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排序方式: 共有267条查询结果,搜索用时 15 毫秒
91.
Sadaf Kayani Manzoor Hussain Mushtaq Ahmad Mir Ajab Khan Maryam Akram Butt Sidra N. Ahmed Sofia Rashid Zafar Jamal Hafiza Mamona Nazir 《Microscopy research and technique》2022,85(4):1465-1482
The pollen morphology, with special reference to exine sculpture, of some species of the gymnosperms was assessed for the first time from the subalpine and alpine zones of western Himalayas northern Pakistan. The pollen of all these species is airborne and allergenic, so pollen morphology helps for identification of this allergenic pollen at specific level. Different morpho-palynological characteristics were analyzed including size range of pollen, polar and equatorial diameter ratio, exine ornamentation, sculpturing, exine thickness, pollen type, and shape. For accurate and quick identification of species, taxonomic key was made based on different morpho-palynological characteristics. The quantitative data were processed using SPSS software. Gymnospermal pollen includes inaperturate, rarely 1-colpate observed in (Cupressaceae), hexazonocolpate in (Ephedraceae), vesiculate, bissacate in (Pinaceae), and inaperturate in (Taxaceae). Different pollen shapes observed were prolate (4 spp), sub-spheroidal (7 spp), and oblate (1 spp). Variation was observed in exine sculpturing granular (4 spp), reticulate (1 spp), areolate-punctate (3 spp), and psilate (2 spp). This is based on the analysis of 10 plants belonging to four families of gymnosperms. Distinct pollen shape has emerged as the most diagnostic feature to separate some genera such as spheroidal in (Cupressaceae, Taxaceae), prolate and radiosymmetrical in (Ephedraceae), and bilateral in (Pinaceae). Exine thickness and sculpturing proved to be helpful at generic and specific levels. The results reinforced the significance of gymnospermal pollen morphological features which were used as aid for valuable taxonomic tool in plant systematics. 相似文献
92.
J. F. Branthaver Muhammed Nazir J. C. Petersen S. M. Dorrence 《Petroleum Science and Technology》2013,31(4):355-369
ABSTRACT Two different asphalts were coated on a Fluoropak support and were oxidized at 130 ± 2°C for 24 hours using a number of metal chelales as additives. After oxidation the recovered asphalts were analyzed by infrared spectrometry to determine enhancements of keto, acid, and anhydride functions. Vanadyl etioporphyrin I was found to be an effective promoter in the oxidation of both asphalts. Vanadyl porphyrins having bulky ring substituents are not as effective as vanadyl etioporphyrin I in promoting asphalt oxidations. 相似文献
93.
A novel mathematical model has been developed to understand the mechanism of blister initiation and propagation. The model employs a two-part theoretical approach encompassing the debondment of a coating film from the substrate, coupled with the design components incorporating diffusion and fracture mechanics, where the latter is derived from equi-biaxial tensile loading. Integrating the two components, a comprehensive mathematical design for the propagation of blister boundaries based on specific toughness functions and mode adjustment parameters has been developed. This approach provided a reliable and efficient prediction method for blister growth rate and mechanisms. The model provided a foundation for holistic design based on diffusion and mechanic components to enable better understanding of the debondment of thin elastic films bonded to a metallic substrate. 相似文献
94.
Persistent sample circulation microextraction combined with graphite furnace atomic absorption spectroscopy for trace determination of heavy metals in fish species marketed in Kermanshah,Iran, and human health risk assessment 下载免费PDF全文
95.
Investigating the effect of material and weave design on comfort properties of bilayer-woven fabrics
Muhammad Umar Nazir Khubab Shaker Yasir Nawab Muhammad Zohaib Fazal Muhammad Imran Khan 《纺织学会志》2017,108(8):1319-1326
The paper focuses on the development of a bilayer-woven fabric and investigating the effect of weave design and material type on its comfort properties. Face layer was plain woven with cotton yarn, while two different weave designs (2/2 and 3/1 twill) and four different materials (cotton, polyester, micropolyester and nylon) were used for the back layer. The comfort properties of fabric, including air permeability (AP), thermal resistance, water vapour resistance and overall moisture management capacity, were determined. It was found that both the layers of fabric as a whole contribute to the comfort properties of bilayer fabric. The highest AP was exhibited by fabrics having both layers of cotton, while 3/1 twill samples have a lower value of thermal resistance as compared to the 2/2 twill samples. The results further showed that micro polyester woven in 3/1 twill weave exhibits better comfort properties. 相似文献
96.
97.
Elidiane C. Rangel Eduardo S. de Souza Nazir M.S. Marins Nilson C. Cruz 《Thin solid films》2010,518(10):2750-2756
The great versatility of polymers has promoted their application in a series of ordinary situations. The development of specific devices from polymers, however, requires modifications to fit specific stipulations. In this work the surface properties of thin films grown onto polyvinylchloride (PVC) were investigated. Hydrogenated amorphous carbon films were deposited onto commercial PVC plates from acetylene and argon plasmas excited by radiofrequency (13.56 MHz, 70 W) power. The proportion of acetylene in the gas feed was varied against that of argon, keeping the total pressure constant at 2.5 Pa. Deposition time was 1800 s. Film elemental composition was analyzed by X-ray photoelectron spectroscopy, XPS. Water contact angle measurements were performed using the sessile drop technique. The root mean squared roughness was derived from 50 × 50 µm2 surface topographic images, acquired by scanning probe microscopy. Nanoindentation and pin-on-disk techniques were employed on the determination of film hardness and sliding wear, respectively. Oxidation resistance was obtained through the etching rate of the samples in oxygen radiofrequency (1.3 Pa, 50 W) plasmas. From XPS analysis it was detected oxygen and nitrogen contamination in all the samples. It was also found that sp3/sp2 ratio depends on the proportion of argon in the plasma. At lower argon concentrations, hardness, wear and oxidation resistances were all improved with respect to the uncoated PVC. In such conditions, the surface wettability is low indicating a moderate receptivity to water. This combination of properties, ascribed to a balance between the ion bombardment and deposition processes, is suitable for materials exposed to rigorous weathering conditions. 相似文献
98.
The photocatalytic decomposition process on TiO2 thin films, was modeled by taking the decay of illumination intensity via Lambert-Beer law into account. For the sake of experimental verification of the proposed model, Ti02 thin films were prepared on a glass substrate by a dip-coating method combined with a sol-gel process and the photocatalyuc activity of the thin films was evaluated by the decomposition of 2-propanol (IPA) in an aqueous solution under illumination of UV light source. The film thickness up to 1.4 μm increased with the withdrawal speed raised to the power 0.6 and was proportional to the number of application (i.e., repetition of dip-coating process). The TiO2 gel films prepared by a dip-coating technique, were subject to firing at 500°C. The photocatalytic decomposition rate could be expressed apparently as first-order with respect to IPA concentration. The observed relationship between apparent first-order rate constant of decomposition and the film thickness could satisfactorily be explained by the proposed model. 相似文献
99.
Zainab Nayyar Muhammad Attique Khan Musaed Alhussein Muhammad Nazir Khursheed Aurangzeb Yunyoung Nam Seifedine Kadry Syed Irtaza Haider 《计算机、材料和连续体(英文)》2021,68(2):2041-2056
Artificial intelligence aids for healthcare have received a great deal of attention. Approximately one million patients with gastrointestinal diseases have been diagnosed via wireless capsule endoscopy (WCE). Early diagnosis facilitates appropriate treatment and saves lives. Deep learning-based techniques have been used to identify gastrointestinal ulcers, bleeding sites, and polyps. However, small lesions may be misclassified. We developed a deep learning-based best-feature method to classify various stomach diseases evident in WCE images. Initially, we use hybrid contrast enhancement to distinguish diseased from normal regions. Then, a pretrained model is fine-tuned, and further training is done via transfer learning. Deep features are extracted from the last two layers and fused using a vector length-based approach. We improve the genetic algorithm using a fitness function and kurtosis to select optimal features that are graded by a classifier. We evaluate a database containing 24,000 WCE images of ulcers, bleeding sites, polyps, and healthy tissue. The cubic support vector machine classifier was optimal; the average accuracy was 99%. 相似文献
100.
Muhammad Amir Khan Adnan Ahmad Salman Noshear Arshad Ahsan Nazir Sheraz Ahmad Muhammad Qamar Khan Amir Shahzad Aamir Naseem Satti Muhammad Bilal Qadir Zubair Khaliq 《应用聚合物科学杂志》2021,138(24):50562
One dimensional (1D) nanostructures and its derivatives can be manipulated to serve special functions like hollow structure, and higher surface area. 1D TiO2 nanotube-in-nanofibers (NF@NT) are developed through triaxial electrospinning followed by a calcination process. A blended solution of polyvinyl pyrrolidone and tetra-butyl titanate is used in outer and inner layers of nanofibers, respectively, while paraffin oil is used in the middle layer. The optimized triaxial nanofibers of 669.4 ± 52.43 nm are developed at 7.5 w/w% concentration, 28 kV applied voltage, and 24 cm spinning distance. TiO2 NF@NT structure is obtained through calcination of optimized triaxial nanofibers at 550°C. Subsequently, the morphology of TiO2 NF@NT and its uniform diameter distribution is confirmed through scanning electron microscopy. Fourier-transform infrared spectroscopy results indicates the formation of TiO2 NF@NT. X-Rays diffraction pattern peaks also reveals the presence of both anatase and rutile crystalline phases. The presence of only titanium (Ti) and oxygen (O) elements in the TiO2 NF@NT is confirmed through energy dispersive X-ray spectroscopy. Brunauer–Emmett–Teller analysis indicates that TiO2 NF@NT has a higher specific surface area of ~141.68 m2/g compared with the solid TiO2 nanofiber (~75.31 m2/g). This study can be adopted to develop TiO2 NF@NT for wide range of application. 相似文献