Mean Path Length Research Articles

Symmetry-guided design of topologies for supercomputer networks

A family of graphs optimized as the topologies for interconnection networks is proposed. The needs of such topologies with minimal diameters and minimal mean path lengths are met by special constructions of the weight vectors in a representation of the symplectic algebra. Such design of topologies can conveniently reconstruct the mesh and hypercube, widely used as network topologies, as well as many other classes of graphs potentially suitable for network topologies.

New track-structure Monte Carlo code for 4D ionizing photon transport

ABSTRACTRadiodiagnosis and radiation treatment, in each of their areas such as imaging, radiotherapy and nuclear medicine, require precise calculations about the energy deposited and scattering of the ionizing radiation used. In healthcare applications, it is required to know the penetration and amount of energy deposited in the biological tissue irradiated by ionizing photons; these parameters are function of the photon interaction processes with matter, which can be analyzed experimentally or by Monte Carlo simulation. Purpose: The aim of this work was to develop a new Monte Carlo code for ionizing photon transport in water with the track structure technique, that allows to discriminate primary and secondary photons, and to determine the energy deposited, interaction coordinates, path length and time of flight (TOF) inside of scatter volume. Methods: C++ programming language was used. In the Compton scattering, the polar angle was sampled by methods: Kahn and EGS. Water spheres centered at the origin with different radius were used, where the isotropic point source was placed at (0, 0, 0) for different energies to compute the energy lost by photons and TOF inside spherical volume. Results: It was determined that the best sampling method for the polar angle generation in each Compton interaction was the EGS method. Energy deposited in target region filled with water was compared with MCNPX 2.6 and others’ results from literature. Mean TOF and pathlength inside region of interest was obtained for 4 radii and 5 energies. Conclusions: Quantities computed with the new code are, according to reported data, and so, the new code is reliable for photon transport in water using the track structure method; this will allow the new code to become a useful tool in the areas of radiology and radiation dosimetry. Also, TOF inside scatter volume was reported.

Balance and lower limb loads distribution after Ilizarov corticotomy

IntroductionNormal balance and symmetric distribution of lower limb loads are associated with adequate muscle strength, joint mobility and proprioception. The aim of this study was to analyze the distribution of lower limb loads and balance prior to and after axis correction and lengthening with Ilizarov method. Materials and methodsThe prospective analysis included 20 patients from our clinic, who have been subjected to distraction-corrective lower limb corticotomies with the Ilizarov method in 2014–2015. Balance and distribution of lower limb loads were determined with a pedobarographic platform. ResultsPrior to the surgery, mean loads on affected and non-affected limbs corresponded to42%and58%of body weight, respectively. Mean loads on affected and non-affected limbs during the postoperative examination did not differ significantly. Mean path length of the center of gravity prior to and after the surgery amounted to143.27 cm and 125.11 cm, respectively. Mean area of the center of gravity was 7.81 cm2prior to the surgery and 5.81 cm2after the procedure. DiscussionOur present study showed that distraction-corrective Ilizarov corticotomy may provide more symmetric distribution of lower limb loads and improvement of balance. This outcome should be considered satisfactory from the perspective of the locomotor system statics. Corticotomies with Ilizarov method provide symmetric distribution of loads between non-affected and operated limb.

Does the superior position of countries in co-authorship networks lead to their high citation performance

The objective of this research was to determine the macro-topological structure and the relationship between citation performance and centrality measures of co-authorship social networks of countries in the field of Nuclear Science and Technology from 2008 to 2010. The present study applied the network analysis method in order to visualize co-authorship networks. Hypothesized relationships were tested using the authors of 24,308 documents cited in the Web of Science. Data relevant to citation performance of a country was based on the articles published by the researchers of the country in a three-year period and the citation data of articles were collected two years after their publication. The investigation of co-authorship social network in the field of Nuclear Science and Technology revealed that the countries which are members of a Nuclear Club hold a prominent position in the network and their influence or power in the network is greater than other countries. Having characteristics like short mean path length, low network diameter (less than or equal to 6) and relatively high clustering coefficient, this network is regarded as a Small World Network. The results of testing the research hypotheses indicated that as the value of centrality of countries rise, the citation performance of researchers in that country is also improved. The analysis of variance confirmed the validity of stepwise regression analysis in predicting the citation performance of researchers (F=816.958 and p>0.000) and through three steps, three components including degree centrality, beta centrality and flow betweenness centrality were concluded to have multiple correlation with citation performance of researchers

Examination of Effective Body Sway Parameters for Healthy Elderly

This study aimed to examine body sway characteristics and to propose effective body sway parameters for healthy elderly. The subjects were 311 healthy elderly and 380 healthy young adults. None of the subjects had evidence or known history of gait, posture, or skeletal disorders. The center of foot pressure measurement for 1 min was performed in 1 trial Using Anima’s stabilometer G5500. The data sampling frequency was 20 Hz. Thirty parameters with high reliability were selected from 5 domains of distance, area, velocity, power spectrum, and body sway vector. In comparison with the results for young adults, the elderly had markedly larger values of mean path length and root mean square of x-axis, as well as for 5 velocity parameters and 4 vector velocity parameters. In addition, approximately 10% of the data for parameters related to body sway velocity, especially front/back body sway, even in the healthy elderly fell in an abnormal range of values (mean ± 3 SD). In conclusion, the following parameters may be useful to adequately and simply evaluate the body sway characteristics of the elderly: sway size, sway velocity, and from a directional viewpoint, sway size in the right/left direction and sway velocity in the front/back direction.

Complexity of searching movement in the European harvester ant Messor wasmanni: effect of temperature and body size

Individual search behavior is an important feature of ant ecology that can be influenced by many factors including environmental constraints, competitive interactions, and morphology. In this study, I investigated the effects of temperature, body size, and leg allometry on search movement in the polymorphic European harvester ant, Messor wasmanni. Temperature is known to increase movement speed, but how it interacts with morphology to influence path sinuosity is unknown. Ants in this study were grouped according to dimension (small, medium, and large) and were filmed moving individually in a neutral arena at three different temperatures: 10, 20, and 30 °C. Movements were analyzed by evaluating mean speed, path length, and path complexity using 5 different indexes to survey tortuosity: Mean Square Displacement (MSD), Straightness (ST), Intensity of Habitat Use (IU), Sinuosity (SI), and Fractal Dimension (Fractal D). Search movement seemed not to be strongly affected by size, even though extreme temperatures faintly diversified the path complexity among castes. Finally, the relationship between body weight and leg length was evaluated to test the ‘size-grain’ hypothesis among dimensional castes. Mean speed was strongly affected by temperature, but not by the size of the ants. Complexity indexes revealed different outcomes through their relationship to speed or path length. Interestingly, leg length and body size were negatively correlated, indicating that legs are proportionally shorter in large rather than in small ants, causing rejection of the ‘size-grain’ hypothesis for this species. Thus, individuals experience a similar roughness of soil surface irrespective of their size.

New ichnotaxa of vertebrate burrows from the Salt Wash Member, Upper Jurassic Morrison Formation, south-eastern Utah (USA)

Large-diameter burrows in pedogenically modified floodplain deposits in the Salt Wash Member, Upper Jurassic Morrison Formation, southeast Utah, U.S.A., are interpreted to have been constructed by mammals. They are distinguished as Daimonelix martini isp. nov., which exhibits a helical shaft down to a horizontal tunnel with a mean depth of 71.4 cm from the inferred palaeosurface. The mean path length of the shaft is 99.4 cm; mean dip of the whorls is 39°. The mean tunnel length is 42.3 cm. Shafts and tunnels are oval or elliptical in cross section with the horizontal diameter slightly larger than the vertical (ratio of ~1.26:1); the shaft averages 9.2 cm wide and 7.3 cm tall; the tunnel averages 10.7 cm wide and 10.7 cm tall. The tracemaker was likely a fossorial mammal that used the burrow as a den to shelter when not foraging above ground; the burrows are domichnia. The other from the same member is Fractisemita henrii igen. nov. et isp. nov., a network of interconnected shafts and tunnels; shaft and tunnel segments are straight, curved, or helical. The segments are at angles of 0–89°; mean length of a section is 30.7 cm. The cross sections of all elements are oval or elliptical; the mean width is 6.3 cm and the mean height is 4.9 cm (ratio of ~1.29:1). The burrows are interpreted as the work of a social mammal and represent multiple tracemaker behaviours: protection, denning, foraging, and possibly food storage. The burrows are polychresichnia. Surficial morphologic features preserved on the burrow walls of both types are interpreted as scratches made by the tracemaker claws and/or teeth. The burrows reveal the actions of small vertebrates not recorded by body fossils showing potential partitioning of the environment and availability of resources for small vertebrates.

Food web structure and ecosystem properties of the largest impounded lake along the eastern route of China's South-to-North Water Diversion Project

Hongze Lake (HZL) is the largest impounded lake along the eastern route of China's South-to-North Water Diversion Project. However, there is surprisingly little ecological understanding on this important ecosystem, especially under the potential water diversion threats. Here, a mass-balance model was constructed to characterize trophic structure and ecosystem properties of HZL. The model outputs indicated that small sized fishes have dominated the food web, and fishery resources were suffered from high pressures of overfishing. Mandarin fish, Northern snakehead, Other piscivores and Large culters occupied the top trophic niche, while macrophytes, phytoplankton and detritus consisted of the main energy sources. HZL food web was fairly based on two main food chains: primary production (49.9%) and detritus pool (50.1%), but transfer efficiencies in both chains were relatively low as 6.37% and 6.49%, respectively. Predator-prey interactions, trophic cascading effects and competition of different components were also exhibited in the mixed trophic impacts map. Results from the network analysis suggested that the HZL ecosystem was a relatively mature ecosystem since the total primary production to respiration (TPP/TR) and to biomass (TPP/TB) were 1.138 and 6.922, and the Finn Cycling Index was 6.77%. Nevertheless, the relatively low values of Connectance Index (0.195) and System Omnivory Index (0.089), together with Finn's Mean path Length (2.849) also indicated that the food web structure was vulnerable, characterized by linear, rather than web-like features. Our results suggested that the HZL ecosystem would be potentially affected by the future inter-basin water diversion, and thus ecosystem-based strategies were also presented accordingly.

Observation of mean path length invariance in light-scattering media.

The microstructure of a medium strongly influences how light propagates through it. The amount of disorder it contains determines whether the medium is transparent or opaque. Theory predicts that exciting such a medium homogeneously and isotropically makes some of its optical properties depend only on the medium's outer geometry. Here, we report an optical experiment demonstrating that the mean path length of light is invariant with respect to the microstructure of the medium it scatters through. Using colloidal solutions with varying concentration and particle size, the invariance of the mean path length is observed over nearly two orders of magnitude in scattering strength. Our results can be extended to a wide range of systems-however ordered, correlated, or disordered-and apply to all wave-scattering problems.

Ecosystem development of Haizhou Bay Ecological Restoration Area from 2003 to 2013

Two Ecopath mass-balance models were implemented for evaluating the structure and function of Haizhou Bay Ecological Restoration Area ecosystem using 14 ecological indicators in two distinctive years (2003 and 2013). The results showed that the size of HZERA ecosystem became larger as total biomass was increased in last decade, especially in primary producer and zooplankton groups. Total system throughput increased from 7496.00 t km−2 yr−1 to 9547.54 t km−2 yr−1. The P/R (production/respiration) ratio decreased over the decade. Finn’s cycling index and Finn’s mean path length increased over the decade. No keystone species (KS) occurred during ten years; however, evidences of top-down control in 2003 and 2013 models were demonstrated by high KS value belonging to Lophius litulon group in food web. Drawing upon Odum’s theory of ecosystem maturity, the structured, web-like ecosystem of 2013 model had developed into a highly mature system compared with that of 2003 model.

Task modulates functional connectivity networks in free viewing behavior

In free visual exploration, eye-movement is immediately followed by dynamic reconfiguration of brain functional connectivity. We studied the task-dependency of this process in a combined visual search-change detection experiment. Participants viewed two (nearly) same displays in succession. First time they had to find and remember multiple targets among distractors, so the ongoing task involved memory encoding. Second time they had to determine if a target had changed in orientation, so the ongoing task involved memory retrieval. From multichannel EEG recorded during 200 ms intervals time-locked to fixation onsets, we estimated the functional connectivity using a weighted phase lag index at the frequencies of theta, alpha, and beta bands, and derived global and local measures of the functional connectivity graphs. We found differences between both memory task conditions for several network measures, such as mean path length, radius, diameter, closeness and eccentricity, mainly in the alpha band. Both the local and the global measures indicated that encoding involved a more segregated mode of operation than retrieval. These differences arose immediately after fixation onset and persisted for the entire duration of the lambda complex, an evoked potential commonly associated with early visual perception. We concluded that encoding and retrieval differentially shape network configurations involved in early visual perception, affecting the way the visual input is processed at each fixation. These findings demonstrate that task requirements dynamically control the functional connectivity networks involved in early visual perception.

How does cryotherapy effect ankle proprioception in healthy individuals?

Objectives To investigate how a 15-min cryotherapy intervention effects proprioception by measuring joint positional sense (JPS) and static single legged balance. Design Repeated measures design. Setting Laboratory. Participants Eighteen healthy university sports team students (11 males, 7 females) aged between 20 and 21 years old. Main outcome measures Participants were treated with 15 min of Aircast Cryo-cuff. The subject’s skin temperature was measured before and immediately after 15 min of cryotherapy treatment. Ankle active joint positional sense (A-JPS) and passive joint positional sense (P-JPS) were measured at pre-test, immediately post-test, and 5 min post-test. Static balance was measured by centre of pressure (CoP) mean path length, medial–lateral (ML) CoP mean deviation, and anterior–posterior (AP) CoP mean deviation and mean time-to-boundary (TtB) minima for AP and ML directions. Results No significant differences were found for the variables of JPS and static single balance testing after 15 min of cryotherapy treatment. However, mean differences for CoP mean path length and ML mean deviation were shown to improve following cryotherapy treatment, results not previously found in the literature. Conclusion Results suggest that 15 min of Cryo-cuff treatment does not significantly affect proprioception. Although the effect of cryotherapy on proprioception depends on cooling modality used, time frame applied, and joint applied to.

Tortuosity of Aligned Channels in Alumina Membranes Produced by Vacuum-Induced Surface Directional Freezing.

Vacuum-induced surface freezing of colloidal alumina was used to produce membranes that have elongated, aligned channels and, hence, are tortuous in the direction perpendicular to ice crystal growth. The effective tortuosity of the membranes was measured by steady-state diffusion of a solute, methylene blue. The resulting diffusion profiles show an initial step-increase in amount of dye reaching the acceptor that is caused by capillarity drawing the donor solution through any non-wetted channels in the membrane. This is followed by a linear steady-state phase whose flux is proportional to dye concentration in the donor and inversely proportional to the colloid’s volume fraction of dispersed phase. From the steady-state flux, the effective tortuosity, τ* = (α/τ)−1, was calculated. This is the reciprocal quotient of the reduced available area for diffusion within the membrane, = A*/A, where A* is the available area and A is the cross-sectional area of the membrane, and the increased mean diffusional path length, i.e., tortuosity , where L* is the mean path length and L is the membrane thickness. The values of τ* lie in the range of 2–38 and increase as the volume fraction of dispersed phase is larger. This latter effect indicates that τ* > 1 results, to a larger extent, from the reduced available diffusion area, α, than from the lengthened pathway, τ, in these aligned porous membranes.

Correction factors to convert microdosimetry measurements in silicon to tissue in 12C ion therapy

Silicon microdosimetry is a promising technology for heavy ion therapy (HIT) quality assurance, because of its sub-mm spatial resolution and capability to determine radiation effects at a cellular level in a mixed radiation field. A drawback of silicon is not being tissue-equivalent, thus the need to convert the detector response obtained in silicon to tissue. This paper presents a method for converting silicon microdosimetric spectra to tissue for a therapeutic 12C beam, based on Monte Carlo simulations. The energy deposition spectra in a 10 μm sized silicon cylindrical sensitive volume (SV) were found to be equivalent to those measured in a tissue SV, with the same shape, but with dimensions scaled by a factor κ equal to 0.57 and 0.54 for muscle and water, respectively. A low energy correction factor was determined to account for the enhanced response in silicon at low energy depositions, produced by electrons. The concept of the mean path length to calculate the lineal energy was introduced as an alternative to the mean chord length because it was found that adopting Cauchy’s formula for the was not appropriate for the radiation field typical of HIT as it is very directional. can be determined based on the peak of the lineal energy distribution produced by the incident carbon beam. Furthermore it was demonstrated that the thickness of the SV along the direction of the incident 12C ion beam can be adopted as . The tissue equivalence conversion method and were adopted to determine the RBE10, calculated using a modified microdosimetric kinetic model, applied to the microdosimetric spectra resulting from the simulation study. Comparison of the RBE10 along the Bragg peak to experimental TEPC measurements at HIMAC, NIRS, showed good agreement. Such agreement demonstrates the validity of the developed tissue equivalence correction factors and of the determination of .

THERE'S AN APP FOR THAT: RELIABILITY OF AN IPHONE APP TO ASSESS UPPER EXTREMITY PROPRIOCEPTION AND STABILITY

BackgroundThe ability to maintain joint stability and motion control of the extremities is important in injury prevention and recovery. Quantitative measurement of proprioception, especially the upper extremity, is difficult and...

Quantitative comparison of operative skill using 2- and 3-dimensional monitors during laparoscopic phantom tasks

The recent development of stereoscopic images using 3-dimensional monitors is expected to improve techniques for laparoscopic operation. Several studies have reported technical advantages in using 3-dimensional monitors with regard to operative accuracy and working speed, but there are few reports that analyze forceps motions by 3-dimensional optical tracking systems during standardized laparoscopic phantom tasks. We attempted to develop a 3-dimensional motion analysis system for assessing laparoscopic tasks and to clarify the efficacy of using stereoscopic images from a 3-dimensional monitor to track forceps movement during laparoscopy. Twenty surgeons performed 3 tasks (Task 1: a simple operation by the dominant hand, Task 2: a simple operation using both hands, Task 3: a complicated operation using both hands) under 2-dimensional and 3-dimensional systems. We tracked and recorded the motion of forceps tips with an optical marker captured by a 3-dimensional position tracker. We analyzed factors such as forceps path lengths, operation times, and technical errors for each task and compared the results of 2-dimensional and 3-dimensional monitors. Mean operation times and technical errors were improved significantly for all tasks performed under the 3-dimensional system compared with the 2-dimensional system; in addition, mean path lengths for the forceps tips were shorter for all tasks performed under the 3-dimensional system. We found that stereoscopic images using a 3-dimensional monitor improved operative techniques with regard to increased accuracy and shorter path lengths for forceps movement, which resulted in a shorter operation time for basic phantom laparoscopic tasks.

Preliminary analysis of the Jimo coastal ecosystem with the ecopath model

The Jimo coast encompasses an area of 2157 km2, and the ecosystem is valuable both socially and economically with regional fisheries substantially contributing to the value. A mass-balanced trophic model consisting of 15 functional ecological groups was developed for the coastal ecosystem using the Ecopath model in Ecopath with Ecosim (EwE) software (version 6.4.3). The results of the model simulations indicated that the trophic levels of the functional groups varied between 1.0 and 3.76, and the total production of the system was estimated to be 5112.733 t km−2 yr−1 with a total energy transfer efficiency of 17.6%. The proportion of the total flow originating from detritus was estimated to be 48%, whereas that from primary producers was 52%, indicating that the grazing food chain dominated the energy flow. The ratio of total primary productivity to total respiration in the system was 3.78, and the connectivity index was 0.4. The fin cycling index and the mean path length of the energy flow were 4.92% and 2.57%, respectively, which indicated that the ecosystem exhibits relatively low maturity and stability. The mixed trophic impact (MTI) procedure suggested that the ecological groups at lower trophic levels dominated the feeding dynamics in the Jimo coastal ecosystem. Overfishing is thought to be the primary reason for the degeneration of the Jimo coastal ecosystem, resulting in a decline in the abundance of pelagic and demersal fish species and a subsequent shift to the predominance of lower-trophic-level functional groups. Finally, we offered some recommendations for improving current fishery management practices.

Preliminary Ecopath model of a tropical coastal estuarine ecosystem around bight of Benin, Nigeria

The tropical coastal estuarine ecosystem around Bight of Benin, Nigeria has huge economic importance with limited information on its status and possible impact of fishing. An Ecopath model was constructed to study the trophic interactions and ecosystem properties of the estuary using fourteen functional groups. The model input parameters were gathered from published reports and catch assessment survey. Using network analysis, the system network was mapped into a linear food chain, and five discrete trophic levels were found with a mean transfer efficiency of 7.0 % from detritus and 6.1 % from primary producer. The mixed trophic impact routine showed that functional groups in lower trophic levels had smattering positive and negative impacts across the food web. The ecosystem indices: total primary productivity to total respiration ratio (6.325), total primary productivity to total biomass ratio (82.621), Finn’s cycling index (1.70), mean path length (2.298), connectance index (0.327), system omnivory index (0.288), ascendency (42.3 %) and overhead (57.7 %) showed that the estuarine ecosystem was at the developing stage, stable, susceptible to stress induced changes and could withstand unexpected external perturbation at its present stage.

Adenosine A1 receptor antagonist mitigates deleterious effects of sleep deprivation on adult neurogenesis and spatial reference memory in rats

Sleep deprivation (SD) upsurges intracellular levels of adenosine, impairs adult neuronal cell proliferation (NCP) and cognition while caffeine, a non-selective adenosine A1 receptor (A1R) antagonist improves cognition and adult NCP during SD. We examined the selective antagonistic effects of adenosine A1R using 8-cyclopentyl-1,3-dimethylxanthine (8-CPT) on impairment of spatial reference memory and adult NCP during 48h SD. Adult male Sprague Dawley rats were sleep deprived for 48h, using an automatic cage vibrating stimulus based on animal activity. Spatial reference memory was tested as a measure of cognitive performance employing Morris Water Maze. Rats were given 8-CPT dissolved in 50% dimethyl sulfoxide (DMSO), twice daily (10mg/kg, i.p.) along with 5-bromo-2-deoxyuridine (BrdU) (50mg/kg/day, i.p.). The rats treated with 8-CPT showed significantly short mean latency and path-length to reach the platform compared to the SD rats. Consistent with these findings, 8-CPT-treated group was found to have significantly increased the number of BrdU, Ki-67 and doublecortin (DCX) positive cells. However, no significant difference was seen in NeuN expression in the Dentate Gyrus (DG). Brain-derived neurotropic factor (BDNF) expression in the DG and CA1 region was observed to decrease significantly after SD and be rescued by 8-CPT treatment. Furthermore, latency to reach platform showed a negative correlation with number of BrdU, DCX type-1 cells and BDNF expression in DG. Thus, it may be concluded that treatment with 8-CPT, an adenosine A1R antagonist during SD mitigates SD induced decline in spatial reference memory and adult NCP possibly via up regulation of BDNF levels in DG and CA1 regions.

SINGLE ANODE TRIPLE GEM TISSUE EQUIVALENT PROPORTIONAL COUNTER AS THE BASIS FOR A PERSONAL NEUTRON DOSIMETER.

This paper reports on a tissue-equivalent proportional counter (TEPC) based on a triple gas electron multiplier structure, with a single pad readout, as a basis for a personal neutron dosimeter. Its dosimetric response was studied using the 252Cf neutron source at the Health Physics Generator Facility of the Canadian Nuclear Laboratories. Measured lineal energy spectra were found to be in agreement with numerical simulations performed with Monte Carlo N-Particle eXtended (MCNPX). Both simulations and measurements showed that the mean pathlength of secondary charged particles in the TEPC gas was best represented by the thickness of the drift region of the device. It was determined that the Cauchy Theorem, used to calculate the mean chord length in spherical and cylindrical TEPCs, overestimated the simulated mean chord length by nearly a factor of two. Important operational characteristics of the device were investigated, including gas gain, sensitivity and dosimetric response, as functions of tissue-equivalent gas pressure. This work demonstrates that the proposed design can serve as the basis for a personal neutron dosimeter device, which would satisfy the angular dosimetric response criteria of the personal dosimeter standard IEC61526.