsequent repeated dislocations over the following 2-day period, the patient reported his injury to the medical staff, who sent him to the physical therapist for evaluation. Anterior-posterior, scapular outlet, and axillary radiographic views demonstrated a bony glenoid lesion consistent with a bony Bankart lesion, which was best seen on the scapular outlet view. A 3-dimensional computed tomography scan was performed to assess the size and displacement of the bony Bankart lesion. Six days following injury, the patient underwent operative fixation of the bony Bankart lesion. Following surgery, the patient completed 5 months of physical therapy and subsequently returned to high-demand upper body activities. At 3 years following surgery, the patient reported full functional ability without shoulder instability or pain.

  11. Prominent effect of soil network heterogeneity on microbial invasion.

    PubMed

    Pérez-Reche, F J; Taraskin, S N; Otten, W; Viana, M P; Costa, L da F; Gilligan, C A

    2012-08-31

    Using a network representation for real soil samples and mathematical models for microbial spread, we show that the structural heterogeneity of the soil habitat may have a very significant influence on the size of microbial invasions of the soil pore space. In particular, neglecting the soil structural heterogeneity may lead to a substantial underestimation of microbial invasion. Such effects are explained in terms of a crucial interplay between heterogeneity in microbial spread and heterogeneity in the topology of soil networks. The main influence of network topology on invasion is linked to the existence of long channels in soil networks that may act as bridges for transmission of microorganisms between distant parts of soil.

  12. 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.

  13. Photon scattering effects in heterogeneous scintillator systems

    SciTech Connect

    Ross, H.H.

    1989-01-01

    This paper describes a new experimental approach that reveals the individual contributions of sample geometry and scattering phenomena in heterogeneous flow-cell detectors. The experimental detector responses obtained using scintillating polystyrene beads with optically smooth surfaces are compared with those obtained using similar beads with highly diffuse surfaces. These comparisons are carried out for both alpha- and beta-emitting nuclides. The experimental detection efficiencies are compared to Monte Carlo simulations of the detection process. Also, a new technique will be described for the fabrication of scintillating beads. 7 refs., 8 figs., 2 tabs.

  14. 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.

  15. 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

  16. Pseudohypoparathyroidism presenting with bony deformities resembling rickets.

    PubMed

    Bajpai, Anurag; Sharma, Jyoti; Hari, Pankaj; Bagga, Arvind

    2004-04-01

    Pseudohypoparathyroidism (PHP), characterized by hypocalcemia, hyperphosphatemia and elevated parathormone level, may rarely be associated with bony deformities resembling rickets. The authors report two siblings with clinical and radiological features suggestive of rickets unresponsive to treatment with vitamin D. Low serum calcium, elevated serum phosphate, normal renal functions, raised tubular maximum of phosphate and high serum parathormone were suggestive of PHP. Treatment with 1-hydroxyvitamin D and calcium carbonate led to decrease in bone pain, increase in height and weight and resolution of radiological features. PHP should be suspected in patients with bony deformities, hypocalcemia, elevated blood phosphate levels and normal renal functions.

  17. Arthroscopic Repair of Posterior Bony Bankart Lesion and Subscapularis Remplissage.

    PubMed

    Luedke, Colten; Tolan, Stefan J; Tokish, John M

    2017-06-01

    Posterior shoulder instability with glenoid bone loss has only a fraction of the prevalence of anterior instability. Unlike the latter, there is a paucity of literature regarding the treatment of posterior bony Bankart lesions and even less with concomitant reverse Hill-Sachs lesions. This combination of pathology leads to a difficult situation regarding treatment options. We present our technique for arthroscopic repair of a posterior bony Bankart lesion and reverse Hill-Sachs lesion. The importance of proper portal placement cannot be overstated. By use of the lateral position and strategically placed portals, the posterior bony Bankart lesion and attached labral complex were appropriately mobilized. We reduced the glenoid bone, with the attached capsulolabral complex, to the glenoid rim and performed fixation using a knotless suture anchor. We then placed 2 double-loaded suture anchors into the reverse Hill-Sachs lesion. The sutures were passed creating horizontal mattress configurations that were tied at the end of the procedure, effectively externalizing the humeral head defect. Our technique results in satisfactory fragment reduction, as well as appropriate capsular tension, and effectively prevents the reverse Hill-Sachs lesion from engaging.

  18. Habitat heterogeneity hypothesis and edge effects in model metacommunities.

    PubMed

    Hamm, Michaela; Drossel, Barbara

    2017-08-07

    Spatial heterogeneity is an inherent property of any living environment and is expected to favour biodiversity due to a broader niche space. Furthermore, edges between different habitats can provide additional possibilities for species coexistence. Using computer simulations, this study examines metacommunities consisting of several trophic levels in heterogeneous environments in order to explore the above hypotheses on a community level. We model heterogeneous landscapes by using two different sized resource pools and evaluate the combined effect of dispersal and heterogeneity on local and regional species diversity. This diversity is obtained by running population dynamics and evaluating the robustness (i.e., the fraction of surviving species). The main results for regional robustness are in agreement with the habitat heterogeneity hypothesis, as the largest robustness is found in heterogeneous systems with intermediate dispersal rates. This robustness is larger than in homogeneous systems with the same total amount of resources. We study the edge effect by arranging the two types of resources in two homogeneous blocks. Different edge responses in diversity are observed, depending on dispersal strength. Local robustness is highest for edge habitats that contain the smaller amount of resource in combination with intermediate dispersal. The results show that dispersal is relevant to correctly identify edge responses on community level. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Computing effective properties of random heterogeneous materials on heterogeneous parallel processors

    NASA Astrophysics Data System (ADS)

    Leidi, Tiziano; Scocchi, Giulio; Grossi, Loris; Pusterla, Simone; D'Angelo, Claudio; Thiran, Jean-Philippe; Ortona, Alberto

    2012-11-01

    In recent decades, finite element (FE) techniques have been extensively used for predicting effective properties of random heterogeneous materials. In the case of very complex microstructures, the choice of numerical methods for the solution of this problem can offer some advantages over classical analytical approaches, and it allows the use of digital images obtained from real material samples (e.g., using computed tomography). On the other hand, having a large number of elements is often necessary for properly describing complex microstructures, ultimately leading to extremely time-consuming computations and high memory requirements. With the final objective of reducing these limitations, we improved an existing freely available FE code for the computation of effective conductivity (electrical and thermal) of microstructure digital models. To allow execution on hardware combining multi-core CPUs and a GPU, we first translated the original algorithm from Fortran to C, and we subdivided it into software components. Then, we enhanced the C version of the algorithm for parallel processing with heterogeneous processors. With the goal of maximizing the obtained performances and limiting resource consumption, we utilized a software architecture based on stream processing, event-driven scheduling, and dynamic load balancing. The parallel processing version of the algorithm has been validated using a simple microstructure consisting of a single sphere located at the centre of a cubic box, yielding consistent results. Finally, the code was used for the calculation of the effective thermal conductivity of a digital model of a real sample (a ceramic foam obtained using X-ray computed tomography). On a computer equipped with dual hexa-core Intel Xeon X5670 processors and an NVIDIA Tesla C2050, the parallel application version features near to linear speed-up progression when using only the CPU cores. It executes more than 20 times faster when additionally using the GPU.

  4. Effective Hydraulic Conductivity of Unsaturated Isotropic Soils with Multidimensional Heterogeneity

    SciTech Connect

    Zhang, Z. F.

    2010-05-01

    Accurate simulation and prediction of flow and transport of solutes in a heterogeneous vadose zone requires the appropriate hydraulic properties corresponding to the spatial scale of interest. Upscaling techniques provide effective properties to describe the vadose zone system’s behavior with information collected at a much smaller scale. Realizing that a saturated system can be considered as a special state of the unsaturated system, the methodologies for upscaling the saturated hydraulic conductivity of heterogeneous isotropic porous media under steady-state flow conditions can be extended for upscaling the unsaturated hydraulic conductivity. An advantage of this approach is that the extended upscaling methods are independent of the choice of hydraulic function models. The Matheron, small-perturbation, and self-consistent upscaling methods were used to demonstrate the approach. The extended upscaling methods were tested using multi-step numerical experiments of gravity-induced flow into Miller-similar synthetic soils with different levels of heterogeneity. Results show that, under 3-D flow conditions in isotropic soils, the self-consistent method applies to all the soil heterogeneity conditions considered while the Matheron and small-perturbation methods are acceptable for soil of relatively low variability.

  5. Endogamy among the Dogon of Boni, Mali.

    PubMed

    Cazes, M H

    1990-01-01

    This paper examines factors influencing endogamy in a Dogon population in Mali. Situated in Boni district, this population of about 5000 individuals is distributed over fifteen villages located on four independent massifs. This population is strongly endogamous (only 4% of all marriages are contracted with neighbouring ethnic groups), and each massif shows high endogamy. The roles of lineage, residence in the same village, and geographical distance in mating choice are examined. These different factors are successively analysed using log-linear statistical models and the results offer a more precise interpretation of endogamy in this population.

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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

  11. Do reduction and healing of the bony fragment really matter in arthroscopic bony Bankart reconstruction?: a prospective study with clinical and computed tomography evaluations.

    PubMed

    Jiang, Chun-Yan; Zhu, Yi-Ming; Liu, Xin; Li, Feng-Long; Lu, Yi; Wu, Guan

    2013-11-01

    Bony Bankart lesions can be treated with arthroscopic repair. However, few studies have evaluated the importance of bony fragment reduction and healing to stability of the glenohumeral joint after arthroscopic bony Bankart repair. To evaluate functional results after surgery and determine the correlation between reduction and healing of the fracture and postoperative stability of the glenohumeral joint. Case series; Level of evidence, 4. A total of 50 patients (47 men, 3 women; average age, 27.6 years; range, 16.5-50.1 years) with bony Bankart lesions and recurrent anterior shoulder dislocations were treated with arthroscopic reduction and internal fixation with suture anchors. The average follow-up period was 32.5 months (range, 24.3-61.2 months). Preoperative and postoperative range of motion and American Shoulder and Elbow Surgeons (ASES), Constant-Murley, and Rowe scores were compared to evaluate the results of the surgeries. Sequential 3-dimensional computed tomography (CT) scans were available for 37 patients and were analyzed to investigate the effect of the bony defect of the glenoid and the correlation between the success of the surgery and reduction and healing of the bony fragment. After surgery, active forward elevation was significantly improved (P < .05). No significant differences were found regarding external and internal rotations after surgery. The ASES, Constant-Murley, and Rowe scores improved significantly after surgery. Redislocations occurred in 3 patients, and a positive anterior apprehension sign was detected in 1 patient during follow-up. The overall failure rate was 8.0% (4/50). The CT scans during the follow-up period showed a nonunion of the bony fragment in 13.5% of cases (5/37). The reconstructed size of the glenoid was <80% in 3 of the 4 failure cases but >80% in all of the successful cases. Arthroscopic reduction and fixation of a bony Bankart lesion can achieve good results in selected cases. The size of the reconstructed glenoid

  12. 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.

  13. Transient dynamics and the destabilizing effects of prey heterogeneity.

    PubMed

    Steiner, Christopher F; Klausmeier, Christopher A; Litchman, Elena

    2012-03-01

    The presence of prey heterogeneity and weakly interacting prey species is frequently viewed as a stabilizer of predator-prey dynamics, countering the destabilizing effects of enrichment and reducing the amplitude of population cycles. However, prior model explorations have largely focused on long-term, dynamic attractors rather than transient dynamics. Recent theoretical work shows that the presence of prey that are defended from predation can have strongly divergent effects on dynamics depending on time scale: prey heterogeneity can counteract the destabilizing effects of enrichment on predator-prey dynamics at long time scales but strongly destabilize systems during transient phases by creating long periods of low predator/prey abundance and increasing extinction probability (an effect that is amplified with increasing enrichment). We tested these general predictions using a planktonic system composed of a zooplankton predator and multiple algal prey. We first parameterized a model of our system to generate predictions and tested these experimentally. Our results qualitatively supported several model predictions. During transient phases, presence of defended algal prey increased predator extinctions at low and high enrichment levels compared to systems with only a single edible prey. This destabilizing effect was moderated at higher dilution rates, as predicted by our model. When examining dynamics beyond initial oscillations, presence of the defended prey increased predator-prey temporal variability at high nutrient enrichment but had no effect at low nutrient levels. Our results highlight the importance of considering transient dynamics when assessing the role of stabilizing factors on the dynamics of food webs.

  14. 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

  15. The "Fish Hook" Technique for Bony Mallet Finger.

    PubMed

    Kim, Dong Hee; Kang, Hong Je; Choi, Ji Woong

    2016-09-01

    This study describes a new technique called the "fish hook" technique for the treatment of bony mallet finger. This technique catches the dorsal fragment with a bent K-wire shaped like a fish hook. Transarticular fixation is performed with another K-wire. This technique does not directly penetrate the bone fragment to prevent fragment comminution. This study included 26 patients with mallet finger fractures who underwent surgery using the fish hook technique between 2010 and 2014. The fractures were classified according to the method of Wehbe and Schneider. The fracture fragment was fixed with a fish hook technique in all patients. The K-wire was removed after 6 weeks, when bone union was achieved. Clinical parameters, including range of motion and extensor lag, were assessed at the distal interphalangeal joint according to Crawford's criteria. The mean follow-up period was 12.8 months. Mean extensor lag was 3°, and mean range of flexion of the distal interphalangeal joint was 76°. All patients achieved bone union after 6 weeks. According to Crawford's criteria, there were 20 excellent results, 5 good results, and 1 fair result. No complications, including skin necrosis, pin loosening, and nail deformity, occurred. The fish hook technique is an effective treatment option for bony mallet finger and provides good clinical and radiologic results. [Orthopedics.2016; 39(5):295-298.]. Copyright 2016, SLACK Incorporated.

  16. 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.

  17. Dosimetric effect of tissue heterogeneity for (125)I prostate implants.

    PubMed

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

    2014-11-01

    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 (125)I prostate implants. 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. 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. 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 D 90 was overestimated by 2.8-3.9% and the rectum D 0.1cc 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. 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.

  18. 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

  19. 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

  20. 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

    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

    2016-07-01

    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. 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. 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 analysis adjusted for stratification

  1. 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

  2. Civic Returns to Higher Education: A Note on Heterogeneous Effects

    PubMed Central

    Brand, Jennie E.

    2011-01-01

    American educational leaders and philosophers have long valued schooling for its role in preparing the nation’s youth to be civically engaged citizens. Numerous studies have found a positive relationship between education and subsequent civic participation. However, little is known about possible variation in effects by selection into higher education, a critical omission considering education’s expressed role as a key mechanism for integrating disadvantaged individuals into civic life. I disaggregate effects and examine whether civic returns to higher education are largest for disadvantaged low likelihood or advantaged high likelihood college goers. I find evidence for significant effect heterogeneity: civic returns to college are greatest among individuals who have a low likelihood for college completion. Returns decrease as the propensity for college increases. PMID:22223924

  3. Hydrological effects of within-catchment heterogeneity of drainage density

    NASA Astrophysics Data System (ADS)

    Di Lazzaro, Michele; Zarlenga, Antonio; Volpi, Elena

    2015-02-01

    Local drainage density (dd) has been traditionally defined as the inverse of twice the distance one has to walk before encountering a channel. This formalization easily allows to derive raster-based maps of dd extracted straight off from digital elevation model data. Maps of local dd, which are continuous in space, are able to reveal the appearance of strong heterogeneities in the geological and geomorphological properties of natural landscapes across different scales. In this work we employ the information provided by these spatial maps to study the potential effects of the within-catchment variability of dd on the hydrologic response. A simple power law relationship between runoff yield at the local scale and the value of dd has been adopted; the hypothesis is supported by a large number of past empirical observations and modeling. The novel framework proposed (ddRWF) embeds this spatially variable runoff weight in the well-known Rescaled Width Function (RWF) framework, based on the more general geomorphological theory of the hydrologic response. The model is applied to four sub-basins in the Cascade Range Region (Oregon, USA) where strong contrasts in dissection patterns due the underlain geology have been broadly addressed in previous literature. The ddRWF approach is compared with the classic RWF in terms of shape, moments and peak of the simulated hydrograph response. Results hint that the variability of runoff yield due to the heterogeneity of dd (i.e. of hillslope lengths) determines a more rapid concentration of runoff, which implies shorter lag times, larger skewness and higher peak floods, especially in the case hillslope velocity is much smaller than channel velocity. The potential of the proposed framework relies on accounting for spatially variable losses related to geomorphologic heterogeneity in lumped rainfall-runoff models, still keeping the simple and robust structure of the IUH approach.

  4. 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

  5. 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.

  6. 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.

  7. Investigating the effects of target heterogeneity on the cratering process.

    NASA Astrophysics Data System (ADS)

    Barnouin, O. S.

    2012-12-01

    momentum using a second order multi-material Eulerian methodology. This code possesses an adaptive mesh refinement that allows investigating the effects of fine-scale target heterogeneity on the cratering process, through the use of a simple microscopic model with complex but resolvable heterogeneous geometries, rather than a complex macroscopic model. Both approaches provide insights on how the thickness of the shock front relative to the average dimension of any pre-exiting structure could be a controlling factor during impact cratering.

  8. 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.

  9. 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

  10. Effects of Soil Heterogeneity on Martian Ground Ice Stability

    NASA Astrophysics Data System (ADS)

    Sizemore, H. G.; Mellon, M. T.

    2005-12-01

    Theoretical investigation of ground-ice stability and analysis of Mars Odyssey Gamma Ray Spectrometer (GRS) data have each been used to infer the depth of the ice-table (the boundary between dry and ice-cemented soil in the martian permafrost). Historically, both methods have assumed the martian soil to be homogeneous. However, imagery of the martian surface clearly shows a complex mixture of soils, rocks, and slopes. Remaining discrepancies between theoretical and GRS-inferred ice-table depths may be related to the natural heterogeneities of the surface layer (Mellon et al., 2004). We have therefore employed a new three-dimensional model to investigate the effects of surface rocks, dust, and albedo variations on Martian ground-ice stability. We find that these heterogeneities produce significant undulations/topography in the ice-table at horizontal length scales of a few meters. Near rocks, the ice-table is deeper than its equilibrium depth in homogeneous soil; dust lenses make the ice-table shallower in their vicinity. Decimeter-scale rocks produce a gross vertical deflection (10-30 cm) over a relatively small horizontal range (1-2 rock radii). Comparably sized dust lenses produce a weak vertical deflection (1-3 cm) over a more extended horizontal range (7-8 lens radii). Albedo variations slightly enhance the effects of dark rocks and bright dust. In general, ice-table depth can vary by 10s of cm under mixed surfaces containing rocks, dust, and average soil poleward of 60° N. We have also investigated the factor-of-two discrepancy between theoretical and observational estimates of ice-table depth noted by Mellon et al., but cannot fully resolve it. Ice-table depths derived from GRS neutron data can be up to 10% deeper than theoretical depths in areas where cumulative fractional rock abundance exceeds 20%. Thus, rocks play a significant but not dominant role in the remote sensing data . Other types of heterogeneities, such as slopes and the layered structure of

  11. The "bony Bankart bridge" procedure: a new arthroscopic technique for reduction and internal fixation of a bony Bankart lesion.

    PubMed

    Millett, Peter J; Braun, Sepp

    2009-01-01

    Arthroscopic treatment of bony Bankart lesions can be challenging. We present a new easy and reproducible technique for arthroscopic reduction and suture anchor fixation of bony Bankart fragments. A suture anchor is placed medially to the fracture on the glenoid neck, and its sutures are passed around the bony fragment through the soft tissue including the inferior glenohumeral ligament complex. The sutures of this anchor are loaded in a second anchor that is placed on the glenoid face. This creates a nontilting 2-point fixation that compresses the fragment into its bed. By use of the standard technique, additional suture anchors are used superiorly and inferiorly to the bony Bankart piece to repair the labrum and shift the joint capsule. We call this the "bony Bankart bridge" procedure.

  12. 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

  13. 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.

  14. 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.

  15. The effects of physical and geochemical heterogeneities on hydro-geochemical transport and effective reaction rates

    NASA Astrophysics Data System (ADS)

    Atchley, Adam L.; Navarre-Sitchler, Alexis K.; Maxwell, Reed M.

    2014-09-01

    The role of coupled physical and geochemical heterogeneities in hydro-geochemical transport is investigated by simulating three-dimensional transport in a heterogeneous system with kinetic mineral reactions. Ensembles of 100 physically heterogeneous realizations were simulated for three geochemical conditions: 1) spatially homogeneous reactive mineral surface area, 2) reactive surface area positively correlated to hydraulic heterogeneity, and 3) reactive surface area negatively correlated to hydraulic heterogeneity. Groundwater chemistry and the corresponding effective reaction rates were calculated at three transverse planes to quantify differences in plume evolution due to heterogeneity in mineral reaction rates and solute residence time (τ). The model is based on a hypothetical CO2 intrusion into groundwater from a carbon capture utilization and storage (CCUS) operation where CO2 dissolution and formation of carbonic acid created geochemical dis-equilibrium between fluids and the mineral galena that resulted in increased aqueous lead (Pb2 +) concentrations. Calcite dissolution buffered the pH change and created conditions of galena oversaturation, which then reduced lead concentrations along the flow path. Near the leak kinetic geochemical reactions control the release of solutes into the fluid, but further along the flow path mineral solubility controls solute concentrations. Simulation results demonstrate the impact of heterogeneous distribution of geochemical reactive surface area in coordination with physical heterogeneity on the effective reaction rate (Krxn,eff) and Pb2 + concentrations within the plume. Dissimilarities between ensemble Pb2 + concentration and Krxn,eff are attributed to how geochemical heterogeneity affects the time (τeq) and therefore advection distance (Leq) required for the system to re-establish geochemical equilibrium. Only after geochemical equilibrium is re-established, Krxn,eff and Pb2 + concentrations are the same for all three

  16. The effects of physical and geochemical heterogeneities on hydro-geochemical transport and effective reaction rates.

    PubMed

    Atchley, Adam L; Navarre-Sitchler, Alexis K; Maxwell, Reed M

    2014-09-01

    The role of coupled physical and geochemical heterogeneities in hydro-geochemical transport is investigated by simulating three-dimensional transport in a heterogeneous system with kinetic mineral reactions. Ensembles of 100 physically heterogeneous realizations were simulated for three geochemical conditions: 1) spatially homogeneous reactive mineral surface area, 2) reactive surface area positively correlated to hydraulic heterogeneity, and 3) reactive surface area negatively correlated to hydraulic heterogeneity. Groundwater chemistry and the corresponding effective reaction rates were calculated at three transverse planes to quantify differences in plume evolution due to heterogeneity in mineral reaction rates and solute residence time (τ). The model is based on a hypothetical CO2 intrusion into groundwater from a carbon capture utilization and storage (CCUS) operation where CO2 dissolution and formation of carbonic acid created geochemical dis-equilibrium between fluids and the mineral galena that resulted in increased aqueous lead (Pb(2+)) concentrations. Calcite dissolution buffered the pH change and created conditions of galena oversaturation, which then reduced lead concentrations along the flow path. Near the leak kinetic geochemical reactions control the release of solutes into the fluid, but further along the flow path mineral solubility controls solute concentrations. Simulation results demonstrate the impact of heterogeneous distribution of geochemical reactive surface area in coordination with physical heterogeneity on the effective reaction rate (Krxn,eff) and Pb(2+) concentrations within the plume. Dissimilarities between ensemble Pb(2+) concentration and Krxn,eff are attributed to how geochemical heterogeneity affects the time (τeq) and therefore advection distance (Leq) required for the system to re-establish geochemical equilibrium. Only after geochemical equilibrium is re-established, Krxn,eff and Pb(2+) concentrations are the same for all

  17. 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...

  18. 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...

  19. 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...

  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. 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.

  2. Directed Bmp4 expression in neural crest cells generates a genetic model for the rare human bony syngnathia birth defect

    PubMed Central

    He, Fenglei; Hu, Xuefeng; Xiong, Wei; Li, Lu; Lin, Lisong; Shen, Bin; Yang, Ling; Gu, Shuping; Zhang, Yanding; Chen, YiPing

    2014-01-01

    Congenital bony syngnathia, a rare but severe human birth defect, is characterized by bony fusion of the mandible to the maxilla. However, the genetic mechanisms underlying this birth defect are poorly understood, largely due to limitation of available animal models. Here we present evidence that transgenic expression of Bmp4 in neural crest cells causes a series of craniofacial malformations in mice, including a bony fusion between the maxilla and hypoplastic mandible, resembling the bony syngnathia syndrome in humans. In addition, the anterior portion of the palatal shelves emerged from the mandibular arch instead of the maxilla in the mutants. Gene expression assays showed an altered expression of several facial patterning genes, including Hand2, Dlx2, Msx1, Barx1, Foxc2 and Fgf8, in the maxillary and mandibular processes of the mutants, indicating mis-patterned cranial neural crest (CNC) derived cells in the facial region. However, despite of formation of cleft palate and ectopic cartilage, forced expression of a constitutively active form of BMP receptor-Ia (caBmprIa) in CNC lineage did not produce the syngnathia phenotype, suggesting a non-cell autonomous effect of the augmented BMP4 signaling. Our studies demonstrate that aberrant BMP4-mediated signaling in CNC cells leads to mis-patterned facial skeleton and congenital bony syngnathia, and suggest an implication of mutations in BMP signaling pathway in human bony syngnathia. PMID:24785830

  3. 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

  4. Arthroscopic Bony Bankart Fixation Using a Modified Sugaya Technique

    PubMed Central

    Gupta, Anil K.; McCormick, Frank M.; Abrams, Geoffrey D.; Harris, Joshua D.; Bach, Bernard R.; Romeo, Anthony A.; Verma, Nikhil N.

    2013-01-01

    Arthroscopic fixation of bony Bankart lesions in the setting of anterior shoulder instability has had successful long-term results. Key factors such as patient positioning, portal placement, visualization, mobilization of bony/soft tissues, and anatomic reduction and fixation are crucial to yield such results. We present a modified Sugaya technique that is reproducible and based on such key principles. This technique facilitates ease of anchor and suture placement to allow for anatomic reduction and fixation. PMID:24265994

  5. 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.

  6. Characterizing the effect of population heterogeneity on evolutionary dynamics on complex networks.

    PubMed

    Tan, Shaolin; Lü, Jinhu

    2014-05-22

    Recently, the impact of network structure on evolutionary dynamics has been at the center of attention when studying the evolutionary process of structured populations. This paper aims at finding out the key structural feature of network to capture its impact on evolutionary dynamics. To this end, a novel concept called heat heterogeneity is introduced to characterize the structural heterogeneity of network, and the correlation between heat heterogeneity of structure and outcome of evolutionary dynamics is further investigated on various networks. It is found that the heat heterogeneity mainly determines the impact of network structure on evolutionary dynamics on complex networks. In detail, the heat heterogeneity readjusts the selection effect on evolutionary dynamics. Networks with high heat heterogeneity amplify the selection effect on the birth-death process and suppress the selection effect on the death-birth process. Based on the above results, an effective algorithm is proposed to generate selection adjusters with desired size and average degree.

  7. 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

  8. 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

  9. 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

  10. 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.

  11. 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

  12. 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.

  13. On the effect of height heterogeneity on canopy turbulence

    NASA Astrophysics Data System (ADS)

    Hamed, A. M.; Sadowski, M. J.; Chamorro, L. P.

    2016-12-01

    The flow development above and within homogeneous and heterogeneous canopies was studied using PIV in a refractive-index-matching open channel. The homogeneous model (base case) is constituted of elements of height h arranged in staggered configuration; whereas the heterogeneous canopy consisted of elements of two heights h1 = h + 1/3 h and h2 = h - 1/3 h alternated every two rows. Both canopies had the same roughness density, element geometry, and mean height. The flow was studied under three submergences H/h = 2, 3, 4, where H denotes the flow depth. High spatial-resolution planar and high-temporal resolution stereo-PIV measurements were performed at Reynolds number ReH = 6500, 11300, and 12300. The planar measurements are aimed at characterizing the flow along the entire length of the canopies, while the stereo measurements focused on quantifying the dispersive stresses at various vertical zones of the flow and the structure of the velocity fluctuations within the developed region. Turbulence statistics complemented with quadrant analysis and proper orthogonal decomposition reveal richer flow dynamics induced by height heterogeneity. Topography-induced spatially-periodic mean flows are observed for the heterogeneous canopy. In contrast to the homogeneous case, non-vanishing vertical velocity is maintained across the entire length of the heterogeneous canopy with increased levels at lower submergence depths. The results indicate that heterogeneous canopy exhibits enhanced vertical turbulent exchange at the canopy interface, suggesting a potential for greater scalar exchange and greater impact on channel hydraulic resistance. The flow development above and within homogeneous and heterogeneous canopies was studied using PIV in a refractive-index-matching open channel. The homogeneous model (base case) is constituted of elements of height h arranged in staggered configuration; whereas the heterogeneous canopy consisted of elements of two heights h1 = h + 1/3 h and h

  14. 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…

  15. 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…

  16. Soil spatial heterogeneity effect on soil electrical resistivity

    USDA-ARS?s Scientific Manuscript database

    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...

  17. 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…

  18. 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…

  19. Mathematical modeling of tumor therapy with oncolytic viruses: effects of parametric heterogeneity on cell dynamics

    PubMed Central

    Karev, Georgy P; Novozhilov, Artem S; Koonin, Eugene V

    2006-01-01

    Background: One of the mechanisms that ensure cancer robustness is tumor heterogeneity, and its effects on tumor cells dynamics have to be taken into account when studying cancer progression. There is no unifying theoretical framework in mathematical modeling of carcinogenesis that would account for parametric heterogeneity. Results: Here we formulate a modeling approach that naturally takes stock of inherent cancer cell heterogeneity and illustrate it with a model of interaction between a tumor and an oncolytic virus. We show that several phenomena that are absent in homogeneous models, such as cancer recurrence, tumor dormancy, and others, appear in heterogeneous setting. We also demonstrate that, within the applied modeling framework, to overcome the adverse effect of tumor cell heterogeneity on the outcome of cancer treatment, a heterogeneous population of an oncolytic virus must be used. Heterogeneity in parameters of the model, such as tumor cell susceptibility to virus infection and the ability of an oncolytic virus to infect tumor cells, can lead to complex, irregular evolution of the tumor. Thus, quasi-chaotic behavior of the tumor-virus system can be caused not only by random perturbations but also by the heterogeneity of the tumor and the virus. Conclusion: The modeling approach described here reveals the importance of tumor cell and virus heterogeneity for the outcome of cancer therapy. It should be straightforward to apply these techniques to mathematical modeling of other types of anticancer therapy. Reviewers: Leonid Hanin (nominated by Arcady Mushegian), Natalia Komarova (nominated by Orly Alter), and David Krakauer. PMID:17018145

  20. Effect of Upper Mantle Heterogeneities on Lithosphere Stresses and Topography

    NASA Astrophysics Data System (ADS)

    Osei Tutu, A.; Steinberger, B.; Rogozhina, I.; Sobolev, S. V.

    2016-12-01

    The orientation and magnitude of lithosphere stresses give us knowledge about most of the processes within the Earth that are not easy to observe. It has been established (Steinberger, Schmeling, and Marquart 2001) that large contribution of the forces producing lithosphere stresses have their source origination from the buoyancies of both the upper and lower mantle acting beneath the lithosphere. The contribution of the crustal thickness to the stresses has been estimated to be less than 10% (Steinberger et al. 2001) in most region and increases in areas with high gravitational potential energy like the Himalayas. In most of these studies, the effect of the crust was determined separately by computing the gravitational potential energy from the crust (Ghosh et al. 2013) and applied as correction. (Artyushkov 1973) showed that the inhomogeneous nature of the crust contribute to the stresses observed as against using constant lithosphere thickness in most studies, due to the complexities for implementing a variable lithosphere. We seek extend the approach of Ghosh et al. (2013) by coupling the Crust 1.0 (Laske et al. 2013) to a varaible lithosphere thickness in our numerical method. Using a 3D global lithosphere-asthenosphere model (Popov and Sobolev 2008) with visco-elasto-plastic rheology, coupled at 300 km depth to a mantle modeled with a spectral technique (Hager and O'Connell, 1981), we compute lithosphere stresses and topography. we compare our model with observations; the World Stress Map, Global Strain Rate Map and the observed topgraphy. We use S40RTS seismic tomography below 300 km depth, with radial viscosity distribution (Steinberger et al 2006). To account for all the heterogeneities in the upper mantle (300 km) we used different 3D temperatures models setups. The first model is the thermal lithosphere model (Artemieva and Mooney, 2001) in continental regions and assumes half-space cooling of sea floor with age (Müller et al. 2008) for oceans. For the

  1. Arthroscopic Repair of a Posterior Bony Bankart Lesion.

    PubMed

    Poehling-Monaghan, Kirsten L; Krych, Aaron J; Dahm, Diane L

    2015-12-01

    Posterior bony defects of the glenoid rim, particularly those associated with instability, are often a frustrating challenge for arthroscopists because of the defects' inaccessibility from standard portals. This challenge is enhanced when the lesion is chronic and fibrous malunion of the fragment makes mobilization difficult. We present our technique for arthroscopic repair of the relatively uncommon chronic posterior bony Bankart lesion. By use of lateral positioning and a standard anterior viewing portal and posterior working portal, as well as a strategically placed posterolateral accessory portal, the lesion is first freed from its malreduced position and ultimately repaired using suture anchor fixation of the bony fragment along with its associated labrum directly to the remaining glenoid rim. This technique, facilitated by precise portal placement, results in satisfactory fragment reduction, appropriate capsular tension, and restoration of anatomy.

  2. Arthroscopic Repair of a Posterior Bony Bankart Lesion

    PubMed Central

    Poehling-Monaghan, Kirsten L.; Krych, Aaron J.; Dahm, Diane L.

    2015-01-01

    Posterior bony defects of the glenoid rim, particularly those associated with instability, are often a frustrating challenge for arthroscopists because of the defects' inaccessibility from standard portals. This challenge is enhanced when the lesion is chronic and fibrous malunion of the fragment makes mobilization difficult. We present our technique for arthroscopic repair of the relatively uncommon chronic posterior bony Bankart lesion. By use of lateral positioning and a standard anterior viewing portal and posterior working portal, as well as a strategically placed posterolateral accessory portal, the lesion is first freed from its malreduced position and ultimately repaired using suture anchor fixation of the bony fragment along with its associated labrum directly to the remaining glenoid rim. This technique, facilitated by precise portal placement, results in satisfactory fragment reduction, appropriate capsular tension, and restoration of anatomy. PMID:26870644

  3. 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

  4. Effects of pore-scale dispersion, degree of heterogeneity, sampling size, and source volume on the concentration moments of conservative solutes in heterogeneous formations

    Treesearch

    Daniele Tonina; Alberto Bellin

    2008-01-01

    Pore-scale dispersion (PSD), aquifer heterogeneity, sampling volume, and source size influence solute concentrations of conservative tracers transported in heterogeneous porous formations. In this work, we developed a new set of analytical solutions for the concentration ensemble mean, variance, and coefficient of variation (CV), which consider the effects of all these...

  5. More than superstition: differential effects of featural heterogeneity and change on subitizing and counting.

    PubMed

    Trick, Lana M

    2008-07-01

    This study investigates the effects of item heterogeneity (differences in color and shape) and moment-to-moment feature change as it relates to the issue of whether subitizing and counting involve different processes. Participants enumerated displays of up to eight items that were either homogeneous or heterogeneous. In situations where the heterogeneous displays always had approximately half of the items of one type and half of the other, heterogeneity significantly sped enumeration in the counting range (6-8 items) and significantly slowed enumeration in the subitizing range (1-3 items), a dissociation that suggests that subitizing and counting involve different operations. Moment-to-moment feature change had no effect on subitizing. However, feature change slowed counting, but only when participants were enumerating heterogeneous items that were half of one type and half of the other, as might be expected if participants were using differences in features to select items by type.

  6. 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.

  7. 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

  8. 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 ...

  9. 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...

  10. 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...

  11. 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 ...

  12. Effect of Regional Heterogeneity on Flood Frequency Estimation

    NASA Astrophysics Data System (ADS)

    Lettenmaier, Dennis P.; Wallis, James R.; Wood, Eric F.

    1987-02-01

    Recent work on regional flood frequency estimation has shown that accurate flood quantile estimates are possible when the underlying flood frequency distributions are identical at all sites in the region except for a scaling factor, particularly when the underlying distribution has a two-parameter form. The class of regional probability-weighted moment (PWM) estimators is investigated for robustness to mis-specification of the assumed distributional form and to regional heterogeneity in moments of order higher than one. Whereas two-parameter distributions belonging to the extreme value family perform quite well when the form of the underlying distribution is close to that of the fitted distribution, large biases can result when the distribution is misspecified. The three-parameter generalized extreme value distribution (GEV), when fitted using the regional PWM method, has been shown to be relatively insensitive to violations of the distributional assumption, and to have low variability and bias. In this paper it is shown that regional estimation methods using the three-parameter GEV distribution are relatively insensitive to modest regional heterogeneity in the coefficient of variation and quite insensitive to regional variation in the skew coefficient. The key determinant of the performance of the regional estimators is shown to be the regional mean coefficient of variation. For high values of the mean coefficient of variation, such as might be encountered in arid regions, an alternate PWM estimation method based on the GEV distribution that accommodates the regional heterogeneity in the higher order moments is preferred. The trade-off between this alternate method and the approach that assumes regional homogeneity in moments higher than order one is sensitive to the record lengths.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Unilateral bony ankylosis of the temporomandibular joint in a case of ankylosing spondylitis.

    PubMed

    de Andrade Freitas Oliveira, Luciana Soares; de Oliveira-Santos, Christiano; de Melo, Daniela Pita; Gomes Torres, Marianna Guanaes; Flores Campos, Paulo Sérgio

    2013-09-01

    Ankylosing spondylitis (AS) is a chronic inflammatory disease with multiple articular and para-articular involvement that has a predilection for the axial skeleton. In spite of its high prevalence, ankylosis secondary to AS is a rare condition. A 31-year-old male diagnosed with AS was referred for computed tomography (CT) of the temporomandibular joint (TMJ) due to severe mouth opening limitation. The patient had a 16-year medical history of AS and sought assistance due to TMJ pain and incapacity to open his mouth. Previous bony scintigraphy revealed involvement of the spine, sacroiliac joints, right knee, and left TMJ. Magnetic resonance imaging revealed erosion of the left condyle and posterior slope of the articular eminence, and a mass of heterogeneous signal intensity between these structures. The left condyle also presented sclerosis/edema of the bone marrow and the disk could not be identified. Sagittal and coronal CT images showed moderate alterations of the TMJ on the right side. On the left side, the images displayed markedly eroded condyle and mandibular fossa, and a bony mass resulting in ankylosis of the osseous components of the joint. TMJ ankylosis in AS patients is rare and very few reports have presented imaging features of the condition through advanced diagnostic techniques.

  18. 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?

  19. 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.

  20. Estimating stream metabolism from oxygen concentrations: Effect of spatial heterogeneity

    NASA Astrophysics Data System (ADS)

    Reichert, Peter; Uehlinger, Urs; AcuñA, Vicenç

    2009-09-01

    Rivers are heterogeneous at various scales. River metabolism estimators based on oxygen time series provide average estimates of net oxygen production at the scale of a river reach. These estimators are derived for homogeneous river reaches. For this reason, they cannot be used to analyze how exactly they average over longitudinal variations in net production, reaeration, oxygen saturation concentration and flow velocity. We try to fill this gap by using a general analytical solution of the transport-reaction equation to (1) demonstrate how downstream oxygen concentration is affected by upstream concentration and (possible) longitudinally varying values of net production, reaeration, oxygen saturation concentration and flow velocity within a reach, and (2) derive how the net production estimate depends on varying upstream river parameters. In addition, we derive a new net production estimator that extends previously suggested estimators. The equations derived in this paper provide a general framework for understanding the assumptions underlying net production estimators. They are used to derive recommendations on the use of single station or two stations measurement layouts to get accurate river metabolism estimates. The estimator is implemented in the freely available statistics and graphics software package R (www.r-project.org). This makes it easily applicable to observed oxygen time series. Empirical evidence of the significance of heterogeneity in rivers is demonstrated by applying the estimator to four subsequent reaches of a river using oxygen measurements from the ends of all reaches.

  1. Is high T-1 slope a significant risk factor for developing interlaminar bony fusion after cervical laminoplasty? A retrospective cohort study.

    PubMed

    Oichi, Takeshi; Oshima, Yasushi; Oka, Hiroyuki; Taniguchi, Yuki; Chikuda, Hirotaka; Matsubayashi, Yoshitaka; Takeshita, Katsushi; Tanaka, Sakae

    2017-09-15

    OBJECTIVE Several investigators have reported the occurrence of interlaminar bony fusion after cervical laminoplasty, which is reportedly associated with reduced postoperative cervical range of motion (ROM). However, to the authors' knowledge, no previous study has investigated the characteristics of patients who were likely to develop interlaminar bony fusion after cervical laminoplasty. Therefore, the objective of this study was to investigate the risk factors for interlaminar bony fusion in patients with cervical spondylotic myelopathy (CSM) following cervical laminoplasty and to investigate the effect of interlaminar bony fusion on surgical outcomes. METHODS The authors retrospectively reviewed data from 92 patients with CSM (63 men and 29 women) after cervical laminoplasty. The presence of interlaminar bony fusion was evaluated by functional radiographs 2 years after surgery. The patients were divided into 2 groups according to the presence of postoperative interlaminar bony fusion: a fusion group (at least 1 new postoperative interlaminar bony fusion) and a nonfusion group (no new interlaminar bony fusion). Potential risk factors for postoperative interlaminar bony fusion were assessed, including diabetes mellitus, smoking status, whether the C-2 lamina was included in the surgical treatment, C2-7 Cobb angle in each cervical position, preoperative cervical ROM, and T-1 slope. The differences in each variable were compared between the fusion and nonfusion groups. Thereafter, multivariate logistic regression analysis was performed to identify the risk factors for postoperative interlaminar bony fusion. For surgical outcomes, the recovery rate based on Japanese Orthopaedic Association scores and the reduction rate of cervical ROM were evaluated 2 years after surgery. RESULTS Interlaminar bony fusion was observed in 60 cases, 52 of which were observed at the C2-3 level. Patients in the fusion group were significantly older, had a significantly larger C2-7 angle

  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 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

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. Effect of Population Heterogenization on the Reproducibility of Mouse Behavior: A Multi-Laboratory Study

    PubMed Central

    Richter, S. Helene; Garner, Joseph P.; Zipser, Benjamin; Lewejohann, Lars; Sachser, Norbert; Touma, Chadi; Schindler, Britta; Chourbaji, Sabine; Brandwein, Christiane; Gass, Peter; van Stipdonk, Niek; van der Harst, Johanneke; Spruijt, Berry; Võikar, Vootele; Wolfer, David P.; Würbel, Hanno

    2011-01-01

    In animal experiments, animals, husbandry and test procedures are traditionally standardized to maximize test sensitivity and minimize animal use, assuming that this will also guarantee reproducibility. However, by reducing within-experiment variation, standardization may limit inference to the specific experimental conditions. Indeed, we have recently shown in mice that standardization may generate spurious results in behavioral tests, accounting for poor reproducibility, and that this can be avoided by population heterogenization through systematic variation of experimental conditions. Here, we examined whether a simple form of heterogenization effectively improves reproducibility of test results in a multi-laboratory situation. Each of six laboratories independently ordered 64 female mice of two inbred strains (C57BL/6NCrl, DBA/2NCrl) and examined them for strain differences in five commonly used behavioral tests under two different experimental designs. In the standardized design, experimental conditions were standardized as much as possible in each laboratory, while they were systematically varied with respect to the animals' test age and cage enrichment in the heterogenized design. Although heterogenization tended to improve reproducibility by increasing within-experiment variation relative to between-experiment variation, the effect was too weak to account for the large variation between laboratories. However, our findings confirm the potential of systematic heterogenization for improving reproducibility of animal experiments and highlight the need for effective and practicable heterogenization strategies. PMID:21305027

  11. 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.

  12. 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.

  13. [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.

  14. PBNR: Percutaneous Blunt Needle Reduction of Bony Mallet Injuries.

    PubMed

    Miranda, Benjamin H; Murugesan, Logendra; Grobbelaar, Adriaan O; Jemec, Barbara

    2015-06-01

    Mallet finger injuries are common; treatment goals include achieving joint stability, preventing extensor lag, and subsequent swan-neck deformity. We describe a simple technique for improving intraoperative bony mallet reduction, which may avoid the requirement for closed Ishiguro extension blocking wires or open fixation, and present a prospective case series (n=12). Intraoperative percutaneous blunt needle reduction (PBNR) is achieved under image intensifier guidance. Using artery forceps, a blunt fill needle tip is manipulated onto the proximal avulsed fragment; this is then guided into a reduced position and maintained using a well-formed Zimmer splint across the distal interphalangeal joint in 15- to 30-degree extension. There were 5 injuries involving >1/3 of the articular surface (Doyle's classification IVb) and 7 injuries involving >1/2 of the articular surface (Doyle's classification IVc). Mean hand therapy follow-up was 10.6±1.0 weeks, extensor lag was 4.6±1.7 degrees, and all patients achieved full functional recovery with return to normal daily activity. No complications were reported. Closed techniques, for example, Ishiguro extension blocking wires, may reduce the risks associated with open reduction, but do not avoid further articular surface damage. PBNR offers the surgeon a useful adjunct to the treatment options for bony mallet injuries, without excluding progression to surgical fixation if required. PBNR represents a less-invasive management option for bony mallet injures where surgical fixation may also be indicated.

  15. Effects of subgrid heterogeneities in soil infiltration capacity and precipitation on regional climate: a sensitivity study

    NASA Astrophysics Data System (ADS)

    Zeng, X.-M.; Zhao, M.; Su, B.-K.; Tang, J.-P.; Zheng, Y.-Q.; Zhang, Y.-J.; Chen, J.

    One of the most pronounced features of the land surface is its heterogeneity. In order to further understand land-atmosphere interactions and improve climate modeling it is very important to investigate effects of subgrid scale heterogeneities, especially hydrological-process heterogeneities. In this paper, after the construction and sensitivity tests of a hydrological model (VXM), which accounts for precipitation heterogeneity (PH) and infiltration heterogeneity (IH), we incorporated VXM into the NCAR (National Center for Atmospheric Research) regional climate model RegCM2 and thus obtained the augmented regional climate model (hereafter, ARCM). By using 3-month (May-July) observational data of 1991 Meiyu season, we conducted numerical experiments with ARCM, analyzed the sensitivities, and found that: (1) The regional climate and surface hydrology are very sensitive to IH as well as PH, i.e., the simulations for the surface fluxes, soil temperature, soil moisture, precipitation and surface runoff can be greatly affected by those heterogeneities. (2) ARCM can effectively improve the simulation of hydrological processes, i.e., it can greatly enhance the surface runoff ratio (i.e., the ratio of surface runoff to precipitation), which is consistent with observations over humid areas in China. (3) It seems that the IH influence on the surface climate is larger than the PH influence. (4) The modeled climate is sensitive to the VXM parameters. For example, it is significantly modified after the surface impermeable fraction has been accounted for, suggesting some features of aridification.

  16. 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…

  17. 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.

  18. Development of numerical framework to study microstructural effects on shock initiation in heterogeneous energetic materials

    NASA Astrophysics Data System (ADS)

    Schmidt, Martin; Rai, Nirmal; Udaykumar, H. S.

    2015-06-01

    Heterogeneous energetic materials like plastic bonded explosives (PBX) have very detailed and non-uniform microstructure. The heterogeneity is mainly because of presence of HMX crystals embedded in a polymer binder matrix. Also, manufacturing defects often creates pores and cracks in the material. Shock interaction with these heterogeneities leads to local heated regions known as hot spots. It is widely accepted that these hot spots are predominantly the cause of triggering reaction and eventually ignition in these energetic materials. There are various physical phenomenon through which hot spot can be created such as pore collapse, inter-granular friction in HMX crystals, shock heating of HMX crystals and binder etc. Hence, microstructural heterogeneity can play a vital role for shock initiation in PBX. In the current work, a general framework has been established for performing mesoscale simulations on heterogeneous energetic material. In order to get an accurate representation of the microstructure, image processing algorithms have been employed on XCMT images of PBX microstructure. The image processing framework has been built up with massively parallel Eulerian code, SCIMITAR3D. Shock simulation on PBX microstructures has been performed and the effect of microstructure geometry has been studied for different shock strengths case. The simulation results have been shown to resolve hot spots created due to various heterogeneities present in the microstructure.

  19. 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.

  20. 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

  1. Evaluating heterogeneous conservation effects of forest protection in Indonesia.

    PubMed

    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.

  2. 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…

  3. 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…

  4. Meta-analysis of the effectiveness of chronic care management for diabetes: investigating heterogeneity in outcomes.

    PubMed

    Elissen, Arianne M J; Steuten, Lotte M G; Lemmens, Lidwien C; Drewes, Hanneke W; Lemmens, Karin M M; Meeuwissen, Jolanda A C; Baan, Caroline A; Vrijhoef, Hubertus J M

    2013-10-01

    The study aims to support decision making on how best to redesign diabetes care by investigating three potential sources of heterogeneity in effectiveness across trials of diabetes care management. Medline, CINAHL and PsycInfo were searched for systematic reviews and empirical studies focusing on: (1) diabetes mellitus; (2) adult patients; and (3) interventions consisting of at least two components of the chronic care model (CCM). Systematic reviews were analysed descriptively; empirical studies were meta-analysed. Pooled effect measures were estimated using a meta-regression model that incorporated study quality, length of follow-up and number of intervention components as potential predictors of heterogeneity in effects. Overall, reviews (n = 15) of diabetes care programmes report modest improvements in glycaemic control. Empirical studies (n = 61) show wide-ranging results on HbA1c, systolic blood pressure and guideline adherence. Differences between studies in methodological quality cannot explain this heterogeneity in effects. Variety in length of follow-up can explain (part of) the variability, yet not across all outcomes. Diversity in the number of included intervention components can explain 8-12% of the heterogeneity in effects on HbA1c and systolic blood pressure. The outcomes of chronic care management for diabetes are generally positive, yet differ considerably across trials. The most promising results are attained in studies with limited follow-up (<1 year) and by programmes including more than two CCM components. These factors can, however, explain only part of the heterogeneity in effectiveness between studies. Other potential sources of heterogeneity should be investigated to ensure implementation of evidence-based improvements in diabetes care. © 2012 John Wiley & Sons Ltd.

  5. 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.

  6. Effect of Material Property Heterogeneity on Biomechanical Modeling of Prostate under Deformation

    PubMed Central

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

    2015-01-01

    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 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 (MRI), 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 heterogeneous prostate model in the calculated displacement differences compared to 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 prostate could bepotentially 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 observed using heterogeneous models

  7. 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

  8. 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

  9. 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

  10. Limited Benefits of Heterogeneous Dual-Task Training on Transfer Effects in Older Adults.

    PubMed

    Lussier, Maxime; Brouillard, Philippe; Bherer, Louis

    2017-09-01

    It has often been reported that cognitive training has limited transfer effects. The present study addresses training context variability as a factor that could increase transfer effects, as well as the manifestation through time of transfer effects. Fifty-eight older adults were assigned to an active placebo or two dual-task training conditions, one in which the training context varies between sessions (heterogeneous training) and the other in a fixed training context (homogeneous training). Transfer was assessed with near and far-modality transfer tasks. Results show that heterogeneous and homogeneous training led to larger near-modality transfer effects than an active placebo (computer lessons). Transfer effects were roughly comparable in both training groups, but heterogeneous training led to a steeper improvement of the dual-task coordination learning curve within training sessions. Also, results indicated that dual-task cost did not improve in the active placebo group from the pre- to the post-training sessions. Heterogeneous training showed modest advantages over homogeneous training. Results also suggest that transfer effects on dual-task cost induced by training take place early on in the post-training session. These findings provide valuable insights on benefits arising from variability in the training protocol for maximizing transfer effects.

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

    PubMed

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

    2007-04-01

    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.

  12. 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.

  13. 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

  14. 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.

  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. 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…

  18. 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.

  19. Effects of fiber type and size on the heterogeneity of oxygen distribution in exercising skeletal muscle.

    PubMed

    Liu, Gang; Mac Gabhann, Feilim; Popel, Aleksander S

    2012-01-01

    The process of oxygen delivery from capillary to muscle fiber is essential for a tissue with variable oxygen demand, such as skeletal muscle. Oxygen distribution in exercising skeletal muscle is regulated by convective oxygen transport in the blood vessels, oxygen diffusion and consumption in the tissue. Spatial heterogeneities in oxygen supply, such as microvascular architecture and hemodynamic variables, had been observed experimentally and their marked effects on oxygen exchange had been confirmed using mathematical models. In this study, we investigate the effects of heterogeneities in oxygen demand on tissue oxygenation distribution using a multiscale oxygen transport model. Muscles are composed of different ratios of the various fiber types. Each fiber type has characteristic values of several parameters, including fiber size, oxygen consumption, myoglobin concentration, and oxygen diffusivity. Using experimentally measured parameters for different fiber types and applying them to the rat extensor digitorum longus muscle, we evaluated the effects of heterogeneous fiber size and fiber type properties on the oxygen distribution profile. Our simulation results suggest a marked increase in spatial heterogeneity of oxygen due to fiber size distribution in a mixed muscle. Our simulations also suggest that the combined effects of fiber type properties, except size, do not contribute significantly to the tissue oxygen spatial heterogeneity. However, the incorporation of the difference in oxygen consumption rates of different fiber types alone causes higher oxygen heterogeneity compared to control cases with uniform fiber properties. In contrast, incorporating variation in other fiber type-specific properties, such as myoglobin concentration, causes little change in spatial tissue oxygenation profiles.

  20. Effects of Fiber Type and Size on the Heterogeneity of Oxygen Distribution in Exercising Skeletal Muscle

    PubMed Central

    Liu, Gang; Mac Gabhann, Feilim; Popel, Aleksander S.

    2012-01-01

    The process of oxygen delivery from capillary to muscle fiber is essential for a tissue with variable oxygen demand, such as skeletal muscle. Oxygen distribution in exercising skeletal muscle is regulated by convective oxygen transport in the blood vessels, oxygen diffusion and consumption in the tissue. Spatial heterogeneities in oxygen supply, such as microvascular architecture and hemodynamic variables, had been observed experimentally and their marked effects on oxygen exchange had been confirmed using mathematical models. In this study, we investigate the effects of heterogeneities in oxygen demand on tissue oxygenation distribution using a multiscale oxygen transport model. Muscles are composed of different ratios of the various fiber types. Each fiber type has characteristic values of several parameters, including fiber size, oxygen consumption, myoglobin concentration, and oxygen diffusivity. Using experimentally measured parameters for different fiber types and applying them to the rat extensor digitorum longus muscle, we evaluated the effects of heterogeneous fiber size and fiber type properties on the oxygen distribution profile. Our simulation results suggest a marked increase in spatial heterogeneity of oxygen due to fiber size distribution in a mixed muscle. Our simulations also suggest that the combined effects of fiber type properties, except size, do not contribute significantly to the tissue oxygen spatial heterogeneity. However, the incorporation of the difference in oxygen consumption rates of different fiber types alone causes higher oxygen heterogeneity compared to control cases with uniform fiber properties. In contrast, incorporating variation in other fiber type-specific properties, such as myoglobin concentration, causes little change in spatial tissue oxygenation profiles. PMID:23028531

  1. Impact of Bony Stress Injuries on Professional Basketball Performance

    PubMed Central

    Khan, Moin; Madden, Kim; Rogowski, Joseph P.; Stotts, Jeff; Burrus, Matthew Tyrrell; Samani, Marisa; Sikka, Robby Singh; Bedi, Asheesh

    2017-01-01

    Objectives: Players in the National Basketball Association (NBA) subject their lower extremities to significant repetitive loading during the season as well as during off-season training. Little is known about the incidence and impact of lower extremity bony stress injuries in these athletes. Methods: Using the player injury database maintained by the NBA Players’ Association, all bony stress injuries from 1992 to May 2016 were identified. Those not involving the lower extremity were excluded from the study. Stress fractures and stress reactions were grouped together. Number of games missed due to the injury as well as player statistics including points per game (ppg), assists per game (apg), steals per game (spg), and blocks per game (bpg) were collected from two years prior to the injury to two years after the injury. Results: 76 lower extremity bony stress injuries were identified involving 75 different NBA players with an average player age of 25.4 ± 4.1 years. 55.3% (42/76) involved the foot, 21.1% (16/76) involved the ankle or fibula, 17.1% (13/76) involved the tibia, and 6.6% (5/76) involved either the knee or patella. The majority of injuries occurred in season 82.9% (63/76) with half of the injuries occurring within the first 6 weeks of the season. 38.2% (29/76) of these injuries were managed surgically. An average of 25.1 ± 21.3 games were missed. 19.7% (15/76) of patients who sustained a stress fracture also had a subsequent injury. 29.2% (21/76) of players were not able to return to professional basketball after the season in which the injury was sustained; however, those who were able to return to the same level of play did not see a significant change in performance as measured by ppg, apg, spg, or bpg when comparing the season prior to the injury and either one or two years after the injury. Stress injuries to the foot carried the worst prognosis, 57.1% (12/21) of those unable to return to professional basketball sustained such an injury

  2. Perceived Heterogeneity and Its Effect on Various Types of Tasks.

    DTIC Science & Technology

    1985-02-01

    and evaluation W instructions o~n a motor task, a creative -cognitive tas’ and a cogni-tiva decision-making task. An anonymous group technique was used...for group, showini DD I1JAN 73 1473 EDITION OF INOV 65IS OBSOLETE Ucasfe -~ O SECURITY CLASSIFICATION OF THI1S PACE 019100 Data "etoE S002 L-19.60 100 7...34S-.- - i ... ... This study investigated the effects of group composition and evaluation instructions on a motor task, a creative -cognitive task

  3. Local injection of substance P increases bony formation during mandibular distraction osteogenesis in rats.

    PubMed

    Zhang, Ya-bo; Wang, Lei; Jia, Sen; Du, Zhao-jie; Zhao, Ying-hua; Liu, Yan-pu; Lei, De-lin

    2014-10-01

    Substance P is a neuropeptide that is distributed in those sensory nerve fibres that innervate the medullary tissues of bone. It is a potent accelerator of proliferation and differentiation of osteoblasts in vitro. However, its capacity for promoting repair of mandibular defects is not known. We have investigated the osteogenic effects of local injections of substance P during mandibular distraction osteogenesis in rats. Twenty Sprague-Dawley rats were randomly assigned to 2 groups (n = 10 in each): substance P 10(-7) mmol/l in normal saline 0.2ml was injected into the experimental group, and saline alone into the controls. The mandibular distraction rate was 0.2mm every 12hours for 10 days. Daily injections of substance P or saline were given during the distraction period. Regeneration of bone was assessed quantitatively on days 15 and 29 using microcomputed tomography (microCT), and histological analysis. The rate of bony union in the group treated with substance P was significantly higher than that in the saline alone group on day 29 (p=0.001) The microCT images and quantitation showed more callus and more mature cortical bone when substance P was given than with control. Histological examination showed that cartilaginous tissues had formed in the middle of the distraction gaps in both groups. Bony bridges were seen only in the substance P group at the final time point (day 29). Injection of substance P into the gap of a rat mandible during mandibular distraction improved formation of good-quality bone and accelerated bony union. Copyright © 2014 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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…

  10. 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…

  11. 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)…

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Pneumatocyst, mimicking a sclerotic bony lesion on magnetic resonance imaging.

    PubMed

    Zarei, Fariba; Iranpour, Pooya

    2010-04-01

    Intravertebral pneumatocyst is an uncommon benign lesion, not related to conditions, such as osteomyelitis and postsurgical state, with only a few cases reported in the literature. The purpose of the study was to report a case of cervical pneumatocyst resembling a sclerotic lesion on magnetic resonance imaging (MRI) and review of literature. The study was designed to be a case report. The patient chosen was a 48-year-old woman with the chief complaint of neck pain and bilateral upper extremity paresthesia of 6 months duration. Neurologic examination and results of routine hematologic and biochemical examination were normal. Cervical spine MRI revealed a low signal bony lesion on T1 and T2 images. Considering the signal characteristics, initial diagnosis of sclerosis was made. Reviewing the cervical X-ray, a round faint lytic lesion was detected. Correlation with cervical computed tomography scan showed the lesion being of air density, compatible with the diagnosis of pneumatocyst. Intraosseous pneumatocyst of cervical spine is a benign finding, which needs no specific treatment; however, it must be included in the differential diagnosis of lucent vertebral lesions seen on conventional radiography and should be differentiated from bony neoplasm and osteomyelitis by its characteristic imaging findings.

  17. 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.

  18. 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

  19. Heterogeneous substitution effects in chlorocyanomethyl radical and chlorocyanocarbene.

    PubMed

    Khuseynov, Dmitry; Dixon, Andrew R; Goebbert, Daniel J; Sanov, Andrei

    2013-10-17

    We report a photoelectron-imaging investigation of the chlorocyanomethyl radical (CHClCN) and the corresponding carbene (CClCN). The results are discussed in comparison with the corresponding dichloro- and dicyano-substituted species, focusing on the divergent effects of the halogen and pseudohalogen (CN) substitutions. A cooperative (captodative) interaction of the π-donor Cl and π-acceptor cyano groups favors the increased stability of the CHClCN radical, but a competition of the two substituents is observed in the singlet-triplet splitting of the carbene. The vertical detachment energy (VDE) of CHClCN(-) is determined to be 2.39 ± 0.04 eV, with the broad photoelectron band consistent with the significant geometry change predicted by theory for the detachment transition. The adiabatic electron affinity of CHClCN, EA = 1.86 ± 0.08 eV, is estimated on the basis of the experimental VDE and the computed difference between the VDE and EA values. This result allows the calculation of the bond dissociation energy of chloroacetonitrile, DH298(H-CHClCN) = 87.0 ± 2.7 kcal/mol. Photoelectron imaging of CClCN(-) reveals two main transitions, assigned to the singlet ((1)A') and triplet ((3)A″) states of the CClCN carbene. The respective VDEs are 2.76 ± 0.05 and 3.25 ± 0.05 eV. The experimental results are in good agreement with the theoretically predicted singlet-triplet vertical energy gap at the anion geometry, but inconclusive with regard to the adiabatic singlet-triplet splitting in CClCN. Consistent with the experimental findings, ab initio calculations using the spin-flip approach in combination with the coupled-cluster theory, indicate that the (1)A' and (3)A″ states are nearly degenerate, with the singlet state lying adiabatically only ∼0.01 eV below the triplet.

  20. 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.

  1. The Heterogeneity of the Cigarette Price Effect on Body Mass Index

    PubMed Central

    Courtemanche, Charles J.

    2012-01-01

    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. PMID:22842751

  2. Calculation of effective slip on rough chemically heterogeneous surfaces using a homogenization approach.

    PubMed

    Lund, Nat J; Zhang, Xingyou Philip; Mahelona, Keoni; Hendy, Shaun C

    2012-10-01

    We present an expression for the effective slip length of a nanoscale rough chemically heterogeneous surface. A heterogeneous surface may be regarded as having an effective slip length generated by extrapolating the uniform velocity profile found in the far field. We consider two-dimensional steady-state Stokes flow over a surface that has periodic roughness and an intrinsic slip length varying over the same period. Using weak convergence methods for partial differential equations, we derive an expression for the effective slip length in terms of the intrinsic slip length and contact area of the surface. The result predicts that roughness causes a significant reduction in effective slip and that slip effects are dominated by the minimum intrinsic slip length of the system.

  3. 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.

  4. Effect of matrix chemical heterogeneity on effective filler interactions in model polymer nanocomposites.

    SciTech Connect

    Hall, Lisa Michelle

    2010-03-01

    The microscopic Polymer Reference Interaction Site Model theory has been applied to spherical and rodlike fillers dissolved in three types of chemically heterogeneous polymer melts: alternating AB copolymer, random AB copolymers, and an equimolar blend of two homopolymers. In each case, one monomer species adsorbs more strongly on the filler mimicking a specific attraction, while all inter-monomer potentials are hard core which precludes macrophase or microphase separation. Qualitative differences in the filler potential-of-mean force are predicted relative to the homopolymer case. The adsorbed bound layer for alternating copolymers exhibits a spatial moduluation or layering effect but is otherwise similar to that of the homopolymer system. Random copolymers and the polymer blend mediate a novel strong, long-range bridging interaction between fillers at moderate to high adsorption strengths. The bridging strength is a non-monotonic function of random copolymer composition, reflecting subtle competing enthalpic and entropic considerations.

  5. The effect of material heterogeneities in long term multiscale seismic cycle simulations

    NASA Astrophysics Data System (ADS)

    Kyriakopoulos, C.; Richards-Dinger, K. B.; Dieterich, J. H.

    2016-12-01

    A fundamental part of the simulation of the earthquake cycles in large-scale multicycle earthquake simulators is the pre-computation of elastostatic Greens functions collected into the stiffness matrix (K). The stiffness matrices are typically based on the elastostatic solutions of Okada (1992), Gimbutas et al. (2012), or similar. While these analytic solutions are computationally very fast, they are limited to modeling a homogeneous isotropic half-space. It is thus unknown how such simulations may be affected by material heterogeneity characterizing the earth medium. We are currently working on the estimation of the effects of heterogeneous material properties in the earthquake simulator RSQSim (Richards-Dinger and Dieterich, 2012). In order to do that we are calculating elastostatic solutions in a heterogeneous medium using the Finite Element (FE) method instead of any of the analytical solutions. The investigated region is a 400 x 400 km area centered on the Anza zone in southern California. The fault system geometry is based on that of the UCERF3 deformation models in the area of interest, which we then implement in a finite element mesh using Trelis 15. The heterogeneous elastic structure is based on available tomographic data (seismic wavespeeds and density) for the region (SCEC CVM and Allam et al., 2014). For computation of the Greens functions we are using the open source FE code Defmod (https://bitbucket.org/stali/defmod/wiki/Home) to calculate the elastostatic solutions due to unit slip on each patch. Earthquake slip on the fault plane is implemented through linear constraint equations (Ali et al., 2014, Kyriakopoulos et al., 2013, Aagard et al, 2015) and more specifically with the use of Lagrange multipliers adjunction. The elementary responses are collected into the "heterogeneous" stiffness matrix Khet and used in RSQSim instead of the ones generated with Okada. Finally, we compare the RSQSim results based on the "heterogeneous" Khet with results from

  6. 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.

  7. 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.

  8. Combined effects of landscape composition and heterogeneity on farmland avian diversity.

    PubMed

    Santana, Joana; Reino, Luís; Stoate, Chris; Moreira, Francisco; Ribeiro, Paulo F; Santos, José L; Rotenberry, John T; Beja, Pedro

    2017-02-01

    Conserving biodiversity on farmland is an essential element of worldwide efforts for reversing the global biodiversity decline. Common approaches involve improving the natural component of the landscape by increasing the amount of natural and seminatural habitats (e.g., hedgerows, woodlots, and ponds) or improving the production component of the landscape by increasing the amount of biodiversity-friendly crops. Because these approaches may negatively impact on economic output, it was suggested that an alternative might be to enhance the diversity (compositional heterogeneity) or the spatial complexity (configurational heterogeneity) of land cover types, without necessarily changing composition. Here, we develop a case study to evaluate these ideas, examining whether managing landscape composition or heterogeneity, or both, would be required to achieve conservation benefits on avian diversity in open Mediterranean farmland. We surveyed birds in farmland landscapes of southern Portugal, before (1995-1997) and after (2010-2012) the European Union's Common Agricultural Policy (CAP) reform of 2003, and related spatial and temporal variation in bird species richness to variables describing the composition, and the compositional and configurational heterogeneity, of the natural and production components of the landscape. We found that the composition of the production component had the strongest effects on avian diversity, with a particularly marked effect on the richness of farmland and steppe bird species. Composition of the natural component was also influential, mainly affecting the richness of woodland/shrubland species. Although there were some effects of compositional and configurational heterogeneity, these were much weaker and inconsistent than those of landscape composition. Overall, we suggest that conservation efforts in our area should focus primarily on the composition of the production component, by striving to maximize the prevalence of biodiversity

  9. 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.

  10. A new "double-pulley" dual-row technique for arthroscopic fixation of bony Bankart lesion.

    PubMed

    Zhang, Jin; Jiang, Chunyan

    2011-09-01

    The double-row technique is a new concept for arthroscopic treatment of bony Bankart lesion in shoulder instability. It presents a new and reproducible technique for arthroscopic fixation of bony Bankart fragments with suture anchors. This technique creates double-mattress sutures which compress the fragment against its bone bed and restores better bony anatomy of the anterior glenoid rim with stable and non-tilting fixation that may improve healing.

  11. 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.

  12. The effect of environmental heterogeneity on species richness depends on community position along the environmental gradient

    PubMed Central

    Yang, Zhiyong; Liu, Xueqi; Zhou, Mohua; Ai, Dexiecuo; Wang, Gang; Wang, Youshi; Chu, Chengjin; Lundholm, Jeremy T.

    2015-01-01

    Environmental heterogeneity is among the most important factors governing community structure. Besides the widespread evidence supporting positive relationships between richness and environmental heterogeneity, negative and unimodal relationships have also been reported. However, few studies have attempted to test the role of the heterogeneity on species richness after removing the confounding effect of resource availability or environmental severity. Here we constructed an individual-based spatially explicit model incorporating a long-recognized tradeoff between competitive ability and stress-tolerance ability of species. We explored the impact of the level of resource availability (i.e. the position of the community along a gradient of environmental severity) on the heterogeneity-diversity relationship (HDR). The results indicate that the shape of HDR depends on the community position along the environmental gradient: at either end of the gradient of environmental severity, a positive HDR occurred, whereas at the intermediate levels of the gradient, a unimodal HDR emerged. Our exploration demonstrates that resource availability/environmental severity should be considered as a potential factor influencing the shape of the HDR. Our theoretical predictions represent hypotheses in need of further empirical study. PMID:26508413

  13. 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.

  14. The effect of environmental heterogeneity on species richness depends on community position along the environmental gradient.

    PubMed

    Yang, Zhiyong; Liu, Xueqi; Zhou, Mohua; Ai, Dexiecuo; Wang, Gang; Wang, Youshi; Chu, Chengjin; Lundholm, Jeremy T

    2015-10-28

    Environmental heterogeneity is among the most important factors governing community structure. Besides the widespread evidence supporting positive relationships between richness and environmental heterogeneity, negative and unimodal relationships have also been reported. However, few studies have attempted to test the role of the heterogeneity on species richness after removing the confounding effect of resource availability or environmental severity. Here we constructed an individual-based spatially explicit model incorporating a long-recognized tradeoff between competitive ability and stress-tolerance ability of species. We explored the impact of the level of resource availability (i.e. the position of the community along a gradient of environmental severity) on the heterogeneity-diversity relationship (HDR). The results indicate that the shape of HDR depends on the community position along the environmental gradient: at either end of the gradient of environmental severity, a positive HDR occurred, whereas at the intermediate levels of the gradient, a unimodal HDR emerged. Our exploration demonstrates that resource availability/environmental severity should be considered as a potential factor influencing the shape of the HDR. Our theoretical predictions represent hypotheses in need of further empirical study.

  15. 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. (c) 2015 APA, all rights reserved).

  16. Evaluation of aquifer heterogeneity effects on river flow loss using a transition probability framework

    USGS Publications Warehouse

    Engdahl, N.B.; Vogler, E.T.; Weissmann, G.S.

    2010-01-01

    River-aquifer exchange is considered within a transition probability framework along the Rio Grande in Albuquerque, New Mexico, to provide a stochastic estimate of aquifer heterogeneity and river loss. Six plausible hydrofacies configurations were determined using categorized drill core and wetland survey data processed through the TPROGS geostatistical package. A base case homogeneous model was also constructed for comparison. River loss was simulated for low, moderate, and high Rio Grande stages and several different riverside drain stage configurations. Heterogeneity effects were quantified by determining the mean and variance of the K field for each realization compared to the root-mean-square (RMS) error of the observed groundwater head data. Simulation results showed that the heterogeneous models produced smaller estimates of loss than the homogeneous approximation. Differences between heterogeneous and homogeneous model results indicate that the use of a homogeneous K in a regional-scale model may result in an overestimation of loss but comparable RMS error. We find that the simulated river loss is dependent on the aquifer structure and is most sensitive to the volumetric proportion of fines within the river channel. Copyright 2010 by the American Geophysical Union.

  17. 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.

  18. Inverted 'V' osteotomy excision arthroplasty for bony ankylosed elbows

    PubMed Central

    2011-01-01

    Background Bony ankylosis of elbow is challenging and difficult problem to treat. The options are excision arthroplasty and total elbow replacement. We report our midterm results on nine patients, who underwent inverted 'V' osteotomy excision arthroplasty in our hospital with good functional results. Materials Our case series includes 9 patients (seven males and two females) with the mean age of 34 years (13-56 years). Five patients had trauma, two had pyogenic arthritis, one had tuberculous arthritis, and one had pyogenic arthritis following surgical fixation. Results The average duration of follow up is 65 months (45 months-80 months). The mean Mayo's elbow performance score (MEPS) preoperatively was 48 (35-70). The MEPS at final follow up was 80 (60-95). With no movement at elbow and fixed in various degrees of either flexion or extension preoperatively, the mean preoperative position of elbow was 64°(30°to 100°). The mean post operative range of motion at final follow up was 27°of extension (20-500), 116°of flexion (1100-1300), and the arc of motion was 88°(800-1000). One patient had ulnar nerve neuropraxia and another patient developed median nerve neuropraxia, and both recovered completely in six weeks. No patient had symptomatic instability of the elbow. All patients were asymptomatic except one patient, who had pain mainly on heavy activities. Conclusion We conclude that inverted 'V' osteotomy excision arthroplasty is a viable option in the treatment of bony ankylosis of the elbow in young patients. PMID:22142391

  19. Inverted 'V' osteotomy excision arthroplasty for bony ankylosed elbows.

    PubMed

    Rex, Chadrabose; Periyasamy, Rameshkumar; Balaji, Subbachandra; Premanand, C; Alva, Shreyas; Reddy, Shiva

    2011-12-05

    Bony ankylosis of elbow is challenging and difficult problem to treat. The options are excision arthroplasty and total elbow replacement. We report our midterm results on nine patients, who underwent inverted 'V' osteotomy excision arthroplasty in our hospital with good functional results. Our case series includes 9 patients (seven males and two females) with the mean age of 34 years (13-56 years). Five patients had trauma, two had pyogenic arthritis, one had tuberculous arthritis, and one had pyogenic arthritis following surgical fixation. The average duration of follow up is 65 months (45 months-80 months). The mean Mayo's elbow performance score (MEPS) preoperatively was 48 (35-70). The MEPS at final follow up was 80 (60-95). With no movement at elbow and fixed in various degrees of either flexion or extension preoperatively, the mean preoperative position of elbow was 64°(30°to 100°). The mean post operative range of motion at final follow up was 27°of extension (20-500), 116°of flexion (1100-1300), and the arc of motion was 88°(800-1000). One patient had ulnar nerve neuropraxia and another patient developed median nerve neuropraxia, and both recovered completely in six weeks. No patient had symptomatic instability of the elbow. All patients were asymptomatic except one patient, who had pain mainly on heavy activities. We conclude that inverted 'V' osteotomy excision arthroplasty is a viable option in the treatment of bony ankylosis of the elbow in young patients.

  20. Heterogeneous treatment effects in stratified clinical trials with time-to-event endpoints.

    PubMed

    Beisel, Christina; Benner, Axel; Kunz, Christina; Kopp-Schneider, Annette

    2017-05-01

    When analyzing clinical trials with a stratified population, homogeneity of treatment effects is a common assumption in survival analysis. However, in the context of recent developments in clinical trial design, which aim to test multiple targeted therapies in corresponding subpopulations simultaneously, the assumption that there is no treatment-by-stratum interaction seems inappropriate. It becomes an issue if the expected sample size of the strata makes it unfeasible to analyze the trial arms individually. Alternatively, one might choose as primary aim to prove efficacy of the overall (targeted) treatment strategy. When testing for the overall treatment effect, a violation of the no-interaction assumption renders it necessary to deviate from standard methods that rely on this assumption. We investigate the performance of different methods for sample size calculation and data analysis under heterogeneous treatment effects. The commonly used sample size formula by Schoenfeld is compared to another formula by Lachin and Foulkes, and to an extension of Schoenfeld's formula allowing for stratification. Beyond the widely used (stratified) Cox model, we explore the lognormal shared frailty model, and a two-step analysis approach as potential alternatives that attempt to adjust for interstrata heterogeneity. We carry out a simulation study for a trial with three strata and violations of the no-interaction assumption. The extension of Schoenfeld's formula to heterogeneous strata effects provides the most reliable sample size with respect to desired versus actual power. The two-step analysis and frailty model prove to be more robust against loss of power caused by heterogeneous treatment effects than the stratified Cox model and should be preferred in such situations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. 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

  2. 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.

  3. 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.

  4. Effects of seed particle size and composition on heterogeneous nucleation of n-nonane

    NASA Astrophysics Data System (ADS)

    Winkler, Paul M.; Hienola, Anca; Steiner, Gerhard; Hill, Gerard; Vrtala, Aron; Reischl, Georg P.; Kulmala, Markku; Wagner, Paul E.

    2008-11-01

    Heterogeneous nucleation of supersaturated n-nonane vapour on seed particles of different size and composition has been investigated using a fast expansion chamber. Monodisperse seed particle sizes were ranging from about 4 nm up to about 24 nm in diameter. By using different types of particle generators WO x, Ag and (NH 4) 2SO 4 particles were generated. For direct comparison between different particle compositions overlapping sizes have been generated for WO x and Ag at about 7 nm particle diameter as well as for Ag and (NH 4) 2SO 4 at about 15 nm. Nucleation temperature was kept constant at about 278 K. Experimental data were compared to Kelvin equation and Fletcher theory including the effect of line tension. It was found that heterogeneous nucleation of n-nonane seems to be independent of seed particle composition and starts well below the Kelvin curve. Good agreement was achieved with Fletcher theory including the effect of line tension.

  5. 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

  6. 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.

  7. 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.

  8. The effect of dose heterogeneity on radiation risk in medical imaging.

    PubMed

    Samei, Ehsan; Li, Xiang; Chen, Baiyu; Reiman, Robert

    2013-06-01

    The current estimations of risk associated with medical imaging procedures rely on assessing the organ dose via direct measurements or simulation. The dose to each organ is assumed to be homogeneous. To take into account the differences in radiation sensitivities, the mean organ doses are weighted by a corresponding tissue-weighting coefficients provided by ICRP to calculate the effective dose, which has been used as a surrogate of radiation risk. However, those coefficients were derived under the assumption of a homogeneous dose distribution within each organ. That assumption is significantly violated in most medical-imaging procedures. In helical chest CT, for example, superficial organs (e.g. breasts) demonstrate a heterogeneous dose distribution, whereas organs on the peripheries of the irradiation field (e.g. liver) might possess a discontinuous dose profile. Projection radiography and mammography involve an even higher level of organ dose heterogeneity spanning up to two orders of magnitude. As such, mean dose or point measured dose values do not reflect the maximum energy deposited per unit volume of the organ. In this paper, the magnitude of the dose heterogeneity in both CT and projection X-ray imaging was reported, using Monte Carlo methods. The lung dose demonstrated factors of 1.7 and 2.2 difference between the mean and maximum dose for chest CT and radiography, respectively. The corresponding values for the liver were 1.9 and 3.5. For mammography and breast tomosynthesis, the difference between mean glandular dose and maximum glandular dose was 3.1. Risk models based on the mean dose were found to provide a reasonable reflection of cancer risk. However, for leukaemia, they were found to significantly under-represent the risk when the organ dose distribution is heterogeneous. A systematic study is needed to develop a risk model for heterogeneous dose distributions.

  9. 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

  10. 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

  11. Flow and transport in unsaturated fractured rock: effects of multiscale heterogeneity of hydrogeologic properties.

    PubMed

    Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur S; Oldenburg, Curtis M

    2003-01-01

    The heterogeneity of hydrogeologic properties at different scales may have different effects on flow and transport processes in a subsurface system. A model for the unsaturated zone of Yucca Mountain, Nevada, is developed to represent complex heterogeneity at two different scales: (1) layer scale corresponding to geologic layering and (2) local scale. The layer-scale hydrogeologic properties are obtained using inverse modeling, based on the available measurements collected from the Yucca Mountain site. Calibration results show a significant lateral and vertical variability in matrix and fracture properties. Hydrogeologic property distributions in a two-dimensional, vertical cross-section of the site are generated by combining the average layer-scale matrix and fracture properties with local-scale perturbations generated using a stochastic simulation method. The unsaturated water flow and conservative (nonsorbing) tracer transport through the cross-section are simulated for different sets of matrix and fracture property fields. Comparison of simulation results indicates that the local-scale heterogeneity of matrix and fracture properties has a considerable effect on unsaturated flow processes, leading to fast flow paths in fractures and the matrix. These paths shorten the travel time of a conservative tracer from the source (repository) horizon in the unsaturated zone to the water table for small fractions of total released tracer mass. As a result, the local-scale heterogeneity also has a noticeable effect on global tracer transport processes, characterized by an average breakthrough curve at the water table, especially at the early arrival time of tracer mass. However, the effect is not significant at the later time after 20% tracer mass reaches the water table. The simulation results also verify that matrix diffusion plays an important role in overall solute transport processes in the unsaturated zone at Yucca Mountain.

  12. 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.

  13. Oral bony outgrowths: prevalence and genetic factor influence. Study of twins.

    PubMed

    Auškalnis, Adomas; Bernhardt, Olaf; Putnienė, Eglė; Šidlauskas, Antanas; Andriuškevičiūtė, Irena; Basevičienė, Nomeda

    2015-01-01

    The aim of the study was to verify the influence of a genetic factor on the etiology of oral bony outgrowths and to determine the prevalence and type of oral bony outgrowths (tori and exostoses) among a group of Lithuanian twins. In total, 162 twins (81 twin pairs) were analyzed for the presence or absence, type, and size of oral bony outgrowths. Statistical analysis was carried out to find the prevalence of bony protuberances and the relationship between zygosity and occurrence of oral bony enlargements. Zygosity of twins was confirmed by DNA analysis. 59.9% of the subjects had oral bony outgrowths. Mandibular tori were found in 56.8% and palatal tori in 1.8% of the sample. Palatal exostoses and mandibular exostoses were present in 1.8% and 3.1% of the sample, respectively, whereas maxillary exostoses were not found. A higher percentage of tori and exostoses were found in the group of older subjects (>18 years old, p=0.025). No significant difference was found between men and women in the prevalence of bony outgrowths. High κ and r values (0.91±0.062) showed very good concordance of oral bony outgrowths between monozygotic and moderate concordance (0.58±0.141) between dizygotic co-twins (p<0.001). The calculation of heritability estimate verifies dominant influence of genetic factor on the etiology of oral bony outgrowths (h(2)=0.658). The most common bony outgrowth was torus mandibularis. Our results show that the genetic factor is dominant in the etiology of oral bony outgrowths. Copyright © 2015 Lithuanian University of Health Sciences. Production and hosting by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

  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. 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.

  16. 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).

  17. 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

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

    PubMed

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

    2010-07-01

    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. 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. 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. 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.

  19. Identifying treatment effect heterogeneity in clinical trials using subpopulations of events: STEPP.

    PubMed

    Lazar, Ann A; Bonetti, Marco; Cole, Bernard F; Yip, Wai-Ki; Gelber, Richard D

    2016-04-01

    Investigators conducting randomized clinical trials often explore treatment effect heterogeneity to assess whether treatment efficacy varies according to patient characteristics. Identifying heterogeneity is central to making informed personalized healthcare decisions. Treatment effect heterogeneity can be investigated using subpopulation treatment effect pattern plot (STEPP), a non-parametric graphical approach that constructs overlapping patient subpopulations with varying values of a characteristic. Procedures for statistical testing using subpopulation treatment effect pattern plot when the endpoint of interest is survival remain an area of active investigation. A STEPP analysis was used to explore patterns of absolute and relative treatment effects for varying levels of a breast cancer biomarker, Ki-67, in the phase III Breast International Group 1-98 randomized clinical trial, comparing letrozole to tamoxifen as adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer. Absolute treatment effects were measured by differences in 4-year cumulative incidence of breast cancer recurrence, while relative effects were measured by the subdistribution hazard ratio in the presence of competing risks using O-E (observed-minus-expected) methodology, an intuitive non-parametric method. While estimation of hazard ratio values based on O-E methodology has been shown, a similar development for the subdistribution hazard ratio has not. Furthermore, we observed that the subpopulation treatment effect pattern plot analysis may not produce results, even with 100 patients within each subpopulation. After further investigation through simulation studies, we observed inflation of the type I error rate of the traditional test statistic and sometimes singular variance-covariance matrix estimates that may lead to results not being produced. This is due to the lack of sufficient number of events within the subpopulations, which we refer to as instability of

  20. 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.

  1. 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. ©2010 The British Psychological Society.

  2. 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.

  3. 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.

  4. 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.

  5. Effect of heterogeneity on radionuclide retardation in the alluvial aquifer near Yucca Mountain, Nevada.

    PubMed

    Painter, S; Cvetkovic, V; Turner, D R

    2001-01-01

    The U.S. Department of Energy is currently studying Yucca Mountain, Nevada, as a potential site for a geological high-level waste repository. In the current conceptual models of radionuclide transport at Yucca Mountain, part of the transport path to pumping locations would be through an alluvial aquifer. Interactions with minerals in the alluvium are expected to retard the downstream migration of radionuclides, thereby delaying arrival times and reducing ground water concentrations. We evaluate the effectiveness of the alluvial aquifer as a transport barrier using the stochastic Lagrangian framework. A transport model is developed to account for physical and chemical heterogeneities and rate-limited mass transfer between mobile and immobile zones. The latter process is caused by small-scale heterogeneity and is thought to control the macroscopic-scale retardation in some field experiments. A geostatistical model for the spatially varying sorption parameters is developed from a site-specific database created from hydrochemical measurements and a calibrated modeling approach (Turner and Pabalan 1999). Transport of neptunium is considered as an example. The results are sensitive to the rate of transfer between mobile and immobile zones, and to spatial variability in the hydraulic conductivity. Chemical heterogeneity has only a small effect, as does correlation between hydraulic conductivity and the neptunium distribution coefficient. These results illustrate how general sensitivities can be explored with modest effort within the Lagrangian framework. Such studies complement and guide the application of more detailed numerical simulations.

  6. 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.

  7. 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

  8. Dealing with heterogeneity of treatment effects: is the literature up to the challenge?

    PubMed

    Gabler, Nicole B; Duan, Naihua; Liao, Diana; Elmore, Joann G; Ganiats, Theodore G; Kravitz, Richard L

    2009-06-19

    Some patients will experience more or less benefit from treatment than the averages reported from clinical trials; such variation in therapeutic outcome is termed heterogeneity of treatment effects (HTE). Identifying HTE is necessary to individualize treatment. The degree to which heterogeneity is sought and analyzed correctly in the general medical literature is unknown. We undertook this literature sample to track the use of HTE analyses over time, examine the appropriateness of the statistical methods used, and explore the predictors of such analyses. Articles were selected through a probability sample of randomized controlled trials (RCTs) published in Annals of Internal Medicine, BMJ, JAMA, The Lancet, and NEJM during odd numbered months of 1994, 1999, and 2004. RCTs were independently reviewed and coded by two abstractors, with adjudication by a third. Studies were classified as reporting: (1) HTE analysis, utilizing a formal test for heterogeneity or treatment-by-covariate interaction, (2) subgroup analysis only, involving no formal test for heterogeneity or interaction; or (3) neither. Chi-square tests and multiple logistic regression were used to identify variables associated with HTE reporting. 319 studies were included. Ninety-two (29%) reported HTE analysis; another 88 (28%) reported subgroup analysis only, without examining HTE formally. Major covariates examined included individual risk factors associated with prognosis, responsiveness to treatment, or vulnerability to adverse effects of treatment (56%); gender (30%); age (29%); study site or center (29%); and race/ethnicity (7%). Journal of publication and sample size were significant independent predictors of HTE analysis (p < 0.05 and p < 0.001, respectively). HTE is frequently ignored or incorrectly analyzed. An iterative process of exploratory analysis followed by confirmatory HTE analysis will generate the data needed to facilitate an individualized approach to evidence-based medicine.

  9. 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

  10. The effect of age on skin color and color heterogeneity in four ethnic groups.

    PubMed

    de Rigal, Jean; Des Mazis, Isabelle; Diridollou, Stephane; Querleux, Bernard; Yang, Grace; Leroy, Frederce; Barbosa, Vietoria Holloway

    2010-05-01

    Few comparative data are available on age-related changes in skin color among different ethnic groups. The aim of the study was to measure and analyze the skin color and color heterogeneity in four different ethnic groups living in the same local environment and to determine the effects of age on these skin color characteristics. Female volunteers (385) from four ethnic populations (African-American, Caucasian, Chinese and Mexicans) living in the same city were enrolled after informed consent. Skin color was measured on two facial areas, forehead and cheek. The subjects were further divided into six age ranges: 19-30, 31-40, 41-50, 51-60, 61-70 and 71-87 years to determine any age-related effects on the skin color and color heterogeneity in both areas. According to the L(*)a(*)b(*) CIE system, clarity (fairness/lightness) was found to be lower in the African-American group whereas the hue was lower in Caucasians, which means more red skin. A clear, statistically significant darkening of the skin with age was observed in all ethnic groups, while evidence of yellowing of the skin was shown in the Chinese volunteers. Overall, the skin color of the face of African-Americans was more heterogeneous than in the other ethnic groups, but showed the least increase with age. Our study revealed interesting differences in skin color and color heterogeneity with respect to ethnicity and age-related alterations. Data obtained are very useful in improving our knowledge about the skin of people of different origins and helps in the development of specific cosmetic products that are well adapted to all these populations.

  11. 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

  12. Potential implications of the bystander effect on TCP and EUD when considering target volume dose heterogeneity.

    PubMed

    Balderson, Michael J; Kirkby, Charles

    2015-01-01

    In light of in vitro evidence suggesting that radiation-induced bystander effects may enhance non-local cell killing, there is potential for impact on radiotherapy treatment planning paradigms such as the goal of delivering a uniform dose throughout the clinical target volume (CTV). This work applies a bystander effect model to calculate equivalent uniform dose (EUD) and tumor control probability (TCP) for external beam prostate treatment and compares the results with a more common model where local response is dictated exclusively by local absorbed dose. The broad assumptions applied in the bystander effect model are intended to place an upper limit on the extent of the results in a clinical context. EUD and TCP of a prostate cancer target volume under conditions of increasing dose heterogeneity were calculated using two models: One incorporating bystander effects derived from previously published in vitro bystander data ( McMahon et al. 2012 , 2013a); and one using a common linear-quadratic (LQ) response that relies exclusively on local absorbed dose. Dose through the CTV was modelled as a normal distribution, where the degree of heterogeneity was then dictated by changing the standard deviation (SD). Also, a representative clinical dose distribution was examined as cold (low dose) sub-volumes were systematically introduced. The bystander model suggests a moderate degree of dose heterogeneity throughout a target volume will yield as good or better outcome compared to a uniform dose in terms of EUD and TCP. For a typical intermediate risk prostate prescription of 78 Gy over 39 fractions maxima in EUD and TCP as a function of increasing SD occurred at SD ∼ 5 Gy. The plots only dropped below the uniform dose values for SD ∼ 10 Gy, almost 13% of the prescribed dose. Small, but potentially significant differences in the outcome metrics between the models were identified in the clinically-derived dose distribution as cold sub-volumes were introduced. In terms of

  13. 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

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

    PubMed

    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

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. The effects of transit time heterogeneity on brain oxygenation during rest and functional activation

    PubMed Central

    Rasmussen, Peter M; Jespersen, Sune N; Østergaard, Leif

    2015-01-01

    The interpretation of regional blood flow and blood oxygenation changes during functional activation has evolved from the concept of ‘neurovascular coupling', and hence the regulation of arteriolar tone to meet metabolic demands. The efficacy of oxygen extraction was recently shown to depend on the heterogeneity of capillary flow patterns downstream. Existing compartment models of the relation between tissue metabolism, blood flow, and blood oxygenation, however, typically assume homogenous microvascular flow patterns. To take capillary flow heterogeneity into account, we modeled the effect of capillary transit time heterogeneity (CTH) on the ‘oxygen conductance' used in compartment models. We show that the incorporation of realistic reductions in CTH during functional hyperemia improves model fits to dynamic blood flow and oxygenation changes acquired during functional activation in a literature animal study. Our results support earlier observations that oxygen diffusion properties seemingly change during various physiologic stimuli, and posit that this phenomenon is related to parallel changes in capillary flow patterns. Furthermore, our results suggest that CTH must be taken into account when inferring brain metabolism from changes in blood flow- or blood oxygenation-based signals . PMID:25492112

  2. Effects of dispersal and environmental heterogeneity on the replacement and nestedness components of β-diversity.

    PubMed

    Gianuca, Andros T; Declerck, Steven A J; Lemmens, Pieter; De Meester, Luc

    2017-02-01

    Traditionally metacommunity studies have quantified the relative importance of dispersal and environmental processes on observed β-diversity. Separating β-diversity into its replacement and nestedness components and linking such patterns to metacommunity drivers can provide richer insights into biodiversity organization across spatial scales. It is often very difficult to measure actual dispersal rates in the field and to define the boundaries of natural metacommunities. To overcome those limitations, we revisited an experimental metacommunity dataset to test the independent and interacting effects of environmental heterogeneity and dispersal on each component of β-diversity. We show that the balance between the replacement and nestedness components of β-diversity resulting from eutrophication changes completely depending on dispersal rates. Nutrient enrichment negatively affected local zooplankton diversity and generated a pattern of β-diversity derived from nestedness in unconnected, environmentally heterogeneous landscapes. Increasing dispersal erased the pattern of nestedness, whereas the replacement component gained importance. In environmentally homogeneous metacommunities, dispersal limitation created community dissimilarity via species replacement whereas the nestedness component remained low and unchanged across dispersal levels. Our study provides novel insights into how environmental heterogeneity and dispersal interact and shape metacommunity structure. © 2016 by the Ecological Society of America.

  3. 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.

  4. The effects of nitrate on the heterogeneous uptake of sulfur dioxide on hematite

    NASA Astrophysics Data System (ADS)

    Kong, L. D.; Zhao, X.; Sun, Z. Y.; Yang, Y. W.; Fu, H. B.; Zhang, S. C.; Cheng, T. T.; Yang, X.; Wang, L.; Chen, J. M.

    2014-09-01

    Nitrate is often found to be associated with atmospheric particles. Surface nitrate can change the hygroscopicity of these particles, and thus impact their chemical reactivity. However, the influence of nitrate on heterogeneous reactions of atmospheric trace gases is poorly understood. In this work, the effects of nitrate on heterogeneous conversion of SO2 with hematite at 298 K are investigated using an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and a White cell coupled with Fourier transform infrared spectroscopy (White cell-FTIR). It is found that nitrate participates in heterogeneous reactions of SO2, accelerates the formation rate of sulfate, and leads to the formation of surface-adsorbed HNO3 and gas-phase N2O and HONO. The results indicate that low to moderate amounts of nitrate significantly enhance the reactivity of hematite-nitrate mixtures, the uptake of SO2, and the formation of sulfate on hematite. For mixtures, the sample containing 24% nitrate exhibits the highest sulfate formation rate, and its corresponding uptake coefficient calculated by geometric surface area is about 5.5 times higher than that of hematite alone. The sample containing 48% nitrate presents the highest Brunauer-Emmett-Teller (BET) uptake coefficient, and the value is about 8 times higher than that of pure hematite. No uptake of SO2 and formation of sulfate are observed on pure nitrate. Evidence presented herein implies a significant contribution of the unreleased HNO3 and HONO in the particles for the conversion of SO2 and the enhanced formation of sulfate in the atmosphere. A possible mechanism for the influence of nitrate on the heterogeneous conversion of SO2 on hematite is proposed, and atmospheric implications based on these results are discussed.

  5. The mammalian bony labyrinth reconsidered, introducing a comprehensive geometric morphometric approach

    PubMed Central

    Gunz, Philipp; Ramsier, Marissa; Kuhrig, Melanie; Hublin, Jean-Jacques; Spoor, Fred

    2012-01-01

    The bony labyrinth in the temporal bone houses the sensory systems of balance and hearing. While the overall structure of the semicircular canals and cochlea is similar across therian mammals, their detailed morphology varies even among closely related groups. As such, the shape of the labyrinth carries valuable functional and phylogenetic information. Here we introduce a new, semilandmark-based three-dimensional geometric morphometric approach to shape analysis of the labyrinth, as a major improvement upon previous metric studies based on linear measurements and angles. We first provide a detailed, step-by-step description of the measurement protocol. Subsequently, we test our approach using a geographically diverse sample of 50 recent modern humans and 30 chimpanzee specimens belonging to Pan troglodytes troglodytes and P. t. verus. Our measurement protocol can be applied to CT scans of different spatial resolutions because it primarily quantifies the midline skeleton of the bony labyrinth. Accurately locating the lumen centre of the semicircular canals and the cochlea is not affected by the partial volume and thresholding effects that can make the comparison of the outer border problematic. After virtually extracting the bony labyrinth from CT scans of the temporal bone, we computed its midline skeleton by thinning the encased volume. On the resulting medial axes of the semicircular canals and cochlea we placed a sequence of semilandmarks. After Procrustes superimposition, the shape coordinates were analysed using multivariate statistics. We found statistically significant shape differences between humans and chimpanzees which corroborate previous analyses of the labyrinth based on traditional measurements. As the geometric relationship among the semilandmark coordinates was preserved throughout the analysis, we were able to quantify and visualize even small-scale shape differences. Notably, our approach made it possible to detect and visualize subtle, yet

  6. 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.

  7. 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

  8. Identifying Treatment Effect Heterogeneity in Clinical Trials Using Subpopulations of Events: STEPP

    PubMed Central

    Lazar, Ann A.; Bonetti, Marco; Cole, Bernard F.; Yip, Wai-ki; Gelber, Richard D.

    2016-01-01

    Background Investigators conducting randomized clinical trials (RCTs) often explore treatment effect heterogeneity to assess whether treatment efficacy varies according to patient characteristics. Identifying heterogeneity is central to making informed personalized health care decisions. Treatment effect heterogeneity can be investigated using subpopulation treatment effect pattern plot (STEPP), a non-parametric graphical approach that constructs overlapping patient subpopulations with varying values of a characteristic. Procedures for statistical testing using STEPP when the endpoint of interest is survival remain an area of active investigation. Motivating Data A STEPP analysis was used to explore patterns of absolute and relative treatment effects for varying levels of a breast cancer biomarker, Ki-67, in the phase III BIG (Breast International Group) 1-98 RCT, comparing letrozole to tamoxifen as adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer. Absolute treatment effects were measured by differences in 4-year cumulative incidence of breast cancer recurrence, while relative effects were measured by the subdistribution hazard ratio in the presence of competing risks using O − E (observed-minus-expected) methodology, an intuitive non-parametric method. While estimation of hazard ratio values based on O − E methodology has been shown, a similar development for the subdistribution hazard ratio has not. Furthermore, we observed that the STEPP analysis, may not produce results, even with 100 patients within each subpopulation. After further investigation through simulation studies, we observed inflation of the type I error rate of the traditional test statistic and sometimes singular variance-covariance matrix estimates that may lead to results not being produced. This is due to the lack of a sufficient number of events within the subpopulations, which we refer to as instability of a STEPP analysis. Methods We introduce

  9. 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

  10. 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

  11. 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

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

    PubMed

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

    2015-07-01

    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. © The Author(s) 2015.

  13. Combined effects of waggle dance communication and landscape heterogeneity on nectar and pollen uptake in honey bee colonies

    PubMed Central

    Steffan-Dewenter, Ingolf; Härtel, Stephan

    2017-01-01

    The instructive component of waggle dance communication has been shown to increase resource uptake of Apis mellifera colonies in highly heterogeneous resource environments, but an assessment of its relevance in temperate landscapes with different levels of resource heterogeneity is currently lacking. We hypothesized that the advertisement of resource locations via dance communication would be most relevant in highly heterogeneous landscapes with large spatial variation of floral resources. To test our hypothesis, we placed 24 Apis mellifera colonies with either disrupted or unimpaired instructive component of dance communication in eight Central European agricultural landscapes that differed in heterogeneity and resource availability. We monitored colony weight change and pollen harvest as measure of foraging success. Dance disruption did not significantly alter colony weight change, but decreased pollen harvest compared to the communicating colonies by 40%. There was no general effect of resource availability on nectar or pollen foraging success, but the effect of landscape heterogeneity on nectar uptake was stronger when resource availability was high. In contrast to our hypothesis, the effects of disrupted bee communication on nectar and pollen foraging success were not stronger in landscapes with heterogeneous compared to homogenous resource environments. Our results indicate that in temperate regions intra-colonial communication of resource locations benefits pollen foraging more than nectar foraging, irrespective of landscape heterogeneity. We conclude that the so far largely unexplored role of dance communication in pollen foraging requires further consideration as pollen is a crucial resource for colony development and health. PMID:28603677

  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. Effect of solutes on the heterogeneous nucleation temperature of supercooled water: an experimental determination.

    PubMed

    Wilson, P W; Haymet, A D J

    2009-04-21

    We investigate the effect of solute concentration on the heterogeneous ice nucleation temperature (T(het)) of aqueous solutions of both NaCl and d-glucose. An automatic lag time apparatus (ALTA) technique allows the dependence of T(het) on solute concentration to be determined with statistical significance. Our results point to the solute-induced lowering of T(het) being a factor of two times the equivalent melting point depression at any fixed concentration, the same factor reported for homogeneous nucleation experiments with small molecular weight solutes.

  17. 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).

  18. Assessment of the effect of reduced compositional heterogeneity on fracture resistance of human cortical bone using finite element modeling.

    PubMed

    Demirtas, Ahmet; Curran, Erin; Ural, Ani

    2016-10-01

    The recent reports of atypical femoral fracture (AFF) and its possible association with prolonged bisphosphonate (BP) use highlighted the importance of a thorough understanding of mechanical modifications in bone due to bisphosphonate treatment. The reduced compositional heterogeneity is one of the modifications in bone due to extensive suppression of bone turnover. Although experimental evaluations suggested that compositional changes lead to a reduction in the heterogeneity of elastic properties, there is limited information on the extent of influence of reduced heterogeneity on fracture resistance of cortical bone. As a result, the goal of the current study is to evaluate the influence of varying the number of unique elastic and fracture properties for osteons, interstitial bone, and cement lines on fracture resistance across seven different human cortical bone specimens using finite element modeling. Fracture resistance of seven human cortical bone samples under homogeneous and three different heterogeneous material levels was evaluated using a compact tension test setup. The simulation results predicted that the crack volume was the highest for the models with homogeneous material properties. Increasing heterogeneity resulted in a lower amount of crack volume indicating an increase in fracture resistance of cortical bone. This reduction was observed up to a certain level of heterogeneity after which further beneficial effects of heterogeneity diminished suggesting a possible optimum level of heterogeneity for the bone tissue. The homogeneous models demonstrated limited areas of damage with extensive crack formation. On the other hand, the heterogeneity in the material properties led to increased damage volume and a more variable distribution of damage compared to the homogeneous models. This resulted in uncracked regions which tended to have less damage accumulation preventing extensive crack propagation. The results also showed that the percent osteonal area

  19. Heterogeneity and the effect of mental health parity mandates on the labor market.

    PubMed

    Andersen, Martin

    2015-09-01

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. 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

  1. Practice based evidence: incorporating clinical heterogeneity and patient-reported outcomes for comparative effectiveness research.

    PubMed

    Horn, Susan D; Gassaway, Julie

    2010-06-01

    Comparative effectiveness research analyzes groups of patients and looks for associations between medical treatments and patient outcomes. To make meaningful comparisons of medical interventions, one must consider clinical heterogeneity of patient populations, intervention combinations, and outcomes. To explain how practice-based evidence (PBE) study methodology measures and controls for heterogeneity of patients, treatments, and outcomes seen in real-world clinical settings. Overview of PBE methodology. PBE study designs address comparative effectiveness by creating a comprehensive set of patient, treatment, and outcome variables, and analyzing them to identify treatments associated with better outcomes for specific types of patients. PBE studies are an alternative to randomized controlled trials, well suited to determine what works best for specific patient types, and provide clinicians with a rational basis for treatment recommendations for individual patients. They provide a holistic picture of patients, treatments, and outcomes, with no preset limits to the number of variables that can be included. Such an approach is needed for high quality comparative effectiveness research.

  2. Random Process Theory Approach to Geometric Heterogeneous Surfaces: Effective Fluid-Solid Interaction

    NASA Astrophysics Data System (ADS)

    Khlyupin, Aleksey; Aslyamov, Timur

    2017-06-01

    Realistic fluid-solid interaction potentials are essential in description of confined fluids especially in the case of geometric heterogeneous surfaces. Correlated random field is considered as a model of random surface with high geometric roughness. We provide the general theory of effective coarse-grained fluid-solid potential by proper averaging of the free energy of fluid molecules which interact with the solid media. This procedure is largely based on the theory of random processes. We apply first passage time probability problem and assume the local Markov properties of random surfaces. General expression of effective fluid-solid potential is obtained. In the case of small surface irregularities analytical approximation for effective potential is proposed. Both amorphous materials with large surface roughness and crystalline solids with several types of fcc lattices are considered. It is shown that the wider the lattice spacing in terms of molecular diameter of the fluid, the more obtained potentials differ from classical ones. A comparison with published Monte-Carlo simulations was discussed. The work provides a promising approach to explore how the random geometric heterogeneity affects on thermodynamic properties of the fluids.

  3. 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.

  4. Effects of Chemical Aging on the Heterogeneous Freezing of Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Collier, K.; Brooks, S. D.

    2014-12-01

    Organic aerosols are emitted into the atmosphere from a variety of sources and display a wide range of effectiveness in promoting the nucleation of ice in clouds. Soot and polycyclic aromatic hydrocarbons (PAHS) arise from incomplete combustion and other pollutant sources. Hydrocarbon compounds in diesel motor oil and other fuel blends include compounds such as octacosane (a straight saturated alkane), squalane (a branched saturated alkane) and squalene (an unsaturated branched alkene). At temperatures above -36°C, the formation of ice crystals in the atmosphere is facilitated by heterogeneous freezing processes in which atmospheric aerosols act as ice nuclei (IN). The variability in ability of organic particles to facilitate heterogeneous ice nucleation causes major uncertainties in predictions of aerosol effects on climate. Further, atmospheric aerosol composition and ice nucleation ability can be altered via chemical aging and reactions with atmospheric oxidants such as ozone. In this study, we take a closer look at the role of chemical oxidation on the efficiency of specific IN during contact freezing laboratory experiments. The freezing temperatures of droplets in contact with representative organic aerosols are determined through the use of an optical microscope apparatus equipped with a cooling stage and a digital camera. Chemical changes at the surface of aerosols due to ozone exposure are characterized using Raman Microspectroscopy and Fourier Transform Infrared Spectroscopy with Horizontal Attenuated Total Reflectance. Our results indicate that oxidation of certain atmospheric organics (soot and PAHS) enhances their ice nucleation ability. In this presentation, results of heterogeneous nucleation on various types of organic aerosols will be presented, and the role of structure in promoting freezing will be discussed.

  5. Palpatory accuracy of lumbar spinous processes using multiple bony landmarks.

    PubMed

    Snider, Karen T; Snider, Eric J; Degenhardt, Brian F; Johnson, Jane C; Kribs, James W

    2011-06-01

    Accurate localization of vertebral segments is crucial for many treatment procedures. The objective of this study was to determine accuracy of identification of lumbar spinous process levels by palpation. Three examiners independently identified the spinous processes of L1-L4 on 60 prone volunteers using multiple bony landmarks including the sacral base, L5, Tuffier's line, T12, and the 12th ribs. The spinous processes were marked with radiopaque skin markers. Location of marker placement and presence of anatomical anomalies were determined by posteroanterior lumbar radiographs. Accuracy of marker placement and interobserver reliability were assessed using weighted κ values. Generalized linear mixed models and Cochran-Mantel-Haenszel tests assessed the relationship of accuracy to training level, presence of anatomical anomalies, and participant characteristics. Examiners identified a spinous process in 91% of vertebral assessments. Correct identification of vertebral level occurred 69% of the time (κ = 0.81; 95% confidence interval, 0.79-0.83). Faculty examiners were significantly more accurate in identifying the correct vertebral level than the resident examiner (67%-78% vs 51%, P ≤ .03). The presence of 12th rib anomalies decreased accuracy for all examiners (P ≤ .05), reducing accuracy from 74% to 55%. Accuracy was higher in male participants than in female participants (P = .01). Obesity significantly decreased accuracy (P = .0003) at L3 (50% vs 73%) and L4 (44% vs 72%). Identification of lumbar spinous processes using multiple landmarks was more accurate than previously reported values. However, accuracy was dependent on examiner experience, presence of anatomical anomalies, and participant characteristics. Copyright © 2011 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.

  6. Continuum heterogeneous biofilm model--a simple and accurate method for effectiveness factor determination.

    PubMed

    Gonzo, Elio Emilio; Wuertz, Stefan; Rajal, Veronica B

    2012-07-01

    We present a novel analytical approach to describe biofilm processes considering continuum variation of both biofilm density and substrate effective diffusivity. A simple perturbation and matching technique was used to quantify biofilm activity using the steady-state diffusion-reaction equation with continuum variable substrate effective diffusivity and biofilm density, along the coordinate normal to the biofilm surface. The procedure allows prediction of an effectiveness factor, η, defined as the ratio between the observed rate of substrate utilization (reaction rate with diffusion resistance) and the rate of substrate utilization without diffusion limitation. Main assumptions are that (i) the biofilm is a continuum, (ii) substrate is transferred by diffusion only and is consumed only by microorganisms at a rate according to Monod kinetics, (iii) biofilm density and substrate effective diffusivity change in the x direction, (iv) the substrate concentration above the biofilm surface is known, and (v) the substratum is impermeable. With this approach one can evaluate, in a fast and efficient way, the effect of different parameters that characterize a heterogeneous biofilm and the kinetics of the rate of substrate consumption on the behavior of the biological system. Based on a comparison of η profiles the activity of a homogeneous biofilm could be as much as 47.8% higher than that of a heterogeneous biofilm, under the given conditions. A comparison of η values estimated for first order kinetics and η values obtained by numerical techniques showed a maximum deviation of 1.75% in a narrow range of modified Thiele modulus values. When external mass transfer resistance, is also considered, a global effectiveness factor, η(0) , can be calculated. The main advantage of the approach lies in the analytical expression for the calculation of the intrinsic effectiveness factor η and its implementation in a computer program. For the test cases studied convergence was

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Thermal heterogeneity mediates the effects of pulsed subsidies across a landscape.

    PubMed

    Armstrong, Jonathan B; Schindler, Daniel E; Omori, Kristen L; Ruff, Casey P; Quinn, Thomas P

    2010-05-01

    Spatial and temporal heterogeneity interact to make the foraging rates of individuals more variable than expected from models assuming that spatial and temporal dimensions of habitat conditions operate independently. For example, trophic resource pulses produce temporal patches of prey superabundance, yet little is known about how spatial heterogeneity in habitat conditions mediates the ability of consumers to exploit these high-quality foraging opportunities. We studied how spatial variation in water temperature regulates the potential for juvenile coho salmon to exploit a seasonal pulsed subsidy of eggs produced by anadromous sockeye salmon. Streams within the Wood River watershed, southwestern Alaska, USA, ranged in mean summer temperature from 3.6 degrees to 14.5 degrees C. Growth of juvenile coho prior to the arrival of the seasonal egg subsidy was positively related to water temperature among streams. An in situ experiment combined with field samples of diets revealed a size threshold for egg consumption; only individuals longer than approximately 70 mm could consume eggs due to gape limitation of smaller individuals. A bioenergetics simulation demonstrated that water temperature regulated whether age-0 coho salmon could grow large enough to exceed the size threshold for egg consumption. Coho salmon that consumed eggs had energy rations that were five times higher than fish that did not consume eggs, resulting in a positive feedback of water temperature on their integrated seasonal growth. Across this landscape, heterogeneity in water temperature mediates individual- and population-level responses to seasonally available resource pulses. Our study illustrates that ecological mechanisms, such as size-based foraging asymmetries, can magnify the effects of climate change compared to predictions based on physiology alone.

  12. Group search algorithm recovers effective connectivity maps for individuals in homogeneous and heterogeneous samples.

    PubMed

    Gates, Kathleen M; Molenaar, Peter C M

    2012-10-15

    At its best, connectivity mapping can offer researchers great insight into how spatially disparate regions of the human brain coordinate activity during brain processing. A recent investigation conducted by Smith and colleagues (2011) on methods for estimating connectivity maps suggested that those which attempt to ascertain the direction of influence among ROIs rarely provide reliable results. Another problem gaining increasing attention is heterogeneity in connectivity maps. Most group-level methods require that the data come from homogeneous samples, and misleading findings may arise from current methods if the connectivity maps for individuals vary across the sample (which is likely the case). The utility of maps resulting from effective connectivity on the individual or group levels is thus diminished because they do not accurately inform researchers. The present paper introduces a novel estimation technique for fMRI researchers, Group Iterative Multiple Model Estimation (GIMME), which demonstrates that using information across individuals assists in the recovery of the existence of connections among ROIs used by Smith and colleagues (2011) and the direction of the influence. Using heterogeneous in-house data, we demonstrate that GIMME offers a unique improvement over current approaches by arriving at reliable group and individual structures even when the data are highly heterogeneous across individuals comprising the group. An added benefit of GIMME is that it obtains reliable connectivity map estimates equally well using the data from resting state, block, or event-related designs. GIMME provides researchers with a powerful, flexible tool for identifying directed connectivity maps at the group and individual levels. Copyright © 2012 Elsevier Inc. All rights reserved.

  13. 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].

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

    PubMed

    Nguyen, Quynh C; Rehkopf, David H; Schmidt, Nicole M; Osypuk, Theresa L

    2016-04-01

    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. 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. 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. 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.

  15. 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

  16. Effect of spatial distribution of porous matrix surface charge heterogeneity on nanoparticle attachment in a packed bed

    NASA Astrophysics Data System (ADS)

    Pham, Ngoc H.; Papavassiliou, Dimitrios V.

    2017-08-01

    In this study, the effect of spatial distribution of the porous matrix surface heterogeneity on nanoparticle deposition is numerically explored using lattice Boltzmann simulation methods and tracking of individual particles with Lagrangian algorithms. Packed beds with four different patterns of surface charge heterogeneity, on which favorable surfaces for particle attachment are located at different locations, are generated. The heterogeneity is binary, so that the porous surface can either accommodate nanoparticle attachment or not. It is found that the heterogeneity pattern has a stronger effect when the rate constant for particle attachment is high, when the particle size is small, and/or when the fraction of the surface area that is favorable to attachment is about 0.5. At fixed conditions, the heterogeneity pattern with randomly and uniformly distributed active surface area is the most favorite for particle attachment, compared to those where the active surface areas are banded perpendicularly to the flow direction. There exists a critical ratio of the Damkohler number to the Peclet number, beyond which the heterogeneity pattern effect becomes more visible.

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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.

  2. Understanding Heterogeneity in the Effects of Birth Weight on Adult Cognition and Wages

    PubMed Central

    Cook, C. Justin; Fletcher, Jason M.

    2015-01-01

    A large economics literature has shown long term impacts of birth weight on adult outcomes, including IQ and earnings that are often robust to sibling or twin fixed effects. We examine potential mechanisms underlying these effects by incorporating findings from the genetics and neuroscience literatures. We use a sample of siblings combined with an “orchids and dandelions hypothesis”, where the IQ of genetic dandelions is not affected by in utero nutrition variation but genetic orchids thrive under advantageous conditions and wilt in poor conditions. Indeed, using variation in three candidate genes related to neuroplasticity (APOE, BDNF, and COMT), we find substantial heterogeneity in the associations between birth weight and adult outcomes, where part of the population (i.e., “dandelions”) is not affected by birth weight variation. Our results help uncover why birth weight affects adult outcomes. PMID:25770970

  3. 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.

  4. Dynamic effective properties of heterogeneous geological formations with spherical inclusions under periodic time variations

    NASA Astrophysics Data System (ADS)

    Rabinovich, A.; Dagan, G.; Miloh, T.

    2013-04-01

    In unsteady groundwater flow (or similar processes of heat/electrical conduction), the heterogeneous medium structure is characterized by two random properties, the conductivity K and the specific storativity S. The average head field ⟨H ⟩and the associated effective properties Kef, Sef are determined for a layer with a periodic head drop between boundaries, such that H is periodic in time, and a medium made up of a matrix with a dilute concentration of spherical inclusions. In the common quasi-steady approximation, Kef is equal to the classical steady solution while Sef = SA, the arithmetic mean. We derive expressions for the frequency dependent Kef, Sef, which are generally complex, i.e., dynamic. The main result is the delineation of the ranges of the parameters: dimensionless frequency (ω) and contrasts of conductivity (κ) and storativity (s) between the matrix and the inclusions, for which dynamic effects are significant.

  5. 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

  6. 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

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

    PubMed

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

    2015-04-22

    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. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  8. 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

  9. Effect of Relative Humidity on the OH-Initiated Heterogeneous Oxidation of Monosaccharide Nanoparticles.

    PubMed

    Fan, Hanyu; Tinsley, Mark R; Goulay, Fabien

    2015-11-12

    The OH-initiated heterogeneous oxidation of solid methyl β-d-glucopyranoside nanoparticles (a cellulose oligomer surrogate) is studied in an atmospheric pressure gas flow reactor coupled to an aerosol mass spectrometer. The decay of the solid reactant relative concentration is measured as a function of OH exposure over a wide range of ambient relative humidities (RHs). The kinetic traces display an initial fast exponential decay followed by a slower decay. For long OH exposure, the fraction of a particle that reacts decreases from 90% at RH = 30% to 60% at RH = 20% and to 40% at RH = 10%. A computational model based on the diffusion and reaction of the radical, monosaccharide, and water is developed in order to further examine the experimental data. The model parameters and validity are discussed on the basis of previous literature data. The experimental data are consistent with a diffusion-controlled heterogeneous oxidation. These findings are discussed toward a better understanding of mass transport in semisolid organic material and their effect on chemical change, in particular during the thermal transformation of cellulosic materials to useful chemicals.

  10. Effects of heterogeneous attenuation on correlation functions of ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Liu, X.; Ben-Zion, Y.

    2013-12-01

    We study effects of attenuation on amplitudes of correlated ambient noise with ray-theory and waveform methods. In the first method, the region of heterogeneous attenuation structure is discretized into a 2D grid and the amplitude reduction between sources and receivers is accounted for with an integral along the ray path. The forward algorithm generates synthetic noise spectra for each station in the 2D grid assuming stationary random noise wavefield. The expected cross-spectra for each station pair can be computed numerically and compared with previously derived theoretical results. In the second method, a 2D finite element algorithm based on the damped wave equation generates noise waveforms with heterogeneous attenuation and velocity structure. Initial results based on ray-theory indicate that the variation of inter-station attenuation relative to the background attenuation is reflected in the normalized cross-spectra. In addition, the correlation function amplitude asymmetry ratio, which varies with frequency, contains information about asymmetric attenuation structure outside the inter-station region. Work based on the finite element method is in development. The different signals and techniques may be combined to form an inversion algorithm for the attenuation structure.

  11. Effect of surface compositional heterogeneities and microphase segregation of fluorinated amphiphilic copolymers on antifouling performance.

    PubMed

    Zhao, Zeliang; Ni, Huagang; Han, Zhiyuan; Jiang, Tengfei; Xu, Yongjuan; Lu, Xiaolin; Ye, Peng

    2013-08-28

    In this paper, a series of fluorinated amphiphilic copolymers composed of 2-perfluorooctylethyl methacrylate (FMA) and 2-hydroxyethyl methacrylate (HEMA) monomers were prepared, and their surface properties and antifouling performance were investigated. Bovine serum albumin (BSA) and human plasma fibrinogen (HFg) were used as model proteins to study protein adsorption onto the fluorinated amphiphilic surfaces. All the fluorinated amphiphilic surfaces exhibit excellent resistant performance of protein adsorption measured by X-ray photoelectron spectroscopy (XPS). The surface compositional heterogeneities on the molecular scale play an important role in the antifouling properties. It was found that the copolymers exhibited better antifouling properties than the corresponding homopolymers did, when the percentage of hydrophilic hydroxyl groups is from 4% to 7% and the percentage of hydrophobic fluorinated moieties is from 4% to 14% on the surface. In addition, the protein molecular size scale and the pattern of microphase segregation domains on the surface strongly affect the protein adsorption behaviors. These results demonstrate the desirable protein-resistant performance from the fluorinated amphiphilic copolymers and provide deeper insight of the effect of surface compositional heterogeneity and microphase segregation on the protein adsorption behaviors.

  12. 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.

  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. Locked bucket-handle type bony Bankart lesion resulting from manipulation.

    PubMed

    Yoo, Yon Sik; Song, Hyun Seok

    2016-06-01

    A patient who underwent manipulation for stiffness accompanying a rotator cuff tear experienced a complication consisting of a bony Bankart lesion connected to the superior and inferior labrum. This lesion was displaced posteriorly, locked behind the humeral head and blocking the reduction. Attachment of the labrum to this fragment made reduction and fixation easier. This bony Bankart lesion was fixed successfully by arthroscopic placement of knotless suture anchors. Level of evidence Case report, Level IV.

  15. 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.

  16. 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.

  17. 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.

  18. Cirrus Heterogeneity Effects on Cloud Optical Properties Retrieved with an Optimal Estimation Method from MODIS VIS to TIR Channels.

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    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 micrometers , 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.

  19. 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

  20. 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.

  1. 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.

  2. 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…

  3. 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

  4. Pore-scale modelling of the combined effect of physical and chemical heterogeneity on reactive flows

    NASA Astrophysics Data System (ADS)

    Oliveira, T. D. S.; Bijeljic, B.; Blunt, M. J.

    2016-12-01

    We perform direct numerical simulations to study the combined impact of physical and chemical heterogeneity in subsurface rock to provide insights into the source of the discrepancy observed between mineral dissolution rates observed in laboratory experiments and in field-scale natural systems. The ultimate goal of this work is to use pore-scale simulation to compute upscaled properties - such as effective reaction rate - for use in larger-scale models.We present a methodology to simulate multispecies reactive flow through pore-space images obtained from micro-tomography. Using the sequential non-iterative approach, we couple the simulation of the transport equations with an advanced geochemical solver designed specifically for applications that require sequential equilibrium calculations. This geochemical solver uses novel numerical methods for the solution of multiphase chemical equilibrium and kinetics problems in a well-stirred batch model. Our model assumes that reactions can be classified into fast reactions, which are considered to be in equilibrium, and slow reactions, considered to be controlled by kinetics. This assumption of partial equilibrium simplifies the problem by replacing differential equations with algebraic ones. We allow for chemical heterogeneity of the solid phase by associating each voxel to a different mineral and reaction rate. A steady-state flow problem is solved in the pore space using a finite volume method to calculate the velocity field. Then we solve an advection-diffusion equation for the concentration and, modelling each liquid voxel as a well-mixed batch with a solid wall where applicable, we calculate reaction using the aforementioned geochemical solver. Both fluid-fluid and fluid-solid reactions are considered, geometry changes due to dissolution and precipitation are taken into account, and the velocity field is updated. We present the validation tests for acidic brine injected into rock for a range of transport (P

  5. 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

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. 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.

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

    PubMed

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

    2015-05-01

    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. 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. 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. 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.

  12. 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

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

    PubMed

    Sánchez-Oliver, Juan S; 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.

  14. Effects of hardware heterogeneity on the performance of SVM Alzheimer's disease classifier.

    PubMed

    Abdulkadir, Ahmed; Mortamet, Bénédicte; Vemuri, Prashanthi; Jack, Clifford R; Krueger, Gunnar; Klöppel, Stefan

    2011-10-01

    Fully automated machine learning methods based on structural magnetic resonance imaging (MRI) data can assist radiologists in the diagnosis of Alzheimer's disease (AD). These algorithms require large data sets to learn the separation of subjects with and without AD. Training and test data may come from heterogeneous hardware settings, which can potentially affect the performance of disease classification. A total of 518 MRI sessions from 226 healthy controls and 191 individuals with probable AD from the multicenter Alzheimer's Disease Neuroimaging Initiative (ADNI) were used to investigate whether grouping data by acquisition hardware (i.e. vendor, field strength, coil system) is beneficial for the performance of a support vector machine (SVM) classifier, compared to the case where data from different hardware is mixed. We compared the change of the SVM decision value resulting from (a) changes in hardware against the effect of disease and (b) changes resulting simply from rescanning the same subject on the same machine. Maximum accuracy of 87% was obtained with a training set of all 417 subjects. Classifiers trained with 95 subjects in each diagnostic group and acquired with heterogeneous scanner settings had an empirical detection accuracy of 84.2±2.4% when tested on an independent set of the same size. These results mirror the accuracy reported in recent studies. Encouragingly, classifiers trained on images acquired with homogenous and heterogeneous hardware settings had equivalent cross-validation performances. Two scans of the same subject acquired on the same machine had very similar decision values and were generally classified into the same group. Higher variation was introduced when two acquisitions of the same subject were performed on two scanners with different field strengths. The variation was unbiased and similar for both diagnostic groups. The findings of the study encourage the pooling of data from different sites to increase the number of

  15. 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

  16. 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…

  17. 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…

  18. Influence of trial duration on the bias of the estimated treatment effect in clinical trials when individual heterogeneity is ignored.

    PubMed

    Cécilia-Joseph, Elsa; Auvert, Bertran; Broët, Philippe; Moreau, Thierry

    2015-05-01

    In randomized clinical trials where the times to event of two treatment groups are compared under a proportional hazards assumption, it has been established that omitting prognostic factors from the model entails an underestimation of the hazards ratio. Heterogeneity due to unobserved covariates in cancer patient populations is a concern since genomic investigations have revealed molecular and clinical heterogeneity in these populations. In HIV prevention trials, heterogeneity is unavoidable and has been shown to decrease the treatment effect over time. This article assesses the influence of trial duration on the bias of the estimated hazards ratio resulting from omitting covariates from the Cox analysis. The true model is defined by including an unobserved random frailty term in the individual hazard that reflects the omitted covariate. Three frailty distributions are investigated: gamma, log-normal, and binary, and the asymptotic bias of the hazards ratio estimator is calculated. We show that the attenuation of the treatment effect resulting from unobserved heterogeneity strongly increases with trial duration, especially for continuous frailties that are likely to reflect omitted covariates, as they are often encountered in practice. The possibility of interpreting the long-term decrease in treatment effects as a bias induced by heterogeneity and trial duration is illustrated by a trial in oncology where adjuvant chemotherapy in stage 1B NSCLC was investigated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Follow-up computed tomography arthrographic evaluation of bony Bankart lesions after arthroscopic repair.

    PubMed

    Park, Jin-Young; Lee, Seung-Jun; Lhee, Sang-Hoon; Lee, Suk-Ha

    2012-04-01

    The follow-up results of bony union after an arthroscopic bony Bankart repair have not been reported. We studied follow-up computed tomography (CT) arthrograms to evaluate radiographic healing of bony Bankart fragments. Among 41 patients who underwent arthroscopy for a bony Bankart lesion between July 2006 and May 2009, 31 cases in 30 patients who had undergone sequential follow-up CT arthrography preoperatively, at 3 months postoperatively, and at 1 year postoperatively were enrolled. Radiologic patterns of fracture healing were classified into bony healing and fibrous healing. The mean age was 23.4 years, and the mean follow-up was 30.5 months. The mean interval from the first trauma to surgery was 32.5 months, and the mean preoperative dislocation number was 12.1. The mean preoperative glenoid defect was 14.1%. The fracture healing patterns included 26 bony and 5 fibrous unions. There was a significant positive relation between the total dislocation number and the preoperative glenoid defect (P = .003). The proportion of the mean fragment dimension to a circle drawn through the outer cortex of the inferior glenoid was 8.4% preoperatively, 6.6% at 3 months postoperatively, and 6.2% at 1 year postoperatively. The fragment size decreased from that measured preoperatively to the size measured 3 months after surgery (P < .05). However, the fragment size was maintained between 3 months and 1 year postoperatively (P > .05). The mean Rowe score at 1 year postoperatively was 97.2. Follow-up CT arthrographic evaluation showed that small bony Bankart fragments survived without resorption until 1 year postoperatively, even with fibrous union, and that reattached bone fragment fixation to the anatomic position with the labrum could survive. Level IV, therapeutic case series. Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

  20. 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. © 2008 American Association of Physicists in Medicine.

  1. 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

  2. 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.

  3. Adsorption of fluids in a pore with chemical heterogeneities: the cooperative effect.

    PubMed

    Feng, Zhikuan; Zhang, Xianren; Wang, Wenchuan

    2008-05-01

    In this work, we study the cooperative adsorption of fluids in a heterogeneous pore, in which the pore walls are composed of homogeneous substrates with chemical groups (CGs) decorating them. The adsorption caused by the homogeneous substrates alone and that by CGs do not add up to the overall adsorption, indicating the existence of a cooperative effect. The cooperative effect is the source of cooperative adsorption, and is characterized in this work by the ratio of the overall adsorption to the sum of adsorption by the substrate only and that by CGs. It is found that the cooperative adsorption does not depend monotonically on the substrate or the CGs. Two different origins of the cooperative adsorption play different roles depending on which one dominates the overall adsorption. Our simulations reveal that, when the homogeneous substrate dominates the overall adsorption, weakening of the attractive fluid-substrate interaction or alternatively strengthening of the fluid-CGs interaction leads to a stronger cooperative effect and enhances the cooperative adsorption. However, when CGs dominate the overall adsorption, weakening of the attractive fluid-CG interaction or strengthening the fluid-substrate interaction results in strong cooperative adsorption. In order to investigate the effects of the distribution of CGs on cooperative adsorption, a design-test method is generalized and used in this work. Simulation results show that the overall adsorption can be significantly affected by the CG distribution.

  4. 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.

  5. CO2 storage in heterogeneous aquifer: A study on the effect of temperature and mineral precipitation

    NASA Astrophysics Data System (ADS)

    Raza, A.; Gholami, R.; Rezaee, R.; Bing, C. H.; Nagarajan, R.; Hamid, M. A.

    2017-06-01

    CO2 storage in suitable geologic media has been recognized as a major strategy taken to have a carbon free environment. This practice can be done in depleted reservoirs as well as brine aquifers where sufficient storage capacity is available to hold carbon dioxide for thousands of years. Storage in an aquifer is often achieved through four trapping mechanisms, among which capillary trapping is a rapid and effective phenomenon. Although, there have been studies pointing out the relationships of different storage related factors with capillary trapping, more studies are still required to recognize other parameters linked to this effective trapping mechanism. The aim of this paper is to evaluate the effect of temperature and mineral precipitation on trapping mechanisms of heterogeneous aquifer. A dynamic numerical simulation was run by the commercial reservoir simulator Eclipse300 to simulate 30 years of CO2 injection. A synthetic but realistic model of a geologic formation was considered to evaluate the efficiency of trapping mechanisms under different temperature and mineral precipitation conditions. The results obtained indicated that trapping mechanisms are affected by both temperature and mineral precipitation in a short and long terms - temperature is indirectly affecting the trapping ability regardless of the precipitation effect. However, precipitation have a severe impact on injectivity as well as trapping mechanisms in the long term. Although some practical conclusions were drawn, the results obtained and presented in this study may need experimental verification before taking into serious consideration.

  6. Serological markers suggest heterogeneity of effectiveness of malaria control interventions on Bioko Island, equatorial Guinea.

    PubMed

    Cook, Jackie; Kleinschmidt, Immo; Schwabe, Christopher; Nseng, Gloria; Bousema, Teun; Corran, Patrick H; Riley, Eleanor M; Drakeley, Chris J

    2011-01-01

    In order to control and eliminate malaria, areas of on-going transmission need to be identified and targeted for malaria control interventions. Immediately following intense interventions, malaria transmission can become more heterogeneous if interventions are more successful in some areas than others. Bioko Island, Equatorial Guinea, has been subject to comprehensive malaria control interventions since 2004. This has resulted in substantial reductions in the parasite burden, although this drop has not been uniform across the island. In 2008, filter paper blood samples were collected from 7387 people in a cross-sectional study incorporating 18 sentinel sites across Bioko, Equatorial Guinea. Antibodies were measured to P. falciparum Apical Membrane Antigen-1 (AMA-1) by Enzyme Linked Immunosorbent Assay (ELISA). Age-specific seropositivity rates were used to estimate seroconversion rates (SCR). Analysis indicated there had been at least a 60% decline in SCR in four out of five regions on the island. Changes in SCR showed a high degree of congruence with changes in parasite rate (PR) and with regional reductions in all cause child mortality. The mean age adjusted concentration of anti-AMA-1 antibodies was mapped to identify areas where individual antibody responses were higher than expected. This approach confirmed the North West of the island as a major focus of continuing infection and an area where control interventions need to be concentrated or re-evaluated. Both SCR and PR revealed heterogeneity in malaria transmission and demonstrated the variable effectiveness of malaria control measures. This work confirms the utility of serological analysis as an adjunct measure for monitoring transmission. Age-specific seroprevalence based evidence of changes in transmission over time will be of particular value when no baseline data are available. Importantly, SCR data provide additional evidence to link malaria control activities to contemporaneous reductions in all

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. Bony injuries in homicide cases (1994-2014). A retrospective study.

    PubMed

    Flieger, Alexander; Kölzer, Sarah C; Plenzig, Stefanie; Heinbuch, Sara; Kettner, Mattias; Ramsthaler, Frank; Verhoff, Marcel A

    2016-09-01

    Even when human skeletal remains are found in contexts indicative of body disposal after homicide, none of the bones may manifest injuries. When skeletons are incomplete, there are two possibilities, the injured bones are missing or none were injured. This leads to the question how frequently bones are injured during homicide, where the injuries tend to be placed, and whether the frequency of injury is related to the type of homicide. To answer these questions, the postmortem reports from all autopsies performed for homicide victims at the Institute of Legal Medicine at the University Hospital in Frankfurt am Main, Germany, between 1994 and 2014, were retrospectively evaluated for bony injuries discovered during autopsy. In 90 cases, a preliminary postmortem computed tomography (pmCT) examination had been performed. The cases were categorized into the following five groups by type of fatal trauma: blunt force, sharp force, gunshot injury, strangulation, or other. In total, the postmortem reports for 897 homicides (527 male, 370 female) were evaluated. The number of victims per trauma category were sharp force, 309; blunt force, 179; gunshot injury, 242; strangulation, 92; and other, 75. Bony injuries had been reported in 70.9 % of the homicides. The "gunshot" category contained the highest proportion of victims with bony injuries (92.6 %). With 80.4 %, the second-highest proportion of victims with bony injuries was in the "blunt force" category, followed by 66.3 % of victims in the "sharp force" group. In contrast, with 53.3 %, the second-lowest proportion of victims with bony injuries was in the "strangulation" category, which contained a preponderance of female victims, followed by 17.3 % of victims with bony injuries in the "other" category. Bony injuries thus occurred in the majority of homicides. Forensic osteological analysis should, therefore, always be performed on badly decomposed human remains. Where necessary, the additional use of visualization

  18. Biomechanical strain characteristics of soft tissue biceps tenodesis and bony tenodesis.

    PubMed

    Levin, Steven D; Wellman, David S; Liu, Charley; Li, Yue; Ren, Yupeng; Shah, Nirav A; Zhang, Li-Qun

    2013-09-01

    Biomechanical analysis of biceps tenodesis procedures has historically focused on load to failure models. Minimal data exists for the analysis of biomechanical strain properties of the biceps tendon in a sub-failure, physiologic cadaver model. Tendon strain characteristics are different between bony and soft tissue tenodesis surgery, and the soft tissue tenodesis procedure reproduces a strain pattern more similar to the native biceps tendon. Eight fresh frozen cadaver upper extremities were mounted onto a custom device that controls shoulder abduction and rotation. Strain on the tendon was measured using a differential variable reluctance transducer as the arm was moved through cycles of abduction and external rotation. Each arm was mounted once, and all 3 testing procedures were performed on each of the 8 specimens. Statistical analysis was completed using ANOVA, followed by multiple comparisons with Bonferroni correction. The bony tenodesis model placed higher strain on the biceps tendon than the soft tissue tenodesis (p = 0.025). Also, the bony tenodesis model increased the strain on the biceps tendon when compared to the native tendon (p = 0.031). In contrast, the soft tissue tenodesis did not significantly alter strain when compared to the native tendon (p = 0.089). The soft tissue tenodesis procedure better maintained the native strain environment when compared to the bony tenodesis using an interference screw. Due to this closer approximation of native biceps tendon biomechanics, the soft tissue procedure may be more preferable clinically than the bony tenodesis. 1, Controlled Laboratory Study.

  19. 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.

  20. Necessity of using heterogeneous ellipsoidal Earth model with terrain to calculate co-seismic effect

    NASA Astrophysics Data System (ADS)

    Cheng, Huihong; Zhang, Bei; Zhang, Huai; Huang, Luyuan; Qu, Wulin; Shi, Yaolin

    2016-04-01

    Co-seismic deformation and stress changes, which reflect the elasticity of the earth, are very important in the earthquake dynamics, and also to other issues, such as the evaluation of the seismic risk, fracture process and triggering of earthquake. Lots of scholars have researched the dislocation theory and co-seismic deformation and obtained the half-space homogeneous model, half-space stratified model, spherical stratified model, and so on. Especially, models of Okada (1992) and Wang (2003, 2006) are widely applied in the research of calculating co-seismic and post-seismic effects. However, since both semi-infinite space model and layered model do not take the role of the earth curvature or heterogeneity or topography into consideration, there are large errors in calculating the co-seismic displacement of a great earthquake in its impacted area. Meanwhile, the computational methods of calculating the co-seismic strain and stress are different between spherical model and plane model. Here, we adopted the finite element method which could well deal with the complex characteristics (such as anisotropy, discontinuities) of rock and different conditions. We use the mash adaptive technique to automatically encrypt the mesh at the fault and adopt the equivalent volume force replace the dislocation source, which can avoid the difficulty in handling discontinuity surface with conventional (Zhang et al., 2015). We constructed an earth model that included earth's layered structure and curvature, the upper boundary was set as a free surface and the core-mantle boundary was set under buoyancy forces. Firstly, based on the precision requirement, we take a testing model - - a strike-slip fault (the length of fault is 500km and the width is 50km, and the slippage is 10m) for example. Because of the curvature of the Earth, some errors certainly occur in plane coordinates just as previous studies (Dong et al., 2014; Sun et al., 2012). However, we also found that: 1) the co

  1. Scale dependence of cirrus horizontal heterogeneity effects on TOA measurements - Part I: MODIS brightness temperatures in the thermal infrared

    NASA Astrophysics Data System (ADS)

    Fauchez, Thomas; Platnick, Steven; Meyer, Kerry; Cornet, Céline; Szczap, Frédéric; Várnai, Tamás

    2017-07-01

    This paper presents a study on the impact of cirrus cloud heterogeneities on MODIS simulated thermal infrared (TIR) brightness temperatures (BTs) at the top of the atmosphere (TOA) as a function of spatial resolution from 50 m to 10 km. A realistic 3-D cirrus field is generated by the 3DCLOUD model (average optical thickness of 1.4, cloud-top and base altitudes at 10 and 12 km, respectively, consisting of aggregate column crystals of Deff = 20 µm), and 3-D thermal infrared radiative transfer (RT) is simulated with the 3DMCPOL code. According to previous studies, differences between 3-D BT computed from a heterogenous pixel and 1-D RT computed from a homogeneous pixel are considered dependent at nadir on two effects: (i) the optical thickness horizontal heterogeneity leading to the plane-parallel homogeneous bias (PPHB) and the (ii) horizontal radiative transport (HRT) leading to the independent pixel approximation error (IPAE). A single but realistic cirrus case is simulated and, as expected, the PPHB mainly impacts the low-spatial-resolution results (above ˜ 250 m) with averaged values of up to 5-7 K, while the IPAE mainly impacts the high-spatial-resolution results (below ˜ 250 m) with average values of up to 1-2 K. A sensitivity study has been performed in order to extend these results to various cirrus optical thicknesses and heterogeneities by sampling the cirrus in several ranges of parameters. For four optical thickness classes and four optical heterogeneity classes, we have found that, for nadir observations, the spatial resolution at which the combination of PPHB and HRT effects is the smallest, falls between 100 and 250 m. These spatial resolutions thus appear to be the best choice to retrieve cirrus optical properties with the smallest cloud heterogeneity-related total bias in the thermal infrared. For off-nadir observations, the average total effect is increased and the minimum is shifted to coarser spatial resolutions.

  2. The Heterogeneous Oxidation of Organic Droplets -Temperature and Physical Phase Effects

    NASA Astrophysics Data System (ADS)

    Hung, H.; Tang, C.; Lin, L.

    2008-12-01

    The heterogeneous reactions of oleic acid droplets with ozone are studied at different temperatures to imitating the atmospheric condition. The reactions are monitored concomitantly by using attenuated total reflectance Fourier Transform infrared spectroscopy (ATR-FT-IR) for the organic species and UV-VIS spectrometry for the ozone concentration, in order to investigate reaction rate discrepancies reported in literature as well as the oxidation mechanism, temperature and physical phase effects. The less and semi- volatile products are identified and resolved by a liquid chromatography and a gas chromatography mass spectrometer, respectively. The identified products are predominantly composed by nananoic acid and azelaic acid and might be due to propagation reactions possibly initiated by a secondary reaction such as the stabilized Criegee intermediates reacting with oleic acid. For temperature effect, the oxidation rate decreases with temperature when the oleic acid droplets are in the same physical phases. As oleic acid turns into the solid phase, the oxidation mechanism is observed to be different from the liquid phase. Furthermore, the concentration of ozone was monitored to examine the kinetics of the oxidation reaction. The integrated ozone profile recorded by UV-VIS spectrometry shows that the consumed ozone represents only approximately 12% of total oleic acid for the solid cases at 4°C in contrast to 30% for the liquid cases at 25°C, and hence confirmed the existence of secondary reactions.

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. Heterogeneity and proliferation of invasive cancer subclones in game theory models of the Warburg effect.

    PubMed

    Archetti, M

    2015-04-01

    The Warburg effect, a switch from aerobic energy production to anaerobic glycolysis, promotes tumour proliferation and motility by inducing acidification of the tumour microenvironment. Therapies that reduce acidity could impair tumour growth and invasiveness. I analysed the dynamics of cell proliferation and of resistance to therapies that target acidity, in a population of cells, under the Warburg effect. The dynamics of mutant cells with increased glycolysis and motility has been assessed in a multi-player game with collective interactions in the framework of evolutionary game theory. Perturbations of the level of acidity in the microenvironment have been used to simulate the effect of therapies that target glycolysis. The non-linear effects of glycolysis induce frequency-dependent clonal selection leading to coexistence of glycolytic and non-glycolytic cells within a tumour. Mutants with increased motility can invade such a polymorphic population and spread within the tumour. While reducing acidity may produce a sudden reduction in tumour cell proliferation, frequency-dependent selection enables it to adapt to the new conditions and can enable the tumour to restore its original levels of growth and invasiveness. The acidity produced by glycolysis acts as a non-linear public good that leads to coexistence of cells with high and low glycolysis within the tumour. Such a heterogeneous population can easily adapt to changes in acidity. Therapies that target acidity can only be effective in the long term if the cost of glycolysis is high, that is, under non-limiting oxygen concentrations. Their efficacy, therefore, is reduced when combined with therapies that impair angiogenesis. © 2015 The Authors Cell Proliferation Published by John Wiley & Sons Ltd.

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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…

  20. 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…

  1. 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

  2. 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).

  3. 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

  4. Estimation of bony orbit depth for optimal selection of the injection technique to correct the tear trough and palpebromalar groove.

    PubMed

    El-Garem, Yehia Farouk

    2015-01-01

    Different techniques have been used for filler injection of the tear trough and palpebromalar groove. Most patients report good results; however, some patients here experienced variable degrees of side effects. To assess if previous estimation of the bony orbit depth could affect the choice between bolus and serial puncture technique, and thereby the procedure outcome. In 32 patients, the periosteum depth was measured by using a 28 G needle at 2 points: Point A at the midpupillary line and Point B at the outer canthus. The bolus technique was performed in the right side, and serial puncture technique was done on the left side. There was a significant difference in the degree of improvement between both sides in 71% of patients: 40% had better improvement on the right side, whereas 31% had better improvement on the left side. Cases with skin-to-periosteum depth less than 0.5 cm showed better results with serial puncture technique, whereas those with more than 0.5 cm depth showed better results with bolus technique. Assessment of bony orbit depth could offer new tool for selecting infraorbital groove injection technique.

  5. 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.

  6. 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.

  7. 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.

  8. The effects of propranolol on heterogeneity of rat cerebral small vein oxygen saturation.

    PubMed

    Chi, O Z; Liu, X; Weiss, H R

    1999-09-01

    beta-Adrenergic receptors are involved in altering cerebral metabolism and blood flow. This study was performed to determine whether propranolol would alter the microregional O2 balance in the brain. Rats were anesthetized with 1.4% isoflurane. Isotonic sodium chloride solution (control group), propranolol 2 mg/kg (low propranolol group) or propranolol 20 mg/kg (high propranolol group) was administered IV to the rats. Twenty minutes later, regional cerebral blood flow (rCBF) was measured using the 14C-iodoantipyrine autoradiographic technique. Small (diameter <70 microm) arterial and venous oxygen saturation (SaO2 and SvO2, respectively) was determined using microspectrophotometry in the alternate slices of the tissue sections used to measure rCBF. In both the low and high propranolol groups, average cortical rCBF was 35% lower than that in the control group. The average O2 consumption of the cortex of the propranolol groups was significantly lower than control (low propranolol: -41%, high propranolol: -49%). In all groups, SaO2 was almost identi-cal. The heterogeneity of the microregional SvO2 expressed as the coefficient of variation (CV = 100 x sD/mean) was significantly lower in the propranolol groups (low propranolol: 8.0+/-2.3, high propranolol: 7.3 +/- 2.9) than in the control group (13.4 +/- 3.5). The proportion of cortical veins with Svo2 <55% was significantly smaller in the low and high propranolol groups (4 of 60 and 3 of 60, respectively) than that in the control group (15 of 60). In the other brain regions, the data followed a similar pattern. Our data demonstrated that propranolol is effective in decreasing O2 consumption, improving microregional O2 balance, and reducing its heterogeneity in the brain. Our data suggest that the linkage of O2 supply and consumption is not tightly coupled under isoflurane anesthesia. beta-Adrenergic blockers may tighten this linkage and reduce the number of low O2-saturated microregions.

  9. 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

  10. 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

  11. Insights into the effects of patchy ice layers on water balance heterogeneity in peatlands

    NASA Astrophysics Data System (ADS)

    Dixon, Simon; Kettridge, Nicholas; Devito, Kevin; Petrone, Rich; Mendoza, Carl; Waddington, Mike

    2017-04-01

    Peatlands in boreal and sub-arctic settings are characterised by a high degree of seasonality. During winter soils are frozen and snow covers the surface preventing peat moss growth. Conversely, in summer, soils unfreeze and rain and evapotranspiration drive moss productivity. Although advances have been made in understanding growing season water balance and moss dynamics in northern peatlands, there remains a gap in knowledge of inter-seasonal water balance as layers of ice break up during the spring thaw. Understanding the effects of ice layers on spring water balance is important as this coincides with periods of high wildfire risk, such as the devastating Fort McMurrary wildfire of May, 2016. We hypothesise that shallow layers of ice disconnect the growing surface of moss from a falling water table, and prevent water from being supplied from depth. A disconnect between the evaporating surface and deeper water storage will lead to the drying out of the surface layer of moss and a greater risk of severe spring wildfires. We utilise the unsaturated flow model Hydrus 2D to explore water balance in peat layers with an impermeable layer representing ice. Additionally we create models to represent the heterogeneous break up of ice layers observed in Canadian boreal peatlands; these models explore the ability of breaks in an ice layer to connect the evaporating surface to a deeper water table. Results show that peatlands with slower rates of moss growth respond to dry periods by limiting evapotranspiration and thus maintain moist conditions in the sub-surface and a water table above the ice layer. Peatlands which are more productive continue to grow moss and evaporate during dry periods; this results in the near surface mosses drying out and the water table dropping below the level of the ice. Where there are breaks in the ice layer the evaporating surface is able to maintain contact with a falling water table, but connectivity is limited to above the breaks, with

  12. 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

  13. 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

  14. 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.

  15. Effect of molecular weight heterogeneity on drug encapsulation efficiency of gelatin nano-particles.

    PubMed

    Saxena, Anita; Sachin, Kumar; Bohidar, H B; Verma, Anita Kamra

    2005-09-25

    Influence of molecular weight heterogeneity and drug solubility, drug loading and hydrodynamic conditions on drug release kinetics from gelatin nanoparticles were investigated. Also to assess the ability of gelatin nanoparticles as a potential intravascular probe for diagnostic purposes and in improving the biodelivery of cycloheximide (CHX), which is being used as a representative drug. Comparative characterization of 75 Bloom (type B, bovine), 175 and 300 Bloom (type A, porcine) gelatin nanoparticles was done to understand the phase behavior and hydrodynamic properties of gelatin chains and its nanoparticles. Gelatin nanoparticles were prepared by two-step desolvation method. Dynamic light scattering studies were performed to estimate hydrodynamic radii as well as intermolecular interaction. Effects of parameters like pH, temperature and molecular weight on the size and stability of the nanoparticles were studied. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements were done for size and stability analysis. Enhanced visco-elastic properties of nanoparticles were observed as compared to normal solutions of gelatin.

  16. Effect of the heterogeneity of metamaterials on the Casimir-Lifshitz interaction

    SciTech Connect

    Azari, Arash; Golestanian, Ramin; Miri, MirFaez

    2010-09-15

    The Casimir-Lifshitz interaction between metamaterials is studied using a model that takes into account the structural heterogeneity of the dielectric and magnetic properties of the bodies. A recently developed perturbation theory for the Casimir-Lifshitz interaction between arbitrary material bodies is generalized to include nonuniform magnetic permeability profiles and used to study the interaction between the magneto-dielectric heterostructures within the leading order. The metamaterials are modeled as two-dimensional arrays of domains with varying permittivity and permeability. In the case of two semi-infinite bodies with flat boundaries, the patterned structure of the material properties is found to cause the normal Casimir-Lifshitz force to develop an oscillatory behavior when the distance between the two bodies is comparable to the wavelength of the patterned features in the metamaterials. The nonuniformity also leads to the emergence of lateral Casimir-Lifshitz forces, which tend to strengthen as the gap size becomes smaller. Our results suggest that the recent studies on Casimir-Lifshitz forces between metamaterials, which have been performed with the aim of examining the possibility of observing the repulsive force, should be revisited to include the effect of the patterned structure at the wavelength of several hundred nanometers that coincides with the relevant gap size in the experiments.

  17. 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.

  18. 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.

  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. Analysis of gold in rock samples using laser-induced breakdown spectroscopy: Matrix and heterogeneity effects

    NASA Astrophysics Data System (ADS)

    Rifai, Kheireddine; Laflamme, Marcel; Constantin, Marc; Vidal, François; Sabsabi, Mohamad; Blouin, Alain; Bouchard, Paul; Fytas, Konstantinos; Castello, Maryline; Kamwa, Blandine Nguegang

    2017-08-01

    We used the laser-induced breakdown spectroscopy (LIBS) technique to determine the concentration of gold in rock samples. 44 reference materials (mostly compressed fine powders) of various chemical compositions, with a quasi-homogeneous concentration of gold varying from 0 to 1000 ppm, were used to establish the calibration curve for the Au I 267.59 nm line. A chemometric study based on the principal component analysis (PCA) showed that 83% of the LIBS spectra variations are attributable to the presence of iron in the samples. Two distinct branches were obtained in the calibration curve: one for Si-rich samples (< 5% of iron) and one for Fe-rich samples (> 13% of iron) with limits of detection of 0.8 ppm and 1.5 ppm, respectively. Different normalization schemes of the gold signal were tested in order to reduce the matrix effects. The LIBS analysis was performed on various mineral samples of practical interest, namely two Si-rich uncompressed ore powders, fine and granular, and three bulk drill cores. The fluctuations in the gold concentration measurements appear to be about two times greater in the granular powder (5-10%) than in the fine one (2-5%). A detailed mapping of the gold concentration on a solid drill core was also performed, revealing multiscale heterogeneity of the gold distribution on the surface of the sample.

  1. 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.

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

    PubMed

    Zúñiga-Benítez, Henry; Peñuela, Gustavo A

    2017-03-01

    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.

  3. 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

  4. Effects of Gardening on the Heterogeneity of Ice Layers in Lunar Cold Traps

    NASA Astrophysics Data System (ADS)

    Hurley, D.; Retherford, K. D.; Lucey, P. G.; Patterson, G. W.

    2016-12-01

    In very cold places, where thermal diffusion does not occur, impact gardening is the primary driver of the depth and lateral distribution of water ice. Using a model of impact gardening, I simulate the evolution of regolith over time in extremely cold lunar permanently shadowed regions. The simulations provide information about the redistribution of ice due to impacts on a large range of size scales. I apply the model to provide the evolution of a putative ice layer over time. The model output is interpreted in terms of how the heterogeneous distribution would appear to various remote sensing techniques including LRO instruments Mini-RF, LEND, LAMP, and LOLA. Factoring in those instruments fields of view and sensitivities, the same ice deposit may appear very different to these different types of measurements. I report on the scenarios (age, initial thickness, number of layers) that are consistent with the existing set of observations from LRO. In contrast, the planet Mercury has pervasive ice deposits. Much more of the surface has temperatures where thermal effects are important, which may be the differentiating factor. Alternatively, Mercury may have access to a greater source of water ice or a more recent episodic event. The model output can also be used to facilitate mission planning for a landed mission in lunar polar regions that aims to acquire samples of volatiles in situ. The implications for the model for site selection, mobility range, and subsurface access are presented.

  5. 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

  6. 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.

  7. Melorheostosis of the hand with complicating bony spur formation and bursal inflammation: diagnosis and treatment.

    PubMed

    Ameen, S; Nagy, L; Gerich, U; Anderson, S E

    2002-08-01

    A 37-year old woman presented with intolerable pain associated with a slowly growing mass on the dorsum of the right hand. The radiographs were characteristic of melorheostosis involving the third and fourth metacarpals, with a cortical bony projection extending from the base of the third metacarpal eroding slightly into the fourth metacarpal, associated with bursal formation. Magnetic resonance imaging (MRI) demonstrated an inflamed bursal collection adjacent to the spur. This region corresponded to the patient's severe clinical, focal pain. To our knowledge, this is the first case report in which melorheostosis of the hand has been associated with bony spur formation and complicated by an inflamed bursa.

  8. 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.

  9. 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.

  10. The Effect of Methyl, Hydroxyl, and Ketone Functional Groups on the Heterogeneous Oxidation of Succinic Acid Aerosol by OH Radicals

    NASA Astrophysics Data System (ADS)

    Chan, M.; Zhang, H.; Wilson, K. R.

    2013-12-01

    The heterogeneous oxidation of atmospheric organic aerosols can influence their effects on climate, human health, and visibility. During oxidation, functionalization occurs when an oxygenated functional group is added to a molecule, leaving the carbon skeleton intact. Fragmentation involves carbon-carbon bond cleavage and produces two products with smaller carbon numbers than the parent compound. To gain better insights into how the molecular structure of more oxygenated organic compounds affects heterogeneous reactivity, succinic acid aerosols are photo-oxidized in an aerosol flow tube reactor, and the reaction products are analyzed using Direct Analysis in Real Time Mass Spectrometry for online chemical analysis. The effect of various functional groups (CH3, OH, C=O) along the carbon backbone on the heterogeneous reaction mechanisms are also investigated using model compounds. For this series of compounds, the formation of more oxygenated products through functionalization can be explained by well-known condensation-phase reactions such as Russell and Bennett and Summers. The number of fragmentation products is found to increase with the presence of OH and CH3 groups. This can be attributed to the increased number of tertiary carbons, enhancing the fragmentation after multiple oxidation steps. Smaller dicaids (oxalic acid and malonic acid) can be formed through the fragmentation processes in the heterogeneous oxidation of succinic acid. The effect of molecular structure on reaction kinetics, volatilization, and the relative importance of functionalization and fragmentation pathways will be discussed.

  11. 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.

  12. Quantifying the effects of migration and mutation on adaptation and demography in spatially heterogeneous environments.

    PubMed

    Débarre, F; Ronce, O; Gandon, S

    2013-06-01

    How do mutation and gene flow influence population persistence, niche expansion and local adaptation in spatially heterogeneous environments? In this article, we analyse a demographic and evolutionary model of adaptation to an environment containing two habitats in equal frequencies, and we bridge the gap between different theoretical frameworks. Qualitatively, our model yields four qualitative types of outcomes: (i) global extinction of the population, (ii) adaptation to one habitat only, but also adaptation to both habitats with, (iii) specialized phenotypes or (iv) with generalized phenotypes, and we determine the conditions under which each equilibrium is reached. We derive new analytical approximations for the local densities and the distributions of traits in each habitat under a migration-selection-mutation balance, compute the equilibrium values of the means, variances and asymmetries of the local distributions of phenotypes, and contrast the effects of migration and mutation on the evolutionary outcome. We then check our analytical results by solving our model numerically, and also assess their robustness in the presence of demographic stochasticity. Although increased migration results in a decrease in local adaptation, mutation in our model does not influence the values of the local mean traits. Yet, both migration and mutation can have dramatic effects on population size and even lead to metapopulation extinction when selection is strong. Niche expansion, the ability for the population to adapt to both habitats, can also be prevented by small migration rates and a reduced evolutionary potential characterized by rare mutation events of small effects; however, niche expansion is otherwise the most likely outcome. Although our results are derived under the assumption of clonal reproduction, we finally show and discuss the links between our model and previous quantitative genetics models. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European

  13. 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.

  14. Heterogeneity in the Effects of Reward- and Deposit-based Financial Incentives on Smoking Cessation.

    PubMed

    Halpern, Scott D; French, Benjamin; Small, Dylan S; Saulsgiver, Kathryn; Harhay, Michael O; Audrain-McGovern, Janet; Loewenstein, George; Asch, David A; Volpp, Kevin G

    2016-10-15

    Targeting different smoking cessation programs to smokers most likely to quit when using them could reduce the burden of lung disease. To identify smokers most likely to quit using pure reward-based financial incentives or incentive programs requiring refundable deposits to become eligible for rewards. We conducted prespecified secondary analyses of a randomized trial in which 2,538 smokers were assigned to an $800 reward contingent on sustained abstinence from smoking, a refundable $150 deposit plus a $650 reward, or usual care. Using logistic regression, we identified characteristics of smokers that were most strongly associated with accepting their assigned intervention and ceasing smoking for 6 months. We assessed modification of the acceptance, efficacy, and effectiveness of reward and deposit programs by 11 prospectively selected demographic, smoking-related, and psychological factors. Predictors of sustained smoking abstinence differed among participants assigned to reward- versus deposit-based incentives. However, greater readiness to quit and less steep discounting of future rewards were consistently among the most important predictors. Deposit-based programs were uniquely effective relative to usual care among men, higher-income participants, and participants who more commonly failed to pay their bills (all interaction P values < 0.10). Relative to rewards, deposits were more effective among black persons (P = 0.022) and those who more commonly failed to pay their bills (P = 0.082). Relative to rewards, deposits were more commonly accepted by higher-income participants, men, white persons, and those who less commonly failed to pay their bills (all P < 0.05). Heterogeneity among smokers in their acceptance and response to different forms of incentives suggests potential benefits of targeting behavior-change interventions based on patient characteristics. Clinical trial registered with www.clinicaltrials.gov (NCT 01526265).

  15. 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.

  16. The effects of acetaldehyde, glyoxal and acetic acid on the heterogeneous reaction of nitrogen dioxide on gamma-alumina.

    PubMed

    Sun, Zhenyu; Kong, Lingdong; Ding, Xiaoxiao; Du, Chengtian; Zhao, Xi; Chen, Jianmin; Fu, Hongbo; Yang, Xin; Cheng, Tiantao

    2016-04-14

    Heterogeneous reactions of nitrogen oxides on the surface of aluminium oxide result in the formation of adsorbed nitrite and nitrate. However, little is known about the effects of other species on these heterogeneous reactions and their products. In this study, diffuse reflectance infrared spectroscopy (DRIFTS) was used to analyze the process of the heterogeneous reaction of NO2 on the surface of aluminium oxide particles in the presence of pre-adsorbed organic species (acetaldehyde, glyoxal and acetic acid) at 298 K and reveal the influence of these organic species on the formation of adsorbed nitrite and nitrate. It was found that the pre-adsorption of organic species (acetaldehyde, glyoxal and acetic acid) on γ-Al2O3 could suppress the formation of nitrate to different extents. Under the same experimental conditions, the suppression of the formation of nitrate by the pre-adsorption of acetic acid is much stronger than that by pre-adsorption of acetaldehyde and glyoxal, indicating that the influence of acetic acid on the heterogeneous reaction of NO2 is different from that of acetaldehyde and glyoxal. Surface nitrite is formed and identified to be an intermediate product. For the heterogeneous reaction of NO2 on the surface of γ-Al2O3 with and without the pre-adsorption of acetaldehyde and glyoxal, it is firstly formed and then gradually disappears as the reaction proceeds, but for the reaction with the pre-adsorption of acetic acid, it is the final main product besides nitrate. This indicates that the pre-adsorption of acetic acid would promote the formation of nitrite, while the others would not change the trend of the formation of nitrite. The possible influence mechanisms of the pre-adsorption of acetaldehyde, glyoxal and acetic acid on the heterogeneous conversion of NO2 on γ-Al2O3 are proposed and atmospheric implications based on these results are discussed.

  17. 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.

  18. 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

  19. Counterfactuals, Causal Effect Heterogeneity, and the Catholic School Effect on Learning.

    ERIC Educational Resources Information Center

    Morgan, Stephen L.

    2001-01-01

    Demonstrates an approach that places regression modeling strategies within a specific and well-developed framework for thinking about causality. Focuses on the Catholic school effect on learning. Provides propensity-score matching estimates of the Catholic school effect for the Catholic schooled to supplement estimates obtained by regression…

  20. Effects of temporal fluctuations, fluid density effects and heterogeneity on mixing of two fluids for a stable stratification

    NASA Astrophysics Data System (ADS)

    Pool, Maria; Dentz, Marco; Post, Vincent E. A.

    2017-04-01

    Mixing and dispersion in coastal aquifers are controlled by density variations, which are influenced by temporal fluctuations on multiple time-scales ranging from days (tides), seasons (pumping and recharge) to glacial cycles (regression and transgressions). Transient forcing effects lead to a complex space and time dependent flow response which induces enhanced spreading and mixing of dissolved substances. We study effective mixing and solute transport in temporally fluctuating flow for a stable stratification of two fluids of different density using detailed numerical simulation as well as accurate column experiments. For the homogeneous case, we quantify the observed transport behaviors and interface evolution by a time-averaged model that is obtained from a two-scale expansion of the full transport problem, and derive explicit expressions for the center of mass and width of the mixing zone between the two fluids (Pool et al., 2016). We find that the magnitude of transient-driven mixing is mainly controlled by the hydraulic diffusivity, the period, and the initial interface location. For the heterogeneous case, transient forcing and density-dependent transport is investigated considering multigaussian random log conductivity fields and more complex heterogeneous fields characterized by connected patterns of high and low conductivity. We find that the mixing potential and 'hot spots' are directly related to the deformation properties and topology of the flow field, specifically its stretching behavior in response to temporal fluctuations. We also find that gravity forces due to density variations cause smoother concentration distribution leading to a decrease in the width of the transition zone. However the mixing potential is similar as the one obtained with constant density. Reference: Pool, M., M. Dentz, and V.E.A. Post (2016), Transient forcing effects on mixing of two fluids for a stable stratification, Water Resour. Res., 52, 7178-7197, doi:10.1002/2016WR

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Effect of heterogeneity correction on dosimetric parameters of radiotherapy planning for thoracic esophageal cancer

    SciTech Connect

    Nakayama, Masao; Yoshida, Kenji; Nishimura, Hideki; Miyawaki, Daisuke; Uehara, Kazuyuki; Okamoto, Yoshiaki; Okayama, Takanobu; Sasaki, Ryohei

    2014-04-01

    The present study aimed to investigate the effect of heterogeneity correction (HC) on dosimetric parameters in 3-dimensional conformal radiotherapy planning for patients with thoracic esophageal cancer. We retrospectively analyzed 20 patients. Two treatment plans were generated for each patient using a superposition algorithm on the Xio radiotherapy planning system. The first plan was calculated without HC. The second was a new plan calculated with HC, using identical beam geometries and maintaining the same number of monitor units as the first. With regard to the planning target volume (PTV), the overall mean differences in the prescription dose, maximum dose, mean dose, and dose that covers 95% of the PTV between the first and second plans were 1.10 Gy (1.8%), 1.35 Gy (2.2%), 1.10 Gy (1.9%), and 0.56 Gy (1.0%), respectively. With regard to parameters related to the organs at risk (OARs), the mean differences in the absolute percentages of lung volume receiving greater than 5, 10, 20, and 30 Gy (lung V{sub 5}, V{sub 10}, V{sub 20}, and V{sub 30}) between the first and second plans were 7.1%, 2.7%, 0.4%, and 0.5%, respectively. These results suggest that HC might have a more pronounced effect on the percentages of lung volume receiving lower doses (e.g., V{sub 5} and V{sub 10}) than on the dosimetric parameters related to the PTV and other OARs.

  6. 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.

  7. 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.

  8. Effect of dynamical heterogeneity on heat capacity at glass transition in typical silicate glasses

    NASA Astrophysics Data System (ADS)

    Li, Y. Z.; Zhao, L. Z.; Sun, Y. T.; Wen, P.; Bai, H. Y.; Wang, W. H.

    2015-12-01

    The heat capacity jump ΔCp at glass transition and the dynamical heterogeneity are two of the most important features of glass forming liquids. In order to reveal the intrinsic relationship between the two properties, a model glass system (Na2O)x(SiO2)1-x (x = 0.2-0.35) was studied by the systematic measurements of the ΔCp and the mechanical relaxation in the supercooled liquid region. A linear increase in ΔCp with increasing content of Na2O was found, indicating direct contributions of the locally fast dynamics around Na2O to ΔCp. This positive correlation between the locally heterogeneous dynamics and ΔCp was further confirmed by the dynamical heterogeneity analyses. Our results might be helpful for understanding the nature of glass transition.

  9. [Defect of the bony roof in the superior semicircular canal and its clinical implications].

    PubMed

    Whyte Orozco, Jaime; Martínez, Claudio; Cisneros, Ana; Obón, Jesús; Gracia-Tello, Borja; Angel Crovetto, Miguel

    2011-01-01

    The aetiology of the superior semicircular canal dehiscence is currently unknown. Our objective was to analyse and discuss different hypotheses about the origin of this pathology. In this study performed on 295 temporal bones, one case of partial alteration of the bony roof in the right superior semicircular canal was described from the anatomical and radiological points of view, and compared with the temporal bone on the other side. Macroscopically, the superior semicircular canal shows deterioration in the bony roof, which consists exclusively of the inner or endosteal layer that separates the canal from the superior semicircular conduct. The Pöschl plane reconstruction showed a whole bony roof, but its thickness decreased from the canal curvature to the defect (from 0.6 to 0.3mm). The presence of partial defects in the bony roof of the superior semicircular canal with absence of the external and middle layers, besides its lesser thickness, makes the canal susceptible to suffering a second event. This could produce its fracture and a dehiscence. Copyright © 2010 Elsevier España, S.L. All rights reserved.

  10. Bony spinal canal changes that differentiate conjoined nerve roots from herniated nucleus pulposus

    SciTech Connect

    Hoddick, W.K.; Helms, C.A.

    1985-01-01

    CT examinations of the lumbar spine in 12 consecutive patients with conjoined nerve roots were reviewed. Asymmetry of the bony spinal canal, seen as slight dilatation of the ipsilateral lateral recess, was present in all cases. This finding, which is not typically associated with extruded free intervertebral disk fragments, should serve to distinguish these two entities.

  11. Arthroscopic Double-Row Suture Anchor Repair of Acute Posterior Bony Bankart Lesion.

    PubMed

    Ly, Justin A; Coleman, Erin M; Kropf, Eric J

    2016-08-01

    The treatment of anterior shoulder instability is well described with various techniques, including arthroscopic double-row repair, an alternative to open stabilization procedures in high-risk groups. The surgical management of posterior instability in high-risk and athletic populations is a less-explored entity. We describe our technique for an all arthroscopic double-row suture anchor repair of a large posterior bony Bankart lesion. We prefer this technique over percutaneous cannulated screw fixation because the double-row suture technique allows for incorporation of capsular plication with bony fixation in an effort to better restore normal anatomy for capsulolabral complex. Double-row repair capsulolabral repair or fixation of the bony Bankart is performed via a suture-bridge technique. Medial row anchors are placed down the glenoid neck and shuttled around the bony fragment and labrum. The lateral-row anchor is placed at the rim of the native glenoid. This repair technique has been shown to increase the surface area for healing and more closely reconstruct the native anatomic capsulolabral complex footprint, improve force distribution, and potentially impart enhanced posterior stability to the glenohumeral joint.

  12. Size of bony labyrinth of human infant and adult compared to that in certain animals.

    PubMed

    Tremble, G E

    1978-01-01

    Comparative anatomic studies of the bony labyrinths of humans and those of a full grown pony, zebra, grizzly bear, seal and domestic cow were performed. Fusible metal was injected into the labyrinths and the resultant casts were then measured. The similarities and differences were noted and discussed.

  13. Another CT sign of sinonasal polyposis: truncation of the bony middle turbinate.

    PubMed

    Liang, E Y; Lam, W W; Woo, J K; Van Hasselt, C A; Metreweli, C

    1996-01-01

    In order to study the features of sinonasal polyposis (SNP) on CT, 100 consecutive coronal sinus CT examinations done for chronic inflammatory sinonasal disease were reviewed. The CT findings of the 27 fully documented SNPs were analyzed. All our SNPs were bilateral. There was a strong tendency for extensive involvement. Nasal polyps were seen in 22 of 27(81%); bony trabecular deossification in 23 of 27 (85%); widening of infundibulum in 26 of 27 (96%). We discovered a new sign "truncation of the bony middle turbinate", where the bulbous part of bony middle turbinate was missing, in 15 of 26 (58%) of SNP patients without a previous history of middle turbinectomy, 12 of 15(80%) were bilateral. The one SNP patient (1 of 27) with previous middle turbinectomy was not regarded to be real truncation. Truncation of the bony middle turbinate is a characteristic and easily recognizable ancillary sign, and is not seen in other patterns of sinusitis. Together with other features on coronal sinus CT, this adds diagnostic confidence in diagnosing sinonasal polyposis.

  14. 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.

  15. 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.

  16. Evaluation of treatment-effect heterogeneity using biomarkers measured on a continuous scale: subpopulation treatment effect pattern plot.

    PubMed

    Lazar, Ann A; Cole, Bernard F; Bonetti, Marco; Gelber, Richard D

    2010-10-10

    The discovery of biomarkers that predict treatment effectiveness has great potential for improving medical care, particularly in oncology. These biomarkers are increasingly reported on a continuous scale, allowing investigators to explore how treatment efficacy varies as the biomarker values continuously increase, as opposed to using arbitrary categories of expression levels resulting in a loss of information. In the age of biomarkers as continuous predictors (eg, expression level percentage rather than positive v negative), alternatives to such dichotomized analyses are needed. The purpose of this article is to provide an overview of an intuitive statistical approach-the subpopulation treatment effect pattern plot (STEPP)-for evaluating treatment-effect heterogeneity when a biomarker is measured on a continuous scale. STEPP graphically explores the patterns of treatment effect across overlapping intervals of the biomarker values. As an example, STEPP methodology is used to explore patterns of treatment effect for varying levels of the biomarker Ki-67 in the BIG (Breast International Group) 1-98 randomized clinical trial comparing letrozole with tamoxifen as adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer. STEPP analyses showed patients with higher Ki-67 values who were assigned to receive tamoxifen had the poorest prognosis and may benefit most from letrozole.

  17. Machines vs. ensembles: effective MAPK signaling through heterogeneous sets of protein complexes.

    PubMed

    Suderman, Ryan; Deeds, Eric J

    2013-01-01

    Despite the importance of intracellular signaling networks, there is currently no consensus regarding the fundamental nature of the protein complexes such networks employ. One prominent view involves stable signaling machines with well-defined quaternary structures. The combinatorial complexity of signaling networks has led to an opposing perspective, namely that signaling proceeds via heterogeneous pleiomorphic ensembles of transient complexes. Since many hypotheses regarding network function rely on how we conceptualize signaling complexes, resolving this issue is a central problem in systems biology. Unfortunately, direct experimental characterization of these complexes has proven technologically difficult, while combinatorial complexity has prevented traditional modeling methods from approaching this question. Here we employ rule-based modeling, a technique that overcomes these limitations, to construct a model of the yeast pheromone signaling network. We found that this model exhibits significant ensemble character while generating reliable responses that match experimental observations. To contrast the ensemble behavior, we constructed a model that employs hierarchical assembly pathways to produce scaffold-based signaling machines. We found that this machine model could not replicate the experimentally observed combinatorial inhibition that arises when the scaffold is overexpressed. This finding provides evidence against the hierarchical assembly of machines in the pheromone signaling network and suggests that machines and ensembles may serve distinct purposes in vivo. In some cases, e.g. core enzymatic activities like protein synthesis and degradation, machines assembled via hierarchical energy landscapes may provide functional stability for the cell. In other cases, such as signaling, ensembles may represent a form of weak linkage, facilitating variation and plasticity in network evolution. The capacity of ensembles to signal effectively will ultimately

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

    PubMed

    Willke, Richard J; Zheng, Zhiyuan; Subedi, Prasun; Althin, Rikard; Mullins, C Daniel

    2012-12-13

    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.

  19. 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

  20. Energy resolution and dynamical heterogeneity effects on elastic incoherent neutron scattering from molecular systems.

    PubMed

    Becker, Torsten; Smith, Jeremy C

    2003-02-01

    Incoherent neutron scattering is widely used to probe picosecond-nanosecond time scale dynamics of molecular systems. In systems of spatially confined atoms the relatively high intensity of elastic incoherent neutron scattering is often used to obtain a first estimate of the dynamics present. For many complex systems, however, experimental elastic scattering is difficult to interpret unambiguously using analytical dynamical models that go beyond the determination of an average mean-square displacement. To circumvent this problem a description of the scattering is derived here that encompasses a variety of analytical models in a common framework. The framework describes the time-converged part of the dynamic structure factor [the elastic incoherent scattering function (EISF)] and lends itself to practical use by explicitly incorporating effects due to the finite energy resolution of the instrument used. The dependence of the elastic scattering on wave vector is examined, and it is shown how heterogeneity in the distribution of mean-square displacements can be related to deviations of the scattering from Gaussian behavior. In this case, a correction to fourth order in the scattering vector can be used to extract the variance of the distribution of mean-square displacements. The formalism is used in a discussion of measurements on dynamics accompanying the glass transition in molecular systems. By fitting to experimental data obtained on a protein solution the present methodology is used to show how the existence of a temperature-dependent relaxation frequency can lead to a transition in the measured mean-square displacement in the absence of an EISF change.

  1. Effects of Porous Media Heterogeneity and Transverse Mixing on Bacterial Growth

    NASA Astrophysics Data System (ADS)

    Werth, C. J.; Zhang, C.; Zilles, J.; Mueller, R.; Kang, Q.

    2009-12-01

    Microbial degradation of contaminants in the subsurface depends to a large extent on the availability of nutrients, which is impacted by porous media heterogeneity and the degree of transverse mixing. The growth of a pure culture (Delftia acidovorans strain R39bR) that degrades (R)-2-(2,4-dichlorophenoxy)propionate (R-2,4-DP) was evaluated in two types of microfluidic pore structures etched into silicon wafers (i.e., micromodels): i) a homogeneous distribution of cylindrical posts, and ii) aggregates of large and small cylindrical posts. Each micromodel was inoculated with suspended cells of R39bR for 5-8 days. Next, aqueous phase O2 and R-2,4-DP were introduced as two separate and parallel streams that mixed transverse to the direction of flow along the centerline of each pore structure. In the homogeneous micromodel, biomass growth was observed as a narrow line along the centerline; in the aggregate micromodel, preferential microbial growth was observed in the inter-aggregate pore spaces. Image analysis indicates the initial rate (i.e., over first 30 days) of microbial growth is greater in the homogeneous micromodel than the aggregate micromodel. Effluent samples were collected and results showed higher R-2,4-DP degradation in the homogeneous pore structure than in the aggregate pore structure. A pore scale reactive transport model was used to simulate flow and substrates distribution in the two different pore structures. Simulation results indicate that biomass growth in intra-aggregate pore structures is limited by diffusion, and preferential growth occurs in inter-aggregate pores due to the high mass flux of nutrients in these spaces. Results from this study contribute to a better understanding of biomass growth in complex porous media systems and will help designing more effective bioremediation systems.

  2. Effect of stratum corneum heterogeneity, anisotropy, asymmetry and follicular pathway on transdermal penetration.

    PubMed

    Barbero, Ana M; Frasch, H Frederick

    2017-08-28

    The impact of the complex structure of the stratum corneum on transdermal penetration is not yet fully described by existing models. A quantitative and thorough study of skin permeation is essential for chemical exposure assessment and transdermal delivery of drugs. The objective of this study is to analyze the effects of heterogeneity, anisotropy, asymmetry, follicular diffusion, and location of the main barrier of diffusion on percutaneous permeation. In the current study, the solution of the transient diffusion through a two-dimensional-anisotropic brick-and-mortar geometry of the stratum corneum is obtained using the commercial finite element program COMSOL Multiphysics. First, analytical solutions of an equivalent multilayer geometry are used to determine whether the lipids or corneocytes constitute the main permeation barrier. Also these analytical solutions are applied for validations of the finite element solutions. Three illustrative compounds are analyzed in these sections: diethyl phthalate, caffeine and nicotine. Then, asymmetry with depth and follicular diffusion are studied using caffeine as an illustrative compound. The following findings are drawn from this study: the main permeation barrier is located in the lipid layers; the flux and lag time of diffusion through a brick-and-mortar geometry are almost identical to the values corresponding to a multilayer geometry; the flux and lag time are affected when the lipid transbilayer diffusivity or the partition coefficients vary with depth, but are not affected by depth-dependent corneocyte diffusivity; and the follicular contribution has significance for low transbilayer lipid diffusivity, especially when flux between the follicle and the surrounding stratum corneum is involved. This study demonstrates that the diffusion is primarily transcellular and the main barrier is located in the lipid layers. Published by Elsevier B.V.

  3. 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.

  4. Effects of source zone heterogeneity on surfactant-enhanced NAPL dissolution and resulting remediation end-points.

    PubMed

    Saenton, S; Illangasekare, T H; Soga, K; Saba, T A

    2002-11-01

    The effectiveness of removal of nonaqueous phase liquids (NAPLs) from the entrapment source zone of the subsurface has been limited by soil heterogeneity and the inability to locate all entrapped sources. The goal of this study was to demonstrate the uncertainty of degree of source removal associated with aquifer heterogeneity. In this demonstration, source zone NAPL removal using surfactant-enhanced dissolution was considered. Model components that simulate the processes of natural dissolution in aqueous phase and surfactant-enhanced dissolution were incorporated into an existing code of contaminant transport. The dissolution modules of the simulator used previously developed Gilland-Sherwood type phenomenological models of NAPL dissolution to estimate mass transfer coefficients that are upscaleable to multidimensional flow conditions found at field sites. The model was used to simulate the mass removal from 10 NAPL entrapment zone configurations based on previously conducted two-dimensional tank experiments. These entrapment zones represent the NAPL distribution in spatially correlated random fields of aquifer hydraulic conductivity. The numerical simulations representing two-dimensional conditions show that effectiveness of mass removal depends on the aquifer heterogeneity that controls the NAPL entrapment and delivery of the surfactant to the locations of entrapped NAPLs. Flow bypassing resulting from heterogeneity and the reduction of relative permeability due to NAPL entrapment reduces the delivery efficiency of the surfactant, thus prolonging the remediation time to achieve desired end-point NAPL saturations and downstream dissolved concentrations. In some extreme cases, the injected surfactant completely bypassed the NAPL source zones. It was also found that mass depletion rates for different NAPL source configurations vary significantly. The study shows that heterogeneity result in uncertainties in the mass removal and achievable end-points that are

  5. Effects of initial telomere length distribution on senescence onset and heterogeneity.

    PubMed

    Eugène, Sarah; Bourgeron, Thibault; Xu, Zhou

    2017-01-21

    Replicative senescence, induced by telomere shortening, exhibits considerable asynchrony and heterogeneity, the origins of which remain unclear. Here, we formally study how telomere shortening mechanisms impact on senescence kinetics and define two regimes of senescence, depending on the initial telomere length variance. We provide analytical solutions to the model, highlighting a non-linear relationship between senescence onset and initial telomere length distribution. This study reveals the complexity of the collective behavior of telomeres as they shorten, leading to senescence heterogeneity. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  6. 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

  7. Arthroscopic repair of small and medium-sized bony Bankart lesions.

    PubMed

    Kim, Young-Kyu; Cho, Seung-Hyun; Son, Won-Su; Moon, Sung-Hoon

    2014-01-01

    There has been no study about treatment guidelines for arthroscopic repair according to the size of bony Bankart lesions of less than 25% of the glenoid width. To evaluate the results of arthroscopic repair for bony Bankart lesions managed with different repair techniques based on their size. Case series; Level of evidence, 4. Between March 2005 and February 2009, 44 of 52 consecutive patients with bony Bankart lesions with a size of less than 25% of the entire glenoid were managed with an arthroscopic approach. Of those patients, 34 (77%) were available for outcome analysis at a minimum 24 months' follow-up (mean, 34 months; range, 24-60 months). The size of the fragment was measured by computed tomography (CT) and classified as small (<12.5% of the inferior glenoid width) and medium (12.5%-25%). Sixteen lesions were classified as small (small group), and 18 were classified as medium (medium group). For small lesions, capsulolabral repair using suture anchors without excision of the bony fragment was performed. For medium lesions, anatomic reduction and fixation using suture anchors was performed, and the adequacy of reduction was assessed by CT postoperatively. The visual analog scale (VAS) for pain score and modified Rowe score for bony Bankart repair were compared and the postoperative recurrence rate investigated. One patient from the small group (6.3%) and 1 patient without anatomic reduction of the bony fragment in the medium group (5.6%) experienced traumatic redislocations. The mean VAS score improved from 1.7 preoperatively to 0.5 at final follow-up, and the mean Rowe score improved from 59 to 91 (both P < .001). The mean postoperative Rowe scores increased from 58 to 92 in the small group and from 60 to 91 in the medium group (both P < .001). Residual joint incongruity measuring ≤2 mm on both axial and coronal scans, which was considered an anatomic reduction, was present in 14 cases (77.8%) in the medium group. In the medium group, the mean

  8. 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

  9. CAT & MAUS: A novel system for true dynamic motion measurement of underlying bony structures with compensation for soft tissue movement.

    PubMed

    Jia, Rui; Monk, Paul; Murray, David; Noble, J Alison; Mellon, Stephen

    2017-09-06

    Optoelectronic motion capture systems are widely employed to measure the movement of human joints. However, there can be a significant discrepancy between the data obtained by a motion capture system (MCS) and the actual movement of underlying bony structures, which is attributed to soft tissue artefact. In this paper, a computer-aided tracking and motion analysis with ultrasound (CAT & MAUS) system with an augmented globally optimal registration algorithm is presented to dynamically track the underlying bony structure during movement. The augmented registration part of CAT & MAUS was validated with a high system accuracy of 80%. The Euclidean distance between the marker-based bony landmark and the bony landmark tracked by CAT & MAUS was calculated to quantify the measurement error of an MCS caused by soft tissue artefact during movement. The average Euclidean distance between the target bony landmark measured by each of the CAT & MAUS system and the MCS alone varied from 8.32mm to 16.87mm in gait. This indicates the discrepancy between the MCS measured bony landmark and the actual underlying bony landmark. Moreover, Procrustes analysis was applied to demonstrate that CAT & MAUS reduces the deformation of the body segment shape modeled by markers during motion. The augmented CAT & MAUS system shows its potential to dynamically detect and locate actual underlying bony landmarks, which reduces the MCS measurement error caused by soft tissue artefact during movement. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. First record of eocene bony fishes and crocodyliforms from Canada's Western Arctic.

    PubMed

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

    2014-01-01

    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. 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). 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 time between the two extant alligatorid lineages Alligator

  11. 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

  12. Theoretical analysis of non-Gaussian heterogeneity effects on subsurface flow and transport

    NASA Astrophysics Data System (ADS)

    Riva, Monica; Guadagnini, Alberto; Neuman, Shlomo P.

    2017-04-01

    Much of the stochastic groundwater literature is devoted to the analysis of flow and transport in Gaussian or multi-Gaussian log hydraulic conductivity (or transmissivity) fields, Y(x)=ln\\func K(x) (x being a position vector), characterized by one or (less frequently) a multiplicity of spatial correlation scales. Yet Y and many other variables and their (spatial or temporal) increments, ΔY, are known to be generally non-Gaussian. One common manifestation of non-Gaussianity is that whereas frequency distributions of Y often exhibit mild peaks and light tails, those of increments ΔY are generally symmetric with peaks that grow sharper, and tails that become heavier, as separation scale or lag between pairs of Y values decreases. A statistical model that captures these disparate, scale-dependent distributions of Y and ΔY in a unified and consistent manner has been recently proposed by us. This new "generalized sub-Gaussian (GSG)" model has the form Y(x)=U(x)G(x) where G(x) is (generally, but not necessarily) a multiscale Gaussian random field and U(x) is a nonnegative subordinator independent of G. The purpose of this paper is to explore analytically, in an elementary manner, lead-order effects that non-Gaussian heterogeneity described by the GSG model have on the stochastic description of flow and transport. Recognizing that perturbation expansion of hydraulic conductivity K=eY diverges when Y is sub-Gaussian, we render the expansion convergent by truncating Y's domain of definition. We then demonstrate theoretically and illustrate by way of numerical examples that, as the domain of truncation expands, (a) the variance of truncated Y (denoted by Yt) approaches that of Y and (b) the pdf (and thereby moments) of Yt increments approach those of Y increments and, as a consequence, the variogram of Yt approaches that of Y. This in turn guarantees that perturbing Kt=etY to second order in σYt (the standard deviation of Yt) yields results which approach those we obtain

  13. Cost-effective raingauge deployment and rainfall heterogeneity effect on hydrograph simulation in mountainous watersheds

    NASA Astrophysics Data System (ADS)

    Huang-Chuan, Jr.; Kao, Shuh-Ji; Chang, Kang-Tsung; Lin, Chuan-Yao; Chang, Pao-Liang

    2008-08-01

    To what extent hydrograph simulation was influenced by the representativeness of rainfall input were examined in meso-scale subtropical mountainous watersheds, accordingly, cost-effective raingauge deployment was suggested. Two nested watersheds in northern Taiwan and two extreme typhoons with torrential rains were undertaken as case studies. The input of radar rainfall estimates with high spatial resolution of 1.3 km2 served as a reference, which was applied onto hydrograph simulation in TOPMODEL. After calibration, optimal parameters were obtained and fixed to examine effect of deviated rainfall on hydrograph. To mimic possible raingauge networks we designed four raingauge number classes: very low (3 points/total pixels), low (10 points/total), medium (20 points/total), and high (50 points/total) based on radar rainfall for the two watersheds in different size, thus, creating wide spectrum of raingauge density. All the corresponding hydrographs were compared with the reference hydrograph to probe errors in event discharge induced by calculated rainfall input. Results showed that with the decreasing of raingauge density the biases (indicated by RMSE) of rainfall field estimates increase and the potential variability in rainfall field due to random sampling in raingauge location is exaggerated. By contrast, biases in model hydrographs are significantly smaller than that in rainfall field. When the raingauge governing area is <10 km2/gauge, the biased rainfall field shows no detectable effect on hydrographs. Incomparably lower RMSE in hydrograph indicates that surplus and deficit rainfalls at different locations were compensated in model simulation. In term of reliable hydrograph simulation, obviously, the criterion for raingauge density is not as high as that for rainfall estimate. When gauge governing is <20 km2/gauge, both the rainfall and discharge were successfully (±10% error) estimated in term of total volume. Accordingly, we suggested that covering area ~20

  14. 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)

  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. 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.

  18. 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.

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

    PubMed Central

    Bradley, Patrick; Wiesenfeld, Kurt; Butera, Robert

    2010-01-01

    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 Type I and Type 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. PMID:20799058

  20. 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:…

  1. 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:…

  2. Toward Unified Correction of Regional Phases for Amplitude and Travel Time Effects of Heterogeneous Structure

    DTIC Science & Technology

    2014-11-01

    simulated. Pn amplitude for the BEM (diamonds) are compared to models with 0.5% RMS (squares), 1.0% RMS (triangles), and 2% RMS (X’s) Vp...basic Earth model ( BEM ) ............................................................................................... .16 16. Reference velocity...Pn amplitudes as a function of distance for all configurations of random volumetric mantle heterogeneity simulated. Pn amplitude for the BEM

  3. 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).

  4. 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.

  5. [Total hip arthroplasty for non-functional bony ankylosed hip in young and middle-aged patients].

    PubMed

    Fu, Yingxu; Yu, Boyong; Asihaerjiang-Maimaitiyiming; Cao, Li; Aili-Rehei

    2014-09-01

    To explore the effectiveness of total hip arthroplasty (THA) for non-functional bony ankylosed hip in young and middle-aged patients. Between January 2010 and March 2013, 14 cases (19 hips) of non-functional bony ankylosed hip were treated by THA. There were 9 males and 5 females, aged 37.5 years on average (range, 23- 58 years). The left hip was involved in 6 cases, the right hip in 3 cases, and bilateral hips in 5 cases. The causes were tuberculosis in 2 patients, ankylosing spondylitis in 5 patients, traumatic arthritis in 5 patients, osteoarthritis in 1 patient, and suppurative infection in 1 patient. The disease duration was 7-18 years with an average of 8.9 years. Flexion stiffness was observed in 10 hips, flexion abduction stiffness in 6 hips, and flexion adduction shortening stiffness in 3 hips. Only 5 patients could walk with a crutch before operation. Harris hip score was 24.368 ± 7.625. The average operation time was 63.4 minutes (range, 50-90 minutes). The average intraoperative blood loss was 196.8 mL (range, 100-400 mL). Patients obtained primary healing of incision; no complication of neurovascular injury, fracture, joint dislocation, or infection occurred. All patients were followed up 2.2 years on average (range, 1 year to 4 years and 3 months). The Harris score was 86.837 ± 7.742 at last follow- up, showing significant difference when compared with preoperative score (t = -41.956, P = 0.000). The results were excellent in 5 hips, good in 11 hips, fair in 2 hips, and poor in 1 hip, with an excellent and good rate of 84.2%. All patients could basically take care of themselves; 2 patients could walk with crutch, and the other patients could walk without crutch. X-ray films showed that prosthesis was in good position; no shifting, loosening, or sinking was found. Heterotopic ossification occurred in 2 hips. THA is an effective surgical approach to treat non-functional bony ankylosed hip in young and middle- aged patients.

  6. The influence of injecting an epidural contrast agent into the sacral canal on the fluoroscopic visibility of bony landmarks for sacroiliac screw fixation: a feasibility study.

    PubMed

    Mendel, Thomas; Radetzki, Florian; Schwan, Stefan; Hofmann, Gunther Olaf; Goehre, Felix

    2015-02-01

    In sacroiliac screw fixation of unstable pelvic injuries in geriatric patients, poor bone quality often obscures important bony landmarks in fluoroscopic images. The authors analyzed the feasibility of injecting a transhiatal contrast agent (CA) into the sacral canal to improve fluoroscopic visualization in the sacral epidural space. Eight fresh cadaveric whole-body specimens from human donors whose mean age at the time of death was 78 years (range 69-87 years) were used. First, to identify bony landmarks without CA enhancement, the authors acquired fluoroscopy images of the native sacral canal, using lateral, inlet, and outlet projections. Through puncture of the sacral hiatus, 8-10 ml of CA was injected into the epidural space. Fluoroscopy images were then acquired in the standard pelvic views to identify the bony landmarks. To assess the effect of the CA enhancement, visibility of the landmarks was assessed before and after CA injection. Each identified landmark was scored as 1, and summative landmark scores of up to 10 were determined for each specimen. The cadaveric specimens were representative of bone structures in the geriatric population. In all specimens, epidural CA injection enhanced the fluoroscopic visualization of the sacral canal and of the S-1 foramina. The enhancement increased the total bony landmark score from 5.9 (range 4-8) without CA injection to 8.1 (range 6-10) after CA injection. Considering only intrasacral landmarks, the score was increased from 1.5 to 3. Injection of a transhiatal epidural CA improves fluoroscopic imaging of the sacral canal and of the neural foramina. Hence, this technique could be applied to help the surgeon identify anatomical landmarks during sacroiliac screw fixation in geriatric patients.

  7. Effects of Algal Diversity on the Production of Biomass in Homogeneous and Heterogeneous Nutrient Environments: A Microcosm Experiment

    PubMed Central

    Weis, Jerome J.; Madrigal, Daniel S.; Cardinale, Bradley J.

    2008-01-01

    generate strong effects of biodiversity on productivity. Rather, heterogeneity must be coupled with variation in the relative fitness of species across patches in order for spatial niche differentiation to generate complementary resource use. PMID:18665221

  8. [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.

  9. 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.

  10. Pore Fluid Effects on Shear Modulus in a Model of Heterogeneous Rocks, Reservoirs, and Granular Media

    SciTech Connect

    Berryman, J G

    2005-03-23

    To provide quantitative measures of the importance of fluid effects on shear waves in heterogeneous reservoirs, a model material called a ''random polycrystal of porous laminates'' is introduced. This model poroelastic material has constituent grains that are layered (or laminated), and each layer is an isotropic, microhomogeneous porous medium. All grains are composed of exactly the same porous constituents, and have the same relative volume fractions. The order of lamination is not important because the up-scaling method used to determine the transversely isotropic (hexagonal) properties of the grains is Backus averaging, which--for quasi-static or long-wavelength behavior--depends only on the volume fractions and layer properties. Grains are then jumbled together totally at random, filling all space, and producing an overall isotropic poroelastic medium. The poroelastic behavior of this medium is then analyzed using the Peselnick-Meister-Watt bounds (of Hashin-Shtrikman type). We study the dependence of the shear modulus on pore fluid properties and determine the range of behavior to be expected. In particular we compare and contrast these results to those anticipated from Gassmann's fluid substitution formulas, and to the predictions of Mavko and Jizba for very low porosity rocks with flat cracks. This approach also permits the study of arbitrary numbers of constituents, but for simplicity the numerical examples are restricted here to just two constituents. This restriction also permits the use of some special exact results available for computing the overall effective stress coefficient in any two-component porous medium. The bounds making use of polycrystalline microstructure are very tight. Results for the shear modulus demonstrate that the ratio of compliance differences R (i.e., shear compliance changes over bulk compliance changes when going from drained to undrained behavior, or vice versa) is usually nonzero and can take a wide range of values, both

  11. Environmental effects on vertebrate species richness: testing the energy, environmental stability and habitat heterogeneity hypotheses.

    PubMed

    Luo, Zhenhua; Tang, Songhua; Li, Chunwang; Fang, Hongxia; Hu, Huijian; Yang, Ji; Ding, Jingjing; Jiang, Zhigang

    2012-01-01

    Explaining species richness patterns is a central issue in biogeography and macroecology. Several hypotheses have been proposed to explain the mechanisms driving biodiversity patterns, but the causes of species richness gradients remain unclear. In this study, we aimed to explain the impacts of energy, environmental stability, and habitat heterogeneity factors on variation of vertebrate species richness (VSR), based on the VSR pattern in China, so as to test the energy hypothesis, the environmental stability hypothesis, and the habitat heterogeneity hypothesis. A dataset was compiled containing the distributions of 2,665 vertebrate species and eleven ecogeographic predictive variables in China. We grouped these variables into categories of energy, environmental stability, and habitat heterogeneity