目的:评估糖尿病和非糖尿病患者白内障超声乳化术后脉络膜厚度(SFCT)和黄斑厚度(CMT)的变化。方法:前瞻性研究。包括53例轻度或中度非增殖性糖尿病视网膜病变(NPDR)无黄斑水肿患者和53例行白内障超声乳化术非糖尿病患者。术前、术后1mo...目的:评估糖尿病和非糖尿病患者白内障超声乳化术后脉络膜厚度(SFCT)和黄斑厚度(CMT)的变化。方法:前瞻性研究。包括53例轻度或中度非增殖性糖尿病视网膜病变(NPDR)无黄斑水肿患者和53例行白内障超声乳化术非糖尿病患者。术前、术后1mo和3mo用 EDI-OCT 测量脉络膜厚度和黄斑厚度,并比较两组的SFCT和CMT变化。结果:糖尿病患者中,基线处CMT为267±32 μm。术后CMT显著升高,术后1mo为291±77 μm( P =0.034),术后3mo为293±75 μm( P =0.047)。基线处SFCT为199± 72 μm 。术后SFCT显著升高,术后1mo为231±73 μm ( P = 0.035),术后3mo为248±91 μm( P =0.026)。在非糖尿病患者中,基线处CMT为264±29 μm。术后显著CMT升高,术后1mo为278±42 μm( P <0.001),术后3mo为 276± 56 μm( P =0.028)。基线处SFCT为236±60 μm。术后SFCT显著提高,术后1mo为265±64 μm( P <0.001),术后3mo为240±60 μm( P =0.234)。两组间CMT的变化无统计学差异(均 P >0.05)。尽管非糖尿病组患者的基线脉络膜较厚,但研究组术后1mo( P =0.97)和术后3mo( P =0.97)的SFCT变化无显著差异。结论:术后两组间CMT和SFCT均显著提高。CMT和SFCT变化在糖尿病和非糖尿病患者间无显著不同。展开更多
AIM: To determine the incidence and risk factors of retinopathy of prematurity(ROP) and the sensitivity of current screening criteria in a tertiary eye center in Tehran, Iran. METHODS: In a cross-sectional observation...AIM: To determine the incidence and risk factors of retinopathy of prematurity(ROP) and the sensitivity of current screening criteria in a tertiary eye center in Tehran, Iran. METHODS: In a cross-sectional observational study, neonates weighing ≤2000 grams at birth or born <34 wk gestational age(GA) and all other infants at risk of ROP admitted to the neonatal intensive care unit(NICU) or referred to our ROP clinic were investigated. The incidence of ROP and severe ROP(i.e. patients needing treatment) were determined. The associations between risk factors and the development and severity of ROP were assessed. We also examined the sensitivity of the current national screening guideline in Iran. RESULTS: Among 207 infants, the incidence of ROP and severe ROP was 33.3% and 11.1%, respectively. Mean GA and birth weight(BW) were significantly lower in ROP vs non-ROP infants(29±2 wk vs 33±3 wk, P<0.001;1274±489 g vs 1916±550 g, P<0.001, respectively). Univariate analysis displayed significant association between ROP incidence and GA, BW, NICU admission period, blood transfusion, surfactant usage, sepsis, intraventricular hemorrhage and patent ductus arteriosus(P<0.05 for all). BW [relative risk(RR): 0.857(0.711-0.873), P<0.001], GA [RR: 0.788(0.711-0.873), P<0.001] and blood transfusion [RR: 1.888(0.995-3.583), P=0.052] were independent ROP risk factors. The sensitivity of country-specific screening guidelines was 95.7% and 100% for overall and severe ROP detection, respectively. CONCLUSION: ROP incidence is relatively high in Iran. Identifying ROP risk factors results in more accurate screening and reduces the risk of irreversible vision loss. The ROP screening criteria utilized in Iran are efficient at the present time.展开更多
In this paper, the Taguchi method with an L9（34） orthogonal array was used as experimental design to determine the optimum conditions for preparing ZnO nanoparticles via a mechanothermal route. ZnSO4·H20 and Na...In this paper, the Taguchi method with an L9（34） orthogonal array was used as experimental design to determine the optimum conditions for preparing ZnO nanoparticles via a mechanothermal route. ZnSO4·H20 and NaECO3 were used as starting materials. The effects of milling time, NaECO3/ZnSO·H20 molar ratio, and ball-to-powder mass ratio （BPR） on the bandgap （Eg） of ZnO nanoparticles were inves- tigated. The ranges of the investigated experimental conditions were 5-15 h for the milling time （t）, 1.0-1.2 for the Na2COa/ZnSO4·H20 mo- lar ratio （M）, and 10-30 for BPR. The milling time and BPR exhibited significant effects; an increase in milling time reduced the bandgap. The optimum conditions from this study were t3 = 15 h, M1 = l, and BPR2 = 20. Only two significant factors （t3, 15 h; BPR2, 20） were used to estimate the performance at the optimum conditions. The calculated bandgap was 3.12 eV, in reasonable agreement with the experimental results obtained under the optimized conditions.展开更多
Gas pipelines are environmentally sensitive because they cross varied fields, rivers, forests, populated areas, desert, hills and offshore and also different parameters in gas transmission progresses are effective. Un...Gas pipelines are environmentally sensitive because they cross varied fields, rivers, forests, populated areas, desert, hills and offshore and also different parameters in gas transmission progresses are effective. Underground gas transmission pipelines have been grown as one of the low risk methods with low cost in the world specially in middle east and Europe. Physical and chemical properties of liquid gas, pipeline properties and also its environmental condition are the main factors of increasing the technical and environmental risk. In this article the quantitative risk assessment has been done by using GIS and overlaying the information layers. For this purpose, all effective risk factors were identified and projected. In order to achieve the same and comparable results, the entire pipeline route was divided into 500 meter intervals and the risk was calculated in each interval, finally the scores of these intervals such as each criterion risk was calculated. The case study of the article is Savadkooh to PoleSefid pipeline in Mazandaran.展开更多
ZnO nano-particles were synthesized via an ammonical ammonium carbonate solution by precipitation method in presence of some additives such as urea, oleic and stearic acid. The morphology and crystallinity of the obta...ZnO nano-particles were synthesized via an ammonical ammonium carbonate solution by precipitation method in presence of some additives such as urea, oleic and stearic acid. The morphology and crystallinity of the obtained zinc oxide particles depend critically on the type of additive which was used. Additives also affected the crystal orientation of precipitate nano-particles. SEM, XRD, BET and UV-visible were used to characterize morphology, microstructure, specific surface area and optical properties of the products.Photo-catalysis properties of the as-prepared ZnO powders were evaluated by degradation of methyl red(acid red) in aqueous solution exposed to UV-light. Results suggested a close relationship among the morphology,size and surface area on photo-catalysis and optical properties of the particles. The widest Egvalue(3.56 e V),highest degradation and decolorization efficiency(99%) were obtained from a sample with the smallest grain size(largest surface area) which were used urea as an additive.展开更多
AIM： To determine the safe dose of intravitreal clonidine（IVC）, a potential drug for neuroprotection and angiogenesis inhibition in rabbits. METHODS： A total of 28 rabbits were divided into four groups. Three grou...AIM： To determine the safe dose of intravitreal clonidine（IVC）, a potential drug for neuroprotection and angiogenesis inhibition in rabbits. METHODS： A total of 28 rabbits were divided into four groups. Three groups received IVC with concentrations of 15（Group A）, 25（Group B）, and 50（Group C） g/0.1 m L and the control group（Group D） received 0.1 m L balanced salt solution（BSS）. To investigate IVC safety, electroretinography（ERG） was performed at baseline, then at 1, 4 and 8 wk after injection. After last ERG, all rabbits were euthanized, their eyes were enucleated and subjected to routine histopathological evaluation, immunohistochemistry for glial fibrillary acidic protein（GFAP） and terminal deoxynucleotidyl transferase d UTP nick end labeling（TUNEL） test.RESULTS： Based on ERG, histopathology, GFAP and TUNEL assay findings, 15 g IVC was determined as the safe dose in rabbit eyes. While, the results of routine histopathology and TUNEL assay were unremarkable in all groups, toxic effects attributed to 25 and 50 g IVC were demonstrated by ERG and GFAP tests. CONCLUSION： Totally 15 g clonidine is determined as the safe dose for intravitreal injection in rabbits. Contribution of IVC in neuroprotection and inhibition of angiogenesis deserve more studies.展开更多
In this paper, the Galerkin projection method is used for solving the semi Sylvester equation. Firstly the semi Sylvester equation is reduced to the multiple linear systems. To apply the Galerkin projection method, so...In this paper, the Galerkin projection method is used for solving the semi Sylvester equation. Firstly the semi Sylvester equation is reduced to the multiple linear systems. To apply the Galerkin projection method, some propositions are presented. The presented scheme is compared with the L-GL-LSQR algorithm in point of view CPU-time and iteration number. Finally, some numerical experiments are presented to show that the efficiency of the new scheme.展开更多
In order to determine the relationship between physiographical factors and regeneration changes in forests, and to improve and model natural regeneration status, Gorazbon district in Kheyrod Forest was selected for th...In order to determine the relationship between physiographical factors and regeneration changes in forests, and to improve and model natural regeneration status, Gorazbon district in Kheyrod Forest was selected for the study. All available regeneration patches in the area were selected. To achieve spatial structure and quantify metrics related to regeneration patches, the analysis of landscape metrics was used. The results show that 692 regeneration patches were identified at the level of different directions. LAND Metric show the most regeneration percent is related to the western (9%), southern (8.66%), flat areas (8.33%), northern (5.68%) and eastern (4.73%), respectively. In total, the patch coverage level percentage was calculated in the landscape (8.31%). The results related to patch shape metric show that most shapes of patches follow polygon structures and do not have fixed shapes. Results related to the average area of the patch metric show that the average level of patches is between 4 and 5 R. The maximum and minimum distance between patches was observed in the survey between 39 and 520 m respectively. According to the results of the distance average between patch metric, the distribution of patches is random in the southern and western directions, flat areas and pile, but it is uniform in northern directions. It should be noted that the distribution and structure of patches in the northern directions has a better distribution and homogeneity than the other directions. Its canals are used as a natural regeneration model to follow the natural phenomena in forest sustainable management.展开更多
In this paper, a new iterative solution method is proposed for solving multiple linear systems A(i)x(i)=b(i), for 1≤ i ≤ s, where the coefficient matrices A(i) and the right-hand sides b(i) are arbitrary in general....In this paper, a new iterative solution method is proposed for solving multiple linear systems A(i)x(i)=b(i), for 1≤ i ≤ s, where the coefficient matrices A(i) and the right-hand sides b(i) are arbitrary in general. The proposed method is based on the global least squares (GL-LSQR) method. A linear operator is defined to connect all the linear systems together. To approximate all numerical solutions of the multiple linear systems simultaneously, the GL-LSQR method is applied for the operator and the approximate solutions are obtained recursively. The presented method is compared with the well-known LSQR method. Finally, numerical experiments on test matrices are presented to show the efficiency of the new method.展开更多
A common way to handle the Tikhonov regularization method for the first kind Fredholm integral equations,is first to discretize and then to work with the final linear system.This unavoidably inflicts discretization er...A common way to handle the Tikhonov regularization method for the first kind Fredholm integral equations,is first to discretize and then to work with the final linear system.This unavoidably inflicts discretization errors which may lead to disastrous results,especially when a quadrature rule is used.We propose to regularize directly the integral equation resulting in a continuous Tikhonov problem.The Tikhonov problem is reduced to a simple least squares problem by applying the Golub-Kahan bidiagonalization(GKB)directly to the integral operator.The regularization parameter and the iteration index are determined by the discrepancy principle approach.Moreover,we study the discrete version of the proposed method resulted from numerical evaluating the needed integrals.Focusing on the nodal values of the solution results in a weighted version of GKB-Tikhonov method for linear systems arisen from the Nystr¨om discretization.Finally,we use numerical experiments on a few test problems to illustrate the performance of our algorithms.展开更多
文摘目的:评估糖尿病和非糖尿病患者白内障超声乳化术后脉络膜厚度(SFCT)和黄斑厚度(CMT)的变化。方法:前瞻性研究。包括53例轻度或中度非增殖性糖尿病视网膜病变(NPDR)无黄斑水肿患者和53例行白内障超声乳化术非糖尿病患者。术前、术后1mo和3mo用 EDI-OCT 测量脉络膜厚度和黄斑厚度,并比较两组的SFCT和CMT变化。结果:糖尿病患者中,基线处CMT为267±32 μm。术后CMT显著升高,术后1mo为291±77 μm( P =0.034),术后3mo为293±75 μm( P =0.047)。基线处SFCT为199± 72 μm 。术后SFCT显著升高,术后1mo为231±73 μm ( P = 0.035),术后3mo为248±91 μm( P =0.026)。在非糖尿病患者中,基线处CMT为264±29 μm。术后显著CMT升高,术后1mo为278±42 μm( P <0.001),术后3mo为 276± 56 μm( P =0.028)。基线处SFCT为236±60 μm。术后SFCT显著提高,术后1mo为265±64 μm( P <0.001),术后3mo为240±60 μm( P =0.234)。两组间CMT的变化无统计学差异(均 P >0.05)。尽管非糖尿病组患者的基线脉络膜较厚,但研究组术后1mo( P =0.97)和术后3mo( P =0.97)的SFCT变化无显著差异。结论:术后两组间CMT和SFCT均显著提高。CMT和SFCT变化在糖尿病和非糖尿病患者间无显著不同。
文摘AIM: To determine the incidence and risk factors of retinopathy of prematurity(ROP) and the sensitivity of current screening criteria in a tertiary eye center in Tehran, Iran. METHODS: In a cross-sectional observational study, neonates weighing ≤2000 grams at birth or born <34 wk gestational age(GA) and all other infants at risk of ROP admitted to the neonatal intensive care unit(NICU) or referred to our ROP clinic were investigated. The incidence of ROP and severe ROP(i.e. patients needing treatment) were determined. The associations between risk factors and the development and severity of ROP were assessed. We also examined the sensitivity of the current national screening guideline in Iran. RESULTS: Among 207 infants, the incidence of ROP and severe ROP was 33.3% and 11.1%, respectively. Mean GA and birth weight(BW) were significantly lower in ROP vs non-ROP infants(29±2 wk vs 33±3 wk, P<0.001;1274±489 g vs 1916±550 g, P<0.001, respectively). Univariate analysis displayed significant association between ROP incidence and GA, BW, NICU admission period, blood transfusion, surfactant usage, sepsis, intraventricular hemorrhage and patent ductus arteriosus(P<0.05 for all). BW [relative risk(RR): 0.857(0.711-0.873), P<0.001], GA [RR: 0.788(0.711-0.873), P<0.001] and blood transfusion [RR: 1.888(0.995-3.583), P=0.052] were independent ROP risk factors. The sensitivity of country-specific screening guidelines was 95.7% and 100% for overall and severe ROP detection, respectively. CONCLUSION: ROP incidence is relatively high in Iran. Identifying ROP risk factors results in more accurate screening and reduces the risk of irreversible vision loss. The ROP screening criteria utilized in Iran are efficient at the present time.
基金financial support of this work by the University of Tehran and the Iran Nanotechnology Initiative Council
文摘In this paper, the Taguchi method with an L9（34） orthogonal array was used as experimental design to determine the optimum conditions for preparing ZnO nanoparticles via a mechanothermal route. ZnSO4·H20 and NaECO3 were used as starting materials. The effects of milling time, NaECO3/ZnSO·H20 molar ratio, and ball-to-powder mass ratio （BPR） on the bandgap （Eg） of ZnO nanoparticles were inves- tigated. The ranges of the investigated experimental conditions were 5-15 h for the milling time （t）, 1.0-1.2 for the Na2COa/ZnSO4·H20 mo- lar ratio （M）, and 10-30 for BPR. The milling time and BPR exhibited significant effects; an increase in milling time reduced the bandgap. The optimum conditions from this study were t3 = 15 h, M1 = l, and BPR2 = 20. Only two significant factors （t3, 15 h; BPR2, 20） were used to estimate the performance at the optimum conditions. The calculated bandgap was 3.12 eV, in reasonable agreement with the experimental results obtained under the optimized conditions.
文摘Gas pipelines are environmentally sensitive because they cross varied fields, rivers, forests, populated areas, desert, hills and offshore and also different parameters in gas transmission progresses are effective. Underground gas transmission pipelines have been grown as one of the low risk methods with low cost in the world specially in middle east and Europe. Physical and chemical properties of liquid gas, pipeline properties and also its environmental condition are the main factors of increasing the technical and environmental risk. In this article the quantitative risk assessment has been done by using GIS and overlaying the information layers. For this purpose, all effective risk factors were identified and projected. In order to achieve the same and comparable results, the entire pipeline route was divided into 500 meter intervals and the risk was calculated in each interval, finally the scores of these intervals such as each criterion risk was calculated. The case study of the article is Savadkooh to PoleSefid pipeline in Mazandaran.
文摘ZnO nano-particles were synthesized via an ammonical ammonium carbonate solution by precipitation method in presence of some additives such as urea, oleic and stearic acid. The morphology and crystallinity of the obtained zinc oxide particles depend critically on the type of additive which was used. Additives also affected the crystal orientation of precipitate nano-particles. SEM, XRD, BET and UV-visible were used to characterize morphology, microstructure, specific surface area and optical properties of the products.Photo-catalysis properties of the as-prepared ZnO powders were evaluated by degradation of methyl red(acid red) in aqueous solution exposed to UV-light. Results suggested a close relationship among the morphology,size and surface area on photo-catalysis and optical properties of the particles. The widest Egvalue(3.56 e V),highest degradation and decolorization efficiency(99%) were obtained from a sample with the smallest grain size(largest surface area) which were used urea as an additive.
文摘AIM： To determine the safe dose of intravitreal clonidine（IVC）, a potential drug for neuroprotection and angiogenesis inhibition in rabbits. METHODS： A total of 28 rabbits were divided into four groups. Three groups received IVC with concentrations of 15（Group A）, 25（Group B）, and 50（Group C） g/0.1 m L and the control group（Group D） received 0.1 m L balanced salt solution（BSS）. To investigate IVC safety, electroretinography（ERG） was performed at baseline, then at 1, 4 and 8 wk after injection. After last ERG, all rabbits were euthanized, their eyes were enucleated and subjected to routine histopathological evaluation, immunohistochemistry for glial fibrillary acidic protein（GFAP） and terminal deoxynucleotidyl transferase d UTP nick end labeling（TUNEL） test.RESULTS： Based on ERG, histopathology, GFAP and TUNEL assay findings, 15 g IVC was determined as the safe dose in rabbit eyes. While, the results of routine histopathology and TUNEL assay were unremarkable in all groups, toxic effects attributed to 25 and 50 g IVC were demonstrated by ERG and GFAP tests. CONCLUSION： Totally 15 g clonidine is determined as the safe dose for intravitreal injection in rabbits. Contribution of IVC in neuroprotection and inhibition of angiogenesis deserve more studies.
文摘In this paper, the Galerkin projection method is used for solving the semi Sylvester equation. Firstly the semi Sylvester equation is reduced to the multiple linear systems. To apply the Galerkin projection method, some propositions are presented. The presented scheme is compared with the L-GL-LSQR algorithm in point of view CPU-time and iteration number. Finally, some numerical experiments are presented to show that the efficiency of the new scheme.
文摘In order to determine the relationship between physiographical factors and regeneration changes in forests, and to improve and model natural regeneration status, Gorazbon district in Kheyrod Forest was selected for the study. All available regeneration patches in the area were selected. To achieve spatial structure and quantify metrics related to regeneration patches, the analysis of landscape metrics was used. The results show that 692 regeneration patches were identified at the level of different directions. LAND Metric show the most regeneration percent is related to the western (9%), southern (8.66%), flat areas (8.33%), northern (5.68%) and eastern (4.73%), respectively. In total, the patch coverage level percentage was calculated in the landscape (8.31%). The results related to patch shape metric show that most shapes of patches follow polygon structures and do not have fixed shapes. Results related to the average area of the patch metric show that the average level of patches is between 4 and 5 R. The maximum and minimum distance between patches was observed in the survey between 39 and 520 m respectively. According to the results of the distance average between patch metric, the distribution of patches is random in the southern and western directions, flat areas and pile, but it is uniform in northern directions. It should be noted that the distribution and structure of patches in the northern directions has a better distribution and homogeneity than the other directions. Its canals are used as a natural regeneration model to follow the natural phenomena in forest sustainable management.
文摘In this paper, a new iterative solution method is proposed for solving multiple linear systems A(i)x(i)=b(i), for 1≤ i ≤ s, where the coefficient matrices A(i) and the right-hand sides b(i) are arbitrary in general. The proposed method is based on the global least squares (GL-LSQR) method. A linear operator is defined to connect all the linear systems together. To approximate all numerical solutions of the multiple linear systems simultaneously, the GL-LSQR method is applied for the operator and the approximate solutions are obtained recursively. The presented method is compared with the well-known LSQR method. Finally, numerical experiments on test matrices are presented to show the efficiency of the new method.
基金supported by the Iran National Science Foundation(INSF)[Grant No.96014705]supporting the project“Direct implementation of Tikhonov regularization for the first kind integral equations”.
文摘A common way to handle the Tikhonov regularization method for the first kind Fredholm integral equations,is first to discretize and then to work with the final linear system.This unavoidably inflicts discretization errors which may lead to disastrous results,especially when a quadrature rule is used.We propose to regularize directly the integral equation resulting in a continuous Tikhonov problem.The Tikhonov problem is reduced to a simple least squares problem by applying the Golub-Kahan bidiagonalization(GKB)directly to the integral operator.The regularization parameter and the iteration index are determined by the discrepancy principle approach.Moreover,we study the discrete version of the proposed method resulted from numerical evaluating the needed integrals.Focusing on the nodal values of the solution results in a weighted version of GKB-Tikhonov method for linear systems arisen from the Nystr¨om discretization.Finally,we use numerical experiments on a few test problems to illustrate the performance of our algorithms.
