Germination and seedling growth of corn (Zea mays l.) under varying levels of copper and zinc     

S. Mahmood  A. Hussain  Z. Saeed  M. Athar 《International Journal of Environmental Science and Technology》2005,2(3):269-274

The heavy metal tolerance in corn (Zea mays L.) var. ‘Neelum’ was assessed at germination and seedling growth after having subjected it to different concentrations of CuSO₄ and ZnSO₄. Germination was not affected by any of the metal tested, whereas initial growth was strongly inhibited by increasing concentrations of ZnSO₄. Seedlings developed toxicity symptoms in the presence of both metals but more chlorotic and necrotic regions were observed at varying levels of ZnSO₄ than CuSO₄. The metal accumulation was concentration dependent. Z. mays seedlings accumulated more copper in roots but greater contents of zinc in their shoots. On the basis of results presented here, it can be concluded that the cultivar of the species tested has shown a marked sensitivity to the presence of small amounts of metals present in the growth medium. The data support the assumption that metal sensitivity is probably due to strong tendency of the species to accumulate them. This justifies that the corn variety ‘Neelum’ is not suitable for the cultivation under situations where water and soil suffer from occasional and/ or transitory metal pollution.  相似文献   

Analytical Solutions for Water Flow and Solute Transport in the Unsaturated Zone     

Mahmood H. Nachabe  Alvaro L. Islas  Tissa H. Illangasekare 《Ground water》1995,33(2):304-310

Analytical solutions for the water flow and solute transport equations in the unsaturated zone are presented. We use the Broadbridge and White nonlinear model to solve the Richards’ equation for vertical flow under a constant infiltration rate. Then we extend the water flow solution and develop an exact parametric solution for the advection-dispersion equation. The method of characteristics is adopted to determine the location of a solute front in the unsaturated zone. The dispersion component is incorporated into the final solution using a singular perturbation method. The formulation of the analytical solutions is simple, and a complete solution is generated without resorting to computationally demanding numerical schemes. Indeed, the simple analytical solutions can be used as tools to verify the accuracy of numerical models of water flow and solute transport. Comparison with a finite-element numerical solution indicates that a good match for the predicted water content is achieved when the mesh grid is one-fourth the capillary length scale of the porous medium. However, when numerically solving the solute transport equation at this level of discretization, numerical dispersion and spatial oscillations were significant.  相似文献   

Land use/land cover changes and regional climate over the Loess Plateau during 2001–2009. Part II: interrelationship from observations     

Xingang Fan  Zhuguo Ma  Qing Yang  Yunhuan Han  Rezaul Mahmood 《Climatic change》2015,129(3-4):441-455

  相似文献   

Land use/land cover changes and regional climate over the Loess Plateau during 2001–2009. Part I: observational evidence     

Xingang Fan  Zhuguo Ma  Qing Yang  Yunhuan Han  Rezaul Mahmood  Ziyan Zheng 《Climatic change》2015,129(3-4):427-440

  相似文献   

Geo-spatial assessment of community vulnerability to flood along the Ravi River,Ravi Town,Lahore, Pakistan     

Mahmood  Shakeel  Hamayon  Kiran 《Natural Hazards》2021,106(3):2825-2844

Natural Hazards - Pakistan is exposed to hydro-meteorological and geological hazards. Flood is one of the hydro-meteorological hazards, and so far 25 major floods have occurred in Indus River...  相似文献   

Transmission of light by slit designed for astronomical spectrograph     

Mahmood A. Ismail 《Astrophysics and Space Science》1986,122(1):1-32

The paper discusses an investigation of linear polarization produced by the transmission of light through an astronomical spectrograph slit. An experimental apparatus was designed and set up to carry out this work. The parallel beam of plane polarized light was rotated in the measuring system, by optically active of half-wave plate. The intensity of normally incident of polarized light of wavelength 0.436 μm transmitted by various slit was measured as a function of slit width. The results indicate:

1. That the degree of polarization increased as thedepth of the narrow slit was increased.
2. That the degree of polarization increased as thewidth of the narrow slit was decreased.
3. That when the width of slit was widened the degree of polarization tended to approach a constant value asymptotically.
4. That the theoretical calculation of Slater (1942) predicts the measured experimental values more accurately than Thiessen (1947) and Jones and Richards (1954).

It is shown that the existence and order of magnitude of all these effects may be predicted from the propagation losses of the electromagnetic theory of light in metallic wave guide. The paper brings out the salient points related to the degree of polarization of light by a dielectric slit of finite depth. The polarization effects from one such slit have been investigated and the results were compared with those for metallic slits.  相似文献   

Predicting mechanical properties and ultimate shear strength of gypsum,limestone and sandstone rocks using Vipulanandan models     

Wael Mahmood  Saman HamaHussein 《Geomechanics and Geoengineering》2020,15(2):90-106

ABSTRACT

In this study, over 1000 data from the literature was used to characterize and compare the density, strengths, modulus, fracture toughness, porosity and the ultimate shear strengths of the gypsum, limestone and sandstone rocks. The compressive modulus and Mode-1 fracture toughness of the gypsum rock, limestone rock and sandstone rocks varied from 0.7 GPa to 70 GPa, and from 0.03 MPa.m^0.5 to 2.6 MPa.m^0.5  respectively. Vipulanandan correlation model was effective in relating the modulus of elasticity, fracture toughness with the relevant strengths of the rocks. A new nonlinear Vipulanandan failure criterion was developed to quantify the tensile strength, pure shear (cohesion) strength and to predict the maximum shear strength limit with applied normal stress on the gypsum, limestone and sandstone rocks. The Vipulanandan failure model predicts the maximum shear strength limit was, as the Mohr-Coulomb failure model does not have a limit on the maximum shear strength. With the Vipulanandan failure model based on the available data, the maximum shear strengths predicted for the gypsum, limestone and sandstone rocks were 64 MPa, 114 MPa and 410 MPa respectively.  相似文献   

The 2014 seismic hazard model of the Middle East: overview and results     

Karin Şeşetyan  Laurentiu Danciu  Mine B. Demircioğlu Tümsa  Domenico Giardini  Mustafa Erdik  Sinan Akkar  Levent Gülen  Mehdi Zare  Shota Adamia  Anooshiravan Ansari  Avetis Arakelyan  Ayşegül Askan  Mher Avanesyan  Hektor Babayan  Tamaz Chelidze  Raffi Durgaryan  Ata Elias  Hossein Hamzehloo  Khaled Hessami  Doğan Kalafat  Özkan Kale  Arkady Karakhanyan  Muhammad Asif Khan  Tahir Mammadli  Mahmood Al-Qaryouti  Mohammad Sayab  Nino Tsereteli  Murat Utkucu  Otar Varazanashvili  Muhammad Waseem  Hilal Yalçın  Mustafa Tolga Yılmaz 《Bulletin of Earthquake Engineering》2018,16(8):3535-3566

The Earthquake Model of Middle East (EMME) Project aimed to develop regional scale seismic hazard and risk models uniformly throughout a region extending from the Eastern Mediterranean in the west to the Himalayas in the east and from the Gulf of Oman in the south to the Greater Caucasus in the North; a region which has been continuously devastated by large earthquakes throughout the history. The 2014 Seismic Hazard Model of Middle East (EMME-SHM14) was developed with the contribution of several institutions from ten countries. The present paper summarizes the efforts towards building a homogeneous seismic hazard model of the region and highlights some of the main results of this model. An important aim of the project was to transparently communicate the data and methods used and to obtain reproducible results. By doing so, the use of the model and results will be accessible by a wide community, further support the mitigation of seismic risks in the region and facilitate future improvements to the seismic hazard model. To this end all data, results and methods used are made available through the web-portal of the European Facilities for Earthquake Hazard and Risk (www.efehr.org).  相似文献   

Changing Land Use a Threat to Surface Water Quality: a Vulnerability Assessment Approach in Zanjanroud Watershed,Central Iran     

Mahsa Mirhosseini  Parvin Farshchi  Ali Akbar Noroozi  Mahmood Shariat  Ali Asghar Aalesheikh 《Water Resources》2018,45(2):268-279

Maintaining the quality of surface water resources as one of the most vital water supplies has always been at the center of global concerns. A set of manifest and latent factors have yet been identified by researchers worldwide that are subject to affect the quality of surface water. Among which, the effect of land use change, due to a spatial and temporal complexity, is often not easily verifiable. The present study attempts to offer an index-based model to quantify vulnerability of surface water resources in a semi arid basin in central Iran against land use changes. For this, water quality data including Na, K, Mg, Ca, Sodium Adsorption Ratio (SAR), total anions (Sum. A), SO₄, Cl, HCO₃, EC, TDS, and pH were collected from hydrometric stations over a period of 26 years (1987?2013). In order to detect land use changes, the land use maps of the years 1987, 1998, 2002, 2009, and 2013 were prepared from TM satellite images using supervised classification method. At next step, changing patterns of different land uses were traced by Shanon’s Diversity Index (SHDI) as a metric of patch diversity indicating diversity and heterogeneity of a landscape over time. Relationship between the SHDI values and water quality indicators revealed the impact of land use changes on quality of surface water resources. Statistical analysis confirmed a significant relationship between nine water quality factors and water discharge in the basin during the study period. From 1998 to 2009, the greatest changes were visible in the total anions, Ca, SO₄, and HCO₃. These parameters along with salinity were increasing in almost all sub-basins. According to the results, conversion of poor rangelands to rain fed agriculture fields is the most apparent land use change occurred in the study area over the study period. In 1987, SHDI as an indicator of the diversity and changes in the basin, showed a significant relationship with good rangelands (R² =–0.835). This indicates that fragmentation of the entire watershed area was initiated in 1987, which reached its peak in 2013. Generally speaking, urbanization, poor rangeland, and irrigated agriculture were recognized as three influential land uses adversely affect the water quality in the study area.  相似文献   

Lower bound limit loads of ship structure components using the m_α-tangent method based on single linear elastic analysis     

S.L. Mahmood  R. Seshadri 《Ocean Engineering》2010,37(13):1139-1148

Limit loads for ship structure components are determined in this paper based on a single linear elastic finite element analysis by invoking the concept of kinematically active reference volume in conjunction with the m_α-tangent method. The method enables rapid determination of lower bound limit loads for ship structure components by taking their kinematically inactive volume into consideration. This method is applied to a number of ship structure components possessing different percentages of inactive volume. Results are compared with the corresponding inelastic finite element results, and available analytical solutions.  相似文献