Evaluation of optimal density weighting for regridding

2007 ◽  
Vol 25 (5) ◽  
pp. 695-702 ◽  
Author(s):  
Mark Bydder ◽  
Alexey A. Samsonov ◽  
Jiang Du
Keyword(s):  
Optimal Density ◽  
Density Weighting

Optimal Density Determination of Bouguer Anomaly Using Fractal Analysis (Case of study: Charak area,IRAN)

2005 ◽  
Vol 1 (1) ◽  
pp. 21-24
Author(s):  
Hamid Reza Samadi
Keyword(s):  
Surface Roughness ◽  
Fractal Dimension ◽  
Fractal Analysis ◽  
Fractal Geometry ◽  
Host Rock ◽  
Bouguer Anomaly ◽  
Research Area ◽  
Density Difference ◽  
Optimal Density

In exploration geophysics the main and initial aim is to determine density of under-research goals which have certain density difference with the host rock. Therefore, we state a method in this paper to determine the density of bouguer plate, the so-called variogram method based on fractal geometry. This method is based on minimizing surface roughness of bouguer anomaly. The fractal dimension of surface has been used as surface roughness of bouguer anomaly. Using this method, the optimal density of Charak area insouth of Hormozgan province can be determined which is 2/7 g/cfor the under-research area. This determined density has been used to correct and investigate its results about the isostasy of the studied area and results well-coincided with the geology of the area and dug exploratory holes in the text area

scholarly journals Influence of dosimetry method on bone lesion absorbed dose estimates in PSMA therapy: application to mCRPC patients receiving Lu-177-PSMA-I&T

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Julia Brosch-Lenz ◽  
Carlos Uribe ◽  
Astrid Gosewisch ◽  
Lena Kaiser ◽  
Andrei Todica ◽  
...  
Keyword(s):  
Organs At Risk ◽  
Bone Lesion ◽  
Absorbed Dose ◽  
Hounsfield Unit ◽  
Outcome Data ◽  
Computational Effort ◽  
Bone Lesions ◽  
Castration Resistant Prostate Cancer ◽  
Percentage Difference ◽  
Density Weighting

Abstract Background Patients with metastatic, castration-resistant prostate cancer (mCRPC) present with an increased tumor burden in the skeleton. For these patients, Lutetium-177 (Lu-177) radioligand therapy targeting the prostate-specific membrane antigen (PSMA) has gained increasing interest with promising outcome data. Patient-individualized dosimetry enables improvement of therapy success with the aim of minimizing absorbed dose to organs at risk while maximizing absorbed dose to tumors. Different dosimetric approaches with varying complexity and accuracy exist for this purpose. The Medical Internal Radiation Dose (MIRD) formalism applied to tumors assumes a homogeneous activity distribution in a sphere with unit density for derivation of tumor S values (TSV). Voxel S value (VSV) approaches can account for heterogeneous activities but are simulated for a specific tissue. Full patient-individual Monte Carlo (MC) absorbed dose simulation addresses both, heterogeneous activity and density distributions. Subsequent CT-based density weighting has the potential to overcome the assumption of homogeneous density in the MIRD formalism with TSV and VSV methods, which could be a major limitation for the application in bone metastases with heterogeneous density. The aim of this investigation is a comparison of these methods for bone lesion dosimetry in mCRPC patients receiving Lu-177-PSMA therapy. Results In total, 289 bone lesions in 15 mCRPC patients were analyzed. Percentage difference (PD) of average absorbed dose per lesion compared to MC, averaged over all lesions, was + 14 ± 10% (min: − 21%; max: + 56%) for TSVs. With lesion-individual density weighting using Hounsfield Unit (HU)-to-density conversion on the patient’s CT image, PD was reduced to − 8 ± 1% (min: − 10%; max: − 3%). PD on a voxel level for three-dimensional (3D) voxel-wise dosimetry methods, averaged per lesion, revealed large PDs of + 18 ± 11% (min: − 27%; max: + 58%) for a soft tissue VSV approach compared to MC; after voxel-wise density correction, this was reduced to − 5 ± 1% (min: − 12%; max: − 2%). Conclusion Patient-individual MC absorbed dose simulation is capable to account for heterogeneous densities in bone lesions. Since the computational effort prevents its routine clinical application, TSV or VSV dosimetry approaches are used. This study showed the necessity of lesion-individual density weighting for TSV or VSV in Lu-177-PSMA therapy bone lesion dosimetry.

Starting-wave and Optimal Density in a Queue

2013 ◽  
pp. 1375-1383
Author(s):  
Akiyasu Tomoeda ◽  
Daichi Yanagisawa ◽  
Takashi Imamura ◽  
Katsuhiro Nishinari
Keyword(s):  
Optimal Density

scholarly journals Intraspecific variation in symbiont density in an insect-microbe symbiosis

2020 ◽  
Author(s):  
Benjamin J. Parker ◽  
Jan Hrček ◽  
Ailsa H.C. McLean ◽  
Jennifer A. Brisson ◽  
H. Charles J. Godfray
Keyword(s):  
Intraspecific Variation ◽  
Fungal Pathogens ◽  
Acyrthosiphon Pisum ◽  
Natural Populations ◽  
Pea Aphid ◽  
Optimal Density ◽  
Evolutionary Forces ◽  
Standing Variation ◽  
Dramatic Decline

AbstractMany insects host vertically-transmitted microbes, which can confer benefits to their hosts but are costly to maintain and regulate. A key feature of these symbioses is variation: for example, symbiont density can vary among host and symbiont genotypes. However, the evolutionary forces maintaining this variation remain unclear. We studied variation in symbiont density using the pea aphid (Acyrthosiphon pisum) and the bacterium Regiella insecticola, a symbiont that can protect its host against fungal pathogens. We found that relative symbiont density varies both between two Regiella phylogenetic clades and among aphid ‘biotypes’. Higher-density symbiont infections are correlated with stronger survival costs, but variation in density has little effect on the protection Regiella provides against fungus. Instead, we found that in some aphid genotypes, a dramatic decline in symbiont density precedes the loss of a symbiont infection. Together, our data suggest that the optimal density of a symbiont infection is likely different from the perspective of aphid and microbial fitness. Regiella might prevent loss by maintaining high within-host densities, but hosts do not appear to benefit from higher symbiont numbers and may be advantaged by losing costly symbionts in certain environments. The standing variation in symbiont density observed in natural populations could therefore be maintained by antagonistic coevolutionary interactions between hosts and their symbiotic microbes.

scholarly journals Optimal density of biological cells

2020 ◽  
Author(s):  
Tin Yau Pang ◽  
Martin J. Lercher
Keyword(s):  
Reaction Kinetics ◽  
Mass Density ◽  
Reaction Rates ◽  
Cellular Growth ◽  
Metabolic Reaction ◽  
Optimal Density ◽  
E Coli ◽  
Background Density ◽  
Model Cell ◽  
Metabolic Reactions

AbstractA substantial fraction of the bacterial cytosol is occupied by catalysts and their substrates. While a higher volume density of catalysts and substrates might boost biochemical fluxes, the resulting molecular crowding can slow down diffusion, perturb the reactions’ Gibbs free energies, and reduce the catalytic efficiency of proteins. Due to these tradeoffs, dry mass density likely possesses an optimum that facilitates maximal cellular growth and that is interdependent on the cytosolic molecule size distribution. Here, we analyse the balanced growth of a model cell with metabolic and ribosomal reactions, accounting systematically for crowding effects on reaction kinetics. We find that changes in cytosolic density affect biochemical efficiency more strongly for ribosomal reactions than for metabolic reactions, which involve much smaller catalysts and reactants. Accordingly, optimal cytosolic density depends on cellular resource allocation into ribosomal vs. metabolic reactions. A shift in the relative contributions of these sectors to the cellular economy explains the 10% difference in the cytosolic density between E. coli bacteria growing in nutrient-rich and -poor environments. We conclude that cytosolic density variation in E. coli is consistent with an optimality principle of cellular efficiency.Significance statementThe cellular cytosol harbours diverse molecules, whose crowding slows down diffusion and perturbs the chemical equilibrium of biochemical reactions. Reaction rates thus depend not only on the reactants themselves, but also on the background density of other molecules; consequently, maximal cell growth requires an optimal density. Here, we simulate a model cell with crowding-adjusted metabolic reaction kinetics. Its cytosol accommodates two types of reactions: metabolic reactions involving small molecules, and protein production reactions involving much larger molecules. These two cellular subsystems have distinct optimal densities, and a shift in their relative contribution to the cellular biomass explains the 10% difference in the cytosolic density between E. coli bacteria growing in nutrient-rich and -poor environments.

Optimal density taper for plasma lenses

1992 ◽  
Author(s):  
T. Katsouleas ◽  
C. H. Lai
Keyword(s):  
Optimal Density

Estimating the economic optimal target density of hybrid canola based on data from a western Canadian meta-analysis

2020 ◽  
Author(s):  
Murray D. Hartman ◽  
Scott R. Jeffrey
Keyword(s):  
Plant Density ◽  
Meta Analysis ◽  
Yield Response ◽  
Western Canada ◽  
Seeding Rate ◽  
Optimal Density ◽  
Herbicide Resistant ◽  
Plant Densities ◽  
Optimal Target ◽  
The Relationship

Canola production in western Canada has expanded such that in many regions canola area rivals the area seeded to wheat. This change can be mainly attributed to adoption of herbicide resistant hybrid varieties, and resulting higher relative profitability. Producers responded to higher seed prices by reducing seeding rates, leading to plant densities that were often lower than industry recommendations. The study objectives were to examine canola yield response to plant density and assess economically optimal density levels relative to industry recommendations and grower practices. A meta-analysis approach was applied to yield response and plant density data with herbicide resistant hybrid canola from multiple studies. Three alternative marginal yield-density functions were estimated and used to calculate economically optimal plant density. Sensitivity of results to key parameters was assessed. Resulting optimal density levels under recent average prices, seed size and emergence were 62-73 plants m-2, consistent with industry recommendations for western Canada. Recent field surveys report lower densities than this range, suggesting that producers are seeding at less than optimal rates. However, there is significant uncertainty associated with canola production, and interaction of seeding rate with other factors. These would impact on optimal plant density, although much of the uncertainty remains until well after seeding. The empirical results represent a foundation for development of more detailed models, highlight the significance of the relationship between plant density and economically optimal yield, and suggest the need to develop decision making tools to support producers in making canola planting decisions.

scholarly journals On the density function on moduli spaces of toric 4-manifolds

2016 ◽  
Vol 16 (3) ◽  
Author(s):  
Alessio Figalli ◽  
Álvaro Pelayo
Keyword(s):  
Density Function ◽  
Moduli Spaces ◽  
Toric Manifold ◽  
Optimal Density

AbstractThe optimal density function assigns to each symplectic toric manifold

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