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81.
Ashfaq Ahmad 《Journal of Materials Science》1992,27(15):4120-4124
Experimental data on X-ray electrical conductivity, thermoelectric coefficient, magnetic hysteresis and infrared absorption spectra of the system Li0.25Cu0.5Fe2.25–x
Al
x
O4 are presented. All the compounds, 0x2.25, showed cubic symmetry. Lattice constant values progressively decreased on increasing the Al3+ content. X-ray intensity calculations, magnetic hysteresis and infrared spectroscopy studies indicated the presence of Li+, Al3+ and Fe3+ at tetrahedral and octahedral sites, while Cu2+ is present only at the octahedral site. The activation energy and threshold frequency increased with increasing values ofx. The compounds withx1.50 aren-type, and those withx2.0 arep-type semiconductors. Magnetic hysteresis indicated that compounds withx1.50 are ferrimagnetic, and those withx2.0 are antiferrimagnetic. High coercive force,H
c, values and remanence ratios (J
R/JS) showed that all the compounds exceptx2.0 exhibit single-domain behaviour. The probable ionic configuration for the system is suggested as Li
0.15
+
Al
0.5
3+
Fe
0.35
3+
[Li
0.1
+
Cu
0.5
2+
Fe
0.4
3+
Al3+]O
4
2–
. 相似文献
82.
83.
Saraj Bahadur Mushtaq Ahmad Muhammad Zafar Saba Gul Asma Ayaz Shomaila Ashfaq Saima Rubab Muhammad Shuaib Shakil Ahmad 《Microscopy research and technique》2020,83(4):345-353
Recent field exploration and collections has led to the findings of several new species in Pakistan. Here we reported two new species Ajuga reptance L and Sphagneticola trilobata (L.) Prusk for the first time in Pakistan flora as these species were neither listed in any other literature nor identified before in Pakistan. These species were found as a result of taxonomic studies performed in the year 2019 in District Rawalpindi and Islamabad, Pakistan. Microscopic techniques were used for the confirmation of foliar epidermal and pollen micromorphological features. Detailed study (morphological, palynological, and foliar epidermal) was provided for the correct identification and delimitation of the species using both light and scanning electron microscopy. Morphological results were compared with the flora of Taiwan and China. 相似文献
84.
Sophia Akhtar Amjad Ali Muhammad Ashfaq Ahmad Muhammad Naveed Aslam Imran Shakir Muhammad Sufyan Javed Muhammad Khurram Qureshi Rizwan Raza 《International Journal of Hydrogen Energy》2021,46(15):9957-9967
Fossil fuels are unable to meet the current energy demands and polluting the environment with the emission of harmful gases. Therefore, clean energy technology is need of the modern era. One of the energy conversion devices is fuel cell which utilized fuel from renewable sources and convert into electricity in an efficient and clean way. However, for commercialization of this technology high operating temperature, degradation of electrodes and manufacture cost is the key challenges in conventional three layer fuel cell. Significant improvements have been made to reduce the cost and operating temperature by selecting suitable materials. Therefore, single layer fuel cell (SLFC) has been got much attention due to simple geometry. The mechanism inside the SLFC is still mystery which has been explained in this paper using quantum mechanical parameters like band gap and effect of particle size on charge transportation.In this research work, nanocomposite materials for single layer fuel cell have been synthesized by chemical routes. The x-ray diffraction shows the cubic perovskite structure with average crystallite size in the range of 23–37 nm. The particle size and surface area is found to be 23 nm and 86.42 m2 g?1, respectively. Raman spectrum of LBSCF-SDC shows a red shift compared to LBSCF and band gap of the composition 3LBSCF-7SDC is found to be 2.51 eV. Moreover, the conductivity of the sample 3LBSCF-7SDC has been found to be 0.02 Scm?1 at 750 °C. The quantum mechanical effects governing the working of single layer fuel cells are observed by different analyses. Photon confinement and Fano-Interactions phenomena resulted in a red shift using Raman analysis technique. The red shift in Raman spectrum is referred to a photon confined in a single layer fuel cell system. These effects are studied in single layer fuel cell for the first time with no previous analyses done in this newly field. 相似文献
85.
86.
87.
MH Saboorian M Kenny R Ashfaq J Albores-Saavedra 《Canadian Metallurgical Quarterly》1996,120(5):501-504
Although the vast majority of eccrine spiradenomas behave in a benign fashion, 23 cases of malignant transformation have been reported to date. We describe a unique example of malignant eccrine spiradenoma that arose in the right breast of a 68-year-old woman. The quiescent mass, which was present for approximately 50 years, experienced sudden enlargement with erythematous changes of the overlying skin and nipple discharge. Microscopically, the tumor showed the typical features of an eccrine spiradenoma with areas of adenocarcinoma, squamous cell carcinoma, and sarcoma. The sarcomatous component consisted of rhabdomyosarcoma and osteosarcoma. The immunoperoxidase staining revealed p53 protein expression only in the carcinomatous and sarcomatous components. This suggests that accumulation of p53 protein may be an important event in the malignant transformation of spiradenomas. Because of its location and biphasic nature, this malignant eccrine spiradenoma should be distinguished from metaplastic breast carcinoma. To our knowledge, this represents the first carcinosarcomatous transformation of eccrine spiradenoma in the breast. This case led us to conclude that breast tissue, which often undergoes apocrine metaplasia and gives rise to apocrine neoplasms, is also capable of originating benign and malignant tumors with eccrine sweat duct phenotype. 相似文献
88.
89.
Albuz E. Kocalar E. Khokhar A.A. 《Knowledge and Data Engineering, IEEE Transactions on》2001,13(5):851-861
This paper presents a scalable content-based image indexing and retrieval system based on vector wavelet coefficients of color images. Highly decorrelated wavelet coefficient planes are used to acquire a search efficient feature space. The feature space is subsequently indexed using properties of all the images in the database. Therefore, the feature key of an image not only corresponds to the content of the image itself but also to how much the image is different from the other images being stored in the database. The search time linearly depends on the number of images similar to the query image and is independent of the database size. We show that, in a database of 5,000 images, query search takes less than 30 msec on a 266 MHz Pentium II processor, compared to several seconds of retrieval time in the earlier systems proposed in the literature 相似文献
90.