141 research outputs found
Effects of Initial Thinning on the Growth and Biomass Characteristics of Zizyphus spina-christi Trees
No full textSeedlings of Zizyphus spina-christi trees grown from seeds were planted intensively in the field at the Experiments and Research Station of College of Agriculture, King Saud University near Riyadh City. After
a year, the trees were subjected to thinning through three consecutive years and evaluated for growth and biomass production. Starting from the second year of thinning, the thinned trees increased stem diameter and
all above-ground biomass components. Branches and foliage biomass ratio also increased due to thinning at the expense of stem biomass ratio. Unthinned trees were superior in biomass production after three years of the treatment application.Corresponding Author:
Prof. Ibrahim Mohammed Aref
Forest Sciences and Environment, College of Food Science and Agiculture, King Saud University
PO. Box 2460, Riyadh, 11451, Saudi Arabia
Email: [email protected]
The effects of light intensity on seed germination and seedling growth of cassia fistula (linn.), enterolobium saman (jacq.) Prain ex king. And delonix
No full textThe present study investigated the effect of 100, 50 , and 25 % light intensities
on seed germination and early seedling development of Cassia fistula, Enterolobium
saman and Delonix regia. The experiment was carried out under temperature of 25°C
- 15°C day and night and 65 % relative humidity, in the greenhouse. One hundred
percent light intensity significantly produced the highest seed germination and
seedling growth of the three species for all growth characteristics measured. Fifty
percent light intensity treatment produced seed germination and seedling growth to
come in the second order and, sometimes, shared full light intensity treatment. The
growth characteristics of Delonix regia seedlings had almost the highest values
among species and in full light intensity treatment. Although Cassia fistula seedlings
had lower growth, in comparison with the other two species, however, they tolerated
low light intensity and had the highest survival and root growth.Corresponding Author:
Prof. Ibrahim Mohammed Aref
Plant Production Department, College of Agriculture, King Saud University, P.O. Box 2460 Riyadh 11451, Saudi Arabia.
Email: [email protected]
Effects of pre-germination treatments and sowing depths upon germination potential of some Acacia species
No full textSeeds of Acacia farnesiana (L.) Willd., A. salicina Lindley, A.
nilotica (L.) Willd. ex Del., A. ehrenbergiana Hayne, A. seyal Del., A.
saligna (Labill.) H. L. Wendl. and A. tortilis (Forssk.) Hayne were
subjected to pre-germination treatment. This was either by soaking
seeds in water for 24 or 48 or 72 hours or by placing them in boiling
water and left them to cool to the room temperature. All seeds were
sowed either at 2 or 4 or 6-cm at soil. The higher germination
percentage for all Acacia species was obtained after boiling seeds in
water and at 2-cm sowing depth apart from A. ehrenbergiana. It
showed no response to boiling in water but had the best result with
soaking in water for 24h. The results of this study suggest that boiling
seeds of the investigated Acacia species in water is recommended with
sowing depth not deeper than 4 cm.Corresponding Author:
Dr. Ibrahim Mohammed Aref
Department of Plant Production, College of Agriculture, King Saud University,
P. O. Box 2460 Riyadh 11451, Saudi Arabia
Email: [email protected]
Performance of Leucaena leucocephala and Albizia lebbeck trees under low irrigation water in the field
No full textGrowth of Leucaena leucocephala and Albizia lebbeck trees was investigated under
low water supply in the field using a complete randomized block design at the
Research and Experiments Station of the College of Food Science and Agriculture,
Riyadh, Saudi Arabia. The trees were irrigated at either 160 (well water supply) or
500 mm (low water supply) of a class "A" evaporation-pan records for two years.
Differences were occurred between L. leucocephala and A. lebbeck trees across
irrigation treatments with greater values for L. leucocephala in most of the growth
characteristics measured. Comparing with L. leucocephala, leaves of A. lebbeck
comprises only small proportion of the total weight of tree while allocated equal
proportions to their branches and roots (41%).while L. leucocephala trees allocated
almost similar proportions to their branches, stem and roots (27-28%). Low water
supply decreased stem by 19.5% with stem diameter was unaffected. Leaf, branches,
stem, root and consequently total dry weight of the trees decreases by 42, 51.5, 45, 51
and 94% in low water supply. However, the performance of L. leucocephala and A.
lebbeck trees endured low irrigation conditions in terms of survival and maintaining
reasonable growth.Corresponding Author:
Prof. Ibrahim Mohammed Aref
Plant Production Department, College of Food Science and Agriculture, King Saud University, P.O. Box 2460 Riyadh 11451 Saudi Arabia.
Email: [email protected]
Exact nonlinear frequency division multiplexing in lossy fibers
No full textThe path-average approximation penalizes NFDM transmission over lumped amplified fiber links.We investigate suitably tapered lossy fibers to overcome the approximation error induced by the path average, making the NFDM transmission exact. Error vector magnitude gains up to 4.8 dB are observed.Accepted Author ManuscriptTeam Sander Wahl
Numerical Evaluation of Dynamic Response by Using Modified Newmark’s Method
No full textIt is well known that the Newmark’s method is considered one of the most popular methods for structural
dynamic analysis. In this study, starting from the basic Newmark’s method, a new accurate method is
investigated and developed. The basic idea of the proposed method is to use Richardson’s extrapolation to
improve the basic Newmark’s method. To observe the accuracy of the proposed method, several numerical
tests are performed for a single degree-of-freedom (SDM) dynamic system and the results are compared with
results from Newmark’s method and the exact solution. The results show that the proposed method improves
the solution accuracy of the structural dynamic problems compared to the Newmark’s method. Moreover, the
results of the free oscillating case show that the modified Newmark’s method has more computational
efficiency compared to the Newmark’s method.Scopu
Properties of charcoal produced from some endemic and exotic acacia species grown in Riyadh, Saudi Arabia
No full textProduction and properties of charcoal from four years old Acacia assak, A. negrii, A.
seyal, A. karroo, A. ampliceps, A. stenophylla and A. salicina grown in the
Experiments and Research Station, College of Agriculture, King Saud University,
Riyadh, Saudi Arabia were studied. The first three species are indigenous while the
others are exotic. 21 trees were felled and disks of 20 cm each from their stem were
cut and shipped to the Wood Testing Laboratory at the Faculty of Agriculture,
Alexandria University, Egypt. Specific gravity, charcoal yield and gross heat of
combustion of the wood of these species were determined. Wood samples were
charcoaled then the physical (apparent density, gross heat of combustion) and
chemical properties (moisture, volatile, ash and fixed carbon content) of the produced
charcoal produced were determined. A. amplecips, A. negrii and A. asak showed
quality charcoal in terms of high gross heat of combustion and fixed carbon content
with low moisture and ash content comparing with the other acacia species under
investigation.Corresponding Author:
Professor Ibrahim Mohammed Aref, 1Plant Production Department, College of Agriculture, King Saud University, P. O. Box 2460 Riyadh 11451, Saudi Arabia. Email: [email protected]
Dynamic posturography findings among patients with liver cirrhosis in Egypt
No full textBackground Liver cirrhosis is a condition that destroys the normal function of the liver, leading to hepatic encephalopathy, which is associated with impairment in postural control and disturbance in balance.
Aim of the studyThe aim of this study was to detect the disturbances in balance and postural control because of hepatic encephalopathy as a result of liver cirrhosis using dynamic posturography.
Participants and methodsIndividuals were divided into two groups: 45 patients with liver cirrhosis and 45 controls. Both groups underwent dynamic posturography to evaluate balance control, number connection test-type A, line tracing test, and serum ammonia (NH3) level to assess encephalopathy.
Results Dynamic posturography findings were significantly weaker in patients with liver cirrhosis than in the controls. They were also weaker in patients with high NH3 than in patients with low NH3. There were significant negative correlations between dynamic posturography findings and number connection test-type A, line tracing test, and NH3 levels.
Conclusion Hepatic encephalopathy because if liver cirrhosis affects balance control and the degree of affection is related to the degree of encephalopathy
54.5 Tb/s WDM Transmission over Field Deployed Fiber Enabled by Neural Network-Based Digital Pre-Distortion
No full textWe demonstrate a record 54.5 Tb/s WDM transmission at 11.35 bit/s/Hz over 48 km of field-deployed SMF connecting business and academic parks enabled by a novel joint I-Q Neural Network-based transmitter digital pre-distortion technique.Accepted Author ManuscriptTeam Sander Wahl
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