Showing papers by "Khawaja Shafique Ahmad published in 2016"

Morpho-anatomical and physiological adaptations to high altitude in some Aveneae grasses from Neelum Valley, Western Himalayan Kashmir

Abstract: Five grasses of tribe Aveneae were collected from low (1100 m.a.s.l.) and highland (2300 m.a.s.l.) mountain range of Western Himalaya, Neelum Valley, to evaluate the physio-anatomical adaptations to altitudinal variability. An evidence to confirm the hypothesis that plants vegetating different altitudes must be different structurally (internal modifications) and functionally due to heterogeneity in environmental gradients. The general response of all grasses to high altitude was growth retardation in terms of total leaf area per plant and dry matter. With exception of Ca2+ content, most of the ionic and chlorophyll content were significantly low at high elevations. Anatomical alterations such as, leaf thickness, intensive sclerification around the vascular bundle and pith area, reduced metaxylem vessel area, high pubescence (increased microhair and trichome density) played an important role in high degree of tolerance of these grasses to cope with altitudinal stresses. The mechanical strength of leaf, which is critical for preventing damage under harsh climate and overall survival of high altitudinal populations, seems to be depended on intensity of sclerification and dense pubescence at abaxial and adaxial surfaces of the leaf. Increase in overall thickness of leaf in high altitude grasses in response to low temperature may protect metabolically active tissue like mesophyll. Also high density of trichomes may be involved in blocking transpiration water and internal heat. Differential response of low and high altitude grasses is highly related to air temperature, pattern of rainfall, and availability of nutrients.

Ecotypic adaptations in Bermuda grass (Cynodon dactylon) for altitudinal stress tolerance

Abstract: Three ecotypes [foot hill (700 m), mid hill (1571 m) and top hill (2804 m)] of a Bermuda grass Cynodon dactylon (L.) Pers. from Pir Chinasi Hill in Western Himalaya were evaluated for their degree of tolerance to altitudinal stress. Differential response of all ecotypes in terms of adequate structural modifications to different elevation leveis was an evident to confirm the hypothesis that plants inhabiting different altitudes show variation in structure (internal modifications) and strategic (response) due to heterogeneity in environmental gradients. Soil at top hill site was more acidic and displayed significant increase in ionic content and total nitrogen. High elevation had severe impact on morpho-anatomical and physiological attributes. A significant decline in shoot fresh weight and total leaf area was observed in top hill ecotype. With exception of Ca2+ and carotenoid, other ionic and chlorophyll content were significantly declined at high elevations. Anatomical alterations such as, increased leaf thickness, intensive sclerification around the vascular bundle and pith area, reduced metaxylem vessel area, high number of silica bodies, high pubescence (increased microhair and trichome density) were some of the promising anatomical adaptations in top hill ecotype which played an important role in high degree of tolerance of this grass to cope with altitudinal stresses. Increased leaf thickness might be a response to lower temperature that protects mesophyll cells and high density of trichomes may be involved in blocking transpiration water and internal heat. The pattern of constant variation suggests that differential response of these ecotypes is highly related to air temperature, pattern of rainfall, availability of nutrients.

Cranial Ultrasonography in Infantile Encephalitic Beriberi: A Useful First-Line Imaging Tool for Screening and Diagnosis in Suspected Cases.

Abstract: BACKGROUND AND PURPOSE: Brain imaging is central to the diagnosis of infantile encephalitic beriberi. Because cranial sonography findings have not been described in infantile encephalitic beriberi, our aim was to investigate its role in the diagnosis of this condition. MATERIALS AND METHODS: We performed a retrospective review of head sonography of infants (admitted between November 1, 2014, and March 31, 2015) who presented with encephalopathy. Cranial ultrasonography scans were studied for the alteration of echogenicity of the basal ganglia. RESULTS: Of the 145 consecutive infants who presented with encephalopathy, 58 had thiamine-responsive encephalopathy (infantile encephalitic beriberi) and 87 had encephalopathy due to other causes. Forty-eight of 145 infants with encephalopathy showed hyperechoic basal ganglia. A hyperechoic appearance of the basal ganglia on cranial ultrasonography was found to have a sensitivity of 71% (41/58) and a specificity of 92% (80/87) in diagnosing infantile encephalitic beriberi. The sensitivity of cranial sonography increased with age. It was a maximum of 93% (14/15) in the 5 months and older age group. Specificity was a maximum of 100% (18/18) in infants older than 5 months of age. Sensitivity was maximum in Wernicke encephalopathy at 90% (18/20) and least in the acidotic form at 43% (10/23). Follow-up showed gradual normalization of the hyperechoic appearance of the basal ganglia during 8 weeks in 26/41 (63%), with mild atrophy of the basal ganglia in 6/41 (15%) CONCLUSIONS: Hyperechogenicity of the basal ganglia on cranial ultrasonography is a sensitive finding for the diagnosis of infantile encephalitic beriberi in infants who present with Wernicke encephalopathy.

Slippage of Steel in High and Normal Strength Concrete

Abstract: Composite action of any reinforced concrete member is only possible if sufficient bond strength exists between steel reinforcing bars and concrete, which can adequately transfer shear stress between them. Bond strength is a function of compressive strength of concrete and hence high strength concrete has higher bond strength [1-2]. Therefore required development length can be reduced. In order to investigate the effect of development length on bond stress and slip relationships, experimental investigation was carried out. In this experimentation 24 pull-out samples of high strength concrete and normal strength concrete were casted and tested. The results of this investigation revealed that by increasing the development length from 5db to 10db bond strength increases for both high and normal strength concrete as shown in Figure 11, 12 and 13. However incase of normal strength concrete increase in bond strength is more compared to that in high strength concrete as it is clear from Figure 11 and Figure 13. The increase in bond strength is observed even at 10db development length but the extent is less for 19 mm than 16 mm bars as shown in Figure 12 and Figure 13. This is in agreement with the earlier findings of Chen et al [3] and Harajli et al [1]. However incase of HSC the total slippage at 10db is 50% greater than at 5db. This may be due to the fact that more no of concrete keys participate in resisting the slippage.

Tetrapogon cenchriformis and Parapholis strigosa, (Poaceae), TwoNew Reports from Pakistan

Abstract: Tetrapogon cenchriformis and Parapholis strigosa (Poaceae) are reported for the first time in Pakistan. Tetrapogon cenchriformis is characterized by spatheolate inflorescence, oval elliptic seeds and large stomatal complex, while Parapholis strigosa has long anthers and straight spikes. Anthers are larger in P. strigosa than in Parapholis incurva (L.) C.E. Hubb. These two new reported species showed marked difference from the other species of Parapholis and Tetrapogon treated in flora of Pakistan.