African
Journals Online
Global Journal of Pure and Applied Sciences
Volume 8 number 3 June 2002
EFFECTS OF TUBER PORTION AND TIME OF HARVESTING ON
ACCUMULATION AND PARTITIONING OF DRY MATTER IN WATER YAM (Dioscorea
alata L.) MINISETT IN UYO, SOUTH EASTERN NIGERIA.
BASSEY A. NDON And NYAUDOH U. NDAEYO
Department of Crop Science, University of Uyo, Uyo .&
Department of Crop Science, University of Uyo, Uyo.
ABSTRACT
The high cost of seed yam is a serious constraint to water yam
production. Therefore a two-year field trial was conducted at the
University of Uyo Teaching and Research Farm to evaluate dry
matter accumulation and partitioning among various plant parts in
water yam (Dioscorea alata L.) minisetts as influenced by
portion of tuber planted and time of harvesting. The experiment
was laid out in a randomised complete block design with a
split-plot arrangement. The main-treatments were portions of
tuber planted (head, middle and tail) and the sub-treatments were
time of harvesting (90, 180 and 270 days after planting –
DAP). The results showed that portions of tuber planted had no
significant effect on dry matter accumulation within leaves,
vines, roots and tuber. Early in the season (i.e. 90 DAP),
leaves, vines and roots collectively accounted for 67, 62 and 57%
of the total plant dry matter for the head, middle, and tail
portions, respectively; thereafter the dry matter content
declined. However, as the plant matured, the partitioning ratios
decreased for leaves, vines and roots, but increased for tubers.
Similarly, dry matter accumulation differed significantly
(p<0.05) among times of harvesting. The highest dry matter
accumulation was attained at 270 DAP. Therefore, it is
recommended that any of the tuber portions could be conveniently
used to raise seed yam, while harvesting should not be done
before 270 DAP for maximum dry matter accumulation.
Key Words: Water yam, Minisett, Dry matter
accumulation.
THE EFFECTS OF AGE ON MUSCLE TEXTURE AND EATING QUALITIES OF
BROILER CHICKENS FOR NIGERIANS
SAMUEL A. OFFIONG, Department of animal Science, Faculty of
Agriculture, University of Uyo, Uyo Nigeria
ISONGESIT P. SOLOMON, Department of Animal Science, Faculty of
Agriculture, University of Uyo, Uyo, Nigeria
BENEDICT I. UMOH, Department of Animal Science, Fculty of
Agriculture, Univesity of Uyo, Uyo, Nigeria
ETOK O. EKANEM, Deparment of Animal Science, faculty of
Agriculture, University of Uyo , Uyo. Nigeria.
ABSTRACT
An experiment was conducted to test the effect of age on the
eating qualities of broiler chickens slaughtered at 7, 8, 9, 10,
11 and 12 weeks of age for the Nigerian consumers. The birds that
provided the meat for the experiment were raised conventionally.
Thigh and drumstick meat of the oven–roasted chickens were
subjected to a 15–man taste–panel for sensory
evaluation, using a rating scale of 1-10, to score for toughness,
flavour, juiciness and general acceptability: like extremely,
like moderately, not like or dislike, dislike moderately, dislike
extremely. There was no significant difference (P>0.05) in
toughness among the 10, 11 and 12 weeks old broiler meat. The 8
and 9 weeks old broiler chicken meat were similar and scored
significantly higher than the 7-week old chicken meat for
toughness. The 7 weeks old broilers scored lowest (not like or
dislike). These toughness scores were reflected in the general
acceptability scores, where 10, 11 and 12 weeks groups were
scored extremely liked. The 9 weeks group was also scored
extremely liked although less tender in the toughness score. The
7 and 8 weeks old broiler meat were scored liked moderately in
general acceptability. Juiciness scores exhibited no significant
differences in the panelists' perception among the treatments,
whereas in flavour perception the 12 weeks old broiler meat was
liked extremely followed by 10 and 11 weeks old broiler meat
which were similar and of equal flavour perception and liked
moderately. Flavour perception of 7, 8, and 9 weeks old broilers
were similar. Age had a profound effect on the meat texture and
thus influenced acceptability.
Key Words: Broiler chickens, age, meat texture, eating
qualities.
LENGTH FREQUENCY DISTRIBUTION OF Ethmalosa fimbriata
(BOWDICH) IN CROSS RIVER ESTUARY AND ADJACENT COASTAL WATERS
BY
D.E.AMA-ABASI & S. HOLZLOEHNER
Institute of Oceanography, University of Calabar, PMB 1115,
Calabar, CRS, Nigeria
ABSTRACT
Studies on the length distribution of bonga, Ethmalosa
fimbriata, in the Cross River estuary and adjacent coastal
waters were conducted from October 1999 to December 2000. A total
of 15,182 specimens of bonga from gill nets, purse seine and boat
seine fisheries were measured. Post-larvae measuring between 2 cm
and 9 cm were found in the lower estuary with a modal length of 4
cm. Juveniles from gill net fishery ranged in length from 8 cm to
20 cm with a modal length of 13cm. Adults and sub-adults ranging
in size from 16 cm to 33 cm were caught from the coastal waters
alongside the juveniles, by the purse seine fishery. Two modal
lengths of 17 cm and 25 cm were observed in the coastal waters.
Three modal length classes were observed in the catches from the
Cross River estuary and adjacent coastal waters: these are 4 cm,
13 cm and 25 cm. It is concluded that the Cross River estuary is
a nursery ground for bonga, Ethmalosa fimbriata.
Key Words: Ethmalosa fimbriata, length
distribution, Cross River estuary, coastal waters, nursery.
EFFECTS OF INDUSTRIAL EFFLUENTS ON SOME HAEMATOLOGICAL
PARAMETERS OF Sarotherodon melanotheron AND Tilapia
guiniensis
C.B.D. DAVIDS1, I. K. E. EKWEOZOR1, E.
R. DAKA1*, W.B. DAMBO1 and E. A. S.
BARTIMAEUS2
1. Department of Biological Sciences
2. Department of Medical Laboratory Sciences
Rivers State University of Science and Technology, P. M. B.
5080, Port Harcourt, Nigeria.
* Author for correspondence
ABSTRACT
The effects of petroleum refinery and fertilizer plant
effluents on some haematological parameters (packed cell volume -
PCV, Total Leucocyte Counts - TLC and Differential Leucocyte
Counts) in two species of cichlids; Sarotherodon melanotheron
and Tilapia guiniensis were studied. This was with a view
to assessing the usefulness of these parameters as indicators of
pollution in Niger Delta Estuaries. Average Packed Cell Volume
(PCV) ranged from 24.4 + 3 to 24.4 + 4.4 cm3
in T. guiniensis while the values for S. melanotheron
ranged form 24.3 + 3 to 26.5 + 4.7 cm3.
PCV is probably not a good indicator for contaminants in both
species. There were high significant differences (p<0.0001) in
Total Leucocyte Counts of the two species from the various sites.
The highest values for both T. guiniensis (18427 +
3896 cells/l) and S. melanotheron (17776 + 3656
cells/l) were found in samples from creeks receiving fertilizer
plant effluents, while values for samples from the control creek
were the lowest giving 9042 + 2859 cells/l for T.
guiniensis and 8662 + 2985 for S. melanotheron.
Key Words: Haematology, Tilapia,
Packed Cell Volume, leucocyte counts, Industrial effluents.
COMPARATIVE EFFECTS OF SCOPOLETIN AND CYANIDE ON SERUM
ELECTROLYTES, UREA, CREATININE AND SOME HAEMATOLOGICAL PARAMETERS
OF RATS
LAWRENCE U. S. EZEANYIKA*1, ONYECHI OBIDOA1,
NIKE B. OLUWASHEMIRE2, TEKEUDO, D. LOUISIANE2
AND ISMAILA A. UMAR2
1 DEPARTMENT OF BIOCHEMISTRY, UNIVERSITY OF NIGERIA, NSUKKA
2. DEPARTMENT OF BIOCHEMISTRY, COLLEGE OF MEDICAL SCIENCES,
UNIVERSITY OF MAIDUGURI, P.M.B. 1069, MAIDUGURI
* AUTHOR FOR CORRESPONDENCE.
ABSTRACT
The effects of scopoletin (6-methoxy 7-hydroxycoumarin) and
cyanide on serum Na+, K+, Urea, creatinine
and some haematological parameters of female Wistar rats were
compared. The rats were randomly divided into six groups, and
administered respectively 7g/ml, 21g/ml, 35g/ml scopoletin,
1.8mg/ml cyanide, 10% dimethyl sulphoxide (the vehicle for the
administration of scopoletin) and 1ml distilled water orally per
kg body weight at 24 hourly intervals. All the rats were
maintained ad libitum on chicks' mash and were sacrificed
after 14 days. Scopoletin at the level found in processed cassava
diet (7g/ml) increased bleeding time, Rbc count, serum urea and K+
levels compared to 1.8mg/ml cyanide which is approximately the
level consumed by a 70kg man in cassava consuming populations per
day. Among the groups administered scopoletin serum levels of K+
and creatinine increased with increasing concentration while Na+
and Urea level decreased with increasing concentration. The
results of this study suggest further investigations on the
effects of scopoletin and cyanide on haematopoiesis and kidney
function.
Key Words: Scopoletin, Cyanide, Kidney function,
haematopoiesis.
SERUM LIPID PROFILES OF A POPULATION OF PREGNANT WOMEN IN
BORNO STATE NIGERIA.
Lawrence U.S. Ezeanyika,*1 Khadija, A. Kasab,
2 Yusuf S. Murtala 2 Isah Yunusa2,
And Fatimah O. Ibrahim2.
1. Department Of Biochemistry, University Of Nigeria, Nsukka
2. Department Of Biochemistry, College Of Medical Sciences,
University Of Maiduguri, P.M.B. 1069, Maiduguri, Nigeria.
ABSTRACT
The serum lipid profiles of 269 pregnant women in
North-eastern Nigeria were studied. Thirty-four apparently
healthy non-pregnant women were used as control subjects. The
results of the study show a significant increase in total
cholesterol, triacylglycerol, low density lipoprotein and
phospholipid levels of pregnant women relative to those of the
control. While serum phospholipid showed a linear increase from
the first trimester of pregnancy to the third, serum total
cholesterol and low density lipoprotein each peaked at the second
trimester. The mean serum high density lipoprotein level of
pregnant women at second trimester, 0.92 0.06mmol/l was
significantly lower than that of control subjects which was 1.43
0.10mmol/l. Changes in lipid metabolism during pregnancy are
physiological and may be related to increased metabolic rate and
the need to prepare the would-be mother for lactation.
Key Words: Serum lipids, pregnancy, North-eastern
Nigeria.
Rb-Sr ISOCHRON DATING OF GRANITOIDS FROM THE KAZAURE SCHIST BELT, NW NIGERIA.
U. A. DANBATTA
Department of Geology, A.B.U. Zaria
ABSTRACT
The results of Rb-Sr isochron dating of granites from the
crystalline basement complex of Kazaure Schist Belt are presented
in this paper. Whole rock Rb-Sr radiometric age determination of
five samples of a syntectonic coarse-grained porphyritic granite
define a 4-point whole-rock Rb-Sr isochron (MSWD=1.2)
corresponding to an age of 592 + 14 Ma, the initial 87Sr/86Sr
ratio being 0.7097 + 0.0004. This is distinctly a
Pan-African age and is taken as the time of emplacement and
crystallization of a granitic magma formed from a reworking of a
pre-existing continental crust. The initial 87Sr/86Sr
ratio indicates a significant contribution of older crustal
materials by partial melting to the granitic magma.
Key Words: Kazaure Belt, Geochronology, Isochron,
Pan-African, Crust.
EFFECTS OF LITHOLOGY ON GEOTHERMAL GRADIENT IN THE
SOUTH-EAST NIGER DELTA, NIGERIA
Etim D. Uko, Arobo R. C. Amakiri and Kingsley D. Alagoa
Geophysics Research Group, Department of Physics, Rivers State
University of Science and Technology, P. M. B. 5080, Port
Harcourt, Nigeria
ABSTRACT
A study of the effects of lithologic formations on geothermal
gradients is carried out in the south-east Niger Delta, Nigeria,
using continuous temperature and lithologic log data from
closely-spaced petroleum wells. The gradient profiles obtained
for the deep wells, logged to depths between 6500 ft (1981m) and
8500ft (2591m), were observed to have markedly different
geothermal gradients with corresponding vertical lithologic
units. For the upper sandy lithology, the Benin Formation, the
temperature gradient ranges between 0.80 oF/100 ft
(1.456 oC/100m) and 1.22 oF/100 ft (2.220 oC/100m)
with an average of 1.03 oF/100 ft (1.875 oC/100m).
For the paralic shaly Agbada Formation segment, the temperature
gradient ranges between 0.92 oF/100 ft (1.674 oC/100m)
and 1.87 oF/100ft (3.403 oC/100m) with an
average of 1.40 oF/100ft (2.548 oC/100m).
The depths of Benin Formation were observed to vary between
4200ft (1280 m) and 5400ft (1879 m). Geothermal gradients are
thus observed to increase with depth and shale units.
Key Words: Subsurface temperature, lithology,
temperature gradient, thermal
conductivity, basin, fluid flow.
MATHEMATICAL MODELLING APPROACH TO THE TREATMENT OF
INSULIN-DEPENDENT DIABETES DISEASE
G.C.E. MBAH
DEPARTMENT OF MATHEMATICS, UNIVERSITY OF NIGERIA,NSUKKA.
ABSTRACT
Medical scientists have various ways of handling cases of
insulin-dependent diabetes diseases of which one of the most
popularly used methods is carrying out experiments on the
patient. However, each time a case is presented, the need for
fresh experiment to determine the treatment procedure will arise.
To therefore reduce the time in experimentation as well as to
save life of the patient by using accurate information of the
patient's state of health, the need for mathematical model
arises. A mathematical model that can be used to estimate the
level of the plasma insulin and glucose levels at all times is
presented. The required insulin dose to be given to the patient
so as to correct the disease with the subsequent doses of glucose
intake without necessarily arousing the disease again is also
determined using this model.
The effect of the pancreatic release of the insulin and the
peripheral response of the cells to the available insulin were
demonstrated. Also it was shown that the reduction in body cell
usage of plasma glucose results mainly to the increase in time of
clearance of glucose in the blood plasma. Equally demonstrated is
the consequence of improper diagnosis of the level of severity of
the disease before recommending certain dose of the insulin to be
given to the patient as a corrective measure. Solutions to the
modeled equations were obtained by linearising the non-linear
equations and then solving analytically.
Key Words: Mathematical modelling, Treatment of Diabetes
Disease.
ON BUILDING AN OR-BASED DECISIONS MODEL VIA COHERENT
PLURALISM
K. J. Bassey and P. E. Chigbu1
University of Nigeria, Nsukka
ABSTRACT
The problems that often arise in any business or commercial
organisations are profit maximization and operating cost
minimization. This work develops a heuristic framework, using
computer science technology in Operations Research (OR) problems,
as a contribution to the use of different techniques and/or
models in combination (i.e. Coherent Pluralism). Three OR
techniques are considered, and a computer high level language
(QBASIC) is used to design a computer program (referred here as a
computer model) that integrates these techniques. Typical data
from a paint manufacturing factory are analysed. On the whole,
the need for the implementation of OR techniques in management
operations is emphasized.
Key Words: Coherent Pluralism; Decision Support System;
Heuristic; OR techniques.
RADIOLOGICAL DOSE IMPLICATIONS OF THE NATURAL RADIOACTIVITY IN
SURFACE SOILS IN EKITI STATE, NIGERIA
I. R. AJAYI
Department of Physics & Electronics
Adekunle Ajasin University
Akungba-Akoko, Nigeria
ABSTRACT
The radiological dose implications of the natural
radioactivity in the surface soil across Ekiti State, Nigeria
have been determined in this study by using a very sensitive
gamma spectroscopic system of measurement. Effective dose at 1.0m
above the ground in the State was found to vary between 0.037 and
0.227mSvy-1 while the fifty years integral dose
obtained ranged from 1.85 to 11.5mSv with a mean of 5.4770+
2.926mSv. The estimated average effective dose equivalent for the
State is 0.109+ 0.058 mSvy-1. This value is far
below the 0.41 mSvy-1 estimated as the world average
by UNSCEAR and the dose limit of 1.0 mSv per year recommended as
the individual dose limit for members of the public by the
International Commission for Radiological Protection (ICRP).
Key Words: Environmental, radioactivity, radiation,
soil dose
SPATIAL AND TEMPORAL DISTRIBUTION OF IONOSPERIC CURRENTS
– 3: LATITUDE-LOCAL TIME AND LATITUDE-LONGITUDE CROSS
SECTIONS OF EQUATORIAL ELECTROJET CURRENT DENSITY AND INTENSITY.
C. AGODI ONWUMECHILI, 1 P. O. EZEMA2 AND
S. O. OKO3
1. 4813 Lackawanna St; College Park MD 20740, USA
2. Department of Physics and Astronomy, University of Nigeria,
Nsukka, Nigeria
3. Department of Computer Science, University of Nigeria,
Nsukka, Nigeria.
ABSTRACT
A comprehensive analysis of the POGO satellites data of 1967
–1969 has enabled us to present the daytime means, based on
09 hr to 15 hr, at each of 36 longitudes, and the all-longitude
means at each of 7 local time hours, for each of 9 parameters of
the equatorial electrojet (EEJ) necessary for the cross sections.
The latitude-local time cross sections of EEJ current density and
intensity each displays three contour cells. The forward current
contour cell peaks at (12h, 00.) and the return
current contour cells peak at (12h, 5.130N) and (12h,
5.130S). The latitude-longitude cross sections of EEJ
current density and intensity each displays nine contour cells.
The three forward current contour cells peat at (00,
1000E), (00, 1900E) and (00,
2900E). The three return current contour cells to the
north peak at (5.350N, 1000E), (5,050N,
1900E) and (5.300, 2900E), while
the three to peak at (5.350S, 1000), (5.050S,
1900E), while the three to the south peak at (5.350S,
1000E), (5.050S, 1900E) and
(5,300S, 290E). The return current spreads thinly over
an area of about four times the area of the forward current.
Consequently, the ratio of the peak return current density or
intensity to the peak forward current density or intensity is
only about one quarter. On the average the percentage ratio is
–23.25 0.41. Arising from the decrease of EEJ with latitude
while at the same time it increases everywhere as the peak
current at the magnetic dip equator increases, the cross sections
show that the contours extend farther in latitude when the peak
current at the dip equator is larger.
Key Words: latitude –local time, latitude.
longitude cross sections, current density, and intensity inonospheric currents
BAND MODELS APPROACH IN ATMOSPHERIC TRANSMISSION FUNCTION
CALCULATION - A REVIEW
S.O. Udo and A.E. Akpan
Department Of Physics, University Of Calabar
Calabar - Nigeria
ABSTRACT
Attempts to proffer solutions to radiative transfer equations
have always been impeded due principally to the presence of
numerous absorption lines whose strength, distribution, spacing
and half width within a particular absorption spectrum of a given
substance is not fixed.
This review looks at the use of band models as solution to the
problem of radiative transfer equation of solar fluxes. Different
band models like the regular (Elsasser), Goody (Statistical or
Random), Random Elsasser and the Quasi random are overtly
examined with special emphasis on their respective operational
conditions, advantages and disadvantages.
SPATIAL AND TEMPORAL DISTRIBUTION OF IONOSPHERIC CURRENTS- 4:
ALTITUDE-LOCAL TIME AND ALTITUDE-LONGITUDE CROSS SECTIONS OF
EQUATORIAL ELECTROJET CURRENT DENSITY.
C. AGODI ONWUMECHILI,1 S.O.OKO2 AND P.O
EZEMA3
1. 4813 Lackawanna St; College Park MD 20740, USA
2. Department of Computer Science, University of Nigeria,
Nsukka, Nigeria.
3. Department of Physics and Astronomy, University of Nigeria,
Nsukka, Nigeria
ABSTRACT
The rare opportunity given by the unprecedented spatial and
temporal coverage of POGO satellites data is exploited to present
all possible cross sections of equatorial electrojet (EEJ)
current in the group of papers. Here the all-longitude means at 7
hours centred on local noon and the daytime means at 36
longitudes, of the vertical distribution parameters of EEJ
current density are provided. The altitude–local time cross
section of EEJ current density has one contour cell peaking at
(12 h, 106 km) while the altitude-longitude cross section of EEJ
current density has three contour cells peaking at (1000E,
106 km), (1900E, 106 km) and (2900E, 106
km). In both cross sections the contour of a given current
density extends farther from the altitude of peak current density
when the peak current density at the centre of EEJ is larger.
This accounts for the wavy nature of the altitude-longitude cross
section. Attention is drawn to two rocket measurements that
support this phenomenon. The following conclusions are also
reached. (a) The continuous distribution of current density model
reproduces the altitude distribution parameters of EEJ current
density very well, (b) the altitude distribution parameters of
EEJ current density in India and Peru are not significantly
different and (c) The altitude distribution parameters of EEJ
current density from rockets data and from POGO Satellites data
are not significantly different and that (d) It is essential to
take into account the lack of symmetry between the vertical
distributions of EEJ current density below and above the altitude
of EEJ peak current density.
Key Words: altitude – local time cross sections,
latitude-longitude cross sections, contour cells, ionospheric
currents.
SPATIAL AND TEMPORAL DISTRIBUTION OF IONOSPHERIC CURRENTS- 4:
ALTITUDE-LOCAL TIME AND ALTITUDE-LONGITUDE CROSS SECTIONS OF
EQUATORIAL ELECTROJET CURRENT DENSITY.
C. AGODI ONWUMECHILI,1 S.O.OKO2 AND P.O
EZEMA3
ABSTRACT
The rare opportunity given by the unprecedented spatial and
temporal coverage of POGO satellites data is exploited to present
all possible cross sections of equatorial electrojet (EEJ)
current in the group of papers. Here the all-longitude means at 7
hours centred on local noon and the daytime means at 36
longitudes, of the vertical distribution parameters of EEJ
current density are provided. The altitude–local time cross
section of EEJ current density has one contour cell peaking at
(12 h, 106 km) while the altitude-longitude cross section of EEJ
current density has three contour cells peaking at (1000E,
106 km), (1900E, 106 km) and (2900E, 106
km). In both cross sections the contour of a given current
density extends farther from the altitude of peak current density
when the peak current density at the centre of EEJ is larger.
This accounts for the wavy nature of the altitude-longitude cross
section. Attention is drawn to two rocket measurements that
support this phenomenon. The following conclusions are also
reached. (a) The continuous distribution of current density model
reproduces the altitude distribution parameters of EEJ current
density very well, (b) the altitude distribution parameters of
EEJ current density in India and Peru are not significantly
different and (c) The altitude distribution parameters of EEJ
current density from rockets data and from POGO Satellites data
are not significantly different and that (d) It is essential to
take into account the lack of symmetry between the vertical
distributions of EEJ current density below and above the altitude
of EEJ peak current density.
Key Words: altitude – local time cross sections,
latitude-longitude cross sections, contour cells, ionospheric
currents.
MEASUREMENT OF SALINITY AND ELECTRICAL CONDUCTIVITY OF SOME
SOIL SAMPLES OF URUAN LOCAL GOVERNMENT AREA OF AKWA IBOM STATE.
Akpan, U. E., Okon, A.A., and Ituen, E. E.
Department of Physics, University of Uyo, Uyo.(same University
of Uyo)
ABSTRACT
The salinity and electrical conductivity of some selected soil
samples from Uruan Local government area of Akwa Ibom state of
the Federal Republic of Nigeria were measured. The results show
that an increase in salinity gives rise to an increase in
electrical conductivity. The salinities of the area under study
falls within the range: 0.025 S 0.1951 ds/cm while the soil
electrical conductivity per unit depth Ec was between
the range 0.192 Ec 2.64 -1cm-1. Comparison
with the United State Department of Agriculture (USDA) soil
classification table, shows that soils in Uruan could be
classified as salt free because their salinities are between 0
and 2, implying that salinity effects on crops in Uruan are
mostly negligible except for most sensitive plants.
Key Words: Salinity, Electrical Conductivity, Soil and
Samples.
VARIABILITY STUDY OF TEMPERATURE FOR A TROPICAL STATION
E. E. Iheonu
Nigerian Building and Road Research Institute
Building Research Department
P.M.B. 1055, Ota, Ogun State, Nigeria.
ABSTRACT
The monthly deviation of maximum temperature from the median
value has been used to carry out a variability study of
temperature for a tropical station, Ibadan (lat. 7.40 N,
long. 3.40 E) Nigeria. The study was undertaken for
different seasons during periods of high and low solar activity.
Results from the assumed linear correlation between solar
activity and maximum temperature suggest that a non-linear form
of equation might be appropriate for the variables. Generally,
the range of variation of the deviations is independent of solar
activity. Negative deviations were greater than positive
deviations for both periods of solar activity. Variations
occurred in the dry season months of February, March and April
during the period of low solar activity, whereas for the wet
season, the range of variation occurred in the months of July and
September for both periods of high and low solar activity.
Temperature variations from the median value do not give thermal
gradients that could portend threats to the environment.
Key Words: Variability, maximum temperature, tropical
station, solar activity, thermal gradients.
GROUND ELECTRICAL CONDUCTIVITY FOR MEDIUM WAVE LINK DESIGN
AT ILORIN, NIGERIA
A.M. Arogunjo
A. M. Arogunjo, Department of Physics, Federal University of
Technology, Akure, Ondo State
ABSTRACT.
Ground electrical properties remain a useful tool for most
applications in engineering and communication, therefore,
reliability and precision is highly required in their
determination. Ground electrical conductivity as a function of
signal frequency has been determined at Ilorin during the dry and
the wet seasons. The study revealed that the mean conductivity
during the wet season is higher than that of dry season. The
values range from 3.5mS/m - 5.0mS/m for the dry season and
4.6mS/m - 6.3mS/m for the wet season. The variation of skin depth
with signal frequency was also investigated. Correlation
coefficients ranging from 0.8598 to 0.9834 were obtained between
the signal frequency and the measured ground electrical
conductivity at different hours of the day for both seasons using
the statistical analysis toolpack of Microsoft Excel 5.0.
Key Words: Ground, Electrical, Conductivity, Season,
Frequency
CONDITIONS FOR THE FORMATION OF DEEP CONVECTIVE ACTIVITIES
OVER NIGERIA
C. U. OKUJAGU
DEPARTMENT OF PHYSICS, UNIVERSITY OF PORT HARCOURT
P.M.B. 5323, CHOBA, PORT HARCOURT
ABSTRACT
Some mean flow parameters and dynamic processes necessary for
the formation of widespread deep convective activities over
Nigeria have been investigated and their interactive roles
identified. These parameters include the low-level and the 700mb
winds known as African Easterly jet (AEJ), spatial distribution
of the vertical shears variability of the Zonal and meridional
winds, the spatial and temporal of the height of the moist layer,
and the anomalies of equivalent potential temperature and
specific humidity. Wide spread thunder storms and/or organized
line squalls were fond to exist on days of well defined African
Easterly Jet (AEJ) with a higher concentration of storms/squalls
around the left entrances and right exists in contrast with the
middle latitude situation where weather development is normally
expected around the right entrances and left exits of jet
streams. Positive (westerly) low-level (boundary layer) zonal and
meridional wind shears were found to be more important to storm
initiation due to their overturning effects. On the other hand,
negative (easterly) low-level shears led to suppression of
convective activities. The depth and strength of convective
activities were found to be affected by a deepening of the moist
layer (represented by the height of the positive meridional (V)
components of the wind) in the preceding twenty-four hours. A
reasonably deep layer of moisture of at least 1.5km favours
widespread deep convection.
Mappings of positive vertical wind shears height of the moist
layer greater than –0.5km were found to have very high
correlation with areas of line squall/thunderstorm occurrence
while anomalies of the equivalent potential temperature and
specific humidity gave minimal correlation with convection.
Key Words: Thunder storms, Line Squall, African
Easterly Jet, Wind Shears, Convection.
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