فهرست مطالب نویسنده:
mr yaghoobi
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در این تحقیق، ریزساختار بتن به کمک یک مدل اجزای محدود سه بعدی شبیه سازی شده است. این مدل دارای دو فاز ملات و سنگدانه های درشت است. شکل سنگدانه ها به صورت کروی و رفتار آن ها به صورت ارتجاعی خطی در نظر گرفته شده است. از منحنی دانه بندی فولر جهت بیان توزیع سنگدانه ها استفاده می شود. رفتار ملات در ساختار خمیری خسارت بیان شده است. در ابتدا، نحوه ی پیاده سازی مدل خمیری خسارت ارائه و در گام بعد، صحت پیاده سازی مدل خمیری خسارت برای یک المان بررسی می شود. در بخش پایانی اثر درصد حجمی سنگدانه، اندازه ی بزرگ ترین سنگدانه و مدول ارتجاعی سنگدانه بر روی مقاومت فشاری مشخصه ی بتن مطالعه و نتایج با دستاوردهای سایر پژوهشگران مقایسه شده است.
کلید واژگان: ریزساختار، مقاومت فشاری بتن، روش اجزای محدود، خمیری، خسارتIn the present paper, the detailed mesostructure of concrete is geometrically generated and its compressive strength is numerically estimated using the 3D finite element method. The models contain two phases of mortar and coarse aggregates. The FE models of concrete are cubic in shape, with a side length of 80 mm. Aggregates are assumed to be spherical and behave in a linear elastic manner. The famous Fuller formula is utilized for the aggregate grading curve, and the simple sequential inhibition (SSI) technique is employed to fill the concrete cubes with the particles. Only aggregates bigger than 4.75 mm in diameter (gravel) are modeled, i.e., the particles smaller than 4.75 mm in diameter (sand) are not considered individually and assumed to be part of the homogenized nonlinear cement paste. A modified version of the plastic-damage model, proposed by Lee and Fenves [J. Lee, G.L. Fenves, International Journal for Numerical Methods in Engineering 50 (2001) 487-506], has been adopted to simulate the inelastic response of the mortar. This constitutive model incorporates two independent hardening variables, namely; equivalent tensile and compressive plastic strains, and, thus, is capable of tracing damage evolution due to both tensile cracking and compressive crushing. In the first stage, the numerical implementation of the plastic-damage model is presented and then its validity is examined in a 3D FE element. Next, the effects of aggregate volume fraction, aggregate maximum diameter, and aggregate elastic modulus on concrete compressive strength are studied. It is shown that: (1) compressive strength remains constant for specimens with aggregate volume fractions of up to 50%, and then increases significantly with grain content, (2) for the range of aggregate volume fractions studied in this paper, the maximum aggregate size has little influence on compressive strength, and (3) any increase in the elastic modulus of aggregates accentuates stress concentration near the aggregates, and, thus, reduces the compressive strength of concrete samples. Finally, the results are satisfactorily compared with those presented by other researchers.
Keywords: Mesostructure, Compressive Strength, Concrete, Finite Element Method, Plastic, Damage -
Sand fly research has a long history in Iran beginning with the work of Adler, Theodor and Lourie in 1930 and followed by Mesghali’s foundational taxonomic work on sand flies in 1943. Since then, research has continued unabated throughout the country and official publications report the existence of at least 44 species of sand flies (26 of the genus Phlebotomus and 18 of genus Sergentomyia) in Iran. So far, seven Phlebotomus species and one Sergentomyia species have been collected and described by Iranian researchers for the first time. Natural promastigote infection have been repeatedly found in 13 species of sand flies and modern molecular techniques are used routinely to characterize Leishmania parasite isolates from endemic areas of cutaneous and visceral leishmaniasis. Because of anthropogenic environmental modifications or human population movements, data on phlebotomine sand flies should be regularly updated and verified at least every five years by fieldwork and taxonomy in foci of leishmaniasis, to incriminate vector species of relevance to the ecology of transmission and to support development and implementation of control programs.Keywords: Sand flies, taxonomy, vectors, Leishmania major, Leishmania tropica, Leishmania infantum, Leishmaniasis, Iran
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BackgroundZoonotic cutaneous leishmaniasis (ZCL) is an increasing health problems in many rural areas of Iran. The aim of this study was to introduce a new alternative rodenticide to control the reservoirs of ZCL, its effect on the vector density and the incidence of the disease in hyperendemic focus of Esfahan County, central Iran.MethodsThe study was carried out from January 2011 to January 2012. In intervention areas, rodent control operation was conducted using zinc phosphide or Coumavec®. Active case findings were done by house-to-house visits once every season during 2011–2012. To evaluate the effect of rodent control operation on the vector density, sand flies were collected twice a month using sticky traps.ResultsThe reduction rate of rodent holes in intervention areas with Coumavec® and zinc phosphide were 48.46% and 58.15% respectively, whereas in control area results showed 6.66 folds intensification. The Incidence of ZCL significantly reduced in the treated areas. Totally, 3200 adult sand flies were collected and identified in the intervention and control areas. In the treated area with zinc phosphide, the density of Phlebotomus papatasi was higher in outdoors in contrast with the treated area by Coumavec® which the density of the sand fly was higher in indoors.ConclusionBoth rodenticides were effective on the incidence of ZCL and the population of the reservoirs as well. Coumavec® seems to be effective on the outdoor density of the vector. This combination of rodenticide-insecticide could be a suitable alternative for zinc phosphide while bait shyness or behavioral resistance is occurred.Keywords: Rodent control, Zinc phosphide, Coumavec®, Zoonotic Cutaneous Leishmaniasis, Iran
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BackgroundCutaneous leishmaniasis due to Leishmania major has become a hot topic in Iran. The objective of this study was to determine some ecological aspects of sand flies in the study area.MethodsSand flies were collected biweekly from indoors and outdoors fixed places in the selected villages, using 30 sticky paper traps from the beginning to the end of the active season of 2006 in Kerman Province, south of Iran. The flies were mounted and identified. Some blood fed and gravid female sand flies of rodent burrows and indoors were dissected and examined microscopically for natural promastigote infection of Leishmania parasite during August to September.ResultsIn total, 2439 specimens comprising 8 species (3 Phlebotomus and 5 Sergentomyia) were identified. The most common sand fly was P. papatasi and represented 87.1% of sand flies from indoors and 57.2% from outdoors. The activity of the species extended from April to end October. There are two peaks in the density curve of this species, one in June and the second in August. Natural promastigote infection was found in P. papatasi (12.7%).ConclusionPhlebotomus papatasi is considered as a probable vector among gerbils and to humans with a high percentage of promastigote infection in this new focus of cutaneous leishmaniasis. The Bahraman area which until recently was unknown as an endemic area seems now to represent a focus of zoonotic cutaneous leishmaniasis transmission in Iran.
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BackgroundBiting habit of mosquitoes plays an important role in the epidemiology of mosquito-borne diseases. Mosquitoes use a set of elaborate sensory modalities to find their preferred hosts by exploiting cues emanating from a nearby host. It has been suggested that the chemical profile of skin can provide further support for anthropophilic mosquito species to find their suitable hosts. This study aimed at revealing the value of skin emanation for a zoophilic species like Anopheles stephensi as a model.MethodsSkin emanations of a man, a cow and a Guinea pig were collected by ethanol soaked cottons. Upwind responses of mosquitoes to 100 and 200 2l of filtered skin materials were non-competitively explored in a dual-choice olfactometer. L-lactic acid and other chemical content of the skin samples were identified by an enzymatic kit and GC-MS, respectively.ResultsUnexpectedly, only human skin emanation was resulted in the statistically significant activation and attraction responses of An. stephensi in the wind tunnel. L-lactic acid content of this skin sample was 10 and 29 times more than the cow and the Guinea pig, respectively. The possible role of lactic acid and a few other identified compounds have been discussed here.ConclusionAn. stephensi showed higher and more specific upwind responses to human skin emanation in the olfactometer. Undoubtedly, the thorough explanation of this unexpected finding needs further investigation. But, if new data verify this result, then, it may be necessary to reconsider the role of skin emanation and thence the human blood index and vectorial capacity of this zoophilic mosquito.
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BackgroundZoonotic cutaneous leishmaniasis (ZCL) is an expanding disease and public health problem in Iran. In the current study, natural Leishmania infection rate and seasonal fluctuation of the infection in Rhombomys opimus population of a hyperendemic focus of ZCL in Iran was investigated.MethodsThe study was conducted from October 2006 to October 2008 in Esfahan Province, central part of Iran. An extensive sampling of rodents using Sherman traps was done in different seasons. Nested PCR assay was used for detection and identification of Leishmania species and the results were confirmed using PCR-RFLP.ResultsLeishmania infection rate was 58.6% (34 of 58) using nested PCR. 44.8% of the gerbils were infected only with L. turanica and 1.7% with L. gerbilli alone. A mixed natural infection with L. major and L. turanica was seen in 12.1% of the rodents. L. major infection alone was not seen in R. opimus population in the study area. The highest and lowest Leishmania infection rates were observed in fall and spring respectively. L. turanica infection was observed throughout the year whereas mixed infections with L. major and L. turanica was not seen in spring.ConclusionIt is concluded that in the study area, L. major, L. gerbilli and L. turanica circulate in the population of R. opimus. Leishmania major infection usually accompanied by L. turanica in naturally infected gerbils with the highest rate in fall. It is recommended that the role of L. turanica in the epidemiology and transmission of ZCL be revisited.
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BackgroundThe control of leishmaniasis, a tropical neglected disease, has been concern of Iranian health authorities due to the increasing number of cases during the last two decades. The objective of this study was to determine deltamethrine residue on the impregnated bed nets using HPTLC technique in a leishmaniasis control program in Iran.MethodsDuring this experimental study, a total of 130 small pieces of polyester netting were sewn to top, upper, and lower sides of some bed nets and then were impregnated with deltamethrin. The treated bed nets were distributed in Isfahan and Mashhad areas in April 2003. The samples were cut randomly after impregnation intervals. Deltamethrin was extracted using acetone from samples and the extract was applied for spotting onto plates. The plates were developed with n-hexane: ethyl acetate, 90+10(v/v), as a mobile phase in a Camage chamber. The qualifying of residue was observed in UV cabinet with λ=254 nm wavelength. Data were analyzed using SPSS version 11.5. and Stata Version 8. A three way ANOVA was used to compare the means of deltamethrin residue in each area, group and measuring time. The Kruskal-Wallis test was used to compare the means of residue for each of these factors with the control separately.ResultsThe retardation factor of deltamethrin was calculated 0.50±0.02. The residues of deltamethrin persisted well on impregnated nets at least for 15 weeks after impregnation. No significant difference could be detected in the loss of residue of insecticide in comparison to measuring times and positions of sampling pieces on the bed nets in these areas.ConclusionBased on the results of the present study the use of HPTLC technique is recommended instead of other chromatographic methods for analysis of insecticide residue on the impregnated bed nets.
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Following annual report of new cases of cutaneous leishmaniasis from different areas of Kuhpayeh district, Esfahan County, an investigation was carried out on some ecological aspects of Phlebotomine sand flies during 2000-2002. Sand flies were collected biweekly from outdoor and indoor resting places with the aid of 30 sticky traps from the be ginning to the end of the active season. Female sand flies from rodent burrows were dissected and examined for the presence of pro-mastigote infection. Blood meals of engorged sand flies were identified by ELISA method. Totally, 4993 sand flies were collected and identified. The following species were found indoors: P. papatasi, P. ser genti, P. caucasicus, P. mongo len sis, P. al exandri, P. ansarii, P. major, P. kandelakii, S. sintoni, and the subsequent species were found outdoors: P. pa patasi, P ser genti, P. caucasicus, P. mongolensis, P. ansarii, P. major, S. sintoni, S. dentata, S. pawlowskyi. The sand flies active season began from May till October in this region. Natural promastigote infections observed in 1.06% of P. papatasi and also in one out of four of P. caucasicus. The human and rodent blood indices in P. papatasi were 61.9% and 20.69%, respectively. It seems that P. papatasi is the probable vector among rodents and also transmit Leishmania major, the causative agent of zoonotic cutaneous leishmaniasis to man, and P. caucasicus transmit the agent of the disease among rodents.
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Reports from the health center of Kerman Province, southern Iran showed an increasing of cutaneous leishmaniasis cases in Orzuieh Rural District, southwest of the province in 2003. The report encouraged the team to carry out an epidemi ological survey in the district during 2003-2004. The objectives were to determine the ecology of sand flies, potential reser voir hosts and human infection. A total of 1075 sand flies were collected by sticky traps and 7 species of sand flies were identified. They comprised 3 species of the genus Phlebotomus (P. papatasi, P. mongolensis and P. bergeroti) and 4 species of the genus Sergentomyia (S. sintoni, S. clydei, S. tiberiadis and S. baghdadis). P. papatasi was the predominant species of the genus Phlebotomus in indoors (90.3%) and outdoors (50.2%). Susceptibility tests on P. papatasi with DDT 4%. Showed that the species was susceptible to this insecticide. A total of 13 rodents consist of Tatera indica (76.9%) and Nesokia indica (23.1%) were collected. A study of prevalence among 2441 inhabitants in four villages showed a rate of 1.1% for active lesions and 10.4% for scars during November- December 2003. In a separate study examination of 1662 school children aged 6-12 years old showed 1.14% for ulcers and 14.7% for scars at the same time. The Leishmania parasites were isolated from man and characterized as Leishmania major using RAPD-PCR method. It seems that cutaneous leishmaniasis due to L. major (CLM) has been prevailed in the district.
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Abstract: Bacground: The aim of this study was to determine the status of the cutaneous leishmaniasis in some nonendemic quarters in the city of Isfahan, Isfahan Province, central Iran.MethodsA total of 16380 primary school students aged 6-17 years old and a total population of 2892 persons in 700 households in four nonendemic quarters were questioned and examined for the presence of ulcer or scar. Sand flies were collected using sticky paper traps.ResultsA rate of 4.18% for scars and 0.3% for active lesions in the primary school children were showed. The households showed a prevalence of 11.3% for scars and 0.5% for ulcers. Two thousand and seventy four sand flies were collected and 10 species were identified. The most common sand fly species in indoor and outdoor resting places was P.sergenti. Conlusion: The present investigation revealed that Anthroponotic Cutaneous Leishmaniasis is in an epidemic status in these quarters. Human is considered the main reservoir and transmission is believed to be from human to human by P.sergenti.
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Zoonotic cutaneous leishmaniasis (ZCL) is an increasing and important public health problem in Iran. The use of repellents is recommended as one of the important means of personal protection against vectors of ZCL. This paper reports the repellency effect of the plant Myrtle, Myrtus communis (Myrtaceae), essential oil for protection against 3-7-day-old unfed females of the sandfly, Phlebotomus papatasi Scopoli for the first time in Iran. The tests were carried out under laboratory conditions, using dose-response testing procedure on white rabbits and the results were compared with commonly used repellent, diethyl-3-methylbenzamid (DEET). The modified Wirtz method using K & D apparatus was employed. Effective Dose (EDs) values were estimated from the probit regression line. ED50 was measured as 0.1140 and 0.0006 mg/cm2 for Myrtle essential oil and DEET, respectively. The laboratory tests showed that both Myrtle essential oil and DEET had repellency effects against P.papatasi. In addition, the insecticidal action of Myrtle oil was also observed. We concluded that the two repellents could be used as a mean of personal protection against sand flies.
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Control of insect pests of agriculture, economic, and medical importance usually focuses on the use of insecticides. The susceptibility levels of eleven strains of German cockroaches, Blattella germanica (L.), were compared with a standard susceptible strain against permethrin and fipronil. The strains were collected from nine infested students’ dormitories and two infested hospitals in Tehran, capital of Iran. The susceptible strain showed LD50 of 0.43 µg and 0.96 ng for permethrin and fipronil respectively. Comparison of the resistance ratio of collected strain with susceptible strain showed resistance ratios of 8.6 to 17.7-folds for permethrin and 1.5 to 2.6-folds for fipronil, respectively. The result of this investigation indicated that the all strains were resistant to permethrin. Resistance spectrum of fipronil to permethrin showed different pattern of susceptibility to fipronil, indicating that there was no relationship between resistance to permethrin and fipronil.
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An outbreak of zoonotic cutaneous leishmaniasis caused by Leishmania major was identified in Ghanavat rural district, Qom province, central Iran, during 1999-2001. Among 1069 inhabitants examined in Dec. 1999, 5.14% showed evidence of active lesions and 12.44% had scar indicative of past infection. The most highly infected age group was 5-9 years old for ulcers with a rate of 6.56%. The incidence of the disease was calculated as 2.7% and 1.4% in 2000 and 2001 respectively. Meriones libycus (66.7%), Nesokia indica (27.3%) and Hemechinus aurithis (6%) were present around the district. No leishmanial infection was seen in the slides. Meriones libycus is the probable reservoir host of the disease in the area. Sixteen dogs appeared to be uninfected because examination showed no active lesion or scar. Most probably Phlebotomus papatasi is the vector because 81.53% of indoor sand flies were of this species. The active season of P.papatasi was from late April to early October in indoors. The occurrence of this outbreak of ZCL in the district seems to be the result of construction of buildings near colonies of rodents and also traveling to other infected foci of Iran
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