Fractal Dimension Analysis of Transient Visual Evoked Potentials: Optimisation and Applications

Purpose The visual evoked potential (VEP) provides a time series signal response to an external visual stimulus at the location of the visual cortex. The major VEP signal components, peak latency and amplitude, may be affected by disease processes. Additionally, the VEP contains fine detailed and non-periodic structure, of presently unclear relevance to normal function, which may be quantified using the fractal dimension. The purpose of this study is to provide a systematic investigation of the key parameters in the measurement of the fractal dimension of VEPs, to develop an optimal analysis protocol for application. Methods VEP time series were mathematically transformed using delay time, τ, and embedding dimension, m, parameters. The fractal dimension of the transformed data was obtained from a scaling analysis based on straight line fits to the numbers of pairs of points with separation less than r versus log(r) in the transformed space. Optimal τ, m, and scaling analysis were obtained by comparing the consistency of results using different sampling frequencies. The optimised method was then piloted on samples of normal and abnormal VEPs. Results Consistent fractal dimension estimates were obtained using τ = 4 ms, designating the fractal dimension = D2 of the time series based on embedding dimension m = 7 (for 3606 Hz and 5000 Hz), m = 6 (for 1803 Hz) and m = 5 (for 1000Hz), and estimating D2 for each embedding dimension as the steepest slope of the linear scaling region in the plot of log(C(r)) vs log(r) provided the scaling region occurred within the middle third of the plot. Piloting revealed that fractal dimensions were higher from the sampled abnormal than normal achromatic VEPs in adults (p = 0.02). Variances of fractal dimension were higher from the abnormal than normal chromatic VEPs in children (p = 0.01). Conclusions A useful analysis protocol to assess the fractal dimension of transformed VEPs has been developed

Development and evaluation of a rapid dipstick assay for serodiagnosis of acute human brucellosis

A dipstick assay for the detection of brucella-specific immunoglobulin M antibodies was evaluated with 707 sera from 247 laboratory-confirmed brucellosis patients and 342 control sera from brucellosis-free individuals. These sera were collected from six different countries. The assay was found to be highly sensitive and specific. In addition, the test is easy to use and does not require specialized training or equipment, and the components are stable without a requirement for refrigeration. All of these factors make the test ideal for developing countries and rural settings

EFFECTS OF PLANTING DATE ON WATER REQUIREMENTS OF MAIN VEGETABLE CROPS IN SAUDI ARABIA

The effects of planting date on the evapotran-spiration (ETC) were studied for Tomato, Egg-plant, Squash, Cucumber, Carrot, Potato, Onion, and Watermelon, in Riyadh, Makkah, Njran, Al-Qassim, Eastern region, Tabuk, Al-Jouf, Aseeir, Al-Madenah, Hail and Jazan Regions based on the crop pattern in each region. The ETC of each crop was estimated based on Penman-Monteith Equa-tion. The results showed that the ETC for crops planted in January, February, March, April or Maywere higher than those crops planed in September, October, November, or December. The average ETC was higher when planting date was closer to summer months (June, July and August). Also, the results showed differences in ETC among the dif-ferent regions. The ETC in Al-Madenah region was higher than the other regions for Tomato and Eggplant. While, Riyadh region had the highest ETC values compared with the other regions for Squash, Cucumber, Carrot, Potato, Onion, and Water melo

EFFECT OF DRIPPER DISCHARGE ON PRODUCTION AND CHARACTERISTICS OF CABBAGE AND ITS NITROGEN CONTENT UNDER MAKKAH REGION CONDITIONS

A two years (2002/2003, 2003/2004) study was conducted at Hada Al-Sham Agriculture Re-search Station, Makkah Region (King Abdulaziz University) to determine the effects of three dif-ferent dripper discharges (0.5, 1, and 2 gph) on cabbage production, characteristics of its part and its nitrogen contents in whole plant and its parts. Results show a significant increase in Copenhagen variety production (38.5 tone/ha) as compared to Bronzweek Variety (30.2 tone/ha). Also, the drip-per discharge significantly affected the cabbage production, characteristics of head, stem, root or leaves area, whereas cabbage production and char-acteristics of all plant parts (head, stem, root and leaves area) were reduced with the increase in dripper discharge more than 0.5 gph, however, the reduction was not significant between discharges of 1 and 2 gph. The cabbage production were 44.3, 29.7 and 28.9 tone/ha for dripper discharges of 0.5, 1 and 2 gph, respectively). In addition, the interaction between season and variety had only significant effects on root length. Also, there were significant effects for the interaction between dripper discharge and season on cabbage produc-tion and root length. Results also showed that first season (2003) produced cabbage plant significant-ly higher than the second season (2004) in nitro-gen content for both whole plant (2.72% and 2.45% for first and second season, respectively) and head (3.63% and 2.72% for first and second season, respectively). Also, Copenhagen variety significantly outweighs Bronzweek variety on nitrogen content in whole plant (2.88% and 2.30% for Copenhagen variety and Bronzweek variety, respectively), leaf (2.69% and 2.16% for Copen-hagen variety and Bronzweek variety, respective-ly), and stem (2.72% and 2.08% for Copenhagen variety and Bronzweek variety, respectively). On the other hand, the increase in dripper discharge more than 0.5 gph resulted significant reduction in nitrogen content for whole plant (3.10%, 2.44% and 2.22% for dripper discharges of 0.5, 1 and 2 gph, respectively) and its parts (head, stem and leaves) whereas the dripper with less discharge (0.5 gph) outweigh the higher discharge drippers (1 and 2 gph). However, the increase of dripper discharge from 1 gph to 2 gph had only significant reduction in the nitrogen content of head. The re-sults also show that interaction between season and variety had only significant effects on nitro-gen content in whole plant. There were also signif-icant effects for the interaction between season and drip discharge on nitrogen content of whole plant and its leaf

Trace elements in the fruits of date palm (Phoenix dactylifera L.) in Jeddah City, Saudi Arabia

Concentrations of selected trace elements (Ag, Al, B, Ba, Cd, Cu, Cr, Fe, Ni, Pb, Se and Zn) in the date palm fruits and their washing fluids were investigated in two locations of Jeddah with different environmental pressure (residential vs urban). Factor Analysis with varimax rotation showed the role of potential sources of the investigate elements. The levels of these elements were found to be greater in the urban site than in the residential one, increasing with the harvest time. The present study has shown that date palm has a strong potential for environmental biomonitoring. However, attention to the safety of dates for human consumption should be payed, in particular to the harvesting time, the environmental pressure of the area with special attention to Ag and Cd, and the possible occurrence of dust storms

Seed germination characteristics of some medicinally important desert plants from the Arabian Peninsula

The arid climate of Saudi Arabia supports many medicinally important species. Germination behaviour is crucial to their establishment in the face of low rainfall and high summer temperatures that produce high evapotranspiration and salt accumulation in the surface soil. We investigated the seed germination biology of three medicinal species from Wadi ad Dayqah in central Saudi Arabia: Salvia spinosa (Lamiaceae), Ochradenus arabicus, and Ochradenus baccatus (Resedaceae). We examined the responses of freshly collected seed to constant and alternating temperature, light, and salinity (NaCl). None of the species showed innate dormancy. All achieved high germination percentages over a wide range of diurnally alternating temperatures (5/15, 10/20, 15/25, 20/30 and 25/35 C). However, the range of temperature for successful germination was narrower at constant temperature, especially for S. spinosa. The rates of germination suggested that all the temperatures examined were suboptimal. Basal temperatures for germination were 5-8 C. Germination of all the species was promoted by light. All were tolerant of salinity up to 80-100 mM NaCl. Osmotically enforced failure to germinate with increasing salinity was reversible after transfer to fresh water. Understanding these adaptive characteristics will assist the development of effective strategies for the conservation of medicinally important species in arid environments