The paediatric wrist revisited - findings of bony depressions in healthy children on radiographs compared to MRI

International Nuclear Information System (INIS)

Avenarius, Derk M.F.; Eldevik, Petter; Ording Mueller, Lil-Sofie; Owens, Catherine M.; Rosendahl, Karen

2012-01-01

The presence of erosions is used for diagnosis and monitoring of disease activity in juvenile idiopathic arthritis (JIA). Assessment of carpal bone erosions in children is challenging due to lack of normal references. To define normal appearances of bony depressions in the wrist on radiographs and MRI. MRI and radiography of the wrist were performed in 88 healthy children, 5-15 years of age. We assessed the number of bony depressions within the carpals/proximal metacarpals on both modalities, separately and combined. A total of 75 carpal depressions were identified on radiography compared to 715 on MRI. The number of bony depressions identified radiographically showed no statistically significant difference across age-groups. Within the metacarpals, there was no significant difference between bony depressions identified by MRI or radiography, except at the bases of the second metacarpal. Bony depressions that resemble erosions are normal findings in the wrist in children. MRI identifies more depressions than radiographs in the carpus. Some bony depressions occur at typical locations and should be accounted for when assessing the wrist in JIA to avoid overstaging. (orig.)

Heterogeneous Causal Effects and Sample Selection Bias

DEFF Research Database (Denmark)

Breen, Richard; Choi, Seongsoo; Holm, Anders

2015-01-01

The role of education in the process of socioeconomic attainment is a topic of long standing interest to sociologists and economists. Recently there has been growing interest not only in estimating the average causal effect of education on outcomes such as earnings, but also in estimating how...... causal effects might vary over individuals or groups. In this paper we point out one of the under-appreciated hazards of seeking to estimate heterogeneous causal effects: conventional selection bias (that is, selection on baseline differences) can easily be mistaken for heterogeneity of causal effects....... This might lead us to find heterogeneous effects when the true effect is homogenous, or to wrongly estimate not only the magnitude but also the sign of heterogeneous effects. We apply a test for the robustness of heterogeneous causal effects in the face of varying degrees and patterns of selection bias...

Blunt chest trauma: bony injury in the thorax.

Science.gov (United States)

Zreik, Nasri H; Francis, Irene; Ray, Arun; Rogers, Benedict A; Ricketts, David M

2016-02-01

The management of blunt chest trauma is an evolving concept with no clear current guidelines. This article explores the bony injuries associated with this, focusing on rib fractures and flail segments and the themes around investigation and best management.

Quantitative computed tomography as a test of endurance for evaluation of bony plates

International Nuclear Information System (INIS)

Melo Filho, E.V.; Costa, L.A.V.S.; Oliveira, D.C.; Freitas, P.M.C.; Teixeira, M.W.; Costa, F.S.

2012-01-01

Quantitative computed tomography was used to determine the radiodensity of bony plates. The CT scans provided information regarding radiodensity of bony plates and allowed to verify the uniformity of bone mineral density in their scope. The proposed methodology should be considered as another tool for determining the resistance of these biomaterials. (author)

Radiographic detection of artificial intra-bony defects in the edentulous area.

Science.gov (United States)

Van Assche, N; Jacobs, R; Coucke, W; van Steenberghe, D; Quirynen, M

2009-03-01

Since intra-bony pathologies might jeopardize implant outcome, their preoperative detection is crucial. In sixteen human cadaver bloc sections from upper and lower jaws, artificial defects with progressively increasing size (n=7) have been created. From each respective defect, analogue and digital intra-oral radiographs were taken, the latter processed via a periodontal filter and afterwards presented in black-white as well as in colour, resulting in three sets of 7 images per bloc section. Eight observers were asked to diagnosis an eventual defect on randomly presented radiographs, and at another occasion to rank each set based on the defect size. The clinicians were only able to identify a defect, when the junctional area was involved, except for bony pieces with a very homogeneous structure. For longitudinal evaluation of healing bone (e.g. after tooth extraction), colour digital images can be recommended. These observations indicate that intra-oral radiographs are not always reliable for the detection of any intra-bony defect.

Arthroscopic Anterior Shoulder Stabilization With Incorporation of a Comminuted Bony Bankart Lesion

OpenAIRE

Lansdown, Drew; Bernardoni, Eamon D.; Cotter, Eric J.; Romeo, Anthony A.; Verma, Nikhil N.

2017-01-01

Bony Bankart lesions are a common finding in patients with anterior glenohumeral dislocation. Although there are no defined guidelines, small bony Bankart fractures are typically treated arthroscopically with suture anchors. The 2 main techniques used are double- and single-row suture anchor stabilization, with debate over superiority. Biomechanical studies have shown improved reduction and stabilization with the double-row over the single-row suture anchor technique; however, this has not be...

Condylar bony changes in patients with temporomandibular disorders: a CBCT study

Energy Technology Data Exchange (ETDEWEB)

Nah, Kyung Soo [Dept. of Oral and Maxillofacial Radiology, School of Dentistry, Pusan National University, Yangsan (Korea, Republic of)

2012-09-15

Diagnosis of osteoarthritis most commonly depends on clinical and radiographic findings. The present study attempted to observe the bony changes in temporomandibular joint (TMJ) patients from all age groups. The first-visit clinical records and cone beam computed tomography (CBCT) data of 440 TMJs from 220 consecutive TMJ patients were reviewed retrospectively. The most frequent condylar bony change observed was sclerosis (133 joints, 30.2%) followed by surface erosion (129 joints, 29.3%), flattening of the articular surface (112 joints, 25.5%), and deviation in form (58 joints, 13.2%), which included 33 TMJs in a cane-shape, 16 with a lateral or medial pole depression, 6 with posterior condylar surface flattening, and 3 with a bifid-shaped condyle. Fifty-three joints (12.0%) showed hypoplastic condyles but only 1 joint showed hyperplasia. Osteophyte was found in 35 joints (8.0%) and subcortical cyst in 24 joints (5.5%), 5 of which had surface erosion as well. One hundred nineteen joints (27.0%) had only one kind of condylar bony change, 66 joints (15.0%) had two, 52 joints (11.8%) had three, 12 joints (5.0%) had four, and 6 joints (1.4%) had five kinds of condylar bony changes at the same time. Eighty-five (65.9%) of 129 joints with surface erosion had pain recorded at the chief complaint. With more widespread use of CBCT, more specific or detailed guidelines for osteoarthritis are needed.

Condylar bony changes in patients with temporomandibular disorders: a CBCT study

International Nuclear Information System (INIS)

Nah, Kyung Soo

2012-01-01

Diagnosis of osteoarthritis most commonly depends on clinical and radiographic findings. The present study attempted to observe the bony changes in temporomandibular joint (TMJ) patients from all age groups. The first-visit clinical records and cone beam computed tomography (CBCT) data of 440 TMJs from 220 consecutive TMJ patients were reviewed retrospectively. The most frequent condylar bony change observed was sclerosis (133 joints, 30.2%) followed by surface erosion (129 joints, 29.3%), flattening of the articular surface (112 joints, 25.5%), and deviation in form (58 joints, 13.2%), which included 33 TMJs in a cane-shape, 16 with a lateral or medial pole depression, 6 with posterior condylar surface flattening, and 3 with a bifid-shaped condyle. Fifty-three joints (12.0%) showed hypoplastic condyles but only 1 joint showed hyperplasia. Osteophyte was found in 35 joints (8.0%) and subcortical cyst in 24 joints (5.5%), 5 of which had surface erosion as well. One hundred nineteen joints (27.0%) had only one kind of condylar bony change, 66 joints (15.0%) had two, 52 joints (11.8%) had three, 12 joints (5.0%) had four, and 6 joints (1.4%) had five kinds of condylar bony changes at the same time. Eighty-five (65.9%) of 129 joints with surface erosion had pain recorded at the chief complaint. With more widespread use of CBCT, more specific or detailed guidelines for osteoarthritis are needed.

Dosimetric evaluation in heterogeneous tissue of anterior electron beam irradiation for treatment of retinoblastoma

International Nuclear Information System (INIS)

Kirsner, S.M.; Hogstrom, K.R.; Kurup, R.G.; Moyers, M.F.

1987-01-01

A dosimetric study of anterior electron beam irradiation for treatment of retinoblastoma was performed to evaluate the influence of tissue heterogeneities on the dose distribution within the eye and the accuracy of the dose calculated by a pencil beam algorithm. Film measurements were made in a variety of polystyrene phantoms and in a removable polystyrene eye incorporated into a tissue substitute phantom constructed from a human skull. Measurements in polystyrene phantoms were used to demonstrate the algorithm's ability to predict the effect of a lens block placed in the beam, as well as the eye's irregular surface shape. The eye phantom was used to measure dose distributions within the eye in both the sagittal and transverse planes in order to test the algorithm's ability to predict the dose distribution when bony heterogeneities are present. Results show (1) that previous treatment planning conclusions based on flat, uniform phantoms for central-axis depth dose are adequate; (2) that a three-dimensional heterogeneity correction is required for accurate dose calculations; and (3) that if only a two-dimensional heterogeneity correction is used in calculating the dose, it is more accurate for the sagittal than the transverse plane

Algodystrophy in children and young adults with isotopic bony hypofixation. A propos of 5 observations

International Nuclear Information System (INIS)

Doury, P.; Pattin, S.; Eulry, F.; Granier, R.; Gaillard, F.

1986-01-01

The authors report 5 observations of young adults 3 teen-agers and 2 children suffering from algodystrophy, and in whom isotopic exploration of the skeleton disclosed a clear bony hypofixation during the entire evolution. These observations confirm their 1981 work concerning a young adult suffering from algodystrophy with isotopic bony hypofixation. Recent Canadian and American studies emphasize also the frequency of isotopic hypofixation in children algodystrophy. It seems, therefore, that isotopic bony hypofixation (linked perhaps to a decreased blood flow), is rather specific of algodystrophy in young subjects [fr

Avifauna of Boni-Dodori National Reserves, Lamu and Garissa ...

African Journals Online (AJOL)

observers conducted a 60 min walk along a designated path in open ... rophoneus viridis were recorded in the Boni-Dodori area for the first time. ..... Mouse-coloured Sunbird Cyanomitra veroxii * .... Expedition Field techniques: Bird Surveys.

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

Science.gov (United States)

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

[Inconformity between soft tissue defect and bony defect in incomplete cleft palate].

Science.gov (United States)

Zhou, Xia; Ma, Lian

2014-12-01

To evaluate the inconformity between soft tissue defect and bony defect by observing the cleft extent of palate with complete secondary palate bony cleft in incomplete cleft palate patient. The patients with incomplete cleft palate treated in Hospital of Stomatology Peking University from July 2012 to June 2013 were reviewed, of which 75 cases with complete secondary palate bony cleft were selected in this study. The CT scan and intraoral photograph were taken before operation. The patients were classified as four types according to the extent of soft tissue defect. Type 1: soft tissue defect reached incisive foremen region, Type 2 was hard and soft cleft palate, Type 3 soft cleft palate and Type 4 submucous cleft palate. Type 1 was defined as conformity group (CG). The other three types were defined as inconformity group (ICG) and divided into three subgroups (ICG-I), (ICG-II) and (ICG-III). Fifty-seven patients were in ICG group, and the rate of inconformity was 76% (57/75). The percentage of ICG-I, ICG-II and ICG-III was 47% (27/57), 23% (13/57) and 30% (17/57), respevtively. There are different types of soft tissue deformity with complete secondary palate bony cleft. The inconformity between soft tissue and hard tissue defect exits in 3/4 of isolated cleft palate patients.

Bony defect of palate and vomer in submucous cleft palate patients.

Science.gov (United States)

Ren, S; Ma, L; Zhou, X; Sun, Z

2015-01-01

The aim of this study was to visualize bony defects of the palate and vomer in submucous cleft palate patients (SMCP) by three-dimensional (3D) computed tomography (CT) reconstruction and to classify the range of bony defects. Forty-eight consecutive non-operated SMCP patients were included. Diagnosis was based on the presence of at least one of three classical signs of SMCP: bifid uvula, a translucent zone in the midline of the soft palate, and a palpable 'V' notch on the posterior border of the bony palate. Patients were imaged using spiral CT. 3D reconstruction models were created of the palate and vomer. The sagittal extent of the bony cleft in SMCP was classified into four types: type I, no V-shaped hard palate cleft (8.3%); type II, cleft involving the partial palate (43.8%); type III, cleft involving the complete palate and extending to the incisive foramen (43.8%); type IV, cleft involving the complete palate and the alveolar bone (4.2%). The extent of the vomer defect was classified into three types: type A, vomer completely fused with the palate (8.3%); type B, vomer partially fused with the palate (43.8%); type C, vomer not fused with the palate up to the incisive foramen (47.9%). Significant variability in hard palate defects in SMCP is the rule rather than the exception. The association of velopharyngeal insufficiency with anatomical malformations may be complex. Copyright © 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

DIAGNOSTIC CRITERIA FOR PROLIFERATIVE THYROID LESIONS IN BONY FISHES

Science.gov (United States)

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...

Patterns of congenital bony spinal deformity and associated neural anomalies on X-ray and magnetic resonance imaging

OpenAIRE

Trenga, Anthony P.; Singla, Anuj; Feger, Mark A.; Abel, Mark F.

2016-01-01

Purpose Congenital malformations of the bony vertebral column are often accompanied by spinal cord anomalies; these observations have been reinforced with the use of magnetic resonance imaging (MRI). We hypothesized that the incidence of cord anomalies will increase as the number and complexity of bony vertebral abnormalities increases. Methods All patients aged ?13 years (n?=?75) presenting to the pediatric spine clinic from 2003?2013 with congenital bony spinal deformity and both radiograph...

Incidence of dehiscence of the bony roof of the superior semicircular canal by CT imaging

International Nuclear Information System (INIS)

Watanabe, Akira

2003-01-01

Dehiscence of the bony roof of the superior semicircular canal (SSCC) is rare, but it has been recognized by otologists since Minor et al first described superior canal dehiscence syndrome (SCDS). In this study, dehiscence of the bony roof of SSCC was incidentally detected in three patients with benign paroxysmal positional vertigo out of 49 serial patients with vertigo and dizziness by multi-slice computed tomography. Although detection of dehiscence of the SSCC by ultra-high-resolution CT imaging of the temporal bones has been required for a diagnosis of SCDS, this study showed that dehiscence of the bony roof of the SSCC can be an incidental finding and therefore is not specific for SCDS. (author)

Bilateral bony fusion around the supraspinatus muscle inducing muscle hypoplasia and shoulder pain

Energy Technology Data Exchange (ETDEWEB)

Son, YeNa; Jin, Wook; Park, So Young [Kyung Hee University Hospital at Gangdong, Department of Radiology, 892, Dongnam-ro, Gangdong-gu, Seoul (Korea, Republic of); Ryu, Kyung Nam; Park, Ji Seon [Kyung Hee University Hospital, Department of Radiology, 23 Kyunghee-daero, Dongdaemun-gu, Seoul (Korea, Republic of)

2017-03-15

We describe the case of a 30-year-old man who developed chronic bilateral shoulder pain that relapsed and remitted over the course of 1 year. The patient was diagnosed with congenital shoulder fusion anomalies. The right shoulder showed anomalous accessory articulation between the distal third of the clavicle and the acromion along with normal articulation of the shoulder on CT. At the left shoulder, bony fusions were present between the distal portion of the clavicle, the acromion, and the coracoid process, and between the coracoid process, upper portion of the glenoid, and upper body of the scapula, which formed a bony canal and was responsible for hypoplasia of the supraspinatus muscle on CT and MRI. To our knowledge, this is the first description of such congenital shoulder anomalies with extreme bony fusion and is an illustrative example of how imaging may be used to differentiate fusion from other congenital abnormalities of the shoulder to aid diagnosis. (orig.)

Bony ankylosis of temporomandibular joint

Energy Technology Data Exchange (ETDEWEB)

Lee, Byeong Do; Yoon, Young Nam; Um, Ki Doo; Ra, Jong Ill; Lee, Wan [School of Dentistry, Wonkwang University, Iksan (Korea, Republic of)

2002-06-15

Ankylosis of joint is defined as limited movement due to infection, trauma, or surgical procedure. A 59-year-old female with a chief complaint of limited movements during mouth opening had a positive history of trauma to her right TMJ area about 5 years ago. From that time, progressive mouth opening limitation and intermittent pain have occurred. At the time of admission the patient showed mandibular deviation to the right side during mouth opening, with a maximum opening limited to 5 mm. On plain radiographs, right condylar enlargement and joint space reduction by newly formed bony tissues were observed. CT scans showed right condylar enlargement, cortical sclerosis, and thickening of the condyle, articular fossa and articular eminence.

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

Science.gov (United States)

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.

Impact of Bony Stress Injuries on Professional Basketball Performance

Science.gov (United States)

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

Local heterogeneity effects on small-sample worths

International Nuclear Information System (INIS)

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

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

Science.gov (United States)

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

Post Pelvic Radiotherapy Bony Changes

Energy Technology Data Exchange (ETDEWEB)

Huh, Seung Jae [Samsung Medical Center, Seoul (Korea, Republic of)

2009-03-15

There has been recent interest in radiation-induced bone injury in clinical conditions, especially for pelvic insufficiency fracture (PIF). A PIF is caused by the effect of normal or physiological stress on bone with demineralization and decreased elastic resistance. Pelvic radiotherapy (RT) can also contribute to the development of a PIF. A PIF has been regarded as a rare complication with the use of megavoltage equipment. However, recent studies have reported the incidence of PIFs as 8.2{approx}20% after pelvic RT in gynecological patients, an incidence that was higher than previously believed. The importance of understanding a PIF lies in the potential for misdiagnosis as a bony metastasis. If patients complain of pelvic pain after whole-pelvis radiation therapy, the presence of a PIF must be considered in the differential diagnosis. The use of multibeam arrangements and conformal RT to reduce the volume and dose of irradiated pelvic bone can be helpful to minimize the risk of fracture. In addition to a PIF, osteonecrosis and avascular necrosis of the femoral head can develop after radiation therapy. Osteoradionecrosis of the pelvic bone is a clinical diagnostic challenge that must be differentiated from an osseous metastasis. A post-radiation bone sarcoma can result as a long-term sequela of pelvic irradiation for uterine cervical cancer.

Patterns of congenital bony spinal deformity and associated neural anomalies on X-ray and magnetic resonance imaging.

Science.gov (United States)

Trenga, Anthony P; Singla, Anuj; Feger, Mark A; Abel, Mark F

2016-08-01

Congenital malformations of the bony vertebral column are often accompanied by spinal cord anomalies; these observations have been reinforced with the use of magnetic resonance imaging (MRI). We hypothesized that the incidence of cord anomalies will increase as the number and complexity of bony vertebral abnormalities increases. All patients aged ≤13 years (n = 75) presenting to the pediatric spine clinic from 2003-2013 with congenital bony spinal deformity and both radiographs and MRI were analyzed retrospectively for bone and neural pathology. Chi-squared analysis was used to compare groups for categorical dependent variables. Independent t tests were used for continuous dependent variables. Significance was set at p formation had a higher incidence of cord anomalies (73 %) than failures of formation (50 %) or segmentation (45 %) alone (p = 0.065). Deformities in the sacrococcygeal area had the highest rate of spinal cord anomalies (13 of 15 patients, 87 %). In 35 cases (47 %), MRI revealed additional bony anomalies that were not seen on the radiographs. As the number of bony malformations increased, we found a higher incidence of cord anomalies. Clinicians should have increased suspicion of spinal cord pathology in the presence of mixed failures of segmentation and formation.

Management of segmental bony defects: the role of osteoconductive orthobiologics.

Science.gov (United States)

McKee, Michael D

2006-01-01

Our knowledge about, and the availability of, orthobiologic materials has increased exponentially in the last decade. Although previously confined to the experimental or animal-model realm, several orthobiologics have been shown to be useful in a variety of clinical situations. As surgical techniques in vascular anastomosis, soft-tissue coverage, limb salvage, and fracture stabilization have improved, the size and frequency of bony defects (commensurate with the severity of the initial injury) have increased, as well. Because all methods of managing segmental bony defects have drawbacks, a need remains for a readily available, void-filling, inexpensive bone substitute. Such a bone substitute fulfills a permissive role in allowing new bone to grow into a given defect. Such potential osteoconductive materials include ceramics, calcium sulfate or calcium phosphate compounds, hydroxyapatite, deproteinized bone, corals, and recently developed polymers. Some materials that have osteoinductive properties, such as demineralized bone matrix, also display prominent osteoconductive properties.

Imaging of the hip and bony pelvis. Techniques and applications

Energy Technology Data Exchange (ETDEWEB)

Davies, A.M. [Royal Orthopaedic Hospital, Birmingham (United Kingdom). MRI Centre; Johnson, K.J. [Princess of Wales Birmingham Children' s Hospital (United Kingdom); Whitehouse, R.W. (eds.) [Manchester Royal Infirmary (United Kingdom). Dept. of Clinical Radiology

2006-07-01

This is a comprehensive textbook on imaging of the bony pelvis and hip joint that provides a detailed description of the techniques and imaging findings relevant to this complex anatomical region. In the first part of the book, the various techniques and procedures employed for imaging the pelvis and hip are discussed in detail. The second part of the book documents the application of these techniques to the diverse clinical problems and diseases encountered. Among the many topics addressed are congenital and developmental disorders including developmental dysplasia of the hip, irritable hip and septic arthritis, Perthes' disease and avascular necrosis, slipped upper femoral epiphysis, bony and soft tissue trauma, arthritis, tumours and hip prostheses. Each chapter is written by an acknowledged expert in the field, and a wealth of illustrative material is included. This book will be of great value to musculoskeletal and general radiologists, orthopaedic surgeons and rheumatologists. (orig.)

Computed tomographic features of the bony canal of the cochlear nerve in pediatric patients with unilateral sensorineural hearing loss

International Nuclear Information System (INIS)

Kono, Tatsuo

2008-01-01

The aim of this study was to evaluate the diameters of the various bony canals of the inner ear in patients with sensorineural hearing loss (SNHL) and establish criteria for detecting hypoplasia of the bony canal of the cochlear nerve. Measurements obtained in 118 patients without inner ear malformations among 160 patients with unilateral SNHL were analyzed. The diameters of the internal auditory canal and the bony canals of the cochlear, vestibular, and facial nerves were measured on transverse or coronal computed tomographic images. Mean values (±standard deviation (SD)) were compared between the affected and unaffected ears, and statistical analysis was done. The diameter of the bony canal of the cochlear nerve was significantly smaller in affected ears than in unaffected ears (P<0.01). The affected ears could be divided into groups with (72 ears) and without (46 ears) bony canal stenosis. Most (60%) of the patients with unilateral SNHL showed a significant difference in the diameters of the bony canals of the cochlear nerve between the affected and unaffected sides; moreover, the mean value was significantly smaller in affected ears. The diameter of <1.7 mm on transverse images or <1.8 mm on coronal images suggests hypoplasia. (author)

Investigating the effect of heterogeneity on infill wells

Directory of Open Access Journals (Sweden)

Mahmood Bagheri

2015-12-01

Full Text Available Abstract In recent years, improving oil recovery (IOR has become an important subject for the petroleum industry. One IOR method is infill drilling, which improves hydrocarbon recovery from virgin zones of the reservoir. Determining the appropriate location for the infill wells is very challenging and greatly depends on different factors such as the reservoir heterogeneity. This study aims to investigate the effect of reservoir heterogeneity on the location of infill well. In order to characterize the effect of heterogeneity on infill well locations, some geostatistical methods, e.g., sequential gaussian simulation, have been applied to generate various heterogeneity models. In particular, different correlation ranges (R were used to observe the effect of heterogeneity. Results revealed that an increase in correlation ranges will lead to (1 a higher field oil production total, and (2 a faster expansion of the drainage radius which consequently reduced the need for infill wells. The results of this study will help engineers to appropriately design infill drilling schemes.

Arthroscopic treatment of bony loose bodies in the subacromial space

Directory of Open Access Journals (Sweden)

Wei Li

2015-01-01

Conclusion: The mechanism of formation of bony loose bodies is not clear, may be associated with synovial cartilage metaplasia. Arthroscopic removal of loose bodies and bursa debridement is a good option for treatment of the loose body in the subacromial space, which can receive good function.

Association between condylar morphology and changes in bony microstructure and subsynovial inflammation in experimental temporomandibular joint arthritis

DEFF Research Database (Denmark)

Kristensen, Kasper Dahl; Hauge, Ellen Margrethe; Dalstra, Michel

2010-01-01

Association between condylar morphology and changes in bony microstructure and subsynovial inflammation in experimental temporomandibular joint arthritis. 86. Congress of the European Orthodontic Society, Slovenien, 2010.......Association between condylar morphology and changes in bony microstructure and subsynovial inflammation in experimental temporomandibular joint arthritis. 86. Congress of the European Orthodontic Society, Slovenien, 2010....

The spectrum of allergy to South African bony fish (Teleosti ...

African Journals Online (AJOL)

Volunteer population-based cohort in the Western Cape. Participants. 105 volunteer subjects with suspected fish allergy were recruited by advertising in the local press. Main outcome. Species-specific bony fish allergy was confirmed or refuted by DBPCFC. Results. The four most common seafood species reported to cause ...

Comparison of carina-based versus bony anatomy-based registration for setup verification in esophageal cancer radiotherapy.

Science.gov (United States)

Machiels, Mélanie; Jin, Peng; van Gurp, Christianne H; van Hooft, Jeanin E; Alderliesten, Tanja; Hulshof, Maarten C C M

2018-03-21

To investigate the feasibility and geometric accuracy of carina-based registration for CBCT-guided setup verification in esophageal cancer IGRT, compared with current practice bony anatomy-based registration. Included were 24 esophageal cancer patients with 65 implanted fiducial markers, visible on planning CTs and follow-up CBCTs. All available CBCT scans (n = 236) were rigidly registered to the planning CT with respect to the bony anatomy and the carina. Target coverage was visually inspected and marker position variation was quantified relative to both registration approaches; the variation of systematic (Σ) and random errors (σ) was estimated. Automatic carina-based registration was feasible in 94.9% of the CBCT scans, with an adequate target coverage in 91.1% compared to 100% after bony anatomy-based registration. Overall, Σ (σ) in the LR/CC/AP direction was 2.9(2.4)/4.1(2.4)/2.2(1.8) mm using the bony anatomy registration compared to 3.3(3.0)/3.6(2.6)/3.9(3.1) mm for the carina. Mid-thoracic placed markers showed a non-significant but smaller Σ in CC and AP direction when using the carina-based registration. Compared with a bony anatomy-based registration, carina-based registration for esophageal cancer IGRT results in inadequate target coverage in 8.9% of cases. Furthermore, large Σ and σ, requiring larger anisotropic margins, were seen after carina-based registration. Only for tumors entirely confined to the mid-thoracic region the carina-based registration might be slightly favorable.

Prostate position relative to pelvic bony anatomy based on intraprostatic gold markers and electronic portal imaging

International Nuclear Information System (INIS)

Schallenkamp, John M.; Herman, Michael G.; Kruse, Jon J.; Pisansky, Thomas M.

2005-01-01

Purpose: To describe the relative positions and motions of the prostate, pelvic bony anatomy, and intraprostatic gold fiducial markers during daily electronic portal localization of the prostate. Methods and Materials: Twenty prostate cancer patients were treated supine with definitive external radiotherapy according to an on-line target localization protocol using three or four intraprostatic gold fiducial markers and an electronic portal imaging device. Daily pretherapy and through-treatment electronic portal images (EPIs) were obtained for each of four treatment fields. The patients' pelvic bony anatomy, intraprostatic gold markers, and a best visual match to the target (i.e., prostate) were identified on simulation digitally reconstructed radiographs and during daily treatment setup and delivery. These data provided quantitative inter- and intrafractional analysis of prostate motion, its position relative to the bony anatomy, and the individual intraprostatic fiducial markers. Treatment planning margins, with and without on-line localization, were subsequently compared. Results: A total of 22,266 data points were obtained from daily pretherapy and through-treatment EPIs. The pretherapy three-dimensional (3D) average displacement of the fiducial markers, as a surrogate for the prostate, was 5.6 mm, which improved to 2.8 mm after use of the localization protocol. The bony anatomy 3D average displacement was 4.4 mm both before and after localization to the prostate (p = 0.46). Along the superior-inferior (SI), anterior-posterior (AP), and right-left (RL) axes, the average prostate displacement improved from 2.5, 3.7, and 1.9 mm, respectively, before localization to 1.4, 1.6, and 1.1 mm after (all p < 0.001). The pretherapy to through-treatment position of the bony landmarks worsened from 1.7 to 2.5 mm (p < 0.001) in the SI axis, remained statistically unchanged at 2.8 mm (p = 0.39) in the AP axis, and improved from 2.0 to 1.2 mm in the RL axis (p < 0.001). There

Bony exostosis of the atlas with resultant cranial nerve palsy

International Nuclear Information System (INIS)

Slavotinek, J.P.; Sage, M.R.; Brophy, B.P.

1991-01-01

A case of tenth and twelfth nerve compression secondary to a bony exostosis of the first cervical vertebra is described. This uncommon phenomenon serves to outline the importance of imaging the course of a cranial nerve when no intracranial abnormality is demonstrable on CT or MRI. The radiologic features of spinal osteochondromas are reviewed. (orig.)

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

Science.gov (United States)

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

2016-06-01

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

The relationship of transverse sinus stenosis to bony groove dimensions provides an insight into the aetiology of idiopathic intracranial hypertension

Energy Technology Data Exchange (ETDEWEB)

Connor, S.E.J.; Stewart, V.R.; O' Flynn, E.A.M. [King' s College Hospital, Neuroradiology Department, Ruskin Wing, London (United Kingdom); Siddiqui, M.A. [Southern General Hospital, Institute of Neurological Sciences, Glasgow (United Kingdom)

2008-12-15

Transverse sinus tapered narrowings are frequently identified in patients with idiopathic intracranial hypertension (IIH); however, it remains unclear whether they are primary stenoses or whether they occur secondary to raised cerebrospinal fluid pressure. Computed tomographic venography demonstrates both the morphology of the venous system and the adjacent bony grooves so it may provide an insight into the aetiology of these transverse sinus stenoses. Tapered transverse sinus narrowings (>50%) were studied in 19 patients without IIH and 14 patients with IIH. Computed tomography vascular studies were reviewed and the dimensions of the venous sinuses and bony grooves at the sites of maximum and minimum transverse sinus area dimensions were recorded. There was demonstrated to be a strong correlation of bony groove height with venous sinus height at the largest portions of the transverse sinus in both IIH patients and non-IIH subjects as well as at the transverse sinus narrowing in non-IIH subjects. There was a discordant relationship between bony groove height and venous sinus height at the site of transverse sinus stenoses in IIH patients. In 5/23 IIH transverse sinus stenoses, the bony groove height was proportionate to that seen in non-IIH subjects. There were a further 8/23 cases where the small or absent sinus was associated with an absent bony groove. Transverse sinus tapered narrowings in subjects without IIH and in the majority of patients with IIH were associated with proportionately small or absent grooves, and these are postulated to be primary or fixed. Some patients with IIH demonstrate tapered transverse sinus stenoses with disproportionately large bony grooves, suggesting a secondary or acquired narrowing. This implies a varied aetiology for the transverse sinus stenoses of IIH. (orig.)

The relationship of transverse sinus stenosis to bony groove dimensions provides an insight into the aetiology of idiopathic intracranial hypertension

International Nuclear Information System (INIS)

Connor, S.E.J.; Stewart, V.R.; O'Flynn, E.A.M.; Siddiqui, M.A.

2008-01-01

Transverse sinus tapered narrowings are frequently identified in patients with idiopathic intracranial hypertension (IIH); however, it remains unclear whether they are primary stenoses or whether they occur secondary to raised cerebrospinal fluid pressure. Computed tomographic venography demonstrates both the morphology of the venous system and the adjacent bony grooves so it may provide an insight into the aetiology of these transverse sinus stenoses. Tapered transverse sinus narrowings (>50%) were studied in 19 patients without IIH and 14 patients with IIH. Computed tomography vascular studies were reviewed and the dimensions of the venous sinuses and bony grooves at the sites of maximum and minimum transverse sinus area dimensions were recorded. There was demonstrated to be a strong correlation of bony groove height with venous sinus height at the largest portions of the transverse sinus in both IIH patients and non-IIH subjects as well as at the transverse sinus narrowing in non-IIH subjects. There was a discordant relationship between bony groove height and venous sinus height at the site of transverse sinus stenoses in IIH patients. In 5/23 IIH transverse sinus stenoses, the bony groove height was proportionate to that seen in non-IIH subjects. There were a further 8/23 cases where the small or absent sinus was associated with an absent bony groove. Transverse sinus tapered narrowings in subjects without IIH and in the majority of patients with IIH were associated with proportionately small or absent grooves, and these are postulated to be primary or fixed. Some patients with IIH demonstrate tapered transverse sinus stenoses with disproportionately large bony grooves, suggesting a secondary or acquired narrowing. This implies a varied aetiology for the transverse sinus stenoses of IIH. (orig.)

Myelotoxicity of Samarium Sm153 lexidronam in patients with painful bony metastases

International Nuclear Information System (INIS)

Ben Ghachem, T.; Mhiri, A.; Slim, I.; Bahloul, A.; Yeddes, I.; Elbez, I.; Meddeb, I.; Ben Slimene, M.F.

2015-01-01

Full text of publication follows. Introduction: the management of bone pain includes analgesia, radiation, hormones, radiofrequency (RF) ablation, chemotherapy, and surgery. Bone pain palliation therapy with radiopharmaceuticals is a cost-effective systemic therapy to relieve pain from skeletal metastases with a consequent decrease in morbidity and an improvement in quality of life. The aim of our study is to evaluate the effect of myelotoxicity of samarium lexidronam (Sm 153 ) in patients with painful bony metastasis. Methods: we reviewed 116 patients aged from 14 to 87 years old, 91 males (78%) and 25 females (22%), having received 1 to 4 treatments of Sm 153 (37 MBq/kg) for painful bony metastases from different primitive tumors: 67 cases of prostate cancer (57.7%), 22 cases of breast cancer (18.9%), 10 cases of pulmonary cancer (8.6%) and others in 14.6% of cases. Clinical follow-up was available for 159 treatments, consisting on blood count each week over at least two months, in order to evaluate myelotoxicity according to WHO classification. Results: no patients had grade 4 toxicity after its cures. A grade 2-3 myelotoxicity was observed after 52 treatments (34%) during the second week and after 50 treatments (32.6%) during the fourth week with a satisfactory reversibility. At 10 weeks of treatment, myelotoxicity was reclassified from 0 to 2 for 139 cures (90,8%). Moreover, we found that prior treatment with radiotherapy or chemotherapy did not affect the rates of myelotoxicity. Conclusion: multiple treatments with samarium Sm 153 lexidronam had no significant effect on myelotoxicity. Patients with bone predominant metastatic disease may survive for extended periods of time and may safely be treated with multiple modalities of therapy. (authors)

A technique for the quantification of the 3D connectivity of thin articulations in bony sutures.

Science.gov (United States)

Maloul, Asmaa; Fialkov, Jeffrey; Hojjat, Seyed-Parsa; Whyne, Cari M

2010-04-19

The anatomy and development of cranial and facial sutures have been studied in detail using histological sections, 2D radiographs and more recently CT imaging. However, little attention has been paid to evaluating and quantifying the connectivity of these thin cortical bone articulations. More recent technological advances such as micro-CT imaging has the potential to be used to provide quantitative measurements of 3D connectivity in bony articulations. This study presents a new technique for quantifying the connectivity of bony projections inside cranial and facial sutures using a combination of skeletonization, thinning algorithms and 3D intensity mapping. The technique is demonstrated in five sutures through semi-automated analysis and image processing of microCT scans. In the sagittal, coronal and frontozygomatic sutures an average bone connectivity of 6.6-11.6% was found with multiple bony projections providing an interlocking structure between adjacent bones. Much higher bone connectivity was present in the zygomaticotemporal and zygomaticomaxillary sutures (22.7-37.4%) with few bony projections. This method combining microCT scanning and image processing techniques was successfully used to quantify the connectivity of thin bone articulations and allowed detailed assessment of sutural fusion in 3D. The wider application of this technique may allow quantification of connectivity in other structures, in particular fracture healing of long bones. Copyright 2009 Elsevier Ltd. All rights reserved.

Effective thermal neutron absorption cross section for heterogeneous mixture

International Nuclear Information System (INIS)

Gabanska, B.; Igielski, A.; Krynicka-Drozdowicz, E.; Woznicka, U.

1989-01-01

The first estimations (basing on Umiastowski's theory) of the influence of the sample heterogeneity of the effective thermal neutron absorption cross section were compared with the results obtained for the homogeneous mixture which components and concentration were the same as those of the heterogeneous sample. An experiment was prepared to determine how good this estimate is. Three artificial heterogeneous cylindrical samples (2R = H = 9 cm) were manufactured from pure silver cylinders embedded in plexiglass, keeping the Ag content and varying the size of cylinders (2R = H = 1.0 cm, 0.6 cm and 0.4 cm). Calculations performed show that the experimental effect of the sample heterogeneity can be significant. 5 figs., 5 tabs, 11 refs. (author)

Natural resources utilization by the Aweer in Boni-lungi and Dodori ...

African Journals Online (AJOL)

A study was conducted to record the utilization of Boni-Lungi and Dodori National Reserves by the Aweer community. Results indicate the procuring of a wide gamut of provisional, regulatory, cultural and supportive services from these reserves by the community ranging from wood forest products utilized in construction to ...

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

International Nuclear Information System (INIS)

Song, Ji Young; 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

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

Energy Technology Data Exchange (ETDEWEB)

Song, Ji Young [Dept. of Oral and Maxillofacial Surgery, Jeju National University Hospital, Jeju National University School of Medicine, Jeju (Korea, Republic of); Kim, Seong Gon; Choi, Hang Moon [School of Dentistry, Gangneung-Wonju National University, Gangneung (Korea, Republic of); Kim, Hyun Jung [Dept. of Anesthesiology and Pain Medicine, Jeju National University School of Medicine, Jeju (Korea, Republic of)

2015-06-15

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.

Human bony labyrinth is an indicator of population history and dispersal from Africa.

Science.gov (United States)

Ponce de León, Marcia S; Koesbardiati, Toetik; Weissmann, John David; Milella, Marco; Reyna-Blanco, Carlos S; Suwa, Gen; Kondo, Osamu; Malaspinas, Anna-Sapfo; White, Tim D; Zollikofer, Christoph P E

2018-04-17

The dispersal of modern humans from Africa is now well documented with genetic data that track population history, as well as gene flow between populations. Phenetic skeletal data, such as cranial and pelvic morphologies, also exhibit a dispersal-from-Africa signal, which, however, tends to be blurred by the effects of local adaptation and in vivo phenotypic plasticity, and that is often deteriorated by postmortem damage to skeletal remains. These complexities raise the question of which skeletal structures most effectively track neutral population history. The cavity system of the inner ear (the so-called bony labyrinth) is a good candidate structure for such analyses. It is already fully formed by birth, which minimizes postnatal phenotypic plasticity, and it is generally well preserved in archaeological samples. Here we use morphometric data of the bony labyrinth to show that it is a surprisingly good marker of the global dispersal of modern humans from Africa. Labyrinthine morphology tracks genetic distances and geography in accordance with an isolation-by-distance model with dispersal from Africa. Our data further indicate that the neutral-like pattern of variation is compatible with stabilizing selection on labyrinth morphology. Given the increasingly important role of the petrous bone for ancient DNA recovery from archaeological specimens, we encourage researchers to acquire 3D morphological data of the inner ear structures before any invasive sampling. Such data will constitute an important archive of phenotypic variation in present and past populations, and will permit individual-based genotype-phenotype comparisons. Copyright © 2018 the Author(s). Published by PNAS.

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

Science.gov (United States)

Ekdale, Eric G.

2013-01-01

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

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

International Nuclear Information System (INIS)

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

2002-01-01

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. (orig.)

Repair of pars defects by segmental transverse wiring for athletes with symptomatic spondylolysis: relationship between bony union and postoperative symptoms.

Science.gov (United States)

Hioki, Akira; Miyamoto, Kei; Sadamasu, Aya; Nozawa, Satoshi; Ogawa, Hiroyasu; Fushimi, Kazunari; Hosoe, Hideo; Shimizu, Katsuji

2012-04-20

Retrospective study of surgery for spondylolysis patients. To assess clinical outcome of bony union using multislice computed tomography after segmental wiring fixation. How bony union affects surgical outcome of spondylolysis repair is unclear. Forty-four athletes with symptomatic spondylolysis (33 men and 11 women; mean age, 24.2 ± 5.4 years) who underwent segmental wiring fixation were evaluated retrospectively at a mean follow-up of 85 ± 17 months. The level of spondylolysis was L5 in 42 cases, and both L4 and L5 in 2 cases, giving a total of 46 operative levels of vertebrae. Bony union using axial and sagittal reconstruction images of computed tomography, the Japanese Orthopaedic Association (JOA) score for back pain, and complications were reviewed. State of bony union was classified as bilateral union, unilateral union, or nonunion. The total score and the improvement ratio of the JOA score were compared among the 3 groups. Bilateral bony union was obtained in 29 cases (31 of 46 vertebrae, 67.4%). Six cases (13%) showed unilateral union, and 9 cases (19.6%) showed nonunion. JOA score increased significantly after surgery in all groups, average improvement rate was 78.9% in the bilateral group, 63.6% in the unilateral group, and 29.8% in the nonunion group; differences among the 3 groups were significant (P spondylolysis repair.

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

International Nuclear Information System (INIS)

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

2007-01-01

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

Giant Atretic Occipital Lipoencephalocele in an Adult with Bony Outgrowth.

Science.gov (United States)

Nimkar, Kshama; Sood, Dinesh; Soni, Pawan; Chauhan, Narvir; Surya, Mukesh

2016-01-01

We present unique case of a giant extracranial atretic occipital lipoencephalocele in an adult patient with new bone formation within it which was not associated with any developmental malformation of brain. Resection of the lipoencephalocele was performed for esthetic reasons. 18 year old female patient presented to the surgery OPD with complains of a large mass in the occipital region present since birth. It was of size of a betel nut at the time of birth and gradually increased in size over a long period of time. It was painless and not associated with any other constitutional symptoms. On examination the rounded fluctuant mass was present in the midline in occipital region covered with alopecic skin with dimpling in the overlying skin. On MRI there was mass showing both T1 and T2 hyperintense signal area suggestive of fat component. Herniation of meninges and atretic brain parenchyma was also seen through a defect in the occipital bone in the midline. There was a Y shaped bony outgrowth seen arising from occipital bone into the mass which was quite unusual in association with an atretic lipoencephalocele. A large lipoencephalocele with bony outgrowth in an adult patient is a rare presentation of atreic occipital encephalocele.

Heterogeneous Economic Integration Agreement Effects

OpenAIRE

Baier, Scott L.; Bergstrand, Jeffrey H.; Clance, Matthew W.

2015-01-01

Gravity equations have been used for more than 50 years to estimate ex post the partial effects of trade costs on international trade flows, and the well-known - and traditionally presumed exogenous – "trade-cost elasticity" plays a central role in computing general equilibrium trade-flow and welfare effects of trade-cost changes. This paper addresses theoretically and empirically the influence of variable and fixed export costs in explaining the likely heterogeneity in the trade-cost elast...

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

International Nuclear Information System (INIS)

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

2006-01-01

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 (α=0.15 Gy -1 and α/β=3.1 Gy) determined in earlier studies were used to calculate the equivalent uniform dose in 2 Gy fractions (EUD 2 ) with respect to three effects: edema, RBE, and dose heterogeneity for 125 I and 103 Pd implants. The EUD 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 100 (volume covered by 100% of prescription dose) decreases from 93% to 91% and 86%, and the D 90 (dose covering 90% of target volume) decrease from 107% to 102% and 94% of prescription dose for 125 I and 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 125 I and 1.3-1.6 for 103 Pd implants. These RBE values are consistent with the RBE data published in the literature. These results may explain why in earlier modeling studies

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

Science.gov (United States)

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

Monte Carlo-narrow resonance calculational techniques for treating double-heterogeneity effects

International Nuclear Information System (INIS)

Gelbard, E.M.; Chen, I.J.

1986-01-01

Reliable methods already exist for computing resonance integrals (RI's) in regular lattices. But lattice structures always contain irregularities. Such effects have been called ''double-heterogeneity'' effects. Two methods for computing double heterogeneity effects on RI's are reviewed and evaluated. 2 refs., 1 tab

Calculation code of heterogeneity effects for analysis of small sample reactivity worth

International Nuclear Information System (INIS)

Okajima, Shigeaki; Mukaiyama, Takehiko; Maeda, Akio.

1988-03-01

The discrepancy between experimental and calculated central reactivity worths has been one of the most significant interests for the analysis of fast reactor critical experiment. Two effects have been pointed out so as to be taken into account in the calculation as the possible cause of the discrepancy; one is the local heterogeneity effect which is associated with the measurement geometry, the other is the heterogeneity effect on the distribution of the intracell adjoint flux. In order to evaluate these effects in the analysis of FCA actinide sample reactivity worth the calculation code based on the collision probability method was developed. The code can handle the sample size effect which is one of the local heterogeneity effects and also the intracell adjoint heterogeneity effect. (author)

Unsharp masking technique as a preprocessing filter for improvement of 3D-CT image of bony structure in the maxillofacial region

International Nuclear Information System (INIS)

Harada, Takuya; Nishikawa, Keiichi; Kuroyanagi, Kinya

1998-01-01

We evaluated the usefulness of the unsharp masking technique as a preprocessing filter to improve 3D-CT images of bony structure in the maxillofacial region. The effect of the unsharp masking technique with several combinations of mask size and weighting factor on image resolution was investigated using a spatial frequency phantom made of bone-equivalent material. The 3D-CT images were obtained with scans perpendicular to and parallel to the phantom plates. The contrast transfer function (CTF) and the full width at half maximum (FWHM) of each spatial frequency component were measured. The FWHM was expressed as a ratio against the actual thickness of phantom plate. The effect on pseudoforamina was assessed using sliced CT images obtained in clinical bony 3D-CT examinations. The effect of the unsharp masking technique on image quality was also visually evaluated using five clinical fracture cases. CTFs did not change. FWHM ratios of original 3D-CT images were smaller than 1.0, regardless of the scanning direction. Those in scans perpendicular to the phantom plates were not changed by the unsharp masking technique. Those in parallel scanning were increased by mask size and weighting factor. The area of pseudoforamina decreased with increases in mask size and weighting factor. The combination of mask size 3 x 3 pixels and weighting factor 5 was optimal. Visual evaluation indicated that preprocessing with the unsharp masking technique improved the image quality of the 3D-CT images. The unsharp masking technique is useful as a preprocessing filter to improve the 3D-CT image of bony structure in the maxillofacial region. (author)

Measuring the effects of heterogeneity on distributed systems

Science.gov (United States)

El-Toweissy, Mohamed; Zeineldine, Osman; Mukkamala, Ravi

1991-01-01

Distributed computer systems in daily use are becoming more and more heterogeneous. Currently, much of the design and analysis studies of such systems assume homogeneity. This assumption of homogeneity has been mainly driven by the resulting simplicity in modeling and analysis. A simulation study is presented which investigated the effects of heterogeneity on scheduling algorithms for hard real time distributed systems. In contrast to previous results which indicate that random scheduling may be as good as a more complex scheduler, this algorithm is shown to be consistently better than a random scheduler. This conclusion is more prevalent at high workloads as well as at high levels of heterogeneity.

Effect of site-specific heterogeneous evolution on phylogenetic reconstruction: a simple evaluation.

Science.gov (United States)

Cheng, Qiqun; Su, Zhixi; Zhong, Yang; Gu, Xun

2009-07-15

Recent studies have shown that heterogeneous evolution may mislead phylogenetic analysis, which has been neglected for a long time. We evaluate the effect of heterogeneous evolution on phylogenetic analysis, using 18 fish mitogenomic coding sequences as an example. Using the software DIVERGE, we identify 198 amino acid sites that have experienced heterogeneous evolution. After removing these sites, the rest of sites are shown to be virtually homogeneous in the evolutionary rate. There are some differences between phylogenetic trees built with heterogeneous sites ("before tree") and without heterogeneous sites ("after tree"). Our study demonstrates that for phylogenetic reconstruction, an effective approach is to identify and remove sites with heterogeneous evolution, and suggests that researchers can use the software DIVERGE to remove the influence of heterogeneous evolution before reconstructing phylogenetic trees.

Vanishing microwave effects : influence of heterogeneity

NARCIS (Netherlands)

Dressen, M.H.C.L.; Kruijs, van de B.H.P.; Meuldijk, J.; Vekemans, J.A.J.M.; Hulshof, L.A.

2007-01-01

A consistent setup of experiments has been conducted to demonstrate an enhanced reaction rate under microwave irradiation as compared to conventional heating, i.e. a real microwave effect. It was found that addition of a cosolvent, diminishing the heterogeneous character of the reaction mixture,

The effect of heterogeneity on invasion in spatial epidemics

DEFF Research Database (Denmark)

Neri, Franco M; Bates, Anne; Füchtbauer, Winnie Sophie

2011-01-01

Heterogeneity in host populations is an important factor affecting the ability of a pathogen to invade, yet the quantitative investigation of its effects on epidemic spread is still an open problem. In this paper, we test recent theoretical results, which extend the established “percolation...... paradigm” to the spread of a pathogen in discrete heterogeneous host populations. In particular, we test the hypothesis that the probability of epidemic invasion decreases when host heterogeneity is increased. We use replicated experimental microcosms, in which the ubiquitous pathogenic fungus Rhizoctonia...

X-ray and neutron tomography on the bony inner ear of baleen whales

International Nuclear Information System (INIS)

Arlt, Tobias; Wieder, Frank; Hampe, Oliver; Manke, Ingo; Ritsche, Indira; Fahlke, Julia M.

2018-01-01

During their evolution whales and dolphins developed a highly specialized hearing organ for orientation in their deep sea territory covering a broad acoustic spectrum. The internal anatomy of the periotic bone, especially the morphology of the cochlea, has a significant influence on the hearing capability of mammals. The bony and fossilized cochleae of several fossil representatives of extinct baleen whales (e.g., Cetotheriidae) and modern rorquals (Balaenopteridae) and right whales, as well as cochleae of an archaeocete and some land mammals are investigated by X-ray and neutron tomography in order to record morphological changes that may be responsible for the development of low frequency hearing. Differences in the cochlear morphology have been determined by means of morphometric parameters, such as the number of turns, the length of the cochlea, and the curvature of the cochlear canal. In particular, X-ray tomography enables a high resolution display of the bony inner ear.

Inverted 'V' osteotomy excision arthroplasty for bony ankylosed elbows

Directory of Open Access Journals (Sweden)

Rex Chadrabose

2011-12-01

Full Text Available Abstract 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.

Effect of heterogeneities on evaluating earthquake triggering of volcanic eruptions

Directory of Open Access Journals (Sweden)

J. Takekawa

2013-02-01

Full Text Available Recent researches have indicated coupling between volcanic eruptions and earthquakes. Some of them calculated static stress transfer in subsurface induced by the occurrences of earthquakes. Most of their analyses ignored the spatial heterogeneity in subsurface, or only took into account the rigidity layering in the crust. On the other hand, a smaller scale heterogeneity of around hundreds of meters has been suggested by geophysical investigations. It is difficult to reflect that kind of heterogeneity in analysis models because accurate distributions of fluctuation are not well understood in many cases. Thus, the effect of the ignorance of the smaller scale heterogeneity on evaluating the earthquake triggering of volcanic eruptions is also not well understood. In the present study, we investigate the influence of the assumption of homogeneity on evaluating earthquake triggering of volcanic eruptions using finite element simulations. The crust is treated as a stochastic media with different heterogeneous parameters (correlation length and magnitude of velocity perturbation in our simulations. We adopt exponential and von Karman functions as spatial auto-correlation functions (ACF. In all our simulation results, the ignorance of the smaller scale heterogeneity leads to underestimation of the failure pressure around a chamber wall, which relates to dyke initiation. The magnitude of the velocity perturbation has a larger effect on the tensile failure at the chamber wall than the difference of the ACF and the correlation length. The maximum effect on the failure pressure in all our simulations is about twice larger than that in the homogeneous case. This indicates that the estimation of the earthquake triggering due to static stress transfer should take account of the heterogeneity of around hundreds of meters.

Optimum measuring net for correcting mineralizing heterogeneity effect in XRF sampling

International Nuclear Information System (INIS)

Zhou Sichun; Zhao Youqing; Zhang Yuhuan

2000-01-01

The mineralizing heterogeneity effect in XRF sampling was investigated with theory of mathematical statistics. A method called 'Optimum measuring Net' has been developed. The theoretical estimation and experimental results show that the mineralizing heterogeneity effect can be cut down to the minimum with the method

Effect of tissue heterogeneity on quantification in positron emission tomography

International Nuclear Information System (INIS)

Blomqvist, G.; Lammertsma, A.A.; Mazoyer, B.; Wienhard, K.

1995-01-01

As a result of the limited spatial resolution of positron emission tomographic scanners, the measurements of physiological parameters are compromised by tissue heterogeneity. The effect of tissue heterogeneity on a number of parameters was studied by simulation and an analytical method. Five common tracer models were assessed. The input and tissue response functions were assumed to be free from noise and systematic errors. The kinetic model was assumed to be perfect. Two components with different kinetics were mixed in different proportions and contrast with respect to the model parameters. Different experimental protocols were investigated. Of three methods investigated for the measurement of cerebral blood flow (CBF) (steady state, dynamic, integral), the second one was least sensitive to errors caused by tissue heterogeneity and the main effect was an underestimation of the distribution volume. With the steady state method, errors in oxygen extraction fraction caused by tissue heterogeneity were always found to be less than the corresponding errors in CBF. For myocardial blood flow the steady state method was found to perform better than the bolus method. The net accumulation of substrate (i.e. rCMR glc in the case of glucose analogs) was found to be comparatively insensitive to tissue heterogeneity. Individual rate constans such as k 2 and k 3 for efflux and metabolism of the substrate in the pool of unmetabolized substrate in the tissue, respectively, were found to be more sensitive. In studies of radioligand binding, using only tracer doses, the effect of tissue heterogeneity on the parameter k on .B max could be considerable. In studies of radioligand binding using a protocol with two experiments, one with high and one with low specific activity, B max was found to be insensitive while K d was very sensitive to tissue heterogeneity. (orig.)

Effect of tissue heterogeneity on quantification in positron emission tomography

Energy Technology Data Exchange (ETDEWEB)

Blomqvist, G [Dept. of Clinical Neuroscience, Experimental Alcohol and Drug Addiction Research Section, Karolinska Hospital, Stockholm (Sweden); Lammertsma, A A [PET Methodology Group, Cyclotron Unit, MRC Clinical Sciences Centre, Royal Postgraduate Medical School, Hammersmith Hospital, London (United Kingdom); Mazoyer, B [Service Hospitalier Frederic Joliot CEA/Dept. de Biologie, Hopital d` Orsay and Antenne d` Informatique Medicale, Hopital Robert Debre, Paris (France); Wienhard, K [Max-Planck-Inst. fuer Neurologische Forschung, Koeln (Germany)

1995-07-01

As a result of the limited spatial resolution of positron emission tomographic scanners, the measurements of physiological parameters are compromised by tissue heterogeneity. The effect of tissue heterogeneity on a number of parameters was studied by simulation and an analytical method. Five common tracer models were assessed. The input and tissue response functions were assumed to be free from noise and systematic errors. The kinetic model was assumed to be perfect. Two components with different kinetics were mixed in different proportions and contrast with respect to the model parameters. Different experimental protocols were investigated. Of three methods investigated for the measurement of cerebral blood flow (CBF) (steady state, dynamic, integral), the second one was least sensitive to errors caused by tissue heterogeneity and the main effect was an underestimation of the distribution volume. With the steady state method, errors in oxygen extraction fraction caused by tissue heterogeneity were always found to be less than the corresponding errors in CBF. For myocardial blood flow the steady state method was found to perform better than the bolus method. The net accumulation of substrate (i.e. rCMR{sub glc} in the case of glucose analogs) was found to be comparatively insensitive to tissue heterogeneity. Individual rate constans such as k{sub 2} and k{sub 3} for efflux and metabolism of the substrate in the pool of unmetabolized substrate in the tissue, respectively, were found to be more sensitive. In studies of radioligand binding, using only tracer doses, the effect of tissue heterogeneity on the parameter k{sub on}.B{sub max} could be considerable. In studies of radioligand binding using a protocol with two experiments, one with high and one with low specific activity, B{sub max} was found to be insensitive while K{sub d} was very sensitive to tissue heterogeneity. (orig.)

On-line image guidance for frameless stereotactic radiotherapy of lung malignancies by cone beam CT: Comparison between target localization and alignment on bony anatomy

International Nuclear Information System (INIS)

Masi, Laura; Casamassima, Franco; Menichelli, Claudia; Pasciuti, Katia; Doro, Raffaela; Polli, Caterina; D'imporzano, Elena; Bonucci, Ivano

2008-01-01

Introduction. Free-breathing stereotactic radiotherapy for lung malignancies requires reliable prediction of respiratory motion and accurate target localization. A protocol was adopted for reproducibility and reduction of respiratory motion and for target localization by CBCT image guidance. Tumor respiratory displacements and tumor positioning errors relative to bony anatomy alignment are analyzed. Materials and method. Image guided SRT was performed for 99 lung malignancies. Two groups of patients were considered: group A did not perform any breathing control; group B controlled visually their respiratory cycle and volumes on an Active Breathing Coordinator (ABC) monitor during the acquisition of simulation CT and CBCT, and treatment delivery. GTV on end inhale and exhale CT data sets were fused in an ITV and the extent of tumor motion evaluated between these 2 phases. A pre-treatment CBCT was acquired and aligned to the reference CT using bony anatomy; for tumor positioning the ITV contour on the reference CT was matched to the visible tumor on CBCT. Interobserver variability of tumor positioning was evaluated. ITV and CBCT tumor dimensions were compared. Results. 3D tumor breathing displacement (mean±SD) was significantly higher for group A (14.7±9.9 mm) than for group B (4.7±3.1 mm). The detected differences between tumor and bony structure alignment below 3 mm were 68% for group B and 45% for group A, reaching statistical significance. Interobserver variability was 1.7±1.1 mm (mean±SD). Dimensions of tumor image on CBCT were consistent with ITV dimensions for group B (max difference 14%). Conclusions. The adopted protocol seems effective in reducing respiratory internal movements and margin. Tumor positioning errors relative to bony anatomy are also reduced. However bony anatomy as a surrogate of the target may still lead to some relevant positioning errors. Target visualization on CBCT is essential for an accurate localization in lung SRT

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

Science.gov (United States)

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. © 2017 John Wiley & Sons Ltd.

Research on the Effects of Heterogeneity on Pedestrian Dynamics in Walkway of Subway Station

Directory of Open Access Journals (Sweden)

Haoling Wu

2016-01-01

Full Text Available The major objective of this paper is to study the effects of heterogeneity on pedestrian dynamics in walkway of subway station. We analyze the observed data of the selected facility and find that walking speed and occupied space were varied in the population. In reality, pedestrians are heterogeneous individuals with different attributes. However, the research on how the heterogeneity affects the pedestrian dynamics in facilities of subway stations is insufficient. The improved floor field model is therefore presented to explore the effects of heterogeneity. Pedestrians are classified into pedestrians walking in pairs, fast pedestrians, and ordinary pedestrians. For convenience, they are denoted as P-pedestrians, F-pedestrians, and O-pedestrians, respectively. The proposed model is validated under homogeneous and heterogeneous conditions. Three pedestrian compositions are simulated to analyze the effects of heterogeneity on pedestrian dynamics. The results show that P-pedestrians have negative effect and F-pedestrians have positive effect. All of the results in this paper indicate that the capacity of walkway is not a constant value. It changes with different component proportions of heterogeneous pedestrians. The heterogeneity of pedestrian has an important influence on the pedestrian dynamics in the walkway of the subway station.

Bony injuries in trauma patients diagnosed by radiological examination

International Nuclear Information System (INIS)

Amponsah, G.; Gorleku, P. N.

2015-01-01

This study was carried out to determine the incidence of bony injuries in trauma patients who had plain radiographs done at the Central Regional Hospital in Cape Coast. This is a retrospective study based on plain radiographs taken by trauma patients who reported to the Central Regional Hospital. The case notes of all patients with a discharge diagnosis of Road Traffic Accident or trauma of all aetiologies that presented to the hospital between January 2005 and December 2011 were retrieved, and those patients that had skeletal radiographic examinations were included in this study. The total number of cases seen was 1,133. The ages of the patients ranged between 1 and 72 years. Sixty-nine (6.1%) of the patients were between 1 and 4 years old, with the majority between 20 and 49 years old, constituting 52.3%, with patients 60 years and above at 9.2%. There was statistically significant difference between male and female patients (p=0.001). A total of 912 (80.5%) patients had radiographic examination done out of which only 324 (35.5%) radiographs could be retrieved. There were 106 (32.7%) radiographs with various bony injuries which was statistically significant (p=0.001). Rib fractures represented 19/106 (17.9%) of which 62.5% had multiple rib fractures. Fifty-eight (54.7%) had long bone fractures. Other anatomical sites included the pelvis and the skull. Conclusion: Trauma is a major public health problem in the country, involving mainly the productive age group. Unnecessary exposure to X-rays is common. Inadequate management of trauma patients negatively impacts on the outcome of trauma patients. Trauma prevention is the best way forward.(au)

Intratumor heterogeneity alters most effective drugs in designed combinations.

Science.gov (United States)

Zhao, Boyang; Hemann, Michael T; Lauffenburger, Douglas A

2014-07-22

The substantial spatial and temporal heterogeneity observed in patient tumors poses considerable challenges for the design of effective drug combinations with predictable outcomes. Currently, the implications of tissue heterogeneity and sampling bias during diagnosis are unclear for selection and subsequent performance of potential combination therapies. Here, we apply a multiobjective computational optimization approach integrated with empirical information on efficacy and toxicity for individual drugs with respect to a spectrum of genetic perturbations, enabling derivation of optimal drug combinations for heterogeneous tumors comprising distributions of subpopulations possessing these perturbations. Analysis across probabilistic samplings from the spectrum of various possible distributions reveals that the most beneficial (considering both efficacy and toxicity) set of drugs changes as the complexity of genetic heterogeneity increases. Importantly, a significant likelihood arises that a drug selected as the most beneficial single agent with respect to the predominant subpopulation in fact does not reside within the most broadly useful drug combinations for heterogeneous tumors. The underlying explanation appears to be that heterogeneity essentially homogenizes the benefit of drug combinations, reducing the special advantage of a particular drug on a specific subpopulation. Thus, this study underscores the importance of considering heterogeneity in choosing drug combinations and offers a principled approach toward designing the most likely beneficial set, even if the subpopulation distribution is not precisely known.

Bony vibration stimulation test combined with magnetic resonance imaging. Can discography be replaced?

Science.gov (United States)

Yrjämä, M; Tervonen, O; Kurunlahti, M; Vanharanta, H

1997-04-01

The results of two noninvasive methods, magnetic resonance imaging and a bony vibration test, were compared with discographic pain provocation findings. To evaluate whether the combination of magnetic resonance imaging and vibration pain provocation tests could be used to replace discography in low back pain diagnostics. Magnetic resonance imaging gives a wealth of visual information on anatomic changes of the spine with often unknown clinical significance. Discographic examination of the spine is still the only widely accepted diagnostic method that can relate the pathoanatomic changes to the patient's clinical pain. Internal anular rupture has been shown to be one of the sources of back pain. The bony vibration test of the spinal processes has been shown correlate well with discographic pain provocation tests in cases of internal anular rupture. The three lowest lumbar discs of 33 patients with back pain were examined by means of magnetic resonance imaging and a bony vibration stimulation test, and the results were compared with those from computed tomography-discography. In cases of intradiscal magnetic resonance imaging findings, the vibration provocation test showed a sensitivity of 0.88 and a specificity of 0.50 compared with the discographic pain provocation test. If the patients with previous back surgery were excluded, the specificity was 0.75. In the cases of total anular rupture, the sensitivity was 0.50, and the specificity was 0.33. The combination of the two noninvasive methods, vibration stimulation and magnetic resonance imaging, gives more information on the origin of the back pain than magnetic resonance imaging alone. The pathoanatomic changes seen in magnetic resonance imaging can be correlated with the patient's disorder more reliably using the vibration provocation test in the cases of partial anular ruptures. The use of discography can be limited mostly to cases with total anular ruptures detected by magnetic resonance imaging.

Valor predicts the thyroid hormones in the evolution the transplant bony marrow

International Nuclear Information System (INIS)

Alonso, C.A.; Carnot, J.; De Castro, R.; Morera, M.L.; Garcia, I.

1998-01-01

In this work you values the valor I predict the thyroid hormones in the bony marrow transplant evolution as factors the metabolisms oxidative and the synthesis albumins. The patients received conditioning treatments to the transplant and in the postoperational. The received radiations were 1000 cGy lateral cube, with blocking lung, to those that were subjected 3 sessions irradiation, they are practiced a transplant marrow allogeneic

The effects of habitat connectivity and regional heterogeneity on artificial pond metacommunities.

Science.gov (United States)

Pedruski, Michael T; Arnott, Shelley E

2011-05-01

Habitat connectivity and regional heterogeneity represent two factors likely to affect biodiversity across different spatial scales. We performed a 3 × 2 factorial design experiment to investigate the effects of connectivity, heterogeneity, and their interaction on artificial pond communities of freshwater invertebrates at the local (α), among-community (β), and regional (γ) scales. Despite expectations that the effects of connectivity would depend on levels of regional heterogeneity, no significant interactions were found for any diversity index investigated at any spatial scale. While observed responses of biodiversity to connectivity and heterogeneity depended to some extent on the diversity index and spatial partitioning formula used, the general pattern shows that these factors largely act at the β scale, as opposed to the α or γ scales. We conclude that the major role of connectivity in aquatic invertebrate communities is to act as a homogenizing force with relatively little effect on diversity at the α or γ levels. Conversely, heterogeneity acts as a force maintaining differences between communities.

Medial depression with bony dehiscence of lamina papyracea as an anatomic variation: CT evaluation

International Nuclear Information System (INIS)

Na, Sun Young; Lee, Young Uk; Youn, Eun Kyung; Suh, Sang Gyung; Kim, Dong Hyun

1994-01-01

To evaluate the incidence and CT findings of the medial depression and bony dehiscence of lamina papyracea as an anatomic variation. 1472 PNS CTs of the patients with symptoms of chronic sinusitis were retrospectively evaluated. The total incidence of depressed lamina papyracea as an anatomic variation was 3.5%(52/1472) on PNS CT. There was a statistically significant correlation between the increasing age and the incidence of depressed lamina papyracea. Depression of lamina papyracea anterior to the basal lamella were more common than those of the posterior depression. Associated findings were herniation of adjacent fatty tissue in all cases and the medial bowing and hypertrophied configuration of the medial rectus muscle without significant herniation in 19 cases(34%). Nontraumatic, asymptomatic depression with bony dehiscence of lamina papyracea as an anatomic variation is not uncommon with the incidence of 3.5%. Recognition of its existence and degree may be helpful in avoiding various ocular complication during ethmoid surgery

Palaeobiology of Hyaenodon exiguus (Hyaenodonta, Mammalia) based on morphometric analysis of the bony labyrinth.

Science.gov (United States)

Pfaff, Cathrin; Nagel, Doris; Gunnell, Gregg; Weber, Gerhard W; Kriwet, Jürgen; Morlo, Michael; Bastl, Katharina

2017-02-01

Species of the extinct genus Hyaenodon were among the largest carnivorous mammals from the Late Eocene through Early Miocene in North America, Europe and Asia. The origin, phylogeny and palaeobiology of Hyaenodonta are still ambiguous. Most previous studies focused on teeth and dental function in these highly adapted species, which might be influenced by convergent morphologies. The anatomy of the bony labyrinth in vertebrates is generally quite conservative and, additionally, was used in functional-morphological studies. This study provides the first anatomical description of the bony labyrinth of the extinct European species Hyaenodon exiguus in comparison to selected extant carnivoran taxa discussed from a functional-morphological perspective. Hyaenodon exiguus may have occupied a hyaena-like dietary niche with a semi-arboreal lifestyle, based on the relative height, width and length of the semicircular canals of the inner ear. However, this contradicts previous functional-morphological studies focusing on the diameter of the canals, which presumably represent the signal of locomotion mode. © 2016 Anatomical Society.

Effects of low heterogeneity in fast critical assemblies

International Nuclear Information System (INIS)

Belov, S.P.; Dulin, V.A.; Zhukov, A.V.; Kuzin, E.N.; Mozhaev, V.K.; Sitnikov, V.I.; Tsibulya, A.M.; Shapar', A.V.; Zayfert, E.; Kuntsman, B.; Khayntsel'man, B.

1989-01-01

The problem of the low heterogeneity of fast critical assemblies, which are used to simulate fast reactors that are under design, has begun to assume increasing importance as the errors in nuclear data and group constants decrease and the capabilities of design codes improve. The design of the fuel channels of the fast critical assemblies of a BFS differs from that of the fuel subassemblies of a power reactor. The principal difference is that critical assemblies have a more heterogeneous structure than a reactor core does. As a result, the effects of this heterogeneity turn out to be appreciable for a number of functionals. Of particular interest was the measurement of the main neutronic characteristics of a fast reactor in its actual design and in the mockup produced by using BFS facilities. The authors measured and calculated the most important functionals (the ratios of the average cross sections of the main absorbing and fissioning elements, etc.) for both a homogeneous medium (fuel assemblies) and a heterogeneous medium (slugs, tubes) of practically identical composition. The objective of this work was to compare the discrepancy between experiment and calculations for the central functionals in the homogeneous and heterogeneous cases after corrections. This is a check of the accuracy of the simulation of homogeneous cores in fast power reactors by using the tools of the BFS fast critical assembly

SU-E-J-33: Comparison Between Soft Tissue Alignment and Bony Alignment for Pancreatic Cancer Radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Suh, Y; Crane, C; Krishnan, S; Das, P; Koay, E; Beddar, S [UT MD Anderson Cancer Center, Houston, TX (United States)

2015-06-15

Purpose An IGRT modality for pancreatic cancer treatment with dose escalation at our institution is in-room daily CT imaging. The purpose of this study is to assess the difference between soft tissue alignment and bony alignment for pancreatic tumor localization. Methods Eighteen patients with pancreatic tumors who underwent IMRT treatment with an inspiration breath-hold technique between July 2012 and February 2015 are included in this study. Prior to each treatment, a CT scan was acquired. The CT image guidance started with auto-alignment to either the bony anatomy (vertebral bodies) or fiducials (for the six patients with the stent in/near the tumor) and then, when necessary, manual adjustments were made based on soft tissue alignment using clinical software (CT-Assisted Targeting system). The difference between soft tissue alignment and bony/fiducial alignment was evaluated. Results Of all 380 treatments, manual adjustment was made in 225 treatments, ranging from 11% (3 treatments out of 28) to 96% (27 treatments out of 28) per patient. The mean of the difference between soft tissue alignment and bony/fiducial alignment per patient ranged from −3.6 to 0.3 mm, −1.5 to 2.8 mm, and −3.3 to 3.4 mm in the AP, SI, and RL directions, respectively. The maximum difference over all treatments was −9.5, −14.6, and −14.6 mm in the AP, SI, and RL directions, respectively. Conclusion About 60% of the time, manual adjustment based on soft tissue alignment was required. The extent of manual adjustment was usually small but varied significantly from patient to patient. The ultimate goal of the IGRT modality using daily CT imaging is not to fully cover the target but to spare organs-at-risk as much as possible to avoid them moving into higher dose gradients than accepted in the treatment plan. To this end, manual adjustment based on soft tissue alignment is critically important.

"Sub Specie Boni": The Comfort Zone of Self-Belief--A Dimension in Counseling Offenders.

Science.gov (United States)

Church, James Lee

1996-01-01

Claims that self-defeating behavior is a rational attempt to satisfy early, introjected messages about the type of person one is, arising from a desire for things perceived as good--sub specie boni. Examines the notion of the comfort zone, toxic shame, and therapists' responsibility to nourish acceptable joy. (RJM)

On the compensation effect in heterogeneous catalysis

DEFF Research Database (Denmark)

Pedersen, Thomas Bligaard; Honkala, Johanna Karoliina; Logadottir, Ashildur

2003-01-01

For a class of heterogeneously catalyzed reactions, we explain the compensation effect in terms of a switching of kinetic regimes leading to a concomitant change in the apparent activation energy and in the prefactor for the overall rate of the reaction. We first use the ammonia synthesis...

Effects of heterogeneity on bank efficiency scores

NARCIS (Netherlands)

Bos, J. W. B.; Koetter, M.; Kolari, J. W.; Kool, C. J. M.

2009-01-01

Bank efficiency estimates often serve as a proxy of managerial skill since they quantify sub-optimal production choices. But such deviations can also be due to omitted systematic differences among banks. In this study, we examine the effects of heterogeneity on bank efficiency scores. We compare

Effect of heterogeneities on the thermoelectric power of pressure vessel steel

International Nuclear Information System (INIS)

Simonet, L.

2006-12-01

In service working conditions, the vessel of the Pressurized Water Reactors (PWR) undergoes an ageing due to irradiation. In order to follow the evolution of the mechanical characteristics of the steel in service, EDF launched a surveillance program which consists to carry out mechanical tests on samples aged in reactor. However, the results of these tests have the disadvantage to be affected by the presence of heterogeneities within the steel. Indeed, because of its manufacturing process, the steel contains segregated areas. Thus, EDF launched Thermoelectric Power Measurements (TEP) on the resilience samples of the surveillance program, to complete the mechanical tests and to help with their interpretation. However, these measurements are today difficult to analyse because they include at the same time the effect of the irradiation and the effect of the metallurgical heterogeneities. The aim of this work consisted in evaluating the effect of the heterogeneities on the TEP of the non-irradiated vessel steel. For that, a numerical model was developed which allows to calculate the TEP of a composite structure. We have shown that the model is pertinent to highlight the effect of the heterogeneities on the TEP of the vessel steel, which is considered like a 'matrix'/'segregation' composite. The model allowed us to put emphasis on the influence of different parameters on the TEP measurement. We have thus showed that the measurements conditions have an important effect on the obtained TEP value (influence of the applied pressure, the position of the sample on the device, the site of the metallurgical heterogeneities,...). (author)

Zero-inflated count models for longitudinal measurements with heterogeneous random effects.

Science.gov (United States)

Zhu, Huirong; Luo, Sheng; DeSantis, Stacia M

2017-08-01

Longitudinal zero-inflated count data arise frequently in substance use research when assessing the effects of behavioral and pharmacological interventions. Zero-inflated count models (e.g. zero-inflated Poisson or zero-inflated negative binomial) with random effects have been developed to analyze this type of data. In random effects zero-inflated count models, the random effects covariance matrix is typically assumed to be homogeneous (constant across subjects). However, in many situations this matrix may be heterogeneous (differ by measured covariates). In this paper, we extend zero-inflated count models to account for random effects heterogeneity by modeling their variance as a function of covariates. We show via simulation that ignoring intervention and covariate-specific heterogeneity can produce biased estimates of covariate and random effect estimates. Moreover, those biased estimates can be rectified by correctly modeling the random effects covariance structure. The methodological development is motivated by and applied to the Combined Pharmacotherapies and Behavioral Interventions for Alcohol Dependence (COMBINE) study, the largest clinical trial of alcohol dependence performed in United States with 1383 individuals.

Physical heterogeneity control on effective mineral dissolution rates

Science.gov (United States)

Jung, Heewon; Navarre-Sitchler, Alexis

2018-04-01

Hydrologic heterogeneity may be an important factor contributing to the discrepancy in laboratory and field measured dissolution rates, but the governing factors influencing mineral dissolution rates among various representations of physical heterogeneity remain poorly understood. Here, we present multiple reactive transport simulations of anorthite dissolution in 2D latticed random permeability fields and link the information from local grid scale (1 cm or 4 m) dissolution rates to domain-scale (1m or 400 m) effective dissolution rates measured by the flux-weighted average of an ensemble of flow paths. We compare results of homogeneous models to heterogeneous models with different structure and layered permeability distributions within the model domain. Chemistry is simplified to a single dissolving primary mineral (anorthite) distributed homogeneously throughout the domain and a single secondary mineral (kaolinite) that is allowed to dissolve or precipitate. Results show that increasing size in correlation structure (i.e. long integral scales) and high variance in permeability distribution are two important factors inducing a reduction in effective mineral dissolution rates compared to homogeneous permeability domains. Larger correlation structures produce larger zones of low permeability where diffusion is an important transport mechanism. Due to the increased residence time under slow diffusive transport, the saturation state of a solute with respect to a reacting mineral approaches equilibrium and reduces the reaction rate. High variance in permeability distribution favorably develops large low permeability zones that intensifies the reduction in mixing and effective dissolution rate. However, the degree of reduction in effective dissolution rate observed in 1 m × 1 m domains is too small (equilibrium conditions reduce the effective dissolution rate by increasing the saturation state. However, in large domains where less- or non-reactive zones develop, higher

Effect of reservoir heterogeneity on air injection performance in a light oil reservoir

Directory of Open Access Journals (Sweden)

Hu Jia

2018-03-01

Full Text Available Air injection is a good option to development light oil reservoir. As well-known that, reservoir heterogeneity has great effect for various EOR processes. This also applies to air injection. However, oil recovery mechanisms and physical processes for air injection in heterogeneous reservoir with dip angle are still not well understood. The reported setting of reservoir heterogeneous for physical model or simulation model of air injection only simply uses different-layer permeability of porous media. In practice, reservoir heterogeneity follows the principle of geostatistics. How much of contrast in permeability actually challenges the air injection in light oil reservoir? This should be investigated by using layered porous medial settings of the classical Dykstra-Parsons style. Unfortunately, there has been no work addressing this issue for air injection in light oil reservoir. In this paper, Reservoir heterogeneity is quantified based on the use of different reservoir permeability distribution according to classical Dykstra-Parsons coefficients method. The aim of this work is to investigate the effect of reservoir heterogeneity on physical process and production performance of air injection in light oil reservoir through numerical reservoir simulation approach. The basic model is calibrated based on previous study. Total eleven pseudo compounders are included in this model and ten complexity of reactions are proposed to achieve the reaction scheme. Results show that oil recovery factor is decreased with the increasing of reservoir heterogeneity both for air and N2 injection from updip location, which is against the working behavior of air injection from updip location. Reservoir heterogeneity sometimes can act as positive effect to improve sweep efficiency as well as enhance production performance for air injection. High O2 content air injection can benefit oil recovery factor, also lead to early O2 breakthrough in heterogeneous reservoir. Well

Effect of chemical and physical heterogeneities on colloid-facilitated cesium transport

Science.gov (United States)

Rod, Kenton; Um, Wooyong; Chun, Jaehun; Wu, Ning; Yin, Xialong; Wang, Guohui; Neeves, Keith

2018-06-01

A set of column experiments was conducted to investigate the chemical and physical heterogeneity effect on colloid facilitated transport under slow pore velocity conditions. Pore velocities were kept below 100 cm d-1 for all experiments. Glass beads were packed into columns establishing four different conditions: 1) homogeneous, 2) mixed physical heterogeneity, 3) sequentially layered physical heterogeneity, and 4) chemical heterogeneity. The homogeneous column was packed with glass beads (diameter 500-600 μm), and physical heterogeneities were created by sequential layering or mixing two sizes of glass bead (500-600 μm and 300-400 μm). A chemical heterogeneity was created using 25% of the glass beads coated with hydrophobic molecules (1H-1H-2H-2H-perfluorooctyltrichlorosilane) mixed with 75% pristine glass beads (all 500-600 μm). Input solution with 0.5 mM CsI and 50 mg L-1 colloids (1-μm diameter SiO2) was pulsed into columns under saturated conditions. The physical heterogeneity in the packed glass beads retarded the transport of colloids compared to homogeneous (R = 25.0), but showed only slight differences between sequentially layered (R = 60.7) and mixed heterogeneity(R = 62.4). The column with the chemical, hydrophobic/hydrophilic, heterogeneity removed most of the colloids from the input solution. All column conditions stripped Cs from colloids onto the column matrix of packed glass beads.

The effect of heterogeneous dynamics of online users on information filtering

International Nuclear Information System (INIS)

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

2015-01-01

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. - Highlights: • We study the effect of heterogeneous dynamics of users on recommendation. • Due to the user heterogeneity, their amount of links in the probe set is different. • The personalized algorithm implementation improves the recommendation performance. • Our results suggest different update frequency for users – recommendation list.

The effect of heterogeneous dynamics of online users on information filtering

Energy Technology Data Exchange (ETDEWEB)

Chen, Bo-Lun [Department of Computer Science, Yangzhou University of China, Yangzhou 225127 (China); Department of Computer Science, Nanjing University of Aeronautics and Astronautics of China, Nanjing 210016 (China); Department of Physics, University of Fribourg, Chemin du Musee 3, CH-1700 Fribourg (Switzerland); Zeng, An, E-mail: anzeng@bnu.edu.cn [School of Systems Science, Beijing Normal University, Beijing 100875 (China); Chen, Ling [Department of Computer Science, Yangzhou University of China, Yangzhou 225127 (China); Department of Computer Science, Nanjing University of Aeronautics and Astronautics of China, Nanjing 210016 (China)

2015-11-06

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. - Highlights: • We study the effect of heterogeneous dynamics of users on recommendation. • Due to the user heterogeneity, their amount of links in the probe set is different. • The personalized algorithm implementation improves the recommendation performance. • Our results suggest different update frequency for users – recommendation list.

SU-E-J-94: Positioning Errors Resulting From Using Bony Anatomy Alignment for Treating SBRT Lung Tumor

International Nuclear Information System (INIS)

Frame, C; Ding, G

2014-01-01

Purpose: To quantify patient setups errors based on bony anatomy registration rather than 3D tumor alignment for SBRT lung treatments. Method: A retrospective study was performed for patients treated with lung SBRT and imaged with kV cone beam computed tomography (kV-CBCT) image-guidance. Daily CBCT images were registered to treatment planning CTs based on bony anatomy alignment and then inter-fraction tumor movement was evaluated by comparing shift in the tumor center in the medial-lateral, anterior-posterior, and superior-inferior directions. The PTV V100% was evaluated for each patient based on the average daily tumor displacement to assess the impact of the positioning error on the target coverage when the registrations were based on bony anatomy. Of the 35 patients studied, 15 were free-breathing treatments, 10 used abdominal compression with a stereotactic body frame, and the remaining 10 were performed with BodyFIX vacuum bags. Results: For free-breathing treatments, the range of tumor displacement error is between 1–6 mm in the medial-lateral, 1–13 mm in the anterior-posterior, and 1–7 mm in the superior-inferior directions. These positioning errors lead to 6–22% underdose coverage for PTV - V100% . Patients treated with abdominal compression immobilization showed positional errors of 0–4mm mediallaterally, 0–3mm anterior-posteriorly, and 0–2 mm inferior-superiorly with PTV - V100% underdose ranging between 6–17%. For patients immobilized with the vacuum bags, the positional errors were found to be 0–1 mm medial-laterally, 0–1mm anterior-posteriorly, and 0–2 mm inferior-superiorly with PTV - V100% under dose ranging between 5–6% only. Conclusion: It is necessary to align the tumor target by using 3D image guidance to ensure adequate tumor coverage before performing SBRT lung treatments. The BodyFIX vacuum bag immobilization method has the least positioning errors among the three methods studied when bony anatomy is used for

A biomechanical analysis of a single-row suture anchor fixation of a large bony bankart lesion.

Science.gov (United States)

Dyskin, Evgeny; Marzo, John M; Howard, Craig; Ehrensberger, Mark

2014-12-01

This study was conducted to assess whether a single-row suture anchor repair of a bony Bankart lesion comprising 19% of the glenoid length restores peak translational force and glenoid depth compared with the intact shoulder. Nine thawed adult cadaveric shoulders were dissected and mounted in 45° of abduction and 30° of external rotation. A bony Bankart lesion was simulated with an anterior longitudinal osteotomy, parallel to the superoinferior axis of the glenoid, equivalent to 19% of the glenoid length. The humeral head was displaced 10 mm anteriorly at a speed of 2 mm/s with a 50-N compressive load applied. Testing was performed with the glenoid intact, a simulated lesion, and the lesion repaired with 3 single-row suture anchors. Median (interquartile range [IQR]) peak translational force and glenoid depth were reported. The Friedman test and post hoc comparisons with the Wilcoxon signed rank test were used for between-group analyses. Peak translational force decreased after osteotomy (13.7 N; IQR, 9.6 to 15.5 N; P = .01) and increased after the repair (18.3 N; IQR, 18.3 to 20.6 N; P = .01) compared with the intact shoulder (23.7 N; IQR, 16.4 to 29.9 N). Glenoid depth significantly decreased after the osteotomy (0.2 mm; IQR, -0.6 to 0.7 mm) compared with baseline (1.7 mm; IQR, 1.3 to 2.0 mm; P = .01) and increased after repair (0.8 mm; IQR, 0.1 to 1.0 mm; P = .03) compared with the osteotomized shoulder. The glenoid depth of the repair was less than the baseline value (P = .01). Repair of an anterior bony Bankart lesion equivalent to 19% of the glenoid length with 3 suture anchors restored the peak translational force needed to anteriorly displace the humerus relative to the glenoid; however, this technique failed to restore the natural glenoid depth in a laboratory setting. Our findings describe the inability of a single-row suture anchor repair to provide anatomic fixation of the bony Bankart lesion equivalent to 19% of the glenoid length

A comparison of the use of bony anatomy and internal markers for offline verification and an evaluation of the potential benefit of online and offline verification protocols for prostate radiotherapy.

Science.gov (United States)

McNair, Helen A; Hansen, Vibeke N; Parker, Christopher C; Evans, Phil M; Norman, Andrew; Miles, Elizabeth; Harris, Emma J; Del-Acroix, Louise; Smith, Elizabeth; Keane, Richard; Khoo, Vincent S; Thompson, Alan C; Dearnaley, David P

2008-05-01

To evaluate the utility of intraprostatic markers in the treatment verification of prostate cancer radiotherapy. Specific aims were: to compare the effectiveness of offline correction protocols, either using gold markers or bony anatomy; to estimate the potential benefit of online correction protocol's using gold markers; to determine the presence and effect of intrafraction motion. Thirty patients with three gold markers inserted had pretreatment and posttreatment images acquired and were treated using an offline correction protocol and gold markers. Retrospectively, an offline protocol was applied using bony anatomy and an online protocol using gold markers. The systematic errors were reduced from 1.3, 1.9, and 2.5 mm to 1.1, 1.1, and 1.5 mm in the right-left (RL), superoinferior (SI), and anteroposterior (AP) directions, respectively, using the offline correction protocol and gold markers instead of bony anatomy. The subsequent decrease in margins was 1.7, 3.3, and 4 mm in the RL, SI, and AP directions, respectively. An offline correction protocol combined with an online correction protocol in the first four fractions reduced random errors further to 0.9, 1.1, and 1.0 mm in the RL, SI, and AP directions, respectively. A daily online protocol reduced all errors to markers is effective in reducing the systematic error. The value of online protocols is reduced by intrafraction motion.

Does bony hip morphology affect the outcome of treatment for patients with adductor-related groin pain?

DEFF Research Database (Denmark)

Hölmich, Per; Thorborg, Kristian; Nyvold, Per

2014-01-01

BACKGROUND: Adductor-related groin pain and bony morphology such as femoroacetabular impingement (FAI) or hip dysplasia can coexist clinically. A previous randomised controlled trial in which athletes with adductor-related groin pain underwent either passive treatment (PT) or active treatment (AT......) showed good results in the AT group. The primary purpose of the present study was to evaluate if radiological signs of FAI or hip dysplasia seem to affect the clinical outcome, initially and at 8-12 years of follow-up. METHODS: 47 patients (80%) were available for follow-up. The clinical result......, there was no significant difference in the distribution of Tönnis grades between hips that had an unchanged or improved outcome compared with hips that had a worse outcome over time (p=0.145). CONCLUSIONS: No evidence was found that bony hip morphology related to FAI or dysplasia prevents successful outcome...

Effect of Heterogeneity in Initial Geographic Distribution on Opinions’ Competitiveness

Directory of Open Access Journals (Sweden)

Alexander S. Balankin

2015-05-01

Full Text Available Spin dynamics on networks allows us to understand how a global consensus emerges out of individual opinions. Here, we are interested in the effect of heterogeneity in the initial geographic distribution of a competing opinion on the competitiveness of its own opinion. Accordingly, in this work, we studied the effect of spatial heterogeneity on the majority rule dynamics using a three-state spin model, in which one state is neutral. Monte Carlo simulations were performed on square lattices divided into square blocks (cells. Accordingly, one competing opinion was distributed uniformly among cells, whereas the spatial distribution of the rival opinion was varied from the uniform to heterogeneous, with the median-to-mean ratio in the range from 1 to 0. When the size of discussion group is odd, the uncommitted agents disappear completely after  3.30 ± 0.05 update cycles, and then the system evolves in a two-state regime with complementary spatial distributions of two competing opinions. Even so, the initial heterogeneity in the spatial distribution of one of the competing opinions causes a decrease of this opinion competitiveness. That is, the opinion with initially heterogeneous spatial distribution has less probability to win, than the opinion with the initially uniform spatial distribution, even when the initial concentrations of both opinions are equal. We found that although the time to consensus , the opinion’s recession rate is determined during the first 3.3 update cycles. On the other hand, we found that the initial heterogeneity of the opinion spatial distribution assists the formation of quasi-stable regions, in which this opinion is dominant. The results of Monte Carlo simulations are discussed with regard to the electoral competition of political parties.

Effect of heterogeneous microvasculature distribution on drug delivery to solid tumour

International Nuclear Information System (INIS)

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

2014-01-01

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. (paper)

Computing effective properties of random heterogeneous materials on heterogeneous parallel processors

Science.gov (United States)

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.

Influence of rotational setup error on tumor shift in bony anatomy matching measured with pulmonary point registration in stereotactic body radiotherapy for early lung cancer

International Nuclear Information System (INIS)

Suzuki, Osamu; Nishiyama, Kinji; Ueda, Yoshihiro; Miyazaki, Masayoshi; Tsujii, Katsutomo

2012-01-01

The objective of this study was to examine the correlation between the patient rotational error measured with pulmonary point registration and tumor shift after bony anatomy matching in stereotactic body radiotherapy for lung cancer. Twenty-six patients with lung cancer who underwent stereotactic body radiotherapy were the subjects. On 104 cone-beam computed tomography measurements performed prior to radiation delivery, rotational setup errors were measured with point registration using pulmonary structures. Translational registration using bony anatomy matching was done and the three-dimensional vector of tumor displacement was measured retrospectively. Correlation among the three-dimensional vector and rotational error and vertebra-tumor distance was investigated quantitatively. The median and maximum rotational errors of the roll, pitch and yaw were 0.8, 0.9 and 0.5, and 6.0, 4.5 and 2.5, respectively. Bony anatomy matching resulted in a 0.2-1.6 cm three-dimensional vector of tumor shift. The shift became larger as the vertebra-tumor distance increased. Multiple regression analysis for the three-dimensional vector indicated that in the case of bony anatomy matching, tumor shifts of 5 and 10 mm were expected for vertebra-tumor distances of 4.46 and 14.1 cm, respectively. Using pulmonary point registration, it was found that the rotational setup error influences the tumor shift. Bony anatomy matching is not appropriate for hypofractionated stereotactic body radiotherapy with a tight margin. (author)

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

Science.gov (United States)

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.

Bony manifestation of rickets in a sunny city - a case report from Yazd, Iran

Directory of Open Access Journals (Sweden)

Mohammadhosain Afrand

2014-01-01

Full Text Available Rickets is disease that occurs in growing bones in which defective mineralization occurs in both the bone and the cartilage of the epiphyseal growth plate, resulting in the retardation of growth and skeletal deformities. Rickets is more common in areas with less sunlight. However, this case report presents a case of the bony manifestation of rickets with the intake of vitamin D supplements in Yazd, a city in central Iran that has sunshine almost every day. A patient was referred to an out-patient general pediatric clinic for deformities of the legs and growth disturbance, with his height far below the normal range. The changes that were most evident in his X-rays were the bowing of the long bones of the legs and forearms and the cupping of the wrist metaphyseal region. In summary, we present a patient with bony manifestation of rickets despite living in a sunny area and taking vitamin D supplements. Thus, it is important to remember that rickets is still a common disease among children in Iran. More studies of this issue should be conducted, including the identification of abnormal cases and rescheduling vitamin D supplementation programs.

Bony manifestation of rickets in a sunny city - a case report from Yazd, Iran

Directory of Open Access Journals (Sweden)

Mohammadhosain Afrand

2014-02-01

Full Text Available Rickets is disease that occurs in growing bones in which defective mineralization occurs in both the bone and the cartilage of the epiphyseal growth plate, resulting in the retardation of growth and skeletal deformities. Rickets is more common in areas with less sunlight. However, this case report presents a case of the bony manifestation of rickets with the intake of vitamin D supplements in Yazd, a city in central Iran that has sunshine almost every day. A patient was referred to an out-patient general pediatric clinic for deformities of the legs and growth disturbance, with his height far below the normal range. The changes that were most evident in his X-rays were the bowing of the long bones of the legs and forearms and the cupping of the wrist metaphyseal region. In summary, we present a patient with bony manifestation of rickets despite living in a sunny area and taking vitamin D supplements. Thus, it is important to remember that rickets is still a common disease among children in Iran. More studies of this issue should be conducted, including the identification of abnormal cases and rescheduling vitamin D supplementation programs

The effect of heterogeneous defectors on the evolution of public cooperation

Science.gov (United States)

Chen, Tong; Hu, Xuezhi; Wang, Yongjie; Wang, Le

2018-06-01

In recent years,more and more private capital join the construction of cultural facilities and the organization of cultural activities in China. Actually, the organization of cultural activities by crowd-funding mechanism is a kind of multi-player game. Not all players who donate different amount of money are real cooperators. In fact, some cunning defectors may donate a little money to avoid the gossip and punishment. This part of people are very tricky. They could be seen as heterogeneous defectors. The role of heterogeneous defectors is investigated in cooperative behaviors of complex social network. Numerical results show that heterogeneous defectors could be a buffer for maintaining the public pool when synergy factor is low in public goods game (PGG). It is relatively easy to be cooperators for heterogeneous defectors when synergy factor is high in PGG. To better improve cooperation, punishment towards heterogeneous defectors and complete defectors is introduced. We are glad to find that when the defectors' loss is equal to or larger than the altruistic cooperators' punishment cost, the mechanism could make great effect. In addition, the role of heterogeneous defectors depends on the relationship between the punishment cost and the defectors' loss.

Price Competition in Two-Sided Markets with Heterogeneous Consumers and Network Effects

NARCIS (Netherlands)

Filistrucchi, L.; Klein, T.J.

We model a two-sided market with heterogeneous customers and two heterogeneous network effects. In our model, customers on each market side care differently about both the number and the type of customers on the other side. Examples of two-sided markets are online platforms or daily newspapers. In

A Comparison of the Use of Bony Anatomy and Internal Markers for Offline Verification and an Evaluation of the Potential Benefit of Online and Offline Verification Protocols for Prostate Radiotherapy

International Nuclear Information System (INIS)

McNair, Helen A.; Hansen, Vibeke N.; Parker, Christopher; Evans, Phil M.; Norman, Andrew; Miles, Elizabeth; Harris, Emma J.; Del-Acroix, Louise; Smith, Elizabeth; Keane, Richard; Khoo, Vincent S.; Thompson, Alan C.; Dearnaley, David P.

2008-01-01

Purpose: To evaluate the utility of intraprostatic markers in the treatment verification of prostate cancer radiotherapy. Specific aims were: to compare the effectiveness of offline correction protocols, either using gold markers or bony anatomy; to estimate the potential benefit of online correction protocol's using gold markers; to determine the presence and effect of intrafraction motion. Methods and Materials: Thirty patients with three gold markers inserted had pretreatment and posttreatment images acquired and were treated using an offline correction protocol and gold markers. Retrospectively, an offline protocol was applied using bony anatomy and an online protocol using gold markers. Results: The systematic errors were reduced from 1.3, 1.9, and 2.5 mm to 1.1, 1.1, and 1.5 mm in the right-left (RL), superoinferior (SI), and anteroposterior (AP) directions, respectively, using the offline correction protocol and gold markers instead of bony anatomy. The subsequent decrease in margins was 1.7, 3.3, and 4 mm in the RL, SI, and AP directions, respectively. An offline correction protocol combined with an online correction protocol in the first four fractions reduced random errors further to 0.9, 1.1, and 1.0 mm in the RL, SI, and AP directions, respectively. A daily online protocol reduced all errors to <1 mm. Intrafraction motion had greater impact on the effectiveness of the online protocol than the offline protocols. Conclusions: An offline protocol using gold markers is effective in reducing the systematic error. The value of online protocols is reduced by intrafraction motion

Effects of soil nutrient heterogeneity on intraspecific competition in the invasive, clonal plant Alternanthera philoxeroides.

Science.gov (United States)

Zhou, Jian; Dong, Bi-Cheng; Alpert, Peter; Li, Hong-Li; Zhang, Ming-Xiang; Lei, Guang-Chun; Yu, Fei-Hai

2012-03-01

Fine-scale, spatial heterogeneity in soil nutrient availability can increase the growth of individual plants, the productivity of plant communities and interspecific competition. If this is due to the ability of plants to concentrate their roots where nutrient levels are high, then nutrient heterogeneity should have little effect on intraspecific competition, especially when there are no genotypic differences between individuals in root plasticity. We tested this hypothesis in a widespread, clonal species in which individual plants are known to respond to nutrient heterogeneity. Plants derived from a single clone of Alternanthera philoxeroides were grown in the greenhouse at low or high density (four or 16 plants per 27·5 × 27·5-cm container) with homogeneous or heterogeneous availability of soil nutrients, keeping total nutrient availability per container constant. After 9 weeks, measurements of size, dry mass and morphology were taken. Plants grew more in the heterogeneous than in the homogeneous treatment, showing that heterogeneity promoted performance; they grew less in the high- than in the low-density treatment, showing that plants competed. There was no interactive effect of nutrient heterogeneity and plant density, supporting the hypothesis that heterogeneity does not affect intraspecific competition in the absence of genotypic differences in plasticity. Treatments did not affect morphological characteristics such as specific leaf area or root/shoot ratio. Results indicate that fine-scale, spatial heterogeneity in the availability of soil nutrients does not increase competition when plants are genetically identical, consistent with the suggestion that effects of heterogeneity on competition depend upon differences in plasticity between individuals. Heterogeneity is only likely to increase the spread of monoclonal, invasive populations such as that of A. philoxeroides in China.

Quantitative computed tomography as a test of endurance for evaluation of bony plates; Utilizacao da tomografia computadorizada quantitativa como teste de resistencia para avaliacao de placas osseas

Energy Technology Data Exchange (ETDEWEB)

Melo Filho, E.V.; Costa, L.A.V.S.; Oliveira, D.C. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil); Freitas, P.M.C. [Escola de Veterinaria - Universidade Federal de Minas Gerais - Belo Horizonte, MG (Brazil); Teixeira, M.W.; Costa, F.S. [Universidade Federal Rural de Pernambuco - Recife, PE (Brazil)

2012-06-15

Quantitative computed tomography was used to determine the radiodensity of bony plates. The CT scans provided information regarding radiodensity of bony plates and allowed to verify the uniformity of bone mineral density in their scope. The proposed methodology should be considered as another tool for determining the resistance of these biomaterials. (author)

Comparison of prostate set-up accuracy and margins with off-line bony anatomy corrections and online implanted fiducial-based corrections.

Science.gov (United States)

Greer, P B; Dahl, K; Ebert, M A; Wratten, C; White, M; Denham, J W

2008-10-01

The aim of the study was to determine prostate set-up accuracy and set-up margins with off-line bony anatomy-based imaging protocols, compared with online implanted fiducial marker-based imaging with daily corrections. Eleven patients were treated with implanted prostate fiducial markers and online set-up corrections. Pretreatment orthogonal electronic portal images were acquired to determine couch shifts and verification images were acquired during treatment to measure residual set-up error. The prostate set-up errors that would result from skin marker set-up, off-line bony anatomy-based protocols and online fiducial marker-based corrections were determined. Set-up margins were calculated for each set-up technique using the percentage of encompassed isocentres and a margin recipe. The prostate systematic set-up errors in the medial-lateral, superior-inferior and anterior-posterior directions for skin marker set-up were 2.2, 3.6 and 4.5 mm (1 standard deviation). For our bony anatomy-based off-line protocol the prostate systematic set-up errors were 1.6, 2.5 and 4.4 mm. For the online fiducial based set-up the results were 0.5, 1.4 and 1.4 mm. A prostate systematic error of 10.2 mm was uncorrected by the off-line bone protocol in one patient. Set-up margins calculated to encompass 98% of prostate set-up shifts were 11-14 mm with bone off-line set-up and 4-7 mm with online fiducial markers. Margins from the van Herk margin recipe were generally 1-2 mm smaller. Bony anatomy-based set-up protocols improve the group prostate set-up error compared with skin marks; however, large prostate systematic errors can remain undetected or systematic errors increased for individual patients. The margin required for set-up errors was found to be 10-15 mm unless implanted fiducial markers are available for treatment guidance.

Bony orbital distances among the Filipino population.

Science.gov (United States)

Barone, Constance M; Jimenez, David F; Laskey, Antoinette; Alcantara, Briccio G; Braddock, Stephen R

2002-03-01

Six hundred and seventy seven radiographs were selected from the logs of films taken in a major hospital in Metro Manila, Philippines over the course of the previous year. Two hundred and eighty-eight female and 389 male, healthy Filipinos between the ages of birth and twenty years were selected based on the availability of a modified Waters' projection and lateral skull film taken at the same time. Measurements for the lateral orbital wall were made at the site of the suture on the medial surface of the zygomatic bone. The medial orbital wall measurement was the distance between the dacrya using a correction factor formula of CF = D-d/D where D is the target film distance and d is the object film distance (1). The actual bony measurements were calculated. The data was gathered and plotted according to sex and in age in years. Graphs were generated using SAS over a graph software. Lines were smooth using cubic spline technique developed by Reinsch with the smoothest value of 75 (2). The mean plus two, four, and six standard deviations were included in each of the curves.

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

Science.gov (United States)

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. © The Author 2015. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The significance of a hypoplastic bony canal for the cochlear nerve in patients with sensorineural hearing loss: CT and MRI findings

International Nuclear Information System (INIS)

Choi, Yoon Jung; Park, Sang Yoo; Kim, Myung Soon; Sung, Ki Jun

2004-01-01

The purpose of this study is to evaluate the significance of the hypoplastic canal for the cochlear nerve in patients with sensorineural hearing loss (SNHL) and the relationship between the hypoplastic bony canal and aplasia or hypoplasia of the cochlear nerve. A retrospective review of high resolution temporal CT(HRCT) and MRI findings was conducted. The narrow bony canal of the cochlear nerve and the relative size of the internal auditory canal were correlated with the cochlear nerve deficiency on MRI. The comparative size of the component nerves (facial, cochlear, superior vestibular, inferior vestibular nerve), and the relative size of the internal auditory canal and the bony canal of the cochlear nerve were measured. The clinical history and the results of the clinical examination were reviewed for each patient. High resolution MRI showed aplasia of the common vestibulocochlear nerve in one patient and a deficiency of the cochlear nerve in 9 patients. These abnormalities occurred in association with a prominent narrowing of the canal for the cochlear nerve and a stenosis of the internal auditory canal, which was observed on temporal bone CT in 9 patients with congenital SNHL. Three patients had normal IAC, despite the presence of a hypoplastic cochlear nerve on the side on which they had SNHL. In one patient, the narrowing of the canal for the cochlear nerve and internal auditory canal were not found to be associated with acquired SNHL. The hypoplastic bony canal for the cochlear nerve might be more highly indicative of congenital cochlear nerve deficiency than that of the narrow internal auditory canal, and the position of the crista falciformis should also be carefully

The significance of a hypoplastic bony canal for the cochlear nerve in patients with sensorineural hearing loss: CT and MRI findings

Energy Technology Data Exchange (ETDEWEB)

Choi, Yoon Jung; Park, Sang Yoo; Kim, Myung Soon; Sung, Ki Jun [College of Medicine, Yonsei Univ., Wonju (Korea, Republic of)

2004-04-01

The purpose of this study is to evaluate the significance of the hypoplastic canal for the cochlear nerve in patients with sensorineural hearing loss (SNHL) and the relationship between the hypoplastic bony canal and aplasia or hypoplasia of the cochlear nerve. A retrospective review of high resolution temporal CT(HRCT) and MRI findings was conducted. The narrow bony canal of the cochlear nerve and the relative size of the internal auditory canal were correlated with the cochlear nerve deficiency on MRI. The comparative size of the component nerves (facial, cochlear, superior vestibular, inferior vestibular nerve), and the relative size of the internal auditory canal and the bony canal of the cochlear nerve were measured. The clinical history and the results of the clinical examination were reviewed for each patient. High resolution MRI showed aplasia of the common vestibulocochlear nerve in one patient and a deficiency of the cochlear nerve in 9 patients. These abnormalities occurred in association with a prominent narrowing of the canal for the cochlear nerve and a stenosis of the internal auditory canal, which was observed on temporal bone CT in 9 patients with congenital SNHL. Three patients had normal IAC, despite the presence of a hypoplastic cochlear nerve on the side on which they had SNHL. In one patient, the narrowing of the canal for the cochlear nerve and internal auditory canal were not found to be associated with acquired SNHL. The hypoplastic bony canal for the cochlear nerve might be more highly indicative of congenital cochlear nerve deficiency than that of the narrow internal auditory canal, and the position of the crista falciformis should also be carefully.

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

Science.gov (United States)

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.

Allergy to fish collagen: Thermostability of collagen and IgE reactivity of patients' sera with extracts of 11 species of bony and cartilaginous fish.

Science.gov (United States)

Kobayashi, Yukihiro; Kuriyama, Takuma; Nakagawara, Ryoko; Aihara, Michiko; Hamada-Sato, Naoko

2016-10-01

Parvalbumin was identified as a major fish allergen, and has been well investigated. Collagen was identified as a second allergen; however, its allergenic properties remain uncharacterized. Although fish is an important staple in coastal countries, its thermostability is unknown. Therefore, we aimed to determine the thermostability of fish collagen as an allergen. Meat of seven bony and four cartilaginous fishes was heated at various temperatures and times, and extracts were analyzed using SDS-PAGE, IgE-ELISA, and SPTs. Collagen was dissolved from heated meat of Pacific mackerel into a crude extract. Collagen in the extracts was degraded at a high heating load-140 °C (10 min) or 100 °C (320 min). However, ELISA revealed the IgE reactivities of patients' sera with the extracts were unchanged even after heating the samples. Patients strongly reacted to extract proteins of other bony fish, which were detected by patients' IgE even after heating at 100 °C (320 min). In contrast, reactivities of the extracts of cartilaginous fish were lower than those of bony fish. SPTs in one patient revealed that all bony and cartilaginous fish extracts prepared from heated meat elicited allergic reactions. The IgE reactivity of patients' sera to fish collagen in extracts was retained even when fish meat was treated by a high heating load. As for the fish collagen, the IgE reactivities to cartilaginous fish were lower than that to bony fish. Reducing IgE reactivity to fish meat using heat is difficult, and other modalities will be required to produce hypoallergenic fish meat. Copyright © 2016 Japanese Society of Allergology. Production and hosting by Elsevier B.V. All rights reserved.

Array-Enhanced Coherence Resonance: Nontrivial Effects of Heterogeneity and Spatial Independence of Noise

International Nuclear Information System (INIS)

Zhou, Changsong; Kurths, Juergen; Hu, Bambi

2001-01-01

We demonstrate the effect of coherence resonance in a heterogeneous array of coupled Fitz Hugh--Nagumo neurons. It is shown that coupling of such elements leads to a significantly stronger coherence compared to that of a single element. We report nontrivial effects of parameter heterogeneity and spatial independence of noise on array-enhanced coherence resonance; especially, we find that (i) the coherence increases as spatial correlation of the noise decreases, and (ii) inhomogeneity in the parameters of the array enhances the coherence. Our results have the implication that generic heterogeneity and background noise can play a constructive role to enhance the time precision of firing in neural systems

[Prevalence and clinical characteristics of oral bony outgrowth in a Moroccan population].

Science.gov (United States)

Oualalou, Y; Azaroual, M F; Zaoui, F; Chbicheb, S; Berrada, S

2014-11-01

Oral bony outgrowths (OBOs) are localized bony protuberances that arise from the cortical plate. Various types of OBOs have been described, the precise designation of which depends on anatomic location such as torus palatinus, torus mandibularis, buccal exostosis, or palatal exostosis. We had for aim to determine the prevalence and clinical characteristics of OBOs in a Moroccan population. This cross-sectional study was conducted between March 15 and June 30, 2011 at the Rabat-Salé teaching hospital dental consultation and treatment center, in Morocco. Three hundred and fifty-three patients (160 female and 193 male patients), 11 to 82 years of age, were examined clinically and radiologically to determine the presence of OBO. Twenty-four patients (6.8%) presented with OBOs. The prevalence for exostosis, torus mandibularis, torus palatinus, and associated OBOs was 3.1%, 2%, 0.8%, and 0.9% respectively. There was a significant difference (P=0,01) between the average age for patients presenting with OBO (43.2±12 years of age) and the average age for patients without any OBO (36.5±16 years of age). The prevalence of OBOs in female patients (7.3%) was higher than in male patients (6.3%) but the difference was not significant (P=0.439). Patients with occlusal parafunctional activity presented with significantly more OBO (P=0.016). The reported prevalence of OBO is extremely variable, according to age, gender, and ethnic group. The occurrence of OBO could be triggered by genetic factors associated with environmental factors. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

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

International Nuclear Information System (INIS)

Samavati, Navid; McGrath, Deirdre M; Ménard, Cynthia; Jewett, Michael A S; Van der Kwast, Theo; 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 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

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

Energy Technology Data Exchange (ETDEWEB)

Wang, Li [Pennsylvania State Univ., State College, PA (United States); Li, Li [Pennsylvania State Univ., State College, PA (United States)

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

Value of diffusion weighted MRI in differentiating benign from malignant bony tumors and tumor like lesions

Directory of Open Access Journals (Sweden)

Samir Zaki Kotb

2014-06-01

Conclusion: DWI has been proven to be highly useful in the differentiation of benign, malignant bone tumors and tumor like bony lesions. Measurement of ADC values improves the accuracy of the diagnosis of bone tumors and tumor like lesions. Moreover, measurement of ADC values can be used in the follow up of tumors and their response to therapy.

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

Science.gov (United States)

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

The effect of soil heterogeneity on ATES performance

Science.gov (United States)

Sommer, W.; Rijnaarts, H.; Grotenhuis, T.; van Gaans, P.

2012-04-01

Due to an increasing demand for sustainable energy, application of Aquifer Thermal Energy Storage (ATES) is growing rapidly. Large-scale application of ATES is limited by the space that is available in the subsurface. Especially in urban areas, suboptimal performance is expected due to thermal interference between individual wells of a single system, or interference with other ATES systems or groundwater abstractions. To avoid thermal interference there are guidelines on well spacing. However, these guidelines, and also design calculations, are based on the assumption of a homogeneous subsurface, while studies report a standard deviation in logpermeability of 1 to 2 for unconsolidated aquifers (Gelhar, 1993). Such heterogeneity may create preferential pathways, reducing ATES performance due to increased advective heat loss or interference between ATES wells. The role of hydraulic heterogeneity of the subsurface related to ATES performance has received little attention in literature. Previous research shows that even small amounts of heterogeneity can result in considerable uncertainty in the distribution of thermal energy in the subsurface and an increased radius of influence (Ferguson, 2007). This is supported by subsurface temperature measurements around ATES wells, which suggest heterogeneity gives rise to preferential pathways and short-circuiting between ATES wells (Bridger and Allen, 2010). Using 3-dimensional stochastic heat transport modeling, we quantified the influence of heterogeneity on the performance of a doublet well energy storage system. The following key parameters are varied to study their influence on thermal recovery and thermal balance: 1) regional flow velocity, 2) distance between wells and 3) characteristics of the heterogeneity. Results show that heterogeneity at the scale of a doublet ATES system introduces an uncertainty up to 18% in expected thermal recovery. The uncertainty increases with decreasing distance between ATES wells. The

On the validity of effective formulations for transport through heterogeneous porous media

Science.gov (United States)

de Dreuzy, Jean-Raynald; Carrera, Jesus

2016-04-01

Geological heterogeneity enhances spreading of solutes and causes transport to be anomalous (i.e., non-Fickian), with much less mixing than suggested by dispersion. This implies that modeling transport requires adopting either stochastic approaches that model heterogeneity explicitly or effective transport formulations that acknowledge the effects of heterogeneity. A number of such formulations have been developed and tested as upscaled representations of enhanced spreading. However, their ability to represent mixing has not been formally tested, which is required for proper reproduction of chemical reactions and which motivates our work. We propose that, for an effective transport formulation to be considered a valid representation of transport through heterogeneous porous media (HPM), it should honor mean advection, mixing and spreading. It should also be flexible enough to be applicable to real problems. We test the capacity of the multi-rate mass transfer (MRMT) model to reproduce mixing observed in HPM, as represented by the classical multi-Gaussian log-permeability field with a Gaussian correlation pattern. Non-dispersive mixing comes from heterogeneity structures in the concentration fields that are not captured by macrodispersion. These fine structures limit mixing initially, but eventually enhance it. Numerical results show that, relative to HPM, MRMT models display a much stronger memory of initial conditions on mixing than on dispersion because of the sensitivity of the mixing state to the actual values of concentration. Because MRMT does not restitute the local concentration structures, it induces smaller non-dispersive mixing than HPM. However long-lived trapping in the immobile zones may sustain the deviation from dispersive mixing over much longer times. While spreading can be well captured by MRMT models, in general non-dispersive mixing cannot.

Effect of catalysts on heterogeneous oxidation of coal

Energy Technology Data Exchange (ETDEWEB)

Glazkova, A P; Kazarova, Yu A; Suslov, A V

1978-01-01

Analyzes the effects of catalysts on the heterogeneous oxidation of coal in deflagration processes of stoichiometric mixtures. The following substances are studied as catalysts: alkali and alkaline-earth metals, and compounds of copper, lead, chromium, iron, and sulfur. In the first case the catalysts are used in the form of nitrates and the nitrate simultaneously plays the role of an oxidizer. In the second case the catalysts are added to stoichiometric mixtures of ammonium nitrate with carbon. It is shown that during carbon oxidation by nitrates the catalytic efficiency of the metals studied forms the following order: sodium > lead > potassium > barium > aluminium > calcium > magnesium > copper. The calculated and experimental parameters of combustion are given. The problem of dependence of combustion rate on combustion heat, the mechanism of the combustion reaction and the catalytic effects of the additives are discussed. Features of heterogeneous catalysis in the oxidation process of carbon by various oxidizers are analyzed. The investigations on the combustion process are important as the process takes place during explosion of coal dust in underground coal mines and during burning of coal in industrial furnaces. (34 refs.) (In Russian)

Comparison of prostate set-up accuracy and margins with off-line bony anatomy corrections and online implanted fiducial-based corrections

International Nuclear Information System (INIS)

Greer, P. B.; Dahl, K.; Ebert, M. A.; Wratten, C.; White, M.; Denham, K. W.

2008-01-01

Full text: The aim of the study was to determine prostate set-up accuracy and set-up margins with off-line bony anatomy-based imaging protocols, compared with online implanted fiducial marker-based imaging with daily corrections. Eleven patients were treated with implanted prostate fiducial markers and online set-up corrections. Pretreatment orthogonal electronic portal images were acquired to determine couch shifts and verification images were acquired during treatment to measure residual set-up error. The prostate set-up errors that would result from skin marker set-up, off-line bony anatomy-based protocols and online fiducial marker-based corrections were determined. Set-up margins were calculated for each set-up technique using the percentage of encompassed isocentres land a margin recipe. The prostate systematic set-up errors in the medial-lateral, superior-inferior and anterior-I posterior directions for skin marker set-up were 2.2, 3.6 and 4.5 mm (1 standard deviation). For our bony anatomy-I based off-line protocol the prostate systematic set-up errors were 1.6, 2.5 and 4.4 mm. For the online fiducial based set-up the results were 0.5, 1.4 and 1.4 mm. A prostate systematic error of 10.2 mm was uncorrected by the off-line bone protocol in one patient. Set-up margins calculated to encompass 98% of prostate set-up shifts were 111-14 mm with bone off-line set-up and 4-7 mm with online fiducial markers. Margins from the van Herk margin I recipe were generally 1-2 mm smaller. Bony anatomy-based set-up protocols improve the group prostate set-up error compared with skin marks; however, large prostate systematic errors can remain undetected or systematic (errors increased for individual patients. The margin required for set-up errors was found to be 10-15 mm unless I implanted fiducial markers are available for treatment guidance.

Bird diversity and environmental heterogeneity in North America: A test of the area-heterogeneity trade-off

Science.gov (United States)

Rachel Chocron; Curtis H. Flather; Ronen Kadmon

2015-01-01

Aim: Deterministic niche theory predicts that increasing environmental heterogeneity increases species richness. In contrast, a recent stochastic model suggests that heterogeneity has a unimodal effect on species richness since high levels of heterogeneity reduce the effective area available per species, thereby increasing the likelihood of stochastic...

Functional Heterogeneity and Senior Management Team Effectiveness

Science.gov (United States)

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…

Selected ophthalmic diagnostic tests, bony orbit anatomy, and ocular histology in sambar deer (Rusa unicolor).

Science.gov (United States)

Oriá, Arianne P; Gomes Junior, Deusdete C; Oliveira, Alberto Vinícius D; Curvelo, Victor P; Estrela-Lima, Alessandra; Pinna, Melissa H; Meneses, Íris D S; Filho, Emanoel F M; Ofri, Ron

2015-01-01

The purpose of this study was to establish reference values for diagnostic ophthalmic tests in sambar deer (Rusa unicolor) as well as to describe the most relevant features of the bony orbital anatomy and ocular histology. Twenty healthy animals, free living in a forest reserve, that were captured for clinical evaluation as part of a health survey were evaluated. Schirmer tear test-1 (STT1), conjunctival microbiota, intraocular pressure (IOP), conjunctival cytology, anatomy of the bony orbit, and ocular histology were studied. Mean ± SD STT1 and IOP values were 18.8 ± 4.7 mm and 11.4 ± 2.8 mmHg, respectively. IOP was significantly higher in adult (4-8 years) animals (P = 0.04). Bacterial growth was present in 100% of the samples, with a prevalence for Staphylococcus sp. and Bacillus sp. The conjunctival cytology revealed predominance of columnar epithelial cells with mild pigmentation. The sambar deer orbit is completely encompassed by bone. The ocular histology was very similar to most mammalians. The findings in this study will be useful in the diagnosis of ocular diseases in Rusa unicolor. © 2014 American College of Veterinary Ophthalmologists.

Daily online bony correction is required for prostate patients without fiducial markers or soft-tissue imaging.

Science.gov (United States)

Johnston, M L; Vial, P; Wiltshire, K L; Bell, L J; Blome, S; Kerestes, Z; Morgan, G W; O'Driscoll, D; Shakespeare, T P; Eade, T N

2011-09-01

To compare online position verification strategies with offline correction protocols for patients undergoing definitive prostate radiotherapy. We analysed 50 patients with implanted fiducial markers undergoing curative prostate radiation treatment, all of whom underwent daily kilovoltage imaging using an on-board imager. For each treatment, patients were set-up initially with skin tattoos and in-room lasers. Orthogonal on-board imager images were acquired and the couch shift to match both bony anatomy and the fiducial markers recorded. The set-up error using skin tattoos and offline bone correction was compared with online bone correction. The fiducial markers were used as the reference. Data from 1923 fractions were analysed. The systematic error was ≤1 mm for all protocols. The average random error was 2-3mm for online bony correction and 3-5mm for skin tattoos or offline-bone. Online-bone showed a significant improvement compared with offline-bone in the number of patients with >5mm set-up errors for >10% (P20% (Pmarkers or daily soft-tissue imaging. Copyright © 2011 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Reconstruction of bony facial contour deficiencies with polymethylmethacrylate implants: case report

Directory of Open Access Journals (Sweden)

Ruy C. C. Abdo Filho

2011-08-01

Full Text Available Facial trauma can be considered one of the most serious aggressions found in the medical centers due to the emotional consequences and the possibility of deformity. In craniofacial surgery, the use of autologous bone is still the first choice for reconstructing bony defects or irregularities. When there is a shortage of donor bone or a patient refuses an intracranial operation, alloplastic materials such as polymethylmethacrylate (PMMA can be used. The PMMA prosthesis can be pre-fabricated, bringing advantages such as reduction of surgical time, easy technical handling and good esthetic results. This paper describes the procedures for rehabilitating a patient with PMMA implants in the region of the face, recovering the facial contours and esthetics of the patient.

Scattering theory and effective medium approximations to heterogeneous materials

International Nuclear Information System (INIS)

Gubernatis, J.E.

1977-01-01

The formal analogy existing between problems studied in the microscopic theory of disordered alloys and problems concerned with the effective (macroscopic) behavior of heterogeneous materials is discussed. Attention is focused on (1) analogous approximations (effective medium approximations) developed for the microscopic problems by scattering theory concepts and techniques, but for the macroscopic problems principally by intuitive means, (2) the link, provided by scattering theory, of the intuitively developed approximations to a well-defined perturbative analysis, (3) the possible presence of conditionally convergent integrals in effective medium approximations

Morphometric Measurements of Bony Nasolacrimal Canal in Children.

Science.gov (United States)

Ela, Araz Server; Cigdem, Kalaycik Ertugay; Karagoz, Yesim; Yigit, Ozgur; Longur, Ecem Sevim

2018-05-01

Morphology and dimensions of the bony nasolacrimal canal duct (BNLD) as a key factor in the development of primary acquired nasolacrimal duct obstruction. We aimed to obtain detailed morphometric analysis of BNLD in children without nasolacrimal duct pathology by using computed tomography and provide standard measurements by means of age which could be utilized in planning management or in invasive interventions. Picture Archiving Communication Systems database of our hospital's radiology department was searched for this retrospective study. Subjects were under 18 years of age who had undergone a paranasal, maxillofacial, or temporal bone high-resolution computed tomography scan in last 2 years with various indications. Those with fractures including facial bones and/or nasolacrimal canal or history of nasolacrimal duct pathology were excluded from the study. We measured the diameter, angle, and surface area of BNLD. A total number of 136 subjects (86 boys, 50 girls) were included in the study. The average age was 7.3 ± 5.1 years. We documented statistically significantly positive correlation between all measured diameters and ages (P  0.050). Our study demonstrated that development of BNLD continues during childhood, regardless of gender.

Immediate Single-Tooth Implant Placement in Bony Defects in the Esthetic Zone : A 1-Year Randomized Controlled Trial

NARCIS (Netherlands)

Slagter, Kirsten W.; Meijer, Henny J. A.; Bakker, Nicolaas A.; Vissink, Arjan; Raghoebar, Gerry M.

Background: This study aims to assess, with regard to marginal bone level (MBL), whether the outcome of immediate implant placement in bony defects in the esthetic zone was non-inferior to delayed implant placement after 1 year. Methods: Forty patients with a failing tooth in the esthetic zone and a

Calcification mechanism and bony bonding studies of calcium carbonate and composite aluminosilicate/calcium phosphate applied as biomaterials by using radioactivation methods

International Nuclear Information System (INIS)

Oudadesse, H.; Derrien, A.C.; Lucas-Girot, A.; Martin, S.; Cathelieau, G.

2007-01-01

Bony grafts are used as a filling biomaterial for defective bone. The introduction of new range of synthetic materials offers to surgeons additional possibilities to avoid virus transmission risks by using natural grafts in bony surgery. In this work, two materials, synthetic calcium carbonate and composite aluminosilicate/calcium phosphate were synthesized by an original method and experimented 'in vivo' as biomaterials for bony filling. Extracted biopsies were studied by several physico chemical and biological methods. The aim was to evaluate the kinetic resorption and bioconsolidation of these materials. We focused on the bioconsolidation between implant and bone by realising cartographies from the implant to the bone and on the calcification mechanism by determination of the origin of Ca and Sr responsible of the neo-formed bone. Neutron activation analysis (NAA), radiotracers 45 Ca* and 85 Sr* and proton-induced X-ray emission (PIXE) were used. Concerning the synthetic calcium carbonate, results show that twelve months after implantation, the mineral composition of implant becomes similar to that of the mature bone. The neoformed bone is composed with Ca and Sr coming from the organism when the Ca and Sr of the implant were progressively eliminated. Concerning the composite geopolymer/calcium phosphate, PIXE and histological studies reveal the intimate links between the bone and the implant starting with the first month after implantation. (author)

Biomechanical Comparison of Arthroscopic Single- and Double-Row Repair Techniques for Acute Bony Bankart Lesions.

Science.gov (United States)

Spiegl, Ulrich J; Smith, Sean D; Todd, Jocelyn N; Coatney, Garrett A; Wijdicks, Coen A; Millett, Peter J

2014-08-01

Single- and double-row arthroscopic reconstruction techniques for acute bony Bankart lesions have been described in the literature. The double-row fixation technique would provide superior reduction and stability of a simulated bony Bankart lesion at time zero in a cadaveric model compared with the single-row technique. Controlled laboratory study. Testing was performed on 14 matched pairs of glenoids with simulated bony Bankart fractures with a defect width of 25% of the glenoid diameter. Half of the fractures were repaired with a double-row technique, while the contralateral glenoids were repaired with a single-row technique. The quality of fracture reduction was measured with a coordinate measuring machine. To determine the biomechanical stability of the repairs, specimens were preconditioned with 10 sinusoidal cycles between 5 and 25 N at 0.1 Hz and then pulled to failure in the anteromedial direction at a rate of 5 mm/min. Loads at 1 mm and 2 mm of fracture displacement were determined. The double-row technique required significantly higher forces to achieve fracture displacements of 1 mm (mean, 60.6 N; range, 39.0-93.3 N; P = .001) and 2 mm (mean, 94.4 N; range, 43.4-151.2 N; P = .004) than the single-row technique (1 mm: mean, 30.2 N; range, 14.0-54.1 N and 2 mm: mean, 63.7 N; range, 26.6-118.8 N). Significantly reduced fracture displacement was seen after double-row repair for both the unloaded condition (mean, 1.1 mm; range, 0.3-2.4 mm; P = .005) and in response to a 10-N anterior force applied to the defect (mean, 1.6 mm; range, 0.5-2.7 mm; P = .001) compared with single-row repair (unloaded: mean, 2.1 mm; range, 1.3-3.4 mm and loaded: mean, 3.4 mm; range, 1.9-4.7 mm). The double-row fixation technique resulted in improved fracture reduction and superior stability at time zero in this cadaveric model. This information may influence the surgical technique used to treat large osseous Bankart fractures and the postoperative rehabilitation protocols

Effects of Heterogeneous Social Interactions on Flocking Dynamics

Science.gov (United States)

Miguel, M. Carmen; Parley, Jack T.; Pastor-Satorras, Romualdo

2018-02-01

Social relationships characterize the interactions that occur within social species and may have an important impact on collective animal motion. Here, we consider a variation of the standard Vicsek model for collective motion in which interactions are mediated by an empirically motivated scale-free topology that represents a heterogeneous pattern of social contacts. We observe that the degree of order of the model is strongly affected by network heterogeneity: more heterogeneous networks show a more resilient ordered state, while less heterogeneity leads to a more fragile ordered state that can be destroyed by sufficient external noise. Our results challenge the previously accepted equivalence between the static Vicsek model and the equilibrium X Y model on the network of connections, and point towards a possible equivalence with models exhibiting a different symmetry.

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

NARCIS (Netherlands)

Cuxart, J.; Wrenger, B.; Martinez-Villagrasa, D.; Reuder, J.; Jonassen, M.O.; Jimenez, M.A.; Lothon, M.; Hartogensis, O.K.; Dunnermann, J.; Conangla, L.; Garai, A.

2016-01-01

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

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

Science.gov (United States)

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.

A Bony Landmark 'RAI Triangle' to Prevent 'Misplaced and Misdirected' Medial Cut in SSRO.

Science.gov (United States)

Rai, Kirthi Kumar; Arakeri, Gururaj; Khaji, Shahanavaj I

2011-03-01

'Rai triangle', a new anatomic landmark on the medial surface of the ramus of the mandible which when identified and taken into consideration, may have a definite advantage. This is especially in terms of performing the medial horizontal cut which is an important and integral part of the sagittal split ramus osteotomy so as to avoid a bad split. The objective of this article is to propose an easily identifiable bony land mark, which is closely related to lingula of mandible that may ease the procedure of osteotomy and avoid bad splits.

Importance of bony analysis for interpreting ear CT scans: part three; ORL - tomodensitometrie de l'oreille. Interet de l'analyse osseuse dans l'interpretation des scanners de l'oreille (troisieme partie)

Energy Technology Data Exchange (ETDEWEB)

Serhal, M.; Dordea, M.; Cymbalista, M. [Hopital de Montfermeil, Service de Radiologie, 93 - Montfermeil (France); Halimi, P. [Hopital Europeen Georges-Pompidou, Service de Radiologie, 75 - Paris (France); Iffenecker, C. [Clinique Radiologique, 62 - Boulogne sur Mer (France); Bensimon, J.L

2003-02-01

The accurate description of bony changes in ear CT scans has a great diagnostic and therapeutic impact. The third part shows the way to analyze bone remodeling when CT scan is performed for tumors in the vicinity of the temporal bone, for intra temporal lesions of the facial nerve and for external auditory canal malformations. It demonstrates how bony analysis should be included in postoperative report of ear CT scan. The importance of bony signs in tumors and pseudo tumors of the inner ear are outlined. (authors)

The Evolution of Bony Vertebrate Enhancers at Odds with Their Coding Sequence Landscape.

Science.gov (United States)

Yousaf, Aisha; Sohail Raza, Muhammad; Ali Abbasi, Amir

2015-08-06

Enhancers lie at the heart of transcriptional and developmental gene regulation. Therefore, changes in enhancer sequences usually disrupt the target gene expression and result in disease phenotypes. Despite the well-established role of enhancers in development and disease, evolutionary sequence studies are lacking. The current study attempts to unravel the puzzle of bony vertebrates' conserved noncoding elements (CNE) enhancer evolution. Bayesian phylogenetics of enhancer sequences spotlights promising interordinal relationships among placental mammals, proposing a closer relationship between humans and laurasiatherians while placing rodents at the basal position. Clock-based estimates of enhancer evolution provided a dynamic picture of interspecific rate changes across the bony vertebrate lineage. Moreover, coelacanth in the study augmented our appreciation of the vertebrate cis-regulatory evolution during water-land transition. Intriguingly, we observed a pronounced upsurge in enhancer evolution in land-dwelling vertebrates. These novel findings triggered us to further investigate the evolutionary trend of coding as well as CNE nonenhancer repertoires, to highlight the relative evolutionary dynamics of diverse genomic landscapes. Surprisingly, the evolutionary rates of enhancer sequences were clearly at odds with those of the coding and the CNE nonenhancer sequences during vertebrate adaptation to land, with land vertebrates exhibiting significantly reduced rates of coding sequence evolution in comparison to their fast evolving regulatory landscape. The observed variation in tetrapod cis-regulatory elements caused the fine-tuning of associated gene regulatory networks. Therefore, the increased evolutionary rate of tetrapods' enhancer sequences might be responsible for the variation in developmental regulatory circuits during the process of vertebrate adaptation to land. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for

Stability of faults with heterogeneous friction properties and effective normal stress

Science.gov (United States)

Luo, Yingdi; Ampuero, Jean-Paul

2018-05-01

Abundant geological, seismological and experimental evidence of the heterogeneous structure of natural faults motivates the theoretical and computational study of the mechanical behavior of heterogeneous frictional fault interfaces. Fault zones are composed of a mixture of materials with contrasting strength, which may affect the spatial variability of seismic coupling, the location of high-frequency radiation and the diversity of slip behavior observed in natural faults. To develop a quantitative understanding of the effect of strength heterogeneity on the mechanical behavior of faults, here we investigate a fault model with spatially variable frictional properties and pore pressure. Conceptually, this model may correspond to two rough surfaces in contact along discrete asperities, the space in between being filled by compressed gouge. The asperities have different permeability than the gouge matrix and may be hydraulically sealed, resulting in different pore pressure. We consider faults governed by rate-and-state friction, with mixtures of velocity-weakening and velocity-strengthening materials and contrasts of effective normal stress. We systematically study the diversity of slip behaviors generated by this model through multi-cycle simulations and linear stability analysis. The fault can be either stable without spontaneous slip transients, or unstable with spontaneous rupture. When the fault is unstable, slip can rupture either part or the entire fault. In some cases the fault alternates between these behaviors throughout multiple cycles. We determine how the fault behavior is controlled by the proportion of velocity-weakening and velocity-strengthening materials, their relative strength and other frictional properties. We also develop, through heuristic approximations, closed-form equations to predict the stability of slip on heterogeneous faults. Our study shows that a fault model with heterogeneous materials and pore pressure contrasts is a viable framework

Concerning the etiology of bony bridges along the sides of the terminal phalanx of the great toe

Energy Technology Data Exchange (ETDEWEB)

Fischer, E.

1987-06-01

Besides in acromegaly bony bridges at the terminal phalanx of the great toe occur in one third of cases with peripheral signs of diffuse idiopathic skeletal hyperostosis, systemic diseases as rheumatoid arthritis or psoriatic arthritis with chronic inflammation of the interphalangeal joint of the great toe respectively extraarticular osseous changes in the terminal phalanx of the great toe do not influence the development of such bridges.

On heterogeneity of treatment effects and clinical freedom.

Science.gov (United States)

Sacristán, J A; Avendaño-Solá, C

2015-01-01

Three decades ago, John R Hampton announced the death of clinical freedom. Since then, evidence-based medicine has been the predominant paradigm in clinical research. By applying a population-based approach, the randomised controlled trial has become the cornerstone for demonstrating the overall effect of a treatment and for developing guidelines. The new patient-centred medicine movement is rediscovering the important implications of heterogeneity of treatment effects for clinical practice and that a better understanding of such variability can contribute to improve health outcomes for individual patients through practicing a science-based clinical freedom. © 2015 The Authors. International Journal of Clinical Practice Published by John Wiley & Sons Ltd.

Interconnecting heterogeneous database management systems

Science.gov (United States)

Gligor, V. D.; Luckenbaugh, G. L.

1984-01-01

It is pointed out that there is still a great need for the development of improved communication between remote, heterogeneous database management systems (DBMS). Problems regarding the effective communication between distributed DBMSs are primarily related to significant differences between local data managers, local data models and representations, and local transaction managers. A system of interconnected DBMSs which exhibit such differences is called a network of distributed, heterogeneous DBMSs. In order to achieve effective interconnection of remote, heterogeneous DBMSs, the users must have uniform, integrated access to the different DBMs. The present investigation is mainly concerned with an analysis of the existing approaches to interconnecting heterogeneous DBMSs, taking into account four experimental DBMS projects.

Self-transparency effects in heterogeneous nonlinear scattering media and their possible use in lasers

International Nuclear Information System (INIS)

Al'tshuler, G.B.; Ermolaev, V.S.; Krylov, K.I.; Manenkov, A.A.; Prokhorov, A.M.

1986-01-01

Transmission of intense laser beams through heterogeneous scattering media is considered. Effects of intensity limitation, self-recovery of the wave front of a transmitted beam, and bistable reflection associated with the laser-induced self-transparency (suppression of scattering) of such media are predicted because of the compensation of the linear refractive-index difference Δn/sub L/ of the heterocomponents of a medium by nonlinear change Δn/sub N//sub L/ for different mechanisms of nonlinearity. Applications of these effects in lasers for Q switching and mode locking are discussed. The observation of self-transparency effects in several heterogeneous media (glass particles in toluene and nitrobenzene, and lead molybdenite powder) for cw Ar- and pulsed Nd- and CO 2 -laser radiation is reported. Q switching and mode locking have also been demonstrated with a YAG:Nd laser using nonlinear scattering in a heterogeneous cell as a control element in a laser resonator

Arthroscopic Suture Anchor Fixation of Bony Bankart Lesions: Clinical Outcome, Magnetic Resonance Imaging Results, and Return to Sports.

Science.gov (United States)

Plath, Johannes E; Feucht, Matthias J; Bangoj, Robert; Martetschläger, Frank; Wörtler, Klaus; Seppel, Gernot; Aboalata, Mohamed; Tischer, Thomas; Imhoff, Andreas B; Vogt, Stephan

2015-08-01

The purpose of this study was to evaluate the outcome, return to sporting activity, and postoperative articular cartilage and bony morphology of shoulders that underwent arthroscopic suture anchor repair of bony Bankart lesions. The inclusion criteria for this retrospective study were anterior glenoid rim fractures after traumatic shoulder instability that were treated with arthroscopic suture anchor repair. Patients were surveyed by a questionnaire including sport-specific outcome, Rowe score, Western Ontario Shoulder Instability Index, and Oxford Instability Score. Three-tesla magnetic resonance imaging could be performed in 30 patients to assess osseous integration, glenoid reconstruction, and signs of osteoarthritis. From November 1999 to April 2010, 81 patients underwent an anterior bony Bankart repair in our department (50 arthroscopic suture anchor repairs, 5 arthroscopic screw fixations, and 26 open repairs). The 55 arthroscopic repairs comprised a consecutive cohort of patients treated by a single surgeon. Of the 50 patients in the suture anchor group, 45 (90%) were available for evaluation. At 82 ± 31 months postoperatively, the mean Rowe score was 85.9 ± 20.5 points, the mean Western Ontario Shoulder Instability Index score was 89.4% ± 14.7%, and the mean Oxford Instability Score was 13.6 ± 5.4 points. Compared with the contralateral shoulder, all scores showed a significantly reduced outcome (P sporting activity after surgery. The number of sports disciplines (P < .001), duration (P = .005), level (P = .02), and risk category (P = .013) showed a significant reduction compared with the pretrauma condition. However, only 19% of patients reported that shoulder complaints were the reason for the reduction in activity. Nonunion occurred in 16.6%, with a higher frequency in patients with chronic lesions (P = .031). Anatomic reduction was achieved in 72%, the medial step-off in patients with nonanatomic reduction averaged 1.8 ± 0.9 mm, and the

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

Science.gov (United States)

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

Effects of fault heterogeneity on seismic energy and spectrum

Science.gov (United States)

Dragoni, Michele; Santini, Stefano

2017-12-01

We study the effects of friction heterogeneity on the dynamics of a seismogenic fault. To this aim, we consider a fault model containing two asperities with different static frictions and a rate-dependent dynamic friction. We consider the seismic events produced by the consecutive failure of the two asperities and study their properties as functions of the ratio between static frictions. In particular, we calculate the moment rate, the stress evolution during fault slip, the average stress drop, the partitioning of energy release, the seismic energy, the far-field waveforms and the spectrum of seismic waves. These quantities depend to various extent on the friction distribution on the fault. In particular, the stress distribution on the fault is always strongly heterogeneous at the beginning of the seismic event. Seismic energy and frictional heat decrease with increasing friction heterogeneity, while seismic efficiency is constant. We obtain an equation relating seismic efficiency to the parameters of the friction law, showing that the efficiency is maximum for smaller values of dynamic friction. The seismic spectrum depends on the friction distribution as to the positions and the values of the minima. However, under the model assumption that the slip durations are the same for both asperities, the corner frequency is independent of the friction distribution, but it depends on the friction law and on the coupling between asperities. The model provides a relation between the total radiated energy and the seismic moment that is consistent with the empirical relation between the two quantities. The fault model with one asperity is also considered as a particular case. The model is applied to the 1965 Rat Islands (Alaska) earthquake and shows the role of fault heterogeneity in controlling the spatial distribution of stress drop as well as the time dependence and the final amount of radiated energy.

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

Science.gov (United States)

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.

Effective Data Acquisition Protocol for Multi-Hop Heterogeneous Wireless Sensor Networks Using Compressive Sensing

Directory of Open Access Journals (Sweden)

Ahmed M. Khedr

2015-10-01

Full Text Available In designing wireless sensor networks (WSNs, it is important to reduce energy dissipation and prolong network lifetime. Clustering of nodes is one of the most effective approaches for conserving energy in WSNs. Cluster formation protocols generally consider the heterogeneity of sensor nodes in terms of energy difference of nodes but ignore the different transmission ranges of them. In this paper, we propose an effective data acquisition clustered protocol using compressive sensing (EDACP-CS for heterogeneous WSNs that aims to conserve the energy of sensor nodes in the presence of energy and transmission range heterogeneity. In EDACP-CS, cluster heads are selected based on the distance from the base station and sensor residual energy. Simulation results show that our protocol offers a much better performance than the existing protocols in terms of energy consumption, stability, network lifetime, and throughput.

Comparison of the bony remodelling of two synthetic biomaterials: aragonite 55% and aragonite 55% with active substance

International Nuclear Information System (INIS)

Oudadesse, H; Derrien, A C; Martin, S; Lucas-Girot, A; Cathelineau, G

2007-01-01

In this work, the in vivo behaviour of pure aragonite and vectabone, which is an association of aragonite and an active substance such as gentamicin, was studied to highlight the kinetic resorption of these two biomaterials with 55% of porosity destined for the filling or replacement of bony defects. The synthesis conditions and parameters we used permit us to obtain a biomaterial without a sintering stage. These conditions allow introducing of active substances at the first stage of the elaboration. In this work, the gentamycin antibiotic was associated with calcium carbonate (aragonite 55% with gentamycin) to deliver this active substance on the surgical site for local treatment. The tricalcium phosphate biomaterial was used as the control because of its high biocompatibility. The bony remodelling of these three biomaterials was studied by in vivo experiments. This study was ensured with neutron activation analysis (NAA). The resorption kinetic was elaborated and comparisons of the remodelling biomaterials CaCO 3 55% and CaCO 3 55% with gentamicin (vectabone) and tricalcium phosphate were carried out. The obtained results show that, 6 months after implantation, the mineral composition of vectabone and tricalcium phosphate becomes close to that of young bone. Twelve months after implantation, it becomes similar to that of mature bone

Analytic Investigation Into Effect of Population Heterogeneity on Parameter Ratio Estimates

International Nuclear Information System (INIS)

Schinkel, Colleen; Carlone, Marco; Warkentin, Brad; Fallone, B. Gino

2007-01-01

Purpose: A homogeneous tumor control probability (TCP) model has previously been used to estimate the α/β ratio for prostate cancer from clinical dose-response data. For the ratio to be meaningful, it must be assumed that parameter ratios are not sensitive to the type of tumor control model used. We investigated the validity of this assumption by deriving analytic relationships between the α/β estimates from a homogeneous TCP model, ignoring interpatient heterogeneity, and those of the corresponding heterogeneous (population-averaged) model that incorporated heterogeneity. Methods and Materials: The homogeneous and heterogeneous TCP models can both be written in terms of the geometric parameters D 50 and γ 50 . We show that the functional forms of these models are similar. This similarity was used to develop an expression relating the homogeneous and heterogeneous estimates for the α/β ratio. The expression was verified numerically by generating pseudo-data from a TCP curve with known parameters and then using the homogeneous and heterogeneous TCP models to estimate the α/β ratio for the pseudo-data. Results: When the dominant form of interpatient heterogeneity is that of radiosensitivity, the homogeneous and heterogeneous α/β estimates differ. This indicates that the presence of this heterogeneity affects the value of the α/β ratio derived from analysis of TCP curves. Conclusions: The α/β ratio estimated from clinical dose-response data is model dependent-a heterogeneous TCP model that accounts for heterogeneity in radiosensitivity will produce a greater α/β estimate than that resulting from a homogeneous TCP model

Bony landmark between the attachment of the medial meniscus posterior root and the posterior cruciate ligament: CT and MR imaging assessment

Energy Technology Data Exchange (ETDEWEB)

Fujii, Masataka; Furumatsu, Takayuki; Miyazawa, Shinichi; Kodama, Yuya; Hino, Tomohito; Kamatsuki, Yusuke; Ozaki, Toshifumi [Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Department of Orthopaedic Surgery, Science of Functional Recovery and Reconstruction, Okayama (Japan)

2017-08-15

(1) To reveal the prevalence of the bony recess (posterior dimple) and (2) to determine the position of the posterior dimple on the tibial plateau using three-dimensional computed tomography (3DCT). In this study, a retrospective review of 112 patients was performed to identify the posterior dimple and to evaluate its position on 3DCT. Magnetic resonance images (MRIs) were also used to determine the positional relationship among the posterior cruciate ligament (PCL), medial meniscus posterior insertion (MMPI), and posterior dimple. The posterior dimple was observed in 100 of 112 knees (89.3%) on 3DCT. The center of the posterior dimple was 13.6 ± 0.8 mm from the medial tibial eminence apex. MRI showed that the posterior dimple separated the tibial attachment of the PCL and MMPI. This is the first study to discuss the prevalence and position of the bony recess in the posterior intercondylar fossa. (orig.)

X-ray and neutron tomography on the bony inner ear of baleen whales; Roentgen- und Neutronentomographie am knoechernen Innenohr der Bartenwale

Energy Technology Data Exchange (ETDEWEB)

Arlt, Tobias [Technische Univ. Berlin (Germany); Wieder, Frank [Bundesanstalt fuer Materialforschung und -pruefung BAM, Berlin (Germany). Fachgruppe 8.3 ' ' Radiologische Verfahren' ' ; Hilger, Andre; Kardjilov, Nikolay [Helmholtz-Zentrum Berlin HZB, Berlin (Germany); Hampe, Oliver [Museum fuer Naturkunde, Berlin (Germany); Manke, Ingo [Helmholtz-Zentrum Berlin (HZB) fuer Materialien und Energie, Berlin (Germany). Fachgruppe ' ' Bildgebende Verfahren' ' ; Ritsche, Indira; Fahlke, Julia M.

2018-04-01

During their evolution whales and dolphins developed a highly specialized hearing organ for orientation in their deep sea territory covering a broad acoustic spectrum. The internal anatomy of the periotic bone, especially the morphology of the cochlea, has a significant influence on the hearing capability of mammals. The bony and fossilized cochleae of several fossil representatives of extinct baleen whales (e.g., Cetotheriidae) and modern rorquals (Balaenopteridae) and right whales, as well as cochleae of an archaeocete and some land mammals are investigated by X-ray and neutron tomography in order to record morphological changes that may be responsible for the development of low frequency hearing. Differences in the cochlear morphology have been determined by means of morphometric parameters, such as the number of turns, the length of the cochlea, and the curvature of the cochlear canal. In particular, X-ray tomography enables a high resolution display of the bony inner ear.

Bony landmark between the attachment of the medial meniscus posterior root and the posterior cruciate ligament: CT and MR imaging assessment

International Nuclear Information System (INIS)

Fujii, Masataka; Furumatsu, Takayuki; Miyazawa, Shinichi; Kodama, Yuya; Hino, Tomohito; Kamatsuki, Yusuke; Ozaki, Toshifumi

2017-01-01

(1) To reveal the prevalence of the bony recess (posterior dimple) and (2) to determine the position of the posterior dimple on the tibial plateau using three-dimensional computed tomography (3DCT). In this study, a retrospective review of 112 patients was performed to identify the posterior dimple and to evaluate its position on 3DCT. Magnetic resonance images (MRIs) were also used to determine the positional relationship among the posterior cruciate ligament (PCL), medial meniscus posterior insertion (MMPI), and posterior dimple. The posterior dimple was observed in 100 of 112 knees (89.3%) on 3DCT. The center of the posterior dimple was 13.6 ± 0.8 mm from the medial tibial eminence apex. MRI showed that the posterior dimple separated the tibial attachment of the PCL and MMPI. This is the first study to discuss the prevalence and position of the bony recess in the posterior intercondylar fossa. (orig.)

Bayesian random-effect model for predicting outcome fraught with heterogeneity--an illustration with episodes of 44 patients with intractable epilepsy.

Science.gov (United States)

Yen, A M-F; Liou, H-H; Lin, H-L; Chen, T H-H

2006-01-01

The study aimed to develop a predictive model to deal with data fraught with heterogeneity that cannot be explained by sampling variation or measured covariates. The random-effect Poisson regression model was first proposed to deal with over-dispersion for data fraught with heterogeneity after making allowance for measured covariates. Bayesian acyclic graphic model in conjunction with Markov Chain Monte Carlo (MCMC) technique was then applied to estimate the parameters of both relevant covariates and random effect. Predictive distribution was then generated to compare the predicted with the observed for the Bayesian model with and without random effect. Data from repeated measurement of episodes among 44 patients with intractable epilepsy were used as an illustration. The application of Poisson regression without taking heterogeneity into account to epilepsy data yielded a large value of heterogeneity (heterogeneity factor = 17.90, deviance = 1485, degree of freedom (df) = 83). After taking the random effect into account, the value of heterogeneity factor was greatly reduced (heterogeneity factor = 0.52, deviance = 42.5, df = 81). The Pearson chi2 for the comparison between the expected seizure frequencies and the observed ones at two and three months of the model with and without random effect were 34.27 (p = 1.00) and 1799.90 (p dispersion attributed either to correlated property or to subject-to-subject variability.

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

Energy Technology Data Exchange (ETDEWEB)

Bagewadi, Shivanand B.; Awasthi, Ujjwala Rastogi; Mody, Bharat M.; Suma, Gundareddy N.; Garg, Shruti [Dept. of Medicine and Radiology, ITS Center for Dental Studies and Research, Ghaziabad, Uttar Pradesh (Korea, Republic of)

2015-09-15

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

Assessment of the effect of three-dimensional mantle density heterogeneity on Earth rotation in tidal frequencies

Directory of Open Access Journals (Sweden)

Lanbo Liu

2016-11-01

Full Text Available In this paper, we report the assessment of the effect of the three-dimensional (3D density heterogeneity in the mantle on Earth orientation parameters (EOP (i.e., the polar motion, or PM, and the length of day, or LOD in the tidal frequencies. The 3D mantle density model is estimated based upon a global S-wave velocity tomography model (S16U6L8 and the mineralogical knowledge derived from laboratory experiment. The lateral density variation is referenced against the preliminary reference earth model (PREM. Using this approach the effects of the heterogeneous mantle density variation in all three tidal frequencies (zonal long periods, tesseral diurnal, and sectorial semidiurnal are estimated in both PM and LOD. When compared with mass or density perturbations originated on the Earth's surface such as the oceanic and barometric changes, the heterogeneous mantle contributes less than 10% of the total variation in PM and LOD in tidal frequencies. However, this is the gap that has not been explained to close the gap of the observation and modeling in PM and LOD. By computing the PM and LOD caused by 3D heterogeneity of the mantle during the period of continuous space geodetic measurement campaigns (e.g., CONT94 and the contribution from ocean tides as predicted by tide models derived from satellite altimetry observations (e.g., TOPEX/Poseidon in the same period, we got the lump-sum values of PM and LOD. The computed total effects and the observed PM and LOD are generally agree with each other. In another word, the difference of the observed PM and LOD and the model only considering ocean tides, at all tidal frequencies (long periods, diurnals, and semidiurnals contains the contributions of the lateral density heterogeneity of the mantle. Study of the effect of mantle density heterogeneity effect on torque-free Earth rotation may provide useful constraints to construct the reference earth model (REM, which is the next major objective in global

Modeling of the bony pelvis from MRI using a multi-atlas AE-SDM for registration and tracking in image-guided robotic prostatectomy.

Science.gov (United States)

Gao, Qinquan; Chang, Ping-Lin; Rueckert, Daniel; Ali, S Mohammed; Cohen, Daniel; Pratt, Philip; Mayer, Erik; Yang, Guang-Zhong; Darzi, Ara; Edwards, Philip Eddie

2013-03-01

A fundamental challenge in the development of image-guided surgical systems is alignment of the preoperative model to the operative view of the patient. This is achieved by finding corresponding structures in the preoperative scans and on the live surgical scene. In robot-assisted laparoscopic prostatectomy (RALP), the most readily visible structure is the bone of the pelvic rim. Magnetic resonance imaging (MRI) is the modality of choice for prostate cancer detection and staging, but extraction of bone from MRI is difficult and very time consuming to achieve manually. We present a robust and fully automated multi-atlas pipeline for bony pelvis segmentation from MRI, using a MRI appearance embedding statistical deformation model (AE-SDM). The statistical deformation model is built using the node positions of deformations obtained from hierarchical registrations of full pelvis CT images. For datasets with corresponding CT and MRI images, we can transform the MRI into CT SDM space. MRI appearance can then be used to improve the combined MRI/CT atlas to MRI registration using SDM constraints. We can use this model to segment the bony pelvis in a new MRI image where there is no CT available. A multi-atlas segmentation algorithm is introduced which incorporates MRI AE-SDMs guidance. We evaluated the method on 19 subjects with corresponding MRI and manually segmented CT datasets by performing a leave-one-out study. Several metrics are used to quantify the overlap between the automatic and manual segmentations. Compared to the manual gold standard segmentations, our robust segmentation method produced an average surface distance 1.24±0.27mm, which outperforms state-of-the-art algorithms for MRI bony pelvis segmentation. We also show that the resulting surface can be tracked in the endoscopic view in near real time using dense visual tracking methods. Results are presented on a simulation and a real clinical RALP case. Tracking is accurate to 0.13mm over 700 frames

Bony changes in cows affected with chronic fluorine poisoning caused by industrial waste

Energy Technology Data Exchange (ETDEWEB)

Lasarov, E; Tatarov, B; Dimitrov, G; Kantschev, L; Kovatschev, K

1972-01-01

Cows affected with chronic fluorine poisoning were thoroughly examined and the findings ff clinical, anatomical-pathological, x-ray, chemical and histological examinations are reported with particular reference to changes of skeletal bones. The most significant bony changes were periosteal hyperostosis on metacarpal and metatarsal bones, local resorption of the compact substance which appeared to have a sponge-like pattern, and a destructive process in the areas surrounding Havers' and Volkmann's canals. Changes of the trabecular pattern were observed in the spongy substance of the above mentioned bones. Trabeculae showed signs of atrophy - they were thinned or coarsely thickened - and their contours were well contrasted. Regularly shaped osteons were not frequently found in the spongy substance. Marked narrowing of the medullary canal was seen.

Heterogeneous Effects of a Nonlinear Price Schedule for Outpatient Care.

Science.gov (United States)

Farbmacher, Helmut; Ihle, Peter; Schubert, Ingrid; Winter, Joachim; Wuppermann, Amelie

2017-10-01

Nonlinear price schedules generally have heterogeneous effects on health-care demand. We develop and apply a finite mixture bivariate probit model to analyze whether there are heterogeneous reactions to the introduction of a nonlinear price schedule in the German statutory health insurance system. In administrative insurance claims data from the largest German health insurance plan, we find that some individuals strongly react to the new price schedule while a second group of individuals does not react. Post-estimation analyses reveal that the group of the individuals who do not react to the reform includes the relatively sick. These results are in line with forward-looking behavior: Individuals who are already sick expect that they will hit the kink in the price schedule and thus are less sensitive to the co-payment. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

The bony crescent sign - a new sign of facial nerve schwannoma

International Nuclear Information System (INIS)

Watts, A.; Fagan, P.

1992-01-01

Schwannomas are relatively uncommon intracranial tumours. They most commonly involve the acoustic nerve followed in frequency by the trigeminal nerve. Other cranial nerves are rarely involved. Facial nerve schwannomas occurring within the petrous temporal bone are very rare. Their diagnosis may be missed prospectively even when appropriate computerized tomography (CT) scans are performed. Even in retrospect the site of abnormality may be difficult to identify, especially if there is an associated middle ear mass such as a cholesteatoma. In the 4 cases presented the facial nerve schwannoma was seen on high resolution CT as a soft tissue mass bounded anteriorly by a thin rim of bone. This bony crescent sign is a previously undescribed feature of facial nerve schwannoma which appears to be strongly indicative of the presence of this tumour. Recognition of this sign makes these tumours arising in the region of the geniculate ganglion easy to diagnose prospectively. 12 refs., 6 figs

Bony cranial ornamentation linked to rapid evolution of gigantic theropod dinosaurs

Science.gov (United States)

Gates, Terry A.; Organ, Chris; Zanno, Lindsay E.

2016-09-01

Exaggerated cranial structures such as crests and horns, hereafter referred to collectively as ornaments, are pervasive across animal species. These structures perform vital roles in visual communication and physical interactions within and between species. Yet the origin and influence of ornamentation on speciation and ecology across macroevolutionary time scales remains poorly understood for virtually all animals. Here, we explore correlative evolution of osseous cranial ornaments with large body size in theropod dinosaurs using a phylogenetic comparative framework. We find that body size evolved directionally toward phyletic giantism an order of magnitude faster in theropod species possessing ornaments compared with unadorned lineages. In addition, we find a body mass threshold below which bony cranial ornaments do not originate. Maniraptoriform dinosaurs generally lack osseous cranial ornaments despite repeatedly crossing this body size threshold. Our study provides novel, quantitative support for a shift in selective pressures on socio-sexual display mechanisms in theropods coincident with the evolution of pennaceous feathers.

Heterogeneity in Preferences and Productivity

DEFF Research Database (Denmark)

Gørtz, Mette

This paper discusses the determinants of the retirement decision and the implications of retirement on economic well-being. The main contribution of the paper is to formulate the role of individual heterogeneity explicitly. We argue that individual heterogeneity in 1) productivity of market work...... choices of expenditure, household production and leisure for people in and around retirement. The unobserved individual heterogeneity factor is isolated by comparing cross-sectional evidence and panel data estimates of the effects of retirement on consumption and time allocation. Based on cross......-section data, we can identify a difference in consumption due to retirement status, but when the panel nature of the data is exploited, the effect of retirement on consumption is small and insignificant. Moreover, the analyses point at a large positive effect of retirement on household production. Our results...

Heterogenization of Homogeneous Catalysts: the Effect of the Support

Energy Technology Data Exchange (ETDEWEB)

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.

Heterogeneity in Consumer Demands and the Income Effect

DEFF Research Database (Denmark)

Christensen, Mette

2014-01-01

This paper uses unique Spanish panel data on household expenditures to test whether unobservable heterogeneity in household demands (taste, etc.) is correlated with total expenditures (income). The main finding is that tastes are indeed correlated with income for about half of the goods considere....... For transportation, the bias is sufficiently large to misclassify the good as a luxury.......This paper uses unique Spanish panel data on household expenditures to test whether unobservable heterogeneity in household demands (taste, etc.) is correlated with total expenditures (income). The main finding is that tastes are indeed correlated with income for about half of the goods considered......, implying that cross-sectional estimates of income elasticities for these goods are biased. The goods are the following: food eaten outside home, alcohol and tobacco, transportation, and energy. The elasticity of alcohol and tobacco is more than halved when taking unobserved heterogeneity into account...

Patterns and effects of GC3 heterogeneity and parsimony informative sites on the phylogenetic tree of genes.

Science.gov (United States)

Ma, Shuai; Wu, Qi; Hu, Yibo; Wei, Fuwen

2018-05-20

The explosive growth in genomic data has provided novel insights into the conflicting signals hidden in phylogenetic trees. Although some studies have explored the effects of the GC content and parsimony informative sites (PIS) on the phylogenetic tree, the effect of the heterogeneity of the GC content at the first/second/third codon position on parsimony informative sites (GC1/2/3 PIS ) among different species and the effect of PIS on phylogenetic tree construction remain largely unexplored. Here, we used two different mammal genomic datasets to explore the patterns of GC1/2/3 PIS heterogeneity and the effect of PIS on the phylogenetic tree of genes: (i) all GC1/2/3 PIS have obvious heterogeneity between different mammals, and the levels of heterogeneity are GC3 PIS  > GC2 PIS  > GC1 PIS ; (ii) the number of PIS is positively correlated with the metrics of "good" gene tree topologies, and excluding the third codon position (C3) decreases the quality of gene trees by removing too many PIS. These results provide novel insights into the heterogeneity pattern of GC1/2/3 PIS in mammals and the relationship between GC3/PIS and gene trees. Additionally, it is necessary to carefully consider whether to exclude C3 to improve the quality of gene trees, especially in the super-tree method. Copyright © 2018 Elsevier B.V. All rights reserved.

Effects of heterogeneous convergence rate on consensus in opinion dynamics

Science.gov (United States)

Huang, Changwei; Dai, Qionglin; Han, Wenchen; Feng, Yuee; Cheng, Hongyan; Li, Haihong

2018-06-01

The Deffuant model has attracted much attention in the study of opinion dynamics. Here, we propose a modified version by introducing into the model a heterogeneous convergence rate which is dependent on the opinion difference between interacting agents and a tunable parameter κ. We study the effects of heterogeneous convergence rate on consensus by investigating the probability of complete consensus, the size of the largest opinion cluster, the number of opinion clusters, and the relaxation time. We find that the decrease of the convergence rate is favorable to decreasing the confidence threshold for the population to always reach complete consensus, and there exists optimal κ resulting in the minimal bounded confidence threshold. Moreover, we find that there exists a window before the threshold of confidence in which complete consensus may be reached with a nonzero probability when κ is not too large. We also find that, within a certain confidence range, decreasing the convergence rate will reduce the relaxation time, which is somewhat counterintuitive.

Effect of heterogeneity and assumed mode of inheritance on lod scores.

Science.gov (United States)

Durner, M; Greenberg, D A

1992-02-01

Heterogeneity is a major factor in many common, complex diseases and can confound linkage analysis. Using computer-simulated heterogeneous data we tested what effect unlinked families have on a linkage analysis when heterogeneity is not taken into account. We created 60 data sets of 40 nuclear families each with different proportions of linked and unlinked families and with different modes of inheritance. The ascertainment probability was 0.05, the disease had a penetrance of 0.6, and the recombination fraction for the linked families was zero. For the analysis we used a variety of assumed modes of inheritance and penetrances. Under these conditions we looked at the effect of the unlinked families on the lod score, the evaluation of the mode of inheritance, and the estimate of penetrance and of the recombination fraction in the linked families. 1. When the analysis was done under the correct mode of inheritance for the linked families, we found that the mode of inheritance of the unlinked families had minimal influence on the highest maximum lod score (MMLS) (i.e., we maximized the maximum lod score with respect to penetrance). Adding sporadic families decreased the MMLS less than adding recessive or dominant unlinked families. 2. The mixtures of dominant linked families with unlinked families always led to a higher MMLS when analyzed under the correct (dominant) mode of inheritance than when analyzed under the incorrect mode of inheritance. In the mixtures with recessive linked families, assuming the correct mode of inheritance generally led to a higher MMLS, but we observed broad variation.(ABSTRACT TRUNCATED AT 250 WORDS)

Is radiographic measurement of bony landmarks reliable for lateral meniscal sizing?

Science.gov (United States)

Yoon, Jung-Ro; Kim, Taik-Seon; Lim, Hong-Chul; Lim, Hyung-Tae; Yang, Jae-Hyuk

2011-03-01

The accuracy of meniscal measurement methods is still in debate. The authors' protocol for radiologic measurements will provide reproducible bony landmarks, and this measurement method of the lateral tibial plateau will correlate with the actual anatomic value. Controlled laboratory study. Twenty-five samples of fresh lateral meniscus with attached proximal tibia were obtained during total knee arthroplasty. Each sample was obtained without damage to the meniscus and bony attachment sites. The inclusion criterion was mild to moderate osteoarthritis in patients with mechanical axis deviation of less than 15°. Knees with lateral compartment osteoarthritic change or injured or degenerated menisci were excluded. For the lateral tibial plateau length measurements, the radiographic beam was angled 10° caudally at neutral rotation, which allowed differentiation of the lateral plateau cortical margins from the medial plateau. The transition points were identified and used for length measurement. The values of length were then compared with the conventional Pollard method and the anatomic values. The width measurement was done according to Pollard's protocol. For each knee, the percentage deviation from the anatomic dimension was recorded. Intraobserver error and interobserver error were calculated. The deviation of the authors' radiographic length measurements from anatomic dimensions was 1.4 ± 1.1 mm. The deviation of Pollard's radiographic length measurements was 4.1 ± 2.0 mm. With respect to accuracy-which represents the frequency of measurements that fall within 10% of measurements-the accuracy of authors' length was 98%, whereas for Pollard's method it was 40%. There was a good correlation between anatomic meniscal dimensions and each radiologic plateau dimensions for lateral meniscal width (R(2) = .790) and the authors' lateral meniscal length (R(2) = .823) and fair correlation for Pollard's lateral meniscal length (R(2) = .660). The reliability of each

A clinico-radiologic study of bony remodeling of the fractured condyles in children

Energy Technology Data Exchange (ETDEWEB)

Cho, Jeong Shin; Park, Chang Seo [Department of Dentistry, The Graduate School, Yonsei University, Seoul (Korea, Republic of)

1995-08-15

Bony remodeling pattern of condyle fractures in children are different from in adult for growing of condyle, also might affect treatment and prognosis of the condyle fracture. Subjects of this clinical and radiologic study were 26 temporomandibular joints diagnosed as condyle fracture in 23 patients under 15 years old age, They were treated with conservative method at Dental Hospital of Yonsei University from Jan., 1986 to Oct., 1994. Bony remodeling related with fracture pattern was evaluated. The results obtained are as follows: 1. The ratio of male to female in patients with condyle fracture was 1 : 0.9 and the difference of sex ratio was not noted. Comparing with preschool-age group and school-age group, age frequency was higher in preschool-age group (83%). 2. Fallen down (54%) was the most frequent cause of condyle fractures. Traffic accident and slip down were followed. 3. The most common clinical sign of condyle fractures was tenderness to palpation (19 cases). Mouth opening limitation (17 cases), swelling (7 cases), malocclusion (3 cases) were next in order. 4. According to sites of condyle fractures, unilateral fractures were in 20 patients and bilateral fractures in 3 patients, therefore total 23 patients-26 cases of condyle fracture were observed. According to fracture distribution, condyle fractures were in 10 patients (44%). Condyle fractures with symphysis fracture (9 patients, 39%), condyle fractures with ascending ramus fracture (2 patients, 9%), condyle fracture with mandibular body fracture (1 patient, 4%), and condyle fractures with mandibular angle fracture (1 patient, 4%) were followed. 5. In displacement pattern of fractured fragment of mandibular condyle, displacement (17 cases, 66%) was most common. Dislocation (5 cases, 19%) and deviation (4 cases, 15%) were next in order. 6. During the observation period of fractured condyles, remodeling patterns of fracture sites related with articular fossa were observed with usual congealer shape in 23

A clinico-radiologic study of bony remodeling of the fractured condyles in children

International Nuclear Information System (INIS)

Cho, Jeong Shin; Park, Chang Seo

1995-01-01

Bony remodeling pattern of condyle fractures in children are different from in adult for growing of condyle, also might affect treatment and prognosis of the condyle fracture. Subjects of this clinical and radiologic study were 26 temporomandibular joints diagnosed as condyle fracture in 23 patients under 15 years old age, They were treated with conservative method at Dental Hospital of Yonsei University from Jan., 1986 to Oct., 1994. Bony remodeling related with fracture pattern was evaluated. The results obtained are as follows: 1. The ratio of male to female in patients with condyle fracture was 1 : 0.9 and the difference of sex ratio was not noted. Comparing with preschool-age group and school-age group, age frequency was higher in preschool-age group (83%). 2. Fallen down (54%) was the most frequent cause of condyle fractures. Traffic accident and slip down were followed. 3. The most common clinical sign of condyle fractures was tenderness to palpation (19 cases). Mouth opening limitation (17 cases), swelling (7 cases), malocclusion (3 cases) were next in order. 4. According to sites of condyle fractures, unilateral fractures were in 20 patients and bilateral fractures in 3 patients, therefore total 23 patients-26 cases of condyle fracture were observed. According to fracture distribution, condyle fractures were in 10 patients (44%). Condyle fractures with symphysis fracture (9 patients, 39%), condyle fractures with ascending ramus fracture (2 patients, 9%), condyle fracture with mandibular body fracture (1 patient, 4%), and condyle fractures with mandibular angle fracture (1 patient, 4%) were followed. 5. In displacement pattern of fractured fragment of mandibular condyle, displacement (17 cases, 66%) was most common. Dislocation (5 cases, 19%) and deviation (4 cases, 15%) were next in order. 6. During the observation period of fractured condyles, remodeling patterns of fracture sites related with articular fossa were observed with usual congealer shape in 23

Flow and transport in unsaturated fractured rock: Effects of multiscale heterogeneity of hydrogeologic properties

International Nuclear Information System (INIS)

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

2002-01-01

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 percent 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

Glioblastoma Multiforme: A Look Inside Its Heterogeneous Nature

International Nuclear Information System (INIS)

Inda, Maria-del-Mar; Bonavia, Rudy; Seoane, Joan

2014-01-01

Heterogeneity is a hallmark of tumors and has a crucial role in the outcome of the malignancy, because it not only confounds diagnosis, but also challenges the design of effective therapies. There are two types of heterogeneity: inter-tumor and intra-tumor heterogeneity. While inter-tumor heterogeneity has been studied widely, intra-tumor heterogeneity has been neglected even though numerous studies support this aspect of tumor pathobiology. The main reason has been the technical difficulties, but with new advances in single-cell technology, intra-tumor heterogeneity is becoming a key area in the study of cancer. Several models try to explain the origin and maintenance of intra-tumor heterogeneity, however, one prominent model compares cancer with a tree where the ubiquitous mutations compose the trunk and mutations present in subpopulations of cells are represented by the branches. In this review we will focus on the intra-tumor heterogeneity of glioblastoma multiforme (GBM), the most common brain tumor in adults that is characterized by a marked heterogeneity at the cellular and molecular levels. Better understanding of this heterogeneity will be essential to design effective therapies against this devastating disease to avoid tumor escape

Glioblastoma Multiforme: A Look Inside Its Heterogeneous Nature

Energy Technology Data Exchange (ETDEWEB)

Inda, Maria-del-Mar, E-mail: mminda@vhio.net; Bonavia, Rudy [Translational Research Program, Vall d’Hebron Institute of Oncology (VHIO), Vall d’Hebron University Hospital, 119-129 Passeig Vall d’Hebron, Barcelona 08035 (Spain); Seoane, Joan [Translational Research Program, Vall d’Hebron Institute of Oncology (VHIO), Vall d’Hebron University Hospital, 119-129 Passeig Vall d’Hebron, Barcelona 08035 (Spain); Catalan Institution of Research and Advanced Studies (ICREA), Barcelona 08035 (Spain)

2014-01-27

Heterogeneity is a hallmark of tumors and has a crucial role in the outcome of the malignancy, because it not only confounds diagnosis, but also challenges the design of effective therapies. There are two types of heterogeneity: inter-tumor and intra-tumor heterogeneity. While inter-tumor heterogeneity has been studied widely, intra-tumor heterogeneity has been neglected even though numerous studies support this aspect of tumor pathobiology. The main reason has been the technical difficulties, but with new advances in single-cell technology, intra-tumor heterogeneity is becoming a key area in the study of cancer. Several models try to explain the origin and maintenance of intra-tumor heterogeneity, however, one prominent model compares cancer with a tree where the ubiquitous mutations compose the trunk and mutations present in subpopulations of cells are represented by the branches. In this review we will focus on the intra-tumor heterogeneity of glioblastoma multiforme (GBM), the most common brain tumor in adults that is characterized by a marked heterogeneity at the cellular and molecular levels. Better understanding of this heterogeneity will be essential to design effective therapies against this devastating disease to avoid tumor escape.

Glioblastoma Multiforme: A Look Inside Its Heterogeneous Nature

Directory of Open Access Journals (Sweden)

Maria-del-Mar Inda

2014-01-01

Full Text Available Heterogeneity is a hallmark of tumors and has a crucial role in the outcome of the malignancy, because it not only confounds diagnosis, but also challenges the design of effective therapies. There are two types of heterogeneity: inter-tumor and intra-tumor heterogeneity. While inter-tumor heterogeneity has been studied widely, intra-tumor heterogeneity has been neglected even though numerous studies support this aspect of tumor pathobiology. The main reason has been the technical difficulties, but with new advances in single-cell technology, intra-tumor heterogeneity is becoming a key area in the study of cancer. Several models try to explain the origin and maintenance of intra-tumor heterogeneity, however, one prominent model compares cancer with a tree where the ubiquitous mutations compose the trunk and mutations present in subpopulations of cells are represented by the branches. In this review we will focus on the intra-tumor heterogeneity of glioblastoma multiforme (GBM, the most common brain tumor in adults that is characterized by a marked heterogeneity at the cellular and molecular levels. Better understanding of this heterogeneity will be essential to design effective therapies against this devastating disease to avoid tumor escape.

Glioblastoma multiforme: a look inside its heterogeneous nature.

Science.gov (United States)

Inda, Maria-Del-Mar; Bonavia, Rudy; Seoane, Joan

2014-01-27

Heterogeneity is a hallmark of tumors and has a crucial role in the outcome of the malignancy, because it not only confounds diagnosis, but also challenges the design of effective therapies. There are two types of heterogeneity: inter-tumor and intra-tumor heterogeneity. While inter-tumor heterogeneity has been studied widely, intra-tumor heterogeneity has been neglected even though numerous studies support this aspect of tumor pathobiology. The main reason has been the technical difficulties, but with new advances in single-cell technology, intra-tumor heterogeneity is becoming a key area in the study of cancer. Several models try to explain the origin and maintenance of intra-tumor heterogeneity, however, one prominent model compares cancer with a tree where the ubiquitous mutations compose the trunk and mutations present in subpopulations of cells are represented by the branches. In this review we will focus on the intra-tumor heterogeneity of glioblastoma multiforme (GBM), the most common brain tumor in adults that is characterized by a marked heterogeneity at the cellular and molecular levels. Better understanding of this heterogeneity will be essential to design effective therapies against this devastating disease to avoid tumor escape.

Bony contact area and displacement of the temporomandibular joint after high-oblique and bilateral sagittal split osteotomy: a computer-simulated comparison.

Science.gov (United States)

Möhlhenrich, Stephan Christian; Kamal, Mohammad; Peters, Florian; Fritz, Ulrike; Hölzle, Frank; Modabber, Ali

2016-04-01

The most common way to move the mandible during orthognathic surgery is by bilateral sagittal split osteotomy (BSSO). The high-oblique sagittal split osteotomy (HSSO) is an alternative, although its use is limited by potential complications, mainly to do with the position of the condyle and reduced contact with bone. The aim of this study was to find out the optimal intercondylar distance and area of contact with the surface of the bone for mandibular advancement and setback in BSSO and HSSO. Data from computed tomographic (CT) images from 40 patients were loaded into special planning software, and virtual operations done for mandibular advancement and setback at 3, 5, 8, and 10mm using BSSO and HSSO, which resulted in 640 individual mandibular displacements. The resultant area of bony contact and intercondylar distance were calculated by the software. The mean (SD) areas of contact with the bony surface after 10mm advancement for HSSO and BSSO were 193.94 (63.76) mm(2) and 967.92 (229.21) mm(2), respectively, and after 10mm setback 202.64 (62.30) mm(2) and 1108.86 (247.38) mm(2). The mean corresponding intercondylar distance after maximum advancement were 86.76 (6.40) mm and 86.59 (6.24) mm, and after maximum setback 74.90 (5.73) mm and 73.06 (6.06) mm. There were significant differences between the two for the area of contact with the surface at each displacement distance (parea of bony contact can be expected at any displacement distance for BSSO, so the changes in intercondylar distance should not be considered when deciding which osteotomy to select. Copyright © 2015 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Heterogeneous continuous-time random walks

Science.gov (United States)

Grebenkov, Denis S.; Tupikina, Liubov

2018-01-01

We introduce a heterogeneous continuous-time random walk (HCTRW) model as a versatile analytical formalism for studying and modeling diffusion processes in heterogeneous structures, such as porous or disordered media, multiscale or crowded environments, weighted graphs or networks. We derive the exact form of the propagator and investigate the effects of spatiotemporal heterogeneities onto the diffusive dynamics via the spectral properties of the generalized transition matrix. In particular, we show how the distribution of first-passage times changes due to local and global heterogeneities of the medium. The HCTRW formalism offers a unified mathematical language to address various diffusion-reaction problems, with numerous applications in material sciences, physics, chemistry, biology, and social sciences.

Heterogeneous policies, heterogeneous technologies: The case of renewable energy

International Nuclear Information System (INIS)

Nicolli, Francesco; Vona, Francesco

2016-01-01

This paper investigates empirically the effect of market regulation and renewable energy policies on innovation activity in different renewable energy technologies. For the EU countries and the years 1980 to 2007, we built a unique dataset containing information on patent production in eight different technologies, proxies of market regulation and technology-specific renewable energy policies. Our main finding is that, compared to privatisation and unbundling, reducing entry barriers is a more significant driver of renewable energy innovation, but that its effect varies across technologies and is stronger in technologies characterised by potential entry of small, independent power producers. In addition, the inducement effect of renewable energy policies is heterogeneous and more pronounced for wind, which is the only technology that is mature and has high technological potential. Finally, ratification of the Kyoto protocol, which determined a more stable and less uncertain policy framework, amplifies the inducement effect of both energy policy and market liberalisation. - Highlights: • We study the effect of market regulation and energy policy on renewable technologies. • Reducing entry barriers is a significant driver of renewable energy innovation. • The Kyoto protocol amplifies the effect of both energy policy and liberalisation. • These effects are heterogeneous across technologies and stronger for wind.

The effects of heterogeneities on memory-dependent diffusion

Science.gov (United States)

Adib, Farhad; Neogi, P.

1993-07-01

Case II diffusion is often seen in glassy polymers, where the mass uptake in sorption is proportional to time t instead of sqrt{t}. A memory dependent diffusion is needed to explain such effects, where the relaxation function used to describe the memory effect has a characteristic time. The ratio of this time to the overall diffusion times is the diffusional Deborah number. Simple models show that case II results when the Deborah number is around one, that is, when the two time scales are comparable. Under investigation are the possible effects of the fact that the glassy polymers are heterogeneous over molecular scales. The averaging form given by DiMarzio and Sanchez has been used to obtain the averaged response. The calculated dynamics of sorption show that whereas case II is still observed, the long term tails change dramatically from the oscillatory to torpid, to chaotic, which are all observed in the experiments. The Deborah number defined here in a self-consistent manner collapses in those cases, but causes no other ill-effects.

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

Science.gov (United States)

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.

Assessment of the effect of three-dimensional mantle density heterogeneity on earth rotation in tidal frequencies.

Science.gov (United States)

Liu, Lanbo; Chao, Benjamin F; Sun, Wenke; Kuang, Weijia

2016-11-01

In this paper we report the assessment of the effect of the three-dimensional (3D) density heterogeneity in the mantle on Earth Orientation Parameters (EOP) (i.e., the polar motion, or PM, and the length of day, or LOD) in the tidal frequencies. The 3D mantle density model is estimated based upon a global S-wave velocity tomography model (S16U6L8) and the mineralogical knowledge derived from laboratory experiment. The lateral density variation is referenced against the Preliminary Reference Earth Model (PREM). Using this approach the effects of the heterogeneous mantle density variation in all three tidal frequencies (zonal long periods, tesseral diurnal, and sectorial semidiurnal) are estimated in both PM and LOD. When compared with mass or density perturbations originated on the earth's surface such as the oceanic and barometric changes, the heterogeneous mantle only contributes less than 10% of the total variation in PM and LOD in tidal frequencies. Nevertheless, including the 3D variation of the density in the mantle into account explained a substantial portion of the discrepancy between the observed signals in PM and LOD extracted from the lump-sum values based on continuous space geodetic measurement campaigns (e.g., CONT94) and the computed contribution from ocean tides as predicted by tide models derived from satellite altimetry observations (e.g., TOPEX/Poseidon). In other word, the difference of the two, at all tidal frequencies (long-periods, diurnals, and semi-diurnals) contains contributions of the lateral density heterogeneity of the mantle. Study of the effect of mantle density heterogeneity effect on torque-free earth rotation may provide useful constraints to construct the Reference Earth Model (REM), which is the next major objective in global geophysics research beyond PREM.

Effects of surface roughness and electrokinetic heterogeneity on electroosmotic flow in microchannel

Energy Technology Data Exchange (ETDEWEB)

Masilamani, Kannan; Ganguly, Suvankar; Feichtinger, Christian; Bartuschat, Dominik; Rüde, Ulrich, E-mail: suva_112@yahoo.co.in [Department of Computer Science 10 University of Erlangen-Nuremberg, Cauerstr.11 91058 Erlangen (Germany)

2015-06-15

In this paper, a hybrid lattice-Boltzmann and finite-difference (LB-FD) model is applied to simulate the effects of three-dimensional surface roughness and electrokinetic heterogeneity on electroosmotic flow (EOF) in a microchannel. The lattice-Boltzmann (LB) method has been employed to obtain the flow field and a finite-difference (FD) method is used to solve the Poisson-Boltzmann (PB) equation for the electrostatic potential distribution. Numerical simulation of flow through a square cross-section microchannel with designed roughness is conducted and the results are critically analysed. The effects of surface heterogeneity on the electroosmotic transport are investigated for different roughness height, width, roughness interval spacing, and roughness surface potential. Numerical simulations reveal that the presence of surface roughness changes the nature of electroosmotic transport through the microchannel. It is found that the electroosmotic velocity decreases with the increase in roughness height and the velocity profile becomes asymmetric. For the same height of the roughness elements, the EOF velocity rises with the increase in roughness width. For the heterogeneously charged rough channel, the velocity profile shows a distinct deviation from the conventional plug-like flow pattern. The simulation results also indicate locally induced flow vortices which can be utilized to enhance the flow and mixing within the microchannel. The present study has important implications towards electrokinetic flow control in the microchannel, and can provide an efficient way to design a microfluidic system of practical interest. (paper)

Dynamic effects of increasing heterogeneity in financial markets

International Nuclear Information System (INIS)

Naimzada, Ahmad K.; Ricchiuti, Giorgio

2009-01-01

Despite canonical behavioural financial market models [Day R, Huang W. Bulls, bears and market sheep. J Econ Behav Org 1990;14:299-329], that use different types of agents (i.e., fundamentalist vs. chartists), we develop a model in which the source of instability is the interaction of groups that are homogeneous in the strategy they use, but have heterogeneous beliefs about the fundamental value of the asset. Specifically, heterogeneity arises among two groups of fundamentalists that follow gurus. We show that an increasing distance between beliefs (the degree of heterogeneity), leads first (i) to a pitchfork bifurcation to arise secondly (ii) it generates, together with a larger reaction to misalignment of both market maker and agents, the appearance of a periodic, or even, chaotic, price fluctuation; (iii) finally a homoclinic bifurcation [Dieci R, Bischi GI, Gardini L. From bi-stability to chaotic oscillations in a macroeconomic model. Chaos, Solitons and Fractals 2001;12:805-22] transforms a two piece chaotic set into a one piece chaotic set that generates bull and bear markets.

Effective IPTV channel management method over heterogeneous environments

Science.gov (United States)

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.

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

Science.gov (United States)

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.

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

Science.gov (United States)

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.

Inertial Effects on Flow and Transport in Heterogeneous Porous Media.

Science.gov (United States)

Nissan, Alon; Berkowitz, Brian

2018-02-02

We investigate the effects of high fluid velocities on flow and tracer transport in heterogeneous porous media. We simulate fluid flow and advective transport through two-dimensional pore-scale matrices with varying structural complexity. As the Reynolds number increases, the flow regime transitions from linear to nonlinear; this behavior is controlled by the medium structure, where higher complexity amplifies inertial effects. The result is, nonintuitively, increased homogenization of the flow field, which leads in the context of conservative chemical transport to less anomalous behavior. We quantify the transport patterns via a continuous time random walk, using the spatial distribution of the kinetic energy within the fluid as a characteristic measure.

Utilization of cone-beam CT for offline evaluation of target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment.

Science.gov (United States)

Paluska, Petr; Hanus, Josef; Sefrova, Jana; Rouskova, Lucie; Grepl, Jakub; Jansa, Jan; Kasaova, Linda; Hodek, Miroslav; Zouhar, Milan; Vosmik, Milan; Petera, Jiri

2012-01-01

To assess target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment and to assess possibility of safety margin reduction. Implementation of IGRT should influence safety margins. Utilization of cone-beam CT provides current 3D anatomic information directly in irradiation position. Such information enables reconstruction of the actual dose distribution. Seventeen prostate patients were treated with daily bony anatomy image-guidance. Cone-beam CT (CBCT) scans were acquired once a week immediately after bony anatomy alignment. After the prostate, seminal vesicles, rectum and bladder were contoured, the delivered dose distribution was reconstructed. Target dose coverage was evaluated by the proportion of the CTV encompassed by the 95% isodose. Original plans employed a 1 cm safety margin. Alternative plans assuming a smaller 7 mm margin between CTV and PTV were evaluated in the same way. Rectal and bladder volumes were compared with the initial ones. Rectal and bladder volumes irradiated with doses higher than 75 Gy, 70 Gy, 60 Gy, 50 Gy and 40 Gy were analyzed. In 12% of reconstructed plans the prostate coverage was not sufficient. The prostate underdosage was observed in 5 patients. Coverage of seminal vesicles was not satisfactory in 3% of plans. Most of the target underdosage corresponded to excessive rectal or bladder filling. Evaluation of alternative plans assuming a smaller 7 mm margin revealed 22% and 11% of plans where prostate and seminal vesicles coverage, respectively, was compromised. These were distributed over 8 and 7 patients, respectively. Sufficient dose coverage of target volumes was not achieved for all patients. Reducing of safety margin is not acceptable. Initial rectal and bladder volumes cannot be considered representative for subsequent treatment.

Blocking effect and numerical study of polymer particles dispersion flooding in heterogeneous reservoir

Science.gov (United States)

Zhu, Weiyao; Li, Jianhui; Lou, Yu

2018-02-01

Polymer flooding has become an effective way to improve the sweep efficiency in many oil fields. Many scholars have carried out a lot of researches on the mechanism of polymer flooding. In this paper, the effect of polymer on seepage is analyzed. The blocking effect of polymer particles was studied experimentally, and the residual resistance coefficient (RRF) were used to represent the blocking effect. We also build a mathematical model for heterogeneous concentration distribution of polymer particles. Furthermore, the effects of polymer particles on reservoir permeability, fluid viscosity and relative permeability are considered, and a two-phase flow model of oil and polymer particles is established. In addition, the model was tested in the heterogeneous stratum model, and three influencing factors, such as particle concentration, injection volume and PPD (short for polymer particle dispersion) injection time, were analyzed. Simulation results show that PPD can effectively improve sweep efficiency and especially improve oil recovery of low permeability layer. Oil recovery increases with the increase of particle concentration, but oil recovery increase rate gradually decreases with that. The greater the injected amount of PPD, the greater oil recovery and the smaller oil recovery increase rate. And there is an optimal timing to inject PPD for specific reservoir.

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

Science.gov (United States)

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. © The Author(s) 2014.

Exact asymptotic relations for the effective response of linear viscoelastic heterogeneous media

Science.gov (United States)

Gallican, Valentin; Brenner, Renald; Suquet, Pierre

2017-11-01

This article addresses the asymptotic response of viscoelastic heterogeneous media in the frequency domain, at high and low frequencies, for different types of elementary linear viscoelastic constituents. By resorting to stationary principles for complex viscoelasticity and adopting a classification of the viscoelastic behaviours based on the nature of their asymptotic regimes, either elastic or viscous, four exact relations are obtained on the overall viscoelastic complex moduli in each case. Two relations are related to the asymptotic uncoupled heterogeneous problems, while the two remaining ones result from the viscoelastic coupling that manifests itself in the transient regime. These results also provide exact conditions on certain integrals in time of the effective relaxation spectrum. This general setting encompasses the results obtained in preceding studies on mixtures of Maxwell constituents [1,2]. xml:lang="fr"

Heterogeneity in pineapple fruit quality results from plant heterogeneity at flower induction.

Science.gov (United States)

Fassinou Hotegni, V Nicodème; Lommen, Willemien J M; Agbossou, Euloge K; Struik, Paul C

2014-01-01

Heterogeneity in fruit quality constitutes a major constraint in agri-food chains. In this paper the sources of the heterogeneity in pineapple in the field were studied in four experiments in commercial pineapple fields. The aims were to determine (a) whether differences in pineapple fruit quality among individual fruits are associated with differences in vigor of the individual plants within the crop at the time of artificial flower induction; and (b) whether the side shoots produced by the plant during the generative phase account for the fruit quality heterogeneity. Two pineapple cultivars were considered: cv. Sugarloaf and cv. Smooth Cayenne. Plant vigor at the time of artificial flower induction was measured by three variates: the number of functional leaves, the D-leaf length and their cross product. Fruit quality attributes measured at harvest time included external attributes (weight and height of fruit, infructescence and crown) and internal quality attributes [total soluble solids (TSS), pH, translucent flesh]. Results showed that the heterogeneity in fruit weight was a consequence of the heterogeneity in vigor of the plants at the moment of flower induction; that effect was mainly on the infructescence weight and less or not on the crown weight. The associations between plant vigor variates at flower induction and the internal quality attributes of the fruit were poor and/or not consistent across experiments. The weight of the slips (side shoots) explained part of the heterogeneity in fruit weight, infructescence weight and fruit height in cv. Sugarloaf. Possibilities for reducing the variation in fruit quality by precise cultural practices are discussed.

Heterogeneity in pineapple fruit quality results from plant heterogeneity at flower induction

Directory of Open Access Journals (Sweden)

V. Nicodeme eFassinou Hotegni

2014-12-01

Full Text Available Heterogeneity in fruit quality constitutes a major constraint in agri-food chains. In this paper the sources of the heterogeneity in pineapple in the field were studied in four experiments in commercial pineapple fields. The aims were to determine (a whether differences in pineapple fruit quality among individual fruits are associated with differences in vigor of the individual plants within the crop at the time of artificial flower induction; and (b whether the side shoots produced by the plant during the generative phase account for the fruit quality heterogeneity. Two pineapple cultivars were considered: cv. Sugarloaf and cv. Smooth Cayenne. Plant vigor at the time of artificial flower induction was measured by three variates: the number of functional leaves, the D-leaf length and their cross product. Fruit quality attributes measured at harvest time included external attributes (weight and height of fruit, infructescence and crown and internal quality attributes (total soluble solids, pH, translucent flesh. Results showed that the heterogeneity in fruit weight was a consequence of the heterogeneity in vigor of the plants at the moment of flower induction; that effect was mainly on the infructescence weight and less or not on the crown weight. The association between plant vigor variates at flower induction and the internal quality attributes of the fruit were poor and/or not consistent across experiments. The weight of the slips (side shoots, explained part of the heterogeneity in fruit weight, infructescence weight and fruit height in cv. Sugarloaf. Possibilities for reducing the variation in fruit quality by precise cultural practices are discussed.

Composition heterogeneity analysis for DUPIC fuel(I) - Statistical analysis

Energy Technology Data Exchange (ETDEWEB)

Choi, Hang Bok [Korea Atomic Energy Research Institute, Taejon (Korea)

1999-08-01

The fuel composition heterogeneity effect on reactor performance parameters was assessed by refueling simulations for three DUPIC fuel options of fuel composition heterogeneity control: the fissile content adjustment, the reactivity control by slightly enriched and depleted uranium, and the reactivity control by natural uranium. For each DUPIC fuel option, the simulations were performed using 30 heterogeneous fuel types which were determined by the agglomerative hierarchical clustering method. The heterogeneity effect was considered during the refueling simulation by randomly selecting fuel types for the refueling operation. The refueling simulations of the heterogeneous core have shown that the key performance parameters such as the maximum channel power (MCP), maximum bundle power (MBP), and channel power peaking factor (CPPF) are close to those of the core that has single fuel type. For the three DUPIC fuel options, the uncertainties of MCP, MBP, and CPPF due to the fuel composition heterogeneity are less than 0.6, 1.5 and 0.8%, respectively, including the uncertainty of the group-average fuel property. This study has shown that the three DUPIC fuel options reduces the composition heterogeneity effectively and the zone power control system has a sufficient margin to adjust the perturbations cased by the fuel composition heterogeneity. 15 refs., 28 figs.,10 tabs. (Author)

Heterogeneous gas core reactor

International Nuclear Information System (INIS)

Han, K.I.

1977-01-01

Preliminary investigations of a heterogeneous gas core reactor (HGCR) concept suggest that this potential power reactor offers distinct advantages over other existing or conceptual reactor power plants. One of the most favorable features of the HGCR is the flexibility of the power producing system which allows it to be efficiently designed to conform to a desired optimum condition without major conceptual changes. The arrangement of bundles of moderator/coolant channels in a fissionable gas or mixture of gases makes a truly heterogeneous nuclear reactor core. It is this full heterogeneity for a gas-fueled reactor core which accounts for the novelty of the heterogeneous gas core reactor concept and leads to noted significant advantages over previous gas core systems with respect to neutron and fuel economy, power density, and heat transfer characteristics. The purpose of this work is to provide an insight into the design, operating characteristics, and safety of a heterogeneous gas core reactor system. The studies consist mainly of neutronic, energetic and kinetic analyses of the power producing and conversion systems as a preliminary assessment of the heterogeneous gas core reactor concept and basic design. The results of the conducted research indicate a high potential for the heterogeneous gas core reactor system as an electrical power generating unit (either large or small), with an overall efficiency as high as 40 to 45%. The HGCR system is found to be stable and safe, under the conditions imposed upon the analyses conducted in this work, due to the inherent safety of ann expanding gaseous fuel and the intrinsic feedback effects of the gas and water coolant

Distribution of internal pressure around bony prominences: implications to deep tissue injury and effectiveness of intermittent electrical stimulation.

Science.gov (United States)

Solis, Leandro R; Liggins, Adrian; Uwiera, Richard R E; Poppe, Niek; Pehowich, Enid; Seres, Peter; Thompson, Richard B; Mushahwar, Vivian K

2012-08-01

The overall goal of this project is to develop interventions for the prevention of deep tissue injury (DTI), a form of pressure ulcers that originates in deep tissue around bony prominences. The present study focused on: (1) obtaining detailed measures of the distribution of pressure experienced by tissue around the ischial tuberosities, and (2) investigating the effectiveness of intermittent electrical stimulation (IES), a novel strategy for the prevention of DTI, in alleviating pressure in regions at risk of breakdown due to sustained loading. The experiments were conducted in adult pigs. Five animals had intact spinal cords and healthy muscles and one had a spinal cord injury that led to substantial muscle atrophy at the time of the experiment. A force-controlled servomotor was used to load the region of the buttocks to levels corresponding to 25%, 50% or 75% of each animal's body weight. A pressure transducer embedded in a catheter was advanced into the tissue to measure pressure along a three dimensional grid around the ischial tuberosity of one hind leg. For all levels of external loading in intact animals, average peak internal pressure was 2.01 ± 0.08 times larger than the maximal interfacial pressure measured at the level of the skin. In the animal with spinal cord injury, similar absolute values of internal pressure as that in intact animals were recorded, but the substantial muscle atrophy produced larger maximal interfacial pressures. Average peak internal pressure in this animal was 1.43 ± 0.055 times larger than the maximal interfacial pressure. Peak internal pressure was localized within a ±2 cm region medio-laterally and dorso-ventrally from the bone in intact animals and ±1 cm in the animal with spinal cord injury. IES significantly redistributed internal pressure, shifting the peak values away from the bone in spinally intact and injured animals. These findings provide critical information regarding the relationship between internal and

Thoracic hyperextension injury with complete “bony disruption” of the thoracic cage: Case report of a potentially life-threatening injury

Directory of Open Access Journals (Sweden)

Bailey James

2012-05-01

Full Text Available Abstract Background Severe chest wall injuries are potentially life-threatening injuries which require a standardized multidisciplinary management strategy for prevention of posttraumatic complications and adverse outcome. Case presentation We report the successful management of a 55-year old man who sustained a complete “bony disruption” of the thoracic cage secondary to an “all-terrain vehicle” roll-over accident. The injury pattern consisted of a bilateral “flail chest” with serial segmental rib fractures, bilateral hemo-pneumothoraces and pulmonary contusions, bilateral midshaft clavicle fractures, a displaced transverse sternum fracture with significant diastasis, and an unstable T9 hyperextension injury. After initial life-saving procedures, the chest wall injuries were sequentially stabilized by surgical fixation of bilateral clavicle fractures, locked plating of the displaced sternal fracture, and a two-level anterior spine fixation of the T9 hyperextension injury. The patient had an excellent radiological and physiological outcome at 6 months post injury. Conclusion Severe chest wall trauma with a complete “bony disruption” of the thoracic cage represents a rare, but detrimental injury pattern. Multidisciplinary management with a staged timing for addressing each of the critical injuries, represents the ideal approach for an excellent long-term outcome.

Investigation on generalized Variational Nodal Methods for heterogeneous nodes

International Nuclear Information System (INIS)

Wang, Yongping; Wu, Hongchun; Li, Yunzhao; Cao, Liangzhi; Shen, Wei

2017-01-01

Highlights: • We developed two heterogeneous nodal methods based on the Variational Nodal Method. • Four problems were solved to evaluate the two heterogeneous nodal methods. • The function expansion method is good at treating continuous-changing heterogeneity. • The finite sub-element method is good at treating discontinuous-changing heterogeneity. - Abstract: The Variational Nodal Method (VNM) is generalized for heterogeneous nodes and applied to four kinds of problems including Molten Salt Reactor (MSR) core problem with continuous cross section profile, Pressurized Water Reactor (PWR) control rod cusping effect problem, PWR whole-core pin-by-pin problem, and heterogeneous PWR core problem without fuel-coolant homogenization in each pin cell. Two approaches have been investigated for the treatment of the nodal heterogeneity in this paper. To concentrate on spatial heterogeneity, diffusion approximation was adopted for the angular variable in neutron transport equation. To provide demonstrative numerical results, the codes in this paper were developed in slab geometry. The first method, named as function expansion (FE) method, expands nodal flux by orthogonal polynomials and the nodal cross sections are also expressed as spatial depended functions. The second path, named as finite sub-element (FS) method, takes advantage of the finite-element method by dividing each node into numbers of homogeneous sub-elements and expanding nodal flux into the combination of linear sub-element trial functions. Numerical tests have been carried out to evaluate the ability of the two nodal (coarse-mesh) heterogeneous VNMs by comparing with the fine-mesh homogeneous VNM. It has been demonstrated that both heterogeneous approaches can handle heterogeneous nodes. The FE method is good at continuous-changing heterogeneity as in the MSR core problem, while the FS method is good at discontinuous-changing heterogeneity such as the PWR pin-by-pin problem and heterogeneous PWR core

Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes

Science.gov (United States)

Yang, Hui; Tang, Ming; Gross, Thilo

2015-08-01

One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes.

Science.gov (United States)

Yang, Hui; Tang, Ming; Gross, Thilo

2015-08-21

One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

The bony labyrinth of the middle Pleistocene Sima de los Huesos hominins (Sierra de Atapuerca, Spain).

Science.gov (United States)

Quam, Rolf; Lorenzo, Carlos; Martínez, Ignacio; Gracia-Téllez, Ana; Arsuaga, Juan Luis

2016-01-01

We performed 3D virtual reconstructions based on CT scans to study the bony labyrinth morphology in 14 individuals from the large middle Pleistocene hominin sample from the site of the Sima de los Huesos (SH) in the Sierra de Atapuerca in northern Spain. The Atapuerca (SH) hominins represent early members of the Neandertal clade and provide an opportunity to compare the data with the later in time Neandertals, as well as Pleistocene and recent humans more broadly. The Atapuerca (SH) hominins do not differ from the Neandertals in any of the variables related to the absolute and relative sizes and shape of the semicircular canals. Indeed, the entire Neandertal clade seems to be characterized by a derived pattern of canal proportions, including a relatively small posterior canal and a relatively large lateral canal. In contrast, one of the most distinctive features observed in Neandertals, the low placement of the posterior canal (i.e., high sagittal labyrinthine index), is generally not present in the Atapuerca (SH) hominins. This low placement is considered a derived feature in Neandertals and is correlated with a more vertical orientation of the ampullar line (LSCm  PPp), and third part of the facial canal (LSCm < FC3). Some variation is present within the Atapuerca (SH) sample, however, with a few individuals approaching the Neandertal condition more closely. In addition, the cochlear shape index in the Atapuerca (SH) hominins is low, indicating a reduction in the height of the cochlea. Although the phylogenetic polarity of this feature is less clear, the low shape index in the Atapuerca (SH) hominins may be a derived feature. Regardless, cochlear height subsequently increased in Neandertals. In contrast to previous suggestions, the expanded data in the present study indicate no difference across the genus Homo in the angle of inclination of the cochlear basal turn (COs < LSCm). Principal components analysis largely confirms these observations. While not

Bony integration of titanium implants with a novel bioactive calcium titanate (Ca4Ti3O10) surface treatment in a rabbit model.

Science.gov (United States)

Haenle, Maximilian; Lindner, Tobias; Ellenrieder, Martin; Willfahrt, Manfred; Schell, Hanna; Mittelmeier, Wolfram; Bader, Rainer

2012-10-01

Nowadays total joint replacement is an indispensable component of modern medicine. The surfaces characteristics of cementless prostheses may be altered to achieve an accelerated and enduring bony integration. Classic surface coatings bear the risk of loosening or flaking from the implant body. This risk is excluded by the chemical conversion of the naturally existing TiO(2) surface layer into calcium titanate. The aim of this experimental animal study was to investigate the bony integration of implants with a new calcium titanate surface (Ca(4)Ti(3)O(10)) compared with a conventional standard Ti6Al4V surface. Cylindrical implants, made of titanium alloy (Ti6Al4V) were implanted in both lateral femoral condyles of New Zealand white rabbits. In each animal, an implant with and without surface treatment was inserted in a blinded manner. Animals were sacrificed after 4, 12, and 36 weeks, respectively. The axial pull-off forces were determined for 25 animals using a universal testing machine (Zwick Z010, Ulm, Germany). Furthermore, a histological analysis of the bony integration of the implants was performed in 12 specimens. In general, the pull-off forces for untreated and treated implants increased with longer survival times of the rabbits. No significant difference could be shown after 4 weeks between treated and untreated implants. After 12 weeks, the treated implants revealed a statistical significant higher pull-off force. After 36 weeks, the pull-off forces for treated and untreated implants aligned again. Titanium implants treated with calcium titanate, may offer an interesting and promising implant surface modification for endoprosthetic implants. They might lead to an accelerated osseointegration of total hip and knee replacements. Copyright © 2012 Wiley Periodicals, Inc.

Effect of Heterogeneity of JSFR Fuel Assemblies to Power Distribution

International Nuclear Information System (INIS)

Takeda, Toshikazu; Shimazu, Yoichiro; Hibi, Koki; Fujimura, Koji

2013-01-01

Conclusion: 1) Strong heterogeneity of JSFR assemblies was successfully calculated by BACH. 2) Verification test of BACH: • Infinite assembly model; • Color set model; • Good agreement with Monte-Carlo results. 3) Core calculations 3 models for inner duct was used; inward model, outward model and homogeneous model. • k eff difference between the inward and out ward model → 0.3%Δk; • ~20% effect on flux and power distributions. Therefore, we have to pay careful attention for the location of inner duct in fuel loading of JSFR

Genetic variants influencing phenotypic variance heterogeneity.

Science.gov (United States)

Ek, Weronica E; Rask-Andersen, Mathias; Karlsson, Torgny; Enroth, Stefan; Gyllensten, Ulf; Johansson, Åsa

2018-03-01

Most genetic studies identify genetic variants associated with disease risk or with the mean value of a quantitative trait. More rarely, genetic variants associated with variance heterogeneity are considered. In this study, we have identified such variance single-nucleotide polymorphisms (vSNPs) and examined if these represent biological gene × gene or gene × environment interactions or statistical artifacts caused by multiple linked genetic variants influencing the same phenotype. We have performed a genome-wide study, to identify vSNPs associated with variance heterogeneity in DNA methylation levels. Genotype data from over 10 million single-nucleotide polymorphisms (SNPs), and DNA methylation levels at over 430 000 CpG sites, were analyzed in 729 individuals. We identified vSNPs for 7195 CpG sites (P mean DNA methylation levels. We further showed that variance heterogeneity between genotypes mainly represents additional, often rare, SNPs in linkage disequilibrium (LD) with the respective vSNP and for some vSNPs, multiple low frequency variants co-segregating with one of the vSNP alleles. Therefore, our results suggest that variance heterogeneity of DNA methylation mainly represents phenotypic effects by multiple SNPs, rather than biological interactions. Such effects may also be important for interpreting variance heterogeneity of more complex clinical phenotypes.

Intratumor and Intertumor Heterogeneity in Melanoma

Directory of Open Access Journals (Sweden)

Tomasz M. Grzywa

2017-12-01

Full Text Available Melanoma is a cancer that exhibits one of the most aggressive and heterogeneous features. The incidence rate escalates. A high number of clones harboring various mutations contribute to an exceptional level of intratumor heterogeneity of melanoma. It also refers to metastases which may originate from different subclones of primary lesion. Such component of the neoplasm biology is termed intertumor and intratumor heterogeneity. These levels of tumor heterogeneity hinder accurate diagnosis and effective treatment. The increasing number of research on the topic reflects the need for understanding limitation or failure of contemporary therapies. Majority of analyses concentrate on mutations in cancer-related genes. Novel high-throughput techniques reveal even higher degree of variations within a lesion. Consolidation of theories and researches indicates new routes for treatment options such as targets for immunotherapy. The demand for personalized approach in melanoma treatment requires extensive knowledge on intratumor and intertumor heterogeneity on the level of genome, transcriptome/proteome, and epigenome. Thus, achievements in exploration of melanoma variety are described in details. Particularly, the issue of tumor heterogeneity or homogeneity given BRAF mutations is discussed.

Molecular Fin Effect from Heterogeneous Self-Assembled Monolayer Enhances Thermal Conductance across Hard-Soft Interfaces.

Science.gov (United States)

Wei, Xingfei; Zhang, Teng; Luo, Tengfei

2017-10-04

Thermal transport across hard-soft interfaces is critical to many modern applications, such as composite materials, thermal management in microelectronics, solar-thermal phase transition, and nanoparticle-assisted hyperthermia therapeutics. In this study, we use equilibrium molecular dynamics (EMD) simulations combined with the Green-Kubo method to study how molecularly heterogeneous structures of the self-assembled monolayer (SAM) affect the thermal transport across the interfaces between the SAM-functionalized gold and organic liquids (hexylamine, propylamine and hexane). We focus on a practically synthesizable heterogeneous SAM featuring alternating short and long molecular chains. Such a structure is found to improve the thermal conductance across the hard-soft interface by 46-68% compared to a homogeneous nonpolar SAM. Through a series of further simulations and analyses, it is found that the root reason for this enhancement is the penetration of the liquid molecules into the spaces between the long SAM molecule chains, which increase the effective contact area. Such an effect is similar to the fins used in macroscopic heat exchanger. This "molecular fin" structure from the heterogeneous SAM studied in this work provides a new general route for enhancing thermal transport across hard-soft material interfaces.

On transport in formations of large heterogeneity scales

International Nuclear Information System (INIS)

Dagan, Gedeon

1990-01-01

It has been suggested that in transport through heterogeneous aquifers, the effective dispersivity increases with the travel distance, since plumes encounter heterogeneity of increasing scales. This conclusion is underlain, however, by the assumption of ergodicity. If the plume is viewed as made up of different particles, this means that these particles move independently from a statistical point of view. To satisfy ergodicity the solute body has to be of a much larger extent than heterogeneity scales. Thus, if the latter are increasing for ever and the solute body is finite, ergodicity cannot be obeyed. To demonstrate this thesis we relate to the two-dimensional heterogeneity associated with transmissivity variations in the horizontal plane. First, the effective dispersion coefficient is defined as half the rate of change of the expected value of the solute body second spatial moment relative to its centroid. Subsequently the asymptotic large time limit of dispersivity is evaluated in terms of the log transmissivity integral scale and of the dimensions of the initial solute body in the direction of mean flow and normal to it. It is shown that for a thin plume aligned with the mean flow the effective dispersivity is zero and the effect of heterogeneity is a slight and finite expansion determined solely by the solute body size. In the case of a solute body transverse to the mean flow the effective dispersivity is different from zero, but has a maximal value which is again dependent on the solute body size and not on the heterogeneity scale. It is concluded that from a theoretical standpoint and for the definition of dispersivity adopted here for non-ergodic conditions, the claim of ever-increasing dispersivity with travel distance is not valid for the scale of heterogeneity analyzed here. (Author) (21 refs., 6 figs.)

Heterogeneity of Rapid Sand Filters and Its Effect on Contaminant Transport and Nitrification Performance

DEFF Research Database (Denmark)

Lopato, Laure Rose; Galaj, Zofia; Delpont, Sébastien

2011-01-01

Laboratory and full-scale experiments were conducted to investigate the development and effect of heterogeneity caused by filter media nonuniformity, biofilm, particles, precipitates, and gas bubbles in rapid sand filters used for drinking-water treatment. Salt tracer experiments were conducted...

Effect of heterogeneity in a horizontal well with multiple fractures on the long term forecast in shale gas reservoirs

Energy Technology Data Exchange (ETDEWEB)

Nobakht, M.; Ambrose, R.; Clarkson, C.R. [Society of Petroleum Engineers (Canada)

2011-07-01

Multiple fracture horizontal wells (MFHWs) are the most popular type of method used for exploiting shale gas reservoirs. When analyzing MFHW's a homogeneous completion model is often used, but this rarely occurs in the field. This paper develops a hybrid method for forecasting MFHWs based on a heterogeneous completion and investigates the effect of completion heterogeneity on production forecasts. First, a current forecasting method for homogeneous completions was modified for heterogeneous completions. The new forecasting method was then validated using a numerical simulation. A relationship between Arps' hyperbolic decline exponent and the heterogeneity of a completion for a particular case was then developed. Lastly, a field case was analyzed to compare the impact of forecasting with and without taking a heterogeneous completion into consideration. Through analysis and simulations this paper found that the long-term forecast of MFHWs can be greatly impacted should heterogeneity of the completion be ignored.

The effect of heterogeneity on the character of density-driven natural convection of CO{sub 2} overlying a brine layer

Energy Technology Data Exchange (ETDEWEB)

Farajzadeh, R. [Shell International Exploration and Production, Houston, TX (United States); Ranganathan, P.; Zitha, P.L.J.; Bruining, J. [Delft Univ. of Technology, Delft (Netherlands)

2010-07-01

This paper investigated the effect of heterogeneity on the character of natural-convection flow of carbon dioxide (CO{sub 2}) in aquifers and on the dissolution rate of CO{sub 2} in brine, contributing to a better understanding of the effect of heterogeneity on CO{sub 2} mass transfer in aquifers, which is necessary for efficient storage of CO{sub 2} in aquifers. The aquifer permeability, which is in practice heterogeneous, largely governs the efficiency of mixing in density-driven natural convection. The aquifer's degree of permeability variance and the correlation length informs the character of flow-driven mixing processes. Numerical simulation was used to identify different flow regimes of a density-driven natural flow regime. Heterogeneous fields were generated using a spectral method that allows the use of power-law variograms. From the simulations it was observed that the rate of mass transfer of carbon dioxide (CO{sub 2}) into water is higher for heterogeneous media. The formulation of the physical model and related equations and the method for generating the permeability fields were described. The simulation results indicated that gravity-induced fingering is the dominant pattern in low heterogeneity, but fingering will not occur in realistic porous media. The results also showed that the permeability field structure dominates at moderate heterogeneity, and that the flow is dispersive at high heterogeneity when the correlation length of the field is small. Heterogeneous media facilitate a larger rate of CO{sub 2} dissolution than homogenous media, which means that the former can store larger volumes of CO{sub 2}. 49 refs., 3 tabs., 13 figs.

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

Science.gov (United States)

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

2016-01-26

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

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

Directory of Open Access Journals (Sweden)

Anne-Constance Franz

2016-01-01

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

Biology of Bony Fish Macrophages

Directory of Open Access Journals (Sweden)

Jordan W. Hodgkinson

2015-11-01

Full Text Available 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.

Biology of Bony Fish Macrophages.

Science.gov (United States)

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

2015-11-30

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.

A method to calculate the effect of heterogeneous composition on bundle power

Energy Technology Data Exchange (ETDEWEB)

Choi, Hang Bok [Korea Atomic Energy Research Institute, Taejon (Korea)

1998-09-01

In the DUPIC fuel cycle, the spent pressurized water reactor (PWR) fuel is used in a Canada deuterium uranium (CANDU) reactor. Depending on the initial condition and burnup history of PWR fuel, the DUPIC fuel composition varies accordingly. In order to see the effect of the fuel composition, a simple and fast method was developed and applied to the DUPIC fuel. This report discusses the method developed to predict the effect of heterogeneous fuel composition on the bundle power. (author). 3 refs., 5 tabs.

Page 1 Heterogeneous doping effects in KC-AlO composites 213 of ...

Indian Academy of Sciences (India)

Heterogeneous doping effects in KC-AlO composites 213 of Al-O in KCl at 500°C for three different sizes of Al-O particles (0-05, 0-3 and. 1-0 um). The figure shows that as the concentration of Al Os increases, the conductivity increases slowly initially, then rather rapidly before it peaks at a 45mol%. Al2O. Moreover, as the ...

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

Science.gov (United States)

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

Effects of heterogeneous wealth distribution on public cooperation with collective risk

Science.gov (United States)

Wang, Jing; Fu, Feng; Wang, Long

2010-07-01

The distribution of wealth among individuals in real society can be well described by the Pareto principle or “80-20 rule.” How does such heterogeneity in initial wealth distribution affect the emergence of public cooperation, when individuals, the rich and the poor, engage in a collective-risk enterprise, not to gain a profit but to avoid a potential loss? Here we address this issue by studying a simple but effective model based on threshold public goods games. We analyze the evolutionary dynamics for two distinct scenarios, respectively: one with fair sharers versus defectors and the other with altruists versus defectors. For both scenarios, particularly, we in detail study the dynamics of the population with dichotomic initial wealth—the rich versus the poor. Moreover, we demonstrate the possible steady compositions of the population and provide the conditions for stability of these steady states. We prove that in a population with heterogeneous wealth distribution, richer individuals are more likely to cooperate than poorer ones. Participants with lower initial wealth may choose to cooperate only if all players richer than them are cooperators. The emergence of pubic cooperation largely relies on rich individuals. Furthermore, whenever the wealth gap between the rich and the poor is sufficiently large, cooperation of a few rich individuals can substantially elevate the overall level of social cooperation, which is in line with the well-known Pareto principle. Our work may offer an insight into the emergence of cooperative behavior in real social situations where heterogeneous distribution of wealth among individual is omnipresent.

Effects of heterogeneous wealth distribution on public cooperation with collective risk.

Science.gov (United States)

Wang, Jing; Fu, Feng; Wang, Long

2010-07-01

The distribution of wealth among individuals in real society can be well described by the Pareto principle or "80-20 rule." How does such heterogeneity in initial wealth distribution affect the emergence of public cooperation, when individuals, the rich and the poor, engage in a collective-risk enterprise, not to gain a profit but to avoid a potential loss? Here we address this issue by studying a simple but effective model based on threshold public goods games. We analyze the evolutionary dynamics for two distinct scenarios, respectively: one with fair sharers versus defectors and the other with altruists versus defectors. For both scenarios, particularly, we in detail study the dynamics of the population with dichotomic initial wealth-the rich versus the poor. Moreover, we demonstrate the possible steady compositions of the population and provide the conditions for stability of these steady states. We prove that in a population with heterogeneous wealth distribution, richer individuals are more likely to cooperate than poorer ones. Participants with lower initial wealth may choose to cooperate only if all players richer than them are cooperators. The emergence of pubic cooperation largely relies on rich individuals. Furthermore, whenever the wealth gap between the rich and the poor is sufficiently large, cooperation of a few rich individuals can substantially elevate the overall level of social cooperation, which is in line with the well-known Pareto principle. Our work may offer an insight into the emergence of cooperative behavior in real social situations where heterogeneous distribution of wealth among individual is omnipresent.

Effect of capillary forces on immiscible two-phase flow in heterogeneous porous media

Energy Technology Data Exchange (ETDEWEB)

van Duijn, C.J.; Molenaar, J.; de Neef, M.J.

1994-12-31

We consider the one-dimensional two-phase flow including capillary effects through a heterogeneous porous medium. The heterogeneity is due to the spatial variation of the absolute permeability and the porosity. Both these quantities are assumed to be piecewise constant. At interfaces where the rock properties are discontinuous, we derive, by a regularization technique, conditions to match the values of the saturation on both sides. There are two conditions: a flux condition and an extended pressure condition. Applying these conditions we show that trapping of the wetting phase may occur near hetergeneities. To illustrate the behavior of the saturation we consider a time-dependent diffusion problem without convection, a stationary convection-diffusion problem, and the full time-dependent convection-diffusion problem (numerically). In particular the last two problems explicitly show the trapping behavior.

Heterogeneity and Networks

OpenAIRE

Goyal, S.

2018-01-01

This chapter shows that networks can have large and differentiated effects on behavior and then argues that social and economic pressures facilitate the formation of heterogenous networks. Thus networks can play an important role in understanding the wide diversity in human behaviour and in economic outcomes.

Engineering Microbial Metabolite Dynamics and Heterogeneity.

Science.gov (United States)

Schmitz, Alexander C; Hartline, Christopher J; Zhang, Fuzhong

2017-10-01

As yields for biological chemical production in microorganisms approach their theoretical maximum, metabolic engineering requires new tools, and approaches for improvements beyond what traditional strategies can achieve. Engineering metabolite dynamics and metabolite heterogeneity is necessary to achieve further improvements in product titers, productivities, and yields. Metabolite dynamics, the ensemble change in metabolite concentration over time, arise from the need for microbes to adapt their metabolism in response to the extracellular environment and are important for controlling growth and productivity in industrial fermentations. Metabolite heterogeneity, the cell-to-cell variation in a metabolite concentration in an isoclonal population, has a significant impact on ensemble productivity. Recent advances in single cell analysis enable a more complete understanding of the processes driving metabolite heterogeneity and reveal metabolic engineering targets. The authors present an overview of the mechanistic origins of metabolite dynamics and heterogeneity, why they are important, their potential effects in chemical production processes, and tools and strategies for engineering metabolite dynamics and heterogeneity. The authors emphasize that the ability to control metabolite dynamics and heterogeneity will bring new avenues of engineering to increase productivity of microbial strains. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intratumor and Intertumor Heterogeneity in Melanoma.

Science.gov (United States)

Grzywa, Tomasz M; Paskal, Wiktor; Włodarski, Paweł K

2017-12-01

Melanoma is a cancer that exhibits one of the most aggressive and heterogeneous features. The incidence rate escalates. A high number of clones harboring various mutations contribute to an exceptional level of intratumor heterogeneity of melanoma. It also refers to metastases which may originate from different subclones of primary lesion. Such component of the neoplasm biology is termed intertumor and intratumor heterogeneity. These levels of tumor heterogeneity hinder accurate diagnosis and effective treatment. The increasing number of research on the topic reflects the need for understanding limitation or failure of contemporary therapies. Majority of analyses concentrate on mutations in cancer-related genes. Novel high-throughput techniques reveal even higher degree of variations within a lesion. Consolidation of theories and researches indicates new routes for treatment options such as targets for immunotherapy. The demand for personalized approach in melanoma treatment requires extensive knowledge on intratumor and intertumor heterogeneity on the level of genome, transcriptome/proteome, and epigenome. Thus, achievements in exploration of melanoma variety are described in details. Particularly, the issue of tumor heterogeneity or homogeneity given BRAF mutations is discussed. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Green's Function and Stress Fields in Stochastic Heterogeneous Continua

Science.gov (United States)

Negi, Vineet

Many engineering materials used today are heterogenous in composition e.g. Composites - Polymer Matrix Composites, Metal Matrix Composites. Even, conventional engineering materials - metals, plastics, alloys etc. - may develop heterogeneities, like inclusions and residual stresses, during the manufacturing process. Moreover, these materials may also have intrinsic heterogeneities at a nanoscale in the form of grain boundaries in metals, crystallinity in amorphous polymers etc. While, the homogenized constitutive models for these materials may be satisfactory at a macroscale, recent studies of phenomena like fatigue failure, void nucleation, size-dependent brittle-ductile transition in polymeric nanofibers reveal a major play of micro/nanoscale physics in these phenomena. At this scale, heterogeneities in a material may no longer be ignored. Thus, this demands a study into the effects of various material heterogeneities. In this work, spatial heterogeneities in two material properties - elastic modulus and yield stress - have been investigated separately. The heterogeneity in the elastic modulus is studied in the context of Green's function. The Stochastic Finite Element method is adopted to get the mean statistics of the Green's function defined on a stochastic heterogeneous 2D infinite space. A study of the elastic-plastic transition in a domain having stochastic heterogenous yield stress was done using Mont-Carlo methods. The statistics for various stress and strain fields during the transition were obtained. Further, the effects of size of the domain and the strain-hardening rate on the stress fields during the heterogeneous elastic-plastic transition were investigated. Finally, a case is made for the role of the heterogenous elastic-plastic transition in damage nucleation and growth.

Relationship of Tree Stand Heterogeneity and Forest Naturalness

Directory of Open Access Journals (Sweden)

BARTHA, Dénes

2006-01-01

Full Text Available The aim of our study was to investigate if compositional (tree species richness andstructural (vertical structure, age-structure, patterns of canopy closure heterogeneity of the canopylayer is related to individual naturalness criteria and to overall forest naturalness at the stand scale. Thenaturalness values of the assessed criteria (tree species composition, tree stand structure, speciescomposition and structure of shrub layer and forest floor vegetation, dead wood, effects of game, sitecharacteristics showed similar behaviour when groups of stands with different heterogeneity werecompared, regardless of the studied aspect of canopy heterogeneity. The greatest difference was foundfor criteria describing the canopy layer. Composition and structure of canopy layer, dead wood andtotal naturalness of the stand differed significantly among the stand groups showing consistentlyhigher values from homogeneous to the most heterogeneous group. Naturalness of the compositionand structure of the shrub layer is slightly but significantly higher in stands with heterogeneous canopylayer. Regarding other criteria, significant differences were found only between the homogeneous andthe most heterogeneous groups, while groups with intermediate level of heterogeneity did not differsignificantly from one extreme. However, the criterion describing effects of game got lowernaturalness values in more heterogeneous stands. Naturalness of site characteristics did not differsignificantly among the groups except for when stands were grouped based on pattern of canopyclosure. From the practical viewpoint it is shown that purposeful forestry operations affecting thecanopy layer cause changes in compositional and structural characteristics of other layers as well as inoverall stand scale forest naturalness.

El epítome floreado de los comentarios de Caio Julio César de Carlos Bonyères

OpenAIRE

Fernández-Savater Martín, María Victoria; Conde Salazar, Matilde

2005-01-01

El presente estudio tiene como objetivo principal el examen del Epítome floreado de los Comentarii de Caio Iulio César, que escribió en castellano el francés Carlos de Bonyéres, a fin de intentar determinar sus fuentes y su posible relación con otros comentarios de la obra cesariana. Tras una lectura detenida, se comprueba que dicha obra es un resumen de la obra de César y no tiene similitud alguna con otros comentarios de César en castellano, en especial con los de Diego Gracián y Gabriel Si...

CT of the canine lumbosacral spine in extension - flexion rotation; part I: bony window

International Nuclear Information System (INIS)

Henninger, W.; Werner, G.

2002-01-01

The canine lumbosacral spine is examined radiographically in extended and flexed lateral position as well as ventrodorsally. Superimposition of bones hinders exact evaluation of the lumbosacral intervertebral foramen in case of cauda equina syndrome, especially when degenerative changes overlap. CT or MRI are more and more indicated to get reliable findings because myelography is not always of diagnostic value. For this study twelve dogs (7 German Shepherd dogs, 4 Cross-breds, and 1 Rottweiler) of different age and sex were taken which had been referred for CT examination of the lumbosacral area. Plain radiographs did not show abnormalities. The anaesthetized dogs were positioned in dorsal recumbency with the legs firstly extended and secondly flexed according to flexion-extension radiography. Slice thickness was 2 mm, the CT images were evaluated in both bony and soft tissue windows. Bony window easily showed vertebral bodies, vertebral canal, pedicles, vertebral laminae, and articular processes of L7 and S1. Median height of the vertebral canal did not change during extension or flexion at the level of L7 and the sacrum. Height and width of the intervertebral foramen and width of the interarcual foramen changed markedly from extension to flexion. Lateral recessus of the vertebral canal always could be observed as ventrolateral widening. In sagittal CT scans of the lumbosacral specimen of a normal German Shepherd dog cranial articular processes of the sacrum were detected to be responsible for maximum height or width of the intervertebral foramen. Evolving from the lateral recessus the intervertebral foramen was initially oval-shaped and got rounded and narrowed by the cranial articular process of the sacrum. Position and shape of the cranial articular processes of the sacrum were evaluated. Surface of the cranial articular processes of S1 were found even with articular spaces congruent, but some also appeared slightly concave or convex where incongruity of the

Bone fragment union and remodeling after arthroscopic bony bankart repair for traumatic anterior shoulder instability with a glenoid defect: influence on postoperative recurrence of instability.

Science.gov (United States)

Nakagawa, Shigeto; Ozaki, Ritsuro; Take, Yasuhiro; Mae, Tatsuo; Hayashida, Kenji

2015-06-01

Although good clinical outcomes have been reported after arthroscopic bony Bankart repair, the extent of bone union is still unclear. To investigate bone union after arthroscopic bony Bankart repair and its influence on postoperative recurrence of instability. Cohort study; Level of evidence, 3. Among 113 consecutive shoulders that underwent arthroscopic bony Bankart repair, postoperative evaluation of bone union by computed tomography (CT) was performed at various times in 81 shoulders. Bone union was investigated during 3 periods: 3 to 6 months postoperatively (first period), 7 to 12 months postoperatively (second period), and 13 months or more postoperatively (third period). The influence of the size of the preoperative glenoid defect and the size of the bone fragment on bone union was investigated, as well as the influence of bone union on postoperative recurrence of instability. In shoulders with bone union, bone fragment remodeling and changes in the glenoid defect size were also investigated. The bone union rate was 30.5% in the first period, 55.3% in the second period, and 84.6% in the third period. Among 53 shoulders with CT evaluation in the second period or later and follow-up for a minimum of 1 year, there was complete union in 33 shoulders (62.3%), partial union in 3 (5.7%), nonunion in 8 (15.1%), and no fragment on CT in 9 (17.0%). The complete union rate was 50% for 22 shoulders with small bone fragments (fragments (5%-10%), and 86.7% for 15 shoulders with large fragments (>10%). The recurrence rate for postoperative instability was only 6.1% for shoulders with complete union, while it was 50% for shoulders with partial union, nonunion, no fragment, and no fragment on CT. The recurrence rate was significantly higher (36.4%) in shoulders with small fragments, but it was significantly lower in shoulders with bone union. In shoulders with bone union, the bone fragment frequently became larger over time, while the size of the glenoid defect decreased

Efficiency effects of observed and unobserved heterogeneity: Evidence from Norwegian electricity distribution networks

International Nuclear Information System (INIS)

Growitsch, Christian; Jamasb, Tooraj; Wetzel, Heike

2012-01-01

Since the 1990s, efficiency and benchmarking analysis has increasingly been used in network utilities research and regulation. A recurrent concern is the effect of observable environmental factors that are beyond the influence of firms and unobserved factors that are not identifiable on measured cost and quality performance of firms. This paper analyses the effect of observed geographic and weather factors and unobserved heterogeneity on a set of 128 Norwegian electricity distribution utilities for the 2001–2004 period. We utilise data on 78 geographic and weather variables to identify real economic inefficiency while controlling for observed and unobserved heterogeneity. We use the Factor Analysis technique to reduce the number of environmental factors into few composite variables and to avoid the problem of multicollinearity. In order to identify firm-specific inefficiency, we then estimate a pooled version of the established stochastic frontier model of Aigner et al. (1977) and the recent true random effects model of Greene (2004; 2005a,b) without and with environmental variables. The results indicate that the observed environmental factors have a rather limited influence on the utilities' average efficiency and the efficiency rankings. Moreover, the difference between the average efficiency scores and the efficiency rankings among the pooled and the true random effects models imply that the type of SFA model used is highly influencing the efficiency estimates.

Orbital Tumors Excision without Bony Marginotomy under Local and General Anesthesia

Directory of Open Access Journals (Sweden)

Robert A. Goldberg

2014-01-01

Full Text Available To present our experience of removing middle to deep orbital tumors using a combination of minimally invasive soft tissue approaches, sometimes under local anesthesia. Methods. In this retrospective case series, 30 patients (13 males and 17 females underwent tumor removal through eyelid crease (17 eyes, conjunctival (nine eyes, lateral canthal (two eyes, and transcaruncular (two eyes approaches. All tumors were located in the posterior half of the orbit. Six cases were removed under monitored anesthesia care with local block, and 24 were under general anesthesia. Results. The median (range age and follow-up duration were 48.5 (31–87 years old and 24.5 (4–375 weeks, respectively. Visual acuity and ocular motility showed improvement or no significant change in all but one patient at the latest followup. Confirmed pathologies revealed cavernous hemangioma (15 cases, pleomorphic adenoma (5 cases, solitary fibrous tumor (4 cases, neurofibroma (2 cases, schwannoma (2 cases, and orbital varix (1 case. None of the patients experienced recurrence. Conclusions. Creating a bony marginotomy increases intraoperative exposure of the deep orbit but adds substantial time and morbidity. Benign orbital tumors can often be removed safely through small soft-tissue incisions, without bone removal and under local anesthesia.

Effect of droplet size on the droplet behavior on the heterogeneous surface

Energy Technology Data Exchange (ETDEWEB)

Choi, Ho Yeon; Son, Sung Wan; Ha, ManYeong [Pusan National University, Busan (Korea, Republic of); Park, Yong Gap [Pusan National University, Busan (Korea, Republic of)

2017-06-15

The characteristics of a three-dimensional hemispherical droplet on a heterogeneous surface were studied using the Lattice Boltzmann method (LBM). The hydrophilic surface has a hydrophobic part at the center. The hemispherical droplets are located at the center of the heterogeneous surface. According to the contact angles of hydrophilic and hydrophobic bottom surfaces, the droplet either separates or reaches a new equilibrium state. The separation time varies according to the change in droplet size, and it affects the status of droplet separation. The droplet separation behavior was investigated by analyzing the velocity vector around the phase boundary line. The shape and separation time of a droplet are determined by the contact angle of each surface. The speed of droplet separation increases as the difference in contact angle increases between the hydrophobic surface and hydrophilic surface. The separation status and the separation time of a droplet are also determined by the change of the droplet size. As the size of the droplet decreases, the effect of surface tension decreases, and the separation time of the droplet also decreases. On the other hand, as the droplet becomes larger, the effect of surface tension increases and the time required for the droplet to separate also increases.

Organizational heterogeneity of vertebrate genomes.

Science.gov (United States)

Frenkel, Svetlana; Kirzhner, Valery; Korol, Abraham

2012-01-01

Genomes of higher eukaryotes are mosaics of segments with various structural, functional, and evolutionary properties. The availability of whole-genome sequences allows the investigation of their structure as "texts" using different statistical and computational methods. One such method, referred to as Compositional Spectra (CS) analysis, is based on scoring the occurrences of fixed-length oligonucleotides (k-mers) in the target DNA sequence. CS analysis allows generating species- or region-specific characteristics of the genome, regardless of their length and the presence of coding DNA. In this study, we consider the heterogeneity of vertebrate genomes as a joint effect of regional variation in sequence organization superimposed on the differences in nucleotide composition. We estimated compositional and organizational heterogeneity of genome and chromosome sequences separately and found that both heterogeneity types vary widely among genomes as well as among chromosomes in all investigated taxonomic groups. The high correspondence of heterogeneity scores obtained on three genome fractions, coding, repetitive, and the remaining part of the noncoding DNA (the genome dark matter--GDM) allows the assumption that CS-heterogeneity may have functional relevance to genome regulation. Of special interest for such interpretation is the fact that natural GDM sequences display the highest deviation from the corresponding reshuffled sequences.

Organizational heterogeneity of vertebrate genomes.

Directory of Open Access Journals (Sweden)

Svetlana Frenkel

Full Text Available Genomes of higher eukaryotes are mosaics of segments with various structural, functional, and evolutionary properties. The availability of whole-genome sequences allows the investigation of their structure as "texts" using different statistical and computational methods. One such method, referred to as Compositional Spectra (CS analysis, is based on scoring the occurrences of fixed-length oligonucleotides (k-mers in the target DNA sequence. CS analysis allows generating species- or region-specific characteristics of the genome, regardless of their length and the presence of coding DNA. In this study, we consider the heterogeneity of vertebrate genomes as a joint effect of regional variation in sequence organization superimposed on the differences in nucleotide composition. We estimated compositional and organizational heterogeneity of genome and chromosome sequences separately and found that both heterogeneity types vary widely among genomes as well as among chromosomes in all investigated taxonomic groups. The high correspondence of heterogeneity scores obtained on three genome fractions, coding, repetitive, and the remaining part of the noncoding DNA (the genome dark matter--GDM allows the assumption that CS-heterogeneity may have functional relevance to genome regulation. Of special interest for such interpretation is the fact that natural GDM sequences display the highest deviation from the corresponding reshuffled sequences.

Continuous Trading Dynamically Effectively Complete Market with Heterogeneous Beliefs

DEFF Research Database (Denmark)

Qin, Zhenjiang

on the heterogeneous posterior variance of dividend throughout [0; T). The market populated with many time-additive exponential-utility investors is dynamically effectively complete, if investors are allowed to trade in only two long-lived securities continuously. The underlying mechanism is that these assumptions...... imply that the Pareto efficient individual consumption plans are measurable with respect to the aggregate consumption. Hence, I may not need a dynamically complete market to facilitate a Pareto efficient allocation of consumption, the securities only have to facilitate an allocation which is measurable...... a sufficient statistic for computation of the price of redundant dividend derivative and the equilibrium portfolios. The investors form their Pareto optimal trading strategies as if they intend to dynamically endogenously replicate the value of the dividend derivative....

A study on cell heterogeneity effects in the Monju core. Evaluation using the continuous energy Monte Carlo code MVP

International Nuclear Information System (INIS)

Morohashi, Yuko; Ishibashi, Junichi; Nishi, Hiroshi

2002-03-01

The criticality analysis of the MONJU initial critical core was conducted based on conventional methods developed by the JUPITER program. Effective cross sections were created, considering self-shielding effects, from the JAERI Fast Set (JFS-3-J3.2); group constants in 70 energy groups, which were processed from the Japanese Evaluated Nuclear Data Library (JENDL-3.2). These were used in the standard calculation method: a 3-Dimensional Hexagonal-Z whole core calculation by diffusion theory. This standard calculation, however, involves several approximations. The continuous neutron energy spectrum is divided into 70 discrete energy groups and continuous spatial coordinates are represented by assembly-wise spatial meshes. Original transport equations are solved by diffusion theory (isotropic scattering) approximation and fine structures in fuel assemblies, such as fuel pins or wrapper tubes, are processed into cell-wise homogeneous mixture. To improve the accuracy of the results, these approximations are compensated for by applying corresponding correction factors. Cell heterogeneity effects, among them, were evaluated to be 0.3-0.4% Δk/kk' by diffusion calculations based on the group constants, obtained by heterogeneous cell model calculations. This method, however, has the drawback that it assumes that there is no interdependency of the related approximations; energy grouping, diffusion approximation, etc. A study on cell heterogeneity effects has been conducted using the continuous energy Monte Carlo method to validate the adequacy of this non-interdependency assumption. As a result, cell heterogeneity effects slightly larger than those from conventional methods have been obtained: 0.54% Δk/kk' for the initial critical core, and 0.50% Δk/kk' for the initial full power core. Dependency on plutonium enrichment and fuel temperature has also been identified, which implies the dependency of the cell heterogeneity effects on the specific core conditions. Grouping

Heterogeneous computing with OpenCL

CERN Document Server

2013-01-01

Heterogeneous Computing with OpenCL teaches OpenCL and parallel programming for complex systems that may include a variety of device architectures: multi-core CPUs, GPUs, and fully-integrated Accelerated Processing Units (APUs) such as AMD Fusion technology. Designed to work on multiple platforms and with wide industry support, OpenCL will help you more effectively program for a heterogeneous future. Written by leaders in the parallel computing and OpenCL communities, this book will give you hands-on OpenCL experience to address a range of fundamental parallel algorithms. The authors explore memory spaces, optimization techniques, graphics interoperability, extensions, and debugging and profiling. Intended to support a parallel programming course, Heterogeneous Computing with OpenCL includes detailed examples throughout, plus additional online exercises and other supporting materials.

Quantification of heterogeneity observed in medical images

International Nuclear Information System (INIS)

Brooks, Frank J; Grigsby, Perry W

2013-01-01

There has been much recent interest in the quantification of visually evident heterogeneity within functional grayscale medical images, such as those obtained via magnetic resonance or positron emission tomography. In the case of images of cancerous tumors, variations in grayscale intensity imply variations in crucial tumor biology. Despite these considerable clinical implications, there is as yet no standardized method for measuring the heterogeneity observed via these imaging modalities. In this work, we motivate and derive a statistical measure of image heterogeneity. This statistic measures the distance-dependent average deviation from the smoothest intensity gradation feasible. We show how this statistic may be used to automatically rank images of in vivo human tumors in order of increasing heterogeneity. We test this method against the current practice of ranking images via expert visual inspection. We find that this statistic provides a means of heterogeneity quantification beyond that given by other statistics traditionally used for the same purpose. We demonstrate the effect of tumor shape upon our ranking method and find the method applicable to a wide variety of clinically relevant tumor images. We find that the automated heterogeneity rankings agree very closely with those performed visually by experts. These results indicate that our automated method may be used reliably to rank, in order of increasing heterogeneity, tumor images whether or not object shape is considered to contribute to that heterogeneity. Automated heterogeneity ranking yields objective results which are more consistent than visual rankings. Reducing variability in image interpretation will enable more researchers to better study potential clinical implications of observed tumor heterogeneity

Quantification of heterogeneity observed in medical images.

Science.gov (United States)

Brooks, Frank J; Grigsby, Perry W

2013-03-02

There has been much recent interest in the quantification of visually evident heterogeneity within functional grayscale medical images, such as those obtained via magnetic resonance or positron emission tomography. In the case of images of cancerous tumors, variations in grayscale intensity imply variations in crucial tumor biology. Despite these considerable clinical implications, there is as yet no standardized method for measuring the heterogeneity observed via these imaging modalities. In this work, we motivate and derive a statistical measure of image heterogeneity. This statistic measures the distance-dependent average deviation from the smoothest intensity gradation feasible. We show how this statistic may be used to automatically rank images of in vivo human tumors in order of increasing heterogeneity. We test this method against the current practice of ranking images via expert visual inspection. We find that this statistic provides a means of heterogeneity quantification beyond that given by other statistics traditionally used for the same purpose. We demonstrate the effect of tumor shape upon our ranking method and find the method applicable to a wide variety of clinically relevant tumor images. We find that the automated heterogeneity rankings agree very closely with those performed visually by experts. These results indicate that our automated method may be used reliably to rank, in order of increasing heterogeneity, tumor images whether or not object shape is considered to contribute to that heterogeneity. Automated heterogeneity ranking yields objective results which are more consistent than visual rankings. Reducing variability in image interpretation will enable more researchers to better study potential clinical implications of observed tumor heterogeneity.

Effects of ionization chamber construction on dose measurements in a heterogeneity

International Nuclear Information System (INIS)

Mauceri, T.; Kase, K.

1987-01-01

Traditionally, measurements have been made in heterogeneous phantoms to determine the factors which should be applied to dose calculations, when calculating a dose to a heterogeneous medium. Almost all measurements have relied on relatively thin-walled ion chambers, with no attempt to match ion chamber wall material to the measuring medium. The recent AAPM dosimetry protocol has established that a mismatch between ion chamber wall and phantom material can have an effect on dose measurement. To investigate the affect of this mismatch of ion chamber wall material to phantom material, two parallel-plate ion chambers were constructed. One ion chamber from solid water, for measurements in a solid water phantom and the other from plastic lung material, for measurements in a plastic lung material phantom. Correction factors measured by matching ion chamber to media were compared to correction factors measured by using a thin-walled cavity ion chamber with no regard for matching wall and media for cobalt-60, 6-, 10- and 20-MV photon beams. The results demonstrated that the matching of ion chamber to measuring media can be ignored, provided that a small, approximately tissue-equivalent, thin-walled ion chamber is used for measuring the correction factors

Surface fluxes in heterogeneous landscape

Energy Technology Data Exchange (ETDEWEB)

Bay Hasager, C

1997-01-01

The surface fluxes in homogeneous landscapes are calculated by similarity scaling principles. The methodology is well establish. In heterogeneous landscapes with spatial changes in the micro scale range, i e from 100 m to 10 km, advective effects are significant. The present work focus on these effects in an agricultural countryside typical for the midlatitudes. Meteorological and satellite data from a highly heterogeneous landscape in the Rhine Valley, Germany was collected in the large-scale field experiment TRACT (Transport of pollutants over complex terrain) in 1992. Classified satellite images, Landsat TM and ERS SAR, are used as basis for roughness maps. The roughnesses were measured at meteorological masts in the various cover classes and assigned pixel by pixel to the images. The roughness maps are aggregated, i e spatially averaged, into so-called effective roughness lengths. This calculation is performed by a micro scale aggregation model. The model solves the linearized atmospheric flow equations by a numerical (Fast Fourier Transform) method. This model also calculate maps of friction velocity and momentum flux pixel wise in heterogeneous landscapes. It is indicated how the aggregation methodology can be used to calculate the heat fluxes based on the relevant satellite data i e temperature and soil moisture information. (au) 10 tabs., 49 ills., 223 refs.

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

Science.gov (United States)

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

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

Science.gov (United States)

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

Thermal properties of heterogeneous fuels

International Nuclear Information System (INIS)

Staicu, D.; Beauvy, M.

1998-01-01

Fresh or irradiated nuclear fuels are composites or solid solutions more or less heterogeneous, and their thermal conductivities are strongly dependent on the microstructure. The effective thermal conductivities of these heterogeneous solids must be determined for the modelling of the behaviour under irradiation. Different methods (analytical or numerical) published in the literature can be used for the calculation of this effective thermal conductivity. They are analysed and discussed, but finally only few of them are really useful because the assumptions selected are often not compatible with the complex microstructures observed in the fuels. Numerical calculations of the effective thermal conductivity of various fuels based on the microstructure information provided in our laboratory by optical microscopy or electron micro-probe analysis images, have been done for the validation of these methods. The conditions necessary for accurate results on effective thermal conductivity through these numerical calculations are discussed. (author)

Oxalic acid as a heterogeneous ice nucleus in the upper troposphere and its indirect aerosol effect

Directory of Open Access Journals (Sweden)

B. Zobrist

2006-01-01

Full Text Available Heterogeneous ice freezing points of aqueous solutions containing various immersed solid dicarboxylic acids (oxalic, adipic, succinic, phthalic and fumaric have been measured with a differential scanning calorimeter. The results show that only the dihydrate of oxalic acid (OAD acts as a heterogeneous ice nucleus, with an increase in freezing temperature between 2 and 5 K depending on solution composition. In several field campaigns, oxalic acid enriched particles have been detected in the upper troposphere with single particle aerosol mass spectrometry. Simulations with a microphysical box model indicate that the presence of OAD may reduce the ice particle number density in cirrus clouds by up to ~50% when compared to exclusively homogeneous cirrus formation without OAD. Using the ECHAM4 climate model we estimate the global net radiative effect caused by this heterogeneous freezing to result in a cooling as high as −0.3 Wm−2.

A tomographic study of positional and bony changes in the temporomandibular joint following orthognathic surgery

International Nuclear Information System (INIS)

Song, Nam Kyu; Kim Min Suk; Koh, Kwang Joon

1992-01-01

The purpose of this study was to aid in the evaluation of prognosis of temporomandibular joint following orthognathic surgery. For this study, 20 patients (40 TMJ) who undergone orthognathic surgery were examined. Preoperative and postoperative tomograms of TMJ were taken. And the subjects were divided into 3 groups according to postoperative periods. The obtained results were as follows : 1. There were no significant differences between preoperative and postoperative changes in joint spaces in each group and between groups (P<0.05). 2. There were no significant differences between preoperative and postoperative ratio of joint spaces (P<0.05).3. There were no significant differences between preoperative and postoperative changes in the range of motion of condylar head (P<0.05). 4. The bony changes of condylar head were observed in 14 (35%) condyles (6 erosion, 2 flattening, 5 double contour, 1 osteophyte).

A tomographic study of positional and bony changes in the temporomandibular joint following orthognathic surgery

Energy Technology Data Exchange (ETDEWEB)

Song, Nam Kyu; Kim Min Suk; Koh, Kwang Joon [Dept. of Oral Radiology, College of Dentistry, Chonpook National University, Chonju (Korea, Republic of)

1992-08-15

The purpose of this study was to aid in the evaluation of prognosis of temporomandibular joint following orthognathic surgery. For this study, 20 patients (40 TMJ) who undergone orthognathic surgery were examined. Preoperative and postoperative tomograms of TMJ were taken. And the subjects were divided into 3 groups according to postoperative periods. The obtained results were as follows : 1. There were no significant differences between preoperative and postoperative changes in joint spaces in each group and between groups (P<0.05). 2. There were no significant differences between preoperative and postoperative ratio of joint spaces (P<0.05).3. There were no significant differences between preoperative and postoperative changes in the range of motion of condylar head (P<0.05). 4. The bony changes of condylar head were observed in 14 (35%) condyles (6 erosion, 2 flattening, 5 double contour, 1 osteophyte).

Large Sample Neutron Activation Analysis of Heterogeneous Samples

International Nuclear Information System (INIS)

Stamatelatos, I.E.; Vasilopoulou, T.; Tzika, F.

2018-01-01

A Large Sample Neutron Activation Analysis (LSNAA) technique was developed for non-destructive analysis of heterogeneous bulk samples. The technique incorporated collimated scanning and combining experimental measurements and Monte Carlo simulations for the identification of inhomogeneities in large volume samples and the correction of their effect on the interpretation of gamma-spectrometry data. Corrections were applied for the effect of neutron self-shielding, gamma-ray attenuation, geometrical factor and heterogeneous activity distribution within the sample. A benchmark experiment was performed to investigate the effect of heterogeneity on the accuracy of LSNAA. Moreover, a ceramic vase was analyzed as a whole demonstrating the feasibility of the technique. The LSNAA results were compared against results obtained by INAA and a satisfactory agreement between the two methods was observed. This study showed that LSNAA is a technique capable to perform accurate non-destructive, multi-elemental compositional analysis of heterogeneous objects. It also revealed the great potential of the technique for the analysis of precious objects and artefacts that need to be preserved intact and cannot be damaged for sampling purposes. (author)

Heterogeneous Rock Simulation Using DIP-Micromechanics-Statistical Methods

Directory of Open Access Journals (Sweden)

H. Molladavoodi

2018-01-01

Full Text Available Rock as a natural material is heterogeneous. Rock material consists of minerals, crystals, cement, grains, and microcracks. Each component of rock has a different mechanical behavior under applied loading condition. Therefore, rock component distribution has an important effect on rock mechanical behavior, especially in the postpeak region. In this paper, the rock sample was studied by digital image processing (DIP, micromechanics, and statistical methods. Using image processing, volume fractions of the rock minerals composing the rock sample were evaluated precisely. The mechanical properties of the rock matrix were determined based on upscaling micromechanics. In order to consider the rock heterogeneities effect on mechanical behavior, the heterogeneity index was calculated in a framework of statistical method. A Weibull distribution function was fitted to the Young modulus distribution of minerals. Finally, statistical and Mohr–Coulomb strain-softening models were used simultaneously as a constitutive model in DEM code. The acoustic emission, strain energy release, and the effect of rock heterogeneities on the postpeak behavior process were investigated. The numerical results are in good agreement with experimental data.

SU-E-J-24: Image-Guidance Using Cone-Beam CT for Stereotactic Body Radiotherapy (SBRT) of Lung Cancer Patients: Bony Alignment or Soft Tissue Alignment?

Science.gov (United States)

Wang, L; Turaka, A; Meyer, J; Spoka, D; Jin, L; Fan, J; Ma, C

2012-06-01

To assess the reliability of soft tissue alignment by comparing pre- and post-treatment cone-beam CT (CBCT) for image guidance in stereotactic body radiotherapy (SBRT) of lung cancers. Our lung SBRT procedures require all patients undergo 4D CT scan in order to obtain patient-specific target motion information through reconstructed 4D data using the maximum-intensity projection (MIP) algorithm. The internal target volume (ITV) was outlined directly from the MIP images and a 3-5 mm margin expansion was then applied to the ITV to create the PTV. Conformal treatment planning was performed on the helical images, to which the MIP images were fused. Prior to each treatment, CBCT was used for image guidance by comparing with the simulation CT and for patient relocalization based on the bony anatomy. Any displacement of the patient bony structure would be considered as setup errors and would be corrected by couch shifts. Theoretically, as the PTV definition included target internal motion, no further shifts other than setup corrections should be made. However, it is our practice to have treating physicians further check target localization within the PTV. Whenever the shifts based on the soft-tissue alignment (that is, target alignment) exceeded a certain value (e.g. 5 mm), a post-treatment CBCT was carried out to ensure that the tissue alignment is reliable by comparing between pre- and post-treatment CBCT. Pre- and post-CBCT has been performed for 7 patients so far who had shifts beyond 5 mm despite bony alignment. For all patients, post CBCT confirmed that the visualized target position was kept in the same position as before treatment after adjusting for soft-tissue alignment. For the patient population studied, it is shown that soft-tissue alignment is necessary and reliable in the lung SBRT for individual cases. © 2012 American Association of Physicists in Medicine.

Thermal inertia and surface heterogeneity on Mars

Science.gov (United States)

Putzig, Nathaniel E.

Thermal inertia derived from temperature observations is critical for understanding surface geology and assessing potential landing sites on Mars. Derivation methods generally assume uniform surface properties for any given observation. Consequently, horizontal heterogeneity and near-surface layering may yield apparent thermal inertia that varies with time of day and season. To evaluate the effects of horizontal heterogeneity, I modeled the thermal behavior of surfaces containing idealized material mixtures (dust, sand, duricrust, and rocks) and differing slope facets. These surfaces exhibit diurnal and seasonal variability in apparent thermal inertia of several 100 tiu, 1 even for components with moderately contrasting thermal properties. To isolate surface effects on the derived thermal inertia of Mars, I mapped inter- annual and seasonal changes in albedo and atmospheric dust opacity, accounting for their effects in a modified derivation algorithm. Global analysis of three Mars years of MGS-TES 2 data reveals diurnal and seasonal variations of ~200 tiu in the mid-latitudes and 600 tiu or greater in the polar regions. Correlation of TES results and modeled apparent thermal inertia of heterogeneous surfaces indicates pervasive surface heterogeneity on Mars. At TES resolution, the near-surface thermal response is broadly dominated by layering and is consistent with the presence of duricrusts over fines in the mid-latitudes and dry soils over ground ice in the polar regions. Horizontal surface mixtures also play a role and may dominate at higher resolution. In general, thermal inertia obtained from single observations or annually averaged maps may misrepresent surface properties. In lieu of a robust heterogeneous- surface derivation technique, repeat coverage can be used together with forward-modeling results to constrain the near-surface heterogeneity of Mars. 1 tiu == J m -2 K -1 s - 2 Mars Global Surveyor Thermal Emission Spectrometer

Spatial Heterogeneity of the Forest Canopy Scales with the Heterogeneity of an Understory Shrub Based on Fractal Analysis

Directory of Open Access Journals (Sweden)

Catherine K. Denny

2017-04-01

Full Text Available Spatial heterogeneity of vegetation is an important landscape characteristic, but is difficult to assess due to scale-dependence. Here we examine how spatial patterns in the forest canopy affect those of understory plants, using the shrub Canada buffaloberry (Shepherdia canadensis (L. Nutt. as a focal species. Evergreen and deciduous forest canopy and buffaloberry shrub presence were measured with line-intercept sampling along ten 2-km transects in the Rocky Mountain foothills of west-central Alberta, Canada. Relationships between overstory canopy and understory buffaloberry presence were assessed for scales ranging from 2 m to 502 m. Fractal dimensions of both canopy and buffaloberry were estimated and then related using box-counting methods to evaluate spatial heterogeneity based on patch distribution and abundance. Effects of canopy presence on buffaloberry were scale-dependent, with shrub presence negatively related to evergreen canopy cover and positively related to deciduous cover. The effect of evergreen canopy was significant at a local scale between 2 m and 42 m, while that of deciduous canopy was significant at a meso-scale between 150 m and 358 m. Fractal analysis indicated that buffaloberry heterogeneity positively scaled with evergreen canopy heterogeneity, but was unrelated to that of deciduous canopy. This study demonstrates that evergreen canopy cover is a determinant of buffaloberry heterogeneity, highlighting the importance of spatial scale and canopy composition in understanding canopy-understory relationships.

Targeting population heterogeneity for optimal cell factories

DEFF Research Database (Denmark)

Heins, Anna-Lena; Carlqvist, Magnus; Helmark, S.

the heterogeneity level of the population. To further investigate these phenomena and gain a deeper understanding of population heterogeneity, Saccharomyces cerevisiae growth reporter strains based on the expression of green fluorescent protein (GFP) were constructed which enabled us to perform single cell level...... analysis, and thereby created the possibility to map population heterogeneity. A factorial design with pH, glucose concentration and oxygen level was performed in batch cultivations using the growth reporter strains to evaluate the effect of those environmental factors on heterogeneity level and amount......To achieve an efficient production process, it is essential to optimize both the strain and the cultivation conditions. Traditionally, a microbial population has been considered homogeneous in optimization studies of fermentation processes. However, research has shown that a typical microbial...

An entropy approach to size and variance heterogeneity

NARCIS (Netherlands)

Balasubramanyan, L.; Stefanou, S.E.; Stokes, J.R.

2012-01-01

In this paper, we investigate the effect of bank size differences on cost efficiency heterogeneity using a heteroskedastic stochastic frontier model. This model is implemented by using an information theoretic maximum entropy approach. We explicitly model both bank size and variance heterogeneity

A carapace-like bony 'body tube' in an early triassic marine reptile and the onset of marine tetrapod predation.

Science.gov (United States)

Chen, Xiao-hong; Motani, Ryosuke; Cheng, Long; Jiang, Da-yong; Rieppel, Olivier

2014-01-01

Parahupehsuchus longus is a new species of marine reptile from the Lower Triassic of Yuan'an County, Hubei Province, China. It is unique among vertebrates for having a body wall that is completely surrounded by a bony tube, about 50 cm long and 6.5 cm deep, comprising overlapping ribs and gastralia. This tube and bony ossicles on the back are best interpreted as anti-predatory features, suggesting that there was predation pressure upon marine tetrapods in the Early Triassic. There is at least one sauropterygian that is sufficiently large to feed on Parahupehsuchus in the Nanzhang-Yuan'an fauna, together with six more species of potential prey marine reptiles with various degrees of body protection. Modern predators of marine tetrapods belong to the highest trophic levels in the marine ecosystem but such predators did not always exist through geologic time. The indication of marine-tetrapod feeding in the Nanzhang-Yuan'an fauna suggests that such a trophic level emerged for the first time in the Early Triassic. The recovery from the end-Permian extinction probably proceeded faster than traditionally thought for marine predators. Parahupehsuchus has superficially turtle-like features, namely expanded ribs without intercostal space, very short transverse processes, and a dorsal outgrowth from the neural spine. However, these features are structurally different from their turtle counterparts. Phylogeny suggests that they are convergent with the condition in turtles, which has a fundamentally different body plan that involves the folding of the body wall. Expanded ribs without intercostal space evolved at least twice and probably even more among reptiles.

A carapace-like bony 'body tube' in an early triassic marine reptile and the onset of marine tetrapod predation.

Directory of Open Access Journals (Sweden)

Xiao-hong Chen

Full Text Available Parahupehsuchus longus is a new species of marine reptile from the Lower Triassic of Yuan'an County, Hubei Province, China. It is unique among vertebrates for having a body wall that is completely surrounded by a bony tube, about 50 cm long and 6.5 cm deep, comprising overlapping ribs and gastralia. This tube and bony ossicles on the back are best interpreted as anti-predatory features, suggesting that there was predation pressure upon marine tetrapods in the Early Triassic. There is at least one sauropterygian that is sufficiently large to feed on Parahupehsuchus in the Nanzhang-Yuan'an fauna, together with six more species of potential prey marine reptiles with various degrees of body protection. Modern predators of marine tetrapods belong to the highest trophic levels in the marine ecosystem but such predators did not always exist through geologic time. The indication of marine-tetrapod feeding in the Nanzhang-Yuan'an fauna suggests that such a trophic level emerged for the first time in the Early Triassic. The recovery from the end-Permian extinction probably proceeded faster than traditionally thought for marine predators. Parahupehsuchus has superficially turtle-like features, namely expanded ribs without intercostal space, very short transverse processes, and a dorsal outgrowth from the neural spine. However, these features are structurally different from their turtle counterparts. Phylogeny suggests that they are convergent with the condition in turtles, which has a fundamentally different body plan that involves the folding of the body wall. Expanded ribs without intercostal space evolved at least twice and probably even more among reptiles.

Effects of farm heterogeneity and methods for upscaling on modelled nitrogen losses in agricultural landscapes

International Nuclear Information System (INIS)

Dalgaard, T.; Hutchings, N.; Dragosits, U.; Olesen, J.E.; Kjeldsen, C.; Drouet, J.L.; Cellier, P.

2011-01-01

The aim of this study is to illustrate the importance of farm scale heterogeneity on nitrogen (N) losses in agricultural landscapes. Results are exemplified with a chain of N models calculating farm-N balances and distributing the N-surplus to N-losses (volatilisation, denitrification, leaching) and soil-N accumulation/release in a Danish landscape. Possible non-linearities in upscaling are assessed by comparing average model results based on (i) individual farm level calculations and (ii) averaged inputs at landscape level. Effects of the non-linearities that appear when scaling up from farm to landscape are demonstrated. Especially in relation to ammonia losses the non-linearity between livestock density and N-loss is significant (p > 0.999), with around 20-30% difference compared to a scaling procedure not taking this non-linearity into account. A significant effect of farm type on soil N accumulation (p > 0.95) was also identified and needs to be included when modelling landscape level N-fluxes and greenhouse gas emissions. - Highlights: → Farm-N balances and the distribution on types of N-losses are modelled for 56 farms. → Farm type significantly affects N-losses and soil-N accumulation. → A non-linear relation between livestock density and ammonia loss is identified. → Approaches for upscaling from farm to landscape level are discussed. → Accounting farm heterogeneity is important when upscaling N-losses. - This study illustrates the importance of including non-linear effects of farm and landscape heterogeneity on the modelling and upscaling of farm nitrogen losses and greenhouse gas emissions in agricultural landscapes.

Effects of farm heterogeneity and methods for upscaling on modelled nitrogen losses in agricultural landscapes

Energy Technology Data Exchange (ETDEWEB)

Dalgaard, T., E-mail: tommy.dalgaard@agrsci.dk [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Hutchings, N. [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Dragosits, U. [CEH Edinburgh, Bush Estate, Penicuik, Midlothian EH26 0QB, Scotland (United Kingdom); Olesen, J.E.; Kjeldsen, C. [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Drouet, J.L.; Cellier, P. [INRA, UMR Environnement et Grandes Cultures, BP 01, 78850 Thiverval-Grignon (France)

2011-11-15

The aim of this study is to illustrate the importance of farm scale heterogeneity on nitrogen (N) losses in agricultural landscapes. Results are exemplified with a chain of N models calculating farm-N balances and distributing the N-surplus to N-losses (volatilisation, denitrification, leaching) and soil-N accumulation/release in a Danish landscape. Possible non-linearities in upscaling are assessed by comparing average model results based on (i) individual farm level calculations and (ii) averaged inputs at landscape level. Effects of the non-linearities that appear when scaling up from farm to landscape are demonstrated. Especially in relation to ammonia losses the non-linearity between livestock density and N-loss is significant (p > 0.999), with around 20-30% difference compared to a scaling procedure not taking this non-linearity into account. A significant effect of farm type on soil N accumulation (p > 0.95) was also identified and needs to be included when modelling landscape level N-fluxes and greenhouse gas emissions. - Highlights: > Farm-N balances and the distribution on types of N-losses are modelled for 56 farms. > Farm type significantly affects N-losses and soil-N accumulation. > A non-linear relation between livestock density and ammonia loss is identified. > Approaches for upscaling from farm to landscape level are discussed. > Accounting farm heterogeneity is important when upscaling N-losses. - This study illustrates the importance of including non-linear effects of farm and landscape heterogeneity on the modelling and upscaling of farm nitrogen losses and greenhouse gas emissions in agricultural landscapes.

Vaccination Games with Peer Effects in a Heterogeneous Hospital Worker Population

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Troy Tassier

2015-01-01

Full Text Available We develop a game theoretic model to analyze the Nash equilibrium of vaccine decisions in a hospital population with heterogeneous contacts. We use the model in conjunction with person-to-person contact data within a large university hospital. We simulate, using agent-based models, the probability of infection for various worker types in the data and use these probabilities to identify the Nash equilibrium vaccine choices of hospital workers. The analysis suggests that there may be large differences in vaccination rates among hospital worker groups. We extend the model to include peer effects within the game. The peer effects may create additional equilibria or may further cement existing equilibria depending on parameter values. Further, depending on the magnitude of the peer effects and the costs of infection and vaccination, peer effects may increase or decrease differences in worker group vaccination rates within the hospital.

Implante de biomateriais e a consolidação óssea em cadelas submetidas à ovariossalpingo-histerectomia Influence of biomaterials on the bony consolidation in spayed female dogs

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A.I. Roque-Rodriguez

2009-10-01

Full Text Available Avaliou-se a hidroxiapatita com alandronato e hidroxiapatita com colágeno na aceleração da consolidação óssea do rádio de cadelas adultas submetidas à ovariossalpingo-histerectomia (OSH. Utilizaram-se 14 cadelas adultas, distribuídas aleatoriamente em dois grupos: grupo-controle e grupo OSH (submetidas à OSH. Quatro meses após a OSH, as cadelas dos dois grupos foram submetidas à cirurgia para produção de uma falha óssea de 4mm de diâmetro nos terços distal e proximal do rádio. No terço distal do membro direito, foi utilizada a hidroxiapatita com alandronato e, no membro esquerdo, a hidroxiapatita com colágeno; no terço proximal, não se utilizou nenhum biomaterial. Houve retardo na consolidação das falhas ósseas nas cadelas submetidas à OSH comparadas com as não submetidas. A hidroxiapatita com alandronato acelerou o processo de reparação e, em todos os animais dos dois grupos, a densidade óssea foi significativamente maior no terço distal onde foi implantada. Os dois biomateriais apresentaram biocompatibilidade, constatada pela ausência de reação inflamatória ou outra reação indesejável.The hydroxyapatite with alendronate and hydroxyapatite with collagen were evaluated in the acceleration of the bony consolidation of adult spayed bitch radius. For that, 14 adult bitches were distributed in two groups (control and spayed. Four months after ovariohysterectomy, the groups were submitted to the surgery for production of a 4mm diameter bony flaw in the distal and proximal third regions of the radius. In the distal region of the right thoracic limb, hydroxyapatite with alendronate was used. In the distal region of the left thoracic limb, hydroxyapatite with collagen was used. Any biomaterial was used in proximal part of the limb. There was a retard in bony flaws consolidation in the spayed bitches. Hydroxyapatite with alendronate showed better result, since the place it was implanted considerably increased the

Unobserved heterogeneity in the power law nonhomogeneous Poisson process

International Nuclear Information System (INIS)

Asfaw, Zeytu Gashaw; Lindqvist, Bo Henry

2015-01-01

A study of possible consequences of heterogeneity in the failure intensity of repairable systems is presented. The basic model studied is the nonhomogeneous Poisson process with power law intensity function. When several similar systems are under observation, the assumption that the corresponding processes are independent and identically distributed is often questionable. In practice there may be an unobserved heterogeneity among the systems. The heterogeneity is modeled by introduction of unobserved gamma distributed frailties. The relevant likelihood function is derived, and maximum likelihood estimation is illustrated. In a simulation study we then compare results when using a power law model without taking into account heterogeneity, with the corresponding results obtained when the heterogeneity is accounted for. A motivating data example is also given. - Highlights: • Consequences of overlooking heterogeneity in similar repairable systems are studied. • Likelihood functions are established for power law NHPP w/ and w/o heterogeneity. • ML estimators for parameters of power law NHPP with heterogeneity are derived. • A simulation study shows the effects of heterogeneity and its ignorance in models

Specification of phase 3 benchmark (Hex-Z heterogeneous and burnup calculation)

International Nuclear Information System (INIS)

Kim, Y.I.

2002-01-01

During the second RCM of the IAEA Co-ordinated Research Project Updated Codes and Methods to Reduce the Calculational Uncertainties of the LMFR Reactivity Effects the following items were identified as important. Heterogeneity will affect absolute core reactivity. Rod worths could be considerably reduced by heterogeneity effects depending on their detailed design. Heterogeneity effects will affect the resonance self-shielding in the treatment of fuel Doppler, steel Doppler and sodium density effects. However, it was considered more important to concentrate on the sodium density effect in order to reduce the calculational effort required. It was also recognized that burnup effects will have an influence on fuel Doppler and sodium worths. A benchmark for the assessment of heterogeneity effect for Phase 3 was defined. It is to be performed for the Hex-Z model of the reactor only. No calculations will be performed for the R-Z model. For comparison with heterogeneous evaluations, the control rod worth will be calculated at the beginning of the equilibrium cycle, based on the homogeneous model. The definitions of rod raised and rod inserted for SHR are given, using the composition numbers

Effects of Heterogeneity in Residential Preferences on an Agent-Based Model of Urban Sprawl

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Daniel G. Brown

2006-06-01

Full Text Available The ability of agent-based models (ABMs to represent heterogeneity in the characteristics and behaviors of actors enables analyses about the implications of this heterogeneity for system behavior. The importance of heterogeneity in the specification of ABMs, however, creates new demands for empirical support. An earlier analysis of a survey of residential preferences within southeastern Michigan revealed seven groups of residents with similar preferences on similar characteristics of location. In this paper, we present an ABM that represents the process of residential development within an urban system and run it for a hypothetical pattern of environmental variation. Residential locations are selected by residential agents, who evaluate locations on the basis of preference for nearness to urban services, including jobs, aesthetic quality of the landscape, and their similarity to their neighbors. We populate our ABM with a population of residential preferences drawn from the survey results in five different ways: (1 preferences drawn at random; (2 equal preferences based on the mean from the entire survey sample; (3 preferences drawn from a single distribution, whose mean and standard deviation are derived from the survey sample; (4 equal preferences within each of seven groups, based on the group means; and (5 preferences drawn from distributions for each of seven groups, defined by group means and standard deviations. Model sensitivity analysis, based on multiple runs of our model under each case, revealed that adding heterogeneity to agents has a significant effect on model outcomes, measured by aggregate patterns of development sprawl and clustering.

Heterogeneity in Models of Electoral Choice

OpenAIRE

Rivers, Douglas

1983-01-01

Heterogeneity or the presence of a variety of decision rules in a population has usually been ignored in voting research. A method for handling heterogeneous preferences using rank order data is developed and applied to a simple issue-voting model. The estimated average effect of partisanship is substantially higher when the assumption of homogeneity is relaxed, though many self-identified partisans also use ideological criteria to evaluate candidates and many independents rely on partisan cr...

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

Science.gov (United States)

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.

Analytic Coarse-Mesh Finite-Difference Method Generalized for Heterogeneous Multidimensional Two-Group Diffusion Calculations

International Nuclear Information System (INIS)

Garcia-Herranz, Nuria; Cabellos, Oscar; Aragones, Jose M.; Ahnert, Carol

2003-01-01

In order to take into account in a more effective and accurate way the intranodal heterogeneities in coarse-mesh finite-difference (CMFD) methods, a new equivalent parameter generation methodology has been developed and tested. This methodology accounts for the dependence of the nodal homogeneized two-group cross sections and nodal coupling factors, with interface flux discontinuity (IFD) factors that account for heterogeneities on the flux-spectrum and burnup intranodal distributions as well as on neighbor effects.The methodology has been implemented in an analytic CMFD method, rigorously obtained for homogeneous nodes with transverse leakage and generalized now for heterogeneous nodes by including IFD heterogeneity factors. When intranodal mesh node heterogeneity vanishes, the heterogeneous solution tends to the analytic homogeneous nodal solution. On the other hand, when intranodal heterogeneity increases, a high accuracy is maintained since the linear and nonlinear feedbacks on equivalent parameters have been shown to be as a very effective way of accounting for heterogeneity effects in two-group multidimensional coarse-mesh diffusion calculations

Heterogeneity of Dutch rainfall

NARCIS (Netherlands)

Witter, J.V.

1984-01-01

Rainfall data for the Netherlands have been used in this study to investigate aspects of heterogeneity of rainfall, in particular local differences in rainfall levels, time trends in rainfall, and local differences in rainfall trend. The possible effect of urbanization and industrialization on the

Practical considerations of reservoir heterogeneities on SAGD projects

Energy Technology Data Exchange (ETDEWEB)

Baker, R.; Fong, C.; Li, T. [Epic Consulting Services Ltd., Calgary, AB (Canada); Bowes, C.; Toews, M. [Calgary Univ., AB (Canada)

2008-10-15

Significant emphasis has been placed on developing cost-effective strategies for the production of large heavy oil and bitumen reserves located in western Canada and around the world. An effective method that has been proven to be effective in this regard is steam-assisted gravity drainage (SAGD). However, determining the optimum and cost-effective strategy is a challenge to any SAGD reservoir. Average rock quality and reservoir heterogeneities have a significant impact on steam chamber development and the overall volumetric sweep. As well, the approach to SAGD simulation varies as heterogeneity changes. This paper examined two well pairs with different degrees of heterogeneity in the Surmont pilot project. The paper also addressed potential geological risk through analogy and the amount of heterogeneity that must be accounted for when developing a representative simulation. The paper provided background information on the Surmont pilot project, which consists of three horizontal SAGD well pairs in the Athabasca oil sands of northeast Alberta. The reservoir simulation model was then described. Results and conclusions were offered. It was concluded that careful production controls and strategy must be applied particular to the reservoir to ensure that the SAGD well pairs were capable of draining the mobilized oil. 5 refs., 1 tab., 25 figs.

Interphase thermodynamic bond in heterogeneous alloys: effects on alloy properties

International Nuclear Information System (INIS)

Savchenko, A.M.; Konovalov, Yu.V.; Yuferov, O.I.

2005-01-01

Inconsistency between a conventional thermodynamic description of alloys as a mechanical mixture of phases and a real alloys state as a common thermodynamic system in which there is a complicated physical-chemical phases interaction has been considered. It is supposed that in heterogeneous alloys (eutectic ones, for instance), so called interphase thermodynamic bond can become apparent due to a partial electron levels splitting under phase interaction. Thermodynamic description of phase equilibrium in alloys is proposed taking into account a thermodynamic bond for the system with phase diagram of eutectic type, and methods of the value of this bond estimation are presented. Experimental evidence (Al-Cu-Si, Al-Si-Mg-Cu, U-Mo + Al) of the effect of interphase thermodynamic bond on temperature and enthalpy of melting of alloys are produced as well as possibility of its effects on alloys electrical conduction, strength, heat and corrosion resistance is substantiated theoretically [ru

Allergy to fish collagen: Thermostability of collagen and IgE reactivity of patients' sera with extracts of 11 species of bony and cartilaginous fish

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Yukihiro Kobayashi

2016-10-01

Conclusions: The IgE reactivity of patients' sera to fish collagen in extracts was retained even when fish meat was treated by a high heating load. As for the fish collagen, the IgE reactivities to cartilaginous fish were lower than that to bony fish. Reducing IgE reactivity to fish meat using heat is difficult, and other modalities will be required to produce hypoallergenic fish meat.

Endoscopic Modified Medial Maxillectomy for Fungal Ball of the Hypoplastic Maxillary Sinus With Bony Hypertrophy.

Science.gov (United States)

Nomura, Kazuhiro; Ikushima, Hiroyuki; Ozawa, Daiki; Shimizu, Yuichi; Arakawa, Kazuya; Suzuki, Jun; Hidaka, Hiroshi; Katori, Yukio; Ohyama, Kenji

2018-05-01

Sinus fungal ball is defined as noninvasive chronic rhino-sinusitis with a clump of mold in the paranasal sinuses, typically affecting the maxillary sinus. Fairly good outcomes of endoscopic surgery have been reported where the ball is removed through the antrostomy. However, the affected sinus tends to have a smaller cavity and thicker bony walls. As such, it is often challenging to maintain a window size that is sufficient to control possible recurrence. The endoscopic modified medial maxillectomy procedure was applied to a 61-year old and a 70-year old female patient with maxillary sinus fungal ball. Using this method, we created a much larger inferior meatal antrostomy without difficulty. The window provided us with an endoscopic view of the whole sinus and complete eradication of the lesion. Endoscopic modified medial maxillectomy is useful as a surgical procedure for maxillary sinus fungal ball and should be considered for better outcomes.

Epidemic Spreading with Heterogeneous Awareness on Human Networks

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Yanling Lu

2017-01-01

Full Text Available The spontaneous awareness behavioral responses of individuals have a significant impact on epidemic spreading. In this paper, a modified Susceptible-Alert-Infected-Susceptible (SAIS epidemic model with heterogeneous awareness is presented to study epidemic spreading in human networks and the impact of heterogeneous awareness on epidemic dynamics. In this model, when susceptible individuals receive awareness information about the presence of epidemic from their infected neighbor nodes, they will become alert individuals with heterogeneous awareness rate. Theoretical analysis and numerical simulations show that heterogeneous awareness can enhance the epidemic threshold with certain conditions and reduce the scale of virus outbreaks compared with no awareness. What is more, for the same awareness parameter, it also shows that heterogeneous awareness can slow effectively the spreading size and does not delay the arrival time of epidemic spreading peak compared with homogeneous awareness.

Modeling the effects of space structure and combination therapies on phenotypic heterogeneity and drug resistance in solid tumors.

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Lorz, Alexander; Lorenzi, Tommaso; Clairambault, Jean; Escargueil, Alexandre; Perthame, Benoît

2015-01-01

Histopathological evidence supports the idea that the emergence of phenotypic heterogeneity and resistance to cytotoxic drugs can be considered as a process of selection in tumor cell populations. In this framework, can we explain intra-tumor heterogeneity in terms of selection driven by the local cell environment? Can we overcome the emergence of resistance and favor the eradication of cancer cells by using combination therapies? Bearing these questions in mind, we develop a model describing cell dynamics inside a tumor spheroid under the effects of cytotoxic and cytostatic drugs. Cancer cells are assumed to be structured as a population by two real variables standing for space position and the expression level of a phenotype of resistance to cytotoxic drugs. The model takes explicitly into account the dynamics of resources and anticancer drugs as well as their interactions with the cell population under treatment. We analyze the effects of space structure and combination therapies on phenotypic heterogeneity and chemotherapeutic resistance. Furthermore, we study the efficacy of combined therapy protocols based on constant infusion and bang-bang delivery of cytotoxic and cytostatic drugs.

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

Science.gov (United States)

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. (PsycINFO Database Record (c) 2007 APA, all rights reserved).

Symmetric wetting heterogeneity suppresses fluid displacement hysteresis in granular piles

Science.gov (United States)

Moosavi, R.; Schröter, M.; Herminghaus, S.

2018-02-01

We investigate experimentally the impact of heterogeneity on the capillary pressure hysteresis in fluid invasion of model porous media. We focus on symmetric heterogeneity, where the contact angles the fluid interface makes with the oil-wet (θ1) and the water-wet (θ2) beads add up to π . While enhanced heterogeneity is usually known to increase hysteresis phenomena, we find that hysteresis is greatly reduced when heterogeneities in wettability are introduced. On the contrary, geometric heterogeneity (like bidisperse particle size) does not lead to such an effect. We provide a qualitative explanation of this surprising result, resting on rather general geometric arguments.

Analysis of Surface Heterogeneity Effects with Mesoscale Terrestrial Modeling Platforms

Science.gov (United States)

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.

Heterogeneous network architectures

DEFF Research Database (Denmark)

Christiansen, Henrik Lehrmann

2006-01-01

is flexibility. This thesis investigates such heterogeneous network architectures and how to make them flexible. A survey of algorithms for network design is presented, and it is described how using heuristics can increase the speed. A hierarchical, MPLS based network architecture is described......Future networks will be heterogeneous! Due to the sheer size of networks (e.g., the Internet) upgrades cannot be instantaneous and thus heterogeneity appears. This means that instead of trying to find the olution, networks hould be designed as being heterogeneous. One of the key equirements here...... and it is discussed that it is advantageous to heterogeneous networks and illustrated by a number of examples. Modeling and simulation is a well-known way of doing performance evaluation. An approach to event-driven simulation of communication networks is presented and mixed complexity modeling, which can simplify...

La displasia cemento ósea florida y su diagnóstico diferencial The Florid cemento-bony dysplasia and the differential diagnosis

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Allan Ulisses Carvalho de Melo

2011-09-01

Full Text Available Las lesiones benignas fibro-óseas de los maxilares constituyen un grupo diverso de enfermedades con una característica histológica común: la sustitución de hueso normal por tejido compuesto de colágeno y fibroblastos, con cantidades variables de una sustancia mineral que puede ser de hueso, cemento o ambos. Estas lesiones incluyen la displasia fibrosa, la displasia cemento-ósea en sus variantes: periapical, focal o florida, el cementoma gigantiforme familiar y el fibroma osificante cemento-osificante. La osteomielitis es un proceso inflamatorio agudo o crónico de los espacios medulares o corticales del hueso, que se extiende más allá del sitio inicial de desenvolvimiento. La osteomielitis esclerosante difusa es más frecuente en adultos, principalmente en la mandíbula. Se presenta radiográficamente como una lesión radiopaca difusa adyacente a los dientes, que puede ser multifocal. El objetivo de este trabajo fue describir un caso inusual de lesión fibro-ósea, cuyo diagnóstico diferencial se hizo también con la osteomielitis de los maxilares. Se concluyó que las lesiones fibro-óseas benignas, presentaron muchas similitudes con respecto a sus aspectos clínicos, radiográficos e histológicos. Por lo tanto, es fundamental el análisis conjunto de estas informaciones para obtener un diagnóstico definitivo.The benign fibrous-bony lesions are a diverse group of diseases with common features: replacement of normal bone by tissue composed of collagen and fibroblasts, with variable amounts of a mineral substance that could be bone, cement or both. These lesions include the fibrous dysplasia, the periapical cement-bony dysplasia, focal or florid, familiar giant cementoma and ossifying fibroma (cement-ossifying. Osteomyelitis is an acute or chronic inflammatory process of medullar or cortical spaces of bone extending beyond the onset site of development. Diffuse sclerosing osteomyelitis involves to adults mainly the mandible and

Primary bony non-Hodgkin lymphoma of the cervical spine: a case report

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Sedrak Mark F

2010-02-01

Full Text Available Abstract Introduction Non-Hodgkin lymphoma primarily originating from the bone is exceedingly rare. To our knowledge, this is the first report of primary bone lymphoma presenting with progressive cord compression from an origin in the cervical spine. Herein, we discuss the unusual location in this case, the presenting symptoms, and the management of this disease. Case presentation We report on a 23-year-old Caucasian-American man who presented with two months of night sweats, fatigue, parasthesias, and progressive weakness that had progressed to near quadriplegia. Magnetic resonance (MR imaging demonstrated significant cord compression seen primarily at C7. Surgical management, with corpectomy and dorsal segmental fusion, in combination with adjuvant chemotherapy and radiation therapy, halted the progression of the primary disease and preserved neurological function. Histological analysis demonstrated an aggressive anaplastic large cell lymphoma. Conclusion Isolated primary bony lymphoma of the spine is exceedingly rare. As in our case, the initial symptoms may be the result of progressive cervical cord compression. Anterior corpectomy with posterolateral decompression and fusion succeeded in preventing progressive neurologic decline and maintaining quality of life. The reader should be aware of the unique presentation of this disease and that surgical management is a successful treatment strategy.

A Carapace-Like Bony ‘Body Tube’ in an Early Triassic Marine Reptile and the Onset of Marine Tetrapod Predation

Science.gov (United States)

Chen, Xiao-hong; Motani, Ryosuke; Cheng, Long; Jiang, Da-yong; Rieppel, Olivier

2014-01-01

Parahupehsuchus longus is a new species of marine reptile from the Lower Triassic of Yuan’an County, Hubei Province, China. It is unique among vertebrates for having a body wall that is completely surrounded by a bony tube, about 50 cm long and 6.5 cm deep, comprising overlapping ribs and gastralia. This tube and bony ossicles on the back are best interpreted as anti-predatory features, suggesting that there was predation pressure upon marine tetrapods in the Early Triassic. There is at least one sauropterygian that is sufficiently large to feed on Parahupehsuchus in the Nanzhang-Yuan’an fauna, together with six more species of potential prey marine reptiles with various degrees of body protection. Modern predators of marine tetrapods belong to the highest trophic levels in the marine ecosystem but such predators did not always exist through geologic time. The indication of marine-tetrapod feeding in the Nanzhang-Yuan’an fauna suggests that such a trophic level emerged for the first time in the Early Triassic. The recovery from the end-Permian extinction probably proceeded faster than traditionally thought for marine predators. Parahupehsuchus has superficially turtle-like features, namely expanded ribs without intercostal space, very short transverse processes, and a dorsal outgrowth from the neural spine. However, these features are structurally different from their turtle counterparts. Phylogeny suggests that they are convergent with the condition in turtles, which has a fundamentally different body plan that involves the folding of the body wall. Expanded ribs without intercostal space evolved at least twice and probably even more among reptiles. PMID:24718682

Effects of Heterogeneity and Uncertainties in Sources and Initial and Boundary Conditions on Spatiotemporal Variations of Groundwater Levels

Science.gov (United States)

Zhang, Y. K.; Liang, X.

2014-12-01

Effects of aquifer heterogeneity and uncertainties in source/sink, and initial and boundary conditions in a groundwater flow model on the spatiotemporal variations of groundwater level, h(x,t), were investigated. Analytical solutions for the variance and covariance of h(x, t) in an unconfined aquifer described by a linearized Boussinesq equation with a white noise source/sink and a random transmissivity field were derived. It was found that in a typical aquifer the error in h(x,t) in early time is mainly caused by the random initial condition and the error reduces as time goes to reach a constant error in later time. The duration during which the effect of the random initial condition is significant may last a few hundred days in most aquifers. The constant error in groundwater in later time is due to the combined effects of the uncertain source/sink and flux boundary: the closer to the flux boundary, the larger the error. The error caused by the uncertain head boundary is limited in a narrow zone near the boundary but it remains more or less constant over time. The effect of the heterogeneity is to increase the variation of groundwater level and the maximum effect occurs close to the constant head boundary because of the linear mean hydraulic gradient. The correlation of groundwater level decreases with temporal interval and spatial distance. In addition, the heterogeneity enhances the correlation of groundwater level, especially at larger time intervals and small spatial distances.

Identifying and quantifying heterogeneity in high content analysis: application of heterogeneity indices to drug discovery.

Directory of Open Access Journals (Sweden)

Albert H Gough

Full Text Available One of the greatest challenges in biomedical research, drug discovery and diagnostics is understanding how seemingly identical cells can respond differently to perturbagens including drugs for disease treatment. Although heterogeneity has become an accepted characteristic of a population of cells, in drug discovery it is not routinely evaluated or reported. The standard practice for cell-based, high content assays has been to assume a normal distribution and to report a well-to-well average value with a standard deviation. To address this important issue we sought to define a method that could be readily implemented to identify, quantify and characterize heterogeneity in cellular and small organism assays to guide decisions during drug discovery and experimental cell/tissue profiling. Our study revealed that heterogeneity can be effectively identified and quantified with three indices that indicate diversity, non-normality and percent outliers. The indices were evaluated using the induction and inhibition of STAT3 activation in five cell lines where the systems response including sample preparation and instrument performance were well characterized and controlled. These heterogeneity indices provide a standardized method that can easily be integrated into small and large scale screening or profiling projects to guide interpretation of the biology, as well as the development of therapeutics and diagnostics. Understanding the heterogeneity in the response to perturbagens will become a critical factor in designing strategies for the development of therapeutics including targeted polypharmacology.

A distributed scheduling algorithm for heterogeneous real-time systems

Science.gov (United States)

Zeineldine, Osman; El-Toweissy, Mohamed; Mukkamala, Ravi

1991-01-01

Much of the previous work on load balancing and scheduling in distributed environments was concerned with homogeneous systems and homogeneous loads. Several of the results indicated that random policies are as effective as other more complex load allocation policies. The effects of heterogeneity on scheduling algorithms for hard real time systems is examined. A distributed scheduler specifically to handle heterogeneities in both nodes and node traffic is proposed. The performance of the algorithm is measured in terms of the percentage of jobs discarded. While a random task allocation is very sensitive to heterogeneities, the algorithm is shown to be robust to such non-uniformities in system components and load.

Effect of porosity heterogeneity on the permeability and tortuosity of gas diffusion layers in polymer electrolyte membrane fuel cells

Science.gov (United States)

Nabovati, Aydin; Hinebaugh, James; Bazylak, Aimy; Amon, Cristina H.

2014-02-01

In this paper, we study the effect of porosity heterogeneity on the bulk hydrodynamic properties (permeability and tortuosity) of simulated gas diffusion layers (GDLs). The porosity distributions of the heterogeneous reconstructed samples are similar to those previously reported in the literature for Toray TGP-H 120™ GDLs. We use the lattice Boltzmann method to perform pore-level flow simulations in the reconstructed GDL samples. Using the results of pore-level simulations, the effect of porosity distribution is characterized on the predicted in- and cross-plane permeability and tortuosity. It was found that porosity heterogeneity causes a higher in-plane permeability and lower in-plane tortuosity, while the effect is opposite in the cross-plane direction, that is a lower cross-plane permeability and a higher cross-plane tortuosity. We further investigate the effect of adding poly-tetra-fluoro-ethylene (PTFE) & binder material to the reconstructed GDL samples. Three fiber volume percentages of 50, 75, and 100% are considered. Overall, increasing the fiber volume percentage reduces the predicted in- and cross-plane permeability and tortuosity values. A previously reported relationship for permeability of fibrous materials is fitted to the predicted permeability values, and the magnitude of the fitting parameter is reported as a function of fiber volume percentage.

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

Directory of Open Access Journals (Sweden)

T. Fauchez

2017-07-01

Full Text Available 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

Dynamic heterogeneity in life histories

DEFF Research Database (Denmark)

Tuljapurkar, Shripad; Steiner, Uli; Orzack, Steven Hecht

2009-01-01

or no fixed heterogeneity influences this trait. We propose that dynamic heterogeneity provides a 'neutral' model for assessing the possible role of unobserved 'quality' differences between individuals. We discuss fitness for dynamic life histories, and the implications of dynamic heterogeneity...... generate dynamic heterogeneity: life-history differences produced by stochastic stratum dynamics. We characterize dynamic heterogeneity in a range of species across taxa by properties of the Markov chain: the entropy, which describes the extent of heterogeneity, and the subdominant eigenvalue, which...... distributions of lifetime reproductive success. Dynamic heterogeneity contrasts with fixed heterogeneity: unobserved differences that generate variation between life histories. We show by an example that observed distributions of lifetime reproductive success are often consistent with the claim that little...

Probing Mantle Heterogeneity Across Spatial Scales

Science.gov (United States)

Hariharan, A.; Moulik, P.; Lekic, V.

2017-12-01

Inferences of mantle heterogeneity in terms of temperature, composition, grain size, melt and crystal structure may vary across local, regional and global scales. Probing these scale-dependent effects require quantitative comparisons and reconciliation of tomographic models that vary in their regional scope, parameterization, regularization and observational constraints. While a range of techniques like radial correlation functions and spherical harmonic analyses have revealed global features like the dominance of long-wavelength variations in mantle heterogeneity, they have limited applicability for specific regions of interest like subduction zones and continental cratons. Moreover, issues like discrepant 1-D reference Earth models and related baseline corrections have impeded the reconciliation of heterogeneity between various regional and global models. We implement a new wavelet-based approach that allows for structure to be filtered simultaneously in both the spectral and spatial domain, allowing us to characterize heterogeneity on a range of scales and in different geographical regions. Our algorithm extends a recent method that expanded lateral variations into the wavelet domain constructed on a cubed sphere. The isolation of reference velocities in the wavelet scaling function facilitates comparisons between models constructed with arbitrary 1-D reference Earth models. The wavelet transformation allows us to quantify the scale-dependent consistency between tomographic models in a region of interest and investigate the fits to data afforded by heterogeneity at various dominant wavelengths. We find substantial and spatially varying differences in the spectrum of heterogeneity between two representative global Vp models constructed using different data and methodologies. Applying the orthonormality of the wavelet expansion, we isolate detailed variations in velocity from models and evaluate additional fits to data afforded by adding such complexities to long

Transient well flow in vertically heterogeneous aquifers

Science.gov (United States)

Hemker, C. J.

1999-11-01

A solution for the general problem of computing well flow in vertically heterogeneous aquifers is found by an integration of both analytical and numerical techniques. The radial component of flow is treated analytically; the drawdown is a continuous function of the distance to the well. The finite-difference technique is used for the vertical flow component only. The aquifer is discretized in the vertical dimension and the heterogeneous aquifer is considered to be a layered (stratified) formation with a finite number of homogeneous sublayers, where each sublayer may have different properties. The transient part of the differential equation is solved with Stehfest's algorithm, a numerical inversion technique of the Laplace transform. The well is of constant discharge and penetrates one or more of the sublayers. The effect of wellbore storage on early drawdown data is taken into account. In this way drawdowns are found for a finite number of sublayers as a continuous function of radial distance to the well and of time since the pumping started. The model is verified by comparing results with published analytical and numerical solutions for well flow in homogeneous and heterogeneous, confined and unconfined aquifers. Instantaneous and delayed drainage of water from above the water table are considered, combined with the effects of partially penetrating and finite-diameter wells. The model is applied to demonstrate that the transient effects of wellbore storage in unconfined aquifers are less pronounced than previous numerical experiments suggest. Other applications of the presented solution technique are given for partially penetrating wells in heterogeneous formations, including a demonstration of the effect of decreasing specific storage values with depth in an otherwise homogeneous aquifer. The presented solution can be a powerful tool for the analysis of drawdown from pumping tests, because hydraulic properties of layered heterogeneous aquifer systems with

Effects of solution viscosity on heterogeneous electron transfer across a liquid/liquid interface

Energy Technology Data Exchange (ETDEWEB)

Bai Yamin; Sun Peng; Zhang Meiqin; Gao Zhao; Yang Zhengyu; Shao Yuanhua

2003-10-15

Scanning electrochemical microscopy (SECM) is employed to investigate the effect of solution viscosity on the rate constants of electron transfer (ET) reaction between potassium ferricyanide in water and 7,7,8,8-tetracyanoquinodimethane (TCNQ) in 1,2-dichloroethane. Either tetrabutylammonium (TBA{sup +}) or ClO{sub 4}{sup -} is chosen as the common ion in both phases to control the interfacial potential drop. The rate constant of heterogeneous ET reaction between TCNQ and ferrocyanide produced in-situ, k{sub 12}, is evaluated by SECM and is inversely proportional to the viscosity of the aqueous solution and directly proportional to the diffusion coefficient of K{sub 4}Fe(CN){sub 6} in water when the concentration of TCNQ in the DCE phase is in excess. The k{sub 12} dependence on viscosity is explained in terms of the longitudinal relaxation time of the solution. The rate constant of the heterogeneous ET reaction between TCNQ{sup -} and ferricyanide, k{sub 21}, is also obtained by SECM and these results cannot be explained by the same manner.

Heterogeneity in the response to gasoline prices: Evidence from Pennsylvania and implications for the rebound effect

International Nuclear Information System (INIS)

Gillingham, Kenneth; Jenn, Alan; Azevedo, Inês M.L.

2015-01-01

The consumer response to changing gasoline prices has long interested economists and policymakers, for it has important implications for the effects of gasoline taxation and vehicle energy efficiency policies. This study examines both the elasticity of driving with respect to changing gasoline prices and heterogeneity in this elasticity by geography, the fuel economy of the vehicle, and the age of the vehicle. We use detailed annual vehicle-level emissions inspection test data from Pennsylvania that include odometer readings, inspection zip codes, and extensive vehicle characteristics. We estimate a short-run gasoline price elasticity of driving demand of − 0.10, and find substantial heterogeneity in this responsiveness. The elasticity is largely driven by low fuel economy vehicles, as well as vehicles between 3 and 7 years old. Our findings help reconcile some of the recent literature and provide guidance on the magnitude of the direct rebound effect from light duty vehicle energy efficiency policies.

Wetting at the nanometer scale: effects of long-range forces and substrate heterogeneities

International Nuclear Information System (INIS)

Checco, Antonio

2003-01-01

Wetting phenomena on the nano-scale remain poorly understood in spite of their growing theoretical and practical interest. In this context, the present work aimed at studying partial wetting of nanometer-sized alkane droplets on 'model' surfaces build by self-assembly of organic monolayers. For this purpose a novel technique, based on 'noncontact' Atomic Force Microscopy (AFM), has been developed to image, with minimal artefacts, drops of adjustable size directly condensed on so- lid surfaces. We have thus shown that contact angle of alkanes, wetting a weakly heterogeneous, silanized substrate, noticeably decreases from its macroscopic value for droplets sizes in the submicron range. The line tension, arising in this case from purely dispersive long-range interactions between the liquid and the substrate, is theoretically too weak to be responsible for the observed effect. Therefore we have supposed that contact angle is affected by mesoscopic chemical heterogeneities of the substrate whenever the droplets size becomes sufficiently small. This scenario has been supported by numerical simulations based on a simplified model of the spatial distribution of surface defects. Similar experiments, performed on different substrates (monolayers made of alkane-thiols self-assembled on gold and of alkyl chains covalently bound onto a silicon surface), have also shown that wetting on small scales is strongly affected by minimal physical and chemical surface heterogeneities. Finally, to provide further examples of the potential of the above mentioned AFM technique, we have studied the wettability of nano-structured surfaces and the local wetting properties of hair. (author) [fr

Forensic age estimation by magnetic resonance imaging of the knee: the definite relevance in bony fusion of the distal femoral- and the proximal tibial epiphyses using closest-to-bone T1 TSE sequence

Energy Technology Data Exchange (ETDEWEB)

Ottow, Christian; Heindel, Walter [University Hospital Muenster, Department of Clinical Radiology, Muenster (Germany); Schulz, Ronald; Pfeiffer, Heidi; Schmeling, Andreas [University Hospital Muenster, Institute of Legal Medicine, Muenster (Germany); Vieth, Volker [University Hospital Muenster, Department of Clinical Radiology, Muenster (Germany); Klinikum Ibbenbueren, Clinic for Radiology, Ibbenbueren (Germany)

2017-12-15

To clarify the relevance of the bony fusion of the distal femoral and the proximal tibial epiphyses by means of magnetic resonance imaging (MRI), a prospective cross-sectional cohort study was performed with a special focus on a reliable determination of the 14th, 16th and 18th years of life. We scanned 658 German volunteers in the age bracket 12-24 years using a 3.0 T MR-scanner and utilising a T1 turbo spin-echo sequence representing true bone anatomy. Minimum, maximum, mean ± standard deviation and median with lower and upper quartiles were defined. Intra- and interobserver agreements were determined (Cohen's kappa). The statistical relevance of sex-related differences was analysed (Mann-Whitney U test, p < 0.05, exact, two-sided). The bony fusion took place before the 18th year of life in both epiphyses. The Mann-Whitney U test results imply significant sex-related differences for most stages. For both epiphyses, the intra observer (κ femur 0.961; tibia 0.971) and interobserver (κ femur 0.941; tibia 0.951) agreement levels were very good. The 14th and the 16th years of life can be determined in both sexes, but the completion of the 18th year of life cannot solely be determined by the bony fusion, as depicted by closest-to-bone MRI. (orig.)

Forensic age estimation by magnetic resonance imaging of the knee: the definite relevance in bony fusion of the distal femoral- and the proximal tibial epiphyses using closest-to-bone T1 TSE sequence

International Nuclear Information System (INIS)

Ottow, Christian; Heindel, Walter; Schulz, Ronald; Pfeiffer, Heidi; Schmeling, Andreas; Vieth, Volker

2017-01-01

To clarify the relevance of the bony fusion of the distal femoral and the proximal tibial epiphyses by means of magnetic resonance imaging (MRI), a prospective cross-sectional cohort study was performed with a special focus on a reliable determination of the 14th, 16th and 18th years of life. We scanned 658 German volunteers in the age bracket 12-24 years using a 3.0 T MR-scanner and utilising a T1 turbo spin-echo sequence representing true bone anatomy. Minimum, maximum, mean ± standard deviation and median with lower and upper quartiles were defined. Intra- and interobserver agreements were determined (Cohen's kappa). The statistical relevance of sex-related differences was analysed (Mann-Whitney U test, p < 0.05, exact, two-sided). The bony fusion took place before the 18th year of life in both epiphyses. The Mann-Whitney U test results imply significant sex-related differences for most stages. For both epiphyses, the intra observer (κ femur 0.961; tibia 0.971) and interobserver (κ femur 0.941; tibia 0.951) agreement levels were very good. The 14th and the 16th years of life can be determined in both sexes, but the completion of the 18th year of life cannot solely be determined by the bony fusion, as depicted by closest-to-bone MRI. (orig.)

Renewal-anomalous-heterogeneous files

International Nuclear Information System (INIS)

Flomenbom, Ophir

2010-01-01

Renewal-anomalous-heterogeneous files are solved. A simple file is made of Brownian hard spheres that diffuse stochastically in an effective 1D channel. Generally, Brownian files are heterogeneous: the spheres' diffusion coefficients are distributed and the initial spheres' density is non-uniform. In renewal-anomalous files, the distribution of waiting times for individual jumps is not exponential as in Brownian files, yet obeys: ψ α (t)∼t -1-α , 0 2 >, obeys, 2 >∼ 2 > nrml α , where 2 > nrml is the MSD in the corresponding Brownian file. This scaling is an outcome of an exact relation (derived here) connecting probability density functions of Brownian files and renewal-anomalous files. It is also shown that non-renewal-anomalous files are slower than the corresponding renewal ones.

Musculo-nasomucosal unit with complete lateral bony freeing and medial rotation for ideal C-shape restoration and retropositioning of the levator veli palatini.

Science.gov (United States)

El-Shazly, Mohamed

2012-11-01

No definitive procedure for cleft repair has been identified yet as the gold standard. Accordingly, this work tried to appraise the hypothesis that if the bony detachment and full retropositioning of the levator veli palatini muscle can ideally present an anatomical C-shape muscular sling restoration and if this is accompanied with pushback palatoplasty, would this present a better result in terms of tissue fistulation and phonetic impairment? A series of 74 different degrees of palatal clefts were operated by pushback palatoplasty combined with a modified approach of the levator vili palatini. This muscle was dissected only from the oral mucosa while kept attached to the nasal one as a musculo-nasomucosal unit. This unit was completely detached from the bony margin of the hard palate and then medially rotated and retropositioned in a typical C-shape mobile sling. Evaluations included suture line assessment and fistula development, and following the child's need for speech therapy. There were no intraoperative complications. Definite anterior fistulae with nasal air and foot leakage were observed in 2 cases. Four cases had postoperative velopharyngeal incompetence with a need for speech therapy. Tension-free closure, lower risk of fistula, good restoration of velopharyngeal functions, ability to be performed on all cleft types, ability to provide a good intraoperative exposure, and being a single stage seem to be the most important advantages of this unpublished technique.

A dose-response relationship for time to bone pain resolution after stereotactic body radiotherapy (SBRT) for renal cell carcinoma (RCC) bony metastases

Energy Technology Data Exchange (ETDEWEB)

Jhaveri, Pavan M. [Dept. of Radiology, Section of Radiation Oncology, Baylor College of Medicine, Houston (United States); Teh, Bin S.; Paulino, Arnold C.; Blanco, Angel I.; Butler, E. Brian [Dept. of Radiation Oncology, The Methodist Hospital/The Methodist Hospital Research Inst., Houston (United States)], email: bteh@tmhs.org; Lo, Simon S. [Dept. of Radiation Oncology, Univ. Hospitals Seidman Cancer Center, Case Western Reserve Univ., Cleveland (United States); Amato, Robert J. [Dept. of Internal Medicine, Div. of Oncology, Univ. of Texas Health Sciences Center, Houston (United States)

2012-05-15

Background. To investigate the utility of stereotactic body radiotherapy (SBRT) in the treatment of painful renal cell carcinoma (RCC) bone metastases, and for a possible dose effect on time to symptom relief. Material and methods. Eighteen patients with 24 painful osseous lesions from metastatic RCC were treated with SBRT. The most common treatment regimens were 24 Gy in 3 fractions and 40 Gy in 5 fractions. The times from treatment to first reported pain relief and time to symptom recurrence were evaluated. Median follow-up was 38 weeks (1-156 weeks). Results. Seventy-eight percent of all patients had pain relief. Patients treated with a BED > 85 Gy achieved faster and more durable pain relief compared to those treated with a BED < 85 Gy. There was decrease in time to pain relief after a change in treatment regimen to 8 Gy x 5 fractions (BED = 86). There was only one patient with grade 1 skin toxicity. No neurological or other toxicity was observed. Conclusions. SBRT can safely and effectively treat painful RCC bony metastases. There appears to be a relationship between radiation dose and time to stable pain relief.

Effects of the Heterogeneity in the Electron Beam Welded Joint on Mechanical Properties of Ti6Al4V Alloy

Science.gov (United States)

Liu, Jing; Gao, Xiao-Long; Zhang, Lin-Jie; Zhang, Jian-Xun

2015-01-01

The aim of this investigation was to evaluate the effect of microstructure heterogeneity on the tensile and low cycle fatigue properties of electron beam welded (EBW) Ti6Al4V sheets. To achieve this goal, the tensile and low cycle fatigue property in the EBW joints and base metal (BM) specimens is compared. During the tensile testing, digital image correlation technology was used to measure the plastic strain field evolution within the specimens. The experimental results showed that the tensile ductility and low cycle fatigue strength of EBW joints are lower than that of BM specimens, mainly because of the effect of microstructure heterogeneity of the welded joint. Moreover, the EBW joints exhibit the cyclic hardening behavior during low fatigue process, while BM specimens exhibit the cyclic softening behavior. Compared with the BM specimens with uniform microstructure, the heterogeneity of microstructure in the EBW joint is found to decrease the mechanical properties of welded joint.

Micromechanics Based Failure Analysis of Heterogeneous Materials

Science.gov (United States)

Sertse, Hamsasew M.

In recent decades, heterogeneous materials are extensively used in various industries such as aerospace, defense, automotive and others due to their desirable specific properties and excellent capability of accumulating damage. Despite their wide use, there are numerous challenges associated with the application of these materials. One of the main challenges is lack of accurate tools to predict the initiation, progression and final failure of these materials under various thermomechanical loading conditions. Although failure is usually treated at the macro and meso-scale level, the initiation and growth of failure is a complex phenomena across multiple scales. The objective of this work is to enable the mechanics of structure genome (MSG) and its companion code SwiftComp to analyze the initial failure (also called static failure), progressive failure, and fatigue failure of heterogeneous materials using micromechanics approach. The initial failure is evaluated at each numerical integration point using pointwise and nonlocal approach for each constituent of the heterogeneous materials. The effects of imperfect interfaces among constituents of heterogeneous materials are also investigated using a linear traction-displacement model. Moreover, the progressive and fatigue damage analyses are conducted using continuum damage mechanics (CDM) approach. The various failure criteria are also applied at a material point to analyze progressive damage in each constituent. The constitutive equation of a damaged material is formulated based on a consistent irreversible thermodynamics approach. The overall tangent modulus of uncoupled elastoplastic damage for negligible back stress effect is derived. The initiation of plasticity and damage in each constituent is evaluated at each numerical integration point using a nonlocal approach. The accumulated plastic strain and anisotropic damage evolution variables are iteratively solved using an incremental algorithm. The damage analyses

Taxonomic composition and trophic structure of the continental bony fish assemblage from the early late cretaceous of Southeastern Morocco.

Science.gov (United States)

Cavin, Lionel; Boudad, Larbi; Tong, Haiyan; Läng, Emilie; Tabouelle, Jérôme; Vullo, Romain

2015-01-01

The mid-Cretaceous vertebrate assemblage from south-eastern Morocco is one of the most diversified continental vertebrate assemblages of this time worldwide. The bony fish component (coelacanths, lungfishes and ray-finned fishes) is represented by relatively complete specimens and, mostly, by fragmentary elements scattered along 250 kilometres of outcrops. Here we revisit the bony fish assemblage by studying both isolated remains collected during several fieldtrips and more complete material kept in public collections. The assemblage comprises several lungfish taxa, with the first mention of the occurrence of Arganodus tiguidiensis, and possibly two mawsoniid coelacanths. A large bichir cf. Bawitius, is recorded and corresponds to cranial elements initially referred to 'Stromerichthys' from coeval deposits in Egypt. The ginglymodians were diversified with a large 'Lepidotes' plus two obaichthyids and a gar. We confirm here that this gar belongs to a genus distinctive from Recent gars, contrary to what was suggested recently. Teleosteans comprise a poorly known ichthyodectiform, a notopterid, a probable osteoglossomorph and a large tselfatiiform, whose cranial anatomy is detailed. The body size and trophic level for each taxon are estimated on the basis of comparison with extant closely related taxa. We plotted the average body size versus average trophic level for the Kem Kem assemblage, together with extant marine and freshwater assemblages. The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems. These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains. They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa.

The effects of spatial heterogeneity and subsurface lateral transfer on evapotranspiration estimates in large scale Earth system models

Science.gov (United States)

Rouholahnejad, E.; Fan, Y.; Kirchner, J. W.; Miralles, D. G.

2017-12-01

Most Earth system models (ESM) average over considerable sub-grid heterogeneity in land surface properties, and overlook subsurface lateral flow. This could potentially bias evapotranspiration (ET) estimates and has implications for future temperature predictions, since overestimations in ET imply greater latent heat fluxes and potential underestimation of dry and warm conditions in the context of climate change. Here we quantify the bias in evaporation estimates that may arise from the fact that ESMs average over considerable heterogeneity in surface properties, and also neglect lateral transfer of water across the heterogeneous landscapes at global scale. We use a Budyko framework to express ET as a function of P and PET to derive simple sub-grid closure relations that quantify how spatial heterogeneity and lateral transfer could affect average ET as seen from the atmosphere. We show that averaging over sub-grid heterogeneity in P and PET, as typical Earth system models do, leads to overestimation of average ET. Our analysis at global scale shows that the effects of sub-grid heterogeneity will be most pronounced in steep mountainous areas where the topographic gradient is high and where P is inversely correlated with PET across the landscape. In addition, we use the Total Water Storage (TWS) anomaly estimates from the Gravity Recovery and Climate Experiment (GRACE) remote sensing product and assimilate it into the Global Land Evaporation Amsterdam Model (GLEAM) to correct for existing free drainage lower boundary condition in GLEAM and quantify whether, and how much, accounting for changes in terrestrial storage can improve the simulation of soil moisture and regional ET fluxes at global scale.

A Comparison of Soft-Tissue Implanted Markers and Bony Anatomy Alignments for Image-Guided Treatments of Head-and-Neck Cancers

International Nuclear Information System (INIS)

Zeidan, Omar A.; Huddleston, Adam J.; Lee, Choonik; Langen, Katja M.; Kupelian, Patrick A.; Meeks, Sanford L.; Manon, Rafael R.

2010-01-01

Purpose: To compare the geometric alignments of soft-tissue implanted markers to the traditional bony-based alignments in head-and-neck cancers, on the basis of daily image guidance. Dosimetric impact of the two alignment techniques on target coverage is presented. Methods and Materials: A total of 330 retrospective alignments (5 patients) were performed on daily megavoltage computed tomography (MVCT) image sets using both alignment techniques. Intermarker distances were tracked for all fractions to assess marker interfractional stability. Using a deformable image registration algorithm, target cumulative doses were calculated according to generated shifts on daily MVCT image sets. Target D95 was used as a dosimetric endpoint to evaluate each alignment technique. Results: Intermarker distances overall were stable, with a standard deviation of <1.5 mm for all fractions and no observed temporal trends. Differences in shift magnitudes between both alignment techniques were found to be statistically significant, with a maximum observed difference of 8 mm in a given direction. Evaluation of technique-specific dose coverage based on D95 of target clinical target volume and planning target volume shows small differences (within ±5%) compared with the kilovoltage CT plan. Conclusion: The use of daily MVCT imaging demonstrates that implanted markers in oral tongue and soft-palate cancers are stable localization surrogates. Alignments based on implanted markers generate shifts comparable overall to the traditional bony-based alignment, with no observed systematic difference in magnitude or direction. The cumulative dosimetric impact on target clinical target volume and planning target volume coverage was found to be similar, despite large observed differences in daily alignment shifts between the two techniques.

Heterogeneous cellular networks

CERN Document Server

Hu, Rose Qingyang

2013-01-01

A timely publication providing coverage of radio resource management, mobility management and standardization in heterogeneous cellular networks The topic of heterogeneous cellular networks has gained momentum in industry and the research community, attracting the attention of standardization bodies such as 3GPP LTE and IEEE 802.16j, whose objectives are looking into increasing the capacity and coverage of the cellular networks. This book focuses on recent progresses,  covering the related topics including scenarios of heterogeneous network deployment, interference management i

Effects of heterogeneity on recrystallization kinetics of nanocrystalline copper prepared by dynamic plastic deformation

DEFF Research Database (Denmark)

Lin, Fengxiang; Zhang, Yubin; Tao, Nairong

2014-01-01

to develop a heterogeneous structure, consisting of regions with different textures and microstructures. This heterogeneity within the deformed structure leads to the formation of severely clustered grains in partially recrystallized samples. The recrystallization kinetic curve shows an Avrami exponent less...... recrystallization kinetics. The hardness of the two samples was measured, and the mechanical properties before and after partial recrystallization of both samples are discussed based on the presence of structural heterogeneities on the macroscopic and the microscopic scale....

Mechanical heterogeneity in ionic liquids

Science.gov (United States)

Veldhorst, Arno A.; Ribeiro, Mauro C. C.

2018-05-01

Molecular dynamics (MD) simulations of five ionic liquids based on 1-alkyl-3-methylimidazolium cations, [CnC1im]+, have been performed in order to calculate high-frequency elastic moduli and to evaluate heterogeneity of local elastic moduli. The MD simulations of [CnC1im][NO3], n = 2, 4, 6, and 8, assessed the effect of domain segregation when the alkyl chain length increases, and [C8C1im][PF6] assessed the effect of strength of anion-cation interaction. Dispersion curves of excitation energies of longitudinal and transverse acoustic, LA and TA, modes were obtained from time correlation functions of mass currents at different wavevectors. High-frequency sound velocity of LA modes depends on the alkyl chain length, but sound velocity for TA modes does not. High-frequency bulk and shear moduli, K∞ and G∞, depend on the alkyl chain length because of a density effect. Both K∞ and G∞ are strongly dependent on the anion. The calculation of local bulk and shear moduli was accomplished by performing bulk and shear deformations of the systems cooled to 0 K. The simulations showed a clear connection between structural and elastic modulus heterogeneities. The development of nano-heterogeneous structure with increasing length of the alkyl chain in [CnC1im][NO3] implies lower values for local bulk and shear moduli in the non-polar domains. The mean value and the standard deviations of distributions of local elastic moduli decrease when [NO3]- is replaced by the less coordinating [PF6]- anion.

Automated bony region identification using artificial neural networks: reliability and validation measurements

International Nuclear Information System (INIS)

Gassman, Esther E.; Kallemeyn, Nicole A.; DeVries, Nicole A.; Shivanna, Kiran H.; Powell, Stephanie M.; Magnotta, Vincent A.; Ramme, Austin J.; Adams, Brian D.; Grosland, Nicole M.

2008-01-01

The objective was to develop tools for automating the identification of bony structures, to assess the reliability of this technique against manual raters, and to validate the resulting regions of interest against physical surface scans obtained from the same specimen. Artificial intelligence-based algorithms have been used for image segmentation, specifically artificial neural networks (ANNs). For this study, an ANN was created and trained to identify the phalanges of the human hand. The relative overlap between the ANN and a manual tracer was 0.87, 0.82, and 0.76, for the proximal, middle, and distal index phalanx bones respectively. Compared with the physical surface scans, the ANN-generated surface representations differed on average by 0.35 mm, 0.29 mm, and 0.40 mm for the proximal, middle, and distal phalanges respectively. Furthermore, the ANN proved to segment the structures in less than one-tenth of the time required by a manual rater. The ANN has proven to be a reliable and valid means of segmenting the phalanx bones from CT images. Employing automated methods such as the ANN for segmentation, eliminates the likelihood of rater drift and inter-rater variability. Automated methods also decrease the amount of time and manual effort required to extract the data of interest, thereby making the feasibility of patient-specific modeling a reality. (orig.)

Automated bony region identification using artificial neural networks: reliability and validation measurements

Energy Technology Data Exchange (ETDEWEB)

Gassman, Esther E.; Kallemeyn, Nicole A.; DeVries, Nicole A.; Shivanna, Kiran H. [The University of Iowa, Department of Biomedical Engineering, Seamans Center for the Engineering Arts and Sciences, Iowa City, IA (United States); The University of Iowa, Center for Computer-Aided Design, Iowa City, IA (United States); Powell, Stephanie M. [The University of Iowa, Department of Biomedical Engineering, Seamans Center for the Engineering Arts and Sciences, Iowa City, IA (United States); University of Iowa Hospitals and Clinics, The University of Iowa, Department of Radiology, Iowa City, IA (United States); Magnotta, Vincent A. [The University of Iowa, Department of Biomedical Engineering, Seamans Center for the Engineering Arts and Sciences, Iowa City, IA (United States); The University of Iowa, Center for Computer-Aided Design, Iowa City, IA (United States); University of Iowa Hospitals and Clinics, The University of Iowa, Department of Radiology, Iowa City, IA (United States); Ramme, Austin J. [University of Iowa Hospitals and Clinics, The University of Iowa, Department of Radiology, Iowa City, IA (United States); Adams, Brian D. [The University of Iowa, Department of Biomedical Engineering, Seamans Center for the Engineering Arts and Sciences, Iowa City, IA (United States); University of Iowa Hospitals and Clinics, The University of Iowa, Department of Orthopaedics and Rehabilitation, Iowa City, IA (United States); Grosland, Nicole M. [The University of Iowa, Department of Biomedical Engineering, Seamans Center for the Engineering Arts and Sciences, Iowa City, IA (United States); University of Iowa Hospitals and Clinics, The University of Iowa, Department of Orthopaedics and Rehabilitation, Iowa City, IA (United States); The University of Iowa, Center for Computer-Aided Design, Iowa City, IA (United States)

2008-04-15

The objective was to develop tools for automating the identification of bony structures, to assess the reliability of this technique against manual raters, and to validate the resulting regions of interest against physical surface scans obtained from the same specimen. Artificial intelligence-based algorithms have been used for image segmentation, specifically artificial neural networks (ANNs). For this study, an ANN was created and trained to identify the phalanges of the human hand. The relative overlap between the ANN and a manual tracer was 0.87, 0.82, and 0.76, for the proximal, middle, and distal index phalanx bones respectively. Compared with the physical surface scans, the ANN-generated surface representations differed on average by 0.35 mm, 0.29 mm, and 0.40 mm for the proximal, middle, and distal phalanges respectively. Furthermore, the ANN proved to segment the structures in less than one-tenth of the time required by a manual rater. The ANN has proven to be a reliable and valid means of segmenting the phalanx bones from CT images. Employing automated methods such as the ANN for segmentation, eliminates the likelihood of rater drift and inter-rater variability. Automated methods also decrease the amount of time and manual effort required to extract the data of interest, thereby making the feasibility of patient-specific modeling a reality. (orig.)

[Clinical application of transport distraction osteogenesis arthroplasty in the treatment of temporomandibular joint bony ankylosis].

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Liang, Cheng; Wang, Xing; Yi, Biao; Li, Zi-li; Wang, Xiao-xia

2013-03-12

To explore the clinical application of transport distraction osteogenesis arthroplasty (TDOAP) in the treatment of temporomandibular joint (TMJ) bony ankylosis. From December 1999 to December 2011, a total of 73 patients (89 sides of TMJ) underwent TDOAP were included. There were 39 males and 34 females with a mean age of 19.6 years (range: 3 - 60). Among them, 27 patients were recurrence cases and 30 cases were accompanied with micrognathia and obstructive sleep apnea-hypopnea syndrome (OSAHS). The mean preoperative degree of mouth opening was 6.6 mm (range: 1 - 20). After a release of ankylosis, a transport disc was performed and fixed to ramus with a distractor. Distraction began at Days 4 - 8 postoperation. The distraction rhythm and rate were 0.25 mm four times daily. Distraction stopped when planning distance was achieved. And a distractor was maintained in place for 3-6 months after completion of distraction and then removed. Active postoperative training of mouth opening was implemented. The mean distance of distraction was 15.3 mm (range: 12 - 23). The range of mouth opening of 65 patients increased to normal and bone formation in gaps were perfect. The mean follow-up period was 44.8 months (range: 18 - 102). Eight cases were recurrent. And 1/37 over 15 years old and 7/36 under 15 years old had recurrence. TDOAP is an effective treatment for TMJ ankylosis. A pediatric patient, especially recurrent, should be operated after adolescence to decrease recurrence. Micrognathia and OSAHS should be also considered during the treatment of ankylosis.

Biosafety of the Novel Vancomycin-loaded Bone-like Hydroxyapatite/Poly-amino Acid Bony Scaffold

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Zhi-Dong Cao

2016-01-01

Full Text Available Background: Recently, local sustained-release antibiotics systems have been developed because they can increase local foci of concentrated antibiotics without increasing the plasma concentration, and thereby effectively decrease any systemic toxicity and side effects. A vancomycin-loaded bone-like hydroxyapatite/poly-amino acid (V-BHA/PAA bony scaffold was successfully fabricated with vancomycin-loaded poly lactic-co-glycolic acid microspheres and BHA/PAA, which was demonstrated to exhibit both porosity and perfect biodegradability. The aim of this study was to systematically evaluate the biosafety of this novel scaffold by conducting toxicity tests in vitro and in vivo. Methods: According to the ISO rules for medical implant biosafety, for in vitro tests, the scaffold was incubated with L929 fibroblasts or rabbit noncoagulant blood, with simultaneous creation of positive control and negative control groups. The growth condition of L929 cells and hemolytic ratio were respectively evaluated after various incubation periods. For in vivo tests, a chronic osteomyelitis model involving the right proximal tibia of New Zealand white rabbits was established. After bacterial identification, the drug-loaded scaffold, drug-unloaded BHA/PAA, and poly (methyl methacrylate were implanted, and a blank control group was also set up. Subsequently, the in vivo blood drug concentrations were measured, and the kidney and liver functions were evaluated. Results: In the in vitro tests, the cytotoxicity grades of V-BHA/PAA and BHA/PAA-based on the relative growth rate were all below 1. The hemolysis ratios of V-BHA/PAA and BHA/PAA were 2.27% and 1.42%, respectively, both below 5%. In the in vivo tests, the blood concentration of vancomycin after implantation of V-BHA/PAA was measured at far below its toxic concentration (60 mg/L, and the function and histomorphology of the liver and kidney were all normal. Conclusion: According to ISO standards, the V-BHA/PAA scaffold

Evaluation of an educational program on deciphering heterogeneity for medical coverage decisions.

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Warholak, Terri L; Hilgaertner, Jianhua W; Dean, Joni L; Taylor, Ann M; Hines, Lisa E; Hurwitz, Jason; Brown, Mary; Malone, Daniel C

2014-06-01

It is increasingly important for decision makers, such as medical and pharmacy managers (or pharmacy therapeutics committee members and staff), to understand the variation and diversity in treatment response as decisions shift from an individual patient perspective to optimizing care for populations of patients. To assess the effectiveness of an instructional program on heterogeneity designed for medical and pharmacy managers. A live educational program was offered to members of the Academy of Managed Care Pharmacy at the fall 2012 educational meeting and also to medical directors and managers attending a national payer roundtable meeting in October 2012. Participants completed a retrospective pretest-posttest assessment of their knowledge, attitudes, and self-efficacy immediately following the program. Participants were offered the opportunity to participate in a follow-up assessment 6 months later. Willing participants for the follow-up assessment were contacted via e-mail and telephone. Rasch rating scale models were used to compare pre- and postscores measuring participants' knowledge about and attitude towards heterogeneity. A total of 49 individuals completed the retrospective pretest-posttest assessment and agreed to be a part of the program evaluation. Fifty percent (n = 25) of participants had heard of the phrase "heterogeneity of treatment effect," and 36 (72%) were familiar with the phrase "individualized treatment effect" prior to the live program. Participants reported a significant improvement in knowledge of heterogeneity (P  less than  0.01) and attitudes about heterogeneity (P  less than  0.01) immediately after attending the program. At the time of the educational program, participants had either never considered heterogeneity (26%) or reported not knowing (28%) whether their organizations considered it when determining basic coverage. Participants were more likely to report "sometimes" considering heterogeneity for determining

Heterogeneous Effects of Direct Hypoxia Pathway Activation in Kidney Cancer.

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Rafik Salama

Full Text Available General activation of hypoxia-inducible factor (HIF pathways is classically associated with adverse prognosis in cancer and has been proposed to contribute to oncogenic drive. In clear cell renal carcinoma (CCRC HIF pathways are upregulated by inactivation of the von-Hippel-Lindau tumor suppressor. However HIF-1α and HIF-2α have contrasting effects on experimental tumor progression. To better understand this paradox we examined pan-genomic patterns of HIF DNA binding and associated gene expression in response to manipulation of HIF-1α and HIF-2α and related the findings to CCRC prognosis. Our findings reveal distinct pan-genomic organization of canonical and non-canonical HIF isoform-specific DNA binding at thousands of sites. Overall associations were observed between HIF-1α-specific binding, and genes associated with favorable prognosis and between HIF-2α-specific binding and adverse prognosis. However within each isoform-specific set, individual gene associations were heterogeneous in sign and magnitude, suggesting that activation of each HIF-α isoform contributes a highly complex mix of pro- and anti-tumorigenic effects.

Scaling properties of conduction velocity in heterogeneous excitable media

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Shajahan, T. K.; Borek, Bartłomiej; Shrier, Alvin; Glass, Leon

2011-10-01

Waves of excitation through excitable media, such as cardiac tissue, can propagate as plane waves or break up to form reentrant spiral waves. In diseased hearts reentrant waves can be associated with fatal cardiac arrhythmias. In this paper we investigate the conditions that lead to wave break, reentry, and propagation failure in mathematical models of heterogeneous excitable media. Two types of heterogeneities are considered: sinks are regions in space in which the voltage is fixed at its rest value, and breaks are nonconducting regions with no-flux boundary conditions. We find that randomly distributed heterogeneities in the medium have a decremental effect on the velocity, and above a critical density of such heterogeneities the conduction fails. Using numerical and analytical methods we derive the general relationship among the conduction velocity, density of heterogeneities, diffusion coefficient, and the rise time of the excitation in both two and three dimensions. This work helps us understand the factors leading to reduced propagation velocity and the formation of spiral waves in heterogeneous excitable media.

Dynamic characteristics of heterogeneous media in vibrational and wave processes

International Nuclear Information System (INIS)

Fedotovskij, V.S.; Sinyavskij, V.F.; Terenik, L.V.; Spirov, V.S.; Kokorev, B.V.

1986-01-01

The complex mechanic systems involving a great quantity of the same type elements, in particular, the rod systems flowed around by the one- or two-phase flow are considered as the two- or three-phase heterogeneous media with certain effective properties. Some recommendations for calculating effective properties and determining those on a base of the dynamic characteristics of various heterogeneous systems are given. (author)

Emergent dynamics of spatio-temporal chaos in a heterogeneous excitable medium.

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Bittihn, Philip; Berg, Sebastian; Parlitz, Ulrich; Luther, Stefan

2017-09-01

Self-organized activation patterns in excitable media such as spiral waves and spatio-temporal chaos underlie dangerous cardiac arrhythmias. While the interaction of single spiral waves with different types of heterogeneity has been studied extensively, the effect of heterogeneity on fully developed spatio-temporal chaos remains poorly understood. We investigate how the complexity and stability properties of spatio-temporal chaos in the Bär-Eiswirth model of excitable media depend on the heterogeneity of the underlying medium. We employ different measures characterizing the chaoticity of the system and find that the spatial arrangement of multiple discrete lower excitability regions has a strong impact on the complexity of the dynamics. Varying the number, shape, and spatial arrangement of the heterogeneities, we observe strong emergent effects ranging from increases in chaoticity to the complete cessation of chaos, contrasting the expectation from the homogeneous behavior. The implications of our findings for the development and treatment of arrhythmias in the heterogeneous cardiac muscle are discussed.

Impact of Heterogeneity in Sexual Behavior on Effectiveness in Reducing HIV Transmission with Test-and-Treat Strategy.

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Ganna Rozhnova

2016-08-01

Full Text Available The WHO's early-release guideline for antiretroviral treatment (ART of HIV infection based on a recent trial conducted in 34 countries recommends starting treatment immediately upon an HIV diagnosis. Therefore, the test-and-treat strategy may become more widely used in an effort to scale up HIV treatment and curb further transmission. Here we examine behavioural determinants of HIV transmission and how heterogeneity in sexual behaviour influences the outcomes of this strategy. Using a deterministic model, we perform a systematic investigation into the effects of various mixing patterns in a population of men who have sex with men (MSM, stratified by partner change rates, on the elimination threshold and endemic HIV prevalence. We find that both the level of overdispersion in the distribution of the number of sexual partners and mixing between population subgroups have a large influence on endemic prevalence before introduction of ART and on possible long term effectiveness of ART. Increasing heterogeneity in risk behavior may lead to lower endemic prevalence levels, but requires higher coverage levels of ART for elimination. Elimination is only feasible for populations with a rather low degree of assortativeness of mixing and requires treatment coverage of almost 80% if rates of testing and treatment uptake by all population subgroups are equal. In this case, for fully assortative mixing and 80% coverage endemic prevalence is reduced by 57%. In the presence of heterogeneity in ART uptake, elimination is easier to achieve when the subpopulation with highest risk behavior is tested and treated more often than the rest of the population, and vice versa when it is less. The developed framework can be used to extract information on behavioral heterogeneity from existing data which is otherwise hard to determine from population surveys.

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

International Nuclear Information System (INIS)

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

2015-01-01

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

The effects of floodplain soil heterogeneity on meander planform shape

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Motta, D.; Abad, J. D.; Langendoen, E. J.; GarcíA, M. H.

2012-09-01

Past analytical studies of meander planform development have mostly focused on the complexity of the governing equations, i.e., hydrodynamics, and less so on the stream bank resistance to erosion, whose spatial heterogeneity is difficult to describe deterministically. This motivated the use of a Monte Carlo approach to examine the effects of floodplain soils and their distribution on planform development, with the goal of including bank erosion properties in the analysis. Simulated bank erosion rates are controlled by the resistance to hydraulic erosion of the bank soils using an excess shear stress approach. The spatial distribution of critical shear stress across the floodplain is delineated on a rectangular, equidistant grid with varying degrees of variability. The corresponding erodibility coefficient is computed using a field-derived empirical relation. For a randomly disturbed distribution, in which the mean resistance to erosion exponentially increases away from the valley centerline, two relevant parameters are identified: the standard deviation of the critical shear stress distribution, which controls skewness and variability of the channel centerline, and the cross-valley increase in soil resistance, which constrains lateral migration and also affects bend skewness. For a purely random distribution, migrated centerlines exhibit larger variability for increasing spatial scales of floodplain soil heterogeneity. For equal stochastic variability of the corresponding governing parameters, relating meander migration to hydraulic erosion of the bank soils produces more variability and shape complexity than the "classic" bank migration approach of Ikeda et al. (1981), which relates migration rate to excess velocity at the outer bank. Finally, the proposed stochastic approach provides a foundation for estimating a suitable spatial density of measurements to characterize the physical properties of floodplain soils and vegetation.

Pharmacogenomics Bias - Systematic distortion of study results by genetic heterogeneity

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Zietemann, Vera

2008-04-01

Full Text Available Background: Decision analyses of drug treatments in chronic diseases require modeling the progression of disease and treatment response beyond the time horizon of clinical or epidemiological studies. In many such models, progression and drug effect have been applied uniformly to all patients; heterogeneity in progression, including pharmacogenomic effects, has been ignored. Objective: We sought to systematically evaluate the existence, direction and relative magnitude of a pharmacogenomics bias (PGX-Bias resulting from failure to adjust for genetic heterogeneity in both treatment response (HT and heterogeneity in progression of disease (HP in decision-analytic studies based on clinical study data. Methods: We performed a systematic literature search in electronic databases for studies regarding the effect of genetic heterogeneity on the validity of study results. Included studies have been summarized in evidence tables. In the case of lacking evidence from published studies we sought to perform our own simulation considering both HT and HP. We constructed two simple Markov models with three basic health states (early-stage disease, late-stage disease, dead, one adjusting and the other not adjusting for genetic heterogeneity. Adjustment was done by creating different disease states for presence (G+ and absence (G- of a dichotomous genetic factor. We compared the life expectancy gains attributable to treatment resulting from both models and defined pharmacogenomics bias as percent deviation of treatment-related life expectancy gains in the unadjusted model from those in the adjusted model. We calculated the bias as a function of underlying model parameters to create generic results. We then applied our model to lipid-lowering therapy with pravastatin in patients with coronary atherosclerosis, incorporating the influence of two TaqIB polymorphism variants (B1 and B2 on progression and drug efficacy as reported in the DNA substudy of the REGRESS

Heterogeneous effects of M-CSF isoforms on the progression of MLL-AF9 leukemia.

Science.gov (United States)

Wang, Rong; Feng, Wenli; Yang, Feifei; Yang, Xiao; Wang, Lina; Chen, Chong; Hu, Yuting; Ren, Qian; Zheng, Guoguang

2018-02-01

Macrophage colony-stimulating factor (M-CSF) regulates both malignant cells and microenvironmental cells. Its splicing isoforms show functional heterogeneity. However, their roles on leukemia have not been well established. Here, the expression of total M-CSF in patients with hematopoietic malignancies was analyzed. The roles of M-CSF isoforms on the progression of acute myeloid leukemia (AML) were studied by establishing MLL-AF9-induced mouse AML models with high level membrane-bound M-CSF (mM-CSF) or soluble M-CSF (sM-CSF). Total M-CSF was highly expressed in myeloid leukemia patients. Furthermore, mM-CSF but not sM-CSF prolonged the survival of leukemia mice. While sM-CSF was more potent to promote proliferation and self-renew, mM-CSF was more potent to promote differentiation. Moreover, isoforms had different effects on leukemia-associated macrophages (LAMs) though they both increase monocytes/macrophages by growth-promoting and recruitment effects. In addition, mM-CSF promoted specific phagocytosis of leukemia cells by LAMs. RNA-seq analysis revealed that mM-CSF enhanced phagocytosis-associated genes and activated oxidative phosphorylation and metabolism pathway. These results highlight heterogeneous effects of M-CSF isoforms on AML progression and the mechanisms of mM-CSF, that is, intrinsically promoting AML cell differentiation and extrinsically enhancing infiltration of macrophages and phagocytosis by macrophages, which may provide potential clues for clinical diagnosis and therapy. © 2017 Australasian Society for Immunology Inc.

Collective Motion in Behaviorally Heterogeneous Systems

Science.gov (United States)

Copenhagen, Katherine

Collective motion is a widespread phenomenon in nature where individuals actively propel themselves, gather together and move as a group. Some examples of collective motion are bird flocks, fish schools, bacteria swarms, cell clusters, and crowds of people. Many models seek to understand the effects of activity in collective systems including things such as environmental disorder, density, and interaction details primarily at infinite size limits and with uniform populations. In this dissertation I investigate the effects of finite sizes and behavioral heterogeneity as it exists in nature. Behavioral heterogeneity can originate from several different sources. Mixed populations of individuals can have inherently different behaviors such as mutant bacteria, injured fish, or agents that prefer individualistic behavior over coordinated motion. Alternatively, agents may modify their own behavior based on some local environmental dependency, such as local substrate, or density. In cases such as mutant cheaters in bacteria or malfunctioning drones in swarms, mixed populations of behaviorally heterogeneous agents can be modelled as arising in the form of aligning and non-aligning agents. When this kind of heterogeneity is introduced, there is a critical carrying capacity of non-aligners above which the system is unable to form a cohesive ordered group. However, if the cohesion of the group is relaxed to allow for fracture, the system will actively sort out non-aligning agents the system will exist at a critical non-aligner fraction. A similar heterogeneity could result in a mixture of high and low noise individuals. In this case there is also a critical carry capacity beyond which the system is unable to reach an ordered state, however the nature of this transition depends on the model details. Agents which are part of an ordered collective may vary their behavior as the group changes environments such as a flock of birds flying into a cloud. Using a unique model of a

Differing effects of attention in single-units and populations are well predicted by heterogeneous tuning and the normalization model of attention.

Science.gov (United States)

Hara, Yuko; Pestilli, Franco; Gardner, Justin L

2014-01-01

Single-unit measurements have reported many different effects of attention on contrast-response (e.g., contrast-gain, response-gain, additive-offset dependent on visibility), while functional imaging measurements have more uniformly reported increases in response across all contrasts (additive-offset). The normalization model of attention elegantly predicts the diversity of effects of attention reported in single-units well-tuned to the stimulus, but what predictions does it make for more realistic populations of neurons with heterogeneous tuning? Are predictions in accordance with population-scale measurements? We used functional imaging data from humans to determine a realistic ratio of attention-field to stimulus-drive size (a key parameter for the model) and predicted effects of attention in a population of model neurons with heterogeneous tuning. We found that within the population, neurons well-tuned to the stimulus showed a response-gain effect, while less-well-tuned neurons showed a contrast-gain effect. Averaged across the population, these disparate effects of attention gave rise to additive-offsets in contrast-response, similar to reports in human functional imaging as well as population averages of single-units. Differences in predictions for single-units and populations were observed across a wide range of model parameters (ratios of attention-field to stimulus-drive size and the amount of baseline response modifiable by attention), offering an explanation for disparity in physiological reports. Thus, by accounting for heterogeneity in tuning of realistic neuronal populations, the normalization model of attention can not only predict responses of well-tuned neurons, but also the activity of large populations of neurons. More generally, computational models can unify physiological findings across different scales of measurement, and make links to behavior, but only if factors such as heterogeneous tuning within a population are properly accounted for.

Study of the heterogeneities effect in the dose distributions of Leksell Gamma Knife (R), through Monte Carlo simulation

International Nuclear Information System (INIS)

Rojas C, E.L.; Al-Dweri, F.M.O.; Lallena R, A.M.

2005-01-01

In this work they are studied, by means of Monte Carlo simulation, the effects that take place in the dose profiles that are obtained with the Leksell Gamma Knife (R), when they are kept in account heterogeneities. The considered heterogeneities simulate the skull and the spaces of air that are in the head, like they can be the nasal breasts or the auditory conduits. The calculations were made using the Monte Carlo Penelope simulation code (v. 2003). The geometry of each one of the 201 sources that this instrument is composed, as well as of the corresponding channels of collimation of the Gamma Knife (R), it was described by means of a simplified model of geometry that has been recently studied. The obtained results when they are kept in mind the heterogeneities they present non worthless differences regarding those obtained when those are not considered. These differences are maximum in the proximities of the interfaces among different materials. (Author)

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

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Juan S. Sánchez-Oliver

2015-12-01

Full Text Available 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.

The effects of hypercapnia on cortical capillary transit time heterogeneity (CTH) in anesthetized mice

DEFF Research Database (Denmark)

Gutiérrez-Jiménez, Eugenio; Angleys, Hugo; Rasmussen, Peter Mondrup

2018-01-01

Capillary flow patterns are highly heterogeneous in the resting brain. During hyperemia, capillary transit-time heterogeneity (CTH) decreases, in proportion to blood's mean transit time (MTT) in passive, compliant microvascular networks. Previously, we found that functional activation reduces...

Complete and phase synchronization in a heterogeneous small-world neuronal network

International Nuclear Information System (INIS)

Fang, Han; Qi-Shao, Lu; Quan-Bao, Ji; Marian, Wiercigroch

2009-01-01

Synchronous firing of neurons is thought to be important for information communication in neuronal networks. This paper investigates the complete and phase synchronization in a heterogeneous small-world chaotic Hindmarsh–Rose neuronal network. The effects of various network parameters on synchronization behaviour are discussed with some biological explanations. Complete synchronization of small-world neuronal networks is studied theoretically by the master stability function method. It is shown that the coupling strength necessary for complete or phase synchronization decreases with the neuron number, the node degree and the connection density are increased. The effect of heterogeneity of neuronal networks is also considered and it is found that the network heterogeneity has an adverse effect on synchrony. (general)

Prevalence of bony septa, antral pathology, and dimensions of the maxillary sinus from a sinus augmentation perspective: A retrospective cone-beam computed tomography study

Energy Technology Data Exchange (ETDEWEB)

Tadinada, Aditya; Jalali, Elnaz; Al Salman, Wesam; Jambhekar, Shantanu; Katechia, Bina [University of Connecticut, School of Dental Medicine, Farmington (United States); Almas, Khalid [Div. of Periodontology, University of Dammam, College of Dentistry, Dammam (Saudi Arabia)

2016-06-15

Sinus elevation procedures have become a routine and reliable way to gain bone volume in the edentulous maxilla for dental implant placement. Presence of bony septations and pathology in the maxillary sinus often cause complications leading to graft or implant failure or both. The aim of this study was to retrospectively evaluate the prevalence of pathology, direction of the septa, and sinus width measured at 2 mm, 5 mm, and 10 mm from the sinus floor in maxillary sinuses using cone-beam computed tomography (CBCT). Seventy-two sinuses from 36 random preoperative CBCT scans referred for implant therapy were retrospectively evaluated for the number, prevalence, and direction of bony septations and presence of pathology. Width of the sinus was also measured at 2 mm, 5 mm, and 10 mm from the sinus floor to account for the amount of bone available for implant placement. Maxillary sinus septa were found in 59.7%. Presence of a single septum was noted in 20 sinuses (27.7%), followed by two septa in 17 sinuses. The most common direction of the septum was the transverse direction. Retention pseudocyst and mucosal thickening were the most commonly seen abnormality/pathology. Based on the high prevalence of septa and sinus pathology in this sample, a preoperative CBCT scan might be helpful in minimizing complications during sinus augmentation procedures for dental implant therapy.

Prevalence of bony septa, antral pathology, and dimensions of the maxillary sinus from a sinus augmentation perspective: A retrospective cone-beam computed tomography study

International Nuclear Information System (INIS)

Tadinada, Aditya; Jalali, Elnaz; Al Salman, Wesam; Jambhekar, Shantanu; Katechia, Bina; Almas, Khalid

2016-01-01

Sinus elevation procedures have become a routine and reliable way to gain bone volume in the edentulous maxilla for dental implant placement. Presence of bony septations and pathology in the maxillary sinus often cause complications leading to graft or implant failure or both. The aim of this study was to retrospectively evaluate the prevalence of pathology, direction of the septa, and sinus width measured at 2 mm, 5 mm, and 10 mm from the sinus floor in maxillary sinuses using cone-beam computed tomography (CBCT). Seventy-two sinuses from 36 random preoperative CBCT scans referred for implant therapy were retrospectively evaluated for the number, prevalence, and direction of bony septations and presence of pathology. Width of the sinus was also measured at 2 mm, 5 mm, and 10 mm from the sinus floor to account for the amount of bone available for implant placement. Maxillary sinus septa were found in 59.7%. Presence of a single septum was noted in 20 sinuses (27.7%), followed by two septa in 17 sinuses. The most common direction of the septum was the transverse direction. Retention pseudocyst and mucosal thickening were the most commonly seen abnormality/pathology. Based on the high prevalence of septa and sinus pathology in this sample, a preoperative CBCT scan might be helpful in minimizing complications during sinus augmentation procedures for dental implant therapy

Heterogeneous Monolithic Integration of Single-Crystal Organic Materials.

Science.gov (United States)

Park, Kyung Sun; Baek, Jangmi; Park, Yoonkyung; Lee, Lynn; Hyon, Jinho; Koo Lee, Yong-Eun; Shrestha, Nabeen K; Kang, Youngjong; Sung, Myung Mo

2017-02-01

Manufacturing high-performance organic electronic circuits requires the effective heterogeneous integration of different nanoscale organic materials with uniform morphology and high crystallinity in a desired arrangement. In particular, the development of high-performance organic electronic and optoelectronic devices relies on high-quality single crystals that show optimal intrinsic charge-transport properties and electrical performance. Moreover, the heterogeneous integration of organic materials on a single substrate in a monolithic way is highly demanded for the production of fundamental organic electronic components as well as complex integrated circuits. Many of the various methods that have been designed to pattern multiple heterogeneous organic materials on a substrate and the heterogeneous integration of organic single crystals with their crystal growth are described here. Critical issues that have been encountered in the development of high-performance organic integrated electronics are also addressed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Communicating why land surface heterogeneity matters

Science.gov (United States)

Tague, C.; Burke, W.; Bart, R. R.; Turpin, E.; Wood, T.; Gordon, D.

2017-12-01

As hydrologic scientists, we know that land surface heterogeneity can have nuanced and sometimes dramatic impacts on the water cycle. Land surface characteristics, including the structure and composition of vegetation and soil storage and drainage properties, alter how incoming precipitation is translated into streamflow and evapotranspiration. Land surface heterogeneity can explain why this partitioning of incoming precipitation cannot always be computed by a simple water budget calculation. We also know that land surface characteristics are dynamic - vegetation grows and changes with fire, disease and human actions and these changes will alter the partitioning of water - how much so, however depends itself on other site characteristics - soil water storage and the timing and magnitude of precipitation. This complex impact of space-time dynamics on the water cycle is something we need to effectively communicate to non-experts. For example, we may want to explain why sometimes forest management practices increase water availability but sometimes they don't - or why the impacts of urbanization or fire are location specific. If we do not communicate these dependencies we risk over-simplifying and eroding scientific credibility when observed effects don't match simple generalizations. On the other hand excessive detail can overwhelm and disengage audiences. So how do we help different communities public, private landowners, other scientists, NGOs, governments to better understand the role of space-time heterogeneity. To address this issue, we present some results from ongoing work that looks at the impact of fuel treatment of forest ecohydrology. This work stem from a collaboration between an ecohydrologic modeling team, social-scientists, a visual artist and compute graphics students. We use a coupled model, validated with field measurements, to show why spatial heterogeneity matters for understanding the impact of fuel treatments on the water cycle for the Sierra

Study of the heterogeneity effects of lung in the evaluation of absorbed dose in radiotherapy

International Nuclear Information System (INIS)

Campos, Luciana Tourinho

2006-02-01

The main objective of radiotherapy is to deliver the highest possible dose to the tumour, in order to destroy it, reducing as much as possible the doses to healthy tissues adjacent to the target volume. Therefore, it is necessary to do a planning of the treatment. The more complex is the treatment, the more difficult the planning will be, demanding computation sophisticated methods in its execution, in order to consider the heterogeneities present in the human body. Additionally, with the appearing of new radiotherapeutic techniques, that used irradiation fields of small area, for instance, the intensity modulated radiotherapy, the difficulties for the execution of a reliable treatment planning, became still larger. In this work it was studied the influence of the lung heterogeneity in the planning of the curves of percentage depth dose, PDP, obtained with the Eclipse R planning system for different sizes of irradiation fields, using the correction algorithms for heterogeneities available in the planning system: modified Batho, general Batho and equivalent tissue-air ratio. A thorax phantom, manufactured in acrylic, containing a region made of cork to simulate the lung tissue, was used. The PDP curves generated by the planning system were compared to those obtained by Monte Carlo simulation and with the use of thermoluminescent, TL, dosimetry. It was verified that the algorithms used by the Eclipse R system for the correction of heterogeneity effects are not able to generate correct results for PDP curves in the case of small fields, occurring differences of up to 100%, when the 1x1 cm 2 treatment field is considered. These differences can cause a considerable subdosage in the lung tissue, reducing the possibility of the patient cure. (author)

Estimating the effect of treatment rate changes when treatment benefits are heterogeneous: antibiotics and otitis media.

Science.gov (United States)

Park, Tae-Ryong; Brooks, John M; Chrischilles, Elizabeth A; Bergus, George

2008-01-01

Contrast methods to assess the health effects of a treatment rate change when treatment benefits are heterogeneous across patients. Antibiotic prescribing for children with otitis media (OM) in Iowa Medicaid is the empirical example. Instrumental variable (IV) and linear probability model (LPM) are used to estimate the effect of antibiotic treatments on cure probabilities for children with OM in Iowa Medicaid. Local area physician supply per capita is the instrument in the IV models. Estimates are contrasted in terms of their ability to make inferences for patients whose treatment choices may be affected by a change in population treatment rates. The instrument was positively related to the probability of being prescribed an antibiotic. LPM estimates showed a positive effect of antibiotics on OM patient cure probability while IV estimates showed no relationship between antibiotics and patient cure probability. Linear probability model estimation yields the average effects of the treatment on patients that were treated. IV estimation yields the average effects for patients whose treatment choices were affected by the instrument. As antibiotic treatment effects are heterogeneous across OM patients, our estimates from these approaches are aligned with clinical evidence and theory. The average estimate for treated patients (higher severity) from the LPM model is greater than estimates for patients whose treatment choices are affected by the instrument (lower severity) from the IV models. Based on our IV estimates it appears that lowering antibiotic use in OM patients in Iowa Medicaid did not result in lost cures.

A weighted U statistic for association analyses considering genetic heterogeneity.

Science.gov (United States)

Wei, Changshuai; Elston, Robert C; Lu, Qing

2016-07-20

Converging evidence suggests that common complex diseases with the same or similar clinical manifestations could have different underlying genetic etiologies. While current research interests have shifted toward uncovering rare variants and structural variations predisposing to human diseases, the impact of heterogeneity in genetic studies of complex diseases has been largely overlooked. Most of the existing statistical methods assume the disease under investigation has a homogeneous genetic effect and could, therefore, have low power if the disease undergoes heterogeneous pathophysiological and etiological processes. In this paper, we propose a heterogeneity-weighted U (HWU) method for association analyses considering genetic heterogeneity. HWU can be applied to various types of phenotypes (e.g., binary and continuous) and is computationally efficient for high-dimensional genetic data. Through simulations, we showed the advantage of HWU when the underlying genetic etiology of a disease was heterogeneous, as well as the robustness of HWU against different model assumptions (e.g., phenotype distributions). Using HWU, we conducted a genome-wide analysis of nicotine dependence from the Study of Addiction: Genetics and Environments dataset. The genome-wide analysis of nearly one million genetic markers took 7h, identifying heterogeneous effects of two new genes (i.e., CYP3A5 and IKBKB) on nicotine dependence. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Coupled Geomechanical-Flow Assessment of CO2 Leakage through Heterogeneous Caprock during CCS

Directory of Open Access Journals (Sweden)

Guan Woo Kim

2018-01-01

Full Text Available The viability of carbon capture sequestration (CCS is dependent on the secure storage of CO2 in subsurface geologic formations. Geomechanical failure of caprock is one of the main reasons of CO2 leakage from the storage formations. Through comprehensive assessment on the petrophysical and geomechanical heterogeneities of caprock, it is possible to predict the risk of unexpected caprock failure. To describe the fracture reactivation, the modified Barton–Bandis model is applied. In order to generate hydro-geomechanically heterogeneous fields, the negative correlation between porosity and Young’s modulus/Poisson’s ratio is applied. In comparison with the homogeneous model, effects of heterogeneity are examined in terms of vertical deformation and the amount of leaked CO2. To compare the effects of heterogeneity, heterogeneous models for both geomechanical and petrophysical properties in coupled simulation are designed. After 10-year injection with petrophysically heterogeneous and geomechanically homogeneous caprock, CO2 leakage is larger than that of the homogeneous model. In contrast, heterogeneity of geomechanical properties is shown to mitigate additional escape of CO2. Vertical displacement of every heterogeneous model is larger than homogeneous model. The model with compressive tectonic stress shows much more stable trapping with heterogeneous caprock, but there is possibility of rapid leakage after homogeneous caprock failure.

Conformity-based cooperation in online social networks: The effect of heterogeneous social influence

International Nuclear Information System (INIS)

Xu, Bo; Wang, Jianwei; Zhang, Xuejun

2015-01-01

This paper extends the conformity model by introducing heterogeneous social influence into the analysis. We associate the influence of a player in the network with its degree centrality assuming that players of higher degree exhibit more social influence on its neighbors. The results show that the equilibrium level of cooperators can be dramatically enhanced if the conformity-driven players are preferentially influenced by neighbors of higher degree. We attribute this finding to two elementary mechanisms in the evolutionary process: (1) degree-based social influence facilitates the formation of strategic clusters around hubs; and (2) payoff-heterogeneity between cooperative clusters and defective clusters contributes to the promotion of cooperation. This research reveals the important role of heterogeneous social influence on the emergence of cooperation in social networks.

Heterogeneous Policies, Heterogeneous Technologies: The Case of Renewable Energy

International Nuclear Information System (INIS)

Nicolli, Francesco; Vona, Francesco

2014-07-01

This paper investigates empirically the effect of market regulation and renewable energy policies on innovation activity in different renewable energy technologies. For the EU countries and the years 1980 to 2007, we built a unique dataset containing information on patent production in eight different technologies, proxies of market regulation and technology-specific renewable energy policies. Our main findings show that lowering entry barriers is a more significant driver of renewable energy innovation than privatisation and un-bundling, but its effect varies across technologies, being stronger in technologies characterised by the potential entry of small, independent power producers. Additionally, the inducement effect of renewable energy policies is heterogeneous and more pronounced for wind, which is the only technology that is mature and has high technological potential. Finally, the ratification of the Kyoto protocol - determining a more stable and less uncertain policy framework - amplifies the inducement effect of both energy policy and market liberalisation. (authors)

Bayesian analysis of heterogeneous treatment effects for patient-centered outcomes research.

Science.gov (United States)

Henderson, Nicholas C; Louis, Thomas A; Wang, Chenguang; Varadhan, Ravi

2016-01-01

Evaluation of heterogeneity of treatment effect (HTE) is an essential aspect of personalized medicine and patient-centered outcomes research. Our goal in this article is to promote the use of Bayesian methods for subgroup analysis and to lower the barriers to their implementation by describing the ways in which the companion software beanz can facilitate these types of analyses. To advance this goal, we describe several key Bayesian models for investigating HTE and outline the ways in which they are well-suited to address many of the commonly cited challenges in the study of HTE. Topics highlighted include shrinkage estimation, model choice, sensitivity analysis, and posterior predictive checking. A case study is presented in which we demonstrate the use of the methods discussed.

Effects of physical and geochemical heterogeneities on mineral transformation and biomass accumulation during biostimulation experiments at Rifle, Colorado.

Science.gov (United States)

Li, Li; Steefel, Carl I; Kowalsky, Michael B; Englert, Andreas; Hubbard, Susan S

2010-03-01

Electron donor amendment for bioremediation often results in precipitation of secondary minerals and the growth of biomass, both of which can potentially change flow paths and the efficacy of bioremediation. Quantitative estimation of precipitate and biomass distribution has remained challenging, partly due to the intrinsic heterogeneities of natural porous media and the scarcity of field data. In this work, we examine the effects of physical and geochemical heterogeneities on the spatial distributions of mineral precipitates and biomass accumulated during a biostimulation field experiment near Rifle, Colorado. Field bromide breakthrough data were used to infer a heterogeneous distribution of hydraulic conductivity through inverse transport modeling, while the solid phase Fe(III) content was determined by assuming a negative correlation with hydraulic conductivity. Validated by field aqueous geochemical data, reactive transport modeling was used to explicitly keep track of the growth of the biomass and to estimate the spatial distribution of precipitates and biomass. The results show that the maximum mineral precipitation and biomass accumulation occurs in the vicinity of the injection wells, occupying up to 5.4vol.% of the pore space, and is dominated by reaction products of sulfate reduction. Accumulation near the injection wells is not strongly affected by heterogeneities present in the system due to the ubiquitous presence of sulfate in the groundwater. However, accumulation in the down-gradient regions is dominated by the iron-reducing reaction products, whose spatial patterns are strongly controlled by both physical and geochemical heterogeneities. Heterogeneities can lead to localized large accumulation of mineral precipitates and biomass, increasing the possibility of pore clogging. Although ignoring the heterogeneities of the system can lead to adequate prediction of the average behavior of sulfate-reducing related products, it can also lead to an

Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof

Energy Technology Data Exchange (ETDEWEB)

Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy, E-mail: jlundholm@smu.ca

2016-05-15

Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%–26% volumetric moisture content) and temperature (21 °C–36 °C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat

Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof

International Nuclear Information System (INIS)

Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy

2016-01-01

Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%–26% volumetric moisture content) and temperature (21 °C–36 °C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat

Effect of Electromagnetic Fields on Transfer Processes in Heterogeneous Systems

Czech Academy of Sciences Publication Activity Database

Levdansky, V.V.; Kim, H. Y.; Kim, H. C.; Smolík, Jiří; Moravec, Pavel

2001-01-01

Roč. 44, č. 5 (2001), s. 1065-1071 ISSN 0017-9310 Institutional research plan: CEZ:AV0Z4072921 Keywords : electromagnetic field * transfer processes * heterogeneous system Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.240, year: 2001

Heterogeneous sharpness for cross-spectral face recognition

Science.gov (United States)

Cao, Zhicheng; Schmid, Natalia A.

2017-05-01

Matching images acquired in different electromagnetic bands remains a challenging problem. An example of this type of comparison is matching active or passive infrared (IR) against a gallery of visible face images, known as cross-spectral face recognition. Among many unsolved issues is the one of quality disparity of the heterogeneous images. Images acquired in different spectral bands are of unequal image quality due to distinct imaging mechanism, standoff distances, or imaging environment, etc. To reduce the effect of quality disparity on the recognition performance, one can manipulate images to either improve the quality of poor-quality images or to degrade the high-quality images to the level of the quality of their heterogeneous counterparts. To estimate the level of discrepancy in quality of two heterogeneous images a quality metric such as image sharpness is needed. It provides a guidance in how much quality improvement or degradation is appropriate. In this work we consider sharpness as a relative measure of heterogeneous image quality. We propose a generalized definition of sharpness by first achieving image quality parity and then finding and building a relationship between the image quality of two heterogeneous images. Therefore, the new sharpness metric is named heterogeneous sharpness. Image quality parity is achieved by experimentally finding the optimal cross-spectral face recognition performance where quality of the heterogeneous images is varied using a Gaussian smoothing function with different standard deviation. This relationship is established using two models; one of them involves a regression model and the other involves a neural network. To train, test and validate the model, we use composite operators developed in our lab to extract features from heterogeneous face images and use the sharpness metric to evaluate the face image quality within each band. Images from three different spectral bands visible light, near infrared, and short

Research Status on the Heterogeneous Sheet Connection Forming Technology

Directory of Open Access Journals (Sweden)

SHI Wen-yong

2017-04-01

Full Text Available The heterogeneous sheet connection forming is one of the effective ways to realize lightweight in many fields，such as equipment manufacturing and transportation. However, there are obvious differences in the material properties，when using the traditional connection methods，there is a certain technical bottlenecks. In this paper, the technological characteristics and research status of the welding method and mechanical connection method are discussed in detail，such as the TIC welding and the laser welding. The advantages and development potential of the technology are introduced in the field of the heterogeneous sheet connection，in combination with the industry development and the use demand，the development of the heterogeneous sheet connection technology is expected，to provide the technical support for the research and development of new heterogeneous sheet connection technology.

Three-phase flow in heterogeneous wettability porous media; Deplacements triphasiques en milieux poreux de mouillabilite heterogene

Energy Technology Data Exchange (ETDEWEB)

Jaffrennou-Laroche, C

1998-11-26

Better understanding and modelling of three-phase flow through porous media is of great interest, especially for improved oil recovery methods such as gas injection processes. Early theoretical and experimental studies have already demonstrated that the wettability characteristics of the solid surface and the spreading characteristics of the fluid system hold the key roles. This observation is confirmed by our theoretical results using DLP theory on the stability and the thickness of static oil films. In most of the works related to three-phase flow processes, homogeneous wettability is assumed. There exist only a few studies demonstrating the tremendous impact of the wettability heterogeneities on gas injection. The objective of the present work is twofold: to demonstrate the effect of small scale wettability heterogeneities on gas injection efficiency, and to develop a tool to predict this impact for various patterns and spatial distributions. To this end an experimental investigation in transparent glass micro-models is performed and a theoretical simulator is developed. Secondary and tertiary gas injections are performed for different heterogeneity patterns obtained by selective silane grafting. Displacement sequences are video-recorded and fluid saturations are determined by image analysis. Visualization of the displacement mechanisms provides the network model with the basic rules for water/oil and water/oil/gas motion. In water/oil displacement, drainage and imbibition occur according to the local wettability. Three-phase displacement is dominated by drainage mechanisms. The simulator allows the flow of oil through wetting films in the oil-wet regions and through spreading films on water in the water-wet regions. The effect of the wettability heterogeneities on: displacement mechanisms, sweep efficiency, and fluid distribution in three-phase gas injection is clearly demonstrated and successfully described by the network simulator. (author) 175 refs.

Pressure dependence of dynamical heterogeneity in water

International Nuclear Information System (INIS)

Teboul, Victor

2008-01-01

Using molecular dynamics simulations we investigate the effect of pressure on the dynamical heterogeneity in water. We show that the effect of a pressure variation in water is qualitatively different from the effect of a temperature variation on the dynamical heterogeneity in the liquid. We observe a strong decrease of the aggregation of molecules of low mobility together with a decrease of the characteristic time associated with this aggregation. However, the aggregation of the most mobile molecules and the characteristic time of this aggregation are only slightly affected. In accordance with this result, the non-Gaussian parameter shows an important decrease with pressure while the characteristic time t* of the non-Gaussian parameter is only slightly affected. These results highlight then the importance of pressure variation investigations in low temperature liquids on approach to the glass transition

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

Science.gov (United States)

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.

Exploring dynamical complexity in diffusion driven predator-prey systems: Effect of toxin producing phytoplankton and spatial heterogeneities

International Nuclear Information System (INIS)

Upadhyay, Ranjit Kumar; Kumari, Nitu; Rai, Vikas

2009-01-01

In this paper, dynamical complexities in two reaction-diffusion (RD) model systems are explored. A spatial heterogeneity in the form of linear spatial gradient in the reproductive growth rate of the phytoplankton is incorporated in both the model systems. Extra mortality of the zooplankton due to toxin production by the phytoplankton is included in the second reaction diffusion model system. Effect of toxin production and spatial heterogeneity in the model systems are studied. Toxin production does not seem to have an appreciable effect on the asymptotic dynamics of the model systems. On the other hand, spatial heterogeneity does influence the dynamics. In particular, it increases the frequency of occurrence of chaos as evident from two dimensional parameter scans. Both these model systems display short term recurrent chaos [Rai V. Chaos in natural populations: edge or wedge? Ecol Complex 2004;1: 127-38] as they reside on 'edges of chaos' (EOC) [Rai V, Upadhyay RK. Evolving to the edge of chaos: chance or necessity? Chaos, Solitons and Fractals 2006;30:1074-87]. This suggests that the ecological systems have a tendency to evolve to EOC. The study corroborates the inferences drawn from an earlier study by Rai and Upadhyay [Rai V, Upadhyay RK. Evolving to the edge of chaos: chance or necessity? Chaos, Solitons and Fractals 2006;30:1074-87]. The system's dynamics is largely unpredictable and admits bursts of short-term predictability.

Cervical spinal cord, root, and bony spine injuries: a closed claims analysis.

Science.gov (United States)

Hindman, Bradley J; Palecek, John P; Posner, Karen L; Traynelis, Vincent C; Lee, Lorri A; Sawin, Paul D; Tredway, Trent L; Todd, Michael M; Domino, Karen B

2011-04-01

The aim of this study was to characterize cervical cord, root, and bony spine claims in the American Society of Anesthesiologists Closed Claims database to formulate hypotheses regarding mechanisms of injury. All general anesthesia claims (1970-2007) in the Closed Claims database were searched to identify cervical injuries. Three independent teams, each consisting of an anesthesiologist and neurosurgeon, used a standardized review form to extract data from claim summaries and judge probable contributors to injury. Cervical injury claims (n = 48; mean ± SD age 47 ± 15 yr; 73% male) comprised less than 1% of all general anesthesia claims. When compared with other general anesthesia claims (19%), cervical injury claims were more often permanent and disabling (69%; P cervical stenosis) were often present, cord injuries usually occurred in the absence of traumatic injury (81%) or cervical spine instability (76%). Cord injury occurred with cervical spine (65%) and noncervical spine (35%) procedures. Twenty-four percent of cord injuries were associated with the sitting position. Probable contributors to cord injury included anatomic abnormalities (81%), direct surgical complications (24% [38%, cervical spine procedures]), preprocedural symptomatic cord injury (19%), intraoperative head/neck position (19%), and airway management (11%). Most cervical cord injuries occurred in the absence of traumatic injury, instability, and airway difficulties. Cervical spine procedures and/or sitting procedures appear to predominate. In the absence of instability, cervical spondylosis was the most common factor associated with cord injury.

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

Science.gov (United States)

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

Magnetism in heterogeneous thin film systems: Resonant X-ray scattering studies

International Nuclear Information System (INIS)

Kortright, J.B.; Jiang, J.S.; Bader, S.D.; Hellwig, O.; Marguiles, D.T.; Fullerton, E.E.

2002-01-01

Magnetic and chemical heterogeneity are common in a broad range of magnetic thin film systems. Emerging resonant soft x-ray scattering techniques are well suited to resolve such heterogeneity at relevant length scales. Resonant x-ray magneto-optical Kerr effect measurements laterally average over heterogeneity but can provide depth resolution in different ways, as illustrated in measurements resolving reversible and irreversible changes in different layers of exchange-spring heterostructures. Resonant small-angle scattering measures in-plane heterogeneity and can resolve magnetic and chemical scattering sources in different ways, as illustrated in measurements of granular alloy recording media

Sources of heterogeneity in studies of the BMI-mortality association.

Science.gov (United States)

Peter, Raphael Simon; Nagel, Gabriele

2017-06-01

To date, the amount of heterogeneity among studies of the body mass index-mortality association attributable to differences in the age distribution and length of follow-up has not been quantified. Therefore, we wanted to quantify the amount of heterogeneity attributable to age and follow-up in results of studies on the body mass index-mortality relation. We used optima of the body mass index mortality association reported for 30 populations and performed meta-regression to estimate the amount of heterogeneity attributable to sex, ethnicity, mean age at baseline, percentage smokers, and length of follow-up. Ethnicity as single factor accounted for 36% (95% CI, 11-56%) of heterogeneity. Mean age and length of follow-up had an interactive effect and together accounted for 56% (95% CI, 24-74%) of the remaining heterogeneity. Sex did not significantly contribute to the heterogeneity, after controlling for ethnicity, age, and length of follow-up. A considerable amount of heterogeneity in studies of the body mass index-mortality association is attributable to ethnicity, age, and length of follow-up. Copyright © 2017 The Authors. Production and hosting by Elsevier B.V. All rights reserved.

Firing rate dynamics in recurrent spiking neural networks with intrinsic and network heterogeneity.

Science.gov (United States)

Ly, Cheng

2015-12-01

Heterogeneity of neural attributes has recently gained a lot of attention and is increasing recognized as a crucial feature in neural processing. Despite its importance, this physiological feature has traditionally been neglected in theoretical studies of cortical neural networks. Thus, there is still a lot unknown about the consequences of cellular and circuit heterogeneity in spiking neural networks. In particular, combining network or synaptic heterogeneity and intrinsic heterogeneity has yet to be considered systematically despite the fact that both are known to exist and likely have significant roles in neural network dynamics. In a canonical recurrent spiking neural network model, we study how these two forms of heterogeneity lead to different distributions of excitatory firing rates. To analytically characterize how these types of heterogeneities affect the network, we employ a dimension reduction method that relies on a combination of Monte Carlo simulations and probability density function equations. We find that the relationship between intrinsic and network heterogeneity has a strong effect on the overall level of heterogeneity of the firing rates. Specifically, this relationship can lead to amplification or attenuation of firing rate heterogeneity, and these effects depend on whether the recurrent network is firing asynchronously or rhythmically firing. These observations are captured with the aforementioned reduction method, and furthermore simpler analytic descriptions based on this dimension reduction method are developed. The final analytic descriptions provide compact and descriptive formulas for how the relationship between intrinsic and network heterogeneity determines the firing rate heterogeneity dynamics in various settings.

Heterogeneous recurrence monitoring and control of nonlinear stochastic processes

Energy Technology Data Exchange (ETDEWEB)

Yang, Hui, E-mail: huiyang@usf.edu; Chen, Yun [Complex Systems Monitoring, Modeling and Analysis Laboratory, University of South Florida, Tampa, Florida 33620 (United States)

2014-03-15

Recurrence is one of the most common phenomena in natural and engineering systems. Process monitoring of dynamic transitions in nonlinear and nonstationary systems is more concerned with aperiodic recurrences and recurrence variations. However, little has been done to investigate the heterogeneous recurrence variations and link with the objectives of process monitoring and anomaly detection. Notably, nonlinear recurrence methodologies are based on homogeneous recurrences, which treat all recurrence states in the same way as black dots, and non-recurrence is white in recurrence plots. Heterogeneous recurrences are more concerned about the variations of recurrence states in terms of state properties (e.g., values and relative locations) and the evolving dynamics (e.g., sequential state transitions). This paper presents a novel approach of heterogeneous recurrence analysis that utilizes a new fractal representation to delineate heterogeneous recurrence states in multiple scales, including the recurrences of both single states and multi-state sequences. Further, we developed a new set of heterogeneous recurrence quantifiers that are extracted from fractal representation in the transformed space. To that end, we integrated multivariate statistical control charts with heterogeneous recurrence analysis to simultaneously monitor two or more related quantifiers. Experimental results on nonlinear stochastic processes show that the proposed approach not only captures heterogeneous recurrence patterns in the fractal representation but also effectively monitors the changes in the dynamics of a complex system.

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

Directory of Open Access Journals (Sweden)

Mary E Blair

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

The effect of correlated neuronal firing and neuronal heterogeneity on population coding accuracy in guinea pig inferior colliculus.

Directory of Open Access Journals (Sweden)

Oran Zohar

Full Text Available It has been suggested that the considerable noise in single-cell responses to a stimulus can be overcome by pooling information from a large population. Theoretical studies indicated that correlations in trial-to-trial fluctuations in the responses of different neurons may limit the improvement due to pooling. Subsequent theoretical studies have suggested that inherent neuronal diversity, i.e., the heterogeneity of tuning curves and other response properties of neurons preferentially tuned to the same stimulus, can provide a means to overcome this limit. Here we study the effect of spike-count correlations and the inherent neuronal heterogeneity on the ability to extract information from large neural populations. We use electrophysiological data from the guinea pig Inferior-Colliculus to capture inherent neuronal heterogeneity and single cell statistics, and introduce response correlations artificially. To this end, we generate pseudo-population responses, based on single-cell recording of neurons responding to auditory stimuli with varying binaural correlations. Typically, when pseudo-populations are generated from single cell data, the responses within the population are statistically independent. As a result, the information content of the population will increase indefinitely with its size. In contrast, here we apply a simple algorithm that enables us to generate pseudo-population responses with variable spike-count correlations. This enables us to study the effect of neuronal correlations on the accuracy of conventional rate codes. We show that in a homogenous population, in the presence of even low-level correlations, information content is bounded. In contrast, utilizing a simple linear readout, that takes into account the natural heterogeneity, even of neurons preferentially tuned to the same stimulus, within the neural population, one can overcome the correlated noise and obtain a readout whose accuracy grows linearly with the size of

Acknowledging patient heterogeneity in economic evaluation : a systematic literature review.

Science.gov (United States)

Grutters, Janneke P C; Sculpher, Mark; Briggs, Andrew H; Severens, Johan L; Candel, Math J; Stahl, James E; De Ruysscher, Dirk; Boer, Albert; Ramaekers, Bram L T; Joore, Manuela A

2013-02-01

Patient heterogeneity is the part of variability that can be explained by certain patient characteristics (e.g. age, disease stage). Population reimbursement decisions that acknowledge patient heterogeneity could potentially save money and increase population health. To date, however, economic evaluations pay only limited attention to patient heterogeneity. The objective of the present paper is to provide a comprehensive overview of the current knowledge regarding patient heterogeneity within economic evaluation of healthcare programmes. A systematic literature review was performed to identify methodological papers on the topic of patient heterogeneity in economic evaluation. Data were obtained using a keyword search of the PubMed database and manual searches. Handbooks were also included. Relevant data were extracted regarding potential sources of patient heterogeneity, in which of the input parameters of an economic evaluation these occur, methods to acknowledge patient heterogeneity and specific concerns associated with this acknowledgement. A total of 20 articles and five handbooks were included. The relevant sources of patient heterogeneity (demographics, preferences and clinical characteristics) and the input parameters where they occurred (baseline risk, treatment effect, health state utility and resource utilization) were combined in a framework. Methods were derived for the design, analysis and presentation phases of an economic evaluation. Concerns related mainly to the danger of false-positive results and equity issues. By systematically reviewing current knowledge regarding patient heterogeneity within economic evaluations of healthcare programmes, we provide guidance for future economic evaluations. Guidance is provided on which sources of patient heterogeneity to consider, how to acknowledge them in economic evaluation and potential concerns. The improved acknowledgement of patient heterogeneity in future economic evaluations may well improve the

Method of improving heterogeneous oil reservoir polymer flooding effect by positively-charged gel profile control

Science.gov (United States)

Zhao, Ling; Xia, Huifen

2018-01-01

The project of polymer flooding has achieved great success in Daqing oilfield, and the main oil reservoir recovery can be improved by more than 15%. But, for some strong oil reservoir heterogeneity carrying out polymer flooding, polymer solution will be inefficient and invalid loop problem in the high permeability layer, then cause the larger polymer volume, and a significant reduction in the polymer flooding efficiency. Aiming at this problem, it is studied the method that improves heterogeneous oil reservoir polymer flooding effect by positively-charged gel profile control. The research results show that the polymer physical and chemical reaction of positively-charged gel with the residual polymer in high permeability layer can generate three-dimensional network of polymer, plugging high permeable layer, and increase injection pressure gradient, then improve the effect of polymer flooding development. Under the condition of the same dosage, positively-charged gel profile control can improve the polymer flooding recovery factor by 2.3∼3.8 percentage points. Under the condition of the same polymer flooding recovery factor increase value, after positively-charged gel profile control, it can reduce the polymer volume by 50 %. Applying mechanism of positively-charged gel profile control technology is feasible, cost savings, simple construction, and no environmental pollution, therefore has good application prospect.

Genetic heterogeneity of retinitis pigmentosa

OpenAIRE

Hartono, Hartono

2015-01-01

Genetic heterogeneity is a phenomenon in which a genetic disease can be transmitted by several modes of inheritance. The understanding of genetic heterogeneity is important in giving genetic counselling.The presence of genetic heterogeneity can be explained by the existence of:1.different mutant alleles at a single locus, and2.mutant alleles at different loci affecting the same enzyme or protein, or affecting different enzymes or proteins.To have an overall understanding of genetic heterogene...

Earthquake ground-motion in presence of source and medium heterogeneities

KAUST Repository

Vyas, Jagdish Chandra

2017-01-01

This dissertation work investigates the effects of earthquake rupture complexity and heterogeneities in Earth structure on near-field ground-motions. More specifically, we address two key issues in seismology: (1) near-field ground-shaking variability as function of distance and azimuth for unilateral directive ruptures, and (2) impact of rupture complexity and seismic scattering on Mach wave coherence associated with supershear rupture propagation. We examine earthquake ground-motion variability associated with unilateral ruptures based on ground-motion simulations of the MW 7.3 1992 Landers earthquake, eight simplified source models, and a MW 7.8 rupture simulation (ShakeOut) for the San Andreas fault. Our numerical modeling reveals that the ground-shaking variability in near-fault distances (< 20 km) is larger than that given by empirical ground motion prediction equations. In addition, the variability decreases with increasing distance from the source, exhibiting a power-law decay. The high near-field variability can be explained by strong directivity effects whose influence weaken as we move away from the fault. At the same time, the slope of the power-law decay is found to be dominantly controlled by slip heterogeneity. Furthermore, the ground-shaking variability is high in the rupture propagation direction whereas low in the directions perpendicular to it. However, the variability expressed as a function of azimuth is not only sensitive to slip heterogeneity, but also to rupture velocity. To study Mach wave coherence for supershear ruptures, we consider heterogeneities in rupture parameters (variations in slip, rise time and rupture speed) and 3D scattering media having small-scale random heterogeneities. The Mach wave coherence is reduced at near-fault distances (< 10 km) by the source heterogeneities. At the larger distances from the source, medium scattering plays the dominant role in reducing the Mach wave coherence. Combined effect of the source and

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

Science.gov (United States)

Green, Christopher T.; Böhlke, John Karl; Bekins, Barbara A.; Phillips, Steven 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, O2 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 O2threshold 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.

Quasi-linear score for capturing heterogeneous structure in biomarkers.

Science.gov (United States)

Omae, Katsuhiro; Komori, Osamu; Eguchi, Shinto

2017-06-19

Linear scores are widely used to predict dichotomous outcomes in biomedical studies because of their learnability and understandability. Such approaches, however, cannot be used to elucidate biodiversity when there is heterogeneous structure in target population. Our study was focused on describing intrinsic heterogeneity in predictions. Because heterogeneity can be captured by a clustering method, integrating different information from different clusters should yield better predictions. Accordingly, we developed a quasi-linear score, which effectively combines the linear scores of clustered markers. We extended the linear score to the quasi-linear score by a generalized average form, the Kolmogorov-Nagumo average. We observed that two shrinkage methods worked well: ridge shrinkage for estimating the quasi-linear score, and lasso shrinkage for selecting markers within each cluster. Simulation studies and applications to real data show that the proposed method has good predictive performance compared with existing methods. Heterogeneous structure is captured by a clustering method. Quasi-linear scores combine such heterogeneity and have a better predictive ability compared with linear scores.

Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof.

Science.gov (United States)

Buckland-Nicks, Michael; Heim, Amy; Lundholm, Jeremy

2016-05-15

Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%-26% volumetric moisture content) and temperature (21°C-36°C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat

Deconstructing transcriptional heterogeneity in pluripotent stem cells

Science.gov (United States)

Shalek, Alex K.; Satija, Rahul; DaleyKeyser, AJay; Li, Hu; Zhang, Jin; Pardee, Keith; Gennert, David; Trombetta, John J.; Ferrante, Thomas C.; Regev, Aviv; Daley, George Q.; Collins, James J.

2014-01-01

SUMMARY Pluripotent stem cells (PSCs) are capable of dynamic interconversion between distinct substates, but the regulatory circuits specifying these states and enabling transitions between them are not well understood. We set out to characterize transcriptional heterogeneity in PSCs by single-cell expression profiling under different chemical and genetic perturbations. Signaling factors and developmental regulators show highly variable expression, with expression states for some variable genes heritable through multiple cell divisions. Expression variability and population heterogeneity can be influenced by perturbation of signaling pathways and chromatin regulators. Strikingly, either removal of mature miRNAs or pharmacologic blockage of signaling pathways drives PSCs into a low-noise ground state characterized by a reconfigured pluripotency network, enhanced self-renewal, and a distinct chromatin state, an effect mediated by opposing miRNA families acting on the c-myc / Lin28 / let-7 axis. These data illuminate the nature of transcriptional heterogeneity in PSCs. PMID:25471879

Uranium (VI) transport in saturated heterogeneous media: Influence of kaolinite and humic acid.

Science.gov (United States)

Chen, Chong; Zhao, Kang; Shang, Jianying; Liu, Chongxuan; Wang, Jin; Yan, Zhifeng; Liu, Kesi; Wu, Wenliang

2018-05-07

Natural aquifers typically exhibit a variety of structural heterogeneities. However, the effect of mineral colloids and natural organic matter on the transport behavior of uranium (U) in saturated heterogeneous media are not totally understood. In this study, heterogeneous column experiments were conducted, and the constructed columns contained a fast-flow domain (FFD) and a slow-flow domain (SFD). The effect of kaolinite, humic acid (HA), and kaolinite/HA mixture on U(VI) retention and release in saturated heterogeneous media was examined. Media heterogeneity significantly influenced U fate and transport behavior in saturated subsurface environment. The presence of kaolinite, HA, and kaolinite/HA enhanced the mobility of U in heterogeneous media, and the mobility of U was the highest in the presence of kaolinite/HA and the lowest in the presence of kaolinite. In the presence of kaolinite, there was no difference in the amount of U released from the FFD and SFD. However, in the presence of HA and kaolinite/HA, a higher amount of U was released from the FFD. The findings in this study showed that medium structure and mineral colloids, as well as natural organic matter in the aqueous phase had significant effects on U transport and fate in subsurface environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Heterogeneous reactors

International Nuclear Information System (INIS)

Moura Neto, C. de; Nair, R.P.K.

1979-08-01

The microscopic study of a cell is meant for the determination of the infinite multiplication factor of the cell, which is given by the four factor formula: K(infinite) = n(epsilon)pf. The analysis of an homogeneous reactor is similar to that of an heterogeneous reactor, but each factor of the four factor formula can not be calculated by the formulas developed in the case of an homogeneous reactor. A great number of methods was developed for the calculation of heterogeneous reactors and some of them are discussed. (Author) [pt

Evaluation of neutron streaming in fast breeder reactor fuel assembly by double heterogeneous modelling

International Nuclear Information System (INIS)

Unesaki, Hironobu; Takeda, Toshikazu

1988-01-01

Neutron streaming in a fast breeder reactor fuel assembly caused by the double heterogeneity structure is estimated by double heterogeneous modelling. The conventional pin cell model, a two-region subassembly model and the exact pin cluster model are used to take into account the streaming effect caused by the pin cell structure and the surrounding wrapper tube structure. The heterogeneity of wrapper tube and its surrounding sodium is explicitly considered. The streaming effect is evaluated based on Benoist's diffusion coefficient. The total streaming effect caused by the double heterogeneity structure of a fuel subassembly is found to be -0.2 % dk/kk' for k eff , which is almost twice that obtained from the conventional pin cell model of -0.1 % dk/kk'. (author)

Methods for selecting fixed-effect models for heterogeneous codon evolution, with comments on their application to gene and genome data.

Science.gov (United States)

Bao, Le; Gu, Hong; Dunn, Katherine A; Bielawski, Joseph P

2007-02-08

Models of codon evolution have proven useful for investigating the strength and direction of natural selection. In some cases, a priori biological knowledge has been used successfully to model heterogeneous evolutionary dynamics among codon sites. These are called fixed-effect models, and they require that all codon sites are assigned to one of several partitions which are permitted to have independent parameters for selection pressure, evolutionary rate, transition to transversion ratio or codon frequencies. For single gene analysis, partitions might be defined according to protein tertiary structure, and for multiple gene analysis partitions might be defined according to a gene's functional category. Given a set of related fixed-effect models, the task of selecting the model that best fits the data is not trivial. In this study, we implement a set of fixed-effect codon models which allow for different levels of heterogeneity among partitions in the substitution process. We describe strategies for selecting among these models by a backward elimination procedure, Akaike information criterion (AIC) or a corrected Akaike information criterion (AICc). We evaluate the performance of these model selection methods via a simulation study, and make several recommendations for real data analysis. Our simulation study indicates that the backward elimination procedure can provide a reliable method for model selection in this setting. We also demonstrate the utility of these models by application to a single-gene dataset partitioned according to tertiary structure (abalone sperm lysin), and a multi-gene dataset partitioned according to the functional category of the gene (flagellar-related proteins of Listeria). Fixed-effect models have advantages and disadvantages. Fixed-effect models are desirable when data partitions are known to exhibit significant heterogeneity or when a statistical test of such heterogeneity is desired. They have the disadvantage of requiring a priori

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

Science.gov (United States)

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.

Scheduling in Heterogeneous Grid Environments: The Effects of DataMigration

Energy Technology Data Exchange (ETDEWEB)

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.

Socioeconomic Heterogeneity in the Effect of Health Shocks on Earnings: Evidence from Population-Wide Data on Swedish Workers

OpenAIRE

Lundborg, Petter; Nilsson, Martin; Vikström, Johan

2011-01-01

In this paper, we estimate socioeconomic heterogeneity in the effect of unexpected health shocks on labor market outcomes, using register-based data on the entire population of Swedish workers. We effectively exploit a Difference-in-Difference-in-Differences design, in which we compare the change in labor earnings across treated and control groups with high and low education levels. If the anticipation effects are similar for individuals with high and low education, any difference in the esti...

Modeling triple-negative breast cancer heterogeneity: effects of stromal macrophages, fibroblasts and tumor vasculature.

Science.gov (United States)

Norton, Kerri-Ann; Jin, Kideok; Popel, Aleksander S

2018-05-08

A hallmark of breast tumors is its spatial heterogeneity that includes its distribution of cancer stem cells and progenitor cells, but also heterogeneity in the tumor microenvironment. In this study we focus on the contributions of stromal cells, specifically macrophages, fibroblasts, and endothelial cells on tumor progression. We develop a computational model of triple-negative breast cancer based on our previous work and expand it to include macrophage infiltration, fibroblasts, and angiogenesis. In vitro studies have shown that the secretomes of tumor-educated macrophages and fibroblasts increase both the migration and proliferation rates of triple-negative breast cancer cells. In vivo studies also demonstrated that blocking signaling of selected secreted factors inhibits tumor growth and metastasis in mouse xenograft models. We investigate the influences of increased migration and proliferation rates on tumor growth, the effect of the presence on fibroblasts or macrophages on growth and morphology, and the contributions of macrophage infiltration on tumor growth. We find that while the presence of macrophages increases overall tumor growth, the increase in macrophage infiltration does not substantially increase tumor growth and can even stifle tumor growth at excessive rates. Copyright © 2018. Published by Elsevier Ltd.

Numerical Study of Critical Role of Rock Heterogeneity in Hydraulic Fracture Propagation

Energy Technology Data Exchange (ETDEWEB)

J. Zhou; H. Huang; M. Deo

2016-03-01

Log and seismic data indicate that most shale formations have strong heterogeneity. Conventional analytical and semi-analytical fracture models are not enough to simulate the complex fracture propagation in these highly heterogeneous formation. Without considering the intrinsic heterogeneity, predicted morphology of hydraulic fracture may be biased and misleading in optimizing the completion strategy. In this paper, a fully coupling fluid flow and geomechanics hydraulic fracture simulator based on dual-lattice Discrete Element Method (DEM) is used to predict the hydraulic fracture propagation in heterogeneous reservoir. The heterogeneity of rock is simulated by assigning different material force constant and critical strain to different particles and is adjusted by conditioning to the measured data and observed geological features. Based on proposed model, the effects of heterogeneity at different scale on micromechanical behavior and induced macroscopic fractures are examined. From the numerical results, the microcrack will be more inclined to form at the grain weaker interface. The conventional simulator with homogeneous assumption is not applicable for highly heterogeneous shale formation.

Influence of exposure differences on city-to-city heterogeneity ...

Science.gov (United States)

Multi-city population-based epidemiological studies have observed heterogeneity between city-specific fine particulate matter (PM2.5)-mortality effect estimates. These studies typically use ambient monitoring data as a surrogate for exposure leading to potential exposure misclassification. The level of exposure misclassification can differ by city affecting the observed health effect estimate. The objective of this analysis is to evaluate whether previously developed residential infiltration-based city clusters can explain city-to-city heterogeneity in PM2.5 mortality risk estimates. In a prior paper 94 cities were clustered based on residential infiltration factors (e.g. home age/size, prevalence of air conditioning (AC)), resulting in 5 clusters. For this analysis, the association between PM2.5 and all-cause mortality was first determined in 77 cities across the United States for 2001–2005. Next, a second stage analysis was conducted evaluating the influence of cluster assignment on heterogeneity in the risk estimates. Associations between a 2-day (lag 0–1 days) moving average of PM2.5 concentrations and non-accidental mortality were determined for each city. Estimated effects ranged from −3.2 to 5.1% with a pooled estimate of 0.33% (95% CI: 0.13, 0.53) increase in mortality per 10 μg/m3 increase in PM2.5. The second stage analysis determined that cluster assignment was marginally significant in explaining the city-to-city heterogeneity. The health effe

Heterogeneity in pineapple fruit quality results from plant heterogeneity at flower induction

NARCIS (Netherlands)

Fassinou Hotegni, V.N.; Lommen, W.J.M.; Agbossou, E.K.; Struik, P.C.

2014-01-01

Heterogeneity in fruit quality constitutes a major constraint in agri-food chains. In this paper the sources of the heterogeneity in pineapple in the field were studied in four experiments in commercial pineapple fields. The aims were to determine (a) whether differences in pineapple fruit quality

The impact of heterogeneous response on coupled spreading dynamics in multiplex networks

Science.gov (United States)

Nie, Xiaoyu; Tang, Ming; Zou, Yong; Guan, Shuguang; Zhou, Jie

2017-10-01

Many recent studies have demonstrated that individual awareness of disease may significantly affect the spreading process of infectious disease. In the majority of these studies, the response of the awareness is generally treated homogeneously. Considering of diversity and heterogeneity in the human behavior which widely exist under different circumstances, in this paper we study heterogeneous response when people are aware of the prevalence of infectious diseases. Specifically, we consider that an individual with more neighbors may take more preventive measures as a reaction when he is aware of the disease. A suppression strength is introduced to describe such heterogeneity, and we find that a more evident heterogeneity may cause a more effective suppressing effect to the spreading of epidemics. A mean-field theory is developed to support the results which are verified on the multiplex networks with different interlayer degree correlation.

The Effect of Mechanical Anisotropy and Heterogeneity of Shear Strength Parameters of Soils on Drained Bearing Capacity of Shallow Foundations

Directory of Open Access Journals (Sweden)

R. Jamshidi Chenari

2017-09-01

Full Text Available Natural formation of soil deposits causes heterogeneity and anisotropy in their strength and stiffness properties. However, most soils in their natural states exhibit some anisotropy with respect to shear strength and heterogeneity with respect to the depth. In this paper, the standard Mohr- Coulomb constitutive law is generalized to anisotropic version in order to consider the effect of cohesion anisotropy of soil. Random field theory coupled with finite difference method was utilized in Monte Carlo simulations with considering the effect of auto-correlation and cross correlation between strength parameters of soil, in order to calculate the bearing capacity of shallow foundation in a strain controlled scheme. The results showed that the bearing capacity of shallow foundation decreases with increasing in variability of strength parameters and increases with increasing in anisotropy ratio.

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

Science.gov (United States)

Shi, Chengyu; Guo, Bingqi; Cheng, Chih-Yao; Eng, Tony; Papanikolaou, Nikos

2010-09-01

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent™ x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V100 reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

Energy Technology Data Exchange (ETDEWEB)

Shi Chengyu; Guo Bingqi; Eng, Tony; Papanikolaou, Nikos [Cancer Therapy and Research Center, University of Texas Health Science Center at San Antonio, TX 78229 (United States); Cheng, Chih-Yao, E-mail: shic@uthscsa.ed [Radiation Oncology Department, Oklahoma University Health Science Center, Oklahoma, OK 73104 (United States)

2010-09-21

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent(TM) x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V{sub 100} reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

International Nuclear Information System (INIS)

Shi Chengyu; Guo Bingqi; Eng, Tony; Papanikolaou, Nikos; Cheng, Chih-Yao

2010-01-01

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent(TM) x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V 100 reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95

Handling preference heterogeneity for river services' adaptation to climate change.

Science.gov (United States)

Andreopoulos, Dimitrios; Damigos, Dimitrios; Comiti, Francesco; Fischer, Christian

2015-09-01

Climate projection models for the Southern Mediterranean basin indicate a strong drought trend. This pattern is anticipated to affect a range of services derived from river ecosystems and consecutively deteriorate the sectoral outputs and household welfare. This paper aims to evaluate local residents' adaptation preferences for the Piave River basin in Italy. A Discrete Choice Experiment accounting for adaptation scenarios of the Piave River services was conducted and the collected data were econometrically analyzed using Random Parameters Logit, Latent Class and Covariance Heterogeneity models. In terms of policy-relevant outcomes, the analysis indicates that respondents are willing to pay for adaptation plans. This attitude is reflected on the compensating surplus to sustain the current state of the Piave, which corresponds to a monthly contribution of 80€ per household. From an econometric point of view, the results show that it is not sufficient to take solely into account general heterogeneity, provided that distinct treatment of the heterogeneity produces rather different welfare estimates. This implies that analysts should examine a set of criteria when deciding on how to better approach heterogeneity for each empirical data set. Overall, non-market values of environmental services should be considered when formulating cost-effective adaptation measures for river systems undergoing climate change effects and appropriate heterogeneity approximation could render these values unbiased and accurate. Copyright © 2015 Elsevier Ltd. All rights reserved.

Accelerating Mathematics Achievement Using Heterogeneous Grouping

Science.gov (United States)

Burris, Carol Corbett; Heubert, Jay P.; Levin, Henry M.

2006-01-01

This longitudinal study examined the effects of providing an accelerated mathematics curriculum in heterogeneously grouped middle school classes in a diverse suburban school district. A quasi-experimental cohort design was used to evaluate subsequent completion of advanced high school math courses as well as academic achievement. Results showed…

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

Science.gov (United States)

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

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

Directory of Open Access Journals (Sweden)

J. M. Chen

2013-07-01

Full Text Available 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

Directional heterogeneity in WTP models for environmental valuation

NARCIS (Netherlands)

Schaafsma, M.; Brouwer, R.; Rose, J.

2012-01-01

Many studies in the stated preference literature on environmental valuation do not include the effects of substitutes and distance in willingness-to-pay (WTP) models, in spite of the relevance of these effects in aggregation and benefit transfer. Heterogeneity in the availability of substitutes over

Optimal resource allocation solutions for heterogeneous cognitive radio networks

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Babatunde Awoyemi

2017-05-01

Full Text Available Cognitive radio networks (CRN are currently gaining immense recognition as the most-likely next-generation wireless communication paradigm, because of their enticing promise of mitigating the spectrum scarcity and/or underutilisation challenge. Indisputably, for this promise to ever materialise, CRN must of necessity devise appropriate mechanisms to judiciously allocate their rather scarce or limited resources (spectrum and others among their numerous users. ‘Resource allocation (RA in CRN', which essentially describes mechanisms that can effectively and optimally carry out such allocation, so as to achieve the utmost for the network, has therefore recently become an important research focus. However, in most research works on RA in CRN, a highly significant factor that describes a more realistic and practical consideration of CRN has been ignored (or only partially explored, i.e., the aspect of the heterogeneity of CRN. To address this important aspect, in this paper, RA models that incorporate the most essential concepts of heterogeneity, as applicable to CRN, are developed and the imports of such inclusion in the overall networking are investigated. Furthermore, to fully explore the relevance and implications of the various heterogeneous classifications to the RA formulations, weights are attached to the different classes and their effects on the network performance are studied. In solving the developed complex RA problems for heterogeneous CRN, a solution approach that examines and exploits the structure of the problem in achieving a less-complex reformulation, is extensively employed. This approach, as the results presented show, makes it possible to obtain optimal solutions to the rather difficult RA problems of heterogeneous CRN.

Quantification of Spatial Heterogeneity in Old Growth Forst of Korean Pine

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Wang Zhengquan; Wang Qingcheng; Zhang Yandong

1997-01-01

Spatial hetergeneity is a very important issue in studying functions and processes of ecological systems at various scales. Semivariogram analysis is an effective technique to summarize spatial data, and quantification of sptail heterogeneity. In this paper, we propose some principles to use semivariograms to characterize and compare spatial heterogeneity of...

Carrying capacity in a heterogeneous environment with habitat connectivity.

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Zhang, Bo; Kula, Alex; Mack, Keenan M L; Zhai, Lu; Ryce, Arrix L; Ni, Wei-Ming; DeAngelis, Donald L; Van Dyken, J David

2017-09-01

A large body of theory predicts that populations diffusing in heterogeneous environments reach higher total size than if non-diffusing, and, paradoxically, higher size than in a corresponding homogeneous environment. However, this theory and its assumptions have not been rigorously tested. Here, we extended previous theory to include exploitable resources, proving qualitatively novel results, which we tested experimentally using spatially diffusing laboratory populations of yeast. Consistent with previous theory, we predicted and experimentally observed that spatial diffusion increased total equilibrium population abundance in heterogeneous environments, with the effect size depending on the relationship between r and K. Refuting previous theory, however, we discovered that homogeneously distributed resources support higher total carrying capacity than heterogeneously distributed resources, even with species diffusion. Our results provide rigorous experimental tests of new and old theory, demonstrating how the traditional notion of carrying capacity is ambiguous for populations diffusing in spatially heterogeneous environments. © 2017 John Wiley & Sons Ltd/CNRS.

Modeling the large-scale effects of surface moisture heterogeneity on wetland carbon fluxes in the West Siberian Lowland

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T. J. Bohn

2013-10-01

Full Text Available We used a process-based model to examine the role of spatial heterogeneity of surface and sub-surface water on the carbon budget of the wetlands of the West Siberian Lowland over the period 1948–2010. We found that, while surface heterogeneity (fractional saturated area had little overall effect on estimates of the region's carbon fluxes, sub-surface heterogeneity (spatial variations in water table depth played an important role in both the overall magnitude and spatial distribution of estimates of the region's carbon fluxes. In particular, to reproduce the spatial pattern of CH4 emissions recorded by intensive in situ observations across the domain, in which very little CH4 is emitted north of 60° N, it was necessary to (a account for CH4 emissions from unsaturated wetlands and (b use spatially varying methane model parameters that reduced estimated CH4 emissions in the northern (permafrost half of the domain (and/or account for lower CH4 emissions under inundated conditions. Our results suggest that previous estimates of the response of these wetlands to thawing permafrost may have overestimated future increases in methane emissions in the permafrost zone.

Effects of upper mantle heterogeneities on the lithospheric stress field and dynamic topography

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Osei Tutu, Anthony; Steinberger, Bernhard; Sobolev, Stephan V.; Rogozhina, Irina; Popov, Anton A.

2018-05-01

The orientation and tectonic regime of the observed crustal/lithospheric stress field contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. In this study, we analyze the influence of the thermal and density structure of the upper mantle on the lithospheric stress field and topography. We use a 3-D lithosphere-asthenosphere numerical model with power-law rheology, coupled to a spectral mantle flow code at 300 km depth. Our results are validated against the World Stress Map 2016 (WSM2016) and the observation-based residual topography. We derive the upper mantle thermal structure from either a heat flow model combined with a seafloor age model (TM1) or a global S-wave velocity model (TM2). We show that lateral density heterogeneities in the upper 300 km have a limited influence on the modeled horizontal stress field as opposed to the resulting dynamic topography that appears more sensitive to such heterogeneities. The modeled stress field directions, using only the mantle heterogeneities below 300 km, are not perturbed much when the effects of lithosphere and crust above 300 km are added. In contrast, modeled stress magnitudes and dynamic topography are to a greater extent controlled by the upper mantle density structure. After correction for the chemical depletion of continents, the TM2 model leads to a much better fit with the observed residual topography giving a good correlation of 0.51 in continents, but this correction leads to no significant improvement of the fit between the WSM2016 and the resulting lithosphere stresses. In continental regions with abundant heat flow data, TM1 results in relatively small angular misfits. For example, in western Europe the misfit between the modeled and observation-based stress is 18.3°. Our findings emphasize that the relative contributions coming from shallow and deep mantle dynamic forces are quite different for the lithospheric stress field and dynamic

Characterizing heterogeneous cellular responses to perturbations.

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Slack, Michael D; Martinez, Elisabeth D; Wu, Lani F; Altschuler, Steven J

2008-12-09

Cellular populations have been widely observed to respond heterogeneously to perturbation. However, interpreting the observed heterogeneity is an extremely challenging problem because of the complexity of possible cellular phenotypes, the large dimension of potential perturbations, and the lack of methods for separating meaningful biological information from noise. Here, we develop an image-based approach to characterize cellular phenotypes based on patterns of signaling marker colocalization. Heterogeneous cellular populations are characterized as mixtures of phenotypically distinct subpopulations, and responses to perturbations are summarized succinctly as probabilistic redistributions of these mixtures. We apply our method to characterize the heterogeneous responses of cancer cells to a panel of drugs. We find that cells treated with drugs of (dis-)similar mechanism exhibit (dis-)similar patterns of heterogeneity. Despite the observed phenotypic diversity of cells observed within our data, low-complexity models of heterogeneity were sufficient to distinguish most classes of drug mechanism. Our approach offers a computational framework for assessing the complexity of cellular heterogeneity, investigating the degree to which perturbations induce redistributions of a limited, but nontrivial, repertoire of underlying states and revealing functional significance contained within distinct patterns of heterogeneous responses.

Effective Wettability of Heterogenous Fracture Surfaces Using the Lattice-Boltzmann Method

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E Santos, J.; Prodanovic, M.; Landry, C. J.

2017-12-01

Fracture walls in the subsurface are often structured by minerals of different composition (potentially further altered in contact with fluids during hydrocarbon extraction or CO2 sequestration), this yields in a heterogeneous wettability of the surface in contact with the fluids. The focus of our work is to study how surfaces presenting different mineralogy and roughness affect multiphase flow in fractures. Using the Shan-Chen model of the lattice-Boltzmann method (LBM) we define fluid interaction and surface attraction parameters to simulate a system of a wetting and a non-wetting fluid. In this work, we use synthetically created fractures presenting different arrangements of wetting and non-wetting patches, and with or without roughness; representative of different mineralogy, similar workflow can be applied to fractures extracted from X-ray microtomography images of fractures porous media. The results from the LBM simulations provide an insight on how the distribution of mineralogy and surface roughness are related with the observed macroscopic contact angle. We present a comparison between the published analytical models, and our results based on surface areas, spatial distribution and local fracture aperture. The understanding of the variables that affect the contact angle is useful for the comprehension of multiphase processes in naturally fractured reservoirs like primary oil production, enhanced oil recovery and CO2 sequestration. The macroscopic contact angle analytical equations for heterogeneous surfaces with variable roughness are no longer valid in highly heterogeneous systems; we quantify the difference thus offering an alternative to analytical models.

Thermal conductivity of heterogeneous LWR MOX fuels

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Staicu, D.; Barker, M.

2013-11-01

It is generally observed that the thermal conductivity of LWR MOX fuel is lower than that of pure UO2. For MOX, the degradation is usually only interpreted as an effect of the substitution of U atoms by Pu. This hypothesis is however in contradiction with the observations of Duriez and Philiponneau showing that the thermal conductivity of MOX is independent of the Pu content in the ranges 3-15 and 15-30 wt.% PuO2 respectively. Attributing this degradation to Pu only implies that stoichiometric heterogeneous MOX can be obtained, while we show that any heterogeneity in the plutonium distribution in the sample introduces a variation in the local stoichiometry which in turn has a strong impact on the thermal conductivity. A model quantifying this effect is obtained and a new set of experimental results for homogeneous and heterogeneous MOX fuels is presented and used to validate the proposed model. In irradiated fuels, this effect is predicted to disappear early during irradiation. The 3, 6 and 10 wt.% Pu samples have a similar thermal conductivity. Comparison of the results for this homogeneous microstructure with MIMAS (heterogeneous) fuel of the same composition showed no difference for the Pu contents of 3, 5.9, 6, 7.87 and 10 wt.%. A small increase of the thermal conductivity was obtained for 15 wt.% Pu. This increase is of about 6% when compared to the average of the values obtained for 3, 6 and 10 wt.% Pu. For comparison purposes, Duriez also measured the thermal conductivity of FBR MOX with 21.4 wt.% Pu with O/M = 1.982 and a density close to 95% TD and found a value in good agreement with the estimation obtained using the formula of Philipponneau [8] for FBR MOX, and significantly lower than his results corresponding to the range 3-15 wt.% Pu. This difference in thermal conductivity is of about 20%, i.e. higher than the measurement uncertainties.Thus, a significant difference was observed between FBR and PWR MOX fuels, but was not explained. This difference

HETEROGENEOUS INTEGRATION TECHNOLOGY

Science.gov (United States)

2017-08-24

AFRL-RY-WP-TR-2017-0168 HETEROGENEOUS INTEGRATION TECHNOLOGY Dr. Burhan Bayraktaroglu Devices for Sensing Branch Aerospace Components & Subsystems...Final September 1, 2016 – May 1, 2017 4. TITLE AND SUBTITLE HETEROGENEOUS INTEGRATION TECHNOLOGY 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER N/A...provide a structure for this review. The history and the current status of integration technologies in each category are examined and product examples are

Investigations on the heterogenous catalytic hydrogenation using isotope effect and gamma- and neutron radiation

Energy Technology Data Exchange (ETDEWEB)

Kudlacek, R; Cabicar, J [Ceske Vysoke Uceni Technicke, Prague (Czechoslovakia). Katedra Jaderne Chemie

1976-01-01

The kinetic and solvent isotope effects during the maleic acid heterogeneous catalytic hydrogenation and deuteration in light and heavy water have been studied. Also the effect of the gamma and neutron irradiation on the Ni-ZnO catalysts (with various ratios of components) on the reaction kinetics and mechanism has been measured, as well as the effect of pH on the adsorption behaviour of maleic acid and the temperature dependence of the reaction rate. Existence of different adsorption centers for hydrogen and maleic acid could be deduced from these experiments. A reaction mechanism based on the two-dimensional diffusion of components in the surface is proposed. The catalyst is formed from Ni and ZnO-microspheres. Hydrogen is bound to nickel and maleic acid is adsorbed on the ZnO-microspheres. The reaction takes place on the boundary layers of these microspheres.

Effects of local biotic neighbors and habitat heterogeneity on tree and shrub seedling survival in an old-growth temperate forest.

Science.gov (United States)

Bai, Xuejiao; Queenborough, Simon A; Wang, Xugao; Zhang, Jian; Li, Buhang; Yuan, Zuoqiang; Xing, Dingliang; Lin, Fei; Ye, Ji; Hao, Zhanqing

2012-11-01

Seedling dynamics play a crucial role in determining species distributions and coexistence. Exploring causes of variation in seedling dynamics can therefore provide key insights into the factors affecting these phenomena. We examined the relative importance of biotic neighborhood processes and habitat heterogeneity using survival data for 5,827 seedlings in 39 tree and shrub species over 2 years from an old-growth temperate forest in northeastern China. We found significant negative density-dependence effects on survival of tree seedlings, and limited effects of habitat heterogeneity (edaphic and topographic variables) on survival of shrub seedlings. The importance of negative density dependence on young tree seedling survival was replaced by habitat in tree seedlings ≥ 4 years old. As expected, negative density dependence was more apparent in gravity-dispersed species compared to wind-dispersed and animal-dispersed species. Moreover, we found that a community compensatory trend existed for trees. Therefore, although negative density dependence was not as pervasive as in other forest communities, it is an important mechanism for the maintenance of community diversity in this temperate forest. We conclude that both negative density dependence and habitat heterogeneity drive seedling survival, but their relative importance varies with seedling age classes and species traits.

Long-term Results of Troublesome CWD Cavity Reconstruction by Mastoid and Epitympanic Bony Obliteration (CWR-BOT) in Adults.

Science.gov (United States)

Vercruysse, Jean-Philippe; van Dinther, Joost J S; De Foer, Bert; Casselman, Jan; Somers, Thomas; Zarowski, Andrzej; Cremers, Cor C; Offeciers, Erwin

2016-07-01

To present the long-term surgical outcome of the bony mastoid and epitympanic obliteration technique with canal wall reconstruction (CWR-BOT) in adults with an unstable cavity after previous canal wall-down surgery for extensive cholesteatoma. Retrospective study. Therapeutic. Tertiary referral center. Fifty consecutive adult patients undergoing a CWR-BOT between 1998 and 2009. (A) Recurrence and residual rates of cholesteatoma, (B) postoperative hygienic status of the ear, including postoperative aspect of the tympanic membrane and external ear canal integrity (EAC), (C) functional outcome, and (D) long-term safety issues. (A) The percentage of ears remaining safe without recurrent or residual disease after CWR-BOT was 96% after a mean follow-up time of 101.8 months. Recurrent cholesteatoma occurred in 2% (n = 1) and a residual cholesteatoma was detected in 2% (n = 1) of the patients. (B) A safe dry, and trouble-free graft and selfcleaning EAC was achieved in 94%. (C) The postoperative hearing results showed a gain of 1.7 dB on pure-tone average air-conduction. (D) Nonecho planar diffusion-weighted imaging (non-EP DW magnetic resonance imaging) documented the residual (n = 1) and recurrent cholesteatoma (n = 1). The 1- and 5-year imaging follow-up revealed no other recurrent or residual disease. The CWR-BOT is a safe and very effective option for treatment of problematic unstable canal wall-down mastoid cavities, resulting in dry trouble-free ears.

A versatile omnibus test for detecting mean and variance heterogeneity.

Science.gov (United States)

Cao, Ying; Wei, Peng; Bailey, Matthew; Kauwe, John S K; Maxwell, Taylor J

2014-01-01

Recent research has revealed loci that display variance heterogeneity through various means such as biological disruption, linkage disequilibrium (LD), gene-by-gene (G × G), or gene-by-environment interaction. We propose a versatile likelihood ratio test that allows joint testing for mean and variance heterogeneity (LRT(MV)) or either effect alone (LRT(M) or LRT(V)) in the presence of covariates. Using extensive simulations for our method and others, we found that all parametric tests were sensitive to nonnormality regardless of any trait transformations. Coupling our test with the parametric bootstrap solves this issue. Using simulations and empirical data from a known mean-only functional variant, we demonstrate how LD can produce variance-heterogeneity loci (vQTL) in a predictable fashion based on differential allele frequencies, high D', and relatively low r² values. We propose that a joint test for mean and variance heterogeneity is more powerful than a variance-only test for detecting vQTL. This takes advantage of loci that also have mean effects without sacrificing much power to detect variance only effects. We discuss using vQTL as an approach to detect G × G interactions and also how vQTL are related to relationship loci, and how both can create prior hypothesis for each other and reveal the relationships between traits and possibly between components of a composite trait.

Pricing Liquidity Risk with Heterogeneous Investment Horizons

NARCIS (Netherlands)

Beber, Alessandro; Driessen, Joost; Neuberger, A.; Tuijp, P

We develop an asset pricing model with stochastic transaction costs and investors with heterogeneous horizons. Depending on their horizon, investors hold different sets of assets in equilibrium. This generates segmentation and spillover effects for expected returns, where the liquidity (risk)

The effects of spatial and temporal heterogeneity on the population dynamics of four animal species in a Danish landscape

Directory of Open Access Journals (Sweden)

Forchhammer Mads C

2009-06-01

Full Text Available Abstract Background Variation in carrying capacity and population return rates is generally ignored in traditional studies of population dynamics. Variation is hard to study in the field because of difficulties controlling the environment in order to obtain statistical replicates, and because of the scale and expense of experimenting on populations. There may also be ethical issues. To circumvent these problems we used detailed simulations of the simultaneous behaviours of interacting animals in an accurate facsimile of a real Danish landscape. The models incorporate as much as possible of the behaviour and ecology of skylarks Alauda arvensis, voles Microtus agrestis, a ground beetle Bembidion lampros and a linyphiid spider Erigone atra. This allows us to quantify and evaluate the importance of spatial and temporal heterogeneity on the population dynamics of the four species. Results Both spatial and temporal heterogeneity affected the relationship between population growth rate and population density in all four species. Spatial heterogeneity accounted for 23–30% of the variance in population growth rate after accounting for the effects of density, reflecting big differences in local carrying capacity associated with the landscape features important to individual species. Temporal heterogeneity accounted for 3–13% of the variance in vole, skylark and spider, but 43% in beetles. The associated temporal variation in carrying capacity would be problematic in traditional analyses of density dependence. Return rates were less than one in all species and essentially invariant in skylarks, spiders and beetles. Return rates varied over the landscape in voles, being slower where there were larger fluctuations in local population sizes. Conclusion Our analyses estimated the traditional parameters of carrying capacities and return rates, but these are now seen as varying continuously over the landscape depending on habitat quality and the mechanisms

A further analysis of the role of heterogeneity in coevolutionary spatial games

Science.gov (United States)

Cardinot, Marcos; Griffith, Josephine; O'Riordan, Colm

2018-03-01

Heterogeneity has been studied as one of the most common explanations of the puzzle of cooperation in social dilemmas. A large number of papers have been published discussing the effects of increasing heterogeneity in structured populations of agents, where it has been established that heterogeneity may favour cooperative behaviour if it supports agents to locally coordinate their strategies. In this paper, assuming an existing model of a heterogeneous weighted network, we aim to further this analysis by exploring the relationship (if any) between heterogeneity and cooperation. We adopt a weighted network which is fully populated by agents playing both the Prisoner's Dilemma or the Optional Prisoner's Dilemma games with coevolutionary rules, i.e., not only the strategies but also the link weights evolve over time. Surprisingly, results show that the heterogeneity of link weights (states) on their own does not always promote cooperation; rather cooperation is actually favoured by the increase in the number of overlapping states and not by the heterogeneity itself. We believe that these results can guide further research towards a more accurate analysis of the role of heterogeneity in social dilemmas.

Genetic heterogeneity of within-family variance of body weight in Atlantic salmon (Salmo salar).

Science.gov (United States)

Sonesson, Anna K; Odegård, Jørgen; Rönnegård, Lars

2013-10-17

Canalization is defined as the stability of a genotype against minor variations in both environment and genetics. Genetic variation in degree of canalization causes heterogeneity of within-family variance. The aims of this study are twofold: (1) quantify genetic heterogeneity of (within-family) residual variance in Atlantic salmon and (2) test whether the observed heterogeneity of (within-family) residual variance can be explained by simple scaling effects. Analysis of body weight in Atlantic salmon using a double hierarchical generalized linear model (DHGLM) revealed substantial heterogeneity of within-family variance. The 95% prediction interval for within-family variance ranged from ~0.4 to 1.2 kg2, implying that the within-family variance of the most extreme high families is expected to be approximately three times larger than the extreme low families. For cross-sectional data, DHGLM with an animal mean sub-model resulted in severe bias, while a corresponding sire-dam model was appropriate. Heterogeneity of variance was not sensitive to Box-Cox transformations of phenotypes, which implies that heterogeneity of variance exists beyond what would be expected from simple scaling effects. Substantial heterogeneity of within-family variance was found for body weight in Atlantic salmon. A tendency towards higher variance with higher means (scaling effects) was observed, but heterogeneity of within-family variance existed beyond what could be explained by simple scaling effects. For cross-sectional data, using the animal mean sub-model in the DHGLM resulted in biased estimates of variance components, which differed substantially both from a standard linear mean animal model and a sire-dam DHGLM model. Although genetic differences in canalization were observed, selection for increased canalization is difficult, because there is limited individual information for the variance sub-model, especially when based on cross-sectional data. Furthermore, potential macro

in Heterogeneous Media

Directory of Open Access Journals (Sweden)

Saeed Balouchi

2013-01-01

Full Text Available Fractured reservoirs contain about 85 and 90 percent of oil and gas resources respectively in Iran. A comprehensive study and investigation of fractures as the main factor affecting fluid flow or perhaps barrier seems necessary for reservoir development studies. High degrees of heterogeneity and sparseness of data have incapacitated conventional deterministic methods in fracture network modeling. Recently, simulated annealing (SA has been applied to generate stochastic realizations of spatially correlated fracture networks by assuming that the elastic energy of fractures follows Boltzmann distribution. Although SA honors local variability, the objective function of geometrical fracture modeling is defined for homogeneous conditions. In this study, after the introduction of SA and the derivation of the energy function, a novel technique is presented to adjust the model with highly heterogeneous data for a fractured field from the southwest of Iran. To this end, the regular object-based model is combined with a grid-based technique to cover the heterogeneity of reservoir properties. The original SA algorithm is also modified by being constrained in different directions and weighting the energy function to make it appropriate for heterogeneous conditions. The simulation results of the presented approach are in good agreement with the observed field data.

Optimal Control of Heterogeneous Systems with Endogenous Domain of Heterogeneity

International Nuclear Information System (INIS)

Belyakov, Anton O.; Tsachev, Tsvetomir; Veliov, Vladimir M.

2011-01-01

The paper deals with optimal control of heterogeneous systems, that is, families of controlled ODEs parameterized by a parameter running over a domain called domain of heterogeneity. The main novelty in the paper is that the domain of heterogeneity is endogenous: it may depend on the control and on the state of the system. This extension is crucial for several economic applications and turns out to rise interesting mathematical problems. A necessary optimality condition is derived, where one of the adjoint variables satisfies a differential inclusion (instead of equation) and the maximization of the Hamiltonian takes the form of “min-max”. As a consequence, a Pontryagin-type maximum principle is obtained under certain regularity conditions for the optimal control. A formula for the derivative of the objective function with respect to the control from L ∞ is presented together with a sufficient condition for its existence. A stylized economic example is investigated analytically and numerically.

X-ray-assisted positioning of patients treated by conformal arc radiotherapy for prostate cancer: Comparison of setup accuracy using implanted markers versus bony structures

International Nuclear Information System (INIS)

Soete, Guy; Cock, Mieke de; Verellen, Dirk; Michielsen, Dirk; Keuppens, Frans; Storme, Guy

2007-01-01

Purpose: The aim of this study was to compare setup accuracy of NovalisBody stereoscopic X-ray positioning using implanted markers in the prostate vs. bony structures in patients treated with dynamic conformal arc radiotherapy for prostate cancer. Methods and Materials: Random and systematic setup errors (RE and SE) of the isocenter with regard to the center of gravity of three fiducial markers were measured by means of orthogonal verification films in 120 treatment sessions in 12 patients. Positioning was performed using NovalisBody semiautomated marker fusion. The results were compared with a control group of 261 measurements in 15 patients who were positioned with NovalisBody automated bone fusion. In addition, interfraction and intrafraction prostate motion was registered in the patients with implanted markers. Results: Marker-based X-ray positioning resulted in a reduction of RE as well as SE in the anteroposterior, craniocaudal, and left-right directions compared with those in the control group. The interfraction prostate displacements with regard to the bony pelvis that could be avoided by marker positioning ranged between 1.6 and 2.8 mm for RE and between 1.3 and 4.3 mm for SE. Intrafraction random and systematic prostate movements ranged between 1.4 and 2.4 mm and between 0.8 and 1.3 mm, respectively. Conclusion: The problem of interfraction prostate motion can be solved by using implanted markers. In addition, the NovalisBody X-ray system performs more accurately with markers compared with bone fusion. Intrafraction organ motion has become the limiting factor for margin reduction around the clinical target volume

3D modeling of carbonates petro-acoustic heterogeneities

Science.gov (United States)

Baden, Dawin; Guglielmi, Yves; Saracco, Ginette; Marié, Lionel; Viseur, Sophie

2015-04-01

Characterizing carbonate reservoirs heterogeneity is a challenging issue for Oil & Gas Industry, CO2 sequestration and all kinds of fluid manipulations in natural reservoirs, due to the significant impact of heterogeneities on fluid flow and storage within the reservoir. Although large scale (> meter) heterogeneities such as layers petrophysical contrasts are well addressed by computing facies-based models, low scale (ultrasonic apparatus and using different sensors allowing acoustic characterization through a bandwidth varying from 50 to 500 kHz. Comprehensive measurements realized on each samples allowed statistical analyses of petro-acoustic properties such as attenuation, shear and longitudinal wave velocity. The cores properties (geological and acoustic facies) were modeled in 3D using photogrammetry and GOCAD geo-modeler. This method successfully allowed detecting and imaging in three dimensions differential diagenesis effects characterized by the occurrence of decimeter-scale diagenetic horizons in samples assumed to be homogeneous and/or different diagenetic sequences between shells filling and the packing matrix. We then discuss how small interfaces such as cracks, stylolithes and laminations which are also imaged may have guided these differential effects, considering that understanding the processes may be taken as an analogue to actual fluid drainage complexity in deep carbonate reservoir.

Homogeneous-heterogeneous reactions in curved channel with porous medium

Science.gov (United States)

Hayat, T.; Ayub, Sadia; Alsaedi, A.

2018-06-01

Purpose of the present investigation is to examine the peristaltic flow through porous medium in a curved conduit. Problem is modeled for incompressible electrically conducting Ellis fluid. Influence of porous medium is tackled via modified Darcy's law. The considered model utilizes homogeneous-heterogeneous reactions with equal diffusivities for reactant and autocatalysis. Constitutive equations are formulated in the presence of viscous dissipation. Channel walls are compliant in nature. Governing equations are modeled and simplified under the assumptions of small Reynolds number and large wavelength. Graphical results for velocity, temperature, heat transfer coefficient and homogeneous-heterogeneous reaction parameters are examined for the emerging parameters entering into the problem. Results reveal an activation in both homogenous-heterogenous reaction effect and heat transfer rate with increasing curvature of the channel.

Quantifying seismic anisotropy induced by small-scale chemical heterogeneities

Science.gov (United States)

Alder, C.; Bodin, T.; Ricard, Y.; Capdeville, Y.; Debayle, E.; Montagner, J. P.

2017-12-01

Observations of seismic anisotropy are usually used as a proxy for lattice-preferred orientation (LPO) of anisotropic minerals in the Earth's mantle. In this way, seismic anisotropy observed in tomographic models provides important constraints on the geometry of mantle deformation associated with thermal convection and plate tectonics. However, in addition to LPO, small-scale heterogeneities that cannot be resolved by long-period seismic waves may also produce anisotropy. The observed (i.e. apparent) anisotropy is then a combination of an intrinsic and an extrinsic component. Assuming the Earth's mantle exhibits petrological inhomogeneities at all scales, tomographic models built from long-period seismic waves may thus display extrinsic anisotropy. In this paper, we investigate the relation between the amplitude of seismic heterogeneities and the level of induced S-wave radial anisotropy as seen by long-period seismic waves. We generate some simple 1-D and 2-D isotropic models that exhibit a power spectrum of heterogeneities as what is expected for the Earth's mantle, that is, varying as 1/k, with k the wavenumber of these heterogeneities. The 1-D toy models correspond to simple layered media. In the 2-D case, our models depict marble-cake patterns in which an anomaly in shear wave velocity has been advected within convective cells. The long-wavelength equivalents of these models are computed using upscaling relations that link properties of a rapidly varying elastic medium to properties of the effective, that is, apparent, medium as seen by long-period waves. The resulting homogenized media exhibit extrinsic anisotropy and represent what would be observed in tomography. In the 1-D case, we analytically show that the level of anisotropy increases with the square of the amplitude of heterogeneities. This relation is numerically verified for both 1-D and 2-D media. In addition, we predict that 10 per cent of chemical heterogeneities in 2-D marble-cake models can

Effect of Heterogeneity of Vertex Activation on Epidemic Spreading in Temporal Networks

Directory of Open Access Journals (Sweden)

Yixin Zhu

2014-01-01

Full Text Available Development of sensor technologies and the prevalence of electronic communication services provide us with a huge amount of data on human communication behavior, including face-to-face conversations, e-mail exchanges, phone calls, message exchanges, and other types of interactions in various online forums. These indirect or direct interactions form potential bridges of the virus spread. For a long time, the study of virus spread is based on the aggregate static network. However, the interaction patterns containing diverse temporal properties may affect dynamic processes as much as the network topology does. Some empirical studies show that the activation time and duration of vertices and links are highly heterogeneous, which means intense activity may be followed by longer intervals of inactivity. We take heterogeneous distribution of the node interactivation time as the research background to build an asynchronous communication model. The two sides of the communication do not have to be active at the same time. One derives the threshold of virus spreading on the communication mode and analyzes the reason the heterogeneous distribution of the vertex interactivation time suppresses the spread of virus. At last, the analysis and results from the model are verified on the BA network.

Quantifying spatial heterogeneity from images

International Nuclear Information System (INIS)

Pomerantz, Andrew E; Song Yiqiao

2008-01-01

Visualization techniques are extremely useful for characterizing natural materials with complex spatial structure. Although many powerful imaging modalities exist, simple display of the images often does not convey the underlying spatial structure. Instead, quantitative image analysis can extract the most important features of the imaged object in a manner that is easier to comprehend and to compare from sample to sample. This paper describes the formulation of the heterogeneity spectrum to show the extent of spatial heterogeneity as a function of length scale for all length scales to which a particular measurement is sensitive. This technique is especially relevant for describing materials that simultaneously present spatial heterogeneity at multiple length scales. In this paper, the heterogeneity spectrum is applied for the first time to images from optical microscopy. The spectrum is measured for thin section images of complex carbonate rock cores showing heterogeneity at several length scales in the range 10-10 000 μm.

Pricing Liquidity Risk with Heterogeneous Investment Horizons

NARCIS (Netherlands)

Beber, A.; Driessen, J.; Tuijp, P.F.A.

2012-01-01

We develop a new asset pricing model with stochastic transaction costs and investors with heterogenous horizons. Short-term investors hold only liquid assets in equilibrium. This generates segmentation effects in the pricing of liquid versus illiquid assets. Specifically, the liquidity (risk) premia

Heterogeneous traffic flow modelling using second-order macroscopic continuum model

Science.gov (United States)

Mohan, Ranju; Ramadurai, Gitakrishnan

2017-01-01

Modelling heterogeneous traffic flow lacking in lane discipline is one of the emerging research areas in the past few years. The two main challenges in modelling are: capturing the effect of varying size of vehicles, and the lack in lane discipline, both of which together lead to the 'gap filling' behaviour of vehicles. The same section length of the road can be occupied by different types of vehicles at the same time, and the conventional measure of traffic concentration, density (vehicles per lane per unit length), is not a good measure for heterogeneous traffic modelling. First aim of this paper is to have a parsimonious model of heterogeneous traffic that can capture the unique phenomena of gap filling. Second aim is to emphasize the suitability of higher-order models for modelling heterogeneous traffic. Third, the paper aims to suggest area occupancy as concentration measure of heterogeneous traffic lacking in lane discipline. The above mentioned two main challenges of heterogeneous traffic flow are addressed by extending an existing second-order continuum model of traffic flow, using area occupancy for traffic concentration instead of density. The extended model is calibrated and validated with field data from an arterial road in Chennai city, and the results are compared with those from few existing generalized multi-class models.

The impact of horizontal heterogeneities, cloud fraction, and liquid water path on warm cloud effective radii from CERES-like Aqua MODIS retrievals

OpenAIRE

Painemal, D.; Minnis, P.; Sun-Mack, S.

2013-01-01

The impact of horizontal heterogeneities, liquid water path (LWP from AMSR-E), and cloud fraction (CF) on MODIS cloud effective radius (re), retrieved from the 2.1 μm (re2.1) and 3.8 μm (re3.8) channels, is investigated for warm clouds over the southeast Pacific. Values of re retrieved using the CERES algorithms are averaged at the CERES footprint resolution (∼20 km), while heterogeneities (Hσ) are calculated as the ratio between the standard deviation and mean 0.64 μm reflectance. ...

Effects of temperature on the heterogeneous oxidation of sulfur dioxide by ozone on calcium carbonate

Directory of Open Access Journals (Sweden)

L. Y. Wu

2011-07-01

Full Text Available The heterogeneous oxidation of sulfur dioxide by ozone on CaCO₃ was studied as a function of temperature (230 to 298 K at ambient pressure. Oxidation reactions were followed in real time using diffuse reflectance infrared Fourier transform spectrometry (DRIFTS to obtain kinetic and mechanistic data. From the analysis of the spectral features, the formation of sulfate was identified on the surface in the presence of O₃ and SO₂ at different temperatures from 230 to 298 K. The results showed that the heterogeneous oxidation and the rate of sulfate formation were sensitive to temperature. An interesting stage-transition region was observed at temperatures ranging from 230 to 257 K, but it became ambiguous gradually above 257 K. The reactive uptake coefficients at different temperatures from 230 to 298 K were acquired for the first time, which can be used directly in atmospheric chemistry modeling studies to predict the formation of secondary sulfate aerosol in the troposphere. Furthermore, the rate of sulfate formation had a turning point at about 250 K. The sulfate concentration at 250 K was about twice as large as that at 298 K. The rate of sulfate formation increased with decreasing temperature at temperatures above 250 K, while there is a contrary temperature effect at temperatures below 250 K. The activation energy for heterogeneous oxidation at temperatures from 245 K to 230 K was determined to be 14.63 ± 0.20 kJ mol⁻¹. A mechanism for the temperature dependence was proposed and the atmospheric implications were discussed.

Shock propagation in a heterogeneous medium

International Nuclear Information System (INIS)

Elbaz, D.

2011-01-01

In the frame of the inertial confinement fusion in direct drive, the use of foams as ablator allows the reduction of hydrodynamic instabilities created on the target by the direct laser irradiation. The foam is made up of carbon (CH) fibers impregnated of cryogenic deuterium-tritium (DT). In the past, studies have been carried out considering this foam to be a homogeneous medium. Yet, the foam presents heterogeneous features. We study the effects of this heterogeneity on the shock velocity when the laser irradiates the target. Thanks to experimental and numerical studies, we show that the shock propagates faster in the heterogeneous medium than in the homogeneous one with the same averaged density. This velocity gap depends on the presence rate of the CH fibers in the foam, the density ratio, the adiabatic coefficient and the foam geometry. We model the foam by different ways, more and more complex. The shock velocity modification is due to the baroclinicity which, during the interaction between the shock front and the interface, creates a vorticity deposition, responsible for the shock acceleration. Accordingly, an interface, which is plane and perpendicular to the front shock, maximizes the vorticity deposition and increases the velocity gaps between heterogeneous and homogeneous media. We found a correlation between the kinetic energy behind the shock front and the velocities relative difference. We compared our results with two analytical models. However, the system is not closed, so we can't for the moment develop a predictive model. (author) [fr

Heterogeneous game resource distributions promote cooperation in spatial prisoner's dilemma game

Science.gov (United States)

Cui, Guang-Hai; Wang, Zhen; Yang, Yan-Cun; Tian, Sheng-Wen; Yue, Jun

2018-01-01

In social networks, individual abilities to establish interactions are always heterogeneous and independent of the number of topological neighbors. We here study the influence of heterogeneous distributions of abilities on the evolution of individual cooperation in the spatial prisoner's dilemma game. First, we introduced a prisoner's dilemma game, taking into account individual heterogeneous abilities to establish games, which are determined by the owned game resources. Second, we studied three types of game resource distributions that follow the power-law property. Simulation results show that the heterogeneous distribution of individual game resources can promote cooperation effectively, and the heterogeneous level of resource distributions has a positive influence on the maintenance of cooperation. Extensive analysis shows that cooperators with large resource capacities can foster cooperator clusters around themselves. Furthermore, when the temptation to defect is high, cooperator clusters in which the central pure cooperators have larger game resource capacities are more stable than other cooperator clusters.

Heterogeneous neutron-leakage model for PWR pin-by-pin calculation

International Nuclear Information System (INIS)

Li, Yunzhao; Zhang, Bin; Wu, Hongchun; Shen, Wei

2017-01-01

Highlights: •The derivation of the formula of the leakage model is introduced. This paper evaluates homogeneous and heterogeneous leakage models used in PWR pin-by-pin calculation. •The implements of homogeneous and heterogeneous leakage models used in pin-cell homogenization of the lattice calculation are studied. A consistent method of cooperation between the heterogeneous leakage model and the pin-cell homogenization theory is proposed. •Considering the computational cost, a new buckling search scheme is proposed to reach the convergence faster. The computational cost of the newly proposed neutron balance scheme is much less than the power-method scheme and the linear-interpolation scheme. -- Abstract: When assembly calculation is performed with the reflective boundary condition, a leakage model is usually required in the lattice code. The previous studies show that the homogeneous leakage model works effectively for the assembly homogenization. However, it becomes different and unsettled for the pin-cell homogenization. Thus, this paper evaluates homogeneous and heterogeneous leakage models used in pin-by-pin calculation. The implements of homogeneous and heterogeneous leakage models used in pin-cell homogenization of the lattice calculation are studied. A consistent method of cooperation between the heterogeneous leakage model and the pin-cell homogenization theory is proposed. Considering the computational cost, a new buckling search scheme is proposed to reach the convergence faster. For practical reactor-core applications, the diffusion coefficients determined by the transport cross-section or by the leakage model are compared with each other to determine which one is more accurate for the Pressurized Water Reactor pin-by-pin calculation. Numerical results have demonstrated that the heterogeneous leakage model together with the diffusion coefficient determined by the heterogeneous leakage model would have the higher accuracy. The new buckling search

Sub-Tg enthalpy relaxation in an unstable oxide glass former: insights into the structural heterogeneity

DEFF Research Database (Denmark)

Yue, Yuanzheng; Zhang, Yanfei

Structural heterogeneity plays a crucial role in determining functionality of glasses. In this work we have found that the sub-Tg enthalpy relaxation pattern in a hyperquenched glass is highly sensitive to structural heterogeneity. As a consequence, the former can be used as an effective approach...... to detect and quantify the structural heterogeneity in glass-forming liquids. However, the chemical nature of structural heterogeneity should be revealed by other means such as high resolution microscopic and spectroscopic methods. To study the impact of the structural heterogeneity on the sub-Tg relaxation...... chemical features and degrees of structural heterogeneity in glass-forming liquids. This finding contributes to the microscopic origin of both the primary and secondary relaxation in terms of structural heterogeneity. Finally the results provide insights into the relation between structural heterogeneity...

Heterogeneity in mammography use across the nation: separating evidence of disparities from the disproportionate effects of geography

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Clayton Laurel

2008-06-01

Full Text Available Abstract Background Mammography is essential for early detection of breast cancer and both reduced morbidity and increased survival among breast cancer victims. Utilization is lower than national guidelines, and evidence of a recent decline in mammography use has sparked concern. We demonstrate that regression models estimated over pooled samples of heterogeneous states may provide misleading information regarding predictors of health care utilization and that comprehensive cancer control efforts should focus on understanding these differences and underlying causal factors. Our study population includes all women over age 64 with breast cancer in the Surveillance Epidemiology and End Results (SEER cancer registries, linked to a nationally representative 5% reference sample of Medicare-eligible women located in 11 states that span all census regions and are heterogeneous in racial and ethnic mix. Combining women with and without cancer in the sample allows assessment of previous cancer diagnosis on propensity to use mammography. Our conceptual model recognizes the interplay between individual, social, cultural, and physical environments along the pathways to health care utilization, while delineating local and more distant levels of influence among contextual variables. In regression modeling, we assess individual-level effects, direct effects of contextual factors, and interaction effects between individual and contextual factors. Results Pooling all women across states leads to quite different conclusions than state-specific models. Commuter intensity, community acculturation, and community elderly impoverishment have significant direct impacts on mammography use which vary across states. Minorities living in isolated enclaves with others of the same race/ethnicity may be either advantaged or disadvantaged, depending upon the place studied. Conclusion Careful analysis of place-specific context is essential for understanding differences across

Understanding heterogeneity in the effects of birth weight on adult cognition and wages.

Science.gov (United States)

Justin Cook, C; Fletcher, Jason M

2015-05-01

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

Heterogeneity maintenance in glioblastoma: a social network.

Science.gov (United States)

Bonavia, Rudy; Inda, Maria-del-Mar; Cavenee, Webster K; Furnari, Frank B

2011-06-15

Glioblastoma multiforme (GBM), the most common intracranial tumor in adults, is characterized by extensive heterogeneity at the cellular and molecular levels. This insidious feature arises inevitably in almost all cancers and has great significance for the general outcome of the malignancy, because it confounds our understanding of the disease and also intrinsically contributes to the tumor's aggressiveness and poses an obstacle to the design of effective therapies. The classic view that heterogeneity arises as the result of a tumor's "genetic chaos" and the more contemporary cancer stem cell (CSC) hypothesis tend to identify a single cell population as the therapeutic target: the prevailing clone over time in the first case and the CSC in the latter. However, there is growing evidence that the different tumor cell populations may not be simple bystanders. Rather, they can establish a complex network of interactions between each other and with the tumor microenvironment that eventually strengthens tumor growth and increases chances to escape therapy. These differing but complementary ideas about the origin and maintenance of tumor heterogeneity and its importance in GBM are reviewed here.

Systemic risk and heterogeneous leverage in banking networks

Science.gov (United States)

Kuzubaş, Tolga Umut; Saltoğlu, Burak; Sever, Can

2016-11-01

This study probes systemic risk implications of leverage heterogeneity in banking networks. We show that the presence of heterogeneous leverages drastically changes the systemic effects of defaults and the nature of the contagion in interbank markets. Using financial leverage data from the US banking system, through simulations, we analyze the systemic significance of different types of borrowers, the evolution of the network, the consequences of interbank market size and the impact of market segmentation. Our study is related to the recent Basel III regulations on systemic risk and the treatment of the Global Systemically Important Banks (GSIBs). We also assess the extent to which the recent capital surcharges on GSIBs may curb financial fragility. We show the effectiveness of surcharge policy for the most-levered banks vis-a-vis uniform capital injection.

Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

Science.gov (United States)

Bagheri, Samira; Muhd Julkapli, Nurhidayatullaili; Bee Abd Hamid, Sharifah

2014-01-01

The lack of stability is a challenge for most heterogeneous catalysts. During operations, the agglomeration of particles may block the active sites of the catalyst, which is believed to contribute to its instability. Recently, titanium oxide (TiO2) was introduced as an alternative support material for heterogeneous catalyst due to the effect of its high surface area stabilizing the catalysts in its mesoporous structure. TiO2 supported metal catalysts have attracted interest due to TiO2 nanoparticles high activity for various reduction and oxidation reactions at low pressures and temperatures. Furthermore, TiO2 was found to be a good metal oxide catalyst support due to the strong metal support interaction, chemical stability, and acid-base property. The aforementioned properties make heterogeneous TiO2 supported catalysts show a high potential in photocatalyst-related applications, electrodes for wet solar cells, synthesis of fine chemicals, and others. This review focuses on TiO2 as a support material for heterogeneous catalysts and its potential applications. PMID:25383380

Spatial heterogeneity in light supply affects intraspecific competition of a stoloniferous clonal plant.

Directory of Open Access Journals (Sweden)

Pu Wang

Full Text Available Spatial heterogeneity in light supply is common in nature. Many studies have examined the effects of heterogeneous light supply on growth, morphology, physiology and biomass allocation of clonal plants, but few have tested those effects on intraspecific competition. In a greenhouse experiment, we grew one (no competition or nine ramets (with intraspecific competition of a stoloniferous clonal plant, Duchesnea indica, in three homogeneous light conditions (high, medium and low light intensity and two heterogeneous ones differing in patch size (large and small patch treatments. The total light in the two heterogeneous treatments was the same as that in the homogeneous medium light treatment. Both decreasing light intensity and intraspecific competition significantly decreased the growth (biomass, number of ramets and total stolon length of D. indica. As compared with the homogeneous medium light treatment, the large patch treatment significantly increased the growth of D. indica without intraspecific competition. However, the growth of D. indica with competition did not differ among the homogeneous medium light, the large and the small patch treatments. Consequently, light heterogeneity significantly increased intraspecific competition intensity, as measured by the decreased log response ratio. These results suggest that spatial heterogeneity in light supply can alter intraspecific interactions of clonal plants.

A Multianalyzer Machine Learning Model for Marine Heterogeneous Data Schema Mapping

Science.gov (United States)

Yan, Wang; Jiajin, Le; Yun, Zhang

2014-01-01

The main challenges that marine heterogeneous data integration faces are the problem of accurate schema mapping between heterogeneous data sources. In order to improve the schema mapping efficiency and get more accurate learning results, this paper proposes a heterogeneous data schema mapping method basing on multianalyzer machine learning model. The multianalyzer analysis the learning results comprehensively, and a fuzzy comprehensive evaluation system is introduced for output results' evaluation and multi factor quantitative judging. Finally, the data mapping comparison experiment on the East China Sea observing data confirms the effectiveness of the model and shows multianalyzer's obvious improvement of mapping error rate. PMID:25250372

Heterogeneity Measurement Based on Distance Measure for Polarimetric SAR Data

Science.gov (United States)

Xing, Xiaoli; Chen, Qihao; Liu, Xiuguo

2018-04-01

To effectively test the scene heterogeneity for polarimetric synthetic aperture radar (PolSAR) data, in this paper, the distance measure is introduced by utilizing the similarity between the sample and pixels. Moreover, given the influence of the distribution and modeling texture, the K distance measure is deduced according to the Wishart distance measure. Specifically, the average of the pixels in the local window replaces the class center coherency or covariance matrix. The Wishart and K distance measure are calculated between the average matrix and the pixels. Then, the ratio of the standard deviation to the mean is established for the Wishart and K distance measure, and the two features are defined and applied to reflect the complexity of the scene. The proposed heterogeneity measure is proceeded by integrating the two features using the Pauli basis. The experiments conducted on the single-look and multilook PolSAR data demonstrate the effectiveness of the proposed method for the detection of the scene heterogeneity.

Stochastic heterogeneous interaction promotes cooperation in spatial prisoner's dilemma game.

Directory of Open Access Journals (Sweden)

Ping Zhu

Full Text Available Previous studies mostly investigate player's cooperative behavior as affected by game time-scale or individual diversity. In this paper, by involving both time-scale and diversity simultaneously, we explore the effect of stochastic heterogeneous interaction. In our model, the occurrence of game interaction between each pair of linked player obeys a random probability, which is further described by certain distributions. Simulations on a 4-neighbor square lattice show that the cooperation level is remarkably promoted when stochastic heterogeneous interaction is considered. The results are then explained by investigating the mean payoffs, the mean boundary payoffs and the transition probabilities between cooperators and defectors. We also show some typical snapshots and evolution time series of the system. Finally, the 8-neighbor square lattice and BA scale-free network results indicate that the stochastic heterogeneous interaction can be robust against different network topologies. Our work may sharpen the understanding of the joint effect of game time-scale and individual diversity on spatial games.

Direct Breakthrough Curve Prediction From Statistics of Heterogeneous Conductivity Fields

Science.gov (United States)

Hansen, Scott K.; Haslauer, Claus P.; Cirpka, Olaf A.; Vesselinov, Velimir V.

2018-01-01

This paper presents a methodology to predict the shape of solute breakthrough curves in heterogeneous aquifers at early times and/or under high degrees of heterogeneity, both cases in which the classical macrodispersion theory may not be applicable. The methodology relies on the observation that breakthrough curves in heterogeneous media are generally well described by lognormal distributions, and mean breakthrough times can be predicted analytically. The log-variance of solute arrival is thus sufficient to completely specify the breakthrough curves, and this is calibrated as a function of aquifer heterogeneity and dimensionless distance from a source plane by means of Monte Carlo analysis and statistical regression. Using the ensemble of simulated groundwater flow and solute transport realizations employed to calibrate the predictive regression, reliability estimates for the prediction are also developed. Additional theoretical contributions include heuristics for the time until an effective macrodispersion coefficient becomes applicable, and also an expression for its magnitude that applies in highly heterogeneous systems. It is seen that the results here represent a way to derive continuous time random walk transition distributions from physical considerations rather than from empirical field calibration.

Characterizing Traffic Conditions from the Perspective of Spatial-Temporal Heterogeneity

Directory of Open Access Journals (Sweden)

Peichao Gao

2016-03-01

Full Text Available Traffic conditions are usually characterized from the perspective of travel time or the average vehicle speed in the field of transportation, reflecting the congestion degree of a road network. This article provides a method from a new perspective to characterize traffic conditions; the perspective is based on the heterogeneity of vehicle speeds. A novel measurement, the ratio of areas (RA in a rank-size plot, is included in the proposed method to capture the heterogeneity. The proposed method can be performed from the perspective of both spatial heterogeneity and temporal heterogeneity, being able to characterize traffic conditions of not only a road network but also a single road. Compared with methods from the perspective of travel time, the proposed method can characterize traffic conditions at a higher frequency. Compared to methods from the perspective of the average vehicle speed, the proposed method takes account of the heterogeneity of vehicle speeds. The effectiveness of the proposed method has been demonstrated with real-life traffic data of Shenzhen (a coastal urban city in China, and the advantage of the proposed RA has been verified by comparisons to similar measurements such as the ht-index and the CRG index.

First-principles study on ferrite/TiC heterogeneous nucleation interface

International Nuclear Information System (INIS)

Yang, Jian; Zhang, Pengfei; Zhou, Yefei; Guo, Jing; Ren, Xuejun; Yang, Yulin; Yang, Qingxiang

2013-01-01

Highlights: ► Interface stability of ferrite (1 0 0)/TiC (1 0 0) was studied. ► The effectiveness of TiC as the heterogeneous nuclei of ferrite was analyzed. ► Ti-termination and C-termination are the two binding modes for ferrite/TiC interface. ► Interfacial energy of the Ti-termination is larger than that of the C-termination. ► On C-termination, ability of TiC promotes ferrite heterogeneous nucleation is strong. -- Abstract: Interface atomic structure, bonding character, cohesive energy and interfacial energy of ferrite (1 0 0)/TiC (1 0 0) were studied using a first-principles density functional plane-wave ultrasoft pseudopotential method. Meanwhile, the effectiveness of TiC as the heterogeneous nuclei of ferrite was analyzed. The results indicated that, TiC bonding is dominated by the C-2p, C-2s and Ti-3d electrons, which exhibits high covalency. With increase of the atomic layers, the interfacial energies of ferrite and TiC are both declined rapidly and stabilized gradually. There are two binding modes for TiC as the heterogeneous nuclei of ferrite, which are Fe atoms above the Ti atoms (Ti-termination) and Fe atoms above the C atoms (C-termination). Interfacial energy of the Ti-termination is larger than that of the C-termination, which means that for Fe atoms above the C atoms, the ability of TiC promotes ferrite heterogeneous nucleation on its surface is larger than that for Fe atoms above the Ti atoms

Heterogeneous effects of health insurance on out-of-pocket expenditure on medicines in Mexico.

Science.gov (United States)

Wirtz, Veronika J; Santa-Ana-Tellez, Yared; Servan-Mori, Edson; Avila-Burgos, Leticia

2012-01-01

Given the importance of health insurance for financing medicines and recent policy changes designed to reduce health-related out-of-pocket expenditure (OOPE) in Mexico, our study examined and analyzed the effect of health insurance on the probability and amount of OOPE for medicines and the proportion spent from household available expenditure (AE) funds. We conducted a cross-sectional analysis by using the Mexican National Household Survey of Income and Expenditures for 2008. Households were grouped according to household medical insurance type (Social Security, Seguro Popular, mixed, or no affiliation). OOPE for medicines and health costs, and the probability of occurrence, were estimated with linear regression models; subsequently, the proportion of health expenditures from AE was calculated. The Heckman selection procedure was used to correct for self-selection of health expenditure; a propensity score matching procedure and an alternative procedure using instrumental variables were used to correct for heterogeneity between households with and without Seguro Popular. OOPE in medicines account for 66% of the total health expenditures and 5% of the AE. Households with health insurance had a lower probability of OOPE for medicines than their comparison groups. There was heterogeneity in the health insurance effect on the proportion of OOPE for medicines out of the AE, with a reduction of 1.7% for households with Social Security, 1.4% for mixed affiliation, but no difference between Seguro Popular and matched households without insurance. Medicines were the most prevalent component of health expenditures in Mexico. We recommend improving access to health services and strengthening access to medicines to reduce high OOPE. Copyright © 2012 International Society for Pharmacoeconomics and Outcomes Research (ISPOR). Published by Elsevier Inc. All rights reserved.

The effects of clinical and statistical heterogeneity on the predictive values of results from meta-analyses

NARCIS (Netherlands)

Melsen, W G; Rovers, M M; Bonten, M J M; Bootsma, M C J|info:eu-repo/dai/nl/304830305

Variance between studies in a meta-analysis will exist. This heterogeneity may be of clinical, methodological or statistical origin. The last of these is quantified by the I(2) -statistic. We investigated, using simulated studies, the accuracy of I(2) in the assessment of heterogeneity and the

Effect of clonal integration on nitrogen cycling in rhizosphere of rhizomatous clonal plant, Phyllostachys bissetii, under heterogeneous light.

Science.gov (United States)

Li, Yang; Chen, Jing-Song; Xue, Ge; Peng, Yuanying; Song, Hui-Xing

2018-07-01

Clonal integration plays an important role in clonal plant adapting to heterogeneous habitats. It was postulated that clonal integration could exhibit positive effects on nitrogen cycling in the rhizosphere of clonal plant subjected to heterogeneous light conditions. An in-situ experiment was conducted using clonal fragments of Phyllostachys bissetii with two successive ramets. Shading treatments were applied to offspring or mother ramets, respectively, whereas counterparts were treated to full sunlight. Rhizomes between two successive ramets were either severed or connected. Extracellular enzyme activities and nitrogen turnover were measured, as well as soil properties. Abundance of functional genes (archaeal or bacterial amoA, nifH) in the rhizosphere of shaded, offspring or mother ramets were determined using quantitative polymerase chain reaction. Carbon or nitrogen availabilities were significantly influenced by clonal integration in the rhizosphere of shaded ramets. Clonal integration significantly increased extracellular enzyme activities and abundance of functional genes in the rhizosphere of shaded ramets. When rhizomes were connected, higher nitrogen turnover (nitrogen mineralization or nitrification rates) was exhibited in the rhizosphere of shaded offspring ramets. However, nitrogen turnover was significantly decreased by clonal integration in the rhizosphere of shaded mother ramets. Path analysis indicated that nitrogen turnover in the rhizosphere of shaded, offspring or mother ramets were primarily driven by the response of soil microorganisms to dissolved organic carbon or nitrogen. This unique in-situ experiment provided insights into the mechanism of nutrient recycling mediated by clonal integration. It was suggested that effects of clonal integration on the rhizosphere microbial processes were dependent on direction of photosynthates transport in clonal plant subjected to heterogeneous light conditions. Copyright © 2018 Elsevier B.V. All rights

Posterior urethral injuries associated with motorcycle accidents and pelvic trauma in adolescents: analysis of urethral lesions occurring prior to a bony fracture using a computerized finite-element model.

Science.gov (United States)

Bréaud, J; Montoro, J; Lecompte, J F; Valla, J S; Loeffler, J; Baqué, P; Brunet, C; Thollon, L

2013-02-01

Adolescent males involved in motorcycle accidents are particularly at risk for pelvic injury, which may provoke a posterior urethral injury. The aim of this study was to develop a model to analyze the association between injuries and fractures of the pelvic ring and the risk of posterior urethral injury. Based on experience with traffic accident modeling, a computerized finite-element model was extrapolated from a computerized tomography scan of a 15-year-old boy. The anatomic structures concerned in urethral and pelvic ring trauma were isolated, rendered in 3D and given biomechanical properties. The model was verified according to available experiments on pelvic ring trauma. To apply the model, we recreated three impact mechanisms on the pelvic ring: lateral impact, antero-posterior impact and a real car‒motorcycle accident situation (postero-lateral impact). In all three situations, stretching of the posterior urethra was identified prior to bony fracture visualization. Application of this model allowed us to analyze precisely the link between trauma of the pelvic ring and lesions of the posterior urethra. The results should help to establish guidelines for urethral catheterization in male adolescents in cases of pelvic trauma, even when no bony fracture is present, in order to prevent iatrogenic worsening of a misdiagnosed posterior urethral trauma. Copyright © 2011 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

[Molecular heterogeneity of malignant pleural mesotheliomas].

Science.gov (United States)

Tranchant, Robin; Montagne, François; Jaurand, Marie-Claude; Jean, Didier

2018-01-01

Malignant pleural mesothelioma (MPM) is predominantly an occupational cancer, most often linked to asbestos exposure. Malignant pleural mesothelioma prognosis is poor with a short survival median, due to the aggressiveness of tumor cells and the weak efficiency of conventional anti-cancer therapies. Clinical, histological, and molecular data suggest tumor heterogeneity between patients as it was also shown for other cancer types. Consequently, there is an urgent need to develop new therapies that take into account this heterogeneity and the molecular characteristics of malignant pleural mesothelioma, in particular by identifying new anti-cancer drugs targeting the molecular specificities of each malignant pleural mesothelioma. Malignant pleural mesothelioma is characterized by numerous molecular alterations at the chromosomal, genetic and epigenetic levels. Molecular classification based on gene expression profile has firstly defined two tumor groups, C1 and C2, and more recently, four groups. By integrating genetic and transcriptomic analysis, a C2 LN tumor subgroup of the C2 group has been identified and characterized. In addition to tumor heterogeneity between patients, intra-tumor heterogeneity is supported by several evidences. Most therapeutic strategies that take into account the tumor molecular characteristics have focused on targeted therapies based on mutated genes. A more appropriate strategy would be to consider better-defined tumor groups on the basis of several molecular alterations types as it has been proposed for the C2 LN subgroup. A robust definition of homogeneous tumor groups sharing common molecular characteristics is necessary for the development of effective precision medicine for malignant pleural mesothelioma. Copyright © 2017 Société Française du Cancer. Published by Elsevier Masson SAS. All rights reserved.

Ethnic heterogeneity, social capital and psychological distress in Sweden.

Science.gov (United States)

Johnson-Singh, Charisse M; Rostila, Mikael; Ponce de Leon, Antonio; Forsell, Yvonne; Engström, Karin

2018-05-25

Ethnic heterogeneity has been linked to both protective and detrimental effects on mental health. Few studies have investigated the role of social capital in this relationship and none have found that it has an explanatory role. The aim of this study is to investigate the relationship between two measures of ethnic heterogeneity and psychological distress in Stockholm County, as well as the explanatory role of social capital for individuals with Swedish-background, foreign-background and those who are foreign-born. This study used data collected from respondents aged 18-64 to the 2002, 2006, 2010 baseline questionnaires of the Stockholm Public Health Cohort and was linked with individual and area-level register information. Ethnic heterogeneity was the main exposure, measured by: 1) ethnic density, defined as the proportion of first and second generation immigrants with 2 foreign-born parents; and 2) ethnic diversity, using the fragmentation index. Social capital measures of individual and contextual-level social support and horizontal trust were the main explanatory factors of interest. The outcome, psychological distress, was assessed using the General Health Questionnaire-12 with a 2/3 cut-off. Prevalence ratios with 95% confidence intervals were estimated using multi-level poisson regression with robust variances. Age and sex adjusted analyses for the whole study population demonstrated that a 10% increase in ethnic density or diversity was associated with a 1.06 (1.05-1.07) times higher prevalence of psychological distress. In the stratified analyses, both foreign-born respondents and those with Swedish-background showed increasing prevalence of psychological distress with increasing ethnic heterogeneity. However, this trend was entirely explained by socioeconomic factors in the Swedish-background respondents and by additional adjustments for individual and contextual social support and horizontal trust for the foreign-born. Further adjustment for contextual

Specification of electron beam quality from ionization distribution in central axis and a study about heterogenity effects in these distributions

International Nuclear Information System (INIS)

Fernandes, R.F.

1984-01-01

Some parameters on physical and terapeutic properties of the electron beams generated by ''nevratron XII'' accelerator of the Hospital of Medicine in Ribeirao Preto - USP, Brasil are evaluated. The effects from heterogenities into an irradiated mean, called ''phantom'' or simulator are studied. (M.J.C.) [pt

The Influence of Particle Charge on Heterogeneous Reaction Rate Coefficients

Science.gov (United States)

Aikin, A. C.; Pesnell, W. D.

2000-01-01

The effects of particle charge on heterogeneous reaction rates are presented. Many atmospheric particles, whether liquid or solid are charged. This surface charge causes a redistribution of charge within a liquid particle and as a consequence a perturbation in the gaseous uptake coefficient. The amount of perturbation is proportional to the external potential and the square of the ratio of debye length in the liquid to the particle radius. Previous modeling has shown how surface charge affects the uptake coefficient of charged aerosols. This effect is now included in the heterogeneous reaction rate of an aerosol ensemble. Extension of this analysis to ice particles will be discussed and examples presented.

Sequence heterogeneity accelerates protein search for targets on DNA

International Nuclear Information System (INIS)

Shvets, Alexey A.; Kolomeisky, Anatoly B.

2015-01-01

The process of protein search for specific binding sites on DNA is fundamentally important since it marks the beginning of all major biological processes. We present a theoretical investigation that probes the role of DNA sequence symmetry, heterogeneity, and chemical composition in the protein search dynamics. Using a discrete-state stochastic approach with a first-passage events analysis, which takes into account the most relevant physical-chemical processes, a full analytical description of the search dynamics is obtained. It is found that, contrary to existing views, the protein search is generally faster on DNA with more heterogeneous sequences. In addition, the search dynamics might be affected by the chemical composition near the target site. The physical origins of these phenomena are discussed. Our results suggest that biological processes might be effectively regulated by modifying chemical composition, symmetry, and heterogeneity of a genome

Sequence heterogeneity accelerates protein search for targets on DNA

Energy Technology Data Exchange (ETDEWEB)

Shvets, Alexey A.; Kolomeisky, Anatoly B., E-mail: tolya@rice.edu [Department of Chemistry and Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005 (United States)

2015-12-28

The process of protein search for specific binding sites on DNA is fundamentally important since it marks the beginning of all major biological processes. We present a theoretical investigation that probes the role of DNA sequence symmetry, heterogeneity, and chemical composition in the protein search dynamics. Using a discrete-state stochastic approach with a first-passage events analysis, which takes into account the most relevant physical-chemical processes, a full analytical description of the search dynamics is obtained. It is found that, contrary to existing views, the protein search is generally faster on DNA with more heterogeneous sequences. In addition, the search dynamics might be affected by the chemical composition near the target site. The physical origins of these phenomena are discussed. Our results suggest that biological processes might be effectively regulated by modifying chemical composition, symmetry, and heterogeneity of a genome.

To leave from social scenario: on heterogeneity and specifity of populism

Directory of Open Access Journals (Sweden)

Sebastián Barros

2009-12-01

Full Text Available This paper is part of a discussion on the specificity of populism. Taking Laclau’s theorerical framework as a starting point, we analise the importance of the concept of heterogeneity in his argument. Later on, we analise Rancière’s understanding of politics as conflict and conclude that the idea of heterogeneity is central to a definition of populism. In this sense, we argue that heterogenity is something which is moved from its natural place in the order of domination, and starts to be taken as a part in the definition of the commonness of the community. This would have three specific effects over the subsequent political articulations. The inclusion of a heterogeneity would demonstrate the inexistance of the community of equals, forcing the need for a new representation of that community, now incarnated in a subject that, in the name of the past tort, claims to represent the universal plenitude of the community. Finally, we analise interventions by Gramsci and Ortega y Gasset in relation to the irruption of heterogeneity.

A Multianalyzer Machine Learning Model for Marine Heterogeneous Data Schema Mapping

Directory of Open Access Journals (Sweden)

Wang Yan

2014-01-01

Full Text Available The main challenges that marine heterogeneous data integration faces are the problem of accurate schema mapping between heterogeneous data sources. In order to improve the schema mapping efficiency and get more accurate learning results, this paper proposes a heterogeneous data schema mapping method basing on multianalyzer machine learning model. The multianalyzer analysis the learning results comprehensively, and a fuzzy comprehensive evaluation system is introduced for output results’ evaluation and multi factor quantitative judging. Finally, the data mapping comparison experiment on the East China Sea observing data confirms the effectiveness of the model and shows multianalyzer’s obvious improvement of mapping error rate.

Design and economic implications of heterogeneity in an LMFBR core

International Nuclear Information System (INIS)

Orechwa, Y.

1983-01-01

Much emphasis is currently being placed in LMFBR design on reducing both the capital cost and the fuel cycle cost of an LMFBR to insure its economic competativeness without a rapid increase in the uranium prices. In this study the relationship between two core design options, their neutronic consequences, and their effect on fuel cycle cost are analyzed. The two design options are the selection of pin diameter and the degree of heterogeneity. In the case of a heterogeneous core, with a low sodium void reactivity worth this ratio of fertile internal blanket to driver assemblies is generally about 0.40. However, some advantages of cores with heterogeneity of 0.08 to 0.2 for a fixed pin diameter have been reported

Viscous fingering with permeability heterogeneity