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1.
Differentiation ; 117: 16, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33454151

RESUMEN

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the authors, with the approval of the Editor-in-Chief. The journal was initially contacted by the corresponding author to report the unavailability of the raw data of the results presented by the article, as well as the similarity between the Western blots from Figure 11A (MMP-3) and Figure 11C (MMP-3). Also, a significant amount of text has been reused from the articles that the authors have previously published in the Experimental Cell Research 341 (2016) 92-104 https://doi.org/10.1016/j.yexcr.2016.01.010 and the Journal of Biological Chemistry 289 (2014) 14380-14391 https://doi.org/10.1074/jbc.M113.526772. All of the authors except Nobuaki Ozeki and Taiki Hiyama have reportedly agreed to retract the article. N. Ozeki left Aichi Gakuin University in March 2018 and does not respond to co-authors inquiries, while T. Hiyama left Aichi Gakuin University and could not be reached. The authors deeply regret this error and any inconvenience it may have caused.

2.
J Mater Cycles Waste Manag ; 24(3): 1194-1204, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35221793

RESUMEN

In this study, total burned household waste and the potential emissions released from waste burning in Semarang City, Indonesia, were estimated. Waste piles were monitored using the transect walk survey method in 16 sub-districts of Semarang City. Carbon monoxide (CO), carbon dioxide (CO2), hydrocarbon (HC), nitrous oxide (NOx), and total particulate matter (TPM) were directly analyzed through a simulation of waste combustion. The potential emissions from other pollutants were predicted by multiplying the weight of the burned waste by the emission factors available in the literature. The estimated waste burned in Semarang City in 2020-2021 was 58.8 Gg/year, or approximately 9.70% of the total waste generated in Semarang City. This estimation exceeds local government estimates of 2020 by two-fold. Peri-urban areas (both inner and outer) were identified as the most significant contributors to waste burning. Further, garden waste was the most burned waste (73.61%), followed by plastic waste (17.45%). Other wastes, including paper, leather, textile, rubber, and food, were also burned. Overall, a decrease in the activity of waste burning is an important step for reducing the potential of air pollution and climate change. Supplementary Information: The online version contains supplementary material available at 10.1007/s10163-022-01371-3.

3.
J Mater Cycles Waste Manag ; 24(5): 1633-1647, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35615496

RESUMEN

Open burning is a waste management practice performed by many people worldwide, especially in developing countries. Lack of detailed data of open burning practices may lead to a misinterpretation during data analysis, especially when estimating global/local emissions and assessing risks. This study presents a comprehensive review of current research trends, methodological assessments, and factors behind open waste burning practices from published literature. This review used systematic methods such as PRISMA 2020 methodology, a bibliometric approach, and qualitative content analysis to determine and assess 84 articles related to open burning. The results show that environmental risks and emission factors related to open burning incidents at the landfill or residential level are preferable topics that will be rising in the years to come. Coupling methods such as a transect-based approach with a questionnaire survey and mobile-static plume sampling to determine the activities and incidents as baseline data for risk assessment will help researchers gain a robust dataset of open burning emission inventory. In addition, it was found that environmental knowledge and awareness levels influence open burning practices, thereby opening up opportunities for future research. Supplementary Information: The online version contains supplementary material available at 10.1007/s10163-022-01430-9.

4.
Differentiation ; 93: 1-14, 2017.
Artículo en Inglés | MEDLINE | ID: mdl-27639333

RESUMEN

While human induced pluripotent stem (hiPS) cells have potential use in regenerative medicine, there are no reports on odontoblastic differentiation of hiPS cells. In the current study, to examine integrin profiles and explore the early signaling cascade of odontoblastic differentiation in hiPS cells, we investigated the regulation of autophagy-related gene (Atg) and wingless/int1 (Wnt) signaling in gelatin scaffold (GS) combined with bone morphogenetic protein (BMP)-4 (GS/BMP-4)-mediated odontoblastic differentiation. Following GS/BMP-4 treatment, there was a dramatic loss of α3 and α6 integrins, and reciprocal strong induction of α1 integrin expression in the differentiated cells. GS/BMP-4 increased the mRNA and protein levels of Atg10, Lrp5/Fzd9 (an Atg10 receptor), and Wnt5 together with the amount of autophagosomes and autophagic fluxes. Treatment with siRNAs against Atg10 and Wnt5a individually suppressed the GS/BMP-4-induced increase in odontoblastic differentiation. The odontoblastic phenotype was inhibited by chloroquine, but increased after treatment with rapamycin (an autophagy enhancer). Taken together with our previous findings, we have replicated our results from the rodent system in a novel human system. We have revealed a unique sequential cascade involving Atg10, Wnt5a, α1 integrin, and matrix metalloproteinase-3 in GS/BMP-4-induced differentiation of hiPS cells into odontoblast-like cells at a relatively early stage.


Asunto(s)
Proteínas Relacionadas con la Autofagia/genética , Diferenciación Celular/genética , Células Madre Pluripotentes Inducidas/efectos de los fármacos , Cadenas alfa de Integrinas/genética , Metaloproteinasa 3 de la Matriz/genética , Proteínas de Transporte Vesicular/genética , Proteína Wnt-5a/genética , Proteína Morfogenética Ósea 4/administración & dosificación , Diferenciación Celular/efectos de los fármacos , Gelatina/administración & dosificación , Gelatina/química , Humanos , Células Madre Pluripotentes Inducidas/citología , Odontoblastos/efectos de los fármacos , ARN Interferente Pequeño/administración & dosificación , Medicina Regenerativa , Transducción de Señal/efectos de los fármacos , Sirolimus/administración & dosificación , Andamios del Tejido
5.
Exp Cell Res ; 347(1): 24-41, 2016 09 10.
Artículo en Inglés | MEDLINE | ID: mdl-27397580

RESUMEN

We established a differentiation method for homogeneous α7 integrin-positive human skeletal muscle stem cell (α7(+)hSMSC)-derived osteoblast-like cells with bone morphogenetic protein (BMP)-2. To explore the early signaling cascade for osteoblastic differentiation, we examined the upregulation of autophagy-related gene (Atg) and wingless/int1 (Wnt) signaling during BMP-2-mediated human osteoblastic differentiation. In a screening experiment, BMP-2 increased the mRNA and protein levels of Atg7, Wnt16, and Lrp5/Fzd2 (a Wnt receptor), but not microtubule-associated protein 1 light chain (LC3; a mammalian homolog of yeast Atg8), TFE3, Beclin1, Atg5, Atg12, Wnt3a, or Wnt5, together with the amounts of autophagosomes and autophagy fluxes. Treatment with siRNAs against Atg7 and Wnt16 individually suppressed the BMP-2-induced increase in osteoblastic differentiation. The osteoblastic phenotype, involving osteocalcin (BGLAP), osteopontin (SPP1), and osterix (SP7) expression, decreased when autophagy was inhibited by chloroquine (an autophagy inhibitor), but increased after treatment with rapamycin (an autophagy enhancer). Taken together with our previous findings, we have revealed a unique sequential cascade of BMP-2→Atg7→Wnt16→Lrp5/Fzd2→matrix metalloproteinase-13→osteoblastic differentiation. This cascade results in a potent increase in osteoblastic cell differentiation, indicating the unique involvement of Atg7, autophagy, and Wnt16 signaling in BMP-2-induced differentiation of α7(+)hSMSCs into osteoblast-like cells at a relatively early stage.


Asunto(s)
Proteína 7 Relacionada con la Autofagia/metabolismo , Proteína Morfogenética Ósea 2/farmacología , Proteína Morfogenética Ósea 4/farmacología , Diferenciación Celular/efectos de los fármacos , Osteoblastos/metabolismo , Células Madre/citología , Proteínas Wnt/metabolismo , Antígenos CD/metabolismo , Autofagia/efectos de los fármacos , Proteína 7 Relacionada con la Autofagia/genética , Biomarcadores/metabolismo , Cloroquina/farmacología , Silenciador del Gen/efectos de los fármacos , Humanos , Cadenas alfa de Integrinas/metabolismo , Modelos Biológicos , Músculo Esquelético/citología , Osteoblastos/efectos de los fármacos , Osteogénesis/efectos de los fármacos , Osteogénesis/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , ARN Interferente Pequeño/metabolismo , Sirolimus/farmacología , Células Madre/efectos de los fármacos , Células Madre/metabolismo , Tretinoina/farmacología
6.
Exp Cell Res ; 341(1): 92-104, 2016 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-26806855

RESUMEN

We previously confirmed a unique and unanticipated role for an α2 integrin, extracellular matrix metalloproteinase inducer (Emmprin), and matrix metalloproteinase (MMP)-3-mediated signaling cascade, in driving the odontoblast-like differentiation of mouse embryonic stem (ES) cells in a collagen type-I scaffold (CS) combined with bone morphogenetic protein (BMP)-4 (CS/BMP-4). To explore the early signaling cascade for odontoblastic differentiation, we examined the upregulation of autophagy-related gene (Atg) and Wnt signaling by CS/BMP-4 mediated odontoblast differentiation. In a screening experiment, CS/BMP-4 increased the mRNA and protein levels of Atg5, Lrp5/Fzd9 (an Atg5 receptor), and Wnt5, but not microtubule-associated protein 1 light chain (LC3; a mammalian homolog of yeast Atg8), TFE3, Beclin1, and Atg12, together with the amount of autophagosomes and autophagy fluxes. Treatment with siRNAs against Atg5 and Wnt5 individually suppressed the CS/BMP-4-induced increase in odontoblast differentiation. The odontoblastic phenotype, involving dentin matrix protein-1 and dentin sialophosphoprotein expression, decreased when autophagy was inhibited by chloroquine, but increased after treatment with rapamycin (an autophagy enhancer). Taken together with our previous findings, we have revealed a unique sequential cascade involving Atg5, Wnt5a, α2 integrin, Emmprin, and MMP-3. This cascade results in a potent increase in odontoblastic cell differentiation, indicating the unique involvement of Atg5, autophagy and Wnt5 signaling in CS/BMP-4-induced differentiation of ES cells into odontoblast-like cells, at a relatively early stage.


Asunto(s)
Diferenciación Celular , Células Madre Embrionarias/citología , Proteínas Asociadas a Microtúbulos/metabolismo , Odontoblastos/citología , Proteínas Wnt/metabolismo , Vía de Señalización Wnt , Animales , Proteína 5 Relacionada con la Autofagia , Células Cultivadas , Células Madre Embrionarias/metabolismo , Ratones , Odontoblastos/metabolismo , Proteína Wnt-5a
9.
Waste Manag ; 175: 110-120, 2024 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-38194796

RESUMEN

This study provided a geographic and technical matching approach supporting low-carbon style recycling systems, demonstrated using polyvinyl chloride waste (PVCW) generated in 2018 in Mie Prefecture, Japan. From a carbon dioxide (CO2) emission basis, mechanical/material recycling (MR) and energy recovery facilities were all allocated full capacity; however, parts of chemical recycling facilities were excluded in the optimal solutions. From the spatial distribution of the allocated result, we confirmed a trend that to achieve the minimum total emissions, the matchings from pretreatment to recycling facilities were done based on a nearby priority rule. From an emission reduction basis, MR accounted for the major proportion of total reductions which was similar to that accessed from an emission basis. Thus, the promotion of MR should be prioritized at the current technical level when optimizing emissions of the whole lifecycle. The number of facilities allocated were substantially reduced; meanwhile, the averaged emission reductions per ton of PVCW disposed were increased from the current level (2.93) to the near-future level (4.99 t-CO2 t-1). Thus, we concluded that this optimization under a higher technical level was effective to make the current recycling system with more emission reductions (low-carbon environmental effect) and require fewer disposal facilities (cost-saving economic effect). Meanwhile, certain long-distance routes found in solutions implied that technical parameters were more important than geolocation parameters to achieve maximum emission reductions.


Asunto(s)
Eliminación de Residuos , Dióxido de Carbono , Desarrollo Industrial , Japón , Reciclaje
10.
Nat Commun ; 15(1): 3493, 2024 Apr 29.
Artículo en Inglés | MEDLINE | ID: mdl-38684653

RESUMEN

Extraterrestrial minerals on the surface of airless Solar System bodies undergo gradual alteration processes known as space weathering over long periods of time. The signatures of space weathering help us understand the phenomena occurring in the Solar System. However, meteorites rarely retain the signatures, making it impossible to study the space weathering processes precisely. Here, we examine samples retrieved from the asteroid Ryugu by the Hayabusa2 spacecraft and discover the presence of nonmagnetic framboids through electron holography measurements that can visualize magnetic flux. Magnetite particles, which normally provide a record of the nebular magnetic field, have lost their magnetic properties by reduction via a high-velocity (>5 km s-1) impact of a micrometeoroid with a diameter ranging from 2 to 20 µm after destruction of the parent body of Ryugu. Around these particles, thousands of metallic-iron nanoparticles with a vortex magnetic domain structure, which could have recorded a magnetic field in the impact event, are found. Through measuring the remanent magnetization of the iron nanoparticles, future studies are expected to elucidate the nature of the nebular/interplanetary magnetic fields after the termination of aqueous alteration in an asteroid.

11.
Nat Astron ; 7(2): 170-181, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36845884

RESUMEN

Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study of space-weathering signatures on the most abundant type of inner solar system body: a C-type asteroid, composed of materials largely unchanged since the formation of the Solar System. Weathered Ryugu grains show areas of surface amorphization and partial melting of phyllosilicates, in which reduction from Fe3+ to Fe2+ and dehydration developed. Space weathering probably contributed to dehydration by dehydroxylation of Ryugu surface phyllosilicates that had already lost interlayer water molecules and to weakening of the 2.7 µm hydroxyl (-OH) band in reflectance spectra. For C-type asteroids in general, this indicates that a weak 2.7 µm band can signify space-weathering-induced surface dehydration, rather than bulk volatile loss.

12.
J Appl Clin Med Phys ; 13(6): 3868, 2012 Nov 08.
Artículo en Inglés | MEDLINE | ID: mdl-23149779

RESUMEN

A computed tomography (CT) image simulation technique based on the point spread function (PSF) was applied to analyze the accuracy of CT-based clinical evaluations of lung nodule density. The PSF of the CT system was measured and used to perform the lung nodule image simulation. Then, the simulated image was resampled at intervals equal to the pixel size and the slice interval found in clinical high-resolution CT (HRCT) images. On those images, the nodule density was measured by placing a region of interest (ROI) commonly used for routine clinical practice, and comparing the measured value with the true value (a known density of object function used in the image simulation). It was quantitatively determined that the measured nodule density depended on the nodule diameter and the image reconstruction parameters (kernel and slice thickness). In addition, the measured density fluctuated, depending on the offset between the nodule center and the image voxel center. This fluctuation was reduced by decreasing the slice interval (i.e., with the use of overlapping reconstruction), leading to a stable density evaluation. Our proposed method of PSF-based image simulation accompanied with resampling enables a quantitative analysis of the accuracy of CT-based evaluations of lung nodule density. These results could potentially reveal clinical misreadings in diagnosis, and lead to more accurate and precise density evaluations. They would also be of value for determining the optimum scan and reconstruction parameters, such as image reconstruction kernels and slice thicknesses/intervals.


Asunto(s)
Interpretación de Imagen Radiográfica Asistida por Computador , Procesamiento de Señales Asistido por Computador , Nódulo Pulmonar Solitario/patología , Tomografía Computarizada por Rayos X , Algoritmos , Simulación por Computador , Humanos , Procesamiento de Imagen Asistido por Computador , Imagenología Tridimensional , Fantasmas de Imagen
13.
Sci Adv ; 8(50): eade2067, 2022 Dec 16.
Artículo en Inglés | MEDLINE | ID: mdl-36525483

RESUMEN

The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: 16O-rich (associated with refractory inclusions) and 16O-poor (associated with chondrules). Both the 16O-rich and 16O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the 16O-rich to 16O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.

14.
Opt Express ; 19(11): 10864-73, 2011 May 23.
Artículo en Inglés | MEDLINE | ID: mdl-21643344

RESUMEN

We have investigated the characteristics of THz emissions from p/n junctions with metallic lines under non-bias conditions. The waveforms, spectra, and polarizations depend on the length and shape of the lines. This indicates that the transient photocurrents from p/n junctions flow into the metallic lines that emit THz waves and act as an antenna. We have successfully demonstrated the non-contact inspection of open defects of multi-layered interconnects in a large-scale integrated circuit using the laser THz emission microscope (LTEM). The p/n junctions connected to the defective interconnects can be identified by comparing the LTEM images of normal and defective circuits.

15.
Med Phys ; 38(7): 3915-23, 2011 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-21858988

RESUMEN

PURPOSE: While the acquisition of projection data in a computed tomography (CT) scanner is generally cqrried out once, the projection data is often removed from the system, making further reconstruction with a different reconstruction filter impossible. The reconstruction kernel is one of the most important parameters. To have access to all the reconstructions, either prior reconstructions with multiple kernels must be performed or the projection data must be stored. Each of these requirements would increase the burden on data archiving. This study aimed to design an effective method to achieve similar image quality using an image filtering technique in the image space, instead of a reconstruction filter in the projection space for CT imaging. The authors evaluated the clinical feasibility of the proposed method in lung cancer screening. METHODS: The proposed technique is essentially the same as common image filtering, which performs processing in the spatial-frequency domain with a filter function. However, the filter function was determined based on the quantitative analysis of the point spread functions (PSFs) measured in the system. The modulation transfer functions (MTFs) were derived from the PSFs, and the ratio of the MTFs was used as the filter function. Therefore, using an image reconstructed with a kernel, an image reconstructed with a different kernel was obtained by filtering, which used the ratio of the MTFs obtained for the two kernels. The performance of the method was evaluated by using routine clinical images obtained from CT screening for lung cancer in five subjects. RESULTS: Filtered images for all combinations of three types of reconstruction kernels ("smooth," "standard," and "sharp" kernels) showed good agreement with original reconstructed images regarded as the gold standard. On the filtered images, abnormal shadows suspected as being lung cancers were identical to those on the reconstructed images. The standard deviations (SDs) for the difference between filtered images and reconstructed images ranged from 1.9 to 23.5 Hounsfield units for all kernel combinations; these SDs were much smaller than the noise SDs in the reconstructed images. CONCLUSIONS: The proposed method has good performance and is clinically feasible in lung cancer screening. This method can be applied to images reconstructed on any scanner by measuring the PSFs in each system.


Asunto(s)
Algoritmos , Neoplasias Pulmonares/diagnóstico por imagen , Tamizaje Masivo/métodos , Intensificación de Imagen Radiográfica/métodos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Tomografía Computarizada por Rayos X/métodos , Estudios de Factibilidad , Humanos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
16.
Gan To Kagaku Ryoho ; 37(9): 1775-8, 2010 Sep.
Artículo en Japonés | MEDLINE | ID: mdl-20841945

RESUMEN

OBJECTIVE: The prognosis for pancreatic cancer with distant metastases is not good. The case reported here is of pancreatic body cancer with multiple liver metastasis in which S-1+gemcitabine (GEM) therapy proved to be effective. CASE: A 77-year old female. She was asymptomatic and diagnosed as a pancreatic body cancer with multiple liver metastases at the end of December 2008 by periodical ultrasonography. After careful examination, GEM 1,200mg/body was administered on days 1 and 15, and S-1 was administered orally at 80mg/day for two weeks, followed by two weeks rest. Currently, at the end of the 10th course, tumor size has been reduced from 26.5mm to 18.9 mm, and two of the five liver metastatic lesions have disappeared, while the remaining three liver lesions have been revealed as scars by CT examination. Tumor marker levels have been remarkably decreased. Ten months from the initial diagnosis, there has been no side effect and chemotherapy is being continued. CONCLUSION: In pancreatic cancer with distant metastases, S-1+GEM therapy may be able to provide a long-term prognosis.


Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Desoxicitidina/análogos & derivados , Neoplasias Hepáticas/tratamiento farmacológico , Ácido Oxónico/uso terapéutico , Neoplasias Pancreáticas/tratamiento farmacológico , Tegafur/uso terapéutico , Anciano , Desoxicitidina/administración & dosificación , Desoxicitidina/uso terapéutico , Combinación de Medicamentos , Femenino , Humanos , Neoplasias Hepáticas/diagnóstico por imagen , Neoplasias Hepáticas/secundario , Ácido Oxónico/administración & dosificación , Neoplasias Pancreáticas/diagnóstico por imagen , Neoplasias Pancreáticas/patología , Tegafur/administración & dosificación , Tomografía Computarizada por Rayos X , Ultrasonografía , Gemcitabina
18.
Nat Commun ; 11(1): 1117, 2020 Feb 28.
Artículo en Inglés | MEDLINE | ID: mdl-32111821

RESUMEN

Extraterrestrial iron sulfide is a major mineral reservoir of the cosmochemically and astrobiologically important elements iron and sulfur. Sulfur depletion on asteroids is a long-standing, yet unresolved phenomenon that is of fundamental importance for asteroid evolution and sulfur delivery to the Earth. Understanding the chemistry of such environments requires insight into the behavior of iron sulfides exposed to space. Here we show that troilite (FeS) grains recovered from the regolith of asteroid 25143 Itokawa have lost sulfur during long-term space exposure. We report the wide-spread occurrence of metallic iron whiskers as a decomposition product formed through irradiation of the sulfide by energetic ions of the solar wind. Whisker growth by ion irradiation is a novel and unexpected aspect of space weathering. It implies that sulfur loss occurs rapidly and, furthermore, that ion irradiation plays an important role in the redistribution of sulfur between solids and gas of the interstellar medium.

19.
Protein Expr Purif ; 64(2): 205-12, 2009 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-19121395

RESUMEN

The gene encoding acetylcholinesterase (AChE) was cloned from common carp muscle tissue. The full-length cDNA was 2368 bp that contains a coding region of 1902 bp, corresponding to a protein of 634 amino acids. The deduced amino acid sequence showed a significant homology with those of ichthyic AChEs and several common features among them, including T peptide encoded by exon T in the C-terminus. Three yeast expression vectors were constructed and introduced into the yeast Pichia pastoris. The transformant harboring carp AChE gene lacking exon T most effectively produced AChE activity extracellularly. The replacement of the native signal sequence with the yeast alpha-factor prepro signal sequence rather decreased the production. A decrease in cultivation temperature from 30 to 15 degrees C increased the activity production 32.8-fold. The purified recombinant AChE lacking T peptide, eluted as a single peak with a molecular mass of about 230 kDa on the gel filtration chromatography, exhibited the specific activity of 4970 U/mg. On the SDS-PAGE, three proteins with molecular masses of 73, 54, and 22 kDa were observed. These proteins were N-glycosylated, and their N-terminal sequence showed that the latter two were produced from the former probably by proteolytic cleavage at the C-terminal region. Thus, the recombinant AChE is homotrimer of three identical subunits with 73 kDa. The optimal temperature and pH of the recombinant were comparable to those of the native enzyme purified previously, but the values of kinetic parameters and the sensitivities to substrate inhibition and inhibitors were considerably different between them.


Asunto(s)
Acetilcolinesterasa/genética , Carpas/genética , Proteínas de Peces/química , Proteínas de Peces/genética , Pichia/metabolismo , Acetilcolinesterasa/química , Acetilcolinesterasa/metabolismo , Animales , Carpas/metabolismo , Clonación Molecular , ADN Complementario/genética , ADN Complementario/metabolismo , Proteínas de Peces/aislamiento & purificación , Dosificación de Gen , Pichia/genética , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/aislamiento & purificación , Proteínas Recombinantes de Fusión/metabolismo , Temperatura
20.
Med Phys ; 36(6): 2089-97, 2009 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-19610298

RESUMEN

A method for verifying the point spread function (PSF) measured by computed tomography has been previously reported [Med. Phys. 33, 2757-2764 (2006)]; however, this additional PSF verification following measurement is laborious. In the present study, the previously described verification method was expanded to PSF determination. First, an image was obtained by scanning a phantom. The image was then two-dimensionally deconvolved with the object function corresponding to the phantom structure, thus allowing the PSF to be obtained. Deconvolution is implemented simply by division of spatial frequencies (corresponding to inverse filtering), in which two parameters are used as adjustable ones. Second, an image was simulated by convolving the object function with the obtained PSF, and the simulated image was compared to the above-measured image of the phantom. The difference indicates the inaccuracy of the PSF obtained by deconvolution. As a criterion for evaluating the difference, the authors define the mean normalized standard deviation (SD) in the difference between simulated and measured images. The above two parameters for deconvolution can be adjusted by referring to the subsequent mean normalized SD (i.e., the PSF is determined so that the mean normalized SD is decreased). In this article, the parameters were varied in a fixed range with a constant increment to find the optimal parameter setting that minimizes the mean normalized SD. Using this method, PSF measurements were performed for various types of image reconstruction kernels (21 types) in four kinds of scanners. For the 16 types of kernels, the mean normalized SDs were less than 2.5%, indicating the accuracy of the determined PSFs. For the other five kernels, the mean normalized SDs ranged from 3.7% to 4.8%. This was because of a large amount of noise in the measured images, and the obtained PSFs would essentially be accurate. The method effectively determines the PSF, with an accompanying verification, after one scanning of a phantom.


Asunto(s)
Algoritmos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Tomografía Computarizada por Rayos X/métodos , Fantasmas de Imagen , Intensificación de Imagen Radiográfica/métodos , Reproducibilidad de los Resultados , Dispersión de Radiación , Sensibilidad y Especificidad , Tomografía Computarizada por Rayos X/instrumentación , Rayos X
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