Directory of Open Access Journals (Sweden)
Wallis Rob
2010-06-01
Full Text Available Abstract Background The curveback lineage of guppy is characterized by heritable idiopathic-type spinal curvature that develops during growth. Prior work has revealed several important developmental similarities to the human idiopathic scoliosis (IS syndrome. In this study we investigate structural and histological aspects of the vertebrae that are associated with spinal curvature in the curveback guppy and test for sexual dimorphism that might explain a female bias for severe curve magnitudes in the population. Methods Vertebrae were studied from whole-mount skeletal specimens of curved and non-curved adult males and females. A series of ratios were used to characterize structural aspects of each vertebra. A three-way analysis of variance tested for effects of sex, curvature, vertebral position along the spine, and all 2-way interactions (i.e., sex and curvature, sex and vertebra position, and vertebra position and curvature. Histological analyses were used to characterize micro-architectural changes in affected vertebrae and the intervertebral region. Results In curveback, vertebrae that are associated with curvature demonstrate asymmetric shape distortion, migration of the intervertebral ligament, and vertebral thickening on the concave side of curvature. There is sexual dimorphism among curved individuals such that for several vertebrae, females have more slender vertebrae than do males. Also, in the region of the spine where lordosis typically occurs, curved and non-curved females have a reduced width at the middle of their vertebrae, relative to males. Conclusions Based on similarities to human spinal curvatures and to animals with induced curves, the concave-convex biases described in the guppy suggest that there is a mechanical component to curve pathogenesis in curveback. Because idiopathic-type curvature in curveback is primarily a sagittal deformity, it is structurally more similar to Scheuermann kyphosis than IS. Anatomical
A major QTL controls susceptibility to spinal curvature in the curveback guppy
Directory of Open Access Journals (Sweden)
Dreyer Christine
2011-01-01
Full Text Available Abstract Background Understanding the genetic basis of heritable spinal curvature would benefit medicine and aquaculture. Heritable spinal curvature among otherwise healthy children (i.e. Idiopathic Scoliosis and Scheuermann kyphosis accounts for more than 80% of all spinal curvatures and imposes a substantial healthcare cost through bracing, hospitalizations, surgery, and chronic back pain. In aquaculture, the prevalence of heritable spinal curvature can reach as high as 80% of a stock, and thus imposes a substantial cost through production losses. The genetic basis of heritable spinal curvature is unknown and so the objective of this work is to identify quantitative trait loci (QTL affecting heritable spinal curvature in the curveback guppy. Prior work with curveback has demonstrated phenotypic parallels to human idiopathic-type scoliosis, suggesting shared biological pathways for the deformity. Results A major effect QTL that acts in a recessive manner and accounts for curve susceptibility was detected in an initial mapping cross on LG 14. In a second cross, we confirmed this susceptibility locus and fine mapped it to a 5 cM region that explains 82.6% of the total phenotypic variance. Conclusions We identify a major QTL that controls susceptibility to curvature. This locus contains over 100 genes, including MTNR1B, a candidate gene for human idiopathic scoliosis. The identification of genes associated with heritable spinal curvature in the curveback guppy has the potential to elucidate the biological basis of spinal curvature among humans and economically important teleosts.
Spinal curvature measurement by tracked ultrasound snapshots.
Ungi, Tamas; King, Franklin; Kempston, Michael; Keri, Zsuzsanna; Lasso, Andras; Mousavi, Parvin; Rudan, John; Borschneck, Daniel P; Fichtinger, Gabor
2014-02-01
Monitoring spinal curvature in adolescent kyphoscoliosis requires regular radiographic examinations; however, the applied ionizing radiation increases the risk of cancer. Ultrasound imaging is favored over radiography because it does not emit ionizing radiation. Therefore, we tested an ultrasound system for spinal curvature measurement, with the help of spatial tracking of the ultrasound transducer. Tracked ultrasound was used to localize vertebral transverse processes as landmarks along the spine to measure curvature angles. The method was tested in two scoliotic spine models by localizing the same landmarks using both ultrasound and radiographic imaging and comparing the angles obtained. A close correlation was found between tracked ultrasound and radiographic curvature measurements. Differences between results of the two methods were 1.27 ± 0.84° (average ± SD) in an adult model and 0.96 ± 0.87° in a pediatric model. Our results suggest that tracked ultrasound may become a more tolerable and more accessible alternative to radiographic spine monitoring in adolescent kyphoscoliosis.
Spine curve modeling for quantitative analysis of spinal curvature.
Hay, Ori; Hershkovitz, Israel; Rivlin, Ehud
2009-01-01
Spine curvature and posture are important to sustain healthy back. Incorrect spine configuration can add strain to muscles and put stress on the spine, leading to low back pain (LBP). We propose new method for analyzing spine curvature in 3D, using CT imaging. The proposed method is based on two novel concepts: the spine curvature is derived from spinal canal centerline, and evaluation of the curve is carried out against a model based on healthy individuals. We show results of curvature analysis of healthy population, pathological (scoliosis) patients, and patients having nonspecific chronic LBP.
Spinal curvature and characteristics of postural change in pregnant women.
Okanishi, Natsuko; Kito, Nobuhiro; Akiyama, Mitoshi; Yamamoto, Masako
2012-07-01
Pregnant women often report complaints due to physiological and postural changes. Postural changes during pregnancy may cause low back pain and pelvic girdle pain. This study aimed to compare the characteristics of postural changes in pregnant compared with non-pregnant women. Prospective case-control study. Pregnancy care center. Fifteen women at 17-34 weeks pregnancy comprised the study group, while 10 non-pregnant female volunteers comprised the control group. Standing posture was evaluated in the sagittal plane with static digital pictures. Two angles were measured by image analysis software: (1) between the trunk and pelvis; and (2) between the trunk and lower extremity. Spinal curvature was measured with Spinal Mouse® to calculate the means of sacral inclination, thoracic and lumbar curvature and inclination. The principal components were calculated until eigenvalues surpassed 1. Three distinct factors with eigenvalues of 1.00-2.49 were identified, consistent with lumbosacral spinal curvature and inclination, thoracic spine curvature, and inclination of the body. These factors accounted for 77.2% of the total variance in posture variables. Eleven pregnant women showed postural characteristics of lumbar kyphosis and sacral posterior inclination. Body inclination showed a variety of patterns compared with those in healthy women. Spinal curvature demonstrated a tendency for lumbar kyphosis in pregnant women. Pregnancy may cause changes in spinal curvature and posture, which may in turn lead to relevant symptoms. Our data provide a basis for investigating the effects of spinal curvature and postural changes on symptoms during pregnancy. © 2012 The Authors Acta Obstetricia et Gynecologica Scandinavica© 2012 Nordic Federation of Societies of Obstetrics and Gynecology.
Clinical workflow for spinal curvature measurement with portable ultrasound
Tabanfar, Reza; Yan, Christina; Kempston, Michael; Borschneck, Daniel; Ungi, Tamas; Fichtinger, Gabor
2016-03-01
PURPOSE: Spinal curvature monitoring is essential in making treatment decisions in scoliosis. Monitoring entails radiographic examinations, however repeated ionizing radiation exposure has been shown to increase cancer risk. Ultrasound does not emit ionizing radiation and is safer for spinal curvature monitoring. We investigated a clinical sonography protocol and challenges associated with position-tracked ultrasound in spinal curvature measurement in scoliosis. METHODS: Transverse processes were landmarked along each vertebra using tracked ultrasound snapshots. The transverse process angle was used to determine the orientation of each vertebra. We tested our methodology on five patients in a local pediatric scoliosis clinic, comparing ultrasound to radiographic curvature measurements. RESULTS: Despite strong correlation between radiographic and ultrasound curvature angles in phantom studies, we encountered new challenges in the clinical setting. Our main challenge was differentiating transverse processes from ribs and other structures during landmarking. We observed up to 13° angle variability for a single vertebra and a 9.85° +/- 10.81° difference between ultrasound and radiographic Cobb angles for thoracic curvatures. Additionally, we were unable to visualize anatomical landmarks in the lumbar region where soft tissue depth was 25-35mm. In volunteers with large Cobb angles (greater than 40° thoracic and 60° lumbar), we observed spinal protrusions resulting in incomplete probe-skin contact and partial ultrasound images not suitable for landmarking. CONCLUSION: Spinal curvature measurement using tracked ultrasound is viable on phantom spine models. In the clinic, new challenges were encountered which must be resolved before a universal sonography protocol can be developed.
A review of methods for quantitative evaluation of spinal curvature
2015-01-01
The aim of this paper is to provide a complete overview of the existing methods for quantitative evaluation of spinal curvature from medical images, and to summarize the relevant publications, which may not only assist in the introduction of other researchers to the field, but also be a valuable resource for studying the existing methods or developing new methods and evaluation strategies. Key evaluation issues and future considerations, supported by the results of the overview, are also disc...
A review of methods for quantitative evaluation of spinal curvature.
Vrtovec, Tomaz; Pernus, Franjo; Likar, Bostjan
2009-05-01
The aim of this paper is to provide a complete overview of the existing methods for quantitative evaluation of spinal curvature from medical images, and to summarize the relevant publications, which may not only assist in the introduction of other researchers to the field, but also be a valuable resource for studying the existing methods or developing new methods and evaluation strategies. Key evaluation issues and future considerations, supported by the results of the overview, are also discussed.
Directory of Open Access Journals (Sweden)
Hawes Martha C
2006-03-01
Full Text Available Abstract Background This review summarizes what is known about the pathological processes (e.g. structural and functional changes, by which spinal curvatures develop and evolve into spinal deformities. Methods Comprehensive review of articles (English language only published on 'scoliosis,' whose content yielded data on the pathological changes associated with spinal curvatures. Medline, Science Citation Index and other searches yielded > 10,000 titles each of which was surveyed for content related to 'pathology' and related terms such as 'etiology,' 'inheritance,' 'pathomechanism,' 'signs and symptoms.' Additional resources included all books published on 'scoliosis' and available through the Arizona Health Sciences Library, Interlibrary Loan, or through direct contact with the authors or publishers. Results A lateral curvature of the spine–'scoliosis'–can develop in association with postural imbalance due to genetic defects and injury as well as pain and scarring from trauma or surgery. Irrespective of the factor that triggers its appearance, a sustained postural imbalance can result, over time, in establishment of a state of continuous asymmetric loading relative to the spinal axis. Recent studies support the longstanding hypothesis that spinal deformity results directly from such postural imbalance, irrespective of the primary trigger, because the dynamics of growth within vertebrae are altered by continuous asymmetric mechanical loading. These data suggest that, as long as growth potential remains, evolution of a spinal curvature into a spinal deformity can be prevented by reversing the state of continuous asymmetric loading. Conclusion Spinal curvatures can routinely be diagnosed in early stages, before pathological deformity of the vertebral elements is induced in response to asymmetric loading. Current clinical approaches involve 'watching and waiting' while mild reversible spinal curvatures develop into spinal deformities with
A Major QTL Controls Susceptibility to Spinal Curvature in the Curveback Guppy
2011-01-01
Background: Understanding the genetic basis of heritable spinal curvature would benefit medicine andaquaculture. Heritable spinal curvature among otherwise healthy children (i.e. Idiopathic Scoliosis and Scheuermannkyphosis) accounts for more than 80% of all spinal curvatures and imposes a substantial healthcare cost throughbracing, hospitalizations, surgery, and chronic back pain. In aquaculture, the prevalence of heritable spinal curvaturecan reach as high as 80% of a stock, and thus impose...
Optimization of the examination posture in spinal curvature assessment
Directory of Open Access Journals (Sweden)
Krejci Jakub
2012-04-01
Full Text Available Abstract To decrease the influence of postural sway during spinal measurements, an instrumented fixation posture (called G was proposed and tested in comparison with the free standing posture (A using the DTP-3 system in a group of 70 healthy volunteers. The measurement was performed 5 times on each subject and each position was tested by a newly developed device for non-invasive spinal measurements called DTP-3 system. Changes in postural stability of the spinous processes for each subject/the whole group were evaluated by employing standard statistical tools. Posture G, when compared to posture A, reduced postural sway significantly in all spinous processes from C3 to L5 in both the mediolateral and anterioposterior directions. Posture G also significantly reduced postural sway in the vertical direction in 18 out of 22 spinous processes. Importantly, posture G did not significantly influence the spinal curvature.
Optimization of the examination posture in spinal curvature assessment.
Krejci, Jakub; Gallo, Jiri; Stepanik, Petr; Salinger, Jiri
2012-04-30
To decrease the influence of postural sway during spinal measurements, an instrumented fixation posture (called G) was proposed and tested in comparison with the free standing posture (A) using the DTP-3 system in a group of 70 healthy volunteers. The measurement was performed 5 times on each subject and each position was tested by a newly developed device for non-invasive spinal measurements called DTP-3 system. Changes in postural stability of the spinous processes for each subject/the whole group were evaluated by employing standard statistical tools. Posture G, when compared to posture A, reduced postural sway significantly in all spinous processes from C3 to L5 in both the mediolateral and anterioposterior directions. Posture G also significantly reduced postural sway in the vertical direction in 18 out of 22 spinous processes. Importantly, posture G did not significantly influence the spinal curvature.
Spinal curvatures of children and adolescents – a cross-sectional study
Directory of Open Access Journals (Sweden)
Grabara Małgorzata
2017-02-01
Full Text Available Study aim: The aim was to assess the spinal curvatures of primary and lower secondary male and female students from Silesia and to identify individual variations that can determine spinal posture.
Kasukawa, Yuji; Miyakoshi, Naohisa; Hongo, Michio; Ishikawa, Yoshinori; Noguchi, Hideaki; Kamo, Keiji; Sasaki, Hiroshi; Murata, Katsuyuki; Shimada, Yoichi
2010-01-01
Spinal mobility and back extensor strength (BES) are important in determining quality of life (QOL) for elderly people. However, the impact of spinal factors on falls remains unclear. The purpose of this study was to clarify spinal factors related to falls in elderly people, including deformity of spinal curvature, spinal mobility and BES. Subjects comprised 92 elderly people divided into 3 groups: subjects without a history of falls or fear of falls (Non-falls group, n = 40); subjects with a history of fear of falls or requiring any support when walking (Fear of falls group, n = 36); and subjects with a history of falls (Falls group, n = 16). Kyphotic angles and mobility of the thoracic and/or lumbar spine, and spinal inclination were measured using a computer-assisted device. Postural imbalance was evaluated using a computerized stabilometer. Isometric BES was also measured. Angle of lumbar kyphosis, spinal inclination, and postural imbalance were significantly higher in the Falls group (p spinal inclination (p = 0.0378), mobility of lumbar spine (0.027), and mobility of spinal inclination (p = 0.0282) were significantly associated with presence/absence of falls in elderly individuals.
Spinal curvature determination from an X-ray image using a deformable model
Sardjono, T.A.; Wilkinson, M.H.F.; Ooijen, P.M.A. van; Veldhuizen, A.G.; Purnama, K.E.; Verkerke, G.J.; Ibrahim, F; Osman, NAA; Usman, J; Kadri, NA
2007-01-01
This paper presents a spinal curvature determination from frontal X-ray images of scoliotic patients. A new deformable model, Modified CPM (Charged Particles Model), has been developed and used to determine the spinal curvature. The Modified CPM is a new approach of a deformable model based on CPM,
Assessment of Spinal Curvature: An Evaluation of the Flexicurve and Associated Means of Analysis.
Caine, M. P.; And Others
1996-01-01
Several interrelated issues pertaining to the measurement of spinal curvature are discussed, including the inherent limitations of the kyphotic index, the most widely used indicator in the evaluation of kyphosis. The paper suggests use of the Flexicurve to quantify spinal posture, suggests modifications to the Flexicurve, and presents results on…
Automatic quantification of spinal curvature in scoliotic radiograph using image processing.
H, Anitha; Prabhu, G K
2012-06-01
Choosing the most suitable treatment for the scoliosis relies heavily on accurate and reproducible spinal curvature measurement from radiographs. Our objective is to reduce the variability in spinal curvature measurement by reducing the user intervention and bias. In order to determine the reliability of the spinal curvature measurement as it is in the clinical measurement of scoliosis a methodological survey has been carried out that concludes with inter and intra observer error variation. The proposed method list out horizontal inclination of all the vertebrae's in terms of slopes using active contour models and morphological operators. This facilitates the radiologist to decide end vertebrae and hence inter/intra observer variation is completely eliminated. Tables 1 and 2 shows the observer error variation between manual and proposed methods in terms of mean and standard deviation.
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Ruairi de Frein
2004-01-01
Full Text Available We present a system designed to study the pressure at various "hot spot" on the back of the body and the deformation of the spine experienced by a patient when strapped to a spinal board, and the potential alleviation of both by the addition of an inflatable "spinal raft" (or other similar devices. In measuring pressure we devised a system of air-filled sacks interfaced with a PC. Each sack, placed under a particular key point on the body, is inflated until its faces just begin to separate and a switch thereby opens. The pressure reading is then captured and displayed by the computer. Seeking a noninvasive method of measuring the curvature of the vertebral columm, we discovered that we could use a magnetometer to measure the vertical displacement of magnetically-tagged verbrae from a fixed horizontal plane. The results of our study will be employed by an independent body to determine the metrits or demerit of the spinal raft.
Quantitative analysis of spinal curvature in 3D: application to CT images of normal spine
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Vrtovec, Tomaz; Likar, Bostjan; Pernus, Franjo [University of Ljubljana, Faculty of Electrical Engineering, Trzaska 25, SI-1000 Ljubljana (Slovenia)], E-mail: tomaz.vrtovec@fe.uni-lj.si, E-mail: bostjan.likar@fe.uni-lj.si, E-mail: franjo.pernus@fe.uni-lj.si
2008-04-07
The purpose of this study is to present a framework for quantitative analysis of spinal curvature in 3D. In order to study the properties of such complex 3D structures, we propose two descriptors that capture the characteristics of spinal curvature in 3D. The descriptors are the geometric curvature (GC) and curvature angle (CA), which are independent of the orientation and size of spine anatomy. We demonstrate the two descriptors that characterize the spinal curvature in 3D on 30 computed tomography (CT) images of normal spine and on a scoliotic spine. The descriptors are determined from 3D vertebral body lines, which are obtained by two different methods. The first method is based on the least-squares technique that approximates the manually identified vertebra centroids, while the second method searches for vertebra centroids in an automated optimization scheme, based on computer-assisted image analysis. Polynomial functions of the fourth and fifth degree were used for the description of normal and scoliotic spinal curvature in 3D, respectively. The mean distance to vertebra centroids was 1.1 mm ({+-}0.6 mm) for the first and 2.1 mm ({+-}1.4 mm) for the second method. The distributions of GC and CA values were obtained along the 30 images of normal spine at each vertebral level and show that maximal thoracic kyphosis (TK), thoracolumbar junction (TJ) and maximal lumbar lordosis (LL) on average occur at T3/T4, T12/L1 and L4/L5, respectively. The main advantage of GC and CA is that the measurements are independent of the orientation and size of the spine, thus allowing objective intra- and inter-subject comparisons. The positions of maximal TK, TJ and maximal LL can be easily identified by observing the GC and CA distributions at different vertebral levels. The obtained courses of the GC and CA for the scoliotic spine were compared to the distributions of GC and CA for the normal spines. The significant difference in values indicates that the descriptors of GC and
Quantitative analysis of spinal curvature in 3D: application to CT images of normal spine.
Vrtovec, Tomaz; Likar, Bostjan; Pernus, Franjo
2008-04-07
The purpose of this study is to present a framework for quantitative analysis of spinal curvature in 3D. In order to study the properties of such complex 3D structures, we propose two descriptors that capture the characteristics of spinal curvature in 3D. The descriptors are the geometric curvature (GC) and curvature angle (CA), which are independent of the orientation and size of spine anatomy. We demonstrate the two descriptors that characterize the spinal curvature in 3D on 30 computed tomography (CT) images of normal spine and on a scoliotic spine. The descriptors are determined from 3D vertebral body lines, which are obtained by two different methods. The first method is based on the least-squares technique that approximates the manually identified vertebra centroids, while the second method searches for vertebra centroids in an automated optimization scheme, based on computer-assisted image analysis. Polynomial functions of the fourth and fifth degree were used for the description of normal and scoliotic spinal curvature in 3D, respectively. The mean distance to vertebra centroids was 1.1 mm (+/-0.6 mm) for the first and 2.1 mm (+/-1.4 mm) for the second method. The distributions of GC and CA values were obtained along the 30 images of normal spine at each vertebral level and show that maximal thoracic kyphosis (TK), thoracolumbar junction (TJ) and maximal lumbar lordosis (LL) on average occur at T3/T4, T12/L1 and L4/L5, respectively. The main advantage of GC and CA is that the measurements are independent of the orientation and size of the spine, thus allowing objective intra- and inter-subject comparisons. The positions of maximal TK, TJ and maximal LL can be easily identified by observing the GC and CA distributions at different vertebral levels. The obtained courses of the GC and CA for the scoliotic spine were compared to the distributions of GC and CA for the normal spines. The significant difference in values indicates that the descriptors of GC and CA
Changes in spinal curvature and proprioception of schoolboys carrying different weights of backpack.
Chow, D H K; Leung, K T Y; Holmes, A D
2007-12-01
Despite evidence linking backpack carriage and back pain, previous studies to examine the effects of backpack carriage have focused on changes in physical performance rather than the direct effects on the spine itself. Spinal curvature and proprioception (in terms of spinal repositioning consistency) of 15 schoolboys during normal upright stance without a backpack and while carrying a specially adapted backpack loaded at 10, 15 and 20% of their bodyweight were measured and compared using repeated measures ANOVA. A significant flattening of the lumbar lordosis and the upper thoracic kyphosis was found with increasing backpack load, as well as a significant decrease in the thoraco-lumbar and lumbar repositioning consistencies. Carriage of a loaded backpack causes immediate changes in spinal curvature and appears to have a direct effect on the repositioning consistency. Further investigation of the changes in spinal curvature and repositioning consistency over time with prolonged backpack carriage is warranted. Daily carriage of a school backpack on the musculoskeletal health of children and adolescents has become an area of concern due to the association between backpack carriage and back pain. Data regarding the direct effect of backpack carriage on the spine in children are limited.
Hayashi, Tatsuro; Zhou, Xiangrong; Chen, Huayue; Hara, Takeshi; Miyamoto, Kei; Kobayashi, Tatsunori; Yokoyama, Ryujiro; Kanematsu, Masayuki; Hoshi, Hiroaki; Fujita, Hiroshi
2010-03-01
X-ray CT images have been widely used in clinical routine in recent years. CT images scanned by a modern CT scanner can show the details of various organs and tissues. This means various organs and tissues can be simultaneously interpreted on CT images. However, CT image interpretation requires a lot of time and energy. Therefore, support for interpreting CT images based on image-processing techniques is expected. The interpretation of the spinal curvature is important for clinicians because spinal curvature is associated with various spinal disorders. We propose a quantification scheme of the spinal curvature based on the center line of spinal canal on CT images. The proposed scheme consists of four steps: (1) Automated extraction of the skeletal region based on CT number thresholding. (2) Automated extraction of the center line of spinal canal. (3) Generation of the median plane image of spine, which is reformatted based on the spinal canal. (4) Quantification of the spinal curvature. The proposed scheme was applied to 10 cases, and compared with the Cobb angle that is commonly used by clinicians. We found that a high-correlation (for the 95% confidence interval, lumbar lordosis: 0.81-0.99) between values obtained by the proposed (vector) method and Cobb angle. Also, the proposed method can provide the reproducible result (inter- and intra-observer variability: within 2°). These experimental results suggested a possibility that the proposed method was efficient for quantifying the spinal curvature on CT images.
Cloud, Beth A; Zhao, Kristin D; Breighner, Ryan; Giambini, Hugo; An, Kai-Nan
2014-07-01
Spinal posture affects how individuals function from a manual wheelchair. There is a need to directly quantify spinal posture in this population to ultimately improve function. A fiber optic system, comprised of an attached series of sensors, is promising for measuring large regions of the spine in individuals sitting in a wheelchair. The purpose of this study was to determine the agreement between fiber optic and optoelectronic systems for measuring spinal curvature, and describe the range of sagittal plane spinal curvatures in natural sitting. Able-bodied adults (n = 26, 13 male) participated. Each participant assumed three sitting postures: natural, slouched (accentuated kyphosis), and extension (accentuated lordosis) sitting. Fiber optic (ShapeTape) and optoelectronic (Optotrak) systems were applied to the skin over spinous processes from S1 to C7 and used to measure sagittal plane spinal curvature. Regions of kyphosis and lordosis were identified. A Cobb angle-like method was used to quantify lordosis and kyphosis. Generalized linear model and Bland-Altman analyses were used to assess agreement. A strong correlation exists between curvature values obtained with Optotrak and ShapeTape (R(2) = 0.98). The mean difference between Optotrak and ShapeTape for kyphosis in natural, extension, and slouched postures was 4.30° (95% LOA: -3.43 to 12.04°), 3.64° (95% LOA: -1.07 to 8.36°), and 4.02° (95% LOA: -2.80 to 10.84°), respectively. The mean difference for lordosis, when present, in natural and extension postures was 2.86° (95% LOA: -1.18 to 6.90°) and 2.55° (95% LOA: -3.38 to 8.48°), respectively. In natural sitting, the mean ± SD of kyphosis values was 35.07 ± 6.75°. Lordosis was detected in 8/26 participants: 11.72 ± 7.32°. The fiber optic and optoelectronic systems demonstrate acceptable agreement for measuring sagittal plane thoracolumbar spinal curvature.
Cloud, Beth A.; Zhao, Kristin D.; Breighner, Ryan; Giambini, Hugo; An, Kai-Nan
2014-01-01
Spinal posture affects how individuals function from a manual wheelchair. There is a need to directly quantify spinal posture in this population to ultimately improve function. A fiber optic system, comprised of an attached series of sensors, is promising for measuring large regions of the spine in individuals sitting in a wheelchair. The purpose of this study was to determine the agreement between fiber optic and optoelectronic systems for measuring spinal curvature, and describe the range of sagittal plane spinal curvatures in natural sitting. Able-bodied adults (n=26, 13 male) participated. Each participant assumed three sitting postures: natural, slouched (accentuated kyphosis), and extension (accentuated lordosis) sitting. Fiber optic (ShapeTape) and optoelectronic (Optotrak) systems were applied to the skin over spinous processes from S1 to C7 and used to measure sagittal plane spinal curvature. Regions of kyphosis and lordosis were identified. A Cobb angle-like method was used to quantify lordosis and kyphosis. Generalized linear model and Bland-Altman analyses were used to assess agreement. A strong correlation exists between curvature values obtained with Optotrak and ShapeTape (R2=0.98). The mean difference between Optotrak and ShapeTape for kyphosis in natural, extension, and slouched postures was 4.30° (95%LOA: −3.43-12.04°), 3.64° (95%LOA: −1.07-8.36°), and 4.02° (95%LOA: −2.80-10.84°), respectively. The mean difference for lordosis, when present, in natural and extension postures is 2.86° (95%LOA: −1.18-6.90°) and 2.55° (95%LOA: −3.38-8.48°), respectively. In natural sitting, the mean±SD of kyphosis values was 35.07± 6.75°. Lordosis was detected in 8/26 participants: 11.72±7.32°. The fiber optic and optoelectronic systems demonstrate acceptable agreement for measuring sagittal plane thoracolumbar spinal curvature. PMID:24909579
The effect of spinal curvature on the photogrammetric assessment on static balance in elderly women.
Drzał-Grabiec, Justyna; Rachwał, Maciej; Podgórska-Bednarz, Justyna; Rykała, Justyna; Snela, Sławomir; Truszczyńska, Aleksandra; Trzaskoma, Zbigniew
2014-05-29
Involutional changes to the body in elderly patients affect the shape of the spine and the activity of postural muscles. The purpose of this study was to assess the influence of age-related changes in spinal curvature on postural balance in elderly women. The study population consisted of 90 women, with a mean age of 70 ± 8.01 years. Static balance assessments were conducted on a tensometric platform, and posturographic assessments of body posture were performed using a photogrammetric method based on the Projection Moiré method. The results obtained were analysed using the Spearman's rank correlation coefficient test. We found a statistically significant correlation between body posture and the quality of the balance system response based on the corrective function of the visual system. The shape of the spinal curvature influenced postural stability, as measured by static posturography. Improvement in the quality of the balance system response depended on corrective information from the visual system and proprioceptive information from the paraspinal muscles. The sensitivity of the balance system to the change of centre of pressure location was influenced by the direction of the change in rotation of the shoulder girdle and spine. Development of spinal curvature in the sagittal plane and maintenance of symmetry in the coronal and transverse planes are essential for correct balance control, which in turn is essential for the development of a properly proportioned locomotor system.
Williams, Jonathan M; Theobald, Peter S; Jones, Michael D
2014-01-01
Lifting presents a significant risk for the development of low back pain. It is not known what effect lifting from a supermarket shopping trolley has on sagittal spinal curvature. The aim of this study is to determine the effect of lifting from a shopping trolley on sagittal spinal curvature. Fifteen female subjects (height 1.67 ± 0.04 m, weight 64.3 ± 5.0 kg) completed lifts of 9 kg from a shopping trolley and a surface matched for height whilst sagittal spinal curvature was measured using Qualysis motion analysis system. Seven retro-reflective markers were placed along spine with angle between three markers representing regional curvature. No constraints on lifting technique were instigated. Results demonstrate no difference in sagittal range of motion or spinal curvature across the two lifts. A small but significant difference in knee flexion angle was observed. These results demonstrate that the chosen lifting strategy was not influenced by the constraint imposed by the shopping trolley. Furthermore the function of knee flexion did not result in change in sagittal curvature during the lifts. Lifting from a shopping trolley has no effect of sagittal spinal curvature.
The shape of anterior-posterior spinal curvature in post-menopausal women with osteoporosis.
Ostrowska, Bozena
2006-10-31
Background. The co-occurrence of kyphotic posture and low bone density in elderly women has never been completely explained. The aim of our study was to assess postural changes (the shape of spinal curvatures) in elderly women with advanced spinal osteoporosis. Material and methods. We examined 62 women (32 with osteoporosis and 30 with normal BMD) 52 to 84 years of age. The photogrammetric method based on the moiré phenomenon was used to measure the spinal contour (kyphosis and lordosis), and DEXA was employed to assess bone mineral density (BMD) at the lumbar spine level. Results. The group with osteoporosis had significantly greater kyphosis (pspinal contour. In the group of women with osteoporosis, the BMI was significantly correlated with the lumbar lordosis angle (pspinal segment (pspinal segment inclination angle and height loss (pspinal segment (p<0.05). Conclusion. The observed changes in body posture in women with osteoporosis result primarily from enlargement of the upper section of thoracic kyphosis.
Influence of trunk muscle co-contraction on spinal curvature during sitting for desk work.
Watanabe, S; Eguchi, A; Kobara, K; Ishida, H
2007-09-01
Nowadays, a lot of office workers are forced to sit at a desk for many hours while doing their jobs. While sitting, the pelvis rotates backwardly, and lumbar lordosis is flattened. At the same time, the load on the intervertebral discs and spine increases. Sitting in a slumped position is known to increase disc pressure even more, and to aggravate chronic low back pain (CLBP). Therefore, it is very important to teach workers about the correct sitting posture. In addition, it has been recognized that co-contraction of the deep spine-stabilizing muscles enhances lumbar segmental stability and the sacro-iliac joint. However, little is known about the influence of co-contraction of the trunk deep muscles on spinal curvature during sitting for while doing desk work. The purpose of this study was to compare EMG (electromyographic) activity of the trunk muscles during slump sitting with that during co-contraction of the trunk muscles and to investigate how this co-contraction influences spinal curvature. Ten healthy male volunteers (21.7 +/- 2.5 years old) without CLBP participated in the study. Bipolar surface electrodes were attached to the rectus abdominis, the obliquus externus abdominis, the obliquus internus abdominis, the lower back extensor muscles (L3) and the multifidus on the right side. EMG signals were continuously recorded during slump sitting and co-contraction of the trunk muscles, simulating a desk work sitting posture; i.e., slightly inclined forward. They were amplified, band-pass filtered, digitized and stored by a data acquisition system. The average muscle activity values over the five-second sample for each sitting posture were normalized to maximal voluntary contractions (%MVC). While the subjects performed both sitting postures, the curvature of the spine was measured using a new skin-surface and hand-held device, the "Spinal Mouse". More significant activities of the trunk muscles, with the exception of the rectus abdominis, were observed during
Noll, Christine; Steitz, Vanessa; Daentzer, Dorothea
2017-01-01
Proprioceptive insoles are known to influence the functions of posture and gait by modulations of the sensory structures at the sole of the foot. Literature has shown that they could improve the position of the upper-body in patients with postural complaints of the musculoskeletal system. The aim of this study was to evaluate the influence of proprioceptive insoles on the spinal curvature in patients with slight idiopathic scoliosis. Eighteen patients were included in this prospective, single-centre, randomized study. All patients needed to have a relevant growth potential and suffered from a slight idiopathic scoliosis. Two groups were used, where group 1 performed physiotherapy twice a week, whereas group 2 was additionally supplied with proprioceptive insoles. Patients underwent three-dimensional rasterstereography for back-shape analysis. Furthermore, a conventional x-ray imaging of the spine was performed at the beginning and 1 year later to document the curvatures. There was no statistical difference in the Cobb angles, and in almost all parameters of the rasterstereography, there was no statistically significant change between and within both groups. According to the results of this study, there was no evidence of any statistical significant effect of proprioceptive insoles on spinal curvature in patients with slight idiopathic scoliosis.
Abnormal spinal curvature as a risk factor for pelvic organ prolapse.
Melli, Manizheh Sayyah; Alizadeh, Mahasti
2007-12-01
To determine the relationship between pelvic organ prolapse and spinal curvature changes, a cross-sectional study was done in Gynecologic and Obstetrics educational hospitals and clinics in North West of Iran. One hundred patients were classified as cases based on the presence of abnormality at the spinal curvature and 100 patients classified as controls with no abnormality. The POP-Q (pelvic organ prolapse quantitation) staging system was used for assessment of prolapse stage and a flexi-curve malleable rod for measurement of thoracic and lumbar length and width, respectively. Main outcome was the stage of prolapses. The stage of prolapse was higher in cases compared to controls. There was a significant statistical difference between prolapse stage in two groups (p-value = 0.035). Among cases, grade II prolapse was the most prevalent abnormally (56%) and the grade III, I and IV were observed in 32, 5 and 7%, respectively. These observations underline the importance of taking into account the abnormal changes in spine curvature of patients when investigating risk factors for development of pelvic organs prolapse.
Lin, Hong
2008-01-01
In this paper, a multilayer feed-forward, back-propagation (MLFF/BP) artificial neural network (ANN) was implemented to identify the classification patterns of the scoliosis spinal deformity. At the first step, the simplified 3-D spine model was constructed based on the coronal and sagittal X-ray images. The features of the central axis curve of the spinal deformity patterns in 3-D space were extracted by the total curvature analysis. The discrete form of the total curvature, including the curvature and the torsion of the central axis of the simplified 3-D spine model was derived from the difference quotients. The total curvature values of 17 vertebrae from the first thoracic to the fifth lumbar spine formed a Euclidean space of 17 dimensions. The King classification model was tested on this MLFF/BP ANN identification system. The 17 total curvature values were presented to the input layer of MLFF/BP ANN. In the output layer there were five neurons representing five King classification types. A total of 37 spinal deformity patterns from scoliosis patients were selected. These 37 patterns were divided into two groups. The training group had 25 patterns and testing group had 12 patterns. The 25-pattern training group was further divided into five subsets. Based on the definition of King classification system, each subset contained all five King types. The network training was conducted on these five subsets by the hold-out method, one of cross-validation variants, and the early stop method. In each one of the five cross-validation sessions, four subsets were alternatively used for estimation learning and one subset left was used for validation learning. Final network testing was conducted with remaining 12 patterns in testing group after the MLFF/BP ANN was trained by all five subsets in training group. The performance of the neural network was evaluated by comparing between two network topologies, one with one hidden layer and another with two hidden layers. The
Influence of trunk muscle co-contraction on spinal curvature during sitting cross-legged.
Watanabe, S; Kobara, K; Ishida, H; Eguchi, A
2010-01-01
In Asia, many activities of daily living (ADL) are performed while sitting cross-legged on the floor. This sitting posture rotates the pelvis in a more dorsal direction and lumbar lordosis is more flattened than while sitting on a chair. Sitting cross-legged induces a greater load on the intervertebral discs and spine, especially when in a slumped position that is known to increase disc pressure even more and to aggravate chronic low back pain (CLBP). Therefore, it is very important to instruct Asian people about the correct sitting posture. In addition, it is known that co-contraction of the deep spine-stabilizing muscles enhances lumbar segmental stability and the sacroiliac joint. However, little is known about the influence of co-contraction of the trunk deep muscles on spinal curvature while sitting cross-legged on the floor. The purpose of this study was to compare EMG (electromyographic) activity of the trunk muscles while slump cross-legged sitting with that during co-contraction of the trunk muscles and to investigate how this co-contraction influences spinal curvature. Ten healthy male volunteers (21.7 +/- 2.5 years old) without CLBP participated in the study. Bipolar surface electrodes were attached to the rectus abdominis, the obliquus externus abdominis, the obliquus internus abdominis, the lower back extensor muscles (L3) and the multifidus on the right side. EMG signals were continuously recorded while slump sitting cross-legged and during co-contraction of the trunk muscles. They were amplified, band-pass filtered, digitized and stored by a data acquisition system. The average muscle activity values over the five-second sample for each sitting posture were normalized to maximal voluntary contractions (%MVC). While the subjects performed both sitting postures, the curvature of the spine was measured using a skin-surface and hand-held device, the "Spinal Mouse". More significant activities of the trunk muscles, with the exception of the rectus
Comparison of portable and conventional ultrasound imaging in spinal curvature measurement
Yan, Christina; Tabanfar, Reza; Kempston, Michael; Borschneck, Daniel; Ungi, Tamas; Fichtinger, Gabor
2016-03-01
PURPOSE: In scoliosis monitoring, tracked ultrasound has been explored as a safer imaging alternative to traditional radiography. The use of ultrasound in spinal curvature measurement requires identification of vertebral landmarks, but bones have reduced visibility in ultrasound imaging and high quality ultrasound machines are often expensive and not portable. In this work, we investigate the image quality and measurement accuracy of a low cost and portable ultrasound machine in comparison to a standard ultrasound machine in scoliosis monitoring. METHODS: Two different kinds of ultrasound machines were tested on three human subjects, using the same position tracker and software. Spinal curves were measured in the same reference coordinate system using both ultrasound machines. Lines were defined by connecting two symmetric landmarks identified on the left and right transverse process of the same vertebrae, and spinal curvature was defined as the transverse process angle between two such lines, projected on the coronal plane. RESULTS: Three healthy volunteers were scanned by both ultrasound configurations. Three experienced observers localized transverse processes as skeletal landmarks and obtained transverse process angles in images obtained from both ultrasounds. The mean difference per transverse process angle measured was 3.00 +/-2.1°. 94% of transverse processes visualized in the Sonix Touch were also visible in the Telemed. Inter-observer error in the Telemed was 4.5° and 4.3° in the Sonix Touch. CONCLUSION: Price, convenience and accessibility suggest the Telemed to be a viable alternative in scoliosis monitoring, however further improvements in measurement protocol and image noise reduction must be completed before implementing the Telemed in the clinical setting.
de Fréin, Ruairí; Flinn, Eoin; Burke, Ted
2004-01-01
We present a system designed to study the pressure at various ‘hot spots’ on the back of the body and the deformation of the spine experienced by a patient when strapped to a spinal board, and the potential alleviation of both by the addition of an inflatable “spinal raft” (or other similar device). In measuring pressure we devised a system of air-filled sacks interfaced with a PC. Each sack, placed under a particular key point on the body, is inflated until its faces just begin to separate a...
Effects of athletic training on the spinal curvature in child athletes.
Betsch, Marcel; Furian, Thimm; Quack, Valentin; Rath, Björn; Wild, Michael; Rapp, Walter
2015-01-01
The purpose of this study was to examine the spinal posture in young athletes depending on training intensity. The spinal curvature of 245 children, age 8 to 12 years, was evaluated using rasterstereography. According to their weekly training time group 1 (mean age: 9.54 ± 1.18) did 2-6, group 2 (mean age: 9.49 ± 0.87) did 6-15 and group 3 (mean age: 9.68 ± 0.87) did over 15 hours of training. Group 1 had a significantly higher weight (p = 0.028) (33.86 ± 7. kg) than those of the more active groups (30.67 ± 6.49 kg and 29.46 ± 4.33 kg). The mean kyphotic angle decreased significantly (p < 0.001) with the amount of training per week from 46.86 ± 8.2° in group 1 to 40.08 ± 8° in group 3. We also found a significant decrease (p = 0.047) in lateral deviation with training from group 1 with 5.3 ± 3 mm to group 2 with 4.1 ± 1.6 mm. The results of our study suggest that higher training time can be associated with lower weight and decreases in thoracic kyphosis and lateral deviation of the spine.
You, Jae Eung; Lee, Hye Young; Kim, Kyoung
2015-06-01
[Purpose] Degree of curvature on the spine is known to affect respiratory function and back muscle activation. We compared pulmonary function and back muscle strength according to the degree of curvature of the spine of healthy adults. [Subjects and Methods] Twenty-three healthy volunteers were enrolled. They were divided into two groups according to the degree of curvature of the spine: the below 2° group, and the above 2° group. The degree of curvature was assessed using the Adams forward bending test and a scoliometer. A pulmonary function test (PFT) was conducted, and back muscle strength was measured. [Results] No significant differences in PFT were found between the below 2° group and the above 2° group, in terms of forced vital capacity (FVC), forced expiratory volume in one second (FEV1), ratio of forced expiratory volume in one second to forced vital capacity (FEV1/FVC), or peak expiratory flow (PEF). However, back muscle strength in the below 2 group was significantly higher than that of the above 2 group. [Conclusion] Our findings indicate that the degree of curvature of the spine is associated with back muscle strength in subjects who have spinal curvature within the normal range. Therefore, evaluation and treatment of back muscle strength might be helpful for preventing the progress of curvature of the spine in adolescents with potential scoliosis.
Directory of Open Access Journals (Sweden)
Stefan Schmid
Full Text Available Although the relevance of understanding spinal kinematics during functional activities in patients with complex spinal deformities is undisputed among researchers and clinicians, evidence using skin marker-based motion capture systems is still limited to a handful of studies, mostly conducted on healthy subjects and using non-validated marker configurations. The current study therefore aimed to explore the validity of a previously developed enhanced trunk marker set for the static measurement of spinal curvature angles in patients with main thoracic adolescent idiopathic scoliosis. In addition, the impact of inaccurate marker placement on curvature angle calculation was investigated.Ten patients (Cobb angle: 44.4±17.7 degrees were equipped with radio-opaque markers on selected spinous processes and underwent a standard biplanar radiographic examination. Subsequently, radio-opaque markers were replaced with retro-reflective markers and the patients were measured statically using a Vicon motion capture system. Thoracolumbar/lumbar and thoracic curvature angles in the sagittal and frontal planes were calculated based on the centers of area of the vertebral bodies and radio-opaque markers as well as the three-dimensional position of the retro-reflective markers. To investigate curvature angle estimation accuracy, linear regression analyses among the respective parameters were used. The impact of inaccurate marker placement was explored using linear regression analyses among the radio-opaque marker- and spinous process-derived curvature angles.The results demonstrate that curvatures angles in the sagittal plane can be measured with reasonable accuracy, whereas in the frontal plane, angles were systematically underestimated, mainly due to the positional and structural deformities of the scoliotic vertebrae. Inaccuracy of marker placement had a greater impact on thoracolumbar/lumbar than thoracic curvature angles. It is suggested that spinal curvature
Effect of backpack load placement on posture and spinal curvature in prepubescent children.
Brackley, Heather M; Stevenson, Joan M; Selinger, Jessica C
2009-01-01
Parents, educators and researchers have expressed concern about the long term impacts of children carrying excessive loads in their backpacks on a daily basis. Although many researchers have investigated appropriate weight limits for children's packs, little research has been conducted on the design of children's backpacks. The purpose of this study was to evaluate the changes in children's trunk forward lean (TFL), cranio-vertebral angle (CVA) and spinal lordosis angle (LA) that occurred with high, medium and low load locations during standing and walking. Ten-year-old children (n = 15) completed a repeated measures designed study while carrying 15% of each child's body weight in a typical backpack with only shoulder straps. A special instrumented backpack (IBP) was designed that allowed the weight to be placed in the proper location and continuously measure changes in spinal curvature. TFL and CVA postures were captured on digital video at five intervals including: standing without a backpack prior to a 1000 m walk; standing with a backpack at the beginning and end of a 1000 m walk; and walking with a backpack at the beginning and end of a 1000 m walk. Results indicated that significant changes occurred in TFL and CVA when the backpack was loaded to 15% body weight. The low load placement in the backpack produced fewer changes in CVA from the initial standing baseline measure than the high and mid placements. When all measures were assessed collectively, there were fewer changes in LA in the low load placement. These findings indicate that future backpack designs should place loads lower on the spine in order to minimize children's postural adaptations.
Yang, Jinmo; Seo, Dongkwon
2015-03-01
[Purpose] The purpose of this study was to investigate the impact of whole body vibration (WBV) on static balance, spinal curvature, pain, and the disability of patients with chronic lower back pain. [Subjects and Methods] The subjects were of 40 patients, who were randomly assigned to WBV and control groups. Twenty-five minutes of lumbar stability training and 5 minutes of WBV were conducted for the WBV group, and 30 minutes of lumbar stability training was conducted for the control group. The training was conducted three times per week for a total of 6 weeks. Static balance, spinal curvature, pain, and disability were measured before and after the intervention. [Results] After the intervention, the WBV group showed a significant differences in static balance, spinal curvature, pain, and disability. The control group presented significant differences in pain, and disability. In the comparison of the two groups, the WBV group showed more significant improvements in the fall index and pain. [Conclusion] WBV can be recommended for the improvement of the balance ability and pain of chronic lower back pain patients.
Watanabe, S; Eguchi, A; Kobara, K; Ishida, H
2008-01-01
Today, many office workers frequently adopt a relaxed or slumped sitting posture for many hours, and often people tend to spend their leisure time reclining against the backrest of a chair while sitting for a long time, as when watching television. While sitting, the pelvis rotates backwardly, and lumbar lordosis is flattened. Simultaneously, the load on the intervertebral discs and spine increases. Sitting in a slumped position is known to increase disc pressure even more, and to aggravate chronic low back pain (CLBP). Therefore, it is very important to teach workers and often people about the correct sitting posture. In addition, it has been recognized that co-contraction of the deep spine-stabilizing muscles enhances lumbar segmental stability and the sacro-iliac joint. However, little is known about the influence of co-contraction of the trunk deep muscles on spinal curvature during sitting reclining against the backrest of a chair. The purpose of this study was to compare the EMG (electromyographic) activity of the trunk muscles during slump sitting with that during co-contraction and to investigate how this cocontraction influences spinal curvature. Ten healthy male volunteers (20.8 +/- 0.8 years old) without CLBP participated in the study. Bipolar surface electrodes were attached to the rectus abdominis, the obliquus externus abdominis, the obliquus internus abdominis, the lower back extensor muscles (L3) and the multifidus on the right side. The EMG signals were continuously recorded during slump sitting and co-contraction of the trunk muscles, reclining against the backrest of chair. They were amplified, band-pass filtered, digitized and stored by a data acquisition system. The average muscle activity values over the five-second sample for each sitting posture were normalized to maximal voluntary contractions (%MVC). While the subjects performed both sitting postures, the curvature of the spine was measured using a new skin-surface and hand-held device
Rosa, Carlos Eduardo da; Kuradomi, Rafael Yutaka; Almeida, Daniela Volcan; Lannes, Carlos Frederico Ceccon; Figueiredo, Márcio de Azevedo; Dytz, Aline Guerra; Fonseca, Duane Barros; Marins, Luis Fernando
2010-06-01
Growth hormone (GH) excess causes an increment in the metabolic rate and in reactive oxygen species generation, which accelerate the ageing process in mammals. Considering that there is no information on this subject in fish, the aim of the present study was to evaluate the excess GH effect on senescence in a zebrafish (Danio rerio) transgenic model. In order to reach this objective, we analyzed the phenotype of spinal curvature and expression of genes related to the anti-oxidant defense system and myogenesis in muscle of 8 and 30 months old GH-transgenic males. Gene expression analyses revealed that both superoxide dismutase isoforms were down-regulated only in 30 months old animals, while glutamate cysteine ligase was down-regulated in GH-transgenic zebrafish. Acceleration of the spinal curvature and a reduction in the expression of miogenin at both ages and MyoD in the old fish were also observed. Although neurolipofuscin accumulation was not significant in GH-transgenic zebrafish, the estimation of maximum longevity based on the von Bertalanffy growth function was significantly lower in this group. The results obtained here indicate that GH overexpression reduces the transcription of anti-oxidant defense system and myogenesis-related genes, which probably accelerates senescence in the zebrafish transgenic model used.
Subbarayalu, Arun Vijay
2016-01-01
The Modified Head Posture Spinal Curvature Instrument (MHPSCI) is an extension of the Head Posture Spinal Curvature Instrument. Two specific modifications were made in the original design by adding a third arm projecting horizontally from the protractor to objectively fix the pivot exactly over the C7 vertebra and the addition of a spirit-level to properly align the instrument. In order to demonstrate reliability and validity, this study was conducted using patients with postural neck pain (N = 65) and healthy subjects (N = 20). All the subjects were working at a selected Information Technology Industry in India and had been recruited using a criterion-based sampling approach. The craniovertebral (CV) angle of each subject was evaluated by two raters consecutively. The measurements were taken by using both MHPSCI and the standard photographic method in a standardized sitting posture for the purpose of establishing criterion-validity of the instrument. The results of this study indicate a good inter-rater reliability (ICC = 0.76; CI = 0.65-0.84) as well as intra-rater reliability (ICC = 0.87; CI = 0.82-0.91) between three successive CV angle measurements (with 2 minutes interval between each measurement) through MHPSCI. While keeping the digital photographic measurement as a standard, this study established that the MHPSCI is a valid tool for measuring the CV angle as shown by non-significant difference (p > 0.01) and high correlation between the two methods (r = 0.79-0.84). This study demonstrates that the MHPSCI is a reliable and valid instrument for measuring CV angle in subjects with or without postural neck pain.
Directory of Open Access Journals (Sweden)
Chun-Ting Li
Full Text Available To investigate the effects of backward adjustable thoracic support on spinal curvature and back muscle activation during wheelchair sitting.Twenty elderly people were recruited for this study. The backward adjustable thoracic support sitting posture was compared with the slumped, normal, and lumbar support sitting postures. Spinal curvatures (pelvic, lumbar, and thoracic angles and muscle activations of 4 back muscles on both sides (maximal voluntary isometric contraction of the lumbar multifidus, lumbar erector spinae, iliocostalis lumborum pars thoracis, and thoracic erector spinae at T9 were measured and compared between the different sitting postures using one-way analysis of variance with repeated measures.The backward adjustable thoracic support sitting posture showed a relatively neutral pelvic tilt (-0.32±4.80° when compared with the slumped (22.84±5.27° and lumbar support (-8.97±3.31° sitting postures (P<0.001, and showed relatively higher lumbar lordosis (-23.38±6.50° when compared with the slumped (14.77±7.83°, normal (0.44±7.47°, and lumbar support (-16.76±4.77° sitting postures (P<0.05. It also showed relatively lower back muscle activity when compared with the normal and lumbar support sitting postures (P<0.05.The backward adjustable thoracic support sitting concept was suggested because it maintains a more neutral pelvic tilt, higher lumbar lordosis, and lower back muscle activation, which may help maintain a better sitting posture and reduce the risk of back pain.
Kahrizi, Sedighe; Parnianpour, Mohammad; Firoozabadi, Seyyed Mohammad; Kasemnejad, Anoshirvan; Karimi, Elham
2007-04-01
A study was performed to investigate how different trunk and knee positions while holding static loads affect the lumbar curvature and internal loads on the lumbar spine at L4-L5. Ten healthy male subjects participated in this study. Two inclinometers were used to evaluate the curvature of lumbar spine, lordosis, while a 3D static biomechanical model was used to predict the spinal compression and shear forces at L4-L5. Eighteen static tasks while holding three level of load (0, 10 and 20 kg), two levels of knee position (45 and 180 degrees of flexion) and three levels of trunk position (neutral, 15 and 30 degree of flexion) were simulated for 10 healthy male subjects. The results of this study revealed that the lordosis of lumbar spine changed to kyphosis with increasing weight of load from 0 to 20 kg in trunk flexion position (pcurvature. The results of this study suggested, at a more flexed trunk and standing position with higher loads both external moment and internal loads increased significantly at L4-L5 level but with 45 knee flexion external moment and compression force increased and shear force decreased significantly (p < 0.05). Subjects made more effort to maintain stability of the body in squat position. The highest external moment and compression force were computed at flexed knee and trunk position with highest loads. Hence holding weight in this position must be avoided by implementing ergonomic change to the workplace.
The Spinal Curvature of Three Different Sitting Positions Analysed in an Open MRI Scanner
Directory of Open Access Journals (Sweden)
Daniel Baumgartner
2012-01-01
Full Text Available Sitting is the most frequently performed posture of everyday life. Biomechanical interactions with office chairs have therefore a long-term effect on our musculoskeletal system and ultimately on our health and wellbeing. This paper highlights the kinematic effect of office chairs on the spinal column and its single segments. Novel chair concepts with multiple degrees of freedom provide enhanced spinal mobility. The angular changes of the spinal column in the sagittal plane in three different sitting positions (forward inclined, reclined, and upright for six healthy subjects (aged 23 to 45 years were determined using an open magnetic resonance imaging (MRI scanner. An MRI-compatible and commercially available office chair was adapted for use in the scanner. The midpoint coordinates of the vertebral bodies, the wedge angles of the intervertebral discs, and the lumbar lordotic angle were analysed. The mean lordotic angles were 16.0±8.5∘ (mean ± standard deviation in a forward inclined position, 24.7±8.3∘ in an upright position, and 28.7±8.1∘ in a reclined position. All segments from T10-T11 to L5-S1 were involved in movement during positional changes, whereas the range of motion in the lower lumbar segments was increased in comparison to the upper segments.
The spinal curvature of three different sitting positions analysed in an open MRI scanner.
Baumgartner, Daniel; Zemp, Roland; List, Renate; Stoop, Mirjam; Naxera, Jaroslav; Elsig, Jean Pierre; Lorenzetti, Silvio
2012-01-01
Sitting is the most frequently performed posture of everyday life. Biomechanical interactions with office chairs have therefore a long-term effect on our musculoskeletal system and ultimately on our health and wellbeing. This paper highlights the kinematic effect of office chairs on the spinal column and its single segments. Novel chair concepts with multiple degrees of freedom provide enhanced spinal mobility. The angular changes of the spinal column in the sagittal plane in three different sitting positions (forward inclined, reclined, and upright) for six healthy subjects (aged 23 to 45 years) were determined using an open magnetic resonance imaging (MRI) scanner. An MRI-compatible and commercially available office chair was adapted for use in the scanner. The midpoint coordinates of the vertebral bodies, the wedge angles of the intervertebral discs, and the lumbar lordotic angle were analysed. The mean lordotic angles were 16.0 ± 8.5° (mean ± standard deviation) in a forward inclined position, 24.7 ± 8.3° in an upright position, and 28.7 ± 8.1° in a reclined position. All segments from T10-T11 to L5-S1 were involved in movement during positional changes, whereas the range of motion in the lower lumbar segments was increased in comparison to the upper segments.
Yoo, Hyunju; Shin, Doochul; Song, Changho
2015-01-01
[Purpose] The aim of this study was to investigate the changes in pain intensity, spinal curvature, and balance and gait ability according to the pregnancy period. [Subjects] Nineteen pregnant women and fifteen nonpregnant women were recruited in this study. [Methods] The pain intensity, spinal curvature, gait, and balance of pregnant women were measured according to the pregnant period (2nd and 3rd trimester). The changes in the pregnant women were also compared with those in the nonpregnant women. [Results] The pain intensity and spinal curvature in the third trimester of pregnancy were significantly increased compared with the second trimester. Only the lumbar spine curvature in the third trimester pregnancy was significantly greater in the pregnant women than in non-pregnant women. The gait velocity and cadence in the third trimester of pregnancy showed a significant decrease compared with the second trimester. The gait speed in the second and third trimester of pregnancy showed a significant decrease in the pregnant women compared with nonpregnant women. Balance in the third trimester of pregnancy showed significant improvement compared with the second trimester. The balance of the pregnant women showed a significant decrease compare with that nonpregnant women only on unstable surfaces. [Conclusion] These research findings can be used as basic data for health promotion programs for sound daily activities in pregnant women.
Takács, Mária; Rudner, Ervin; Kovács, Attila; Orlovits, Zsanett; Kiss, Rita M
2015-02-01
In children's posture examinations the question often arises whether an X-ray examination is necessary or appropriate. On screening and in other cases when X-ray is contraindicated, alternative-non-invasive-examinations are available. To measure the shapes of the children's spines beside the Spinal Mouse also the Zebris ultrasound-based spine measuring instrument is accessible and nowadays commonly used. The main aim of the study is to determine the shape of the school-age children's spines in the sagittal plane with an alternative, non-invasive, radiation-free measuring method. From the results calculated from the values measured with the ultrasound-based motion analysing system-geared to age and height-the normal range of the values of kyphosis (TK), lordosis (LL) and inclination (TTI and LI) is determined. The subjects were children between the ages of 6 and 15 and between the heights of 120 and 180 cm (530 healthy, 394 with bad posture and 332 with flat feet). They were divided into groups according to their height with 5 cm long intervals. The age within the groups was irrelevant. So it is appropriate to give normal values according to height and not according to age. It was revealed that both in healthy children, in children with bad posture and in those with pes planus in the height groups, there was a significant difference between the values of males and females. On the basis of these results, normal values should be divided according to the gender. The measurement results also showed that in some of the height groups the pes planus and bad posture significantly affected the spinal curvatures.
Directory of Open Access Journals (Sweden)
Marcel Betsch
Full Text Available INTRODUCTION: The assessment of spinal deformities with rasterstereography can enhance the understanding, as well as can reduce the number of x-rays needed. However, to date this technique only allows measurements under static conditions. Since it would be of great value to be able to also analyze the spine in dynamic conditions, the present study evaluated a novel rasterstereographic system. MATERIALS AND METHODS: A new rasterstereographic device was evaluated in a comparison with the gold standard in motion analysis, the VICON system. After initial testing using 12 flat infrared markers adhered to a solid plate, the two systems were evaluated with the markers adhered onto the backs of 8 test subjects. Four triangles were defined using the markers, and the sides of each triangle were measured under static and dynamic conditions. RESULTS: On the solid plate, the sides of the 4 triangles were measured with a measuring tape and then by the two optical systems. Rasterstereography showed a high accuracy in marker detection on the solid plate. Under dynamic conditions, with the subjects walking on a treadmill, the rasterstereographically-measured side lengths were compared with the lengths measured by the VICON system as an assessment of marker detection. No significant differences (p>0.05 were found between the systems, differing only 0.07-1.1% for all sides of the four triangles with both systems. DISCUSSION: A novel rasterstereographic measurement device that allows surface and spine topography under dynamic conditions was assessed. The accuracy of this system was with one millimeter on a solid plate and during dynamic measurements, to the gold standard for motion detection. The advantage of rasterstereography is that it can be used to determine a three-dimensional surface map and also allows the analysis of the underlying spine.
Debnam, J Matthew; Ketonen, Leena; Guha-Thakurta, Nandita
2012-01-01
Background. Abnormal spinal curvature is routinely assessed with plain radiographs, MDCT, and MRI. MDCT can provide two-dimensional (2-D) orthogonal as well as reconstructed three-dimensional volume-rendered (3-D VR) images of the spine, including the translucent display: a computer-generated image set that enables the visualization of surgical instrumentation through bony structures. We hypothesized that the 3-D VR series provides additional information beyond that of 2-D orthogonal MDCT in the evaluation of abnormal spinal curvature in patients evaluated at a major cancer center. Methods. The 3-D VR series, including the translucent display, was compared to 2-D orthogonal MDCT studies in patients with an abnormal spinal curvature greater than 25 degrees and scored as being not helpful (0) or helpful (1) in 3 categories: spinal curvature; bony definition; additional findings (mass lesions, fractures, and instrumentation). Results. In 38 of 48 (79.2%) patients assessed, the 3-D VR series were scored as helpful in 63 of 144 (43.8%) total possible categories (32 spinal curvature; 14 bony definition; 17 additional findings). Conclusion. Three-dimensional MDCT images, including the translucent display, are complementary to multiplanar 2-D orthogonal MCDT in the evaluation of abnormal spinal curvature in patients treated at a major cancer center.
Energy Technology Data Exchange (ETDEWEB)
De Smet, A.A.
1985-01-01
This book offers the only comprehensive, concise summary of both the clinical and radiologic features of thoracic and lumbar spine deformity. Emphasis is placed on idiopathic scoliosis, which represents 85% of all patients with scoliosis, but less common areas of secondary scoliosis, kyphosis and lordosis are also covered.
Idiopathic type 1 diabetes in Dallas, Texas: a 5-year experience
National Research Council Canada - National Science Library
Piñero-Piloña, A; Litonjua, P; Aviles-Santa, L; Raskin, P
2001-01-01
To describe the clinical course of individuals with idiopathic type 1 diabetes after a mean of 5 years from diagnosis and to compare glycemic control between those treated with diet and/or oral agents...
Lang-Tapia, Morin; España-Romero, Vanesa; Anelo, Juan; Castillo, Manuel J
2011-05-01
This aim was to examine differences on lumbar lordosis and thoracic kyphosis in standing position by gender, age and weight status in healthy subjects using a noninvasive method. A total of 297 women (36.6 ± 7.3 years) and 362 men (39.8 ± 7.5 years) participated in this study. Participants were categorized according to the international BMI (kg/m2) cut-off points. Age was stratified by ten years increments starting from 20 y. Men showed smaller lumbar lordosis (17.3 ± 9.3) and larger thoracic kyphosis (42.8 ± 8.8°) than women (29.6 ± 11.3 and 40.4 ± 9.5° respectively; both p curvature. The results of this study suggest that gender could be the only determinant factor of lumbar lordosis in healthy people.
Guevar, Julien; Penderis, Jacques; Faller, Kiterie; Yeamans, Carmen; Stalin, Catherine; Gutierrez-Quintana, Rodrigo
2014-01-01
The objectives of this study were: To investigate computer-assisted digital radiographic measurement of Cobb angles in dogs with congenital thoracic vertebral malformations, to determine its intra- and inter-observer reliability and its association with the presence of neurological deficits. Medical records were reviewed (2009-2013) to identify brachycephalic screw-tailed dog breeds with radiographic studies of the thoracic vertebral column and with at least one vertebral malformation present. Twenty-eight dogs were included in the study. The end vertebrae were defined as the cranial end plate of the vertebra cranial to the malformed vertebra and the caudal end plate of the vertebra caudal to the malformed vertebra. Three observers performed the measurements twice. Intraclass correlation coefficients were used to calculate the intra- and inter-observer reliabilities. The intraclass correlation coefficient was excellent for all intra- and inter-observer measurements using this method. There was a significant difference in the kyphotic Cobb angle between dogs with and without associated neurological deficits. The majority of dogs with neurological deficits had a kyphotic Cobb angle higher than 35°. No significant difference in the scoliotic Cobb angle was observed. We concluded that the computer assisted digital radiographic measurement of the Cobb angle for kyphosis and scoliosis is a valid, reproducible and reliable method to quantify the degree of spinal curvature in brachycephalic screw-tailed dog breeds with congenital thoracic vertebral malformations.
Directory of Open Access Journals (Sweden)
Dariusz Czaprowski
2017-01-01
Full Text Available Objectives. The aim of the study was to assess the change of sagittal spinal curvatures in children with generalized joint hypermobility (GJH instructed with “straighten your back” command (SYB. Methods. The study included 56 children with GJH. The control group consisted of 193 children. Sacral slope (SS, lumbar lordosis (LL, global thoracic kyphosis (TK, lower thoracic kyphosis (LK, and upper thoracic kyphosis (UK were assessed with Saunders inclinometer both in spontaneous positions (standing and sitting and after the SYB. Results. Children with GJH after SYB presented the following: in standing, increase in SS and decrease in TK, LK, and UK (P<0.01, with LL not significantly changed; in sitting: decrease in global thoracic kyphosis (35.5° (SD 20.5 versus 21.0° (SD 15.5, P<0.001 below the standards proposed in the literature (30–40° and flattening of its lower part (P<0.001. The same changes were observed in the control group. Conclusions. In children with generalized joint hypermobility, the “straighten your back” command leads to excessive reduction of the global thoracic kyphosis and flattening of its lower part. Therefore, the “straighten your back” command should not be used to achieve the optimal standing and sitting positions.
Directory of Open Access Journals (Sweden)
Julien Guevar
Full Text Available The objectives of this study were: To investigate computer-assisted digital radiographic measurement of Cobb angles in dogs with congenital thoracic vertebral malformations, to determine its intra- and inter-observer reliability and its association with the presence of neurological deficits. Medical records were reviewed (2009-2013 to identify brachycephalic screw-tailed dog breeds with radiographic studies of the thoracic vertebral column and with at least one vertebral malformation present. Twenty-eight dogs were included in the study. The end vertebrae were defined as the cranial end plate of the vertebra cranial to the malformed vertebra and the caudal end plate of the vertebra caudal to the malformed vertebra. Three observers performed the measurements twice. Intraclass correlation coefficients were used to calculate the intra- and inter-observer reliabilities. The intraclass correlation coefficient was excellent for all intra- and inter-observer measurements using this method. There was a significant difference in the kyphotic Cobb angle between dogs with and without associated neurological deficits. The majority of dogs with neurological deficits had a kyphotic Cobb angle higher than 35°. No significant difference in the scoliotic Cobb angle was observed. We concluded that the computer assisted digital radiographic measurement of the Cobb angle for kyphosis and scoliosis is a valid, reproducible and reliable method to quantify the degree of spinal curvature in brachycephalic screw-tailed dog breeds with congenital thoracic vertebral malformations.
2012-01-01
Background. Abnormal spinal curvature is routinely assessed with plain radiographs, MDCT, and MRI. MDCT can provide two-dimensional (2-D) orthogonal as well as reconstructed three-dimensional volume-rendered (3-D VR) images of the spine, including the translucent display: a computer-generated image set that enables the visualization of surgical instrumentation through bony structures. We hypothesized that the 3-D VR series provides additional information beyond that of 2-D orthogonal MDCT in ...
There are four natural curves in the spinal column. The cervical, thoracic, lumbar, and sacral curvature. The curves, along with the intervertebral disks, help to absorb and distribute stresses that occur from everyday activities such as walking or from ...
Right thoracic curvature in the normal spine
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Masuda Keigo
2011-01-01
Full Text Available Abstract Background Trunk asymmetry and vertebral rotation, at times observed in the normal spine, resemble the characteristics of adolescent idiopathic scoliosis (AIS. Right thoracic curvature has also been reported in the normal spine. If it is determined that the features of right thoracic side curvature in the normal spine are the same as those observed in AIS, these findings might provide a basis for elucidating the etiology of this condition. For this reason, we investigated right thoracic curvature in the normal spine. Methods For normal spinal measurements, 1,200 patients who underwent a posteroanterior chest radiographs were evaluated. These consisted of 400 children (ages 4-9, 400 adolescents (ages 10-19 and 400 adults (ages 20-29, with each group comprised of both genders. The exclusion criteria were obvious chest and spinal diseases. As side curvature is minimal in normal spines and the range at which curvature is measured is difficult to ascertain, first the typical curvature range in scoliosis patients was determined and then the Cobb angle in normal spines was measured using the same range as the scoliosis curve, from T5 to T12. Right thoracic curvature was given a positive value. The curve pattern was organized in each collective three groups: neutral (from -1 degree to 1 degree, right (> +1 degree, and left ( Results In child group, Cobb angle in left was 120, in neutral was 125 and in right was 155. In adolescent group, Cobb angle in left was 70, in neutral was 114 and in right was 216. In adult group, Cobb angle in left was 46, in neutral was 102 and in right was 252. The curvature pattern shifts to the right side in the adolescent group (p Conclusions Based on standing chest radiographic measurements, a right thoracic curvature was observed in normal spines after adolescence.
Institute of Scientific and Technical Information of China (English)
李鹏飞; 房根强; 李华; 靳宪辉; 张庆胜; 丁文元; 张为; 崔胜杰
2013-01-01
Objective To investigate the clinical significance of applicating posterior internal fixation for regulating spinal curvature in thoracolumbar compression fractures. Methods Between May 2006 and May 2009, 63 patients with thoracolumbar compression fractures were treated, and the clinical data were retrospectively analyzed. Among them, 33 patients received traditional posterior internal fixation in control group; 30 patients underwent posterior internal fixation with spinal curvature correction under C-arm X-ray device in trial group. There was no significant difference in age, gender, cause of injury, injured segment, grade of fracture, and time from injury to operation between 2 groups (P > 0.05). The Cobb angle, height of injured vertebral body, and disc height were measured by X-ray examination; loosening and breakage of internal fixation were observed and compared between 2 groups. The recovery rate was calculated according to pre- and post-operative visual analogue scale (VAS) and Oswestry disability index (ODI) scores for each patient. Results All cases were followed up 20-45 months (mean, 31 months). The postoperative VAS score, ODI, Cobb angle, height of injured vertebral body, and disc height were improved significantly when compared with preoperative values in 2 groups (P < 0.05). At last follow-up, VAS and ODI scores of trial group were significantly better than those of control group (P < 0.05); loss of Cobb angle was (2.1 ± 1.7)° in trial group and (4.2 ± 3.2)° in control group, showing significant difference (t=1.457, P=0.000); loss of disc height was (1.4 ± 1.2) mm in trial group and (3.4 ± 2.3) mm in control group, showing significant difference ((=9.336, P= 0.000); loss of height of injured vertebral body was 1.8% ± 0.6% in trial group and 5.4% + 2.1% in control group, showing significant difference (t=3.435, P=0.000). Broken screw and loosening screw occurred in 1 case of control group, respectively (6.1%), but no broken or loosening screw
Extrinsic Curvature Embedding Diagrams
Lu, J L
2003-01-01
Embedding diagrams have been used extensively to visualize the properties of curved space in Relativity. We introduce a new kind of embedding diagram based on the {\\it extrinsic} curvature (instead of the intrinsic curvature). Such an extrinsic curvature embedding diagram, when used together with the usual kind of intrinsic curvature embedding diagram, carries the information of how a surface is {\\it embedded} in the higher dimensional curved space. Simple examples are given to illustrate the idea.
Stability of Curvature Measures
Chazal, Frédéric; Lieutier, André; Thibert, Boris
2008-01-01
We address the problem of curvature estimation from sampled compact sets. The main contribution is a stability result: we show that the gaussian, mean or anisotropic curvature measures of the offset of a compact set K with positive $\\mu$-reach can be estimated by the same curvature measures of the offset of a compact set K' close to K in the Hausdorff sense. We show how these curvature measures can be computed for finite unions of balls. The curvature measures of the offset of a compact set with positive $\\mu$-reach can thus be approximated by the curvature measures of the offset of a point-cloud sample. These results can also be interpreted as a framework for an effective and robust notion of curvature.
... curvature of the penis after surgery or radiation treatment for prostate cancer. Peyronie's disease is uncommon. It affects men ages 40 to 60 and older. Curvature of the penis can occur along with Dupuytren's contracture . This is a cord-like thickening across the ...
DEFF Research Database (Denmark)
diffusion to volume growth. We are e.g. interested in obtaining precise bounds for mean exit times for Brownian motions and for isoperimetric inequalities. One way to obtain such bounds are via curvature controlled comparison with corresponding values in constant curvature spaces and in other tailor-made so...
Debus, J -D; Succi, S; Herrmann, H J
2015-01-01
By inspecting the effect of curvature on a moving fluid, we find that local sources of curvature not only exert inertial forces on the flow, but also generate viscous stresses as a result of the departure of streamlines from the idealized geodesic motion. The curvature-induced viscous forces are shown to cause an indirect and yet appreciable energy dissipation. As a consequence, the flow converges to a stationary equilibrium state solely by virtue of curvature-induced dissipation. In addition, we show that flow through randomly-curved media satisfies a non-linear transport law, resembling Darcy-Forchheimer's law, due to the viscous forces generated by the spatial curvature. It is further shown that the permeability can be characterized in terms of the average metric perturbation.
Laser triangulation measurements of scoliotic spine curvatures.
Čelan, Dušan; Jesenšek Papež, Breda; Poredoš, Primož; Možina, Janez
2015-01-01
The main purpose of this research was to develop a new method for differentiating between scoliotic and healthy subjects by analysing the curvatures of their spines in the cranio-caudal view. The study included 247 subjects with physiological curvatures of the spine and 28 subjects with clinically confirmed scoliosis. The curvature of the spine was determined by a computer analysis of the surface of the back, measured with a non-invasive, 3D, laser-triangulation system. The determined spinal curve was represented in the transversal plane, which is perpendicular to the line segment that was defined by the initial point and the end point of the spinal curve. This was achieved using a rotation matrix. The distances between the extreme points in the antero-posterior (AP) and left-right (LR) views were calculated in relation to the length of the spine as well as the quotient of these two values LR/AP. All the measured parameters were compared between the scoliotic and control groups using the Student's t-Test in case of normal data and Kruskal-Wallis test in case of non-normal data. Besides, a comprehensive diagram representing the distances between the extreme points in the AP and LR views was introduced, which clearly demonstrated the direction and the size of the thoracic and lumbar spinal curvatures for each individual subject. While the distances between the extreme points of the spine in the AP view were found to differ only slightly between the groups (p = 0.1), the distances between the LR extreme points were found to be significantly greater in the scoliosis group, compared to the control group (p < 0.001). The quotient LR/AP was statistically significantly different in both groups (p < 0.001). The main innovation of the presented method is the ability to differentiate a scoliotic subject from a healthy subject by assessing the curvature of the spine in the cranio-caudal view. Therefore, the proposed method could be useful for human posture
Penile Curvature (Peyronie's Disease)
... use mechanical traction and vacuum devices aimed at stretching or bending the penis to reduce curvature. Surgery ... Communication Programs FAQs About NIDDK Meet the Director Offices & Divisions Staff Directory Budget & Legislative Information Advisory & Coordinating ...
The influence of elongation exercises on the anterior-posterior spine curvatures
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Drzał-Grabiec Justyna
2014-01-01
Full Text Available Introduction: Elongation exercises are designed to reduce existing pathological or increased physiological curvatures of the spine. The aim of the study was to evaluate the changes occurring in the parameters describing the anterior-posterior spinal curvatures during the performance of symmetric elongation exercises.
... who undergo a spinal tap (lumbar puncture) or spinal anesthesia. Both procedures require a puncture of the tough ... fluid is withdrawn from your spinal canal. During spinal anesthesia, medication is injected into your spinal canal to ...
Directory of Open Access Journals (Sweden)
Liu Chiao Yi
2008-04-01
Full Text Available OBJETIVO: Verificar a relação entre a excursão do músculo diafragma e as curvaturas da coluna vertebral em crianças respiradoras bucais. MÉTODOS: Foram avaliadas 52 crianças de 5 a 12 anos de idade, de ambos os sexos. Por meio de avaliação otorrinolaringológica, foram divididas em dois grupos: respiradores bucais e respiradores nasais. Todos os participantes foram submetidos a exame de videofluoroscopia do músculo diafragma e a avaliação postural. A excursão do diafragma foi analisada pelo programa Adobe Photoshop®, e a avaliação postural através de fotografias em norma lateral esquerda, sendo analisadas pelo Software de Avaliação Postural. RESULTADOS: Os grupos estudados apresentaram diferença estatisticamente significante quanto ao comportamento das curvaturas da coluna vertebral (lordose cervical: p = 0,003; lordose lombar: p = 0,001; cifose torácica: p = 0,002; posição da pelve: p = 0,001 e da excursão do músculo diafragma (diafragma lado direito: p = 0,001; diafragma lado esquerdo: p = 0,001. O grupo respirador bucal apresentou diminuição da lordose cervical, aumento da cifose torácica, aumento da lordose lombar e anteversão da posição da pelve. A distância excursionada pelo músculo diafragma em crianças respiradoras bucais é menor que em crianças respiradoras nasais. Não houve significância estatística ao relacionar o comportamento das curvaturas da coluna vertebral com a excursão do músculo diafragma. CONCLUSÃO: Não há relação entre as curvaturas da coluna vertebral com a excursão do músculo diafragma nos grupos estudados.OBJECTIVE: To investigate the relationship between excursion of the diaphragm muscle and spinal curvatures in mouth breathing children. METHODS: A total of 52 children of both sexes, aged from 5 to 12 years, were studied. After otorhinolaryngological assessment, the children were divided into two groups: mouth breathers and nose breathers. All of the children underwent
Wolf, Joseph A
2010-01-01
This book is the sixth edition of the classic Spaces of Constant Curvature, first published in 1967, with the previous (fifth) edition published in 1984. It illustrates the high degree of interplay between group theory and geometry. The reader will benefit from the very concise treatments of riemannian and pseudo-riemannian manifolds and their curvatures, of the representation theory of finite groups, and of indications of recent progress in discrete subgroups of Lie groups. Part I is a brief introduction to differentiable manifolds, covering spaces, and riemannian and pseudo-riemannian geomet
Leonard, C Danielle; Allison, Rupert
2016-01-01
Current constraints on spatial curvature show that it is dynamically negligible: $|\\Omega_{\\rm K}| \\lesssim 5 \\times 10^{-3}$ (95% CL). Neglecting it as a cosmological parameter would be premature however, as more stringent constraints on $\\Omega_{\\rm K}$ at around the $10^{-4}$ level would offer valuable tests of eternal inflation models and probe novel large-scale structure phenomena. This precision also represents the "curvature floor", beyond which constraints cannot be meaningfully improved due to the cosmic variance of horizon-scale perturbations. In this paper, we discuss what future experiments will need to do in order to measure spatial curvature to this maximum accuracy. Our conservative forecasts show that the curvature floor is unreachable - by an order of magnitude - even with Stage IV experiments, unless strong assumptions are made about dark energy evolution and the optical depth to the CMB. We also discuss some of the novel problems that arise when attempting to constrain a global cosmological...
Curvature calculations with GEOCALC
Energy Technology Data Exchange (ETDEWEB)
Moussiaux, A.; Tombal, P.
1987-04-01
A new method for calculating the curvature tensor has been recently proposed by D. Hestenes. This method is a particular application of geometric calculus, which has been implemented in an algebraic programming language on the form of a package called GEOCALC. They show how to apply this package to the Schwarzchild case and they discuss the different results.
The curvature coordinate system
DEFF Research Database (Denmark)
Almegaard, Henrik
2007-01-01
hyperbolas. This means that when a plane orthogonal system of curves for which the vertices in a mesh always lie on a circle is mapped on a surface with positive Gaussian curvature using inverse mapping, and the mapped vertices are connected by straight lines, this network will form a faceted surface...
Forman curvature for complex networks
Sreejith, R. P.; Mohanraj, Karthikeyan; Jost, Jürgen; Saucan, Emil; Samal, Areejit
2016-06-01
We adapt Forman’s discretization of Ricci curvature to the case of undirected networks, both weighted and unweighted, and investigate the measure in a variety of model and real-world networks. We find that most nodes and edges in model and real networks have a negative curvature. Furthermore, the distribution of Forman curvature of nodes and edges is narrow in random and small-world networks, while the distribution is broad in scale-free and real-world networks. In most networks, Forman curvature is found to display significant negative correlation with degree and centrality measures. However, Forman curvature is uncorrelated with clustering coefficient in most networks. Importantly, we find that both model and real networks are vulnerable to targeted deletion of nodes with highly negative Forman curvature. Our results suggest that Forman curvature can be employed to gain novel insights on the organization of complex networks.
Dynamic Characteristic Analysis of Spinal Motor Control Between 11- and 15-Year-Old Children.
Chow, Daniel H; Lau, Newman M
2016-07-01
Spinal motor control can provide substantial insight for the causes of spinal musculoskeletal disorders. Its dynamic characteristics however, have not been fully investigated. The objective of this study is to explore the dynamic characteristics of spinal motor control via the fractional Brownian motion mathematical technique. Spinal curvatures and repositioning errors of different spinal regions in 64 children age 11- or 15-years old during upright stance were measured and compared for the effects of age and gender. With the application of the fractional Brownian motion analytical technique to the changes of spinal curvatures, distinct persistent movement behaviors could be determined, which could be interpreted physiologically as open-loop behaviors. Moreover, it was found that the spinal motor control of 15-year-old children was better than that of 11-year-old children with smaller repositioning error and less curvature variability as well as shorter response time and smaller curvature deformation.
Institute of Scientific and Technical Information of China (English)
朱继超; 刘晓光; 刘忠军; 姜亮; 韦峰; 于淼; 吴奉梁
2013-01-01
cervical curvature after expansive open-door laminoplasty for cervical myelopathy,and to investigate the relationship between cervical curvature and spinal cord shift.Methods:63 cases of cervical myelopathy undergoing traditional expansive open-door laminoplasty between January 2005 and December 2011 were reviewed retrospectively,the pathogenesis included cervical spondylotic myelopathy(26 cases),ossification of posterior longitudinal ligament(OPLL,20 cases) and developmental cervical spinal stenosis(17 cases).Traditional expansive open-door laminoplasty was performed because of multisegmental disc disease,multilevel OPLL or developmental cervical stenosis.All cases were divided into three groups according to the cervical curvature:the kyphosis group(n=16),the straight group(n=18) and the normal alignment group(n=29).The posterior shift of center of spinal cord(PCS) at each level of laminoplasty(C3-C7) was measured and calculated through the midsagittal images of MRI T2-weighted before and after surgery.Statistic analysis was performed to analyze the difference of PCS at each level (C3-C7) among three groups.The neurofunction for each patient was estimated by using the Japanese Orthopedic Association(JOA) score before surgery and at final follow-up,and the JOA recovery rate was calculated.Statistic analysis was performed to analyze the difference of the JOA recovery rate at final follow-up among three groups.Results:There was no statistical difference in the age,sex ratio,duration of symptoms,entity,follow-up time or the preoperative JOA score(P＞0.05).Posterior migration of spinal cord was observed in all three groups,and there was no significant difference with respect to the mean PCS at C3-C7 level among three groups(P＞0.05).The mean follow-up was 47±24(range 15-90) months,and the mean JOA recovery rate at final follow-up of each group was 59.81％,69.25％ and 54.44％ respectively,which showed no statistical difference(P＞0.05).No linear correlation was found
Forman curvature for directed networks
Sreejith, R P; Saucan, Emil; Samal, Areejit
2016-01-01
A goal in network science is the geometrical characterization of complex networks. In this direction, we have recently introduced the Forman's discretization of Ricci curvature to the realm of undirected networks. Investigation of Forman curvature in diverse model and real-world undirected networks revealed that this measure captures several aspects of the organization of complex undirected networks. However, many important real-world networks are inherently directed in nature, and the Forman curvature for undirected networks is unsuitable for analysis of such directed networks. Hence, we here extend the Forman curvature for undirected networks to the case of directed networks. The simple mathematical formula for the Forman curvature in directed networks elegantly incorporates node weights, edge weights and edge direction. By applying the Forman curvature for directed networks to a variety of model and real-world directed networks, we show that the measure can be used to characterize the structure of complex ...
Directory of Open Access Journals (Sweden)
Mohammed Larbi Labbi
2007-12-01
Full Text Available The $(2k$-th Gauss-Bonnet curvature is a generalization to higher dimensions of the $(2k$-dimensional Gauss-Bonnet integrand, it coincides with the usual scalar curvature for $k = 1$. The Gauss-Bonnet curvatures are used in theoretical physics to describe gravity in higher dimensional space times where they are known as the Lagrangian of Lovelock gravity, Gauss-Bonnet Gravity and Lanczos gravity. In this paper we present various aspects of these curvature invariants and review their variational properties. In particular, we discuss natural generalizations of the Yamabe problem, Einstein metrics and minimal submanifolds.
Anisotropic cubic curvature couplings
Bailey, Quentin G
2016-01-01
To complement recent work on tests of spacetime symmetry in gravity, cubic curvature couplings are studied using an effective field theory description of spacetime-symmetry breaking. The associated mass dimension 8 coefficients for Lorentz violation studied do not result in any linearized gravity modifications and instead are revealed in the first nonlinear terms in an expansion of spacetime around a flat background. We consider effects on gravitational radiation through the energy loss of a binary system and we study two-body orbital perturbations using the post-Newtonian metric. Some effects depend on the internal structure of the source and test bodies, thereby breaking the Weak Equivalence Principle for self-gravitating bodies. These coefficients can be measured in solar-system tests, while binary-pulsar systems and short-range gravity tests are particularly sensitive.
Lumbar spine disc heights and curvature: upright posture vs. supine compression harness
Lee, Shi-Uk; Hargens, Alan R.; Fredericson, Michael; Lang, Philipp K.
2003-01-01
INTRODUCTION: Spinal lengthening in microgravity is thought to cause back pain in astronauts. A spinal compression harness can compress the spine to eliminate lengthening but the loading condition with harness is different than physiologic conditions. Our purpose was to compare the effect of spine compression with a harness in supine position on disk height and spinal curvature in the lumbar spine to that of upright position as measured using a vertically open magnetic resonance imaging system. METHODS: Fifteen healthy subjects volunteered. On day 1, each subject lay supine for an hour and a baseline scan of the lumbar spine was performed. After applying a load of fifty percent of body weight with the harness for thirty minutes, the lumbar spine was scanned again. On day 2, after a baseline scan, a follow up scan was performed after kneeling for thirty minutes within the gap between two vertically oriented magnetic coils. Anterior and posterior disk heights, posterior disk bulging, and spinal curvature were measured from the baseline and follow up scans. RESULTS: Anterior disk heights increased and posterior disk heights decreased compared with baseline scans both after spinal compression with harness and upright posture. The spinal curvature increased by both loading conditions of the spine. DISCUSSION: The spinal compression with specially designed harness has the same effect as the physiologic loading of the spine in the kneeling upright position. The harness shows some promise as a tool to increase the diagnostic capabilities of a conventional MR system.
Lumbar spine disc heights and curvature: upright posture vs. supine compression harness
Lee, Shi-Uk; Hargens, Alan R.; Fredericson, Michael; Lang, Philipp K.
2003-01-01
INTRODUCTION: Spinal lengthening in microgravity is thought to cause back pain in astronauts. A spinal compression harness can compress the spine to eliminate lengthening but the loading condition with harness is different than physiologic conditions. Our purpose was to compare the effect of spine compression with a harness in supine position on disk height and spinal curvature in the lumbar spine to that of upright position as measured using a vertically open magnetic resonance imaging system. METHODS: Fifteen healthy subjects volunteered. On day 1, each subject lay supine for an hour and a baseline scan of the lumbar spine was performed. After applying a load of fifty percent of body weight with the harness for thirty minutes, the lumbar spine was scanned again. On day 2, after a baseline scan, a follow up scan was performed after kneeling for thirty minutes within the gap between two vertically oriented magnetic coils. Anterior and posterior disk heights, posterior disk bulging, and spinal curvature were measured from the baseline and follow up scans. RESULTS: Anterior disk heights increased and posterior disk heights decreased compared with baseline scans both after spinal compression with harness and upright posture. The spinal curvature increased by both loading conditions of the spine. DISCUSSION: The spinal compression with specially designed harness has the same effect as the physiologic loading of the spine in the kneeling upright position. The harness shows some promise as a tool to increase the diagnostic capabilities of a conventional MR system.
On Nonlinear Higher Spin Curvature
Manvelyan, Ruben(Yerevan Physics Institute, Alikhanian Br. St. 2, Yerevan, 0036, Armenia); Mkrtchyan, Karapet; Rühl, Werner; Tovmasyan, Murad
2011-01-01
We present the first nonlinear term of the higher spin curvature which is covariant with respect to deformed gauge transformations that are linear in the field. We consider in detail the case of spin 3 after presenting spin 2 as an example, and then construct the general spin s quadratic term of the deWit-Freedman curvature.
On nonlinear higher spin curvature
Energy Technology Data Exchange (ETDEWEB)
Manvelyan, Ruben, E-mail: manvel@physik.uni-kl.d [Department of Physics, Erwin Schroedinger Strasse, Technical University of Kaiserslautern, Postfach 3049, 67653 Kaiserslautern (Germany); Yerevan Physics Institute, Alikhanian Br. Str. 2, 0036 Yerevan (Armenia); Mkrtchyan, Karapet, E-mail: karapet@yerphi.a [Department of Physics, Erwin Schroedinger Strasse, Technical University of Kaiserslautern, Postfach 3049, 67653 Kaiserslautern (Germany); Yerevan Physics Institute, Alikhanian Br. Str. 2, 0036 Yerevan (Armenia); Ruehl, Werner, E-mail: ruehl@physik.uni-kl.d [Department of Physics, Erwin Schroedinger Strasse, Technical University of Kaiserslautern, Postfach 3049, 67653 Kaiserslautern (Germany); Tovmasyan, Murad, E-mail: mtovmasyan@ysu.a [Yerevan Physics Institute, Alikhanian Br. Str. 2, 0036 Yerevan (Armenia)
2011-05-09
We present the first nonlinear term of the higher spin curvature which is covariant with respect to deformed gauge transformations that are linear in the field. We consider the case of spin 3 after presenting spin 2 as an example, and then construct the general spin s quadratic term of the de Wit-Freedman curvature.
Environmental influences on DNA curvature
DEFF Research Database (Denmark)
Ussery, David; Higgins, C.F.; Bolshoy, A.
1999-01-01
DNA curvature plays an important role in many biological processes. To study environmentalinfluences on DNA curvature we compared the anomalous migration on polyacrylamide gels ofligation ladders of 11 specifically-designed oligonucleotides. At low temperatures (25 degreesC and below) most...... for DNAcurvature and for environmentally-sensitive DNA conformations in the regulation of geneexpression....
Bedno, Sheryl A; Gardiner, Bradley; Li, Yuanzhang; Wiesen, Andrew R; Firestone, Jordan A; Niebuhr, David W
2011-05-01
Selective accession waivers for medically disqualifying conditions like spinal curvature are one way the military meets its manpower needs. We evaluated retention patterns during the first 2 years of service of a cohort of military recruits with waivers for pathological curvature of the spine (spinal curvature). Recruits waived for spinal curvature (n = 417), who accessed from 1998 to 2005 were identified and matched with 3 qualified recruits. Kaplan-Meier survival analysis and Cox proportional hazards model were used to compare survival patterns and adjusted attrition hazard estimates. Waived recruits experienced significantly increased risk of "all cause" discharge (relative risk = 1.3; 95% confidence interval: 1.1, 1.5) and "existing prior to service" discharge (relative risk = 2.4; confidence interval: 1.6, 3.5). Despite the increased risk of discharge, current waiver criteria allowed a majority with spinal curvature to complete at least 2 years of service. Policy makers must consider risks and benefits before modifying the current accession standard for spinal curvature.
CURVATURE COMPUTATIONS OF 2-MANIFOLDS IN IRk
Institute of Scientific and Technical Information of China (English)
Guo-liang Xu; Chandrajit L. Bajaj
2003-01-01
In this paper, we provide simple and explicit formulas for computing Riemannian cur-vatures, mean curvature vectors, principal curvatures and principal directions for a 2-dimensional Riemannian manifold embedded in IRk with k ≥ 3.
Lectures on mean curvature flows
Zhu, Xi-Ping
2002-01-01
"Mean curvature flow" is a term that is used to describe the evolution of a hypersurface whose normal velocity is given by the mean curvature. In the simplest case of a convex closed curve on the plane, the properties of the mean curvature flow are described by Gage-Hamilton's theorem. This theorem states that under the mean curvature flow, the curve collapses to a point, and if the flow is diluted so that the enclosed area equals \\pi, the curve tends to the unit circle. In this book, the author gives a comprehensive account of fundamental results on singularities and the asymptotic behavior of mean curvature flows in higher dimensions. Among other topics, he considers in detail Huisken's theorem (a generalization of Gage-Hamilton's theorem to higher dimension), evolution of non-convex curves and hypersurfaces, and the classification of singularities of the mean curvature flow. Because of the importance of the mean curvature flow and its numerous applications in differential geometry and partial differential ...
EAU guidelines on penile curvature.
Hatzimouratidis, Konstantinos; Eardley, Ian; Giuliano, François; Hatzichristou, Dimitrios; Moncada, Ignacio; Salonia, Andrea; Vardi, Yoram; Wespes, Eric
2012-09-01
Penile curvature can be congenital or acquired. Acquired curvature is secondary due to La Peyronie (Peyronie's) disease. To provide clinical guidelines on the diagnosis and treatment of penile curvature. A systematic literature search on the epidemiology, diagnosis, and treatment of penile curvature was performed. Articles with the highest evidence available were selected and formed the basis for assigning levels of evidence and grades of recommendations. The pathogenesis of congenital penile curvature is unknown. Peyronie's disease is a poorly understood connective tissue disorder most commonly attributed to repetitive microvascular injury or trauma during intercourse. Diagnosis is based on medical and sexual histories, which are sufficient to establish the diagnosis. Physical examination includes assessment of palpable nodules and penile length. Curvature is best documented by a self-photograph or pharmacologically induced erection. The only treatment option for congenital penile curvature is surgery based on plication techniques. Conservative treatment for Peyronie's disease is associated with poor outcomes. Pharmacotherapy includes oral potassium para-aminobenzoate, intralesional treatment with verapamil, clostridial collagenase or interferon, topical verapamil gel, and iontophoresis with verapamil and dexamethasone. They can be efficacious in some patients, but none of these options carry a grade A recommendation. Steroids, vitamin E, and tamoxifen cannot be recommended. Extracorporeal shock wave treatment and penile traction devices may only be used to treat penile pain and reduce penile deformity, respectively. Surgery is indicated when Peyronie's disease is stable for at least 3 mo. Tunical shortening procedures, especially plication techniques, are the first treatment options. Tunical lengthening procedures are preferred in more severe curvatures or in complex deformities. Penile prosthesis implantation is recommended in patients with erectile dysfunction
Sigma Models with Negative Curvature
Alonso, Rodrigo; Manohar, Aneesh V.
2016-01-01
We construct Higgs Effective Field Theory (HEFT) based on the scalar manifold H^n, which is a hyperbolic space of constant negative curvature. The Lagrangian has a non-compact O(n,1) global symmetry group, but it gives a unitary theory as long as only a compact subgroup of the global symmetry is gauged. Whether the HEFT manifold has positive or negative curvature can be tested by measuring the S-parameter, and the cross sections for longitudinal gauge boson and Higgs boson scattering, since the curvature (including its sign) determines deviations from Standard Model values.
Solving higher curvature gravity theories
Energy Technology Data Exchange (ETDEWEB)
Chakraborty, Sumanta [IUCAA, Pune (India); SenGupta, Soumitra [Indian Association for the Cultivation of Science, Theoretical Physics Department, Kolkata (India)
2016-10-15
Solving field equations in the context of higher curvature gravity theories is a formidable task. However, in many situations, e.g., in the context of f(R) theories, the higher curvature gravity action can be written as an Einstein-Hilbert action plus a scalar field action. We show that not only the action but the field equations derived from the action are also equivalent, provided the spacetime is regular. We also demonstrate that such an equivalence continues to hold even when the gravitational field equations are projected on a lower-dimensional hypersurface. We have further addressed explicit examples in which the solutions for Einstein-Hilbert and a scalar field system lead to solutions of the equivalent higher curvature theory. The same, but on the lower-dimensional hypersurface, has been illustrated in the reverse order as well. We conclude with a brief discussion on this technique of solving higher curvature field equations. (orig.)
Effects of Curvature on Dynamics
Dutta, Gautam
2010-01-01
In this article we discuss the effect of curvature on dynamics when a physical system moves adiabatically in a curved space. These effects give a way to measure the curvature of the space intrinsically without referring to higher dimensional space. Two interesting examples, the Foucault Pendulum and the perihelion shift of planetary orbits, are presented in a simple geometric way. A paper model is presented to see the perihelion shift.
Spatial curvature endgame: Reaching the limit of curvature determination
Leonard, C. Danielle; Bull, Philip; Allison, Rupert
2016-07-01
Current constraints on spatial curvature show that it is dynamically negligible: |ΩK|≲5 ×10-3 (95% C.L.). Neglecting it as a cosmological parameter would be premature however, as more stringent constraints on ΩK at around the 10-4 level would offer valuable tests of eternal inflation models and probe novel large-scale structure phenomena. This precision also represents the "curvature floor," beyond which constraints cannot be meaningfully improved due to the cosmic variance of horizon-scale perturbations. In this paper, we discuss what future experiments will need to do in order to measure spatial curvature to this maximum accuracy. Our conservative forecasts show that the curvature floor is unreachable—by an order of magnitude—even with Stage IV experiments, unless strong assumptions are made about dark energy evolution and the Λ CDM parameter values. We also discuss some of the novel problems that arise when attempting to constrain a global cosmological parameter like ΩK with such high precision. Measuring curvature down to this level would be an important validation of systematics characterization in high-precision cosmological analyses.
Discrete Curvature Theories and Applications
Sun, Xiang
2016-08-25
Discrete Di erential Geometry (DDG) concerns discrete counterparts of notions and methods in di erential geometry. This thesis deals with a core subject in DDG, discrete curvature theories on various types of polyhedral surfaces that are practically important for free-form architecture, sunlight-redirecting shading systems, and face recognition. Modeled as polyhedral surfaces, the shapes of free-form structures may have to satisfy di erent geometric or physical constraints. We study a combination of geometry and physics { the discrete surfaces that can stand on their own, as well as having proper shapes for the manufacture. These proper shapes, known as circular and conical meshes, are closely related to discrete principal curvatures. We study curvature theories that make such surfaces possible. Shading systems of freeform building skins are new types of energy-saving structures that can re-direct the sunlight. From these systems, discrete line congruences across polyhedral surfaces can be abstracted. We develop a new curvature theory for polyhedral surfaces equipped with normal congruences { a particular type of congruences de ned by linear interpolation of vertex normals. The main results are a discussion of various de nitions of normality, a detailed study of the geometry of such congruences, and a concept of curvatures and shape operators associated with the faces of a triangle mesh. These curvatures are compatible with both normal congruences and the Steiner formula. In addition to architecture, we consider the role of discrete curvatures in face recognition. We use geometric measure theory to introduce the notion of asymptotic cones associated with a singular subspace of a Riemannian manifold, which is an extension of the classical notion of asymptotic directions. We get a simple expression of these cones for polyhedral surfaces, as well as convergence and approximation theorems. We use the asymptotic cones as facial descriptors and demonstrate the
... this page: //medlineplus.gov/ency/article/000029.htm Spinal injury To use the sharing features on this page, ... move anyone who you think may have a spinal injury, unless it is absolutely necessary. For example, if ...
Equi-Gaussian Curvature Folding
Indian Academy of Sciences (India)
E M El-Kholy; El-Said R Lashin; Salama N Daoud
2007-08-01
In this paper we introduce a new type of folding called equi-Gaussian curvature folding of connected Riemannian 2-manifolds. We prove that the composition and the cartesian product of such foldings is again an equi-Gaussian curvature folding. In case of equi-Gaussian curvature foldings, $f:M→ P_n$, of an orientable surface onto a polygon $P_n$ we prove that (i) $f\\in\\mathcal{F}_{EG}(S^2)\\Leftrightarrow n=3$ (ii) $f\\in\\mathcal{F}_{EG}(T^2)\\Rightarrow n=4$ (iii) $f\\in\\mathcal{F}_{EG}(\\# 2T^2)\\Rightarrow n=5, 6$ and we generalize (iii) for $\\# nT^2$.
Integral Menger curvature for surfaces
Strzelecki, Paweł; von der Mosel, Heiko
2009-01-01
We develop the concept of integral Menger curvature for a large class of nonsmooth surfaces. We prove uniform Ahlfors regularity and a $C^{1,\\lambda}$-a-priori bound for surfaces for which this functional is finite. In fact, it turns out that there is an explicit length scale $R>0$ which depends only on an upper bound $E$ for the integral Menger curvature $M_p(\\Sigma)$ and the integrability exponent $p$, and \\emph{not} on the surface $\\Sigma$ itself; below that scale, each surface with energy...
Surface meshing with curvature convergence
Li, Huibin
2014-06-01
Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.
Environmental influences on DNA curvature
DEFF Research Database (Denmark)
Ussery, David; Higgins, C.F.; Bolshoy, A.
1999-01-01
of the sequences exhibited a degree of anomalous migration. Increasedtemperature had a significant effect on the anomalous migration (curvature) of some sequencesbut limited effects on others; at 50 degrees C only 1 sequence migrated anomalously. Mg2+ hada strong influence on the migration of certain sequences...
The geometric curvature of the spine during the sirshasana, the yoga's headstand.
Campos, Mário Hebling; Giraldi, Nayane Martins; Gentil, Paulo; de Lira, Claudio Andre Barbosa; Vieira, Carlos A; de Paula, Marcelo Costa
2016-07-26
This study analysed the behaviour of the geometric curvature of the spine during sirshasana. The position of dorsal retroreflective markers was computed via stereophotogrammetric analysis in six males and five females (29.4 ± 8.8 years, 63.0 ± 11.4 kg, 1.66 ± 0.08 m [average ± standard deviation]). The spinal points were projected onto the sagittal and frontal planes of the trunk, a polynomial was fitted to the data and the two-dimensional geometric curvature was quantified. The inferior lumbar lordosis decreased compared to the orthostatic position and gait, which may favour the posterior protrusion of the lumbar spinal nucleus pulposus in people with posterior herniation. The lateral deviation at the middle of the thoracic spine increases during sirshasana, which may reflect increased difficulties for postural control and spinal loads. It could be useful for promoting positive spinal structural and functional chronic adaptations for healthy participants, if the yoga programme is carefully planned and the spinal alignment is carefully monitored during a headstand. However, it may aggravate some spinal diseases, especially scoliosis.
Tay, Bobby K-B; Deckey, Jeffrey; Hu, Serena S
2002-01-01
Spinal infections can occur in a variety of clinical situations. Their presentation ranges from the infant with diskitis who is unwilling to crawl or walk to the adult who develops an infection after a spinal procedure. The most common types of spinal infections are hematogenous bacterial or fungal infections, pediatric diskitis, epidural abscess, and postoperative infections. Prompt and accurate diagnosis of spinal infections, the cornerstone of treatment, requires a high index of suspicion in at-risk patients and the appropriate evaluation to identify the organism and determine the extent of infection. Neurologic function and spinal stability also should be carefully evaluated. The goals of therapy should include eradicating the infection, relieving pain, preserving or restoring neurologic function, improving nutrition, and maintaining spinal stability.
On mean curvatures in submanifolds geometry
Institute of Scientific and Technical Information of China (English)
2008-01-01
By using moving frame theory,first we introduce 2p-th mean curvatures and(2p+1)-th mean curvature vector fields for a submanifold.We then give an integral expression of them that characterizes them as mean values of symmetric functions of principle curvatures.Next we apply it to derive directly the celebrated Weyl-Gray tube formula in terms of integrals of the 2p-th mean curvatures and some Minkowski-type integral formulas.
Tali, E Turgut; Koc, A Murat; Oner, A Yusuf
2015-05-01
Spinal involvement in human brucellosis is a common condition and a significant cause of morbidity and mortality, particularly in endemic areas, because it is often associated with therapeutic failure. Most chronic brucellosis cases are the result of inadequate treatment of the initial episode. Recognition of spinal brucellosis is challenging. Early diagnosis is important to ensure proper treatment and decrease morbidity and mortality. Radiologic evaluation has gained importance in diagnosis and treatment planning, including interventional procedures and monitoring of all spinal infections.
... Pharyngitis, Adenitis Syndrome (Juvenile) Polymyalgia Rheumatica Psoriatic Arthritis Raynaud's Phenomenon Reactive Arthritis Rheumatoid Arthritis Scleroderma Sjogren's Syndrome Spinal Stenosis Spondyloarthritis Systemic Lupus Erythematosus (Juvenile) Takayasu's ...
Cosmological model with dynamical curvature
Stichel, Peter C
2016-01-01
We generalize the recently introduced relativistic Lagrangian darkon fluid model (EPJ C (2015) 75:9) by starting with a self-gravitating geodesic fluid whose energy-momentum tensor is dust-like with a nontrivial energy flow. The corresponding covariant propagation and constraint equations are considered in a shear-free nonrelativistic limit whose analytic solutions determine the 1st-order relativistic correction to the spatial curvature. This leads to a cosmological model where the accelerated expansion of the Universe is driven by a time-dependent spatial curvature without the need for introducing any kind of dark energy. We derive the differential equation to be satisfied by the area distance for this model.
Quantum Complexity and Negative Curvature
Brown, Adam R; Zhao, Ying
2016-01-01
As time passes, once simple quantum states tend to become more complex. For strongly coupled k-local Hamiltonians, this growth of computational complexity has been conjectured to follow a distinctive and universal pattern. In this paper we show that the same pattern is exhibited by a much simpler system: classical geodesics on a compact two-dimensional geometry of uniform negative curvature. This striking parallel persists whether the system is allowed to evolve naturally or is perturbed from the outside.
Substrate curvature regulates cell migration
He, Xiuxiu; Jiang, Yi
2017-06-01
Cell migration is essential in many aspects of biology. Many basic migration processes, including adhesion, membrane protrusion and tension, cytoskeletal polymerization, and contraction, have to act in concert to regulate cell migration. At the same time, substrate topography modulates these processes. In this work, we study how substrate curvature at micrometer scale regulates cell motility. We have developed a 3D mechanical model of single cell migration and simulated migration on curved substrates with different curvatures. The simulation results show that cell migration is more persistent on concave surfaces than on convex surfaces. We have further calculated analytically the cell shape and protrusion force for cells on curved substrates. We have shown that while cells spread out more on convex surfaces than on concave ones, the protrusion force magnitude in the direction of migration is larger on concave surfaces than on convex ones. These results offer a novel biomechanical explanation to substrate curvature regulation of cell migration: geometric constrains bias the direction of the protrusion force and facilitates persistent migration on concave surfaces.
Mean curvature 1 surfaces in hyperbolic 3-space with low total curvature. I
Rossman, Wayne; Umehara, Masaaki; Yamada, Kotaro
2004-01-01
A complete surface of constant mean curvature 1 (CMC-1) in hyperbolic 3- space with constant curvature $-1$ has two natural notions of ‘‘total curvature’’—one is the total absolute curvature which is the integral over the surface of the absolute value of the Gaussian curvature, and the other is the dual total absolute curvature which is the total absolute curvature of the dual CMC-1 surface. In this paper, we completely classify CMC-1 surfaces with dual total absolute curvature...
Quantifying cervical-spine curvature using Bézier splines.
Klinich, Kathleen D; Ebert, Sheila M; Reed, Matthew P
2012-11-01
Knowledge of the distributions of cervical-spine curvature is needed for computational studies of cervical-spine injury in motor-vehicle crashes. Many methods of specifying spinal curvature have been proposed, but they often involve qualitative assessment or a large number of parameters. The objective of this study was to develop a quantitative method of characterizing cervical-spine curvature using a small number of parameters. 180 sagittal X-rays of subjects seated in automotive posture with their necks in neutral, flexed, and extended postures were collected in the early 1970s. Subjects were selected to represent a range of statures and ages for each gender. X-rays were reanalyzed using advanced technology and statistical methods. Coordinates of the posterior margins of the vertebral bodies and dens were digitized. Bézier splines were fit through the coordinates of these points. The interior control points that define the spline curvature were parameterized as a vector angle and length. By defining the length as a function of the angle, cervical-spine curvature was defined with just two parameters: superior and inferior Bézier angles. A classification scheme was derived to sort each curvature by magnitude and type of curvature (lordosis versus S-shaped versus kyphosis; inferior or superior location). Cervical-spine curvature in an automotive seated posture varies with gender and age but not stature. Average values of superior and inferior Bézier angles for cervical spines in flexion, neutral, and extension automotive postures are presented for each gender and age group. Use of Bézier splines fit through posterior margins offers a quantitative method of characterizing cervical-spine curvature using two parameters: superior and inferior Bézier angles.
Kim, Hyo-Sil
2011-01-01
We study the motion-planning problem for a car-like robot whose turning radius is bounded from below by one and which is allowed to move in the forward direction only (Dubins car). For two robot configurations $\\sigma, \\sigma'$, let $\\ell(\\sigma, \\sigma')$ be the shortest bounded-curvature path from $\\sigma$ to $\\sigma'$. For $d \\geq 0$, let $\\ell(d)$ be the supremum of $\\ell(\\sigma, \\sigma')$, over all pairs $(\\sigma, \\sigma')$ that are at Euclidean distance $d$. We study the function $\\dub(d) = \\ell(d) - d$, which expresses the difference between the bounded-curvature path length and the Euclidean distance of its endpoints. We show that $\\dub(d)$ decreases monotonically from $\\dub(0) = 7\\pi/3$ to $\\dub(\\ds) = 2\\pi$, and is constant for $d \\geq \\ds$. Here $\\ds \\approx 1.5874$. We describe pairs of configurations that exhibit the worst-case of $\\dub(d)$ for every distance $d$.
Mirror with thermally controlled radius of curvature
Neil, George R.; Shinn, Michelle D.
2010-06-22
A radius of curvature controlled mirror for controlling precisely the focal point of a laser beam or other light beam. The radius of curvature controlled mirror provides nearly spherical distortion of the mirror in response to differential expansion between the front and rear surfaces of the mirror. The radius of curvature controlled mirror compensates for changes in other optical components due to heating or other physical changes. The radius of curvature controlled mirror includes an arrangement for adjusting the temperature of the front surface and separately adjusting the temperature of the rear surface to control the radius of curvature. The temperature adjustment arrangements can include cooling channels within the mirror body or convection of a gas upon the surface of the mirror. A control system controls the differential expansion between the front and rear surfaces to achieve the desired radius of curvature.
... lower part of the body. It resembles a “horse’s tail” ( cauda equina in Latin). What Causes Spinal ... of the spine fails, it usually places increased stress on other parts of the spine. For example, ...
Directory of Open Access Journals (Sweden)
I.A. Norkin
2010-06-01
Full Text Available The given article considers the modern view on etiology, pathogenesis, classifications, clinical picture, diagnosis and treatment of spinal hemangiomas. Advantages of vertebroplasty over the other techniques of treatment of studied pathology are presented
... risk. Diseases such as arthritis and scoliosis can cause spinal stenosis, too. Symptoms might appear gradually or not at all. They include Pain in your neck or back Numbness, weakness, cramping, or pain in ...
... infections may occur following surgery or spontaneously in patients with certain risk factors. Risk factors for spinal infections include poor nutrition, immune suppression, human immunodeficiency virus (HIV) infection, cancer, diabetes and obesity. Surgical risk factors ...
I.A. Norkin; S.V. Likhachev; A.Yu. Chomartov; A.I. Norkin; D.M. Puchinian
2010-01-01
The given article considers the modern view on etiology, pathogenesis, classifications, clinical picture, diagnosis and treatment of spinal hemangiomas. Advantages of vertebroplasty over the other techniques of treatment of studied pathology are presented
... vertebrae. These include: treatment of a fractured (broken) vertebra; correction of deformity (spinal curves or slippages); elimination of pain from painful motion; treatment of instability; and treatment of some cervical disc herniations. One of the less controversial reasons ...
S-curvature of isotropic Berwald metrics
Institute of Scientific and Technical Information of China (English)
Akbar TAYEBI; Mehdi RAFIE-RAD
2008-01-01
Isotropic Berwald metrics are as a generalization of Berwald metrics. Shen proved that every Berwald metric is of vanishing S-curvature. In this paper, we generalize this fact and prove that every isotropic Berwald metric is of isotropic S-curvature. Let F = α + β be a Randers metric of isotropic Berwald curvature. Then it corresponds to a conformal vector field through navigation representation.
A Stringy (Holographic) Pomeron with Extrinsic Curvature
Qian, Yachao
2014-01-01
We model the soft pomeron in QCD using a scalar Polyakov string with extrinsic curvature in the bottom-up approach of holographic QCD. The overall dipole-dipole scattering amplitude in the soft pomeron kinematics is shown to be sensitive to the extrinsic curvature of the string for finite momentum transfer. The characteristics of the diffractive peak in the differential elastic $pp$ scattering are affected by a small extrinsic curvature of the string.
Curvature and bubble convergence of harmonic maps
Kokarev, Gerasim
2010-01-01
We explore geometric aspects of bubble convergence for harmonic maps. More precisely, we show that the formation of bubbles is characterised by the local excess of curvature on the target manifold. We give a universal estimate for curvature concentration masses at each bubble point and show that there is no curvature loss in the necks. Our principal hypothesis is that the target manifold is Kaehler.
Curvatures for Parameter Subsets in Nonlinear Regression
1986-01-01
The relative curvature measures of nonlinearity proposed by Bates and Watts (1980) are extended to an arbitrary subset of the parameters in a normal, nonlinear regression model. In particular, the subset curvatures proposed indicate the validity of linearization-based approximate confidence intervals for single parameters. The derivation produces the original Bates-Watts measures directly from the likelihood function. When the intrinsic curvature is negligible, the Bates-Watts parameter-effec...
Higher curvature supergravity and cosmology
Energy Technology Data Exchange (ETDEWEB)
Ferrara, Sergio [Th-Ph Department, CERN, Geneva (Switzerland); U.C.L.A., Los Angeles, CA (United States); INFN - LNF, Frascati (Italy); Sagnotti, Augusto [Scuola Normale Superiore, Pisa (Italy); INFN, Pisa (Italy)
2016-04-15
In this contribution we describe dual higher-derivative formulations of some cosmological models based on supergravity. Work in this direction started with the R + R{sup 2} Starobinsky model, whose supersymmetric extension was derived in the late 80's and was recently revived in view of new CMB data. Models dual to higher-derivative theories are subject to more restrictions than their bosonic counterparts or standard supergravity. The three sections are devoted to a brief description of R + R{sup 2} supergravity, to a scale invariant R{sup 2} supergravity and to theories with a nilpotent curvature, whose duals describe non-linear realizations (in the form of a Volkov-Akulov constrained superfield) coupled to supergravity. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
On the Ricci Curvature of a Randers Metric of Isotropic S-curvature
Institute of Scientific and Technical Information of China (English)
Xiao Huan MO; Chang Tao YU
2008-01-01
We derive the integral inequality of a Randers metric with isotropic S-curvature in terms of its navigation representation. Using the obtained inequality we give some rigidity results under the condition of Ricci curvature. In particular, we show the following result: Assume that an n-dimensional compact Randers manifold (M, F)hasconstantS-curvature c.Then(M, F) must be Riemannian ifits Ricci curvature satisfies that Ric < - (n - 1)c2.
Application of computer graphics for assessment of spinal deformities.
Vandegriend, B; Hill, D; Raso, J; Durdle, N; Zhang, Z
1995-03-01
A graphical portrayal system to assess spinal deformities is described. The system is based on software to display and manipulate three-dimensional images of the spine and trunk surface. Qualitative measurements of internal spinal alignment and trunk appearance are provided. The graphics display is developed using graPHIGS routines in conjunction with the C programming language and the UNIX operating system. This software provides clinicians with a computer-aided measurement tool that rapidly conveys clear and concise information about the deformities associated with abnormal spinal curvatures.
Lattice QCD simulation of the Berry curvature
Yamamoto, Arata
2016-01-01
The Berry curvature is a fundamental concept describing topological order of quantum systems. While it can be analytically tractable in non-interacting systems, numerical simulations are necessary in interacting systems. We present a formulation to calculate the Berry curvature in lattice QCD.
BIFURCATION IN PRESCRIBED MEAN CURVATURE PROBLEM
Institute of Scientific and Technical Information of China (English)
马力
2002-01-01
This paper discusses the existence problem in the study of some partial differential equations. The author gets some bifurcation on the prescribed mean curvature problem on the unit ball, the scalar curvature problem on the n-sphere, and some field equations. The author gives some natural conditions such that the standard bifurcation or Thom-Mather theory can be used.
The geometric curvature of the lumbar spine during restricted and unrestricted squats.
Hebling Campos, Mário; Furtado Alaman, Laizi I; Seffrin-Neto, Aldo A; Vieira, Carlos A; Costa de Paula, Marcelo; Barbosa de Lira, Claudio A
2017-06-01
The main purpose of this study was to analyze the behavior of the geometric curvature of the lumbar spine during restricted and unrestricted squats, using a novel investigative method. The rationale for our hypothesis is that the lumbar curvature has different patterns at different spine levels depending on the squat technique used. Spine motion was collected via stereo-photogrammetric analysis in nineteen participants (11 males, 8 females). The reconstructed spine points at the upright neutral position and at the deepest position of the squat exercise were projected onto the sagittal plane of the trunk, a polynomial was fitted to the data, and were quantified the two-dimensional geometric curvature at lower, central and higher lumbar levels, besides the inclination of trunk and lumbosacral region, the overall geometric curvature and overall angle of the lumbar spine. The mean values for each variable were analysed with paired t-test (Pposture to deepest point of the movement, but for the lower lumbar the flexion is less intense if the knees travel anteriorly past the toes. The trunk and the lumbosacral region lean forward in both squat techniques and these effects are also reduced in unrestricted squats. The data collected in the study are evidence that during barbell squats the lumbar curvature has different patterns at different spinal levels depending on the exercise technique. The lower lumbar spine appears to be less overloaded during unrestricted squats.
Strong curvature effects in Neumann wave problems
DEFF Research Database (Denmark)
Willatzen, Morten; Pors, A.; Gravesen, Jens
2012-01-01
equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important...... to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear......-in-curvature contribution originates from parity symmetry breaking of eigenstates in circular-sector tori and hence vanishes in a torus with a complete circular cross section. The same strong curvature effect is not present in waveguides subject to Dirichlet boundary conditions where curvature contributions contribute...
Importance of plan curvature in watershed modeling
Boll, J.; Ribail, J.; Zhao, M.
2016-12-01
A hillslope's hydrologic response to precipitation events is largely controlled by the topographic features of a given hillslope, specifically the profile and plan curvature. Many models simplify hillslope topography and ignore the curvature properties, and some use alternate measures such as a topographic index or the hillslope width function. Models that ignore curvature properties may be calibrated to produce the statistically acceptable integrated response of runoff at a watershed outlet, but incorporating these properties is necessary to model accurately hydrologic processes such as surface flow, erosion, subsurface lateral flow, location of runoff generation and drainage response. In this study, we evaluated the sensitivity of rainfall-runoff modelling to profile and plan curvature in two models. In the first model, the Water Erosion Prediction Project (WEPP) model, hillslope uses a representative width to the hillslope by dividing the drainage area by the average surface channel length. Profile curvature is preserved with a limited spatial resolution due to the number of overland flow elements. In the second model, the distributed Soil Moisture Routing (SMR) model, the geographic information system uses the D8 algorithm to capture profile and plan curvature. Sensitivity to topographic features was tested for three profile curvatures (convex, concave, straight) combined with three plan curvatures (diverging, converging, uniform) resulting in a total of nine hillslopes. Each hillslope was subjected to different rainfall events to detect threshold behavior for when topographic features cannot be ignored. Our findings indicate that concave and convex plan curvature need to be included when subsurface flow processes are the dominant flow process for surface flow runoff generation. We present thresholds for acceptable cases when profile and plan curvature can be simplified in larger spatial hydrologic units.
Energy Technology Data Exchange (ETDEWEB)
Gao, Dengliang
2013-03-01
In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm, and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome known to be formed by tectonic folding and faulting, curvature helps define the crestal portion of the reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps better define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, the current study based on an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In certain fractured reservoirs such as at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to detect fracture volume and connectivity, and to model fracture networks.
Curvature function and coarse graining
Díaz-Marín, Homero; Zapata, José A.
2010-12-01
A classic theorem in the theory of connections on principal fiber bundles states that the evaluation of all holonomy functions gives enough information to characterize the bundle structure (among those sharing the same structure group and base manifold) and the connection up to a bundle equivalence map. This result and other important properties of holonomy functions have encouraged their use as the primary ingredient for the construction of families of quantum gauge theories. However, in these applications often the set of holonomy functions used is a discrete proper subset of the set of holonomy functions needed for the characterization theorem to hold. We show that the evaluation of a discrete set of holonomy functions does not characterize the bundle and does not constrain the connection modulo gauge appropriately. We exhibit a discrete set of functions of the connection and prove that in the abelian case their evaluation characterizes the bundle structure (up to equivalence), and constrains the connection modulo gauge up to "local details" ignored when working at a given scale. The main ingredient is the Lie algebra valued curvature function F_S (A) defined below. It covers the holonomy function in the sense that exp {F_S (A)} = Hol(l= partial S, A).
Forced hyperbolic mean curvature flow
Mao, Jing
2012-01-01
In this paper, we investigate two hyperbolic flows obtained by adding forcing terms in direction of the position vector to the hyperbolic mean curvature flows in \\cite{klw,hdl}. For the first hyperbolic flow, as in \\cite{klw}, by using support function, we reduce it to a hyperbolic Monge-Amp$\\grave{\\rm{e}}$re equation successfully, leading to the short-time existence of the flow by the standard theory of hyperbolic partial differential equation. If the initial velocity is non-negative and the coefficient function of the forcing term is non-positive, we also show that there exists a class of initial velocities such that the solution of the flow exists only on a finite time interval $[0,T_{max})$, and the solution converges to a point or shocks and other propagating discontinuities are generated when $t\\rightarrow{T_{max}}$. These generalize the corresponding results in \\cite{klw}. For the second hyperbolic flow, as in \\cite{hdl}, we can prove the system of partial differential equations related to the flow is ...
Magnetophoretic Induction of Root Curvature
Hasenstein, Karl H.
1997-01-01
The last year of the grant period concerned the consolidation of previous experiments to ascertain that the theoretical premise apply not just to root but also to shoots. In addition, we verified that high gradient magnetic fields do not interfere with regular cellular activities. Previous results have established that: (1) intracellular magnetophoresis is possible; and (2) HGMF lead to root curvature. In order to investigate whether HGMF affect the assembly and/or organization of structural proteins, we examined the arrangement of microtubules in roots exposed to HGMF. The cytoskeletal investigations were performed with fomaldehyde-fixed, nonembedded tissue segments that were cut with a vibratome. Microtubules (MTs) were stained with rat anti-yeast tubulin (YOL 1/34) and DTAF-labeled antibody against rat IgG. Microfilaments (MFs) were visualized by incubation in rhodamine-labeled phalloidin. The distribution and arrangement of both components of the cytoskeleton were examined with a confocal microscope. Measurements of growth rates and graviresponse were done using a video-digitizer. Since HGMF repel diamagnetic substances including starch-filled amyloplasts and most The second aspect of the work includes studies of the effect of cytoskeletal inhibitors on MTs and MFs. The analysis of the effect of micotubular inhibitors on the auxin transport in roots showed that there is very little effect of MT-depolymerizing or stabilizing drugs on auxin transport. This is in line with observations that application of such drugs is not immediately affecting the graviresponsiveness of roots.
Programming curvature using origami tessellations
Dudte, Levi H.; Vouga, Etienne; Tachi, Tomohiro; Mahadevan, L.
2016-05-01
Origami describes rules for creating folded structures from patterns on a flat sheet, but does not prescribe how patterns can be designed to fit target shapes. Here, starting from the simplest periodic origami pattern that yields one-degree-of-freedom collapsible structures--we show that scale-independent elementary geometric constructions and constrained optimization algorithms can be used to determine spatially modulated patterns that yield approximations to given surfaces of constant or varying curvature. Paper models confirm the feasibility of our calculations. We also assess the difficulty of realizing these geometric structures by quantifying the energetic barrier that separates the metastable flat and folded states. Moreover, we characterize the trade-off between the accuracy to which the pattern conforms to the target surface, and the effort associated with creating finer folds. Our approach enables the tailoring of origami patterns to drape complex surfaces independent of absolute scale, as well as the quantification of the energetic and material cost of doing so.
Automated determination of spinal centerline in CT and MR images
Štern, Darko; Vrtovec, Tomaž; Pernuš, Franjo; Likar, Boštjan
2009-02-01
The spinal curvature is one of the most important parameters for the evaluation of spinal deformities. The spinal centerline, represented by the curve that passes through the centers of the vertebral bodies in three-dimensions (3D), allows valid quantitative measurements of the spinal curvature at any location along the spine. We propose a novel automated method for the determination of the spinal centerline in 3D spine images. Our method exploits the anatomical property that the vertebral body walls are cylindrically-shaped and therefore the lines normal to the edges of the vertebral body walls most often intersect in the middle of the vertebral bodies, i.e. at the location of spinal centerline. These points of intersection are first obtained by a novel algorithm that performs a selective search in the directions normal to the edges of the structures and then connected with a parametric curve that represents the spinal centerline in 3D. As the method is based on anatomical properties of the 3D spine anatomy, it is modality-independent, i.e. applicable to images obtained by computed tomography (CT) and magnetic resonance (MR). The proposed method was evaluated on six CT and four MR images (T1- and T2-weighted) of normal spines and on one scoliotic CT spine image. The qualitative and quantitative results for the normal spines show that the spinal centerline can be successfully determined in both CT and MR spine images, while the results for the scoliotic spine indicate that the method may also be used to evaluate pathological curvatures.
On different curvatures of spheres in Funk geometry
Olin, Eugeny A
2011-01-01
We compute the series expansions for the normal curvatures of hyperspheres, the Finsler and Rund curvatures of circles in Funk geometry as the radii tend to infinity. These three curvatures are different at infinity in Funk geometry.
Campbell, James A.; Hargens, Alan R.; Murthy, G.; Ballard, R. E.; Watenpaugh, D. E.; Hargens, Alan, R.; Sanchez, E.; Yang, C.; Mitsui, I.; Schwandt, D.; Fechner, K. P.; Holton, Emily M. (Technical Monitor)
1998-01-01
Weight bearing by the spinal column during upright posture often plays a role in the common problem of low back pain. Therefore, we developed a non-ferromagnetic spinal compression harness to enable MRI investigations of the spinal column during axial loading. Human subjects were fitted with a Nest and a footplate which were connected by adjustable straps to an analog load cell. MRI scans of human subjects (5 males and 1 female with age range of 27-53 yrs) during loaded and unloaded conditions were accomplished with a 1.5 Tesla GE Signa scanner. Studies of two subjects undergoing sequentially increasing spinal loads revealed significant decreases (r(sup 2) = 0.852) in spinal length between T4 and L5 culminating in a 1.5 to 2% length decrease during loading with 75% body weight. Sagittal vertebral body angles of four subjects placed under a constant 50% body weight load for one hour demonstrated increased lordotic and kyphotic curvatures. In the lumbar spine, the L2 vertebral body experienced the greatest angular change (-3 deg. to -5 deg.) in most subjects while in the thoracic spine, T4 angles increased from the unloaded state by +2 deg. to +9 deg. Overall, our studies demonstrate: 1) a progressive, although surprisingly small, decrease in spinal length with increasing load and 2) relatively large changes in spinal column angulation with 50% body weight.
Magnetic curvature effects on plasma interchange turbulence
Li, B.; Liao, X.; Sun, C. K.; Ou, W.; Liu, D.; Gui, G.; Wang, X. G.
2016-06-01
The magnetic curvature effects on plasma interchange turbulence and transport in the Z-pinch and dipole-like systems are explored with two-fluid global simulations. By comparing the transport levels in the systems with a different magnetic curvature, we show that the interchange-mode driven transport strongly depends on the magnetic geometry. For the system with large magnetic curvature, the pressure and density profiles are strongly peaked in a marginally stable state and the nonlinear evolution of interchange modes produces the global convective cells in the azimuthal direction, which lead to the low level of turbulent convective transport.
Directory of Open Access Journals (Sweden)
Alessio Arbuatti
2013-03-01
Conclusions: Possible causes for spinal curvature in fish are discussed on the basis of the current literature. While it is not possible to determine the exact cause(s of spinal deformities observed in the present study, traumatic injuries, nutritional imbalances, genetic defects or a combination of these factors can be supposed to be involved in the pathogenesis of such lesions.
Curvature constraints from Large Scale Structure
Di Dio, Enea; Raccanelli, Alvise; Durrer, Ruth; Kamionkowski, Marc; Lesgourgues, Julien
2016-01-01
We modified the CLASS code in order to include relativistic galaxy number counts in spatially curved geometries; we present the formalism and study the effect of relativistic corrections on spatial curvature. The new version of the code is now publicly available. Using a Fisher matrix analysis, we investigate how measurements of the spatial curvature parameter $\\Omega_K$ with future galaxy surveys are affected by relativistic effects, which influence observations of the large scale galaxy distribution. These effects include contributions from cosmic magnification, Doppler terms and terms involving the gravitational potential. As an application, we consider angle and redshift dependent power spectra, which are especially well suited for model independent cosmological constraints. We compute our results for a representative deep, wide and spectroscopic survey, and our results show the impact of relativistic corrections on the spatial curvature parameter estimation. We show that constraints on the curvature para...
Generalized Strong Curvature Singularities and Cosmic Censorship
Rudnicki, W; Kondracki, W
2002-01-01
A new definition of a strong curvature singularity is proposed. This definition is motivated by the definitions given by Tipler and Krolak, but is significantly different and more general. All causal geodesics terminating at these new singularities, which we call generalized strong curvature singularities, are classified into three possible types; the classification is based on certain relations between the curvature strength of the singularities and the causal structure in their neighborhood. A cosmic censorship theorem is formulated and proved which shows that only one class of generalized strong curvature singularities, corresponding to a single type of geodesics according to our classification, can be naked. Implications of this result for the cosmic censorship hypothesis are indicated.
Curvature of Indoor Sensor Network: Clustering Coefficient
Directory of Open Access Journals (Sweden)
2009-03-01
Full Text Available We investigate the geometric properties of the communication graph in realistic low-power wireless networks. In particular, we explore the concept of the curvature of a wireless network via the clustering coefficient. Clustering coefficient analysis is a computationally simplified, semilocal approach, which nevertheless captures such a large-scale feature as congestion in the underlying network. The clustering coefficient concept is applied to three cases of indoor sensor networks, under varying thresholds on the link packet reception rate (PRR. A transition from positive curvature (“meshed” network to negative curvature (“core concentric” network is observed by increasing the threshold. Even though this paper deals with network curvature per se, we nevertheless expand on the underlying congestion motivation, propose several new concepts (network inertia and centroid, and finally we argue that greedy routing on a virtual positively curved network achieves load balancing on the physical network.
Holomorphic curvature of complex Finsler submanifolds
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Let M be a complex n-dimensional manifold endowed with a strongly pseudoconvex complex Finsler metric F. Let M be a complex m-dimensional submanifold of M, which is endowed with the induced complex Finsler metric F. Let D be the complex Rund connection associated with (M, F). We prove that (a) the holomorphic curvature of the induced complex linear connection on (M, F) and the holomorphic curvature of the intrinsic complex Rund connection ～* on (M, F) coincide; (b) the holomorphic curvature of ～* does not exceed the holomorphic curvature of D; (c) (M, F) is totally geodesic in (M, F) if and only if a suitable contraction of the second fundamental form B(·, ·) of (M, F) vanishes, i.e., B(χ, ι) = 0. Our proofs are mainly based on the Gauss, Codazzi and Ricci equations for (M, F).
Modular Curvature for Noncommutative Two-Tori
Connes, Alain
2011-01-01
Starting from the description of the conformal geometry of noncommutative 2-tori in the framework of modular spectral triples, we explicitly compute the local curvature functionals determined by the value at zero of the zeta functions affiliated with these spectral triples. We give a closed formula for the Ray-Singer analytic torsion in terms of the Dirichlet quadratic form and the generating function for Bernoulli numbers applied to the modular operator. The gradient of the Ray-Singer analytic torsion is then expressed in terms of these functionals, and yields the analogue of scalar curvature. Computing this gradient in two ways elucidates the meaning of the complicated two variable functions occurring in the formula for the scalar curvature. Moreover, the corresponding evolution equation for the metric produces the appropriate analogue of Ricci curvature. We prove the analogue of the classical result which asserts that in every conformal class the maximum value of the determinant of the Laplacian on metrics...
Cosmological Attractor Models and Higher Curvature Supergravity
Cecotti, Sergio
2014-01-01
We study cosmological $\\alpha$-attractors in superconformal/supergravity models, where $\\alpha$ is related to the geometry of the moduli space. For $\\alpha=1$ attractors \\cite{Kallosh:2013hoa} we present a generalization of the previously known manifestly superconformal higher curvature supergravity model \\cite{Cecotti:1987sa}. The relevant standard 2-derivative supergravity with a minimum of two chiral multiplets is shown to be dual to a 4-derivative higher curvature supergravity, where in general one of the chiral superfields is traded for a curvature superfield. There is a degenerate case when both matter superfields become non-dynamical and there is only a chiral curvature superfield, pure higher derivative supergravity. Generic $\\alpha$-models \\cite{Kallosh:2013yoa} interpolate between the attractor point at $\\alpha=0$ and generic chaotic inflation models at large $\\alpha$, in the limit when the inflaton moduli space becomes flat. They have higher derivative duals with the same number of matter fields as...
Higher Curvature Supergravity, Supersymmetry Breaking and Inflation
Ferrara, Sergio
2014-01-01
In these lectures, after a short introduction to cosmology, we discuss the supergravity embedding of higher curvature models of inflation. The supergravity description of such models is presented for the two different formulations of minimal supergravity.
Curvature Gradient Driving Droplets in Fast Motion
Lv, Cunjing; Yin, Yajun; Tseng, Fan-gang; Zheng, Quanshui
2011-01-01
Earlier works found out spontaneous directional motion of liquid droplets on hydrophilic conical surfaces, however, not hydrophobic case. Here we show that droplets on any surface may take place spontaneous directional motion without considering contact angle property. The driving force is found to be proportional to the curvature gradient of the surface. Fast motion can be lead at surfaces with small curvature radii. The above discovery can help to create more effective transportation technology of droplets, and better understand some observed natural phenomena.
GDP growth and the yield curvature
DEFF Research Database (Denmark)
Møller, Stig Vinther
2014-01-01
This paper examines the forecastability of GDP growth using information from the term structure of yields. In contrast to previous studies, the paper shows that the curvature of the yield curve contributes with much more forecasting power than the slope of yield curve. The yield curvature also...... predicts bond returns, implying a common element to time-variation in expected bond returns and expected GDP growth....
Spherical gravitational curvature boundary-value problem
Šprlák, Michal; Novák, Pavel
2016-08-01
Values of scalar, vector and second-order tensor parameters of the Earth's gravitational field have been collected by various sensors in geodesy and geophysics. Such observables have been widely exploited in different parametrization methods for the gravitational field modelling. Moreover, theoretical aspects of these quantities have extensively been studied and well understood. On the other hand, new sensors for observing gravitational curvatures, i.e., components of the third-order gravitational tensor, are currently under development. As the gravitational curvatures represent new types of observables, their exploitation for modelling of the Earth's gravitational field is a subject of this study. Firstly, the gravitational curvature tensor is decomposed into six parts which are expanded in terms of third-order tensor spherical harmonics. Secondly, gravitational curvature boundary-value problems defined for four combinations of the gravitational curvatures are formulated and solved in spectral and spatial domains. Thirdly, properties of the corresponding sub-integral kernels are investigated. The presented mathematical formulations reveal some important properties of the gravitational curvatures and extend the so-called Meissl scheme, i.e., an important theoretical framework that relates various parameters of the Earth's gravitational field.
Nonadditive Compositional Curvature Energetics of Lipid Bilayers
Sodt, A. J.; Venable, R. M.; Lyman, E.; Pastor, R. W.
2016-09-01
The unique properties of the individual lipids that compose biological membranes together determine the energetics of the surface. The energetics of the surface, in turn, govern the formation of membrane structures and membrane reshaping processes, and thus they will underlie cellular-scale models of viral fusion, vesicle-dependent transport, and lateral organization relevant to signaling. The spontaneous curvature, to the best of our knowledge, is always assumed to be additive. We describe observations from simulations of unexpected nonadditive compositional curvature energetics of two lipids essential to the plasma membrane: sphingomyelin and cholesterol. A model is developed that connects molecular interactions to curvature stress, and which explains the role of local composition. Cholesterol is shown to lower the number of effective Kuhn segments of saturated acyl chains, reducing lateral pressure below the neutral surface of bending and favoring positive curvature. The effect is not observed for unsaturated (flexible) acyl chains. Likewise, hydrogen bonding between sphingomyelin lipids leads to positive curvature, but only at sufficient concentration, below which the lipid prefers negative curvature.
Total mean curvature, scalar curvature, and a variational analog of Brown-York mass
Mantoulidis, Christos
2016-01-01
Let $(\\Omega, g)$ be a compact Riemannian 3-manifold with nonnegative scalar curvature, and with a mean-convex boundary $\\Sigma$ which is topologically a 2-sphere. We demonstrate that the total mean curvature of $\\Sigma$ is bounded from above by a constant depending only on the induced metric on $\\Sigma$. As an application, we define a variational analog of the Brown-York quasi-local mass of $\\Sigma$ in $(\\Omega, g)$ without assuming that $\\Sigma$ has positive Gauss curvature. We also cast this discussion in the light of a natural variational problem on compact 3-manifolds with boundary and nonnegative scalar curvature.
Learning about Spinal Muscular Atrophy
... News Release Fischbeck Group Learning About Spinal Muscular Atrophy What is spinal muscular atrophy? What are the ... for Spinal Muscular Atrophy What is spinal muscular atrophy? Spinal muscular atrophy is a group of inherited ...
Institute of Scientific and Technical Information of China (English)
Gong Ju; Jian Wang; Yazhou Wang; Xianghui Zhao
2014-01-01
Spinal cord injury is a major cause of disability with devastating neurological outcomes and lim-ited therapeutic opportunities, even though there are thousands of publications on spinal cord injury annually. There are two major types of spinal cord injury, transaction of the spinal cord and spinal cord contusion. Both can theoretically be treated, but there is no well documented treatment in human being. As for spinal cord contusion, we have developed an operation with fabulous result.
Acquired lumbar spinal stenosis.
Deasy, JoAnn
2015-04-01
Lumbar spinal stenosis is the most frequent reason for spinal surgery in patients over age 65 years. In this condition, narrowing of the lumbar spinal canal and nerve root canals leads to painful, debilitating compression of spinal nerves and blood vessels. As the population ages, an increasing number of patients will be diagnosed and treated for lumbar spinal stenosis by primary care providers. This article reviews the pathophysiology, diagnosis, and management of lumbar spinal stenosis in adults over age 50 years.
Strong curvature effects in Neumann wave problems
Willatzen, M.; Pors, A.; Gravesen, J.
2012-08-01
Waveguide phenomena play a major role in basic sciences and engineering. The Helmholtz equation is the governing equation for the electric field in electromagnetic wave propagation and the acoustic pressure in the study of pressure dynamics. The Schrödinger equation simplifies to the Helmholtz equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear-in-curvature contribution originates from parity symmetry breaking of eigenstates in circular-sector tori and hence vanishes in a torus with a complete circular cross section. The same strong curvature effect is not present in waveguides subject to Dirichlet boundary conditions where curvature contributions contribute to second-order in the curvature only. We demonstrate this finding by considering wave propagation in a circular-sector torus corresponding to Neumann and Dirichlet boundary conditions, respectively. Results for relative eigenfrequency shifts and modes are determined and compared with three-dimensional finite element method results. Good agreement is found between the present analytical method using a combination of differential geometry with perturbation theory and finite element results for a large range of curvature ratios.
Strong curvature effects in Neumann wave problems
Energy Technology Data Exchange (ETDEWEB)
Willatzen, M.; Pors, A. [Mads Clausen Institute, University of Southern Denmark, Alsion 2, DK-6400 Sonderborg (Denmark); Gravesen, J. [Department of Mathematics, Technical University of Denmark, Matematiktorvet, DK-2800 Kgs. Lyngby (Denmark)
2012-08-15
Waveguide phenomena play a major role in basic sciences and engineering. The Helmholtz equation is the governing equation for the electric field in electromagnetic wave propagation and the acoustic pressure in the study of pressure dynamics. The Schroedinger equation simplifies to the Helmholtz equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear-in-curvature contribution originates from parity symmetry breaking of eigenstates in circular-sector tori and hence vanishes in a torus with a complete circular cross section. The same strong curvature effect is not present in waveguides subject to Dirichlet boundary conditions where curvature contributions contribute to second-order in the curvature only. We demonstrate this finding by considering wave propagation in a circular-sector torus corresponding to Neumann and Dirichlet boundary conditions, respectively. Results for relative eigenfrequency shifts and modes are determined and compared with three-dimensional finite element method results. Good agreement is found between the present analytical method using a combination of differential geometry with perturbation theory and finite element results for a large range of curvature ratios.
Directory of Open Access Journals (Sweden)
Q Wang
Full Text Available Non-ionizing radiation imaging assessment has been advocated for the patients with adolescent idiopathic scoliosis (AIS. As one of the radiation-free methods, ultrasound imaging has gained growing attention in scoliosis assessment over the past decade. The center of laminae (COL method has been proposed to measure the spinal curvature in the coronal plane of ultrasound image. However, the reliability and validity of this ultrasound method have not been validated in the clinical setting.To evaluate the reliability and validity of clinical ultrasound imaging on lateral curvature measurements of AIS with their corresponding magnetic resonance imaging (MRI measurements.Thirty curves (ranged 10.2°-68.2° from sixteen patients with AIS were eligible for this study. The ultrasound scan was performed using a 3-D ultrasound unit within the same morning of MRI examination. Two researchers were involved in data collection of these two examinations. The COL method was used to measure the coronal curvature in ultrasound image, compared with the Cobb method in MRI. The intra- and inter-rater reliability of the COL method was evaluated by intra-class correlation coefficient (ICC. The validity of this method was analyzed by paired Student's t-test, Bland-Altman statistics and Pearson correlation coefficient. The level of significance was set as 0.05.The COL method showed high intra- and inter-rater reliabilities (both with ICC (2, K >0.9, p0.9, p<0.05.The ultrasound imaging could provide a reliable and valid measurement of spinal curvature in the coronal plane using the COL method. Further research is needed to validate the proposed ultrasound measurement in larger clinical trial and to optimize the ultrasound scanning and measuring procedure.
Assessment of scoliosis by direct measurement of the curvature of the spine
Dougherty, Geoff; Johnson, Michael J.
2009-02-01
We present two novel metrics for assessing scoliosis, in which the geometric centers of all the affected vertebrae in an antero-posterior (A-P) radiographic image are used. This is in contradistinction to the existing methods of using selected vertebrae, and determining either their endplates or the intersections of their diagonals, to define a scoliotic angle. Our first metric delivers a scoliotic angle, comparable to the Cobb and Ferguson angles. It measures the sum of the angles between the centers of the affected vertebrae, and avoids the need for an observer to decide on the extent of component curvatures. Our second metric calculates the normalized root-mean-square curvature of the smoothest path comprising piece-wise polynomial splines fitted to the geometric centers of the vertebrae. The smoothest path is useful in modeling the spinal curvature. Our metrics were compared to existing methods using radiographs from a group of twenty subjects with spinal curvatures of varying severity. Their values were strongly correlated with those of the scoliotic angles (r = 0.850 - 0.886), indicating that they are valid surrogates for measuring the severity of scoliosis. Our direct use of positional data removes the vagaries of determining variably shaped endplates, and circumvented the significant interand intra-observer errors of the Cobb and Ferguson methods. Although we applied our metrics to two-dimensional (2- D) data in this paper, they are equally applicable to three-dimensional (3-D) data. We anticipate that they will prove to be the basis for a reliable 3-D measurement and classification system.
Measuring Berry curvature with quantum Monte Carlo
Kolodrubetz, Michael
2014-01-01
The Berry curvature and its descendant, the Berry phase, play an important role in quantum mechanics. They can be used to understand the Aharonov-Bohm effect, define topological Chern numbers, and generally to investigate the geometric properties of a quantum ground state manifold. While Berry curvature has been well-studied in the regimes of few-body physics and non-interacting particles, its use in the regime of strong interactions is hindered by the lack of numerical methods to solve it. In this paper we fill this gap by implementing a quantum Monte Carlo method to solve for the Berry curvature, based on interpreting Berry curvature as a leading correction to imaginary time ramps. We demonstrate our algorithm using the transverse-field Ising model in one and two dimensions, the latter of which is non-integrable. Despite the fact that the Berry curvature gives information about the phase of the wave function, we show that our algorithm has no sign or phase problem for standard sign-problem-free Hamiltonians...
Rossman, Wayne; Umehara, Masaaki; Yamada, Kotaro
2001-01-01
We survey our recent results on classifying complete constant mean curvature 1 (CMC-1) surfaces in hyperbolic 3-space with low total curvature. There are two natural notions of "total curvature"-- one is the total absolute curvature which is the integral over the surface of the absolute value of the Gaussian curvature, and the other is the dual total absolute curvature which is the total absolute curvature of the dual CMC-1 surface. Here we discuss results on both notions (proven in two other...
Dark energy, curvature and cosmic coincidence
Franca, U
2006-01-01
The fact that the energy densities of dark energy and matter are similar currently, known as the coincidence problem, is one of the main unsolved problems of cosmology. We present here a phenomenological model in which a spatial curvature of the universe can lead to a transition in the present epoch from a matter dominated universe to a scaling dark energy dominance in a very natural way. In particular, we show that if the exponential potential of the dark energy field depends linearly on the spatial curvature density of a closed universe, the observed values of some cosmological parameters can be obtained assuming acceptable values for the present spatial curvature of the universe, and without fine tuning in the only parameter of the model. We also comment on possible variations of this model.
On the curvature effect of thin membranes
Wang, Duo; Jiao, Xiangmin; Conley, Rebecca; Glimm, James
2013-01-01
We investigate the curvature effect of a thin, curved elastic interface that separates two subdomains and exerts a pressure due to a curvature effect. This pressure, which we refer to as interface pressure, is similar to the surface tension in fluid mechanics. It is important in some applications, such as the canopy of parachutes, biological membranes of cells, balloons, airbags, etc., as it partially balances a pressure jump between the two sides of an interface. In this paper, we show that the interface pressure is equal to the trace of the matrix product of the curvature tensor and the Cauchy stress tensor in the tangent plane. We derive the theory for interfaces in both 2-D and 3-D, and present numerical discretizations for computing the quality over triangulated surfaces.
Total positive curvature of circular DNA
DEFF Research Database (Denmark)
Bohr, Jakob; Olsen, Kasper Wibeck
2013-01-01
molecules, e.g., plasmids, it is shown to have implications for the total positive curvature integral. For small circular micro-DNAs it follows as a consequence of Fenchel's inequality that there must exist a minimum length for the circular plasmids to be double stranded. It also follows that all circular...... micro-DNAs longer than the minimum length must be concave, a result that is consistent with typical atomic force microscopy images of plasmids. Predictions for the total positive curvature of circular micro-DNAs are given as a function of length, and comparisons with circular DNAs from the literature......The properties of double-stranded DNA and other chiral molecules depend on the local geometry, i.e., on curvature and torsion, yet the paths of closed chain molecules are globally restricted by topology. When both of these characteristics are to be incorporated in the description of circular chain...
Extrinsic and intrinsic curvatures in thermodynamic geometry
Energy Technology Data Exchange (ETDEWEB)
Hosseini Mansoori, Seyed Ali, E-mail: shossein@bu.edu [Department of Physics, Boston University, 590 Commonwealth Ave., Boston, MA 02215 (United States); Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Mirza, Behrouz, E-mail: b.mirza@cc.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Sharifian, Elham, E-mail: e.sharifian@ph.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)
2016-08-10
We investigate the intrinsic and extrinsic curvatures of a certain hypersurface in thermodynamic geometry of a physical system and show that they contain useful thermodynamic information. For an anti-Reissner–Nordström-(A)de Sitter black hole (Phantom), the extrinsic curvature of a constant Q hypersurface has the same sign as the heat capacity around the phase transition points. The intrinsic curvature of the hypersurface can also be divergent at the critical points but has no information about the sign of the heat capacity. Our study explains the consistent relationship holding between the thermodynamic geometry of the KN-AdS black holes and those of the RN (J-zero hypersurface) and Kerr black holes (Q-zero hypersurface) ones [1]. This approach can easily be generalized to an arbitrary thermodynamic system.
Gaussian Curvature on Hyperelliptic Riemann Surfaces
Indian Academy of Sciences (India)
Abel Castorena
2014-05-01
Let be a compact Riemann surface of genus $g ≥ 1, _1,\\ldots,_g$ be a basis of holomorphic 1-forms on and let $H=(h_{ij})^g_{i,j=1}$ be a positive definite Hermitian matrix. It is well known that the metric defined as $ds_H^2=\\sum^g_{i,j=1}h_{ij}_i\\otimes \\overline{_j}$ is a K\\"a hler metric on of non-positive curvature. Let $K_H:C→ \\mathbb{R}$ be the Gaussian curvature of this metric. When is hyperelliptic we show that the hyperelliptic Weierstrass points are non-degenerated critical points of $K_H$ of Morse index +2. In the particular case when is the × identity matrix, we give a criteria to find local minima for $K_H$ and we give examples of hyperelliptic curves where the curvature function $K_H$ is a Morse function.
Integrating curvature: from Umlaufsatz to J^+ invariant
Lanzat, Sergei
2011-01-01
Hopf's Umlaufsatz relates the total curvature of a closed immersed plane curve to its rotation number. While the curvature of a curve changes under local deformations, its integral over a closed curve is invariant under regular homotopies. A natural question is whether one can find some non-trivial densities on a curve, such that the corresponding integrals are (possibly after some corrections) also invariant under regular homotopies of the curve in the class of generic immersions. We construct a family of such densities using indices of points relative to the curve. This family depends on a formal parameter q and may be considered as a quantization of the total curvature. The linear term in the Taylor expansion at q=1 coincides, up to a normalization, with Arnold's J^+ invariant. This leads to an integral expression for J^+.
Anisotropic membrane curvature sensing by antibacterial peptides
Gómez-Llobregat, Jordi; Lindén, Martin
2014-01-01
Many proteins and peptides have an intrinsic capacity to sense and induce membrane curvature, and play crucial roles for organizing and remodeling cell membranes. However, the molecular driving forces behind these processes are not well understood. Here, we describe a new approach to study curvature sensing, by simulating the direction-dependent interactions of single molecules with a buckled lipid bilayer. We analyze three antimicrobial peptides, a class of membrane-associated molecules that specifically target and destabilize bacterial membranes, and find qualitatively different sensing characteristics that would be difficult to resolve with other methods. These findings provide new insights into the microscopic mechanisms of antimicrobial peptides, which might aid the development of new antibiotics. Our approach is generally applicable to a wide range of curvature sensing molecules, and our results provide strong motivation to develop new experimental methods to track position and orientation of membrane p...
Riemann curvature of a boosted spacetime geometry
Battista, Emmanuele; Scudellaro, Paolo; Tramontano, Francesco
2014-01-01
The ultrarelativistic boosting procedure had been applied in the literature to map the metric of Schwarzschild-de Sitter spacetime into a metric describing de Sitter spacetime plus a shock-wave singularity located on a null hypersurface. This paper evaluates the Riemann curvature tensor of the boosted Schwarzschild-de Sitter metric by means of numerical calculations, which make it possible to reach the ultrarelativistic regime gradually by letting the boost velocity approach the speed of light. Thus, for the first time in the literature, the singular limit of curvature through Dirac's delta distribution and its derivatives is numerically evaluated for this class of spacetimes. Eventually, the analysis of the Kteschmann invariant and the geodesic equation show that the spacetime possesses a scalar curvature singularity within a 3-sphere and it is possible to define what we here call boosted horizon, a sort of elastic wall where all particles are surprisingly pushed away, as numerical analysis demonstrates. Thi...
Anomalous Coupling Between Topological Defects and Curvature
Vitelli, Vincenzo; Turner, Ari M.
2004-11-01
We investigate a counterintuitive geometric interaction between defects and curvature in thin layers of superfluids, superconductors, and liquid crystals deposited on curved surfaces. Each defect feels a geometric potential whose functional form is determined only by the shape of the surface, but whose sign and strength depend on the transformation properties of the order parameter. For superfluids and superconductors, the strength of this interaction is proportional to the square of the charge and causes all defects to be repelled (attracted) by regions of positive (negative) Gaussian curvature. For liquid crystals in the one elastic constant approximation, charges between 0 and 4π are attracted by regions of positive curvature while all other charges are repelled.
Cosmic curvature from de Sitter equilibrium cosmology.
Albrecht, Andreas
2011-10-01
I show that the de Sitter equilibrium cosmology generically predicts observable levels of curvature in the Universe today. The predicted value of the curvature, Ω(k), depends only on the ratio of the density of nonrelativistic matter to cosmological constant density ρ(m)(0)/ρ(Λ) and the value of the curvature from the initial bubble that starts the inflation, Ω(k)(B). The result is independent of the scale of inflation, the shape of the potential during inflation, and many other details of the cosmology. Future cosmological measurements of ρ(m)(0)/ρ(Λ) and Ω(k) will open up a window on the very beginning of our Universe and offer an opportunity to support or falsify the de Sitter equilibrium cosmology.
Hypersurfaces of constant curvature in Hyperbolic space
Guan, Bo
2010-01-01
We show that for a very general and natural class of curvature functions, the problem of finding a complete strictly convex hypersurface satisfying f({\\kappa}) = {\\sigma} over (0,1) with a prescribed asymptotic boundary {\\Gamma} at infinity has at least one solution which is a "vertical graph" over the interior (or the exterior) of {\\Gamma}. There is uniqueness for a certain subclass of these curvature functions and as {\\sigma} varies between 0 and 1, these hypersurfaces foliate the two components of the complement of the hyperbolic convex hull of {\\Gamma}.
Fingerprint Feature Extraction Based on Macroscopic Curvature
Institute of Scientific and Technical Information of China (English)
Zhang Xiong; He Gui-ming; Zhang Yun
2003-01-01
In the Automatic Fingerprint Identification System (AFIS), extracting the feature of fingerprint is very important. The local curvature of ridges of fingerprint is irregular, so people have the barrier to effectively extract the fingerprint curve features to describe fingerprint. This article proposes a novel algorithm; it embraces information of few nearby fingerprint ridges to extract a new characteristic which can describe the curvature feature of fingerprint. Experimental results show the algorithm is feasible, and the characteristics extracted by it can clearly show the inner macroscopic curve properties of fingerprint. The result also shows that this kind of characteristic is robust to noise and pollution.
Fingerprint Feature Extraction Based on Macroscopic Curvature
Institute of Scientific and Technical Information of China (English)
Zhang; Xiong; He; Gui-Ming; 等
2003-01-01
In the Automatic Fingerprint Identification System(AFIS), extracting the feature of fingerprint is very important. The local curvature of ridges of fingerprint is irregular, so people have the barrier to effectively extract the fingerprint curve features to describe fingerprint. This article proposes a novel algorithm; it embraces information of few nearby fingerprint ridges to extract a new characterstic which can describe the curvature feature of fingerprint. Experimental results show the algorithm is feasible, and the characteristics extracted by it can clearly show the inner macroscopic curve properties of fingerprint. The result also shows that this kind of characteristic is robust to noise and pollution.
Energy Technology Data Exchange (ETDEWEB)
Izzo, R., E-mail: roberto1766@interfree.it [Neuroradiology Department, A. Cardarelli Hospital, Naples (Italy); Popolizio, T., E-mail: t.popolizio1@gmail.com [Radiology Department, Casa Sollievo della Sofferenza Hospital, San Giovanni Rotondo (Fg) (Italy); D’Aprile, P., E-mail: paoladaprile@yahoo.it [Neuroradiology Department, San Paolo Hospital, Bari (Italy); Muto, M., E-mail: mutomar@tiscali.it [Neuroradiology Department, A. Cardarelli Hospital, Napoli (Italy)
2015-05-15
Highlights: • Purpose of this review is to address the current concepts on the pathophysiology of discogenic, radicular, facet and dysfunctional spinal pain, focusing on the role of the imaging in the diagnostic setting, to potentially address a correct approach also to minimally invasive interventional techniques. • Special attention will be given to the discogenic pain, actually considered as the most frequent cause of chronic low back pain. • The correct distinction between referred pain and radicular pain contributes to give a more correct approach to spinal pain. • The pathogenesis of chronic pain renders this pain a true pathology requiring a specific management. - Abstract: The spinal pain, and expecially the low back pain (LBP), represents the second cause for a medical consultation in primary care setting and a leading cause of disability worldwide [1]. LBP is more often idiopathic. It has as most frequent cause the internal disc disruption (IDD) and is referred to as discogenic pain. IDD refers to annular fissures, disc collapse and mechanical failure, with no significant modification of external disc shape, with or without endplates changes. IDD is described as a separate clinical entity in respect to disc herniation, segmental instability and degenerative disc desease (DDD). The radicular pain has as most frequent causes a disc herniation and a canal stenosis. Both discogenic and radicular pain also have either a mechanical and an inflammatory genesis. For to be richly innervated, facet joints can be a direct source of pain, while for their degenerative changes cause compression of nerve roots in lateral recesses and in the neural foramina. Degenerative instability is a common and often misdiagnosed cause of axial and radicular pain, being also a frequent indication for surgery. Acute pain tends to extinguish along with its cause, but the setting of complex processes of peripheral and central sensitization may influence its evolution in chronic
Timelike Constant Mean Curvature Surfaces with Singularities
DEFF Research Database (Denmark)
Brander, David; Svensson, Martin
2014-01-01
We use integrable systems techniques to study the singularities of timelike non-minimal constant mean curvature (CMC) surfaces in the Lorentz–Minkowski 3-space. The singularities arise at the boundary of the Birkhoff big cell of the loop group involved. We examine the behavior of the surfaces at ...
Timelike Constant Mean Curvature Surfaces with Singularities
DEFF Research Database (Denmark)
Brander, David; Svensson, Martin
2014-01-01
We use integrable systems techniques to study the singularities of timelike non-minimal constant mean curvature (CMC) surfaces in the Lorentz–Minkowski 3-space. The singularities arise at the boundary of the Birkhoff big cell of the loop group involved. We examine the behavior of the surfaces...
Geometrical Constraint on Curvature with BAO experiments
Takada, Masahiro
2015-01-01
The spatial curvature ($K$ or $\\Omega_K$) is one of the most fundamental parameters of isotropic and homogeneous universe and has a close link to the physics of early universe. Combining the radial and angular diameter distances measured via the baryon acoustic oscillation (BAO) experiments allows us to unambiguously constrain the curvature. The method is primarily based on the metric theory, but not much on the theory of structure formation other than the existence of BAO scale and is free of any model of dark energy. In this paper, we estimate a best-achievable accuracy of constraining the curvature with the BAO experiments. We show that an all-sky, cosmic-variance-limited galaxy survey covering the universe up to $z>4$ enables a precise determination of the curvature to an accuracy of $\\sigma(\\Omega_K)\\simeq 10^{-3}$. When we assume a model of dark energy, either the cosmological constraint or the $(w_0,w_a)$-model, it can achieve a precision of $\\sigma(\\Omega_K)\\simeq \\mbox{a few}\\times 10^{-4}$. These fo...
Geodesic curvature driven surface microdomain formation.
Adkins, Melissa R; Zhou, Y C
2017-09-15
Lipid bilayer membranes are not uniform and clusters of lipids in a more ordered state exist within the generally disorder lipid milieu of the membrane. These clusters of ordered lipids microdomains are now referred to as lipid rafts. Recent reports attribute the formation of these microdomains to the geometrical and molecular mechanical mismatch of lipids of different species on the boundary. Here we introduce the geodesic curvature to characterize the geometry of the domain boundary, and develop a geodesic curvature energy model to describe the formation of these microdomains as a result of energy minimization. Our model accepts the intrinsic geodesic curvature of any binary lipid mixture as an input, and will produce microdomains of the given geodesic curvature as demonstrated by three sets of numerical simulations. Our results are in contrast to the surface phase separation predicted by the classical surface Cahn-Hilliard equation, which tends to generate large domains as a result of the minimizing line tension. Our model provides a direct and quantified description of the structure inhomogeneity of lipid bilayer membrane, and can be coupled to the investigations of biological processes on membranes for which such inhomogeneity plays essential roles.
Local surface orientation dominates haptic curvature discrimination
Wijntjes, M.W.A.; Sato, A.; Hayward, V.; Kappers, A.M.L.
2009-01-01
Prior studies have shown that local surface orientation is a dominant source of information for haptic curvature perception in static conditions. We show that this dominance holds for dynamic touch, just as was shown earlier for static touch. Using an apparatus specifically developed for this purpos
Einstein Hermitian Metrics of Positive Sectional Curvature
Koca, Caner
2011-01-01
In this paper we will prove that the only compact 4-manifold M with an Einstein metric of positive sectional curvature which is also hermitian with respect to some complex structure on M, is the complex projective plane CP^2, with its Fubini-Study metric.
Curvature controlled wetting in two dimensions
DEFF Research Database (Denmark)
Gil, Tamir; Mikheev, Lev V.
1995-01-01
. As the radius of the substrate r0→∞, the leading effect of the curvature is adding the Laplace pressure ΠL∝r0-1 to the pressure balance in the film. At temperatures and pressures under which the wetting is complete in planar geometry, Laplace pressure suppresses divergence of the mean thickness of the wetting...
Riemann curvature of a boosted spacetime geometry
Battista, Emmanuele; Esposito, Giampiero; Scudellaro, Paolo; Tramontano, Francesco
2016-10-01
The ultrarelativistic boosting procedure had been applied in the literature to map the metric of Schwarzschild-de Sitter spacetime into a metric describing de Sitter spacetime plus a shock-wave singularity located on a null hypersurface. This paper evaluates the Riemann curvature tensor of the boosted Schwarzschild-de Sitter metric by means of numerical calculations, which make it possible to reach the ultrarelativistic regime gradually by letting the boost velocity approach the speed of light. Thus, for the first time in the literature, the singular limit of curvature, through Dirac’s δ distribution and its derivatives, is numerically evaluated for this class of spacetimes. Moreover, the analysis of the Kretschmann invariant and the geodesic equation shows that the spacetime possesses a “scalar curvature singularity” within a 3-sphere and it is possible to define what we here call “boosted horizon”, a sort of elastic wall where all particles are surprisingly pushed away, as numerical analysis demonstrates. This seems to suggest that such “boosted geometries” are ruled by a sort of “antigravity effect” since all geodesics seem to refuse to enter the “boosted horizon” and are “reflected” by it, even though their initial conditions are aimed at driving the particles toward the “boosted horizon” itself. Eventually, the equivalence with the coordinate shift method is invoked in order to demonstrate that all δ2 terms appearing in the Riemann curvature tensor give vanishing contribution in distributional sense.
Resolving curvature singularities in holomorphic gravity
Mantz, C.L.M.; Prokopec, T.
2011-01-01
We formulate a holomorphic theory of gravity and study how the holomorphy symmetry alters the two most important singular solutions of general relativity: black holes and cosmology. We show that typical observers (freely) falling into a holomorphic black hole do not encounter a curvature singularity
Geodesic curvature driven surface microdomain formation
Adkins, Melissa R.; Zhou, Y. C.
2017-09-01
Lipid bilayer membranes are not uniform and clusters of lipids in a more ordered state exist within the generally disorder lipid milieu of the membrane. These clusters of ordered lipids microdomains are now referred to as lipid rafts. Recent reports attribute the formation of these microdomains to the geometrical and molecular mechanical mismatch of lipids of different species on the boundary. Here we introduce the geodesic curvature to characterize the geometry of the domain boundary, and develop a geodesic curvature energy model to describe the formation of these microdomains as a result of energy minimization. Our model accepts the intrinsic geodesic curvature of any binary lipid mixture as an input, and will produce microdomains of the given geodesic curvature as demonstrated by three sets of numerical simulations. Our results are in contrast to the surface phase separation predicted by the classical surface Cahn-Hilliard equation, which tends to generate large domains as a result of the minimizing line tension. Our model provides a direct and quantified description of the structure inhomogeneity of lipid bilayer membrane, and can be coupled to the investigations of biological processes on membranes for which such inhomogeneity plays essential roles.
Change in corneal curvature induced by surgery
G. van Rij (Gabriel)
1987-01-01
textabstractThe first section deals with the mechanisms by which sutures, incisions and intracorneal contact lenses produce a change in corneal curvature. To clarify the mechanisms by which incisions and sutures produce astigmatism, we made incisions and placed sutures in the corneoscleral limbus of
Level-Slope-Curvature - Fact or Artefact?
R. Lord (Roger); A.A.J. Pelsser (Antoon)
2005-01-01
textabstractThe first three factors resulting from a principal components analysis of term structure data are in the literature typically interpreted as driving the level, slope and curvature of the term structure. Using slight generalisations of theorems from total positivity, we present sufficient
Energy Technology Data Exchange (ETDEWEB)
Tali, E. Turgut E-mail: turguttali@gazi.edu.tr
2004-05-01
Spinal infections can be thought of as a spectrum of disease comprising spondylitis, discitis, spondylodiscitis, pyogenic facet arthropathy, epidural infections, meningitis, polyradiculopathy and myelitis. Radiological evaluations have gained importance in the diagnosis, treatment planning, treatment and treatment monitoring of the spinal infections. Conventional radiographs are usually the initial imaging study. The sensitivity and specificity of the plain radiographs are very low. The sensitivity of CT is higher while it lacks of specificity. Conventional CT has played minor role for the diagnosis of early spondylitis and disc space infection and for follow-up, researches are going on the value of MDCT. MRI is as sensitive, specific and accurate as combined nuclear medicine studies and the method of choice for the spondylitis. Low signal areas of the vertebral body, loss of definition of the end plates and interruption of the cortical continuity, destruction of the cortical margins are typical on T1WI whereas high signal of affected areas of the vertebral body and disc is typical on T2WI. Contrast is mandatory and increases conspicuity, specificity, and observer confidence in the diagnosis and facilitates the treatment planning. Contrast enhancement is the earliest sign and pathognomonic in the acute inflammatory episode and even in the subtle infection then persists to a varying degree for several weeks or months. The outcome of the treatment is influenced by the type of infection and by the degree of neurologic compromise before treatment. There is an increasing move away from surgical intervention towards conservative therapy, percutaneous drainage of abscess or both. It is therefore critical to monitor treatment response, particularly in the immuno-deficient population.
Iatrogenic Spinal Cord Injury in a Trauma Patient with Ankylosing Spondylitis.
Maarouf, Ahmad; McQuown, Colleen M; Frey, Jennifer A; Ahmed, Rami A; Derrick, Lisa
2017-01-01
The recommended practice for over 30 years has been to routinely immobilize patients with unstable cervical spinal injuries using cervical spinal collars. It is shown that patients with Ankylosing spondylitis (AS) are four times more likely to suffer a spinal fracture compared to the general population and have an eleven-fold greater risk of spinal cord injury. Current protocols of spinal immobilization were responsible for secondary neurologic deterioration in some of these patients. To describe an iatrogenic injury resulting from the use of a rigid spinal board and advocate for the use of alternative immobilization methods or no immobilization at all. We present our case here of a 68-year-old male with a history of AS. The patient was ambulatory on scene after a low speed car accident, but immobilized with a rigid backboard by paramedics. He developed back pain and paraplegia suddenly when the backboard was lifted for transport to the hospital. A CT scan revealed an extension fraction of T10 to T11 with involvement of the posterior column. Emergency spinal fusion was performed. Patient died of complications in the hospital. This case shows that spinal immobilization should be avoided in cases of ambulatory patients without a clear indication. Alternative transport methods such as vacuum mattresses should be considered when spinal immobilization is indicated, especially for patients with predispositions to spinal injury, particularly AS, to maintain the natural alignment of the spinal curvature.
The influence of handlebar-hands position on spinal posture in professional cyclists.
Muyor, José M
2015-01-01
Systematic repetition or prolonged posture in specific postures adopted during training could generate modifications on the sagittal spinal curvatures. Spinal alteration in its physiologic curvatures in the sagittal plane has been associated with predisposition to spinal disorders. The objective was to evaluate and compare the changes produced on the sagittal thoracic and lumbar spinal curvatures, and pelvic tilt from standing posture on the floor to upper, middle, lower and aerodynamic handlebars postures adopted on their own road bicycles. A total of twenty-eight male professional cyclists (179.92 ± 5.78 cm; 67.18 ± 5.74 kg) participated in the study. Cyclists had an experience of 17.22 ± 6.16 years in cycling, and spent 6.52 ± 0.51 days per week and 3.78 ± 0.61 hours per day training on their bicycles. Sagittal spinal curvatures (thoracic and lumbar) and pelvic tilt were measured in the standing position on the floor and while sitting on a bicycle with different handlebar-hand positions (high, middle, low and aerodynamic) using a Spinal Mouse system. The thoracic spine showed significantly greater angular values while in a standing posture than on the bicycle in all handlebar-hands postures evaluated. The lumbar curvature changed from lordosis (negative values – anterior convexity) in standing posture to kyphosis (positive values – posterior convexity) in all handlebar-hands positions on the bicycle. The aerodynamic handlebar positions showed the greatest lumbar flexion (lumbar kyphosis) and anterior pelvic tilt. Professional cyclists passively maintain their thoracic spine straighter on the bicycle due to handlebar-hands support than in standing posture. However, the lumbar spine is flexed on the bicycle in all handlebar-hands evaluated. The pelvis is modified to greater anterior pelvic tilt when the handlebar-hands position is farther and lower regarding the saddle of the bicycle.
Methods for Assessing Curvature and Interaction in Mixture Experiments
Energy Technology Data Exchange (ETDEWEB)
Piepel, Gregory F.(BATTELLE (PACIFIC NW LAB)); Hicks, Ruel D.(ASSOC WESTERN UNIVERSITY); Szychowski, Jeffrey M.(ASSOC WESTERN UNIVERSITY); Loeppky, Jason L.(ASSOC WESTERN UNIVERSITY)
2002-05-01
The terms curvature and interaction traditionally are not defined or used in the context of mixture experiments because curvature and interaction effects are partially confounded due to the mixture constrain that the component proportions sum to 1.
Exact and Approximate Quadratures for Curvature Tensor Estimation
Langer, Torsten; Belyaev, Alexander; Seidel, Hans-Peter; Greiner, Günther; Hornegger, Joachim; Niemann, Heinrich; Stamminger, Marc
2005-01-01
Accurate estimations of geometric properties of a surface from its discrete approximation are important for many computer graphics and geometric modeling applications. In this paper, we derive exact quadrature formulae for mean curvature, Gaussian curvature, and the Taubin integral representation of the curvature tensor. The exact quadratures are then used to obtain reliable estimates of the curvature tensor of a smooth surface approximated by a dense triangle me...
Kim, Yoon Hyuk; Dorj, Ariunzaya; Han, Ahreum; Kim, Kyungsoo; Nha, Kyung Wook
2016-07-01
Since the correlation between spinal and lower extremity alignments is high, high tibial osteotomy (HTO) surgery may also affect spinal alignment, where the spinal alignment parameters are the most important parameters for the evaluation of spinal disorders. In this study, the effect of HTO surgery on spinal alignment during gait was investigated by comparing spinal alignment parameters between patients with knee osteoarthritis (OA) and healthy young controls. Eight patients (age, 55.0±5.1years; height, 160.3±7.0cm; weight, 71.3±14.1kg) with a medial compartment knee OA participated in the gait experiment two times approximately one week before and one year after HTO surgery and eight healthy young controls (age, 26.7±1.7years; height, 163.4±6.5cm; weight, 58.4±11.3kg) participated only once. Cervical curvature angle, thoracic curvature angle, lumbar curvature angle, coronal vertical axis, and coronal pelvic tilt in the coronal plane and cervical lordosis, thoracic kyphosis, lumbar lordosis, sagittal vertical axis, and sagittal pelvic tilt in the sagittal plane were estimated using motion analysis system with skin markers. All spinal alignment parameters after HTO surgery were significantly closer to those of healthy young subjects than those before HTO, especially in the coronal plane. These findings suggest that the HTO had a positive effect on spinal alignment, as well as lower extremity alignment, and moreover, reduced the abnormality that may result in spinal problems such as degeneration or pain.
Collineations of the curvature tensor in general relativity
Indian Academy of Sciences (India)
Rishi Kumar Tiwari
2005-07-01
Curvature collineations for the curvature tensor, constructed from a fundamental Bianchi Type-V metric, are studied. We are concerned with a symmetry property of space-time which is called curvature collineation, and we briefly discuss the physical and kinematical properties of the models.
Self-Dual Manifolds with Positive Ricci Curvature
Lebrun, Claude; Nayatani, Shin; Nitta, Takashi
1994-01-01
We prove that the connected sums CP_2 # CP_2 and CP_2 # CP_2 # CP_2 admit self-dual metrics with positive Ricci curvature. Moreover, every self-dual metric of positive scalar curvature on CP_2 # CP_2 is conformal to a metric with positive Ricci curvature.
On a curvature-statistics theorem
Energy Technology Data Exchange (ETDEWEB)
Calixto, M [Departamento de Matematica Aplicada y Estadistica, Universidad Politecnica de Cartagena, Paseo Alfonso XIII 56, 30203 Cartagena (Spain); Aldaya, V [Instituto de Astrofisica de Andalucia, Apartado Postal 3004, 18080 Granada (Spain)], E-mail: Manuel.Calixto@upct.es
2008-08-15
The spin-statistics theorem in quantum field theory relates the spin of a particle to the statistics obeyed by that particle. Here we investigate an interesting correspondence or connection between curvature ({kappa} = {+-}1) and quantum statistics (Fermi-Dirac and Bose-Einstein, respectively). The interrelation between both concepts is established through vacuum coherent configurations of zero modes in quantum field theory on the compact O(3) and noncompact O(2; 1) (spatial) isometry subgroups of de Sitter and Anti de Sitter spaces, respectively. The high frequency limit, is retrieved as a (zero curvature) group contraction to the Newton-Hooke (harmonic oscillator) group. We also make some comments on the physical significance of the vacuum energy density and the cosmological constant problem.
Discrete Curvatures and Discrete Minimal Surfaces
Sun, Xiang
2012-06-01
This thesis presents an overview of some approaches to compute Gaussian and mean curvature on discrete surfaces and discusses discrete minimal surfaces. The variety of applications of differential geometry in visualization and shape design leads to great interest in studying discrete surfaces. With the rich smooth surface theory in hand, one would hope that this elegant theory can still be applied to the discrete counter part. Such a generalization, however, is not always successful. While discrete surfaces have the advantage of being finite dimensional, thus easier to treat, their geometric properties such as curvatures are not well defined in the classical sense. Furthermore, the powerful calculus tool can hardly be applied. The methods in this thesis, including angular defect formula, cotangent formula, parallel meshes, relative geometry etc. are approaches based on offset meshes or generalized offset meshes. As an important application, we discuss discrete minimal surfaces and discrete Koenigs meshes.
Scalar Curvature for the Noncommutative Two Torus
Fathizadeh, Farzad
2011-01-01
We give a local expression for the {\\it scalar curvature} of the noncommutative two torus $ A_{\\theta} = C(\\mathbb{T}_{\\theta}^2)$ equipped with an arbitrary translation invariant complex structure and Weyl factor. This is achieved by evaluating the value of the (analytic continuation of the) {\\it spectral zeta functional} $\\zeta_a(s): = \\text{Trace}(a \\triangle^{-s})$ at $s=0$ as a linear functional in $a \\in C^{\\infty}(\\mathbb{T}_{\\theta}^2)$. A new, purely noncommutative, feature here is the appearance of the {\\it modular automorphism group} from the theory of type III factors and quantum statistical mechanics in the final formula for the curvature. This formula coincides with the formula that was recently obtained independently by Connes and Moscovici in their recent paper.
Space-time curvature and cosmology
Nurgaliev, I. S.; Ponomarev, V. N.
1982-10-01
The possibility is considered of obtaining a steady-state cosmological solution in the framework of the Einstein-Cartan theory. It is found that the Einstein-Cartan equations without the cosmological constant admit a solution in the form of the static de Sitter metric for a specific value of the spin-spin gravitational interaction constant, whose introduction is required by gauge theory. It is shown that the steady-state solution might serve as a model for the pre-Friedmann stage of the expansion of the universe, when the spin-curvature interaction was comparable to the interaction between space-time curvature and energy-momentum. A value of about 10 to the -20th is obtained for the spin-spin interaction constant in the case where the de Sitter stage occurs at quantum densities (10 to the 94th g/cu cm).
Effect of intrinsic curvature on semiflexible polymers
Ghosh, Surya K.; Singh, Kulveer; Sain, Anirban
2009-11-01
Recently many important biopolymers have been found to possess intrinsic curvature. Tubulin protofilaments in animal cells, FtsZ filaments in bacteria and double stranded DNA are examples. We examine how intrinsic curvature influences the conformational statistics of such polymers. We give exact results for the tangent-tangent spatial correlation function C(r)=⟨t̂(s).t̂(s+r)⟩ , both in two and three dimensions. Contrary to expectation, C(r) does not show any oscillatory behavior, rather decays exponentially and the effective persistence length has strong length dependence for short polymers. We also compute the distribution function P(R) of the end to end distance R and show how curved chains can be distinguished from wormlike chains using loop formation probability.
Measuring Intrinsic Curvature of Space with Electromagnetism
Mabin, Mason; Becker, Maria; Batelaan, Herman
2016-10-01
The concept of curved space is not readily observable in everyday life. The educational movie "Sphereland" attempts to illuminate the idea. The main character, a hexagon, has to go to great lengths to prove that her world is in fact curved. We present an experiment that demonstrates a new way to determine if a two-dimensional surface, the 2-sphere, is curved. The behavior of an electric field, placed on a spherical surface, is shown to be related to the intrinsic Gaussian curvature. This approach allows students to gain some understanding of Einstein's theory of general relativity, which relates the curvature of spacetime to the presence of mass and energy. Additionally, an opportunity is provided to investigate the dimensionality of Gauss's law.
Scaling up the curvature of mammalian metabolism
Directory of Open Access Journals (Sweden)
Juan eBueno
2014-10-01
Full Text Available A curvilinear relationship between mammalian metabolic rate and body size on a log-log scale has been adopted in lieu of thelongstanding concept of a 3/4 allometric relationship (Kolokotrones et al. 2010. The central tenet of Metabolic Ecology (ME states that metabolism at the individual level scales-up to drive the ecology of populations, communities and ecosystems. If this tenet is correct, the curvature of metabolism should be perceived in other ecological traits. By analyzing the size scaling allometry of eight different mammalian traits including basal and field metabolic rate, offspring biomass production, ingestion rate, costs of locomotion, life span, population growth rate and population density we show that the curvature affects most ecological rates and
On the curvature of the real amoeba
Passare, Mikael
2011-01-01
For a real smooth algebraic curve $A \\subset (\\mathhbb{C}^*)^2$, the amoeba $\\mathcal{A} \\subset \\mathbb{R}^2$ is the image of $A$ under the map Log : $(x,y) \\mapsto (\\log |x|, \\log | y |)$. We describe an universal bound for the total curvature of the real amoeba $\\mathcal{A}_{\\mathbb{R} A}$ and we prove that this bound is reached if and only if the curve $A$ is a simple Harnack curve in the sense of Mikhalkin.
Curvature Could Give Fish Fins Their Strength
National Research Council Canada - National Science Library
2017-01-01
... maneuverable is by having the ability to generate varying amounts of force on the water when flapping a fin,” said Shreyas Mandre, an assistant professor in Brown’s School of Engineering and a co-author of the research. “We think that fish modulate curvature at the base of the fin to make it stiffer or softer, which alters the force they gene...
Transformation optics, curvature and beyond (Conference Presentation)
McCall, Martin W.
2016-04-01
Although the transformation algorithm is very well established and implemented, some intriguing questions remain unanswered. 1) In what precise mathematical sense is the transformation optics algorithm `exact'? The invariance of Maxwell's equations is well understood, but in what sense does the same principle not apply to acoustics (say)? 2) Even if the fields are transformed in a way that apparently mimic vacuum perfectly, it is easy to construct very simple examples where the impedance of the transformed medium is no longer isotropic and homogeneous. This would seem to imply a fundamental shortcoming in any claim that electromagnetic cloaking has been reduced to technology. 3) Transformations are known to exist that introduce a discrepancy between the Poynting vector and the wave-vector. Does this distinction carry any physical significance? We have worked extensively on understanding a commonality between transformation theories that operates at the level of rays - being interpreted as geodesics of an appropriate manifold. At this level we now understand that the *key* problem underlying all attempts to unify the transformational approach to disparate areas of physics is how to relate the transformation of the base metric (be it Euclidean for spatial transformation optics, or Minkowskian for spacetime transformation optics) to the medium parameters of a given physical domain (e.g. constitutive parameters for electromagnetism, bulk modulus and mass density for acoustics, diffusion constant and number density for diffusion physics). Another misconception we will seek to address is the notion of the relationship between transformation optics and curvature. Many have indicated that transformation optics evinces similarities with Einstein's curvature of spacetime. Here we will show emphatically that transformation optics cannot induce curvature. Inducing curvature in an electromagnetic medium requires the equivalent of a gravitational source. We will propose a scheme
Menger curvature and rectifiability in metric spaces
2012-01-01
We show that for any metric space $X$ the condition \\[ \\int_X\\int_X\\int_X c(z_1,z_2,z_3)^2\\, d\\Hm z_1\\, d\\Hm z_2\\, d\\Hm z_3 < \\infty, \\] where $c(z_1,z_2,z_3)$ is the Menger curvature of the triple $(z_1,z_2,z_3)$, guarantees that $X$ is rectifiable.
Gravitational curvature an introduction to Einstein's theory
Frankel, Theodore
2011-01-01
This classic text and reference monograph applies modern differential geometry to general relativity. A brief mathematical introduction to gravitational curvature, it emphasizes the subject's geometric essence, replacing the often-tedious analytical computations with geometric arguments. Clearly presented and physically motivated derivations express the deflection of light, Schwarzchild's exterior and interior solutions, and the Oppenheimer-Volkoff equations. A perfect choice for advanced students of mathematics, this volume will also appeal to mathematicians interested in physics. It stresses
Curvature of spacetime: A simple student activity
Wood, Monika; Smith, Warren; Jackson, Matthew
2016-12-01
The following is a description of an inexpensive and simple student experiment for measuring the differences between the three types of spacetime topology—Euclidean (flat), Riemann (spherical), and Lobachevskian (saddle) curvatures. It makes use of commonly available tools and materials, and requires only a small amount of construction. The experiment applies to astronomical topics such as gravity, spacetime, general relativity, as well as geometry and mathematics.
Ultrafast Drop Movements Arising from Curvature Gradient
Lv, Cunjing; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Zheng, Quanshui
2011-01-01
We report experimental observation of a kind of fast spontaneous movements of water drops on surfaces of cones with diameters from 0.1 to 1.5 mm. The observed maximum speed (0.22 m/s) under ambient conditions were at least two orders of magnitude higher than that resulting from any known single spontaneous movement mechanism, for example, Marangoni effect due to gradient of surface tension. We trapped even higher spontaneous movement speeds (up to 125 m/s) in virtual experiments for drops on nanoscale cones by using molecular dynamics simulations. The underlying mechanism is found to be universally effective - drops on any surface either hydrophilic or hydrophobic with varying mean curvature are subject to driving forces toward the gradient direction of the mean curvature. The larger the mean curvature of the surface and the lower the contact angle of the liquid are, the stronger the driving force will be. This discovery can lead to more effective techniques for transporting droplets.
Intrinsically disordered proteins drive membrane curvature
Busch, David J.; Houser, Justin R.; Hayden, Carl C.; Sherman, Michael B.; Lafer, Eileen M.; Stachowiak, Jeanne C.
2015-07-01
Assembly of highly curved membrane structures is essential to cellular physiology. The prevailing view has been that proteins with curvature-promoting structural motifs, such as wedge-like amphipathic helices and crescent-shaped BAR domains, are required for bending membranes. Here we report that intrinsically disordered domains of the endocytic adaptor proteins, Epsin1 and AP180 are highly potent drivers of membrane curvature. This result is unexpected since intrinsically disordered domains lack a well-defined three-dimensional structure. However, in vitro measurements of membrane curvature and protein diffusivity demonstrate that the large hydrodynamic radii of these domains generate steric pressure that drives membrane bending. When disordered adaptor domains are expressed as transmembrane cargo in mammalian cells, they are excluded from clathrin-coated pits. We propose that a balance of steric pressure on the two surfaces of the membrane drives this exclusion. These results provide quantitative evidence for the influence of steric pressure on the content and assembly of curved cellular membrane structures.
... drugs The infection often begins in the bone ( osteomyelitis ). The bone infection may cause an epidural abscess ... Boils Cerebral spinal fluid (CSF) collection Epidural abscess Osteomyelitis Pulmonary tuberculosis Sepsis Spinal cord trauma Swelling Review ...
Spinal and epidural anesthesia
... you epidural or spinal anesthesia is called an anesthesiologist. First, the area of your back where the ... Chan VWS. Spinal, epidural, and caudal anesthesia. In: Miller RD, ed. Miller's Anesthesia . 8th ed. Philadelphia, PA: ...
Extradural spinal meningioma: MRI
Energy Technology Data Exchange (ETDEWEB)
Sato, N. [Department of Diagnostic Radiology, Yale University School of Medicine, P. O. Box 20 8042, New Haven, CT 06520-8042 (United States); Sze, G. [Department of Diagnostic Radiology, Yale University School of Medicine, P. O. Box 20 8042, New Haven, CT 06520-8042 (United States)
1997-06-01
We report a case of extradural spinal meningioma with pathologically proven features of malignant transformation. The MRI findings of extradural spinal meningioma and differences in the findings from intradural meningiomas are discussed. (orig.). With 1 fig.
... Habits for TV, Video Games, and the Internet Spinal Muscular Atrophy (SMA) KidsHealth > For Parents > Spinal Muscular Atrophy (SMA) Print ... treatment for the disease's most troubling symptoms. About SMA Normally, healthy nerve cells in the brain called ...
... roots may be cut to relieve pain. In adults, surgery to free (detether) the spinal cord can reduce the size ... is a neurological disorder caused by tissue attachments that limit the movement of the spinal cord ...
Department of Veterans Affairs — The Spinal Cord Dysfunction (SCD) module supports the maintenance of local and national registries for the tracking of patients with spinal cord injury and disease...
National Research Council Canada - National Science Library
D'Amico, Adele; Mercuri, Eugenio; Tiziano, Francesco D; Bertini, Enrico
2011-01-01
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by degeneration of alpha motor neurons in the spinal cord, resulting in progressive proximal muscle weakness and paralysis...
Spinal muscular atrophy (SMA) is a genetic disease that attacks nerve cells, called motor neurons, in the spinal cord. These cells communicate with your voluntary muscles - the ones you can control, like in your ...
Adolescent idiopathic scoliosis and spinal fusion do not substantially impact on postural balance.
Schimmel, J.J.; Groen, B.E.; Weerdesteijn, V.G.M.; Kleuver, M. de
2015-01-01
BACKGROUND: The spinal curvature in patients with Adolescent Idiopathic Scoliosis (AIS) causes an asymmetry of upper body postural alignment, which might affect postural balance. However, the currently available studies on balance in AIS patients are not consistent. Furthermore, it is not known whet
Adolescent idiopathic scoliosis and spinal fusion do not substantially impact on postural balance.
Schimmel, J.J.; Groen, B.E.; Weerdesteijn, V.G.M.; Kleuver, M. de
2015-01-01
BACKGROUND: The spinal curvature in patients with Adolescent Idiopathic Scoliosis (AIS) causes an asymmetry of upper body postural alignment, which might affect postural balance. However, the currently available studies on balance in AIS patients are not consistent. Furthermore, it is not known
Distributed mean curvature on a discrete manifold for Regge calculus
Conboye, Rory; Ray, Shannon
2015-01-01
The integrated mean curvature of a simplicial manifold is well understood in both Regge Calculus and Discrete Differential Geometry. However, a well motivated pointwise definition of curvature requires a careful choice of volume over which to uniformly distribute the local integrated curvature. We show that hybrid cells formed using both the simplicial lattice and its circumcentric dual emerge as a remarkably natural structure for the distribution of this local integrated curvature. These hybrid cells form a complete tessellation of the simplicial manifold, contain a geometric orthonormal basis, and are also shown to give a pointwise mean curvature with a natural interpretation as a fractional rate of change of the normal vector.
Free-streaming radiation in cosmological models with spatial curvature
Wilson, M. L.
1982-01-01
The effects of spatial curvature on radiation anisotropy are examined for the standard Friedmann-Robertson-Walker model universes. The effect of curvature is found to be very important when considering fluctuations with wavelengths comparable to the horizon. It is concluded that the behavior of radiation fluctuations in models with spatial curvature is quite different from that in spatially flat models, and that models with negative curvature are most strikingly different. It is therefore necessary to take the curvature into account in careful studies of the anisotropy of the microwave background.
A curvature theory for discrete surfaces based on mesh parallelity
Bobenko, Alexander Ivanovich
2009-12-18
We consider a general theory of curvatures of discrete surfaces equipped with edgewise parallel Gauss images, and where mean and Gaussian curvatures of faces are derived from the faces\\' areas and mixed areas. Remarkably these notions are capable of unifying notable previously defined classes of surfaces, such as discrete isothermic minimal surfaces and surfaces of constant mean curvature. We discuss various types of natural Gauss images, the existence of principal curvatures, constant curvature surfaces, Christoffel duality, Koenigs nets, contact element nets, s-isothermic nets, and interesting special cases such as discrete Delaunay surfaces derived from elliptic billiards. © 2009 Springer-Verlag.
... damages the vertebrae or other parts of the spine, this can also injure the spinal cord. Other spinal cord problems include Tumors Infections such as meningitis and polio Inflammatory diseases Autoimmune diseases Degenerative diseases such as amyotrophic lateral sclerosis and spinal ...
... Your 1- to 2-Year-Old Spinal Muscular Atrophy (SMA) KidsHealth > For Parents > Spinal Muscular Atrophy (SMA) A A A What's in this article? ... Outlook en español Atrofia muscular espinal Spinal muscular atrophy, or SMA, is an inherited condition that causes ...
... your body and your brain. A spinal cord injury disrupts the signals. Spinal cord injuries usually begin with a blow that fractures or ... bone disks that make up your spine. Most injuries don't cut through your spinal cord. Instead, ...
On the Riemann Curvature Operators in Randers Spaces
Rafie-Rad, M.
2013-05-01
The Riemann curvature in Riemann-Finsler geometry can be regarded as a collection of linear operators on the tangent spaces. The algebraic properties of these operators may be linked to the geometry and the topology of the underlying space. The principal curvatures of a Finsler space (M, F) at a point x are the eigenvalues of the Riemann curvature operator at x. They are real functions κ on the slit tangent manifold TM0. A principal curvature κ(x, y) is said to be isotropic (respectively, quadratic) if κ(x, y)/F(x, y) is a function of x only (respectively, κ(x, y) is quadratic with respect to y). On the other hand, the Randers metrics are the most popular and prominent metrics in pure and applied disciplines. Here, it is proved that if a Randers metric admits an isotropic principal curvature, then F is of isotropic S-curvature. The same result is also established for F to admit a quadratic principal curvature. These results extend Shen's verbal results about Randers metrics of scalar flag curvature K = K(x) as well as those Randers metrics with quadratic Riemann curvature operator. The Riemann curvature Rik may be broken into two operators Rik and Jik. The isotropic and quadratic principal curvature are characterized in terms of the eigenvalues of R and J.
Fiber Fabry-Perot interferometer for curvature sensing
Monteiro, Catarina S.; Ferreira, Marta S.; Silva, Susana O.; Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Frazão, Orlando
2016-07-01
A curvature sensor based on an Fabry-Perot (FP) interferometer was proposed. A capillary silica tube was fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity lengths were developed and subjected to curvature and temperature. The FP sensor with longer cavity showed three distinct operating regions for the curvature measurement. Namely, a linear response was shown for an intermediate curvature radius range, presenting a maximum sensitivity of 68.52 pm/m-1. When subjected to temperature, the sensing head produced a similar response for different curvature radii, with a sensitivity varying from 0.84 pm/°C to 0.89 pm/°C, which resulted in a small cross-sensitivity to temperature when the FP sensor was subjected to curvature. The FP cavity with shorter length presented low sensitivity to curvature.
All unitary cubic curvature gravities in D dimensions
Energy Technology Data Exchange (ETDEWEB)
Sisman, Tahsin Cagri; Guellue, Ibrahim; Tekin, Bayram, E-mail: sisman@metu.edu.tr, E-mail: e075555@metu.edu.tr, E-mail: btekin@metu.edu.tr [Department of Physics, Middle East Technical University, 06531 Ankara (Turkey)
2011-10-07
We construct all the unitary cubic curvature gravity theories built on the contractions of the Riemann tensor in D-dimensional (anti)-de Sitter spacetimes. Our construction is based on finding the equivalent quadratic action for the general cubic curvature theory and imposing ghost and tachyon freedom, which greatly simplifies the highly complicated problem of finding the propagator of cubic curvature theories in constant curvature backgrounds. To carry out the procedure we have also classified all the unitary quadratic models. We use our general results to study the recently found cubic curvature theories using different techniques and the string generated cubic curvature gravity model. We also study the scattering in critical gravity and give its cubic curvature extensions.
Fiber Fabry-Perot interferometer for curvature sensing
Monteiro, Catarina S.; Ferreira, Marta S.; Silva, Susana O.; Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Frazão, Orlando
2016-12-01
A curvature sensor based on an Fabry-Perot (FP) interferometer was proposed. A capillary silica tube was fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity lengths were developed and subjected to curvature and temperature. The FP sensor with longer cavity showed three distinct operating regions for the curvature measurement. Namely, a linear response was shown for an intermediate curvature radius range, presenting a maximum sensitivity of 68.52 pm/m-1. When subjected to temperature, the sensing head produced a similar response for different curvature radii, with a sensitivity varying from 0.84 pm/°C to 0.89 pm/°C, which resulted in a small cross-sensitivity to temperature when the FP sensor was subjected to curvature. The FP cavity with shorter length presented low sensitivity to curvature.
Spinal epidural hematoma; Spinales epidurales Haematom
Energy Technology Data Exchange (ETDEWEB)
Papanagiotou, P. [Universitaetsklinikum des Saarlandes, Klinik fuer Diagnostische und Interventionelle Neuroradiologie, Homburg/Saar (Germany)
2012-05-15
Spinal epidural hematoma is an accumulation of blood in the potential space between the dura and bone. On unenhanced computed tomography epidural hemorrhage appears as a high-density spinal canal mass with variable cord compression. Magnetic resonance imaging is the modality of choice for evaluating spinal epidural hematoma and can demonstrate the extent of the hematoma and degree of cord compression. When treated surgically the outcome depends on the extent of preoperative neurological deficits and on the operative timing interval. (orig.) [German] Das spinale epidurale Haematom ist eine Blutansammlung zwischen Dura und Knochen. Die klinische Praesentation ist aehnlich dem akuten Bandscheibenvorfall, die Symptomatik ist allerdings in der Regel progredient. In der CT stellt sich ein frisches Haematom hyperdens dar. Die MRT ist die Methode der Wahl zur Diagnose spinaler epiduraler Haematome und kann die Ausdehnung sowie auch das Ausmass der Kompression darstellen. Die wichtigste Differenzialdiagnose vom epiduralen Haematom ist das epidurale Empyem. (orig.)
Directory of Open Access Journals (Sweden)
S. V. Vissarionov
2013-01-01
Full Text Available The article presents the historical and contemporary aspects of the state of the question correct scoliosis spine with dorsal and ventral spinal systems. The variants of spinal deformity correction method from Harrington to modern surgical techniques using both hook and metal screw. Detailed technological aspects of surgical interventions for the correction of spinal deformity using a variety of spinal structures. A comparative estimate of the correction of spinal deformity, the impact on the result of the initial mobility of the spine, level metallofiksatsii vertebral-motor segment, as well as the degree of true derotation vertebrae at the top of the curvature in a variety of surgical procedures. Describes the advantages and disadvantages of options for surgery.
Extrinsic curvature induced 2-d gravity
Viswanathan, K S
1993-01-01
Abtract: 2-dimensional fermions are coupled to extrinsic geometry of a conformally immersed surface in ${\\bf R}^3$ through gauge coupling. By integrating out the fermions, we obtain a WZNW action involving extrinsic curvature of the surface. Restricting the resulting effective action to surfaces of $h\\sqrt g=1$, an explicit form of the action invariant under Virasaro symmetry is obtained. This action is a sum of the geometric action for the Virasaro group and the light-cone action of 2-d gravity plus an interaction term. The central charges of the theory in both the left and right sectors are calculated.
Variational formulas of higher order mean curvatures
Xu, Ling
2011-01-01
In this paper, we establish the first variational formula and its Euler-Lagrange equation for the total $2p$-th mean curvature functional $\\mathcal {M}_{2p}$ of a submanifold $M^n$ in a general Riemannian manifold $N^{n+m}$ for $p=0,1,...,[\\frac{n}{2}]$. As an example, we prove that closed complex submanifolds in complex projective spaces are critical points of the functional $\\mathcal {M}_{2p}$, called relatively $2p$-minimal submanifolds, for all $p$. At last, we discuss the relations between relatively $2p$-minimal submanifolds and austere submanifolds in real space forms, as well as a special variational problem.
Scalar Curvature and Intrinsic Flat Convergence
Sormani, Christina
2016-01-01
Herein we present open problems and survey examples and theorems concerning sequences of Riemannian manifolds with uniform lower bounds on scalar curvature and their limit spaces. Examples of Gromov and of Ilmanen which naturally ought to have certain limit spaces do not converge with respect to smooth or Gromov-Hausdorff convergence. Thus we focus here on the notion of Intrinsic Flat convergence, developed jointly with Wenger. This notion has been applied successfully to study sequences that arise in General Relativity. Gromov has suggested it should be applied in other settings as well. We first review intrinsic flat convergence, its properties, and its compactness theorems, before presenting the applications and the open problems.
Curvature and shape determination of growing bacteria
Mukhopadhyay, Ranjan; Wingreen, Ned S.
2009-12-01
Bacterial cells come in a variety of shapes, determined by the stress-bearing cell wall. Though many molecular details about the cell wall are known, our understanding of how a particular shape is produced during cell growth is at its infancy. Experiments on curved Escherichia coli grown in microtraps, and on naturally curved Caulobacter crescentus, reveal different modes of growth: one preserving arc length and the other preserving radius of curvature. We present a simple model for curved cell growth that relates these two growth modes to distinct but related growth rules—“hooplike growth” and “self-similar growth”—and discuss the implications for microscopic growth mechanisms.
Curvature, zero modes and quantum statistics
Energy Technology Data Exchange (ETDEWEB)
Calixto, M [Departamento de Matematica Aplicada y EstadIstica, Universidad Politecnica de Cartagena, Paseo Alfonso XIII 56, 30203 Cartagena (Spain); Aldaya, V [Instituto de AstrofIsica de AndalucIa, Apartado Postal 3004, 18080 Granada (Spain)
2006-08-18
We explore an intriguing connection between the Fermi-Dirac and Bose-Einstein statistics and the thermal baths obtained from a vacuum radiation of coherent states of zero modes in a second quantized (many-particle) theory on the compact O(3) and noncompact O(2, 1) isometry subgroups of the de Sitter and anti-de Sitter spaces, respectively. The high frequency limit is retrieved as a (zero-curvature) group contraction to the Newton-Hooke (harmonic oscillator) group. We also make some comments on the vacuum energy density and the cosmological constant problem. (letter to the editor)
Double curvature mirrors for linear concentrators
Lance, Tamir; Ackler, Harold; Finot, Marc
2012-10-01
Skyline Solar's medium concentration photovoltaic system uses quasi-parabolic mirrors and one axis tracking. Improvements in levelized cost of energy can be achieved by effective management of non-uniformity of the flux line on the panels. To reduce non uniformity of the flux line due to mirror to mirror gaps, Skyline developed a dual curvature mirror that stretches the flux line along the panel. Extensive modeling and experiments have been conducted to analyze the impact of this new design and to optimize the design.
Amplification of curvature perturbations in cyclic cosmology
Zhang, Jun; Liu, Zhi-Guo; Piao, Yun-Song
2010-12-01
We analytically and numerically show that through the cycles with nonsingular bounce, the amplitude of curvature perturbation on a large scale will be amplified and the power spectrum will redden. In some sense, this amplification will eventually destroy the homogeneity of the background, which will lead to the ultimate end of cycles of the global universe. We argue that for the model with increasing cycles, it might be possible that a fissiparous multiverse will emerge after one or several cycles, in which the cycles will continue only at corresponding local regions.
Curvature sensor for ocular wavefront measurement.
Díaz-Doutón, Fernando; Pujol, Jaume; Arjona, Montserrat; Luque, Sergio O
2006-08-01
We describe a new wavefront sensor for ocular aberration determination, based on the curvature sensing principle, which adapts the classical system used in astronomy for the living eye's measurements. The actual experimental setup is presented and designed following a process guided by computer simulations to adjust the design parameters for optimal performance. We present results for artificial and real young eyes, compared with the Hartmann-Shack estimations. Both methods show a similar performance for these cases. This system will allow for the measurement of higher order aberrations than the currently used wavefront sensors in situations in which they are supposed to be significant, such as postsurgery eyes.
Scalar Curvature of a Causal Set
Benincasa, Dionigi M. T.; Dowker, Fay
2010-05-01
A one parameter family of retarded linear operators on scalar fields on causal sets is introduced. When the causal set is well approximated by 4 dimensional Minkowski spacetime, the operators are Lorentz invariant but nonlocal, are parametrized by the scale of the nonlocality, and approximate the continuum scalar D’Alembertian □ when acting on fields that vary slowly on the nonlocality scale. The same operators can be applied to scalar fields on causal sets which are well approximated by curved spacetimes in which case they approximate □-(1)/(2)R where R is the Ricci scalar curvature. This can used to define an approximately local action functional for causal sets.
Directory of Open Access Journals (Sweden)
Hua-Jun Wang
Full Text Available BACKGROUND: Abnormal posture and spinal mobility have been demonstrated to cause functional impairment in the quality of life, especially in the postmenopausal osteoporotic population. Most of the literature studies focus on either thoracic kyphosis or lumbar lordosis, but not on the change of the entire spinal alignment. Very few articles reported the spinal alignment of Chinese people. The purpose of this study was threefold: to classify the spinal curvature based on the classification system defined by Satoh consisting of the entire spine alignment; to identify the change of trunk mobility; and to relate spinal curvature to balance disorder in a Chinese population. METHODOLOGY/PRINCIPAL FINDINGS: 450 osteoporotic volunteers were recruited for this study. Spinal range of motion and global curvature were evaluated noninvasively using the Spinal-Mouse® system and sagittal postural deformities were characterized. RESULTS: We found a new spine postural alignment consisting of an increased thoracic kyphosis and decreased lumbar lordosis which we classified as our modified round back. We did not find any of Satoh's type 5 classification in our population. Type 2 sagittal alignment was the most common spinal deformity (38.44%. In standing, thoracic kyphosis angles in types 2 (58.34° and 3 (58.03° were the largest and lumbar lordosis angles in types 4 (13.95° and 5 (-8.61° were the smallest. The range of flexion (ROF and range of flexion-extension (ROFE of types 2 and 3 were usually greater than types 4 and 5, with type 1 being the largest. CONCLUSIONS/SIGNIFICANCE: The present study classified and compared for the first time the mobility, curvature and balance in a Chinese population based on the entire spine alignment and found types 4 and 5 to present the worst balance and mobility. This study included a new spine postural alignment classification that should be considered in future population studies.
Spacetime curvature induced corrections to Lamb shift
Zhou, Wenting
2012-01-01
The Lamb shift results from the coupling of an atom with vacuum fluctuations of quantum fields, so corrections are expected to arise when the spacetime is curved since the vacuum fluctuations are modified by the presence of spacetime curvature. Here, we calculate the curvature-induced correction to the Lamb shift outside a spherically symmetric object and demonstrate that this correction can be remarkably significant outside a compact massive astrophysical body. For instance, for a neutron star or a stellar mass black hole, the correction is $\\sim$ 25% at a radial distance of $4GM/c^2$, $\\sim$ 16% at $10GM/c^2$ and as large as $\\sim$ 1.6% even at $100GM/c^2$, where $M$ is the mass of the object, $G$ the Newtonian constant, and $c$ the speed of light. In principle, we can look at the spectra from a distant compact supper-massive body to find such corrections. Therefore, our results suggest a possible way of detecting fundamental quantum effects in astronomical observations.
Emergent gravity in spaces of constant curvature
Alvarez, Orlando; Haddad, Matthew
2017-03-01
In physical theories where the energy (action) is localized near a submanifold of a constant curvature space, there is a universal expression for the energy (or the action). We derive a multipole expansion for the energy that has a finite number of terms, and depends on intrinsic geometric invariants of the submanifold and extrinsic invariants of the embedding of the submanifold. This is the second of a pair of articles in which we try to develop a theory of emergent gravity arising from the embedding of a submanifold into an ambient space equipped with a quantum field theory. Our theoretical method requires a generalization of a formula due to by Hermann Weyl. While the first paper discussed the framework in Euclidean (Minkowski) space, here we discuss how this framework generalizes to spaces of constant sectional curvature. We focus primarily on anti de Sitter space. We then discuss how such a theory can give rise to a cosmological constant and Planck mass that are within reasonable bounds of the experimental values.
Multidimensional integrable vacuum cosmology with two curvatures
Gavrilov, V R; Melnikov, V N
1996-01-01
The vacuum cosmological model on the manifold R \\times M_1 \\times \\ldots \\times M_n describing the evolution of n Einstein spaces of non-zero curvatures is considered. For n = 2 the Einstein equations are reduced to the Abel (ordinary differential) equation and solved, when (N_1 = dim M_1, N_2 = dim M_2) = (6,3), (5,5), (8,2). The Kasner-like behaviour of the solutions near the singularity t_s \\to +0 is considered (t_s is synchronous time). The exceptional ("Milne-type") solutions are obtained for arbitrary n. For n=2 these solutions are attractors for other ones, when t_s \\to + \\infty. For dim M = 10, 11 and 3 \\leq n \\leq 5 certain two-parametric families of solutions are obtained from n=2 ones using "curvature-splitting" trick. In the case n=2, (N_1, N_2)= (6,3) a family of non-singular solutions with the topology R^7 \\times M_2 is found.
Suppressing Super-Horizon Curvature Perturbations
Sloth, M S
2006-01-01
We consider the possibility of suppressing superhorizon curvature perturbations after the end of the ordinary slow-roll inflationary stage. This is the opposite of the curvaton limit. We assume that large curvature perturbations are created by the inflaton and investigate to which extent they can be diluted or suppressed by a second very homogeneous field which starts to dominate the energy density of the universe shortly after the end of inflation. The suppression is non-trivial to achieve, but we demonstrate two examples where it works. The mechanism is shown to work if the decay rate of the second field has a certain time-dependence leading to an intrinsic non-adiabatic energy transfer or if the second field is an axion field with a very non-linear periodic potential leading to a non-vanishing intrinsic non-adiabatic pressure perturbation. This opens the possibility of having much larger inflaton perturbations created during inflation than normally allowed by the COBE bound. It relaxes the upper bound on t...
Engineering curvature in graphene ribbons using ultrathin polymer films.
Li, Chunyu; Koslowski, Marisol; Strachan, Alejandro
2014-12-10
We propose a method to induce curvature in graphene nanoribbons in a controlled manner using an ultrathin thermoset polymer in a bimaterial strip setup and test it via molecular dynamics (MD) simulations. Continuum mechanics shows that curvature develops to release the residual stress caused by the chemical and thermal shrinkage of the polymer during processing and that this curvature increases with decreasing film thickness; however, significant deformation is only achieved for ultrathin polymer films. Quite surprisingly, explicit MD simulations of the curing and annealing processes show that the predicted trend not just continues down to film thicknesses of 1-2 nm but that the curvature development is enhanced significantly in such ultrathin films due to surface tension effects. This combination of effects leads to very large curvatures of over 0.14 nm(-1) that can be tuned via film thickness. This provides a new avenue to engineer curvature and, thus, electromagnetic properties of graphene.
Timelike surfaces with zero mean curvature in Minkowski 4-space
Ganchev, Georgi
2011-01-01
On any timelike surface with zero mean curvature in the four-dimensional Minkowski space we introduce special geometric (canonical) parameters and prove that the Gauss curvature and the normal curvature of the surface satisfy a system of two natural partial differential equations. Conversely, any two solutions to this system determine a unique (up to a motion) timelike surface with zero mean curvature so that the given parameters are canonical. We find all timelike surfaces with zero mean curvature in the class of rotational surfaces of Moore type. These examples give rise to a one-parameter family of solutions to the system of natural partial differential equations describing timelike surfaces with zero mean curvature.
Ricci Curvature on Polyhedral Surfaces via Optimal Transportation
Directory of Open Access Journals (Sweden)
Benoît Loisel
2014-03-01
Full Text Available The problem of correctly defining geometric objects, such as the curvature, is a hard one in discrete geometry. In 2009, Ollivier defined a notion of curvature applicable to a wide category of measured metric spaces, in particular to graphs. He named it coarse Ricci curvature because it coincides, up to some given factor, with the classical Ricci curvature, when the space is a smooth manifold. Lin, Lu and Yau and Jost and Liu have used and extended this notion for graphs, giving estimates for the curvature and, hence, the diameter, in terms of the combinatorics. In this paper, we describe a method for computing the coarse Ricci curvature and give sharper results, in the specific, but crucial case of polyhedral surfaces.
Geometric and spectral consequences of curvature bounds on tessellations
Keller, Matthias
2016-01-01
This is a chapter of a forthcoming Lecture Notes in Mathematics "Modern Approaches to Discrete Curvature" edited by L. Najman and P. Romon. It provides a survey on geometric and spectral consequences of curvature bounds. The geometric setting are tessellations of surfaces with finite and vanishing genus. We consider a curvature arising as an angular defect. Several of the results presented here have analogues in Riemannian geometry. In some cases one can go even beyond the Riemannian results ...
Operation principle of a novel curvature plastic fiber optic sensor
Institute of Scientific and Technical Information of China (English)
Fu Yili; Liu Renqiang; Wang Shuguo
2005-01-01
The operation principle of a new type of intensity modulate macrobend curvature optical fiber senor was presented based on surface light scattering theory. Sensor's static and dynamic performance was investigated. This type of sensor can distinguish between positive and negative bending directions. When curvature radius is larger than 50mm, the sensor will keep good linearity. Two-dimensional shape measurement experiments using curvature sensors have been implemented.
Incidence of penile curvature in various forms of hypospadias
2009-01-01
Introduction. Hypospadias is a congenital anomaly of the penis, characterised by ectopically positioned urethral meatus and associated anomalies (cryptorchidism, inguinal hernia, penile curvature). Proximal forms of hypospadias, as severe cases, are particularly accompanied by penile curvature (chordee). Distal types are considered to be mild degrees. Objective. To determine the incidence of congenital curvature within various forms of hypospadias in order to signify preoperative and intraope...
An $\\varepsilon$-regularity Theorem For The Mean Curvature Flow
Han, Xiaoli; Sun, Jun
2011-01-01
In this paper, we will derive a small energy regularity theorem for the mean curvature flow of arbitrary dimension and codimension. It says that if the parabolic integral of $|A|^2$ around a point in space-time is small, then the mean curvature flow cannot develop singularity at this point. As an application, we can prove that the 2-dimensional Hausdorff measure of the singular set of the mean curvature flow from a surface to a Riemannian manifold must be zero.
Sectional and Ricci Curvature for Three-Dimensional Lie Groups
Directory of Open Access Journals (Sweden)
Gerard Thompson
2016-01-01
Full Text Available Formulas for the Riemann and Ricci curvature tensors of an invariant metric on a Lie group are determined. The results are applied to a systematic study of the curvature properties of invariant metrics on three-dimensional Lie groups. In each case the metric is reduced by using the automorphism group of the associated Lie algebra. In particular, the maximum and minimum values of the sectional curvature function are determined.
On the curvature of the present-day universe
Energy Technology Data Exchange (ETDEWEB)
Buchert, Thomas [Universite Lyon 1, Centre de Recherche Astrophysique de Lyon, CNRS UMR 5574, 9 avenue Charles Andre, F-69230 Saint-Genis-Laval (France); Carfora, Mauro [Dipartimento di Fisica Nucleare e Teorica, Universita degli Studi di Pavia, via A. Bassi 6, I-27100 Pavia (Italy)], E-mail: buchert@obs.univ-lyon1.fr, E-mail: mauro.carfora@pv.infn.it
2008-10-07
We discuss the effect of curvature and matter inhomogeneities on the averaged scalar curvature of the present-day universe. Motivated by studies of averaged inhomogeneous cosmologies, we contemplate on the question of whether it is sensible to assume that curvature averages out on some scale of homogeneity, as implied by the standard concordance model of cosmology, or whether the averaged scalar curvature can be largely negative today, as required for an explanation of dark energy from inhomogeneities. We confront both conjectures with a detailed analysis of the kinematical backreaction term and estimate its strength for a multi-scale inhomogeneous matter and curvature distribution. Our main result is a formula for the spatially averaged scalar curvature involving quantities that are all measurable on regional (i.e. up to 100 Mpc) scales. We propose strategies to quantitatively evaluate the formula, and pinpoint the assumptions implied by the conjecture of a small or zero averaged curvature. We reach the conclusion that the standard concordance model needs fine tuning in the sense of an assumed equipartition law for curvature in order to reconcile it with the estimated properties of the averaged physical space, whereas a negative averaged curvature is favoured, independent of the prior on the value of the cosmological constant.
Evolution of the curvature perturbations during warm inflation
Energy Technology Data Exchange (ETDEWEB)
Matsuda, Tomohiro, E-mail: matsuda@sit.ac.jp [Laboratory of Physics, Saitama Institute of Technology, Fusaiji, Okabe-machi, Saitama 369-0293 (Japan)
2009-06-15
This paper considers warm inflation as an interesting application of multi-field inflation. Delta-N formalism is used for the calculation of the evolution of the curvature perturbations during warm inflation. Although the perturbations considered in this paper are decaying after the horizon exit, the corrections to the curvature perturbations sourced by these perturbations can remain and dominate the curvature perturbations at large scales. In addition to the typical evolution of the curvature perturbations, inhomogeneous diffusion rate is considered for warm inflation, which may lead to significant non-Gaussianity of the spectrum.
3D face recognition with asymptotic cones based principal curvatures
Tang, Yinhang
2015-05-01
The classical curvatures of smooth surfaces (Gaussian, mean and principal curvatures) have been widely used in 3D face recognition (FR). However, facial surfaces resulting from 3D sensors are discrete meshes. In this paper, we present a general framework and define three principal curvatures on discrete surfaces for the purpose of 3D FR. These principal curvatures are derived from the construction of asymptotic cones associated to any Borel subset of the discrete surface. They describe the local geometry of the underlying mesh. First two of them correspond to the classical principal curvatures in the smooth case. We isolate the third principal curvature that carries out meaningful geometric shape information. The three principal curvatures in different Borel subsets scales give multi-scale local facial surface descriptors. We combine the proposed principal curvatures with the LNP-based facial descriptor and SRC for recognition. The identification and verification experiments demonstrate the practicability and accuracy of the third principal curvature and the fusion of multi-scale Borel subset descriptors on 3D face from FRGC v2.0.
Evolving extrinsic curvature and the cosmological constant problem
Capistrano, Abraão J. S.; Cabral, Luis A.
2016-10-01
The concept of smooth deformation of Riemannian manifolds associated with the extrinsic curvature is explained and applied to the Friedmann-Lemaître-Robertson-Walker cosmology. We show that such deformation can be derived from the Einstein-Hilbert-like dynamical principle may produce an observable effect in the sense of Noether. As a result, we show how the extrinsic curvature compensates both quantitative and qualitative differences between the cosmological constant Λ and the vacuum energy {ρ }{vac} obtaining the observed upper bound for the cosmological constant problem at electroweak scale. The topological characteristics of the extrinsic curvature are discussed showing that the produced extrinsic scalar curvature is an evolving dynamical quantity.
Evolution of the curvature perturbations during warm inflation
Matsuda, Tomohiro
2009-06-01
This paper considers warm inflation as an interesting application of multi-field inflation. Delta-N formalism is used for the calculation of the evolution of the curvature perturbations during warm inflation. Although the perturbations considered in this paper are decaying after the horizon exit, the corrections to the curvature perturbations sourced by these perturbations can remain and dominate the curvature perturbations at large scales. In addition to the typical evolution of the curvature perturbations, inhomogeneous diffusion rate is considered for warm inflation, which may lead to significant non-Gaussianity of the spectrum.
Curvature optical fiber sensor by using bend enhanced method
Institute of Scientific and Technical Information of China (English)
Jianrong ZHANG; Hairong LIU; Xinkun WU
2009-01-01
Deflection curvature measurement can offer a number of advantages compared with the well-established strain measurement alternative. It is able to measure thin structure; fiber has no resistance with force, which leads to a high precision. There are many kinds of curvature gauges with different operation principles. A low-cost curvature optical fiber sensor using bend enhanced method to improve its curvature measurement sensitivity was devel-oped in recent years. This sensor can distinguish between convex bending and concave bending and has a good linearity in measuring large curvature deformation. Whisper gallery ray theory and Monte Carlo simulation are new achievements by computer experiment. The operation mechanism of this curvature optical fiber sensor is presented based on light scattering theory. The attenuation is ascribed to the transmission mode changing by the curvature of the fiber, which affects the attenuation of the surface scattering. The mathematical model of relationship among light loss, bending curvature, surface roughness, and parameters of the fiber's configuration is also presented. We design different kinds of shapes of sensitive zones; each zone has different parameters. Through detecting their output optical attenuations in different curvatures and fitting the results by exponential decaying functions, the proposed model is demonstrated by experimental results. Also, we compare the experi-mental results with the theoretical analysis and discuss the sensitivity dependence on bending direction.
Management of Spinal Meningiomas.
Ravindra, Vijay M; Schmidt, Meic H
2016-04-01
Spinal meningiomas are the most common spinal tumors encountered in adults, and account for 6.5% of all craniospinal tumors. The treatment for these lesions is primarily surgical, but emerging modalities may include chemotherapy and radiosurgery. In this article, the current management of spinal meningiomas and the body of literature surrounding conventional treatment is reviewed and discussed. Copyright © 2016 Elsevier Inc. All rights reserved.
Yau, Michelle S; Demissie, Serkalem; Zhou, Yanhua; Anderson, Dennis E; Lorbergs, Amanda L; Kiel, Douglas P; Allaire, Brett T; Yang, Laiji; Cupples, L Adrienne; Travison, Thomas G; Bouxsein, Mary L; Karasik, David; Samelson, Elizabeth J
2017-01-01
Hyperkyphosis is a common spinal disorder in older adults, characterized by excessive forward curvature of the thoracic spine and adverse health outcomes. The etiology of hyperkyphosis has not been firmly established, but may be related to changes that occur with aging in the vertebrae, discs, joints, and muscles, which function as a unit to support the spine. Determining the contribution of genetics to thoracic spine curvature and the degree of genetic sharing among co-occurring measures of spine health may provide insight into the etiology of hyperkyphosis. The purpose of our study was to estimate heritability of thoracic spine curvature using T4–T12 kyphosis (Cobb) angle and genetic correlations between thoracic spine curvature and vertebral fracture, intervertebral disc height narrowing, facet joint osteoarthritis (OA), lumbar spine volumetric bone mineral density (vBMD), and paraspinal muscle area and density, which were all assessed from computed tomography (CT) images. Participants included 2063 women and men in the second and third generation offspring of the original cohort of the Framingham Study. Heritability of kyphosis angle, adjusted for age, sex, and weight, was 54% (95% confidence interval [CI], 43% to 64%). We found moderate genetic correlations between kyphosis angle and paraspinal muscle area ( ρ^G, −0.46; 95% CI, −0.67 to −0.26), vertebral fracture ( ρ^G, 0.39; 95% CI, 0.18 to 0.61), vBMD ( ρ^G,−0.23; 95% CI, −0.41 to −0.04), and paraspinal muscle density ( ρ^G,−0.22; 95% CI, −0.48 to 0.03). Genetic correlations between kyphosis angle and disc height narrowing ( ρ^G, 0.17; 95% CI, −0.05 to 0.38) and facet joint OA ( ρ^G, 0.05; 95% CI, −0.15 to 0.24) were low. Thoracic spine curvature may be heritable and share genetic factors with other age-related spine traits including trunk muscle size, vertebral fracture, and bone mineral density. PMID:27455046
MULTIPLE SPINAL CANAL MENINGIOMAS
Directory of Open Access Journals (Sweden)
Nandigama Pratap Kumar
2016-10-01
Full Text Available BACKGROUND Meningiomas of the spinal canal are common tumours with the incidence of 25 percent of all spinal cord tumours. But multiple spinal canal meningiomas are rare in compare to solitary lesions and account for 2 to 3.5% of all spinal meningiomas. Most of the reported cases are both intra cranial and spinal. Exclusive involvement of the spinal canal by multiple meningiomas are very rare. We could find only sixteen cases in the literature to the best of our knowledge. Exclusive multiple spinal canal meningiomas occurring in the first two decades of life are seldom reported in the literature. We are presenting a case of multiple spinal canal meningiomas in a young patient of 17 years, who was earlier operated for single lesion. We analysed the literature, with illustration of our case. MATERIALS AND METHODS In September 2016, we performed a literature search for multiple spinal canal meningiomas involving exclusively the spinal canal with no limitation for language and publication date. The search was conducted through http://pubmed.com, a wellknown worldwide internet medical address. To the best of our knowledge, we could find only sixteen cases of multiple meningiomas exclusively confined to the spinal canal. Exclusive multiple spinal canal meningiomas occurring in the first two decades of life are seldom reported in the literature. We are presenting a case of multiple spinal canal meningiomas in a young patient of 17 years, who was earlier operated for solitary intradural extra medullary spinal canal meningioma at D4-D6 level, again presented with spastic quadriparesis of two years duration and MRI whole spine demonstrated multiple intradural extra medullary lesions, which were excised completely and the histopathological diagnosis was transitional meningioma. RESULTS Patient recovered from his weakness and sensory symptoms gradually and bladder and bowel symptoms improved gradually over a period of two to three weeks. CONCLUSION Multiple
Differential geometry connections, curvature, and characteristic classes
Tu, Loring W
2017-01-01
This text presents a graduate-level introduction to differential geometry for mathematics and physics students. The exposition follows the historical development of the concepts of connection and curvature with the goal of explaining the Chern–Weil theory of characteristic classes on a principal bundle. Along the way we encounter some of the high points in the history of differential geometry, for example, Gauss' Theorema Egregium and the Gauss–Bonnet theorem. Exercises throughout the book test the reader’s understanding of the material and sometimes illustrate extensions of the theory. Initially, the prerequisites for the reader include a passing familiarity with manifolds. After the first chapter, it becomes necessary to understand and manipulate differential forms. A knowledge of de Rham cohomology is required for the last third of the text. Prerequisite material is contained in author's text An Introduction to Manifolds, and can be learned in one semester. For the benefit of the reader and to establ...
Curvature effects in thin magnetic shells.
Gaididei, Yuri; Kravchuk, Volodymyr P; Sheka, Denis D
2014-06-27
A magnetic energy functional is derived for an arbitrary curved thin shell on the assumption that the magnetostatic effects can be reduced to an effective easy-surface anisotropy; it can be used for solving both static and dynamic problems. General static solutions are obtained in the limit of a strong anisotropy of both signs (easy-surface and easy-normal cases). It is shown that the effect of the curvature can be treated as the appearance of an effective magnetic field, which is aligned along the surface normal for the case of easy-surface anisotropy and is tangential to the surface for the case of easy-normal anisotropy. In general, the existence of such a field excludes the solutions that are strictly tangential or strictly normal to the surface. As an example, we consider static equilibrium solutions for a cone surface magnetization.
Coarse-grained Modeling of DNA Curvature
Freeman, Gordon S; Lequieu, Joshua P; Whitmer, Jonathan K; de Pablo, Juan J
2014-01-01
Modeling of DNA-protein interactions is a complex process involving many important time and length scales. This can be facilitated through the use of coarse-grained models which reduce the number of degrees of freedom and allow efficient exploration of binding configurations. It is known that the local structure of DNA can significantly affect its protein-binding properties (i.e. intrinsic curvature in DNA-histone complexes). In a step towards comprehensive DNA-protein modeling, we expand the 3SPN.2 coarse-grained model to include intrinsic shape, and validate the refined model against experimental data including melting temperature, local flexibility, persistence length, and minor groove width profile.
Natural curvature for manifest T-duality
Energy Technology Data Exchange (ETDEWEB)
Poláček, Martin; Siegel, Warren [C. N. Yang Institute for Theoretical PhysicsState University of New York, Stony Brook, NY 11794-3840 (United States)
2014-01-08
We reformulate the manifestly T-dual description of the massless sector of the closed bosonic string, directly from the geometry associated with the (left and right) affine Lie algebra of the coset space Poincaré/Lorentz. This construction initially doubles not only the (spacetime) coordinates for translations but also those for Lorentz transformations (and their “dual”). As a result, the Lorentz connection couples directly to the string (as does the vielbein), rather than being introduced ad hoc to the covariant derivative as previously. This not only reproduces the old definition of T-dual torsion, but automatically gives a general, covariant definition of T-dual curvature (but still with some undetermined connections)
Polarized Curvature Radiation in Pulsar Magnetosphere
Wang, P F; Han, J L
2014-01-01
The propagation of polarized emission in pulsar magnetosphere is investigated in this paper. The polarized waves are generated through curvature radiation from the relativistic particles streaming along curved magnetic field lines and co-rotating with the pulsar magnetosphere. Within the 1/{\\deg} emission cone, the waves can be divided into two natural wave mode components, the ordinary (O) mode and the extraord nary (X) mode, with comparable intensities. Both components propagate separately in magnetosphere, and are aligned within the cone by adiabatic walking. The refraction of O-mode makes the two components separated and incoherent. The detectable emission at a given height and a given rotation phase consists of incoherent X-mode and O-mode components coming from discrete emission regions. For four particle-density models in the form of uniformity, cone, core and patches, we calculate the intensities for each mode numerically within the entire pulsar beam. If the co-rotation of relativistic particles with...
Natural curvature for manifest T-duality
Polacek, Martin
2013-01-01
We reformulate the manifestly T-dual description of the massless sector of the closed bosonic string, directly from the geometry associated with the (left and right) affine Lie algebra of the coset space Poincare/Lorentz. This construction initially doubles not only the (spacetime) coordinates for translations but also those for Lorentz transformations (and their dual). As a result, the Lorentz connection couples directly to the string (as does the vielbein), rather than being introduced ad hoc to the covariant derivative as previously. This not only reproduces the old definition of T-dual torsion, but automatically gives a general, covariant definition of T-dual curvature (but still with some undetermined connections).
Band geometry, Berry curvature, and superfluid weight
Liang, Long; Vanhala, Tuomas I.; Peotta, Sebastiano; Siro, Topi; Harju, Ari; Törmä, Päivi
2017-01-01
We present a theory of the superfluid weight in multiband attractive Hubbard models within the Bardeen-Cooper-Schrieffer (BCS) mean-field framework. We show how to separate the geometric contribution to the superfluid weight from the conventional one, and that the geometric contribution is associated with the interband matrix elements of the current operator. Our theory can be applied to systems with or without time-reversal symmetry. In both cases the geometric superfluid weight can be related to the quantum metric of the corresponding noninteracting systems. This leads to a lower bound on the superfluid weight given by the absolute value of the Berry curvature. We apply our theory to the attractive Kane-Mele-Hubbard and Haldane-Hubbard models, which can be realized in ultracold atom gases. Quantitative comparisons are made to state of the art dynamical mean-field theory and exact diagonalization results.
Apparent surface curvature affects lightness perception.
Knill, D C; Kersten, D
1991-05-16
The human visual system has the remarkable capacity to perceive accurately the lightness, or relative reflectance, of surfaces, even though much of the variation in image luminance may be caused by other scene attributes, such as shape and illumination. Most physiological, and computational models of lightness perception invoke early sensory mechanisms that act independently of, or before, the estimation of other scene attributes. In contrast to the modularity of lightness perception assumed in these models are experiments that show that supposedly 'higher-order' percepts of planar surface attributes, such as orientation, depth and transparency, can influence perceived lightness. Here we show that perceived surface curvature can also affect perceived lightness. The results of the earlier experiments indicate that perceiving luminance edges as changes in surface attributes other than reflectance can influence lightness. These results suggest that the interpretation of smooth variations in luminance can also affect lightness percepts.
A Field Theory with Curvature and Anticurvature
Directory of Open Access Journals (Sweden)
M. I. Wanas
2014-01-01
Full Text Available The present work is an attempt to construct a unified field theory in a space with curvature and anticurvature, the PAP-space. The theory is derived from an action principle and a Lagrangian density using a symmetric linear parameterized connection. Three different methods are used to explore physical contents of the theory obtained. Poisson’s equations for both material and charge distributions are obtained, as special cases, from the field equations of the theory. The theory is a pure geometric one in the sense that material distribution, charge distribution, gravitational and electromagnetic potentials, and other physical quantities are defined in terms of pure geometric objects of the structure used. In the case of pure gravity in free space, the spherical symmetric solution of the field equations gives the Schwarzschild exterior field. The weak equivalence principle is respected only in the case of pure gravity in free space; otherwise it is violated.
Quantum Gravity and Higher Curvature Actions
Bojowald, M; Bojowald, Martin; Skirzewski, Aureliano
2006-01-01
Effective equations are often useful to extract physical information from quantum theories without having to face all technical and conceptual difficulties. One can then describe aspects of the quantum system by equations of classical type, which correct the classical equations by modified coefficients and higher derivative terms. In gravity, for instance, one expects terms with higher powers of curvature. Such higher derivative formulations are discussed here with an emphasis on the role of degrees of freedom and on differences between Lagrangian and Hamiltonian treatments. A general scheme is then provided which allows one to compute effective equations perturbatively in a Hamiltonian formalism. Here, one can expand effective equations around any quantum state and not just a perturbative vacuum. This is particularly useful in situations of quantum gravity or cosmology where perturbations only around vacuum states would be too restrictive. The discussion also demonstrates the number of free parameters expect...
Domain wall brane in squared curvature gravity
Liu, Yu-Xiao; Zhao, Zhen-Hua; Li, Hai-Tao
2011-01-01
We suggest a thick braneworld model in the squared curvature gravity theory. Despite the appearance of higher order derivatives, the localization of gravity and various bulk matter fields is shown to be possible. The existence of the normalizable gravitational zero mode indicates that our four-dimensional gravity is reproduced. In order to localize the chiral fermions on the brane, two types of coupling between the fermions and the brane forming scalar is introduced. The first coupling leads us to a Schr\\"odinger equation with a volcano potential, and the other a P\\"oschl-Teller potential. In both cases, the zero mode exists only for the left-hand fermions. Several massive KK states of the fermions can be trapped on the brane, either as resonant states or as bound states.
The Scalar Curvature of a Causal Set
Benincasa, Dionigi M T
2010-01-01
A one parameter family of retarded linear operators on scalar fields on causal sets is introduced. When the causal set is well-approximated by 4 dimensional Minkowski spacetime, the operators are Lorentz invariant but nonlocal, are parametrised by the scale of the nonlocality and approximate the continuum scalar D'Alembertian, $\\Box$, when acting on fields that vary slowly on the nonlocality scale. The same operators can be applied to scalar fields on causal sets which are well-approximated by curved spacetimes in which case they approximate $\\Box - {{1/2}}R$ where $R$ is the Ricci scalar curvature. This can used to define an approximately local action functional for causal sets.
Cervical spinal meningioma mimicking intramedullary spinal tumor.
Senturk, Senem; Guzel, Aslan; Guzel, Ebru; Bayrak, Aylin Hasanefendioğlu; Sav, Aydin
2009-01-01
Case report. To report a very unusual spinal meningioma, mimicking an intramedullary spinal tumor. Spinal meningiomas, usually associated with signs and symptoms of cord or nerve root compression, are generally encountered in women aged over 40. Radiologic diagnosis is often established by their intradural extramedullary location on magnetic resonance images. A 60-year-old woman had a 6-month history of progressive weakness in her upper extremities, difficulty in walking, and cervical pain radiating through both arms. Neurologic examination revealed motor strength deficiency in all her extremities, with extensor reflexes, clonus, and bilateral hyper-reflexiveness. A sensory deficit was present all over her body. Magnetic resonance images revealed that the spinal cord appeared expanded with an ill-defined, homogeneously contrast-enhanced, lobulated, eccentric mass at the C1-C3 level. The patient was operated with a preliminary diagnosis of an intramedullary tumor. At surgery, the mass was found to be extramedullary, and gross total resection was performed. Histopathological examination revealed a meningioma characterized by the presence of fibrous and meningothelial components. The patient was able to ambulate with a cane, and extremity strength and sensation improved 2 months after surgery. Spinal meningiomas can mimic intramedullary tumors, and should be considered in differential diagnosis of intradural tumors with atypical appearance.
Streamline curvature and bed resistance in shallow water flow
De Vriend, H.J.
1979-01-01
The relationship between streamline curvature and bed resistance in shallow water flow with little side constraint, as derived in 1970 by H.J. Schoemaker, is reconsidered. Schoemaker concluded that the bed resistance causes the curvature of a free streamline to grow exponentially with the distance a
Constant mean curvature surfaces via integrable dynamical system
Konopelchenko, B G
1995-01-01
It is shown that the equation which describes constant mean curvature surface via the generalized Weierstrass-Enneper inducing has Hamiltonian form. Its simplest finite-dimensional reduction has two degrees of freedom, integrable and its trajectories correspond to well-known Delaunay and do Carmo-Dajzcer surfaces (i.e., helicoidal constant mean curvature surfaces).
Effect of Rolling Parameters on Plate Curvature during Snake Rolling
Institute of Scientific and Technical Information of China (English)
FU Yao; XIE Shuisheng; XIONG Baiqing; HUANG Guojie; CHENG Lei
2012-01-01
In order to predict the plate curvature during snake rolling,FE model was constructed based on plane strain assumption.The accuracy of the FE model was verified by the comparison between the plate curvature conducted by FE model and experiment respectively.By using FE model,the effect of offset distance,speed ratio,reduction,roll radius and initial plate thickness on the plate curvature during snake rolling was investigated.The experimental results show that,a proper offsetting distance can efficiently decrease plate curvature,however an excessive offsetting distance will increase plate curvature.A larger speed ratio,reduction will cause a large plate curvature,however a larger roll radius has effect to reduce plate curvature.Plate which undergoes a larger reduction and plate with a larger initial thickness always need a larger offset distance to keep the plate the minimum plate curvature,but for a larger roll radius a smaller offset distance is needed.
Systematic evaluation of a new combinatorial curvature for complex networks
Sreejith, R P; Saucan, Emil; Samal, Areejit
2016-01-01
We have recently introduced Forman's discretization of Ricci curvature to the realm of complex networks. Forman curvature is an edge-based measure whose mathematical definition elegantly encapsulates the weights of nodes and edges in a complex network. In this contribution, we perform a comparative analysis of Forman curvature with other edge-based measures such as edge betweenness, embeddedness and dispersion in diverse model and real networks. We find that Forman curvature in comparison to embeddedness or dispersion is a better indicator of the importance of an edge for the large-scale connectivity of complex networks. Based on the definition of the Forman curvature of edges, there are two natural ways to define the Forman curvature of nodes in a network. In this contribution, we also examine these two possible definitions of Forman curvature of nodes in diverse model and real networks. Based on our empirical analysis, we find that in practice the unnormalized definition of the Forman curvature of nodes wit...
Intramanual and intermanual transfer of the curvature aftereffect
van der Horst, B.J.; Duijndam, M.J.A.; Ketels, M.F.M.; Wilbers, M.T.J.M.; Zwijsen, S.A.; Kappers, A.M.L.
2008-01-01
The existence and transfer of a haptic curvature aftereffect was investigated to obtain a greater insight into neural representation of shape. The haptic curvature aftereffect is the phenomenon whereby a flat surface is judged concave if the preceding touched stimulus was convex and vice versa. Sing
On the total mean curvature of non-rigid surfaces
Alexandrov, Victor
2008-01-01
Using Green's theorem we reduce the variation of the total mean curvature of a smooth surface in the Euclidean 3-space to a line integral of a special vector field and obtain the following well-known theorem as an immediate consequence: the total mean curvature of a closed smooth surface in the Euclidean 3-space is stationary under an infinitesimal flex.
On complete submanifolds with parallel mean curvature in product spaces
Fetcu, Dorel
2011-01-01
We prove a Simons type formula for submanifolds with parallel mean curvature vector field in product spaces of type $M^n(c)\\times\\mathbb{R}$, where $M^n(c)$ is a space form with constant sectional curvature $c$, and then we use it to characterize some of these submanifolds.
A Simons type formula for surfaces with parallel mean curvature
Fetcu, Dorel
2011-01-01
We prove a Simons type equation for non-minimal surfaces with parallel mean curvature vector (pmc surfaces) in $M^n(c)\\times\\mathbb{R}$, where $M^n(c)$ is an $n$-dimensional space form. Then, we use this equation in order to characterize complete non-minimal pmc surfaces with non-negative Gaussian curvature.
How to obtain Transience from Bounded Radial Mean Curvature
DEFF Research Database (Denmark)
Markvorsen, Steen; Palmer, Vicente
2005-01-01
We show that Brownian motion on any unbounded submanifold P in an ambient manifold N with a pole P is transient if the following conditions are satisfied: The p-radial mean curvatures of P are sufficiently small outsidea compact set and the p-radial sectional curvatures of N are sufficiently nega...
The scalar curvature problem on the four dimensional half sphere
Ben-Ayed, M; El-Mehdi, K
2003-01-01
In this paper, we consider the problem of prescribing the scalar curvature under minimal boundary conditions on the standard four dimensional half sphere. We provide an Euler-Hopf type criterion for a given function to be a scalar curvature for some metric conformal to the standard one. Our proof involves the study of critical points at infinity of the associated variational problem.
Generalised functions and distributional curvature of cosmic strings
Clarke, C J S; Wilson, J P
1996-01-01
A new method is presented for assigning distributional curvature, in an invariant manner, to a space-time of low differentiability, using the techniques of Colombeau's `new generalised functions'. The method is applied to show that curvature of a cone is equivalent to a delta function. The same is true under small enough perturbations.
Dynamics and Control of Adaptive Shells with Curvature Transformations
1995-01-01
Adaptive structures with controllable geometries and shapes are rather useful in many engineering applications, such as adaptive wings, variable focus mirrors, adaptive machines, micro-electromechanical systems, etc. Dynamics and feedback control effectiveness of adaptive shells whose curvatures are actively controlled and continuously changed are evaluated. An adaptive piezoelectric laminated cylindrical shell composite with continuous curvature changes is studied, and its natural frequencie...
Spinal arteriography: a primer
Institute of Scientific and Technical Information of China (English)
David A KUMPE
2005-01-01
Spinal arteriography is an esoteric procedure that is seldom performed by peripheral interventionalists. This presentation is intended to outline some of the essential points that the interventionalist performing the procedure should be aware of, especially about spinal dural arteriovenous fistulae (SDAVF).
Glioblastoma with spinal seeding
Energy Technology Data Exchange (ETDEWEB)
Fakhrai, N.; Fazeny-Doerner, B.; Marosi, C. [Clinical Div. of Oncology, Dept. of Medicine I, Univ. of Vienna (Austria); Czech, T. [Dept. of Neurosurgery, Univ. of Vienna (Austria); Diekmann, K. [Dept. of Radiooncology, Univ. of Vienna (Austria); Birner, P.; Hainfellner, J.A. [Clinical Inst. for Neurology, Univ. of Vienna (Austria); Prayer, D. [Dept. of Neuroradiology, Univ. of Vienna (Austria)
2004-07-01
Background: extracranial seeding of glioblastoma multiforme (GBM) is very rare and its development depends on several factors. This case report describes two patients suffering from GBM with spinal seeding. In both cases, the anatomic localization of the primary tumor close to the cerebrospinal fluid (CSF) was the main factor for spinal seeding. Case reports: two patients with GBM and spinal seeding are presented. After diagnosis of spinal seeding, both patients were highly symptomatic from their spinal lesions. Case 1 experienced severe pain requiring opiates, and case 2 had paresis of lower limbs as well as urinary retention/incontinence. Both patients were treated with spinal radiation therapy. Nevertheless, they died 3 months after diagnosis of spinal seeding. Results: in both patients the diagnosis of spinal seeding was made at the time of cranial recurrence. Both tumors showed close contact to the CSF initially. Even though the patients underwent intensive treatment, it was not possible to keep them in a symptom-free state. Conclusion: because of short survival periods, patients deserve optimal pain management and dedicated palliative care. (orig.)
Garg, Ravindra Kumar; Somvanshi, Dilip Singh
2011-01-01
Spinal tuberculosis is a destructive form of tuberculosis. It accounts for approximately half of all cases of musculoskeletal tuberculosis. Spinal tuberculosis is more common in children and young adults. The incidence of spinal tuberculosis is increasing in developed nations. Genetic susceptibility to spinal tuberculosis has recently been demonstrated. Characteristically, there is destruction of the intervertebral disk space and the adjacent vertebral bodies, collapse of the spinal elements, and anterior wedging leading to kyphosis and gibbus formation. The thoracic region of vertebral column is most frequently affected. Formation of a ‘cold’ abscess around the lesion is another characteristic feature. The incidence of multi-level noncontiguous vertebral tuberculosis occurs more frequently than previously recognized. Common clinical manifestations include constitutional symptoms, back pain, spinal tenderness, paraplegia, and spinal deformities. For the diagnosis of spinal tuberculosis magnetic resonance imaging is more sensitive imaging technique than x-ray and more specific than computed tomography. Magnetic resonance imaging frequently demonstrates involvement of the vertebral bodies on either side of the disk, disk destruction, cold abscess, vertebral collapse, and presence of vertebral column deformities. Neuroimaging-guided needle biopsy from the affected site in the center of the vertebral body is the gold standard technique for early histopathological diagnosis. Antituberculous treatment remains the cornerstone of treatment. Surgery may be required in selected cases, e.g. large abscess formation, severe kyphosis, an evolving neurological deficit, or lack of response to medical treatment. With early diagnosis and early treatment, prognosis is generally good. PMID:22118251
DEFF Research Database (Denmark)
Aartun, Ellen; Hartvigsen, Jan; Wedderkopp, Niels
2014-01-01
BACKGROUND: The severity and course of spinal pain is poorly understood in adolescents. The study aimed to determine the prevalence and two-year incidence, as well as the course, frequency, and intensity of pain in the neck, mid back, and low back (spinal pain). METHODS: This study was a school...
Effects of Iris Surface Curvature on Iris Recognition
Energy Technology Data Exchange (ETDEWEB)
Thompson, Joseph T [ORNL; Flynn, Patrick J [ORNL; Bowyer, Kevin W [University of Notre Dame, IN; Santos-Villalobos, Hector J [ORNL
2013-01-01
To focus on objects at various distances, the lens of the eye must change shape to adjust its refractive power. This change in lens shape causes a change in the shape of the iris surface which can be measured by examining the curvature of the iris. This work isolates the variable of iris curvature in the recognition process and shows that differences in iris curvature degrade matching ability. To our knowledge, no other work has examined the effects of varying iris curvature on matching ability. To examine this degradation, we conduct a matching experiment across pairs of images with varying degrees of iris curvature differences. The results show a statistically signi cant degradation in matching ability. Finally, the real world impact of these ndings is discussed
Dynamics and Control of Adaptive Shells with Curvature Transformations
Directory of Open Access Journals (Sweden)
H.S. Tzou
1995-01-01
Full Text Available Adaptive structures with controllable geometries and shapes are rather useful in many engineering applications, such as adaptive wings, variable focus mirrors, adaptive machines, micro-electromechanical systems, etc. Dynamics and feedback control effectiveness of adaptive shells whose curvatures are actively controlled and continuously changed are evaluated. An adaptive piezoelectric laminated cylindrical shell composite with continuous curvature changes is studied, and its natural frequencies and controlled damping ratios are evaluated. The curvature change of the adaptive shell starts from an open shallow shell (30° and ends with a deep cylindrical shell (360°. Dynamic characteristics and control effectiveness (via the proportional velocity feedback of this series of shells are investigated and compared at every 30° curvature change. Analytical solutions suggest that the lower modes are sensitive to curvature changes and the higher modes are relatively insensitive.
Curvature sensor based on a Fabry-Perot interferometer
Monteiro, Catarina; Ferreira, Marta S.; Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Frazão, Orlando
2016-05-01
A curvature sensor based on a Fabry-Perot interferometer is proposed. A capillary tube of silica is fusion spliced between two single mode fibers, producing a Fabry-Perot cavity. The light propagates in air, when passing through the capillary tube. Two different cavities are subjected to curvature and temperature. The cavity with shorter length shows insensitivity to both measurands. The larger cavity shows two operating regions for curvature measurement, where a linear response is shown, with a maximum sensitivity of 18.77pm/m-1 for the high curvature radius range. When subjected to temperature, the sensing head produces a similar response for different curvature radius, with a sensitivity of 0.87pm/°C.
DEFF Research Database (Denmark)
Nielsen, Jens Bo
2016-01-01
interneurons and exert a direct (willful) muscle control with the aid of a context-dependent integration of somatosensory and visual information at cortical level. However, spinal networks also play an important role. Sensory feedback through spinal circuitries is integrated with central motor commands...... the central motor command by opening or closing sensory feedback pathways. In the future, human studies of spinal motor control, in close collaboration with animal studies on the molecular biology of the spinal cord, will continue to document the neural basis for human behavior. Expected final online...... and contributes importantly to the muscle activity underlying voluntary movements. Regulation of spinal interneurons is used to switch between motor states such as locomotion (reciprocal innervation) and stance (coactivation pattern). Cortical regulation of presynaptic inhibition of sensory afferents may focus...
[Spontaneous spinal cord herniation].
Rivas, J J; de la Lama, A; Gonza Lez, P; Ramos, A; Zurdo, M; Alday, R
2004-10-01
Spontaneous spinal cord herniation through a dural defect is an unusual condition. This entity has been probably underestimated before the introduction of MRI. We report a case of a 49-year-old man with a progressive Brown-Sequard syndrome. MRI and CT myelogram showed a ventrally displaced spinal cord at level T6-T7 and expansion of the posterior subarachnoid space. Through a laminectomy, a spinal cord herniation was identified and reduced. The anterior dural defect was repaired with a patch of lyophilized dura. The patient recovered muscle power but there was no improvement of the sensory disturbance. The diagnosis of spontaneous spinal cord herniation must be considered when progressive myelopathy occurs in middle-aged patients, without signs of spinal cord compression and typical radiological findings. Surgical treatment may halt the progressive deficits and even yield improvement in many cases.
International Spinal Cord Injury
DEFF Research Database (Denmark)
Dvorak, M F; Itshayek, E; Fehlings, M G
2015-01-01
the final version. RESULTS: The data set consists of nine variables: (1) Intervention/Procedure Date and start time (2) Non-surgical bed rest and external immobilization, (3) Spinal intervention-closed manipulation and/or reduction of spinal elements, (4) Surgical procedure-approach, (5) Date and time......STUDY DESIGN: Survey of expert opinion, feedback and final consensus. OBJECTIVE: To describe the development and the variables included in the International Spinal Cord Injury (SCI) Spinal Interventions and Surgical Procedures Basic Data set. SETTING: International working group. METHODS...... of the completion of the intervention or surgical closure; (6) Surgical procedure-open reduction, (7) Surgical procedure-direct decompression of neural elements, and (8 and 9) Surgical procedure-stabilization and fusion (spinal segment number and level). All variables are coded using numbers or characters. Each...
On the Signal-Image Intensity-Curvature Content
Directory of Open Access Journals (Sweden)
Carlo Ciulla
2013-04-01
Full Text Available The biomedical engineering problem addressed in this work is the one of finding a novel signal-image content measure called intensity-curvature functional making use of all of the second order derivatives of the model function fitted to the data. Given a signal-image made of a sequel of discrete samples and given a model function which embeds the property of second order differentiability, it is possible to quantify the content of the signal-image through a novel approach based on both of the intensity and of the total curvature of the signal-image. The signal-image is fitted with the model function. The total curvature can be calculated through the sum of all of the second order derivatives of the Hessian of the model function fitted to the data. The intensity-curvature functional is defined as the ratio between: (i the integral of the multiplication between the value of the signal modeled through an interpolation function and the total curvature of the signal-image; both of them at the temporal-spatial location of its sampling (the grid nodes and, (ii the integral of the value of the multiplication between the signal modeled through an interpolation function and the total curvature of the signal-image; both of them at any given temporal-spatial location of its re-sampling (intra-pixel location. This manuscript shows both of the formulae and the qualitative results of: the intensity-curvature functional and the intensity-curvature measures which are conceptually linked to the intensity-curvature functional. The formulations here presented make the engineering innovation. The intensity-curvature functional depends on both of the model function fitting the signal-image and the magnitude of re-sampling employed to calculate the second order derivatives of the Hessian of the model function.
Haptic perception of object curvature in Parkinson's disease.
Directory of Open Access Journals (Sweden)
Jürgen Konczak
Full Text Available BACKGROUND: The haptic perception of the curvature of an object is essential for adequate object manipulation and critical for our guidance of actions. This study investigated how the ability to perceive the curvature of an object is altered by Parkinson's disease (PD. METHODOLOGY/PRINCIPAL FINDINGS: Eight healthy subjects and 11 patients with mild to moderate PD had to judge, without vision, the curvature of a virtual "box" created by a robotic manipulandum. Their hands were either moved passively along a defined curved path or they actively explored the curved curvature of a virtual wall. The curvature was either concave or convex (bulging to the left or right and was judged in two locations of the hand workspace--a left workspace location, where the curved hand path was associated with curved shoulder and elbow joint paths, and a right workspace location in which these joint paths were nearly linear. After exploring the curvature of the virtual object, subjects had to judge whether the curvature was concave or convex. Based on these data, thresholds for curvature sensitivity were established. The main findings of the study are: First, 9 out 11 PD patients (82% showed elevated thresholds for detecting convex curvatures in at least one test condition. The respective median threshold for the PD group was increased by 343% when compared to the control group. Second, when distal hand paths became less associated with proximal joint paths (right workspace, haptic acuity was reduced substantially in both groups. Third, sensitivity to hand trajectory curvature was not improved during active exploration in either group. CONCLUSION/SIGNIFICANCE: Our data demonstrate that PD is associated with a decreased acuity of the haptic sense, which may occur already at an early stage of the disease.
The geometric curvature of the spine of runners during maximal incremental effort test.
Campos, Mário Hebling; de Paula, Marcelo Costa; Deprá, Pedro Paulo; Brenzikofer, René
2015-04-13
This study sought to analyse the behaviour of the average spinal posture using a novel investigative procedure in a maximal incremental effort test performed on a treadmill. Spine motion was collected via stereo-photogrammetric analysis in thirteen amateur athletes. At each time percentage of the gait cycle, the reconstructed spine points were projected onto the sagittal and frontal planes of the trunk. On each plane, a polynomial was fitted to the data, and the two-dimensional geometric curvature along the longitudinal axis of the trunk was calculated to quantify the geometric shape of the spine. The average posture presented at the gait cycle defined the spine Neutral Curve. This method enabled the lateral deviations, lordosis, and kyphosis of the spine to be quantified noninvasively and in detail. The similarity between each two volunteers was a maximum of 19% on the sagittal plane and 13% on the frontal (ppostural signature. The data showed the descriptive capability of a new method to analyse spinal postures during locomotion; however, additional studies, and with larger sample sizes, are necessary for extracting more general information from this novel methodology. Copyright © 2015 Elsevier Ltd. All rights reserved.
Accelerated Observers, Thermal Entropy, and Spacetime Curvature
Kothawala, Dawood
2016-01-01
Assuming that an accelerated observer with four-velocity ${\\bf u}_{\\rm R}$ in a curved spacetime attributes the standard Bekenstein-Hawking entropy and Unruh temperature to his "local Rindler horizon", we show that the $\\rm \\it change$ in horizon area under parametric displacements of the horizon has a very specific thermodynamic structure. Specifically, it entails information about the time-time component of the Einstein tensor: $\\bf G({\\bf u}_{\\rm R}, {\\bf u}_{\\rm R})$. Demanding that the result holds for all accelerated observers, this actually becomes a statement about the full Einstein tensor, $\\rm \\bf G$. We also present some perspectives on the free fall with four-velocity ${\\bf u}_{\\rm ff}$ across the horizon that leads to such a loss of entropy for an accelerated observer. Motivated by results for some simple quantum systems at finite temperature $T$, we conjecture that at high temperatures, there exists a universal, system-independent curvature correction to partition function and thermal entropy of...
Berry curvature and various thermal Hall effects
Zhang, Lifa
2016-10-01
Applying the approach of semiclassical wave packet dynamics, we study various thermal Hall effects where carriers can be electron, phonon, magnon, etc. A general formula of thermal Hall conductivity is obtained to provide an essential physics for various thermal Hall effects, where the Berry phase effect manifests naturally. All the formulas of electron thermal Hall effect, phonon Hall effect, and magnon Hall effect can be directly reproduced from the general formula. It is also found that the Strěda formula can not be directly applied to the thermal Hall effects, where only the edge magnetization contributes to the Hall effects. Furthermore, we obtain a combined formula for anomalous Hall conductivity, thermal Hall electronic conductivity and thermal Hall conductivity for electron systems, where the Berry curvature is weighted by a different function. Finally, we discuss particle magnetization and its relation to angular momentum of the carrier, change of which could induce a mechanical rotation; and possible experiments for thermal Hall effect associated with a mechanical rotation are also proposed.
Characterizing repulsive gravity with curvature eigenvalues
Luongo, Orlando; Quevedo, Hernando
2014-10-01
Repulsive gravity has been investigated in several scenarios near compact objects by using different intuitive approaches. Here, we propose an invariant method to characterize regions of repulsive gravity, associated to black holes and naked singularities. Our method is based upon the behavior of the curvature tensor eigenvalues, and leads to an invariant definition of a repulsion radius. The repulsion radius determines a physical region, which can be interpreted as a repulsion sphere, where the effects due to repulsive gravity naturally arise. Further, we show that the use of effective masses to characterize repulsion regions can lead to coordinate-dependent results whereas, in our approach, repulsion emerges as a consequence of the spacetime geometry in a completely invariant way. Our definition is tested in the spacetime of an electrically charged Kerr naked singularity and in all its limiting cases. We show that a positive mass can generate repulsive gravity if it is equipped with an electric charge or an angular momentum. We obtain reasonable results for the spacetime regions contained inside the repulsion sphere whose size and shape depend on the value of the mass, charge and angular momentum. Consequently, we define repulsive gravity as a classical relativistic effect by using the geometry of spacetime only.
Programming curvature using origami tessellations.
Dudte, Levi H; Vouga, Etienne; Tachi, Tomohiro; Mahadevan, L
2016-05-01
Origami describes rules for creating folded structures from patterns on a flat sheet, but does not prescribe how patterns can be designed to fit target shapes. Here, starting from the simplest periodic origami pattern that yields one-degree-of-freedom collapsible structures-we show that scale-independent elementary geometric constructions and constrained optimization algorithms can be used to determine spatially modulated patterns that yield approximations to given surfaces of constant or varying curvature. Paper models confirm the feasibility of our calculations. We also assess the difficulty of realizing these geometric structures by quantifying the energetic barrier that separates the metastable flat and folded states. Moreover, we characterize the trade-off between the accuracy to which the pattern conforms to the target surface, and the effort associated with creating finer folds. Our approach enables the tailoring of origami patterns to drape complex surfaces independent of absolute scale, as well as the quantification of the energetic and material cost of doing so.
Cosmic acceleration from matter-curvature coupling
Zaregonbadi, Raziyeh; Farhoudi, Mehrdad
2016-10-01
We consider f( {R,T} ) modified theory of gravity in which, in general, the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor. We indicate that in this type of the theory, the coupling energy-momentum tensor is not conserved. However, we mainly focus on a particular model that matter is minimally coupled to the geometry in the metric formalism and wherein, its coupling energy-momentum tensor is also conserved. We obtain the corresponding Raychaudhuri dynamical equation that presents the evolution of the kinematic quantities. Then for the chosen model, we derive the behavior of the deceleration parameter, and show that the coupling term can lead to an acceleration phase after the matter dominated phase. On the other hand, the curvature of the universe corresponds with the deviation from parallelism in the geodesic motion. Thus, we also scrutinize the motion of the free test particles on their geodesics, and derive the geodesic deviation equation in this modified theory to study the accelerating universe within the spatially flat FLRW background. Actually, this equation gives the relative accelerations of adjacent particles as a measurable physical quantity, and provides an elegant tool to investigate the timelike and the null structures of spacetime geometries. Then, through the null deviation vector, we find the observer area-distance as a function of the redshift for the chosen model, and compare the results with the corresponding results obtained in the literature.
National Oceanic and Atmospheric Administration, Department of Commerce — Profile curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Profile curvature describes the rate...
National Oceanic and Atmospheric Administration, Department of Commerce — Curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Curvature describes the rate of change of...
National Oceanic and Atmospheric Administration, Department of Commerce — Plan curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Plan curvature describes the rate of...
Directory of Open Access Journals (Sweden)
Nicolás Siderakis
2012-06-01
Full Text Available OBJETIVO: Determinar el comportamiento del segmento lumbar, no artrodesado, en el plano coronal luego de fusiones torácicas selectivas en pacientes con escoliosis idiopática del adolescente con curvas Lenke 1. MÉTODOS: Se evaluaron 21 pacientes con un seguimiento promedio de 29,71 meses (rango: 24-60 meses mediante análisis clínico y radiográfico retrospectivos de pacientes que presentaron escoliosis idiopáticas del adolescente, con curvas Lenke tipo 1 (ABC. RESULTADOS: En todos los pacientes, en los que se produjo un desequilibrio en el plano coronal, se constató la progresión del valor angular de la curva lumbar no artrodesada al final del seguimiento. CONCLUSIÓN: La curva lumbar no artrodesada progresó al final del seguimiento, en todos los pacientes con desequilibrio confirmado en el plano coronal (3/21.OBJETIVO: Determinar o comportamento do segmento lombar sem artrodese no plano coronal, após fusões torácicas seletivas na escoliose idiopática do adolescente com curvaturas de Lenke 1. MÉTODOS: Foram avaliados 21 pacientes com acompanhamento médio de 29,71 meses (faixa: 24 a 60 meses, por meio de análise clínica e radiográfica retrospectiva de pacientes que apresentaram escoliose idiopática do adolescente com curvaturas de Lenke tipo 1 (ABC. RESULTADOS: Constatou-se aumento do ângulo da curva lombar sem artrodese no final do acompanhamento em todos os pacientes que apresentaram desequilíbrio no plano coronal. CONCLUSÃO: O total dos pacientes nos quais se confirmou desequilíbrio no plano coronal (3/21 apresentaram progressão da curva lombar sem artrodese no final do acompanhamento.OBJECTIVE: To determine the outcome of lumbar segment without arthrodesis in the coronal plane, after selective thoracic fusions for with curvature of Lenke type 1 adolescent idiopathic scoliosis with curvature of Lenke type 1. METHODS: Twenty one patients were evaluated, with a mean follow-up of 29.71 months (range: 24-60 months with
3D curvature of muscle fascicles in triceps surae.
Rana, Manku; Hamarneh, Ghassan; Wakeling, James M
2014-12-01
Muscle fascicles curve along their length, with the curvatures occurring around regions of high intramuscular pressure, and are necessary for mechanical stability. Fascicles are typically considered to lie in fascicle planes that are the planes visualized during dissection or two-dimensional (2D) ultrasound scans. However, it has previously been predicted that fascicles must curve in three-dimensional (3D) and thus the fascicle planes may actually exist as 3D sheets. 3D fascicle curvatures have not been explored in human musculature. Furthermore, if the fascicles do not lie in 2D planes, then this has implications for architectural measures that are derived from 2D ultrasound scans. The purpose of this study was to quantify the 3D curvatures of the muscle fascicles and fascicle sheets within the triceps surae muscles and to test whether these curvatures varied among different contraction levels, muscle length, and regions within the muscle. Six male subjects were tested for three torque levels (0, 30, and 60% maximal voluntary contraction) and four ankle angles (-15, 0, 15, and 30° plantar flexion), and fascicles were imaged using 3D ultrasound techniques. The fascicle curvatures significantly increased at higher ankle torques and shorter muscle lengths. The fascicle sheet curvatures were of similar magnitude to the fascicle curvatures but did not vary between contractions. Fascicle curvatures were regionalized within each muscle with the curvature facing the deeper aponeuroses, and this indicates a greater intramuscular pressure in the deeper layers of muscles. Muscle architectural measures may be in error when using 2D images for complex geometries such as the soleus.
Influence of Coanda surface curvature on performance of bladeless fan
Li, Guoqi; Hu, Yongjun; Jin, Yingzi; Setoguchi, Toshiaki; Kim, Heuy Dong
2014-10-01
The unique Coanda surface has a great influence on the performance of bladeless fan. However, there is few studies to explain the relationship between the performance and Coanda surface curvature at present. In order to gain a qualitative understanding of effect of the curvature on the performance of bladeless fan, numerical studies are performed in this paper. Firstly, three-dimensional numerical simulation is done by Fluent software. For the purpose to obtain detailed information of the flow field around the Coanda surface, two-dimensional numerical simulation is also conducted. Five types of Coanda surfaces with different curvature are designed, and the flow behaviour and the performance of them are analyzed and compared with those of the prototype. The analysis indicates that the curvature of Coanda surface is strongly related to blowing performance, It is found that there is an optimal curvature of Coanda surfaces among the studied models. Simulation result shows that there is a special low pressure region. With increasing curvature in Y direction, several low pressure regions gradually enlarged, then begin to merge slowly, and finally form a large area of low pressure. From the analyses of streamlines and velocity angle, it is found that the magnitude of the curvature affects the flow direction and reasonable curvature can induce fluid flow close to the wall. Thus, it leads to that the curvature of the streamlines is consistent with that of Coanda surface. Meanwhile, it also causes the fluid movement towards the most suitable direction. This study will provide useful information to performance improvements of bladeless fans.
Spacetime Curvature in terms of Scalar Field Propagators
Saravani, Mehdi; Kempf, Achim
2015-01-01
We show how quantum fields can be used to measure the curvature of spacetime. In particular, we find that knowledge of the imprint that spacetime curvature leaves in the correlators of quantum fields suffices, in principle, to reconstruct the metric. We then consider the possibility that the quantum fields obey a natural ultraviolet cutoff, for example, at the Planck scale. We investigate how such a cutoff limits the spatial resolution with which curvature can be deduced from the properties of quantum fields. We find that the metric deduced from the quantum correlator exhibits a peculiar scaling behavior as the scale of the natural UV cutoff is approached.
Numerical studies of transverse curvature effects on transonic flow stability
Macaraeg, M. G.; Daudpota, Q. I.
1992-01-01
A numerical study of transverse curvature effects on compressible flow temporal stability for transonic to low supersonic Mach numbers is presented for axisymmetric modes. The mean flows studied include a similar boundary-layer profile and a nonsimilar axisymmetric boundary-layer solution. The effect of neglecting curvature in the mean flow produces only small quantitative changes in the disturbance growth rate. For transonic Mach numbers (1-1.4) and aerodynamically relevant Reynolds numbers (5000-10,000 based on displacement thickness), the maximum growth rate is found to increase with curvature - the maximum occurring at a nondimensional radius (based on displacement thickness) between 30 and 100.
3-manifolds with(out) metrics of nonpositive curvature
Leeb, B
1994-01-01
In the context of Thurstons geometrisation program we address the question which compact aspherical 3-manifolds admit Riemannian metrics of nonpositive curvature. We show that non-geometric Haken manifolds generically, but not always, admit such metrics. More precisely, we prove that a Haken manifold with, possibly empty, boundary of zero Euler characteristic admits metrics of nonpositive curvature if the boundary is non-empty or if at least one atoroidal component occurs in its canonical topological decomposition. Our arguments are based on Thurstons Hyperbolisation Theorem. We give examples of closed graph-manifolds with linear gluing graph and arbitrarily many Seifert components which do not admit metrics of nonpositive curvature.
Geometry-specific scaling of detonation parameters from front curvature
Energy Technology Data Exchange (ETDEWEB)
Jackson, Scott I [Los Alamos National Laboratory; Short, Mark [Los Alamos National Laboratory
2011-01-20
It has previously been asserted that classical detonation curvature theory predicts that the critical diameter and the diameter-effect curve of a cylindrical high-explosive charge should scale with twice the thickness of an analogous two-dimensional explosive slab. The varied agreement of experimental results with this expectation have led some to question the ability of curvature-based concepts to predict detonation propagation in non-ideal explosives. This study addresses such claims by showing that the expected scaling relationship (hereafter referred to d = 2w) is not consistent with curvature-based Detonation Shock Dynamics (DSD) theory.
On Hypersurfaces with two Distinct Principal Curvatures in Space Forms
Indian Academy of Sciences (India)
Bing Ye Wu
2011-11-01
We investigate the immersed hypersurfaces in space forms $\\mathbb{N}^{n+1}(c),n≥ 4$ with two distinct non-simple principal curvatures without the assumption that the (high order) mean curvature is constant. We prove that any immersed hypersurface in space forms with two distinct non-simple principal curvatures is locally conformal to the Riemannian product of two constant curved manifolds. We also obtain some characterizations for the Clifford hypersurfaces in terms of the trace free part of the second fundamental form.
Motion on constant curvature spaces and quantization using Noether symmetries.
Bracken, Paul
2014-12-01
A general approach is presented for quantizing a metric nonlinear system on a manifold of constant curvature. It makes use of a curvature dependent procedure which relies on determining Noether symmetries from the metric. The curvature of the space functions as a constant parameter. For a specific metric which defines the manifold, Lie differentiation of the metric gives these symmetries. A metric is used such that the resulting Schrödinger equation can be solved in terms of hypergeometric functions. This permits the investigation of both the energy spectrum and wave functions exactly for this system.
Effect of membrane curvature on lateral distribution of membrane proteins
DEFF Research Database (Denmark)
Bendix, Pól Martin
2015-01-01
Several membrane proteins exhibit interesting shapes that increases their preference for certain membrane curvatures. Both peripheral and transmembrane proteins are tested with respect to their affinity for a spectrum of high membrane curvatures. We generate high membrane curvatures by pulling...... membrane tubes out of Giant Unilamellar lipid Vesicles (GUVs). The tube diameter can be tuned by aspirating the GUV into a micropipette for controlling the membrane tension. By using fluorescently labled proteins we have shown that sorting of proteins like e.g. FBAR onto tubes is significantly increased...
Surfaces with parallel mean curvature vector in complex space forms
Fetcu, Dorel
2010-01-01
We consider a quadratic form defined on the surfaces with parallel mean curvature vector of an any dimensional complex space form and prove that its $(2,0)$-part is holomorphic. When the complex dimension of the ambient space is equal to $2$ we define a second quadratic form with the same property and then determine those surfaces with parallel mean curvature vector on which the $(2,0)$-parts of both of them vanish. We also provide a reduction of codimension theorem and prove a non-existence result for $2$-spheres with parallel mean curvature vector.
Correlation between thoracolumbar curvatures and respiratory function in older adults
Directory of Open Access Journals (Sweden)
Rahman NNAA
2017-03-01
Full Text Available Nor Najwatul Akmal Ab Rahman,1 Devinder Kaur Ajit Singh,1 Raymond Lee2 1Physiotherapy Programme, School of Rehabilitation Sciences, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, Kuala Lumpur, Malaysia; 2School of Applied Sciences, London South Bank University, London, UK Abstract: Aging is associated with alterations in thoracolumbar curvatures and respiratory function. Research information regarding the correlation between thoracolumbar curvatures and a comprehensive examination of respiratory function parameters in older adults is limited. The aim of the present study was to examine the correlation between thoracolumbar curvatures and respiratory function in community-dwelling older adults. Thoracolumbar curvatures (thoracic and lumbar were measured using a motion tracker. Respiratory function parameters such as lung function, respiratory rate, respiratory muscle strength and respiratory muscle thickness (diaphragm and intercostal were measured using a spirometer, triaxial accelerometer, respiratory pressure meter and ultrasound imaging, respectively. Sixty-eight community-dwelling older males and females from Kuala Lumpur, Malaysia, with mean (standard deviation age of 66.63 (5.16 years participated in this cross-sectional study. The results showed that mean (standard deviation thoracic curvature angle and lumbar curvature angles were -46.30° (14.66° and 14.10° (10.58°, respectively. There was a significant negative correlation between thoracic curvature angle and lung function (forced expiratory volume in 1 second: r=-0.23, P<0.05; forced vital capacity: r=-0.32, P<0.05, quiet expiration intercostal thickness (r=-0.22, P<0.05 and deep expiration diaphragm muscle thickness (r=-0.21, P<0.05. The lumbar curvature angle had a significant negative correlation with respiratory muscle strength (r=-0.29, P<0.05 and diaphragm muscle thickness at deep inspiration (r=-0.22, P<0.05. However, respiratory rate
Holomorphic Bisectional Curvatures, Supersymmetry Breaking, and Affleck-Dine Baryogenesis
Dutta, Bhaskar
2012-01-01
Working in $D=4, N=1$ supergravity, we utilize relations between holomorphic sectional and bisectional curvatures of Kahler manifolds to constrain Affleck-Dine baryogenesis. We show the following No-Go result: Affleck-Dine baryogenesis cannot be performed if the holomorphic sectional curvature at the origin is isotropic in tangent space; as a special case, this rules out spaces of constant holomorphic sectional curvature (defined in the above sense) and in particular maximally symmetric coset spaces. We also investigate scenarios where inflationary supersymmetry breaking is identified with the supersymmetry breaking responsible for mass splitting in the visible sector, using conditions of sequestering to constrain manifolds where inflation can be performed.
Engineering Curvature-Induced Anisotropy in Thin Ferromagnetic Films
Tretiakov, Oleg A.; Morini, Massimiliano; Vasylkevych, Sergiy; Slastikov, Valeriy
2017-08-01
We investigate the effect of large curvature and dipolar energy in thin ferromagnetic films with periodically modulated top and bottom surfaces on magnetization behavior. We predict that the dipolar interaction and surface curvature can produce perpendicular anisotropy which can be controlled by engineering special types of periodic surface structures. Similar effects can be achieved by a significant surface roughness in the film. We demonstrate that, in general, the anisotropy can point in an arbitrary direction depending on the surface curvature. Furthermore, we provide simple examples of these periodic surface structures to show how to engineer particular anisotropies in thin films.
Curvature-driven assembly in soft matter.
Liu, Iris B; Sharifi-Mood, Nima; Stebe, Kathleen J
2016-07-28
Control over the spatial arrangement of colloids in soft matter hosts implies control over a wide variety of properties, ranging from the system's rheology, optics, and catalytic activity. In directed assembly, colloids are typically manipulated using external fields to form well-defined structures at given locations. We have been developing alternative strategies based on fields that arise when a colloid is placed within soft matter to form an inclusion that generates a potential field. Such potential fields allow particles to interact with each other. If the soft matter host is deformed in some way, the potential allows the particles to interact with the global system distortion. One important example is capillary assembly of colloids on curved fluid interfaces. Upon attaching, the particle distorts that interface, with an associated energy field, given by the product of its interfacial area and the surface tension. The particle's capillary energy depends on the local interface curvature. We explore this coupling in experiment and theory. There are important analogies in liquid crystals. Colloids in liquid crystals elicit an elastic energy response. When director fields are moulded by confinement, the imposed elastic energy field can couple to that of the colloid to define particle paths and sites for assembly. By improving our understanding of these and related systems, we seek to develop new, parallelizable routes for particle assembly to form reconfigurable systems in soft matter that go far beyond the usual close-packed colloidal structures.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.
... indicated by a total lack of sensory and motor function below the level of injury. People who survive a spinal cord injury will most likely have medical complications such as chronic pain and bladder and bowel ...
Conventional Spinal Anaesthesia
African Journals Online (AJOL)
patients scheduled for clcctive unilateral lower limb surgery. ... the conventional group were turned supine immediately after injection. Blood pressure, heart rate, respiratory rate and oxygen .... Characteristic Type of spinal anaesthcsia P-value.
Meningitis after spinal anesthesia
National Research Council Canada - National Science Library
Mouchrif, Issam; Berdaii, Adnane; Labib, Ismail; Harrandou, Moustapha
2016-01-01
Meningitis is a rare but serious complication of epidural and spinal anesthesia. Bacterial meningitis is mainly caused by Gram-positive cocci, implying an exogenous contamination which suggests a lack of asepsis...
... Videos by Topic and Question Videos by Family Relationship Videos by Experts Resources The Short List Government Programs Family and Caregiver Support Financial Help Active Lifestyle Advocacy Employment and Education Adaptive Technology Recent Medical Research Good Things to Read Spinal ...
... Videos by Topic and Question Videos by Family Relationship Videos by Experts Resources The Short List Government Programs Family and Caregiver Support Financial Help Active Lifestyle Advocacy Employment and Education Adaptive Technology Recent Medical Research Good Things to Read Spinal ...
Extradural Spinal Arachnoid Cysts
Directory of Open Access Journals (Sweden)
J Gordon Millichap
2007-11-01
Full Text Available A 14-year-old boy with multiple spinal arachnoid cysts and paraplegia, and 37 similar cases in the literature are reviewed by neurosurgeons and radiologist at Univ of Sao Paulo, Brazil.
Applications in spinal imbalance.
Husson, J-L; Mallet, J-F; Parent, H; Cavagna, R; Vital, J-M; Blamoutier, A; Violas, P
2010-05-04
The pelvis may be seen as a single vertebra, between the spine and the femurs. The anatomy of this pelvic vertebra has changed with the evolution of species, notably with the transition to bipedalism, with the consequent appearance of lumbar lordosis. The lumbosacral angle, almost non-existent in other mammals, is at its greatest in humans. Pelvic and spinal radiological parameters reflect the sagittal balance of the spine in bipedal humanity. Applications in the management of spinal imbalance are numerous. Arthrogenic or degenerative kyphosis is the stereotypic example of spinal aging. Postoperative flat back following spine surgery is hard to prevent. Scoliosis surgery in adults should now take greater account of the patient's individual sagittal balance, by analyzing the pelvic and spinal parameters. The extent of arthrodeses performed during adolescence to manage idiopathic scoliosis may also induce problems of balance in adulthood if these elements are not taken into account. Copyright © 2010 Elsevier Masson SAS. All rights reserved.
Spinal dysraphism: MRI evaluation
Directory of Open Access Journals (Sweden)
Ramacharya
2015-08-01
Conclusion: Thus we conclude that Spinal dysraphism were common in young females, with commonest anomaly being vertebral anomaly (Spina bifida, commonest location is lumbar region, Diastematomyelia common in young aged female. Magnetic resonance imaging is an accurate, noninvasive, safe and advanced modality for evaluation of the congenital spinal disorders and help in better management of these patients with prompt and accurate diagnosis. [Int J Res Med Sci 2015; 3(8.000: 1937-1941
A mean curvature estimate for cylindrically bounded submanifolds
Alias, Luis J
2010-01-01
We extend the estimate obtained in [1] for the mean curvature of a cylindrically bounded proper submanifold in a product manifold with an Euclidean space as one factor to a general product ambient space endowed with a warped product structure.
Comment on "On curvature coupling and quintessence fine-tuning"
Franca, U
2005-01-01
In this comment, we show explicitly that the phenomenological model in which the quintessence field depends linearly on the energy density of the spatial curvature can provide acceleration for the universe, contrary to recent claims it could not.
Inverse lyotropic phases of lipids and membrane curvature
Energy Technology Data Exchange (ETDEWEB)
Shearman, G C; Ces, O; Templer, R H; Seddon, J M [Department of Chemistry, Imperial College London, SW7 2AZ (United Kingdom)
2006-07-19
In recent years it has become evident that many biological functions and processes are associated with the adoption by cellular membranes of complex geometries, at least locally. In this paper, we initially discuss the range of self-assembled structures that lipids, the building blocks of biological membranes, may form, focusing specifically on the inverse lyotropic phases of negative interfacial mean curvature. We describe the roles of curvature elasticity and packing frustration in controlling the stability of these inverse phases, and the experimental determination of the spontaneous curvature and the curvature elastic parameters. We discuss how the lyotropic phase behaviour can be tuned by the addition of compounds such as long-chain alkanes, which can relieve packing frustration. The latter section of the paper elaborates further on the structure, geometric properties, and stability of the inverse bicontinuous cubic phases.
Curvature-based Hyperbolic Systems for General Relativity
Choquet-Bruhat, Y; Anderson, A; Choquet-Bruhat, Yvonne; York, James W.; Anderson, Arlen
1998-01-01
We review curvature-based hyperbolic forms of the evolution part of the Cauchy problem of General Relativity that we have obtained recently. We emphasize first order symmetrizable hyperbolic systems possessing only physical characteristics.
Abnormalities of penile curvature: chordee and penile torsion.
Montag, Sylvia; Palmer, Lane S
2011-07-28
Congenital chordee and penile torsion are commonly observed in the presence of hypospadias, but can also be seen in boys with the meatus in its orthotopic position. Varying degrees of penile curvature are observed in 4-10% of males in the absence of hypospadias. Penile torsion can be observed at birth or in older boys who were circumcised at birth. Surgical management of congenital curvature without hypospadias can present a challenge to the pediatric urologist. The most widely used surgical techniques include penile degloving and dorsal plication. This paper will review the current theories for the etiology of penile curvature, discuss the spectrum of severity of congenital chordee and penile torsion, and present varying surgical techniques for the correction of penile curvature in the absence of hypospadias.
Bacterial cell curvature through mechanical control of cell growth
DEFF Research Database (Denmark)
Cabeen, M.; Charbon, Godefroid; Vollmer, W.
2009-01-01
The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure...... that collapses into a helix when detached from the cell membrane, suggesting that it is normally maintained in a stretched configuration. Crescentin causes an elongation rate gradient around the circumference of the sidewall, creating a longitudinal cell length differential and hence curvature. Such curvature...... can be produced by physical force alone when cells are grown in circular microchambers. Production of crescentin in Escherichia coli is sufficient to generate cell curvature. Our data argue for a model in which physical strain borne by the crescentin structure anisotropically alters the kinetics...
Abnormalities of Penile Curvature: Chordee and Penile Torsion
Directory of Open Access Journals (Sweden)
Sylvia Montag
2011-01-01
Full Text Available Congenital chordee and penile torsion are commonly observed in the presence of hypospadias, but can also be seen in boys with the meatus in its orthotopic position. Varying degrees of penile curvature are observed in 4–10% of males in the absence of hypospadias. Penile torsion can be observed at birth or in older boys who were circumcised at birth. Surgical management of congenital curvature without hypospadias can present a challenge to the pediatric urologist. The most widely used surgical techniques include penile degloving and dorsal plication. This paper will review the current theories for the etiology of penile curvature, discuss the spectrum of severity of congenital chordee and penile torsion, and present varying surgical techniques for the correction of penile curvature in the absence of hypospadias.
Quasi-Maxwell interpretation of the spin-curvature coupling
Natario, J
2007-01-01
We write the Mathisson-Papapetrou equations of motion for a spinning particle in a stationary spacetime using the quasi-Maxwell formalism and give an interpretation of the coupling between spin and curvature.
Changes on the corneal thickness and curvature after orthokeratology
Mitsui, Iwane; Yamada, Yoshiya
2004-07-01
To evaluate the corneal thickness and curvature changes after Orthokeratology contact lens wear, using the ORBSCAN II corneal topography system, corneal thickness and corneal curvature were measured on one hundred and twenty eyes of sixty patients before and after wearing the custom rigid gas permeable contact lenses for Orthokeratology. The contact lenses were specially designed for each eye. The subjects wore the orthokeratology lenses for approximately Four hours with their eyes closed. The corneal thickness of the subjects was increased on fifty-five eyes at not only the peripheral zone but also the center of the cornea. The average increase of central and peripheral corneal thickness was 18 micrometer and 22micrometer, respectively. The mean anterior curvature of corneal surface changed 1.25D. The mean posterior curvature of corneal endothelium side changed 0.75D.
A compactness theorem for surfaces with Bounded Integral Curvature
Debin, Clément
2016-01-01
We prove a compactness theorem for metrics with Bounded Integral Curvature on a fixed closed surface $\\Sigma$. As a corollary, we obtain a compactification of the space of Riemannian metrics with conical singularities, where an accumulation of singularities is allowed.
A Method for Wavefront Curvature Ranging of Speech Sources ...
African Journals Online (AJOL)
A Method for Wavefront Curvature Ranging of Speech Sources. ... A new approach for estimating the location of a speech source in a reverberant environment is presented. The approach ... EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT
Curvature-induced stiffening of a fish fin
Nguyen, Khoi; Bandi, Mahesh M; Venkadesan, Madhusudhan; Mandre, Shreyas
2016-01-01
Fish behaviour and its ecological niche require modulation of its fin stiffness. Using mathematical analyses of rayed fish fins, we show that curvature transverse to the rays is central to fin stiffness. We model the fin as rays with anisotropic bending that are connected by an elastic membrane. For fins with transverse curvature, external loads that bend the rays also splay them apart, which stretches the membrane. This coupling, between ray bending and membrane stretching, underlies the curvature-induced stiffness. A fin that appears flat may still exhibit bending-stretching coupling if the principal bending axes of adjacent rays are misaligned by virtue of intrinsic geometry, i.e. morphologically flat yet functionally curved. Analysis of the pectoral fin of a mackerel shows such functional curvature. Furthermore, as identified by our analyses, the mackerel's fin morphology endows it with the potential to modulate stiffness over a wide range.
The probability equation for the cosmological comoving curvature perturbation
Energy Technology Data Exchange (ETDEWEB)
Riotto, Antonio; Sloth, Martin S., E-mail: antonio.riotto@pd.infn.it, E-mail: sloth@cern.ch [CERN, PH-TH Division, CH-1211, Genève 23 (Switzerland)
2011-10-01
Fluctuations of the comoving curvature perturbation with wavelengths larger than the horizon length are governed by a Langevin equation whose stochastic noise arise from the quantum fluctuations that are assumed to become classical at horizon crossing. The infrared part of the curvature perturbation performs a random walk under the action of the stochastic noise and, at the same time, it suffers a classical force caused by its self-interaction. By a path-interal approach and, alternatively, by the standard procedure in random walk analysis of adiabatic elimination of fast variables, we derive the corresponding Kramers-Moyal equation which describes how the probability distribution of the comoving curvature perturbation at a given spatial point evolves in time and is a generalization of the Fokker-Planck equation. This approach offers an alternative way to study the late time behaviour of the correlators of the curvature perturbation from infrared effects.
Curvature-Squared Cosmology In The First-Order Formalism
Shahid-Saless, Bahman
1993-01-01
Paper presents theoretical study of some of general-relativistic ramifications of gravitational-field energy density proportional to R - alpha R(exp 2) (where R is local scalar curvature of space-time and alpha is a constant).
Curvature Control of Silicon Microlens for THz Dielectric Antenna
Lee, Choonsup; Chattopadhyay, Goutam; Cooper, Ken; Mehdi, Imran
2012-01-01
We have controlled the curvature of silicon microlens by changing the amount of photoresist in order to microfabricate hemispherical silicon microlens which can improve the directivity and reduce substrate mode losses.
Facial landmark localization by curvature maps and profile analysis
National Research Council Canada - National Science Library
Lippold, Carsten; Liu, Xiang; Wangdo, Kim; Drerup, Burkhard; Schreiber, Kristina; Kirschneck, Christian; Moiseenko, Tatjana; Danesh, Gholamreza
2014-01-01
.... This study wants to evaluate and present an objective method for measuring selected facial landmarks based on an analysis of curvature maps and of sagittal profile obtained by a laser-scanning method...
Springback prediction of three-dimensional variable curvature tube bending
National Research Council Canada - National Science Library
Zhang, Shen; Wu, Jianjun
2016-01-01
.... The springback prediction of three-dimensional variable curvature bent tube is projected on each discrete osculating and rectifying plane, and then the three-dimensional problem can be transformed into two dimensions...
Curvature Control of Silicon Microlens for THz Dielectric Antenna
Lee, Choonsup; Chattopadhyay, Goutam; Cooper, Ken; Mehdi, Imran
2012-01-01
We have controlled the curvature of silicon microlens by changing the amount of photoresist in order to microfabricate hemispherical silicon microlens which can improve the directivity and reduce substrate mode losses.
Modeling spinal cord biomechanics
Luna, Carlos; Shah, Sameer; Cohen, Avis; Aranda-Espinoza, Helim
2012-02-01
Regeneration after spinal cord injury is a serious health issue and there is no treatment for ailing patients. To understand regeneration of the spinal cord we used a system where regeneration occurs naturally, such as the lamprey. In this work, we analyzed the stress response of the spinal cord to tensile loading and obtained the mechanical properties of the cord both in vitro and in vivo. Physiological measurements showed that the spinal cord is pre-stressed to a strain of 10%, and during sinusoidal swimming, there is a local strain of 5% concentrated evenly at the mid-body and caudal sections. We found that the mechanical properties are homogeneous along the body and independent of the meninges. The mechanical behavior of the spinal cord can be characterized by a non-linear viscoelastic model, described by a modulus of 20 KPa for strains up to 15% and a modulus of 0.5 MPa for strains above 15%, in agreement with experimental data. However, this model does not offer a full understanding of the behavior of the spinal cord fibers. Using polymer physics we developed a model that relates the stress response as a function of the number of fibers.
Strong curvature singularities in quasispherical asymptotically de Sitter dust collapse
Gonçalves, S M C V
2001-01-01
We study the occurrence, visibility, and curvature strength of singularities in dust-containing Szekeres spacetimes (which possess no Killing vectors) with a positive cosmological constant. We find that such singularities can be locally naked, Tipler strong, and develop from a non-zero-measure set of regular initial data. When examined along timelike geodesics, the singularity's curvature strength is found to be independent of the initial data.
A novel curvature-controllable steerable needle for percutaneous intervention.
Bui, Van Khuyen; Park, Sukho; Park, Jong-Oh; Ko, Seong Young
2016-08-01
Over the last few decades, flexible steerable robotic needles for percutaneous intervention have been the subject of significant interest. However, there still remain issues related to (a) steering the needle's direction with less damage to surrounding tissues and (b) increasing the needle's maximum curvature for better controllability. One widely used approach is to control the fixed-angled bevel-tip needle using a "duty-cycle" algorithm. While this algorithm has shown its applicability, it can potentially damage surrounding tissue, which has prevented the widespread adoption of this technology. This situation has motivated the development of a new steerable flexible needle that can change its curvature without axial rotation, while at the same time producing a larger curvature. In this article, we propose a novel curvature-controllable steerable needle. The proposed robotic needle consists of two parts: a cannula and a stylet with a bevel-tip. The curvature of the needle's path is controlled by a control offset, defined by the offset between the bevel-tip and the cannula. As a result, the necessity of rotating the whole needle's body is decreased. The duty-cycle algorithm is utilized to a limited degree to obtain a larger radius of curvature, which is similar to a straight path. The first prototype of 0.46 mm (outer diameter) was fabricated and tested with both in vitro gelatin phantom and ex vivo cow liver tissue. The maximum curvatures measured 0.008 mm(-1) in 6 wt% gelatin phantom, 0.0139 mm(-1) in 10 wt% gelatin phantom, and 0.0038 mm(-1) in cow liver. The experimental results show a linear relationship between the curvature and the control offset, which can be utilized for future implementation of this control algorithm.
Curvature-induced stiffening of a fish fin
Nguyen, Khoi; Yu, Ning; Bandi, Mahesh M.; Venkadesan, Madhusudhan; Mandre, Shreyas
2016-01-01
How fish modulate their fin stiffness during locomotive manoeuvres remains unknown. We show that changing the fin's curvature modulates its stiffness. Modelling the fin as bendable bony rays held together by a membrane, we deduce that fin curvature is manifested as a misalignment of the principal bending axes between neighbouring rays. An external force causes neighbouring rays to bend and splay apart, and thus stretches the membrane. This coupling between bending the rays and stretching the ...
Influence of curvature on the losses of doubly clad fibers.
Marcuse, D
1982-12-01
The loss increase of the HE(11) mode of a doubly clad (depressed-index) fiber due to constant curvature is considered. The calculations presented in this paper are based on a simplified theory. We find that for typical fibers the leakage loss of the HE(11) mode begins to increase significantly when the radius of curvature of the fiber axis reaches the 1-10-cm range.
No fast food for solving higher curvature gravity
Zhao, Liu
2011-01-01
Nowadays, gravity theories with higher curvature terms have attracted considerable attentions. Due to the complicated form of the equations of motion, an effective action method, basically based on substituting a metric ansatz into the action and then replacing the original action by the resulting "effective action", is often practiced while finding solutions to such theories. We indicate via explicit example, however, that this procedure is mathematically inconsistent, thus calling for an end for using this method in analyzing higher curvature gravities.
Abnormalities of Penile Curvature: Chordee and Penile Torsion
2011-01-01
Congenital chordee and penile torsion are commonly observed in the presence of hypospadias, but can also be seen in boys with the meatus in its orthotopic position. Varying degrees of penile curvature are observed in 4–10% of males in the absence of hypospadias. Penile torsion can be observed at birth or in older boys who were circumcised at birth. Surgical management of congenital curvature without hypospadias can present a challenge to the pediatric urologist. The most widely used surgical ...
Incidence of penile curvature in various forms of hypospadias
Directory of Open Access Journals (Sweden)
Đorđević Miroslav
2009-01-01
Full Text Available Introduction. Hypospadias is a congenital anomaly of the penis, characterised by ectopically positioned urethral meatus and associated anomalies (cryptorchidism, inguinal hernia, penile curvature. Proximal forms of hypospadias, as severe cases, are particularly accompanied by penile curvature (chordee. Distal types are considered to be mild degrees. Objective. To determine the incidence of congenital curvature within various forms of hypospadias in order to signify preoperative and intraoperative diagnosis of chordee as a part of hypospadias repair. Methods. The total of 454 patients with hypospadias were treated surgically in a five-year period (2001-2006. at the University Children's Hospital of Belgrade. The patients were divided into two groups according to the surgeon who had treated them. Only the first group of patients was tested for chordee as a part of standard procedure and complete treatment. In both groups we analyzed the number of patients treated for penile curvature within various types of hypospadias. We also compared scores in the two groups using Fisher test and χ2-test. Results. Scanning retrospective, 104 cases (22.9% of diagnosed and surgically corrected chordee were determined. In 31.6% of patients from the first group and 11.6% of patients from the second group we diagnosed and corrected some form of penile curvature was. Chordee was significantly more frequent in the first group, regarding hypospadias in general (p<0.01, as well as distal (p<0.05 and mid shaft forms (p<0.01. Conclusion. Penile curvature is not uncommon in hypospadias. In this study we report a significantly higher frequency as related to the patients in the second group who were not tested for curvature during hypospadias treatment. This is why standard techniques in hypospadias repair should definitely include the diagnosis and surgical correction of penile curvature.
Topographic mapping of biological specimens: flexure and curvature characterization
Baron, William S.; Baron, Sandra F.
2004-07-01
Shape quantification of tissue and biomaterials can be central to many studies and applications in bioengineering and biomechanics. Often, shape is mapped with photogrammetry or projected light techniques that provide XYZ point cloud data, and shape is quantified using derived flexure and curvature calculations based on the point cloud data. Accordingly, the accuracy of the calculated curvature depends on the properties of the point cloud data set. In this study, we present a curvature variability prediction (CVP) software model that predicts the distribution, i.e., the standard deviation, of curvature measurements associated with surface topography point cloud data properties. The CVP model point cloud data input variables include XYZ noise, sampling density, and map extent. The CVP model outputs the curvature variability statistic in order to assess performance in the curvature domain. Representative point cloud data properties are obtained from an automated biological specimen video topographer, the BioSpecVT (ver. 1.02) (Vision Metrics, Inc.,). The BioSpecVT uses a calibrated, structured light pattern to support automated computer vision feature extraction software for precisely converting video images of biological specimens, within seconds, into three dimensional point cloud data. In representative sample point cloud data obtained with the BioSpecVT, sampling density is about 11 pts/mm2 for an XYZ mapping volume encompassing about 16 mm x 13.5 mm x 18.5 mm, average XY per point variability is about +/-2 μm, and Z axis variability is about +/-40 μm (50% level) with a Gaussian distribution. A theoretical study with the CVP model shows that for derived point cloud data properties, curvature mapping accuracy increases, i.e. measurement variability decreases, when curvature increases from about 30 m-1 to 137 m-1. This computed result is consistent with the Z axis noise becoming less significant as the measured depth increases across an approximately fixed XY
Approximations of the Wiener sausage and its curvature measures
Rataj, Jan; Meschenmoser, Daniel; 10.1214/09-AAP596
2009-01-01
A parallel neighborhood of a path of a Brownian motion is sometimes called the Wiener sausage. We consider almost sure approximations of this random set by a sequence of random polyconvex sets and show that the convergence of the corresponding mean curvature measures holds under certain conditions in two and three dimensions. Based on these convergence results, the mean curvature measures of the Wiener sausage are calculated numerically by Monte Carlo simulations in two dimensions. The corresponding approximation formulae are given.
Existence of conformal metrics on spheres with prescribed Paneitz curvature
Ben-Ayed, M
2003-01-01
In this paper we study the problem of prescribing a fourth order conformal invariant (the Paneitz curvature) on the n-spheres, with n >= 5. Using tools from the theory of critical points at infinity, we provide some topological conditions on the level sets of a given function defined on the sphere, under which we prove the existence of conformal metric with prescribed Paneitz curvature.
Pseudo-umbilical Biharmonic Submanifolds in Constant Curvature Spaces
Institute of Scientific and Technical Information of China (English)
DU Li; ZHANG Juan
2012-01-01
The conjecture [1] asserts that any biharmonic submanifold in sphere has constant mean curvature.In this paper,we first prove that this conjecture is true for pseudo-umbilical biharmonic submanifolds Mn in constant curvature spaces Sn+P(c)(c ＞ 0),generalizing the result in [1].Secondly,some sufficient conditions for pseudo-umbilical proper biharmonic submanifolds Mn to be totally umbilical ones are obtained.
Curvature-driven acceleration: a utopia or a reality?
Energy Technology Data Exchange (ETDEWEB)
Das, Sudipta [Relativity and Cosmology Research Centre, Department of Physics, Jadavpur University, Calcutta-700 032 (India); Banerjee, Narayan [Relativity and Cosmology Research Centre, Department of Physics, Jadavpur University, Calcutta-700 032 (India); Dadhich, Naresh [Inter University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007 (India)
2006-06-21
The present work shows that a combination of nonlinear contributions from the Ricci curvature in Einstein field equations can drive a late time acceleration of expansion of the universe. The transit from the decelerated to the accelerated phase of expansion takes place smoothly without having to resort to a study of asymptotic behaviour. This result emphasizes the need for thorough and critical examination of models with nonlinear contribution from the curvature.
Curvature driven acceleration an utopia or a reality ?
Das, S; Dadhich, N; Das, Sudipta; Banerjee, Narayan; Dadhich, Naresh
2005-01-01
The present work shows that a combination of nonlinear contribution from the Ricci curvature in Einstein field equations can drive a late time acceleration of expansion of the universe. The transit from the decelerated to the accelerated phase of expansion takes place smoothly without having to resort to a study of asymptotic behaviour. This result emphasizes the need for thorough and critical examination of models with nonlinear contribution from the curvature.
The effect of illuminant position on perceived curvature.
Curran, W; Johnston, A
1996-05-01
In shaded scenes surface features can appear either concave or convex, depending upon the viewer's judgement about the direction of the prevailing illumination. If other curvature cues are added to the image this ambiguity can be removed. However, it is not clear to what extent, if any, illuminant position exerts an influence on the perceived magnitude of surface curvature. Subjects were presented with pairs of spherical surface patches in a curvature matching task. The patches were defined by shading and texture cues. The perceived curvature of a standard patch was measured as a function of light source position. We found a clear effect of light source position on apparent curvature. Perceived curvature decreased as light source tilt increased and as light source slant decreased. We also found that the strength of this effect is determined partly by a surface's reflectance function and partly by the relative weight of the texture cue. When a specular component was added to the stimuli, the effect of light source orientation was weakened. The weight of the texture cue was manipulated by disrupting the regular distribution of texture elements. We found an inverse relationship between the strength of the effect and the weight of the texture cue: lowering the texture cue weight resulted in an enhancement of the illuminant position effect.
Monolayer spontaneous curvature of raft-forming membrane lipids
Kollmitzer, Benjamin; Heftberger, Peter; Rappolt, Michael; Pabst, Georg
Monolayer spontaneous curvatures for cholesterol, DOPE, POPE, DOPC, DPPC, DSPC, POPC, SOPC, and egg sphingomyelin were obtained using small-angle X-ray scattering (SAXS) on inverted hexagonal phases (HII). Spontaneous curvatures of bilayer forming lipids were estimated by adding controlled amounts to a HII forming template following previously established protocols. Spontanous curvatures of both phosphatidylethanolamines and cholesterol were found to be at least a factor of two more negative than those of phosphatidylcholines, whose J0 are closer to zero. Interestingly, a significant positive J0 value (+0.1 1/nm) was retrieved for DPPC at 25 {\\deg}C. We further determined the temperature dependence of the spontaneous curvatures J0(T) in the range from 15 to 55 \\degC, resulting in a quite narrow distribution of -1 to -3 * 10^-3 1/nm{\\deg}C for most investigated lipids. The data allowed us to estimate the monolayer spontaneous curvatures of ternary lipid mixtures showing liquid ordered / liquid disordered phase coexistence. We report spontaneous curvature phase diagrams for DSPC/DOPC/Chol, DPPC/DOPC/Chol and SM/POPC/Chol and discuss effects on protein insertion and line tension.
Non-additive compositional curvature energetics of lipid bilayers
Sodt, A.J.; Venable, R.M.; Lyman, E.; Pastor, R.W.
2016-01-01
The unique properties of the individual lipids that compose biological membranes together determine the energetics of the surface. The energetics of the surface in turn govern the formation of membrane structures and membrane reshaping processes, and will thus underlie cellular-scale models of viral fusion, vesicle-dependent transport, and lateral organization relevant to signaling. The spontaneous curvature, to the best of our knowledge, is always assumed to be additive. The letter describes observations from simulations of unexpected non-additive compositional curvature energetics of two lipids essential to the plasma membrane: sphingomyelin and cholesterol. A model is developed that connects molecular interactions to curvature stress, and which explains the role of local composition. Cholesterol is shown to lower the number of effective Kuhn segments of saturated acyl chains, reducing lateral pressure below the neutral surface of bending and favoring positive curvature. The effect is not observed for unsaturated (flexible) acyl chains. Likewise, hydrogen bonding between sphingomyelin lipids leads to positive curvature, but only at sufficient concentration, below which the lipid prefers negative curvature. PMID:27715135
Nanoscale Membrane Curvature detected by Polarized Localization Microscopy
Kelly, Christopher; Maarouf, Abir; Woodward, Xinxin
Nanoscale membrane curvature is a necessary component of countless cellular processes. Here we present Polarized Localization Microscopy (PLM), a super-resolution optical imaging technique that enables the detection of nanoscale membrane curvature with order-of-magnitude improvements over comparable optical techniques. PLM combines the advantages of polarized total internal reflection fluorescence microscopy and fluorescence localization microscopy to reveal single-fluorophore locations and orientations without reducing localization precision by point spread function manipulation. PLM resolved nanoscale membrane curvature of a supported lipid bilayer draped over polystyrene nanoparticles on a glass coverslip, thus creating a model membrane with coexisting flat and curved regions and membrane radii of curvature as small as 20 nm. Further, PLM provides single-molecule trajectories and the aggregation of curvature-inducing proteins with super-resolution to reveal the correlated effects of membrane curvature, dynamics, and molecular sorting. For example, cholera toxin subunit B has been observed to induce nanoscale membrane budding and concentrate at the bud neck. PLM reveals a previously hidden and critical information of membrane topology.
Solitary Wave and Wave Front as Viewed From Curvature
Institute of Scientific and Technical Information of China (English)
LIU Shi-Kuo; FU Zun-Tao; LIU Shi-Da; LIANG Fu-Ming; XIN Guo-Jun
2004-01-01
The solitary wave and wave front are two important behaviors of nonlinear evolution equations. Geometri cally, solitary wave and wave front are all plane curve. In this paper, they can be represented in terms of curvature c(s), which varies with arc length s. For solitary wave when s →±∞, then its curvature c(s) approaches zero, and when s = 0, the curvature c(s) reaches its maximum. For wave front, when s →±∞, then its curvature c(s) approaches zero, and when s = 0, the curvature c(s) is still zero, but c'(s) ≠ 0. That is, s = 0 is a turning point. When c(s) is given, the variance at some point (x, y) in stream line with arc length s satisfies a 2-order linear variable-coefficient ordinary differential equation. From this equation, it can be determined qualitatively whether the given curvature is a solitary wave or wave front.
Solitary Wave and Wave Front as Viewed From Curvature
Institute of Scientific and Technical Information of China (English)
LIUShi-Kuo; FUZun-Tao; LIUShi-Da; LIANGFu-Ming; XINGuo-Jun
2004-01-01
The solitary wave and wave front are two important behaviors of nonlinear evolution equations. Geometrically, solitary wave and wave front are all plane curve. In this paper, they can be represented in terms of curvature c(s),which varies with arc length s. For solitary wave when s→±∞, then its curvature c(s) approaches zero, and whens = 0, the curvature c(s) reaches its maximum. For wave front, when s→±∞, then its curvature c(s) approaches zero,and when s = 0, the curvature c(s) is still zero, but c'(s)≠0. That is, s = 0 is a turning point. When c(s) is given,the variance at some point (x, y) in stream line with arc length s satisfies a 2-order linear variable-coeffcient ordinary differential equation. From this equation, it can be determined qualitatively whether the given curvature is a solitary wave or wave front.
Directory of Open Access Journals (Sweden)
Nurbek N Nadirov
2016-06-01
Full Text Available Aim. To compare the results of surgical correction of spinal deformity in children with idiopathic thoracic scoliosis with the use of transpedicular screw spinal systems with different pedicle screw placement. Material and methods. Thirty-one patients (14–17 years with spinal curvature with a Cobb angle from 40° to 79° were operated on. Surgical correction of the deformity was performed using two methods, depending on the possible placement of a pedicle screw. The first group included 16 patients for whom the transpedicular support elements were placed on both sides, throughout the completely deformed spine. The second group included 15 patients for whom the pedicle screws were not placed for two or more vertebrae on the concave side of the curve, at the top of the main curve. Results. The mean percent correction of the spinal deformity for the first and second groups was 92.5% and 82.6%, respectively. The mean percentage of derotation of the apical vertebra for the first and second groups was 73.9% and 23%, respectively. Conclusion. The use of data based on the anatomical and anthropometric features of the vertebral body with scoliosis facilitates selection of the best option for correction of thoracic curve in children with idiopathic scoliosis using pedicle multi-support metal construction. The use of the spinal pedicle system for correction of spinal deformity in children with idiopathic scoliosis enabled a uniform load distribution along the support elements of the metal construction and maintained the correction in the late postoperative follow-up period.
Curvature recognition and force generation in phagocytosis
Directory of Open Access Journals (Sweden)
Prassler Jana
2010-12-01
Full Text Available Abstract Background The uptake of particles by actin-powered invagination of the plasma membrane is common to protozoa and to phagocytes involved in the immune response of higher organisms. The question addressed here is how a phagocyte may use geometric cues to optimize force generation for the uptake of a particle. We survey mechanisms that enable a phagocyte to remodel actin organization in response to particles of complex shape. Results Using particles that consist of two lobes separated by a neck, we found that Dictyostelium cells transmit signals concerning the curvature of a surface to the actin system underlying the plasma membrane. Force applied to a concave region can divide a particle in two, allowing engulfment of the portion first encountered. The phagosome membrane that is bent around the concave region is marked by a protein containing an inverse Bin-Amphiphysin-Rvs (I-BAR domain in combination with an Src homology (SH3 domain, similar to mammalian insulin receptor tyrosine kinase substrate p53. Regulatory proteins enable the phagocyte to switch activities within seconds in response to particle shape. Ras, an inducer of actin polymerization, is activated along the cup surface. Coronin, which limits the lifetime of actin structures, is reversibly recruited to the cup, reflecting a program of actin depolymerization. The various forms of myosin-I are candidate motor proteins for force generation in particle uptake, whereas myosin-II is engaged only in retracting a phagocytic cup after a switch to particle release. Thus, the constriction of a phagocytic cup differs from the contraction of a cleavage furrow in mitosis. Conclusions Phagocytes scan a particle surface for convex and concave regions. By modulating the spatiotemporal pattern of actin organization, they are capable of switching between different modes of interaction with a particle, either arresting at a concave region and applying force in an attempt to sever the particle
Congenital spinal malformations; Kongenitale spinale Malformationen
Energy Technology Data Exchange (ETDEWEB)
Ertl-Wagner, B.B.; Reiser, M.F. [Klinikum Grosshadern, Ludwig-Maximilians-Univ. Muenchen (Germany). Inst. fuer Klinische Radiologie
2001-12-01
Congenital spinal malformations form a complex and heterogeneous group of disorders whose pathogenesis is best explained embryologically. Radiologically, it is important to formulate a diagnosis when the disorder first becomes symptomatic. However, it is also crucial to detect complications of the disorder or of the respective therapeutic interventions in the further course of the disease such as hydromyelia or re-tethering after repair of a meningomyelocele. Moreover, once a congenital spinal malformation is diagnosed, associated malformations should be sought after. A possible syndromal classification such as in OEIS- or VACTERL-syndromes should also be considered. (orig.) [German] Kongenitale spinale Malformationen stellen eine komplexe Gruppe an Stoerungen dar, deren Genese sich am einfachsten aus der Embryologie heraus erklaeren laesst. Bei der klinisch-radiologischen Begutachtung ist zunaechst ihre korrekte Klassifikation im Rahmen der Erstdiagnose wichtig. Im weiteren Verlauf ist es jedoch zudem entscheidend, moegliche Komplikationen wie beispielsweise eine Hydromyelie oder ein Wiederanheften des Myelons nach Operation einer Spina bifida aperta zu erkennen. Zudem sollte bei der Diagnosestellung einer kongenitalen spinalen Malformation immer auch auf assoziierte Fehlbildungen, wie z.B. die Diastematomyelie oder das intraspinale Lipom bei der Spina bifida aperta, sowie auf eine moegliche syndromale Einordnung wie beispielsweise beim OEIS-oder VACTERL-Syndrom geachtet werden. (orig.)
Calculation of Scale-Dependent Curvatures of Geological Surfaces
Bergbauer, S.; Mukerji, T.; Pollard, D. D.; Hennings, P. H.
2001-12-01
A comparison between a spectral and a factorial kriging analysis is presented for the calculation of scale -dependent normal surface curvatures. Knowledge of scale -dependent curvatures of geological surfaces plays an important role in quantitative structural geology. Often, curvature analyses of geological surfaces, such as horizon tops, are performed to estimate the strain resulting from deformation. The final shape of the horizon, however, is a superposition of natural structures of different sizes ranging from the grain scale to the basin scale. Performing a curvature analysis on the raw data often leads to patchy, un-interpretable surface curvatures. Separating the surface curvature of the overall structure from the curvature of minor surface undulations can therefore be crucial in any quantitative structural analysis that uses the absolute value of surface curvature. The two methods are applied to a seismically mapped and depth-converted horizon of domal structures from the North Sea to investigate their applicability in a sub-surface context. For the spectral analysis the surface is transformed into a discrete frequency spectrum. When the overall curvature of the horizon is of interest, only the low-frequency components of the spectrum are used for the curvature analysis. The frequency bin width is determined such that only those frequencies that make up the overall surface structure are used, and that aliasing is minimized. The remaining high-frequency spectrum can be added back to address quantitatively the alias introduced by this filtering. In geostatistical factorial kriging analyses, the spatial covariance (variogram) is estimated from the data, and modeled as a sum of independent factors with different ranges. Short range variogram factors correspond to high frequency spectral components of the surface while long range factors contribute low frequency components. Using the modeled variogram, factorial kriging filters out the desired long range
Energy Technology Data Exchange (ETDEWEB)
Goethem, J.W.M. van [Universitair Ziekenhuis Antwerpen, University of Antwerp, Belgium, Department of Radiology, Edegem (Belgium); Algemeen Ziekenhuis Maria Middelares, Department of Radiology, Sint-Niklaas (Belgium); Maes, Menno; Oezsarlak, Oezkan; Hauwe, Luc van den; Parizel, Paul M. [Universitair Ziekenhuis Antwerpen, University of Antwerp, Belgium, Department of Radiology, Edegem (Belgium)
2005-03-01
Because it may cause paralysis, injury to the spine is one of the most feared traumas, and spinal cord injury is a major cause of disability. In the USA approximately 10,000 traumatic cervical spine fractures and 4000 traumatic thoracolumbar fractures are diagnosed each year. Although the number of individuals sustaining paralysis is far less than those with moderate or severe brain injury, the socioeconomic costs are significant. Since most of the spinal trauma patients survive their injuries, almost one out of 1000 inhabitants in the USA are currently being cared for partial or complete paralysis. Little controversy exists regarding the need for accurate and emergent imaging assessment of the traumatized spine in order to evaluate spinal stability and integrity of neural elements. Because clinicians fear missing occult spine injuries, they obtain radiographs for nearly all patients who present with blunt trauma. We are influenced on one side by fear of litigation and the possible devastating medical, psychologic and financial consequences of cervical spine injury, and on the other side by pressure to reduce health care costs. A set of clinical and/or anamnestic criteria, however, can be very useful in identifying patients who have an extremely low probability of injury and who consequently have no need for imaging studies. Multidetector (or multislice) computed tomography (MDCT) is the preferred primary imaging modality in blunt spinal trauma patients who do need imaging. Not only is CT more accurate in diagnosing spinal injury, it also reduces imaging time and patient manipulation. Evidence-based research has established that MDCT improves patient outcome and saves money in comparison to plain film. This review discusses the use, advantages and disadvantages of the different imaging techniques used in spinal trauma patients and the criteria used in selecting patients who do not need imaging. Finally an overview of different types of spinal injuries is given
Estimates and Nonexistence of Solutions of the Scalar Curvature Equation on Noncompact Manifolds
Indian Academy of Sciences (India)
Zhang Zonglao
2005-08-01
This paper is to study the conformal scalar curvature equation on complete noncompact Riemannian manifold of nonpositive curvature. We derive some estimates and properties of supersolutions of the scalar curvature equation, and obtain some nonexistence results for complete solutions of scalar curvature equation.
Turning maneuvers in sharks: Predicting body curvature from axial morphology.
Porter, Marianne E; Roque, Cassandra M; Long, John H
2009-08-01
Given the diversity of vertebral morphologies among fishes, it is tempting to propose causal links between axial morphology and body curvature. We propose that shape and size of the vertebrae, intervertebral joints, and the body will more accurately predict differences in body curvature during swimming rather than a single meristic such as total vertebral number alone. We examined the correlation between morphological features and maximum body curvature seen during routine turns in five species of shark: Triakis semifasciata, Heterodontus francisci, Chiloscyllium plagiosum, Chiloscyllium punctatum, and Hemiscyllium ocellatum. We quantified overall body curvature using three different metrics. From a separate group of size-matched individuals, we measured 16 morphological features from precaudal vertebrae and the body. As predicted, a larger pool of morphological features yielded a more robust prediction of maximal body curvature than vertebral number alone. Stepwise linear regression showed that up to 11 features were significant predictors of the three measures of body curvature, yielding highly significant multiple regressions with r(2) values of 0.523, 0.537, and 0.584. The second moment of area of the centrum was always the best predictor, followed by either centrum length or transverse height. Ranking as the fifth most important variable in three different models, the body's total length, fineness ratio, and width were the most important non-vertebral morphologies. Without considering the effects of muscle activity, these correlations suggest a dominant role for the vertebral column in providing the passive mechanical properties of the body that control, in part, body curvature during swimming. (c) 2009 Wiley-Liss, Inc.
Novel tilt-curvature coupling in lipid membranes
Terzi, M. Mert; Deserno, Markus
2017-08-01
On mesoscopic scales, lipid membranes are well described by continuum theories whose main ingredients are the curvature of a membrane's reference surface and the tilt of its lipid constituents. In particular, Hamm and Kozlov [Eur. Phys. J. E 3, 323 (2000)] have shown how to systematically derive such a tilt-curvature Hamiltonian based on the elementary assumption of a thin fluid elastic sheet experiencing internal lateral pre-stress. Performing a dimensional reduction, they not only derive the basic form of the effective surface Hamiltonian but also express its emergent elastic couplings as trans-membrane moments of lower-level material parameters. In the present paper, we argue, though, that their derivation unfortunately missed a coupling term between curvature and tilt. This term arises because, as one moves along the membrane, the curvature-induced change of transverse distances contributes to the area strain—an effect that was believed to be small but nevertheless ends up contributing at the same (quadratic) order as all other terms in their Hamiltonian. We illustrate the consequences of this amendment by deriving the monolayer and bilayer Euler-Lagrange equations for the tilt, as well as the power spectra of shape, tilt, and director fluctuations. A particularly curious aspect of our new term is that its associated coupling constant is the second moment of the lipid monolayer's lateral stress profile—which within this framework is equal to the monolayer Gaussian curvature modulus, κ¯ m. On the one hand, this implies that many theoretical predictions now contain a parameter that is poorly known (because the Gauss-Bonnet theorem limits access to the integrated Gaussian curvature); on the other hand, the appearance of κ¯ m outside of its Gaussian curvature provenance opens opportunities for measuring it by more conventional means, for instance by monitoring a membrane's undulation spectrum at short scales.
Spinal canal stenosis; Spinalkanalstenose
Energy Technology Data Exchange (ETDEWEB)
Papanagiotou, P.; Boutchakova, M. [Klinikum Bremen-Mitte/Bremen-Ost, Klinik fuer Diagnostische und Interventionelle Neuroradiologie, Bremen (Germany)
2014-11-15
Spinal stenosis is a narrowing of the spinal canal by a combination of bone and soft tissues, which can lead to mechanical compression of spinal nerve roots or the dural sac. The lumbal spinal compression of these nerve roots can be symptomatic, resulting in weakness, reflex alterations, gait disturbances, bowel or bladder dysfunction, motor and sensory changes, radicular pain or atypical leg pain and neurogenic claudication. The anatomical presence of spinal canal stenosis is confirmed radiologically with computerized tomography, myelography or magnetic resonance imaging and play a decisive role in optimal patient-oriented therapy decision-making. (orig.) [German] Die Spinalkanalstenose ist eine umschriebene, knoechern-ligamentaer bedingte Einengung des Spinalkanals, die zur Kompression der Nervenwurzeln oder des Duralsacks fuehren kann. Die lumbale Spinalkanalstenose manifestiert sich klinisch als Komplex aus Rueckenschmerzen sowie sensiblen und motorischen neurologischen Ausfaellen, die in der Regel belastungsabhaengig sind (Claudicatio spinalis). Die bildgebende Diagnostik mittels Magnetresonanztomographie, Computertomographie und Myelographie spielt eine entscheidende Rolle bei der optimalen patientenbezogenen Therapieentscheidung. (orig.)
Spinal actinomycosis: A rare disease
Directory of Open Access Journals (Sweden)
Dua Rakesh
2010-01-01
Full Text Available Actinomycosis is an indolent, slowly progressive infection caused by Actinomyces species. Of human actinomycosis, the spinal form is rare and actinomycosis-related spinal neurological deficit is uncommon. We report two cases with cervical and dorsal actinomycosis and one of them with spinal neurological deficit.
Spinal cord swelling and candidiasis
Energy Technology Data Exchange (ETDEWEB)
Ho, K.; Gronseth, G.; Aldrich, M.; Williams, A.
1982-11-01
Fusiform swelling of the spinal cord was noted myelographically in a patient with Hodgkin's disease. Autopsy revealed that the swelling was caused by Candida infection of the spinal cord. It is suggested that fungal infection be included in the differential diagnosis of spinal cord swelling in the immunosuppressed cancer patient.
Intramedullary spinal melanocytoma
Directory of Open Access Journals (Sweden)
Meic H. Schmidt
2010-06-01
Full Text Available Meningeal melanocytoma is a benign lesion arising from leptomeningeal melanocytes that at times can mimic its malignant counterpart, melanoma. Lesions of the spine usually occur in extramedullary locations and present with spinal cord compression symptoms. Because most reported spinal cases occur in the thoracic region, these symptoms usually include lower extremity weakness or numbness. The authors present a case of primary intramedullary spinal meningeal melanocytoma presenting with bilateral lower extremity symptoms in which the patient had no known supratentorial primary lesions. Gross total surgical resection allowed for full recovery, but early recurrence of tumor was detected on close follow-up monitoring, allowing for elective local radiation without loss of neurological function. Case reports of such tumors discuss different treatment strategies, but just as important is the close follow-up monitoring in these patients even after gross total surgical resection, since these tumors can recur.
Naumann, N; Shariat, K; Ulmer, S; Stippich, C; Ahlhelm, F J
2012-05-01
Infarction of the spinal cord can cause a variety of symptoms and neurological deficits because of the complex vascular supply of the myelon. The most common leading symptom is distal paresis ranging from paraparesis to tetraplegia caused by arterial ischemia or infarction of the myelon. Venous infarction, however, cannot always be distinguished from arterial infarction based on the symptoms alone.Modern imaging techniques, such as computed tomography angiography (CTA) and magnetic resonance angiography (MRA) assist in preoperative planning of aortic operations to reliably identify not only the most important vascular structure supplying the spinal cord, the artery of Adamkiewicz, but also other pathologies such as tumors or infectious disorders. In contrast to CT, MRI can reliably depict infarction of the spinal cord.
The role of curvature in silica mesoporous crystals
Miyasaka, Keiichi
2012-02-08
Silica mesoporous crystals (SMCs) offer a unique opportunity to study micellar mesophases. Replication of non-equilibrium mesophases into porous silica structures allows the characterization of surfactant phases under a variety of chemical and physical perturbations, through methods not typically accessible to liquid crystal chemists. A poignant example is the use of electron microscopy and crystallography, as discussed herein, for the purpose of determining the fundamental role of amphiphile curvature, namely mean curvature and Gaussian curvature, which have been extensively studied in various fields such as polymer, liquid crystal, biological membrane, etc. The present work aims to highlight some current studies devoted to the interface curvature on SMCs, in which electron microscopy and electron crystallography (EC) are used to understand the geometry of silica wall surface in bicontinuous and cage-type mesostructures through the investigation of electrostatic potential maps. Additionally, we show that by altering the synthesis conditions during the preparation of SMCs, it is possible to isolate particles during micellar mesophase transformations in the cubic bicontinuous system, allowing us to view and study epitaxial relations under the specific synthesis conditions. By studying the relationship between mesoporous structure, interface curvature and micellar mesophases using electron microscopy and EC, we hope to bring new insights into the formation mechanism of these unique materials but also contribute a new way of understanding periodic liquid crystal systems. © 2012 The Royal Society.
Rim curvature anomaly in thin conical sheets revisited.
Wang, Jin W
2011-12-01
This paper revisits one of the puzzling behaviors in a developable cone (d-cone), the shape obtained by pushing a thin sheet into a circular container of radius R by a distance η. The mean curvature was reported to vanish at the rim where the d-cone is supported. We investigate the ratio of the two principal curvatures versus sheet thickness h over a wider dynamic range than was used previously, holding R and η fixed. Instead of tending toward 1 as suggested by previous work, the ratio scales as (h/R)(1/3). Thus the mean curvature does not vanish for very thin sheets as previously claimed. Moreover, we find that the normalized rim profile of radial curvature in a d-cone is identical to that in a "c-cone" which is made by pushing a regular cone into a circular container. In both c-cones and d-cones, the ratio of the principal curvatures at the rim scales as (R/h)(5/2)F/(YR(2)), where F is the pushing force and Y is the Young's modulus. Scaling arguments and analytical solutions confirm the numerical results.
Curvature-induced stiffening of a fish fin.
Nguyen, Khoi; Yu, Ning; Bandi, Mahesh M; Venkadesan, Madhusudhan; Mandre, Shreyas
2017-05-01
How fish modulate their fin stiffness during locomotive manoeuvres remains unknown. We show that changing the fin's curvature modulates its stiffness. Modelling the fin as bendable bony rays held together by a membrane, we deduce that fin curvature is manifested as a misalignment of the principal bending axes between neighbouring rays. An external force causes neighbouring rays to bend and splay apart, and thus stretches the membrane. This coupling between bending the rays and stretching the membrane underlies the increase in stiffness. Using three-dimensional reconstruction of a mackerel (Scomber japonicus) pectoral fin for illustration, we calculate the range of stiffnesses this fin is expected to span by changing curvature. The three-dimensional reconstruction shows that, even in its geometrically flat state, a functional curvature is embedded within the fin microstructure owing to the morphology of individual rays. As the ability of a propulsive surface to transmit force to the surrounding fluid is limited by its stiffness, the fin curvature controls the coupling between the fish and its surrounding fluid. Thereby, our results provide mechanical underpinnings and morphological predictions for the hypothesis that the spanned range of fin stiffnesses correlates with the behaviour and the ecological niche of the fish. © 2017 The Author(s).
The behaviour of curvature functions at cusps and inflection points
Shiba, Shohei
2011-01-01
At a 3/2-cusp of a given plane curve $\\gamma(t)$, both of the Euclidean curvature $\\kappa_g$ and the affine curvature $\\kappa_A$ diverge. In this paper, we show that each of $\\sqrt{|s_g|}\\kappa_g$ and $(s_A)^2 \\kappa_A$ (called the Euclidean and affine normalized curvature, respectively) at a 3/2-cusp is a smooth function of the variable $t$, where $s_g$ (resp. $s_A$) is the Euclidean (resp. affine) arclength parameter of the curve corresponding to the 3/2-cusp $s_g=0$ (resp. $s_A=0$). Moreover, we give a characterization of the behaviour of the curvature functions $\\kappa_g$ and $\\kappa_A$ at 3/2-cusps. On the other hand, inflection points are also singular points of curves in affine geometry. We give a similar characterization of affine curvature functions near generic inflection points. As an application, new affine invariants of 3/2-cusps and generic inflection points are given.
Experimental measurement of the Berry curvature from anomalous transport
Wimmer, Martin; Price, Hannah M.; Carusotto, Iacopo; Peschel, Ulf
2017-06-01
The geometric properties of energy bands underlie fascinating phenomena in many systems, including solid-state, ultracold gases and photonics. The local geometric characteristics such as the Berry curvature can be related to global topological invariants such as those classifying the quantum Hall states or topological insulators. Regardless of the band topology, however, any non-zero Berry curvature can have important consequences, such as in the semi-classical evolution of a coherent wavepacket. Here, we experimentally demonstrate that the wavepacket dynamics can be used to directly map out the Berry curvature. To this end, we use optical pulses in two coupled fibre loops to study the discrete time evolution of a wavepacket in a one-dimensional geometric `charge’ pump, where the Berry curvature leads to an anomalous displacement of the wavepacket. This is both the first direct observation of Berry curvature effects in an optical system, and a proof-of-principle demonstration that wavepacket dynamics can serve as a high-resolution tool for mapping out geometric properties.
Curvature and Quantum Mechanics on Covariant Causal Sets
Gudder, Stanley
2015-01-01
This article begins by reviewing the causal set approach in discrete quantum gravity. In our version of this approach a special role is played by covariant causal sets which we call $c$-causets. The importance of $c$-causets is that they support the concepts of a natural distance function, geodesics and curvature in a discrete setting. We then discuss curvature in more detail. By considering $c$-causets with a maximum and minimum number of paths, we are able to find $c$-causets with large and small average curvature. We then briefly discuss our previous work on the inflationary period when the curvature was essentially zero. Quantum mechanics on $c$-causets is considered next. We first introduce a free wave equation for $c$-causets. We then show how the state of a particle with a specified mass (or energy) can be derived from the wave equation. It is demonstrated for small examples that quantum mechanics predicts that particles tend to move toward vertices with larger curvature.
Experimental Measurement of the Berry Curvature from Anomalous Transport
Wimmer, Martin; Carusotto, Iacopo; Peschel, Ulf
2016-01-01
Geometrical properties of energy bands underlie fascinating phenomena in a wide-range of systems, including solid-state materials, ultracold gases and photonics. Most famously, local geometrical characteristics like the Berry curvature can be related to global topological invariants such as those classifying quantum Hall states or topological insulators. Regardless of the band topology, however, any non-zero Berry curvature can have important consequences, such as in the semi-classical evolution of a wave packet. Here, we experimentally demonstrate for the first time that wave packet dynamics can be used to directly map out the Berry curvature. To this end, we use optical pulses in two coupled fibre loops to study the discrete time-evolution of a wave packet in a 1D geometrical "charge" pump, where the Berry curvature leads to an anomalous displacement of the wave packet under pumping. This is both the first direct observation of Berry curvature effects in an optical system, and, more generally, the proof-of-...
Representation of tactile curvature in macaque somatosensory area 2.
Yau, Jeffrey M; Connor, Charles E; Hsiao, Steven S
2013-06-01
Tactile shape information is elaborated in a cortical hierarchy spanning primary (SI) and secondary somatosensory cortex (SII). Indeed, SI neurons in areas 3b and 1 encode simple contour features such as small oriented bars and edges, whereas higher order SII neurons represent large curved contour features such as angles and arcs. However, neural coding of these contour features has not been systematically characterized in area 2, the most caudal SI subdivision in the postcentral gyrus. In the present study, we analyzed area 2 neural responses to embossed oriented bars and curved contour fragments to establish whether curvature representations are generated in the postcentral gyrus. We found that many area 2 neurons (26 of 112) exhibit clear curvature tuning, preferring contours pointing in a particular direction. Fewer area 2 neurons (15 of 112) show preferences for oriented bars. Because area 2 response patterns closely resembled SII patterns, we also compared area 2 and SII response time courses to characterize the temporal dynamics of curvature synthesis in the somatosensory system. We found that curvature representations develop and peak concurrently in area 2 and SII. These results reveal that transitions from orientation tuning to curvature selectivity in the somatosensory cortical hierarchy occur within SI rather than between SI and SII.
Studying biomolecule localization by engineering bacterial cell wall curvature.
Directory of Open Access Journals (Sweden)
Lars D Renner
Full Text Available In this article we describe two techniques for exploring the relationship between bacterial cell shape and the intracellular organization of proteins. First, we created microchannels in a layer of agarose to reshape live bacterial cells and predictably control their mean cell wall curvature, and quantified the influence of curvature on the localization and distribution of proteins in vivo. Second, we used agarose microchambers to reshape bacteria whose cell wall had been chemically and enzymatically removed. By combining microstructures with different geometries and fluorescence microscopy, we determined the relationship between bacterial shape and the localization for two different membrane-associated proteins: i the cell-shape related protein MreB of Escherichia coli, which is positioned along the long axis of the rod-shaped cell; and ii the negative curvature-sensing cell division protein DivIVA of Bacillus subtilis, which is positioned primarily at cell division sites. Our studies of intracellular organization in live cells of E. coli and B. subtilis demonstrate that MreB is largely excluded from areas of high negative curvature, whereas DivIVA localizes preferentially to regions of high negative curvature. These studies highlight a unique approach for studying the relationship between cell shape and intracellular organization in intact, live bacteria.
DEFF Research Database (Denmark)
Meier, Kaare
2014-01-01
pain after failed back surgery syndrome (FBSS)(4), pain due to peripheral nerve injury, stump pain(5), peripheral vascular disease(6) and diabetic neuropathy(7,8); whereas phantom pain(9), postherpetic neuralgia(10), chronic visceral pain(11), and pain after partial spinal cord injury(12) remain more......Spinal cord stimulation (SCS) is a surgical treatment for chronic neuropathic pain that is refractory to other treatment. Originally described by Shealy et al. in 1967(1), it is used to treat a range of conditions such as complex regional pain syndrome (CRPS I)(2), angina pectoris(3), radicular...
Maladaptive spinal plasticity opposes spinal learning and recovery in spinal cord injury
Directory of Open Access Journals (Sweden)
Adam R Ferguson
2012-10-01
Full Text Available Synaptic plasticity within the spinal cord has great potential to facilitate recovery of function after spinal cord injury (SCI. Spinal plasticity can be induced in an activity-dependent manner even without input from the brain after complete SCI. The mechanistic basis for these effects is provided by research demonstrating that spinal synapses have many of the same plasticity mechanisms that are known to underlie learning and memory in the brain. In addition, the lumbar spinal cord can sustain several forms of learning and memory, including limb-position training. However, not all spinal plasticity promotes recovery of function. Central sensitization of nociceptive (pain pathways in the spinal cord may emerge with certain patterns of activity, demonstrating that plasticity within the spinal cord may contribute to maladaptive pain states. In this review we discuss interactions between adaptive and maladaptive forms of activity-dependent plasticity in the spinal cord. The literature demonstrates that activity-dependent plasticity within the spinal cord must be carefully tuned to promote adaptive spinal training. Stimulation that is delivered in a limb position-dependent manner or on a fixed interval can induce adaptive plasticity that promotes future spinal cord learning and reduces nociceptive hyper-reactivity. On the other hand, stimulation that is delivered in an unsynchronized fashion, such as randomized electrical stimulation or peripheral skin injuries, can generate maladaptive spinal plasticity that undermines future spinal cord learning, reduces recovery of locomotor function, and promotes nociceptive hyper-reactivity after spinal cord injury. We review these basic phenomena, discuss the cellular and molecular mechanisms, and discuss implications of these findings for improved rehabilitative therapies after spinal cord injury.
Evolution of curvature perturbation in generalized gravity theories
Energy Technology Data Exchange (ETDEWEB)
Matsuda, Tomohiro, E-mail: matsuda@sit.ac.j [Laboratory of Physics, Saitama Institute of Technology, Fusaiji, Okabe-machi, Saitama 369-0293 (Japan)
2009-07-21
Using the cosmological perturbation theory in terms of the deltaN formalism, we find the simple formulation of the evolution of the curvature perturbation in generalized gravity theories. Compared with the standard gravity theory, a crucial difference appears in the end-boundary of the inflationary stage, which is due to the non-ideal form of the energy-momentum tensor that depends explicitly on the curvature scalar. Recent study shows that ultraviolet-complete quantum theory of gravity (Horava-Lifshitz gravity) can be approximated by using a generalized gravity action. Our paper may give an important step in understanding the evolution of the curvature perturbation during inflation, where the energy-momentum tensor may not be given by the ideal form due to the corrections from the fundamental theory.
Curvature affects Doppler investigation of vessels: implications for clinical practice.
Balbis, S; Roatta, S; Guiot, C
2005-01-01
In clinical practice, blood velocity estimations from Doppler examination of curved vascular segments are normally different from those of nearby straight segments. The observed "accelerations," sometimes considered as a sort of stochastic disturbances, can actually be related to very specific physical effects due to vessel curvature (i.e., the development of nonaxial velocity [NAV] components) and the spreading of the axial velocity direction in the Doppler sample volume with respect to the insonation axis. The relevant phenomena and their dependence on the radius of curvature of the vessels and on the insonation angle are investigated with a beam-vessel geometry as close as possible to clinical setting, with the simplifying assumptions of steady flow, mild vessel curvature, uniform ultrasonic beam and complete vessel insonation. The insonation angles that minimize the errors are provided on the basis of the study results.
Curvature-dependent surface energy and implications for nanostructures
Chhapadia, P.; Mohammadi, P.; Sharma, P.
2011-10-01
At small length scales, several size-effects in both physical phenomena and properties can be rationalized by invoking the concept of surface energy. Conventional theoretical frameworks of surface energy, in both the mechanics and physics communities, assume curvature independence. In this work we adopt a simplified and linearized version of a theory proposed by Steigmann-Ogden to capture curvature-dependence of surface energy. Connecting the theory to atomistic calculations and the solution to an illustrative paradigmatical problem of a bent cantilever beam, we catalog the influence of curvature-dependence of surface energy on the effective elastic modulus of nanostructures. The observation in atomistic calculations that the elastic modulus of bent nanostructures is dramatically different than under tension - sometimes softer, sometimes stiffer - has been a source of puzzlement to the scientific community. We show that the corrected surface mechanics framework provides a resolution to this issue. Finally, we propose an unambiguous definition of the thickness of a crystalline surface.
Two-Dimensional Graphs Moving by Mean Curvature Flow
Institute of Scientific and Technical Information of China (English)
CHEN Jing Yi; LI Jia Yu; TIAN Gang
2002-01-01
A surface Σ is a graph in R4 if there is a unit constant 2-form ω on R4 such that initial surface, then the mean curvature flow has a global solution and the scaled surfaces converge to a self-similar solution. A surface ∑ is a graph in M1 × M2 where M1 and M2 are Riemann surfaces,surface with scalar curvature R, v0 ≥1/√2 on the initial surface, then the mean curvature flow has a global solution and it sub-converges to a minimal surface, if, in addition, R ≥ 0 it converges to a totally geodesic surface which is holomorphic.
Relics of spatial curvature in the primordial non-gaussianity
Energy Technology Data Exchange (ETDEWEB)
Clunan, Tim; Seery, David, E-mail: T.P.Clunan@damtp.cam.ac.uk, E-mail: D.Seery@damtp.cam.ac.uk [Centre for Theoretical Cosmology, Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)
2010-01-01
We study signatures in the Cosmic Microwave Background (CMB) induced by the presence of strong spatial curvature prior to the epoch of inflation which generated our present universe. If inflation does not last sufficiently long to drive the large-scale spatial curvature to zero, then presently observable scales may have left the horizon while spatial slices could not be approximated by a flat, Euclidean geometry. We compute corrections to the power spectrum and non-gaussianity of the CMB temperature anisotropy in this scenario. The power spectrum does not receive significant corrections and is a weak diagnostic of the presence of curvature in the initial conditions, unless its running can be determined with high accuracy. However, the bispectral non-gaussianity parameter f{sub NL} receives modifications on the largest observable scales. We estimate that the maximum signal would correspond to f{sub NL} ∼ 0.3, which is out of reach for present-day microwave background experiments.
Fermi Normal Coordinates and Fermion Curvature Couplings in General Relativity
Dey, Anshuman; Sarkar, Tapobrata
2014-01-01
We study gravitational curvature effects in circular and radial geodesics in static, spherically symmetric space-times, using Fermi normal coordinates. We first set up these coordinates in the general case, and then use this to study effective magnetic fields due to gravitational curvature in the exterior and interior Schwarzschild, Janis-Newman-Winicour, and Bertrand space-times. We show that these fields can be large for specific parameter values in the theories, and thus might have observational significance. We discuss the qualitative differences of the magnetic field for vacuum space-times and for those seeded by matter. We estimate the magnitude of these fields in realistic galactic scenarios and discuss their possible experimental relevance. Gravitational curvature corrections to the Hydrogen atom spectrum for these space-times are also discussed briefly.
Effective inhomogeneous inflation: curvature inhomogeneities of the Einstein vacuum
Energy Technology Data Exchange (ETDEWEB)
Buchert, Thomas [Universite Lyon 1, Centre de Recherche Astrophysique de Lyon, 9 Avenue Charles Andre, F-69230 Saint-Genis-Laval (France); Obadia, Nathaniel, E-mail: buchert@obs.univ-lyon1.fr, E-mail: nathaniel.obadia@ens-lyon.fr [Ecole Normale Superieure de Lyon, Centre de Recherche Astrophysique de Lyon, 46 Allee d' Italie, F-69364 Lyon Cedex 07 (France)
2011-08-21
We consider spatially averaged inhomogeneous universe models and argue that, already in the absence of sources, an effective scalar field arises through foliating and spatially averaging inhomogeneous geometrical curvature invariants of the Einstein vacuum. This scalar field (the 'morphon') acts as an inflaton, if we prescribe a potential of some generic form. We show that, for any initially negative average spatial curvature, the morphon is driven through an inflationary phase and leads-on average-to a spatially flat, homogeneous and isotropic universe model, providing initial conditions for pre-heating and, by the same mechanism, a possibly natural self-exit. (fast track communication)
Quadratic Error Metric Mesh Simplification Algorithm Based on Discrete Curvature
Directory of Open Access Journals (Sweden)
Li Yao
2015-01-01
Full Text Available Complex and highly detailed polygon meshes have been adopted for model representation in many areas of computer graphics. Existing works mainly focused on the quadric error metric based complex models approximation, which has not taken the retention of important model details into account. This may lead to visual degeneration. In this paper, we improve Garland and Heckberts’ quadric error metric based algorithm by using the discrete curvature to reserve more features for mesh simplification. Our experiments on various models show that the geometry and topology structure as well as the features of the original models are precisely retained by employing discrete curvature.
Vertex Normals and Face Curvatures of Triangle Meshes
Sun, Xiang
2016-08-12
This study contributes to the discrete differential geometry of triangle meshes, in combination with discrete line congruences associated with such meshes. In particular we discuss when a congruence defined by linear interpolation of vertex normals deserves to be called a ŉormal’ congruence. Our main results are a discussion of various definitions of normality, a detailed study of the geometry of such congruences, and a concept of curvatures and shape operators associated with the faces of a triangle mesh. These curvatures are compatible with both normal congruences and the Steiner formula.
Horizontal Connection and Horizontal Mean Curvature in Carnot Groups
Institute of Scientific and Technical Information of China (English)
Kang Hai TAN; Xiao Ping YANG
2006-01-01
In this paper we give a geometric interpretation of the notion of the horizontal mean curvature which is introduced by Danielli-Garofalo-Nhieu and Pauls who recently introduced sub-Riemannian minimal surfaces in Carnot groups. This will be done by introducing a natural nonholonomic connection which is the restriction (projection) of the natural Riemannian connection on the horizontal bundle. For this nonholonomic connection and (intrinsic) regular hypersurfaces we introduce the notions of the horizontal second fundamental form and the horizontal shape operator. It turns out that the horizontal mean curvature is the trace of the horizontal shape operator.
Visualizing Spacetime Curvature via Gradient Flows I: Introduction
Lake, Kayll
2012-01-01
Traditional approaches to the study of the dynamics of spacetime curvature in a very real sense hide the intricacies of the nonlinear regime. Whether it be huge formulae, or mountains of numerical data, standard methods of presentation make little use of our remarkable skill, as humans, at pattern recognition. Here we introduce a new approach to the visualization of spacetime curvature. We examine the flows associated with the gradient fields of invariants derived from the spacetime. These flows reveal a remarkably rich structure, and offer fresh insights even for well known analytical solutions to Einstein's equations. This paper serves as an overview and as an introduction to this approach.
Sectional Curvature Bounds in Gravity: Regularisation of the Schwarzschild Solution
Schuller, F P; Schuller, Frederic P.; Wohlfarth, Mattias N.R.
2004-01-01
A general geometrical scheme is presented for the construction of novel classical gravity theories whose solutions obey two-sided bounds on the sectional curvatures along certain subvarieties of the Grassmannian of two-planes. The motivation to study sectional curvature bounds comes from their equivalence to bounds on the acceleration between nearby geodesics. A universal minimal length scale is a necessary ingredient of the construction, and an application of the kinematical framework to static, spherically symmetric spacetimes shows drastic differences to the Schwarzschild solution of general relativity by the exclusion of spacelike singularities.
Sectional curvature bounds in gravity: regularisation of the Schwarzschild singularity
Energy Technology Data Exchange (ETDEWEB)
Schuller, Frederic P. [Perimeter Institute for Theoretical Physics, Waterloo N2J 2W9, Ontario (Canada)]. E-mail: fschuller@perimeterinstitute.ca; Wohlfarth, Mattias N.R. [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)]. E-mail: m.n.r.wohlfarth@damtp.cam.ac.uk
2004-10-18
A general geometrical scheme is presented for the construction of novel classical gravity theories whose solutions obey two-sided bounds on the sectional curvatures along certain subvarieties of the Grassmannian of two-planes. The motivation to study sectional curvature bounds comes from their equivalence to bounds on the acceleration between nearby geodesics. A universal 'minimal length' scale is a necessary ingredient of the construction, and an application of the kinematical framework to static, spherically symmetric spacetimes shows drastic differences to the Schwarzschild solution of general relativity by the exclusion of spacelike singularities.
Mixed-symmetry multiplets and higher-spin curvatures
Bekaert, Xavier; Francia, Dario
2015-01-01
We study the higher-derivative equations for gauge potentials of arbitrary mixed-symmetry type obtained by setting to zero the divergences of the corresponding curvature tensors. We show that they propagate the same reducible multiplets as the Maxwell-like second-order equations for gauge fields subject to constrained gauge transformations. As an additional output of our analysis, we provide a streamlined presentation of the Ricci-like case, where the traces of the same curvature tensors are set to zero, and we present a simple algebraic evaluation of the particle content associated with the Labastida and with the Maxwell-like second-order equations.
String theory triplets and higher-spin curvatures
Francia, Dario
2010-01-01
Unconstrained local Lagrangians for higher-spin gauge theories are bound to involve auxiliary fields, whose integration in the partition function generates geometric, effective actions expressed in terms of curvatures. When applied to the triplets, emerging from the tensionless limit of open string field theory, the same procedure yields interesting alternative forms of geometric Lagrangians, whose rather simple pattern is essentially the same for bosons and fermions. This shows that higher-spin curvatures might play a role in the dynamics, regardless of whether the Fronsdal-Labastida constraints are assumed or not.
String theory triplets and higher-spin curvatures
Energy Technology Data Exchange (ETDEWEB)
Francia, Dario, E-mail: francia@apc.univ-paris7.f [AstroParticule et Cosmologie (APC), Universite Paris VII - Campus Paris Rive Gauche, 10, rue Alice Domon et Leonie Duquet, F-75205 Paris Cedex 13 (France)
2010-06-07
Unconstrained local Lagrangians for higher-spin gauge theories are bound to involve auxiliary fields, whose integration in the partition function generates geometric, effective actions expressed in terms of curvatures. When applied to the triplets, emerging from the tensionless limit of open string field theory, the same procedure yields interesting alternative forms of geometric Lagrangians, expressible for both bosons and fermions as squares of field-strengths. This shows that higher-spin curvatures might play a role in the dynamics, regardless of whether the Fronsdal-Labastida constraints are assumed or forgone.
Rupture of the lesser gastric curvature after a Heimlich maneuver.
Gallardo, A; Rosado, R; Ramírez, D; Medina, P; Mezquita, S; Sánchez, J
2003-09-01
We present a case of lesser gastric curvature injury after a Heimlich maneuver due to obstruction of the breathing tract that was repaired by laparoscopic surgery. A patient with perforation of the lesser gastric curvature as a result of closed abdominal traumatism was operated on using the laparoscopic approach with the use of four trocars as work openings. With this technique, the diagnosis was confirmed, the injury repaired, and the abdominal cavity washed. The postoperative period was favorable and the patient was released from the hospital on day 7 without any complications. Laparoscopic surgery can be technically reproduced in the treatment of gastric injury as a result of closed abdominal traumatism.
Maladaptive spinal plasticity opposes spinal learning and recovery in spinal cord injury
Ferguson, Adam R.; Huie, J. Russell; Crown, Eric D.; Baumbauer, Kyle M.; Hook, Michelle A.; Garraway, Sandra M.; Lee, Kuan H.; Hoy, Kevin C.; Grau, James W.
2012-01-01
Synaptic plasticity within the spinal cord has great potential to facilitate recovery of function after spinal cord injury (SCI). Spinal plasticity can be induced in an activity-dependent manner even without input from the brain after complete SCI. A mechanistic basis for these effects is provided by research demonstrating that spinal synapses have many of the same plasticity mechanisms that are known to underlie learning and memory in the brain. In addition, the lumbar spinal cord can sustain several forms of learning and memory, including limb-position training. However, not all spinal plasticity promotes recovery of function. Central sensitization of nociceptive (pain) pathways in the spinal cord may emerge in response to various noxious inputs, demonstrating that plasticity within the spinal cord may contribute to maladaptive pain states. In this review we discuss interactions between adaptive and maladaptive forms of activity-dependent plasticity in the spinal cord below the level of SCI. The literature demonstrates that activity-dependent plasticity within the spinal cord must be carefully tuned to promote adaptive spinal training. Prior work from our group has shown that stimulation that is delivered in a limb position-dependent manner or on a fixed interval can induce adaptive plasticity that promotes future spinal cord learning and reduces nociceptive hyper-reactivity. On the other hand, stimulation that is delivered in an unsynchronized fashion, such as randomized electrical stimulation or peripheral skin injuries, can generate maladaptive spinal plasticity that undermines future spinal cord learning, reduces recovery of locomotor function, and promotes nociceptive hyper-reactivity after SCI. We review these basic phenomena, how these findings relate to the broader spinal plasticity literature, discuss the cellular and molecular mechanisms, and finally discuss implications of these and other findings for improved rehabilitative therapies after SCI. PMID
DEFF Research Database (Denmark)
Meier, Kaare
2014-01-01
pain after failed back surgery syndrome (FBSS)(4), pain due to peripheral nerve injury, stump pain(5), peripheral vascular disease(6) and diabetic neuropathy(7,8); whereas phantom pain(9), postherpetic neuralgia(10), chronic visceral pain(11), and pain after partial spinal cord injury(12) remain more...
Barczyk-Pawelec, Katarzyna; Sipko, Tomasz
2017-10-01
Evidence is limited regarding the regional changes in spinal posture after self-correction. The aim of the present study was to evaluate whether active self-correction improved standing and sitting spinal posture. Photogrammetry was used to assess regional spinal curvatures and vertical global spine orientation (GSO) in 42 asymptotic women aged 20-24 years. Upper thoracic spine angle and GSO increased in response to self-correction, while the thoracolumbar and lumbosacral angles decreased. Self-correction in the standing position resulted in decreased inclination of the upper thoracic and thoracolumbar spinal angles. Correction of sitting posture reduced the angle of the upper thoracic spine and GSO. The effects of active self-correction on spinal curvature and GSO were different for the standing versus sitting position; the greatest effects of active correction were noted in the thoracic spine. Balanced and lordotic postures were most prevalent in the habitual and actively self-corrected standing positions, whereas the kyphotic posture was most prevalent in the habitual sitting position, indicative that self-correction back posture in the standing position could be an important health-related daily activity, especially during prolonged sitting.
Bagshaw, S. L.; Cleland, R. E.
1990-01-01
Gravitropic curvature results from unequal growth rates on the upper and lower sides of horizontal stems. These unequal growth rates could be due to differences in wall extensibility between the two sides. To test this, the time course of curvature of horizontal sunflower (Helianthus annuus L.) hypocotyls was determined and compared with the time courses of changes in Instron-measured wall extensibility (PEx) of the upper and lower epidermal layers. As gravicurvature developed, so did the difference in PEx between the upper and lower epidermis. The enhanced growth rate on the lower side during the period of maximum increase in curvature was matched by PEx values greater than those of the vertical control, while the inhibited growth rate on the upper side was accompanied by PEx values below that of the control. The close correlation between changes in growth rates and alterations in PEx demonstrates that changes in wall extensibility play a major role in controlling gravicurvature.
Defining the Free-Energy Landscape of Curvature-Inducing Proteins on Membrane Bilayers
Tourdot, Richard W; Radhakrishnan, Ravi
2015-01-01
Curvature-sensing and curvature-remodeling proteins are known to reshape cell membranes, and this remodeling event is essential for key biophysical processes such as tubulation, exocytosis, and endocytosis. Curvature-inducing proteins can act as curvature sensors as well as induce curvature in cell membranes to stabilize emergent high curvature, non-spherical, structures such as tubules, discs, and caveolae. A definitive understanding of the interplay between protein recruitment and migration, the evolution of membrane curvature, and membrane morphological transitions is emerging but remains incomplete. Here, within a continuum framework and using the machinery of Monte Carlo simulations, we introduce and compare three free-energy methods to delineate the free-energy landscape of curvature-inducing proteins on bilayer membranes. We demonstrate the utility of the Widom test-particle/field insertion methodology in computing the excess chemical potentials associated with curvature-inducing proteins on the membra...
Spinal lordosis optimizes the requirements for a stable erect posture.
Wagner, Heiko; Liebetrau, Anne; Schinowski, David; Wulf, Thomas; de Lussanet, Marc H E
2012-04-16
Lordosis is the bending of the lumbar spine that gives the vertebral column of humans its characteristic ventrally convex curvature. Infants develop lordosis around the time when they acquire bipedal locomotion. Even macaques develop a lordosis when they are trained to walk bipedally. The aim of this study was to investigate why humans and some animals develop a lumbar lordosis while learning to walk bipedally. We developed a musculoskeletal model of the lumbar spine, that includes an asymmetric, dorsally shifted location of the spinal column in the body, realistic moment arms, and physiological cross-sectional areas (PCSA) of the muscles as well as realistic force-length and force-velocity relationships. The model was used to analyze the stability of an upright body posture. According to our results, lordosis reduces the local joint torques necessary for an equilibrium of the vertebral column during an erect posture. At the same time lordosis increases the demands on the global muscles to provide stability. We conclude that the development of a spinal lordosis is a compromise between the stability requirements of an erect posture and the necessity of torque equilibria at each spinal segment.
Spinal lordosis optimizes the requirements for a stable erect posture
Directory of Open Access Journals (Sweden)
Wagner Heiko
2012-04-01
Full Text Available Abstract Background Lordosis is the bending of the lumbar spine that gives the vertebral column of humans its characteristic ventrally convex curvature. Infants develop lordosis around the time when they acquire bipedal locomotion. Even macaques develop a lordosis when they are trained to walk bipedally. The aim of this study was to investigate why humans and some animals develop a lumbar lordosis while learning to walk bipedally. Results We developed a musculoskeletal model of the lumbar spine, that includes an asymmetric, dorsally shifted location of the spinal column in the body, realistic moment arms, and physiological cross-sectional areas (PCSA of the muscles as well as realistic force-length and force-velocity relationships. The model was used to analyze the stability of an upright body posture. According to our results, lordosis reduces the local joint torques necessary for an equilibrium of the vertebral column during an erect posture. At the same time lordosis increases the demands on the global muscles to provide stability. Conclusions We conclude that the development of a spinal lordosis is a compromise between the stability requirements of an erect posture and the necessity of torque equilibria at each spinal segment.
Curvature Properties of Lorentzian Manifolds with Large Isometry Groups
Energy Technology Data Exchange (ETDEWEB)
Batat, Wafaa [Ecole Normale Superieure de L' Enseignement Technique d' Oran, Departement de Mathematiques et Informatique (Algeria)], E-mail: wafa.batat@enset-oran.dz; Calvaruso, Giovanni, E-mail: giovanni.calvaruso@unile.it; Leo, Barbara De [University of Salento, Dipartimento di Matematica ' E. De Giorgi' (Italy)], E-mail: barbara.deleo@unile.it
2009-08-15
The curvature of Lorentzian manifolds (M{sup n},g), admitting a group of isometries of dimension at least 1/2n(n - 1) + 1, is completely described. Interesting behaviours are found, in particular as concerns local symmetry, local homogeneity and conformal flatness.
Controlling Protein Oligomerization with Surface Curvature on the Nanoscale
Kurylowicz, Marty; Dutcher, John
2011-03-01
We investigate the effect of surface curvature on the conformation of beta-lactoglobulin (β LG) using Single Molecule Force Spectroscopy. β LG is a model interfacial protein which stabilizes oil droplets in milk and is known to undergo structural rearrangement when adsorbed onto a surface. We reliably control nanoscale surface curvature by creating close-packed monolayers of monodisperse polystyrene (PS) nanoparticles with diameters of 20, 40, 60, 80 and 140 nm, which are stable in aqueous buffer. By adsorbing β LG onto these hydrophobic surfaces and collecting force-extension curves in the fluid phase we can compare the conformation of β LG on 5 different surface curvatures with that on a flat PS film. We demonstrate a transition from oligomeric to monomeric β LG as the surface curvature is increased. Histograms of contour length from fits to peaks in the force-extension curves show a single maximum near 30 nm for β LG adsorbed onto nanoparticles with diameters less than 80 nm. For the larger nanoparticles, the histogram approaches that observed for β LG adsorbed onto a flat PS film, with maxima indicative of β LG dimers and trimers.
CURVATURE-DEPENDENT PARAMETERIZATION OF CURVES AND SURFACES
KOSTERS, M
1991-01-01
An efficient way of drawing parametric curves and surfaces is to approximate the curve or surface by a sequence of straight-line segments or a mesh of polygons, respectively. In such an approximation, many small line segments or polygons are needed in regions of high curvature, and fewer and larger
Cosmological models with positive scalar spatial curvature and Λ>0
Ponce de Leon, J.
1987-12-01
Some exact spherically symmetric solutions of the Einstein field equations with Λ>0 and positive three-curvature are given. They have reasonable physical properties and represent universes which do not undergo inflation but have a non-de Sitter behaviour for large times. This paper extends some previous results in the literature. Permanent address: Apartado 2816, Caracas 1010-A, Venezuela.
The Dynamics of Pendulums on Surfaces of Constant Curvature
Energy Technology Data Exchange (ETDEWEB)
Coulton, P. [Eastern Illinois University, Mathematics Department (United States)], E-mail: prcoulton@eiu.edu; Foote, R. [Wabash College (United States)], E-mail: footer@wabash.edu; Galperin, G. [Eastern Illinois University, Mathematics Department (United States)], E-mail: ggalperin@eiu.edu
2009-05-15
We define the notion of a pendulum on a surface of constant curvature and study the motion of a mass at a fixed distance from a pivot. We consider some special cases: first a pivot that moves with constant speed along a geodesic, and then a pivot that undergoes acceleration along a fixed geodesic.
Curvature-induced symmetry breaking in nonlinear Schrodinger models
DEFF Research Database (Denmark)
Gaididei, Yuri Borisovich; Mingaleev, S. F.; Christiansen, Peter Leth
2000-01-01
We consider a curved chain of nonlinear oscillators and show that the interplay of curvature and nonlinearity leads to a symmetry breaking when an asymmetric stationary state becomes energetically more favorable than a symmetric stationary state. We show that the energy of localized states decrea...
Soliton surfaces via zero-curvature representation of differential equations
Grundland, A M
2011-01-01
The main aim of this paper is to introduce a new version of the Fokas-Gel'fand formula for immersion of surfaces in Lie algebras. The paper contains a detailed exposition of the technique for obtaining exact forms of surfaces associated with any solution of a given nonlinear ordinary differential equation (ODE) which can be written in zero-curvature form. That is, for any generalized symmetry of the zero-curvature condition of the associated integrable model, it is possible to construct soliton surfaces whose Gauss-Mainardi-Codazzi equations are equivalent to infinitesimal deformations of the zero-curvature representation of the considered model. Conversely, it is shown (Proposition 1) that for a given immersion function of a 2D-soliton surface in a Lie algebra, it possible to derive the associated generalized vector field in evolutionary form which characterizes all symmetries of the zero-curvature condition. The theoretical considerations are illustrated via surfaces associated with the Painlev\\'e equations...
Other Earths: Search for Life and the Constant Curvature
Directory of Open Access Journals (Sweden)
Khoshyaran M. M.
2015-07-01
Full Text Available The objective of this paper is to propose a search methodology for finding other exactly similar earth like planets (or sister earths. The theory is based on space consisting of Riemann curves or highways. A mathematical model based on constant curvature, a moving frame bundle, and gravitational dynamics is introduced.
Are all forces due to spin-curvature coupling
Energy Technology Data Exchange (ETDEWEB)
Harris, E.G. (Tennessee Univ., Knoxville (USA). Dept. of Physics and Astronomy)
1980-02-11
Starting from the Dirac equation for a particle in a gravitational field and an arbitrary gauge field, the Heisenberg and classical equations of motion are derived. The force term is a generalization of the Lorentz force. It may be interpreted as the interaction between a generalized spin and the curvature of a fiber bundle.
Quasi-Maxwell interpretation of the spin-curvature coupling
Natario, Jose
2007-01-01
We write the Mathisson-Papapetrou equations of motion for a spinning particle in a stationary spacetime using the quasi-Maxwell formalism and give an interpretation of the coupling between spin and curvature. The formalism is then used to compute equilibrium positions for spinning particles in the NUT spacetime.
Quasi-Maxwell interpretation of the spin-curvature coupling
Natário, José
2007-09-01
We write the Mathisson-Papapetrou equations of motion for a spinning particle in a stationary spacetime using the quasi-Maxwell formalism and give an interpretation of the coupling between spin and curvature. The formalism is then used to compute equilibrium positions for spinning particles in the NUT spacetime.
Continuous-Curvature Path Generation Using Fermat's Spiral
Directory of Open Access Journals (Sweden)
Anastasios M. Lekkas
2013-10-01
Full Text Available This paper proposes a novel methodology, based on Fermat's spiral (FS, for constructing curvature-continuous parametric paths in a plane. FS has a zero curvature at its origin, a property that allows it to be connected with a straight line smoothly, that is, without the curvature discontinuity which occurs at the transition point between a line and a circular arc when constructing Dubins paths. Furthermore, contrary to the computationally expensive clothoids, FS is described by very simple parametric equations that are trivial to compute. On the downside, computing the length of an FS arc involves a Gaussian hypergeometric function. However, this function is absolutely convergent and it is also shown that it poses no restrictions to the domain within which the length can be calculated. In addition, we present an alternative parametrization of FS which eliminates the parametric speed singularity at the origin, hence making the spiral suitable for path-tracking applications. A detailed description of how to construct curvature-continuous paths with FS is given.
Phase error correction in wavefront curvature sensing via phase retrieval
DEFF Research Database (Denmark)
Almoro, Percival; Hanson, Steen Grüner
2008-01-01
Wavefront curvature sensing with phase error correction system is carried out using phase retrieval based on a partially-developed volume speckle field. Various wavefronts are reconstructed: planar, spherical, cylindrical, and a wavefront passing through the side of a bare optical fiber. Spurious...
Active optics for high-dynamic variable curvature mirrors
Hugot, Emmanuel; Lemaitre, Gerard R; Madec, Fabrice; Vives, Sebastien; Chardin, Elodie; Mignant, David Le; Cuby, Jean Gabriel
2014-01-01
Variable curvature mirrors of large amplitude are designed by using finite element analysis. The specific case studied reaches at least a 800 {\\mu}m sag with an optical quality better than {\\lambda}/5 over a 120 mm clear aperture. We highlight the geometrical nonlinearity and the plasticity effect.
Flow by Mean Curvature inside a Moving Ambient Space
Magni, Annibale; Tsatis, Efstratios
2013-01-01
We show some computations related in particular to the motion by mean curvature flow of a submanifold inside an ambient Riemannian manifold evolving by Ricci or backward Ricci flow. Special emphasis is given to the analogous of Huisken's monotonicity formula and its connection with the validity of some Li-Yau-Hamilton Harnack-type inequalities in a moving manifold.
Equilibrium models of coronal loops that involve curvature and buoyancy
Hindman, Bradley W
2013-01-01
We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios.
Equilibrium Models of Coronal Loops That Involve Curvature and Buoyancy
Hindman, Bradley W.; Jain, Rekha
2013-12-01
We construct magnetostatic models of coronal loops in which the thermodynamics of the loop is fully consistent with the shape and geometry of the loop. This is achieved by treating the loop as a thin, compact, magnetic fibril that is a small departure from a force-free state. The density along the loop is related to the loop's curvature by requiring that the Lorentz force arising from this deviation is balanced by buoyancy. This equilibrium, coupled with hydrostatic balance and the ideal gas law, then connects the temperature of the loop with the curvature of the loop without resorting to a detailed treatment of heating and cooling. We present two example solutions: one with a spatially invariant magnetic Bond number (the dimensionless ratio of buoyancy to Lorentz forces) and the other with a constant radius of the curvature of the loop's axis. We find that the density and temperature profiles are quite sensitive to curvature variations along the loop, even for loops with similar aspect ratios.
On the Curvature and Heat Flow on Hamiltonian Systems
Directory of Open Access Journals (Sweden)
Ohta Shin-ichi
2014-01-01
Full Text Available We develop the differential geometric and geometric analytic studies of Hamiltonian systems. Key ingredients are the curvature operator, the weighted Laplacian, and the associated Riccati equation.We prove appropriate generalizations of the Bochner-Weitzenböck formula and Laplacian comparison theorem, and study the heat flow.
Intracellular magnetophoresis of amyloplasts and induction of root curvature
Kuznetsov, O. A.; Hasenstein, K. H.
1996-01-01
High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, delta(H2/2), was about 10(9) Oe2.cm-1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 +/- 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 +/- 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.
Non-minimal curvature-matter couplings in modified gravity
Bertolami, Orfeu; Lobo, Francisco S N; Páramos, Jorge
2008-01-01
Recently, in the context of f(R) modified theories of gravity, it was shown that a curvature-matter coupling induces a non-vanishing covariant derivative of the energy-momentum, implying non-geodesic motion and, under appropriate conditions, leading to the appearance of an extra force. We study the implications of this proposal and discuss some directions for future research.
Positivity of Curvature-Squared Corrections in Gravity
Cheung, Clifford
2016-01-01
We study the Gauss-Bonnet (GB) term as the leading higher-curvature correction to pure Einstein gravity. Assuming a tree-level ultraviolet completion free of ghosts or tachyons, we prove that the GB term has a nonnegative coefficient in dimensions greater than four. Our result follows from unitarity of the spectral representation for a general ultraviolet completion of the GB term.
Supported lipid bilayers with controlled curvature via colloidal lithography
DEFF Research Database (Denmark)
Sundh, Maria; Manandhar, Michal; Svedhem, Sofia
2011-01-01
Supported lipid bilayers (SLBs) at surfaces provide a route to quantitatively study molecular interactions with and at lipid membranes via different surface-based analytical techniques. Here, a method to fabricate SLBs with controlled curvatures, in the nanometer regime over large areas, is prese...
Positivity of Curvature-Squared Corrections in Gravity.
Cheung, Clifford; Remmen, Grant N
2017-02-03
We study the Gauss-Bonnet (GB) term as the leading higher-curvature correction to pure Einstein gravity. Assuming a tree-level ultraviolet completion free of ghosts or tachyons, we prove that the GB term has a nonnegative coefficient in dimensions greater than 4. Our result follows from unitarity of the spectral representation for a general ultraviolet completion of the GB term.
The Affine Complete Hypersurfaces of Constant Gauss-Kronecker Curvature
Institute of Scientific and Technical Information of China (English)
Bao Fu WANG
2009-01-01
Given a bounded convex domain Ω with C∞ boundary and a function φ∈ C∞ ( partial deriv Ω), Li-Simon-Chen can construct an Euclidean complete and W-complete convex hypersurface M with constant affine Gauss-Kronecker curvature, and they guess the M is also affine complete. In this paper, we give a confirmation answer.
Generalized Curvature-Matter Couplings in Modified Gravity
Directory of Open Access Journals (Sweden)
Tiberiu Harko
2014-07-01
Full Text Available In this work, we review a plethora of modified theories of gravity with generalized curvature-matter couplings. The explicit nonminimal couplings, for instance, between an arbitrary function of the scalar curvature R and the Lagrangian density of matter, induces a non-vanishing covariant derivative of the energy-momentum tensor, implying non-geodesic motion and, consequently, leads to the appearance of an extra force. Applied to the cosmological context, these curvature-matter couplings lead to interesting phenomenology, where one can obtain a unified description of the cosmological epochs. We also consider the possibility that the behavior of the galactic flat rotation curves can be explained in the framework of the curvature-matter coupling models, where the extra terms in the gravitational field equations modify the equations of motion of test particles and induce a supplementary gravitational interaction. In addition to this, these models are extremely useful for describing dark energy-dark matter interactions and for explaining the late-time cosmic acceleration.
The Paneitz curvature problem on lower dimensional spheres
Ben-Ayed, M
2003-01-01
In this paper we prescribe a fourth order conformal invariant (the Paneitz curvature) on the n-spheres, with n is an element of left brace 5, 6 right brace. Using dynamical and topological methods involving the study of critical points at infinity of the associated variational problem, we prove some existence results.
11 A METHOD FOR WAVEFRONT CURVATURE RANGING OF ...
African Journals Online (AJOL)
algorithm estimates the curvature of the incident wavefront of the source with ... A narrow-band (NB) filter is used to increase the SNR of the measured signal ..... oCher-scua:s cootn'bute to the varimce about this mean. This property forms the ...
In vitro dimensions and curvatures of human lenses.
Rosen, Alexandre M; Denham, David B; Fernandez, Viviana; Borja, David; Ho, Arthur; Manns, Fabrice; Parel, Jean-Marie; Augusteyn, Robert C
2006-03-01
The purpose of this study was to determine dimensions and curvatures of excised human lenses using the technique of shadowphotogrammetry. A modified optical comparator and digital camera were used to photograph magnified sagittal and coronal lens profiles. Equatorial diameter, anterior and posterior sagittal thickness, anterior and posterior curvatures, and shape factors were obtained from these images. The data were used to calculate lens volumes, which were compared with the lens weights. Measurements were made on 37 human lenses ranging in age from 20 to 99 years. These showed that lens dimensions and the anterior radius of curvature increase linearly throughout adult life while posterior curvature remains constant. The relative shape (or aspect ratio) of the posterior lens is unchanged through adult life since both equatorial diameter and posterior thickness increase at the same rate. The ratio of anterior thickness to posterior thickness is constant at 0.70. It is suggested that in vivo forces alter the apparent location of the lens equator, that the in vitro lens shape corresponds to the maximally accommodated shape in vivo and that the shapes of the accommodated and unaccommodated lens progressively converge toward each other due to lens growth with age, with a convergence point located near the age of total loss of accommodation (55-60 years). Together, these observations provide additional support for the Helmholtz theory of accommodation.
Harnack inequality for the negative power Gaussian curvature flow
Li, Yi
2011-01-01
In this paper, we study the power of Gaussian curvature flow of a compact convex hypersurface and establish its Harnack inequality when the power is negative. In the Harnack inequality, we require that the absolute value of the power is strictly positive and strictly less than the inverse of the dimension of the hypersurface.
The Bernoulli jets and the zero mean curvature equation
Valdinoci, E
2005-01-01
We consider an elliptic PDE problem related with fluid mechanics. We show that level sets of rescaled solutions satisfy the zero mean curvature equation in a suitable weak viscosity sense. In particular, such level sets cannot be touched by below (above) by a convex (concave) paraboloid in a suitably small neighborhood.
Enhancement of damage indicators in wavelet and curvature analysis
Indian Academy of Sciences (India)
B K Raghu Prasad; N Lakshmanan; K Muthumani; N Gopalakrishnan
2006-08-01
Damage in a structural element induces a small perturbation in its static or dynamic displacement proﬁle which can be captured by wavelet analysis. The paper presents the wavelet analysis of damaged linear structural elements using DB4 or BIOR6·8 family of wavelets. An expression is developed for computing the natural frequencies of a damaged beam using ﬁrst order perturbation theory. Starting with a localized reduction of EI at the mid-span of a simply supported beam, damage modelling is done for a typical steel beam element. Wavelet analysis is performed for this damage model for displacement, rotation and curvature mode shapes as well as static displacement proﬁles. Damage indicators like displacement, slope and curvature are magniﬁed under higher modes. Instantaneous step-wise linearity is assumed for all the nonlinear elements. A localization scheme with arbitrararily located curvature nodes within a pseudo span is developed for steady state dynamic loads, such that curvature response and damages are maximized and the scheme is numerically tested and proved.
The effect of anterior cruciate ligament injury on bone curvature
DEFF Research Database (Denmark)
Hunter, D J; Lohmander, Stefan; Makovey, J
2014-01-01
OBJECTIVE: Investigate the 5-year longitudinal changes in bone curvature after acute anterior cruciate ligament (ACL) injury, and identify predictors of such changes. METHODS: In the KANON-trial (ISRCTN 84752559), 111/121 young active adults with an acute ACL tear to a previously un-injured knee ...
Effect of asymmetric auxin application on Helianthus hypocotyl curvature
Migliaccio, F.; Rayle, D. L.
1989-01-01
Indole-3-acetic acid was applied asymmetrically to the hypocotyls of sunflower (Helianthus annuus L.) seedlings. After 5 hours on a clinostat, auxin gradients as small as 1 to 1.3 produced substantial (more than 60 degrees) hypocotyl curvature. This result suggests the asymmetric growth underlying hypocotyl gravitropism can be explained by lateral auxin redistribution.
Negative voltage bandgap reference with multilevel curvature compensation technique
Xi, Liu; Qian, Liu; Xiaoshi, Jin; Yongrui, Zhao; Lee, Jong-Ho
2016-05-01
A novel high-order curvature compensation negative voltage bandgap reference (NBGR) based on a novel multilevel compensation technique is introduced. Employing an exponential curvature compensation (ECC) term with many high order terms in itself, in a lower temperature range (TR) and a multilevel curvature compensation (MLCC) term in a higher TR, a flattened and better effect of curvature compensation over the TR of 165 °C (-40 to 125 °C) is realised. The MLCC circuit adds two convex curves by using two sub-threshold operated NMOS. The proposed NBGR implemented in the Central Semiconductor Manufacturing Corporation (CSMC) 0.5 μm BCD technology demonstrates an accurate voltage of -1.183 V with a temperature coefficient (TC) as low as 2.45 ppm/°C over the TR of 165 °C at a -5.0 V power supply; the line regulation is 3 mV/V from a -5 to -2 V supply voltage. The active area of the presented NBGR is 370 × 180 μm2. Project supported by the Fund of Liaoning Province Education Department (No. L2013045).
Remarks on the boundary curve of a constant mean curvature topological disc
DEFF Research Database (Denmark)
Brander, David; Lopéz, Rafael
2017-01-01
We discuss some consequences of the existence of the holomorphic quadratic Hopf differential on a conformally immersed constant mean curvature topological disc with analytic boundary. In particular, we derive a formula for the mean curvature as a weighted average of the normal curvature of the bo......We discuss some consequences of the existence of the holomorphic quadratic Hopf differential on a conformally immersed constant mean curvature topological disc with analytic boundary. In particular, we derive a formula for the mean curvature as a weighted average of the normal curvature...
Differential diagnoses of spinal tumors; Differenzialdiagnose spinaler Tumoren
Energy Technology Data Exchange (ETDEWEB)
Yilmaz, U. [Universitaetsklinikum des Saarlandes, Klinik fuer Diagnostische und Interventionelle Neuroradiologie, Homburg/Saar (Germany)
2011-12-15
A wide variety of degenerative, inflammatory and vascular diseases can resemble the clinical presentation and imaging findings of spinal tumors. This article provides an overview of the most frequent diseases which are important to recognize for diagnostic imaging of the spine. (orig.) [German] Eine Vielzahl degenerativer, entzuendlicher und vaskulaerer Erkrankungen kann das klinische Bild und radiologische Befunde spinaler Tumoren imitieren. Dieser Artikel dient der Uebersicht ueber die haeufigsten dieser Erkrankungen, deren Kenntnis wichtig fuer die spinale Bildgebung ist. (orig.)
Spinal Cord Monitoring Data in Pediatric Spinal Deformity Patients With Spinal Cord Pathology.
Aleem, Alexander W; Thuet, Earl D; Padberg, Anne M; Wallendorf, Michael; Luhmann, Scott J
2015-01-01
Retrospective. The purpose of this study is to review the efficacy of monitoring data and outcomes in pediatric patients with spinal cord pathology. The incidence of spinal cord pathology in pediatric patients with scoliosis has been reported between 3% and 20%. Previous studies demonstrated that intraoperative spinal cord monitoring (IOM) during scoliosis surgery can be reliable despite underlying pathology. A single-center retrospective review of 119 spinal surgery procedures in 82 patients with spinal cord pathology was performed. Diagnoses included Arnold-Chiari malformation, syringomyelia, myelomeningocele, spinal cord tumor, tethered cord, and diastematomyelia. Baseline neurologic function and history of prior neurosurgical intervention were identified. Outcome measures included ability to obtain reliable monitoring data during surgery and presence of postoperative neurologic deficits. Results were compared for 82 patients with adolescent idiopathic scoliosis (AIS). Usable IOM data were obtained in 82% of cases (97/119). Twenty-two cases (18%) had no lower extremity data. Patients with Arnold-Chiari malformation or syringomyelia pathologies, in isolation or together, had a significantly higher rate of reliable data compared to other pathologies (p < .0001). Among study group cases with usable data, there were 1 false negative (1%) and 4 true positive (4%) outcomes. There were no permanent neurologic deficits. The spinal cord pathology group demonstrated 80% sensitivity and 92% specificity. Spinal cord monitoring is a valuable tool in pediatric patients with spinal cord pathology undergoing spinal deformity surgeries. When obtained, data allow to detect changes in spinal cord function. Patients with a diagnosis of Arnold-Chiari or syringomyelia have monitoring data similar to those patients with AIS. Patients with other spinal cord pathologies have less reliable data, and surgeons should have a lower threshold for performing wake-up tests to assess spinal cord
Imaging of Spinal Metastatic Disease
Directory of Open Access Journals (Sweden)
Lubdha M. Shah
2011-01-01
Full Text Available Metastases to the spine can involve the bone, epidural space, leptomeninges, and spinal cord. The spine is the third most common site for metastatic disease, following the lung and the liver. Approximately 60–70% of patients with systemic cancer will have spinal metastasis. Materials/Methods. This is a review of the imaging techniques and typical imaging appearances of spinal metastatic disease. Conclusions. Awareness of the different manifestations of spinal metastatic disease is essential as the spine is the most common site of osseous metastatic disease. Imaging modalities have complimentary roles in the evaluation of spinal metastatic disease. CT best delineates osseous integrity, while MRI is better at assessing soft tissue involvement. Physiologic properties, particularly in treated disease, can be evaluated with other imaging modalities such as FDG PET and advanced MRI sequences. Imaging plays a fundamental role in not only diagnosis but also treatment planning of spinal metastatic disease.
Transverse myelitis following spinal anesthesia
Directory of Open Access Journals (Sweden)
Jha Sanjeev
2006-01-01
Full Text Available Spinal anesthesia is widely used during surgical procedures. It is generally safe and the frequency of severe, permanent neurological complications associated with it has been reported to be extremely low. We report a patient, who developed paraplegia following spinal anesthesia. A 29-year-old male was referred with acute, flaccid, sensory motor paraplegia, with bladder and bowel involvement. He developed this immediately after an operation for inguinal hernia under spinal anesthesia. Spinal magnetic resonance imaging revealed hemorrhagic myelitis in the conus at D12. He was referred after he did not respond to intravenous methylprednisolone for 10 days. This case brings up the difficulty encountered in determination of the interspace used for spinal anesthesia and the potential for traumatic injury to the spinal cord. It also demonstrates the tragic outcome after a clinician violates some important, standard and established guidelines.
Cortical and spinal assessment
DEFF Research Database (Denmark)
Fischer, I W; Gram, Mikkel; Hansen, T M
2017-01-01
BACKGROUND: Standardized objective methods to assess the analgesic effects of opioids, enable identification of underlying mechanisms of drug actions in the central nervous system. Opioids may exert their effect on both cortical and spinal levels. In this study actions of morphine at both levels...... subjects was included in the data analysis. There was no change in the activity in resting EEG (P>0.05) after morphine administration as compared to placebo. During cold pressor stimulation, morphine significantly lowered the relative activity in the delta (1-4Hz) band (P=0.03) and increased the activity...... morphine administration (P>0.05). CONCLUSIONS: Cold pressor EEG and the nociceptive reflex were more sensitive to morphine analgesia than resting EEG and can be used as standardized objective methods to assess opioid effects. However, no correlation between the analgesic effect of morphine on the spinal...
Veintemillas Aráiz, M T; Beltrán Salazar, V P; Rivera Valladares, L; Marín Aznar, A; Melloni Ribas, P; Valls Pascual, R
2016-04-01
Spinal misalignments are a common reason for consultation at primary care centers and specialized departments. Misalignment has diverse causes and is influenced by multiple factors: in adolescence, the most frequent misalignment is scoliosis, which is idiopathic in 80% of cases and normally asymptomatic. In adults, the most common cause is degenerative. It is important to know the natural history and to detect factors that might predict progression. The correct diagnosis of spinal deformities requires specific imaging studies. The degree of deformity determines the type of treatment. The aim is to prevent progression of the deformity and to recover the flexibility and balance of the body. Copyright © 2016 SERAM. Published by Elsevier España, S.L.U. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Puijlaert, J.B.C.M.; Vielvoye, G.J.; Dulken, H. van
1985-05-01
Two cases of spinal arachnoid cysts are reported. One is extradurally located, the other intradurally. The first is only documented with myelography, the second also by subsequent CT scanning. Some clinical and diagnostic aspects of the lesion are discussed. The aim of this report is to add two new cases to the literature and to emphasize the role of high-resolution CT scanning in the diagnosis of these lesions.
Energy Technology Data Exchange (ETDEWEB)
Chelli Bouaziz, Mouna; Ladeb, Mohamed Fethi; Chakroun, Mohamed; Chaabane, Skander [Institut M T Kassab d' orthopedie, Department of Radiology, Ksar Said (Tunisia)
2008-09-15
Brucellosis is a zoonosis of worldwide distribution, relatively frequent in Mediterranean countries and in the Middle East. It is a systemic infection, caused by facultative intra-cellular bacteria of the genus Brucella, that can involve many organs and tissues. The spine is the most common site of musculoskeletal involvement, followed by the sacroiliac joints. The aim of this study was to assess the clinical, biological and imaging features of spinal brucellosis. (orig.)
Aspergillus spinal epidural abscess
Energy Technology Data Exchange (ETDEWEB)
Byrd, B.F. III (Vanderbilt Univ. School of Medicine, Nashville, TN); Weiner, M.H.; McGee, Z.A.
1982-12-17
A spinal epidural abscess developed in a renal transplant recipient; results of a serum radioimmunoassay for Aspergillus antigen were positive. Laminectomy disclosed an abscess of the L4-5 interspace and L-5 vertebral body that contained hyphal forms and from which Aspergillus species was cultured. Serum Aspergillus antigen radioimmunoassay may be a valuable, specific early diagnostic test when systemic aspergillosis is a consideration in an immunosuppressed host.
Spontaneous spinal epidural abscess.
LENUS (Irish Health Repository)
Ellanti, P
2011-10-01
Spinal epidural abscess is an uncommon entity, the frequency of which is increasing. They occur spontaneously or as a complication of intervention. The classical triad of fever, back pain and neurological symptoms are not always present. High index of suspicion is key to diagnosis. Any delay in diagnosis and treatment can have significant neurological consequences. We present the case of a previously well man with a one month history of back pain resulting from an epidural abscess.
Spinal sensory circuits in motion
2016-01-01
International audience; The role of sensory feedback in shaping locomotion has been long debated. Recent advances in genetics and behavior analysis revealed the importance of proprioceptive pathways in spinal circuits. The mechanisms underlying peripheral mechanosensation enabled to unravel the networks that feedback to spinal circuits in order to modulate locomotion. Sensory inputs to the vertebrate spinal cord were long thought to originate from the periphery. Recent studies challenge this ...
[Information analysis of spinal ganglia].
Lobko, P I; Kovaleva, D V; Kovalchuk, I E; Pivchenko, P G; Rudenok, V V; Davydova, L A
2000-01-01
Information parameters (entropia and redundancy) of cervical and thoracic spinal ganglia of albino rat foetuses, mature animals (cat and dog) and human subjects were analysed. Information characteristics of spinal ganglia were shown to be level-specified and to depend on their functional peculiarities. Information parameters of thoracic spinal ganglia of man and different animals are specie specified and may be used in assessment of morphological structures as information systems.
Pain following spinal cord injury
2004-01-01
The aims of this thesis were to assess and characterise nociceptive and neuropathic pain, the use of pharmacological and non-pharmacological pain treatment, and the influence of pain on the quality of sleep in a population following spinal cord injury (SCI). This thesis is divided into five separate studies: I. Pain in a Swedish spinal cord injury population. II. Gender related differences in pain in spinal cord injured individuals. III. Use of analgesic drugs in indi...
Growth of Fundamental Group for Finsler Manifolds with Integral Ricci Curvature Bound
Indian Academy of Sciences (India)
Bing Ye Wu
2014-08-01
In this paper, an upper bound on the growth of fundamental group for a class of Finsler manifolds with integral Ricci curvature bound is given. This generalizes the corresponding results with pointwise Ricci curvature in literature.
Spinal dysraphism: MR imaging rationale.
Rossi, A; Cama, A; Piatelli, G; Ravegnani, M; Biancheri, R; Tortori-Donati, P
2004-01-01
Spinal cord development occurs through the three consecutive periods of gastrulation (weeks 2-3), primary neurulation (weeks 3-4), and secondary neurulation (weeks 5-6). Spinal cord malformations derive from defects in these early embryonic stages, and are collectively called spinal dysraphisms. Spinal dysraphisms may be categorized clinically into open and closed, based on whether the abnormal nervous tissue is exposed to the environment or covered by skin. Open spinal dysraphisms include myelomeningocele and other rare abnormalities such as myelocele, hemimyelomeningocele, and hemimyelocele, and are always associated with a Chiari II malformation. Closed spinal dysraphisms are further divided into two subsets based on whether a subcutaneous mass is present in the low back. Closed spinal dysraphisms with mass comprise lipomyelocele, lipomyelomeningocele, meningocele, and myelocystocele. Closed spinal dysraphisms without mass comprise simple dysraphic states (tight filum terminale, filar and intradural lipomas, persistent terminal ventricle, and dermal sinuses) and complex dysraphic states. The latter category involves abnormal notochordal development, either in the form of failed midline integration (ranging from complete dorsal enteric fistula to neurenteric cysts and diastematomyelia) or of segmental agenesis (caudal agenesis and spinal segmental dysgenesis). Magnetic resonance imaging is the imaging modality of choice for evaluation of this complex group of disorders.
Do adult men with untreated ventral penile curvature have adverse outcomes?
Menon, Vani; Breyer, Benjamin; Copp, Hillary L; Baskin, Laurence; Disandro, Michael; Schlomer, Bruce J
2016-02-01
Congenital ventral penile curvature without hypospadias is often treated surgically in childhood. The history of untreated ventral curvature is unknown. This study's aim was to examine the association of untreated ventral penile curvature with various sexual and psychosexual outcomes. An electronic survey was advertised to men older than 18 years on Facebook. Men with possible ventral penile curvature identified themselves by choosing sketches that most closely represented their anatomy. Outcomes assessed included: Sexual Health Inventory for Men, difficulty of intercourse because of curvature, International Prostate Symptom Score, Penile Perception Score, psychosexual milestones, paternity, infertility, sitting to urinate, and the CDC HRQOL-4 module. Among participants, 81 out of 684 men (11.8%) reported untreated ventral penile curvature. Participants with self-reported curvature noted more difficulty with intercourse because of curvature (4.5 vs 4.9, p < 0.001), more unhealthy mental days (8.6 vs 6.2, p = 0.02), and increased dissatisfaction with penile self-perception compared with men without reported curvature (8.6 vs 9.5, p < 0.001). Men with possible untreated ventral curvature reported worse penile perception scores, more mentally unhealthy days, and increased difficulty with intercourse secondary to curvature compared with men without curvature. A limitation to this study is selection bias; responses collected were self-reported from survey volunteers. Additionally, the question identifying ventral penile curvature is not validated but performed well in pretesting. Most questions were from validated surveys, but some were modeled after validated surveys and/or contained high face validity types of questions. Men with possible untreated ventral penile curvature reported more dissatisfaction with penile appearance, increased difficulty with intercourse, and more unhealthy mental days. Given high success rates, low complications, and improved outcomes after
Berry curvature, triangle anomalies, and the chiral magnetic effect in Fermi liquids.
Son, Dam Thanh; Yamamoto, Naoki
2012-11-02
In a three-dimensional Fermi liquid, quasiparticles near the Fermi surface may possess a Berry curvature. We show that if the Berry curvature has a nonvanishing flux through the Fermi surface, the particle number associated with this Fermi surface has a triangle anomaly in external electromagnetic fields. We show how Landau's Fermi liquid theory should be modified to take into account the Berry curvature. We show that the "chiral magnetic effect" also emerges from the Berry curvature flux.
Directory of Open Access Journals (Sweden)
Roland Zemp
Full Text Available Soft tissue artefact affects the determination of skeletal kinematics. Thus, it is important to know the accuracy and limitations of kinematic parameters determined and modelled based on skin marker data. Here, the curvature angles, as well as the rotations of the lumbar and thoracic segments, of seven healthy subjects were determined in the sagittal plane using a skin marker set and compared to measurements taken in an open upright MRI scanner in order to understand the influence of soft tissue artefact at the back. The mean STA in the flexed compared to the extended positions were 10.2±6.1 mm (lumbar/9.3±4.2 mm (thoracic and 10.7±4.8 mm (lumbar/9.2±4.9 mm (thoracic respectively. A linear regression of the lumbar and thoracic curvatures between the marker-based measurements and MRI-based measurements resulted in coefficients of determination, R2, of 0.552 and 0.385 respectively. Skin marker measurements therefore allow for the assessment of changes in the lumbar and thoracic curvature angles, but the absolute values suffer from uncertainty. Nevertheless, this marker set appears to be suitable for quantifying lumbar and thoracic spinal changes between quasi-static whole body postural changes.
Transient neurological symptoms after spinal anesthesia
National Research Council Canada - National Science Library
Muhammet Gozdemir; Bunyamin Muslu; Huseyin Sert; Burhanettin Usta; Ruveyda Irem Demircioglu; Hulya Kasikara
2016-01-01
...) after spinal anesthesia with levobupivacaine, bupivacaine, articaine or lidocaine. The patients (n=400) were randomly assigned to receive spinal anesthesia with levobupivacaine, bupivacaine, articaine or isobaric lidocaine...
Directory of Open Access Journals (Sweden)
A. Bhat
2015-06-01
Conclusions: Penile torque is more common and severe in distal hypospadias, while ventral curvature is seen more often in proximal hypospadias. The degree of torsion is inversely proportional to the severity of ventral curvature. Techniques for the repair of penile torque and ventral curvature include penile degloving and mobilization of the urethral plate with the corpus spongiosum and the urethra.
Effect of nano-scale curvature on the intrinsic blood coagulation system
Kushida, Takashi; Saha, Krishnendu; Subramani, Chandramouleeswaran; Nandwana, Vikas; Rotello, Vincent M.
2014-01-01
The intrinsic coagulation activity of silica nanoparticles strongly depends on their surface curvature. Nanoparticles with higher surface curvature do not denature blood coagulation factor XII on its surface, providing a coagulation ‘silent’ surface, while nanoparticles with lower surface curvature shows denaturation and concomitant coagulation.
Medicolegal cases for spinal epidural hematoma and spinal epidural abscess.
French, Keisha L; Daniels, Eldra W; Ahn, Uri M; Ahn, Nicholas U
2013-01-01
Spinal epidural hematoma and spinal epidural abscess are rare surgical emergencies resulting in significant neurologic deficits. Making the diagnosis for spinal epidural hematoma and spinal epidural abscess can be challenging; however, a delay in recognition and treatment can be devastating. The objective of this retrospective analysis study was to identify risk factors for an adverse outcome for the provider. The LexisNexis Academic legal search database was used to identify a total of 19 cases of spinal epidural hematoma and spinal epidural abscess filed against medical providers. Outcome data on trial verdicts, age, sex, initial site of injury, time to consultation, time to appropriate imaging studies, time to surgery, and whether a rectal examination was performed or not were recorded. The results demonstrated a significant association between time to surgery more than 48 hours and an unfavorable verdict for the provider. The degree of permanent neurologic impairment did not appear to affect the verdicts. Fifty-eight percent of the cases did not present with an initial deficit, including loss of bowel or bladder control. All medical professionals must maintain a high level of suspicion and act quickly. Physicians who are able to identify early clinical features, appropriately image, and treat within a 48 hour time frame have demonstrated a more favorable medicolegal outcome compared with their counterparts in filed lawsuits for spinal epidural hematoma and spinal epidural abscess cases.
Generating Ekpyrotic Curvature Perturbations Before the Big Bang
Lehners, J L; Steinhardt, P J; Turok, N G; Fadden, Paul Mc; Lehners, Jean-Luc; Steinhardt, Paul J.; Turok, Neil
2007-01-01
We analyze a general mechanism for producing a nearly scale-invariant spectrum of cosmological curvature perturbations during a contracting phase preceding a big bang, that can be entirely described using 4d effective field theory. The mechanism, based on first producing entropic perturbations and then converting them to curvature perturbations, can be naturally incorporated in cyclic and ekpyrotic models in which the big bang is modelled as a brane collision, as well as other types of cosmological models with a pre-big bang phase. We show that the correct perturbation amplitude can be obtained and that the scalar spectral tilt n tends to range from slightly blue to red, with 0.97 < n < 1.02 for the simplest models, a range compatible with current observations but shifted by a few per cent towards the blue compared to the prediction of the simplest, large-field inflationary models.
On the breakdown of the curvature perturbation $\\zeta$ during reheating
Algan, Merve Tarman; Kutluk, Emine Seyma
2015-01-01
It is known that in single scalar field inflationary models the standard curvature perturbation \\zeta, which is supposedly conserved at superhorizon scales, diverges during reheating at times d\\Phi/dt=0, i.e. when the time derivative of the background inflaton field vanishes. This happens because the comoving gauge \\phi=0, where \\phi\\ denotes the inflaton perturbation, breaks down when d\\Phi/dt=0. The issue is usually bypassed by averaging out the inflaton oscillations but strictly speaking the evolution of \\zeta\\ is ill posed mathematically. We solve this problem by introducing a family of smooth gauges that still eliminates the inflaton fluctuation \\phi\\ in the Hamiltonian formalism and gives a well behaved curvature perturbation \\zeta, which is now rigorously conserved at superhorizon scales. In the linearized theory, this conserved variable can be used to unambiguously propagate the inflationary perturbations from the end of inflation to subsequent epochs. We discuss the implications of our results for th...
Monolayer curvature stabilizes nanoscale raft domains in mixed lipid bilayers
Meinhardt, Sebastian; Schmid, Friederike
2013-01-01
According to the lipid raft hypothesis, biological lipid membranes are laterally heterogeneous and filled with nanoscale ordered "raft" domains, which are believed to play an important role for the organization of proteins in membranes. However, the mechanisms stabilizing such small rafts are not clear, and even their existence is sometimes questioned. Here we report the observation of raft-like structures in a coarse-grained molecular model for multicomponent lipid bilayers. On small scales, our membranes demix into a liquid ordered (lo) and a liquid disordered (ld) phase. On large scales, phase separation is suppressed and gives way to a microemulsion-type state that contains nanometer size lo domains in a ld environment. Furthermore, we introduce a mechanism that generates rafts of finite size by a coupling between monolayer curvature and local composition. We show that mismatch between the spontaneous curvatures of monolayers in the lo and ld phase induces elastic interactions, which reduce the line tensi...
Curvature-guided motility of microalgae in geometric confinement
Ostapenko, Tanya; Böddeker, Thomas; Kreis, Christian; Cammann, Jan; Mazza, Marco G; Bäumchen, Oliver
2016-01-01
Microorganisms often live in microhabitats that consist of a liquid phase and a plethora of typically curved interfaces. The ways in which motile cells possessing propulsive appendages sense and interact with the physical nature of their environment remains unclear today. For pusher-type microswimmers with rear-mounted flagella, such as bacteria and spermatozoa, cell trapping at a wall was attributed to contrasting microscopic mechanisms, namely hydrodynamic and contact interactions. Here, we demonstrate that, in confined spaces, the geometry of the habitat controls the motility of microalgae that propel themselves by the beating of two anterior flagella. Brownian dynamics simulations and analytical theory both quantitatively match the experimental data and capture a characteristic curvature scaling observed in the experiments. This curvature-guided navigation of the microalgae originates from only two essential ingredients: excluded volume resulting in predominantly ballistic swimming in confinement and the ...
Primordial black hole formation from non-Gaussian curvature perturbations
Klimai, P A
2012-01-01
We consider several early Universe models that allow for production of large curvature perturbations at small scales. As is well known, such perturbations can lead to production of primordial black holes (PBHs). We briefly review the Gaussian case and then focus on two models which produce strongly non-Gaussian perturbations: hybrid inflation waterfall model and the curvaton model. We show that limits on the values of curvature perturbation power spectrum amplitude are strongly dependent on the shape of perturbations and can significantly (by two orders of magnitude) deviate from the usual Gaussian limit of ${\\cal P}_\\zeta \\lesssim 10^{-2}$. We give examples of PBH mass spectra calculations for each case.
Reeves, Matthew; Stratford, Kevin; Thijssen, Job H. J.
Bicontinuous Pickering emulsions (bijels) are a physically interesting class of soft materials with many potential applications including catalysis, microfluidics and tissue engineering. They are created by arresting the spinodal decomposition of a partially-miscible liquid with a (jammed) layer of interfacial colloids. Porosity $L$ (average interfacial separation) of the bijel is controlled by varying the radius ($r$) and volume fraction ($\\phi$) of the colloids ($L \\propto r/\\phi$). However, to optimize the bijel structure with respect to other parameters, e.g. quench rate, characterizing by $L$ alone is insufficient. Hence, we have used confocal microscopy and X-ray CT to characterize a range of bijels in terms of local and area-averaged interfacial curvatures. In addition, the curvatures of bijels have been monitored as a function of time, which has revealed an intriguing evolution up to 60 minutes after bijel formation, contrary to previous understanding.
Surface Curvature-Induced Directional Movement of Water Droplets
Lv, Cunjing; Yin, Yajun; Zheng, Quanshui
2010-01-01
Here we report a surface curvature-induced directional movement phenomenon, based on molecular dynamics simulations, that a nanoscale water droplet at the outer surface of a graphene cone always spontaneously moves toward the larger end of the cone, and at the inner surface toward the smaller end. The analysis on the van der Waals interaction potential between a single water molecule and a curved graphene surface reveals that the curvature with its gradient does generate the driving force resulting in the above directional motion. Furthermore, we found that the direction of the above movement is independent of the wettability, namely is regardless of either hydrophobic or hydrophilic of the surface. However, the latter surface is in general leading to higher motion speed than the former. The above results provide a basis for a better understanding of many reported observations, and helping design of curved surfaces with desired directional surface water transportation.
The Ricci Curvature of Half-flat Manifolds
Ali, T; Ali, Tibra; Cleaver, Gerald B.
2007-01-01
We derive expressions for the Ricci curvature tensor and scalar in terms of intrinsic torsion classes of half-flat manifolds by exploiting the relationship between half-flat manifolds and non-compact $G_2$ holonomy manifolds. Our expressions are tested for Iwasawa and more general nilpotent manifolds. We also derive expressions, in the language of Calabi-Yau moduli spaces, for the torsion classes and the Ricci curvature of the \\emph{particular} half-flat manifolds that arise naturally via mirror symmetry in flux compactifications. Using these expressions we then derive a constraint on the K\\"ahler moduli space of type II string theory on these half-flat manifolds.
Preference for Curvature: A Historical and Conceptual Framework
Gómez-Puerto, Gerardo; Munar, Enric; Nadal, Marcos
2016-01-01
That people find curved contours and lines more pleasurable than straight ones is a recurrent observation in the aesthetic literature. Although such observation has been tested sporadically throughout the history of scientific psychology, only during the last decade has it been the object of systematic research. Recent studies lend support to the idea that human preference for curved contours is biologically determined. However, it has also been argued that this preference is a cultural phenomenon. In this article, we review the available evidence, together with different attempts to explain the nature of preference for curvature: sensoriomotor-based and valuation-based approaches. We also argue that the lack of a unifying framework and clearly defined concepts might be undermining our efforts towards a better understanding of the nature of preference for curvature. Finally, we point to a series of unresolved matters as the starting point to further develop a consistent research program. PMID:26793092
Membrane curvature in cell biology: An integration of molecular mechanisms.
Jarsch, Iris K; Daste, Frederic; Gallop, Jennifer L
2016-08-15
Curving biological membranes establishes the complex architecture of the cell and mediates membrane traffic to control flux through subcellular compartments. Common molecular mechanisms for bending membranes are evident in different cell biological contexts across eukaryotic phyla. These mechanisms can be intrinsic to the membrane bilayer (either the lipid or protein components) or can be brought about by extrinsic factors, including the cytoskeleton. Here, we review examples of membrane curvature generation in animals, fungi, and plants. We showcase the molecular mechanisms involved and how they collaborate and go on to highlight contexts of curvature that are exciting areas of future research. Lessons from how membranes are bent in yeast and mammals give hints as to the molecular mechanisms we expect to see used by plants and protists.
Gravitational wave detector response in terms of spacetime Riemann curvature
Koop, Michael J
2013-01-01
Gravitational wave detectors are typically described as responding to gravitational wave metric perturbations, which are gauge-dependent and --- correspondingly --- unphysical quantities. This is particularly true for ground-based interferometric detectors, like LIGO, space-based detectors, like LISA and its derivatives, spacecraft doppler tracking detectors, and pulsar timing arrays detectors. The description of gravitational waves, and a gravitational wave detector's response, to the unphysical metric perturbation has lead to a proliferation of false analogies and descriptions regarding how these detectors function, and true misunderstandings of the physical character of gravitational waves. Here we provide a fully physical and gauge invariant description of the response of a wide class of gravitational wave detectors in terms of the Riemann curvature, the physical quantity that describes gravitational phenomena in general relativity. In the limit of high frequency gravitational waves, the Riemann curvature...
On M-theory fourfold vacua with higher curvature terms
Energy Technology Data Exchange (ETDEWEB)
Grimm, Thomas W., E-mail: grimm@mpp.mpg.de; Pugh, Tom G., E-mail: pught@mpp.mpg.de; Weißenbacher, Matthias, E-mail: mweisse@mpp.mpg.de
2015-04-09
We study solutions to the eleven-dimensional supergravity action, including terms quartic and cubic in the Riemann curvature, that admit an eight-dimensional compact space. The internal background is found to be a conformally Kähler manifold with vanishing first Chern class. The metric solution, however, is non-Ricci-flat even when allowing for a conformal rescaling including the warp factor. This deviation is due to the possible non-harmonicity of the third Chern-form in the leading order Ricci-flat metric. We present a systematic derivation of the background solution by solving the Killing spinor conditions including higher curvature terms. These are translated into first-order differential equations for a globally defined real two-form and complex four-form on the fourfold. We comment on the supersymmetry properties of the described solutions.
Generation of Curvature Perturbations with Extra Anisotropic Stress
Kojima, Kazuhiko; Mathews, Grant J
2009-01-01
We study the evolution of curvature perturbations and the cosmic microwave background (CMB) power spectrum in the presence of an hypothesized extra anisotropic stress in the early universe. Such extra anisotropic stress terms might arise, for example, from the presence of the dark radiation term in brane-world cosmology. For the first time we evolve the scalar modes of such perturbations before and after neutrino decoupling and analyze their effects on the CMB spectrum. A novel result of this work is that the cancellation of the neutrino and extra anisotropic stress could lead to a spectrum of residual curvature perturbations which by themselves could reproduce the observed CMB power spectrum. This possibility may be testable as it would generate non-Gaussian fluctuations which could be constrained by future observations of density fluctuations.
Effective theories of connections and curvature: abelian case
Diaz-Marin, Homero G
2011-01-01
We introduce a notion of measuring scales for quantum abelian gauge systems. At each measuring scale a finite dimensional affine space stores information about the evaluation of the curvature on a discrete family of surfaces. Affine maps from the spaces assigned to finer scales to those assigned to coarser scales play the role of coarse graining maps. This structure induces a continuum limit space which contains information regarding curvature evaluation on all piecewise linear surfaces with boundary. The evaluation of holonomies along contractible loops is also encoded in the spaces introduced here; thus, our framework is closely related to loop quantization and it allows us to discuss effective theories in a sensible way. We develop basic elements of measure theory on the introduced spaces which are essential for the applicability of the framework to the construction of quantum abelian gauge theories.
Curvature-Induced Asymmetric Spin-Wave Dispersion
Otálora, Jorge A.; Yan, Ming; Schultheiss, Helmut; Hertel, Riccardo; Kákay, Attila
2016-11-01
In magnonics, spin waves are conceived of as electron-charge-free information carriers. Their wave behavior has established them as the key elements to achieve low power consumption, fast operative rates, and good packaging in magnon-based computational technologies. Hence, knowing alternative ways that reveal certain properties of their undulatory motion is an important task. Here, we show using micromagnetic simulations and analytical calculations that spin-wave propagation in ferromagnetic nanotubes is fundamentally different than in thin films. The dispersion relation is asymmetric regarding the sign of the wave vector. It is a purely curvature-induced effect and its fundamental origin is identified to be the classical dipole-dipole interaction. The analytical expression of the dispersion relation has the same mathematical form as in thin films with the Dzyalonshiinsky-Moriya interaction. Therefore, this curvature-induced effect can be seen as a "dipole-induced Dzyalonshiinsky-Moriya-like" effect.
Thermodynamics in Modified Gravity with Curvature Matter Coupling
Directory of Open Access Journals (Sweden)
M. Sharif
2013-01-01
Full Text Available The first and generalized second laws of thermodynamics are studied in f(R,Lm gravity, a more general modified theory with curvature matter coupling. It is found that one can translate the Friedmann equations to the form of first law accompanied with entropy production term. This behavior is due to the nonequilibrium thermodynamics in this theory. We establish the generalized second law of thermodynamics and develop the constraints on coupling parameters for two specific models. It is concluded that laws of thermodynamics in this modified theory are more general and can reproduce the corresponding results in Einstein, f(R gravity, and f(R gravity with arbitrary as well as nonminimal curvature matter coupling.
Kaluza-Klein Reduction of a Quadratic Curvature Model
Baskal, S
2010-01-01
Palatini variational principle is implemented on a five dimensional quadratic curvature gravity model, rendering two sets of equations which can be interpreted as the field equations and the stress-energy tensor. Unification of gravity with electromagnetism and the scalar dilaton field is achieved through the Kaluza-Klein dimensional reduction mechanism. The reduced curvature invariant, field equations and the stress-energy tensor in four dimensional spacetime are obtained. The structure of the interactions among the constituent fields is exhibited in detail. It is shown that the Lorentz force naturally emerges from the reduced field equations and the equations of the standard Kaluza-Klein theory is demonstrated to be intrinsically contained in this model.
Glauber theory and the quantum coherence of curvature inhomogeneities
Giovannini, Massimo
2016-01-01
The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose-Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.
DNA Origami with Complex Curvatures in Three-Dimensional Space
Energy Technology Data Exchange (ETDEWEB)
Han, Dongran; Pal, Suchetan; Nangreave, Jeanette; Deng, Zhengtao; Liu, Yan; Yan, Hao
2011-04-14
We present a strategy to design and construct self-assembling DNA nanostructures that define intricate curved surfaces in three-dimensional (3D) space using the DNA origami folding technique. Double-helical DNA is bent to follow the rounded contours of the target object, and potential strand crossovers are subsequently identified. Concentric rings of DNA are used to generate in-plane curvature, constrained to 2D by rationally designed geometries and crossover networks. Out-of-plane curvature is introduced by adjusting the particular position and pattern of crossovers between adjacent DNA double helices, whose conformation often deviates from the natural, B-form twist density. A series of DNA nanostructures with high curvature—such as 2D arrangements of concentric rings and 3D spherical shells, ellipsoidal shells, and a nanoflask—were assembled.
Glauber theory and the quantum coherence of curvature inhomogeneities
Giovannini, Massimo
2017-02-01
The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose–Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third- and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.
On M-theory fourfold vacua with higher curvature terms
Directory of Open Access Journals (Sweden)
Thomas W. Grimm
2015-04-01
Full Text Available We study solutions to the eleven-dimensional supergravity action, including terms quartic and cubic in the Riemann curvature, that admit an eight-dimensional compact space. The internal background is found to be a conformally Kähler manifold with vanishing first Chern class. The metric solution, however, is non-Ricci-flat even when allowing for a conformal rescaling including the warp factor. This deviation is due to the possible non-harmonicity of the third Chern-form in the leading order Ricci-flat metric. We present a systematic derivation of the background solution by solving the Killing spinor conditions including higher curvature terms. These are translated into first-order differential equations for a globally defined real two-form and complex four-form on the fourfold. We comment on the supersymmetry properties of the described solutions.
Gravitomagnetism and the significance of the curvature scalar invariants
Costa, L Filipe O; Natário, José
2016-01-01
The curvature invariants have been subject of recent interest due to the debate concerning the notions of intrinsic/extrinsic frame-dragging, the use of the electromagnetic analogy in such classification, and the question of whether there is a fundamental difference between the gravitomagnetic field arising from the translational motion of the sources, detected with Lunar Laser Raging and in the observations of binary pulsars, and the gravitomagnetic field produced by the rotation of the Earth, detected in the LAGEOS Satellites data and by the Gravity Probe-B mission. In this work we clarify both the algebraic and physical meaning of the curvature invariants and their electromagnetic counterparts. The structure of the invariants of the astrophysical setups of interest is studied in detail, and its relationship with the gravitomagnetic effects is dissected. Finally, a new classification for intrinsic/extrinsic gravitomagnetism is put forth.
The Parallelometer: a mechanical device to study curvature
Rojo, Alberto G; Gil, Salvador
2008-01-01
A simple mechanical device is introduced, the parallelometer, that can be used to measure curvatures of surfaces. The device can be used as a practical illustration of parallel transport of a vector and to study Berry phase shift when it is carried along a loop on the surface. Its connection to the Foucault pendulum is discussed. The experimental results can be successfully compared with the theoretical expectations. The experiment is inexpensive and conceptually easy to perform and understand for a beginner.
Axially symmetric volume constrained anisotropic mean curvature flow
Palmer, Bennett
2011-01-01
We study the long time existence theory for a non local flow associated to a free boundary problem for a trapped non liquid drop. The drop has free boundary components on two horizontal plates and its free energy is anisotropic and axially symmetric. For axially symmetric initial surfaces with sufficiently large volume, we show that the flow exists for all time. Numerical simulations of the curvature flow are presented.
The -Curvature Images of Convex Bodies and -Projection Bodies
Indian Academy of Sciences (India)
Songjun Lv; Gangsong Leng
2008-08-01
Associated with the -curvature image defined by Lutwak, some inequalities for extended mixed -affine surface areas of convex bodies and the support functions of -projection bodies are established. As a natural extension of a result due to Lutwak, an -type affine isoperimetric inequality, whose special cases are -Busemann–Petty centroid inequality and -affine projection inequality, respectively, is established. Some -mixed volume inequalities involving -projection bodies are also established.
Effect of symmetry breaking on level curvature distributions
Hussein, M S; Pato, M P
2002-01-01
An exact general formalism is derived that expresses the eigenvector and the eigenvalue dynamics as a set of coupled equations of motion in terms of the matrix elements dynamics. Combined with an appropriate model Hamiltonian, these equations are used to investigate the effect of the presence of a discrete symmetry in the level curvature distribution. It is shown that this distribution exhibits a nontrivial behavior that explains the recent data regarding frequencies of acoustic vibrations of quartz block.