Search

The conventional approach to intensity-modulated radiation therapy treatment planning involves two distinct strategies: optimizing an evaluation function while accounting for dose constraints, and solving feasibility problems using feasibility-seeking projection methods that incorporate inequality constraints. This paper introduces a novel iterative scheme within the framework of continuous dynamical systems, wherein constraint conditions dynamically evolve to enhance the optimization process. The validity of dynamically varying dose constraints is theoretically established through the foundation of continuous-time dynamical systems theory. In particular, we formalize a system of differential equations, with both beam coefficients and dose constraints modeled as state variables. The asymptotic stability of the system's equilibrium is rigorously proven, ensuring convergence to a solution. In practical terms, we leverage a discretized iteration formula derived from the continuous-time system to achieve rapid computational speed. The mathematical structure of the proposed approach, which directly incorporates dose-volume constraints into the objective function, facilitates significant computational efficiency and solution refinement. The proposed method has an inherent dynamics that approaches more desirable solutions within the set of solutions when the solution to the optimization problem is not an isolated point. This property guarantees the identification of optimal solutions that respect the prescribed dose-volume constraints while enhancing accuracy when such constraints are feasible. By treating dose constraints as variables and concurrently solving the optimization problem with beam coefficients, we can achieve more accurate results when compared with using fixed values for prescribed dose conditions. [ABSTRACT FROM AUTHOR]

In this paper, we propose a method for optimizing the parameter values in iterative reconstruction algorithms that include adjustable parameters in order to optimize the reconstruction performance. Specifically, we focus on the power divergence-based expectation-maximization algorithm, which includes two power indices as adjustable parameters. Through numerical and physical experiments, we demonstrate that optimizing the evaluation function based on the extended power-divergence and weighted extended power-divergence measures yields high-quality image reconstruction. Notably, the optimal parameter values derived from the proposed method produce reconstruction results comparable to those obtained using the true image, even when using distance functions based on differences between forward projection data and measured projection data, as verified by numerical experiments. These results suggest that the proposed method effectively improves reconstruction quality without the need for machine-learning techniques in parameter selection. Our findings also indicate that this approach is useful for enhancing the performance of iterative reconstruction algorithms, especially in medical imaging, where high-accuracy reconstruction under noisy conditions is required. [ABSTRACT FROM AUTHOR]

Computed tomography (CT) imaging plays a crucial role in various medical applications, but noise in projection data can significantly degrade image quality and hinder diagnosis accuracy. Iterative algorithms for tomographic image reconstruction outperform transform methods, especially in scenarios with severe noise in projections. In this paper, we propose a method to dynamically adjust two parameters included in the iterative rules during the reconstruction process. The algorithm, named the parameter-extended expectation-maximization based on power divergence (PXEM), aims to minimize the weighted extended power divergence between the measured and forward projections at each iteration. Our numerical and physical experiments showed that PXEM surpassed conventional methods such as maximum-likelihood expectation-maximization (MLEM), particularly in noisy scenarios. PXEM combines the noise suppression capabilities of power divergence-based expectation-maximization with static parameters at every iteration and the edge preservation properties of MLEM. The experimental results demonstrated significant improvements in image quality in metrics such as the structural similarity index measure and peak signal-to-noise ratio. PXEM improves CT image reconstruction quality under high noise conditions through enhanced optimization techniques. [ABSTRACT FROM AUTHOR]

Recently, an extended family of power-divergence measures with two parameters was proposed together with an iterative reconstruction algorithm based on minimization of the divergence measure as an objective function of the reconstructed images for computed tomography. Numerical experiments on the reconstruction algorithm illustrated that it has advantages over conventional iterative methods from noisy measured projections by setting appropriate values of the parameters. In this paper, we present a novel neural network architecture for determining the most appropriate parameters depending on the noise level of the projections and the shape of the target image. Through experiments, we show that the algorithm of the architecture, which has an optimization sub-network with multiplicative connections rather than additive ones, works well. [ABSTRACT FROM AUTHOR]

Iterative image reconstruction algorithms have considerable advantages over transform methods for computed tomography, but they each have their own drawbacks. In particular, the maximum-likelihood expectation-maximization (MLEM) algorithm reconstructs high-quality images even with noisy projection data, but it is slow. On the other hand, the simultaneous multiplicative algebraic reconstruction technique (SMART) converges faster at early iterations but is susceptible to noise. Here, we construct a novel algorithm that has the advantages of these different iterative schemes by combining ordered-subsets EM (OS-EM) and MART (OS-MART) with weighted geometric or hybrid means. It is theoretically shown that the objective function decreases with every iteration and the amount of decrease is greater than the mean between the decreases for OS-EM and OS-MART. We conducted image reconstruction experiments on simulated phantoms and deduced that our algorithm outperforms OS-EM and OS-MART alone. Our algorithm would be effective in practice since it incorporates OS-EM, which is currently the most popular technique of iterative image reconstruction from noisy measured projections. [ABSTRACT FROM AUTHOR]

Simple Summary: Pyrethrum is a botanical insecticide derived from pyrethrum flowers. Feeding deterrence caused by pyrethrum has been noted for several insect species. However, it is unclear whether the deterrent property results from a single component or from a combination of the six insecticidal active ingredients, known as pyrethrins. Here, we determined the feeding deterrence of natural pyrethrins and their two main components (pyrethrins I and II) on the blowfly, Phormia regina, in a dual-choice feeding assay. We found that natural pyrethrins and synthetic pyrethrins I/II in sucrose solution induced feeding deterrence at a concentration 16 times lower than the lowest concentration at which insecticidal action occurs. These results demonstrate that pyrethrins act as a feeding deterrent at sub-lethal concentrations. At the deterring concentration, feeding bouts were interrupted by intensive grooming of the proboscis, suggesting that pyrethrins acted instantly on the oral gustatory system of flies. The potent feeding deterrence of pyrethrins may provide effective protection for pyrethrum plants by rapidly deterring insects from feeding before insecticidal activities occur. Pyrethrum is a botanical insecticide derived from pyrethrum flowers. Feeding deterrence caused by pyrethrum has been reported in several sucking insects; however, there is no account of the cause of deterrence—whether from a single component or the combination of six active ingredients, called pyrethrins. We determined the feeding deterrence of natural pyrethrins, their two main components (pyrethrins I and II), and pyrethroid insecticides on the blowfly, Phormia regina. In a dual-choice feeding assay that minimized tarsal contact with food sources but allowed feeding through proboscises, natural pyrethrins, synthetic pyrethrins I/II, and allethrin were observed to induce deterrence at a concentration 16 times lower than the lowest concentration at which the knockdown rate increased. Feeding bouts were interrupted by intensive grooming of the proboscis at the deterring concentration, but no such grooming was observed to occur while feeding on the unpalatable tastants—NaCl, quinine, and tartaric acid. The underlying mode of action for the feeding deterrence of pyrethrins at sub-lethal concentrations probably occurs on the fly oral gustatory system, while differing from that of unpalatable tastants. The potent feeding deterrence of pyrethrins may provide effective protection for pyrethrum plants by rapidly deterring insects from feeding, before insecticidal activities occur. [ABSTRACT FROM AUTHOR]

Iterative reconstruction of density pixel images from measured projections in computed tomography has attracted considerable attention. The ordered-subsets algorithm is an acceleration scheme that uses subsets of projections in a previously decided order. Several methods have been proposed to improve the convergence rate by permuting the order of the projections. However, they do not incorporate object information, such as shape, into the selection process. We propose a block-iterative reconstruction from sparse projection views with the dynamic selection of subsets based on an estimating function constructed by an extended power-divergence measure for decreasing the objective function as much as possible. We give a unified proposition for the inequality related to the difference between objective functions caused by one iteration as the theoretical basis of the proposed optimization strategy. Through the theory and numerical experiments, we show that nonuniform and sparse use of projection views leads to a reconstruction of higher-quality images and that an ordered subset is not the most effective for block-iterative reconstruction. The two-parameter class of extended power-divergence measures is the key to estimating an effective decrease in the objective function and plays a significant role in constructing a robust algorithm against noise. [ABSTRACT FROM AUTHOR]

Background and Aim: Knowledge on the risk of gastrointestinal (GI) bleeding in hemodialysis patients is limited. We evaluated the risk of GI bleeding in hemodialysis patients compared with non‐hemodialysis patients. Methods: We performed a retrospective cohort study from 1996 to 2017 at the Graduate School of Medicine, University of Tokyo, and Horinouchi Hospital. We analyzed patients on hemodialysis for chronic renal failure and controls not on hemodialysis. The primary endpoint was GI bleeding. A survival analysis was performed to estimate the cumulative incidence and hazard ratio of GI bleeding. Results: A total of 14 451 patients were analyzed (417 hemodialysis and 14 034 non‐hemodialysis patients). In total, 524 GI bleeding events occurred. Upper and lower GI bleeding occurred in 432 and 92 patients in the hemodialysis and non‐hemodialysis groups, respectively. The most frequent source of upper and lower GI bleeding was gastric ulcer and colonic diverticular bleeding, respectively. The cumulative incidence of GI bleeding was 4.44% at 1 year, 7.15% at 3 years, and 10.40% at 5 years in hemodialysis patients; the respective rates were 2.35%, 2.98%, and 3.79% in non‐hemodialysis patients during a mean follow‐up period of 3.5 years. Hemodialysis was significantly associated with an increased risk of GI bleeding after adjustment (hazard ratio 1.67, P = 0.01, 95% confidence interval 1.13–2.50). Conclusions: Hemodialysis patients had a GI bleeding rate of 10% over 5 years, and hemodialysis was a risk factor for GI bleeding. [ABSTRACT FROM AUTHOR]

Multivalued discrete tomography involves reconstructing images composed of three or more gray levels from projections. We propose a method based on the continuous-time optimization approach with a nonlinear dynamical system that effectively utilizes competition dynamics to solve the problem of multivalued discrete tomography. We perform theoretical analysis to understand how the system obtains the desired multivalued reconstructed image. Numerical experiments illustrate that the proposed method also works well when the number of pixels is comparatively high even if the exact labels are unknown. [ABSTRACT FROM AUTHOR]

Introduction Pancreaticoduodenectomy (PD) combined with extended right hemicolectomy (RH) is a challenging procedure for locally advanced malignancies. However, information concerning the reconstruction method of the digestive system is limited. Here, we present a case and surgical technique of a novel intestinal rotation method for digestive reconstruction after PD combined with RH. Presentation of case A 62-year-old man with locally advanced pancreatic cancer received conversion surgery combined with PD and RH after preoperative chemotherapy. With respect to the reconstruction of the digestive system, the entire intestinal mesentery was rotated 180° forward counterclockwise around the axis of the superior mesenteric artery, and then the reconstruction, according to Child’s method, was performed. The patient recovered without problems in gastroenterological functions after the operation. Discussion With respect to the reconstruction of the digestive system in patients undergoing combined PD and RH, practitioners should pay close attention to twisting of the intestinal mesentery when bringing up the proximal jejunum for pancreatojejunostomy and hepatojejunostomy and the distal ileum for ileocolic anastomosis. This intestinal rotation method enables a smooth and uneventful reconstruction of the digestive system. Conclusion This is the first detailed description of an intestinal rotation method for digestive reconstruction after combined PD and extended RH. The intestinal rotation method can be an alternative and helpful technical option for digestive reconstruction in patients with combined PD and RH. [ABSTRACT FROM AUTHOR]

Non-diapausing spider mites (Tetranychus urticae) live on the undersurface of host leaves during summer, but diapausing mites overwinter in dark hibernacula. The light environments of these habitats differ: visible radiation (VIS) but not ultraviolet radiation (UV) reaches the undersurface of leaves, but neither enters dark hibernacula. Thus, mites of either seasonal form could locate their preferred habitat by photo-orientation responses to UV and VIS. To investigate this possibility, we analysed the mites' locomotion behaviour on a virtual field with a programmed chequered pattern of light and dark patches in a micro-locomotion compensator. Both non-diapausing and diapausing mites moved away from UV-illuminated patches into dark patches. Non-diapausing mites moved towards VIS-Nluminated patches, whereas diapausing mites did not show a preference. Our results show that non-diapausing mites avoid UV and are attracted to VIS, suggesting that this can guide them beneath a leaf. Diapausing mites simply avoid UV. The lack of a preference for VIS during diapause could be due to changes in carotenoid metabolism, which also involve orange pigmentation of diapausing mites. We consider that a diapause-mediated switch of the response to VIS, together with regular avoidance of UV, plays a key role in the seasonal change of habitat selection in this species. This seasonal polyphenism involves alterations in not only reproductive state and pigmentation, but also in photo-spectral responses. [ABSTRACT FROM AUTHOR]

To examine the effect of storage temperature on the emission of methane (CH4) and carbon dioxide (CO2) and on recovery of nutrients from raw dairy manure slurry (RS) and slurry digested in a methane digester (DS), both slurries were stored in closed 100 L steel tanks under psychrophilic conditions (5, 10, 15 and 20°C) for a 150 day period. As the storage temperature increased, total methane emission increased in both types of slurry. The amount of methane emitted per unit of volatile solids of the RS and DS was 0.19 L/g and 0.10 L/g, respectively. The respective carbon dioxide emissions were 0.20 L/g for RS and 0.12 L/g for DS at 20°C of storage temperature. At temperatures greater than 15°C, the methane concentration in the emitted gas remained more than 40% of the total gas. During the experimental period, in excess of 90% of the total Kjeldahl nitrogen in these slurries was recovered (91.4–93.7% for RS and 93.7–98.4% for DS) after storage, and ammonium nitrogen was recovered in excess of 100% (100.1–143.2% for RS and 106.7–143.2% for DS storage tanks) because of the mineralization of organic nitrogen in the influent. These results indicate that manure slurry characteristics and storage temperature have significant impacts on methane emission. It can be concluded that on typical farms located in northern Japan, methane emission from manure storage tanks during late fall, winter and early spring may be negligible, because of manure temperatures less than 10°C. During late spring, summer and early fall, methane emissions can be substantially reduced by using underground storage to maintain lower manure temperatures. [ABSTRACT FROM AUTHOR]

Changes in the characteristics of CuInGaSe2 solar cells in response to light irradiation were investigated. Then these changes, which suggest long-term degradation, were clarified using the measurement technique by feeble light. The thin-film cell of this type is considered to be “ever stable”. A stable result over the short term was also obtained in the light accelerated test of 2-SUN performed in this experiment. On the other hand, it was found that the characteristics measured with feeble light show a remarkable change over time. As a result of measuring at 0.065–105 mW/cm2 light intensity, the change rate of cell output power was so intense the measurement light was weak. This finding reflects the increase in an internal defect and suggests a possibility that light irradiation exerts the influence on long-term cell performance. Moreover, by measuring with feeble light, we found that the changed output recovers by reverse voltage application. The phenomenon of recovery up on comparatively low reverse voltage can be considered as an application for maintaining stability. [Copyright &y& Elsevier]

The problem of tomographic image reconstruction can be reduced to an optimization problem of finding unknown pixel values subject to minimizing the difference between the measured and forward projections. Iterative image reconstruction algorithms provide significant improvements over transform methods in computed tomography. In this paper, we present an extended class of power-divergence measures (PDMs), which includes a large set of distance and relative entropy measures, and propose an iterative reconstruction algorithm based on the extended PDM (EPDM) as an objective function for the optimization strategy. For this purpose, we introduce a system of nonlinear differential equations whose Lyapunov function is equivalent to the EPDM. Then, we derive an iterative formula by multiplicative discretization of the continuous-time system. Since the parameterized EPDM family includes the Kullback–Leibler divergence, the resulting iterative algorithm is a natural extension of the maximum-likelihood expectation-maximization (MLEM) method. We conducted image reconstruction experiments using noisy projection data and found that the proposed algorithm outperformed MLEM and could reconstruct high-quality images that were robust to measured noise by properly selecting parameters. [ABSTRACT FROM AUTHOR]

Chondro-4-sulfatase and chondro-6-sulfatase from Proteus vulgaris and &Delta4hexuronate-2-suIfatase from Flavobacterium heparinum are potentially useful tools for structural studies of chondroitin sulfate and dermatan sulfate. Their substrate specificities were investigated with various structurally defined, sulfated hexasaccharides isolated from chondroitin sulfate as described in the accompanying report [Sugahara, K., Nadanaka, S., Takeda. K. &kojima, T. (1996) Eur. J.Biochem, 239, 871-880]. The results indicated that Δ4 hexuronate-2-sulfatase released an ester sulfate from C2 position of the Δ hexuronate residue located at tile non-reducing terminus, while chondro-4-sulfatase removed an ester sulfate from the C6 position of the GaINAc residue at the reducing end of the hexasaccharides, Chondro-4-su1fatase acted preferentially on an ester sulfate on the C4 position of the GaINAc residue at the reducing end under mild incubation conditions. but also released a sulfate group under harsh conditions from the C4 position of the GalNAc residue at the internal positions of the hexasaccharide chains, unless the GaINAc residue had another ester sulfate on its C6 position. The results demonstrated the usefulness of the sulfatases as tools for the structural characterization of chondroitin sulfate oligosaccharides. [ABSTRACT FROM AUTHOR]

The enzymatic action of highly purified chondroitin ABC lyase from Proteus vulgaris is dependent on the size of the substrate. and the enzyme does not cleave tetrasaccharides, irrespective of their sulfation profiles [Sugahara, K . Shigeno. K.., Masuda, M., Fujii. N.,. Kurosaka, A. & Takeda. K. (1994) Carbohydr Res. 255. 145- 1631. To characterize the enzyme action in more detail we isolated nine sulfated hexasaccharides from commercial shark cartilage chondroitin sulfate D. after partial digestion with highly purified chondroitin ABC lyase. by means of gel chromatography and HPLC on an amine-bound silica column. Structural analysis by 500-MHz iH-NMR spectroscopy. and enzymatic digestion in conjunction with HPLC. demonstrated that these hexasaccharides, with the common core saccharide structure Δ4HexA(α1-3 )Ga1NAc(β1-4)GIcA(Β1 -3 )GalNAc(β1 -4)GlcA (β1-3)GaINAc (where ΔHexA and GlcA represent 4-deoxy-α-L-threo-hex-4-enepyranosyluronic acid and glucuronic acid, respectively) near three or four sulfate groups in different combinations. In the hexasaccharides, the D disaccharide unit GIcA2- SO3- (β3 )GaINAc6SO3- which is characteristic of chondroitin sulfate D, was arranged on the reducing side of the A disaccharide unit GlcA(β1-3)GalNAc4SO3- and thus formed an A- D- tetrasaccharide sequence GlcA(β1-3)Ga1NAc4SO3- (β1-4)GIcA2SO3- (β1-3)GaINAc6SO3-. Analysis of the degradation products of these hexasaucharides with highly purified chondroitin ABC lyase indicated that the enzyme preferentially acted on the unsaturated hexasaecharides in an exolytic fashion and removed an unsaturated disaccharide unit from the non-reducing termini, irrespective of the sulfation profiles of the hexasaceharides. [ABSTRACT FROM AUTHOR]

Differences in the Mode of Lethality Produced through Intravenous and Oral Administration of Organophosphorus Insecticides in Rats. TAKAHASHI, H., KOJIMA, T., IKEDA, T., TSUDA, S. and SHIRASU, Y. (1991). . 16, 459–468. This study was undertaken to investigate the possibility that mechanisms other than cholinesterase (ChE) inhibition account for the acute toxicity of organophosphorus insecticide. Both the P═O type insecticide (direct ChE inhibitors: chlorfenvinphos and dichlorvos) and the P═S type insecticide (indirect ChE inhibitors: diazinon and fenthion) were employed. Rats treated with lethal doses of intravenous and oral P═O type insecticides and oral P═S type insecticides exhibited typical signs of anti-ChE poisoning along with marked inhibition of brain and erythrocyte ChE activity. In contrast, rats given lethal doses of intravenous P═S type insecticides exhibited tonic convulsions and opisthotonos, with only slight inhibition of ChE activities. When P═O type insecticides were intravenously administered to anesthetized and conscious rats, animals exhibited typical anti-ChE poisoning signs in cardiorespiration: hypertension and apnea which were antagonized by atropine. After administration of lethal doses of P═O type insecticides, breathing disappeared before the cessation of heart beats. Rats receiving lethal doses of intravenous P═S type insecticides did not show hypertension, but exhibited transient cessation of breathing and heart beats. Breathing was observed after the disappearance of heart beats. The electroencephalogram (EEG) was characterized by spike and wave complexes. The EEG and cardiorespiratory changes were not antagonized by atropine. It was concluded that lethality following intravenous P═S type insecticides may be independent of ChE inhibition. [ABSTRACT FROM PUBLISHER]

Pretreatment of Rats with an Organophosphorus Insecticide, Chlorfenvinphos, Protects against Subsequent Challenge with the Same Compound. IKEDA, T., KOJIMA, T., YOSHIDA, M., TAKAHASHI, H., TSUDA, S., AND SHIRASU, Y. (1990). . , 560–567. A single oral pretreatment of rats with chlorfenvinphos (CVP) reduced toxicity of the same compound subsequently administered. This protection occurred 8 hr and became maximal 24 hr after the oral pretreatment at a dose of 15 mg/kg (about half of its LD50). The 24-hr pretreatment with CVP increased the LD50 of CVP threefold, but did not change the type of toxic signs and time to death caused by CVP. The CVP pretreatment did not appreciably change the toxicities of the cholinergic agonists, carbachol and oxotremorine, but significantly increased the toxicity of another organophosphate, dichlorvos. Oral treatment of rats with CVP (15 mg/ kg) inhibited brain acetylcholinesterase (AChE) activity. This inhibition became maximal at 4 hr (about 20% of control) and lasted more than 24 hr after the administration. Twenty-four hours after oral administration of CVP (15 mg/kg), the second dose (CVP 30 mg/kg, po) was less effective in inhibiting cholinesterase activities of the brain, erythrocyte, and plasma compared with naive rats treated with the same dose. The difference in brain AChE activity between control and CVP pretreatment groups was greater in magnitude than that measured in erythro-cytes. CVP concentration in plasma after the oral administration of CVP (30 mg/kg) was decreased by the CVP pretreatment. Area under the concentration vs time curve (AUC) in the CVP-pretreated group was about one-fourth of AUC in the control group. This decrease in the AUC was comparable to the decrease in the toxicity of CVP. Thus, the protection against subsequent CVP challenge may be due to the reduction in the inhibition of brain AChE activity caused by the decrease in plasma CVP concentration. [ABSTRACT FROM PUBLISHER]

Reflection high-energy electron diffraction (RHEED) intensity oscillation during sublimation of GaAs is observed at high substrate temperatures above 690 °C. This post-growth RHEED intensity oscillation suggests that the sublimation occurs layer by layer. One period of this oscillation precisely corresponds to sublimation of one monolayer. Aluminum arsenide acts as a sublimation stopper. The sublimation rate was measured accurately as a function of substrate temperature. [ABSTRACT FROM AUTHOR]

Iterative reconstruction (IR) algorithms based on the principle of optimization are known for producing better reconstructed images in computed tomography. In this paper, we present an IR algorithm based on minimizing a symmetrized Kullback-Leibler divergence (SKLD) that is called Jeffreys’ J-divergence. The SKLD with iterative steps is guaranteed to decrease in convergence monotonically using a continuous dynamical method for consistent inverse problems. Specifically, we construct an autonomous differential equation for which the proposed iterative formula gives a first-order numerical discretization and demonstrate the stability of a desired solution using Lyapunov’s theorem. We describe a hybrid Euler method combined with additive and multiplicative calculus for constructing an effective and robust discretization method, thereby enabling us to obtain an approximate solution to the differential equation. We performed experiments and found that the IR algorithm derived from the hybrid discretization achieved high performance. [ABSTRACT FROM AUTHOR]